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Issue 12, 2014
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Hydrothermal synthesis of octahedra-based layered niobium oxide and its catalytic activity as a solid acid

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Abstract

Layered-structure-type niobium oxides were synthesized by the hydrothermal method by using ammonium niobium oxalate as a precursor. The X-ray diffraction pattern (Cu-Kα) of the synthesized niobium oxide showed characteristic peaks at 2θ = 22.7° and 46.2°, indicating the linear corner-sharing of NbO6 octahedra in the c-direction. From Raman measurements, the layered-structure-type niobium oxide was composed of NbO6 octahedra and {Nb6O21} pentagonal units. The presence of micropores was confirmed by N2 adsorption at low pressure (1.0 × 10−6), indicating that the arrangement of the ab plane was an interconnection of the crystal structure motifs of {Nb6O21} units and micropore channels but without long-range order (deformed orthorhombic). Ammonium cations and water were desorbed from the deformed orthorhombic niobium oxide by calcination at 400 °C, and Brønsted acid sites were formed. The deformed orthorhombic niobium oxide showed high catalytic activity as a solid acid compared to the catalytic activities of other crystalline niobium oxides. The order of catalytic activity for the alkylation of benzyl alcohol and anisole was deformed orthorhombic Nb2O5 > TT-Nb2O5, amorphous Nb2O5 ≫ T-Nb2O5, pyrochlore Nb2O5.

Graphical abstract: Hydrothermal synthesis of octahedra-based layered niobium oxide and its catalytic activity as a solid acid

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The article was received on 02 Jun 2014, accepted on 18 Jul 2014 and first published on 18 Jul 2014


Article type: Paper
DOI: 10.1039/C4CY00713A
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Catal. Sci. Technol., 2014,4, 4250-4257

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    Hydrothermal synthesis of octahedra-based layered niobium oxide and its catalytic activity as a solid acid

    T. Murayama, J. Chen, J. Hirata, K. Matsumoto and W. Ueda, Catal. Sci. Technol., 2014, 4, 4250
    DOI: 10.1039/C4CY00713A

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