汽车尾气净化催化剂Ag-ZSM-5选择性催化还原NO

The selective catalytic reducting NO of automobile exhaust purification catalyst Ag-ZSM-5.

评价了Ag-ZSM-5分子筛催化剂选择性还原NO的活性,并运用原位漫反射红外光谱研究NO在该催化剂上的选择性还原机理.结果表明,以丙烯为还原剂,有O2(3.6%)存在时,Ag-ZSM-5有良好活性,在773K时NO还原成N2的转化率达68.8%.基于漫反射红外光谱,认为NO还原为N2的过程中,NO以NOx吸附态形式与丙烯的活化物种CxHy或CxHyOz反应,生成有机-氮氧化物(R-NO2或R-ONO)中间体,再进一步反应,最终生成N2;催化剂表面形成有机-氮氧化物是关键步骤,Ag的作用是促进形成NOx,O2 的作用是促进C3H6活化及NO转化成NOx,并且O2是有效产生有机-氮氧化物不可缺少的条件.

The activity of Ag-ZSM-5 molecular sieve catalyst was assessed, and the selective catalytic reduction of NO was studied by in-situ diffuse reflectance FTIR spectroscopy(DRIFTS). The results show that the prepared catalyst hashigher activity and the conversion of NO reduction to N2 is 68.8% at the oxygen concentration of 3.6% and 773K. Based on in-situ DRIFTS, a reaction mechanism is proposed that NO is first transformed to NOx surface adsorbates, then NOx reacts with CxHy or CxHyOz to form organo-nitro or organo-nitrito adsorbed species as key intermediates, these intermediates are reacted to form finally nitrogen. The role of Ag is to promote NOx content. NO and propene are easily activated in oxygen; furthermore, the presence of oxygen is necessary to form organo-NOx intermediates.