Synthesis Of Copper-Based MOFs And Its Mechanism Of SCR Denitration Synergistic Mercury Removal

Nitrogen oxides（NO_x）and mercury（Hg⁰）produced by coal combustion are harmful to the atmospheric environment.How to cefficiently remove NO_x and Hg⁰ has become a research ho tspot.As the NH₃-SCR process is widely used in the flue gas denitration of coal-fired power plants,it is the most direct,simple and economic technology to use the existing SCR denitration process to achieve efficient mercury removal.Therefore,it is of practical significance to develop a highperformance SCR denitration synergistic mercury removal catalyst to removal pollutants from coal-fired flue gas.Metal organic framework materials（MOFs）have large specific surface area,more unsaturated metal active sites,and more significant porosity to be used in the field of environmental protection.Based on this,a series of catalysts are synthesized by the hydrothermal method.Their physicochemical properties are studied by SEM-EDS,XRD,FT-IR,Raman,BET,TG,XPS characterization.Through the NH₃-SCR reaction,the synergistic performance of denitration and mercury removal is investigated.The main achievements are as follows:（1）The effect of seven different carboxylic acid ligands on the effective construction of CuBTC is studied.The results show that the catalyst synthesized with 1,3,5-phenylenetricarboxylic acid and 1,2,4-phenylenetricarboxylic acid as ligands have a typical metal organic framework structure.On this basis,the catalyst performance is investigated by NH₃-SCR reaction.Cu-BTC synthesized with 1,3,5-benzenetricarboxylic acid as ligand shows a better NO conversion,reaching 77.51%at 240℃.（2）The synthesis conditions of the Cu-BTC catalyst（hydrothermal time,hydrothermal temperature,molar ratio of substrate to ligand）are optimized by using the control variable method.The results shows that when the molar ratio of substrate（Cu（NO3）2·3H₂O）to ligand（1,3,5benzenetricarboxylic acid）is 1:1,the hydrothermal time is 12 h,and the temperature is 120℃,the synthesized Cu-BTC has a good structure,and the highest yield is 98.71%.On this basis,the catalyst performance is investigated by NH₃-SCR,and Cu-BTC shows a good denitration and mercury removal performance.The removal rates of NO and Hg⁰ reach 73.64%and 53.14%respectively at 240℃.（3）Cu-Ce-BTC catalyst is synthesized by directional regulation of Cu-BTC through the onepot hydrothermal method,which further improves the catalyst’s denitration and mercury removal performance.The structural characterization shows that Cu-Ce-BTC retains both Cu-BTC and Ce-BTC characteristic peaks,indicating that the Ce element successfully enters the skeleton structure of Cu-BTC.On this basis,the catalytic performance of Cu-Ce-BTC is investigated by NH₃-SCR.It is found that the addition of Ce has a particular promotion effect on the catalytic activity.When the Cu/Ce ratio is 2:1,Cu-Ce-BTC shows good denitration and mercury removal performance.The removal rates of NO and Hg⁰ reach 88.38%and 77.14%at 240℃,respectively.（4）Halogens（Cl,Br,I）are introduced into Cu-Ce-BTC by pre and post-modification,which improve the catalytic performance of denitration and mercury removal,and systematically study the mechanism of halogen on catalytic denitration and mercury removal.The structural characterization shows that before and after halogen modification,the Cu-Ce-BTC catalyst maintains its original structural characteristics,and C-X（Cl,Br,I）bonds appear,indicating that the halogen successfully enters the skeleton structure of Cu-Ce-BTC.The performance of the catalyst is investigated by NH₃-SCR reaction.It shows that the catalytic activity of Cu-Ce-BTC is improved by halogen post modification as follows:Cl>Br>I.（5）The effect of different Cl content on the structure and performance of Cu-Ce-BTC are studied.The structure characterization shows that Cu-Ce-BTC catalyst maintains its original crystal structure.By XPS analysis,covalent C-Cl species appear on the catalyst surface,which can effectively capture Hg⁰.The catalyst performance is investigated by NH₃-SCR reaction.When the Cl content is 7%,the removal rates of NO and Hg⁰ are 96.19%and 84.64%at 240℃.（6）The effect of flue gas component on the performance of Cu-Ce-BTC-7%-Cl catalyst for denitration and mercury removal is investigated.The results show that O₂ significantly promotes the removal of NO and Hg⁰.NO has little effect on the removal of NO and Hg⁰.NH₃ can promote the removal of NO and inhibit the removal of Hg⁰.SO₂ and H₂O have a particular inhibitory effect on the removal of NO and Hg⁰,and H₂O has a more apparent inhibitory effect.