No abstract

The effects of air pollutants on UV-stimulated HT oxidation were studied by selecting CCl 4 as a model pollutant. Mixture gases consisting of H 2 +HT, O 2 and CCl 4 were irradiated with a high pressure mercury lamp. 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 function of the partial pressure of CCl 4 . The reaction took place in two stages. During the first stage, the extent of the reaction increased almost linearly with time. During the second stage, the rate became faster with time, showing a similar feature to 282 HASEGAWA ET AL.autocatalytic reactions. It was found that those rates were considerably increased with the pressure of CCl 4 . 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 CCl 4 -assisted UV-stimulated HT oxidation showed a 5×10 4 -5×10 5 times greater reaction rate than the ß ray-induced radiochemical HT oxidation. With the aid of computer simulation including 47 relevant elementary reactions, the enhanced acceleration of the reaction was understood as a result of the formation of new reaction paths such as Cl H HO 2 H 2 O and Cl H HO 2 OH H 2 O, which lacked in the UV-stimulated HT oxidation mechanism.