Evaluation of PCDD/F oxidation catalysts: Confronting studies on model molecules with tests on PCDD/F-containing gas stream

Titania supported vanadium oxide is a renowned catalyst for the abatement of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) from gas effluents. To develop more active formulations, researchers mainly rely on lab-scale experiments on “PCDD/Fs-mimicking substances”, like (chloro)-benzene. Using such model compounds is convenient whereas handling PCDD/Fs in the laboratory is potentially hazardous and complicated. Recent studies, however, challenged some foremost conclusions of model compound based studies, starting from the observation that different model compounds gave contrasted results. Thus the present work aims at confronting some of these dubious conclusions with direct experimental tests on PCDD/Fs. One reference V2O5/TiO2 catalyst and three modified formulations (V2O5/TiO2–SO4, V2O5–MoO3/TiO2, and V2O5–WO3/TiO2) have been evaluated. A dedicated apparatus was used which allows safe and reliable tests on a mixture of PCDD/Fs congeners. Some of the previously proposed catalyst improvement strategies actually prove to be disadvantageous in the removal of PCDD/Fs. In particular, MoO3- and WO3-modified catalysts were significantly less active than the reference catalyst. These observations show that conclusions from model compound based studies must be drawn with care and should ideally be confronted with tests on the actual target pollutants.

Research highlights
► V2O5/TiO2 catalysts are recognized catalysts for the abatement of PCDD/Fs.
► Most studies rely on the use of model compounds.
► Contrasted results were obtained with different model.
► Tests on PCDD/Fs are necessary to make relevant recommendations.
► MoO3 and WO3-promoted catalysts are in fact less active.