| Pervaporation (PV) compared with other traditional separation methods such as distillation and extraction, has far more excellent characters due to high separation effective, less equipment investment, simplicity operation, low energy consumption. It is widely used in multi-field, especially for separating of heat-sensitive liquid mixtures and azeotrope, has especially value. The organic-inorganic hybrid membranes have the advantages of polymer and inorganic particle, integrate their from molecule level, introduce inorganic particles in polymer matrix, change net structure of membranes, offer stress support point, enhance durability, appropriate adjustment the free volume, and the of size and number of network pore, hydrophile and hydrophobe of membranes, increase permeate flux and selectivity. The hybrid membranes have large flux, high mechanical intensity, chemical stability of inorganic particle, and have high separation active, ideal membrane-forming property and flexibility of polymer.Nano silica is a widely used inorganic nano particle in applications. Now sol-gel and co-mix methods are commonly used in composite produce, explored in pervaporation field, acquire some favorable achievement. But up to the present, the researches of membranes preparation method beside sol-gel and co-mix methods are rare; and only used one sort of nano silica in composite membranes; the systematically researches on effect of hydrophile or hydrophobe of nano silica, effect of different shape of nano silica in PV process and PV mechanism are also rare. In this dissertation, emulsion polymerization method was introduced into membranes preparation; the effects of hydrophile nano silica sol and hydrophobe nano silica (Vinyl-POSS) in CPL/water PV process have been systematically investigated; investigated the effects of different shape and surface character on PV mechanism and PV flux and separation factor by used alkyl-SiO2and high crystalline POSS in silicone rubber membranes in DMC/MeOH PV process; analyzed the diffusivity/sorptivity selectivity, investigated the effects of nano silica in PV mechanism. The investigation of this dissertation has been divided into four parts:(a) Emulsion polymerization used in nano silica/polyacrylate hybrid membranes preparation and PV performance characterizationIn this dissertation, nano silica/polyacrylate hybrid membranes were prepared through emulsion polymerization, and their structure and PV performance had been further characterized. By the scanning electron microscopy analysis (SEM), it was found that the outer surfaces of the composite membranes were different with pure polyacrylate membranes. The interaction between nano silica and polyacrylate influence the move of polymer chain, let water through membranes easier. The PV experimental results indicate nano silica/polyacrylate hybrid membranes had higher flux in CPL/water system. It was larger than PVA and other polymer membranes in literature. The nano silica/polyacrylate hybrid membranes had best flux J=1138g/(m2h), separation factor was350at the same condition.(b) PVA/nano silica hybrid membranes preparation and PV performance characterizationIn this section, PVA/nano silica hybrid membranes were prepared by co-mix nano silica sol and PVA solution, and their structure and PV performance had been further characterized. By the X-ray diffraction measurements (XRD), it was found that the crystallinity of the hybrid membranes was decreased with increasing nano silica content; by the contact angles analysis, it was found that the hydrophilicity of the surface of hybrid membranes was improved. The PV experimental results indicate introducing nano silica can increase permeation flux in CPL/water system, particularly, as the nano silica content in hybrid membranes increased, the separation factor decreased. The best flux J=3.8Kg/(m2h), separation factor was150at the same condition. The investigation of diffusivity/sorptivity selectivity and activation energy indicated in PV process that the diffusivity selectivity has more contribution in membranes selectivity.(c) POSS/PVA hybrid membranes preparation and PV performance characterizationIn this part, PVA/POSS silica hybrid membranes were prepared by co-mix Vinyl-POSS and PVA solution, and their structure and PV performance had been further characterized. By the X-ray diffraction measurements (XRD), it was found that the crystallinity of the hybrid membranes was decreased with increasing POSS content, and the cage structure of POSS has been reserved; The PV experimental results indicate introducing POSS can increase permeation flux in CPL/water system, particularly, as the POSS content in hybrid membranes increased, the separation factor decreased. The best flux J=2.2Kg/(m2h), separation factor was220at the same condition. The investigation of diffusivity/sorptivity selectivity indicated in PV process that the diffusivity selectivity has more contribution in membranes selectivity. The hydrophobe of POSS let CPL leave membrane surface to gas phase more difficultly, but through membrane quickly. The influence of water was contrarily.(d) Nano silica/silicone rubber hybrid membranes preparation and PV performance characterizationIn this section, nano silica/silicone rubber hybrid membranes were prepared by co-mix Vinyl-POSS or alkyl-SiO2with RTV silicone rubber, and their structure and PV performance had been further characterized. By the X-ray diffraction measurements (XRD), it was found that the crystallinity of the hybrid membranes was decreased with increasing POSS or alkyl-SiO2content, and the cage structure of POSS has been reserved. By the scanning electron microscopy analysis (SEM), it was found that the crystalline POSS in the outer surfaces of the Vinyl-POSS/silicone rubber hybrid membrane, and spherical silica in the outer surfaces of the alkyl-SiO2/silicone rubber hybrid membrane. The PV experimental results indicate introducing POSS or alkyl-SiO2all can increase permeation flux in DMC/MeOH system; the separation factor was decreased with increased POSS; but increased until alkyl-SiO2increased at a certain content, after then the separation factor was decreased. The best flux of POSS/silicone rubber hybrid membrane M-3J=4.9Kg/(m2h), separation factor was2.31at the temperature50℃. The best flux of alkyl-SiO2/silicone rubber hybrid membrane M-3J=3.8Kg/(m2h), separation factor was4.42at the temperature50℃. The best separation factor of POSS/silicone rubber hybrid membrane M-6was4.04, the flux was1.0Kg/(m2h) at the temperature30℃. The best separation factor of alkyl-SiO2/silicone rubber hybrid membrane M-5was5.60, the flux was1.2Kg/(m2h) at the temperature30℃. It was favorable than other polymer membranes for DMC/MeOH PV preference DMC permeation in literature.The investigation of diffusivity/sorptivity selectivity indicated in DMC/MeOH azeotrope PV process, it was different with CPL/water solution, that the sorptivity selectivity has more contribution in membranes selectivity. The different shape and surface property of Vinyl-POSS and alkyl-SiO2bring distinct interaction between PDMS and nano SiO2, alkyl-SiO2was more compatibility with PDMS. When Vinyl-POSS and alkyl-SiO2added under critical degree, the intimately area between alkyl-SiO2and PDMS was absent by POSS/silicone rubber membrane, it caused the difference of separation performance. |
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