凝胶体系NaA沸石膜及其水热稳定性的研究

发布时间：2018-06-25 04:10

本文选题：NaA沸石膜 + 渗透蒸发　；参考：《大连理工大学》2015年硕士论文

【摘要】：针对NaA沸石膜应用渗透蒸发技术进行有机物脱水中的沸石膜水热稳定性问题,使用大孔β-Al2O3为载体,采用凝胶合成液体系与澄清合成液体系成功制备NaA沸石膜,比较二者在不同醇类脱水中的水热稳定性,初步探讨了影响水热稳定性的因素。(1)在不添加模板剂的情况下,采用水热合成法,考察了不同硅源(硅溶胶,Na2SiO3·9H2O, TEOS)对NaA分子筛的结晶度、形貌、粒径的影响。采用硅溶胶作为硅源成功合成了立方晶体状的亚微米级NaA分子筛。以硅溶胶为硅源,探讨了陈化时间、晶化时间、无机盐对分子筛产物的作用。优化后的合成条件为：30℃陈化15h,90℃晶化16h。无机盐同样对NaA分子筛有影响。添加NaCl显著提高了产物的结晶度,NaCl浓度越高,结晶度越高；添加Na2SO4则出现了其他晶体,说明在Na2SO4作用下,产物趋向于生成更稳定的晶体,影响产品纯度。添加0.05 Na2SO4,产物中出现了NaX；添加0.1 Na2SO4产物中出现了方钠石。(2)在固定硅铝比的情况下,按照摩尔比Al2O3:2SiO2:XNa2O:YH2O,研究了膜合成因素凝胶合成液碱度,水量,晶化时间对膜性能的影响规律。优化确定最佳合成液摩尔组成Al2O3:2SiO2:2.2Na2O:240H2O,晶化时间为4-4.5h。用扫描电镜表征膜的形貌和厚度。SEM显示形成厚度为5-7μm连续致密的膜层。利用乙醇含量为90wt.%的乙醇水原料液在348K进行渗透蒸发实验来考察其分离性能。PV测试实验结果显示渗透侧水含量为99.8583wt.%,其分离因数α≥6,000以上,通量F可达1.970kg/(m2·h)。(3)按照组成摩尔比Al2O3:5SiO2:50Na2O:1000H2O配置澄清合成液,在25℃陈化6h,80℃动态晶化5h,在管式α-Al2O3载体表面成功制得NaA沸石膜(膜X),其厚度为4-5μm。将其与凝胶合成液制得的膜(膜N)进行水热稳定性的对比,膜N与膜X进行连续性的PV实验,做通量F与渗透侧水含量的时间依存性曲线。实验结果表明：(a)膜N在不同醇水分离体系、不同温度、不同水量的原料液中,均具有优异的水热稳定性,经过长时间的PV实验,仍保持较高的分离效果,但通量出现了明显的下降；(b)膜X在经过连续性的PV测试后,完全丧失分离效果,即a=1,同时通量出现了大幅升高。且水量越高、温度越高,失去分离效果的时间越短。膜X在低水含量的条件下相对稳定； (c)膜X在PV后的SEM中可见裂痕及针孔状缺陷,表明在载体管与膜的热膨胀系数不匹配,晶间相在高水含量下不稳定。膜N的SEM图中未见针孔及裂痕。PV测试后,膜N与膜X的结晶度少量提高,并出现了新的特征峰,推测可能为SOD。
[Abstract]:The hydrothermal stability of zeolite membrane in the dehydration of organic matter by pervaporation was applied to the NaA zeolite membrane. Using the macroporous beta -Al2O3 as the carrier, the NaA zeolite membrane was successfully prepared by using the gel synthesis liquid system and the synthetic liquid system. The hydrothermal stability of the two groups in different alcohols dehydration was compared, and the water thermal stability was preliminarily discussed. (1) the influence of different silicon sources (silica sol, Na2SiO3. 9H2O, TEOS) on the crystallinity, morphology and particle size of NaA molecular sieves was investigated by hydrothermal synthesis without the addition of template agent. The cubic crystalline submicron NaA molecular sieve was successfully synthesized by silica sol as a silicon source. The silica sol was used as the silicon source to explore Chen Huashi. The optimum synthesis conditions are: aging 15h at 30 C and crystallization of 16h. inorganic salts at 90 degrees C also have an effect on NaA molecular sieves. Adding NaCl significantly improves the crystallinity of the products, the higher the NaCl concentration, the higher the crystallinity, and the addition of Na2SO4 to other crystals, indicating that the production of Na2SO4 is produced under the action of Na2SO4. The product tends to produce a more stable crystal and affects the purity of the product. Adding 0.05 Na2SO4, NaX appears in the product, and the addition of 0.1 Na2SO4 products in the product. (2) under the condition of the ratio of fixed silicon to aluminum, the film synthesis factors are studied in accordance with the molar ratio Al2O3:2SiO2:XNa2O:YH2O. The optimum composition of the synthetic liquid was determined by Al2O3:2SiO2:2.2Na2O:240H2O. The crystallization time was 4-4.5h.. The morphology and thickness of the membrane were characterized by scanning electron microscope (SEM) and the thickness of.SEM was shown to form a continuous and dense film with a thickness of 5-7 mu m. The separation performance.PV was investigated by the pervaporation experiment of ethanol water raw material with ethanol content as 90wt.% in 348K. The test results show that the water content of the osmotic side is 99.8583wt.%, the separation factor is more than 6000 and the flux F can reach 1.970kg/ (m2. H). (3) the clarified synthetic liquid is arranged in accordance with the molar ratio Al2O3:5SiO2:50Na2O:1000H2O, and the 5h is crystallized dynamically at 25, 80, and 6h, and the NaA zeolite membrane (X) is successfully prepared on the surface of the tubular alpha -Al2O3 carrier. The thickness of the membrane is of the thickness. The thermal stability of the membrane (membrane N) produced by the gel synthesis solution is compared with 4-5 m.. The membrane N and the membrane X are continuous PV experiments, and the time dependence of the flux F and the osmotic water content is made. The experimental results show that (a) the membrane N has excellent water and heat stability in different alcohol water separation systems, different temperature and different water content. Qualitatively, after a long time PV experiment, the high separation effect remained high, but the flux decreased obviously; (b) after the continuous PV test, the membrane X completely lost the separation effect, that is, a=1, and the flux increased greatly. And the higher the water, the higher the temperature, the shorter the time of the separation effect. The condition of the membrane X in the low water content It is relatively stable; (c) the crack and needle hole like defects of the membrane X in the SEM after PV show that the thermal expansion coefficient of the carrier tube and the membrane is not matched, the intercrystalline phase is unstable under the high water content. The crystallinity of the membrane N and the membrane X is slightly higher after the SEM diagram of the membrane N is not tested, and a new characteristic peak is presented, presumably for SOD..
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.893

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