Unraveling the Influence of Water on the Catalytic Activity of Furfural-Acetone Aldol Condensation Over Metal Oxide Catalysts

The conversion of biomass into biofuels is imperative for sustainable energy production. Aldol condensation, which facilitates the formation of new C–C bonds from small molecules to larger compounds, represents an efficient strategy for harnessing biomass-derived products. In this study, we conducted a combined investigation employing density functional theory (DFT) calculations to elucidate the key factors enhancing the activity of aldol condensation over various metal oxide catalysts (ZnO, TiO2, CeO2, and ZrO2). Our results demonstrate a strong correlation between the ability of lattice oxygen to accept hydrogen and the aldol condensation activity in the absence of water. Furthermore, we investigated the impact of water on the aldol condensation reaction and discovered that the ability to dissociate water molecules is closely linked to their activity in aldol condensation reactions in the presence of water. Interestingly, catalysts with lower water dissociation ability exhibit enhanced aldol condensation activity in the presence of water. However, an excessively low water dissociation ability can impede the formation of active surface hydroxyl species, transforming water dissociation into a rate-determining step rather than promoting aldol condensation. Our study presents the significance of comprehending the role of water in aldol condensation reactions and provides valuable insights into optimizing catalyst design for efficient biofuel production from biomass-derived feedstocks.