NaA分子筛膜的合成及渗透性能研究

【作者】 吕丹；

【导师】 王金渠；

【作者基本信息】 大连理工大学 ， 化学工艺， 2004， 硕士

【摘要】 由于沸石分子筛膜具有耐高温、耐腐蚀，以及优异的分离性能，因而具有巨大的应用前景，近十多来，沸石膜的研究取得了较大的发展。A型沸石分子筛膜因其独有的小孔径（0.41nm）和亲水特性，在小分子气体分离和渗透蒸发分离有机物中的水分方面有很好的应用前景。本文结合目前A型膜研究的热点和国内研究现状，通过研究影响成膜的多种因素，优化合成条件，用原位水热合成法在大孔α-Al₂O₃载体上制备连续致密的NaA型沸石分子筛膜，并用XRD、SEM、单组分气体渗透对制备的A型膜进行表征，同时尝试了在α-Al₂O₃陶瓷管载体内表面合成NaA分子筛膜。 一、通过考察晶化温度、合成液浓度、合成液碱度、晶化时间等条件对分子筛合成的影响，得到合成NaA分子筛的最佳条件是：按照摩尔配比Na₂O：SiO₂：Al₂O₃：H₂O=7.5：2：1：600选取原料配置分子筛合成液，在95～98℃下晶化3～4小时即得NaA分子筛，其晶体是边长为2.5μm的立方体；通过SEM和XRD确定了在合成NaA分子筛过程中出现的杂晶为P型沸石；依据NaA分子筛的热重分析曲线制定了其焙烧的升温过程。 二、通过考察合成液对NaA分子筛膜合成的影响，选择稀溶液作为合成液较浓溶液易形成连续的分子筛膜；重复晶化可以弥补分子筛膜缺陷，合成出致密的分子筛膜，重复晶化6次的NaA分子筛膜的H₂／N₂理想分离因数达到3.94，超过了Knudsen扩散值3.74：振荡预涂晶种可以填补载体表面较大的缝隙，用水玻璃作为分子筛晶体分散液可以加快分子筛膜的生长；讨论了焙烧分子筛膜产生缝隙的原因及避免方法。以长度为250mm的α-Al₂O₃陶瓷管为载体，采用实验中确定的最佳条件合成NaA分子筛膜，其H₂、N₂、C₃H₈的渗透率分别为1.52×10⁶mol／m²·s·Pa、3.71×10^-7mol／m²·s·Pa、3.11×10^-7mol／m²·s·Pa，H₂／N₂、H₂／C₃H₈的理想分离因数分别为4.10和4.89，超过了Knudsen扩散值3.74和4.69。 三、采用动态水热合成的方法在α-Al₂O₃陶瓷管载体内表面合成致密的分子筛膜，膜厚为20μm，形成的NaA分子筛晶体是“去边”的立方体。膜管的H₂、N₂、C₃H₈的渗透率分别为7.66×10^-7mol／m²·s·Pa、2.32x10^-7mol／m²·s·Pa和1.58×10^-7mol／m²·s·Pa，H₂／N₂和H₂／C₃H₈的理想分离因数分别为3.38和4.87，接近Knudsen扩散值。更多还原

【Abstract】 Zeolite membrane have been attracted much during the last decade because of their unique characteristics, such as thermal, chemical and structural properties compared to polymeric membranes, and great potential applications in the separation. Because of the small pore size (0.41nm) and its hydrophile property, NaA zeolite membrane can be used in the separation of small molecules or separating water from organic substance by penetration.The main work of this thesis is1. In the process of synthesizing NaA zeolite, the influence of crystallization temperature, crystallization solution, crystallization time was studied thoroughly. The result showed that the best crystallization solution was Na2O:SiO2.Al2O3.H2O=7.5:2:1:600, the best crystallization temperature was 95-98 C and the crystallization time was 3-4h. The crystal of NaA zeolite was cube with 2.5 m side.The other crystal in the process of synthesizing NaA zeolite was zeolite P. The process of baking NaA zeolite was set according to TGA.2. Effectsof some important factors on the preparation of zeolite membranes are thoroughly studied. The NaA zeolite membrane was prepare on the a-Al2O3 support. The penetration of H2, N2 and C3Hg were 1.52 10-6mol/m2s-Pa, 3.71 10-7 mol/m2-s-Pa, 3.11 10-7 mol/m2-s-Pa correspondingly. The ideal selectivities of H2/N2, HT/ C3Hg were 4.10, 4.89.3. NaA zeolite membrane was synthesized on a porous a-Al2O3 tube support’s inner surface by a dynamic hydrothermal method. The thickness of membrane was 20 m and zeolite crystals were cubes without side. The penetration of H2 , N2 and C3H8 were 7.66 10-7mol/m2-s-Pa, 2.32 10-7mol/m2-s-Pa, 1.58 10-7mol/m2-s-Pa correspondingly. The ideal selectivities of H2/N2, H2/ C3H8 were 3.38, 4.87.更多还原