CO2 to fuels and chemicals course material final version

NCCR Online Course Series

Dr. Balasubramanian Viswanathan

National Centre of Catalysis Research (NCCR)

IIT Madras

NCCR

National Centre for Catalysis Research

Online Course Series

For further information:

http://www.eprints.iitm.ac.in/

http://www.eprints.iitm.ac.in/

Dr. Balasubramanian Viswanathan

Carbon Dioxide to Fuels and Chemicals Course Materials

COURSE OUTLINE

1. CO2 Conversion – Relevance and Importance

1.1. Introduction (CO2 Utilization for Global

Sustainability)

1.2. CO2 as a Raw Material for Fuels

1.3. CO2 as a Raw Material for Organic

Chemicals

1.4. Overview on Conversion Processes

1.5. Prospects

2. Surface chemistry of CO2

2.1. Thermodynamic and Kinetic Considerations

2.2. Bonding in CO2

2.3. Adsorption of CO2 on Metal Surfaces

2.3.1. Adsorption of CO2 at sp- Metal Surfaces

2.3.2. Interaction of CO2 with Single Metal

Crystals

2.3.3. Adsorption of CO2 at Copper Surfaces

2.4. Chemisorption of CO2 at Oxide Surfaces

2.5. Reactions of Adsorption of CO2 with Co-

adsorbed Species

2.6. Alkali Metal Activation of CO2 at Metal

Surfaces

3. CO2 - Capture and Storage

3.1. Introduction and Role in Mitigating Climate

Change

3.2. CO2 - Capture

3.2.1. Conventional Chemical Absorptions

3.2.2. Emerging Methods in CO2 Capture

3.2.3. New Materials for CO2 Capture

3.2.4. Opportunities and Challenges

3.3. CO2 - Storage

3.3.1. Options and Characteristics

3.3.2. Current Status and Storage Possibilities

3.3.3. Technical and Economical Potentials

3.3.4. Implications - Local Health, Safety and

Environmental

3.4. Perspectives

4. Hydrogenation of CO2

4.1. Introduction

4.2. Homogeneous Hydrogenation of Carbon

Dioxide

4.2.1. Producing Formic Acid or Formate Salts

4.2.1.1. Via Carbon Monoxide

4.2.1.2. Via Carbonate

4.2.1.3. Via Normal CO2 Insertion into M-H

Bond

4.2.1.4. Via Abnormal CO2 Insertion into M-

H Bond

4.2.1.5. Via Hydride Transfer

4.2.2. Producing Methanol, Methane and

Carbon Monoxide

4.2.3. Producing Alkyl Formates from

Alcohols


4.2.3.2. Via Formic Acid

4.2.3.3. Methanolysis

4.2.4. Producing Alkyl Formates from Alkyl

Halides

4.2.5. Producing Formamides or

Methylamines from Amines


4.2.5.2. Via Formic Acid

4.2.5.3. Aminolysis

4.2.5.4. Via Carbamates or Carbonates

4.2.5.5. Formation of Methylamine

4.2.6. Producing diols and diol formates from

Oxiranes

4.2.7. Homogeneous Hydrogenation of

Supercritical CO2

4.2.8. Perspectives

4.3. Heterogeneous Hydrogenation of Carbon

Dioxide

4.3.1. Introduction

4.3.2. Synthesis of carbon monoxide via

reverse water gas shift reaction

4.3.2.1. Metal Based Heterogeneous

Catalysts

4.3.2.2. Reactor Aspects

4.3.2.3. Reaction Mechanism

4.3.3. Methanation of Carbon Dioxide

4.3.3.1. Metal Based Heterogeneous

Catalysts


4.3.4. Synthesis of Hydrocarbons

4.3.5. Production of Methanol

4.3.5.1. Limitation in Methanol Formation


4.3.5.3. Catalysts and Performances

4.3.5.4. Addition of Precursors

4.3.5.5. Water as an Exhibitor

4.3.5.6. Theoretical Studies

4.3.6. Synthesis of Dimethyl Ether

4.3.6.1. Hybrid Oxide-Based Catalysts

4.3.6.2. Theoretical Studies

4.3.7. Synthesis of Higher Alcohols

4.3.8. Concluding Remarks and Perspectives

5. Biochemical reduction of CO2

5.1. Introduction

5.2. CO2 Fixation

5.3. Computational Studies on CO2 Fixation

5.4. Hydrogen Utilization

5.5. CO2 Capture

5.6. Host Development

5.7. Prospects and Concluding Remarks

6. Photochemical reduction of CO2

6.1. Introduction

6.2. Basics of CO2 Photo reduction Systems

6.3. Typical Mechanisms

6.4. Limiting Steps and Strategies for

Enhancement

6.5. Comparison between different Systems

6.5.1. Biological Systems

6.5.2. Semiconductor Systems

6.5.2.1. TiO2 Based Systems

6.5.2.2. Other Semiconductors

6.5.2.3. Metal-Organic Complexes

6.5.2.4. Hybrid Systems

6.6. Summary and Outlook

7. Photoelectrochemical reduction of CO2

7.1. Introduction

7.2. Principles and Mechanisms

7.3. Homogeneous PEC reduction

7.4. Heterogeneous PEC reduction

7.4.1. Aqueous Media

7.4.2. Non-aqueous Media

7.5. The Mechanism of CO2 Reduction on

Semiconductor Surfaces

7.6. PEC Reduction of CO2 at

Semiconductor/Molecular Catalyst Junctions

7.7. Homogeneous PEC Reduction of CO2 at

Semiconductor/Molecular Catalyst Junctions

7.8. Heterogeneous PEC Reduction of CO2 by

Molecular Catalysts anchored to

Semiconductor Surface

7.9. Challenges and Prospects

8. Electrochemical reduction of CO2

8.1. Introduction

8.2. Direct Electrochemical Reduction at Inert

Electrodes

8.3. Basic Principles and Fundamentals

8.3.1. Redox and Chemical Catalysis

8.3.2. Overpotential and Turnover Frequency

in Homogeneous and heterogeneous

Cataysis

8.3.3. Understanding Catalytic Responses

through Cyclic voltammetry

8.4. Homogeneous Catalysis of Reduction of CO2

8.5. Heterogeneous Catalysis of Reduction of CO2

8.6. Bioelectrochemical Reduction of CO2

8.7. Product Selectivity in the Electrocatalytic

Reduction of CO2

8.8. Catalyst Stability, Activity Degradation and

Mitigation Strategies

8.9. Technological Challenges in Electroreduction

of CO2

8.10. Summary and Prospects

References

9. Perspectives - CO2 Conversion to fuels and

Chemicals

TABLE OF CONTENTS

Lectures (Page No) Topics

Lecture 1 (1) Introduction

Lecture 2 (6) Attempts at Carbon Dioxide

Reduction

Lecture 3 (14) Hydrogenation of Carbon

Dioxide to CO, CH3OH,CH4

Lecture 4 (35) Metal Cathodes employed for

Photoreduction of Carbon

Dioxide

Lecture 5 (58) Photoelectroreduction of

Carbon Dioxide

Lecture 6 (79) Reforming of Carbon Dioxide

with Methane for Synthesis

Gas

Lecture 7 (112) The concept of Trireforming

Lecture 8 (147) Carbon as a stock for

Chemicals and Fuels

Lecture 9 (172) Fundamentals of

Electrocatalytic Redution of

CO2 metal surfaces only to

small molecules and fuels.

Basic Information

Lecture 10 (215) Fundamentals of

Electrocatalytic Reduction of

CO2 on Surfaces to Molecules

and Fuels

Lecture 11 (241) The Question on

Electrocatalytic Reduction on

CO2

Lecture 12 (268) Synthesis of Linear

Carbamates

Lecture 13 (290) Reflection on the

Electrochemical Reduction of

Carbon dioxide on Metallic

Surfaces

Lecture 14 (319) Electrocatalytic Reduction of

Carbon Dioxide

Lecture 15 (351) Bocarsly’s work on CO2

reduction from 1994

Lecture 16 (368) Photocatalytic Reduction of

Carbon Dioxide by Metal

complexes : Single Component

System

Lecture 17 (390) Muticomponent Systems for

Carbon dioxide Reduction

Lecture 18 (411) Carbon Dioxide Reduction on

Semiconductors

Lecture 19 (435) Reflections on Heterogeneous

Photocatalysis


Carbon Dioxide : Product

Analysis and Systematics


Carbon Dioxide: Product

Analysis and Systematics.

Continuation

Lecture 22 (500) Why Titanium Dioxide

Receives Maximum Attention?

Lecture 23 (524) Other Semiconductors Used

for Carbon Dioxide

Conversion

Lecture 24 (541) Biochemical Routes For

Carbon Dioxide Reduction :

An Introduction

Lecture 25 (571) Concluding Remarks

CARBON DIOXIDE TO FUELS AND CHEMICALS – INTRODUCTION

LECTURE 1

• WHY THIS NEW COURSE ?

• WHAT WILL BE THE COVERAGE?

• WHAT WILL NOT BE CONSIDERED IN THIS AREA?

• WHAT WILL BE THE PARTICIPANT GET?

• COVERAGE LEVEL- MOSTLY UP-TO-DATE AND CURRENT SCIENTIFIC LITERATURE

1

CARBON DIOXIDE TO FUELS AND CHEMICALS

• SOME FUNDAMENTAL KNOWLEDGE ASSUMED

1. CHEMISTRY

2. PHYSICS

3. ELECTRONIC STRUCTURE OF SOLIDS

4. ELECTRONICS

5. MATERIALS

6. REACTOR DESIGNS

7. PROCESS CONTROL2

POSSIBLE COVERAGE(MAY INCLUDE OTHER ASPECTS)

• INTERFACES WITH RESPECT TO SEMICONDUCTOR

• PRINCIPLES OF PEC AND ITS RELEVANCE TO PHOTOCATALYTIC REDUCTION

• MATERIALS FOR PHOTOCATALYSIS

• POSSIBLE PHOTOCATALYTIC REACTIONS

• PHOTOSYNTHESIS AND RELATED AREAS

• ELECTROCATALYSIS

• REFORMING

• BIOCHEMICAL REDUCTION

3

TENTATIVE SYLLABUS FOR THE COURSE

• Chapter 1: Introduction and analysis of carbon dioxide sources. Harnessing carbon dioxide methods. Carbon dioxide is a waste or wealth for carbon dioxide conversion. (2-3L)

• Chapter 2: Reforming Carbon dioxide possibilities and features (2-3L)

• Chapter 3: Electrochemical reduction of carbon dioxide to chemicals (4-5L)

• Chapter 4: Photochemical conversion of carbon dioxide (2-3L)

• Chapter 5: Photo electrochemical/ Photocatalytic conversion of carbon dioxide (4-5L)

• Chapter 6: Biochemical Possibilities (1-2L)

• Chapter 7: Future possibilities (1-2L)

WARNING: THE COURSE WILL COVER THIS ASPECTS IN ABOUT 20-25LECTURES THERE ARE OTHER ASPECTS WHICH WILL NOT BECOVERED. KINDLY NOTE THIS. 4

CARBON DIOXIDE TO FUELS AND CHEMICALS

ATTEMPTS AT CARBON DIOXIDE REDUCTIONLECTURE 2

FEBRUARY 14

6

Course on Carbon dioxide to Chemicals and Fuels

PRESENTATION - THREE

17TH February 2014

On Line Course of NCCR

(Total Number of Projections for this Lecture is 21)

14

The thermodynamics are neutral or favorable because of the production

of water from hydrogen but economics are unfavorable for the same

reason

Hydrogenation of CO2 → CO, CH3OH, CH4

P.G.Jessop, Chem. Rev. 95 (2), (1995) 259

CO2(aq) + H2(aq) -------- CO(aq) + H2O(l)

ΔG 0 = 11 KJ/mol; ΔH 0 = 11KJ/mol;ΔS0 = - 8 J/(mol.K)

15

Diols and Diol Formates from Oxiranes

CO2 with methyloxirane in the presence of H2 →1,2- diols & their formates

in addition to cyclic carbonate

P.G.Jessop, Chem. Rev. 95 (2), (1995) 259

16

Catalytic Hydrogenation of CO2 in Supercritical CO2in the presence of Additional substrates

The hitherto solely highly selective catalytic C–C coupling reaction

using CO2 as substrate can also be realized in compressed CO2

17

Cycloco-Oligomerisation of CO2 & Alkynes in compressed Carbon Dioxide

Styrene or Cyclooctene react in a catalytic system → Epoxidation as

well as the reaction to cyclic carbonates

18

• The potential of this types of catalytic reaction is by

no means yet explored.

• The field of homogeneous catalysis in compressed

CO2 will attract major interest in future.

• The development of new CO2 soluble catalysts,

understanding how to prevent deactivation

reactions with CO2 as well as the control of the fine

tuning of the reaction parameters in supercritical

CO2 are starting points to discover new selective

catalysis in supercritical CO2.

19

If pure hydrogen from renewable sources

(e.g. hydroelectric power) is available, an

easiest method for converting it to methanol

with CO2 is to combine both gases in a

thermal reactor at about 220 °C under

moderate pressure (20 - 50 bar).

A. Bill, A. Wokaun, Energy Convers. Mgmt. 38,

(1997) 415

20

Catalyst: Fe supported on MY-zeolite (M=Li, Na, K, Rb)

Hydrogenation of CO2 to hydrocarbons over group VIII metals proceeds in two

steps.

1. Partial reduction of CO2 to CO by reverse water gas shift (RWGS) reaction

2. Subsequent F-T synthesis

S.S. Nam et al., Applied Catalysis A: General 179 (1999) 155

21

S.S. Nam et al., Applied Catalysis A: General 179 (1999) 155

22

(Cu-La2 Zr207 ) → Alcohols & HC from CO + H2 & CO2 + H2

feeds

Addn. oxides, e.g., ZnO or ZrO2 → Good MeOH selectivity

Addn. trans. metal promoter like Co → C2 + alcohols & C2 +

hydrocarbons

Cu-La2 Zr207 + HY zeolite → Mainly C2 + hydrocarbons

Hydrogenation of CO & CO2 → Methanol, Alcohols & HC

R. Kieffer et al., Catalysis Today 36 (1997) 15

23

CO2 to Hydrocarbons

Fe promoted with Cr & Mn → Conversion of CO2 ↑& Selectivity of C2 - C4 alkenes↑

Zn promoted iron catalyst → Unusually very high selectivity for C2- C4 alkenes

With smaller ratio of Zn in Fe:Zn → Alkene selectivity↑

S.S. Nam et al., Energy Convers. Mgmt. 38, (1997) 397

24

CO2 to Hydrocarbons

Zn promoted iron catalyst → Unusually very high selectivity

for C2- C4 alkenes

With smaller ratio of Zn in Fe:Zn → Alkene selectivity↑

S.S. Nam et al.,Energy Convers. Mgmt. 38, (1997) 397

25

CO2 –Hydrogenation to Ethanol

Well balanced multi-functional FT-type composite catalysts

Fe-based Cu-based Pd/Gd addition

↓ ↓ ↓

CO2 to CO C–C bond formation Stabilize optimum

reductive –OH group formation state of catalyst

Difference in alcohol distribution for different catalysts

T.Inui et al., Applied Catalysis A: General 186 (1999) 39526

Electrochemical Reduction of CO2


M. A. Scibioh & B. Viswanathan, Proc. Indn. Natl. Acad. Sci., 70 A (3), 2004.

27

Reduction of CO2 under Protic, and Aprotic Conditions

Protic

Aprotic

Aq. solutions leads to formic acid production (C1 products)

M. A. Scibioh & B. Viswanathan, Proc. Indn. Natl. Acad. Sci., 70 A (3), 2004.28

Reduction of CO2 under Partially aprotic conditions

Aprotic solvents favor dimerization of CO2 leading to Cn products

M. A. Scibioh & B. Viswanathan, Proc. Indn. Natl. Acad. Sci., 70 A (3), 2004.29

Variation of solubility of CO2 with pressure for several solvents at T = 293K and 333K

Solubility of CO2

30

Solubility of CO2 with temperature for several solvents

used in electrochemistry

Solubility of CO2

31

CO2 Electro-reduction on sp Metal Electrodes(kindly read next three slides together)

M. Jitaru, J. Appl. Elec. Chem 27 (1997) 875

32

CO2 Electro-reduction on sp Metal Electrodes

(kindly read this slide with the previous slide)

M. Jitaru, J. Appl. Elec.Chem 27 (1997) 875

33


M. Jitaru , J. Appl. Elec. Chem. , 27 (1997) 875

(kindly read this slide with previous two)

34


PRESENTATION - FOUR

20TH February 2014

On Line Course of NCCR(Total Number of Projections for this Lecture is 22 )

35

Periodic Table for CO2 Reduction Products

At –2.2 V /SCE in low temperature, 0.05 M KHCO3 solution

Y Hori et al., J. Chem. Soc. Chem. Commun, (1987) 728 36

Summary of Metal Cathodes Employed for

Electroreduction of CO2

M. A. Scibioh & B. Viswanathan, Proc. Indn. Natl. Acad. Sci., 70 A (3), 2004

38

Influence of Pressure on Mechanism – An Example

Comparative mechanism of high-pressure CO2 electroreduction (A) &

Electroreduction of CO2 at atmospheric pressure (B) on Ni cathode

M. Jitaru, J. Appl. Elec.Chem ., 27 (1997)875

39

Electro-catalytic Reduction of CO2

(a) Molecular electrocatalysts in solution; (b) Cathodic materials modified by

surface deposition of molecular electrocatalysts

M. A. Scibioh & B. Viswanathan, Proc. Indn. Natl. Acad. Sci., 70 A (3), 2004

40

Electrochemical reduction of carbon dioxide in

copper particle suspended methanol

Adopted from the publication of S.Kaneco et al

41

Electrochemical reduction of carbon dioxide in copper

particle suspended methanol

Reproduced from the publication of S.Kaneco et al 42

• Phthalocyanine complexes

• Porphyrin complexes

• Metal complexes of 2,2’-bipyridine & related

ligands

• Phosphine complexes

• Metal clusters and polymetallic complexes

• Biphenanthroline hexaazacyclophane complexes

• Azamacrocylic complexes

• Macrocyclic ligands related to macromolecular

functions

J.P. Collin & J.P. Sauvage, Coord. Chem. Rev. 93 (1989) 245

Transition Metal Complexes – Electro-catalysts to reduce CO2

43

Transition metal complexes – Electrocatalysts to reduce CO2

Porphyrins and phthalocyanines Tetraaza macrocyclic complexes


J. Costamagna et al., Coord. Chem. Rev.: 148 (1996) 221

Fuels from the reduction of CO2

45

Coordination Compounds with Acyclic Ligands

General cycle for the generation of CO2 reduction products with various complexes of

acyclic ligands as electro-catalysts [Also valid for electro-catalysis with macrocyclic

ligands]


46

Coordination compounds with macrocyclic ligands

Cyclam & cyclam derivatives47

Porphyrin and phthalocyanine derivative complexes


• Binding of CO2 to a metal centre leads to a net electron transfer from

metal to LUMO of CO2 & thus leads to its activation.

• Hence, coordinated CO2 undergoes reactions that are impossible for

free CO2.

• Many stoichiometric & most catalytic reactions involving CO2

activation proceed via formal insertion of CO2 into highly reactive

M–E bonds → formation of new C–E bonds.

• These reactions might not necessarily require strong coordination of

CO2 as in stable complexes, but are generally initiated by

nucleophilic attack of E at Lewis acidic carbon atom of CO2.

• Weak interaction between the metal & the lone pairs of one oxygen

atom of CO2 may play a role in supporting the insertion process.

• Although we are more knowledgeable about CO2 activation, the

effective activation of CO2 by transition metal complexes is still a

goal!

CO2 Activation by Metal Complexes- Perception

49

Direct photo-reduction of CO2

At the surface of

semiconducting materials; p-

Si, p-CdTe, p-InP, pGaP, n-

GaAs

Direct photo-reduction of CO2

Three principles of photo-

catalytic cycles of CO2

reduction

D. Walther et al.,Coord Chem Rev 182 (1999) 67 50

Photo-reduction of CO2

T. Xie et al., Mater Chem Phy 70 (2001) 103

Energy band modes of an n-type

semiconductor with a Schottky-type barrier:

(a) band–band transition;

(b) surface state population transition. Vs

and Vs0,

surface potential difference; CB, conduction

band; VB, valence band; Et, surface state

level; EF, Fermi level.

Pd/RuO2/TiO2 photoreduction of CO2

51

L. G. Wang et al., Phy. Rev Let. 89 (7) (2002) 075506-1

Role of the Nanoscale in Surface Reactions: CO2 on CdSe

Electron transfer from surfaces or

nanocrystals to the CO2 molecule. The

localized energy level near the valence band

edge is caused by a Se vacancy

The total energy of a CO2 molecule

chemisorbed in a Se vacancy on the CdSe (1010)

surface as a function of the vertical distance

between C atom & ideal truncated surface

52

Photocatalytic reduction of CO2

Photocatalytic reduction of CO2 with H2O on the anchored

titanium oxide

M. Anpo, J.Electroanal Chem 396 (1995) 21

53

Photocatalytic reduction of CO2 : Formation of MeOH

Reaction time profiles:

To produce CH4 (a) &

CH3OH (b) on TiO2/Y-

zeolite

Product distribution: Photocatalytic reduction

.

The yields of CH4 and

CH3OH in the Photo-

catalytic reduction of CO2

with H2O TiO2 powder (a),

TS-1 (b), Ti-MCM-41 (c),

Ti-MCM-48 (d), Pt-loaded

Ti-MCM- 48 (e)catalysts.

H. Yamashita et al., Catalysis Today 45 (1998) 221

CO2 with H2O: anatase TiO2

powder (a),Imp-Ti-oxide/Yzeolite

(10.0 wt% as TiO2) (b), Imp-Ti

-oxide/Y-zeolite (1.0 wt% as TiO2)

(c), Ex-Ti-oxide/Y-zeolite

(1.1 wt% asTiO2) (d),Pt-loaded

ex-Ti-oxide/Y-zeolite (e) catalysts

Photocatalytic reduction of CO2 : Formation of MeOH

54

PHOTOCHEMICAL REDUCTION OF CO2


Formation of HCOOH Formation of Methane

55


J.P. Collin & J.P. Sauvage ,Coord. Chem. Rev. 93 (1989) 245

HOMOGENEOUS SYSTEM MICROHETEROGENEOUS SYSTEM

Light driven catalytic cycle reducing CO2.

Light reaction: terphenyl (TP) -

photocatalyst, triethylamin (TEA) -

reductive quencher (electron donor).

Dark reaction: cyclam cobalt complex -

electron relay (a) oxidising - terphenyl

radical anion & (b) reducing CO2.

Light driven carboxylation of lactic acid to form malic acid (MV2+ , methylviologendication, FNR, ferredoxin-NADPreductase;ME, malic enzyme).

56

Photo-reduction of CO2 - Perception

Unsolved Problems!

• TON (mol reduction product of CO2 / mol catalyst) are still low

• Efficiencies of the reactions is unsatisfactory-both the amount of reduction products of CO2

(usually C1 products) & oxidation products of the sacrificial donor

• The tuning of the single components w.r.t. their redox potentials, life times and selectivity is

not well understood.

• Necessary to device systems which do not require sacrificial donors light energy is also used

for degradation of sacrificial donors, influencing the energy balance of the reactions unfavorably

• Macro-cyclic complexes of transition metal ions- satisfy the requirements of a useful relay.

They may play a dual role as a catalysts and relays

• Even with transition metal complexes – Reduction products have not been of great economic

value (usually only C1 products)

• Multicomponent systems containing photoactive center, electron relays and/or molecular

electro-catalysts in addition to possible micro-heterogeneous systems will be discovered.57


PRESENTATION - FIVE

24TH February 2014

On Line Course of NCCR(Total Number of Projections for this Lecture is 20)

58

PHOTOELECTROREDUCTION OF CO2

Principle An Example


Appealing Approach!

An important energy input contribution from light might be

expected, thus diminishing electricity consumption

59

A study on photo-electro-reduction of CO2

Possible Mechanistic Route

By insitu-IR

J, O‘M. Bockris & J. C. Wass, Mater Chem Phys, 22 (1989) 249

Photovoltomogram, λ= 560 nm (0.5 mW \cm2)60

Metal islet catalysts deposited on a p-CdTeelectrode in DMF-0.1 M TEAP/5% H20

MPc catalysts adsorbed on a p-CdTe electrodein DMF-0.1 M TEAP/5% H20

Product analysis results for CO2 reduction on phthalocyanine/p-CdTe


Study on photo-electro-reduction of CO2

61

Current-potential curves for trinuclear carbonyl catalystsadsorbed on a p-CdTe electrode in DMF-0.1 M TEAP/5% H20.

Product analysis results for CO2 reduction on carbonyl/p-CdTc

Iron carbonyl is the best among the three carbonyls studied


Study on Photo-electro-reduction of CO2

62

Product analysis results

Current-potential curves for crown ether catalysts added to the electrolyte for a p-CdTe

electrode in DMF-0.1 M TEAP/S% H20


Study on photo-electro-reduction of CO2

63

Catalytic shift (ΔE) times the CO faradaic

efficiency for metal catalysts on p-CdTe as a

function of M-O bond energy

For metal-phthalocyanine catalysts on p-

CdTe as a function of M-O bond energy

ΔE values for CO production are linear

Catalytic shift (ΔE)

J, O‘M. Bockris & J. C. Wass

Mater Chem Phys, 22 (1989) 24964

For trinuclear carbonyl catalysts on p-CdTe

as a function of M-C bond energy

Catalytic Shift (ΔE)


65

• Fertilization of open waters to increase primary

production & hence to absorb more carbon in

fixed form

• Disposal of captured carbon dioxide directly

into oceanic waters

• Injection of captured CO2 into sub-seabed

geological formations

CARBON MANAGEMENT

66

• High cost of capturing, processing, &

transporting anthropogenic CO2

• Incomplete understanding of reservoir

processes

• Underdeveloped monitoring & verification

technologies

• Unclear emissions trading regulations

• Potential conflicts of interest between

sequestration & EOR or natural gas recovery

Barriers to wider implementation

CO2 sequestration

67

The technology is in its infancy and unproven

• The technology is too costly

• Not enough is known about the long-term storage of

CO2

• The capture and storage of CO2 are seen as being

energy intensive

• The option presents an enormous engineering and

infrastructure challenge

• It is not a long-term solution

Barriers can only be overcome by research and design

& effective demonstration of the technology

Public Perception

CO2 Sequestration

68

Perceptions: Large-Scale CO2 Utilization &

Sequestration

69

Utilization

70

Utilization

TRASPORTATION COST

71

WHAT HAS BEEN COVERED SO FAR

The electronic structure of Carbon dioxide

72

CHEMICAL REDUCTION OF CARBONDIOXIDE

ADDING HYDROGEN AND ELIMINATING WATER

M. A. Scibioh & B. Viswanathan,Proc. Indn. Natl. Acad. Sci., 70 A (3), 2004.407-46273


The possible electrochemical Reactions and the corresponding

potentials

REACTION E0 ΔG0 (Kcal/mol)

H2O to H2(g)+ 0.5O2(g) 1.23 56.7

CO2 + H2 to HCOOH 5.1

CO2 + H2O to HCOOH + 0.5O2 1.34 61.8

CO2 + H2 to CO + H2O 4.6

CO2 to CO + 0.5O2 1.33 61.3

CO2 + 3H2 to CH3OH + H2O -4.1

CO2 + 4H2 to CH3OH + 2 H2O -31.3

CO2 + 2 H2O to CH3OH + 1.5O2 1.20 166

CO2 + 2 H2O to CH4 + 2 O2 1.03 19574

SECTOR % COMPOSITION

Land Use and Forestry 17

Industry 19

Residential and Commercial 8

Buildings

Transportation 13

Power 26

Waste and Waste Water 3

Sector-wise contribution of CO2 emissions

75

Scheme.1.Chemical Transformations of CO276

(1) the magnitude of environmental consequences,

(2) the economic costs of these consequences,

(3) options available that could help avoid or diminish the

damage to our environment and the economy

(4) the environmental and economic consequences for each

of these options

(5) an estimate of cost for developing the technology to

implement these options and

(6) a complete energy balance which accounts for energy

demanding steps and their costs.

Barriers for Further Progress

77

Suggested Some References

1. A Beher, Carbon Dioxide Activation by Metal Complexes VCH, Weinheim (1988)2. Catalytic Activation of Carbon Dioxide (ACS Symp Ser) (1988) 3633. M. Aulice Scibioh and V.R. Vijayaraghavan, J. Sci. Indus. Res., 1998, 57, 111-123.4. M. Aulice Scibioh and B. Viswanathan, Proc. Indn. Natl. Acad.Sci., 70 A (3), 2004, 407-4625. M. Aulice Scibioh and B. Viswanathan, Editor. Satoshi Kaneco, Japan, Photo/ Electrochemistry

and Photobiology for Environment,Energy and Fuel, 2002, 1- 46, ISBN: 81-7736-101-5.6. F. Bertilsson and H. T. Karlsson, Energy Convers. Mgmt Vol. 37,No. 12, pp. 1725-1731, 19967. I. Omae, Catalysis Today 115 (2006) 33528. M. Gattrell, N. Gupta and A. Co, J. Electroanal Chem, 594, (2006),1-19.9. Enzymatic and Model Carboxylation and Reduction Reaction for Carbon Dixoide Utilization

(NATO ASF Ser C 314 (1990)10. Electrochemical and Electrocatalytic Reaction of Carbon Dioxide (Eds B P Sullivan, K Krist and

H E Guard) Elsevier Amsterdam (1993)11. M M Halmann Chemical Fixation of Carbon Dixoide CRC Boca Raton (1993) D Walther Coord

Chem Rev 79 (1987) 135.12. P. G. Jessop, F. Jo, C-C Tai, Coordination Chemistry Reviews 248 (2004) 2425-2442

78


PRESENTATION - SIX

27TH February 2014

On Line Course of NCCR(Total Number of Projections for this Lecture is 32)

79

FOCUS

This Lecture mainly deals with reforming of carbon dioxide with methane for synthesis gas

80

COVERAGE

THERMODYNAMICSTEMPERATURE RANGECATALYST SYSTEMSROLE OF THE COMPONENTSOTHER RELEVANT REACTIONSREACTORS

81

Reproduced from Hongyan Ma presentation82

Halmann, Martin M. (1993). "Carbon Dioxide Reforming". Chemical fixation of carbon dioxide: methods for recycling CO2 into useful products. CRC Press. ISBN 978-0-8493-4428-2

Carbon dioxide reforming (dry reforming) is for

producing synthesis gas by the reaction of CO2 with

hydrocarbons especially methane. Synthesis gas is

conventionally produced via the steam reforming of

naphtha. This has relevance to the concern on the

greenhouse gases to global warming. It is a method

of replacing steam as reactant with carbon dioxide.

The methane carbon dioxide reforming reaction is:

CO2 + CH4 → 2H2 + 2CO

Halmann, Martin M. (1993). Carbon di oxide reforming. Chemical fixation of carbon dioxide: methods for recycling CO2 into useful products. CRC Press. ISBN 978-0-8493-4428-2

DRY REFORMING OF CARBON DIOXIDE

83

http://books.google.com/books?id=R5NuqNaCkkkC&pg=PA34

http://en.wikipedia.org/wiki/International_Standard_Book_Number

http://en.wikipedia.org/wiki/Special:BookSources/978-0-8493-4428-2

Mun-Sing Fan et al., ChemCatChem, 1,192 (2009)

Catalyst Technology for carbon dioxide reforming with methane to synthesis gas

84

Carbon dioxide Reforming Scheme

• O=C=O Methane

Catalyst(?)

SYN GAS (CO /H2)

TRANSPORT SECTOR AUTOMOBILES,DIESEL ENGINES

AEROPLANES

STORAGE Gas stations

Storage in gas Pressure vessels

85

RELEVANT REACTIONS• (1) CH4+ CO2 ↔ 2CO + 2H2 ΔH0

298=247 ΔG0=61770-67.3T

• (2) CH4+H2O ↔ CO + 3H2 =206;

• (3) CH4↔ C + 2H2 75; 2190-26.5T

• (4) 2CO↔CO2+ C -171; 39810+40.9T

• (5) CO2+ H2 ↔ CPO + H2O 41; -8545+7.84T

• (6) CO + H2↔ C + H2O -131

• The first figure refer to the ΔH0298 in kJ/mol

• The second figure refer to ΔG0

• Reaction T (K)

• DRM 913

• Methane cracking (3) 830

• Boudouard Reaction (4) 973

• RWGS (5) 1093

• Limiting temperatures for different reactions DRM 86

Catalyst component Proposed mechanism

Metal active site (M(as)) CH4 + 2M(as)↔CH3-M(as)+ H-M(as)

CH3-M(as)+ M(as)↔CH2-M(as) + H-M(as)

CH2-M(as) + M(as)↔CH-M(as)+H-M(as)

CH-M(as) + M(as)↔C-M(as) + H-M(as)

2h-M(as)↔ H2(g) +2M+(as)

Catalyst component and corresponding proposed mechanism

Mun-Sing Fan et al., ChemCatChem, 1,192 (2009)87

Catalyst component Proposed Mechanism

Support ( Acidic support)

Support ( BASIC SUPPORT)

CO(g)↔CO2(metal)

CO2(metal)↔CO(metal) + O(metals)

CO(metal)↔CO(g)

CO2(g) ↔ CO2(support)

CO2(support) + O2-

(support) ↔CO3(support)2-

2H(metal)↔ 2H(support)

CO3(support)2-

+2H(support)↔HCO3-(s)

+ OH

-

(s)

CO(support)↔CO(g)


88

Catalyst component Proposed Mechanism

Promoter

CO(g)↔CO(support)+ O(promoter)

O(promoter) + C(metal) ↔CO(g)


89

Catalyst Temp.

(K)

Conversion % Remarks

NiO/CaO/CoO-MgO/MgO 873-1123 80-100(CH4) High selectivity

Ru/SiO2/MgO/TiO2 973-1073 28-35 deactivation

Co/SiO2/MgO-SiO2 873 41-46(CH4) Better than Ni

Ir/Al2O3 873 18-50 preparation

Different types of catalysts used for the DRM reaction


90

Characterization of DRM reaction catalysts

Catalyst type Techniques Aspects

Monometallic supported catalysts Ni/CeO2,Pt/Al2O3,Ni/SiO2,Ru/SiO2,Ir/Al2O3

XRD,TPR,XPS,EPR,TPO,TPH Metal dispersion, reducibility, coke

Bimetallic supported catalysts Ni-Co, Ni-Rh

XRD,XRF,XPS,TG,DTA, chemisorption

Composition, phase, coke, metal dispersion

Metal oxide supported catalysts CoO-MgO/CeO2

TPO, XRD,XPS Resistance to C, phases

Promoted supported catalysts on alumina Ni-K,Ni-Sn,Ni-Ca,Ni-Mn

TG,TPH,TPR,XRD,TEM,TPO Carbon, active sites, reduction behaviour

Perovskite catalysts, LaNiOx, LaNiMgOx, LaNiCoOx, LaSrNiOx,LaCeNiOx

XRD,TPR,TPO,TEM,SEM Calcination temp, structure, phases, reversibility, sintering


91



92



94



96



97

CO2 reforming on Ni/Cu catalyst

• Factors like addition of copper to supported Ni systemsurface geometry, electronic structure, the extent of CH2species, and hydrogen spill over contribute to Ni-Cu/supportcatalyst in CO2 reforming.

1. 1 wt% Cu , 8 wt% Ni/SiO2 stability >7600C

2. active site is stabilized by Cu

3. Carbon formation same as Ni and Ni/Cu

4. Cu-Ni species inhibit the C formation

5. Cu addition promotes CH4 cracking and inactive Coke doesnot accumulate on Cu/Ni catalyst

• H-W Chen et al., Catalysis Today 97,173 (2004) 98

• TD favours carbon formation

• Noble metals and Ni alleviate this problem

99

Summary of Catalytic Reforming of CO2/CH4

Catalyst

CO2/CH4 conversion (%) Temp (K)

Ni/NaY 1:1 84.0 873

Ni/Al2O3 1:1 36.3 873

Ni/SiO2 1:1 14.9 873

Pd/NaY 1:1 29.2 873

Pt/NaY 1:1 156.3 873

KNiCa/Al2O3 1:1 17 923

KNiCa/SiO2 1:1 21 923

KNiCa/ZSI 1:1 78 923

Rh/TiO2 1:1 88.2 893

Rh/SiO2 1:1 5.1 893

Rh/Al2O3 1:1 85.1 893

Ni/Al2O3 1:1 80−90 1050

Pd/Al2O3 1:1 70−75 1050

Ru/Al2O3 1:1 60−70 1050

Rh/Al2O3 1:1 85−90 1050

Ir/Al2O3 1:1 85−90 1050

Wang et al, Energy & Fuels, 10,896 (1996) 100

Catalyst Conversion % Temperature, K

Ni/NaY/Al2O3/SiO2/ 15-85 873

Pd/NaY/Al2O3/MgO 29, 70-75,84 873,1050,963

Pt/NaY/MgO 156,85 873,963

Rh/TiO2/SiO2/Al2O3 88,5,85 893

Ni/Al2O3/MgO-Al2O3/CaO-Al2O3/CaO-TiO2Al2O3 75,,100,86,88,100 1050,1213

Ru/Al2O3/Eu2O3/MgO 60,75,90, 1050,923,963

Ir/Eu2O3/Al2O3/ 88,85 1000,1050

Table Catalytic reforming of CO2/CH4 with 1:1 mixture on various

catalysts collected from literature

101

Co,MgO/C 1:1 65−75 923

Ni/CaO-MgO 1:1 80 1123

Rh/Al2O3 1:1 85 1073

Ru/Al2O3 1:1 83 1073

Ru/Eu2O3 1:1 75 923

Ir/Eu2O3 1:1 88 1000

Ru/MgO 1:1 90 963

Rh/MgO 1:1 88 963

Pt/MgO 1:1 85 963

Pd/MgO 1:1 84 963

Ni/Al2O3 2.38:1 100 1213

Ni/MgO−Al2O3 2.38:1 86 1211

Ni/CaO−Al2O3 2.01:1 88 1211

Ni/CaO−TiO2−Al2O3 2.01:1 100 1223

Summary of Catalytic Reforming of CO2/CH4

Wang et al, Energy & Fuels, 10,896 (1996)

102

metal activity metal loading (wt %) temp (K)

1. Al2O3

Rh > Pd > Ru > Pt > Ir 1 823

Rh>Pd>Pt>Ru 0.5−1 823−973

Ir > Rh > Pd > Ru 1 1050

Ni>Co >>Fe 9 773−973

Ni>Co>> Fe 10 1023

Ru > Rh 0.5 873

Ru > Ru 0.5 923−1073

2. SiO2

Ru > Rh > Ni > Pt > Pd 1 973

Ni > Ru > Rh >Pt > Pd >> Co 0.5 893

3. MgO

Rh > Ru > Ir > Pt > Pd 0.5 1073

Ru > Rh > Ni > Pd > Pt 1 973

Ru> Rh ~Ni > Ir > Pt > Pd 1 823

Ru > Rh > Pt > Pd 1 913

4. Eu2O3

Ru > Ir 1−5 873−973

5. NaY

Ni > Pd > Pt 2 873

Catalytic Activities of Metals on Various Supports

Wang et al, Energy & Fuels, 10,896 (1996) 103

Effect of Support on Catalyst Activity

activity order

temp (K) metal loading (wt %)

Ru

Al2O3 > TiO2 > SiO2 893 0.5

TiO2 > Al2O3 > SiO2 893 0.5

Pd

TiO2 > Al2O3 > NaY > SiO2 > MgO > Na-ZSM-5 773 5

TiO2 > Al2O3 > SiO2 > MgO 773 1

Rh

YSZ > Al2O3 >TiO2 >SiO2>> MgO923 0.5

Al2O3 > SiO2 > TiO2 > MgO 773 1

Ni

Al2O3 > SiO2 800−1000 40

Al2O3 > SiO2 873 10

NaY > Al2O3 > SiO2 873 2

SiO2 > ZrO2 > La2O3 > MgO > TiO2 823 4

Wang et al, Energy & Fuels, 10,896 (1996)

104

Synthesis gas over Ni/ZrO2-SiO2

• Helium treatment –generate distribution of active Ni sites

• Heterogeneity of Ni sites on hydrogen treatment

• CO treatment carbon covered metallic sites deactivation

Dapeng Liu, Yifan Wang, Daming Shi, Xinli Jia, Xin Wang, Armando Borgna,

Raymond Lau and Yanhui Yang, Internationl Journal of Hydrogen energy,37,10135 (2012)105

CO2 reforming on Co-Pd/Al2O3

• Co containing promoted by noble metal (Pd) with respect to activity, selectivity, resistance to carbon formation Co-Pd/Al2O3 depend on composition and process conditions. Oxygenates are produced.

Sh.S.Itkulova et al., Bull Korean chem.soc., 26,2017 (2005) 106

Stable CO2 reforming over modified Ni/Al2O3

• Ni/Al2O3 promotedbyC,Cu,Zr,Mn,Mo,Ti,Ag and Sn

• Cu,Co,Zr improved Mn reduces carbon formation

Jae-Sung Choi, Kwang-ik Moon, Young Gul Kim, Jae Sung Lee, Cheol-Hyun Kim, and

David L.Trim, catalysis Letters, 52,43 (1998)

107

Table 2. Catalyst component and corresponding proposed mechanism.

Catalyst component Proposed mechanismMetal active site (M(as)) CH4+2 M(as)⇌CH3-M(as)+H-M(as)

CH3-M(as)+M(as)⇌CH2-M(as)+H-M(as) CH2-M(as)+M(as)⇌CH-M(as)+H-M(as) CH-M(as)+M(as)⇌C-M(as)+H-M(as) 2 H-M(as)⇌H2(g)+2 M(as)

Support Acidic support: CO2(g)⇌CO2(metal)

CO2(metal)⇌CO(metal)+O(metal) CO(metal)⇌CO(g)Basic support:

CO2(g)⇌CO2(support) CO2(support)+O 2-

(support)⇌ CO32-

(support)

2 H(metal)⇌2 H(support)CO3

2-(support) +2 H(support)⇌ HCO3

-(support) + OH-

(support)

CO(support)⇌CO(g)Promoter CO2(g)⇌O(promoter)+CO(support)

O(promoter)+C(metal)⇌CO(g)

Mun-Sing Fan et al., ChemCatChem.,1,192 (2009)

108

Processes occurring in the catalytic membrane reactor during the combined POM/DRM reaction

109

In this work, we have performed first principle calculations to study the

adsorption of hydrogen on combined TM-decorated B-doped graphene

surface. We found that transition metals Ni, Pd and Co show the great

advantage of both hydrogen adsorption and H spill over method in the

hydrogen storage process. Our results show that all the calculated

activation barriers are sufficiently low for the H diffusion along the Ni-

Pd and Pd-Co paths, indicating that a fast H diffusion on the substrate

can be achieved under ambient conditions. Moreover, the calculated

desorption energies of the hydrogen molecules on these TM decorated

B-doped surface are close to the energies required to obtain reversible

storage at room temperature and hence the proposed TM decorated

boron doped graphene surface will be a good candidate to enhance the

reversible hydrogen storage capacity.

110

Different isotope dependences on reaction kinetics have been observed during RBM

of pure Mg powder and Mg–Ti powder mixtures. For pure Mg, gas absorption

depends on the isotope nature and the rls is assigned to H(D)-diffusion in MgH2

phase. In contrast, in presence of Ti, the diffusion lengths in MgH2 phase are

strongly shortened due to the abrasive properties of TiH(D)2. Thus, gas absorption

turns to be isotope independent and the rls is assigned to the milling efficiency.

Analysis of hydrogen and deuterium kinetic curves under isothermal conditions

(548 K) has highlighted outstandingly fast reaction rates for the nanocomposite.

Absorption is diffusion controlled whereas desorption depends on the Mg/MgH2

interface displacement.

Finally, we have shown by means of HP-DSC the superior cycling stability of

0.7MgH2–0.3TiH2 nanocomposite over 100 cycles. Though, the crystallite growth

associated to cycling at moderate temperatures (<650 K) induces modifications in

the absorption mechanism, which changes on cycling from extended MgH2

nucleation at Mg/TiH2 interfaces to H-diffusion across the MgH2 layer.

Nevertheless, the composite material exhibits excellent kinetics and cycling

properties as compared to pure Mg.

111


PRESENTATION - SEVEN

3rd MARCH 2014

On Line Course of NCCR(Total Number of Projections for this Lecture is )

112

The concept of tri Reforming

• A novel tri-reforming process - involves a synergeticcombination of CO2 reforming, steam reforming, and partialoxidation of methane in a single gasification reactor foreffective production of useful synthesis gas for use in F-TProcess.

• The novel tri-reforming concept represents alternate way ofthinking for both conversion and utilization of CO2 and CH4without separation that can be applied to industrial flue gas aswell.

• The Novel tri-reforming catalytic system can not only producebiomass synthesis gas (CO + H2) with H2/CO ratios (1.5–2.0),but also could eliminate carbon formation which is usually aserious problem in the CO2 reforming of methane and biomassgasification.

• This area has assumed importance in the last 10-15 years.113

Advantages of Tri Reforming

• Therefore, the proposed tri-reforming can solve two important problems that are encountered in individual processing.

• The incorporation of low partial pressures of O2 in the partial oxidation reaction generates heat in-situ that can be used to increase energy efficiency and O2 also reduces or eliminates the carbon formation on the reforming catalyst. The selection of catalyst support is critical.

114

.

Z.Jiang et al, Phil.Trans.Roy.Soc., A368,3343 (2010)

115

Song and colleagues have pioneered a novel process centred on the

unique advantages of directly utilizing flue gas, rather than pre-

separated and purified CO2 from flue gases, for the production of

hydrogen-rich syngas from methane reforming of CO2 (so-called ‘dry

reforming’). The overall process, named ‘tri-reforming’, couples the

processes of CH4/CO2 reforming, steam reforming of CH4, and partial

oxidation and complete oxidation of CH4. The reactions involved are

itemized in the table above together with the corresponding enthalpies

of reaction (298 K).

.Z.Jiang et al, Phil.Trans.Roy.Soc., A368,3343 (2010)

116

Coupling CO2 and H2O can give syngas with the desired H2/CO ratios

for methanol and dimethyl ether synthesis and higher-carbon Fischer–

Tropsch synthesis of fuels.

CH4→ C + 2H2O

2CO→ C + CO2

It also helps to avoid the formation of particulate (solid) carbon

deposits arising from reactions such as Experimental studies have

shown that the introduction of the CO2 tri-reforming reaction may also

enhance the durability and lifetime of metal nanoparticle catalysts

owing to the addition of oxygen (and consequent oxidation of carbon

deposits).


117

It is possible to achieve up to 95 per cent methane conversion by this

process at equilibrium temperatures in the range 1073–1123 K. To

achieve effective conversion (of both CO2 and CH4), the flue gas is

combined with natural gas and used as chemical feedstocks for the

production of syngas (CO+H2) with desired H2/CO ratios. In addition,

the process makes use of ‘waste heat’ in the power plant and heat

generated in situ from partial oxidation of methane (POM) with the

O2 present in the flue gas (above table). In effect, the two endothermic

reactions noted in the table above are thermally sustained by the waste

heat content of the exhaust gases, and the partial combustion of the

primary methane fuel.


118

The main advantages of Tri reforming1.Prevention of carbon deposit2.appropriate CO/H2 ratio3.more autothemic reaction enthalpy than dry reforming.Z.Jiang et al, Phil.Trans.Roy.Soc., A368,3343 (2010)

119

Reaction Stoichiometry ∆H0298 (kJ/mol)

enthalpy

CO2 reforming of methane (DRM) CH4 +CO2↔2CO +2H2 +247.3 (endo)

Steam reforming of methane (SRM) CH4 + H2O↔CO + 3H2 +206.3 (endo)

Partial oxidation of methane (POM) CH4 + 1/2O2↔CO + 2H2 -35.6 (exo)

Catalytic combustion of

methane(CCM)

CH4+ 2O2↔CO2+2H2O -880 (exo)

Main reactions for syngas production by tri reforming of natural gas

120

Table 1 Reaction steps of methane tri-reforming process1. Reaction steps

a. CH4(g)+ CO2(g) → 2CO(g)+ 2H2(g)

b. CH4(g) + H2O(g) → CO(g) + 3H2(g)

c. CH4(g) + _O2(g) → CO(g) + 2H2(g)

d. CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)

e. CH4(g) → C(s) + 2H2(g)+. 2CO(g) + C(s) → CO2(g)

g. CO2(g) + H2(g) → CO(g) + H2O(g)

h. C(s) + H2O(g) → CO(g) + H2(g)

m. C(s) + O2(g) → CO2(g)

n. 5CH4(g) + 7/2O2(g) → 9H2(g) + 4CO(g) + CO2(g)+ H2O(g)

2. Observed reaction steps

I. CH4(g) + 5/8O2(g) → CO(g) + 7/4H2(g) + _H2O(g)

II. CH4(g) → C(s) + 2H2(g) (Methane Cracking)

III. 2CO(g) →2 C(s) + CO2(g) (Boudouard Reaction)

IV. CO2(g) + H2(g) → CO(g)+ H2O(g) (Reverse Water Gas)

121

Steam Reforming−H0

298(kJ/mol)

1. CH4 + H2O CO + H2 −206

2. CnHm + nH2O nCO + (n + m/2) H2 −1175 (for nC7H16)

3. CO + H2O CO2 + H2 (WGS) +41

CO2 (dry) reforming

4. CH4 + CO2 2CO + 2H2 −247

Auto Thermal Reforming (ATR)

5. CH4 + 1. O2 CO + 2H2O +520

6. CH4 + H2O CO + 3H2 −206

7. CO + H2O CO2 + H2 +41

Catalytic Partial Oxidation (CPO)

8. CH4 + 1/2O2 CO + 2H2 +38

Total oxidation

9. CH4 + 2O2→ CO2 + 2H2O +802

Boudouard reaction

10. 2CO C + CO2 +172

The main chemical products from natural gas are summarized

122

REFORMING –STEAM-DRY-BI-TRI

STEAM REFORMING

CnHm + nH2O → nCO + (n+0.5m)H2 ∆Ho298 =206kJ/mol

Dry Reforming

CH4 + CO2→ 2CO + 2H2 ∆Ho298 =247kJ/mol

Water Gas Shift (WGS)

CO + H2O → CO2 + H2 ∆H0298 = -41 kJ/mol

Boudouard Reaction

2CO→ C + CO2 ∆H0298 = -173 kJ/mol

Methane Decomposition

CH4 → C + 2H2 ∆H0298 = 75 kJ/mol

123

TRI REFORMING A NEW PROCESS FOR REDUCING CARON DI OXIDE EMISSIONS

CO2 separated, recovered and purified by absorption, adsorption or membrane separation. Refer database

But require energy input in power plants nearly 20%

May be possible to reduce this

Tri reforming (Penn State University)is a three step process avoids separation step, can be cost efficient for synthesis gas production

124

CO2 Emissions from different sectors in USA ( in Million Metric Tons of Carbon)

Emissions Source 1980 1985 1990 1995 1997

Residential sector 248 246 253 270 286

Commercial sector 178 190 207 218 237

Industrial Sector 485 425 454 465 483

Transportation Sector 378 384 432 459 473

End use total 1289 1245 1346 1412 1479

Electric Utilities 418 439 477 495 523

125

Top 10 Countries• Canada

• China

• Germany

• India

• Italy

• Japan

• Russia

• South Korea

• UK

• USA

• Alphabetical order 126

Typical Flue Gas Composition

•Flue gas 8-10% CO218-20% H2O,2-3% O2, 67-72% N2 from natural gas fired power plants

•12-14% CO2, 8-10% H2O,3-5% O2,72-77% N2, coal based boilers

127

TRI REFORMING PROCESS

• CH4 + CO2→ 2CO + 2H2 247.3 kJ/mol

• CH4 + H2O →CO + H2 206.3 kJ/mol

• CH4 + 1/2O2 → CO + 2H2 -35.6kJ/mol

• CH4 + 2O2→CO2 + 2H2O -880kJ/mol

• Coupling CO2 reforming with steam reforming will give synthesis gas fit for FT H2/CO =2

• Dry reforming is endothermic

• Carbon formation a major problem

128

OTHER REACTIONS

• CH4 → C + 2H2 74.9 kJ/mol

• 2CO→C + CO2 -172kJ/mol

• C + CO2→2CO 172kJ/mol

• C + H2O → CO + H2 131 kJ/mol

• C+O2 → CO2 -393kJ/mol

• Steam reforming

• Syngas desired H2/CO mitigate carbon formation heat is also generated

• NG or flue gas waste heat

129

Electric power plant Coal, NG fired IGCC

Glue gas CO2,O2,H2O, N2

O2CO2-H2O reforming of CH4

NG input Process waste heat exchange

Syngas CO+H2+ unreacted gas

Fuels Chemicals Electricity

Proposed CO2 based tri generation concept

IGCC Integrated gasification combined cycle

130

PICTORIAL REPRESENTATION OF ROLE OF SUPPORT AND

PROMOTER 131

The energy sector, which is the largest source of CO2 emissions, is responsible

for approximately 25% of global CO2 emissions. Great efforts have been

conducted in the past to use carbon dioxide as a chemical raw material with a

very low or even negative cost rather than as a waste, e.g. CO2 reductions under

photoirradiation, or under electrolytic conditions, or production of synthesis gas

by reforming natural gas. However, many of these reactions produce rather

simple molecules such as carbon monoxide and formic acid. CO2 has the

advantages of being nontoxic, abundant, and economical, attractive as an

environmentally

friendly chemical reagent, especially useful as a phosgene substitute. The

largest obstacle for establishing industrial processes based on CO2 as a raw

material is its low energy level. In other

words, a large energy input is required to transform CO2. There are several

methodologies to transform CO2 into useful chemicals, such as the use of high-

energy starting materials such as hydrogen, unsaturated compounds, small-

membered ring compounds, and organometallics; the choice of oxidized low-

energy synthetic targets such as organic carbonates or the supply of physical

energy such as light or electricity. Selecting appropriate reactions can lead

to a negative Gibbs free energy of the reaction .

Ioana et al., Catalysis Today 189,212(2012)132

Carbon di oxide to fuels have been studied largely as a complementary

technology to carbon sequestration (CSS) and storage. CSS requires the

minimization of hydrogen consumption to produce fuels.

From this perspective, the preferable option is to produce alcohols (preferably

≥C2) by use of solar energy to produce the protons and electrons necessary for

CO2 reduction. The chemical transformation of CO2 includes a reverse water–

gas shift reaction and hydrogenation to produce hydrocarbons, alcohols,

dimethyl ether and formic acid, a reaction with hydrocarbons to syngas (such as

dry reforming of methane), and photo- and electro-catalytic and

thermochemical conversions.

CO2 can be used as a building block in organic syntheses to obtain valuable

chemicals and materials has been discussed in many reports and review articles.

The main applications of CO2 as chemical raw materials are syntheses of

polycarbonates and polyurethanes.

Ioana et al., Catalysis Today 189,212(2012)

133

Organic carbonates are roughly categorized into cyclic and linear carbonates, which both

compounds have three oxygens in each molecule, and are suitable from a thermodynamic

point of view as synthetic targets starting from CO2. Four industrially important organic

carbonates are ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate

(DMC), and diphenyl carbonate (DPC). EC, DMC and DPC are useful intermediates for

manufacturing polycarbonates through a non-phosgene process . In addition, EC, PC and

DMC are employed as electrolytes in lithium ion batteries and are widely used as aprotic

polar solvents. Furthermore, the excellent properties of DMC as a fuel additive have attracted

much attention. DMC can be synthesised from methanol and CO2, over homogeneous

catalysts or heterogeneous such as

solid acid catalysts of zirconia modified by Ce and acid additives such as phosphoric acid, or

as a support for heteropolyacids, or via cyclic carbonates (CO2 with epoxides), the

cycloaddition of oxiranes and oxetanes and CO2 over e.g. CeO2–ZrO2 or homogeneous metal

complexes catalysts, or coplymerisation of CO2 and oxiranes on metal complexes, the

synthesis of urea (CO2 + NH3) and urethane derivatives, e.g. CO2 + secondary or primary

amines giving carbamic acid which reacts with organic halides or alcohols giving carbamates

(urethanes) or are dehydrated to isocyanate without using phosgene, the synthesis of

carboxylic acids, e.g. acrylic acid, the synthesis of esters and lactones by combining CO2 with

unsaturated

compounds such as vinyl ethers, the hydrogenation and hydroformylation of alkenes by CO2

and H2, and so forth


134

Currently, the utilization of CO2 as a chemical feedstock is limited

to a few processes, such as the synthesis of urea (for nitrogen

fertilizers and plastics), salicylic acid (a pharmaceutical ingredient)

and polycarbonates (for plastics). It is worth noting that the actual

use of CO2 corresponds to a small percentage of the potential CO2

that is suitable to be converted into chemicals; thus, a chemical

transformation of CO2 may significantly contribute to a reduction

of its emissions, in particular for the fuel pool, the worldwide

consumption of which is two orders of magnitude greater than that

of chemicals. Note that CO2 transformation requires energy, which

may produce CO2. Thus, the importance of the transformation of

CO2 into useful chemicals should be closely related to the

importance of utilizing a renewable feedstock .


135

Different options exist in heterogeneous catalysis for the conversion of CO2. The

hydrogenation of CO2 to form oxygenates and/or hydrocarbons are the most intensively

investigated area of CO2 conversion. Methanol synthesis from CO2 and H2 has been investigated

at the pilot-plant stage with promising results.

An alternative possibility is the production of DME, which is a potential diesel substitute.

Ethanol formation, either directly or via methanol homologation, and the conversion of CO2 to

formic acid are also potentially interesting routes. Methanol, ethanol, and formic acid may also

be used as feedstocks in fuel cells, which provide a route to store energy from CO2 and then

produce electricity.

The hydrogenation of carbon dioxide to hydrocarbons consumes much more hydrogen (per unit

of product) than the formation of oxygenates. Therefore, this route is, in principle, only valuable

when hydrogen is made primarily from renewable or non-fossil resources; however, other

thermodynamic aspects must also be considered. The dry reforming of methane with CO2 is a

known technology that is available on a nearly industrial scale, although the positive impact on

CO2 emissions is questionable.

Specifically, it is important to ensure that CO2 emissions due to energy consumption are not

greater than the amount of CO2 consumed in the reaction. An improvement in the positive

direction is tri-reforming, which operates autothermically and does not require a pure CO2 feed

stream; however, large-scale demonstration units are necessary. The conversion of CO2 at room

temperature and atmospheric pressure using solar light represents a highly challenging approach

to close the CO2 cycle and develop approaches that mimic photosynthesis. An interesting

solution could be a photo-electrochemical (PEC) reactor that operates in the gas phase and uses

nanoconfined electrodes that differ from those used in conventional PEC systems.

136

CH4/CO2/H2O/O2/Ar Temp K conversion % Mole ratio H2/CO

CH4 CO2 H2O

1/0.475/0.475/0.1/7.5

973 90.9 75.9 73.4 2.13

1/0.475/0.475/0.1/15 973 95.6 80.6 78.6 2.13

1/0.475/0.475/2.75/15 973 99.5 16.5 9.4 1.85

1/0.475/0.475/2.0/15 813 65 28 2.42

Results of thermodynamic calculations for equilibrium conversion of the reagents in the

methane tri reforming process

Data from S.A.Solov’ev et al.,Theoretical and Experimental Chemistry, 48,199 (2012)

137

Catalyst component composition Temp K Conversion % H2/CO Yield %

CH4 CO2 O2 H2O Ar CH4 CO2 H2 CO

NiAl 1 0.9 0 0.65 13 983 99.8 68 1.59 80 70

NiLaAl 1 0.95 0 0.7 14.5 878 88 65 1.46 69 65

NiCeAl 1 0.7 0 0.65 14.5 978 98 74 1.71 76 70

1 0.7 0.4 0.7 14.5 833 85 9 2.02 57 45

Ni2CeAl 1 0.45 0.2 0.55 15 888 91 16 1.73 78 75

1 1 0.2 0.55 15 888 94 34 1.42 64 72

Parameters of methane Trireforming in Ni-Al2O3 catalysts modified by

rare earth oxides on structured cordierite supports.

Data from S.A.Solov’ev et al.,Theoretical and Experimental Chemistry,

48,199 (2012)

138

A generic energy cycle using captured or sequestered CO2 and sustainable or renewable

hydrogen to yield carbon-neutral or renewable carbonaceous fuels (courtesy of M. L.

Jiang Z et al. Phil. Trans. R. Soc. A 2010;368:3343-3364©2010 by The Royal Society139

Some Experimental Observations

Aerogel Co/Al2O3 catalysts for CH4–CO2 reforming. (a) (i) Conventional and (ii) magnetic

fluidized bed. (b) Conversions of (i) CH4 and (ii) CO2. (c) Microstructure of the catalysts after

20 h operation: (i) magnetic fluidized bed, (ii) fluidized bed and (iii) fixed bed. Note that in

the fluidized-bed operation mode, (i), carbon deposition is mainly of particulates, while in the

fixed-bed mode, (iii), we see extensive filamentous, graphitic carbon, causing deactivation of

the catalyst. Symbols: (b) (i) filled squares, magnetic fluidized bed; filled triangles, fluidized

bed; filled inverted triangles, fixed bed; dotted line, equilibrium conversion; (ii) open squares,

magnetic fluidized bed; open triangles, fluidized bed; open inverted triangles, fixed bed;

dotted line, equilibrium conversion..Reproduced fromZ.Jiang et al, Phil.Trans.Roy.Soc., A368,3343 (2010)

140

http://rsta.royalsocietypublishing.org/content/368/1923/3343/F9.expansion.html

http://rsta.royalsocietypublishing.org/content/368/1923/3343/F9.expansion.html

Gibbs free energy of formation for selected chemicals (data compiled and calculated from

NIST database, http://webbook.nist.gov/chemistry/name-ser.html).

Jiang Z et al. Phil. Trans. R. Soc. A 2010;368:3343-3364©2010 by The Royal Society141

The enthalpy of reaction for syngas production and Fischer–Tropsch (FT)

synthesis of methanol and dimethyl ether.

Jiang Z et al. Phil. Trans. R. Soc. A 2010;368:3343-3364©2010 by The Royal Society

142

The interest for tri-reforming process is:

1. The attractive possibility of potential integration of this technology into gas-

turbine-based electric power cycles, having very low overall CO2 emissions.

2. Detailed experimental studies, computational analysis and engineering

evaluations are being carried out on the tri-reforming process.

3. The CO2 in power plant exhausts could be used directly in catalytic

processes to generate a syngas suitable for ultimately delivering energy

fuels (and a variety of chemical products).


143

The Development of CatalystsThe majority of developments are directed on the CH4–CO2 reforming

component of the tri-reforming process.

Both Ni and Co have frequently been employed as active metal components

owing to their high intrinsic catalytic activities, wide availability and

(relatively) low costs .

The drawback of these catalytic materials centres on serious carbon deposition

in the industrial CO2reforming of methane.

This leads to rapid catalyst deactivation and reaction inhibition

Carbon deposition was strongly influenced by the precise mode of operation of

the chemical conversion process.

Fluidized-bed reforming leads to significant enhancement in the

CH4 conversion process and a considerably reduced carbon deposition when

compared with the fixed-bed operation process Further optimization of the

fluidized-bed configuration has taken the form of innovative approaches using a

fluidized bed assisted by an external, axial magnetic field.

Ref: Z.Jiang et al, Phil.Trans.Roy.Soc., A368,3343 (2010) 144

Hao et al. (2008) have recently reported studies of CH4–CO2 reforming on

aerogel Co/Al2O3 nanoparticulate catalysts in a magnetic fluidized bed. In their

study, Co was introduced as the active catalyst component for the reforming

process; here, they have taken advantage of the high Curie temperature of Co

(ca 1120°C) that makes it ideally suited for the high operating temperatures of

between 700 and 1000°C necessary for the reforming process. In addition, the

influence of an external magnetic field on the catalytic activity and stability of

these catalyst systems was investigated in detail and compared with data for a

conventional fluidized bed and a static bed. These impressive studies are

summarized in figure 9, which is a compilation of conversion efficiencies for

both CH4 and CO2. Also shown are images of the operating catalysts that

clearly demonstrate that carbon deposition is considerably reduced through

improving the gas–solid efficiency by the use of the external magnetic field.

For these ferromagnetic particulate catalysts, it is quite clear that magnetic-

field enhancement of operating process properties may be a most important

avenue for future, major studies.145

http://rsta.royalsocietypublishing.org/content/368/1923/3343.full#ref-15

http://rsta.royalsocietypublishing.org/content/368/1923/3343.full#F9

Reaction Stoichiometry ∆H0298 (kJ/mol)

enthalpy

CO2 reforming of methane (DRM) CH4 +CO2↔2CO +2H2 +247.3 (endo)

Steam reforming of methane (SRM) CH4 + H2O↔CO + 3H2 +206.3 (endo)

Partial oxidation of methane (POM) CH4 + 1/2O2↔CO + 2H2 -35.6 (exo)

Catalytic combustion of

methane(CCM)

CH4+ 2O2↔CO2+2H2O -880 (exo)

Main reactions for syngas production by tri reforming of natural gas

146


PRESENTATION - EIGHT

6 MARCH 2014


147

CARBON DIOXIDE AS FEEDSTOCK FOR CHEMICALS AND FUELS

• The objective is to develop new industrial processes for fuels like gasoline, diesel, jet fuel and industrial chemicals.

• This places a condition that carbon dioxide has to captured from the sources like flue gas and purified.(tri reforming possibly avoids this step)

• Different technologies for separation keeping cost in mind are (i) use of basic solids like zeolites, polymeric amines, new materials or liquids Monoethanolamine(MEA) and water

148

Most common chemicals from carbon dioxide

• Sodium bicarbonate (NaHCO3) and sodium carbonate(Na2CO3) by Solvay process

• Urea and salycilic acid by thermal process

• Methanol production through the syngas orcarboxylation of ethene epoxide ( direct methanolproduction from carbon dioxide is under developmentwhich we will see subsequently)

149

THE STARTING POINT IN DIRECT CARBON DIOXIDE

STARTED FROM THE OBSERVATION THAT IN 1975, IT WAS

SHOWN THAT TRANSITION METAL COMPLEXES CAN

ACTIVATE THIS INERT MOLECULE

Aresta et al., New nickel-carbon dioxide complex: synthesis properties,

and crystallographic characterization of (carbon dioxide)-

bis(tricyclohexylphosphine)nickel, J Chem.Soc., Chem.commun.,636-

637 (1975)

This leaves us to a question why do we concentrate on certain complexes

like nitrogen, phosphorus containing ligands this has to be linked with

the coordinating ability and also the nature of coordination as compared

with other ligands containing coordinating species like oxygen, sulphur

and other such species.

150

The Situation Now

Carbon dioxide is used now for the production of urea, organic and inorganic carbonates, salicylic acid and in food conservation.

However the total use of carbon dioxide is only 0.6% of the anthropogenic CO2 emissions which is around 33 Gt.y-1

Out of this only 200 Mt/y is used for these chemicals.

151

Possible Processes

Homogeneous, heterogeneized, heterogeneous and enzymaticare the possibilities.

Carbon dioxide can be considered to be in the potential wellstable molecule

Two ways of activating this molecule

Low energy process where CO2 is incorporated in the organicor inorganic substrates.

High energy process ( where oxidation state of carbon from 4to upto a minimum of -4.

152

CaCO3 (s) −1130

C2O42-(aq) −671

HCO3-(aq) −586

CO32-(aq) −528

CO2 (g) −394

HCOOH(l) −361

CH3OH(l) −166

CO(g) −137

CH3C(O)CH3 (g) −113

HC(O)H(l) −102

CH4 (g) −51

C6 H14 (I) −4

C2H4 (g) +68

C6H6 (I) +124

C6H6( g) +130

Gibbs free energy of formation (∆G0f)

for some C1 and Cn compounds(kJ/mol)

CO2 insertion (exoergonic)

C1 reduced H and increased H

require energy (endoergonic)

153

Homogeneous Catalysis

Production of carbonates, carbamates, urethanes, lactones, pyrones formic acid and derivatives –homogeneous catalysts are better than heterogeneous catalysts.

154

Heterogeneous Catalysis

Dimethyl carbonate

Cyclic carbamates

Synthesis gas ( already discussed in reforming)

Methanol by CO2hydrogenation

155

Synthesis of Methanol

• CO2 + 3H2 → CH3OH + H2O

90 methanol plants – 75Metric tons

Methanol to formaldehyde (resin) PET PTA

3CH4 + CO2 +2H2 O→ 4CO + 8H2 to methanol

Olah Metgas (CO-2H2)

Another is tri reforming which we have already discussed the three reactions

Dry reforming, steam reforming and POM

CH4+ CO2 →2CO + H2 247 kJ/mol

• CH4 + H2O →CO + H2 206.3 kJ/mol

• CH4 + 1/2O2 → CO + 2H2 -35.6kJ/mol

• Coupling CO2 reforming with steam reforming will give synthesis gas for methanol H2/CO =2

• Dry reforming is endothermic

• Carbon formation a major problem which is avoided in tri reforming

• Methanol to dimethyl carbonate dimethyl ether fuel additive.

• Homogeneous catalyst low temperature Ru phosphine complex TON 221 at 413K

156

Factors for heterogeneous catalysts

• The metal and catalyst structure

• The uniform particle size of metal

• The distribution of the metal on support

• The surface area

• The active sites

• The stability and long term operation

• The type of promoter and support

• The growth of the metal particle

• Cu/ZnO – Cu/ZnO/ZrO2

• Al2O3,TiO2 Ga2O3-Vox, MnOx MgO

• MTO (ethylene and propylene) TOTAL Honeywell and china Dow Union Carbide

157

Catalytic Hydrogenation of CO2Key issue: H2 sources

Since molecular hydrogen does not naturally exist in its pure form, it is typically derived

from natural gas, oil, coal, biomass, and water by means of various chemical, physico-

chemical, photolytic, electrolytic or biological transformations. From an environmental

viewpoint, it is crucial that its production is also CO2 emission free. Since hydrogen can

actually substitute fossil fuels, it opens the possibility to even have a positive CO2 balance,

i.e. reducing overall CO2 production, when generating heat and energy upon hydrogen

combustion yielding H2O as the only product. Hydrogen can be produced from fossil

fuels water and biomass. The emphasis will be on their environmental impact and

economy in CO2 hydrogenation to value-added chemicals.

Steam reforming of methane

CH4+ H2O→ 3H2 +CO

H2O + CO → CO2 + H2 (WGS)

Energy intensive endothermic

CO2 (from fossil fuel ) autothermal reforming

Economic needs, H:CO ratio, deactivation air separation required

Biomass can also be converted through liquefaction, pyrolysis, gasification

Gasification requires sulphur and carbon tolerant catalysts and separation technologies

CxHyOz + H2O → H2 + CO + CO2+ CnHm +tar

Water electrolysis will be dealt with separately subsequently158

CO2 Hydrogenation by Heterogeneous Catalysts

Hydrogen and methane are two high-energy materials, which can be used

for the large-scale transformation of carbon dioxide to valuable products.

Fig. illustrates the most attractive

heterogeneously catalyzed routes. It is important to highlight that the H2-

based routes directly yield fuels or chemical building blocks, while the

CO2 conversion with CH4 results in syngas, which can be converted to

the above products in an additional process step. From an economic

point of view, the direct transformation of CO2 is preferable.

159

Conversion of CO2 to hydrocarbonsThe hydrogenation of CO2 to CH4 is highly important from an

industrial viewpoint. There are several uses of methane

1. Steam reforming of methane

2. Heat and electricity generation

3. As substitute for gasoline, diesel or liquid petroleum

Audi AG builds windmill electricity and hydrogen to convert biomass

based carbon dioxide

Projected production is 1 kt of methane will consume 2.8kt of CO2

Catalysts employed are given in table 1

CO2 to CH4 is exothermic and low temperature operation favourable to

suppress WGS

100% yield of methane at 453 K on Ru/TiO2

New experiments are necessary smaller nanoparticles usage

160

FT ProcessCarbon dioxide hydrogenated to HC by FT cobalt catalyst does not give Schulz-Flory distribution low activity for RWGS.Iron based catalysts are not selectiveMn, Cu, K, Ce promotersMn,Cu improve reducibility of ironK is better for increased adsorption of CO2

Ce selectivity advantage to C2-C5

161

FT ProcessFe catalyst activity methane formation has to be addressedThe process economics has to be addressedcaptureconversionclassical FT shown in Fig

162

Formation of oxygenates from CO2

CO2 to methanol Lurgi 30 years ago2011 carbon recycling international (CRI) 4Kt(40Kt) methanol no details are availableLurgi and air liquide forschung and otherscommercial methanol synthesis catalystCO-CO2 based water formation, alcohol, HC,Esters and ketones

163

Di-methyl ether (DME) a substitute to diesel when a methanol catalyst is coupled with an acid catalyst like aluminaLurgi MegaDME heat integration methanol formation and subsequent dehydration

169

Catalysts Cu/ZnO the role of ZnO is to keep morphology and stabilize copper species.Promoter like ZrO2,SiO2, Al2O3, La2O3

dispersion of copperdirect relation of TON with monoclinic ZrO2

morphology and nano state play a role

170

Carbon dioxide to Chemicals and Fuels

PRESENTAION NINENCCR on line course10th March 2014(this presentation contains projections)

172

FUNDAMENTALS OF ELECTROCATALYTIC REDUCTION OF CARBON DIOXIDE ON METAL

SURFACES ONLY TO SMALL MOLECULES AND FUELS

Basic information

173

Why CO2 appears important today?

• Increase of CO2 one of the causes of green house effect and global warming issues

• Electro-catalytic reduction of CO2 to liquid fuels

• Carbon balance by recycling into usable fuels

• There are other reasons for utilizing carbon dioxide – these will be subsequently taken up

174

1.Carbon dioxide is a stable moleculeProduced by fossil fuel combustion and respiration 2. Returning CO2 to useful state on the same scale as its current production rates is beyond our current scientific and technical abilityNo commercial available process for the conversion of CO2 to fuels and chemicals – challenges are great potential rewards enormous .Fundamental knowledge for activation of CO2

3.Require catalysts that operate near TD equilibrium potentials and high rates3. novel catalyst systems are required multi-active site systems complex process like C-O,C-C,C-H multi-step, multi electron, charge and atom transfer reactions

175

Increase of Carbon dioxide in the atmosphereelectro-catalytic reduction is one possible way to mitigate the carbon balanceNo commercial process for conversion of carbon dioxide to selective product

176

Understanding of the chemistry of activation of carbon dioxidemulti-functional catalystsC-O bond activation C-H and C-C bond formationenergy input and reasonable selectivity are the main objectives

177

Electrochemical conversion of CO2+ is reverse of

electrochemical reactions taking place at anode offuel cells at the anode of the fuel cell fuel isoxidized to carbon dioxide and water.a process of converting electrical energy tochemical energy though high selectivity may bepossible, the reactions involve Gibbs free energy isalways positive due to overvoltage is >1 V inaqueous medium, water reduction is a competingprocess – high Hydrogen overvoltage metals likeHg suppress H2 evolution leads to HCOO- at highover-potentials

178

Copper different from other metals CO2 to HC- CH4 or C2H4 - 5-10 mA/cm2

Current efficiency >69%copper single crystals, ad-atom cu, cu alloys, H2 ,CH4,C2H4 and CO Hythane combined fuel can be produced in aqueous electrolyte

179

CO2 reduction in gas phase GDE or SPEIsopropanol and C4 oxygenates inGDE CNT-encapsulated metal catalysts although small amounts but can open up new avenues for electro-catalytic conversion to liquid fuels

180

Current knowledgemetal electrodes GDE, SPEHomogeneous catalysis is efficient we have considered it before and hence it is not included in this presentation

181

Liquid fuels like HCOOH, isopropanol, HC and fuel precursor CO The equilibrium potentials are negative with respect to hydrogen evolution (HER) in aqueous electrolyte solutions

182

Fundamental challengesThe primary reactions at pH = 7 at 298 K against NHECO2+H2O+2e→HCOO- + OH- (-0.43V)CO2 +H2O+2e=CO+ 2OH-(-0.52V)CO2+6H2O=8e=CH4+8OH-(-0.25V)2CO2+8H2O +12e=C2H4 +12OH-(-0.34V)2CO2+9H2O+12e= C2H5OH +12OH- (-0.33V)3CO2+13H2O+18e=C3H7OH+18OH-(-0.32V)2H2O+2e= 2OH- +H2 (-0.41V)

183

However reduction of CO2 does not occur at equilibrium values more negative potentials since single electron reductionCO2 + E = CO2

- (-1.90 V) due to large reorganizational energy between the linear molecule and bent radical anion first step

CO2 + e === CO2.(-1.90V)184

The equilibrium potential that is considered is dependent on pHCO2+8H+ +8e=CH4 +2H2O (+0.17V) at pH = 0 while it changes with pH shown in Fig.1.

185

BASIC ELECTROCHEMISTRYPotential scale

Negative values

Positive values

186

REACTIONS AT ELECTRODE FOLLOWSSO CALLED NERNST EQUATIONIF TRUE THERMODYNAMIC EQUALIBRIUM WERE TO EXISTIF NOT DEVIATIONS POSSIBLE

187

OVER VOLTAGECONVENTIONALLY THE DEVIATION FROM EQUILIBRIUM POTENTIALOHMICconcentrationACTIVATION and many more possibleMany of these concepts are seemingly not fully understood

WhyFull picture of Electrode/Electrolyte can be described with all precision

188

Even though the potentials for various reactions in CO2 are known the actual values at which these reactions will occur depends on the medium that is used ( ionic strength influence) and the changes that can take place – so called pH dependenceconcentration even though solubility data are known

189

In general the electrode/electrolyte interface is less defined why?

190

What is CO2 reduction?Assembling nuclei formation of chemical bonds to convert the simple molecule into more complex and energetic moleculeskinetic control since low equilibrium potentialsTD Methane and ethylene should occur at less cathodic potential than hydrogen, kinetically does not happen

192

The product distribution for CO2

on Cu is shown as a function of potential in Fig.2.1. Initially CO and HCOO at -1.12V then hydrocarbon first ethylene and methane form- these potential dependent and predominates at around -1.35 V. So both TD and kinetics are important

193

HER in aqueous electrolyte competes with CO2 reduction HER predominates in acid and CO2

does not exist in basic and hence most of the measurements have to be done in neutral medium

194

The product selectivity depends on many factorsconcentration, electrode potential , temperature, electro-catalyst material, electrolyteproduct on electro-catalyst material if other factors are remain the same.

195

Four groups1st groupPb Hg, In,Sn,Cd,Tl, Bi high hydrogen overvoltage negligible CO adsorption high overvoltages for CO2 to CO2

radical ion weak stabilisation of the CO2 radical ion. Major product is formate

196

Second groupAu,Ag,Znmedium hydrogen overvoltage, weak CO adsorption major product is CO C-O bond break and desorb CO

197

Third group Ni, Fe,Pt,Ti low hydrogen overvoltage strong CO adsorption major product is H2

198

Fourth groupCu Unique more reduced species like methane ethylene

199

Under potential deposition copper -1.44 V Co selectivity is 60% while that of Cd and Pd adatom modified Cu is 82% and 0 respectively.

201

Reaction mechanismlimited from charge transfer coefficients and reaction orders

202

CO2 adsorbed as CO2δ-

promoted by defects alkali metals and irraditionsCO2 is amphoteric - both acidic and basicto adsorb as CO2

δ-

depends on electrode surface carbon or oxygen or mixed coordination anion radical is first step where is the excess charge on C as a nucleophilic agent Std potential -1.9vs SHE or -2.21 C vs SCE Transfer coefficient is 0.67 in aqueous and non aqueous solutions CO2

-

Two main pathways to CO or formate depends on metal Fig 4

203

on Hg the major product is formateCO2 by one electron transfer to for CO2

.-

at the negative potential of -1.6 V it will take a proton from water H will not be bonded to oxygen atom since the pKa I 1.4 formate radical is reduced to formate ion subsequently The steps CO2

.- (ads) + H2O === HCOO. + OH- -HCOO. + e == HCOO-

or directlyCO2

.- + Hads=== HCOO-

205

The reaction scheme is suitable to other metal electrodes like Ag, Au, Cu and Zn. Sequence of CO selectivity follows the electrode potential only that stabilizes carbon dioxide anion radical CO is main product - weak CO adsorption

207

HER side reaction for CO2 reduction in aqueous mediumpH dependent in acid and independent in alkaline mediumH+ + e-

→ Hads2Hads → H2Hads + H+ + e-

→ H2

Hads. H+ are the hydrogen source for CO2

reductionPt/Fe/Ni/Ti CO is strongly adsorbed and major product is H2

208

Cu Based electro-catalystsCO2 → CH4 /C2H4/alcoholsAt low over potential CO/COO- yield appreciable at -1.1V C2H4 increasesCO/HCOO- precursors to HC/alcoholsCO linear adsorbed at -0.6 V Coverage high heat (17.7 kcal/mol) appropriate. So subsequent reduction CO to HC/alcohols

209

COads to HCCH4 more negative potential than C2H4 (1.22 to 1.12V)C2H4, CH4 through different reactions CO bond is broken since alcohol is not formedCH4 CO anion radical Cu-C bond decrease C-O bond increaseTwo PathsCo anion radical proton and second electron transfer CH4 formation irreversible (5b)Co anon radical + adsorbed hydrogen C----O H addition (5c)C2H4 associated pairCh2ads two dimeriseOr CO-CH3 (Fig.6)

210

Crystal face (100) for copper Pi-CO two oxygen atoms close to Cu(111) CH4 formation more negative potential(110) 2/3 carbon productdifferent over potentialSurface treatment Cu AlloyCH3 OH intentional peroxideAlloy Cu-Ni, Cu-Fr, hydrogen increases and CH4C2H4 decrease Cu-Cd CH4, ethyleneother alloys CO and formateCu-Au majority is CO

212


PRESENTATION TENNCCR on line course13th March 2014(This Presentation Contains Projections)

215

FUNDAMENTALS OF ELECTROCATALYTIC REDUCTION

OF CARBON DIOXIDE ON SURFACES TO MOLECULES AND

FUELS

216

Under potential deposition copper -1.44 V Co selectivity is 60% while that of Cd and Pd adatom modified Cu is 82% and 0 respectively.

218

Reaction mechanismlimited from charge transfer coefficients and reaction orders

219

on Hg the major product is formateCO2 by one electron transfer to for CO2

.-

at the negative potential of -1.6 V it will take a proton from water H will not be bonded to oxygen atom since the pKa I 1.4 formate radical is reduced to formate ion subsequently The steps CO2

.- (ads) + H2O === HCOO. + OH- -HCOO. + e == HCOO-

or directlyCO2

.- + Hads=== HCOO-

220

The reaction scheme is suitable to other metal electrodes like Ag, Au, Cu and Zn. Sequence of CO selectivity follows the electrode potential only that stabilizes carbon dioxide anion radical CO is main product - weak CO adsorption

222

HER side reaction for CO2 reduction in aqueous mediumpH dependent in acid and independent in alkaline mediumH+ + e-

→ Hads2Hads → H2Hads + H+ + e-

→ H2

Hads. H+ are the hydrogen source for CO2

reductionPt/Fe/Ni/Ti CO is strongly adsorbed and major product is H2

223

Cu Based electro-catalystsCO2 → CH4 /C2H4/alcoholsAt low over potential CO/COO- yield appreciable at -1.1V C2H4 increasesCO/HCOO- precursors to HC/alcoholsCO linear adsorbed at -0.6 V Coverage high heat (17.7 kcal/mol) appropriate. So subsequent reduction CO to HC/alcohols

224

COads to HCCH4 more negative potential than C2H4 (1.22 to 1.12V)C2H4, CH4 through different reactions CO bond is broken since alcohol is not formedCH4 CO anion radical Cu-C bond decrease C-O bond increaseTwo PathsCo anion radical proton and second electron transfer CH4 formation irreversible (5b)Co anon radical + adsorbed hydrogen C----O H addition (5c)C2H4 associated pairCh2ads two dimeriseOr CO-CH3 (Fig.6)

225

Crystal face (100) for copper Pi-CO two oxygen atoms close to Cu(111) CH4 formation more negative potential(110) 2/3 carbon productdifferent over potentialSurface treatment Cu AlloyCH3 OH intentional peroxideAlloy Cu-Ni, Cu-Fr, hydrogen increases and CH4C2H4 decrease Cu-Cd CH4, ethyleneother alloys CO and formateCu-Au majority is CO

227

GDE/SPECO2 to fuel precursor COCO2 to CO 2nd group Au Ag H2O to H2CO2+H2O to CO + H2 (1:2) GDE Au/Ag Cathode (Fig8)Time dependent

229

CO2 to C1-C2 fuelsCO2 to HCOOH Pb impregnated GDECO2 to higher than C2 SPECopper catalyst Cation/anion exchange membrane (CEM/AEMOnly 20-25% current efficientyProduct depends on CEM/AEMCO2 long chain HCChallenge Upto C6 Cu electrodeFT distribution

230

Product distribution IPA, Acetone, Ethanol, acetaldehydeand methanol in Fe encapsulated CNT

231

1.CO2 is stable2.Electrocatalytic method high potential3.Energy efficiency TD/rate4.Mechanism limited knowledge5.Beyond current ability6.New methods approaches of activating7.Novel catalysts multi-site8.C-O bond cleavage C-C and C-H 9.Multi step, multi-electron transformations10.Space restrictions intermediates

11.Model catalysts single crystals, ad-atom, electro-deposited

232

ELECTROCATALYTIC HYDROGENATION OF CARBON DIOXIDE

Long history since 19th century

Homogeneous catalysts can facilitate

Cell design to be such that analysis of products must be possible Electrodes Products

CO2 reduction Copper HC

Au,Ag,Zn CO

Pb,Hg,In,Sn,Cd,Tl HCOO-

Ni,Fe,Pt,Ti,Ga H2

233


• Why this classification (adsorption and over potential)

• Inactive metals C,Al,Si,V,Cr,Mn,Nb,Mo,Rh,Ru,Hf,Ta,W,Re and Ir

• Different faces (100) favour ethylene, (111) methane(110) alcohols

234


• High overpotential

• Low solubility

• The formation of mixture of products

• The fouling and deactivation of the electrodes

• GDE

235


1.Modifying the metal electrode with oxide

2.Operating at high temp molten or solid electrolyte

3. Using ionic liquids water free conditions preventing hydrogen evolution

4.Biological microorganisms or photons

236


• Modification – electrodeposition of thin layer of cuprous oxide HC to methanol

• Sn/SnO2 CO HCOOH 3-4 times stabilization of CO2 radical ion

• Low Faradaic efficiencies, current densities mechanism not better understood

237

Laboratory cells used for electrochemical CO2 conversion: (a) two-compartment cell, (b)

cell with electrodes separated by an H+ conducting membrane, and (c) cell with a gas

diffusion electrode238

Comparison of the energy efficiencies and current densities for CO2

reduction to formic acid ( ), syngas ( ), and hydrocarbons ( ).

This figure is from JPC letters,2010,1,3451.239

ELECTROCATALYTIC HYDROGENATION

OF CARBON DIOXIDE

Solid oxide electrodes

High temperature >673 K

TD and kinetically more attractive

Molton carbonate or solid electrolyte Zirconia stabilized by

Yttrium oxide

Cofeeding of hydrogen was required

Proton conducting electrolyzers

BaCeO0.5 Zr0.3Y0.16 Zn0.04 O3-δ to convert to CO and methane

Co is more than methane hydrogen transport limited240

The question on electro-catalytic reduction of carbon-di-oxide

Four groups of metals for CO2 reduction based on high hydrogenovervoltage, CO adsorption strength, high hydrogen producing metalsand HC forming Copper

The three class of metals are understandable but why copper behavesdifferently and also why this metal shows phase specificity

What makes copper to promote C-C coupling reaction

The answer is not yet known

241

Cyclic CarbonatesEthene carbonate (EC) propene carbonate (PC), Styrene carbonate solvents, precursor for polycarbonates, electrolyte in Li batteries, Pharmaceuticals and chemical reaction raw materials. The reaction shown is atom economy and green process carboxylation of epoxides example

Reproduced from J Chem Technol.Biotechnol,89,334 (2014) 245

Other attempts include starting from olefins without intermediate formation of epoxideDMF dialkylacetamide (DAA) is used as solvent since promote carboxylationPd catalyzed fixation of CO2 cobalt complexes coupling of CO2 with epoxide

Reproduced from J Chem Technol.Biotechnol,89,334 (2014)

246

Use of ionic liquidsthermal and chemical stabilityselective solubility for org and inorgreusability of catalystcarbon dioxide solubilitywater Lewis base catalysts show high activity

247

Super critical carbon dioxideanother reaction medium no flammability, non toxic, absence of gas liquid phase boundary and easy work upmetalloporphrins reusableTriazine high nitrogen centres to inorganicecarbonatespolymer supported IL epoxide to cyclic carbonates


Cobalt complex active for cyclic carbonate and polycarbonate synthesis.


Other options for cyclic carbonate synthesis are the

reactions of CO2 with cyclic ketals, propargylic alcohols,

diols and the direct oxidative carboxylation of olefins. The

latter appears to be a very interesting synthetic methodology

to synthesize cyclic carbonates

starting from cheap and easily available reagents such as

CO2 and O2

250

The direct oxidative carboxylation of olefins has great

potential and has many advantages. It does not require

carbon dioxide free of dioxygen. This feature makes it

attractive because of the purification cost of carbon

dioxide, which may discourage its use. Moreover, the

direct oxidative carboxylation of olefins can couple

two processes, the epoxidation of the olefins and the

carboxylation of the epoxides. The process makes

direct use of olefins which are available on the market

at a low price, and are abundant feedstock.

Reproduced from J Chem Technol.Biotechnol,89,334 (2014)251

Only a few examples are reported in the literature of

the direct oxidative carboxylation of olefins such as

the direct functionalization of propene and styrene.

Using RhClP3 as catalyst, under homogeneous

conditions, it was demonstrated that two classes of

compounds are formed: the first one is due to ‘one

oxygen’ transfer to the olefin with formation of

epoxide and its isomerization products and carbonate

; the second class of products is due to ‘two oxygen’

transfer to the olefin with formation of aldehydes, as

effect of the addition of the oxygen to the C–C double

bond with cleavage of the double bond of the olefin,

and the relevant acids252

Using heterogeneous conditions it has been demonstrated that oxidation

of the olefin does not follow the peroxocarbonate pathway, more likely

it is a radical process which can be started by the catalyst which plays a

very important role in the carbonation step. The carbonate yield depends

on the catalyst used. The selectivity of the process (that reaches a

maximum of 50% with respect to the olefin) is still affected by the

formation of by-products such as benzaldehyde, benzoic acid,

acetophenone, phenylacetaldehyde, 1,2-ethanediol-1-phenyl and

a benzoic acid ester. After a short induction time, benzaldehyde is

formed in higher amounts than the epoxide which becomes the

predominant product after 45 min. The carbonate formation starts after 1

h and steadily increases with time, while the concentration

of the epoxide and benzaldehyde reach a steady status. The life of the

catalyst is of days and the catalyst is easily recovered at the end of the

catalytic run.


253

By reacting cyclic ketals with carbon dioxide under supercritical conditions in organic solvents a

cyclic carbonate has been obtained under relatively mild conditions (10 MPa and 370 K)

using a suitable catalyst


254

The coproduct cyclohexanone may react with 1,2-ethane-diol in the presence of FeCl3 to afford, with almost quantitative yield, the cyclic ketal (Equation 16) which can be reused.


255

Several metal systems were tested, either oxides [ZnO, Nb2O5, ZrO2, TiO2], or metal

halides [ZnCl2, FeCl2], or else metal complexes [FeCl2 · 1.5 THF], CuL2, FeClL.

The most active catalysts have been found to be CuL2 and FeClL (L=C11H7F4O2), i.e.

those bearing perfluoro alkyl groups, which are soluble in sc-CO2 under the reaction

conditions


256

Cyclic carbonates have also been synthesized from propargylic alcohol derivatives and CO2

as the starting materials. This synthetic approach (Equation 17) is based on the cyclizationof the propargylic carbonate moiety (HC≡CCH2OCO2 –) into the corresponding α-alkylidenecyclic carbonate in the presence of a suitable catalyst such as ruthenium, cobalt, palladium,copper, or phosphine.


257

Ikarya has reported the use of imidazolin-2-ylidenes with N-alkyl and N-aryl

substituents and their CO2 adducts as catalyst of the carboxylative cyclization of

internal and terminal propargylic alcohols. The reaction of internal propargyl alcohols

with CO2 has been carried out also under supercritical conditions. Ikariya et al. have

developed a synthetic process to afford Z-alkylidene cyclic carbonates promoted by

P(n-C4H9)3 with high efficiency.


258

Oxidative carboxylation of styrene under homogeneous conditions.



259

Ionic liquid (1-butyl-3-methylimidazolium

benzene sulfonate ([BMIm][PhSO3])) has also

been used as reaction medium for the synthesis

of α-methylene cyclic carbonates from CO2

and propargyl alcohols using transition metal

salts as catalyst


Among the catalysts used, CuCl was revealed to be

the most efficient. On the contrary, when Pd(II),

Rh(III), Ru(III), and Au(III) salts were used as

catalysts no carbonate was produced, also if the

substrate has been converted. This is due to the

formation of the kind of polymer (black tar is

found on the inner wall of the reactor) that occurs

when the noble metal salts/ [BMIm] [PhSO3]

systems are used. In the absence of metal salt as

catalyst, the reaction did not yield any product even

after a long reaction time


Starting from propargyl alcohols using

supercritical carbon dioxide in the presence

of bicyclic guanidines as catalysts

α-methylene cyclic carbonates is obtained


262

Cyclic carbonates can be produced from diols

and carbon dioxide in the presence of suitable

catalysts

The thermodynamics of this reaction are not very favourable

and the major drawback is related to the coproduction of

water, which may involve modification or deactivation of the

catalyst with negative effects on the conversion rate.


Ceria based catalysts and CeO2–ZrO2 solid

solution catalysts have been reported to be very

efficient catalyst for the synthesis of ethene

carbonate and propene carbonate by reaction of

CO2 with ethene glycol and propene glycol,

respectively.

The catalytic activity has been shown to be

dependent on the composition and the

calcination temperature of catalysts


264

Different metallic acetates have been used in acetonitrile

which acts not only as solvent but also as dehydrating agent to

eliminate the effect of the water produced during the reaction.

In this way, the thermodynamic equilibrium is shifted and the

yield of cyclic carbonates improved. Organic super bases such

as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-

diazabicyclo[4.3.0]non-5-ene (DBN), or 1,5,7-

triazabicyclo[4.4.0]dec-5-ene (TBD) have also been used as

effective promoters in the synthesis of propene carbonate

from propene glycol and carbon dioxide in the presence of

acetonitrile (yield 15.3%, selectivity 100% under the optimal

conditions)


The reaction of polyols with urea is a recent

strategy to afford cyclic carbonates. Efficient

catalysts have been used for the synthesis of

glycerol carbonate that has been used as

platform molecule for the synthesis of several

chemicals, including epichlorohydrin.


266

SYNTHESIS OF LINEAR CARBONATES

267

Caution:This presentation has a great limitation since the presenter has very limited and possibly very little knowledge of Organic Chemistry and the ramifications of this wonderful scientific field.

268

Important ones are dimethyl carbonate (DMC), Monomer for polymers and for trans esterification for preparation of other carbonates or alkylating agent, carboxylating agent agrochemical and Pharmaceuticals and additive to gasoline (need can increase) using phosgene or oxidative carbonylation of methanol

Journal of Chemical Technology and Biotechnology, Volume 89, Issue 3, pages 334–353, March 2014 269

other carbonates of importance are:diethyl carbonate (DEC) and diphenylcarbonate (DPC). How carbon dixoide andalcohol can be used for forming thesechemicals will be considered – meets therequirements of green chemistrythermodynamically not feasible one has tochose conditions to favour the products tomake industrially attractive

Journal of Chemical Technology and Biotechnology, Volume 89, Issue 3, pages 334–353, March 2014270

Important reaction 2CH3OH + CO2→ MeOC(O)OMe + H2OBoth homogeneous and heterogeneous catalysts are employedn-dibutyldialkoxy stannaes (n-Bu2Sn(OR)2 ( R = Me, Et,n-butyl) and other alkoxides of Ti(IV) and group 5 metals are catalytic precursors


271

Table . DMC or DEC yields in the direct carboxylation of alcohols using

homogeneous metal alkoxides. (Yields are determined with respect to

alcohol)

Catalysts DMC Yield % DEC Yield % Pressure Mpa Temperature K Time h Bu2Sn(OMe)2 0.17 6.6 423 6 Bu2Sn(OEt)2 0.19 6.6 423 6 Bu2Sn(OBu)2 0.43 6.6 423 6 Sn (OEt)4 0.45 6 423 6 Ti (OEt)4 0.17 6 423 6 Ti (OBu)4 0.4 6 423 6 Nb(OEt)5 1.6 5.5 410 30 Nb(OMe)5 1.8 5.5 423 30 VO(OiPr)3 0 5.5 410 30 Ta(OEt)5 0.1 5.5 410 30

Bu2Sn(OR)2 with R = -Bu gave better performance than shorter chain alkoxidesRecovery of final product is difficult;


The catalytic species is hemicarbonate formed by reaction of the monomeric penta-alkoxospecies with CO2


273

Use of carbon dioxide as feedstock for chemicals and fuels: homogeneous and heterogeneous catalysis


The catalytic species is hemicarbonate formed by reaction of

the monomeric penta-alkoxo species with CO2 this then reacts

with alcohol to give the carbonate regenerating alkoxide

Regeneration of homogeneous catalyst and

hydrolysis of the metal complex due to water

formation

274

Heterogenized or heterogeneous metal systems like niobium methoxide tethered to polystyrene inorganic oxides like zirconia, ceria, and titania, H3PO4/ZrO2 and other mixed oxides


275

Table 3. DMC or DEC yields in the direct carboxylation of alcohols using heterogeneous catalysts (yields are determined with respect to alcohol)

Catalyst DMCYield % DEC Yield% Pr Mpa Temp K Time h

ZrO2 0.37 5 433 5

Al3%/Ce 0.43 5 408 3

CeO2-ZrO2(Ce/Ce + Zr = 0.33 0.76 5 383 2

H3PO4/ZrO2 (P/ Zr = 0.05) 0.31 4 403 2

H3PW12O40/ZrO2 4 - 373 3.5

H3PMo12O40 1.05 0.12 310 1

Cu1.5PMo12O40 1.29 0.12 310 1

CeO2 0.35 5 408 3

Al3%/Ce 0.16 5 408 3

Nb3%/Ce 0.3 5 408 3

ceria and zircona are good for DMC formationRecoverable, stable nano size


SYNTHESIS OF ORGANIC CARBOMATES

AND UREAS

277

Reaction of amines with CO2

Monoethanoamine Diethanolamine and poly amines are used as CO2 scrubbers for CO2 capture from flue gasesreacting CO2 with amines in presence of metal or metal species give carbamate moiety RRNCO2

“RR’NH + CO2 →”RR’NCO2-


As precursor of urea, isocianates,carbamic acidRRNCOOH can give back amine and carbon dioxideamino silanes react with CO2 to give ammonium carbonateionic liquids amine containing dendrimers, polymers


The use of heterogeneous catalysts in the synthesis of urethanes from aliphatic and aromatic amines, CO2 and alkyl halides is explored only recently. Titanosilicate molecular sieves, metal phtalocyanine complexes encapsulated in zeolite-Y, beta-zeolites and mesoporous silica (MCM-41) containing ammonium cations as the templates, and adenine modified Ti-SBA-15have been tried as effective catalysts even without any additional base. Aziridines and azetidines have been co-polymerized with CO2 to afford polymeric materials (polyurethans). CeO2 seems to be even better than γ-Al2O3, TiO2, ZrO2, MgO and Y2O3, as catalyst for the reaction of CO2 with aminoalcohols to form cyclic carbamates, with alcohols and amines to form linear carbamates and with CO2 and diamines to form cyclic ureas.

280

SYNTHESIS OF CARBOXYLIC ACID, ESTERS AND LACTONES

281

Transition-metal-mediated carboxylation of organic substrates with CO2 is of interest for the development of sustainable chemical processes based on the utilization of CO2 in organic synthesis. The direct C–H carboxylation with CO2 has been achieved only in a few cases and requires a stepwise approach based on the combination of C–H activation and CO2 fixation.R-H + CO2 RCOOHGrignard reagents, organolithium compounds, other metallorganic reagents, including organoboron, organozinc, organotin reagents, usually obtained reacting an organic halide with a metal compound or by the direct metallation of a C–H bond, have been used for the stoichiometric carboxylation of organic substrates


282

Rh-phenyl complexes are easily converted into thecorresponding Rh-benzoate. Examples of C–Hcarboxylation are ‘metal assisted’ carboxylation in whichone mol of metal is used per mol of organic product. Theapplication is quite limited to special products, like naturalproducts and biologically active molecules, but is not usablefor the synthesis of bulk chemicals which require catalyticprocesses with high TOF and TON.Direct catalytic C–H carboxylation is of interest. Recently,transition-metal systems such as Pd, Ir, Rh, Pt, Au, havebeen used to activate the C–H bonds. Carboxylic acid suchas acetic acid can be obtained reacting CO2 with CH4 in thepresence of V or Pd based catalysts and K2S2O8 (15 mol%)which acts as oxidizing agent with a yield of 7%

283

Reacting ethene with CO2 acrylic acid can be obtained.The reaction is an example of atom economy as all carbon atoms of the reagents are found in the products.CH2=CH2 + CO2 to give CH2=CH-COOHThe reaction has been studied using several transition metal systems as promoters, but the spontaneous release of acrylic acid has not been detected. In particular, the reaction of CO2 with ethene at metal centres affords hydrido acrylate or a metallacycle-carboxylate

Reaction of CO2 and ethylene at metal centres affording hydrido-metal-acrylate (A) or

metalla-cycle carboxylate (B)


Aromatic carboxylic acid is obtained starting from aromatics under

mild conditions with 85% conversionExample

Para xylene + CO2 (AlCl3/Al,313 K 18h) 1,4 dimethyl 2benzoic acid +

1,3 dimentyl 4 carboxylic acid .


285

The chemistry of conjugated- (butadiene),and cumulated-dienes

(allene), has been investigated. The telomerization of 1,3-butadiene

with CO2 affords δ- and γ-lactones, carboxylic acids together with

smaller amounts of linear esters.



287

We have tried to discuss how to convert carbon dioxide into value-added

chemicals and fuels. Most of them are in the research phase and are current level of

research.

Several types of catalysts (homo, hetero, photo, ( to be dealt with later on ) electro

and biocatalysts ( to be done)) have been developed and are being developed.

However, CO2 is quite inert and its conversion is highly kinetically and

thermodynamically limiting, so it is of importance to develop highly efficient and

selective catalysts that do not undergo rapid deactivation and in overcoming the

thermodynamic barrier. The thermodynamic limitation could be overcome by

adopting either a physical or a chemical approach. Attention has to be directed on

the design of active catalysts for CO2 conversion by combining the properties of

both homo- and heterogeneous catalysts. The addition of metal precursor, ionic

liquids and either methanol, epoxides, acetal, ortho-ester or others species in the

catalytic system is reported to be effective for the conversion of carbon dioxide into

of methanol, cyclic carbonate and DMC.

The utilization of carbon dioxide represents a fundamental option for the carbon

management strategy.

Also offers an opportunity to use a renewable raw material for several

applications.

288

The utilization of carbon dioxide represents a

fundamental option for the carbon management

strategy

Also offers an opportunity to use a renewable raw

material for several applications.


CO2 to Chemicals and Fuels

Presentation 13

(24th March 2014)

290

Reflections on the electrochemical reduction of CO2

on metallic surfaces

• We have already seen that the metals can be grouped on the basis of high over-voltage for hydrogen evolution, CO adsorption and classified all metals in four groups.

• This was shown in the form of a flow chart in one of the previous presentations

• This presentation is repeated in the next projection for recollection

291

(a) A schematic diagram of a nanopore of the silver electrocatalyst with highly curved internal

surface. (b) scanning electron micrograph of np-ag dealloyed in 5 wt% hcl for 15 min and

further in 1 wt% hcl for 30 min (scale bar, 500 nm).

G.S.Hutchings et al, Nature Communications January 2014 ;doi:10.1038/ncomms4242

297

CO2 REDUCTION ACTIVITY OF NP-AG AND POLYCRYSTALLINE SILVER AT (A)

−0.60 V, AND NP-AG AT (B) −0.50 V AND (C) −0.40 V VERSUS RHE. TOTAL

CURRENT DENSITY VERSUS TIME ON (LEFT AXIS) AND CO FARADAIC

EFFICIENCY VERSUS TIME (RIGHT AXIS).

G.S.Hutchings et al, Nature communications January 2014 ; doi:10.1038/ncomms4242 298

OVERPOTENTIAL VERSUS CO PRODUCTION PARTIAL CURRENT DENSITY

ON POLYCRYSTALLINE SILVER AND NP-AG.

G.S.Hutchings et al, Nature communications January 2014 ; doi:10.1038/ncomms4242

299

The alkynyl-substituted ReI complex [Re(5,5′-bisphenylethynyl-2,2′-bipyridyl)(CO)3Cl]

was immobilized by electropolymerization onto a Pt-plate electrode. The polymerized

film exhibited electrocatalytic activity for the reduction of CO2 to CO. Cyclic

voltammetry studies and bulk controlled-potential electrolysis experiments were

performed by using a CO2-saturated acetonitrile solution. The CO2 reduction,

determined by cyclic voltammetry, occurs at approximately −1150 mV versus the

normal hydrogen electrode (NHE). Quantitative analysis by GC and IR spectroscopy

was used to determine a Faradaic efficiency of approximately 33 % for the formation of

CO. Both values of the modified electrode were compared to the performance of the

homogenous monomer [Re(5,5′-bisphenylethynyl-2,2′-bipyridyl)(CO)3Cl] in acetonitrile.

The polymer formation and its properties were studied by using SEM, AFM, and

attenuated total reflectance (ATR) FTIR and UV/Vis spectroscopy

300

Structure of [Re(5,5′-bisphenylethynyl-2,2′-bipyridyl)(CO)3Cl] (1).

301

Possible substructure of the rhenium sites within the polymer film 2 in which

X represents a chloride or a substituted ligand from the reaction medium.

Electrocatalytic Reduction of Carbon Dioxide to Carbon Monoxide by a

Polymerized Film of an Alkynyl-Substituted Rhenium(I) Complex

N.S.Sariciftc et al, Chem Cat.Chem., 5,1790, 92013).

302

Electrocatalytic and photocatalytic reduction of carbon dioxide to carbon monoxide using the alkynyl-substituted rhenium(I) complex 5,50-bisphenylethynyl-2,20-bipyridyl)Re(CO)3ClEngelbert Portenkirchner , Kerstin Oppelt , Christoph Ulbricht Daniel A.M. Egbe ,Helmut Neugebauer , Günther Knör , Niyazi Serdar Sariciftci Journal of Organometallic Chemistry (2012)1-7.

The rhenium complex fac-(5,50-bisphenylethynyl-2,20- bipyridyl)Re(CO)3Cl was used as a novel catalyst for the electro- andphotochemical reduction of CO2 to CO in homogeneous solution. Theresults were compared to (2,20-bipyridyl)Re(CO)3Cl as a benchmarkcompound. Cyclic voltammetric studies as well as bulk controlledpotential electrolysis experiments were performed using a CO2saturated solution in acetonitrile. (5,50-bisphenylethynyl-2,20-bipyridyl)Re(CO)3Cl showed a 6.5-fold increase in current densityunder CO2 at 1750 mV versus normal hydrogen electrode (NHE) ascompared to the operation without CO2. Quantitative analysis by gaschromatography (GC) and infrared spectroscopy showed a Faradaicefficiency of around 45% for the formation of CO.

303

Some significant redox values

Table 1

Redox potentials vs. NHE for the one- and multi-electronreduction of CO2 in an aqueous solution at pH 7

Redox reaction E0 /V

CO2 → CO2 1.90

2CO2 + 2e → ¼ CO + CO32- 0.65

CO2 + 2H++ 2e → HCOOH 0.61

CO2 + 2H+ + 2e = CO + H2O 0.53

CO2 + 4H++ 4e =HCHO + H2O 0.48

CO2 + 6H+ + 6e = CH3OH + H2O 0.38

CO2 + 8H+ + 8e = CH4 + H2O 0.24

304

Cyclic voltammograms of compound 1 in nitrogen- (black solid line) and CO2-

saturated electrolyte solution (red solid line), respectively. The scan in the presence of

CO2 shows large current enhancement due to a catalytic reduction of CO2 to CO.

Voltammograms are recorded at 100 mV s1 in acetonitrile, Pt working electrode, Pt

counter electrode, and a catalyst concentration of 1 mM. A scan with no catalyst present

under CO2 (blue dashed line) shows little to no reductive current.

E. Portenkirchner, et al., Journal of Organometallic Chemistry (2012)

http://dx.doi.org/10.1016/j.jorganchem.2012.05.021

305

Iridium dihydride complexes supported by PCP-type pincer ligands rapidly insert CO2

to yield κ2-formate monohydride products in THF. In acetonitrile/water mixtures, thesecomplexes become efficient and selective catalysts for electro-catalytic reduction ofCO2 to formate. Electrochemical and NMR studies provided mechanistic details.

J. Am. Chem. Soc. (2012) 134,5500–5503 306

E. Portenkirchner, et al., Journal of Organometallic Chemistry (2012), http://dx.doi.org/10.1016/j.jorganchem.2012.05.021

Cyclic voltammograms of compound 2 in nitrogen- (black solid line) and CO2-saturated

electrolyte solution (red solid line), respectively. The scan in the presence of CO2 shows a large

current enhancement due to a catalytic reduction of CO2 to CO. Voltammograms are recorded at

100 mV s1 in acetonitrile, Pt working electrode, Pt counter electrode, and a catalyst concentration

of 1 mM.307

High surface area tin oxide nanocrystals prepared by a facile hydrothermal

method and have been evaluated as electrocatalysts toward CO2 reduction to

formate.

At these novel nanostructured tin catalysts, CO2 reduction occurs selectively to

formate at overpotentials as low as 340 mV.

In aqueous NaHCO3 solutions, maximum Faradaic efficiencies for formate

production of >93% have been reached with high stability and current

densities of >10 mA/cm2 on graphene supports. The notable reactivity toward

CO2 reduction achieved may arise from a compromise between the strength of

the interaction between CO2• and the nanoscale tin surface and subsequent

kinetic activation toward protonation and further reduction.

J. Am. Chem. Soc., , (5), pp 1734–1737 DOI: 10.1021/ja4113885

308

Nanostructured Tin Catalysts for Selective Electrochemical Reduction of

Carbon Dioxide to Formate

J. Am. Chem. Soc., , (5), pp 1734–1737 DOI:10.1021/ja4113885

309

The chemical reduction of CO2 will be one of the most important reactions

for the 21st century from many points of view like waste disposal, raw

material, and also to sustain living beings.

As a so called greenhouse gas, CO2 supposed to contribute to global climate

change, and therefore anthropogenic emission of CO2 is resulting in

increasing global concern. This has been stressed at various stages.

In order to limit the global mean temperature increase by 2.0-2.4 °C, the

global CO2 emission would have to be reduced by 50-80% by 2050 (based

on the emission level in 2000). However there are controversies on this

assumption.

The most effective, route to decreasing anthropogenic CO2 emissions would

be the replacement of all current (13 Terawatt) and future (23 Terawatt by

2050) global energy requirements with non-emissive and renewable

resources. Electricity generation by emission free sources or adopt

methodology for emission conversion.310

1. With foreseeable new policies gearing towards the reduction of carbon

emissions, enabling technologies capable of efficient chemical reduction of CO2

to fuels and materials is crucial.

The management of large-scale CO2 emissions, such as from coal- and gas-fired

power plants, can be achieved in many different ways which we have been

discussing at various stages.

At present, CO2 capture and sequestration (CCS) is the closest to practical

application.

Despite being the most straightforward solution, the extremely large scale

coupled with the energy requirements and the potential for environmental

consequences as well as CO2 leakage result in significant obstacles and concern

for the implementation of CCS.

On the other hand, the reduction of CO2 to fuels using non-carbon based energy

sources (such as solar, wind, nuclear, or geothermal), although highly

challenging, is expected to be a truly sustainable alternative to CO2 emission.

Among the leading synthetic approaches for CO2 reduction include

electrochemical reduction, solar driven photochemical reduction to be seen later

on and thermal catalysis such as hydrogenation. (already discussed) 311

Despite their potential, much fundamental work is required for each approach to

improve the overall energy efficiencies and product selectivity to practical and

implementable levels.

While the need to overcome the over potential or kinetic limitation of initial CO2

reduction step is a common critical reaction across the different technologies, the grand

challenge lies in the ability to convert CO2 to valuable products without increasing

anthropogenic CO2 emissions.

Although technologies for the sequential conversion of CO2 to CO and further to higher

hydrocarbons exist (through Fischer-Tropsch synthesis), the efficiencies of these

processes are low.

The development of energy efficient technologies for the reduction of CO2¬ to high

energy density fuels without a net increase in anthropogenic CO2 emissions is essential

and will require interdisciplinary synergy.

To date, the communication and cooperativity between disciplines and between

different approaches has been limited in spite of the many common features. Is this so?

In particular, the need to reduce CO2 while avoiding high energy intermediates would

suggest that interplay between theoretical and experimental research for the many

different approaches should be highly synergistic in that the understanding gained from

one approach should compliment others.312

The initial complexation/adsorption of CO2 is thought to define the subsequent

reactivity both for heterogeneous and homogeneous catalysts.

The number of interactions and the nature of the interactions is expected to

influence the reactivity due to the activation or deactivation of either oxygen or

carbon or both.

The activation through carbon centre and oxygen centre has been already

discussed by us.

For catalysts that bind through carbon, reactivity at oxygen may be expected,

and thereby the formation of CO as an initial product or intermediate.

For catalysts that bind through oxygen, reactivity at carbon may be preferred,

such as the hydride transfer to carbon to produce formate.

These trends are expected to be general for the different approaches and may be

best elucidated through a combination of theoretical and experimental

techniques. 313

The difficulties in cleaving the CO2, on the one hand, necessitate high reaction

temperature to overcome the activation energy barrier for C-O bond cleavage.

On the other hand, the high temperature reaction favors the formation of C1

molecules such as carbon monoxide due to higher kinetic energy, preventing

the formation of longer chain molecules.

To overcome this problem, it is crucial to understand the characteristics of CO2

adsorption, the interactions with catalyst surface and reductants, as well as the

molecular energetics so that catalysts that are active at lower temperatures can

be developed.

Effects such as surface defects/kinks/steps, oxygen mobility and ionicity,

surface acidity/basicity, shape confinement, hydrogen and oxygen spill over are

among the important parameters that can potentially influence the catalytic CO2

reduction.

Establishing these fundamental appreciations of surface molecular catalysis is

highly critical in the designing of lower temperature catalytic surfaces with

improved reactivity and selectivity for more complex molecules 314

The cornerstone in heterogeneous electrochemical reduction of CO2 was recently

discussed by Hori. (those of us interested in this mode must be fully aware of the

pioneering work of Prof Hori’s group for a long time)

The challenge is that no effective and selective electro-catalyst material for CO2

reduction is yet known. Metals are the most studied and also we have discussed it

in terms of over potential, hydrogen evolution, CO adsorption but these may be

true for metallic surfaces but for other molecular systems the scientific principles

have to be different.

[this aspect will be taken up for discussion in this short presentation]

In fact, only copper and its alloys have been shown to be capable of producing

significant quantities of hydrocarbons from CO2, but they do so very inefficiently.

Even on Cu, reduction of CO2 takes place only at very low potentials and with a

large fraction of the current being wasted in hydrogen evolution.

Hydrocarbons like methane and ethylene are only produced at reducing potentials.

What role this parameter has is not yet established.

However, the detailed reaction mechanism is still not known.

Furthermore, an understanding of how to lower the over potential on the electro

catalyst and increase the selectivity compared to hydrogen evolution is still

missing. {Any guesses} 315

The use of molecular catalysis can improve selectivity and lower over potentials while

increasing mechanistic understanding of CO2 reduction.

Promising examples of molecular electro catalysts include transition metal catalysts

such as palladium triphosphine complexes, rhenium bipyridine complexes, and

bimetallic copper complexes . What is the speciality of these systems?

Additionally, non-metal-based molecular systems have also been reported, including

the recent work of Bocarsly. We may like to consider the work of Prof Bocarsly

separately in one presentation? Analysis of pyridinium catalyzed electrochemical

and photoelectrochemical reduction of CO2: Chemistry and economic impact,

IJC-A Vol.51A(09-10) [September-October 2012] and references therein we shall have

a full presentation on this work as it is a different approach.

Molecular complexes can serve multiple functions for the development of electro

catalysts for CO2 reduction:

These catalysts could be used directly in solution or immobilized at an electrode

surface, or the insight gained from molecular electro catalysts can be extended to

development of heterogeneous electro catalysts.

How one can exploit this aspect is an important component of Electro Catalysis and

a few projections will be attempted and the remaining will evolve as one progresses. 316

http://nopr.niscair.res.in/handle/123456789/14638

The chemical reduction of CO2 will be one of the most important

reactions in the 21st century.

As a greenhouse gas, CO2 contributes to global climate change, and

therefore anthropogenic emission of CO2 is resulting in increasing

global concern.

In order to limit the global mean temperature increase by 2.0-2.4 °C,

the global CO2 emission would have to be reduced by 50-80% by

2050 (based on the emission level in 2000).

The most effective, route to decreasing anthropogenic CO2

emissions would be the replacement of all current (13 Terawatt) and

future (23 Terawatt by 2050) global energy requirements with non-

emissive and renewable resources.

317

Some Key References[1] B. Metz et al., Climate Change 2007: Mitigation of Climate Change, Contribution of

Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on

Climate Change, Cambridge University Press, New York, 2007.

[2] P.V. Kamat, J. Phys. Chem. C, 2007, 111, 2834.

[3] S. Bachu, Prog. Combust. Energy Sci. 2008, 34, 254.

[4] E.S. Benson et al., Chem. Soc. Rev., 2009, 38, 89.

[5] S.C. Yan et al., Angew. Chem. Int. Ed. 2010, 122, 6544.

[6] W. Wang et al., Chem. Soc. Rev., 2011, 40, 3703.

[7] T.M. Mata et al., Renewable Sustainable Energy Rev., 2010, 14, 217.

[8] D.T. Whipple et al., J. Phys. Chem. Lett., 2010, 1, 3451.

[9] S. Sharma et al., J. Catal. 2011, 278, 297.

[10] E. Vesselli et al., J. Am. Chem. Soc., 2008, 130, 11417.

[11] G. Kresse et al., Phys. Rev. B, 1996, 54, 11169.

[12] J.P. Perdew et al., Phys. Rev. B, 1992, 45, 13244.

[13] Y. Hori. Electrochemical CO2 reduction on metal electrodes, in Modern Aspects of

Electrochemistry, Vol. 42, chapter 3, pp. 89–189, Springer, New York, 2008.

[14] A.A. Peterson et al., Energy Environ. Sci., 2010, 3, 1311–1315

[15] Savéant, J.-M. Chem. Rev. 2008, 108, 2348.

[16] DuBois et al. Acc. Chem. Res. 2009, 42, 1974318

CO2 to Chemicals and FuelsElectro-catalytic Reduction

Presentation 14

(27th March 2014)

319

Some Land Mark References (Other than those already referred)

1. New and Future Developments in Catalysis (Editor Suib,S.L.), Elsevier 2013 Activation of Carbon dioxide one chapter on “ELECTRO-CATALYTIC REDUCTION OF CARBON DIOXIDE” 2. Electrochemical reduction of carbon dioxide on ¯at metallic cathodes, JOURNAL OF APPLIED ELECTROCHEMISTRY 27 (1997) 875-8893. A review of catalysts for the electro-reduction of carbon dioxide to produce low-carbon fuels, Chem. Soc. Rev., 2014,43, 631-675.4. A selective and efficient electro-catalyst for carbon dioxide reduction, Nature communications, January 2014 ( already discussed in one of the presentations)5. Future challenges in CO2 reduction, University of Bremen October 2012.6. Electrocatalytic Reduction of CO2 to Small Organic Molecule Fuels on Metal Catalysts, Wenzhen Li, 2010 (discussed in the presentations at various points) and many more A few of them have been already given in our earlier presentations however a compilation of all possible references will be made at the end of the course and will be available to all participants

320

Let us Get Some clarity• In the last presentation a number of questions were raised

and it appeared that it is a never ending list and the answers to these questions do not seem to be within reach in the near future

• We need at least to get clarity on some of these and this will be our first attempt

• (a) why metals form only four groups – is it potential induced perturbation of the density of states? May be one of you can take to identify the density of states of some of the metals and also project what will be the alterations in these as a function of applied potential. The final answer may not be encouraging but worth the attempt

321

Seeking Clarity (Continued)

• Why specificity is identified with respect to specific planes?

• B. Viswanathan Indian Journal of Chemistry A 51, 166 (2012).

322

Electronic energy levels cannot be the cause since the highest occupied level in CO2 is around -16 eV(1Πg) (lone pair on oxygen) and the lowest unoccupied state in CO2 is approximately at -12 eV (3σg) and the transfer of electrons to these states from metal surfaces should have been a facile process. The effective transfer of electrons depends essentially on the adsorption of CO2 and its geometry in the adsorbed state which can facilitate the facile electron transfer. The adsorption geometries that have been considered do they or any of them fall under this category?

323

In spite of these possiblities, intense research in carbon dioxide conversion over the past 30

years has consistently shown low conversion efficiencies possibly because of the high over

potentials (~ >1 V) required. In spite of the persistent efforts for reducing the overvoltage

and also improving the electro-chemical cell components, no commercially viable process

for converting carbon dixoide into fuels has evolved till date. This frustration is reflected in

the following statement of the DOE report by Bell [2] “ The major obstacle preventing

efficient conversion of carbon dioxide into energy bearing products is the lack of (suitable

and appropriate) catalysts…..Only intermittent research has been conducted into the

electrochemical reduction of carbon dixoide over the last 20 years, despite the fact that

electrochemical generation of chemical products is a mature technology and already

practiced on enormous scales…..Electron conversion efficiencies of greater than 50% can be

obtained but at the expense of very high overpotentials (ca.1.5V)”.

324

1.What are the factors one has to consider, for selecting the appropriate electrode for

carbon dioxide reduction?

2.Which is most important for consideration - Is it the reduction potential or the

activation of the molecular carbon dioxide?

3.In selecting the metallic system, should one consider the mode of activation of

carbon dioxide in the associated form or in the dissociated form?

4.Does the nature of wave functions of the frontier wave functions of the electrode

material and that of CO2 have to be considered for symmetry and energy

compatibility?

5.It is argued in the literature that copper and copper- zinc systems are most

appropriate. How does this evolve? What are the governing principles?

6. It is usually stated in the literature that the formation of anion radical is important

and essential step in the electrochemical reduction of CO2. Can any light be thrown

on this aspect?

7. It is also argued that the bond angle must be reduced from 180o in the activated

state. Does the formation of anion radical favor this postulate?

8.The reduction reaction is capable of forming a variety of products and how does one

control the required selectivity?

9.One of the intriguing questions in the study of this reaction is the product analysis.

This can be achieved either analyzing the gas phase or the liquid phase and which

one is most appropriate and why? Is there any reasoning for this choice?

10.The literature often argues in terms of the relative adsorptive or evolution capacity

for hydrogen from water or CO poisoning. How to make a judgment on the relative

importance of these steps? 325

One of the recent reviews looks at the opportunities and prospects in the chemical recycling of carbon dioxide to fuels, as a complementary technology to carbon sequestration and storage (CSS). The requisites for this objective are:(i) minimize as much as possible the consumption of hydrogen (or hydrogen

sources), (ii) produce fuels that can be easily stored and transported, and (iii) use renewable energy sources. The different topics discussed in the review include CO2 (i) reverse water–gas shift and (ii) hydrogenation to hydrocarbons, alcohols, dimethyl ether and formic acid, (iii) reaction with hydrocarbons to syngas, (iv) photo- and electrochemical/catalytic conversion, and (v) thermochemical conversion. Other relevant options, such as the use of micro-algae or other bio-catalysis based processes, or the use of microwave and plasma processes .

Therefore, the area of carbon dioxide conversion to fuels and chemicals is a very active

Gabriele Centi and Siglinda Perathoner,Catalysis Today, 148, 191 (2009)

326

Critical look at Electro-catalytic reductionWhat is the role of potential selectivity or another mode of activation?The reaction medium is different from conventional catalysis? Both surface and adsorptionLimitations on the type of electrodes that can be employed.Molecular species – possible to alter the redox values and hence selectivity in the desired directionsAnchoring what does it do to the molecular species does the value of redox potential altered if so what factors or order of magnitude?

327

New insights into the electrochemical reduction of carbon dioxide on metallic

copper surfaces

new insights into the electrochemical reduction of CO2 on a metallic copper surface

development of an experimental methodology with unprecedented sensitivity for the

Custom electrochemical cell designed to maximize product concentrations coupled to

gas chromatography and nuclear magnetic resonance

A total of 16 different CO2 reduction products, five of which are reported for the first

time.

Taking into account the chemical identities of the wide range of C1–C3 products

generated and the potential-dependence of their turnover frequencies,

mechanistic information is deduced.

A scheme for the formation of multicarbon products involving enol-like surface

intermediates as a possible pathway, accounting for the observed selectivity

for eleven distinct C2+ oxygenated products including aldehydes, ketones, alcohols, and

carboxylic

Kendra P. Kuhl,a Etosha R. Cave,b David N. Abramc and Thomas F. Jaramillo, Energy

Environ. Sci., 2012, 5, 7050

328

A simplified scheme for the possible routes for the electrochemical reduction of CO2

329

Table 1 Products of CO2 reduction along with the number of electrons needed to produce each

one and its standard reduction potential at pH 6.8. Products shown in green appear in only a few

past studies, and products shown in blue are reported here for the first time

Product # e− E Product #e− E

Formate 2 −0.02 Acetaldehyde 10 0.05

Carbon monoxide 2 −0.10 Ethanol 12 0.09

Methanol 6 0.03 ethylene 12 0.08

Glyoxal 6 −0.16 Hydroxyacetone 14 0.46

Methane 8 0.17 acetone 16 −0.14

Acetate 8 −0.26 allyl alcohol 16 0.11

Glycolaldehyde 8 −0.03 Proppionaldehyde16 0.14

Ethyleneglycol 10 0.20 1-propanol 18 0.21

332

Carbon dioxide reduction sustainable economy and chemical industry alternative for the fuel productionit is possible to couple two fields but the catalyst must be suitable or amenable for both the fields.

333

None of the electro-catalysts are suitable main products fuel precursor, CO and formate not a fuel like alcohols or Hydrocarbonsover potential of about 1 volt required for alcohol or hydrocarbon production - CO is an important intermediate

334

Large area, low volume and analysis1. 16 different products have been identified- 12 of them C2 and C3

hydrocarbons and alcohols2. TOF track that of ethylene3. By dehydroxylation of an earlier less reduced product in its enol or diol form

335

Structure effects on the energetics of the electrochemical reduction of CO2 by

copper surfaces, William J.Durand, Andrew A.Peterson, Felix Studt, Frank Abild-

Pederson, Jens K.Norskov, surface Science, 605,1354-1359 (2011)

344

Structure effects on the energetics of the electrochemical reduction of CO2 by copper surfaces, William J.Durand, Andrew A.Peterson, Felix Studt, Frank Abild-Pederson, Jens K.Norskov, surface Science, 605,1354-1359 (2011)

345

Structure effects on the energetics of the electrochemical reduction of CO2 by copper

surfaces, William J.Durand, Andrew A.Peterson, Felix Studt, Frank Abild-Pederson, Jens

K.Norskov, surface Science, 605,1354-1359 (2011)346




347




348

Structure effects on the energetics of the electrochemical reduction of CO2 by copper

surfaces, William J.Durand, Andrew A.Peterson, Felix Studt, Frank Abild-Pederson,

Jens K.Norskov, surface Science, 605,1354-1359 (2011) 349

Structure effects on the energetics of the electrochemical reduction of CO2 by copper surfaces, William J.Durand, Andrew A.Peterson, Felix Studt, Frank Abild-Pederson, Jens K.Norskov, Surface Science, 605,1354-1359 (2011)

350


PRESENTATION - 15

31st MARCH 2014


(Total Number of Projections for this Lecture is )

351

Bocarsly’s work on CO2 reduction from 1994

• In 1992 Bocarsly group reported that pyridiniumcould catalyze the reduction of CO2 to methanol at30% yield at hydrogenated palladium electrodes.

• This chemistry was subsequently extended toplatinum metal electrodes, also resulting in methanolformation at about 30% yield.

• In 2004, a mechanism for the reduction of CO2 atplatinum was proposed as follows, including bothsurface and solution based catalytic steps as well as akey intermediate, the reduced pyridinium-CO2 radicaladduct:

352

The evidence for this mechanism includes the detection of formic acid and

formaldehyde as well as methanol in solutions following electrolysis, cyclic

voltammetry with electrochemical modeling of pyridinium in the presence

and absence of CO2 as well as possible intermediates (formic acid and

formaldehyde) and pressure and temperature studies.

354

The chemistry has been expanded to other metal and semiconductor

electrodes, including demonstration of 96% faradaic efficiency for methanol

formation at p-GaP electrodes at an under potential of -0.32 V.4 Pyridinium

derivatives have also been found to catalyze the reduction of CO2 to products

including isopropanol and ethanol.

Current work in the lab is focused on further mechanistic understanding of

CO2 reduction, especially the C-C bond formation observed in higher order

reduced products. Work continues on novel catalysts and surfaces, with

particular attention to observing reaction intermediates in situ using FTIR,

EPR, and Raman spectroscopies. Electrochemical techniques including cyclic

voltammetry and bulk electrolysis are used frequently in the lab as well as

surface science techniques such as XPS, XRD, SEM, and TEM. It is hoped

that greater understanding of the parameters controlling catalysis will lead to

the design of more efficient, robust and fast catalysts for CO2 reduction, as

well as further the knowledge of CO2 activation and C-O bond breakage, and

C-C and C-H bond formation.

355

Seshadri, G.; Lin, C.; Bocarsly, A. B. A new homogeneous electrocatalyst for the reduction of carbon dioxide to methanol at low overpotential. J. Electroanal. Chem. 1994, 372, 145-50.

2. Barton, C. E.; Lakkaraju, P. S.; Rampulla, D. M.; Morris, A. J.; Abelev, E.; Bocarsly, A. B. Using a One-Electron Shuttle for the Multielectron Reduction of CO2 to Methanol: Kinetic, Mechanistic, and Structural Insights. J. Am. Chem. Soc. 2010, 132.

3. Morris, A. J.; McGibbon, R. T.; Bocarsly, A. B. Electrocatalyticcarbon dioxide activation: The rate-determining step of pyridinium-catalyzed CO2 reduction. ChemSusChem 2011, 4, 191-196.

4. Barton, E. E.; Rampulla, D. M.; Bocarsly, A. B. Selective Solar-Driven Reduction of CO2 to Methanol Using a Catalyzed p-GaP Based Photoelectrochemical Cell. J. Am. Chem. Soc. 2008, 130, 6342-6344.

356

The Questions?Only some obvious ones are given1. What is the role of the added catalyst in this case Pyridinium species?2. Is there any generalization that is possible for the catalytic species to be used?3.What fundamental parameter is being manipulated by use of these species as catalysts?The authors in the reaction scheme shown in one of the projections postulated regarding electron transfer (either single or multiple in sequence) can one postulate that the species added facilitate this stepThese are only a few obvious questions on this aspect of CO2 reduction based on this work.

357

Some possible Answers Kindly note these are only guesses

1. The species used should be capable of making an adduct with CO2 These need not be nitrogen containing species it can be a species that can link to the carbon of CO2 can be any of the heteroatom containing species. Why?

2. The adduct facilitates the electron transfer? How?

3. The adduct should be structurally feasibly but not to be too stable since one has to regenerate ultimately the catalytic species in situ.

4. The species not only initiates the initial electron transfer but also helps in subsequent electron transfer steps.

5. The product slate depends on the nature of the catalytic species since the total number of electrons transferred need to be dependent on the nature of the species

358

Adsorption Modes

359

Potential energy diagram for methanol synthesis on Cu (1 1 1) and Cu29 nanoparticle. Thin and thick horizontal bars represent stable intermediates and transition states, respectively.

360

Potential energy diagram for methanol synthesis on Cu(1 1 1) from CO2 hydrogenation

361

Reaction network for methanol synthesis from CO2 and hydrogen

362

Potential energy diagram for methanol synthesis on Cu(1 1 1) from CO2 hydrogenation363

Schematic mechanism of the initial steps of CO2 hydrogenation on In2O3

364

Schematic potential energy diagrams of CO2 hydrogenation to formate and to CO on (a) drySubstrate supported Ni4 and (b) partially hydroxylated substrate supported Ni4. Only transition state (TS) with the highest barrier for each path is shown 365

Electrocatalysissome general remarks for basic understanding1. The nature of the electrode - Metal or others- DOS2. The nature of surface sites3. The applied potential and the field at each site4. What does one mean when he applied a potential?5. How does this application of potential affect the electrochemical process?6. Many of these questions have to be understood before we explore the electro-catalytic reduction of CO2

These aspects will be briefly discussed in this last presentation on Electro-catalysis of CO2 reduction.All the doubts on this topic may be raised now

366

Your reflections and questions on this topic will be taken up for discussion for the remainder of the time

367


Presentation 163rd April 2014Time 4.30 to 5.10 p.m.

368

The need for CO2 to Chemicals and Fuels need not be outlined in essence the reasons are(i) Shortage of energy(ii) Shortage of carbon sources(iii) Global warming solution to develop practical system that can convert CO2 to Chemicals and Fuels

369

The essential features of Artificial Photo-synthesis(i) Efficient use of solar radiation in addition to the UV radiation alone(ii) water as a source for electron and hydrogen(iii) Efficient reduction of CO2

since it is in the fully oxidised state

370

CO2+ e →CO2-∙ E0= -1.9 V

Highly endothermic at pH = 7 in aqueous solutions too reactive other multi-electron reduction reactions with lower energies.The reactions of relevance are:CO2 + 2H++2e → HCCOH; E0=-061VCO2 + 2H++2e → CO+H2O; E0=-0.53VCO2 + 4H++4e → HCHO +H2O; E0 = -0.48VCO2 + 6H++6e → CH3OH; H2O; E0= -0.38VCO2 + 8H++8e → CH4 + H2O;E0= -0.24V

371

Photo-catalyst usually constructedusing a catalyst and sensitizerone electron or multi-electron transfer catalystsensitizer metal complexes, metal particles and enzymesboth functions in one and the same is rhenium(I) complexes

372

Two categoriesHomogeneous catalysts ( mainly Transition metal complexes)Heterogeneous catalysts ( mainly semiconductors)

373

Evaluated on the following parameters(i) Product selectivity – product to total products

(ii) Quantum Yield ϕ = [Product/mol]/ [Absorbed photons/Einstein](one can use the input electrons in the numerator)(iii) TN = [product/mol]/[photocatalyst/mol or unit mass](iv) TF = TN/ [Reaction time / mins or hours]

374

Photo-catalytic Reduction of CO2 by Metal Complexes

Single Component Systems

375

Photochemical reduction of CO2 on metal complexescomplex studied[Re(bipy)(CO)3X]n+

1 : X = Cl– , n = 02a : X = P(OEt)3, n = 13a : X = PPh3 , n = 13b : X = P(n-Bu)3 , n = 13c : X = PEt3 , n = 14 : X = py , n = 15 : X = NCS- , n = 06 : X = CN- , n = 07 : X = DMF or TEOA , n = 1Triethanolamine donor product CO quantum yield high 0.38potential 1.3 to 1.67V

Top Curr Chem (2011) 303: 151–184, DOI: 10.1007/128_2011_139; # Springer-Verlag

Berlin Heidelberg 2011 376

[Re(Pp’Ysubbipy) ( CO)3(P(OET)3]+

2a : Y = H2b : Y = MeO2c= CF3similar results[Re(para para’subbipy)(CO)2(PR3)28 : R = p–FPh, R′ = p– FPh9 : R = OiPr, R′ = OiPr10 : R = p–FPh, R′ = OiPr

Top Curr Chem (2011) 303: 151–184, DOI: 10.1007/ 128_2011_139; # Springer- Verlag

Berlin Heidelberg 2011377

Top Curr Chem (2011) 303: 151–184, DOI: 10.1007/128_2011_139; # Springer-Verlag Berlin

Heidelberg 2011378


Berlin Heidelberg 2011 379

[Re(bpy)(CO)3X]+ + hν→[ReII(bpy-)( CO)3X]+ (X= PPh3,or Py)(1)[ReII(bpy)(CO)3X]+ +TEOA →[RsI(bpy-)(CO)3X] +TEOA- (2)[ReI(bpy-)(CO)3X] + S → [ReI(bpy-)(CO)3S] + X (3)[ReI(bpy-)(CO)3S] + {reI(bpy)(CO)3X]+ → 7 + [ReI(bpy-)(CO)3X] (4)



380


Heidelberg 2011381

Three species Cl-;NCS-;CN-(1,5,6) 5 isbetter catalytically active due to thelability of the anionic ligand. OERspecies accumulate for 5 and 6.17 electron species reacts with CO2 toform the adduct. This receives anotherelectron and gives rise to CO and thestarting complex recovers

382

Fe (TPP) or Co(TPP) H2TPP 5,10,15,20 tetraphenyl-21H,23H-porphyrin) in triethylamine (>320 nm) CO2 reductionFe(TPP) CO Co(TPP) HCOOHMIII(TPP) is reduced to MI by photon induced electron transfer from TEA which then dis-proportionates to M0(TPP) the active species.Top Curr Chem (2011) 303: 151–184, DOI: 10.1007/128_2011_139; # Springer-

Verlag Berlin Heidelberg 2011 383


Heidelberg 2011384

Irradiation of iron and cobalt porphyrins (13: Fe(TPP), 14: Co(TPP),

H2TPP 5,10,15,20-tetraphenyl-21H,23H-porphyrin) in the presence of

triethylamine (TEA) using > 320-nm light caused the photo-catalytic

reduction of CO2. When Fe comple was used as a photocatalyst, CO

was detected with TNCO 70 after 180-h irradiation. Formic acid was

the main product when Co complex was employed as a photo-catalyst.

The reaction mechanism proposed on the basis of UV–vis absorption

changes during photolysis and radiolysis, and electrochemical

measurements are shown in Scheme 3. MIII(TPP) is reduced to

MI(TPP) by photoinduced electron transfer from TEA, which

subsequently disproportionates to M0(TPP), the proposed

catalytically-active species.


Heidelberg 2011

385

Irradiation using > 290-nm light of a mixed system of p-

terphenyl (TP) and TEA gives TP.-. . Because TP -. has a very

strong reduction power (E0 = 2.2 V vs NHE), TP-. can directly

reduce CO2 and formation of HCOOH is observed.

The system is deactivated quickly since it is reduced to the

dihydroform. Thequantum yield of formic acid is 0.072 and

TN =4Top Curr Chem (2011) 303: 151–184, DOI: 10.1007/128_2011_139; # Springer-Verlag Berlin

Heidelberg 2011 386

MULTICOMPONENT SYSTEMSphotocatalysts for the two-electron reduction of CO2 should have both a

photosensitizing component for initiating photoinduced one-electron transfer and a

catalyst component for activating and introducing two electrons to CO2.



387


Presentation: SeventeenDate 7th April 20144.30 p.m.

390

MULTICOMPONENT SYSTEMSphotocatalysts for the two-electron reduction of CO2 should have both a

photosensitizing component for initiating photoinduced one-electron transfer and a

catalyst component for activating and introducing two electrons to CO2.



The examples shown in this presentation are mostly reprouced from the above source

Article title: Photocatalytic Reduction of CO2: From Molecules to Semiconductors

Tatsuto Yui, Yusuke Tamaki, Keita Sekizawa, and Osamu Ishitani

391

Top Curr Chem (2011) 303: 151–184 DOI: 10.1007/128_2011_139; # Springer-Verlag Berlin

Heidelberg 2011; Published online: 28 April 2011; Photocatalytic Reduction of CO2: From

Molecules to Semiconductors Tatsuto Yui, Yusuke Tamaki, Keita Sekizawa, and Osamu

Ishitani

392




Ishitani393

PhotosensitizersRu-N complexes long life time of excited states, 3MLCTMixed system (biPy and bpz) Ru or Os colloi , TEOA violgen electron relay produce >400 nm H2 and CH4

394

[Ru(bpy)2(CO)2]2+ TEOA HCOOH

TEOA and BNAH (1-benzyl-1,4-dihydronicotinamide) electron transfer from TEOA or BNAH to excited state of photosensitizerEven though the OER is clear the subsequent electron transfers are not clearsome times reduced catalyst precipitates

395

Ni(Cyclam)]2+ 1,4,8,11-tetrazacyclotetradecane and ascorbic acid 340-600 nmCO and H2 Labelled CO2 proved CO is coming from CO2

396




Ishitani397

Two roles for the Rhenium complexes1. one electron reductant (OER)2.Give 17 electron system with ligand dissociation and produce CO2 adduct.Based on these principles 2b photosensitizer and 25 Re(bpy)(CO)3(CH3CN)]+ with TEPA CO formation with quantum efficiency of 0.59

398

Organic photosensitizers15 and Co(cyaclam)]3+ with TEA gave CO Use of TEOA improves the efficiencyCo(HMD)}2+ as catalystPhenazine and Co(cyaclam) with TEA gave HCCOH

399

Supra molecular photo catalystsRu(phen)3]

2+ photosensitizer 23 catalyst gave COsupramolecular complex 30 gave CO

400




Ishitani401

Re(II)-Co(III)32 in presence of TEOA CO and H2

402

Re(II)-Re(I)Re complexes low absorbance and low TNsupramolecular Re (I) with Re (II) photosensitizer to CO

403

34a is the first example of supra molecular photocatalyst

404

Photo catalyst with inorganic SCFujishima et al 1979 CO2 rednlow selectivity low quantum yield durability high

405

At the surface of semiconducting materials; p-Si, p-CdTe, p-InP, pGaP, n-GaAsDirect photoreduction of CO2

Three principles of photocatalytic cycles of CO2 reduction

Direct photoreduction of CO2,Coord Chem Rev 182 (1999) 67

406

Energy band modes of an n-typesemiconductor with a Schottky-type barrier:(a) band–band transition;(b) surface state population transition. Vs and Vs0,surface potential difference; CB, conduction band;VB, valence band; ET, surface state level; EF, Fermilevel.

Pd/RuO2/TiO2 photoreduction of CO2

T. Xie et al., Mater Chem Phy 70 (2001) 103

407

The total energy of a CO2 moleculechemisorbed in a Se vacancy on the CdSesurface as a function of the vertical distancebetween C atom & ideal truncated surface

Electron transfer from surfaces or nanocrystals to the CO2 molecule. The localized energy level nearthe valence band edge is caused by a Se vacancy

L. G. Wang et al., Phy. Rev Let. 89 (7) (2002)

Role of the Nanoscale in Surface Reactions: CO2 on CdSe

408

Photocatalytic reduction of CO2 with H2O on the anchored titanium oxide

M. Anpo J.Electroanal Chem 396 (1995) 21

Photocatalytic reduction of CO2

409

Photoreduction of CO2 - Perception

TON (mol reduction product of CO2 / mol catalyst) are still low

• Efficiencies of the reactions is unsatisfactory-both the amount of reduction products

of

CO2 (usually C1 products) & oxidation products of the sacrificial donor

• The tuning of the single components w.r.t. their redox potentials, life times and

selectivity is not well understood.

• Necessary to device systems which do not require sacrificial donors light energy is

also

used for degradation of sacrificial donors, influencing the energy balance of the

reactions

unfavorably

• Macrocyclic complexes of transition metal ions- satisfy the requirements of a useful

relay. They may play a dual role as a catalysts and relays

• Even with transition metal complexes – Reduction products have not been of great

economic value (usually only C1 products)410


18th PRESENTATION

14TH APRIL 2014

4.30 P.M.

411

CO2 REDUCTION ON SEMICONDUCTORS

412

The Situation Today

• 15-17 TW is used 25-27 TW in 2050; 81 % fossil fuels and 13% other sources

• Maximum from wind, tides, biomass and geothermal is maximum 20 TW

• Converting 10% of solar energy on0.3% of land surface would suffice the projected demand in 2050.

• 37Gt of CO2 to day and it can go upto 43 Gt in 2035

• CO2 cycle involves about 90Gt

• Methanol economy

413

• Catalysis is generally ∆G is negative and catalyst is only reducing the barrier

• In this sense CO2 reduction is not catalytic process since ∆G for this process is positive

• Still this strict definition is ignored conventionally called artificial photosynthesis but this is also not appropriate.

• Photo-catalysis is not a precise term but we still refer by this term

414

• Nearly 40 years of research

• Still only tens of micromoles/hour

• The first report is by Inoue et al ,Nature,277,637-8(1979).

• In this presentation we shall deal with the process of photo-catalytic reduction of CO2, methods to quantify the efficiency(this is required to compare the results of different groups and possibly see the photo catalytic systems studies, oxides, sulphides and phosphides

415

Photoinduced formation of an electron–hole pair in a semiconductor with possible decay paths. A=electron acceptor, D=electron donor. 416

Transfer of a photo generated electron from a semiconductor to the

acceptor molecule via the metal co-catalyst.

417

Thermodynamic constraints on the transfer of charge carriers to the adsorbed molecules.

DE represents the kinetic over potential of the reduction process

418

Conduction band, valence band potentials, and band gap energies of various semiconductor

Photo-catalysts relative to the redox potentials at pH 7 of compounds involved in CO2

reduction.419

CO2 + 2H+ + 2e → HCOOH E0 redox = -0.61 V (1)

CO 2 + 2H + + 2e → CO + H2O E0redox -0:53 V (2)

CO 2 + 4H + + 4e → HCHO + H2 O E0redox= - 0.48 V (3)

CO2 + 6H + + 6e → CH3OH + H2 O E0 redox= - 0.38 V (4)

CO2+ 8H + + 8e → CH4 + 2H2O E0redox = -0.24V (5)

2H+ + 2e → H2 E0Redox = -0.41V (6)

420

Exact steps of CO2 reduction is stillnot clear. All we know is the product formed by a variety of analytical techniques GC, Ion, IR,EPR,AES,PESradical speciesCO2 linear Dȹh electrophilic carbon bends C2v symmetry contributes to the high value of LUMO and low electron affinityCO2 + e → CO2

._ E0redox= -1.90V no SC

provides sufficient potential to place the electron in LUMO level this step improbable

421

Subsequent proton assisted transfer is a feasible the energy is similar to proton reduction though it is a single electron process-potential is less negative with respect to conduction band of SC making these reactions feasible.

422

Now there are various questions left unansweredthey are if the barrier is so high how is it that one observes reduced CO2 species like CO, HCOOH, CH3OH and CH4. we are attempting answers but one need to realize these are only imaginations at present

423

1. Is the LUMO level of CO2 is altered in the adsorbed state?2. if this is true to what level this alteration can occur?3. on what type of sites this reduction in the energy of LUMO level of CO2 can take place and the questions are endless like this

424

Let us imaginatively look one or two possible adsorption modes for CO2 on semiconductor surfacesIt is known that CO2 adsorption on stoichiometric defect free TiO2 is not strong enough so the LUMO level alteration can not take place on this surface

425

Let us first consider a anion defectanatase surface. On this surface ifCO2 were to be adsorbed throughoxygen then it can lower the barrierand give rise to the dissociation ofCO2 to give rise to CO and theoxygen released can fill (heal) thevacancy

426

Another mode is since there is an oxygen ion vacancy will be the two titanium ions giving rise to a bidentatespecies with the oxygen atoms of CO2

This is another possibility

427

We have also shown many modes of CO2 adsorption in the previous presentations one is requested to reflect back on those modes of adsorption of CO2 through carbon atom or carbon atom and one oxygen atom or other modes.

428

In the case of metal loaded SC can also be a facile situation not only for the appropriate adsorption centre for CO2 but also for the facile transfer from the d state of metal to the pi* orbitalwe have also repeatedly considered that step sits can be suitable for CO2 adsorptionpresence of metal can not only facilitate the first electron transfer but can also facilitate subsequent steps

429

Dipolar character of the solvent can also reduce the barrierthe conduction band position can also be altered by the pH E0 = E0(pH=0)-0.06pH not only the conduction band edge the electrochemical potential of the reduction steps 1-6 are also affected by pH

430

Other interactions are also relevantwith water it can give rise to carbonic acid which in alkaline medium give bicarbonate species and thus they may facilitate the electron transfer stepsdifferent forms of CO2 adsorbed and hence different reduction pathsin non aqueous solutions proton adsorption of proton on SC alters the conduction band edge. In protic solvents the conduction band edgeis more positive than in aprotic solvents like acetonitrile or DMF

431

In water decomposition both gets equal attention in CO2 the reduction step appears to be importantso more difficult and complexthis means oxygen evolution may still take place but it is a process involving four holes and hence oxygen evolution appears to be not a facile process in water decompostion

432

This surface oxygen species can also oxidise the reduced species and thus account for the various productsthis science is called the sacrificial agents like TEOA, TEA or alcohols

433

Tertiary amines form a charge transfer complex like CO2

-. And TEA.+ and this charge transfer complex activates the CO2 this is the reason why pyridine CO2

adduct ( liquid light) and also Bacorsly work which we have already discussed

434

Reflections on Heterogeneous Photo-Catalysis

19th April 2014

435

The Purpose of this presentation1.How to unify the activity data2. Photo-reduction of CO2 on SC3. Some clarity on TiO2based systems

436

Measures of Efficiency1.Photocatalysis is a complex process2. no single measure of efficiency3. Amount of catalyst or intensity of illumination

4. same scale as Heterogeneous catalysis

437

Catalyst based Measures1.Amount of product formed per time or per amount of catalyst that is R = [product]/time [catalyst]cascade of reactions omission of products H2 formation is a competing reaction how to include thisproduct accumulation does not vary systematically -saturation curve with sacrificial agent – start time is ill defined start of illumination or burst of product – burst is due to carbon residue and not due to CO2

in fact it should start after the burst- steady state for comparisonamount of the catalyst if co catalyst is used Light intensity effectTONTOF = 1/Na(dN/dt)active site poorly defined surface area, TO rateTurn overs are independent of Photon flux and hence inadequate

438

Light based Measuresphoton efficiency multiple electron multiple photocatalytic eventsphotocatalystic efficiency =

φ = Nproduct events/Nadsorbed photons

N = ΣniMi

Photonic efficiency, or external quantum efficiency or IPCE does not take into account of the amount of catalyst light source

power conversion efficiency = η = ΣiΔH0C,Iri/P

439

Photo-reduction of CO2 on Semiconductorssmall band gap use large portion of solar radiationoxides most of them VB oxygen wave function and CB metal and hence large band gapred shift dyes(Ru based, organic) coupled SC extend absorption edge LUMO of dye, orientation, distance of the light absorbing unit with respect to surfacesize or fluxibility of the anchoring unit

440

SensitizationDoping, to create intra band states or by forming solid solutions (raise VB) impurity states oxygen vacancyCo catalyst, role of nanostructure and crystallographic properties

442

Photo-catalytic Properties of TiO2

444

Category best

possibility

co-catalyst Major

product

Rmax

P-25 in suspension particle - CH3OH 3.4

Anatase particle - CH4 0.4

TiO2 in propanol particle - HCOOH 1.2

TiO2 SC fluid particles - CH4 1.8

Sensitized TiO2 Ag/TiO2 Ag CH4, CH3OH 10.5

Sensitized TiO2 Cu,, Pd Cu or Pd CH3OH, CH4 0.3 to 1602

TiO2 Pellets CH4 0.22

Ti-MCM41,48,SBA15 CH4 106

optical fibre coated

TiO2

Ag,Cu, Cu-Fe Co, CH4 0.5 to 17.5

TiO2 nanorods TiO2/Pt Pt CH4 6

TiO2 on zeolites Pt CH4 0.3 to 12.3

Titania based photocatalytic systems for CO2 reductionRmax in micromoles per gram per hour.

445

Reproduced from Nature materials, 12,798-801 (2013)

447

a,b, Comparison of the total and ion-decomposed electronic density of states of anatase (a) and rutile (b) TiO2 calculated using the HSE06 hybrid density functional

Reproduced from Nature materials, 12,798-801 (2013)

448

Figure 3: Band alignment between rutile and anatase from XPS and QM/MM

Graphic of the hybrid QM/MM cluster used for rutile in the positive charge state. The cluster is divided into hemispheres to highlight the different regions in the model. Hole density iso-surfaces are shown (semi-transparent purple) in the QM region b)Schematic QM/MM alignment of rutile and anatase c) Ti 2p spectra1:1,2:1,1:2 d) Schematic of the XPS alignment between anatase and rutile,

Reproduced from Nature materials, 12,798-801 (2013)449

25NMAT25

Semiconductor state band gap co catalyst Major product

ZnS nano 3.66 Cd2+, Zn2+ HCOOH

CdS Nano 2.4 Cd2+ Co

MnS particle 3.0 - HCOOH

Bi2S3/CdS Particle .28 - CH3OH

CuxAgyInzZnkSm nano 1.4 RuO2 CH3OH

CUzZNSnS4 photocatalyst 1.5 Ru Comples HCOOH

WO3 crystals 2.79 - CH4

W8O49 Nanowires 2.7 CH4

ZrO2 particle 5-.0 Cu CO

SrTiO3 particle 3.2 Pt CH4

BaTiO3 particle 3.2 HCOOH

K2Ti6O13 particle >3.0 Pt CH4

BaLa4Ti4O15 particle 3.8 Ag CO

KNbO3 sintered particle 3.1 Pt CH4

NaNbO3 crystal 3.29 Pt CH4

LiNbO3 Particle 3.6 HCOOH

N-Ta2O5 nano 2.4 Ru-dcbpy HCOOH

BiVO4 crystals 2.24 C2H5OH

Bi2WO6 nano 2.75 CH4

InTaO4 particle 2.6 NiO CH3OH

N-InTaO4 sintered particle 2.28 Ni,NiO CH3OH

InNbO4 sintered particle 2.5 NiO CH3OH

Zn2GeO4 mesoporous 4.5 Pt CH4

Zn2SnO4 nano 3.87 Pt, RuO2 CH4

beta-Ga2O3 mesoporous 4.9 CO

ZnGa2O4 mesoporous 4.4 RuO2 CH4

CuCaO2 sintered particle 2.6 CO

p-GaP pathocathode 2.3 Pyridine CH3Oh

p.InP photocathode 1.35 Ry complex HCOOH

HNb3O8 nanobelts 3.66 - CH4

454

Why do we search for alternate SC?1.To alter the VB and CB – to decrease Eg reductive power2. quantum efficiency, exciton life time SA, active sites

455

SulphidesVB 3p level of S narrow band gapnot stable oxidise S2-

ZnS ECB= 1.85VCdS 2.4 eV ECB=-0.9V COMnS 3.0 eVBi2S31.28 eVCuxAgyInzZnkSmZnS + Cu2S+ AgInS2 1.4 eVCu2ZnSnS4 1.5 eV ECB=-1.3 V

456

Formation routes are not yet clearnew materialschemical pathway selectivityefficiency formation rate/photonic efficiencyalternate for activity scalesacrificial e donor short termcommercial scale materialsseparation of two half reactionsnot yet ready to implement

457


20th presentation

24th April 2014

458

Few Humble Suggestions

• As we are nearing our completion of this course, you need to consolidate and formulate your suggestions and questions.

• While we are thankful and grateful for your participation, we also hope that we have not wasted your time and energy in this on line course

• We do propose to start another on line course soon and there are few suggestions available with us if you have any alternate suggestions please provide us information on that

459

What do we intend to cover in this presentation?

• Analysis protocol

• Why combine water oxidation and CO2 reduction

• Conceptual fuel cell

• Catalytic cycles

• Relation to Photosynthesis

• TiO2 why this system is preferred

460

The coverage today….?Even though we have said many things in 19th presentation

in the 20th presentation we shall concentrate only on the analysis of reaction system for photo-catalytic reduction of CO2 only due to time limitations.

Why this is so?

Analysis is the crucial for (i) the comparison of activity (ii) design of catalyst system (iii) the scale to be developed (iv) even for the basic understanding of the process itself.

461

Limitations ?

• Only certain analytical methods have been tested and established

• Interferences are not clearly known till now though it is realized.

• Preferential analytical methods why?

• Unconventional analytical methods why are they not yet fully found use?

• Some answers …….

462

Photo-catalytic reduction of carbon dioxide: product analysis and systematics

Jindui Hong, Wei Zhang, Jia Ren and Rong XuAnal Methods, 5, 1086-1097 (2013)some basic ideas are borrowed from this reference and few others (needs critical evaluation) are generated in this presentation.

463

CO2 to Chemicals is a complex situation as already mentioned multi-electron process in the gas phase range from CO, methane to higher HC liquid phase alcohols, aldehydes, carboxylic acids and so on

465

various

Various tabulations have been already given this is

also one of them466

1.Can one detect the most likely products accurately? How to identify the product from carbon contamination.2. organic additives affect the product analysis?sacrificial agents, solvents, photo-catalysts, sensitizers homogeneous molecular

systems.3. Do the detected products truly originate from the reduction of CO2

467

Gaseous Products CO methanehigher hydrocarbons and un-reacted carbon dioxide TCD and FID analysis, column contamination, needing frequent regeneration of the column

468

Liquid ProductsGC, GC-MS,HPLC,IEC,UV (colorimetric)

470

Aldehydes colorimetricTCD/FID ( only higher concentration with respect to alcohols)HCHO lower aldehydes HPLC derivatization

472

Carboxylic AcidsGC, NMR,IEC, HPLC

473

Gas and liquid phase low concentration by GC and HPLCorganic additives solvents sensitizers sacrificial agentsalcohol sensitive to organic additivesaldehydes and acid analyses by HPLC are not affected by organic additives DRIFT, NMR and GC MS

475

Major products in both liquid and gas phases from CO2 photoreduction can be detected

accurately with low detection limits by a combination of GC and HPLC methods.

Fig. summarizes the analysis methods and the detection limits of the major chemical

species in both gas and liquid phases in the absence of organic additives. The effects of

several organic additives including commonly used solvents, photosensitizers

and sacrificial reagents in photoreaction were investigated. It has been found that

alcohol analysis by GC methods is more sensitive to organic additives while aldehyde

and acid analyses by HPLC methods are not affected by most of the organics

investigated. The importance of carbon source verification is highlighted and

several techniques such as DRIFT, NMR and GC-MS can be used.

Anal. Methods, 2013, 5, 1086–1097 476

Concept of a fuel cell supplied with hydrogen and oxygen (or air) that converts

chemical energy to electricity. The solar fuel cell uses light to separate holes and

electrons that oxidize water and reduce protons, respectively. Source: Lewis and Nocera

[9]. Copyright (2007) National Academy of Sciences, USA. 477

Combination of water oxidation catalyst and the reduction of protons to H2 or CO2 to fuels. The

reduction is promoted as a result of charge separation under light irradiation. The reduction

catalyst might be assembled on an electrode, a suspension of nanoparticles, or conducting organic

or inorganic membranes capable of directing charge transport. From Hurst [7].

Reprinted with permission from AAAS. 478

Feasibility test of a fuel cell consisting of a TiO2 photocatalyst for methanol oxidation, a Pt

catalyst for the production of H2, and an H+-conducting polymer between them. Copyright

(2009) American Chemical Society. 479

1. Masakazu Anpo, Photocatalytic reduction of CO with H2O on highly dispersed Ti-Oxide

catalysts as a model of artificial photosynthesis, Journal of CO2 utilisation 1, 8-17 (2013).

2. Rakshit Ameta, Shikha Panchaol, Noopur Ameta and Suresh C.Ametal, Photo-catalytic

reduction of carbon dioxide, Materials Science Forum Vol. 5, 83-96 (2013).

3. Yucheng Lan, Yalin Lu, and Zhifeng Ren, Mini Review on Photo-catalysis of titanium dioxide

nanoparticles and their solar applications, Nano Energy, 2,1031-1045 (2013).

4. Jeffrey C.S.Wu and Hung-Ming Lin, Photo-reduction of CO2 to methanol via TiO2 photo-

catalyst, International Journal of Photoenergy, Vol.7.115-119 (2005).

5. Richard Reithmeier, Christian Bruckmeier and Bernhard Rieger, Conversion of CO2 via visible

light promoted Homogeneous redox catalysis, catalysts, 2, 544-571 2012).

6. Kihsuke Mori, Hiromi Yamashita and Masakazu Anpo, Photo-catalytic reduction of CO2 with

water on various titanium oxide photo-catalysts, RSC Advances, 2, 31165-3172 (2012).

7. Shifwru Kohtani, Eito Yoshioka and Hideto Miyabe, Photo-catalytic hydrogenation on

semiconductor particles, Intech, Chapter 12,291-307 (2012).

8. Yasuo Izumi, Recent advances in the photo-catalytic conversion of carbon dioxide to fuels with

water and/or hydrogen using solar energy and beyond, Coordination Chemistry Reviews, 257,

171-186 (2013).

9. Jindui Hong, Wei Zhang, Jia Ren and Rong Zu, Photo-catalytic reduction of CO2: a brief

review on product analysis and systematic methods, Analytical methods, 5, 1086-1097 (2013).

10. Severin N. Habisreutinger, Lukas Schmidt-Mende, and Jacek K. Stolarczyk, Photo-catalytic

Reduction of CO2 on TiO2 and Other Semiconductors, Angewante Chemie, 52, 7372-7408

(2013).

485

CO2 to chemicals and Fuels

21st presentation

28th April 2014

486

Reproduced from Yasuo Izumi, Coordination chemistry Reviews, 257,171 (2013)

487

Thermo-chemical conversion of CO2

• 4.3 X 1020 joule per hour

• 4.7 X 1016 joules per hour 9200 hours

• 2MoO2 → 2MO2- δ + δO2(g)

• δH2O + 2MO2- δ → MO2 + δH2(g)

• δCO2 + 2MO2- δ → MO2 + δCO(g) (where M is Ce, Zn,) Fe

• CO2 with water to methanol and oxygen is +689kJ/mol

• Water to hydrogen and oxygen is 457.2 kJ/mol.

488

What do we intend to cover in this presentation?• Analysis protocol Brief see for details 20th

• Why combine water oxidation and CO2 reduction

• Conceptual fuel cell

• Catalytic cycles

• Relation to Photosynthesis

• TiO2 why this system is preferred

• The presentation today are based on the references given at the end and these are already available with you all.

489

Few Humble Suggestions

• As we are nearing our completion of this course, you need to consolidate and formulate your suggestions and questions.

• While we are thankful and grateful for your participation, we also hope that we have not wasted your time and energy in this on line course

• We do propose to start another on line course soon and there are few suggestions available with us if you have any alternate suggestions please provide us information on that

490

1. Masakazu Anpo, Photocatalytic reduction of CO with H2O on highly dispersed Ti-Oxide catalysts as a model of artificial

photosynthesis, Journal of CO2 utilisation 1, 8-17 (2013).

2. Rakshit Ameta, Shikha Panchaol, Noopur Ameta and Suresh C.Ametal, Photo-catalytic reduction of carbon dioxide,

Materials Science Forum Vol. 5, 83-96 (2013).

3. Yucheng Lan, Yalin Lu, and Zhifeng Ren, Mini Review on Photo-catalysis of titanium dioxide nanoparticles and their solar

applications, Nano Energy, 2,1031-1045 (2013).

4. Jeffrey C.S.Wu and Hung-Ming Lin, Photo-reduction of CO2 to methanol via TiO2 photo-catalyst, International Journal of

Photoenergy, Vol.7.115-119 (2005).

5. Richard Reithmeier, Christian Bruckmeier and Bernhard Rieger, Conversion of CO2 via visible light promoted

Homogeneous redox catalysis, catalysts, 2, 544-571 2012).

6. Kihsuke Mori, Hiromi Yamashita and Masakazu Anpo, Photo-catalytic reduction of CO2 with water on various titanium

oxide photo-catalysts, RSC Advances, 2, 31165-3172 (2012).

7. Shifwru Kohtani, Eito Yoshioka and Hideto Miyabe, Photo-catalytic hydrogenation on semiconductor particles, Intech,

Chapter 12,291-307 (2012).

8. Yasuo Izumi, Recent advances in the photo-catalytic conversion of carbon dioxide to fuels with water and/or hydrogen

using solar energy and beyond, Coordination Chemistry Reviews, 257, 171-186 (2013).

9. Jindui Hong, Wei Zhang, Jia Ren and Rong Zu, Photo-catalytic reduction of CO2: a brief review on product analysis and

systematic methods, Analytical methods, 5, 1086-1097 (2013).

10. Severin N. Habisreutinger, Lukas Schmidt-Mende, and Jacek K. Stolarczyk, Photo-catalytic Reduction of CO2 on TiO2

and Other Semiconductors, Angewante Chemie, 52, 7372-7408 (2013).

491


492


493


494


495


497


498


499

CO2 TO CHEMICALS AND FUELS

22ND PRESENTATION

ON 1ST May 2014

Time 5.30 p.m.(most probably)

Kindly Note the Change in Time of Presentation

500

The coverage1.Why TiO2 receives maximum attention?Upto 70 only upto 50 paper per year2012-13 over 10000 papers per year 2. Bulk and isolated Ti-O polyhedron –behaviour3. Are we ready for uniform activity scale?4. Other possibilities (i) production of chemicals (ii) environmental protection(iii) fuel production

501

Photocatalytic reduction of CO2 with H2O on various titanium oxide

photocatalysts by Kohsuke Mori, Hiromi Yamashita and Masakazu Anpo, RSC

Adv., 2,3165-3172 (2012)

502

http://www.chemspider.com/Chemical-Structure.937.html

Photocatalytic reduction of CO2 with H2O on various titanium oxide photocatalysts

by Kohsuke Mori, Hiromi Yamashita and Masakazu Anpo, RSC Adv., 2,3165-3172

(2012) 503




Adv., 2,3165-3172 (2012)

504




Adv., 2,3165-3172 (2012) 505




Adv., 2,3165-3172 (2012) 506


Aaron M. AppelJohn E. BercawAndrew B. BocarslyHolger

DobbekDaniel L. DuBois*Michel DupuisJames G. FerryEtsuko

FujitaRuss HillePaul J. A. Kenis Cheryl A. KerfeldRobert H.

MorrisCharles H. F. PedenArchie R. Portis Stephen W.

Ragsdale*Thomas B. Rauchfuss*¶Joost N. H. ReekLance C.

SeefeldtRudolf K. ThauerGrover L. Waldrop,

Frontiers, Opportunities, and Challenges in Biochemical and

Chemical Catalysis of CO2 Fixation, Chemical Reviews, 113,6621-

6638 (2013)

522

http://pubs.acs.org/action/doSearch?action=search&author=Appel,+A+M&qsSearchArea=author

http://pubs.acs.org/action/doSearch?action=search&author=Bercaw,+J+E&qsSearchArea=author

http://pubs.acs.org/action/doSearch?action=search&author=Bocarsly,+A+B&qsSearchArea=author

http://pubs.acs.org/action/doSearch?action=search&author=Dobbek,+H&qsSearchArea=author

http://pubs.acs.org/action/doSearch?action=search&author=DuBois,+D+L&qsSearchArea=author

http://pubs.acs.org/action/doSearch?action=search&author=Dupuis,+M&qsSearchArea=author

http://pubs.acs.org/action/doSearch?action=search&author=Ferry,+J+G&qsSearchArea=author

http://pubs.acs.org/action/doSearch?action=search&author=Fujita,+E&qsSearchArea=author

http://pubs.acs.org/action/doSearch?action=search&author=Hille,+R&qsSearchArea=author

http://pubs.acs.org/action/doSearch?action=search&author=Kenis,+P+J+A&qsSearchArea=author

http://pubs.acs.org/action/doSearch?action=search&author=Kerfeld,+C+A&qsSearchArea=author

http://pubs.acs.org/action/doSearch?action=search&author=Morris,+R+H&qsSearchArea=author

http://pubs.acs.org/action/doSearch?action=search&author=Peden,+C+H+F&qsSearchArea=author

http://pubs.acs.org/action/doSearch?action=search&author=Portis,+A+R&qsSearchArea=author

http://pubs.acs.org/action/doSearch?action=search&author=Ragsdale,+S+W&qsSearchArea=author

http://pubs.acs.org/action/doSearch?action=search&author=Rauchfuss,+T+B&qsSearchArea=author

http://pubs.acs.org/action/doSearch?action=search&author=Reek,+J+N+H&qsSearchArea=author

http://pubs.acs.org/action/doSearch?action=search&author=Seefeldt,+L+C&qsSearchArea=author

http://pubs.acs.org/action/doSearch?action=search&author=Thauer,+R+K&qsSearchArea=author

http://pubs.acs.org/action/doSearch?action=search&author=Waldrop,+G+L&qsSearchArea=author

CO2 TO CHEMICALS AND FUELS

23rd PRESENTATION

ON 5th May 2014

Time 4.30 p.m.

524

What do we deal with……

• What and why other semiconductors are used for the PCR reaction? Position of CB and VB relevance absorption, sensitization mobility

• Sulphides, nitrides, phosphides band structure are they favourable

• How to modulate VB without affecting CB? why?

• Sensitization any new logic possible or be content with the logic pursued?

525

Some critical issues CB slightly negative- VB more positive-absorption limited - sensitization did not address the issues - localized mobility restricted

526

TiO2

Anatase,(tetragonal) rutile (tetragonal), Brookite(orthorhombic) and monoclinic TiO2

TiO6orthorhombic distortionTi_Ti distance vertices, edgesCB 0.2 above for anatase 10 ns 90% recombination free energy of formation 15kJ lower for anataserecombination rate lower for anataseP25 degussa Evonik trap states

527

Metal oxideschalcogenidesNitridesPhosphidesBand structuresulphides 3p VB-moves upsulphide to sulphur and sulphatesulphite, thio and hypophosphite

528

1) raising the valence band energy to decrease the

band gap;

2) moving the conduction band to more reductive

potentials;

3) improving the quantum efficiency of exciton

formation

and reducing charge recombination; and

4) using novel nanoscale morphologies to provide a

large surface area with multiple photocatalytically

active sites

536

4.0 eV

NaTaO3AgTaO3

3.4 eV

O 2p and Ag 4d

NaNbO3AgNbO3

2.8 eV

Ta 5d Nb4d

O 2p and Ag 4d

537

Semiconductor state band gap co catalyst Major product

ZnS nano 3.66 Cd2+, Zn2+ HCOOH

CdS Nano 2.4 Cd2+ Co

MnS particle 3.0 - HCOOH

Bi2S3/CdS Particle .28 - CH3OH

CuxAgyInzZnkSm nano 1.4 RuO2 CH3OH

CUzZNSnS4 photocatalyst 1.5 Ru Comples HCOOH

WO3 crystals 2.79 - CH4

W8O49 Nanowires 2.7 CH4

ZrO2 particle 5-.0 Cu CO

SrTiO3 particle 3.2 Pt CH4

BaTiO3 particle 3.2 HCOOH

K2Ti6O13 particle >3.0 Pt CH4

BaLa4Ti4O15 particle 3.8 Ag CO

KNbO3 sintered particle 3.1 Pt CH4

NaNbO3 crystal 3.29 Pt CH4

LiNbO3 Particle 3.6 HCOOH

N-Ta2O5 nano 2.4 Ru-dcbpy HCOOH

BiVO4 crystals 2.24 C2H5OH

Bi2WO6 nano 2.75 CH4

InTaO4 particle 2.6 NiO CH3OH

N-InTaO4 sintered particle 2.28 Ni,NiO CH3OH

InNbO4 sintered particle 2.5 NiO CH3OH

Zn2GeO4 mesoporous 4.5 Pt CH4

Zn2SnO4 nano 3.87 Pt, RuO2 CH4

beta-Ga2O3 mesoporous 4.9 CO

ZnGa2O4 mesoporous 4.4 RuO2 CH4

CuCaO2 sintered particle 2.6 CO

p-GaP pathocathode 2.3 Pyridine CH3Oh

p.InP photocathode 1.35 Ry complex HCOOH

HNb3O8 nanobelts 3.66 - CH4

538

CH4 generation over a) Zn1.7GeN1.8O, b) 1 wt% Pt-loaded Zn1.7GeN1.8O, c) 1 wt% RuO2-loaded Zn1.7GeN1.8O, and d) 1 wt% RuO2 and 1 wt% Pt co-loaded Zn1.7GeN1.8O as a function of irradiation times with visible light.

539

Perspectiveonly tens of micromoles/ghigh over potential and first electron transfer rate controllingvarious possibilities measure combine or evolve newsacrificial agents not feasibleseparation of two half reactionshybrid PEC and PCnot yet to implement but can become

540

CO2 to Chemicals and FuelsBiochemical routes for CO2

reduction –an Introduction 24th Presentation8th May, 20144.30 p.m.

541

Biochemical fixation of CO2C-O bond length short 0.116 nm IP 13.6 eV (water 12.6 ammonia 10)

Carbon localized LUMO nucleo-phile and susceptible for reduction frontier orbitals

Localized wave function LUMO bent mode alone multiple electron reduction possible

542

Biochemical reduction of CO2 C-O bond cleavage C-C and C-H bond formation billion of years enzyme processes2008 Bell report identifies “the processes to convert carbon dioxide to energy bearing products is the lack of catalysts”

Living organisms have evolved methods to interconvert energy from variety of sources especially from environment- own method for alcohols ammonia etc energy by chemical bonds

543

Can learn from metabolic processesEnzyme structure molecular speciesproton reduction to hydrogen

544

Hydrogenase –2H+ + 2e H2 organometallic sites two iron sitesFe-Ni or Fe-guanylpyridinol cofactor (1,2 and 3)

545

Carbonyl or thiolate CN ligandmetalloenzymes – low spin complexes strong ligands ligand field- similar systems at negative potentials base line for structure/activity relations

546

Ligand dithiolate two distant Fe atoms amine

547

Henry constant is 29.76 atm (mol/L) at 293 K that is 0.033 mole at 1 atm compare hydrogen, nitrogen and oxygenhydration eq.constant 1.7 X 10-3

H2CO3 pka 3.6

549

Six pathways fixing inorganic carbon in organic material used for cell biomassThe reductive pentose phosphate (Calvin-Benson-Bassham cycle predominat mechanism plants fix CO2

550

Another rcycle is the reductive citric acid cycle

552

Six pathways fixing inorganic carbon in organic material used for cell biomassThe reductive pentose phosphate (calvin-Benson-Bassham cycle predominat mechanism plants fix CO2

553

Four of the five CO2 fixation8H ++ 8e + 2CO2 + HSCoA → Acetyl-CoA + 3H2O acetyl-CoA bacteria and methonogenic archaea anabolic (biosynthesis) or catabolic (energy)purposes two reduction steps to formate and to CO.

554

Another cycle is the reductive citric acid cycle also known as reductive TCA and Arnon-Buchanan cycle

556

dicarboxylate 4-hydroxybutyrate cycle3-hydroxypropionate/4-hydroxybutyrate cycle3-hydroxy propionate bicycle10H+ + 10e +3CO2 → pyrivic acid and 3H 2O

557

Structure of the active site of the [FeFe] hydrogenase with simplified depiction of the associated connectivity for electron,

hydrogen, and proton transport.

Published in: Aaron M. Appel; John E. Bercaw; Andrew B. Bocarsly; Holger Dobbek; Daniel L. DuBois; Michel Dupuis; James G. Ferry; Etsuko

Fujita; Russ Hille; Paul J. A. Kenis; Cheryl A. Kerfeld; Robert H. Morris; Charles H. F. Peden; Archie R. Portis; Stephen W. Ragsdale; Thomas B.

Rauchfuss; Joost N. H. Reek; Lance C. Seefeldt; Rudolf K. Thauer; Grover L. Waldrop; Chem. Rev. 2013, 113, 6621-6658.

DOI: 10.1021/cr300463y

Copyright © 2013 American Chemical Society

558

Wave function iso-probability contours for the highest occupied molecular orbital (HOMO) (left side panel) and lowest

unoccupied molecular orbital (LUMO) (right side panel) of bent CO2. The surfaces illustrate the strong charge localization

associated with these frontier orbitals.




DOI: 10.1021/cr300463y


559




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560

Ball-and-stick drawing of the active site of [NiFe] CO dehydrogenase.




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563




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565




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568

Methanogenesis to methane 8 electron to methyltetrahydrofolate Wood Ljungdahl processCO dehydrogenases formate dehydrogenasesCODH high TON for CO oxidation CO2 reduction [Fe4S4Ni] soft and hard bimetallic sites Ni-Fe cooperative interaction

569

• Ni-C=O… histine

• │

• Ly. O – Fe

• [MoCu] CO dehydrognease

• MoW formate dehydrogenase

• Oxygen sensitive

• W(IV) and Mo(IV) S ligand

570

CO2 to Chemicals and Fuels 25th & concluding Presentation12th May, 20144.30 p.m.Thanks to all the participants for the continued support

571

This being the concluding presentation on this topic and NCCR wishes all participants all success on their research endeavours and NCCR also hopes that its maiden attempt to reach the research scholars of this country possibly yielded some semblance of result

572

The Purpose1. To test -on line course by NCCR2.To assess - in a frontier area 3.To be as meaningful as possible4. To summarise day to day activity5. To instil some excitement

whether any semblance of success …?

573

ORIGINAL OBJECTIVES OF THE COURSE1. To review the literature in this area2. To identify the issues where knowledge is not yet complete and why this process is not yet feasible?3. To outline the issues where further knowledge

domain has to be evolved.4. To evolve an on line complete course for NCCR on a frontier research topic5. To make available in a single place the necessary documentation on this important topic

Have we achieved all of them or not is up to you to

judge?

574

Coverage AttemptedIn view of the vast literature,the course attempted only a tiny portion of this areaIt attempted to look at the status of CO2 to chemicals and fuels.In this also restricted to chemical, electrochemical, photo-catalytic and to a small extent biochemical methods

575

The General Questionssome of them only1. Is there promise to make this process viable?2. Chemical process How & what stage are they?3. Electrochemical pathway? What is the situation-only metals or other electrodes possible?4. Photo-catalytic or hybrid process which one and why?5.Biochemical - only for lessons to be learnt or more?

576

Some Specific Questions….1. Analytical methods2. Energetics3.Quantitative measure4. Formulation guidelines

577

We have some analysis Issues1.Major ones is the interferences2. Appropriate Analytical Method3. How to resolve these issues and what is the way forward?

581

Some issues on electro-catalytic reduction of carbon dioxide1. Metal systems are grouped in four groups – is this the best possible classification2. Is there any possibility of generating new and composite electrode systems for this reaction?3. The scope of electro-catalytic process?

582

Chemical Processes

The presentation was based on specific products obtainable is there alternate ways of synthesis of this knowledge?

What is the future of chemical routes for CO2

reduction-only product based or process based?

583

Some Data on our on line Course – informationTotal life time view 662Average view 26 per presentationLast month alone 263last month 1142 MinsIndia, USA, Turkey, Egypt and UK

586

Presentation Date Views Total mins

CO2 to chemicals and fuels(34) April-14 13(4.9%) 112

CO2 to chemicals and fuels (25) April-18 13 (4.9%) 36




CO2 to chemicals and fuels (33) May-1 17(6.5%) 97

CO2 to chemicals and fuels(37) May-5 25(9.5%) 182

Table: Some typical presentations

587

Adopted from Aerosol and air quality research, 14, 533-549 (2014)

588

Turning carbon dioxide into fuel

Z. Jiang, T. Xiao, V. L. Kuznetsov and P. P. Edwards, Phil. Trans. R. Soc. A 28 July

2010 vol. 368 no. 1923 3343-3364 see all the references in this paper

591

http://rsta.royalsocietypublishing.org/search?author1=Z.+Jiang&sortspec=date&submit=Submit

Turning carbon dioxide into fuel, Z. Jiang, T. Xiao, V. L. Kuznetsov and P. P.

Edwards, Phil. Trans. R. Soc. A 28 July 2010 vol. 368 no. 1923 3343-3364 592



Edwards, Phil. Trans. R. Soc. A 28 July 2010 vol. 368 no. 1923 3343-3364

593


Any suggestions for the plausible mechanism of

the shape evolution of {001} facets TiO2 particles

with increase in hydrothermal time?

Is it time to think other catalyst than

TiO2 for water splitting?

596

https://email.iitm.ac.in/owa/redir.aspx?C=Yctfy5jBDEWXu0UxBLFvg4nU_SI3QdEIob7tMwnhdvujtllvIcXxLBkg-2OEtbNJfVAgkBODB9M.&URL=http://www.researchgate.net/post/Any_suggestions_for_the_plausible_mechanism_of_the_shape_evolution_of_001_facets_TiO2_particles_with_increase_in_hydrothermal_time?pli%3d1%26loginT%3da1i1fcQ7V6KttX5wqGob8ipFAETMEEedV5m5Rzm8uqA*%26uid%3da83e26a1-d649-4fa0-a0f8-667f7d760216%26cp%3dre221_b1m_p32%26ch%3dreg

THANK YOU ALL FOR PARTICIPATING

THIS COURSE

597

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55) Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on

56) Climate Change, Cambridge University Press, New York, 2007.

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65) E. Vesselli et al., J. Am. Chem. Soc., 2008, 130, 11417.

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68) Y. Hori. Electrochemical CO2 reduction on metal electrodes, in Modern Aspects of

69) Electrochemistry, Vol. 42, chapter 3, pp. 89–189, Springer, New York, 2008.

70) A.A. Peterson et al., Energy Environ. Sci., 2010, 3, 1311–1315

71) Savéant, J.-M. Chem. Rev. 2008, 108, 2348.

72) DuBois et al. Acc. Chem. Res. 2009, 42, 1974

73) New and Future Developments in Catalysis (Editor Suib,S.L.), Elsevier 2013 Activation of

Carbon dioxide one chapter on “ELECTRO-CATALYTIC REDUCTION OF CARBON

DIOXIDE”

74) Electrochemical reduction of carbon dioxide on ¯at metallic cathodes, JOURNAL OF

APPLIED ELECTROCHEMISTRY 27 (1997) 875-889

75) A review of catalysts for the electro-reduction of carbon dioxide to produce low-carbon

fuels, Chem. Soc. Rev., 2014,43, 631-675.

76) A selective and efficient electro-catalyst for carbon dioxide reduction, Nature

communications, January 2014 ( already discussed in one of the presentations)

77) Future challenges in CO reduction, University of Bremen October 2012.

78) Electrocatalytic Reduction of CO2 to Small Organic Molecule Fuels on Metal Catalysts,

Wenzhen Li, 2010

79) B. Viswanathan Indian Journal of Chemistry A 51, 166 (2012).

80) Gabriele Centi and Siglinda Perathoner,Catalysis Today, 148, 191 (2009)

81) Kendra P. Kuhl,a Etosha R. Cave,b David N. Abramc and Thomas F. Jaramillo, Energy

Environ. Sci., 2012, 5, 7050

82) William J.Durand, Andrew A.Peterson, Felix Studt, Frank Abild-Pederson, Jens

K.Norskov, Structure effects on the energetics of the electrochemical reduction of CO2 by

copper surfaces, , surface Science, 605,1354-1359 (2011).

83) Seshadri, G.; Lin, C.; Bocarsly, A. B. A new homogeneous electrocatalyst for the reduction

of carbon dioxide to methanol at low overpotential. J. Electroanal. Chem. 1994, 372, 145-

50.

84) Barton, C. E.; Lakkaraju, P. S.; Rampulla, D. M.; Morris, A. J.; Abelev, E.; Bocarsly, A. B.

Using a One-Electron Shuttle for the Multielectron Reduction of CO2 to Methanol: Kinetic,

Mechanistic, and Structural Insights. J. Am. Chem. Soc. 2010, 132.

85) Morris, A. J.; McGibbon, R. T.; Bocarsly, A. B. Electrocatalytic carbon dioxide activation:

The rate-determining step of pyridiniumcatalyzed CO2 reduction. ChemSusChem, 2011, 4,

191-196.

86) Barton, E. E.; Rampulla, D. M.; Bocarsly, A. B. Selective SolarDriven Reduction of CO2

to Methanol Using a Catalyzed p-GaP Based Photoelectrochemical Cell. J. Am. Chem.

Soc. 2008, 130, 6342-6344.

87) Tatsuto Yui, Yusuke Tamaki, Keita Sekizawa, and Osamu Ishitani , Photocatalytic

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online: 28 April 2011;

88) Direct photoreduction of CO Coord Chem Rev 182 (1999) 67

89) T. Xie et al., Mater Chem Phy 70 (2001) 103

90) L. G. Wang et al., Phy. Rev Let. 89 (7) (2002)

91) M. Anpo J.Electroanal Chem 396 (1995) 21

92) Nature materials, 12,798-801 (2013)

93) Anal. Methods, 2013, 5, 1086–1097

94) Masakazu Anpo, Photocatalytic reduction of CO2 with H2O on highly dispersed Ti-Oxide

catalysts as a model of artificial photosynthesis, Journal of CO2 utilisation 1, 8-17 (2013)

95) Rakshit Ameta, Shikha Panchaol, Noopur Ameta and Suresh C.Ametal, Photo-catalytic


96) Yucheng Lan, Yalin Lu, and Zhifeng Ren, Mini Review on Photo-catalysis of titanium

dioxide nanoparticles and their solar applications, Nano Energy, 2,1031-1045 (2013).

97) Jeffrey C.S.Wu and Hung-Ming Lin, Photo-reduction of CO2 to methanol via TiO2

photocatalyst,International Journal of Photoenergy, Vol.7.115-119 (2005)

98) Richard Reithmeier, Christian Bruckmeier and Bernhard Rieger, Conversion of CO2 light

promoted Homogeneous redox catalysis, catalysts, 2, 544-571 2012).

99) Kihsuke Mori, Hiromi Yamashita and Masakazu Anpo, Photo-catalytic reduction of CO2

withwater on various titanium oxide photo-catalysts, RSC Advances, 2, 31165-3172

(2012).

100) Shifwru Kohtani, Eito Yoshioka and Hideto Miyabe, Photo-catalytic hydrogenation on

Semiconductor particles, Intech, Chapter 12,291-307 (2012).

101) Yasuo Izumi, Recent advances in the photo-catalytic conversion of carbon dioxide to fuels

with water and/or hydrogen using solar energy and beyond, Coordination Chemistry

Reviews, 257,171-186 (2013)

102) Jindui Hong, Wei Zhang, Jia Ren and Rong Zu, Photo-catalytic reduction of CO2 : a brief

review on product analysis and systematic methods, Analytical methods, 5, 1086-1097

(2013)

103) Severin N. Habisreutinger, Lukas Schmidt-Mende, and Jacek K. Stolarczyk, Photo-

catalytic Reduction of CO2 on TiO2 and Other Semiconductors, Angewante Chemie, 52,

7372-7408, (2013)

104) Yasuo Izumi, Coordination chemistry Reviews, 257,171 (2013)

105) Masakazu Anpo, Photocatalytic reduction of CO2 with H2O on highly dispersed Ti-Oxide

catalysts as a model of artificial photosynthesis, Journal of CO2 utilisation 1, 8-17 (2013).

106) Rakshit Ameta, Shikha Panchaol, Noopur Ameta and Suresh C.Ametal, Photo-catalytic


107) Yucheng Lan, Yalin Lu, and Zhifeng Ren, Mini Review on Photo-catalysis of titanium

dioxide nanoparticles and their solar applications, Nano Energy, 2,1031-1045 (2013).

108) Jeffrey C.S.Wu and Hung-Ming Lin, Photo-reduction of CO2 to methanol via TiO2 photo-

catalyst, International Journal of Photoenergy, Vol.7.115-119 (2005).

109) Richard Reithmeier, Christian Bruckmeier and Bernhard Rieger, Conversion of CO2 via

visible light promoted, Homogeneous redox catalysis, catalysts, 2, 544-571 2012).

110) Kihsuke Mori, Hiromi Yamashita and Masakazu Anpo, Photo-catalytic reduction of CO2

with water on various titanium oxide photo-catalysts, RSC Advances, 2, 31165-3172 (2012).

111) Shifwru Kohtani, Eito Yoshioka and Hideto Miyabe, Photo-catalytic hydrogenation on

semiconductor particles, Intech,Chapter 12,291-307 (2012).

112) Yasuo Izumi, Recent advances in the photo-catalytic conversion of carbon dioxide to fuels

with water and/or hydrogen using solar energy and beyond, Coordination Chemistry

Reviews, 257, 171-186 (2013).

113) Jindui Hong, Wei Zhang, Jia Ren and Rong Zu, Photo-catalytic reduction of CO2: a brief

review on product analysis and systematic methods, Analytical methods, 5, 1086-1097

(2013).

114) Severin N. Habisreutinger, Lukas Schmidt-Mende, and Jacek K. Stolarczyk, Photo-

catalytic Reduction of CO2 on TiO2 and Other Semiconductors, Angewante Chemie, 52,

7372-7408 (2013)

115) Photocatalytic reduction of CO2 with H2O on various titanium oxide photocatalysts by

Kohsuke Mori, Hiromi Yamashita and Masakazu Anpo, RSC Adv., 2,3165-3172 (2012)

116) Aaron M. AppelJohn E. BercawAndrew B. BocarslyHolger,DobbekDaniel L.

DuBois*Michel DupuisJames G. FerryEtsuko,FujitaRuss HillePaul J. A. Kenis Cheryl A.

KerfeldRobert H.,MorrisCharles H. F. PedenArchie R. Portis Stephen W.,,Ragsdale*Thomas

B. Rauchfuss*¶Joost N. H. ReekLance C. SeefeldtRudolf K. ThauerGrover L.

Waldrop,Frontiers, Opportunities, and Challenges in Biochemical and Chemical Catalysis of

CO Fixation, Chemical Reviews, 113,6621-6638 (2013)

117) Aerosol and air quality research, 14, 533-549 (2014)

118) Z. Jiang, T. Xiao, V. L. Kuznetsov and P. P. Edwards, Turning carbon dioxide into fuel,

Phil. Trans. R. Soc. A 28 July 2010 vol. 368 no. 1923 3343-3364

CO2 to fuels and chemicals course material final version

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