The Effect of Oxygen on the Formation and Destruction of the Products of Incomplete Combustion from the Combustion of Polyethylene and o-Dichlorobenzene

Abstract

The effect of oxygen and chlorine on the chemistry of the products of incomplete combustion, (PICs), in the combustion process appears to be more dramatic than the effect of temperature alone. A series of combustion experiments were carried out on pure polyethylene in a laboratory thermal oxidizer (LTOX). The combustion conditions for all of the experiments were identical with the exception of the oxygen concentration. As the oxygen concentration increased, progressive cyclization of polyethylene fragments was observed. No oxygen containing products were found.

A similar study was conducted on o-dichlorobenzene. Like the polyethylene, the oxygen concentration was also varied. In this case, however, as the oxygen concentration was increased, oxygen was eventually incorporated into the various PIC molecule. Among the compounds formed were chlorinated phenols, furans and dioxins. As oxygen concentrations were increased phenols appear first, followed by the furans and finally the dioxins. Above the soot point of the flame (no soot emitted), the formation of long and branched chain hydrocarbons, aldehydes, carboxylic acids and esters became predominant. This latter pattern appears to be independent of the previous soot and PIC chemistry and is prevalent in the highly acidic atmosphere produced when burning chlorinated fuels under lean conditions.