A highly efficient Ga/ZSM-5 catalyst prepared by formic acid impregnation and in situ treatment for propane aromatization

Abstract

A simple method for the preparation of a Ga/ZSM-5 catalyst for propane aromatization was established by formic acid impregnation and in situ treatment. The catalyst prepared by this novel method showed remarkably superior activity of propane aromatization. Under the conditions T = 540 °C, P = 100 kPa, WHSV = 6000 ml g⁻¹·h⁻¹ and with a N₂/C₃H₈ molar ratio of 2, the highest propane conversion and selectivity to BTX (benzene, toluene and xylene) achieved on H–Ga/SNSA catalyst was 53.6% and 58.0%, respectively, much higher than that of the catalyst prepared using the traditional impregnation method (38.8% and 48.2%). The catalysts were characterized by nitrogen physical adsorption, ICP-AES, DRIFT, py-FTIR, NH₃-TPD, H₂-TPR, XPS and ²⁷Al MAS NMR techniques. The characterization data indicated that this facile methodology enhanced the dispersion of the Ga species and promoted the formation of highly dispersed (GaO)⁺ species, which could exchange with the acidic protons (Brønsted acid sites) of the zeolite framework, contributing to the strong Lewis acidity. The super catalytic behavior was attributed to the synergistic effect between the strong Lewis acid sites generated by the (GaO)⁺ species and the Brønsted acid sites.