Journal
ACS CATALYSIS
Volume 1, Issue 6, Pages 574-582Publisher
AMER CHEMICAL SOC
DOI: 10.1021/cs2000472
Keywords
steam reforming; deactivation; coking; nickel; rhodium; Ni-Rh; catalyst; DFT; stepped surfaces; reforming; EXAFS
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Funding
- U.S. Department of Energy National Energy Technology Laboratory [DE-NT0004396]
- U.S. Office of Naval Research [N00014-06-1-0320]
- ConocoPhillips Corp.
- U.S. Department of Energy, Office of Basic Energy Sciences, Office of Science (DOE-BES-SC) [W-31-109-Eng-38]
- Department of Energy
- MRCAT member institutions
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Supported nickel catalysts are widely used in hydrocarbon steam reforming for producing hydrogen. Carbon deposition is a major cause of Ni catalyst deactivation. In this work, supported Ni and Ni/Rh catalysts were synthesized and tested for liquid hydrocarbon steam reforming. Carbon analysis on the spent catalysts illustrates that the carbon deposition is significantly reduced with inclusion of Rh. Extended X-ray Absorption Fine Structure (EXAFS) analysis indicates close interactions between Ni and Rh atoms. Density functional theory (DFT) results show that a Ni/Rh alloy is thermodynamically more stable than Ni and Rh alone at the synthesis and reaction temperatures. Adsorption, diffusion, and oxidation of carbon atoms over Ni and Ni/Rh alloy surfaces were examined by DFT calculations. Alloying with Rh reduces the stability of deposited carbon atoms an clusters over both terraces and steps: of the catalyst Moreover, Rh addition enhances the competition of oxidation reactions against carbon deposition by altering the relative diffusion rates and bond formation rates of the two processes.
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