Recent advances in sulfur poisoning of selective catalytic reduction (SCR) denitration catalysts

Selective catalytic reduction (i.e., SCR) denitrification has become the most popularly used denitrification technique owing to its high denitrification efficiency, clean process, and mature reliability. However, SO2 in the flue gas stream can poison catalysts and lead to catalyst deactivation. Thus, it is of great significance to investigate the poisoning mechanisms and anti-sulfur poisoning measures of the catalysts. This paper systematically reviews the sulfur poisoning mechanisms of several SCR catalysts (e.g., vanadium-based, cerium-based, manganese-based, copper-based, and iron-based), anti-sulfur measures (including doping of metal and non-metal elements, the use of carriers, and the control of catalyst morphology and structure). Results showed that the sulfur poisoning mechanisms of SCR catalyst mainly includes formation of ammonium sulfates and metal sulfates to block the catalyst pore and cover the active sites, competitive adsorption of SO2 and NOx, and the consumption of active components caused by SO2. Doping other elements and modifying morphology and structure of catalyst can protect the active sites of catalysts and alleviate the sulfate deposition and pore blockage issues. Doping elements can raise the denitrification efficiency of the catalyst by more than 20–70%, and modifying morphology and structure of catalyst can increase the denitrification efficiency by about 20%. Besides, regeneration of sulfur-poisoning catalyst was also reviewed. The most common methods of sulfur-poisoning catalysts regeneration are thermal regeneration and water-washing regeneration. Finally, some suggestions and prospects for design and development of anti-sulfur poisoning SCR catalyst in the future are commented.