【摘要】 以柠檬酸燃烧法制备的Ni/MgO,Ni/CeO2-MgO和Ni/CeO2为催化剂,CH4为碳源,采用化学气相沉积法制备多壁碳纳米管(MWCNTs),通过N2吸附、X射线衍射、H2程序升温还原和X射线光电子能谱对催化剂进行表征,并运用热重和透射电镜表征了碳纳米管的质量和形貌.结果表明,CeO2的加入可有效地降低还原温度和增加易还原Ni物种的含量,并使电子发生转移,还原后的Ni/CeO2-MgO催化剂中,Ni晶粒尺寸较小.这表明CeO2的加入使得Ni物种的化学环境发生改变,导致它和载体间的相互作用减弱,从而促进Ni物种的还原,且还原后,高度分散在CeO2-MgO载体上,从而催化剂的催化活性增加.相比Ni/MgO催化剂,Ni/CeO2-MgO为催化剂上生长的CNTs质量更高.另外,由CeO2助Ni/MgO催化剂制备出基本没有无定形碳、结晶度好的碳纳米管.更多还原

【Abstract】 Ni/MgO,Ni/CeO2-MgO,and Ni/CeO2 catalysts were prepared by the citric acid combustion method.Their catalytic properties for the synthesis of multi-walled carbon nanotubes(MWCNTs)by chemical vapor deposition using CH4 as carbon source were evaluated.The catalysts were characterized with N2 adsorption,X-ray diffraction(XRD),H2 temperature-programmed reduction(H2-TPR),and X-ray pho-toelectron spectroscopy(XPS).The quality and structure of the CNTs were characterized by thermogravimetry(TG)and transmission elec-tron microscopy(TEM).H2-TPR showed that CeO2 helped decrease the reduction temperature and increase the content of an easily reducible Ni species.XPS showed an energy shift of the Ni catalyst that was modified by CeO2.XRD showed that the reduced nickel maintained their small particle sizes in the Ni/CeO2-MgO catalysts.These findings suggested that the addition of CeO2 changed the chemical environment of the nickel species,which resulted in a weaker interaction between the nickel and the support and increased the reducibility of the Ni species.Moreover,the reduced nickel was highly dispersed on the CeO2-MgO support.The change enhanced the catalytic activity for the growth of carbon nanotubes(CNTs).Characterization by TG and TEM showed that the quality of the CNTs grown on Ni/CeO2-MgO was better than those grown on Ni/MgO catalyst.更多还原