低温NH_(3)-SCR脱硝催化剂抗SO_(2)中毒性能的研究进展

Research progress in the SO_(2) resistance of denitration catalysts in low-temperature NH_(3)-SCR reactions

氨选择性催化还原(NH_(3)-SCR)是目前应用最广的脱硝技术之一,其中催化剂是NH_(3)-SCR技术的核心,但由于NH_(3)-SCR催化剂的低温活性一般较差且容易SO_(2)中毒失活,因此研究脱硝催化剂的低温抗硫性能成为热点.本文综述了NH_(3)-SCR脱硝催化剂在SO_(2)存在下的失活机理.催化剂的失活主要是由于SO_(2)与NH_(3)、金属活性中心发生反应,生成的硫酸铵盐堵塞催化剂孔道进而影响催化效率,生成的金属硫酸盐会导致活性中心的不可逆失活,SO_(2)和NO竞争吸附导致失活.根据催化剂失活机理提出抗SO_(2)中毒的几种有效策略,可以通过降低SO_(2)的吸附和氧化,构建牺牲位点保护活性位点和促进硫酸盐的分解来保护活性中心,进一步提高催化剂的抗硫性能,从而梳理出几种提高脱硝催化剂抗SO_(2)中毒性能的方法,如金属改性、催化剂的特殊结构、载体的选择、酸化催化剂等.最后对低温抗硫NH_(3)-SCR脱硝催化剂的发展前景进行了展望.

NH_(3)-SCR reaction is one of the most widely used denitration technologies at present,and the catalyst is the core of the NH_(3)-SCR technology.Because of its low-temperature activity and easy deactivation in the presence of SO_(2),the research on the low-temperature sulfur-resistance of denitration catalysts becomes a hot spot.In this review,the deactivation mechanism of NH_(3)-SCR catalysts in the presence of SO_(2)is reviewed.It is found that the deactivation of the catalysts is mainly due to the reaction of SO_(2)with NH_(3)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 SO_(2)and NO will also cause the deactivation of the catalysts.Based on the known mechanism of catalyst deactivation,some effective strategies for improving the SO_(2)tolerance are proposed:reducing the adsorption and oxidation of SO_(2),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 lowtemperature sulfur-resistant NH_(3)-SCR denitration catalysts is prospected.