cycloalkanols on dehydration gives
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Photocatalysis represents one of the promising technologies for photoenergy conversion started with the pioneer findings of Fujishima and Honda [1]. Its applications in water recycling, air-pollution treatment, as well as in organic synthesis have found a great interest [2–6].
There are many studies focused on the photocatalytic oxidation and degradation of several classes of organic compounds catalyzed by Ti semiconductor particulates [7–13].
Photocatalytic oxidation and degradation of alcohols catalyzed by Ti and other semiconductor particulates have found some interest. For example, Harvey et al. [14] studied photocatalytic oxidation of liquid propan-2-ol to propanone using suspensions of titanium dioxide irradiated with filtered UV radiation. The dependence of reaction rate on the square root of the intensity of the incident radiation, together with low quantum yields, reflects the dominance of photoelectron and photohole recombination within the Ti. Cameron and Bocarsly [15] studied the photocatalytic oxidation of ethanol, benzyl alcohol, cinnamyl alcohol, n-hexyl alcohol, isopropyl alcohol, cyclopentanol, and cyclohexanol which converted to the corresponding aldehyde or ketone by using oxygen gas and visible light 488 nm (85 mW) illumination from an Ar laser. The process was catalyzed by the presence of PtC and CuC.
Nishimoto et al. [16] studied the photocatalytic dehydrogenation of aliphatic alcohols by aqueous suspensions of platinized titanium dioxide, photoirradiation ( nm) of Ar-purged aqueous propan-2-ol solution gave hydrogen and acetone. The regioselectivity in the semiconductor-mediated photooxidation of 1,4-pentanediol was studied in 1989 by Fox et al. [17].
We also studied the photocatalytic oxidation of selected aryl alcohols [18, 19]. The main oxidation products were the corresponding aldehydes or ketones and acids. Kinetic studies revealed a second-order reaction rate for benzyl alcohol as a model alcohol. Also photocatalytic oxidation of fluoren-9-ol and 4,5-diazafluoren-9-ol in nonaqueous oxygen saturated Ti suspension to the corresponding ketones was formed in a high yield, in addition to minor amount of the corresponding hydrocarbon and other decomposition products. Interestingly, photocatalytic oxidation of the parent fluorene afforded fluorenone under the same conditions. Similarly, Phenyl-4-pyridylmethanolas an acyclic simulant gave the corresponding ketone and hydrocarbon. Furthermore, the effect of solvent polarity has been tested [18, 19].
Pillai and Salhe-Demessie [20] studied the selective oxidation of primary and secondaryaliphatic alcohols to their corresponding carbonyl compounds in gas phase. In 2006, Wu et al. [21] studied the long-term photocatalytic stability of C-modified P25-Ti powders for the production from aqueous ethanol solution. In this paper, the long-term stability of photocatalytic activity of C doped P25-Ti nanoparticles for hydrogen production from aqueous ethanol solution was discussed in detail using a photoelectrochemical method.
It is clear from the previous survey that the effect of ring size and conditions on the photocatalytic oxidations of secondary cycloalkanols has not been tackled. So, this study will be of great interest.