Abstract:

1% (w)Pd/γ-Al₂O₃ catalysts were prepared by the impregnation method using nano γ-Al₂O₃ (10 nm) and γ-Al₂O₃ (200-300 nm) as support materials. The catalysts were tested for catalytic oxidation of o-xylene and the difference of catalyst activity before and after hydrogen reduction was investigated. The results indicate that 1% (w)Pd/γ-Al₂O₃ (nano) has the highest catalytic activity for o-xylene oxidation after H₂ reduction, and the T₉₀ (The temperature of conversion rate of o-xylene reaches 90%) was 150℃. The structure-activity relationships of the catalysts were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), while the specific surface area was determined using the Brunauer-Emmett-Teller (BET) isotherm. The results show that the reduced Pd is the active species for catalytic oxidation of o-xylene. Pd particle size has a significant influence on the catalyst activity and a small Pd particle size is favorable. There is a strong interaction between the supporter (nano γ-Al₂O₃) and the Pd species, which facilitates the particle size control and Pd dispersion, thereby increasing the catalyst activity of the 1% (w)Pd/γ-Al₂O₃(nano) catalyst.

Key words: γ-Al₂O₃, Noble metal catalyst, Catalytic oxidation, o-Xylene