Isokinetic behaviour in gas phase catalytic haloarene hydrodehalogenation reactions: Mechanistic considerations

Mark A. Keane, Ragnar Larsson

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Compensation behaviour is established for the gas phase hydrodehalogenation of a range of haloarenes over a common Ni/SiO2 catalyst. Analysis of the experimental results delivers an isokinetic temperature (Tiso) at 658 ± 2 K associated with the following reactants: chlorobenzene, 4-chlorotoluene, 3-chlorophenol, 1,3,-dichlorobenzene, 4-chlorophenol, 3,5-dichlorophenol, 1,4-dichlorobenzene, bromobenzene, 2,6-dichlorophenol, 2-chlorophenol, 1,2-dichlorobenzene and 1,3-dibromobenzene. The occurrence of a Tiso is accounted for using the Selective Energy Transfer (SET) model that is based on the premise of resonance between a vibrational mode of the catalyst and a vibrational mode of the reactant with a transferral of resonance energy from the catalyst to the reactant to generate the "activated complex" with subsequent reaction. In this study of a single catalyst promoting a common (hydrodehalogenation) reaction for a family of haloarene reactants, we establish the complimentary vibrational modes as the out-plane C-H vibrations of substituted benzene and Ni-H vibration at high hydrogen surface coverage. The proposed surface rate-determining step is the C-H "out-of-plane" activation favouring an sp2 to sp3 transformation. © 2006 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)158-165
Number of pages8
JournalJournal of Molecular Catalysis A: Chemical
Volume249
Issue number1-2
DOIs
Publication statusPublished - 18 Apr 2006

Keywords

  • Compensation effect
  • Haloarenes
  • Hydrodehalogenation
  • Isokinetic temperature
  • Ni/SiO 2
  • Selective Energy Transfer model

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