INFLUENCE OF THE PRESENCE OF CHLORINE ON THE SELECTIVITY TO ETHANE AND ETHENE DURING METHANE COUPLING OVER SAMARIUM-BASED CATALYSTS

The oxidative coupling of methane to ethane and ethene has been investigated on chlorine-containing catalysts. The sensitivity of the product distribution to temperature, gas composition, flow-rate, catalyst mass, and reactor dimensions has been demonstrated. It has been found that a long contact time is an important factor in raising the C2H4/C2H6 ratio, and that reactions within the catalyst bed are important for the conversion of ethane to ethene. Back-mixing of the reagents into the gas space above the catalyst bed tended to lead to combustion, but appeared to have little influence on enhancing the C2H4/C2H6 ratio. Experiments have been performed with Sm2O3, SmOCl and SmCl3 and with various pairs of these catalysts when separated by a gas space. These experiments have demonstrated the importance, under certain circumstances, of gas phase chlorine species, especially radicals, in the conversion of ethane to ethene. However, the results also show that these chlorine-induced gas phase reactions occur within the voids between the particles in the catalyst bed and not in the free gas space outside the catalyst bed.