Research progress of low-temperature SCR denitration catalysts

Abstract

Nitrogen oxide NOx (NO, NO_2, and N_2O) is one of the major pollutants in the air pollution, it can cause environmental problems such as photochemical smog, acid rain, and ozone layer destruction, which has posed threat to people's living environment and quality of life, and attracted great attention from the world. Countries made stricter emission standards for burning emissions from both fixed and mobile sources. The major denitrification technologies include selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR), oxidative denitrification, and activated carbon adsorption and denitrification at present. The SNCR has higher conditions in industrial applications, the main factors affecting successful operation are temperature, ammonia-nitrogen ratio, distribution of ammonia gas in the flue gas and residence time, so there were certain limitations in industrial application of SNCR. Compared with other denitrification technologies, SCR denitration technology is more widely used in industrial application, in which denitration is mostly arranged after dust removal and desulfurization, at this time, the temperature is mostly between 100~250℃. The performance of SCR denitrification in low-temperature must be improved, which is one of the most promising flue gas DeNOx technology. In this paper, the recent works on low-temperature SCR catalysts were reviewed on manganese-based catalysts, vanadium-based catalysts and carbon-based catalysts. Single-component Mn-based catalysts, supported Mn-based catalysts and composite Mn-based catalysts were reviewed, the effects of preparation of V-based catalysts on the de-dumping and denitrification mechanisms were described. The effect of transition metal doping on C-based catalysts was reviewed. The influence of H_2O and SO_2 resistance on low-temperature NH_3-SCR catalytic activity and reaction mechanism were also discussed. Finally, the virtues advantages and defects of low temperature SCR catalysts were summarized, and the future development direction was also given out. Key learning points: (1) Catalysts for different systems were reviewed. The problems of manganese-based catalysts, vanadium-based catalysts and carbon-based catalysts were analyzed. The preparation methods were used to improve the water and sulfur resistance and catalytic activity of the catalysts. (2) Denitrification mechanism. From the currently reported denitration mechanism to analyze the activity of the catalyst, it is expected that the mechanism rsearches will improve the low temperature performance of the catalyst. (3) Water and sulfur resistance of low temperature catalyst. The presence of SO_2 at low temperatures tends to result in ABS deposition.