2 Materials and methods

2.1 Chemicals

Aluminum sulfate octadecahydrate (Al2(SO4)3.18H2O), silica sol (40 wt% aqueous solution) and sodium chloride (NaCl) were purchased from Aladdin Co., Ltd. Tetrapropylammonium hydroxide (TPAOH, 25 wt% aqueous solution) was purchased from Innochem Co., Ltd. C4-olefin was provided from Shanghai Petrochemical Company.

2.2 Catalyst preparation

Four operating processes for the synthesis of ZSM-5 zeolites, including RPB premix - static crystallization, RPB premix - dynamic crystallization, STR premix - static crystallization, and STR premix - dynamic crystallization, are schematically showed in Fig. 1.