Wet oxidation of trichloroethylene over well-characterized CoO _x /TiO₂ catalysts

Abstract

The 5% CoO _x /TiO₂ catalyst, well-characterized earlier, consisting of complete CoTiO _x overlayers on Co₃O₄ nano-particles (“Type A”) after calcination at 843 K but of clean Co₃O₄ particles (“Type B”) after a continuous wet oxidation of trichloroethylene (TCE) at 310 K forca. 6 h, has been used to investigate the influence of operating variables on the activity and the stability of the Type B Co₃O₄ particles during wet catalysis. At 310 K, the catalyst exhibited a 48% steady-state conversion with a transient behavior in activity up toca. 1 h on stream. As the reaction temperature increased, higher performances were achieved and the transient period disappeared, which might be due to easier decapsulation of the Type A Co₃O₄ particles at higher temperatures to form the Type B Co₃O₄ particles very active for this wet oxidation reaction. All wet activities were equal to those based on the concentration of Cl⁻ ions produced, implying the complete oxidation of TCE to HCl and CO₂, and significant decrease in pH occurred because of the HCl formation. The supported CoO _x was very stable for the wet oxidation at 310 K, even forca. 36 h, and XPS measurements of samples of the catalyst following the wet oxidation for desired hours were in good agreement with our earlier proposed model for CoO _x species.