Synthesis Of Co-based Bimetallic MOF-74 Catalysts And Its Application In CO-SCR

Nitrogen oxides(NO_x)produced by fossil fuels combustion are a major pollutant that caused manifold environment problems such as photochemical smog,acid rain,and ozone depletion in recent years.Carbon monoxide(CO)is also a highly toxic pollutant in human blood and nervous system.Both these gases usually coexist in industrial waste gas.Totally,selective catalytic reduction of NO(SCR)is a widely-used NO_x removal technologies method.Moreover,selective catalytic reduction of NO with CO(CO-SCR)is recognized as a more attractive and promising denitration technology because it can not only remove the NO and CO of exhaust gases simultaneously,but also eliminate the cost of purchase,carry and reserve of an additional reducing agent.Catalysts are the crux of CO-SCR system and the development of catalysts is a hot research topic in this field.Metal-organic skeleton(MOFs)is a new porous crystalline material composed of metal group and organic link group.Because of its high specific surface area,strong adsorption capacity,multi-functional metal center and modifiable pore structure,the metal-organic skeleton is a new type of porous crystalline material which is composed of metal group and organic link group.It has been widely used in many fields such as gas storage separation,chemical sensing and catalysis.In particular,MOF-74-M(M=Mn,Co,Ni,Mg,and Zn)exhibited a honeycomb structure in which doping metals are coordinated and coordinated to oxygen atoms.MOF-74 is capable of exposing a plenty of coordinatively unsaturated metal sites as catalytically active centers for the reduction of NO.However,to the best of our knowledge,the preparation of MOFs and their application in CO-SCR have been seldom reported.Therefore,in this study,bimetallic MOF-74-CoMn and MOF-74-CoNi catalysts were prepared and applied in CO-SCR The purpose of improving the denitrification efficiency of CO-SCR reaction was achieved due to the synergetic effect between both metal ions.The main results are as follows:1.Bimetallic MOF-74-CoMn catalysts with different molar ratios were synthesized by solvothermal method and their CO-SCR activity was tested.The experimental results show that the NO_x conversion of bimetallic MOF-74-CoMn catalyst is generally higher than that of single metal MOF-74-Co catalyst,and the reaction temperature window is wider.The MOF-74-Co1Mn2 catalyst with a Co/Mn ratio of 1:2 has the best denitrification effect.In the temperature range of 175 ~oC,the conversion of NO_x was close to 100%.2.XPS characterization show that the synergistic effect between metal Co and Mn could change the charge balance on the catalyst surface,which could promote the formation of oxygen vacancies and produce unsaturated chemical bonds on the catalyst surface,and then promote the catalytic activity in CO-SCR.The results of In-situ FTIR characterization showed that the CO-SCR catalytic reaction on the surface of bimetallic MOF-74-CoMn catalyst followed the L-H mechanism.3.Bimetallic MOF-74-CoNi catalysts with different molar ratios were synthesized by solvothermal method.The results of TGA showed that the synthesized materials had good stability.It was found that:The NO_x conversion of bimetallic MOF-74-CoNi catalyst was significantly higher than that of pure MOF-74-Co,and 1:4 was the best ratio of Co/Ni.