ZrO₂-Promoted Cu-Co, Cu-Fe and Co-Fe Catalysts for Higher Alcohol Synthesis

Abstract

The development of efficient catalysts for the direct synthesis of higher alcohols (HA) via CO hydrogenation has remained a prominent research challenge. While modified Fischer−Tropsch synthesis (m-FTS) systems hold great potential, they often retain limited active site density under operating conditions for industrially relevant performance. Aimed at improving existing catalyst architectures, this study investigates the impact of highly dispersed metal oxides of Co-Cu, Cu-Fe, and Co-Fe m-FTS systems and demonstrates the viability of ZrO 2 as a general promoter in the direct synthesis of HA from syngas. A volcano-like composition-performance relationship, in which 5−10 mol % ZrO 2 resulted in maximal HA productivity, governs all catalyst families. The promotional effect resulted in a 2.5-fold increase in HA productivity for the optimized Cu 1 Co 4 @ZrO 2 -5 catalyst (Cu:Co = 1:4, 5 mol % ZrO 2 ) compared to its ZrO 2 -free counterpart and placed Co 1 Fe 4 @ZrO 2 -10 among the most productive systems (345 mg HA h −1 g cat −1) reported in this category under comparable operating conditions, with stable performance for at least 300 h. ZrO 2 assumes an amorphous and defective nature on the catalysts, leading to enhanced H 2 and CO activation, facilitated formation of metallic and carbide phases, and structural stabilization.