An elementary reaction kinetic model of the gas-phase formation of polychlorinated dibenzofurans from chlorinated phenols

A 30-reaction core kinetic model has been developed that accounts for the major features in the homogeneous formation of polychlorinated dibenzofurans (PCDF) from the high-temperature oxidation of 2,4,6-trichlorophenol (TCP). The core, purely gas-phase scheme provides agreement within a factor of 1.5-2 between experimental and calculated yields of PCDD/Fs using the REACT kinetic program. It is demonstrated that the formation of PCDF is due to the conversion of TCP to 2,4-dichlorophenol (DCP), which subsequently forms a keto resonance structure of the 2,4-dichlorophenoxyl radical (DCṖ). The conversion of TCP to DCP provides an ortho hydrogen that is necessary for the formation of PCDF. Ab initio calculations were utilized to calculate the activation energies of the key reactions involved in the gas-phase formation of PCDF.