The Research On Preparation And Modification Of Low Temperature SCR Catalyst Ce-Mn/TiO₂

Recently,the harm of NO_X to environment and human has been more and more serious.Low temperature SCR technology has received widespread attention for the advantages of low running energy consumption and easy to implement transformation in power plants,etc.Therefore,developing SCR catalyst with excellent low temperature activity and SO₂ tolerance is the key to achieving the layout of tail end SCR.In this paper,the low temperature SCR catalyst Ce-Mn/TiO₂ is prepared,then respectively be modified by doping metal and nonmetal elements.The effects of modification on low temperature activity and SO₂ tolerance are studied.Firstly,The preparation conditions of Ce-Mn/Ti O₂ are preferred.The study find that the optimal preparation method: impregnation method;the optimal loading: Ce/TiO₂ is 20%,Mn/TiO₂ is 5.2%（mass ratio）;the optimal calcination conditions: with synthetic air,calcine 2 h at 500℃.Catalyst prepared according to the above conditions has optimal low temperature denitration activity.At 160℃,the NO_X conversion rate is 99%.Secondly,the effects of Mn/Ce codoping on low temperature activity in NO_X removal are studied.Activity evaluation and characterization results show that Mn/Ce codoping improves the surface reactive oxygen species of catalyst,which facilitates the oxidation of NO to NO₂.The simultaneous presence of NO and NO₂ promote the Fast SCR reaction,thereby significantly reduce the activity temperature of the catalyst.Then,on the basis of Ce-Mn/TiO₂ above,the catalyst is modified by doping metal element X（Fe,Cu,Co）.Fe-doped catalyst shows best denitration activity at low temperature,NO_X conversion rate nearly 96% at 100℃.But doping Fe reduces the catalyst tolerance to SO₂.Doping Fe enhances the catalyst surface acidity,especially the amount of strong acid,which promotes the adsorption of NH₃,playing an important role in improving the low temperature activity.Finally,Ce-Mn/TiO₂ is modified by doping nonmetal element F.Doping F by sol-gel method improves the low temperature activity,instead by impregnation method reduces low temperature activity.Further study of F-doped catalyst prepared by sol-gel method shows that when F/Ti is c%（mole ratio）,NO_X conversion rate close to 61% at 100℃.The resistance to SO₂ is similar with undoped catalyst.