Investigation Of Activated Carbon Supported Metal Oxides Catalysts For HC-SCR Of NO

Nitric oxides?NO_X?are a major cause of air pollution and are main contributors to photochemical smog,acid rain and haze,Consequently,more strict emission controls of NO_X emissions is under investigation.In a variety of denitration techniques,the Selective catalytic reduction of NO_X using NH₃ as a reductant?NH₃-SCR?is considered one of the most efficient approaches.However,NH₃-SCR denitration technology has some disadvantages.such as high operating temperature and narrow temperature operating window,secondary environmental pollution caused by waste catalyst,andhigh toxicity of NH₃ as a reductant,etc.Therefore,it is urgent to develop efficient,environmentally friendly and low-temperature SCR denitrification technology.Hydrocarbons?CxHy?have good reducibility.In contrast,researchers at home and abroad have carried out a lot of researchs on HC-SCR flue gas denitration technology.In this paper,an environmentally friendly SCR denitrification technology at moderate and low temperatures was developed using safer C₂H₄ as reductant,low-cost activated carbon with large specific surface area as carrier and environmentally friendly metal oxides as active ingredients,and its catalytic performance and stability were studied.Firstly,a series of Mn/AC,Fe/AC,Cu/AC catalysts were prepared by equal volume impregnation.Based on fixed bed reactor,the effects of temperature,loading and composition on catalytic performance were investigated.The results show that Mn/AC catalyst has better denitrification performance at low temperature?150-200°C?.But there are also phenomena of rapid decline in catalytic activity and low stability.Taking 3%Mn/AC as an example,the possible reasons for the poor stability of the catalyst were explained by BET,SEM,EDS,XRD,Raman,TEM,XPS and other characterization methods.The results show that the active component of the catalyst is composed of highly active MnO₂ during the catalyst reaction.It turned into low-activity Mn₃O₄ and accumulated.Secondly,in the catalytic reaction process,C₂H₄ decomposes into carbon black and forms new polymers with active components to deposit in the catalyst pore,blocking the pore size,and the reactant molecules can not easily diffuse into the pore,thus reducing the catalytic activity of HC-SCR catalyst.Aiming at the poor stability of monometallic catalysts,A series of Fe-Mn/AC catalysts were prepared by equal volume impregnation.The effects of Fe doping on the catalytic performance of Mn/AC were investigated by characterization of BET,SEM,EDS,XRD and Raman.The results showed that there was a strong synergistic effect between Fe and Mn,and a new active component Fe₃Mn₃O₈ was formed,which significantly improved the denitrification performance and catalytic stability of the catalyst.