Inverse CeO2/Ni Interface Engineering for Low-Temperature Acetic Acid Ketonization with Selective Acetone Formation

Selective ketonization of biomass-derived carboxylic acids provides an attractive route for producing ketones through simultaneous C–C coupling and deoxygenation. However, conventional oxide catalysts generally require high reaction temperatures, while metal-containing catalysts may promote undesired decomposition pathways. In this study, conventional Ni/CeO2 and inverse CeO2/Ni catalysts were synthesized and evaluated for acetic acid ketonization, using commercial CeO2 as a reference catalyst. Structural and surface characterization revealed that Inv-CeO2/Ni possessed smaller CeO2 domains, higher surface area, stronger Ni–CeO2 interaction, a higher fraction of Ce3+-associated defect sites, and more favorable acid–base properties than Con-Ni/CeO2. Catalytic testing showed that Ref-CeO2 was highly selective toward acetone but exhibited limited low-temperature activity, giving only 3% acetic acid conversion at 275 °C. Con-Ni/CeO2 improved the conversion to 19% at 275 °C and 86% at 400 °C, but acetone selectivity decreased from 88% to 39%, indicating enhanced decomposition/cracking. In contrast, Inv-CeO2/Ni achieved 33% conversion with 97% acetone selectivity at 275 °C and reached complete conversion with 73% acetone selectivity at 400 °C. The activation energy for acetic acid conversion decreased from 73.54 kJ/mol over Ref-CeO2 to 28.70 kJ/mol over Inv-CeO2/Ni, indicating enhanced acetic acid activation. In situ DRIFTS analysis indicated that the inverse catalyst favored acetate/carboxylate and carbonyl-containing oxygenated intermediates while suppressing extensive CO-related decomposition features. These results demonstrate that inverse CeO2/Ni architecture enhances low-temperature acetic acid conversion and selectively directs the reaction toward acetone formation.