钒钛基SCR脱硝催化剂碱土金属中毒

Study on alkaline earth metal poisoning of vanadium-titanium based SCR denitration catalyst

分别制备了钒钨体系和钒钼体系的新鲜催化剂,并通过浸渍法、固态扩散法与干混法分别制备了碱土金属中毒的催化剂,比较了中毒方法、碱土金属以及催化助剂种类等因素对催化剂脱硝活性的影响,并利用程序升温脱附(NH_3-TPD)、程序升温还原(H_2-TPR)和X射线光电子能谱分析(XPS)等表征手段进行分析。结果表明,3种中毒方法中,浸渍法碱土金属中毒对催化剂毒害作用最大;Ca对催化剂的毒性大于Mg,且钒钼体系催化剂比钒钨体系催化剂具有更强的抗碱土金属中毒性能。碱土金属的存在会降低催化剂表面的总酸量与酸位点的强度,提高催化剂的还原温度,改变活性组分的价态并降低催化剂上表面活性氧的比例。

Fresh V-W and V-Mo based SCR catalysts were prepared, and then poisoned by alkaline earth metals through three methods, i.e., impregnation, solid phase diffusion and dry mixing. Experiments were performed to investigate the denitrification activity of the catalysts affected by the poisoning method, alkaline earth metal type, catalyst promoter type and other factors. In addition, the catalysts were characterized by temperature programmed desorption (NH3-TPD), temperature programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The results showed that among the three poisoning methods, impregnation exhibited the most significant poisoning effect on the catalysts. Ca was more toxic to the catalyst than Mg. V-Mo based catalyst possessed better anti-poisoning performance than V-W based catalyst. The presence of alkaline earth metal had many significant effects on the catalysts, including reducing the total acid sites and the acidity intensity on the catalyst surface, increasing the catalyst reduction temperature, altering the valence of the active component, and decreasing the proportion of surface active oxygen.