Understanding the impact of promoters on enhancing and inhibiting the sulphur resistance and regeneration of supported Pd catalysts for complete methane oxidation

The efficient treatment of methane emissions from natural gas-powered engines is necessary due to the high potency and global warming potential of methane. Promoters are often employed to enhance catalysts’ performance and stability for methane oxidation. It is therefore important to understand the impact of promoters on Pd activity, especially under practically relevant conditions. Here, we report the enhancement and inhibition effect of promoters (ZrO₂, CeO₂, and TiO₂) on the sulfur resistance and regeneration of alumina-supported Pd catalysts for complete methane oxidation in the presence and absence of moisture. The type of promoter employed and the presence of moisture influence the type of sulfur species formed on the alumina-supported Pd catalysts, as well as their catalytic performance and regeneration. Whereas ZrO₂ enhances both the activity and SO₂ resistance and enhances the regeneration of the poisoned catalysts under both dry and wet reaction conditions, more stable sulfate species are formed in the presence of CeO₂ and TiO₂, inhibiting both the catalysts’ performance and regeneration. In addition, the presence of ZrO₂ protects the active Pd sites from progressive deactivation over sulfur poisoning and regeneration cycles. The results of this work provide insights into how promoters influence the activity, sulfur poisoning and regeneration of methane oxidation catalysts in the presence and absence of moisture, which have implications for the practical design of industrially relevant catalysts.