Hangzhou Institute of Advanced Studies, Zhejiang Normal University, 1108 Gengwen Road, Hangzhou 311231, China.
Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
Int J Mol Sci. 2021 Aug 12;22(16):8668. doi: 10.3390/ijms22168668.
The synthesis of ester compounds is one of the most important chemical processes. In this work, Zn-Mg-Al mixed oxides with different Zn/Mg molar ratios were prepared via co-precipitation method and supported gold nanoclusters to study the direct oxidative esterification of aldehyde and alcohol in the presence of molecular oxygen. Various characterization techniques such as N-physical adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and CO temperature programmed desorption (TPD) were utilized to analyze the structural and electronic properties. Based on the results, the presence of small amounts of Zn ions (~5 wt.%) provoked a remarkable modification of the binary Mg-Al system, which enhanced the interaction between gold with the support and reduced the particle size of gold. For oxidative esterification reaction, the Au/ZnMgAl-400 catalyst showed the best performance, with the highest turnover frequency (TOF) of 1933 h. The active center was believed to be located at the interface between metallic gold with the support, where basic sites contribute a lot to transformation of the substrate.
酯类化合物的合成是最重要的化学过程之一。在这项工作中，通过共沉淀法制备了不同 Zn/Mg 摩尔比的 Zn-Mg-Al 混合氧化物，并负载金纳米簇，以研究在氧气存在下醛和醇的直接氧化酯化反应。利用 N-物理吸附、X 射线衍射（XRD）、透射电子显微镜（TEM）、X 射线光电子能谱（XPS）和 CO 程序升温脱附（TPD）等多种表征技术对结构和电子性能进行了分析。结果表明，少量 Zn 离子（~5wt%）会显著改变二元 Mg-Al 体系，从而增强了金与载体之间的相互作用，并降低了金的粒径。对于氧化酯化反应，Au/ZnMgAl-400 催化剂表现出最佳的性能，其最高的周转频率（TOF）为 1933h。活性中心被认为位于金属金与载体的界面处，其中碱性位对底物的转化有很大贡献。
