金属改性分子筛型催化剂低温SCR反应机理  

Mechanism of the Low-Temperature SCR Reaction on Metal Modified ZSM-5 Catalysts

作　　者：李晓东[1] 吕刚[1] 宋崇林[1] 宋金瓯[1] 宾峰[1] 吴少华[1] 

机构地区：[1]天津大学内燃机燃烧学国家重点实验室,天津300072

出　　处：《燃烧科学与技术》2014年第4期341-347,共7页Journal of Combustion Science and Technology

基　　金：国家自然科学基金资助项目(51176139);天津市应用基础及前沿技术研究计划资助项目(10JCZDJC24900)

摘　　要：使用离子交换法制备得到金属改性ZSM-5催化剂,并对其进行了一系列的表征,包括:傅里叶变换红外光谱(FT-IR),氨气程序升温脱附(NH3-TPD),原位漫反射红外光谱分析(In situ DRIFTS).FT-IR实验说明金属的掺杂并未对ZSM-5的结构造成破坏.DRIFTS实验证实,金属改性ZSM-5催化剂低温下的SCR反应主要遵循Langmuir-Hinshelwood机理,即活化的NOx物种和活化的NH3物种进行反应.与Cu/ZSM-5催化剂相比,CuCe0.75Zr0.25Oy/ZSM-5催化剂可以加速氧化NO成为NO2,使得CuCexZr1-xOy/ZSM-5催化剂更容易生成—NO2物种,这对去除NOx催化的低温活性有很大的帮助.催化剂表面上的大部分硝酸盐和亚硝酸盐物种都是活性物种,但连二亚硝酸盐是个例外.Metal modified ZSM-5 catalysts were prepared by the ion exchange method and were characterized by Fourier transform infrared spectroscopy（FT-IR）,temperature-programmed desorption of ammonia（NH3-TPD）,and in situ diffuser reflection infrared Fourier transform spectroscopy（in situ DRIFTS）. FT-IR experiment shows that the structure of ZSM-5 was not damaged. The selective catalytic reduction（SCR） reaction over metal modified ZSM-5 catalysts mainly followed the Langmuir-Hinshelwood mechanism;i. e.,reaction of activated NOx species with activated NH3 species. Compared with Cu/ZSM-5 catalyst,the CuCe0.75Zr0.25Oy/ZSM-5 catalyst caused the amount of —NO2 species to increase after NO＋O2 adsorption,resulting in the temperature range for optimum NOx reduction（95%）extending to lower temperature. Most nitrate and nitrite species on the surface of catalysts are active intermediate species and the hyponitrites nitrate is an exception.

关 键 词：改性ZSM-5分子筛 选择性催化还原 氮氧化物 反应机理 过渡态物种 

分 类 号：TK421.5[动力工程及工程热物理—动力机械及工程]