An investigation of the comparative reactivities of ethane and ethylene in the presence of oxygen over Li/MgO and Ca/Sm₂O₃ catalysts in relation to the oxidative coupling of methane.

In order to examine the importance of the further oxidation of the desired C₂ products in the oxidative coupling of methane, ethylene and ethane have been added to the feed (containing methane and oxygen) to a Li/MgO or Ca/Sm₂O₃ catalyst. The results of these measurements show that neither of these C₂ molecules is stable under these conditions with either of the catalysts. Additionally, the rates of the oxidation of ethane and of ethylene alone have been measured using a gradientless reactor for both catalysts as well as for a quartz bed. It was found that the Ca/Sm₂O₃ material had higher activities for the oxidation of C₂H₆ and C₂H₄ (and also of CH₄) than had the Li/MgO material. These higher activities result in a lower optimal reaction temperature for the oxidative coupling of methane and are (at least partially) responsible for the lower selectivity to C₂ products observed with the Ca/Sm₂O₃ catalyst compared to that with the Li/MgO catalyst.