Regeneration of a sulfur-poisoned selective catalytic reduction catalyst at ambient conditions

Abstract

Despite the high sulfur resistance of vanadia-titania catalysts with physically mixed zeolite in the selective catalytic reduction of NOx (SCR), their regeneration is still challenging because it typically requires a large amount of energy or hazardous chemicals. This paper proposes an innovative regeneration strategy for prolonging the lifetime of the sulfur-poisoned catalyst. Our spectroscopic results revealed that the adsorbed water in the catalyst dissolves the deactivating material, ammonium bisulfate (ABS). We developed a regeneration protocol based on this finding, which was facilitated by dissolution of ABS in water adsorbed on the catalyst during the exposure to humid air at ambient temperature. The superior hydrophilic nature of zeolite resulted in a different water content between two physically mixed domains, promoting ABS migration from the vanadia active sites to zeolite and thus recovering the catalytic activity. This strategy is beneficial for the development of energy-efficient and environmentally friendly SCR systems.