Selective oxidation of cyclohexane to cyclohexanone using chromium oxide supported mesoporous MCM-41 nanospheres: Probing the nature of catalytically active chromium sites

Betsy, Kurisingal J., Nayak, Chandrani, Lazar, Anish, Krishnan, Athira, Bhattacharyya, Dibyendu, Jha, Shambhu N. and Vinod, Chathakudath P. (2018) Selective oxidation of cyclohexane to cyclohexanone using chromium oxide supported mesoporous MCM-41 nanospheres: Probing the nature of catalytically active chromium sites. ChemCatChem, 10 (15), 3291-3298. (doi:10.1002/cctc.201800309).

Abstract

Highly dispersed chromium oxide supported mesoporous MCM‐41 nanosphere catalysts have been synthesized using a simple wet impregnation method. This work is devoted to a systematic study to reveal the active Cr sites in chromium oxide supported MCM‐41 nanosphere catalysts for the selective oxidation of cyclohexane to cyclohexanone. To probe the nature of the active species, we synthesized 0.5–10 wt % Cr loaded catalysts and characterized them by using XRD, UV/Vis spectroscopy, Raman spectroscopy, X‐ray photoelectron spectroscopy, extended X‐ray absorption fine structure analysis, X‐ray absorption near edge structure analysis, N2 sorption analysis, FTIR spectroscopy, 29Si NMR spectroscopy, SEM, and TEM. The liquid‐phase oxidation of cyclohexane to cyclohexanone (99 % selectivity) was performed under mild reaction conditions, and the results reveal clearly that the 5 wt % Cr loaded catalyst was optimum for the reaction. The initial composition of isolated Cr3+ species in the catalyst is the major factor that influences the enhanced activity for cyclohexane oxidation.

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