Knowledge Management System Of Institute of process engineering,CAS
|Place of Conferral||北京|
|Keyword||渗透汽化 杂化膜 渗透通量 分离因子|
渗透汽化是一种利用被分离溶液各组分在膜中的溶解扩散速率的不同实现分离的膜分离技术。渗透汽化具有能耗低、分离性能高、无污染等优点，在挥发性有机物溶液 (如乙醇-水) 的分离和浓缩过程中，具有明显的技术优势和经济优势。目前，渗透汽化透醇膜的渗透通量和分离因子都比较低，难于满足工业需求。本论文采用水热合成法制备全硅沸石，系统地研究了有机杂化膜的制备，并制备了高性能的复合膜，探讨了渗透汽化的传质过程。首先，本论文分别在碱性(OH)和中性(F)条件下合成了两种对乙醇具有优良吸附性的全硅沸石(silicalite-1(OH)和silicalite-1(F))。通过研究反应温度、反应时间、模板剂含量和水含量等，优化了沸石的合成工艺。利用FT-IR，XRD，NMR，IGA等方法表征全硅沸石，结果表明silicalite-1(OH)和silicalite-1(F)都具有MFI型晶体结构， 且silicalite-1(F)的粒径明显大于silicalite-1(OH)，silicalite-1(F)的疏水性要高于silicalite-1(OH)。以PDMS为有机基体，全硅沸石为填充材料，系统地研究了不同沸石种类、沸石填充量对渗透汽化均质膜性能的影响。研究表明，在50 oC下分离5 wt%的乙醇-水溶液，silicalite-1(F)均质膜的分离因子最高为23.8，silicalite-1(OH)均质膜的分离因子最高为23。在相同填充量下，silicalite-1(F)均质膜的分离因子要高于silicalite-1(OH)均质膜。但由于silicalite-1(F)的粒径较大，silicalite-1(F)的最大填充量仅为40 wt%，而silicalite-1(OH)的最大填充量为60 wt%。采用多种硅烷偶联剂对silicalite-1(OH)进行疏水改性，提高silicalite-1(OH)与PDMS之间的兼容性，减少两者界面处的缺陷。通过FT-IR，CA，TGA，NMR等测试表明硅烷偶联剂成功地接枝到沸石表面，沸石的疏水性得到极大提高。其中，以乙烯基三乙氧基硅烷为偶联剂对沸石改性后，沸石与PDMS的亲合性最好，最佳分离因子为34.3。以Maxwell模型为基础，进一步研究了沸石填充量与渗透汽化均质膜性能的关系，成功地建立了关于沸石填充量与渗透汽化杂化膜性能的数学模型，此模型与实验数据吻合性良好。在上述研究基础上，为进一步提高渗透汽化膜的渗透通量，采用聚丙烯腈 (PAN)超滤膜为基膜制备渗透汽化复合膜。此外，采用等离子体技术将正十六烯引入PAN膜表面，修饰PAN膜的孔道，并提高PAN膜表面的疏水性，进而制备渗透汽化复合膜。当料液温度为50 oC，分离5 wt%的乙醇-水溶液，渗透通量为1733 g·m-2h-1，分离因子为17.7。以改性沸石杂化均质膜，研究了料液温度、乙醇浓度、料液流速、下游侧压力等操作参数对渗透汽化膜性能的影响。利用Aspen V7.3.2 计算了乙醇的气液平衡曲线，发现渗透汽化膜的分离性能远高于气液平衡线。根据串联阻力模型，计算得到渗透汽化膜和渗透汽化边界层的传质阻力。通过增加料液流速，可以有效地抑制膜表面的浓差极化现象。同时，研究了料液温度、乙醇浓度、料液流速、下游侧压力等对复合膜的性能的影响。;
Pervaporation (PV) is a membrane separation technology, which separates liquid mixture by the different solubility and diffusivity through a dense membrane. PV has obviously technical and economical superiority in recovery volatile organic compounds from dilute solution (ethanol-water) due to its remarkable advantage such as low energy cost, high separation efficiency and environment-friendly. In this paper, silicalite-1 was prepared by hydrothermal synthesis and then incorporated into Polydimethysiloxane (PDMS) to prepare PV membranes. And the preparation of dense membranes and composite membranes were studied indetail as well as the mass transfer in PV process.In this thesis, silicalite-1(OH) and silicalite-1(F) with high adsorbability to ethanol were prepared in alkaline (OH) and fluoride media (F) respectively and the preparing conditions such as reaction temperature, reaction time, and the amount of template and water were optimized. And these silicalite-1 particles were characterized by FT-IR, XRD, NMR and IGA. The results indicated that both the silicalite-1(OH) and silicalite-1(F) were the MFI type. And compared with silicalite-1(OH), silicalite-1(F) showed larger size and was more hydrophobic.These silicalite-1 particles were incorporated into PDMS to prepare dense membranes and the performance of the corresponding membranes was investigated in details. When used to separate a 5 wt% ethanol solution at 50 oC, for the PDMS/ silicalite-1(OH) hybrid membranes, the highest separation factor (23.0) was obtained at 60 wt% silicalite-1 loading, while it was found to be 23.8 at 40 wt% silicalite-1 loading for the PDMS/silicalite-1(F) membrane. To further improve the hydrophobicity of silicalite-1(OH), several silane coupling agents were used to modify silicalite-1(OH). The modified silicalite-1 and corresponding membranes were characterized by FT-IR, CA and TGA. These results confirmed that the silicalite-1 was successfully modified by various alkoxysilanes. After modification, the hydrophobicity of silicalite-1 was greatly improved. Silicalite-1 grafted with vinyl group showed the best compatibility with PDMS, and the resulting membranes had the highest separation factor (34.3) to ethanol. In order to further study the effect of silicalite-1 loading on the performance of the hybrid membranes, a novel model based on Maxwell model was proposed to predict the performance of the hybrid membranes. And both the permeability and selectivity obtained by the proposed model were in consistent with the experiment data.In order to increase the flux of PV membranes, based on dense membranes, composite membranes were prepared by dip-coating used polyacrylonitrile (PAN) ultrafiltration membranes as the support. In addition, the PAN support was grafted with 1-hexadecene by plasma. The pore size of the support was modified and the surface was more hydrophobic. This novel PDMS/Silicalite-1/PAN composite membrane exhibited a flux of 1733 g·m-2h-1 with the separation factor of 17.7。Based on dense membranes, effects of feed temperature, ethanol concentration, downstream pressure and feed flow rate on the performance of PV membranes were studied in detail. The vapor liquid equilibrium for ethanol was computed using Aspen V7.3.2. It was found that the performance of PV membranes was far beyond the vapor liquid equilibrium. According to the model of resistance in series, the resistance of mass transfer for membrane and boundary layer were calculated. The concentration polarization could be eliminated by increasing the flow rate. In addition, effects of feed temperature, ethanol concentration, downstream pressure and feed flow rate on the performance of composite membranes were investigated.
|庄晓杰. 新型有机无机杂化渗透汽化透醇膜的研制及性能研究[D]. 北京. 中国科学院研究生院,2015.|
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