Government regulations have placed very strict limits on polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs) emissions around the world. Catalytic oxidation is the most cost effective method for PCDD/F destruction. Our previous research focused on the complete oxidation of chlorinated aromatics over vanadium oxide catalysts to further our understanding of PCDD/F oxidation. In this study, we examine the complete oxidation of chlorinated aromatics in the presence of steam over various V₂O₅/TiO₂ catalysts.

Kinetic results obtained with a 3.6wt.% V₂O₅/TiO₂ catalyst, indicate that in the presence of steam, a local maximum is observed in conversion near 275ºC. At temperatures below the maximum, significant improvement in the catalyst activity is observed in the presence of steam. At temperatures above the maximum, the conversion decreases below that observed during dry oxidation, before it increases again at temperatures above 350ºC. The selectivity of CO₂ also follows the same trend. Additionally, the trace quantities of chlorinated maleic anhydrides were identified.

In-situ FTIR experiments were conducted to determine whether any changes take place in the reaction pathway when steam is added. The same surface species were observed under dry and wet conditions, although the relative peak intensities were different in the two cases. NH₃-TPD was also used to identify changes in the acidity of the catalyst upon exposure to steam.

The results of the catalytic and FTIR studies suggest that the effect of steam is due to changes in the surface structure of the active species. The results of on-going investigations with various weight loadings of vanadium oxide on titania will also be used to support these findings.

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