The mechanism of formation of dioxins and furans in petroleum refining processes

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were first detected in effluents from petroleum refineries in 1989. In the critical process, catalytic reforming, coked catalyst is regenerated at temperatures of 380 to 525;Consequently, a series of experiments with a bed of Fe/FeCl;Coked and regenerated catalyst samples were analyzed for PCDDs, PCDFs and possible PCDD/F precursors by gas chromatography-mass spectrometry (GC-MS). No PCDDs or PCDFs were detected in these samples. However, a large number of aromatic hydrocarbons, from one up to five ring systems, was found. Some of them were alkylated, but no chlorinated and only few oxygenated compounds were identified. Analyses of the flue gas from burning coked catalysts revealed the presence of unchlorinated dibenzofuran (DBF) produced at a ratio of...