SO_2对Fe-Mo/ZSM-5催化剂上NO_x催化还原性能的影响

Effect of SO_2 on the Performance of Fe-Mo/ZSM-5 Catalyst for the Selective Catalytic Reduction of NO_x with Ammonia

分别采用共浸渍法和气相离子交换法制备了Fe-Mo/ZSM-5(CI)和Fe-Mo/ZSM-5(VIE)样品,研究了SO2对Fe-Mo/ZSM-5催化剂上以NH3为还原剂的NOx-SCR反应的影响.同时利用暂态响应实验、SO2-TPD以及FT-IR等技术对SO2的影响行为进行了分析.结果发现,VIE样品较CI样品具有更好的SCR催化活性.SO2只在低于300℃时对Fe-Mo/ZSM-5催化剂的活性有影响,而在高于300℃对催化活性几乎没有影响,而且温度越高,SO2对催化剂活性的抑制作用越小.研究表明,SO2在低温下对催化活性的抑制作用主要来源于其在催化剂表面的吸附作用,SO2在催化剂表面形成吸附态SO2-4离子,少量的硫酸盐沉积在催化剂表面,减少了催化剂表面活性中心的数量.

Fe-Mo/ZSM-5 catalysts were prepared respectively by wet impregnation method and chemical vapor ion exchange method, which named as Fe-Mo/ZSM-5 （CI） and Fe-Mo/ZSM-5 （VIE）. The effect of the presence of SO2 on catalytic reduction of NO〈SCR with NH3 over Fe-Mo/ZSM-5 was studied. And the transient response experiment, SO2-TPD and FT-IR were also used to analyze the properties of the catalysts. The results show that the catalytic activity of sample VIE is higher than the sample CI. And SO2 has an effect on the activity of Fe-Mo/ZSM-5 catalyst only at low temperature （〈300 ℃）, while it has little effect on the catalyst activity at the temperature higher than 300 ℃. Moreover, the higher the temperature, the smaller the inhibition of SO2 has. The results demonstrate that the inhibi- tion of SO2 to the catalytic activity at low temperature is due to the adsorption on the surface of the catalyst. The adsorption state of SOz on the surface of the catalyst is SO4 2- ion, and a small amount of sulfate is deposited on the catalyst surface, which can reduce the number of active sites.