Study On The Deactivation Mechanism Of Ce/TiO₂ SCR Catalyst Under The Coexistence Of Multiple Poisoning Compositions

With the gradually increase of disposal capacity of municipal solid waste incineration（MSWI）in China in recent years,many environmental problems brought by it have attracted much attention.Nitrogen oxides（NO_x）as the main gaseous pollutants in MSWI flue gas,not only damage ozone layers,but also lead to the formation of acid rain and photochemical smoke.They have a serious impact on both biology and environment.In order to effectively control the nitrogen oxides produced by MSWI,selective catalytic reduction（SCR）of NO_xwith NH₃ has been put into extensive application.Especially,stable and efficient catalysts are the key factor of this technology.The commonly used vanadium-based catalysts are difficult to meet increasingly strict standards for engineering applications due to their narrow operating temperature range,biological toxicity and vulnerability to the deactivation of multiple pollutants in flue gas.Compared to coal-fired power plants,the flue gas composition of MSWI is more complex,wherein the heavy metals,alkali metals and acidic gases can significantly reduce the performance of SCR catalysts.However,the deactivation of catalysts by multiple poisoning compositions has rarely been studied in practical application.Therefore,cerium-titanium oxide catalyst with good SCR activity at medium temperature was selected as the research object in this study.And the deactivation mechanisms under the coexistence of multiple poisoning compositions were discussed detailly.In this paper,Ce/Ti O₂ catalysts were prepared by sol gel method and their SCR performance were evaluated under the coexistence of multiple poisoning compositions.XRD,BET,XPS,H₂-TPR,NH₃ and NO-TPD and in situ DRIFT were carried out to systematically study the deactivation effects of cerium-based catalyst under the coexistence of heavy metals,alkali metals and acidic gases.The study reveals that Zn could severely block the active sites of catalyst,resulting in the loss of surface acid sites and the decrease in redox capacity.The adsorption of reactants on the surface of catalyst is inhibited,which further reducing the catalyst SCR activity.The treatment of HCl could increase the number of strong acid sites on the surface of catalyst,and enhance the adsorption capacity and reactivity of NH₃.Therefore,a deactivation offset effect is discovered when Zn and HCl coexist on Ce Ti catalyst.The SCR activity of catalyst at low and medium temperatures is significantly inhibited when Zn and S coexist on the catalyst.However,the treatment of S could generate new active sites,which improves the adsorption capacity and SCR activity of catalyst at higher temperatures.The active sites of catalyst are severely damaged or blocked when Zn,K,and S coexist on Ce Ti catalyst.The adsorption capacity of catalyst is extremely inhibited and the reactivity of adsorbed species is also affected.As a consequence,the SCR performance of catalyst is greatly weakened.