Photo-catalytic oxidation of cyclohexane over TiO2: A novel interpretation of temperature dependent performance

A.R. Almeida, Ana Rita Almeida, Rob Berger, Jacob A. Moulijn, Guido Mul

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10 Citations (Scopus)

Abstract

The rate of cyclohexane photo-catalytic oxidation to cyclohexanone over anatase TiO2 was studied at temperatures between 23 and 60 °C by in situATR-FTIR spectroscopy, and the kinetic parameters were estimated using a microkinetic model. At low temperatures, surface cyclohexanone formation is limited by cyclohexane adsorption due to unfavorable desorption of H2O, rather than previously proposed slow desorption of the product cyclohexanone. Up to 50 °C, the activation energy for photocatalytic cyclohexanone formation is zero, while carboxylates are formed with an activation energy of 18.4 ± 3.3 kJ mol−1. Above 50 °C, significant (thermal) oxidation of cyclohexanone contributes to carboxylate formation. The irreversibly adsorbed carboxylates lead to deactivation of the catalyst, and are most likely the predominant cause of the non-Arrhenius behavior at relatively high reaction temperatures, rather than cyclohexane adsorption limitations. The results imply that elevating the reaction temperature of photocatalytic cyclohexane oxidation reduces selectivity, and is not a means to suppress catalyst deactivation
Original languageEnglish
Pages (from-to)1345-1355
Number of pages11
JournalPhysical chemistry chemical physics
Volume13
Issue number4
DOIs
Publication statusPublished - 2011

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Keywords

  • IR-95290
  • METIS-280550

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