Nanosized ZSM-5 zeolites: Seed-induced synthesis and the relation between the physicochemical properties and the catalytic performance in the alkylation of naphthalene

摘要

ZSM-5 nanocrystals with Si/Al ratios in the range of 30-80 have been synthesised successfully by a seed-induced method. The physicochemical properties of the ZSM-5 nanocrystals were characterised by XRD, SEM, N2 adsorption, FT-IR, TG/DTG, ~(27)AL MAS NMR, NH3-TPD and Py-IR. The catalytic activities of HZSM-5 with different Si/Al ratios (H-ZN-x) were evaluated at a temperature of 400 °C and a weight hourly space velocity (WHSV) of 0.5 h~(-1) by the methylation of naphthalene. The H-ZN-65 (Si/Al = 65) catalyst exhibited the highest activity (naphthalene conversion of 74.3%), which is attributed to the strong acidity and large external surface area of the zeolites. H-ZN-30 (Si/Al = 30) showed higher selectivity for the (3 and (3' site of dimethylnaphthalene, which is associated closely with the intermediate acidity and shape selectivity of ZSM-5 with its large micropore volume (0.154 cm~3/g).