Gas phase hydrogenation of nitrocyclohexane over supported gold catalysts

Xiaodong Wang, Noemie Perret, Mark A Keane

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21 Citations (Scopus)

Abstract

We report the first continuous (gas phase) hydrogenation of nitrocyclohexane over oxide (Al2O3, TiO2, CeO2 and ZrO2) supported Au catalysts. Thermochemical analysis has established possible thermodynamic constraints and product distribution at equilibrium. The catalysts have been characterised by temperature-programmed reduction (TPR), H-2/O-2 chemisorption/temperature-programmed desorption (TPD), BET surface area/porosity, X-ray diffraction (XRD) and scanning/transmission electron microscopy (STEM/TEM) measurements. The effects of space velocity (2-6 x 10(4) h(-1)), temperature (353 and 473 K) and H-2 partial pressure (8 x 10(-4)-0.93 atm) on catalyst performance have been examined. Selectivity to the target cyclohexanone oxime is sensitive to H-2 pressure, where an increase in temperature favours cyclohexanone with amine/ketone condensation and subsequent reduction to dicyclohexylamine. An increase in turnover frequency was observed with decreasing (surface area weighted) mean Au size (from 7.0 to 4.3 nm) but a lower value was obtained for 3.0 nm Au (on CeO2) that is linked to suppressed H-2 chemisorption (under reaction conditions) resulting from strong interaction with the partially reduced support. We establish a critical surface interplay between imine, H and -OH that governs selectivity. Au/Al2O3 exhibited the highest activity and oxime selectivity (maximum = 95%), Au/CeO2 promoted near exclusive production of cyclohexanone whereas Au/TiO2 and Au/ZrO2 generated a cyclohexylamine/cyclohexanone mixture. (C) 2013 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)575-584
Number of pages10
JournalApplied Catalysis A: General
Volume467
DOIs
Publication statusPublished - 2 Oct 2013

Keywords

  • Gas phase hydrogenation
  • Nitrocyclohexane
  • Cyclohexanone oxime
  • Supported Au catalysts
  • Thermochemical analysis
  • Hydrogen partial pressure
  • SELECTIVE HYDROGENATION
  • P-CHLORONITROBENZENE
  • NITRO-COMPOUNDS
  • CO OXIDATION
  • ACTIVE-SITES
  • CHEMOSELECTIVE HYDROGENATION
  • BECKMANN REARRANGEMENT
  • CYCLOHEXANONE OXIME
  • OXYGEN VACANCIES
  • CHEMISORPTION

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