PROMOTION BY TETRACHLOROMETHANE OF THE OXIDATIVE COUPLING OF METHANE ON SILICA-SUPPORTED ALKALINE-EARTH OXIDES

The introduction of a small quantity of tetrachloromethane into the feed stream has been shown to remarkably enhance the oxidative coupling of methane over alkaline earth oxides supported on silica. That this enhancement, in terms of both selectivity and yield to CZ hydrocarbons, occurs over a wide range of catalyst loading, feed composition, reaction temperature, and contact time has been illustrated using BaO/SiO2 as the catalyst. It has been demonstrated that over this catalyst, the coupling and the nonselective oxidation processes occur predominantly independently of each other. The high ratio of C2H4/C2H6 observed in the products is accounted for by the rapid homogeneous oxidative dehydrogenation of C2H6, a process which is evidently further enhanced by the presence of TCM. It is suggested that TCM promotes the coupling reaction by facilitating the hydrogen abstraction step from methane. Continuous cofeeding of the additive is required to maintain high selectivity and yield of C2 hydrocarbons in the products. © 1990.