Chromium oxide-catalyzed disproportionation of chlorodifluoromethane: A mechanism study

D. R. Coulson, P. W.J.G. Wijnen, J. J. Lerou, L. E. Manzer

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

The facile dispropartionation of CHF2Cl over chrome(III) oxide-based catalysts has allowed the study of catalyst activation and disproportionation as separate processes. Using both a conventional plug-flow microreactor and a TAP reactor, we have found evidence that chrome oxides, in the presence ofCHF2Cl, undergo at least two separate surface transformations before becoming catalytically active toward disproportionation. The first transformation involves a reductive deoxygenation of high-valent surface-Cr species resulting in the formation of CO2 and other oxidized products. This reduced surface then reacts with CHF2Cl to form CO and a halogenated, catalytically active surface. It is proposed that catalysis occurs on coordinatively unsaturated halogenated Cr3+ active sites. An increase in Lewis acidity of the catalyst surface was shown to accompany each transformation step. A brief kinetic study of the disproportionation gave evidence that the reaction does not proceed by a Rideal-Eley mechanism. Examination of initial product distributions, arising from a CHF3-activated catalyst, gave evidence that is consistent with a monomolecular halogen-exchange mechanism.

Original languageEnglish (US)
Pages (from-to)103-120
Number of pages18
JournalJournal of Catalysis
Volume140
Issue number1
DOIs
StatePublished - Mar 1993

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Physical and Theoretical Chemistry

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