Slow combustion of pentachlorophenol in toluene

Upon ‘lean’ slow combustion 0f 2 mol % of PCP in toluene at 700 °C, the outflow contains a > 102 fold excess of Cl-free phenol on remaining PCP. Next to dibenzofuran (DF) — the condensation product of 2 phenoxy radicals - (1,2,3,4-)TCDF is observed, but almost no TODD. The TCDF is explained to arise from a phenoxy and a pentachlorophenoxy radical; reactions between (chloro)phenoxy radicals and (chloro)phenols — as in the ‘Shaub and Tsang’ mechanism — appear to be of minor importance. The significance of these results for the formation in incinerators of lower chlorinated DFs and DDs — which could be precursors t0 PCDD/Fs generated in the cooling zone — is also discussed.