THE ROLE OF CHLORINE IN THE PARTIAL OXIDATION OF METHANE TO ETHENE ON MGO CATALYSTS

The effect of dichloromethane on the activity and selectivity of an MgO catalyst in the methane coupling reaction has been investigated. The results indicate that the primary role of chlorine is to modify the surface of the catalyst so as to enhance the selectivity to ethane and ethene. The response of ethene and ethane to the introduction of dichloromethane is different, and this is taken as evidence that the dehydrogenation of ethane to ethene is not due to gas-phase reactions involving chlorine radicals. The physical properties of the catalyst before and after treatment with dichloromethane have been investigated using surface area measurements, X-ray diffraction and analytical transmission electron microscopy. Substantial changes in the morphology of the catalyst particles are observed but these do not account for the trends in catalytic properties. X-ray photoelectron spectroscopy has been used to determine the surface composition of the catalysts before and after treatment. Chlorine is observed in the treated catalyst at a surface concentration of 3%.