磁性核壳结构二氧化铈负载Ru催化剂的制备、表征及在苯甲醇绿色氧化中的应用

Ru Catalyst Supported by Magnetic Core-Shell Structured Cerium Oxide: Preparation, Characterization and Application in Green Oxidation of Benzyl Alcohol

摘要: 通过乙二醇溶剂热法合成了尺寸均一的磁性Fe₃O₄纳米球，采用模板沉淀法对其进行介孔二氧化铈(mCeO₂)层包裹，再将Ru纳米粒子负载在mCeO₂表面制得Ru/Fe₃O₄@mCeO₂磁性核壳结构催化剂。通过X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、N₂低温物理吸附和电感耦合等离子发射光谱(ICP-AES)等手段对催化剂进行表征，并将其应用于催化苯甲醇的绿色氧化。结果表明：通过添加模板剂的方法包覆介孔CeO₂层，不仅使Ru较均匀地分散在载体表面，而且可以防止Ru在催化反应体系中的流失；利用H₂还原法得到的金属Ru纳米颗粒，粒径为3~6 nm；Ru负载量为3.3%的催化剂，催化苯甲醇的分子氧氧化，353 K下反应7h后，苯甲醇的转化率为68.7%，苯甲醛选择性为84.7%；反应后催化剂可以通过外加磁场进行分离，循环5次以后，转化率和选择性都没有明显降低。

Abstract: Ru/Fe₃O₄@mCeO₂ (mesoporous CeO₂) magnetic core-shell structured catalyst was fabricated by templated precipitation of mCeO₂ layer onto solvothermally prepared Fe₃O₄ nanospheres, followed by loading of Ru nanoparticles onto mCeO₂. The catalyst was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), low-temperature N₂ adsorption and inductively coupled plasma atomic emission spectroscopy (ICP-AES) analyses, and utilized to catalyze the green oxidation of benzyl alcohol. The template-coated mCeO₂ layer not only enables uniform dispersion of Ru on the support, but also prevents the loss of Ru in the catalytic reaction system. Ru nanoparticles with an average size of 3 - 6 nm were produced through the H₂ reduction. For selective oxidation of benzyl alcohol by molecular oxygen at 353 K, the catalyst with 3.30% Ru loading resulted in 68.7% conversion of benzyl alcohol and 84.7% selectivity for benzal-dehyde. The catalyst can be magnetically separated and recycled without significant loss of catalytic efficiency even after 5 catalytic runs.