Document Type

Thesis

Date of Award

12-31-1986

Degree Name

Master of Science in Environmental Engineering - (M.S.)

Department

Civil and Environmental Engineering

First Advisor

Joseph W. Bozzelli

Second Advisor

Richard B. Trattner

Third Advisor

R. P. T. Tomkins

Abstract

This study examines the reaction of l,2-dichloroethane with water vapor. The linear-flow method is utilized, assuming plug flow without axial diffusion. Normal operation is at atmospheric pressure and the reactor is a quartz tube in a thermal region 45 cm in length. Two reactor diameters of 0.4 cm and l.05 cm are used. Water and l,2-dichloroethane enter the system in liquid phase via syringe pumps. After vaporizing in heated tubing, they are combined with argon, the reactor carrier gas. The molar ratio of water to l,2-dichloroethane is 55:l and varied residence times are achieved by changing the argon flowrate. Reactor products are identified using GC/MS. Product distributions are measured by gas chromatography.

By keeping the molar ratio of water to l,2-dichloroethane very high (55:l), the rate of decomposition of 1,2-dichloroethane is of the first order. A plot of ln(C/CO) versus t results in a straight line through the origin with a slope of ka. Performing this procedure at more than one temperature allows one to graph ln ka versus (l/T). This Arrhenius plot results in a straight line with a slope of -Ea/R and y-intercept of Aa. By utilizing a relationship between the overall rate constant and rate constants for parallel reactions at the reactor wall and in the bulk stream, decoupled activation energies can be determined.

The reaction was studied at three temperatures: 590°C, 630°C, and 680°C. Values of the activation energy for parallel reactions at both the wall and in the bulk stream have been calculated. They were found to be 35.4 kcal/mol and 29.0 kcal/mol, respectively. These results are in close agreement to unimolecular decomposition data in literature.

Methods to correct rate constants in order to account for axial diffusion and wall reactions have been utilized. It was found that these corrections are negligible.

Total decomposition of 1,2-dichloroethane occurs at temperatures greater than 800°C for a residence time range of 0.8 to l.2 sec. The principle reaction products at temperatures lower than 700°C are vinyl chloride, l-buten-3- yne, and 2-chloro-l,3-butadiene. At temperatures greater than 800°C, major reaction products include vinyl chloride, acetylene, ethene, benzene, and l,3-butadiyne.

Identification of variables:

Aa - apparent frequency factor, directly from experimental results (sec-1)

C - concentration of unreacted l,2-dichloroethane

C - initial concentration of l,2-dichloroethane entering reactor

Ea - apparent activation energy, directly from experimental results (kcal/mol)

ka - apparent first order rate constant, directly from experimental results (sec-l)

R - gas constant, l.987 x 10-3 kcal/mol deg

T - temperature (°K)

t - residence time in reactor (sec)

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