The promoting effect of introducing Zn into nano-ZSM-5 zeolites by conventional impregnation method and isomorphous substitution on the performance of 1-hexene aromatization was investigated. The nano-ZSM-5 zeolite was synthesized by a seed-induced method without organic templates. The Zn-modified nano-ZSM-5 zeolite catalysts, xZ n/HNZ5 and y Zn/Al-HNZ5, were prepared by the conventional impregnation method and isomorphous substitution, respectively. The structure, chemical composition and acidity of the catalysts were characterized by XRD, XRF, N2 adsorption, SEM, NH3-TPD and Py-IR, while the catalytic properties were evaluated at 480 °C and a weight hourly space velocity（WHSV） of 2.0 h-1 in the aromatization procedure of 1-hexene. Compared with xZ n/HNZ5, y Zn/Al-HNZ5 exhibited smaller particles and higher dispersion of Zn species, which led to greater intergranular mesopore and homogeneous acidity distribution. Experimental results indicated that the synergy effect between the Brnsted and Lewis acid sites of the isomorphously substituted nano-ZSM-5 zeolites could significantly increase aromatics yield and improve catalytic stability in the 1-hexene aromatization.
分别采用盐酸、草酸、柠檬酸对晶种引导的无模板剂合成的纳米ZSM-5分子筛进行脱铝改性,利用XRD、N2吸附-脱附、27 Al NMR、XRF、NH3-TPD、Py-IR等方法对其进行表征,并考察了不同种类的酸脱铝对ZSM-5分子筛的结构、酸性及其催化萘与甲醇的烷基化反应性能的影响。结果表明,盐酸、柠檬酸与草酸均可脱除分子筛的骨架铝和非骨架铝,但3种酸对分子筛的脱铝程度不同。纳米ZSM-5分子筛经酸脱铝后,在脱除了部分强酸中心的同时产生了一定比例的二次介孔,有效地改善了反应物和产物的扩散性能,使催化萘与甲醇的烷基化反应的萘转化率、2,6-二甲基萘(2,6-DMN)选择性和产物中n(2,6-DMN)/n(2,7-DMN)均有不同程度的提高,并且表现出更强的抗失活能力。
