Study On The Properties,Characterization And Application Of Mn-Ce Series Catalysts

SCR technology has been one of the most popular NO_x removal technology in the world as the best effect of denitrification,the most widely used and the most mature technology of denitrification technology.The catalyst,as the core of SCR technology,has always been the focus of attention of researchers.Manganese oxide has been confirmed with good low-temperature SCR activity,while cerium oxide has attracted widly attention because of its unique redox ability and oxygen storage capacity.Therefore,it has important scientific and practical significance for the study of them.In this paper,a series of MnO_x-CeO₂ catalysts with excellent performance were prepared by using CeO₂ as additive and carrier.The catalysts with better performance were supported on carriers to expand the actual production.In this paper,we first used the hydrothermal deposition method,with potassium permanganate and cerium nitrate as raw material.Using the oxidation-reduction reaction between them prepare different Mn/Ce ratio of Mn-Ce non-supported catalysts.NH₃-SCR denitrification performance test results showed that it has the best denitrification performance when the Mn/Ce ratio is 3:In the range of 100¹80?denitrification rates are maintained at above 95%.XRD,TG and BET results showed that the catalyst has good dispersion,low crystallinity and a large specific surface area,Mn mainly in the form of MnO₂ with high priced.H₂-TPR results showed that the catalyst has a better reduction performance than the catalysts with other ratio,MnO₂ is reduced to MnO will be divided into two steps:MnO₂ is first reduced to Mn₃O₄ and Mn₃O₄ then be reduced to MnO.DRIFTS results showed that the NH₃-SCR reaction on the surface of 3MC catalyst followed the Eley-Rideal mechanism.Firstly,NH₃ is adsorbed on the surface of the catalyst?mainly in the Lewis acid position?to form the coordination state of ammonia,and then react with the gas phase NO reaction generated intermediate product NH₂NO,and finally decomposed into N₂ and H₂O.Two methods of impregnation and hydrothermal deposition were used to load MnO_x on CeO₂,to explore the effect of CeO₂ as a carrier.It is found that both of the two methods showed the best denitrification performance with the Mn/Ce mole ratio at 0.4,and the performance of the hydrothermal deposition method was better than the impregnation method.At 180?,the denitrification rate of 0.4MC-i was less than70%,while the 0.4MC-h could reach 80%.Manganese oxides were well dispersed in the 0.4Mn/CeO₂ catalysts prepared by both of the two methods,but 0.4MC-h had larger specific surface area,pore volume,pore size and higher reducibility than0.4MC-i,and manganese oxide existed in the form of nanorods in the 0.4MC-h is more favorable for the contact between the active component and the reactive gas.All of these are beneficial to the SCR reaction.The Mn-Ce composite oxide was used as the active component,which was respectively supported on P25 TiO₂,Al₂O₃ and activated carbon?AC?.The results showed that the denitrification performance of Mn-Ce/TiO₂ and Mn-Ce/Al₂O₃ was significantly higher than that of Mn-Ce/AC.When the reaction temperature was lower than 160?,3MCT sample with TiO₂ as the carrier had the best performance of denitrification?reach 98%at 120??,and when the reaction temperature was higher than 160?,the denitrification performance of 3MCA sample with Al₂O₃ as the carrier rose above the 3MCT.XRD and H₂-TPR results showed that 3MCT has better Mn-Ce dispersion and reduction ability than 3MCA.To change the content of Ce in Mn-Ce/TiO₂,it was found that the appropriate Ce addition would increase the low temperature denitrification activity of Mn/TiO₂ catalyst.XRD results showed that Ce doping could reduce the crystallinity of Mn oxide on the TiO₂ support and increase the dispersion of active ingredient.H₂-TPR results showed that Ce doping could improve the reduction ability of the catalyst.All of these are beneficial to the SCR reaction.Compared with common catalyst preparation methods,hydrothermal deposition method could get excellent performance of Mn-Ce/TiO₂ without heat treatment.Heat treatment would reduce the performance of the catalyst and the active temperature window would shift to the high temperature segment.XRD,BET and H₂-TPR results indicated that heat treatment would result in the reduction of the specific surface area and pore volume of the catalyst.Furthermore,The addition of Ce could effectively improve the ability of anti SO₂ poisoning of the catalyst.Reducing the specific surface area and pore volume losses of catalyst during poisoning.