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PHOTOCATALYTIC REACTORS AND KINETICS FOR CLEAN CHEMICAL SYNTHESIS [POSTER PRESENTATION]
Citation:
SahleDemessie*, E, T. Denlein, D. Tran, M A. Gonzalez*, AND J Enriquez*. PHOTOCATALYTIC REACTORS AND KINETICS FOR CLEAN CHEMICAL SYNTHESIS [POSTER PRESENTATION]. Presented at American Institute of Chemical Engineers Annual Meeting, Dallas, TX, 11/2/99.
Description:
Semiconductor photocatalysis has been tested at a potential technology for synthesizing alcohols, ketones and aldehydes from linear and cyclic hydrocarbons. The technology couples UV light with photocatalyst overcoming many of the drawbacks of conventional reacors. 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. The effects of irradiation, oxygen concentration, contact time and moisture on the conversion and selectivity of partial oxidation of model hydrocarbons, cyclohexane and toluene were studied. 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. Three types of reactors, magnetically stirred annular reactor, and packed bed coil reactor were used for gas phase and a falling film reactor was used for liquid phase.
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.