碱中毒对烧结烟气SCR催化剂脱硝脱二噁英的影响

Effect of alkali poisoning on simultaneous removal NO and dioxins over SCR catalysts for sintering flue gas

采用湿式浸渍法对商用V2O5-WO3/TiO2催化剂进行了碱金属硫酸盐(Na/K/Rb)中毒实验。在模拟铁矿烧结烟气条件下,对比了新鲜和中毒催化剂同时脱除NOx和二噁英的活性(以氯苯作为二噁英的模拟物),并通过N2吸脱附、XRD、NH3-TPD、H2-TPR和XPS等检测手段对催化剂进行了表征。结果表明:中毒催化剂的脱除NOx和催化降解氯苯活性明显降低,失活率顺序为K2SO4>Rb2SO4>Na2SO4。催化剂中毒后,碱金属离子可以占据催化剂表面化学吸附氧空位,导致表面化学吸附氧数量减少,物质的量之比n(V^5+)/n(V^4+)降低,V物种可还原性减弱。

The commercial V2O5-WO3/TiO2 catalysts were poisoned with alkali metal sulfate(Na/K/Rb)by the wet impregnation method.The simultaneous removal of NOx and dioxins activity on the fresh and poisoned catalyst was investigated(chlorobenzene(CB)was used as the dioxins simulant)under simulated conditions of iron ore sintering flue gas.The catalysts were characterized by N2adsorption-desorption,XRD,NH3-TPD,H2-TPR and XPS.The results indicate that the activities of NOx removal and catalytic degradation of chlorobenzene by poisoned catalysts are significantly reduced,and the deactivation rate is K2SO4>Rb2SO4>Na2SO4.Alkali metal ions could occupy chemisorption oxygen vacancies on the catalyst surface after the catalysts poisoned,resulting in a decrease in the amount of the surface chemisorbed oxygen.Simultaneously,the molar ratio of V^5+/V^4+ and reducibility of vanadium species were also decreased,leading to the activities of catalysts dropped.