【作者】 顾明兰；

【导师】 田丹碧；

【作者基本信息】 南京工业大学 ， 应用化学， 2005， 硕士

【摘要】 KF/Al₂O₃ 催化剂作为一种固体超强碱催化剂,具有比液体碱更优越的应用性能,比如:与反应产物易分离;可重复使用;立体选择性高;对环境没有污染等。近几年,有关KF/Al₂O₃催化剂在有机反应中的报道也越来越多,特别是在诸如Michael 加成、Knoevenagel 缩合、Witting 反应等十分重要的合成反应中的应用成功。所以制备出高效的KF/Al2O3催化剂就显得尤为重要。KF/Al₂O₃ 催化剂的传统制备方法是将一定量的KF 用浸渍法负载在层析Al₂O₃ 表面。用此法制备出来的KF/Al₂O₃ 催化剂:KF 分散差、表面积小,催化效果不够理想。而且催化剂的表面结构、催化机理等还不够清楚。本论文就如何提高KF/Al₂O₃催化剂的表面积,如何改善KF 在Al₂O₃表面的均匀性展开了研究工作,并对催化剂的催化剂结构和催化机理进行了探索。随着纳米技术在材料科学中应用的不断发展,纳米技术在催化剂制备中的应用的报道也越来越多。其中溶胶-凝胶法:要求的反应温度较低;可以从材料处理的最初阶段即纳米尺度上对材料进行控制;而且在反应过程中可以定量地引入某种成份,使该组分均匀地掺杂在其它组分中,制备出来的材料具有高度的均一性和纯度。在这种思路的启发下论文第一部分用有机溶胶-凝胶法,有机酸作为催化剂合成了50nm 的Al₂O₃粉体。分别考察了:加入的水量、加水方式、凝胶化时间、催化剂的种类、催化剂的用量、超声波技术的使用等对生成的纳米Al2O3颗粒大小的影响。讨论了湿凝胶粉体干燥技术的改进。对制备出的干凝胶和纳米Al2O3粉体进行了扫描电镜分析（SEM）、红外分析（IR）、热分析（TG-DSC）和X 射线衍射分析（XRD）。第二部分首先用有机溶胶-凝胶法,KF 为催化剂,合成了80nm 的Al₂O₃粉体,然后用溶胶-凝胶法成功地合成了KF/ Al₂O₃催化剂:即在纳米Al₂O₃形成过程中,将KF 均匀地掺杂进去,此时KF 既是Al₂O₃形成过程的催化剂,同时又与生成的Al₂O₃发生作用产生碱性活性中心。本部分选用Knoevenagel 缩和（苯甲醛与氰乙酸乙酯缩和）及Michael 加成（丙二酸二乙酯与丙烯腈加成）反应对所制纳米KF/Al₂O₃复合催化剂的性能进更多还原

【Abstract】 KF/Al₂O₃ as a kind of solid base catalyst is superior to the liquid alkali in many aspects, such as: easier separation from the final products, better reutilization, high stereoselectivity, environmental protection and et al. In recent years, KF/Al₂O₃ has been employed in many organic reactions, especially in Michael addition 、Knoevenagel condensation、Witting reactions and so on, which all play a key role in various compounds’synthesis. So it is very import to develop an efficient KF/Al₂O₃ solid base catalyst. The classical KF/Al₂O₃ was prepared by immersing Al2O3 powder into KF hydrous solution. The disadvantages of this catalyst are: the uneven distribution of the KF on Al₂O₃, the lower surface area of the catalyst, which all lead to the worse catalytic performance. It has also been obscure of KF/Al₂O₃’s surface morphology, catalytic mechanisms. In this paper the study on increasing the catalyst’surface area and improving the uniformity of KF on Al₂O₃ surface have been done. Meanwhile, the substance which has the catalytic capacity and mechanism of the catalyst have also been discussed. With the development of the nanometer technologies, the literatures about its application in the preparation of catalysts are more and more. The Sol-gel method is particularly attractive for its advantages such as: lower processing temperature, the control of the catalyst at the initial time, high homogeneity and purity of the final materials. Enlightened by above ideas, firstly 50nm Al₂O₃ has been prepared by the organic Sol-gel method with organic acid catalyst. The effects of way of adding water、quantity of water、time of gelation、different species of catalyst、quantity of catalyst and ultrasonic technology on particles size were studied. A series of techniques of characterization, e.g. scanning electron microscope （SEM）, powder X-ray diffraction （XRD）, temperature weight and differential scanning calorimetry were used to characterize the intermediate and final products. In the second part, 80nm Al2O3 has been synthesized by Sol-gel method with KF catalyst. Then, 50nm KF/Al2O3 has been synthesized by Sol-gel method. In the process, KF acted with the surface Al2O3 in some way to form the active base center while as a catalyst in the synthesis of nano-Al2O3. Knoevenagel condensation and Michael addition reactions have been selected to test the catalyst’s performance and “Even Design”software are also used to optimize the preparation process. As for the Knoevenagel condensation reaction, the optimal conditions of preparation of KF/Al2O3 were: KF·2H2O: 1.9g, reaction time: 5h, reaction temperature: 80℃; calcinations temperation, 400℃and the α-cyanocinnamic acid ethyl ester yield is 94.5%. For Michael addition reaction, the optimal conditions were: KF·2H2O: 2.9g, reaction time: 5h and the（2-cyanoethyl）malonic acid diethyl ester yield is 88.0%. In addition , nano-KF/Al2O3 also has high stereoselectivity for the Knoevenagel condensation reaction and excellent reutilization performance. In the third part, the catalyst was been characterized by several technologies of characterization including scanning electron microscope （SEM）, powder X-ray diffraction （XRD） , temperature programmer desorption （CO2-TPD） and X-ray photoelection spectrometry（XPS）. From the analysis, it can be concluded that nano-KF/Al2O3 catalyst has three basic sites, [Al-OH…F] species may be response to Knoevenagel reactions and K3AlF6 may be response to Michael addition reaction.更多还原