Theoretical study of the side reactions of the catalytic conversion of ethanol to butadiene on metal oxide catalysts

Side reactions of the ethanol-to-butadiene conversion catalyzed by MgO or ZnO were analyzed by density functional theory. We examined acetaldehyde disproportion to generate ethyl acetate, the hydrolysis of ethyl acetate to acetic acid, and the ketonization of acetic acid to generate acetone and CO2. The reactivities of these reactions on MgO and ZnO were compared. Our results revealed that among the three reactions, the difference in reactivity between the two oxides was greatest for the ketonization reaction—there was a higher activation barrier on MgO than on ZnO. This would cause the higher ratio of by-products on ZnO than on MgO. [Display omitted] •MgO has a higher activation barrier than ZnO.•Formation of ethyl acetate from acetaldehyde occurs on both MgO and ZnO catalysts.•Hydrolysis of ethyl acetate readily occurs on both MgO and ZnO catalysts.•Ketonization of acetic acids has a higher activation barrier on MgO than on ZnO.