Sulfuric acid etching CeO2 nanoparticles to promote high KA-Oil selectivity in cyclohexane selective oxidation

Abstract

Nanostructured ceria has attracted much attention in the field of redox catalysts due to the numerous active sites with excellent redox ability. Based on the acidic medium etching strategy, we constructed the strong binding centers (hydroxyl sites and strong acid sites) on the surfaces of nanostructured ceria, which regulate the adsorption process of KA-Oil (the mixture of cyclohexanol and cyclohexanone) and to promote high KA-Oil selectivity in cyclohexane oxidation. The three CeO₂ (nanocube, nanorod and nanopolyhedron) with different exposed crystal planes were treated by acid etching to change the surface sites and catalytic properties. The transition behavior of surface sites during etching was revealed, abundant strong binding centers were proved to be constructed successfully. And especially for the nanorod treated by acid (Acid@CeO₂-NR) with the strongest response for sulfuric acid etching, the strong adsorption of cyclohexanone by strong binding centers was confirmed based on the in-situ DRIFTs. The sulfuric acid etching strategy to enhance the selective oxidation of cyclohexane based on the construction of strong binding centers was proved to be feasible and effective, Acid@CeO₂-NR with strongest etching response achieved the dramatic promotion of KA-Oil selectivity from 64.1% to 92.3%.