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Photocatalytic oxidation of cyclohexanol (1), cyclopentanol (2), and cycloheptanol (3) was investigated by using titanium dioxide (Degussa P25) as a semiconductor photocatalyst .The effect of different operational parameters such as the catalyst, the solvent, time, and oxidant was also studied. Results showed a high percentage of conversion for 1-3 (71.6%, 94.2%, and 100%, resp.) and that the primary photocatalytic oxidation products are the corresponding cycloalkanones (4-6). They were formed with high selectivity (>85%). Several other products were also identified using GC, GC/MS techniques and authentic samples. The photocatalytic activity is explained by a photoinduced electron transfer mechanism through the formation of electron-hole pair at the surface of the semiconductor particles. A first-order kinetic model was observed for the photocatalytic oxidation of the investigated cycloalkanols.

The superiority of silver-doped titania for photocatalytic oxidation (PCO) of organic compounds inspired us to investigate PCO of 1,2-cyclohexanediol. Ag/TiO 2 was prepared, characterized (nanosize 19-24 nm) and used for oxidation of 1,2-cyclohexanediol (1) in acetonitrile. The photolysate was analyzed using GC and GC/MS techniques. The PCO products are 2-hydroxylcyclohexanone (2), 1,2-cyclohexandione (3), 2-cyclohexenone(4), cyclohexanone (5), and adipic acid (6).The formation of electron-hole pair at the surface of the catalyst followed by oxidation reactions was the suggested mechanism. Kinetic studies revealed first-order mechanism for PCO of 1 and rate constant (k) = À0.145 h -1 .

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