Aqueous-phase reforming − a pathway toweb.abo.fi/projekt/poke/Saarenmaa/Aqueous_phase...y, %...

Alexey Kirilin

Aqueous-phase reforming − a pathway to

chemicals and fuels

Laboratory of Industrial Chemistry and Reaction Engineering Process Chemistry Centre

Åbo Akademi

POKE meeting, 14-th of August, 2014

Agenda

Short Introduction, biomass, what is APR?

Main tasks of the doctoral research

Experimental methods

Choice of catalytic systems

Catalytic results

Summary

2


Introduction - Biomass


3

Cellulose

Hemicellulose

Aldoses

Sugar alcohols

Hydrogenation

Fuels

Lubricants

Esterification Chemicals

Hydrolysis Oxidation

Sugar acids

Oligomers

Hydrolysis Catalytic transformation of biomass

Aqueous reforming

4


Aqueous phase reforming (APR)

Biomass

RR=11/5

5


Biomass

RR=11/5

Aqueous phase reforming (APR) 5


• Task 1. Investigation of reaction products and intermediates

• Task 2. Synthesis and characterization of catalysts

• Task 3. Catalyst stability studies

• Task 4. Investigation of reactant structure on process properties

• Task 5. Influence of a second metal (Re)

• Task 6. Modelling of reaction kinetics

The main tasks of the research 6


Reaction conditions:

• 0.5 g of a catalyst

• 225°C

• 30 bar

• Carrier gas N2 (30 ml/min)

Experimental setup

Continuous fixed-bed reactor

10 wt.% of xylitol used as a feed

Reagents in the liquid phase

7


N2 (1% He)

mass flow controller furnace

sampling

GC

P effluent

pressure controller

safety valve

MFC

catalyst

MFC

MFC

collector

HPLC pump

H2 (for reduction)

Reactor’s scheme 8


APR of Polyols

Gas phase Liquid phase

Micro-GC HPLC TOC

TOC – total organic carbon analysis

Mass balance – 95-100% (by carbon analysis)

On-line sampling

Product analysis

Volatile compounds were identified by means of Solid-phase microextraction (SPME) + GC-MS

9


G

L

H2, CO2, alkanes

Oxygenates

100%

• Catalyst activity, stability and selectivity to H2

• Product distribution between phases

• Ratio H2/CO2

Important parameters in APR

Selectivity to H2 (%) = %100/1)(

)( 2 RRCv

Hv

gasin

RR – reforming H2/CO2 ratio

(11/5 fo xylitol)


10

Ni

Ru

Pd

Pt

Al2O3

TiO2

C

MgO

Based on catalytic activity in the APR of ethylene glycol

Choice of active metal and support 11


Pt/Al2O3, Pt/TiO2, Pt/C and bimetallic catalyst PtRe/TiO2

Ni

Ru

Pd

Pt

Al2O3

TiO2

C

MgO

Based on catalytic activity in the APR of ethylene glycol

Choice of active metal and support

C-C cleavage

WGS activity

11


0 30 60 90 120

1.0

1.2

1.4

1.6

1.8

Bil

dnin

gsh

asti

ghet

[x104],

mol/

min

Time on stream, h

Time. h CO2[104]. mol ∑(X∙CxHy)[10

5]. mol ∑CxHy/CO2

7 1.7 6.9 0.4

123 1.6 6.4 0.4

Catalyst showed stable performance within more than 120 h time on stream

Catalyst stability

Fo

rma

tio

n r

ate

[x1

04],

mo

l/m

in

12


0.5 1.0 1.5 2.0 2.5 3.0

0

20

40

60

80

100Liquid

Car

bo

n c

on

ten

t, %

MVKV, t-1

Gas

G

L

H2, CO2, alkanes

Oxygenates

100%

Distribution of carbon

WHSV, h-1 WHSV – weight hourly space velocity

gsubs/gcat/hour [h–1]

benchmark catalyst – Pt/Al2O3

13


0.5 1.0 1.5 2.0 2.5 3.0

0

20

40

60

80

100Liquid

Car

bo

n c

on

ten

t, %

WHSV, h-1

Gas

G

L

H2, CO2, alkanes

Oxygenates

100%


WHSV, h-1 WHSV – weight hourly space velocity



13


0.5 1.0 1.5 2.0 2.5 3.0

0

20

40

60

80

100Liquid

Car

bo

n c

on

ten

t, %

WHSV, h-1

Gas

WHSV – weight hourly space velocity


G

L

H2, CO2, alkanes

Oxygenates

100%


WHSV, h-1 WHSV, h-1


13


0 1 2 30

15

30

45

60

CO2

H2

Yie

ld, %

WHSV, h-1

0.5 1.0 1.5 2.0 2.5 3.0

0.0

0.5

1.0

1.5

2.0

2.5

3.0propane

MKMV, t-1

Yie

ld, %

СО

n-butane

etane

0.5 1.0 1.5 2.0 2.5 3.00.00

0.05

0.10

0.15

0.20

0.25

WHSV, h-1

iso-butanen-hexaneY

ield

, %

n-pentane

Gas phase composition

Studied by micro-GC and GC-MS, benchmark catalyst – Pt/Al2O3

WHSV, h-1 WHSV, h-1

WHSV, h-1

14


Carbon in liquid. %

Product distribution. % Total amount

detected. % Alcohols Diols

Triols

Ketons

Acids

Other

24.4 17.3 49.9 4.2 5.0 4.9 18.7 90.6

изосорбид isosorbid

Liquid phase Studied by HPLC and SPME


15


Higher selectivity to alkanes at lower

space velocities

Higher yields of hydrogen for xylitol – substrate

with shorter carbon chain

Conditions: 225°С, 30 atm., N2 30 ml/min, 10 wt.% solution, Pt/Al2O3

Influence of reactant structure

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

5

10

15

20

25

30

WHSV, h-1

Reforming of sorbitol

Alk

ane

sele

ctiv

ity, %

Reforming of xyltiol

1.0 1.5 2.0 2.5 3.0 3.5 4.0

10

15

20

25

30


Yie

ld o

f H

2,

%

WHSV, h-1


16



space velocities



0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

5

10

15

20

25

30

WHSV, h-1


Alk

ane

sele

ctiv

ity, %


1.0 1.5 2.0 2.5 3.0 3.5 4.0

10

15

20

25

30


Yie

ld o

f H

2,

%

WHSV, h-1




16



space velocities



0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

5

10

15

20

25

30

WHSV, h-1


Alk

ane

sele

ctiv

ity, %


1.0 1.5 2.0 2.5 3.0 3.5 4.0

10

15

20

25

30


Yie

ld o

f H

2,

%

WHSV, h-1




16


xylitol

xylitol

Catalysts

one commercial Pt/C (Degussa) four prepared and characterized materials

5% Pt/C (Degussa)

2.5% Pt/TiC-CDC (CDC – carbide-derived carbon)

5% Pt/Sibunit from (NH3)4 Pt (HCO3)2

5% Pt/Sibunit H2PtCl6

5% Pt/BAC (Birch active carbon)

Pt/TiO2,

Pt-Re/TiO2

Re/TiO2

2. Effect of a support material and support structure

1. Effect of a second metal: series

Prepared by incipient wetness impregnation, from

HReO4 and or (NH3)4Pt(NO3)2

17


Catalysts

one commercial Pt/C (Degussa) four prepared and characterized materials

5% Pt/C (Degussa)

2.5% Pt/TiC-CDC (CDC – carbide-derived carbon)

5% Pt/Sibunit from (NH3)4 Pt (HCO3)2

5% Pt/Sibunit H2PtCl6

5% Pt/BAC (Birch active carbon)

Pt/TiO2,

Pt-Re/TiO2

Re/TiO2

2. Effect of a support material and support structure

1. Effect of a second metal: series

To enhance selectivity to hydrocarbons

17


Higher selectivity to alkanes in the

presence of bimetallic Pt-Re catalyst

Higher yields of hydrogen

for monometallic Pt catalyst

1 2 3 4 5 6

5

10

15

20

25

30

35

Pt/TiO2

Yie

ld o

f H

2, %

WHSV, h-1

Pt-Re/TiO2

Pt/Al2O

3

In cooperation with prof. C. Hardacre from Queen’s University, Belfast

Conditions: 225°С, 30 atm., N2 30 ml/min, 10 wt.% solution

Example: APR of xylitol over Pt-Re/TiO2 18


Slightly higher selectivity to alkanes in the

presence of bimetallic Pt-Re catalyst

Higher yields of hydrogen

for monometallic Pt catalyst

1 2 3 4 5 6

5

10

15

20

25

30

35

Pt/TiO2

Yie

ld o

f H

2, %

WHSV, h-1

Pt-Re/TiO2

Pt/Al2O

3

1 2 3 4 5 6

5

10

15

20

25

30

35

Pt/TiO2

Sele

cti

vit

y t

o a

lkan

es,

%

WHSV, h-1

Pt/Al2O

3

Pt-Re/TiO2

Example: APR of xylitol over Pt-Re/TiO2

In cooperation with prof. C. Hardacre from Queen’s University, Belfast

19

Conditions: 225°С, 30 atm., N2 30 ml/min, 10 wt.% solution


2 4 6 8 10 12 14 16

0

5

10

15

20

Pt/BAC

d, nm

Fre

que

ncy, %

Transmission electron microscopy

300 350 400 450 500

0.0

0.1

0.2

0.3

0.4

0.5

0.6

379 K

386 K

370 K

358 K

20 Kmin-1

15 Kmin-1

5 Kmin-1

10 Kmin-1

3 Kmin-1

349 K

Conce

ntr

atio

n o

f N

H3, %

Temperature, K

0 50 100 150 200 250 300 350 400 450

180°C

350°C

Upta

ke o

f H

2, a.u

.

Temperature, °C

75°C

Particle size distribution

Temperature programmed reduction (H2) Temperature programmed desorption (NH3)

~2 nm

20 nm

Pt/Al2O3 Pt/Al2O3

Pt/BAC

Characterization 20


Effect of acidity

APR of xylitol over Pt/C

In cooperation with prof. B. Etzold from University of Erlangen-Nürnberg

0 20 40 60 80 100 120 140 160

0.4

0.6

0.8

1.0

1.2

1.4

1.6

NH3 desorbed, molg

Rate

of

alk

an

es

fo

rma

tio

n [

x10

5],

mo

lm

in-1

1.9

2.0

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

3.0

H2/C

O2

Supervised visiting PhD student Benjamine Hasse for 2 months

21


Reaction pathways Based on experimental data 22


Reaction pathways Based on experimental data

Pathway to hydrogen

22


Pathway to hydrogen



Pathway to alkanes




Pathway to alkanes

22



Pathway to hydrogen

Pathway to alkanes

A.V. Kirilin, J. Wärnå, T. Salmi, D. Yu. Murzin, “Kinetic Modeling of Sorbitol Aqueous-Phase

Reforming over Pt/Al2O3”, Ind. Eng. Chem. Res., 2014, 53, 4580–4588

Modelling of kinetics was performed at ÅA

22

Modeling

Two main pathways are selected

23

Modeling 24

eff

obs

cD

Rr 2

Weisz-Prater modulus for 1-st order reaction Φ < 1,

for 0 order reaction Φ < 6

for 2 order reaction Φ < 0.3

robs — maximal initial reaction rate

R — mean radius of the catalyst particle

c —substrate concentration.

In our case R = 1.25×10-4 m (125 µm)

DDef 6.0

)(

218 )(104.7

AbB

BAB

o

V

TMD

effective diffusion coefficient (Deff) of substrate

(sorbitol) in water

porosity (0.3-0.6)

tortuosity (2-5)

Wilke-Chang:

[cm2/s]

= 2.6 (water), MB is molecular weight of solvent, B = 0.11888 cP is solvent

dynamic viscosity, T (K) = 498K, P=30 bar), Vb(A) = 122.15 cm3×mol-1 is liquid molar

volume at solute’s normal boiling point.

Assuming / = 1/10 the diffusion coefficient of sorbitol is calculated to be Def

=1.1810-9 m2/s (498 K and 30 bar).

The concentration of the substrate in the solvent is equal to 0.515 mol×l-1.

rmax= 1.93×10-4 mol×l-1×s-1 at 2.7 h-1

Φ=0.005 substrate diffusion inside the catalyst pores does not affect the reaction

rate

Modeling 25

N(1)

: COHHOCHOC 212551466

N(2)


N(3)


N(4)

: COHHOCHOC 2622833

N(5)

: 222 HCOOHCO

N(6)

: OHHCHHOC 210421044 44

N(7)

: OHHCHHOC 2832833 33

N(8)

: OHHCHHOC 2622622 22

Reaction pathways

P=S+W-I, where S is the number of steps, W is the number of balance (link)

equations, and I is the number of intermediates

P=17+2-11=8 basic routes (no intermediates are there)

D. Murzin & J. Wärnå

26

VHOCHOC CK 14661466 1 VHOCHOC CK

12551255 3 and so on for each component

''10441044 12 VHOCHOC CK

on metal sites:

on acid sites:

OHHOCHOCHOCHOCHOC

VCKCKCKCKCKCK

2622833104412551466 10975311

1

6228331044 1614121

1'

HOCHOCHOC

VCKCKCK

OHHOCHOCHOCHOCHOC

HOC

VHOCHOC

CKCKCKCKCKCK

CKk

CKkkr

2622833104412551466

1466

14661466

1097531

12

122

)1(

1

)1(1466 rd

dC HOC

Total coverage:

Rate for basic route 1:

Generation rate for compound:


27

OHHOCHOCHOCHOCHOC

HOC

VHOCHOC

CKCKCKCKCKCK

CKk

CKkkr

2622833104412551466

1466

14661466

1097531

12

122

)1(

1

1466

'

2

)1(

HOCCkr

Simplification of the model because

of overparametrization

83318

)9( ' HOCCkr

)9()1(1466 rrd

dC HOC

...

0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.40

0.5

1

1.5

2

2.5

3

3.5x 10

-4

WHSVh

C6O

H

Modeling


97%

28

Summary

1. Aqueous-phase reforming of two most abundant polyols has been studied over stable catalysts

2. Effect of reactants structure on selectivity to main product formation reveals that higher

selectivities to hydrogen can be achieved in APR of xyltiol compared to sorbitol (up to 85%)

3. Addition of Re as a second metal component leads to enhanced alkane formation

4. Advanced reaction scheme was proposed on the basis of experimental data

5. For the first time reaction sensitivity in APR of xylitol was studied over Pt/C

6. The reaction kinetics was modeled based on kinetic data and mechanistic considerations for

sorbitol transformation during APR.

29


APR is a powerfull method for hydrogen production from renewables

Kinetic model proposed can be further developed and applied to description of APR data for

other substrates as well as for APD/H process

Financial support

Graduate School in Chemical Engineering (GSCE, 2010-2013)

Fortum Foundation (2009-2011)

Academy of Finland in cooperation with North European Innovative Energy Research Programme (N-Inner, 2010-2013)

Haldor Topsøe Scholarship Programme (2010-2012)

COST–Action CM0903 (UbioChem, 2010-2013)

30


Alexey Kirilin

Aqueous-phase reforming − a pathway to

chemicals and fuels

Laboratory of Industrial Chemistry and Reaction Engineering Process Chemistry Centre

Åbo Akademi


Aqueous-phase reforming − a pathway toweb.abo.fi/projekt/poke/Saarenmaa/Aqueous_phase...y, %...

Documents

Transcript of Aqueous-phase reforming − a pathway toweb.abo.fi/projekt/poke/Saarenmaa/Aqueous_phase...y, %...