Study On The Effect Of Boron-modified Support On The Denitration Performance Of V₂O₅/TiO₂ Catalyst

Nitrogen oxide（NO_X）emissions not only have a certain impact on human health,but can also cause serious environmental pollution.The country has the strictest emissions regulations on nitrogen oxides in history.Selective Catalytic Reduction（SCR）of NO_X by NH₃（NH₃-SCR）technology is considered to be the most effective method to reduce NO_X emission at present.The catalyst is one of the most important parts of the technology.At present,the flue gas emission of the fixed source is characterized by lower exhaust temperature,while the exhaust temperature of the mobile source is also lower when it operates under low load.The traditional V₂O₅/Ti O₂ catalyst has poor low-temperature denitrification activity,and it is difficult to meet the strict emission regulations.Given the existing problems of the V₂O₅/Ti O₂catalyst,the modification of the V₂O₅/Ti O₂ catalyst was studied.To improve the conversion efficiency of nitrogen oxides,we designed and developed a catalyst with a wide active temperature window and good applicability.The preparation and performance test of the catalyst was carried out.Boron-modified V₂O₅/Ti O₂ catalyst was prepared by sol-gel and impregnation methods.Through the activity test,it is found that the Boron-modified catalyst can not only improve the low-temperature activity of the catalyst,but also broaden the activity temperature window.Moreover,different doping amounts of Boron and different calcination temperatures of support and load also have a certain influence on catalyst activity.The optimum preparation process parameters were obtained through the evaluation of catalyst activity:Boron 2.0wt.%,the calcination temperature of the support 600℃,and the calcination temperature of the load 350℃.Under these conditions,the NO_X conversion of the catalyst can reach 94.3%at 210℃.Characterization and analysis of the catalyst were carried out.To explore the effect of Boron modification on the structure and performance of the catalyst,a series of modern characterization techniques were used to study it.XRD results show that Boron modification can promote the transformation of Ti O₂ crystal form from rutile to anatase.The BET results show that the specific surface area and pore volume of the catalyst can be increased by Boron modification.SEM results show that Boron modification can promote the dispersion of active components and make the catalyst grain more uniform.XPS analysis showed that part of Boron entered the void of Ti O₂lattice and formed Ti-O-B structure,and part of Boron formed B₂O₃.In addition,the Boron modification can enhance the acidity of the sample surface and facilitate the generation of superoxide atom O^2-.According to the results of reducibility and surface acidity analysis,the Boron-modified catalyst can not only enhance its reducibility but also improve the surface acidity of the catalyst.The suitability and stability of Boron-modified catalyst were studied.The applicability and stability of the Boron-modified V₂O₅/Ti O₂ catalyst were investigated by activity tests at different reaction temperatures,space velocities,ammonia/nitrogen ratio,O₂ content,and NO inlet concentration.It was found that the activity of the catalyst was highly dependent on the reaction temperature,while the inlet concentration of NO had little effect on the activity of the catalyst.The stability experiment of the catalyst shows that the catalyst has high stability and durability.Sulfur and water resistance tests show that the catalyst still has high denitration activity under complex conditions.Transient response experiments show that SCR reaction on this catalyst follows E-R mechanism.The reaction kinetics of Boron-modified catalyst was studied.The reaction kinetics experiments were carried out on Boron-modified V₂O₅/Ti O₂ catalyst.The experimental results show that the conversion rate of NO was a first-order reaction with NO and the nearly half-order with O₂.The activation energy of Boron-modified V₂O₅/Ti O₂ catalyst is 64969.2 J·mol^-1,which is lower than that of traditional V₂O₅/Ti O₂ catalyst,indicating that the Boron-modified catalyst can effectively reduce the reaction activation energy and improve the activity of the catalyst.