Pd/Y-Al2O3催化剂催化氧化邻-二甲苯

摘要

1％ (w) Pd/Y-Al2O3 catalysts were prepared by the impregnation method using nano Y-Al2O3 (10 nm) and Y-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/y-Al2O3 (nano) has the highest catalytic activity for o-xylene oxidation after H2 reduction,and the Tg0 (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 Y-Al2O3) and the Pd species,which facilitates the particle size control and Pd dispersion,thereby increasing the catalyst activity of the 1％ (w) Pd/y-Al2O3(nano)catalyst.%利用纳米Y-Al2O3 (10 nm)和普通Y-Al2O3 (200-300 nm),采用浸渍法制备了1％ (w) Pd/Y-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/Y-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/Y-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Y-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/Y-Al2O3 (nano)催化剂的活性.