Reaction routes for methane conversion on transition metals at low temperature

Two new metal catalysed routes for methane conversion are discussed: methane oligomerization and methane addition to olefins. These reactions are realized in a reaction cycle consisting of several steps. In both reaction sequences methane is first dissociatively adsorbed on a reduced transition metal catalyst between 500 and 800 K resulting in surface carbon and hydrogen. A particular highly reactive surface carbonaceous intermediate is found to produce C2+ hydrocarbons upon hydrogenation between 300 and 400 K. The maximum yield for higher hydrocarbons is 13% obtained on a Ru/SiO2 catalyst. When olefins are co-adsorbed together with surface carbon generated from methane, more C2+ hydrocarbons are produced. Experiments with 13C labelled CH4 and unlabelled olefins demonstrate that surface carbon from methane is incorporated into the co-adsorbed olefins