Formation of chlorinated aromatic hydrocarbons during high temperature pyrolysis of chlorobenzene

Abstract

A study of pyrolysis of chlorobenzene at high temperature is presented. Experiments were performed in a laminar plug flow reactor under a nitrogen atmosphere, stationary conditions were used, the temperature was ranging from 800 to 1200 °C, and residence time from 1.1 to 1.6 s. The concentrations of chlorobenzene in the gas stream were 0.1 and 0.6% on a molar basis. A complete analysis of gaseous products from C1 to C14 was done. The main species formed during the degradation of the molecule are benzene, acetylene, hydrogen chloride and hydrogen, the influence of temperature on the formation of these species can be explained by the different mechanisms of aromatic ring breakdown. Substantial amounts of methane were analyzed, the formation of this molecule can be explained if the formation of five carbon atoms rings is assumed. Naphthenic species were also quantified, and a different behaviour was observed for naphthalene and chloronaphthalene. This suggests that two mechanisms may be involved in the formation of these two species: the HACA mechanism for naphthalene; and a side reaction of the chlorobiphenyle formation mechanism for the chlorinated molecule. Mono- and di-chlorobiphenyles were identified and quantified, and the isomer distribution of monochlorobiphenyles shows that the meta position is the most probable.