Photocatalytic oxidation of cyclohexane over TiO2nanoparticles by molecular oxygen under mild conditions

Xinyong Li, Guohua Chen, Yue Po-Lock, Charles Kutal

Research output: Journal article publicationJournal articleAcademic researchpeer-review

42 Citations (Scopus)

Abstract

The structure, physical characteristics and photocatalytic selective oxidation properties of nanometer-size TiO2particles produced by a sol-gel method were studied by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR) and photocatalytic selective oxidation measurements. Analysis of the XRD results shows that sol-gel-produced TiO2nanoparticles have the anatase structure at annealing temperatures ≤973 K, that the rutile structure begins to emerge at annealing temperatures ≥973 K and the particles have the pure rutile structure at 1023 K. DRS indicates that the obtained TiO2nanoparticles exhibit a blue shift with decreasing crystallite size. Analysis of the XPS results shows that the TiO2nanoparticles have a lot of oxygen vacancies. The EPR spectrum of TiO2at 77 K is composed of a strong isotropic EPR Surface-Ti3+signal(I) at g = 1.926 and a weak broad Bulk-Ti3+signal (II) at g = 1.987. Quantitative EPR indicates that both signals show a size and temperature dependence. Photocatalytic oxidation of cyclohexane into cyclohexanol with high selectivity and activity has been obtained by activation of molecular oxygen over sol-gel-produced TiO2nanoparticles under mild conditions in dry solvent, which reveals that the quantum size effect and surface state effect of nanoparticles are key points for governing the selective photocatalytic reaction. The photocatalytic oxidation mechanism under dry solvent is different from that in aqueous solutions.
Original languageEnglish
Pages (from-to)1246-1251
Number of pages6
JournalJournal of Chemical Technology and Biotechnology
Volume78
Issue number12
DOIs
Publication statusPublished - 1 Dec 2003
Externally publishedYes

Keywords

  • Cyclohexane
  • Nanosize particles
  • Oxide semi-conductors
  • Photocatalytic selective oxidation
  • Titanium dioxide

ASJC Scopus subject areas

  • Biotechnology
  • Chemical Engineering(all)
  • Renewable Energy, Sustainability and the Environment
  • Fuel Technology
  • Waste Management and Disposal
  • Pollution
  • Organic Chemistry
  • Inorganic Chemistry

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