NJIT eTD::njit-etd1995-015::Chiang, Hong-Ming::"Dichloromethane pyrolysis and oxidation : formation of chlorinated aromatic precursors to PCDD/F"

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 C_p(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.

Title:	Dichloromethane pyrolysis and oxidation : formation of chlorinated aromatic precursors to PCDD/F
Author:	Chiang, Hong-Ming
Document Type:	Dissertation
Department:	Department of Chemical Engineering, Chemistry and Environmental Science
Degree:	Doctor of Philosophy
Major:	Environmental Science
Advisory Committee:	Bozzelli, Joseph W. Trattner, Richard B. Baltzis, Basil Krasnoperov, Lev N. Altwicker, E. R.
Thesis Date:	1995, May
Keywords:	Pyrolysis And Oxidation Of Dichloromethane Degradation Of Dichloromethane Chlorinated Intermediate Products
Availability:	Unrestricted
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 C_p(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.
Complete Thesis:	njit-etd1995-015 (398 pages ~ 19,112 KB pdf)
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