可循环磁性Pt/Fe_3O_4-MCNT催化剂上的肉桂醛选择性加氢反应

Selective Hydrogenation of Cinnamaldehyde on Magnetically Recyclable Pt/Fe_3O_4-MCNT Catalysts

采用多步法依次将制备的Fe3O4纳米颗粒和Pt纳米颗粒负载到多壁碳纳米管(MCNT)上得到Pt/Fe3O4-MCNT磁性催化剂,以X射线衍射(XRD)、透射电镜(TEM)、超导量子干涉磁强计(SQUID)和热重-差热分析(TG-DTA)对Pt/Fe3O4-MCNT磁性催化剂的结构和磁性质进行了表征。研究发现预制备的Fe3O4纳米颗粒与Pt纳米颗粒均匀地分散于MCNT上,新制备以及多次使用后的Pt/Fe3O4-MCNT室温下都具有良好的超顺磁性。研究了Pt/Fe3O4-MCNT磁性催化剂上的肉桂醛选择性加氢反应,结果显示催化剂具有良好的C=O加氢活性,肉桂醛转化率在50%左右时,肉桂醇选择性可达96%以上。尺寸均一的Pt粒子均匀的分散在催化剂上可能是催化剂具有良好的C=O加氢选择性的重要原因。在外加磁场作用下催化剂可以高效地从液相反应体系中分离,经多次循环使用后仍具有良好的催化性能。

A multi-step method was adopted to prepare a magnetic Pt/Fe3O4-MCNT catalyst by loading as-prepared Fe3O4 and Pt nanoparticles onto multi-walled carbon nanotubes （MCNT）. The structure and magnetic properties of the prepared Pt/Fe3O4-MCNT catalyst were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, superconducting quantum interference device （SQUID）, and thermogravimetry-differential thermal analysis （TG-DTA）. The results reveal that the as-prepared Fe3O4 and Pt nanoparticles are well dispersed on the MCNT. Additionally, the magnetic measurements show that both fresh and recycled magnetic Pt/Fe3O4-MCNT catalysts display excellent superparamagnetic properties at room temperature. The selective hydrogenation of cinnamaldehyde to cinnamyl alcohol was performed on the magnetic Pt/Fe3O4-MCNT catalyst, showing a superior activity in the hydrogenation of the C=O bond. A selectivity of 96% to cinnamyl alcohol can be achieved at a cinnamaldehyde conversion of about 50%. The reason of the good selectivity probably ascribes to the high dispersion of the uniformed Pt particles on the MCNT. Additionally, the catalyst can be easily recovered from the reaction medium under the external magnetic field and maintain its catalytic properties after used for several recycles.