Promoter action of KCl on CuCl 2/SiO 2 catalysts used for the oxyhydrochlorination of methane

Abstract

The effect of KCl addition on the catalytic activity and product distribution of SiO 2-supported CuCl 2 catalysts has been investigated. The activity of these K-containing catalysts can be related to the release of chlorine atoms from the surface which initiate a gas phase chain reaction. The active phase of these catalysts is molten under reaction conditions (700 Torr, 670 K). In this case, the presence of KCl in the melt increases the catalytic activity and favors the regeneration of the catalyst. However, overdoses of KCl have a negative effect on both, catalyst activity and stability. When KCl is not added to the CuCl 2 catalyst, the reaction can still proceed by an alternative path over the solid surface, probably involving the dissociative chemisorption of methane. As opposed to the effect observed at 670 K, at lower temperatures, e.g., 500 K, the addition of KCl reduces the catalytic activity by blocking copper chloride active sites.