The plasma-driven gas-phase thermal decomposition of methane yielding hydrogen and solid-phase carbon has been suggested as an environmentally friendly alternative to conventional methods of producing hydrogen from natural gas. The advantage of the process is that hydrogen is obtained directly from methane without producing CO2 as a byproduct. The process was experimentally examined using a modified version of a dc plasma reactor originally developed for the conversion of methane to acetylene. Carbon yields of 30%, a factor of 6 increase, with a corresponding decrease in acetylene yield were obtained by simply increasing the residence or reaction time. A detailed kinetic model that includes the reaction mechanisms resulting in the formation of acetylene and heavier hydrocarbons through benzene is described. A model for solid carbon nucleation and growth is included. The model is compared to experimental results and is used to examine process optimization.

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This report describes the experimental demonstration of a process for the direct thermal conversion of methane to acetylene. The process utilizes a thermal plasma heat source to dissociate methane. The dissociation products react to form a mixture of acetylene and hydrogen. The use of a supersonic expansion of the hot gas is investigated as a method of rapidly cooling (quenching) the product stream to prevent further reaction or thermal decomposition of the acetylene which can lower the overall efficiency of the process.

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