A Research On V₂O₅-WO₃/TiO₂catalysts For Selective Catalytic Reduction Of Automotive Diesel Engine NO_x

In recent years, Nitrogen oxides emissions continue to increase in ourcountry.Nitrogen oxides (NOx) are not only hazardous to human health but also harmful tothe environment. It is the best method to develop the advaneed technology about dieselengines and exhaust aftertreatmenis for redueing the pollutants from vehieles.In recentyears, the practial application of diesel engines are widely applied in medium/heavypassenger cars or trucks with the advantages of big power and low consumption.Nevertheless, due to the high NOx and PM emissions, it is restricted by relevantenvironmental laws and regulations.V2O5-WO3/TiO2catalysts were developed forselective catalytie reduetion of NOxin the exhaust of diesel engine.V2O5-WO3/TiO2catalysts were prepared by impregnating method. The effects of theloading of V2O5on the activities of DeNOxwere investigated. As V2O5load increases, thefour different V2O5load samples labeled in turn V1WTi, V2WTi, V3WTi, V4WTi. Theresults showed that when the reaction temperature below300oC,NO conversion wereenhanced as the V2O5loading increased; when the reaction temperature above400oC,NOconversion were decreased as the V2O5loading increased,which is mainly due to theenhancement of catalysts activity as the temperature rises, the side reaction of NH3oxidation not only consumed the NH3but also generated NO, causing NO conversionrates dropped sharply.It was found that the catalyst exhibits highest performance withappropriate content vanadia loading(W2VTi); in the temperature range of253oC-443oC,NO conversion was above90%.And the hydrothermal stability of the catalysts was alsoinvestigated. after aging at700oC for12h in5wt%H2O/air, aging samples,were labeledin turn V1WTi-A, V2WTi-A, V3WTi-A, V4WTi-A. It was found that the catalyst(W1VTi) exhibits better performance.Further increase of vanadia content only promotesTiO2sintering, phase transition and loss of surface area, resulting in the deactivation ofcatalysts.The effects of space velocity, NH3/NO ratio, and NO concentration on thecatalytic activity over V2WTi catalyst were also examined in the reaction ofNH3-SCR,then determined the optimum operating conditions of the catalytic reaction.