Green BTX production from methyl oleate over hierarchical HZSM-5 zeolites prepared by NaOH treatment

Abstract

BTX production from methyl oleate over four HZSM-5 zeolites with various pore structure was evaluated in a fixed-bed microreactor. HZSM-5 zeolite (SiO2/Al2O3 = 38) was synthesized by the hydrothermal method, and treated using NaOH solutions with different concentrations (0.1 M, 0.3 M, and 0.5 M) to prepare hierarchical HZSM-5 zeolites with different cavity volumes and mesopores in shells. Multi-characterizations (including XRD, NH3-TPD, SEM, TEM, Py-IR, XPS and N2 adsorption–desorption isotherms) revealed that the NaOH treatment induced the formation of hollow structures and mesopores in the HZSM-5 crystals without destroying the topological structure, increased the acid amount and pore volume and decreased the molar SiO2/Al2O3 ratio and BET surface, resulting in high aromatic yields in the catalytic aromatization of methyl oleate. The BTX yields and aromatic content in liquid over hierarchical HZSM-5 zeolites increased with increasing NaOH concentration. The HZSM-5 zeolite treated with a 0.5 M NaOH solution with a high amount of acid and large cavity volume led to a high aromatic yield of 51.28 wt%.