The oxidation of chlorinated organic compounds over W-modified Pt/CeO2 catalysts

Abstract

Pt-xW/CeO2 catalysts, prepared by co-impregnation with aqueous solutions of (NH4)6-H2W12O40 and H2PtCI6, were applied in the catalytic oxidation of benzene (B), chlorobenzene (CB), and 1,2-dichlorobenzene (1,2-DCB). Characterization by various methods identified CeO2 as cubic fluorite, and WOx in the form of monoxo monotungstate. The interaction of WOx with CeO2 and Pt species led to the formations of W–O–Ce and Pt–O–W, of which W–O–Ce increased oxygen vacancies and acidity, while Pt–O–W promoted the reducibility and availability of surface oxygen. In the oxidation of CB and 1,2-DCB, Pt-xW/CeO2 catalysts presented high activity and TOF at 225 °C of 1.8–18.6 and 1.4–7.3 × 10−4 s−1, respectively. During 50-h stability tests, Pt–O–W and W–O–Ce structures remained unchanged, even in the presence of water. The availability of surface oxygen was responsible for stable high activity. At 90% conversion, almost no chlorination products were detected. In situ FT-IR showed that CB reacted with hydroxyl groups to produce phenolate, which was sequentially converted by lattice oxygen into acetaldehyde and carboxylates, while surface oxygen oxidized the partial oxidation products to CO2.