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Abstract
The effects of air pollutants on UV‐stimulated HT oxidation were studied by selecting CCl4 as a model pollutant. Mixture gases consisting of H2+HT, O2 and CCl4 were irradiated with a high pressure mercury lamp. The reaction products were found to be HTO and TCl. The role of CCl4 was evaluated by measuring the formation rate of HTO+TCl as a function of the partial pressure of CCl4. 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 autocatalytic reactions. It was found that those rates were considerably increased with the pressure 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 5×104‐5×105 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→ HO2→ H2O and Cl→ H→ HO2→ OH→ H2O, which lacked in the UV‐stimulated HT oxidation mechanism.