Bimetallic Ni-Cu catalyst supported on CeO2 for high-temperature water-gas shift reaction: Methane suppression via enhanced CO adsorption

The formation of methane as the undesired side product is one of the major issues in the water-gas shift (WGS) reaction, particularly for nickel-based catalysts. A detailed study of Ni-Cu bimetallic catalyst supported on nanopowder CeO2 is extensively investigated to suppress the methanation reaction as well as maintain high WGS reaction rate. XRD, EXAFS, H-2-TPR and XPS reveal the formation of Ni-Cu alloy, while CO-TPR-MS, CO-TPD-MS and in situ DRIFTS show the enhancement of CO adsorption on Ni-Cu alloy at high temperature. The Ni-Cu/CeO2 catalyst with Ni/Cu ratio of 1 exhibits high reaction rate with the least methane formation due to the formation of Ni-Cu alloy phase. The Ni-Cu alloy phase is found to be the active site for WGS reaction with methane suppression as Ni-Cu alloy can enhance CO adsorption which prevents CO dissociation during high-temperature WGS reaction. Kinetic studies performed reveal that one-site carboxyl mechanism could be the main reaction pathway with formate as spectator. However, there could be other possibilities for the real reaction mechanism on Ni-Cu/CeO2 catalyst. (c) 2014 Elsevier Inc. All rights reserved.