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SYNTHESIZING ORGANIC COMPOUNDS USING LIGHT-ACTIVATED TIO2
Citation:
SahleDemessie**, E AND M A. Gonzalez*. SYNTHESIZING ORGANIC COMPOUNDS USING LIGHT-ACTIVATED TIO2. Presented at American Chemical Society National Meeting, New Orleans, LA, August 22-26, 1999.
Description:
High-value organic compounds have been synthesized successfully from linear and cyclic hydrocarbons, by photocatalytic oxidation using a semiconductor material, titanium dioxide (TiO2). Various hydrocarbons were partially oxgenated in both liquid and gaseous phase reactors using ultraviolet light and titanium dioxide at mild conditions. The conversions and selectivities obtained for partial oxidation of hydrocarbons have been comparable to those achieved with the conventional method. Vapor phase photocatalytic oxidations of toluene with air, at 160oC and 27 mW/cm2 irradiation, showed overall conversion of 12 % to benzaldehyde and benzoic acid, with 95% selectivity to benzaldehyde. Experiments with cyclohexane have demonstrated that the major products are cyclohexanol, and cyclohexanone. Cyclohexane conversion of 2 - 6% was achieved for this reaction with no detectable formation of CO2. Oxidation of n-pentane showed formation of 2-pentanol as a major product and a small quantity of 3-pentanol. Gas phase reactions eliminate the separation step involved with liquid solvents and minimize the adsorption of products to the catalyst.
Initial life-cycle analysis showed that the technology has the potential to reduce water contaminations and eliminate the use of toxic catalysts. Light-induced catalysis opens up possibilities of the use of oxygen in partial oxidation reactions now being conducted with far more expensive polluting oxidants. This technology promises the potential of visible light-induced chemistry for the commercially important syntheses. The high selectivity of the mild photochemical routes will be especially attractive for the manufacturing of fine chemicals.