Characteristics of surface acidity site and low temperature denitrification performance of VPO catalysts
Vanadium phosphorus oxygen catalysts VPO/TiO2 with different surface acidity characteristics were prepared using vanadium phosphorus oxygen(VPO)as active component and TiO2 as support by changing the preparation conditions.Their low temperature denitrification activities and surface acidity were studied.The results showed that when HCl/V molar ratio was 3,V/P molar ratio was 5 and the calcination temperature of VPO was 450℃,the obtained VPO/TiO2 catalyst exhibited excellent denitration activity,with nearly 100％ denitration rate at 200℃.The main active crystal phases of VPO/TiO2 catalysts were(VO)2P2O7,V2O5 and VOPO4.VPO/TiO2 surface had a large number of acidic sites,and the correlation between the denitrification activity and the amount of acid on the catalyst surface was established by data fitting,which showed that the low-temperature denitrification activities of all VPO/TiO2 catalysts were positively correlated with the weak Lewis acid content(correlation coefficient＞0.9).In addition,the denitrification mechanism studies revealed that the NH3 adsorbed on VPO/TiO2 surface in state of coordination NH3 or NH4+,and participate in the further selective catalytic reduction reaction.The NO was oxidized to NO2,monodentate nitrate before eventually reduced.SCR reaction over VPO/TiO2 followed the Eley-Rideal and Langmuir-Hinshelwood mechanism simutanously.
low temperature denitrificationSCRVPO/TiO2surface acidity sitedenitration mechanism
万方数据
维普
