Steam Reforming of Ethanol over Ni on High Surface Area Ceria Support: Influence of Redox Properties on the Catalyst Stability and Product Selectivities

Abstract

The steam reforming of ethanol over Ni on high surface area CeO2 support, synthesized by a surfactant-assisted approach, (Ni/CeO2 (HSA)) were studied under solid oxide fuel cell (SOFC) operating conditions. The catalyst provides significantly higher reforming reactivity and excellent resistance toward carbon deposition compared to Ni/Al2O3 and Ni on conventional ceria (Ni/CeO2 (LSA)) under the same conditions. At the temperature above 800{degree sign}C, the main products from the reforming processes over Ni/CeO2 (HSA) were H2, CO, and CO2 with small amount of CH4 depending on the inlet ethanol/steam ratio, whereas high hydrocarbon compounds i.e., C2H4 and C2H6 were also observed from the reforming of ethanol over Ni/CeO2 (LSA) and Ni/Al2O3 in the range of conditions studied (700-1000{degree sign}C). The excellent ethanol reforming performances of Ni/CeO2 (HSA) in terms of stability, reactivity, and product selectivities are due to the high redox property of CeO2 (HSA). During the ethanol reforming process, in addition to the reactions on Ni surface, the gas- solid reactions between the gaseous components presented in the system (C2H5OH, C2H6, C2H4, CH4, CO2, CO, H2O, and H2) and the lattice oxygen (Ox) on ceria surface also take place. Among these redox reactions, the reactions of adsorbed surface hydrocarbons with the lattice oxygen (Ox) can eliminate the formation of high hydrocarbons (C2H6 and C2H4), which easily decompose and form carbon species on Ni surface.