Method for thermal conversion of methane and reactor for carrying out the method

In a method of thermal conversion of methane to hydrocarbons of higher molecular weight in an elongated reaction zone, comprising a heating zone and a cooling zone following said heating zone, said method comprising circulating a charge comprising a gas mixture containing methane in the heating zone in a direction of flow substantially parallel to the axis of the elongated reaction zone, said heating zone comprising a plurality of electric heating means arranged in substantially parallel sheets which form a bundle of triangular, square or rectangular pitch in transverse elevation, said heating means being grouped in successive cross sections substantially normal to the direction of the reaction zone, the sections being independent of one another and supplied with electricity so as to establish at least two parts in the heating zone, the first part enabling the charge to be brought to a maximum temperature of above about 750.degree. C. to no more than about 1500.degree. C. and the second part, which follows the first, enabling the charge to be maintained at a temperature substantially equal to said maximum temperature, and cooling effluent from the heating zone by introducing a cooling fluid into the cooling zone and collecting said hydrocarbons of higher molecular weight at the end of the reaction zone, the improvement wherein the electric heating means are insulated from direct contact with the gas mixture containing methane by sheaths into which a gas containing hydrogen is fed, said sheaths having sufficient permeability and said gas fed into said sheaths being at a sufficient pressure, such that at least part of the hydrogen is diffused from the inside of said sheaths to at least selected locations on the outside of said sheaths.