Study On The Mechanism Of Selective Catalytic Reduction Of No With Propylene By Using Composite Metal Oxides Prepared By MOFs

In this paper,the research focuses on the preparation of metal oxide CeO₂-ZnO and MnO_x-ZnO catalysts by using MOF-5 as a template for the removal of nitrogen oxides in the field of environmental protection.The NO adsorption properties and the mechanism of selective reduction of NO on complex metal oxides CeO₂-ZnO and MnO_x-ZnO catalysts were studied by using C₃H₆ as reducing agent.The main research results are as follows:?1?A series of CeO₂-ZnO and MnO_x-ZnO catalysts were prepared by solvothermal-impregnation method.The properties of the doped metal can be well dispersed in the mixed metal oxide,and the specific surface area and pore volume of the catalysts are improved.The gas adsorption and reaction activity of catalysts were increased by this way.Besides,manganese shows the more uniform dispersion.?2?The catalysts doped of cerium increase the reducibility of the catalyst.The catalysts doped of manganese shows the characteristic peaks of Mn₃O₂ was reduced to Mn₃O₄ and Mn₃O₄ was reduced to Mn O.MnO_x-Zn O catalyst series is more reductive than CeO₂-ZnO catalyst series,probably because manganese is more abundant and dispersed more evenly.?3?Metal doping significantly improved the NO adsorption performance of the catalyst,and the best doping amount is 5%.The MnO_x-ZnO catalyst series has stronger adsorption and higher desorption ability than the CeO₂-Zn O catalyst series NO.?4?DRIFTS results show that,at 250?,NO and O₂ adsorb on the surface of5%CeO₂-ZnO and then monodentate nitrates and bridged bidentate nitrites produced.Propene is adsorbed on the surface of the catalyst and then??CH?,acetate and alkene?CH₂?produced and these intermediate products react with nitrates to produce H₂O and CO₂.For 5%MnO_x-ZnO,NO and O₂ produce bridged bidentate nitrites on the surface of the catalyst,and then the bridged bidentate nitrites convert to bidentate nitrites and monodentate nitrates.Then the C₃H₆-SCR reaction produce acrylate,formate and acetate,accompanied by H₂O and CO₂.MnO_x-ZnO catalyst series havse more type of nitrates than CeO₂-ZnO nitrate.Mn doping promoted the increase of Lewis acid sites on the catalyst surface.