Study on SO₂ Poisoning and Regeneration of the Low-Temperature Fe–Sn–Mn/TiO₂ Catalyst for Simultaneous Removal of NO_x and Mercury

Abstract

A catalyst of Fe−Sn−Mn/TiO 2 was synthesized by the impregnation method employed for selective catalytic reduction (SCR) to remove NOx and mercury at a low temperature. The effects of SO 2 on the performance and poisoning of the catalyst Fe−Sn−Mn/TiO 2 and the regeneration of water washing, acid washing, and thermal reduction on the activity restoration of the deactivated catalyst were investigated. The sulfur poisoning and regeneration mechanisms were determined through a comprehensive array of characterization methods. The findings show that SO 2 causes irreversible deactivation of the Fe−Sn−Mn/TiO 2 catalyst. The consumption of metal active components and deposition of metal sulfates/sulfites, as well as ammonium sulfates/sulfites on the catalyst surface, are proven to be the primary cause to the deactivation. Stirring water washing and sulfur acid washing effectively remove ammonium sulfates/sulfites and metal sulfates/ sulfites adhered to the catalyst surface so that the poisoned catalyst is recovered to its original activity as effectively as the fresh one. The thermal reduction regeneration exhibits effectiveness in eliminating ammonium sulfates/sulfites yet falls short of completely removing metal sulfates/sulfites, and the acid sites are consumed under NH 3 atmosphere, leading to 80% recovery of the activity compared with the fresh catalyst.