Influence of zeolite hydrothermal treatment on the aromatization performance of modified HZSM-5 catalysts without the presence of hydrogen

Two Zn, G, and P modified HZSM-5 zeolite catalysts, ZnGaP/HZ and ZnGaP/HZ (3 h), were prepared by co-impregnation using HZSM-5 zeolite prior and post to hydrothermal treatment, respectively. The influence of hydrothermal treatment and reaction conditions on the aromatization performance of the catalysts without the presence of hydrogen was studied using n-heptane as probe molecule. The framework structure of HZSM-5 zeolite was largely kept after the hydrothermal treatment, but the surface area, total acid amount, and the number of strong acid sites of ZnGaP/HZ (3 h) catalyst were considerably reduced. The coke formation on ZnGaP/HZ (3 h) catalyst during n-heptane aromatization was suppressed. Under a reaction pressure of 0.1 MPa, reaction temperature of 400°C, and a WHSV of 2/hr, the n-heptane aromatization over ZnGaP/HZ (3 h) catalyst exhibited lower initial conversion, less aromatics selectivity, higher liquid yield, but with less aromatics in the liquid product, and better catalytic stability when compared with ZnGaP/HZ catalyst.