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Effect of P/Fe ratio on the structure and ammoxidation functionality of Fe-P-O catalysts

Paper ID Volume ID Publish Year Pages File Format Full-Text
43185 45958 2008 10 PDF Available
Title
Effect of P/Fe ratio on the structure and ammoxidation functionality of Fe-P-O catalysts
Abstract

Bulk FePO4 catalysts, with varying P/Fe atomic ratio in the range of 1–1.6, were prepared and characterized by XRD, FT-IR, TPR, Potentiometric titration, Laser Raman, TEM, XPS and TG/DTA techniques in order to study the influence of P/Fe atomic ratio on the nature and extent of the active phase formation. The data obtained from XRD and Laser Raman techniques suggested predominant formation of the quartz type iron phosphate at close to stoichiometric P/Fe ratio, but as the ratio increased beyond 1.4 a progressive transformation of monomeric phosphate into its polymeric form was observed. XPS spectra reflected the presence of iron in its 3+ state when P/Fe ≤ 1.2 and exists as Fe2+ and Fe3+ when P/Fe ≥ 1.4. The catalytic properties of these iron phosphates were studied in the vapor phase ammoxidation, taking 2-methylpyrazine (MP) to 2-cyanopyrazine (CP) as an example. The ammoxidation activity of the catalysts was found to be proportional to the extent of quartz phase formed which in turn was proportional to the redox property, as observed by the oxidation functionality of the catalysts in benzyl alcohol transformation. However, the selectivity to nitrile was found to be dependent on the acid strength of the catalysts.

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Keywords
Iron phosphate; Ammoxidation; 2-Methyl pyrazine; 2-Cyano pyrazine
First Page Preview
Effect of P/Fe ratio on the structure and ammoxidation functionality of Fe-P-O catalysts
Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 334, Issues 1–2, 1 January 2008, Pages 10–19
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis