功能化的介孔分子筛碱催化性能的研究

以苯甲醛与氰乙酸乙酯的Knoevenagel缩合为模型反应，研究了用γ－氨丙基三乙氧基硅烷或γ－乙二胺丙基三甲氧基硅烷功能化的纯硅介也分子筛HMS（Hexagonal mesoporous silica）的碱催化性能。结果表明，除个别碱基负载量高的样品外，功能化样品对反应显示很高的催化活性，反应的初期活性不仅取决于催化剂上活性中心的密度，而且与载体的孔道结构有关。大孔径载体有利于反应物、产物的扩散，故在高负载量时，大孔径样品比小孔样品有更高的活性。此外，还考察了反应温度、溶剂、反应物配比和催化剂用量等条件的影响以及催化剂的重复使用情况。结果表明，反应可在低于100℃的温和条件下进行，有明显的溶剂效应，反应物配比和催化剂用量存在一最佳值；随使用次数的增加，催化剂逐渐中毒而失活。

BASE CATALYSIS RESEARCHING OF FUNCTIONALISED HEXAGONAL MESOPOROUS SILICA

Base-catalytic performances of HMS(Hexagonal mesoporous silica) mesoporous molecular sieves functionalised by 3-aminopropyltriethoxysilane and 3-ethyldiaminopropyltrimethoxysilane were studied by using Knoevenagel condensation reaction of benzaldehyde with ethyl cyanoacetate as a model reaction. It was shown that the functionalised HMS were effective catalysts with high activity for this reaction except of a few samples with higher basic group loadings. Initial activity of the reaction depended not only on the density of basic groups on the catalyst, but also on the pore structure of the support. The larger pore diameter of the support is favorable to the diffusion of reactants and products. Therefore, the activity of sample with larger pore diameter is higher than that with smaller pore diameter when the amount of loading is large. The effects of reaction temperature, solvent type, molar ratio of reactants and mass of catalyst on the activity and the recycling of the catalyst were also investigated. It was found that the reaction could carried out under mild condition, solvent effect was obvious during the reaction and both molar ratio of reactant and dosage of catalyst had a optimum va- lue. The activity of catalyst gradually decreases during the recycling due to poisoning.