Document Type

Dissertation

Date of Award

Spring 5-31-1995

Degree Name

Doctor of Philosophy in Environmental Science - (Ph.D.)

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

Joseph W. Bozzelli

Second Advisor

Richard B. Trattner

Third Advisor

Basil Baltzis

Fourth Advisor

Lev N. Krasnoperov

Fifth Advisor

E. R. Altwicker

Abstract

The pyrolysis and oxidation of dichloromethane is studied in a tubular reactor at 1 atmosphere pressure, residence time between 0.3 to 2.0 seconds and in the temperature range 680 - 840°T. Four reactant concentration ratios are:
I. CH2Cl2 : Ar =1 : 99 II. CH2Cl2 : CH4 : Ar = 1 : 1:98
III.CH2Cl2 : O2 : Ar = 1:4 : 95 IV. CH2Cl2: CH4 : O2 Ar = 1: 4: 94

The degradation of dichloromethane, intermediate product formation and decomposition, and final products are studied in both pyrolytic and oxidative reaction environments. Chlorinated intermediate products: CH3Cl, C2HCl, C2H3CI, CH2CCl2, CHClCHCl, and C2HCl3 are shown to be important in all systems but more difficult to destroy in the pyrolysis than in the oxidation. The conversion of these chloro-methyl radicals to corresponding chloro-formaldehydes, CO andCO2 is observed to be slow by this reaction sequence. The demonstration of this bottleneck is another important result of this thesis. Results show that conversion primarily occurs through combination of 2 chloro-methyl radicals to chloro-ethanes, then ethylenes, then chloro-vinyl radicals. The major chloro-methyl radical conversion path under combustion condition is the chlor vinyl radical + O2. Thermodynamic parameters: ΔH298, S298 and Cp(T) for all species in the reaction mechanism are evaluated and illustrated.

A reaction mechanism consisting of 635 elementary reactions and 215 species, to C6 compounds, has been developed to simulate the thermal decomposition of dichloromethane and for use in predicting the formation of aromatics and intermediate molecular weight growth species in C1 andC2 chlorocarbon combustion. All reactions in the mechanism are elementary or derived from analysis of reaction systems encompassing elementary reaction steps. All reactions are thermochernically consistent and follow principles of Thermochernical Kinetics. Model data show good agreement for reagent decay and major product distribution in both pyrolytic and oxidative environments.

Unimolecular dissociation of CH2Cl2 and of chlorinated ethylenes is analyzed by nimolecular quantum RRK. Combination and addition reactions such as: CH2O + O2, CHCl2 + O2, CH3 + CH2Cl, CH3 + CHCl2, CH2Cl + CH2Cl, CH2Cl + CHCl2, CHCl2 + CHCl2, C2H3 + O2, CH2CCl + O2, CHClCH + O2, CHCICCI + O2, CCl2CH + O2, and C2Cl3 + O2 are treated with bimolecular quantum RRK analysis for k(E), combined with modified strong collision approach and/or Master equation analysis for fall-off effects.

Hydrocarbon and chlorocarbon radical addition to unsaturated species is responsible for molecular weight growth and ultimate formation of precursors to polychlorinated dibenzo dioxins and furans.

Reactions of HSO + O, SO + OH, H +SO2,OH + SO2, H + SO3,OH + HSO, and H + HOSO are analyzed as functions of pressure and temperature.

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