Effect of Sn on the production of methanol during syngas conversion over Co/alumina

Abstract Hydrocarbons are the main reaction products of syngas conversion over cobalt-based catalysts. Methanol is also produced as a minor by-product and has been proposed to be produced via a specific reaction pathway involving formates species located at the interface with the support. The poisoning of a Co/alumina catalyst with Sn was studied here and showed to induce a strong decline in methanol production, similar to that of hydrocarbons. The addition of Sn did not prevent the formation of formates as observed by operando diffuse reflectance FT-IR spectroscopy. However, the reactivity of formates was markedly lowered in the presence of Sn. We propose that these observations have two possible origins. Firstly, Sn addition reduced significantly the H 2 adsorption capacity of the Sn-modified samples. Hydrogen, which is required for the hydrogenation of formates to methanol, is probably activated on the cobalt metal particles, some sites of which were strongly poisoned by Sn. Secondly, Sn addition could also have specifically poisoned interfacial sites, where the most reactive formates are present.