Study of the alkylation of benzene with methanol for the selective formation of toluene and xylene over Co3O4-La2O3/ZSM-5

HZSM-5 zeolite was prepared by alkali treatment and NH4+-exchange, followed by modification with cobalt nitrate and lanthanum nitrate via impregnation. The samples were characterized by XRD, SEM, FT-IR, nitrogen adsorption and NH3-TPD. The catalytic performance of Co3O4-La2O3/ZSM-5 for benzene alkylation with methanol under different conditions was investigated. Alkali-treated ZSM-5 zeolite showed a high catalytic activity but a low selectivity for xylene in the reaction. However, the performance of HZSM-5 loaded with Co3O4 and La2O3 was excellent; the total selectivity of toluene and xylene reached 89.02%, and the benzene conversion reached 47.99%. The optimum conditions for benzene alkylation over Co3O4-La2O3/ZSM-5 were also determined. The best results were achieved at 723 K under a pressure of 0.1 Mpa for a feed ratio of 1 : 1 benzene-methanol at a space velocity of 3 h(-1). The total selectivity of toluene and xylene was 90.66%, xylene selectivity was 38.07%, and the benzene conversion was 51.36%.