Effect of Co/Cu Ratio and Na Promotion on CO ₂ Hydrogenation to Alcohols over CoCu/MgAl ₂ O ₄ Catalysts

High Resolution Image Download MS PowerPoint Slide CO 2 is one of the primary greenhouse gases, and its catalytic hydrogenation to ethanol represents a promising strategy for both CO 2 mitigation and the production of value-added chemicals. However, the high thermodynamic stability of CO 2, along with the challenges of C–C coupling and selectivity control, makes this transformation particularly demanding. In this work, we investigate a series of Co 10- x Cu x /MgAl 2 O 4 catalysts ( x = 0, 1, 5, 9, and 10, with total metal loading of 10 wt %) as catalysts for CO 2 hydrogenation to alcohols, exploring the impact of chemical composition and metal–oxide interfacial properties. Insights from related reactions, such as ethanol steam reforming (ESR) and the reverse water gas shift (RWGS) reaction at ambient pressure, were used to support the understanding of Co and Cu site roles in CO 2 hydrogenation. Among the tested catalysts, prereduced Co 5 Cu 5 exhibited the highest performance under high-pressure conditions, achieving productivities of 29 mg MeOH g CoCu –1 h –1 and 6 mg EtOH g CoCu –1 h –1 . A prereduction step led to the formation of a CoCu alloy and modifications in the Co/Cu surface ratio, which contributed to enhanced catalytic activity. Co 5 Cu 5 displayed the best balance between activity and selectivity, while Na promotion enabled C 2+ alcohol formation, demonstrating the tandem action of Cu 0 and CoCu alloy sites. These findings highlight the synergistic effects of Co–Cu interactions and alkali metal promotion in tuning catalyst reducibility and improving selectivity toward higher alcohols.