Effect of alkali modification to ZSM-5 zeolite on the aromatization of methanol

ZSM-5 zeolites were modified by desilication with sodium acetate and sodium citrate. The physicochemical properties of ZSM-5 zeolites, such as crystal structure, acid content, surface area and pore volume, were characterized by XRD, SEM, NH₃-TPD, ²⁷Al MAS NMR, pyridine adsorption infrared spectroscopy and N₂ adsorption-desorption isotherms. The results indicate that pore size of the zeolite increases and mesoporous structures are formed by alkali modification, and the amount of Lewis and Brönsted acid contents decreases obviously. When the concentration of sodium acetate solution is 0.5 mol/L, the modified zeolite has a suitable B/L value for the aromatization of methanol while forming a large number of mesoporous structures. Compared with microporous ZSM-5, the catalyst life is increased from 20 h to 74 h, and the highest yield of aromatics is increased from 20.97% to 40.05%.