A Relevant Estimation of the TOF for Methanol Oxidation Over Au/CeO2: A Combined SSITKA and FTIR Operando Contribution

Abstract

The importance to eliminate methanol from the environment arises from its classification as a volatile organic compound. For this purpose, it is advantageous to use effective catalysts that operate under ambient conditions. The cerium oxide doped with gold is a good candidate thanks to the high reducibility of ceria and the gold activity at low temperatures. Indeed, in previous studies it was evidenced that Au/CeO2 are highly effective not only for room temperature methanol trapping (upon adsorption) but also for catalytic full oxidation with air. Aiming at understanding the reaction mechanism, the FTIR operando survey of the catalyst under reaction flow conditions was performed. Distinct adsorbed species were observed and among them both spectators and reaction intermediates ones. More precisely, methoxy species formed upon methanol dissociative adsorption over CeO2 seemed to behave both as spectator and intermediate species most probably depending on their proximity with gold nanoparticles. Combining the Steady State Isotopic Transient Kinetic Analysis method and Fourier Transform Infrared spectroscopy operando setup, a more precise description of the methanol oxidation was possible thanks to the observation of the delayed evolution of distinct species at the catalyst surface. Moreover, in order to optimize the reaction conditions when moving from the laboratory scale to the industrial scale (pilot) it is of primary importance to know the intrinsic reaction rate parameters. The kinetic constants and the fraction of involved superficial sites were thus computed allowing an evaluation of a relevant turn over frequency.