Elucidating deactivation of titania-supported cobalt Fischer-Tropsch catalysts under simulated high conversion conditions

The study of titania-supported cobalt nanoparticles is relevant for industrial Fischer-Tropsch synthesis (FTS). Herein, we report about various deactivation pathways of cobalt supported on P25 titania (cobalt loading 2-8 wt%) under simulated high conversion conditions using in situ Mossbauer spectroscopy. A fraction of metallic cobalt was oxidized under humid FTS conditions. The absolute amount of oxidized cobalt was ti 1.2 wt% independent of the cobalt loading, indicating that specific cobalt-titanol interac-tions are involved in the oxidation process. The formation of cobalt-titanate-like compounds was only observed under very high water-to-hydrogen ratios in the absence of carbon monoxide. Steam consider-ably enhances cobalt sintering under FTS conditions. As such, deactivation under humid FTS conditions is not only caused by cobalt oxidation but also by enhancing sintering of the active phase.(c) 2023 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

This study reports various deactivation pathways of cobalt nanoparticles supported on P25 titania under simulated high conversion conditions using in situ Mossbauer spectroscopy. It was found that a fraction of metallic cobalt was oxidized under humid Fischer-Tropsch synthesis (FTS) conditions, and the amount of oxidized cobalt was independent of the cobalt loading. The formation of cobalt-titanate-like compounds was observed only under very high water-to-hydrogen ratios in the absence of carbon monoxide. Steam significantly enhanced cobalt sintering under FTS conditions, suggesting that deactivation under humid FTS conditions is not only caused by cobalt oxidation but also by enhancing sintering of the active phase.