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Catalysts for Hydrogen Production in Membrane and Sorbent Reformers

Catalysts for Hydrogen Production in Membrane and Sorbent Reformers. Paul van Beurden, Eric van Dijk, Yvonne van Delft, Ruud van den Brink , Daan Jansen. Hydrogen Production with CO 2 Capture. Conventional CO 2 /H 2 separation (PSA, scrubbers) involves many steps: Efficiency losses.

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Catalysts for Hydrogen Production in Membrane and Sorbent Reformers

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  1. Catalysts for Hydrogen Production in Membrane and Sorbent Reformers Paul van Beurden, Eric van Dijk, Yvonne van Delft, Ruud van den Brink, Daan Jansen

  2. Hydrogen Production with CO2 Capture • Conventional CO2/H2 separation (PSA, scrubbers) involves many steps: Efficiency losses N2, H2O Air O2, 79% N2 HTS GTCC H2 LTS Natural gas or Coal Reforming or Coal Gasification H2/CO2 separation Shift CO2

  3. Integration of shift- and CO2 capture steps N2, H2O Separation-Enhanced Water Gas Shift Air GTCC H2 Natural gas or Coal Reforming or Coal Gasification CO2

  4. One-step reforming and CO2 separation N2, H2O Separation-Enhanced Reforming Air GTCC H2 Natural gas CO2

  5. CH CH CH + H + H + H O O O 4 4 4 2 2 2 = Catalyst Separation-enhanced Reforming Steam reforming: CH4 + H2O 3 H2 + CO (H = 206 kJ/mol) Water-gas shift: CO + H2O H2 + CO2 (H = – 41 kJ/mol) Overall: CH4 + 2 H2O 4 H2 + CO2 CH CH CH + H + H + H O O O 4 4 4 2 2 2 Sorption- enhanced reactors Membrane reactors SMR-catalyst + CO2 adsorbent H2 Pd-alloy membrane H2 catalyst CO2 CO2 (+ traces CO, CH4, H2) steam H2(+ traces CO, CH4)

  6. The Water Gas Shift Equilibrium CO + H2O H2 + CO2 (H = – 41 kJ/mol) CO conversion Temperature

  7. Water Gas Shift Catalysts • Low-temperature shift catalysts • CuO /ZnO2 /Al2O3 • Operating Temperature: 185 – 275°C • Sulphur tolerance < 0.1 ppm • High-temperature shift catalysts • Fe3O4 / Cr2O3 • Operating Temperature: 350 – 520°C • Sulphur tolerance 50 ppm • Sulphur-tolerant shift catalysts • CoMoS • Operating Temperature: 250 – 500°C • > 100 ppm of sulphur is required in the feed

  8. HTS catalyst in separation enhanced CO2 capture

  9. The Methane Steam Reforming Reaction CH4 + 2 H2O 4H2 + CO2 (H = 165 kJ/mol) CH4 conversion Temperature

  10. Methane Steam Reforming Catalysts • Ni-based catalysts • Used in industrial reforming at 800 – 1000 °C • Prone to oxidation and carbon formation • Noble-metal based catalysts • Mainly Rhodium as active metal • Used/developed for low-temperature reforming and more dynamic reforming

  11. 70 60 50 40 Dispersion (%) 30 20 10 0 Activity at 400°C • CeO2 and ZrO2 seem to promote activity at low temperature CH4 2.9% H2O 17.5% N2 79.6% Flow 25 sccm T = 400 °C P = 1 atm 25 20 15 Activity (a.u.) 10 5 0 Rh/CZA Rh/LCZ Rh/TiO2 Rh/ZrO2 Rh/CeO2 Rh/Al2O3 Rh/MgAl2O4 Rh/Mordenite Rh/LaCaCrOx

  12. Activity at higher temperatures 70 60 Rh/CeZrO2 CH4 2.9% H2O 17.5% N2 79.6% Flow 25 sccm P = 1 atm Dilution 1:5 50 Rh/ZrO2 40 CH4 Conversion [%] Rh/Al2O3 30 20 Rh/CeO2 10 0 175 225 275 325 375 425 475 525 Temperature [C]

  13. Stability of commercial catalysts 70 Ni-catalyst Vendor A CH4 2.9% H2O 17.5% N2 79.6% Flow 25 sccm T = 500 °C P = 1 atm 60 50 Noble Metal catalyst Vendor B 40 Noble metal catalyst Vendor C CH4 Conversion [%] 30 Noble metal catalyst ECN Noble metal catalyst Vendor A 20 10 0 0 20 40 60 80 100 Time [hr]

  14. Membrane reformer:Experimental • ECN PdAg-membrane on ceramic support • Catalyst: Nickel based reforming catalyst • T = 650°C • Feed pressure = 11 bar(a) • Steam/CH4 ratio = 3

  15. Coke formation ! Membrane reformer • Equilibrium is shifted at lower space velocities 100% MR FBR 75% Thermo conversion 50% 4 CH 25% 0% 0,0 1,0 2,0 3,0 4,0 5,0 CH feed flow [nl/min] 4

  16. Materials Research – Experimental Apparatus Experimental conditions • 100 ml/min flows • 1 – 5 grams sample • 1 – 4 bar(a) • Sorbent only or sorbent/catalyst mixture Materials • Commercially available noble-metal based catalyst • 22 wt% K2CO3-Hydrotalcites

  17. Sorption-enhanced reforming: three individual cycles ads ads desorption ads desorption desorption ads 1.0 100% 0.9 90% CH 4 0.8 80% CO 2 Conversion 0.7 70% 0.6 60% concentration [vol%] 0.5 50% CH4 conversion [%] 0.4 40% 0.3 30% 0.2 20% 0.1 10% 0.0 0% 0 50 100 150 200 250 Time [min] Breakthrough of methane before CO2 Reaction conditions: 2.9% CH4, 17.5% H2O, 79.5% N2, 400°C

  18. Sorption-enhanced reforming • Using a higher amount of catalyst suppresses methane breakthrough • Amount of catalyst much higher than necessary to reach equilibrium 0.8 adsorption desorption solid line: 3.0 g cat + 3.0 g ads CO2 dashed line: 1.5 g cat + 3.0 g ads 0.6 Concentration [%] 0.4 CH4 0.2 0 0 10 20 30 40 Elapsed time [min] Reaction conditions: 2.9% CH4, 17.5% H2O, 79.5% N2, 400°C

  19. SESMR SESMR membrane Catalyst type 1wt% Rh Ni-based 1 wt% Rh Temperature [°C] 400 400 650 Sorbent/membrane [M Euro /yr] 2.7 2.7 0.9 Catalyst [M Euro /yr] 138 8 4.6 Natural gas [M Euro /yr] 96 96 97 Preliminary cost calculations for 400 MW NGCC • For sorption-enhanced reformers, noble-metal catalyst costs are enormous. • Rhodium-based catalyst costs are 5 times as high as Pd-membrane costs.

  20. Costs of Rhodium are very high at the moment…

  21. Challenges for catalysts in separation enhanced reactions • High activity at relatively low temperatures • Resistant to carbon formation

  22. Carbon formation • Possible routes to carbon formation: • Decomposition of CH4: CH4 2H2 + C (high T) • Boudouard: 2CO  CO2 + C (low T) 10 400 °C SR 500 °C 600 °C 8 700 °C ATR 6 H2 withdrawal H/C 4 Carbon Formation 2 DR 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 O/C

  23. Challenges for catalysts in separation enhanced reactions • High activity at relatively low temperatures • Resistant to carbon formation • Stability under high carbon or strongly reducing conditions • SERP: resistant to pure steam in sorbent regeneration step: Ni-based catalysts oxidise. • Membrane: no negative interaction with PdAg-membrane

  24. Conclusions • The catalyst is an issue for both membrane and sorption-enhanced reforming! • Nickel-based catalyst showed coking in membrane reactor experiment • Rh-based catalysts are very active, but price is too high. • Ce and Zr promote low-temperature activity • Stability uncertain

  25. Future work • Continue study of (pre)commercial catalysts • Study mechanism of low-temperature reforming and coke formation and development of low-cost catalysts. • Dutch CATHY-project with Technical University of Eindhoven. • Kinetics

  26. Acknowledgement CATO is the Dutch national research programme on CO2 Capture and Storage. CATO is financially supported by the Dutch Ministry of Economic Affairs (EZ) and the consortium partners. (www.co2-cato.nl) GCEP: Global Climate and Energy Program: • Stanford University • ExxonMobil, GE, Toyota, Schlumberger

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