Study On Multi-stage Optimization Of MnCo-BTC@SiO₂-HPMo Denitration Catalyst And Improvement Of Resistance To SO₂ And H₂O

H2O and SO2 in industrial flue gas decrease the denitrification activity of catalyst,and improving the anti-sulfur and anti-water performance of catalyst is one of the most important and difficult problems in denitrification technology.Metal organic framework(MOFs)catalysts have special morphology and gas adsorption properties,which can improve the overall denitrification performance(activity,selectivity,sulfur resistance and water resistance).Based on the common law of catalysts with excellent low temperature denitrification properties,the selfassembled MOFs catalyst was constructed,and the mechanism of catalytic reaction and resistance enhancement were explained.Firstly,MnCo-BTC catalyst with honeycomb morphology and spinel structure was synthesized by hydrothermal method.The selected MnCo-BTC catalyst(DMF:ethanol:water=5:1 solvent,calcination temperature 500℃)can maintain more than 95%SCR denitrification efficiency in the range of 150-300℃.The surface of MnCo-BTC catalyst is rich in active surface oxygen,Mn3+,Mn4+,Co3+,and Lewis acid sites.The honeycomb morphology and spinel crystal structure can improve the SCR denitrification efficiency and the adsorption characteristics of gas molecules,and inhibit the surface adsorption of SO2.At 200℃ and 100 ppm SO2,95%NOx conversion was maintained.However,the catalyst still has the disadvantage of low water resistance and N2 selectivity.Secondly,in order to improve the water resistance of the catalyst,MnCoBTC@SiO2 catalyst was synthesized by one-step hydrothermal method.It is found that MnCo-BTC@SiO2 has a large specific surface area,strong oxidationreduction and acidity,and has good water resistance.The NOx conversion is over 90%at 150-300℃ at 10 vol.%H2O.The hydrophobicity of catalyst is adjusted by SiO2 surface layer,and large pores are not conducive to condensation of water in catalyst channels due to capillary action,which is the main reason for its excellent water resistance.Finally,based on the strong acidity and high oxygen content of heteropolyacid,the N2 selectivity of catalyst was further improved by supported phosphomolybdate(H3PMo12O40,HPMo).The modified MnCo-BTC@SiO2HPMo catalyst has excellent NOx conversion(approximately 95%at 150-300℃)and N2 selectivity(100-300℃ higher than 90%).HPMo species reduced the high oxidation-reduction capacity of MnCo-BTC@SiO2,increased Br?nsted acid sites and N2 selectivity.HPMo modification inhibited excessive dehydrogenation of ammonia and enhanced adsorption of NH3 species at Br?nsted acid sites,which promoted L-H mechanism reaction.This study provides technical support for the industrial application and popularization of MOFs denitrification catalyst.