A transient kinetic study of the carbon dioxide reforming of methane over supported Ru catalysts

Carbon dioxide reforming of methane has been studied over ruthenium catalysts supported on silica, gamma-alumina, and a high surface area graphite. Transient kinetic analysis and temporal analysis of products were used to unravel the reaction mechanism and point out the specificity of each support. Over silica support, the most inert material, the whole reforming process occurs on the ruthenium phase and the fast ageing of the catalyst is related to a large residence time of surface carbon intermediates favouring polymerisation and graphitisation. Over graphite the support acts as a collector of CH(x) species which reduces the residence time of carbon species on the Ru phase and therefore leads to a very stable catalyst. Over alumina support the dry reforming of methane involves a complex reaction network in which the alumina hydroxyl groups feed continuously the active Ru phase in ii and O adspecies, which also limits the catalyst ageing. Accumulation of CO(x) adspecies on alumina also occurs during the reaction. (C) 1999 Academic Press.