THE ROLE OF CL- IN A LI-ZNO-CL- CATALYST ON THE OXIDATIVE COUPLING OFMETHANE AND THE OXIDATIVE DEHYDROGENATION OF ETHANE()

The effect of Cl- ion addition to a Li+ -ZnO catalyst has been studied with respect to the oxidative coupling of CH4 and the oxidative dehyd rogenation (OXD) of C2H6. Increasing the Cl/Li ratio from 0.65 to 0.90 had relatively little effect on the CH4 conversion, whereas the C2H4/ C2H6 ratio was enhanced significantly as a result of an increase in th e OXD reaction rate. Conversely, loss of Cl- from the catalyst during the reaction had a much more deleterious effect on ethane OXD activity than on methane coupling activity. Addition of Cl- ions at a Cl/Li ra tio of 0.9 caused a decrease both in the number of basic sites and in the basic strength of these sites, as determined by temperature-progra mmed desorption of CO2. The similarities between the results obtained over Li+ -ZnO-Cl- catalysts and those previously reported for Li+ -MgO -Cl- catalysts confirm that basicity of the host oxide plays only a mi nor role in determining the properties of these chlorided catalysts.