| The ordered mesostructured membranes are becoming research focus in chemistry field, owing to their superior properties and great potential applications in many scientific fields. Mesoporous membranes with pore size of 2-50 nm not only have excellent properties, such as thermal and chemical stability, mechanical strength, antibacterial and so on, that inorganic membranes possess but have regular arrays of uniform channels and the dimensions. Among the mesoporous membranes, the type which possess 3D pore structures have more and more attentions for the good transportation. And the MCM-48 membrane with 3D pore structure is a promising material for membrane-based separation processes, catalysts, and chemical sensors, etc.However, it is difficult to prepare a compact MCM-48 membrane which has good hydrothermal stability, so the researches on theoretical foundation of the formation of MCM-48 membrane are very few, many problems are urgently to be solved. Study on the preparation, modification and application of MCM-48 membrane will have a theoretical and practical significance. In this works, the preparation and mechanism of the compact mesoporous MCM-48 membrane on the porousα-Al2O3 tube were studied in detail. The MCM-48 membranes were also silylated to enhance the hydrothermal stability and hydrophobic property, which were suitable for the separation of EA/H2O system. Besides this, the immobilized enzyme membrane reactor was installed by the immobilized papain and the silylated MCM-48 membrane, which could separate the products as the reaction was continuous. This thesis mainly includes several aspects:1. The MCM-48 membranes were in-suit prepared on the supports with pore size of about 1μm with optimized synthesis. The membranes had the permeation for N2 of 3.2×10-7 mol/(m2.s.Pa) and the H2/N2 separation factor of 2.95. The results showed that the factors including the large pore size of the supports and the times of hydrothermal synthesis played an important role in the compactness of membrane. The stress in the membrane was increased with increasing the times of synthesis at the presence of large pore size. With more than three time's synthesis the membrane tended to be crack. At the same time, in the high alkaline sol, there present not only the self-assembly of the inorganic precursor and the surfactant, but also the partly depolymerization of the in-suit membrane. As a result, the membrane could not grow much thicker and thicker with increasing the times of synthesis. 2. The MCM-48 membranes were formed on the porous supports (A, 3-5μm; B,～1μm) which were prefilled by silica sol. The silica sol could reduce the pore size of the supports to prevent the penetration of the synthesis sol and favor for the growing of the MCM-48 membrane on surface by the bond of Si-O-Si. But because of the exiting of much stress contained in the dry silicon gel, the membrane would be much crack in the process of calcinations. As a result, the Knudsen contribution to the total flux for N2 was about 70% and 85% for A and B tube, respectively. Basing on the good effect of the prefilled methods, a silica transition was made on the surface of B tube. The results showed that the transition layer not only prevented the penetration of the synthesis sol, but also favored for the formation of more compact membrane with little crack. The membrane had the permeation for N2 of 4.52×10-7 mol/(m2.s.Pa), and relative high H2/N2 separation factor and Knudsen contribution (K%), 3.1 and 87%, respectively.3. More compact MCM-48 membrane was prepared on the B supports with dip-coating seeds layer. The mesoporous seeds had a good effect on inducing the growing of membrane on the supports. But the dip-coating seeds layer was not tight for synthesis sol and resulted to the penetration into the supports. Fortunately, the problem could be resolved by the vacuumed coating methods. The MCM-48 particles with appropriate size could stuff the mouths of the surface pores strongly by pressure-driven. Then a thin and compact mesoporous MCM-48 membrane impermeable for N2 had been successfully synthesized on B supports with optimized synthesis. After calcinations, the MCM-48 membrane had the the permeation for N2 of 1.91×10-7 mol/(m2.s.Pa), and the relative high H2/N2 separation factor and the Knudsen contribution (K%), 3.1 and 87%, respectively.4. The MCM-48 membranes were silylated by silane coupling agent with different alkyl chain. The effect on the hydrothermal stability of MCM-48 membrane was investigated. And the silylated MCM-48 membrane was successfully applied in the separation of EA/H2O mixture. The results showed that the silylated MCM-48 membrane had a good effect on the separation of EA/H2O system with EA concentration of 5% (w/w). The C8H17-MCM-48 membrane had a relative high separation factor for EA/H2O and large total flux, 71 and 1.5 kg/(m2.h), respectively. Although the C3H7-MCM-48 and CH3-MCM-48 membranes had the larger total flux, the separation factor was decreased to 62 and 36, respectively. The hydrophobic membrane was formed by the interconnection of the alkyl group and the adsorpted EA molecules. The EA molecules could penetrate the membrane selectively following the adsorption-diffusion mechanism.5. The immobilized enzyme membrane reactor was prepared by enclosing the immobilized papain in the shell pass of tubular MCM-48 membrane separator. The little molecules, such as H2O and tyrosine, could penetrated through the silylated MCM-48 membrane, while the larger molecules could be rejected in the shell pass. As the reaction time went on, both the degradation rate of casein and the absorbance at 275nm of penetration liquid underwent a process from dramatic decline to relatively stable period. When the reaction was continuous for 5hours, the degradation rate and the absorbance of penetration liquid were 24.6% and 0.35, 18.4% and 0.26, respectively for the feed back 5ml/min and 10ml/min. |
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