Chlorophenols PCDD formation

Oberg, L.G., Rappe, C., Biochemical formation of PCDD/F from chlorophenols, Chemosphere 25, 1992, 49-52. 

Inhibition of CaO on the Formation of PCDD/Fs from Chlorophenols and Chlorobenzenes (LIU Wenbin, China)... 

Both pathways have been shown to be relevant for PCDD/F formation in municipal-waste incinerations. Chlorophenols can be converted to PCDD by copper species known in synthetic chemistry as the Ullmann type II coupling reaction. By use of isotope labeling techniques in competitive concurrent reactions with both reactions performed in laboratory experiments it was shown that precursor theory pathways from chlorophenols may be more important compared to the de novo pathway, but either competing pathway strongly depends on such conditions as temperature, air flow rate, and residence time. It may be difficult to model the complex reahty of large incinerators using relevant laboratory experiments. 

Oberg LG, Rappe C (1992) Biochemical Formation of PCDD/Fs from Chlorophenols. Chemosphere 25 49... 

Wittsiepe J, Kullmann Y, Schrey P, Selenka F, Wilhelm M (2000) Myeloperoxidase-Catalyzed Formation of PCDD/F from Chlorophenols. Chemosphere 40 963... 

Bridle TR, Afghan BK, Wilkinson RJ, et al. 1984. The formation and fate of PCDDs and PCDFs during chlorophenol combustion. Proc - APCA Annu Meet 77 1-15. 

Ballschmiter K, Braunmiller I, Niemczyk R, Swerev M (1988), Chemosphere 17 995-1005.. .Reaction pathways for the formation of polychlorodibenzodioxins (PCDD) and -furans (PCDF) in combustion processes II Chlorobenzenes and chlorophenols as precursors in the formation of polychlorodibenzodioxins and -dibenzofurans in flame chemistry"... 

After PCDEs were detected in a fly ash from a municipal waste incinerator in Finland [36], the occurrence of PCDEs in combustion wastes has not been studied much. PCDEs could be formed during incomplete combustion by condensation from chlorophenols as has been indicated for PCDDs [54], but de novo synthesis is also possible [55]. The formation of chlorinated compounds is always possible during combustion in the presence of organic material and chloride. The formation of PCDEs de novo in combustion has been described in the literature review of Kurz s thesis [4]. Briefly, diphenyl can be formed from the phenoxy radical and benzene which in turn can be formed from alkene radicals. If the formed molecule does not already contain chlorine, chlorination of diphenyl ether can occur, e.g., in the presence of HCl. It has been suggested, however, that PCDEs, in contrast to PCDDs and PCDFs, are not formed to a great extent de novo on solid surfaces or in the gas phase in thermal processes during metal reclamation processes [56]. When PCDEs were analyzed in emission samples of a metal reclamation plant in Finland, all PCDEs were below 4 ng nr3. 

Uncontrolled reactions which lead to the formation of chlorophenols as a side reaction product have the potential to generate PCDFs and/or PCDDs in the following ways ... 

PCDD and PCDF arise, unlike most other organochlorine contaminants, almost exclusively as byproducts of anthropogenic activities. Recent research has also confirmed the formation of trace amounts of PCDD and PCDF in enzymatically catalysed reactions. For example, they may be biosynthesised by microbial peroxidases in sewage sludge contaminated with chlorophenols. The most important primary emission sources were or still are ... 

---