Abstract

The effect of lanthanum concentration on the physicochemical and catalytic properties of HZSM-5 zeolite in a reaction of toluene alkylation with isopropanol was studied in a temperature range of 250–350°C. Based on the data obtained by X-ray diffraction analysis, low-temperature nitrogen adsorption (BET method), and IR spectroscopy, it was shown that an increase in lanthanum concentration in HZSM-5 from 1.0 wt % to 7.0 wt % reduces both the specific surface area and the pore volume of the zeolite despite the retention of its crystalline structure. This also results in redistribution of acid sites, specifically decreases the concentration of strong Brønsted acid sites (B) and increases that of moderate Lewis acid sites (L), thus decreasing the B/L ratio from 3.53 to 0.20. All these occurrences have a crucial effect on the selectivity of reaction products and, in particular, on the p-isopropyl toluene (4-IPT) selectivity. Maximum selectivity, making up 72.4%, is achieved by a zeolite containing 5.0 wt % lanthanum at a B/L ratio of 0.25.

中文翻译：

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镧修饰的ZSM-5沸石上甲苯与异丙醇的烷基化

摘要

在250–350°C的温度范围内，研究了镧浓度对甲苯烷基化与异丙醇反应中HZSM-5沸石的理化和催化性能的影响。根据通过X射线衍射分析，低温氮吸附（BET法）和红外光谱获得的数据，表明HZSM-5中的镧浓度从1.0 wt％增加到7.0 wt％都会降低沸石的比表面积和孔体积，尽管保留了其晶体结构。这也导致酸位点的重新分布，特别是降低了强布朗斯台德酸位点（B）的浓度，并增加了中等路易斯酸位点（L）的浓度，因此B / L比值从3.53降低到0.20。对异丙基甲苯（4-IPT）选择性。通过以5.0的B / L比包含5.0重量％的镧的沸石达到72.4％的最大选择性。