Alkylation of Toluene with Isopropanol on Lantanum Modified ZSM-5 Zeolite

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 Bronsted 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.