Mechanisms of dioxin formation from the high-temperature oxidation of 2-chlorophenol.
The homogeneous, gas-phase oxidative thermal degradation of 2-chlorophenol was studied in a 1 cm i.d., fused silica flow reactor at a concentration of 88 ppm, reaction time of 2.0 s, over a temperature range of 300 to 1000 degrees C. Observed products in order of yield were as follows: 4,6-dichlorodibenzofuran (4,6-DCDF) > dibenzo-p-dioxin (DD) > 1-monochlorodibenzo-p-dioxin (1-MCDD), 4-chlorodibenzofuran (4-MCDF), dibenzofuran (DF), naphthalene, chloronaphthalene, 2,4-dichlorophenol, 2,6-dichlorophenol, phenol, chlorobenzene, and benzene. In contrast to pyrolysis, 4,6-DCDF is the major product rather than DD, and 1-MCDD and naphthalene are formed at temperatures as low as 400 degrees C. Under oxidative conditions, .OH and Cl. are the major carriers, which favors 4,6-DCDF formation over DD or 1-MCDD through abstraction of H. through diketo- and ether- intermediates. It is proposed that below 500 degrees C, unimolecular tautomerization/HCI elimination and CO elimination/isomerization reactions result in the formation of 1-MCDD and naphthalene, respectively.
Evans
Catherine S
CS
Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
Dellinger
Barry
B
D002733:Chlorophenols / Q000737:chemistry*; D004147:Dioxins / Q000032:analysis / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry; D016877:Oxidants / Q000737:chemistry; D010084:Oxidation-Reduction; D012822:Silicon Dioxide; D013696:Temperature
D002733:Chlorophenols; D004147:Dioxins; D016877:Oxidants; D017665:Hydroxyl Radical; D012822:Silicon Dioxide; C030683:2-chlorophenol