Selective three-phase hydrogenation of aromatic nitro-compounds over β-molybdenum nitride

Fernando Cardenas-Lizana, Daniel Lamey, Santiago Gomez-Quero, Noemie Perret, Lioubov Kiwi-Minsker, Mark A. Keane

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

A tetragonal molybdenum nitride (ß-Mo2N) has been prepared by temperature programmed treatment of MoO3 in flowing N2 + H2 and for the first time shown to catalyze the liquid phase selective hydrogenation (T = 423 K; PH2 = 11 bar) of a series of para-substituted (-H, -OH, -O-CH3, -CH3, -Cl, -I and -NO2) nitrobenzenes to give the corresponding aromatic amine. Reaction over Pd/Al2O3, as a benchmark catalyst (Pd particle size ca. 18 nm), resulted in a composite hydrodechlorination/hydrogenation of p-chloronitrobenzene (as a representative nitroarene) to generate nitrobenzene and aniline. ß-Mo2N has been characterized in terms of temperature-programmed reduction (TPR), H2 chemisorption/temperature programmed desorption (TPD), BET surface area/pore volume, elemental analysis, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning (SEM) and transmission (TEM) electronic microscopy. Elemental analysis, XRD, SEM and TEM have confirmed the formation of tetragonal ß-Mo2N, characterized by an agglomeration of flake-like crystallites. Post-synthesis, the nitride was passivated by contact with 1% (v/v) O2/He at ambient temperature and XPS analysis has demonstrated the formation of a superficial passivating oxide overlayer without bulk oxidation. Pre-reaction, activation by TPR to 673 K was necessary to remove the passivating film. Hydrogen TPD has revealed significant hydrogen uptake (0.7 µmol m-2) associated with ß-Mo2N. Nitro group reduction kinetics have been subjected to a Hammett treatment where the reaction constant (p = 0 4) is diagnostic of an increase in rate due to the presence of electron-withdrawing substituents on the aromatic ring, consistent with a nucleophilic mechanism. The results presented in this study establish the viability of ß-Mo2N to promote selective nitroarene hydrogenation. © 2011.

Original languageEnglish
Pages (from-to)53-61
Number of pages9
JournalCatalysis Today
Volume173
Issue number1
DOIs
Publication statusPublished - 1 Sep 2011

Keywords

  • β-Mo nitride
  • Amine
  • Hammett relationship
  • Liquid phase
  • Nitroarene
  • Selective hydrogenation

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