Preparation of Metal-Incorporated SAPO-34 catalysts and their Catalytic Performance in Selective Catalytic Reduction of Nitric Oxide

Abstract Metal-incorporated SAPO-34 catalysts were prepared by one-step hydrothermal method. Effects of various parameters including the types of metal ions, Cu2+ sources, structure directing agents (SDAs), hydrothermal temperature and time on catalyst activity of the metal-incorporated SAPO-34 catalysts were investigated. Three types of metal-incorporated SAPO-34 catalysts (Cu/SAPO-34, Fe/SAPO-34 and Mn/SAPO-34) were successfully obtained. Compared with Fe/SAPO-34 and Mn/SAPO-34 catalysts, Cu/SAPO-34 catalyst revealed complete cubic-like microstructure, wide active temperature window and high conversion rate in selective catalytic reduction (SCR) of nitric oxide. After defined Cu2+ was the favorable active site of SAPO-34 catalyst, the effects of four Cu2+ sources on SCR performance were further investigated, and found Cu2+ sources did not produce significant influence on nitric oxide conversion rates. SDAs determined the formation of Cu/SAPO-34 catalyst, and the Cu/SAPO-34 catalyst adopting tetraethylenepentamine (TEPA) as SDA could maintain higher crystal integrity and active sites, which were in favor of the SCR reaction. Moreover, hydrothermal temperature and time had great influences on the formation of Cu/SAPO-34 catalyst. When the hydrothermal temperature was higher than 150 oC and the hydrothermal time was longer than 3 days, the Cu/SAPO-34 catalyst with a cubic-like structure and high catalyst activity could be obtained.

摘要：本研究采用一步水热法制备了金属掺杂磷酸硅铝分子筛-34（SAPO-34）催化剂，系统考察了金属离子种类、Cu²+源、结构导向剂（structure directing agents，SDAs）、水热温度及水热时长等多种参数对金属掺杂SAPO-34催化剂催化活性的影响。实验成功合成了三类金属掺杂SAPO-34催化剂，分别为铜掺杂SAPO-34（Cu/SAPO-34）、铁掺杂SAPO-34（Fe/SAPO-34）及锰掺杂SAPO-34（Mn/SAPO-34）。相较于铁掺杂SAPO-34与锰掺杂SAPO-34催化剂，铜掺杂SAPO-34催化剂在一氧化氮选择性催化还原（selective catalytic reduction，SCR）反应中展现出完整的类立方微观形貌、较宽的活性温度窗口以及优异的NO转化率。在明确Cu²+为SAPO-34催化剂的适宜活性位点后，本研究进一步探究了四种Cu²+源对SCR反应性能的影响，结果显示Cu²+源对一氧化氮转化率无显著影响。结构导向剂决定了铜掺杂SAPO-34催化剂的形成过程，以四乙烯五胺（tetraethylenepentamine，TEPA）作为结构导向剂的铜掺杂SAPO-34催化剂可保持更高的晶体完整性与活性位点密度，更利于SCR反应的进行。此外，水热温度与水热时长对铜掺杂SAPO-34催化剂的形成具有显著调控作用：当水热温度高于150℃、水热时长超过3天时，即可得到具有类立方结构且催化活性优异的铜掺杂SAPO-34催化剂。