Formation of polychlorinated dibenzo-p-dioxins and dibenzofurans from chlorinated soot Original Research Article

Chlorinated soot, prepared from o-dichlorobenzene combustion and containing 1.7 wt% organic chlorine, was tested for polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) formation under various conditions. The soot showed both uncatalyzed reactivity, i.e., considerable PCDD/F formation as a mixture with silica but without metal chlorides, and formation in an inert (nitrogen) atmosphere when mixed with CuCl2 and silica. The soot also produced high yields of PCDD/F (up to ∼6000 ng/g) at low [Cu2+] (<0.75 wt%) in 10% O2/N2. The optimum temperature for catalyzed formation was between 250 and 300 °C. The behavior of carbon–chlorine bonds during annealing in oxygen was explored by the use of Na37Cl/Cu37Cl2; showing that chlorine atoms from the soot were incorporated in PCDD/F. Chlorinated soots may be very reactive when formed in the combustion process.