Thermochemistry and kinetics in pyrolysis and oxidation of oxygenated chlorocarbons and chlorinated aromatics

Author

Li Zhu, New Jersey Institute of Technology

Document Type

Dissertation

Date of Award

Fall 1-31-2003

Degree Name

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

Department

Chemistry and Environmental Science

First Advisor

Joseph W. Bozzelli

Second Advisor

Lev N. Krasnoperov

Third Advisor

Tamara M. Gund

Fourth Advisor

Sanjay V. Malhotra

Fifth Advisor

Javad Tavakoli

Abstract

Thermochemical. properties, Δf_H°₂₉₈, S°₂₉₈, and Cp°(T) (5<=T/K<=6000), are determined using different ab inifio and density functional theory methods for three chloromethyl radicals, CH₂Cl, CHCl₂, CCl₃, all chlorobenzenes from monochlorobenzene to hexachlorobenzene, and all chlorophenols from ortho-, meta-, para-chlorophenol to pentachlorophenol. The B3LYP/6-31G(d,p) method is used in the structure optimization. The B3LYP/6-31G(3df,2p), QCISD(T)/6-3 I G(d,p), and CB S-Q methods are used in single point calculations of total electronic energies. Harmonic vibration frequencies are scaled for zero point energies and thermal corrections. Isodesmic reaction(s) are utilized at each calculation level to determine Δf_H°₂₉₈ of each species. Contributions to S°₂₉₈ and Cp°(T) from translation, vibration, and external rotations are calculated using the rigidrotor-harmonic-oscillator approximation. Hindered internal rotational contributions to entropies and heat capacities are calculated by summation over the energy levels obtained from direct diagonalizations of the Hamiltonian matrix of the internal rotation. The C-H and C-Cl bond energies in methyl chlorides are also calculated. Group values are derived for use of group additivity estimation for higher chlorinated or oxy-chlorinated molecules.

Trends of kinetic parameters are estimated for: (1) association reactions of chloromethyl radicals, (2) association reactions of C1 atom with chloroalkyl radicals, (3) addition reactions of chlorine atom with chloroethylenes, (4) three types of abstraction reactions, including Cl + RX -> HCI + R*Y, Cl + R -+ HCI + Ro (hydrocarbons only), and H + RCI --> HCI + Ro (or R*X).

Elementary reaction kinetic models for the thermal pyrolysis and oxidation of chloroform, 1,3hexachlorobutadiene, and ortho-chlorophenol, are developed. Thermochemical properties, Δf_H° ₂₉₈, S°₂₉₈, and C_p°(T), for reactants, intermediate species, and products are determined by ab initio or density functional theory when no literature are available, or from a modified group additivity. Highpressure limit rate constants are also calculated by ab initio or density functional theory or in some cases, or are estimated based on trends of chlorinated species when no literature data are available. Pressure and temperature dependent (I atm Ar and 808 - 1073 K for chloroform, I atm air and 773 1373 K for 1,3-hexachlorobutadiene, 4% O₂ in I atm He and 400 - 800 K for orthochlorophenol) mechanisms are constructed utilizing QRRK for k(E) with master equation for fall-off. The mechanisms are compared with corresponding experimental profiles, respectively.

Recommended Citation

Zhu, Li, "Thermochemistry and kinetics in pyrolysis and oxidation of oxygenated chlorocarbons and chlorinated aromatics" (2003). Dissertations. 569.
https://digitalcommons.njit.edu/dissertations/569