Unraveling role of oxygen vacancies in catalytic deoxygenation of biomass-derived carboxylic acids over ceria

Catalytic deoxygenation by ceria (CeO₂) represents an effective approach for upgrading bio-oil, yet the relationship between oxygen vacancies (O_V) of CeO₂and catalytic ability remains controversial. To address this issue, three CeO₂samples calcined in different atmospheres were adopted in catalytic deoxygenation of n-octanoic acid. Characterization results revealed that these CeO₂exhibited identical crystal structure and different O_Vcontents and surface acid-base properties. Catalytic tests demonstrated that O₂-calcined CeO₂primarily promoted ketone production at 400–600 °C while facilitated the formation of alkenes and aromatics at 600 °C. For the three CeO₂catalysts, the highest O_Vcontent in H₂-calcined CeO₂endowed it with optimal acid-base pairs for enhancing both ketonization and aromatization reactions, thus achieving superior deoxygenation performance. Density functional theory calculations confirmed that O_Vsignificantly reduced the adsorption energy of active species during ketonization. This study provides evidence that surface O_Vof CeO₂boost deoxygenation activity by optimizing acid-base pair sites.