Preparation And Performance Of Fe-Ti-based Catalyst For Selective Catalytic Reduction Of NO_x With Ammoni

Nitrogen oxides cause acid rain and photochemical smog,which are serious risks to human health.Therefore,it is crucial to reduce NOx emissions.Among the many technologies to control NOx emissions,the NH3-SCR process is currently the most effective means.And the catalyst is the center of the SCR reaction.Due to the development of rapid industrialization,high sulfur coal has been used in a vast number of thermal power plants,which will increase the sulfur content in the flue gas,and the traditional vanadium-based catalysts cannot meet the requirements of denitration.Therefore,it is necessary to prepare an environmentally friendly catalyst with excellent catalytic activity in the flue gas with high sulfur content.Iron oxide is a suitable component for NH3-SCR denitrification reaction catalyst because it is easy to obtain and green,but its own activity is very poor.In addition,TiO2 is often used as one of the important components of SCR catalysts based on its properties.Therefore,in this paper,Fe-Ti-based oxides were used as catalysts for the study,which were modified by sulfation and addition of Ce and Sm.NH3-SCR denitrification catalysts with good sulfur and water resistance were designed and synthesized,and various characterization tools were used to investigate the effects of catalyst structure and physicochemical properties on catalytic performance.A series of CemFeTiOx(a=0.05,0.1,0.2)catalysts modified with Ce were synthesized by solvothermal method.Using multiple characterizations,the addition of Ce was found to increase the specific surface area of the catalyst,improve the redox ability of the catalyst and increase the acidity.Among them,Ce0.1FeTiOx samples possessed the best catalytic activity and also showed good resistance to water and sulfur.In addition,the reaction mechanism of the catalysts and the reasons for the enhanced water and sulfur resistance were investigated in detail using in situ DRIFTS tests.However,in the presence of high SO2 concentration,the catalytic activity of the catalyst was not satisfactory and needs to be further improved.Sulfation strategies were used to improve the sulfur resistance of the catalysts.FeTi4Ox-S and FeCe0.5Ti4Ox-S catalysts were synthesized using co-precipitation method.The effect of sulfated treatment on the anti-sulfur ability and the effect of Ce addition on the catalytic activity are investigated,and with the help of various characterizations,it was found that the acidity of the sulfated catalysts increases significantly and the antisulfur ability was improved substantially.The FeCe0.5Ti4Ox-S catalyst displayed the best active temperature window and can reach 100%NO conversion,good N2 selectivity in the temperature range of 290-450℃ and excellent resistance to sulfur poisoning.However,its resistance to water is poor.The water resistance of FeCe0.5Ti4Ox-S catalyst was improved by Sm.A series of FeCe0.5SmaTi4Ox-S(a=0.1,0.3,0.5)catalysts with different amounts of Sm were synthesized by coprecipitate method.The effects of Sm addition on the physicochemical properties of the catalysts and the catalytic activity in the presence of SO2 and H2O were investigated in detail using various characterization methods.Among these catalysts,FeCe0.5Sm0.3Ti4Ox-S showed the best catalytic activity,with 100%NO conversion at 260450℃.It was shown that the addition of appropriate amount of Sm was beneficial to increase the acidic sites and redox ability of the catalyst surface.In addition,in situ DRIFTS studies demonstrated that Sm addition produced new sulfate species that can generate new B acid sites with H2O,which promoted the adsorption of NH3 and thus improving the water resistance of the catalyst.In this paper,based on Fe-Ti oxide,the addition of Ce and Sm successfully prepared NH3-SCR denitrification catalyst with wide active temperature window and excellent water and sulfur resistance,and the mechanism of the effect of Ce and Sm addition on the catalyst activity and water and sulfur resistance was studied in detail.It lays a foundation for the application of iron-based oxide catalyst in industrial flue gas denitrification.