A heterogeneous mechanism for the catalytic decomposition of hydroperoxides and oxidation of alkanes over CeO2 nanoparticles: A combined theoretical and experimental study

• Published in: Journal of catalysis Vol. 344; pp. 334 - 345
• Main Authors: López-Ausens, Tirso, Boronat, Mercedes, Concepción, Patricia, Chouzier, Sandra, Mastroianni, Sergio, Corma, Avelino
• Format: Journal Article
• Language: English
• Published: San Diego Elsevier Inc 01.12.2016; Elsevier BV
• Subjects: Acid-base; Alkane oxidation; Catalysis; Catalysts; Catalytic oxidation; Ceria; DFT; Heterogeneous catalysis; in situ IR; Nanoparticles; Redox; Alkane oxidation; Heterogeneous catalysis; DFT; Ceria; Redox; in situ IR; Acid-base
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2016.09.032

[Display omitted] •CeO2 nanoparticles catalyse cyclohexane oxidation to K/A-oil using hydroperoxides.•Cyclohexane activation is structure-sensitive and preferentially occurs at particle edges.•Both acid-base and redox properties of CeO2 play a role in the mechanism.•A Mars van Krevelen mechanism is proposed based on DFT and in situ IR spectroscopy. A nanoparticulate CeO2 catalyst is presented that is able to oxidize cyclohexane to K/A-oil (a mixture of cyclohexanone and cyclohexanol) using hydroperoxides as oxidizing species. The improvement in selectivity with decreasing particle size suggests the existence of a structure-activity relationship in this process, and points to a preferential activation of cyclohexane at defective corner or edge sites. A detailed theoretical study of the reaction mechanism over three different CeO2 catalyst models shows that cyclohexane is preferentially activated by bicoordinated oxygen atoms present at the edges of small particles, following a Mars van Krevelen mechanism which has been confirmed by in situ IR spectroscopy and 18O/16O isotopic exchange experiments. The process is fully heterogeneous, and the catalyst can be reused without loss of activity up to four cycles.