采用浸渍法制备了一系列Pt/Ru质量比不同的Fe₃O₄修饰的Pt-Ru/Fe₃O₄/C催化剂, 运用透射电镜(TEM)、能量弥散X射线谱(EDX)、X射线光电子能谱(XPS)、X射线粉末衍射(XRD)等手段对Pt-Ru/Fe₃O₄/C一系列催化剂进行了表征, 并考察了Pt/Ru质量比不同对催化剂Pt-Ru/Fe₃O₄/C在无溶剂条件下催化邻氯硝基苯(o-CNB)选择性加氢制备邻氯苯胺(o-CAN)催化性能的影响. 研究结果表明, 催化剂的催化活性和对目标产物的选择性跟活性组分Pt、Ru比例有关. 随着Pt/Ru比例的减小, 目标产物o-CAN的选择性有所升高, 然而反应物o-CNB的转化率有所下降. 当Pt/Ru的质量比为2时, o-CNB的转化率降为76.5%, 而目标产物o-CAN的选择性仍然为100%. 与此同时, 我们还对Pt-Ru/Fe₃O₄/C催化剂高的催化活性和目标产物的高选择性可能的原因进行了分析.

A series of Fe₃O₄-modified Pt-Ru/C nanocomposite catalysts were prepared by impregnation and hydrazine hydrate reduction of Pt and Ru precursors. Various Pt/Ru mass ratios of the catalysts were examined in terms of catalytic activity. They were characterized by transmission electron microscopic measurements (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The average diameters of the catalysts with different mass ratios of Pt/Ru were in a range of 2.2-2.5 nm with narrow size distributions. The valence states of the nanoparticles indicate strong interactions between the Pt and the carbon support or with Fe₃O₄. The XRD patterns of the 8Pt-1Ru/Fe₃O₄/C, 6Pt-1Ru/Fe₃O₄/C, 4Pt-1Ru/Fe₃O₄/C, and 2Pt-1Ru/Fe₃O₄/C catalysts have similar profiles, which are attributed to the cubic phase of pure Fe3O4 (i.e., no Pt or Ru present). These catalysts selectively hydrogenate ortho-chloronitrobenzene (o-CNB) to the corresponding ortho-chloroaniline (o-CAN) under solvent-free conditions that not only allowed high substrate concentrations promoting the hydrogenation reaction, but also enabled easy product separation and purification. They exhibited excellent catalytic activity (turnover frequency (TOF) range: 0.98-2.09 mol.mol^-1.s^-1) and up to 100% o-CAN selectivity, which was composition-dependent. The o-CAN yield selectivity monotonically increased with the proportion of Ru; however, the catalytic activity decreased. The high catalytic activity and selectivity of Pt-Ru/Fe₃O₄/Cnanoparticles are attributed to electron transfer between the two metals and Fe₃O₄.