An elementary reaction model for thermal decomposition of CF2Cl2 in a H2 atmosphere and experimental studies on oxidation of CH3OH plus CH4 under fuel rich, stoichiometric and fuel lean conditions

Author

Cheng Guo, New Jersey Institute of Technology

Document Type

Thesis

Date of Award

5-31-1993

Degree Name

Master of Science in Applied Chemistry - (M.S.)

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

Joseph W. Bozzelli

Second Advisor

Carol A. Venanzi

Third Advisor

Tamara M. Gund

Abstract

Pyrolysis of CF₂CL₂ in an atmosphere of H₂, has been studied in a tubular flow reactor, 723 to 873 K. Overall eaction conversion proceeds via loss of Cl with CHF₂CL formation, then loss of the second Cl atom and CH₂F₂ product. Initiation occurs by unimolecular Cl atom loss. Subsequent chain propagation steps rapidly generate active H atoms which abstract Cl atoms, but abstraction of fluo-rine atoms by atomic hydrogen is slow at the temperatures of this study.

A small mechanism, about 35 elementary reaction steps, and a thermodynamic data base were developed to model the reaction system. Agreement of the mechanism with the data at varied time and temperature is reasonable. Rate constants were determined to be in the fall-off regime for the unimolecular dissociation reactions, Cl elimination, and were evaluated by Quantum Kassel Theory coupled with Transition State Theory. HCl and HF molecular elimination paths (both 1,1 and 1,2) and insertion of ¹:CF₂ are also projected to be important in the high temperature chemistry of chloro-fluoro carbons.

Carbene elimination, both ¹:CF₂ and ¹:CFCl from CHF₂CL, and thermal reaction of CHF₂Cl as well as subsequent formation of CH₂F₂ via ¹:CF₂ into H₂ under reaction conditions similar to those utilized in this study can be important.

Part II of this study is the tubular flow reactor experiments on methanol oxidation in the presence of methane fuel at varied fuel equivalence ratios of 0.7-1.7, at 1 atmosphere pressure with residence times of 0.3 to 2.0 seconds and temperature range of 500-850 C.

The extensive experimental data will be used as a basis for developing a detailed elementary reaction model for methanol/methane oxidation. Intermediate products: dimethyl ether (CH₃OCH₃) and formaldehyde dimethyl acetal(CH₃OCH₂OCH₃), are observed in the low temperature regime (550-650C) and reported for the first time in this study. These products arise from the combination and addition reactions of CH₃O and CH₃ radicals with themselves and with CH₂O or CH₂OH radical which are important and readily occur. It is a surprise that they have not been previously observed or anticipated. These observations reveal some new pathways in the methanol combustion process. The new reactions will be included in our reac-tion modeling studies so that the model can be extended to conditions outside our experimental validation range.

Recommended Citation

Guo, Cheng, "An elementary reaction model for thermal decomposition of CF2Cl2 in a H2 atmosphere and experimental studies on oxidation of CH3OH plus CH4 under fuel rich, stoichiometric and fuel lean conditions" (1993). Theses. 1761.
https://digitalcommons.njit.edu/theses/1761