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

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, 27Al 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 β and β′ site of dimethylnaphthalene, which is associated closely with the intermediate acidity and shape selectivity of ZSM-5 with its large micropore volume (0.154 cm3/g).

Graphical abstractZSM-5 nanocrystals with Si/Al ratios of 30–80 have been synthesized successfully by a seed-induced method.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► ZSM-5 nanocrystals were synthesized by a seed-induced crystallization. ► Strong acidity and Brønsted acidity sites lead to a low 2,6-DMN selectivity. ► Large micropore volume and size of pore mouth result in a high 2,6-DMN selectivity.