Abstract: A process for converting a gaseous reactant comprising methane or natural gas to higher molecular weight hydrocarbon products is disclosed which comprises: (1) contacting said gaseous reactant with an oxidative coupling catalyst at a reaction temperature of at least about 900.degree. C. for an effective period of time to form an intermediate product comprising ethane, ethylene or a mixture thereof, said catalyst being characterized by a melting point above said reaction temperature; and (2) pyrolyzing said intermediate product at a temperature of at least about 900.degree. C. for an effective period of time to form said higher molecular weight hydrocarbon products using exothermic heat generated by the formation of said intermediate product. Novel oxidative-coupling catalysts having melting points above about 900.degree. C. are also disclosed.