Preparation Of Hydrophobic SBA-15/PDMS Hybrid Membrane And Its Pervaporation For Ethanol-Water Solution

Pervaporation is a new technology of membrane separation, which has unique advantages in dealing with azeotropic or close boiling mixture separation system as well as the removal of trace water or organic matter and the separation of organic mixtures. It has extensive application prospect in petrochemical industry, pharmacy, foods, environmental sector, biotech, energy and other industrial areas. In this paper, the hydrophobic mesoporous molecular sieves SBA-15 with different hydrophobic groups were prepared by co-condensation method. Then hydrophobic SBA-15/PDMS hybrid membranes were prepared, and the performance has been studied in the separation of ethanol/water solution. The result showed that hybrid membranes filled with 30% C16H33-SBA-15 has the best separate performance. This paper consists essentially of the following four parts:1. The modified SBA-15 (CH3-SBA-15, C8H17-SBA-15 and C16H33-SBA-15) were prepared by co-condensation method with three kinds of silane (MTES,OTES,CTMS) co-condensation respectively, while PEO20-PPO70-PEO20 was used as surfactant and TEOS as silica source. The modified SBA-15 samples were characterized by FT-IR,XRD spectra, which indicated that there were periodic hexagonal channels in modified SBA-15, and the organic groups had been incorporated on the surface successfully.2. Hydrophobic SBA-15/PDMS hybrid membrane was prepared by blending modified SBA-15, PDMS, crosslinking agent and catalyst. Quality relationships among the reactants in the hybrid membrane were determined by way of optimum membrane-preparing conditions. The weight ratio of PDMS:TEOS:DBTL was 35:10:1.3. In this paper, the film-forming properties of hybrid membrane was investigated by examining varying contents of different modified SBA-15 filled PDMS. And it showed that filled content of C16H33-SBA-15 was 30%. Took 10% C16H33-SBA-15 filled hybrid membranes as the research object, swelling properties of hybrid membranes were analyzed from these aspects such as the soaking temperature, ethanol concentration and filled content of C16H33-SBA-15. Results were demonstrated that the degree of swelling of hybrid membranes decreased with the increasing temperature when ethanol concentration was 6%. The degree of swelling was close to zero in pure water when the temperature was kept at 313K, and it also increased with the ethanol concentration from 0% to 12%. The degree of swelling of hybrid membrane increased with the change of filled contents of C16H33-SBA-15 within the same temperature and ethanol solution. Since the degree of swelling was low that the concentration was less than 0.06g/g, the hybrid membranes were considered to be appropriate for ethanol/ water separation. The surface structure can be obtained by the characterization of SEM. The results indicated that the membranes had smooth surface and molecular sieve was dispersed homogeneously.4. Preliminary research on pervaporation performance of the hybrid membrane in ethanol/water separating system was carried out. The influencing factors of operating temperature, feed concentration, variety and contents of modified SBA-15 filled have been researched to separate the mixtures of ethanol/water when the concentration ranged from 6% to 12%. Results showed that the pervaporation performance was best when the temperature is 323K and feed concentration is 9%. Under these conditions, separation factor of 10% C16H33-SBA-15 filled hybrid membrane is 7.52, which could be improved by 272% and 24% compared with 10% CH3-SBA-15 and 10% C8H17-SBA-15 filled respectively; and separation factor of 30% C16H33-SBA-15 filled hybrid membrane is up to 10.98, the permeate flux is 1870g/(m2'h), which has a little decreased.The preparation of hydrophobic SBA-15/PDMS hybrid membrane and its pervaporation for the low concentration of ethanol/water solution have been research. It can not only expand the applications of modified SBA-15, but also play a significant role in developing a new-type composite membrane of high selective permeability and high permeate flux.