Document Type

Thesis

Date of Award

9-30-1988

Degree Name

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

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

Joseph W. Bozzelli

Second Advisor

Arthur Greenberg

Third Advisor

Arthur B. Ritter

Abstract

The kinetics of thermal decomposition of chlorobenzene and dichlorobenzene in a hydrogen and helium atmosphere were further studied to investigate formation of soot and light hydrocarbons. The experiments were performed at atmosphere pressure with residence times rangeing from 0.2 to 1.2 seconds, and the temperature ranges of 850°C to 925°C for chlorobenzene and 870°C to 910°C for dichlorobenzene. Flame ionization detectors, which were connected to GC columns, were utilized for the qualitative and quantitative analysis of the reaction products. A methyl silicone capillary column was used analyzing of heavy aromatics and a Carbosive G was used to analyze light hydrocarbons. Light hydrocarbon products identified in the pyrolysis reactions of chlorobenzene or dichlorobenzene were CH4, C2H2, C2H4, and C2H6. While in hydrogen atmosphere, C2H4 was formed but no C2H2. In a helium atmospere, C2H2 was produced as an end product and less than 0.1% yield of C2H4 were converted. All the light hydrocarbons from the pyrolysis of chlorobenzene or dichlorobenzene are less than 5% of the reactant initial concentration. The formation of light hydrocarbons is studied and the reaction pathways are presented.

GC/MS was employed in the quantitative analysis of the soot products. The soot amount is calculated by the difference method of mass balance. Nearly 50% of reactants was found converted to soot in the systems of chloro- and dichlorobenzene pyrolysis reactions at temperatures above 900°C. Meanwhile, larger amount of soot was generated in the system of chloro or dichlorobenzene in helium bath.

The pyrolysis reactions of acetylene and benzene at high temperatures were also conducted so as to investigate the kinetics and reaction pathways of forming those light hydrocarbons and soot products. The reaction conditions used for acetylene was 1 atmosphere pressure at 700 to 900°C. Major products from the pyrolysis of acetylene in hydorgen are CH4, C2H4, C2H6 and carbon solids. Over 20% of C2H2 was converted to soot at 900°C. No benzene was observed in the pyrolysis reaction of acetylene with hydrogen. A mechanism for the pyrolysis of benzene in hydrogen is proposed. Even though a small amount of benzene was broken down to form light hydrocarbons, the only major product from the pyrolysis of benzene is soot at our reaction temperature range. The pyrolysis of benzene is not a first order reaction.

The kinetic parameters collected for acetylene, chlorobenzene, and dichlorobenzene fit the following Arrhenius equations:

The kinetic parameters collected for acetylene, chlorobenzene, and dichlorobenzene fit the following Arrhenius equations:

acetylene in H2: kexp = 5.34 x 108 exp(-43.5/RT)

chlorobenzene in H2: kexp = 9.1 x 1010 exp(-62/RT)

Dichlorobenzene in H2: kexp = 4.1 x 1012 exp(-65/RT)

Here, Ea is in Kcal/mole unit.

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