Influence of preparation methods and structure of niobium oxide-based catalysts in the epoxidation reaction

• The epoxidation reaction is structure-sensitive on crystalline Nb2O5.
• In crystalline samples the T-phase Nb2O5 enhances the hydrolysis of epoxide.
• The dispersion of the active NbO4 tetrahedra is the most important factor affecting the oxirane selectivity.

The catalytic activity of niobium oxide-based materials, containing the same amount of Nb2O5 (∼15 wt%) and prepared by different methods, with that of pure Nb2O5 in the epoxidation of methyl oleate with hydrogen peroxide was compared.The catalytic performances of the catalyst prepared by impregnation do not differ substantially from the ones of Nb2O5. The performances of Nb-supported catalysts prepared by sol–gel can be modulated by controlling the process parameters. The high dispersion of the active NbOx species obtained by this preparation method gives very higher selectivity than in the case of pure Nb2O5. Morphologic and structural characterization of the catalysts helped justifying the obtained catalytic results in terms of activity and selectivity.

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