Study of methanol shape-selective aromatization over ZnO/SiO₂/ZSM-5 modified with mental oxide and silicon deposition

ZnO/SiO₂/ZSM-5 zeolites were prepared from ZSM-5 by vacuum metal impregnation of metallic oxides and silicon deposition. The resulted zeolite were characterized by XRD, BET, NH₃-TPD, SEM and TEM. Furthermore, the influence of silicon deposition time and the content of impregnated ZnO to the selectivity and yield of p-xylene (PX) on the reaction of aromatization of methanol was investigated. The results indicated that by twice silicon deposition and 2.0% ZnO, the modified ZSM-5 had the highest PX selectivity. The yield of PX could reach up to 28% at 420 ℃, 0.2 MPa and 1.25 h^-1 of methanol WHSV.