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The superiority of silver-doped titania for photocatalytic oxidation (PCO) of organic compounds inspired us to investigate PCO of 1,2-cydohexanediol. Ag/Ti02 was prepared, characterized (nanosize 19-24 nm) and used for oxidation of 1,2-cydohexanediol (1) in acetonitrile. The photolysate was analyzed using GC and GC/MS techniques. The PCO products are 2-hydroxylcydohexanone (2), 1,2-cydohexandione (3), 2-cydohexenone(4), cydohexanone (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 (fc) =-0.145 h- [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: The present article embraces the photocatalytic oxidation (PCO) of three selected cyclohexyl alcohols namely cyclohexylmethanol (1), 2-cyclohexylethanol (2) and 1-cyclohexylethanol (3) using nanoparticles titanium dioxide (TiO2-P25) as a semiconductor photocatalyst in acetonitrile under aerated conditions. The photocatalytic experiments showed moderate conversion ratios (55.2%, 51.8% and 60.3%, respectively). The primary photocatalytic oxidation products are the corresponding aldehydes or ketones and acids. The photocatalytic oxidation products were identified mainly by GC and GC/MS techniques using authentic samples. Formation of electron–hole pair at the surface of the semiconductor nanoparticles followed by oxidation reaction was the suggested mechanism. A first-order kinetic model was observed for the photocatalytic oxidation of the investigated alcohols and the rate constants were calculated. [Copyright &y& Elsevier]

Photocatalytic oxidation of the title compounds 1 and 2 in nonaqueous oxygen saturated TiO2 suspension was carried out. The corresponding ketones were 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 (3) afforeded fluorenone under the same conditions. Also, compound 4 as an acyclic simulant gave the corresponding ketone and hydrocarbon. Furthermore, the effect of solvent polarity has been tested.An electron–hole pair generated on the irradiated TiO2 surface is suggested for the semiconductor-mediated photocatalysis. [Copyright &y& Elsevier]