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Insight into the structure and molybdenum species in mesoporous molybdena-alumina catalysts over isobutane dehydrogenation

Abstract

The relationship of the structure and Mo species of the mesoporous molybdena-alumina catalysts and their catalytic performance over isobutane dehydrogenation has been investigated detailedly. The characterizations of XRD, HADDF-STEM, EDX, FT-IR and N2 physisorption illustrated that ordered mesoporous catalysts (OM-Al, MoAl(F) and MoAl(C)) possessed amorphous alumina phase and non-ordered mesoporous catalysts (M-Al and MoAl) exhibited γ-Al2O3 phase. Mo species were high dispersion over all the catalysts due to that Mo surface densities were about 1.0 Mo/nm2. Moreover, Mo species were uniformly distributed over MoAl(F) catalyst with the Mo species confined in the ordered mesoporous structure, deduced by XPS and ICP-OES techniques. Higher dehydrogenation stability, less coke formation rate albeit lower catalytic conversion was obtained over MoAl(F) by comparison with MoAl(C) and MoAl on account of its stronger metal-support interaction by means of H2-TPR technique. The catalyst with γ-Al2O3 phase exhibited stronger acidity and higher activity than the corresponding catalyst with the amorphous phase. The acidity of the catalysts was greatly enhanced by the addition of Mo species according to the NH3-TPD characterization. However, not all the acidic sites were the active sites for dehydrogenation activity. The moderately and strongly acidic sites and the Mo species including Mo6+ and lower valence Mo species were probably contributed to the dehydrogenation reactivity. Moreover, the deactivation of the catalysts was mainly the coke formation over the spent catalysts.

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Publication details

The article was received on 16 May 2017, accepted on 16 Jun 2017 and first published on 16 Jun 2017


Article type: Paper
DOI: 10.1039/C7CY00975E
Citation: Catal. Sci. Technol., 2017, Accepted Manuscript
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    Insight into the structure and molybdenum species in mesoporous molybdena-alumina catalysts over isobutane dehydrogenation

    H. Zhao, H. Song, L. Chou, J. Zhao, J. Yang and L. Yan, Catal. Sci. Technol., 2017, Accepted Manuscript , DOI: 10.1039/C7CY00975E

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