Effect of the Pt oxidation state and Ce3+/Ce4+ ratio on the Pt/TiO2-CeO2 catalysts in the phenol degradation by catalytic wet air oxidation (CWAO)

Abstract Pt/TiO 2 -Ce catalysts were synthesized with different concentrations of Ce at 1, 3, 5 and 10 wt% for being used in catalytic wet air oxidation (CWAO) of aqueous solution of phenol (1000 ppm). The supports were prepared by sol–gel and impregnated to 2.5 wt% of Pt. The catalysts were characterized by different techniques: specific surface areas (BET), ICP-OES, XRD, pyridine-FTIR, X-ray photoelectron spectroscopy (XPS), CO-FTIR, TPO and transmission electron microscopy (TEM). Phenol oxidation was realized in a batch reactor at 160 °C and 10 bar of O 2 . Samples taken during the reaction course were analyzed using a total organic carbon analyzer (TOC) and gas chromatography (GC). The results showed that the specific surface areas of the Pt/TiO 2 -Ce catalysts increased with Ce content. By XPS it was found that a ratio of Pt 0 /Pt 2+ and Ce 3+ /Ce 4+ of 55%/45% and 71%/29% in Pt/TiO 2 -Ce3% catalyst showing the highest phenol conversion (96%) and selectivity to CO 2 (100%). The Pt/TiO 2 -Ce3% and the Pt/TiO 2 -Ce5% catalysts presented the lowest Pt particle size, around 3.7–5.8 nm leading to high activity (96% and 92% respectively). They displayed the high Lewis acid sites and good stability to deposits of carbonaceous species on the catalysts. The responsible of the good performance of these catalysts is related to the addition to CeO 2 to TiO 2 that produces an increase in the oxygen storage capacity (OSC) in these catalysts.