Development of highly active natural gas reforming by yyc13060

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									                             SCIENCE,
 DEPARTMENT OF ENGINEERING SCIENCE
 UNIVERSITY OF OXFORD, 17 PARKS ROAD,
 OXFORD, UNITED KINGDOM OX1 3PJ




Development of Highly Active Nanocrystalline
Catalyst for Internal Reforming of Natural Gas
          in Low Temperature SOFC

                                  Jiexun Di

            GERG Academic Network Event, 5th June 2009
                           Background
Environmental
Damage

           CO2, SO2, NOx
           Emissions ↑
                                                  Clean + Efficient
                                                  Energy
                                                  Solution:

Energy
Shortage
                                                  SOFC
                                                  (+ ISMR)




           Crude Oil Price ↑




                 Development of Highly Active Natural Gas Reforming Catalyst for Internal Reforming in Low Temperature SOFC
                     What is SOFC?
A solid oxide fuel cell (SOFC) is an electrochemical
conversion device that produces electricity directly from
oxidizing a fuel (working temperature 800 -1000oC).




                                                                              AIR




Reactions:
  at cathode                                               O2 + 4 e- → 2 O2-
  at anode                                                 2 H2 + 2 O2- → 2 H2O + 4 e-
  overall                                                  2 H 2 + O2 → 2 H 2 O

                Development of Highly Active Natural Gas Reforming Catalyst for Internal Reforming in Low Temperature SOFC
                  Advantages of SOFC
Common Benefits of Fuel Cell                                Extra Benefits of SOFC


                                                                Variety of
Simplicity/                                                     Applications
Sighting
Flexibility
                                                                 High CO
                                                                 Tolerant
High Energy
Efficiency (up                                                                                Fuel
                                                                Cogeneration                  Flexibility
to 85% overall)
                                                                Potential

Quiet                                                                                         Reuse of
Operation/                                                       Internal                     Heat /Steam
No SO2/NOx                                                       Reforming
                                                                                              High Cooling
                                                                                              Efficiency



                   Development of Highly Active Natural Gas Reforming Catalyst for Internal Reforming in Low Temperature SOFC
Internal Steam Methane Reforming of
             Natural Gas




Reactions:
1. CH4 + H2O = CO + 3H2   (ΔH298°= +206.1kJ/mol)
2. CO + H2O = CO2 + H2    (ΔH298°= -41.5kJ/mol)
3. CH4 + 2H2O = CO2 + 4H2 (ΔH298°= +165.0 kJ/mol)

             Development of Highly Active Natural Gas Reforming Catalyst for Internal Reforming in Low Temperature SOFC
A High Operating Temperature is required
   Cathode: has to catalytically split O2 molecular as well as having a
    high electronic conductivity. Lanthanum strontium manganite
    (LSM) material currently used attains appropriate electrochemical
    activity only at high temperatures.

   Electrolyte: Yttrium stabilized zirconia (YSZ) material has the
    required oxygen ion conductivity at 900-1000oC. At lower
    temperature, the conductivity falls rapidly.

   Anode: has to catalyze the reaction between H2 and O2- to
    produce water as well as having electronic conductivity. Ni
    supported YSZ currently used achieves the required
    electrochemical characters at the high temperature.

   Internal reforming: works at 800-1000oC. Current catalyst for
    steam reforming shows low activity at low temperature.


                    Development of Highly Active Natural Gas Reforming Catalyst for Internal Reforming in Low Temperature SOFC
       Disadvantages - High Operating
               Temperature

                 Special Manufacturing Materials



                 Thermal Expansion/Contraction

High
Operating        Solid State Diffusion (eg.Cr)                                             High Cost/
Temperature                                                                                Low Lifetime
(800~1000oC)
                 Melting of Sealing Materials



                 Deactivation of Steam Reforming
                 Catalyst



               Development of Highly Active Natural Gas Reforming Catalyst for Internal Reforming in Low Temperature SOFC
Research Trends – Low Temperature SOFC
    Cathode/Andode: New materials with appropriate
     electrochemical activity at lower temperature.

    Electrolyte: New materials with high ionic oxide
     conductivity at lower temperature.

    Seal: Good quality seals need to be developed.

    Interconnect: Inexpensive and robust materials for
     interconnect.

    Steam reforming of CH4 : A catalyst with high activity
     at low temperature for internal methane steam
     reforming.

                  Development of Highly Active Natural Gas Reforming Catalyst for Internal Reforming in Low Temperature SOFC
                Research Objectives

   To make a inexpensive catalyst system for internal
    reforming of natural gas in the SOFC anode
    environment.

   To enhance activity with respect to conventional nickel
    catalyst at low temperature.

   To reduce the “light off” temperature of steam methane
    reforming reaction.

   To improve catalyst’s lifetime, resistance to carbon
    deposition and sulfur tolerance.

                  Development of Highly Active Natural Gas Reforming Catalyst for Internal Reforming in Low Temperature SOFC
                 Catalytic Studies
 Active metals:
 Ni (conventional metal, low cost, low activity)
 Platinum group metals: Pd, Rh etc. (high cost, high
  activity)

Our solutions:
 Ni catalyst doped with small amount of highly active
  metal
 Use promoters (eg. ZrO2 , La2O3)
 Catalyst size in nanoscale
 A precursor for highly dispersion – layered double
  hydroxide (LDH)
               Development of Highly Active Natural Gas Reforming Catalyst for Internal Reforming in Low Temperature SOFC
           Layered Double Hydroxide




General formula: [MII1-xMIIIx(OH)2]x+[A x/kk- . nH2O]

   Easy to prepare and coat
   Easy to vary composition
   Variety of metal doping (promoters)
   High level of dispersion
   Catalysts in nanoscale

                 Development of Highly Active Natural Gas Reforming Catalyst for Internal Reforming in Low Temperature SOFC
               LDH System Selected

   Basic LDH: Ni0.75Al0.25 (OH)2(CO3) 0.125 (x=y=0) is
    prepared by co-precipitation method.


   LDHs prepared are based on this structure and have a
    general formula of
    Ni0.75-x AxAl0.25-yBy (OH)2(CO3) 0.125 •nH2O, where
    A = platinum group and divalent metal ion;
    B = trivalent, tetravalent metal ion.


   Basic LDH is chosen as a reference.

                  Development of Highly Active Natural Gas Reforming Catalyst for Internal Reforming in Low Temperature SOFC
       Characterization of Catalyst
  EDX spectrum of Ref.LDH derived catalyst Zr doped LDH precipitate
   EDX spectrum of catalyst derived from Pd,
   XRD: Phase identification, crystal structures, d-
           XRD Pattern of fresh Ref.LDH derived
      Bright field imageof Ref. LDH precipitate catalyst
       XRD Pattern of oxides derived from Ref. LDH
       precipitate calcined at 550oC
    spacing.

   TPR: H2 consumption, NiO
                          reduction temperature.
                           NiO
   TEM: Surface morphology, particle sizes.
                                                                     NiO
   EDX: Catalysts composition (elemental)

   BET: Specific surface area




                 Development of Highly Active Natural Gas Reforming Catalyst for Internal Reforming in Low Temperature SOFC
Experimental Set-up for Activity Test
     On/Off
      Valve                  MFC       Heating Zone (Temp: 150°C)
    Ar
                             MFC
                                                                      Furnace
    O2                                                                                        To
                                                Mixing                                        Vent
                             MFC                                      Reactor

    CH4                                                               Furnace
                             MFC
    H2
                                  Steamer


    H2O


               Water
               Pump                                       GC                            MS




              Development of Highly Active Natural Gas Reforming Catalyst for Internal Reforming in Low Temperature SOFC
           Typical Catalyst Performance




Product profiles of steam reforming over catalyst derived from ref.LDH precipitate (S/M =3.5, P=1 bar)


                          Development of Highly Active Natural Gas Reforming Catalyst for Internal Reforming in Low Temperature SOFC
Effect of Substitutions on Catalyst Activity
Fresh catalyst loaded

        Pd                                       Rh                                         Cu




After reaction at low S/M ratio




     Carbon Deposition




                                                    (S/M =3.5, P=1 bar)


                                  Development of Highly Active Natural Gas Reforming Catalyst for Internal Reforming in Low Temperature SOFC
                              Conclusions
   Catalysts prepared by LDH precursor are nanosized after
    pretreatment. The sizes of the crystallites derived from sols are
    smaller than those derived from precipitates.

   Catalyst derived from LDH sol has higher activity at lower
    temperatures than that derived from LDH precipitate. The activity of
    the catalyst is seen to be dependent on crystallite size.

   The light off temperatures for steam methane reforming on the
    tested catalyst in the work are round 300-350oC.

   Additional platinum group metals enhance the activity of Ni catalyst.
    The order of the enhancement is Pd>Pt>Rh.

                     Development of Highly Active Natural Gas Reforming Catalyst for Internal Reforming in Low Temperature SOFC
Jiexun Di
Department of Engineering Science, University of Oxford
Tel: +44 (0) 1865613451
E-mail: Jiexun.di@eng.ox.ac.uk




                          Thank You!




                      Development of Highly Active Natural Gas Reforming Catalyst for Internal Reforming in Low Temperature SOFC
Please Contact:

   Supervisor: Prof: Ashok Bhattacharya
    Department of Engineering Science, University of
    Oxford Parks Road, Oxford, UK OX1 3PJ
    Tel: +44 (0) 18652 73627
    Tel: Ashok.Bhattacharya@eng.ox.ac.uk

   Jiexun Di
    Department of Engineering Science, University of
    Oxford, Parks Road, Oxford, UK OX1 3PJ
    Tel: +44 (0) 18656 13451
    E-mail: Jiexun.di@eng.ox.ac.uk


                 Development of Highly Active Natural Gas Reforming Catalyst for Internal Reforming in Low Temperature SOFC

								
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