Conversion of Methane to Benzene over Transition Metal Ion ZSM-5 Zeolites: II. Catalyst Characterization by X-Ray Photoelectron Spectroscopy

Abstract

X-ray photoelectron spectroscopy (XPS) has been used to determine the state of the transition metal ions (V, Cr, Fe, W, and Mo) on impregnated and ion-exchanged H-ZSM-5 zeolites that are active for the catalytic conversion of methane to benzene at 750°C. During an induction period, transition metal suboxides are formed on all of the impregnated catalysts except Mo/H-ZSM-5 for which Mo2C is formed. Ion-exchanged samples became more active after treatment with CO at 500°C. For the Fe/H-ZSM-5 sample, this treatment resulted in the migration of the metal to the external surface of the zeolite and the formation of an iron oxide phase.