Characterization And Selective Photo-oxidation Of Cyclohexane On Lanthanon-doped Nano-TiO₂

Characterization and selective photo-oxidation of cyclohexane on nano-TiO2 powder were studied in this paper. Eu³⁺,Nd³⁺,Tb³⁺,Dy³⁺ were adoped to enhance the photocatalytic activity. The technics and kinetics of photo-oxidation of cyclohexane were discussed simultaneously.First, Eu, Nd, Tb, Dy-doped nano-TiO₂ were prepared by sol-gel method, and nano-TiO₂ was analyzed by XRD,UV,IR,PL,TG etc, The results indicated that the absorption of the sample annealed at 500 ℃ is strong because it is composed of anatase and rutile sized about 10¹00nm (ref. XRD). From IR,TG,XRD lanthanon restrain the growth of grain and the conversion of anatase to rutile .This improves the TiO₂ heat stability. From IR and UV these lanthanon into titania could efficiently extend photo-response from UV to visible regions and improve the UV adoption. Second, the photo-oxidation of cyclohexane on titanium dioxide and over V₂O₅/Al₂O₃ was investigated in neat cyclohexane to synthesize cyclohexanone and cylohexanol. The results indicated high temperature,high O₂ concentration,high BET areas is advantaged to the product of cyclohexanone. The characteristic of reaction over V₂O₅/Al₂O₃ is a reasonable ketone/alcohol ratio.These lanthanon into titania could efficiently extend photoactivity.Titanium dioxide doped with Eu or Tb exhibits the high selectivity to partial oxidation compounds.Finally, the mechanisms and the kinetics of photo-oxidation of cyclohexane were discussed, the rate of photo-oxidation of cyclohexane can be expressed in zero-order kinetics model. Cyclohexanol is likely formed firstly, cyclohexanol is further oxidized to form cyclohexanone, then cyclohexanone is deeply oxidized to form carbon dioxide.