Catalytic combustion of toluene on Pd/CeO₂-TiO₂ catalysts

Pd/TiO₂ and Pd/CeO₂ were reported to be very active to destruct toluene. Combination of TiO₂ and CeO₂ is an interesting candidate to achieve a catalyst with higher activity. In this study, a series of Pd/CeO₂-TiO₂ catalysts with various Pd loadings were prepared. CeO₂-TiO₂ was prepared by impregnation of aqueous solution of cerium nitrate into TiO₂ support. It was then calcined at 400 °C. Pd was loaded by incipient-wetness impregnation method. The Pd loadings in all samples were fixed at 0.5 wt.%. The catalysts were characterized by powder X-ray diffraction, transmission electron microscopy, high resolution transmission electron microscopy, temperature-programmed reduction of hydrogen, and X-ray photoelectron spectroscopy. The catalysts were tested for total oxidation of toluene. The feed concentration of toluene was 8.564 g/m³ (2085 ppm), with GHSV = 10, 000 h^-1. Pd particle sizes were 3-5 nm and well-dispersed on the support. CeO₂ on TiO₂ was easier to reduce than the bulk CeO₂, therefore it could enhance the activity of VOC destruction. Pd/CeO₂-TiO₂ was more active than Pd/CeO₂ and Pd/TiO₂. Pd/CeO₂-TiO₂ with Ce/Ti ratio of 2/8 was very active for toluene destruction, due to its lower oxygen reduction temperature of ceria and higher concentration of Pd⁰.