Oxidation of dimethyl-ether and ethylene in the atmosphere and combustion environment and thermodynamic studies on hydrofluorocarbons using ab initio calculation methods

Author

Takahiro Yamada, New Jersey Institute of Technology

Document Type

Dissertation

Date of Award

Fall 1-31-1999

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

Carol A. Venanzi

Fourth Advisor

Lev N. Krasnoperov

Fifth Advisor

Robert P. Hesketh

Abstract

Reaction pathways and kinetics are analyzed on CH₃OC·H₂ unimolecular decay and on the complete CH₃OC·H₂ + O₂ reaction system using thermodynamic properties (ΔH_f°₂₉₈, S°₂₉₈, and C(T) 300≤T/K≤1500) derived by two ab initio calculation methods, CBS-q and G2. These are used to determine thermodynamic properties of reactants, intermediate radicals and transition state (TS) compounds. Quantum Rice-Ramsperger-Kassel (QRRK) analysis is used to calculate energy dependent rate constants, k(E), and master equation is used to account for collisional stabilization. Comparison of calculated fall-off with experiment indicates that the CBS-q and G2 calculated E_a,rxn for the rate controlling transition state (-scission reaction to C·H₂O + C·H₂OOH) needs to be lowered by factor of 3.3 kcal/mol and 4.0 kcal/mol respectively in order to match the data of Sehested et al. Experimental results on dimethyl-ether pyrolysis and oxidation reaction systems are compared with a detailed reaction mechanism model. The computer code CHEMKIN II is used for numerical integration. Overall agreement of the model data with experimental data is very good.

Reaction pathways are analyzed and kinetics are determined on formation and reactions of the adduct resulting from OH addition to ethylene using the above ab initio methods. Hydrogen atom tunneling is included by use of Eckart formalism. Rate constants are compared with experimentally determined product branching ratios (C·H₂CH₂OH stabilization : CH₂O + CH₃ : CH₃CHO + H).

ab initio calculations are performed to estimate thermodynamic properties of nine fluorinated ethane compounds (fluoroethane to hexafluoroethane), eight fluoropropane (1-fluoropropane, 1,1- and 1,2-difluoropropane, 1,1,1- and 1,1,2-trifluoropropane, 1,1,1,2- and 1,1,2,2-tetrafluoropropane and 1,1,2,2-pentafluoropropane), and 2- fluoro,2-methylpropane. Standard entropies and heat capacities are calculated using the rigid-rotor-harmonic-oscillator approximation with direct integration over energy levels of the intramolecular rotation potential energy curve. Enthalpies of formation are estimated using G2MP2 total energies and isodesmic reactions. Thermodynamic properties for fluorinated carbon groups C/C/F/H2, C/C/F2/H, C/C/F3, C/C2/F/H, C/C2/F2 and C/C3/F for fluorinated alkane compounds, CD/F/H and CD/F2 for fluorinated alkene compounds and CT/F for fluorinated alkyne compounds are estimated. Fluorine-fluorine interaction terms F/F, 2F/F, 3F/F, 2F/2F, 3F/2F and 3F/3F for alkane compounds, F//F, 2F//F and 2F/2F for alkene compounds, and F///F for alkyne compound are also estimated.

Recommended Citation

Yamada, Takahiro, "Oxidation of dimethyl-ether and ethylene in the atmosphere and combustion environment and thermodynamic studies on hydrofluorocarbons using ab initio calculation methods" (1999). Dissertations. 994.
https://digitalcommons.njit.edu/dissertations/994