高铝含量b取向ZSM-5分子筛膜的制备及渗透性能研究

发布时间：2019-03-20 16:45

【摘要】：ZSM-5分子筛膜在催化及分离等领域均有广泛的应用前景,是当前材料领域的研究热点。b轴取向ZSM-5分子筛膜因短的扩散路径、较低的晶粒互生程度而具有高的渗透通量,预计具有优异的分离和催化性能。但低Si/Al比、高b取向ZSM-5分子筛膜的合成是目前的难点之一。本文采用原位生长法制备b取向ZSM-5分子筛膜并进行结构表征,研究生长条件、载体性质、铝源及铝含量对分子筛膜微观结构的影响规律,探索取向ZSM-5分子筛膜的形成机制。在孔径不同的氧化铝、二氧化钛、氧化锆陶瓷载体上制备了Si/Al比为100(合成液中)的ZSM-5分子筛膜,研究了载体组成和粗糙度对分子筛膜结构的影响。发现,在富含Ti-OH的锐钛矿型二氧化钛载体上,ZSM-5分子筛膜的b取向性及连续性最好。在不锈钢片载体上合成了不同Si/Al比b轴取向ZSM-5分子筛膜,研究了Al3+含量对分子筛膜结构的影响。发现,Al3+的含量不影响分子筛晶粒的取向,但影响分子筛膜的连续性。HP-DSC表征确认,Al3+对分子筛的成核有明显的抑制作用,从而导致分子筛膜的连续性下降。采用多种铝源包括硝酸铝、偏铝酸钠、拟薄水铝石、碱式醋酸铝、异丙醇铝制备了ZSM-5分子筛膜。发现,铝源不影响膜的取向,但影响膜的连续性、骨架Si/Al比和酸强度。采用拟薄水铝石和偏铝酸钠,可以制备得到骨架Si/Al比最低为57和19、连续性大于80%的b取向ZSM-5分子筛膜。采用硝酸铝制备的分子筛膜,酸强度最高,而用异丙醇铝制备的分子筛,酸强度最弱。在多种多孔载体上制备了ab、bb、cb取向的双层分子筛膜。氮气渗透试验结果表明,bb取向的双层分子筛膜具有最高的N2渗透率(2.256?10-5molPa-1s-1m-2),分别较ab和cb取向的双层膜高0.448?10-5molPa-1s-1m-2和0.076?10-5molPa-1s-1m-2。
[Abstract]:ZSM-5 molecular sieve membranes have wide application prospects in the fields of catalysis and separation. The b-axis oriented ZSM-5 molecular sieve membranes have high permeation flux due to their short diffusion path and low grain interaction degree, which are the current research hotspots in the field of materials, and the results show that the b-axis oriented ZSM-5 molecular sieve membranes have high permeation flux due to their short diffusion path and low grain interaction degree. It is expected to have excellent separation and catalytic properties. However, the synthesis of ZSM-5 molecular sieve membranes with low Si/Al ratio and high b-orientation is one of the most difficult problems at present. In this paper, b-oriented ZSM-5 molecular sieve membrane was prepared by in-situ growth method and its structure was characterized. The effects of growth conditions, carrier properties, aluminum source and Al content on the microstructure of molecular sieve membrane were studied. To explore the formation mechanism of oriented ZSM-5 molecular sieve membrane. ZSM-5 molecular sieve membranes with Si/Al ratio of 100 (in synthetic solution) were prepared on alumina, titanium dioxide and zirconia ceramic carriers with different pore sizes. The effects of carrier composition and roughness on the structure of molecular sieve membranes were studied. It was found that the b-orientation and continuity of ZSM-5 molecular sieve membrane were the best on Ti-OH-rich anatase titanium dioxide carrier. ZSM-5 molecular sieve membranes with different Si/Al ratio b-axis orientation were synthesized on stainless steel substrate. The effect of Al3 content on the structure of molecular sieve membranes was studied. It was found that the content of Al3 did not affect the grain orientation of molecular sieve, but affected the continuity of molecular sieve membrane. It was confirmed by HP-DSC that Al3 obviously inhibited the nucleation of molecular sieve, which led to the decrease of continuity of molecular sieve membrane. ZSM-5 molecular sieve membranes were prepared from various aluminum sources including aluminum nitrate sodium metaluminate pseudo-thin bauxite basic aluminum acetate and aluminium isopropyl alcohol. It was found that the Al source did not affect the orientation of the film, but affected the continuity of the film, the Si/Al ratio of the skeleton and the acid strength. By using pseudo-boehmite and sodium metaluminate, the b-oriented ZSM-5 molecular sieve membranes with the lowest skeleton Si/Al ratios of 57 and 19 and continuity of more than 80% can be prepared. The molecular sieve membrane prepared by aluminum nitrate has the highest acid strength, while the molecular sieve prepared with aluminum isopropyl alcohol has the weakest acid strength. Ab,bb,cb oriented bilayer molecular sieve membranes were prepared on various porous supports. The results of nitrogen permeation test show that the bb-oriented bilayer zeolite membrane has the highest N _ 2 permeability (2.256?10-5molPa-1s-1m-2). Compared with ab and cb oriented bilayers, respectively, the bilayer films were higher 0.448?10-5molPa-1s-1m-2 and 0.076 脳 10 mol Pa ~ (1) / s ~ (- 1) m ~ (2) 路(2).
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.893

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