Catalyst Deactivation Rate During Hydrogenation of CO₂ to Longer-Chained Hydrocarbons Over 6 wt% Potassium-Promoted Co/Al₂O₃ Catalyst

The deactivation rate of 15%Co-6%K/Al₂O₃ Fischer–Tropsch catalyst during hydrogenation of CO₂ to longer-chained hydrocarbons was investigated. The catalysts used were synthesized by incipient wetness impregnation of gamma alumina- support and characterized by TPR, BET, XPS, and XRD. The presence of CO₂ in the feed displayed a negative impact on the catalyst stability and in the production of longer-chain hydrocarbons. The main product generated was methane; this was due to the presence of the cobalt carbide which led to decreased C₅₊ selectivity with a concomitant increase of CH₄ formation. As the TOS was increasing, carbonaceous deposits formed on the catalyst. These deposits tend to lean towards methane formation, decrease CO₂ conversion, and C₅₊ selectivity as observed in this study. Cobalt carbide formation in the spent catalyst in this study can account, at least in part, for the observed catalyst deactivation with time on stream. Graphic Abstract: [Figure not available: see fulltext.].