Methanation of gas streams containing carbon monoxide and hydrogen

A cyclic process for the production of methane from carbon monoxide-containing gas streams comprising:

• (a) passing a carbon monoxide-containing gas stream having a hydrogen concentration of at least about 50% by volume, based on the volume of CO present in said stream, through a hydrogen separation unit to separate said hydrogen in a recoverable form from said gas stream;
• (b) passing the thus-preheated carbon monoxide-containing gas stream over a catalyst present in a metal state and capable of catalyzing the disproportionation of carbon monoxide at a pressure of from about 1 to about 100 atmos and a temperature of from about 100.degree. C. to about 350.degree. C., said carbon monoxide thereby being decomposed to form carbon dioxide and an active surface carbon that is deposited on said catalyst, said gas stream being passed over the catalyst for a time sufficient to deposit a surface layer of said active surface carbon on the catalyst essentially without the subsequent formation of inactive coke thereon;
• (c) contacting said layer of active surface carbon deposited on the catalyst with said hydrogen removed from the carbon monoxide-containing gas stream of step (b) above at a pressure of from about 1 to about 100 atmos and a temperature of from about 100.degree. C. to about 400.degree. C. for a period of time sufficient to convert said active surface carbon to methane;
• and
• (d) passing additional carbon monoxide-continuing gas through said pretreatment hydrogen separation zone, and over said catalyst from step (c) and repeating steps (b) and (c) on a cyclic basis,
• whereby relatively pure methane can conveniently be produced from carbon monoxide-consuming gas streams containing appreciable quantities of hydrogen on a cyclic basis, the use of said hydrogen removed from the feed gas for the conversion of the active surface carbon to methane enhancing the utilization of the CO content of said feed and the overall process for the production of relatively pure, low-cost methane therefrom.