Influence of Zn species in HZSM-5 on ethylene aromatization

Zn-containing HZSM-5 zeolites with different Zn contents were prepared by ion exchange and physically mixing methods, and were characterized by X-ray diffraction, scanning electron microscope, N-2 adsorption-desorption, NH3 temperature programmed desorption, pyridine adsorption infrared spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. Zn species introduced into HZSM-5 were identified as ZnO crystals, ZnO clusters in the zeolite channel and Zn(OH). species formed from a solid state reaction between dispersed ZnO and the protons in the zeolite. The preparation method has a significant influence on the distribution of the Zn species. The catalytic behavior of Zn-containing HZSM-5 with different Zn contents showed that the Zn(OH)(+) and ZnO species were responsible for aromatic formation from ethylene. (C) 2015, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.