Towards the Next Level of Molecular Control in the Sol-Gel Preparation of Mixed Oxides

本项目探索使用溶胶-凝胶法制备混合氧化物以获得可预测的结构或结构，并将其应用于酸性催化剂的合成。具体研究了二氧化钛-二氧化硅和氧化铝-二氧化硅；硅前驱体具有明显较慢的反应性，这允许预水解用作调节变量。通过改变预水解比例，可以得到不同微观结构的凝胶网络。产品性质的表征可以提供均匀性与酸度的相关性。氮吸附、x射线衍射、热分析、吡啶吸附和1-丁烯异构化表征了混合氧化物的结构、结构和催化性能。还研究了替代前体，如双金属烷氧化物和溶胶，以及通过共沉淀法制备的混合氧化物。这项工作将为设计具有特定性能的混合氧化物提供手段。虽然所使用的程序已经很好地建立起来，但关于所涉及的变量如何影响产品特性的系统工作却很少。（换句话说，混合氧化物制备与其说是“科学”，不如说是“艺术”。）虽然这项研究着眼于催化性能，但如果成功，它显然可以扩展到使用混合氧化物的其他应用，比如光波导。＊＊＊

ABSTRACT CTS-9522066 This project explores the use of sol-gel preparation of mixed oxides to achieve predictable structures or textures and to apply this to the synthesis of acid catalysts. Specifically, titania-silica and alumina-silica are studied; the silicon precursor has significantly slower reactivity and this permits prehydrolysis to be used as a tuning variable. By varying the prehydrolysis ratio, gel networks of various microstructures can be obtained. Characterization of the product properties may provide a correlation of homogeneity with acidity. Nitrogen adsorption, X-ray diffraction, thermal analysis, pyridine adsorption, and 1-butene isomerization are used to characterize the textural, structural, and catalytic properties of the mixed oxides. Alternative precursors such as double metal alkoxides and performed sols are also studied, as are mixed oxides prepared by coprecipitation. This effort should provide the means to design mixed oxides with specific properties. Although the procedures to be used are well established, little systematic work on how the variables involved affect product properties has been done. (In other words, mixed oxide preparation is more "art" than "science".) Although this effort looks at catalytic properties, if successful it would clearly be extendable to other applications using mixed oxides, such as optical waveguides. ***