The kinetics of methane oxidative coupling have been investigated over a Li/Pb/Ca catalyst in the presence Of CO2 in the feed gas. The reduction in CH4 conversion and increase in C2 selectivity, observed when CO2 is added to the feed gas, are accounted for by modifying rate equations for the heterogeneous reactions. The modification assumes that the number of active sites on the catalyst is determined by the equilibrium established between active Li2O2 and inactive Li2CO3. An Eley-Rideal type rate equation best describes a range of experimental data obtained at 700-degrees-C, including data acquired with CO2 added to the feed. Furthermore, the observed beneficial effect of adding auxiliary O2 to the midpoint of the catalyst in a fixed bed reactor is predicted by the model. Accordingly, the auxiliary O2 is thought to regenerate the catalyst thereby increasing CH4 conversion.