NaY沸石膜结构的调控及其渗透蒸发性能的研究

发布时间：2018-03-07 15:56

  本文选题：二次生长法　切入点：NaY沸石膜　出处：《太原理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：NaY沸石膜有效孔径为0.74 nm,具有较强的亲水性和极性,适用于大分子物质的分离或者一些性质相似但存在极性差异体系的分离。碳酸二甲酯(DMC)作为一种绿色环保的化工产品,在工业生产中DMC是以甲醇(MeOH)作为原料进行合成的,在反应之后通常存在MeOH和DMC的共沸物,传统分离工艺难以将其分离。MeOH分子动力学直径小于DMC,而且其亲水性和极性均高于DMC。因此,用NaY沸石膜通过渗透蒸发技术分离MeOH/DMC体系时,能够优先吸附MeOH。本论文详细研究了晶种类型及尺寸、载体表面性质和分散介质组成及性质对晶种层质量及成膜的影响,并进一步探讨了恒温和变温晶化对NaY沸石膜微结构的影响。通过透射电子显微镜(TEM)、扫描电子显微镜(SEM)、X-射线衍射仪(XRD)等手段对所合成的沸石晶种、载体、晶种层及制备的NaY沸石膜进行了分析表征,并对沸石膜进行了渗透蒸发分离性能的检测,结果表明:1、晶种尺寸影响晶种层的质量,晶种粒径过小,团聚严重;晶种粒径过大,担载不均匀,有载体裸露。以500 600 nm的小粒径NaY沸石为晶种时,可完全铺满载体。2、载体的表面性质对晶种层的担载及成膜有一定影响,以α-Al_2O_3和多孔不锈钢为载体时,晶种均可以完全铺满载体;其中多孔不锈钢制备的晶种层更为平整,但合成的沸石膜,由于与载体结合力差,存在局部脱落现象。3、以水为单一分散介质,晶种能完全铺满载体,晶种层比无水乙醇作单一分散介质更加平整;而以0.6 wt%的聚二烯二甲基氯化铵溶液(PDDA)作混合分散介质时,晶种可以非常平整的铺满载体,无任何载体裸露,合成的沸石膜也完整致密。4、以小粒径NaY沸石为晶种,以0.6wt%的PDDA水溶液为混合分散介质,在α-Al_2O_3载体上制备高质量晶种层,经100℃恒温晶化7 h,可合成出致密连续的NaY沸石膜;而经过变温晶化(140℃2 h→100℃6 h)合成出的沸石膜,较恒温晶化膜层更薄,但致密性不如前者。5、将100℃恒温晶化7 h的NaY沸石膜在50℃条件下渗透分离MeOH/DMC体系,随着原料液中甲醇浓度的增大(20 80 wt%),总渗透通量增加(0.648 0.796 Kg/(m~2·h)),分离因子降低(24.52 3.24);随着原料液温度的升高(20 70℃),总渗透通量增大(0.278 1.224 Kg/(m~2·h)),分离因子降低(23.52 2.78)。
[Abstract]:The effective pore size of NaY zeolite membrane is 0.74 nm, which has strong hydrophilicity and polarity. It is suitable for the separation of macromolecular substances or some systems with similar properties but different polarity. Dimethyl carbonate (DMC) is a green and environmentally friendly chemical product. In industrial production, DMC is synthesized from methanol MeOH. After the reaction, there are azeotropic compounds of MeOH and DMC. It is difficult for the traditional separation process to separate. MeOH molecular dynamic diameter is smaller than that of DMC, and its hydrophilicity and polarity are higher than that of DMC.Therefore, when NaY zeolite membrane is used to separate MeOH/DMC system by osmotic evaporation, In this paper, the effects of seed type and size, surface properties of carrier, composition and properties of dispersing medium on the quality and film formation of seed layer were studied in detail. The effect of constant temperature and variable temperature crystallization on the microstructure of NaY zeolite membrane was further discussed. The crystal seed and carrier of the synthesized zeolite were obtained by means of transmission electron microscope (TEM) and scanning electron microscope (SEM). The seed layer and NaY zeolite membrane were analyzed and characterized, and the pervaporation separation performance of zeolite membrane was tested. The results showed that the size of seed affected the quality of seed layer, the particle size of seed was too small, the agglomeration was serious, and the particle size of seed was too large. When the small diameter NaY zeolites with a diameter of 500 ~ 600nm are used as seed seeds, the carrier. 2. The surface properties of the carrier have a certain effect on the loading and film formation of the seed layer. When 伪 -Al _ 2O _ 2O _ 3 and porous stainless steel are used as the carrier, the surface properties of the carrier have a certain effect on the loading and film formation of the seed layer, when 伪 -Al _ 2O _ 2O _ 3 and porous stainless steel are used as carriers, The seed layer prepared by porous stainless steel is more smooth, but the synthesized zeolite membrane, due to its poor adhesion with the carrier, has the phenomenon of partial shedding. With water as the single dispersing medium, the seed can be completely covered with the carrier. The seed layer is more smooth than anhydrous ethanol as a single dispersing medium, and when the mixture medium is 0.6 wt% polydiene dimethylammonium chloride (PDDA), the seed can be very flat and covered with the carrier without any naked carrier. The synthesized zeolite membrane is also compact and compact. Using small diameter NaY zeolite as seed and 0.6 wt% PDDA aqueous solution as mixed dispersion medium, high quality seed layer is prepared on 伪 -Al _ 2O _ 3 carrier. After crystallization at 100 鈩，

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