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.