Synthesis, characterisation and hydrogenation performance of ternary nitride catalysts

Perret, N., Alexander, A.-M., Hunter, S. M., Chung, P., Hargreaves, J. S.J. , Howe, R. F. and Keane, M. A. (2014) Synthesis, characterisation and hydrogenation performance of ternary nitride catalysts. Applied Catalysis A: General, 488, pp. 128-137. (doi:10.1016/j.apcata.2014.09.026)

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Publisher's URL: http://dx.doi.org/10.1016/j.apcata.2014.09.026

Abstract

Synthesis of phase pure Co<sub>3</sub>Mo<sub>3</sub>N and Fe<sub>3</sub>Mo<sub>3</sub>N by temperature programmed ammonolysis has been established by XRD and elemental analysis. The ternary nitrides are characterised by a η-6 structure and low surface area (4-9 m<sup>2</sup> g<sup>−1</sup>). Pseudomorphic transformation of cobalt nitrate generated rod-shaped crystals while the use of iron chloride resulted in Fe<sub>3</sub>Mo<sub>3</sub>N aggregates with irregular morphology and wide size distribution. XPS measurements have revealed surface N enrichment relative to the bulk where the passivated samples show a range of oxidation states; Co<sub>3</sub>Mo<sub>3</sub>N exhibited Mo<sup>2+</sup> and Co<sup>n+</sup> (0 ≤ n ≤ 3) whereas Fe<sub>3</sub>Mo<sub>3</sub>N was characterised by higher oxidation states (Fe<sup>3+</sup> and Mo<sup>3+</sup>). Temperature programmed reduction (TPR) to 823 K served to remove the passivation layer where subsequent H<sub>2</sub>chemisorption and temperature programmed desorption (TPD) has demonstrated greater uptake on Fe<sub>3</sub>Mo<sub>3</sub>N relative to Co<sub>3</sub>Mo<sub>3</sub>N, resulting in a higher nitrobenzene hydrogenation rate (to aniline). Fe<sub>3</sub>Mo<sub>3</sub>N promoted selective reduction of–NO<sub>2</sub> in p-chloronitrobenzene to generate p-chloroaniline as sole product whereas Co<sub>3</sub>Mo<sub>3</sub>N favoured C-Cl scission with the formation of nitrobenzene (in addition to p-chloroaniline). Hydrodechlorination properties were further established for Co<sub>3</sub>Mo<sub>3</sub>N in the conversion of chlorobenzene (to benzene) under conditions where Fe<sub>3</sub>Mo<sub>3</sub>N was inactive. A temporal deactivation of both nitrides is associated with Cl poisoning of Co3Mo3N and structural changes to Fe<sub>3</sub>Mo<sub>3</sub>N.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Alexander, Miss Anne-Marie and Chung, Mr Peter and Hargreaves, Professor Justin and Hunter, Mr Stuart
Authors: Perret, N., Alexander, A.-M., Hunter, S. M., Chung, P., Hargreaves, J. S.J., Howe, R. F., and Keane, M. A.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:Applied Catalysis A: General
Publisher:Elsevier
ISSN:0926-860X
ISSN (Online):1873-3875

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