Catalytic oxidation of PCDD/F on a V2O5-WO3/TiO2 catalyst: Effect of chlorinated benzenes and chlorinated phenols.

Catalytic oxidation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) is a well-proven technique, applied in a rising number of Municipal Solid Waste Incineration plants, yet the simultaneous and possibly competitive co-oxidation of other compounds, such as chlorinated benzenes (CBz) or phenols (CP), is still poorly documented. In this study, a grinded commercial catalyst (vanadium-tungsten supported on titanium dioxide) was submitted to exploratory testing: the PCDD/F present in a gas test flow were catalytically oxidised (200°C, 10,000h-1), either as such or in the presence of benzene (Bz), monochlorobenzene (MCBz), and 1,2-dichlorobenzene (DCBz) and the effect of these additions on the catalytic destruction of PCDD/F was verified experimentally. Both removal efficiency (RE) and destruction efficiency (DE) declined during the exploratory testing and, importantly, some DCBz even converted into supplemental PCDD/F. Also, the occurrence of carbon deposition negatively influenced catalytic oxidation activity. Regeneration with oxygen or air allowed to remove the deposited carbon and the original catalytic activity was largely restored after calcination. In a second part of this study, the PCDD/F-formation from DCBz, hexachlorobenzene (HCBz), o-monochlorophenol (o-MCP) and pentachlorophenol (PeCP) was demonstrated and tentatively explored. To prepare for further elucidation of the reaction mechanism, a complete isomer-specific analysis was prepared.