Ethanol conversion over Ga2O3–ZrO2 solid solution: empirical evidence of the reaction pathway, the surface acid–base properties, and the role of gallium ions

Abstract

Ethanol conversion over Ga₂O₃–ZrO₂ solid solution was examined in the temperature range of 573–773 K, and acetone/isobutene formation was confirmed under cofeeding of H₂O vapor. The reaction pathway was empirically investigated with the contact time dependency and reactivity of the five possible intermediates. The surface acid–base properties were discussed with 1-butene isomerization, 2-butanol decomposition and the poisoning experiment, the dehydration/dehydrogenation selectivity of C3–C4 primary and secondary alcohols, and CO₂-TPD. The Ga₂O₃–ZrO₂ catalyst was less basic than ZrO₂ itself and exhibited a stronger dehydrogenation property. Alcohol dehydrogenation over Ga₂O₃–ZrO₂ was suggested to be promoted by the specific dehydrogenation property of isolated Ga³⁺ species. Acetaldehyde formed by ethanol dehydrogenation was converted into acetone, mainly via acetate species in the presence of H₂O. Coexistence of ZrO₂, doped elements with dehydrogenation capability, surface acid–base properties, and H₂O vapor is important for ethanol to acetone/isobutene reaction.