Document Type

Thesis

Date of Award

9-30-1988

Degree Name

Master of Science in Environmental Science - (M.S.)

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

Joseph W. Bozzelli

Second Advisor

Henry Shaw

Third Advisor

Piero M. Armenante

Fourth Advisor

Anthony M. Dean

Abstract

The thermal decomposition of a dichloromethane/1 , 1 , 1-trichloroethane mixture diluted in hydrogen was conducted in tubular flow reactors at 1 atmosphere total pressure. The thermal degradation of each species was analyzed systematically over temperature ranges from 475 - 810 °C, residence times of 0.05 - 2.0 seconds and three different surface to volume ratio flow reactors.

It was found that the conversions of each species in the mixture were a function of both temperature and residence time. Complete decay occurs at about 810 °C for dichloromethane and around 570 °C for 1,1,1-trichloroethane at 1 second residence time. The major products observed were dichloroethylene, vinyl chloride, methyl chloride and dichloroethane at about 570 °C. Ethylene, methane, ethane, methyl chloride and HCl were the products at more complete conversions which occured near 810 °C and above. The hydrocarbon production increased approximately linearly with temperature. An increase in surface to volume ratio of the reactor tube was observed to accelerate the species decomposition in hydrogen, but it had no effect on the distribution of major products.

This study demonstrated that selective formation of HCl can result from thermal reaction of dichloromethane/1,1,1-trichloroethane mixture and showed that synergistic effects of 1,1,1-trichloroethane decomposition accelerate the rate of dichloromethane decomposition. A detailed kinetic reaction mechanism was developed and used to model results obtained from the experimental reaction system. The detailed kinetic reaction mechanism was based on thermochemical principle and transition state theory.

Rate constants obtained for initially important decomposition of dichloromethane and 1,1,1-trichioroethane over the temperature range 475 to 810 °C are: A (1/s) Ea (Kcal/mol) CH2Cl2 ----> CH2Cl + Cl 1.1E16 82.8 CH3CCl3 ----> CH2CCl2 + HCl 3.8E13 47.9 CH3CCl3 ----> CH3CCl2 + Cl 2.4E16 73.2

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