Cu-SSZ-13柴油机SCR催化剂水热老化试验

Experiment on Hydrothermal Aging over Cu-SSZ-13 Diesel SCR Catalyst

为了完善柴油机铜基分子筛选择性催化还原(SCR)催化剂的失活机理,使用流动反应试验系统对一步合成法Cu-SSZ-13催化剂样品进行水热老化处理以及标准SCR、NH_3氧化、NH_3程序升温脱附(NH_3-TPD)等评价测试,并基于X射线衍射(XRD)、原位漫反射傅里叶变换红外光谱(DRIFTS)以及H_2程序升温还原(H_2-TPR)技术对样品进行微观表征分析.结果表明:850,℃水热老化会造成催化剂分子筛骨架结构垮塌,NH_3吸附活性位数目急剧下降,催化剂大幅度失活;而750,℃水热老化会造成催化剂布朗斯特(Br?nsted)酸性位减少,并发生孤立的Cu^(2+)位置迁移以及铜氧化物(CuO_x)生成等现象,使得催化剂SCR活性在一定程度上降低.

For the improvement of the deactivation mechanism of diesel copper-based zeolite selective catalytic reduction(SCR)catalysts,a flow reactor experimental system was used in hydrothermal aging treatment and activity measurement for one-pot method synthesized Cu-SSZ-13 catalyst,such as standard SCR,NH3 oxidation and NH3-TPD.The catalysts were also characterized based on X-ray diffraction(XRD),in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)and H2 temperature programmed reduction(H2-TPR).Through analyzing the measurement results,it is found that the catalyst framework can be crashed by 850,℃hydrothermal treatment,losing most of its SCR activity and number of NH3 active absorption sites.After 750,℃hydrothermal treatment,the numbers of Br?nsted active sites reduces,the position of some copper active sites changes and the copper oxide is generated.As a result,the catalyst activity is lost to a certain extent.