Gas-phase reactions of methylene chloride and methylene chloride-trichloroethylene mixture with methane in tubular flow reactor and atmospheric pressure

Author

Javad Tavakoli-Attar, New Jersey Institute of Technology

Document Type

Dissertation

Date of Award

Spring 10-31-1988

Degree Name

Doctor of Engineering Science in Chemical Engineering

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

Joseph W. Bozzelli

Second Advisor

Tamara M. Gund

Third Advisor

Dana E. Knox

Fourth Advisor

Samir S. Sofer

Fifth Advisor

R. C. Ahlert

Abstract

Reactions of methylene chloride diluted in methane and Argon and a mixture of methylene chloride + trichloroethylene diluted in methane and argon are studied in three flow reactors of different surface to volume ratios 4, 10.5, and 16 mm ID , atmospheric pressure and over a temperature range of 750-1000 °C. Experiments were conducted isothermally, ±5 °C over central 80% of oven length using a three zone oven. Argon was added as a diluent in order to limit carbon (s) formation. The concentration ratios of methylene chloride/methane/argon and methylene chloride/trichloroethylene/methane/argon was held constant at 1:4:10 and 1:1:40:40 respectively, throughout the study. An on line gas chromatograph and GC/MS spectrometer were used for analysis of reactor products. Acetylene, ethylene, benzene, chloromethane, and HC1 were observed as the major products, for temperatures above 750 °K and residence times of 0.08 to 2 secs.

First order plug flow model was utilized to analyze the experimental data. In addition the homogeneous and wall rate constants were decoupled and separately evaluated. The following overall rate equations were found to fit the reaction systems studied.

Methylene Chloride in CH2C12/CH4/Ar :
k = 1.166E09 * Exp(-44.85/RT) (1/sec)

Methylene chloride in C2HCl3/CH2Cl2/CH4/Ar :
k = 8.11E08 * Exp(-43.2/RT) (1/sec)

Trichloroethylene in C2HCl3/CH2Cl2/CH4/Ar :
k = 1.13E05 * Exp(-30.67/RT) (1/sec)

A detailed kinetic reaction mechanism was developed and used to model the reaction systems and fit the experimentally determined product distribution. Fundamental principles in Transition State Theory and Quantum RRK theory were used in developing reaction rate constants for the model. A mechanism composed of 68 elementary reactions for CH2Cl2/CH4 system and another one with 72 reactions for mixture of C2HCl3+CH2C12/CH4 system were found to reproduce experimental results. A rate constant for :

CH2Cl2 ----> CH2Cl + Cl of k = 1.88*10¹⁶*Exp(-82.8/RT)

chlorine elimination from methylene chloride was found to dominate HC1 elimination by 5 orders of magnitude with rate constants and E_a's was determined for this elementary reaction over our experimental conditions. The important initial reactions in C2HCl3/CH2Cl2/CH4 system were determined as:

C2HC13 ----> C2Cl2 + HCl k = 7.1*10¹³*Exp(-77.61/RT)

C2HCl3 ----> C2HCl2. + Cl. k = 1.74*10¹⁵*Exp(-92.1/RT)

CH2Cl2 ----> CH2C1. + Cl. k = 1.88*10¹⁶*Exp(-82.8/RT)

QRRK analysis and regression of rate constants against experimental data have lead to rate constants for the reactions:

CH2Cl + CH2Cl ⁽¹⁾<---->_(-1) [C2H4C12]⁴ ---> C2H3C12+H (2)
---> C2H4C1+Cl (3)
---> C2H3Cl+HC1 (4)
---> C2H4C12 STABILIZED

CH3 + CH2Cl ⁽¹⁾<----><---->_(-1) [C2H5Cl]# ---> C2H4Cl+H (2)
---> C2H5+Cl (3)
---> C2H4+HC1 (4)
---> C2H5C1 STABILIZED

CH3 + C2Cl2 ⁽¹⁾<---->_(-1) [C3H3Cl2]# ---> C3H3Cl+ Cl (2)
---> C3H3C12 STABILIZED

C2HCl3 + CH3 ⁽¹⁾<---->_(-1) [C3H4Cl3]# ---> C3H4Cl2+Cl (2)
---> C3H4Cl3 STABILIZED

The CHEMKIN computer code was incorporated to model the kinetic schemes and good agreement was obtained between calculated and experimental resutls.

Recommended Citation

Tavakoli-Attar, Javad, "Gas-phase reactions of methylene chloride and methylene chloride-trichloroethylene mixture with methane in tubular flow reactor and atmospheric pressure" (1988). Dissertations. 1221.
https://digitalcommons.njit.edu/dissertations/1221