Development of Innovative Catalysts for PEM Fuel Processors National Chemical Laboratory, Pune...

Development of Innovative Catalysts for PEM Fuel

Processors

National Chemical Laboratory, Pune

National Seminar on “Creating Infrastructure for Adoption of Fuel cell Technology”, NTPC, Noida

C V V Satyanarayana

Outline of Presentation

1. Introduction to CSIR Fuel Cell Programme2. Introduction to Fuel Processor catalysts 3. Development of Steam Reforming Catalysts &

some results on (a) Ethanol and LPG Steam Reforming (b) Steam Reforming of iso-octane and Methane4. Development of PROX Catalysts and Results5. Remarks and Conclusions.6. Future plans at NCL

National Seminar on “Creating Infrastructure for Adoption of Fuel cell Technology”, NTPC, Noida 2

Objective of the CSIR Fuel Cell programme

Development of 5 and 25 kW PEMFC power packs for stationary applications

Funded by

New Millennium Indian Technology Leadership Initiative (NMITLI)

Scheme, CSIR, New DelhiProject Partners

National Chemical Laboratory Spic Science Foundation

Bharat Heavy Electricals LimitedSud-Chemie India Limited


Fuel Input

POWERCONDITIONER

Water

DC Power Output

Hydrogen Rich Gas

HEATRECOVERY

Fuel Processing Preheating

FUELCELL

STACK

FUEL PROCESSOR

Oxygen AIR

AC Power Output

Fuel Cell Power Pack

Main Components

Fuel Processor : Fuel processor is an integrated unit used for the conversion of raw fuel to hydrogen rich gas suitable for the fuel cell (NCL, SCIL)

Fuel Cell Stack :The hydrogen rich gas and oxygen (air) are fed to fuel cell stack to generate DC power (SPIC)

Power Conditioner: The DC power output is converted into useful AC power (BHEL)


Fuel Processing


Raw fuel cleaning

Fuel conversion CO reduction

COMPONENTS OF A PEM FUEL PROCESSOR

Desulphurizer Reformer

Water gas shift reactor ( HTS , LTS) Pref. Oxidation (PROX)

Reformate cleanup

Steam reformer

Partial Oxidation

Autothermal reformer

Fuel


Catalysts in a PEM Fuel Processor

Catalyst Temp

oC

Reactions

DS Ni-Mo-ZnO 350 ZnO + H2S ZnS + H2O

SR Ni-Ce-Zr 700 CnH2n+2+nH2O nCO + (2n+1)H2

HTS Fe-Cr 380 CO + H2O CO2+H2

LTS Cu-Zn-Al 200 CO + H2O CO2+H2

PROX Pt-Zeolite 140 CO + 1/2O2 CO2

All reactors are fixed bed type


CH4 + H2O CO + 3 H2; H = + 210 kJ/mol H2O / C = 2.5-3.0 (mol); 800-1000ºC, ~30 BAR GHSV = 10000 – 15000 h-1

Ni ON REFRACTORY SUPPORTS SUPPORTS: CaAl2O4 FOR CH4 FEED; MgAl2O4 SPINEL, K2O- FOR C3+ REFORMING ACTIVITY DEPENDS ON Ni AREA EQUILIBRIUM CONVERSION AND SELECTIVITYFor MeOH Conventional CuO-ZnO-Al2O3 operate at sufficiently low temperatures

Current steam reforming catalysts


DRAWBACKS OF CONVENTIONAL Ni - BASED S R CATALYSTS

HIGH TEMPERATURES (800-1000ºC) SENSITIVE TO SULFUR (<0.05 PPM); HDS OF HEAVIES IS DIFFICULT IN A FUEL PROCESSOR SUSPECT FOR DEACTIVATION IN THE PRESENCE OF OLEFINS NOT PROVEN FOR OTHER FUELS SUCH AS EtOH


Highly active to convert 100% of the hydrocarbon to its equilibrium composition of CO, CO2, methane and H2 at the reaction temperature.

Should work at lowest possible steam/carbon ratios without deactivation due to filamental carbon.

Capable of handling high space velocities to achieve small catalyst volumes. Durability under long steady state continuous operation (>5000 hrs)

Should have high crush/mechanical strength under steam. Has to withstand frequent On/Off cycles. Tolerance to sulphur and other poisons.

10

Attributes of a good SR catalyst


Role of a support in SR Catalysts To Improve mechanical strength and thermo-resistance To enhance and stabilise metal dispersion (eg: Ni,Pt, Rh) To suppress coke formation

Features of current SR catalyst supports Refractory basic oxides (MgAl2O4, CaAl2O4, Al2O3

Coke reduction by oxides of K, Mg, Mo, W, Ce, Sn Ceria-Zirconia supportsThe Ce3+ Ce4+ couple is more reversible in CeO2-ZrO2

than CeO2 indicating that Ce ions in CeO2-ZrO2 are more accessible. This can arise from the smaller size of the CeO2 crystallites in CeO2-ZrO2.


Selection of feed stocks and Steam reforming catalysts

Naptha and natural gas are the preferred feeds for H2 production in Industrial Steam Reforming.

Due to wide distribution network, gasoline, diesel, kerosine, CNG and LPG are preferred for PEMFC.

Renewable feeds such as agro-ethanol and bio-gas does not lead to net CO2 emissions.

Ni, Pd, Pt, Rh based catalysts are most suited for SR. Ni based catalysts are the best in terms of cost and good performance. Ni is known to catalyse the breaking of C-C bond.


Preparation of Ni Steam Reforming catalysts » Aim is to develop catalysts that work for SR of multiple

fuels, viz., LPG, agro-ethanol, natural gas, methanol and naphtha.

» Ni supported on oxides that have red-ox properties such as CeO2, TiO2, CeO2-ZrO2, CeO2-ZrO2-TiO2 have been prepared and screened.,

» Unique co-precipitation methodologies developed to yield nano-NiO particles (3-6nm) on high surface area supports.

» Preliminary characterization is carried out by powder XRD and BET surface area measurements. NiO crystallite sizes are calculated using Scherrer equation. Temperature programmed reduction studies carried out to monitor reducibility of the NiO on these supports.


0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 4000

10

20

30

40

50

60

70

80

90

100

TOS in hours

VO

LU

ME

PE

RC

EN

T O

F G

AS

H2 VOLUME CONVERSION

23

24

25

26

27

28

29

30

31

32

33

34

H2O/C = 2.5

H2O/C = 3

H2O/C = 4

SR of EtOH On NiO-CeO2-ZrO

2 Catalyst

Catalyst 2.5cc, Temp. 6500C, Steam/carbon 2.5-4E

than

ol in

the fe

ed

(Wt%

)

Ethanol Wt% in the feed

National Seminar on Fuel cell-Materials, Systems & Accessories, NMRL, Ambernath 14

0 50 100 150 200 25010

20

30

40

50

60

70

80

90

100

Temp. 700-7300C,Steam /Carbon=4.0,GHSV=21750-87000 h-1SR OF LPG ON SCALE-UP CATALYST FROM SCIL

CONV

H2

CO2

CO

HTSMTS

GHSV

87,000 h-1

65,250 h-1

43,500 h-1

21,750h-1

Time on Stream (Hrs)

Vo

lum

e P

erc

en

t

0

5

10

15

20

Vo

lum

e P

erc

en

t


0 20 40 60 80 100 120 140 160 1800

20

40

60

80

100

BUTANE & iso-BUTYLENE STEAM REFORMING

CATALYST 1.5cc, TEMP. 7000C, GHSV 14500 h-1, Steam/Carbon=4

iso-BUTYLENE REFORMINGBUTANE REFORMING

Conversion H2 Volume

VO

LU

ME

PE

RC

EN

T

TOS in hours


0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 320

20

40

60

80

Steam Reforming of Iso-octane on 40%Ni/CeO2-ZrO

2

Reaction Temp 725 oC, Steam/Carbon=3.6/1

TIME ON STREAM (Hrs)

% V

olu

me

per

cen

t

Conversion H2 CO2

0

2

4

6

8

GHSV=31000

GHSV=15500

CA

RB

ON

MO

NO

XID

E V

OL

%

CO


600 625 650 675 700 7250

20

40

60

80

100

SR of Methane on NiO-CeO2-ZrO

2 catalyst at various temperatures

Co

nve

rsio

n /vo

lum

e%

Temperature(degrees)

CH4conv H2con COconc


SALIENT FEATURES OF NCL REFORMING CATLYSTS

Common catalyst for steam reforming of EtOH, LPG and Natural gas.

LPG supplied by Indian refineries has high content of olefins in addition to C3 and C4. Reforming of 100% Isobutylene was a good example to show that NCL catalyst can handle high concentrations of olefins in the feed

Variations in LPG composition does not have any bearing on performance. Catalysts show stable activity at full conversion even for 100% n-Butane

The Steam reforming catalysts developed at NCL show sulfur tolerance to low levels of sulfur. Hence, during steam reforming of agro-ethanol, desulfurisation of feed is not a pre-requisite.


Requirements of A PROX CatalystA PROX catalyst should be highly active (CO conv >99.8%) such that it can handle high space velocities.It has to operate in the temperature zone of LTS outlet temperature (200 oC) and PEM fuel cell stack inlet temperature (80 oC)It should have good CO oxidation selectivity in order not to consume valuable H2.Should operate at lower O2/CO ratios, preferably O2/CO 1No methanation of CO should occur at reaction temperatures.Presence of water and CO2 should not lead to any deterioration in the long term performance.


DEVELOPMENT OF PROX CATALYSTS Using HTS and LTS catalysts in series, the level of CO is

brought down to 0.3 – 1.0%. The gas stream after the Shift reaction is further reacted with a preferential oxidation catalyst prepared at NCL, to bring down the CO to <10 ppm.

Supported gold catalysts using reducible oxide supports of Fe, Mn, Co, Cr and Co-Mn oxide catalysts were prepared and evaluated in PROX reactor either in series with the steam reforming reactor or separately using typical gas mixtures. Mn and Mn-CO supports gave excellent results while other supported catalysts deactivated. Successful catalysts were tested for more than 100 hrs with various CO concentrations.

Since Pt based catalysts have been reported to work at high GHSV’s with better stability, we have developed Pt based catalysts that work in 130-160 oC range and a zeolite based Pt catalyst has been scaled up to use in our processor programme.


0 10 20 30 40 50 60 70 80 90 100-10-8-6-4-202468

1012141618202224

PROX CATALYST: Au/ metal oxide, GHSV : 5000 h-1

TEMPERATURE: 80-900C,

FEED 9600 PPM COFEED 5100 PPM CO

CO in PPM

CO

NC

EN

TR

AT

ION

(P

PM

)

TOS in hours


0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 340.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

TOS in hours

CO

in

pp

m

CO

2500

5000

7500

10000

12500

15000

17500

20000

22500

OXIDATION OF CO ON Pt/Al2O

3 CATALYST

Temp-175OC, CO- 9500ppm, O2/CO = 1.25

GH

SV

GHSV


0 2 4 6 8 10 12 14 16 180

20

40

60

80

100

Time on Stream

Vo

l %

Hyd

rog

en

0

2

4

6

8

10

12

14

16

18

20

Preferential Oxidation of CO on Pt-Zeolite Feed- H

2 74.17%, CO

2 23.26%, CO 4900 ppm CO/O

2=1

Temp

20,000 h -1

GHSV

15,000 h-1

10,000 h-1

1450C1350C

CO

pp

m


Conclusions and RemarksNovel supports and co-precipitation techniques developed to

yield good SR catalysts containing nano-particles of NiO.Common catalyst for SR of EtOH, LPG, CH4 and MeOH.

100% conversions are achieved at reasonable temperatures. These catalysts have capability to handle high space velocities.

Presence of olefins do not affect the performance. Variations in LPG composition has no bearing on the performance.

NCL’s SR catalysts show sulfur tolerance to some extent. As a result, desulfurisation of the feed is not a must during the steam reforming of agro-ethanol.

NCL’s PROX catalyst works in the temperature window of 135-150 oC and at O2/CO = 1. These less severe conditions help in saving of valuable H2.

Scale up and evaluation of these catalysts at Kg level has been successfully completed. A Fuel processor using complete train of these catalysts is operational at NCL.


Future plans at NCL Development of honeycomb based monolith ATR

catalysts that combine SR and oxidation. Development of cheaper transition metal based PROX

catalysts. Development of non-pyrophoric precious metal based

steam reforming catalysts that can withstand on-off cycles and also have high sulphur resistance.

Development of sulphur resistant precious and non-precious metal catalysts that can handle higher space velocities (>10,000 h-1) compared to the present water gas shift catalysts.

To develop selective methanation catalysts that methanate CO in the presence of excess CO2.


Development of Innovative Catalysts for PEM Fuel Processors National Chemical Laboratory, Pune...

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