原位漫反射红外光谱研究NO在Ag/SAPO-34催化剂上的选择性催化还原

In situ Diffuse Reflectance FTIR Sectroscopy Study of the Selective Catalytic Reduction Reaction of NO over Ag/SAPO-34 Catalysis

原位漫反射红外光谱研究NO在Ag/SAPO 34催化剂上的选择性催化还原过程。考察了以丙烯为还原剂 ,在富氧及 573～ 773K温度条件下的反应。通过比较初始混合气中加氧或不加氧时反应的原位光谱 ,探讨了氧在NO还原过程中的作用。结果表明 ,氧能充分促进丙稀活化以及增加NOx 吸附态含量 ,并且氧的存在是有效产生有机 氮氧化物 (R NO2 ,R ONO)不可缺少的条件。基于光谱实验 ,认为反应机理为 :NO ,丙烯和氧反应 ,在Ag/SAPO 34催化剂上生成吸附的有机 氮氧化物 ,再由这些吸附物种分解成N2 ,催化还原的关键是形成有机 氮氧化物中间体。

An in situ diffuse reflectance FTIR spectroscopy (DRIFTS) study of the selective catalytic reduction(SCR) of NO with propene in the presence of excess O 2 was carried out over Ag/SAPO-34 catalyst. The SCR reaction was investigated at temperatures from 573 to 773 K, and the role of oxygen in the NO reduction process was determined by comparing experiments using an initial reaction mixture containing oxygen and without oxygen. The results show that both NO and propene are easily activated in oxygen. Furthermore, the presence of oxygen is necessary to form organo-NO x adsorbed species. Based on these experiments, a reaction mechanism is proposed that NO, propene and oxygen react to form organo-nitro and organo-nitrito adsorbed species as key intermediates, and then these intermediates decompose to nitrogen.