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

摘要

Steam reforming of ethanol over Ni on high surface area CeO{sub}2 support, synthesized by a surfactant-assisted approach, (Ni/CeO{sub}2 (HSA)), was 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/Al{sub}2O{sub}3 and Ni on conventional ceria (Ni/CeO{sub}2 (LSA)) under the same conditions. Above 800°C, the main products from the reforming processes over Ni/CeO{sub}2 (HSA) were H{sub}2, CO, and CO{sub}2 with small amount of CH{sub}4 depending on the inlet ethanol/steam ratio, whereas high hydrocarbon compounds i.e., C{sub}2H{sub}4 and C{sub}2H{sub}6 were also observed from the reforming of ethanol over Ni/CeO{sub}2 (LSA) and Ni/Al{sub}2O{sub}3 in the range of conditions studied (700-1000°C). Excellent ethanol reforming performances of Ni/CeO{sub}2 (HSA) in terms of stability, reactivity, and product selectivities are due to the high redox property of CeO{sub}2 (HSA). During the ethanol reforming process, in addition to the reactions on Ni surface, gas-solid reactions between the gaseous components presented in the system (C{sub}2H{sub}5OH, C{sub}2H{sub}6, C{sub}2H{sub}4, CH{sub}4, CO{sub}2, CO, H{sub}2O, and H{sub}2) and the lattice oxygen (O{sub}x) on ceria surface also take place. Among these redox reactions, reactions of adsorbed surface hydrocarbons with lattice oxygen (O{sub}x) can eliminate the formation of high hydrocarbons (C{sub}2H{sub}6 and C{sub}2H{sub}4), which easily decompose and form carbon species on Ni surface.