Research progress in the SO<sub>2</sub> resistance of denitration catalysts in low-temperature NH<sub>3</sub>-SCR reactions

Abstract

<p indent="0mm">NH₃-SCR reaction is one of the most widely used denitration technologies at present, and the catalyst is the core of the NH₃-SCR technology. Because of its low-temperature activity and easy deactivation in the presence of SO₂, the research on the low-temperature sulfur-resistance of denitration catalysts becomes a hot spot. In this review, the deactivation mechanism of NH₃-SCR catalysts in the presence of SO₂ is reviewed. It is found that the deactivation of the catalysts is mainly due to the reaction of SO₂ with NH₃ and metal-active sites; the formation of ammonium sulfates or ammonium bisulfates will block the pores of the catalysts and affect the efficiency of the catalysts; the metal sulfates will lead to the deactivation of the active sites of the catalysts and cause the irreversible deactivation of the catalysts; the competitive adsorption of SO₂ and NO will also cause the deactivation of the catalysts. Based on the known mechanism of catalyst deactivation, some effective strategies for improving the SO₂ tolerance are proposed: reducing the adsorption and oxidation of SO₂, constructing sacrificial sites to protect active sites and promoting the decomposition of sulfates. It is found that the sulfur resistance of the catalysts can be improved by some methods: such as metal modification, the special structure of catalysts, the influence of supports, acid catalysts. Finally, the development prospect of low-temperature sulfur-resistant NH₃-SCR denitration catalysts is prospected.