The photoassisted monooxygenation of C6H12 to C6H10O and C6H11OH by molecular oxygen has been studied on TiO2 powder catalyst dispersed in neat C6H12 and in C6H12/CH2Cl2 mixtures. The composition of the mixed solvent has a strong influence on the selectivity of the process: an increase in the content of CH2Cl2 brings about both an enhancement in the rate of formation of mono-oxygenated products and a decrease in the production of CO2. At the same time, the alcohol to ketone ratio increases in the mixed solvent. An explanation of this behavior is proposed which is based on the observed decrease in the adsorption strength of intermediates (C6H11OH and radicals) as the solvent composition is varied from pure C6H12 to mixtures of it with increasing amounts of CH2Cl2. The results of experiments with different O2 partial pressures are reported. The process is unaffected for O2 partial pressures > 200 Torr. For lower values the formation of dicyclohexyl becomes significant and reaches a maxim...
Photocatalytic oxygenation of cyclohexane on titanium dioxide suspensions: a study on the effect of the solvent and of oxygen
CARASSITI, Vittorio;MALDOTTI, Andrea;AMADELLI, Rossano
1998
Abstract
The photoassisted monooxygenation of C6H12 to C6H10O and C6H11OH by molecular oxygen has been studied on TiO2 powder catalyst dispersed in neat C6H12 and in C6H12/CH2Cl2 mixtures. The composition of the mixed solvent has a strong influence on the selectivity of the process: an increase in the content of CH2Cl2 brings about both an enhancement in the rate of formation of mono-oxygenated products and a decrease in the production of CO2. At the same time, the alcohol to ketone ratio increases in the mixed solvent. An explanation of this behavior is proposed which is based on the observed decrease in the adsorption strength of intermediates (C6H11OH and radicals) as the solvent composition is varied from pure C6H12 to mixtures of it with increasing amounts of CH2Cl2. The results of experiments with different O2 partial pressures are reported. The process is unaffected for O2 partial pressures > 200 Torr. For lower values the formation of dicyclohexyl becomes significant and reaches a maxim...I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
