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Facile synthesis of highly ordered mesoporous chromium–alumina catalysts with improved catalytic activity and stability
Published online by Cambridge University Press: 20 March 2014
Abstract
The highly ordered mesoporous chromium–alumina catalysts (denoted as OMCA(x)) with different nAl/nCr ratios of 10 and 20 have been successfully synthesized via an evaporation-induced self-assembly (EISA) pathway associated with thermal treatment and were applied to the liquid phase oxidation of cyclohexane with hydrogen peroxide (H2O2) as an oxidant. For comparison studies, a chromium catalyst with the nAl/nCr ratio of 10 supported on an ordered mesoporous alumina support [denoted as Cr/OMA(10)] was also prepared by an incipient wetness impregnation (IWI) method. Although both kinds of catalysts retained a unidimensionally ordered mesoporous structure, textural properties of the catalysts were significantly affected by the preparation method. The characteristic results from XRD, N2 adsorption, TEM, UV-Vis, 27Al MNS NMR, and H2-TPR showed that the OMCA(x) catalysts exhibited much more highly ordered hexagonal mesostructure, narrower pore-size distribution, higher Brunauer-Emmett-Teller surface area and pore volume, and more homogeneous distribution of Cr species in mesoporous alumina framework in the form of tetrahedrally coordinated hexavalent Cr-oxide moieties than those of Cr/OMA(10) synthesized by an IWI method. In addition, in comparison with Cr/OMA(10), OMCA(x) catalysts showed higher catalytic activity and stability for the liquid phase oxidation of cyclohexane.
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- Copyright © Materials Research Society 2014
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