Pd/γ-Al2O3催化剂催化氧化邻-二甲苯
Catalytic Oxidation of o-Xylene over Pd/γ-Al2O3 Catalysts

利用纳米γ-Al2O3（10 nm）和普通γ-Al2O3（200-300 nm），采用浸渍法制备了1%（w）Pd/γ-Al2O3催化剂，考察了其催化氧化邻-二甲苯的性能以及催化剂的活性在氢气还原前后的区别。实验结果发现1%（w）Pd/γ-Al2O3（nano）在H2还原后催化氧化邻-二甲苯的活性最高，T90为150℃。利用X射线衍射（XRD）、比表面积（BET）、透射电镜（TEM）、X射线光电子能谱（XPS）等表征手段，研究了1%（w）Pd/γ-Al2O3催化剂物性结构与催化性能之间的构效关系。结果表明，还原态Pd是H2还原后催化剂催化氧化邻-二甲苯的活性物种；Pd的颗粒大小与催化剂活性有显著的关系，小粒径有利于催化剂活性提高；纳米γ-Al2O3载体与Pd之间的相互作用强，有利于Pd的粒径控制和分散，从而提高1%（w）Pd/γ-Al2O3（nano）催化剂的活性。
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