Suchergebnisse

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. ; The authors thank Solvay, MINECO (Consolider Ingenio 2010-MULTICAT, CSD2009-00050 and Severo Ochoa program, SEV-2012-0267), Generalitat Valenciana (PROMETEOII/2013/011 Project) and the European Union (ERC-AdG-2014-671093 — SynCatMatch) for financial support. Red Española de Supercomputación (RES) and Centre de Càlcul de la Universitat de València are gratefully acknowledged for computational facilities and technical assistance. The technical support of the Electronic Microscopy Service of UPV is kindly appreciated. T.L.-A. thanks ITQ for a contract. ; Peer Reviewed