Relative reaction velocities for thermal chlorination of trichloroethylene and perchloroethylene were 20, 30 and 70, and 6-8, 10 and 15 at 350°C, 400°C and 450°C, respectively, when a thermal decomposition velocity of a pure tetrachloroethane*
2 at 400°C was set as 10 (Preceeding Report I).
The thermal chlorination of tetrachloroethane was followed by the following competitive reactions and an optimum reaction temperature was around 475-500°C for formation of perchloroethylene:
Tetrachloroethane (1) trichloroethylene (2) pentachloroethane (3) perchloroethylene (4) hexachloroethane. The reaction velocities of each of these reactions at above 400°C were in order of (1)>(3)>(2)>(4). The dehydrochlorinating reaction of (1) was far rapider than that of the thermal decomposition system of tetrachloroethane with an addition of a small amount of chlorine. However, in case of a poor mixing of chlorine, which caused the thermal decomposition of a part of tetrachloroethane without chlorine, the reaction velocity of (1) was decreased considerably.This fact may be attributed to the formation of a retarder by the thermal decomposition of tetrachloroethane. The side reaction in the thermal chlorination of tetrachloroethane was mainly caused by the thermal change of trichloroethylene which was produced by the thermal decomposition of tetrachloroethane.It was assumed that this side reaction had a close relation with the formation of retarder.
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