Study On The Preparation And The Performance Of Titanium Base And Vanadium Base Catalysts For Catalytic Ozonation Of NO_x

In recent years,the emission problem of nitrogen oxides?NO_x?has attracted great attention from people and the government.Due to industrial furnaces,sinter machines and other small and medium-sized coal-fired boilers,there is the low-temperature flue gas,and the denitrification technology of selective catalytic reduction?SCR?is not suitable?temperature range 320⁴00°C?.For the denitrification of low-temperature flue gas,especially the flue gas denitration under 160°C,NO is oxidized to soluble advanced nitrogen oxides by O₃,then the technology of both desulfurization and denitration was carried out by absorbing,which possess a place in terms of research and application.But the most critical part of this technology is the oxidation reaction,there is a problem of excessive O₃,that is the molar ratio of O₃/NO>1.0,resulting in higher denitration cost.Therefore,in order to reduce the amount of O₃ used in this study,the preparation of low-concentration catalytic O₃ oxidation?O₃/NO=0.6?catalysts,the corresponding activity and mechanism of NO_X removal were studied,providing a theoretical basis for catalyst design and engineering application in this direction.Firstly,black-TiO₂ and TiO₂ prepared?both are anatase phases?by a sol-gel method was tested for NO_x removal by catalytic O₃ oxidation.The activity of NO_x oxidation by catalytic O₃ over black TiO₂ and ordinary TiO₂ was compared,finding:black TiO₂ presented a 21.2%increase in NO_x removal as compared to O₃ alone;interestingly,black TiO₂ also performed an8.6%improvement in NO conversion in comparison to TiO₂ catalyst.Then the structures of catalysts were characterized by XRD,Raman,UV-vis,XPS and H₂-TPR,and the radicals were detected by EPR,suggesting that large numbers of oxygen vacancies and corresponding absorpted surface hydroxyls formed on black-TiO₂,which promoted the formation of HO₂·radicals,thus promoted deep oxidation from NO to HNO₃.Secondly,different amounts of F doped TiO₂ were used to obtain F-TiO₂ catalysts with different amounts of oxygen vacancies,and the structures of catalysts were characterized by XRD,UV-vis,Raman,PL and TG,suggesting that the oxygen vacancies concentration of catalysts followed the order of black-TiO₂>F-TiO₂-0.1>F-TiO₂-0.15>F-TiO₂-0.2>TiO₂.Then,the catalysts were tested for NO_X conversion by catalytic O₃ oxidation,F-TiO₂-0.15?The molar batching ratio of F/TiO₂ was 0.15?performed the highest NO conversion,the NO conversion was improved by about 19%over F-TiO₂-0.15 compared to TiO₂ and about 11%compared to O₃+H₂O alone.The catalyst structure-activity relationship,in-situ infrared and radicals detection characterization were investigated.Suggesting that the F sites and oxygen vacancies over F-TiO₂ were conducive to the conversion of O₃ to multiple ¹O₂,thereby promoting the highly selective conversion of NO to NO₂.In the process of NO_x absorption after O₃ oxidation,NO is difficult to be absorbed,and higher NO conversion is conducive to improving the denitrification efficiency.Finally,in order to further improve NO conversion,the surface of V₂O₅ catalyst was modified by F loading?F/V₂O₅?and the catalytic O₃ oxidation of NO_x over F/V₂O₅ was studied.Compared with the O₃+H₂O system and the V₂O₅ system,F/V₂O₅-1?The molar batching ratio of F/V₂O₅ was 1?performed 20.5%and 13.5%increase of NO conversion,respectively,and performed extremely high NO conversion,total 71%of NO conversion.Through the characterization of catalysts by SEM and XPS,it was found that the introduction of F decomposed the massive V₂O₅ into small strips,increased its surface area,and provided more active sites and reaction sites.Combining the detection of radicals and the analysis of activity data,finding that the catalyst promoted the decomposition of O₃ into·OH radicals,HO₂·radicals and ¹O₂,thereby achieving efficient conversion of NO.