Study On The Mn-Ce/ZSM-5 Catalysts For Selective Catalytic Reduction Of NO_x With Ammonia

Nitrogen oxides,as major air pollutants,are resulting in a series of environmental issues,such as photochemical smog,acid rain and ozone depletion.Due to the harmful and multi environmental impacts on the atmosphere and people,NOx emission legislation is becoming increasingly strict among countries all over the world.Therefore,it is imminent to reduce and eliminate NOx pollution problem.Currently,the technology of ammonia selective catalytic reduction(SCR)is still the most efficient and widely used technology for reducing NOx emissions,and the key to this technique is the choice of an excellent catalyst.Outstanding activity and selectivity,in additionof good thermal stability,make it considerable that zeolites and modified zeolites have practical application prospect.Furthermore,ZSM-5 zeolites loaded by transition metal have been the research topic in academic circles.In this paper,Mn-zeolite catalysts were prepared by impregnation method,we changed conditions of carriers,active coponents,silica/alumina ratio and Ce doping modification to discuss their capacity of NOx removal.In our experiment,Mn/HZSM-5 was also studied focusing on its tolerance to H2O and its resistance to SO2,and we compared those with Mn/?Al2O3,Mn/TiO2 and V-W/TiO2.The main conclusions of this study areas follows:1.HZSM-5 was modified by various Mn loadings(1%,5%,10%,20%),the catalytic performance of the catalysts for NH3-SCR of NO could be improved by add ing amo unt o f M n.2.We changed silica/alumina ratio(25,38,50,80)of Mn/HZSM-5,the catalytic performance of the catalysts for NH3-SCR of NO are improved by the increase of the ratio,but when it exceeded 50,the denitrification activity of catalysts reduced.If Ce was doped in the Mn/HZSM-5,the Mn-Ce/HZSM-5 exhibits a broad temperature window for high NO conversions.3.Sulfur resistance is enhanced by the increase of silica/alumina ratio of Mn/HZSM-5,but when the ratio is more than 50,the capability of sulfur resistance is weakened;on this occasion,Mn-Ce/HZSM-5 exhibits superior tolerance to SO2;compared with Mn/?Al2O3?Mn/TiO2?V-W/TiO2 catalysts,Mn/HZSM-5 catalysts show the outstanding performance in the sulfur resistance4.the presence of H2O brings a slight decline for catalytic activity of Mn/y-Al2O3 and Mn/TiO2 at low temperatures(220? and 250? respectively),while it brings a slight promotion for catalytic activity of Mn/HZSM-5 and V-W/TiO2 at high tenperatures(350? and 400? respectively),in general,addition of 5%H2O(v/v)has little effect on the catalytic activity...