Hydrocarbon formation from methane by a low-temperature 2-step reaction sequence

At atmospheric pressure thermodynamics limits direct conversion of methane to higher hydrocarbons to temperatures above 1200 K. Converting methane at lower temperatures requires at least two steps occurring under different conditions. This paper reports such a low-temperature conversion route toward ethane, propane, butane, and pentane without using oxygen. The overall reaction consists of two steps. Methane is dissociatively adsorbed on a Group VIII transition-metal catalyst at a temperature around 700 K, resulting in surface carbonaceous species and hydrogen. In the second step a particular carbonaceous intermediate is able to produce small alkanes upon hydrogenation around 373 K. The maximum yield to CnH2n+2 (n > 1) obtained on a Ru catalyst is 13%.