纳米Pd/Al2O3催化剂的表征及其选择性加氢反应性能

 采用氢电弧等离子体法制备的纳米钯粉制备了纳米Pd/Al2O3催化剂，采用X射线粉末衍射（XRD）、扫描电镜（SEM）、透射电镜（TEM）、X光电子能谱（XPS）和程序升温还原（TPR）等物理化学手段对其进行了表征，并在裂解汽油一段加氢反应中考察了其催化活性和选择性。结果表明，纳米Pd/Al2O3催化剂表面的Pd原子排列有序，表面呈蜂窝状，其载体的内部没有Pd元素，而浸渍法所得的Pd/Al2O3催化剂载体内部有Pd元素；纳米Pd/Al2O3的Pd3d5/2结合能比壳型Pd/Al2O3的Pd3d5/2结合能高；前者XRD谱图中未发现Pd和PdO的特征峰。两种样品的程序升温还原研究表明纳米Pd和载体Al2O3发生了强相互作用。在裂解汽油一段加氢选择性反应中，纳米Pd/Al2O3催化剂显示出较高的催化活性和优异的选择加氢性能。

THE CHARACTERIZATION AND SELECTIVE HYDROGENATION PERFORMANCE OF NANO-Pd/Al2O3 CATALYST

The nano-Pd/Al2O3 catalyst was prepared by Al2O3 and nano-palladium powder,which was produced by hydrogen arc plasma method.The new catalyst was characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),electron probe microanalysis(EPMA),X-ray photoelectron spectroscopy(XPS) and temperature-programmed reduction(TPR).Its catalytic activity and selective hydrogenation performance were evaluated by pyrolysis naphtha primary hydrogenation as a probe reaction.The results indicated that the Pd atoms were ordered on the surface of nano-Pd/Al2O3 and the surface was honeycomb-like.There was no any Pd atom in the interior of Al2O3 support of nano-Pd/Al2O3,while Pd atoms were in the support interior of the commercial Pd/Al2O3 catalyst prepared by impregnation method.The Pd3d5/2 binding energy of nano-Pd/Al2O3 was higher than that of commercial Pd/Al2O3 suggested by XPS.There was no characteristic peak of Pd and PdO in the XRD profile of nano-Pd/Al2O3.The temperature programmed reduction(TPR) of the two samples showed the stronger interaction between Pd and support on the nano-Pd/Al2O3 catalyst.In contrast with commercial Pd/Al2O3 catalyst,nano-Pd/Al2O3 catalyst possessed higher catalytic activity and excellent selective hydrogenation performance in pyrolysis naphtha primary hydrogenation reaction.