【作者】 孔爱国；

【导师】 单永奎；

【作者基本信息】 华东师范大学 ， 无机化学， 2005， 硕士

【摘要】 多金属含氧簇合物同时具有酸性、氧化-还原性、“假液相”行为等催化特性,在原子经济反应和环境友好催化方面有着诱人的实用前景。特别是其组成-结构-性能可调变,被认为是实现催化剂分子设计的最理想材料之一,从而也成为催化理论方面研究的热点。 实现多金属含氧簇合物的分子设计需要我们建立其组成-结构-物理化学性质和催化性能之间的关系。热解性质是物质的重要的物理化学性质,热分解温度则是催化剂实际应用设计中的重要参数。但目前很多文献对其热解性质的研究局限于采用单一热分析方法对个别化合物的零散研究,缺乏系统性,不利于正确评价其组成-结构-热解性质的关系。特别是由于缺少统一合理的热分解判断依据等原因,同一多金属含氧簇合物的热分解温度在不同文献中常常有不同报道,这为其在实际应用中的催化设计带来了不便。另外,多会属含氧簇合物还存在比面积小、机械强度低等不足;文献常用的浸滞等简单负载方法虽然能改善上述的缺点,但却不能克服多金属含氧簇合物在极性溶剂中使用易溶脱流失等问题,不利于催化剂的重复利用和产物的分离等。 本文试图对它们进行研究,探索解决办法,为多金属含氧簇合物催化剂的实际应用和实现其分子设计提供一定的实验数据。具体内容如下: 1,利用变温XRD,变温IR以及TG-DTA等现代测试手段,详尽地研究了常见的具有Keggin结构Y_mH_nXM₁₂O₄₀和Dawson结构Y_mH_nP₂M₁₈O₆₂(X=P、Si、Ge,M=W、Mo,Y=NH₄⁺,K⁺,Cu²⁺,m,n为抗衡离子数)两个系列共二十四个化合物的热解性质。对多金属含氧簇合物热分解的判断方法进行了系统的研究,并提出新的见解。并获得了这些种多金属含氧簇合物较为准确的热分解温度;探讨了它们的热分解过程,对其主要的热分解产物作了初步鉴定。探讨了影响多金属含氧簇合物的组成-结构-热解性质之间关系的某些规律。 2,利用硅烷化试剂,将H₃PW₁₂O₄₀多金属含氧簇合物嫁接固定于具有较高热稳定性,高规整性介孔孔道的TiO₂分子筛表面,得到的TiO₂/APTS/H₃PW₁₂O₄₀材更多还原

【Abstract】 Polyoxometalates （POM） are useful materials as acidic and oxidation catalysts for various reactions and have been practically applied in industry. As solid acid catalysts, especially characterized in providing a unique "pseudoliquid phase" reaction environment, POM catalysts should find more and more practical applications in green/sustainable and atomic economic reactions. In particular, owing to their changeable properties of the composition, structure and thus performance, polyoxometalates are thought as one of the most suitable materials to be artificially designed, and then more attentions are also been paid to them in theory.To realize the molecular design of polyoxometalates, the necessary prerequisite is to masterly predominate the following four levels of information: i), catalytic performance; ii), chemical and physical property; iii), molecular and bulk composition and structure; iiii), method of catalyst preparation. Thermal decomposition behavior and thermal stability are the essential physical and chemical properties, and the thermal decomposition temperature is especially an important parameter for the design and preparation of the applicable catalysts. However, the present research results, especially their decomposition temperatures, are disillusionary due to many reasons such as different determinant criterion of polyoxometalates etc. This will be unconducive for understanding and exploring the fundamental chemistry of polyoxometalates and the catalysis of the related catalysts. Besides, the practical applications of polyoxometalates have been limited due to some shorts such as their low surface area and low mechanical intensity, etc. The developed loading method-inpregnation can usually be used to improve the problems above, but it can not solve the leaching of the loaded polyoxometallates in polar solvent.We aim to explore the methods to solve the problems, and make foundations for the applications and the molecular design of polyoxometallates. The main contents are as follows:First; the thermal decomposition behavior of the polyoxometalates with Keggin structure Y_mH_mXM₁2O₄0 and Dawson structure Y_mH_mXM₁8O₆2 （X=P Si Ge, M=W Mo,Y=NH₄⁺ K⁺ Cu²+） was investigated systematically using modern thecniques shuch as X-ray diffraction and IR Spectra at different temperatures, TG-DTA etc.Their precise decomposed temperatures were obtained, and the procedure of decomposition was also explored. The determinant criterions of thermal decomposition and the factors of affecting on the thermal properties for the polyoxometalates were discussed and some new views were presented. At the same time, the main decomposition products were identified by XRD for the prepared polyoxometalates.Second; heteropoly acid （H₃PW₁2O₄0 and H₅PMo_V3O₄0） with Keggin structure was immobilized onto the surface of mesoporous TiO₂ sieves with high thermal stability and order channel through chemical bonding with amine groups which was introduced into the system during an aminosilylation procedure, resulting in strong anchoring of heteropoly anions. Thus, polyoxometalates leaching in polar solvent media was efficiently prevented. The prepared material could catalyze more effectively in photodecomposition of methyl orange and hydroxylation of benzene to phenol by molecular oxygen respectively.更多还原