Research On Modification Of Low Temperature V₂O₅/TiO₂ SCR Catalysts

Under the background of the Blue Sky Protection Campaign,ultra-low NOx emission in the non-electric industry is imperative.At present,selective catalytic reduction(SCR)technology is an effective method for controlling NOx emissions.Catalyst is the key part of SCR technology whose optimum applicable temperature range is 300～400℃.The primary problem of SCR technology in the non-electric industry is that the flue gas temperature is usually lower than 300℃,which can not reach the temperature range of the SCR denitration catalyst.At low temperatures,the active components are easy to be sulfated and NH4HSO4 is easy to be generated,which causes the sulfur poisoning of the catalyst and affects the stable operation of the SCR system.Therefore,it is of great significance to develop the SCR catalyst for low-temperature.In this paper,the most widely used V2O5-WO3/TiO2 and V2O5-MoO3/TiO2 catalysts were selected as the research objects to study their activity at low temperatures.The microscopic mechanism of action between NH4HSO4 and catalyst surface was studied.On this basis,the modification of the V2O5-MoO3/TiO2 catalyst was carried out.The main results were as follows:3V2O5-10WO3/TiO2 and 3V2O5-10MoO3/TiO2 catalysts were prepared by incipient wetness impregnation method.The interaction mechanism between NH4HSO4 and the catalyst was analyzed by simulating the poisoning.In addition,the formation and decomposition characteristics of NH4HSO4 on the catalyst surface were studied.The results showed that NH4HSO4 blocked the catalyst micropores,reduced the ratio of V5+,and increased the content of chemisorbed oxygen on the catalyst surface,which reduced the catalyst activity.The 3V2O5-10MoO3/TiO2 catalyst had good denitration activity at low temperatures.On one hand,SO2 was weakly adsorbed on the catalyst surface to form intermediates,which slowed down the formation of NH4HSO4.On the other hand,the interaction bet-ween the catalyst surface and NH4HSO4 was weak,so it was easy for NH4HSO4 to break down.Based on the above results,the 3V2O5-10MoO3/TiO2 catalyst was selected as the modification object to further improve its low temperature activity.The influence of different sulfate additives on the low temperature activity of 3V2O5-10MoO3/TiO2 catalyst was explored.It was found that the 2MnSO4-3V2O5-10MoO3/TiO2 catalyst prepared by 2%manganese sulfate modification had the best activity which was about 7%higher than that of the unmodified catalyst.At 240℃,the denitrification efficiency of the modified catalyst reached 83%.The characterization results showed that MnSO4 increased the number of acid sites on the catalyst surface,thereby improving the reaction activity.In addition,MnSO4 increased the proportion of Mo6+in the catalyst surface to weak the formation of NH4HSO4.The results indicated that the addition of MnSO4 could effectively improve the sulfur resistance of the 3V2O5-10MoO3/TiO2 catalyst at low temperatures,which provided a theoretical basis for the industrial modification of low temperature catalysts.