双金属改性ZSM-5/L复合分子筛的制备及其芳构化反应性能

采用分级改性的方法制备Zn-ZSM-5/Pt-L核壳型双金属催化剂，通过改变金属负载量的组配方式对催化剂表面酸性进行调控，利用X射线衍射（XRD）、氮气吸附脱附、氨气程序升温脱附（NH3-TPD）、吡啶-原位傅里叶变换红外（Py-FTIR）等手段进行表征，并以正戊烷为原料对催化剂的轻烃芳构化性能进行评价。结果表明，在复合分子筛核壳结构的基础上，分级引入双金属的改性方式有效地调控了催化剂表面的酸分布以及L/B酸比例，使双金属催化剂更好地发挥L酸和B酸的协同催化作用，当Zn和Pt负载量分别为1.0%和0.6%时所表现出的催化性能最优，其正戊烷芳构化反应的转化率为99.1%、芳烃选择性达到47.2%。

SYNTHESIS OF BIMETAL ZSM-5/L COMPOSITE ZEOLITE AND ITS AROMATIZATION PERFORMANCE FOR AROMATIZATION REACTION

The core-shell composite zeolite Zn-ZSM-5/Pt-L was prepared via step by step modification. The surface acidity was regulated by changing the ratio of two metals. The physical and chemical properties were investigated by X-ray diffraction (XRD), N2 adsorption-desorption, ammonia temperature-programmed desorption (NH3-TPD) and in situ Py-FTIR spectroscopy. The light hydrocarbon aromatization performance of catalysts was evaluated using n-pentane as the raw material. The results exhibit that the modification of introducing active metal step-by-step effectively regulates the L/B acid ratio and distribution on the catalyst surface, which could cause more excellent synergism between B acid and L acid. At the loading of Zn and Pt metal of 1.0% and 0.6%, respectively, the catalytic performance reaches the best. The conversion rate of pentane aromatization is 99.1 % and aromatic selectivity is up to 47.2%.