不同因素对V2O5-WO3-TiO2催化剂低温NO转化率的影响

Effects of Different Factors on Low-temperature NO Conversion of V2O5-WO3/TiO2 Catalysts

考察不同V2O5负载量、O2体积分数、NO体积分数、SO2体积分数、H2O体积分数、n(NH3)/n(NO)、空速和在线加热再生等因素对浸渍法制备的V2O5-WO3/Ti O2催化剂低温NO转化率的影响.综合分析,选定V2O5最佳负载质量分数为3%,当反应温度为160℃时,NO转化率为93. 7%. 110~320℃时,N2选择性大于98%,SO2氧化率低于1. 0%. NO转化率随O2体积分数增加而明显上升,随入口NO体积分数增加而有不同程度下降,但NOx去除量逐渐提高. n(NH3)/n(NO)≤1时,催化剂最优活性约等于各自n(NH3)/n(NO),n(NH3)/n(NO)> 1对催化剂活性没有明显提升.增大空速,催化剂高活性温区变窄,活性呈现不同程度的下降.表征结果表明,在含有SO2和H2O的选择性催化还原法(selective catalytic reduction,SCR)反应后,催化剂比表面积和孔容减小,活性组分流失,且沉积了包含NH4+和SO42-的副反应产物.热再生过程中催化剂延缓硫酸铵盐分解,导致催化剂抗中毒能力变差,活性难以恢复.

The effects of V2O5 loading, the volume fractions of O2, NO, SO2 and H2O, n (NH3 )/ n(NO), gas hourly space velocity and online heat regeneration on NO conversion of V2O5-WO3 / TiO2 catalyst prepared by impregnation method were investigated. Combined with the experimental results, 3% V2O5 was selected as the optimal loading, and NO conversion of 3% V2O5-WO3 / TiO2 catalyst was 93.7% at 160 ℃. The selectivity of N2 was more than 98% and SO2 oxidation was less than 1% in the range of 110-320 ℃. NO conversion of catalyst increased with the increase of the volume fraction of O2, and decreased with the increase of the volume fraction of NO, however, the NOx removal amount gradually increased. When n(NH3)/ n(NO)≤1, the optimal activity of catalyst equalled the respective n(NH3)/ n(NO), and when n(NH3)/ n(NO)>1, the activity was barely improved. With the increase of the space velocity, the high activity temperature range of the catalyst was narrowed, and the activity decreased in varying degrees. The characterization results show that the morphology of catalyst is blurred and the surface covered with irregular flocs, specific surface area and pore volume decrease in different degrees, and tiny pores are preferred to be blocked after selective catalytic reduction (SCR) reaction containing SO2 and H2O. The contents of V2O5 are reduced 0.98% and WO3 reduced 1.6%, the side reaction products include NH4^+ and SO4^2-. During the process of online heat regeneration, catalyst delayed the decomposition of ammonium sulfate, which caused the catalyst’s resistance to poisoning to be worse and the activity was difficult to be recover.