Heterogeneous photocatalysis: Photoassisted oxidation of isopropanol to acetone and photodegradation of volatile organic compounds

Date of Completion

January 1997


Health Sciences, Occupational Health and Safety|Chemistry, Analytical|Chemistry, Inorganic|Engineering, Chemical|Engineering, Civil|Health Sciences, Public Health




Recently, a highly efficient photocatalyst consisting of amorphous manganese oxide (AMO) has been developed. Photoassisted catalytic oxidation of isopropanol has been studied by using amorphous manganese oxide catalysts with magnesium oxide as a diluent. When AMO or AMO/MgO is illuminated with UV-visible light in the presence of isopropanol vapor and oxygen at room temperature, the primary organic oxidation product is acetone. Enhanced yields for photooxidation of isopropanol with AMO/MgO mixtures have been observed. A continuous supply of oxygen may be achieved by adsorbing molecular oxygen on AMO and AMO/MgO during simultaneous irradiation in the UV-visible range. Temperature programmed desorption and oxygen isotopic exchange results support previously proposed mechanisms of photoassisted catalytic oxidation. Oxygen is adsorbed as O$\sb2\sp-$ species on the surface of the catalyst and plays an important role in this photooxidation. The observed effect of magnesium oxide suggests that hydroxyl groups promote the catalytic activity.^ The contamination of indoor air by volatile organic compounds (VOCs) has become a serious public health problem in recent years. The purpose of this study is to investigate photocatalytic activity of TiO$\sb2$ under kinetic conditions and the application of photocatalysts for decomposition of VOCs. The photocatalytic degradation of trichloroethylene, toluene, and triethylamine over TiO$\sb2$ (anatase) has been investigated by using a flat plate photochemical reactor. TiO$\sb2$ was used as a thin film coated on a microscope slide. The degradation of the three compounds, trichloroethylene, toluene, and triethylamine in a continuous flow mode, approximates first-order kinetics. The Langmuir-Hinshelwood kinetics have been used to rationalize the first-order behavior in solid-gas reaction. The deactivation of the catalyst also was investigated. ^