金属有机骨架材料MIL-53(Al)负载钴催化剂的CO催化氧化反应性能

采用溶剂法合成了热稳定性高的金属有机骨架材料MIL-53(Al)(MIL:Materials of Institut Lavoisier),用此材料为载体负载钴催化剂用于CO的催化氧化反应,并与Al2O3负载的钴催化剂进行了对比.采用热重-差热扫描量热(TG-DSC)、傅里叶变换红外(FTIR)光谱、X射线衍射(XRD)、N2物理吸附-脱附、透射电子显微镜(TEM)、氢气程序升温还原(H2-TPR)等方法对催化剂的结构性质进行了表征.TG和N2物理吸附-脱附结果表明,载体MIL-53(Al)有好的稳定性和高的比表面积;XRD以及TEM结果表明Co/MIL-53(Al)上负载的Co3O4颗粒粒径(平均约为5.03 nm)明显小于Al2O3上Co3O4颗粒粒径(平均约为7.83 nm).MIL-53(Al)的三维多孔结构中分布均匀的位点能很好地分散固定Co3O4颗粒,高度分散的Co3O4颗粒有利于CO的催化氧化反应.H2-TPR实验发现Co/MIL(Al)催化剂的还原温度低于Co/Al2O3催化剂的还原温度,低的还原温度表现为高的催化氧化活性.CO催化氧化结果表明,MIL-53(Al)负载钴催化剂的催化活性明显高于Al2O3负载钴催化剂,MIL-53(Al)负载钴催化剂在160°C时使CO氧化的转化率达到98%,到180°C时CO则完全转化,催化剂的结构在催化反应过程中保持稳定.

Performance of a Metal-Organic Framework MIL-53(Al)-Supported Cobalt Catalyst in the CO Catalytic Oxidation Reaction

Ametal-organic framework (MOF) material MIL-53(Al) (MIL: Materials of Institut Lavoisier) with high thermal stability was prepared by the solvothermal method, and it served as a support material for a cobalt catalyst in the CO oxidation reaction. A comparison between the catalytic performance of the MIL-53(Al) and the Al₂O₃ support material was carried out to understand the catalytic behavior of the catalysts. The catalysts were characterized by thermogravimetric-differential scanning calorimeter (TG-DSC), Fourier-transform infrared (FTIR) spectroscopy, N₂ adsorption-desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), and hydrogen temperature-programmed reduction (H₂-TPR). The TG and N₂ adsorption-desorption analyses showed that MIL-53(Al) had good stability and high surface area. XRD and TEM results indicated that the size of the Co₃O₄ nanoparticles (5.03 nm) supported on MIL-53(Al) was smaller than that (7.83 nm) on the Al₂O₃ support. The highly dispersed Co₃O₄ nanoparticles from the three-dimensional porous structure of MIL-53(Al) led to superior catalytic activity during CO oxidation. The H₂-TPR spectra showed that the reduction in temperature of the Co/MIL-53(Al) catalyst was significantly lower than that of the Co/Al₂O₃ catalyst, implying a higher catalytic activity for the Co/MIL-53(Al) catalyst. Indeed, the heterogeneous catalytic composite material Co/MIL-53(Al) catalyst exhibited much higher activity than the Co/Al₂O₃ catalyst in the CO oxidation test with 98% conversion at 160 ℃ and 100% conversion at 180 ℃. The catalytic activity and structure of the Co/MIL-53(Al) catalyst were stable during the reaction.