Continuous Catalytic Condensation of Ethanol into 1‑Butanol: The Role of Metallic Oxides (M = MgO, BaO, ZnO, and MnO) in Cu-M/Graphite Catalysts

Bifunctional catalysts supported over high-surface-area graphite comprising copper and a series of metallic oxides (MgO, BaO, ZnO, or MnO) that exhibit different acid/base properties were studied in the ethanol condensation reaction to 1-butanol in a continuous flow reactor. This condensation reaction goes through the Guerbet mechanism, consisting of a multistep process based on hydrogenation/dehydrogenation reactions as well as base-catalyzed aldol condensation and acid-catalyzed dehydration reactions. The catalytic tests were performed in a fixed-bed reactor working in the gas phase at 50 bar and 503 K. The catalyst 5Cu-Mn/G exhibited the highest yield toward 1-butanol followed closely by 5Cu-Mg/G, unlike their counterparts with BaO and ZnO as the metal oxide. The cooperative action between the metal function as the hydrogenating/dehydrogenating agent and the suitable quantity of medium-high-strength basic sites and medium-weak-strength acid sites is responsible for the highest 1-butanol yields.