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 GTCC Air O 2, 79% N 2 N 2, H 2 O LTS Reforming or Coal Gasification Shift H 2 /CO 2 separation CO 2 H2H2 HTS Natural gas or Coal

GTCC Air N 2, H 2 O Reforming or Coal Gasification Separation-Enhanced Water Gas Shift CO 2 H2H2 Natural gas or Coal Integration of shift- and CO 2 capture steps

Separation-Enhanced Reforming Natural gas One-step reforming and CO 2 separation GTCC N 2, H 2 O Air CO 2 H2H2

Separation-enhanced Reforming Steam reforming: CH 4 + H 2 O 3 H 2 + CO (  H = 206 kJ/mol) Water-gas shift: CO + H 2 O H 2 + CO 2 (  H = – 41 kJ/mol) Overall: CH H 2 O 4 H 2 + CO 2 CH 4 + H 2 OCH 4 + H 2 OCH 4 + H 2 O SMR-catalyst + CO 2 adsorbent H 2 (+ traces CO, CH 4 ) Sorption- enhanced reactors CH 4 + H 2 OCH 4 + H 2 OCH 4 + H 2 O Pd-alloy membrane catalyst Membrane reactors H2H2 H2H2 steam CO 2 (+ traces CO, CH 4, H 2 ) = Catalyst

The Water Gas Shift Equilibrium CO + H 2 O H 2 + CO 2 (  H = – 41 kJ/mol) CO conversion Temperature

Water Gas Shift Catalysts Low-temperature shift catalysts ‑ CuO /ZnO 2 /Al 2 O 3 ‑ Operating Temperature: 185 – 275°C ‑ Sulphur tolerance < 0.1 ppm High-temperature shift catalysts ‑ Fe 3 O 4 / Cr 2 O 3 ‑ 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

HTS catalyst in separation enhanced CO 2 capture H 2 membranesCO 2 sorbents T > 520 °CIn case of high CO concentration Pre-shift necessary, high steam demand Oxidation by steamMay be an issueIn regeneration mode: Hydrogen co-feeding Reduction because CO 2 /CO ratio too low -May be an issue at high temperature Interaction with membrane / sorbent Possible Separate catalyst from membrane Possible Not observed in experiments

The Methane Steam Reforming Reaction CH H 2 O 4H 2 + CO 2 (  H = 165 kJ/mol) CH 4 conversion Temperature

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

Activity at 400°C CeO 2 and ZrO 2 seem to promote activity at low temperature Rh/LCZ Rh/CZA Rh/ZrO2 Rh/CeO2 Rh/TiO2 Rh/Al2O3 Rh/MgAl2O4 Rh/Mordenite Rh/LaCaCrOx Activity (a.u.) Dispersion (%) CH 4 2.9% H 2 O 17.5% N % Flow 25 sccm T = 400 °C P = 1 atm

Activity at higher temperatures Temperature [C] CH4 Conversion [%] CH 4 2.9% H 2 O 17.5% N % Flow 25 sccm P = 1 atm Dilution 1:5 Rh/CeZrO 2 Rh/ZrO 2 Rh/Al 2 O 3 Rh/CeO 2

Stability of commercial catalysts Time [hr] CH4 Conversion [%] Ni-catalyst Vendor A Noble Metal catalyst Vendor B Noble metal catalyst Vendor C Noble metal catalyst Vendor A Noble metal catalyst ECN CH 4 2.9% H 2 O 17.5% N % Flow 25 sccm T = 500 °C P = 1 atm

Membrane reformer: Experimental ECN PdAg-membrane on ceramic support Catalyst: Nickel based reforming catalyst T = 650°C Feed pressure = 11 bar(a) Steam/CH 4 ratio = 3

Membrane reformer Equilibrium is shifted at lower space velocities 0% 25% 50% 75% 100% 0,01,02,03,04,05,0 CH 4 feed flow [nl/min] CH 4 conversion MR FBR Thermo Coke formation !

Experimental conditions -100 ml/min flows -1 – 5 grams sample -1 – 4 bar(a) -Sorbent only or sorbent/catalyst mixture Materials Research – Experimental Apparatus Materials -Commercially available noble-metal based catalyst -22 wt% K 2 CO 3 -Hydrotalcites

Sorption-enhanced reforming: three individual cycles Time [min] concentration [vol%] 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% desorption ads CH 4 CO 2 Conversion Reaction conditions: 2.9% CH 4, 17.5% H 2 O, 79.5% N 2, 400°C Breakthrough of methane before CO 2 CH 4 conversion [%]

Sorption-enhanced reforming Using a higher amount of catalyst suppresses methane breakthrough Amount of catalyst much higher than necessary to reach equilibrium Reaction conditions: 2.9% CH 4, 17.5% H 2 O, 79.5% N 2, 400°C Elapsed time [min] Concentration [%] adsorptiondesorption solid line: 3.0 g cat g ads dashed line: 1.5 g cat g ads CH 4 CO 2

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.

Costs of Rhodium are very high at the moment…

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

Carbon formation Possible routes to carbon formation: ‑ Decomposition of CH 4 : CH 4  2H 2 + C (high T) ‑ Boudouard: 2CO  CO 2 + C (low T) O/C H/C 400 °C 500 °C 600 °C 700 °C Carbon Formation ATR SR H 2 withdrawal DR

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

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

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

Acknowledgement CATO is the Dutch national research programme on CO 2 Capture and Storage. CATO is financially supported by the Dutch Ministry of Economic Affairs (EZ) and the consortium partners. ( GCEP: Global Climate and Energy Program: ‑ Stanford University ‑ ExxonMobil, GE, Toyota, Schlumberger