Ni/CeO2-SiO2催化剂的制备、表征及其甲烷部分氧化制合成气性能

以硝酸亚铈（Ce（NO₃）₃·6H₂O）和正硅酸四乙酯（C₈H₂₀O₄Si）为前驱体，采用溶胶-凝胶法合成了系列具有大比表面积的xCeO₂-（1-x）SiO₂（x = 0，0.25，0.50，0.75，1）复合氧化物载体，然后浸渍活性组分Ni制得用于甲烷部分氧化制合成气的Ni催化剂。运用N₂物理吸附-脱附、X射线粉末衍射、扫描电镜、紫外-可见漫反射光谱、氢程序升温还原、氨程序升温脱附和热重等手段对所得催化剂的组织结构、还原性、表面酸性和积炭行为等进行了表征；同时考察了催化剂的组成、焙烧温度和反应时间等对催化剂在甲烷部分氧化制合成气中催化性能的影响。表征结果表明，该系列Ni/CeO₂-SiO₂催化剂具有大比表面积，CeO₂晶粒较小，NiO的分散性好且易被还原，表面酸性弱，不容易积炭。当Ce/Si摩尔比为1：1，活性组分Ni的质量分数为10%，焙烧温度为700℃时，所制备的Ni/CeO₂-SiO₂催化剂表现出较好的稳定性、最高的CH₄转化率（~84%）和对产物CO及H₂的选择性（>87%）。

Preparation and characterization of Ni/CeO2-SiO2 catalysts and their performance in catalytic partial oxidation of methane to syngas

Hexahydrated cerium(Ⅲ) nitrate (Ce(NO₃)₃·6H₂O) and tetraethyl orthosilicate (C₈H₂₀O₄Si) were used as the precursors for the synthesis of a series of xCeO₂-(1-x)SiO₂ (x = 0, 0.25, 0.5, 0.75, 1) composite oxides using a sol-gel process under acidic conditions. The active component, Ni, was loaded on the as-synthesized composite oxides, producing supported Ni catalysts for catalytic partial oxidation of methane to syngas. The properties of the as-synthesized products, such as textural structure, reduction behavior, surface acidity, and carbon deposition, were determined using N₂ physical adsorption/desorption, X-ray diffraction, scanning electron microscopy, ultraviolet-visible diffuse reflectance spectroscopy, temperature-programmed reduction by H₂, temperature-programmed desorption of NH₃, and thermogravimetric analysis. The effects of catalyst composition, calcination temperature, and reaction time on the catalytic performance were investigated. The characterization results showed that these Ni/CeO₂-SiO₂ catalysts have large surface area, small CeO₂ crystals, weak acidity, and low carbon deposition. Highly dispersed NiO is present and is easy to be reduced. The Ni/CeO₂-SiO₂ catalyst with a Ce/Si molar ratio of 1:1, w(Ni) = 10%, and calcined at 700℃ exhibited good stability and the highest CH₄ conversion (~84%) and CO and H₂ selectivity (> 87%).