Promoting effect of Si on MnOx catalysts for low-temperature NH3-SCR of NO: Enhanced N2 selectivity and SO2 resistance

Abstract

Manganese-based catalysts have excellent catalytic performance for the effective removal of NOx in low-temperature flue gas through selective catalytic reduction with NH3 (NH3-SCR). However, the catalysts suffer from poor SO2 resistance and N2 selectivity in the actual process, which still need to be solved. In this study, MnOx-SiO2 mixed oxide catalysts were designed and prepared by coprecipitation method to improve the SO2 resistance and N2 selectivity in NH3-SCR process. In the presence of 100 ppm SO2, MnOx-SiO2(0.72) catalyst showed excellent sulfur resistance with the conversion of NOx reached 95 % even after introducing SO2 for 8 h. The doping of SiO2 greatly improved the specific surface area and surface acidity of the catalyst, which was conducive to the adsorption of NH3. Meanwhile, the redox performance of the catalyst was decreased, improving the N2 selectivity. The study on the sulfur resistance mechanism revealed that the doping of SiO2 reduced the adsorption of SO2 on the surface of catalyst, protecting the active components and avoiding the accumulation of sulfates, thus achieving good sulfur resistance performance. This work provided an environmentally friendly NH3-SCR catalyst by inhibiting SO2 adsorption to have good catalytic performance and SO2 resistance.