NO和NO_2在V_2O_5/AC催化剂表面的反应行为

Reaction of NO and NO_2 with NH_3 over V_2O_5/AC Catalyst

采用程序升温脱附、在线质谱和原位漫反射红外光谱等手段,比较了NO和NO2在V2O5及V2O5/AC催化剂表面的选择催化还原(SCR)反应行为.结果表明,氨以质子态NH4+和共价态NH3分子两种形态吸附于纯V2O5表面,V=O为氨的主要吸附活性位.无氧状态下,NO和NO2皆可与吸附于V2O5表面的NH3反应,并且NO2与吸附态NH3的反应活性高于NO.但在V2O5/AC催化剂表面,同样在无氧条件下,NO几乎不与吸附态NH3反应,而NO2却可以反应并生成N2.在V2O5/AC表面,NO很容易被气相O2氧化为NO2,然后参与SCR反应.可见,NO2是NO在V2O5/AC表面发生SCR反应的中间体.

Temperature-programmed desorption, on-line mass spectroscopy, and in situ diffuse reflectance infrared Fourier transform spectroscopy were preformed to study selective catalytic reduction （SCR） of NO and NO2 with NH3 over V2O5 and activated carbon （AC）-supported V2O5 （V2O5/AC）. The results show that both protonated （NH4＋） and molecularly coordinated （NH3） ammonia species form on the V2O5 surface and V=O bond is the primary active site. Both NO2 and NO can react with the adsorbed ammonia in the absence of oxy- gen, but the activity of NO2 is superior to that of NO. On the V2O5/AC surface, NO2 still can react with the adsorbed NH3 species to form N2, but NO shows little activity unless oxygen is present. SCR of NO on V2O5/AC proceeds through oxidation of NO to NO2 by oxygen on the AC surface followed by reaction of NO2 with NH3 species adsorbed and activated on the V2O5 surface.