Research On The Preparation Of MnO_x/SEP Catalyst And The Performance In Removal Of NO By SCR At Low Temperature

Selective catalytic reduction(SCR)of nitrogen oxides had proven to be the main viable technology for removing fixed source nitrogen oxides.In recent years,Mn-based denitration catalysts had been widely used in the SCR field due to their excellent denitration activity.The SCR activity of most catalysts in the low temperature range(<250 ?)was not ideal.The nanostructure of the catalyst support was beneficial to the low-temperature SCR reaction,making more and more researchers pay attention to the research of nanostructure catalyst supports.Sepiolite is a natural one-dimensional nanofibrous clay mineral,which has a large specific surface area and a large number of acid sites on the surface,and has the performance characteristics of a low-temperature SCR catalyst carrier.In this paper,sepiolite as the carrier for the first time to prepare manganese based catalysts(MnOx/SEP).In this paper,MnOx was loaded onto sepiolite(SEP)by in-situ deposition,impregnation and precipitation methods respectively to prepare a series of MnOx/SEP catalysts.The effects of different preparation methods on the denitrification activity of the catalyst and the dispersibility of the active component on the surface of the carrier were investigated.The results showed that the surface active components prepared by the in-situ deposition method were loaded more evenly and uniformly,and the denitrification activity was up to 100%at 200 ?.Therefore,for the adoption of sepiolite as carrier,in situ deposition method was a potential ideal preparation method to prepare low-temperature catalyst.Based on the comparison and optimization of the preparation methods,the MnOx/SEP catalyst prepared by the in-situ growth method was the main research object,and the influence of the preparation parameters(precursor,manganese loading,reactant ratio)and operating conditions(velocity,temperature,sulfur resistance)on the low temperature SCR denitration performance of the catalyst were investigated.The relationship between the preparation methods and conditions and the structure characteristics of the catalysts was thoroughly investigated.Through analysis and discussion of the structure-activity relationship between the catalyst structure characteristics and denitrification performance,the mechanism and chemistry nature of the low-temperature SCR denitrification activity of the catalysts studied in this article were revealed.The results showed that the MnOx/SEP catalyst prepared with n(Mn(AC)2)/n(KMnO4)of 3:2 with manganese acetate as precursor had the best SCR denitrification activity.The catalyst prepared under this condition had a maximized specific surface area and enables the active component to be highly dispersed on the support surface and had an optimal Mn4+/Mn3+ ratio.Because of the existence of SO2 in the flue gas during the practical application of SCR catalyst,which is also the main reason for most of the SCR catalysts to be poisoned and deactivated at low temperature.Therefore,the anti-toxicity performance of the prepared MnOx/SEP catalyst in sulfur-containing atmosphere was also evaluated and the improved method was explored.The anti-poisoning performance in the atmosphere was evaluated and an improvement was explored.The results showed that the sulfur resistance of MnOx/SEP catalysts was not ideal,but the effect of improving the sulfur resistance of MnOx/SEP catalysts by doping CeO2.Mn-Ce/SEP catalyst prepared by in-situ deposition method had the best sulfur-tolerant denitration activity when the molar ratio of Mn(CH3COO)2)/n(KMnO4)/n(Ce(NO3)3)was 1:1:1.