Density functional theory study of aldol condensation between furfural and 2-butanone over magnesium oxide

Abstract

Understanding of mechanistic and thermodynamic insights of the aldol condensation reaction is crucial to efficient catalytic conversion of biomass-derived oxygenates to fuel-range hydrocarbons. In this study, the aldol condensation of furfural and 2-butanone on magnesium oxide (MgO) catalyst was investigated using density functional theory (DFT) calculations. Energy profiles were computed for elementary steps, including Step 1: Formation of 2-butanone enolate, Step 2: Enolate addition at the carbonyl group of adsorbed furfural, and Step 3: Dehydration to form the condensation product. The DFT results showed that the enolization of 2-butanone was the rate-determining step. The methyl enolate can bind to MgO surface with low energy. The methylene enolate route (generating branched product) was favored compared to the methyl enolate route (yielding linear product) due to lower activation energy. The DFT results offer a base-catalyzed basis for understanding reaction mechanism and could provide a guideline for studying reaction on mixed oxide catalyst.