Surface Functionalization Of Hms Mesoporous Molecular Sieves And Alkali Catalyst Performance Study

Since the synthesis of mesoporous molecular sieves was first reported in 1992, many of the researches were focused on the synthesis of M41S using ionic surfactant as template, the surface functionalization and the applications of MCM-41. However, few reports on the surface anchoring of basic functional groups and the catalytic research of funationalized mesoporous silica were published.In this dissertation ,we investigated the synthesis of HMS-type mesoporous materials using non-ionic surfactants (primary amines) as template and the surface anchoring of basic functional groups. Two organosilanes, 3-aminopropyltriethoxysilane(AM) and 3-ethyldiaminopropyltrimethoxysilane (ED), were used to react with calcined hexagonal-like mesoporous silica HMS. respectively, to produce functionalised mesoporous molecular sieves. Effects of functionalization conditions, such as the dosage of organosilane, the reaction temperature and the size of functional groups, on the loadings and the bonding degree of functional molecules were also systematically investigated for the first time. The results show that the increase of the dosage of organosilanes and the channel size of samples, and the decease of reaction temperature are favorable to the grafting of functional molecules on the surface. When functionalization conditions are the same, the order of loadings on DDA-HMS is ED>AM. On ODA-HMS, however, the loading of AM is similar to that of ED.Furthermore, the application of functionalized HMS in the catalysis of Knoevenagel condensation is studied in detail. It is shown that the functionalised HMS are effective catalysts with high activity for this reaction except a few samples with higher loadings. Initial activity of the reaction depends not only on the density of basic groups on the catalysts, but also on the pore structure of the supports. 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 diameters when the loading is high. In addition, the effect of reaction temperature, solvent, molar ratio of reactants and mass of catalyst on the activity and the recycling of the catalyst areinvestigated. It is found that solvent effect exhibited in the reaction is associated not only with the relative polarity of solvent and catalyst. The activity of catalyst gradually decreases during the recycling due to poisoning.