Coals were converted to gaseous products containing benzene as a main organic product and methane, other aliphatic hydrocarbons and acetone as organic by-products, and carbon dioxide by reaction with a mixture of copper(II) dioxide and aqueous potassium carbonate solution at 400 degrees C. The relation of the yield of benzene and the carbon content of coals was bell-shaped, in which the maximum yield was observed in the intermediate carbon content region.