介孔沸石在NaA沸石分子筛膜合成中的应用

发布时间：2018-05-22 20:21

  本文选题：NaA沸石分子筛膜 + 介孔NaA沸石晶体　； 参考：《浙江大学》2015年硕士论文

【摘要】：NaA沸石分子筛膜具有很强的亲水性,在有机物脱水领域有着广泛的应用前景。虽然目前国内外已经有NaA沸石分子筛膜渗透汽化的工业化装置,但是降低NaA沸石分子筛膜的成本仍然是重要的研究方向。采用中空纤维和大孔氧化铝管作载体有望降低NaA沸石分子筛膜的成本。采用中空纤维作载体时可以获得高通量的沸石分子筛膜,但是常用的纳米晶种的制备过程复杂；而采用廉价的大孔氧化铝管作载体时沸石分子筛膜的通量较低。针对这两个问题,本论文进行了以下两个方面的研究：(1)提出采用介孔沸石晶体制备纳米晶种,使用浸涂-滚擦法涂晶,利用二次生长法在中空纤维表面制备沸石分子筛膜；(2)为了充分利用介孔沸石的低扩散阻力,在大孔氧化铝管表面构建介孔沸石组成的分子筛膜。主要的研究内容和结果如下：(1)由介孔NaA沸石剥离的纳米晶体作晶种制备NaA沸石分子筛膜合成了带有介孔的NaA沸石分子筛晶体,简称介孔NaA沸石。通过简单的刮擦和研磨证明了介孔NaA晶体的机械强度低于普通NaA晶体。研磨10 min可以由微米级的介孔NaA晶体得到约10%的纳米晶体,而从普通NaA沸石晶体得到的碎块非常少。因此,采用研磨的介孔NaA晶体晶种液在氧化铝中空纤维载体表面由浸涂法涂晶后,100℃合成仅2h可以诱导生成致密的NaA沸石分子筛膜。将此晶种液离心除去微米级颗粒后,在中空纤维表面浸涂-滚擦涂晶,100℃合成3 h得到的膜层致密均一,对90 wt%的乙醇/水溶液在75℃下的分离因子大于10,000,通量达到8.38kgm-2h-1。而由普通NaA晶体采用相同方法制得的膜层由于缺少足够的晶种而存在明显的孔洞和缺陷。总而言之,纳米NaA晶体容易通过研磨微米级的介孔NaA晶体和低速离心分离(或较长时间沉降)而获得,避免了传统方法合成纳米沸石晶体所需的复杂分离步骤,且收率高。由此获得的纳米沸石晶体不仅能用于沸石分子筛膜的制备,还有望用于催化等其他领域。(2)介孔沸石晶体直接作晶种制备NaA沸石分子筛膜将介孔沸石晶体直接作为晶种采用浸涂-滚擦的涂晶方式,在氧化铝中空纤维载体表面成功制备了NaA沸石分子筛膜。考察了以含有不同介孔体积的NaA-1、NaA-3和NaA-5为晶种合成的膜层分离性能,结果表明沸石晶体含有的介孔体积越高,越容易诱导合成出致密的沸石分子筛膜。当使用NaA-5介孔晶体为晶种时,水热合成1h即可以得到分离因子大于10,000的约600 nm厚的超薄膜,通量高达9.32kgm-2h-1。通过与传统方法合成的180 nm纳米晶体诱导的膜层进行对比,证明了介孔NaA-5晶体刮擦涂晶后在载体表面覆盖了一层大小约为120nm的晶体的晶种层,而且小晶体对于中空纤维载体上成膜具有更好的促进作用。(3)介孔NaA沸石分子筛膜的制备研究尝试了在大孔氧化铝管上构建介孔NaA沸石分子筛膜,考察了合成方式、晶种类型、涂晶方式、合成液碱度和致介孔剂TPHAC(二甲基十六烷基[3-(三甲氧基硅基)丙基]氯化铵)含量以及硅源类型对于介孔NaA沸石分子筛膜形貌和分离性能的影响,然后通过焙烧去除致介孔剂,最后对焙烧后的膜层进行修复。研究结果表明,转动合成的方式能够保证致介孔剂TPHAC在合成液中均匀分散,而且普通NaA沸石晶体比介孔沸石晶体作为晶种更容易诱导致密膜层。与此同时,较低的晶化速率以及适中的TPHAC含量有利于形成致密的介孔NaA沸石分子筛膜,例如以九水硅酸钠为硅源时,采用2.5 Na2O:SiO2:0.67 A12O3:200 H2O: 0.03 TPHAC的配方；或者以晶化速度较慢的硅酸钠为硅源,采用2.2 Na2O:2 SiO2: A12O3:150 H2O:0.03 TPHAC的配方。在除去致介孔剂的方式上,通过350℃焙烧理论上可以除去TPHAC,但是膜层结构发生了坍塌、变形和开裂。采用再次合成的方式可以对焙烧后的NaA沸石分子筛膜进行一定的修复,提高膜层的分离因子。
[Abstract]:NaA zeolite membrane has a very strong hydrophilic property and has a wide application prospect in the field of organic dehydration. Although there have been an industrial device for Pervaporation of zeolite membrane of NaA zeolite at home and abroad, it is still an important research direction to reduce the cost of molecular sieve membrane of NaA zeolite. It is expected to reduce the cost of NaA zeolite membrane. The high throughput zeolite membrane can be obtained when hollow fiber is used as carrier, but the preparation process of the commonly used nanocrystalline species is complex, while the flux of zeolite membrane is low when the cheap macroporous alumina tube is used as the carrier. The following two problems are discussed in this paper. The two aspects: (1) the preparation of nanocrystalline crystals by mesoporous zeolite crystals, the use of dip coating and scrubbing, and the preparation of zeolite membranes on the surface of hollow fibers by the two growth method; (2) in order to make full use of the low diffusion resistance of mesoporous zeolite, the mesoporous zeolite membrane is constructed on the surface of the mesoporous alumina tube. The contents and results are as follows: (1) the mesoporous NaA zeolite membrane was prepared from the mesoporous NaA zeolite to prepare the mesoporous zeolite molecular sieve crystal, which was referred to as mesoporous NaA zeolite. Through simple scraping and grinding, the mechanical strength of the mesoporous NaA crystal was lower than that of the ordinary NaA crystal. The mesoporous NaA crystals of the rice grade obtained about 10% of the nanocrystalline crystals, and the fragments obtained from the ordinary NaA zeolite crystals were very small. Therefore, the grained mesoporous NaA crystal seed liquid was coated on the surface of the alumina hollow fiber carrier by dip coating, and the synthesis of only 2H could induce the formation of dense NaA zeolite membrane. After removing the micron grade particles, dipping on the surface of the hollow fiber and rolling the coated crystal, the film is compact and homogeneous at 100 C for 3 h. The separation factor of the 90 wt% ethanol / water solution at 75 C is greater than 10000, the flux is up to 8.38kgm-2h-1. and the membrane made by the same method by the common NaA crystal is obvious because of the lack of enough crystal. In conclusion, nano NaA crystals are easily obtained by grinding micron mesoporous NaA crystals and low velocity centrifugation (or long time settlement), avoiding the complex separation steps required by traditional methods for the synthesis of nanoscale crystals, and high yield. It is also expected to be used in catalysis and other fields. (2) the mesoporous zeolite crystal is directly prepared for the preparation of NaA zeolite membrane, and the mesoporous zeolite crystal is directly used as the seed of the crystal. The NaA zeolite membrane has been successfully prepared on the surface of the alumina hollow fiber carrier. The NaA-1 with different mesoporous volume is investigated. NaA-3 and NaA-5 are the membrane separation properties synthesized by the crystal. The results show that the higher the mesoporous volume of the zeolite crystal is, the more easy to induce the synthesis of dense zeolite membrane. When NaA-5 mesoporous crystal is used as the crystal, the hydrothermal synthesis of 1H can get a super thin film with a separation factor of about 600 nm thicker than 10000, and the flux is as high as 9.32kgm-2h-1. By comparing the 180 nm nanocrystalline films prepared with the traditional method, it is proved that the mesoporous NaA-5 crystal is covered with a layer of 120nm crystals on the surface of the carrier, and the small crystal has a better promoting effect on the film formation on the hollow fiber carrier. (3) the preparation of mesoporous NaA zeolite membrane The preparation of mesoporous NaA zeolite membrane on the macroporous alumina tube was studied. The synthesis method, crystal type, coating mode, synthetic liquid base degree and mesoporous TPHAC (two methyl sixteen alkyl [3- propyl propyl) ammonium chloride) content and silicon source type on the morphology and separation properties of mesoporous NaA zeolite molecular sieve membrane were investigated. The results show that the method of rotation synthesis can ensure that the mesoporous TPHAC is uniformly dispersed in the synthetic liquid, and that the ordinary NaA zeolite crystal is more likely to induce the compact membrane than the mesoporous zeolite crystal as the crystal. Meanwhile, the lower crystal is lower. The rate and the moderate TPHAC content are beneficial to the formation of dense mesoporous NaA zeolite membrane, for example, using nine sodium silicate as the silicon source, using 2.5 Na2O:SiO2:0.67 A12O3:200 H2O: 0.03 TPHAC, or the silicon source with slower crystallization rate of sodium silicate, using the formula of 2.2 Na2O:2 SiO2: A12O3:150 H2O:0.03 TPHAC. In the way of making mesoporous agent, TPHAC can be removed theoretically by calcination at 350 degrees C, but the structure of the membrane is collapsed, deformed and cracked. The re synthesis method can be used to repair the NaA zeolite membrane after roasting and improve the separation factor of the film.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.893

【参考文献】

相关期刊论文 前1条

1 徐晓春,杨维慎,刘杰,林励吾;微波场中NaA型分子筛膜的快速合成[J];科学通报;2000年08期

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本文编号：1923477