Rutile-type Cr/Sb mixed oxides as heterogeneous catalysts for the ammoxidation of propane to acrylonitrile |
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Authors: | Ballarini N. Cavani F. Giunchi C. Masetti S. Trifirò F. Ghisletti D. Cornaro U. Catani R. |
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Affiliation: | (1) Dipartimento di Chimica Industriale e dei Materiali, Universitá di Bologna, Viale Risorgimento 4, 40136 Bologna, Italy;(2) Dipartimento di Chimica Industriale e dei Materiali, Universitá di Bologna, Viale Risorgimento 4, 40136 Bologna, Italy;(3) EniTecnologie, Via Maritano 26, S. Donato Milanese, Mi, Italy;(4) Snamprogetti, Via Maritano 26, S. Donato Milanese, Mi, Italy |
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Abstract: | Cr/Sb mixed oxides with a rutile-type structure were synthesized by calcining (700°C) a mixture of oxohydrates obtained by coprecipitation from an alcohol solution containing the required amount of the components. The samples were characterized using X-ray powder diffraction (XRD), FT-IR spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). In the Cr/Sb/O compound prepared with Cr/Sb 1/0.8 (atomic ratio), an almost stoichiometric CrSbO4develops (no antimony or chromium oxides are found), which however is characterized by enrichment in Sb in outmost rutile atomic layers, and thus by a non-homogeneous intracrystalline distribution of the two components. For Cr/Sb ratios lower than 1, the amount of Sb in the rutile-type structure exceeds the stoichiometric value. The reactivity of Cr/Sb/O catalysts with increasing Sb contents (from Cr/Sb 1/0.8 to 1/2.8) is slightly affected by the Cr/Sb atomic ratio. In particular, the selectivity increases with increasing Sb content, while the catalytic activity is higher for the samples having higher Cr/Sb ratios. The Cr/Sb/O system presents considerable differences with respect to the V/Sb/O rutile system; these differences are discussed in reference to the properties of the transition metal components of the rutile mixed oxides. |
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Keywords: | acrylonitrile propane ammoxidation rutile mixed oxides chromium-antimony mixed oxides |
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