Document Type

Thesis

Date of Award

5-31-1989

Degree Name

Master of Science in Chemical Engineering - (M.S.)

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

Joseph W. Bozzelli

Second Advisor

Henry Shaw

Third Advisor

Edward Robert Ritter

Abstract

The thermal decomposition of 1,1,1-trichloroethane in methane/oxygen mixtures and argon bath gas was carried out at 1 atmosphere total pressure in a tubular flow reactors. The thermal degradation of 1,1,1-trichloroethane and methane were analyzed systematically over temperature ranges from 500 to 800°C, with average residence times in the range of 0.05 to 2.5 seconds. Five reactants ratio sets in three different size flow reactors were studied.

It was found that the complete decay (99%) of the 1,1,1-trichloroethane at 1 second residence time occurs at about 600°C for all the reactants ratio sets. The major product for 1,1,1-trichloroethane decomposition are 1,1-dichloroethylene and HCl. Oxygen has almost no effect on the decay of 1,1,1-trichloroethane in our study. Formation of CH2CCl2 as one of major product from CH3CCl3 increases with increasing temperature to a maximum near 600°C at 1.0 sec residence time and is independent of reactant ratio here. It then drops quickly with increasing temperature and increased O2. Faster decay of compounds, such as C2H3Cl, C2H2, C2H4, C3H6+ C3H8 formed at lower temperature occurs when the reactor temperature is above 650°C, and higher oxygen levels in the mixture. The higher ratio of O2 to CH4, the lower the temperature needed to observe formation of CO and CO2' The major products at temperatures above 750°C are HCl and non-chlorinated hydrocarbons: C2H2, C2H4, C3H6, C3H8, CO and CO2.

An increase in surface to volume ratio of reactor tube was observed to accelerate the decomposition process in this study, but it had no effect on distribution of principal products.

A detailed kinetic reaction mechanism was developed and used to model results obtained from the experimental reaction system. A sensitivity analysis of the model was done to show the most important reactions in the mechanism. The kinetic reaction mechanism was based on thermochemical principles and transition state theory.

Rate constants obtained for initially important decomposition of 1,1,1-trichloroethane over the temperature range 500 - 800°C are:

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