A methane-containing gas such as natural gas is converted to a clean-burning hydrocarbon liquid fuel in a process wherein the gas is fed to a reaction vessel to contact a metallic catalyst grid that is formed from windings of a transition metal supported on an iron frame immersed in a liquid petroleum fraction, in such a manner that a voltage is generated in the grid between the windings and the frame. Product gas in the vapor phase is drawn from the head space above the liquid level and condensed to form the product fuel.