The Study On Combined Denitration Performance At Low Temperature By MOFs And P-n Composite Catalyst

In recent years,nitrogen oxides（NOx）as one of the main pollutants in the atmosphere,not only seriously endanger the ecological environment,but also pose a threat to human health.The traditional SCR technology has high denitrification efficiency but its active window is narrow.Although the photocatalytic technology is green and environmentally friendly,its treatment of pollutants concentration is low.Therefore,in this paper,SCR technology and photocatalysis are combined to treat high-concentration NOx,and a new type of high-efficiency catalytic material is prepared to achieve high-efficiency removal of NOx at low temperatures.In this experiment,modified MOFs and Ag₂O/TiO₂ were prepared.The denitrification performance of nitrogen oxides was investigated.The samples were characterized by XRD,BET,XPS,UV-vis,thermogravimetry,H₂-TPR and photocurrent,and the reaction mechanism was discussed.In this paper,the MOFs materials such as MIL-53,Cu-BTC,MOF-5 were prepared by microwave hydrothermal method.The SCR reaction activity was optimized by functionalization modification and element doping.The results show that MIL-53-NH₂（Zr10%）has the best denitration efficiency,and the NOx removal efficiency can reach more than 80%at 200℃,which is nearly 50%higher than that of unmodified MIL-53.The results show that the modified MOFs have good thermal stability and adsorption performance.XPS and H₂-TPR results show that amino modification and Zr doping can improve the oxygen storage capacity of MIL-53,increase surface active oxygen species,and help improve the catalyst’s rapid SCR reaction activity.In this experiment,Ag₂O/TiO₂ catalyst was successfully prepared,and the photocatalytic denitrification experiment was carried out at room temperature.When the Ag:Ti ratio is 10%,the prepared Ag₂O/TiO₂（10%）has the best photocatalytic performance.When the NOx concentration is 16.9-23.6mg/m³,its denitration efficiency can reach more than 80%,and the highest can reach 91.7%.Compared with commercial catalysts,it has increased by nearly 35%.Combined with the characterization and analysis,it can be known that the TiO₂ and composite TiO₂ with anatase phase crystal form were successfully prepared in this paper.The study found that the recombination of Ag₂O can reduce the band gap of TiO₂ from 2.94e V to 1.94e V,broaden the visible light response range of TiO₂,inhibit the recombination of photogenerated electron-hole pairs,reduce carrier recombination,and improve the visible light utilization rate and photocatalytic activity.In addition,Ag₂O/TiO₂（10%）has excellent water resistance,SO₂ poisoning resistance and reusabilitCombining the above-mentioned high-efficiency denitrification material MIL-53-NH₂（Zr10%）with the heterojunction catalyst Ag₂O/TiO₂ to treat high concentrations of nitrogen oxides,the denitration efficiency is significantly higher than that of SCR alone,and the NOx removal efficiency can reach 97%,which broadened the applicable range of NOx concentration and realized low temperature and high efficiency denitrification.In addition,the combination of MOFs and Ag₂O/TiO₂ has good continuous performance,and the denitration efficiency can still reach more than 90%after three times of continuous use.