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首页> 外文期刊>Journal of Materials Science >On the structure and surface properties of NiO/MgO-La2O3 catalyst: Influence of the support composition and preparation method
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On the structure and surface properties of NiO/MgO-La2O3 catalyst: Influence of the support composition and preparation method

机译：NiO / MgO-La2O3催化剂的结构和表面性能：载体组成和制备方法的影响

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摘要

This work addresses the effect of catalyst preparation method and the carrier compositions (MgO-La2O3) over the NiO-support interaction, which affect the reducibility, textural properties and the different oxygen species chemisorbed at different temperatures over MgO-La2O3 supported NiO catalysts. The materials were prepared by wet sequential impregnation and wet co-impregnation with different Mg molar fractions [Mg/(La+Mg)]. The samples were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), infrared (IR) spectroscopy, scanning electron microscopy (SEM), changes of surface potential and BET surface area measurements. The total oxidation of methane was use as model reaction. It has been found that the catalyst formulations (i.e. NiO/MgO-La2O3) and the preparation methods not only affect the interaction among the catalyst components, but also the texture and material morphology as a result of different degrees of particle aggregation. The wet sequential impregnation-prepared catalysts showed a stronger MgO-La2O3 interaction than wet co-impregnation-prepared samples. A marked tendency of NiO to react with MgO rather than La2O3 following a mechanism of lattice substitution is observed. Mg-free catalyst showed LaNiO3 and NiO as major crystalline Ni-containing phases. The ternary Ni-Mg-La-O system, on the other hand, facilitates the formation of poorly reducible Ni phase, whereas the La-free catalyst (i.e. NiO/MgO) displayed the lowest content of Ni-reducible phase, owing to the formation of Ni1-xMgxO solid solution. Measurements of surface potential changes together with catalytic studies suggest that La-containing catalysts present oxygen vacancies, which markedly affect the chemical nature of the surface oxygen species and hence their catalytic behaviour.
机译：这项工作解决了催化剂制备方法和载体组成（MgO-La2O3）对NiO-载体相互作用的影响，这影响了MgO-La2O3负载的NiO催化剂的还原性，组织性质以及在不同温度下化学吸附的不同氧种类。通过湿法连续浸渍和以不同的Mg摩尔分数[Mg /（La + Mg）]进行湿共浸渍来制备材料。通过X射线衍射（XRD），程序升温还原（TPR），红外（IR）光谱，扫描电子显微镜（SEM），表面电势变化和BET表面积测量来表征样品。甲烷的总氧化用作模型反应。已经发现，催化剂配方（即NiO / MgO-La 2 O 3）和制备方法不仅影响催化剂组分之间的相互作用，而且由于不同程度的颗粒聚集而影响质地和材料形态。湿法顺序浸渍制备的催化剂显示出比湿法共浸渍制备的样品更强的MgO-La2O3相互作用。观察到了遵循晶格取代机制的NiO与MgO而不是La2O3反应的明显趋势。无镁催化剂显示LaNiO3和NiO为主要的结晶含镍相。另一方面，三元Ni-Mg-La-O系统促进了难还原的Ni相的形成，而无La的催化剂（即NiO / MgO）由于Ni-Mg-La-O体系的Ni还原相含量最低。 Ni1-xMgxO固溶体的形成。对表面电势变化的测量以及催化研究表明，含La的催化剂存在氧空位，这会明显影响表面氧物种的化学性质，进而影响其催化性能。

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