ACCELERATION OF THE UV-STIMULATED HT OXIDATION BY CCL4

The effects of air pollutants on UV-stimulated HT oxidation were studi ed by selecting CCl4 as a model pollutant. Mixture gases consisting of H-2+HT, O-2 and CCl4 were irradiated with a high pressure mercury lam p. The reaction products were found to be HTO and TCl. The role of CCl 4 was evaluated by measuring the formation rate of HTO-TCl as a functi on of the partial pressure of CCl4. The reaction took place in two sta ges. During the first stage, the extent of the reaction increased almo st linearly with time. During the second stage, the rate became faster with time, showing a similar feature to autocatalytic reactions. It w as found that those rates were considerably increased with the pressur e of CCl4. In the case of 1.0 Torr, the rate of the first stage was 60 times greater than that of the UV-stimulated HT oxidation previously reported, and that of the second stage was about 10 times that of the first stage. As a whole, the CCl4-assisted UV-stimulated HT oxidation showed a 5x10(4)-5x10(5) times greater reaction rate than the beta ray -induced radiochemical HT oxidation. With the aid of computer simulati on including 47 relevant elementary reactions, the enhanced accelerati on of the reaction was understood as a result of the formation of new reaction paths such as Cl--> HE--> HO2--> H2O and Cl--> H--> HO2--> OH --> H2O, which lacked in the UV-stimulated HT oxidation mechanism.