Mechanistic aspects of the dry reforming of methane over ruthenium catalysts

Carbon dioxide reforming of methane has been studied over two ruthenium cat alysts supported on silica and on gamma-alumina. Catalytic activity measure ments, infrared spectroscopic analysis and isotopic tracing experiments app lied to the study of the surface hydroxyl groups of the supports have allow ed different reaction mechanisms to be proposed on the bases of the detecte d surface species, their mobility, stability and reactivity. Activation of both reactants takes place on the ruthenium surface for Ru/SiO2 catalyst. T he accumulation of carbon adspecies formed from methane decomposition on th e metallic particles finally impedes carbon dioxide dissociation and induce s rapid deactivation of this catalyst. The alumina support provides an alte rnate route for CO2 activation by producing formate intermediates on its su rface that subsequently decompose releasing CO. This bifunctional mechanism , in which the hydroxyl groups of the support play a key role, induces grea ter stability on the Ru/Al2O3 catalyst by significantly decreasing the rate of carbon deposition on the metal. The proposed reaction pathway requires continuous surface mobility of species from the metal to the support and vi ce versa. (C) 2000 Elsevier Science B.V. All rights reserved.