INVESTIGATION OF THE PARTIAL OXIDATION OF HYDROCARBONS ON METHANE COUPLING CATALYSTS

The conversion of methane, ethane and ethene has been investigated both as a homogeneous reaction and as a catalysed reaction over a wide range of temperatures. In the homogeneous reaction it was observed that the relative activities increased in the order methane<ethane<ethene. It was found that silicon carbide is a very effective material for quenching destructive gas-phase reactions and can be used to effectively eliminate the contribution from gas-phase reactions during the investigation of oxidation catalysts. A range of catalysts has been studied for the oxidation of these three hydrocarbons. In most cases it was observed that the rate of reaction increased in the order methane<ethene<ethane. The fact that ethene is lesstive than ethane is in conflict with recently published information but it is believed that the discrepancies may be due to contributions from gas-phase reactions in earlier published work. Very significantly, it has been found that a LiCl-promoted manganese oxide catalyst is capable of activating these hydrocarbons strictly according to the strengths of the C-H bonds. Thus, on this catalyst the order of reactivity increases in the order ethene<methane<ethane. The significance of these results in the modelling of the methane coupling reaction and the possibility of obtaining catalysts which allow the so-called "30%" yield limit to be breached are discussed. © 1990.