Fullerene black is an active catalyst for the dehydrogenation of methane. Hydrogen and pyrocarbon are formed as the main products in the first hours of pyrolysis at 1000 degrees C. The methane conversion decreases with time on account of the formation of pyrocarbon, and C2+ hydrocarbons appear in the products. During pyrolysis of an initial mixture of methane with 50 mol.% hydrogen, in contrast to the thinning of methane with argon, from the very start of the process the dehydrodimerization of methane occurs with a stable methane conversion (4.2%) and a selectivity with respect to ethylene of 89-94% without the formation of pyrocarbon.