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Membrane Separation

JOURNAL REPORT. Membrane Separation. Qian Jiang 2012.11.23. A novel poly(dimethyl siloxane)/poly(oligosilsesquioxanes) composite membrane for pervaporation desulfurization. Qiu Gen Zhang, Bing Cheng Fan, Qing Lin Liu, Ai Mei Zhu, Feng Feng Shi.

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Membrane Separation

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  1. JOURNALREPORT Membrane Separation Qian Jiang 2012.11.23

  2. A novel poly(dimethyl siloxane)/poly(oligosilsesquioxanes) composite membrane for pervaporation desulfurization Qiu Gen Zhang, Bing Cheng Fan, Qing Lin Liu, Ai Mei Zhu, Feng Feng Shi Journal of Membrane Science 366 (2011) 335–341

  3. Introduction Being a hydrophobic polymer with good chain flexibility, large free volume and high permeability to permeants, PDMS has been widely used as a membrane material for separation of organic compounds. POSS has high hydrophobicity due to their CH3 groups, which can make the composite membranes increase or retain preferential sorption for thiophene. Inverse gas chromatography (IGC) can be used to determine the infinite dilution solubility coefficient and diffusion coefficient to evaluate pervaporation performance of a membrane.

  4. Membrane preparation PDMS(10g) Stired at room temperature for 2h POSS(wt%) Stired for 1h n-heptane(84g) TEOS(5g) Casted on a porous cellulose acetate dibutyltin dilaurate(1g) 40℃ for 8h Peeled off

  5. IGC experiments The composite with 5.0wt% POSS loading has the strongest affinity for thiophene, benzene and toluene.

  6. Characterization of membranes The composite membranes have a sharp peak around 2θ =10◦ with the incorporation of POSS, and this is in agreement with the XRD curve of POSS.

  7. Characterization of membranes • The PDMS membrane has a homogeneous surface. • The particles observed are due to the aggregation of the POSS . • Thickness of the separation layer is about 18μm. SEM image of the surface and cross-section of the PDMS/POSS composite membrane

  8. Pervaporation performance The sorption and diffusion behaviors of components are in agreement with the flux and enrichment factor.

  9. Conclusions and helps ●The solubility coefficients and diffusion coefficients of thiophene, benzene and toluene in the composites at infinite dilution are greater than the other four solvents. ●The addition of POSS enhanced solubility and diffusion coefficients of thiophene, benzene and toluene below 5wt% POSS loading. Helps: ◆通过加入与膜材料性质差异较大的物质可以改变膜的性能。 ◆反气相色谱（IGC）可以用来预测某些膜的分离性能。

  10. Tailoring the Separation Behavior of Hybrid Organosilica Membranes by Adjusting the Structure of the Organic Bridging Group Hessel L. Castricum , Goulven G. Paradis , Marjo C. Mittelmeijer-Hazeleger , Robert Kreiter , Jaap F. Vente , and Johan E. ten Elshof Adv. Funct. Mater. 2011, 21, 2319–2329

  11. Introduction Traditional membrane materials: Organic polymers: lack mechanical stability, lack stability in organic solvent. Zeolite: difficult to grow defect-free thin films. Metal oxides: lack stability for application in water-containing mixtures. Introduce a new membrane material: An organosilica-based hybrid membrane composed of both organic and unorganic covalent links. A key advantage of hybrid organosilica materials is that they combine the network stability of inorganic silica and the versatility of organic polymers.

  12. Membrane preparation 倍半硅氧烷前驱体 使用DLS监测 制备溶胶（控制平均粒径为6nm） 均匀涂覆在ϒ-Al2O3支撑层表面 几种不同的前驱体 热固化（523K，2h，N2环境）

  13. Reactivity The generalized reactions can be described as follows: Step1: Hydrolysis Step2: Condensation

  14. Membrane Structure The thicknesses of the membranes are all in the same range.

  15. Gas Permeation Performance ●H2/N2在M和E中透过比率最高，主要是由于膜的筛分作用，使动力学 直径较小的H2更容易通过。 ● CO2/H2通过比率大于1，主要是由于CO2在膜中的溶解扩散性好，有 机桥接基团起到了重要作用。 ● CO2动力学直径小于CH4，但CO2通量比CH4大，这是筛分与溶解扩散共同作用的结果。

  16. Membrane Pervaperation Performance ●M、E和B膜的分离因子最高。 ●O膜的分离因子低是因为其憎水性强，同时有机桥接基团与正丁醇作用较大，使正丁醇易通过。 ●BP膜分离因子低，主要是由于桥接基团的刚性结构使其膜孔径较大，从而使正丁醇通量增加。

  17. Conclusions and helps ●The membranes separation properties in gas permeation and pervaporation was affected both by the length of the organic bridges and the affinity to adsorption. ● Materials with the shortest bridges may be suitable for size-based molecular sieving. ●CO2 tansports through these materials is dominated by the strong affinity to CO2. ●Strong hydrophobic character may result in a high n-butanol flux in pervaporation. Helps: ◆根据所要分离物质的特性，选择长度、柔韧性合适的桥接基团。 ◆使用动态光衍射（DLS）观测胶粒大小，从而控制合成一定尺寸的胶粒。

  18. Thank you!

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