Aggregates of superfine ZSM-5 crystals: The effect of NaOH on the catalytic performance of methanol to propylene reaction

Loose aggregates of superfine ZSM-5 crystals (S-ZSM-5) were synthesized by a seed-induced method in the presence of cetyltrimethylammonium bromide (CTAB), characterized by XRD, SEM, N-2 adsorption and desorption, XRF, NH3-TPD, Al-27 MAS NMR, TG analysis, FTIR and TEM, and studied for the methanol to propylene (MTP) reaction. The results showed that CTAB played a curial role in the formation of SZSM-5 zeolites: NaOH concentration had a significant effect on the textural properties of S-ZSM-5 zeolites, with the morphology being controllable from cuboid to sphere by varying the NaOH/SO2 ratios from o to 0.27. Compared with the catalysts synthesized by the conventional seed-induced method without CTAB, all S-ZSM-5 catalysts showed much higher stability and higher propylene selectivity in the MTP reaction. The excellent catalytic performance can be attributed to the aggregates of superfine ZSM-5 crystals with abundant mesopores and more weak acid sites, which hinder various side reactions such as hydrogen-transfer reactions. (C) 2016 Elsevier Inc. All rights reserved.