Development of Innovative Catalysts for PEM Fuel Processors

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Development of Innovative Catalysts for PEM Fuel
Processors
C V V Satyanarayana

• National Chemical Laboratory, Pune

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Outline of Presentation

• 1. Introduction to CSIR Fuel Cell Programme
• 2. Introduction to Fuel Processor catalysts
• Development of Steam Reforming Catalysts some
  results on
• (a) Ethanol and LPG Steam Reforming
• (b) Steam Reforming of iso-octane and
  Methane
• 4. Development of PROX Catalysts and Results
• 5. Remarks and Conclusions.
• 6. Future plans at NCL

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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
Delhi Project Partners National Chemical
Laboratory Spic Science Foundation Bharat Heavy
Electricals Limited Sud-Chemie India Limited
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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)

Oxygen
AIR
FUEL PROCESSOR
FUELCELLSTACK
AC Power Output
DC Power Output
Fuel Input
Hydrogen Rich Gas
Water
HEATRECOVERY
Fuel Processing Preheating
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Fuel Processing
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COMPONENTS OF A PEM FUEL PROCESSOR
Desulphurizer
Reformer
Reformate cleanup
Fuel
Raw fuel cleaning
Fuel conversion
CO reduction
Steam reformer
      Water gas shift reactor ( HTS ,
LTS)     Pref. Oxidation (PROX)
Partial Oxidation
Autothermal reformer
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Catalysts in a PEM Fuel Processor
All reactors are fixed bed type
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Current steam reforming catalysts

• 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
• SELECTIVITY
• For MeOH Conventional CuO-ZnO-Al2O3 operate at
  sufficiently low temperatures

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DRAWBACKS OF CONVENTIONAL Ni - BASED S R
CATALYSTS

• HIGH TEMPERATURES (800-1000ºC)
• SENSITIVE TO SULFUR (lt0.05 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

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Attributes of a good SR catalyst

• 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 (gt5000
  hrs)
• Should have high crush/mechanical strength under
  steam.
• Has to withstand frequent On/Off cycles.
• Tolerance to sulphur and other poisons.

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• 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 supports
• The 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.

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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.

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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.

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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.
  

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Requirements of A PROX Catalyst

• A PROX catalyst should be highly active (CO conv
  gt99.8)
• 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 ? 1
• No methanation of CO should occur at reaction
  temperatures.
• Presence of water and CO2 should not lead to any
• deterioration in the long term performance.

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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 lt10 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 GHSVs 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.

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Conclusions and Remarks

• Novel 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.
• NCLs 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.
• NCLs 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.

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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 (gt10,000 h-1) compared to
  the present water gas shift catalysts.
• To develop selective methanation catalysts that
  methanate CO in the presence of excess CO2.

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Thanks
For your Attention NTPC RD for Invitation