Oxidative Coupling of Methane on MgO–MgSO4 Catalysts in the Presence and Absence of Carbon Tetrachloride

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Abstract
The effect of carbon tetrachloride (CCl4) on the oxidative coupling of methane on binary catalysts containing MgO and MgSO4 was studied at 1048 K. With no CCl4 in the feedstream the conversion of methane increased with increasing content of MgO in the binary catalyst, but was even further enhanced by introducing a small partial pressure of CCl4. The selectivity to ethylene increased upon the addition of CCl4, but was not dependent on either the concentration of CCl4 in the feedstream or the relative amounts of the two components in the catalyst. X-Ray photoelectron spectroscopic analyses of the used catalysts showed that the sulfate is partially transformed into the oxide as well as the formation of Cl species in the near-surface region of the catalysts during the methane conversion process. The addition of CCl4 enhances the conversion of sulfate to oxide. The oxide formed by the decomposition of the sulfate and the chlorine species plays different roles in improving the catalytic activities by introducing CCl4.