On the role of cobalt carbidization in higher alcohol synthesis over hydrotalcite-based Co-Cu catalysts

Abstract

Co-Cu-based catalysts are widely applied in higher alcohol synthesis (HAS) from synthesis gas. Although the nature of the active sites is still not fully understood, the formation of Co 2 C under HAS conditions seems to play a major role. A CO pretreatment procedure was developed allowing a systematic investigation of the influence of cobalt carbidization on the structural properties and catalytic performance of the catalysts. By exposing the catalyst to a CO-containing atmosphere prior to HAS, Co enrichment of the catalyst surface occurred followed by carbide formation. This surface modification decreased the formation of hydrocarbons and enhanced the formation of C 2+ OH. The catalyst pretreated with CO at 20 bar achieved the highest selectivity to ethanol and the lowest hydrocarbon selectivity. CO pretreatment at elevated pressure enhances the selectivities to linear alcohols through surface cobalt enrichment and carbide formation.