小孔沸石分子筛膜的制备、表征及渗透性能研究

发布时间：2018-03-03 15:12

本文选题：小孔沸石分子筛膜　切入点：大孔载体　出处：《大连理工大学》2015年博士论文　论文类型：学位论文

【摘要】：在微孔材料中,小孔沸石分子筛(如：SAPO-34、AlPO-34及DD3R)由于具有较小的孔径和良好的热力学、化学及结构稳定性,被广泛认为是理想的气体分离膜材料,尤其对小分子气体具有较好的渗透分离作用。然而多数小孔沸石分子筛成膜困难,为使其在载体表面成核均匀、获取较高的分离选择性,通常将其制备于表面平均孔径较小的载体上,这不但极大提升了制膜成本,也使气体渗透通量大幅度降低,不利于工业化进程的推进。本文以廉价的大孔α-Al2O3为载体,制定不同的制膜策略,构建高性能小孔沸石分子筛膜,主要工作如下： (1)为修饰大孔载体表面缺陷,提高载体与晶种层之间的结合力,从而在廉价大孔载体上制备出高性能的SAPO-34分子筛膜,提出蒸汽辅助转化涂晶方法,将含有晶种的干凝胶浆料涂覆于大孔载体表面,经过蒸汽转化作用使凝胶层晶化成晶种层,并系统考察了掺杂晶种尺寸及干凝胶浆料涂覆次数对SAPO-34分子筛膜的影响。研究发现,当涂覆2次含500nm晶种的干凝胶浆料时制得的晶种层薄而连续,在此基础上制备的SAPO-34分子筛膜显示了良好的气体分子筛分作用,其中H2通量高达6.96×10-6mol·m-2s-1Pa01, H2对CH4、C3H8及i-C4H10的理想选择性分别为14.8、26.5及53.0。 (2)为简化SAPO-34分子筛膜的制膜工艺,有效利用有机模板剂,提出晶种诱导干凝胶转化法。通过优化制膜条件,分别考察了涂覆干凝胶的浓度、凝胶中掺杂晶种的尺寸及蒸汽相组成对成膜的影响,从而得到高质量的SAPO-34分子筛膜,对该膜进行气体渗透性能表征,H2通量为7.04×10-6mol·m-2s-1Pa-1, H2/C3H8和H2/i-C4H10理想选择性可达25.4及50.6。探讨了该方法的成膜机理,当蒸汽相中含有模板剂时,其与干凝胶中的模板剂共同作用,有利于凝胶层中晶核的生成,进而有效填补了晶间缺陷。 (3)为提高大孔载体表面晶体成核密度,制备出连续且孪生性较好的AlPO-34分子筛膜,采用绿色可循环的离子液体作为溶剂,利用二次生长法,在无模板剂N-甲基咪唑(N-MIm)的条件下分别对HF含量、晶种层的种类及水的含量等条件进行考察。在适量水及晶种层的共同作用下,制备得到了高质量的AlPO-34分子筛膜,并取得了较好的气体渗透性能,H2通量为9.74×10-8mol·m-2s-1Pa1, H2/CO2、H2/CH4、H2/C3H8以及H2/i-C4H10理想选择性分别为7.49、14.6、39.3及65.8,优于离子热下制备的其它分子筛膜。 (4)为缩短Si-DD3R分子筛的诱导期,利用微波辅助法,在氟离子及乙二胺(EDA)的双助剂作用下,可得到含晶核的前躯体,经干凝胶转化后制备了尺寸约为30nm的Si-DD3R分子筛,合成时间由25天缩短至4天。利用前躯体中晶核的诱导作用,经球磨晶种诱导干凝胶转化涂晶法,提高载体表面成核点,考察了干凝胶转化时间对晶种层及膜层的影响,其中转化3天后的晶种层可诱导出连续且结晶度较高的膜层,H2/i-C4H10理想选择性为43.8。为进一步提高膜的性能,提出二次修补法,以Si-DD3R的缺陷膜为基底膜,进行打磨处理,使大量晶核暴露出来,增加载体表面成核密度。优化二次生长条件,在较高合成凝胶浓度下所制得的Si-DD3R分子筛膜具有良好的渗透分离性能,H2通量为7.35×10-8mol·m-2s-1Pa-1,H2对CH4、C3H8及i-C4H10理想选择性分别达到8.77、29.2及57.4。对其进行温度依存性测试,并与SAPO-34及AlPO-34分子筛膜对比,Si-DD3R分子筛膜在较苛刻的条件下依然可以保持较高的分离性能,展示了小孔分子筛膜在一些实际分离中的潜在应用价值。
[Abstract]:In microporous materials, pore zeolite molecular sieve (such as: SAPO-34, AlPO-34 and DD3R) as with a smaller pore size and good thermal, chemical and structural stability, is widely regarded as the ideal gas separation membrane materials, especially for small molecular gas has good separation effect. However, the majority of penetration into the hole zeolite molecular sieve in order to make the film difficult, on the surface of the carrier nucleation uniformity, obtain higher selectivity, usually the preparation of carrier on the surface of average pore size smaller, which not only greatly enhance the preparation cost, the gas permeation flux is greatly reduced, is not conducive to the advancement of industrialization. In this paper, macroporous alpha -Al2O3 cheap as the carrier, making films of different strategies, construct high performance pore zeolite membrane, the main work is as follows:
(1) for the modified macroporous carrier surface defects, improve the binding force between the carrier and the seed layer, thus producing high performance SAPO-34 molecular sieve membrane in inexpensive macroporous support system, put forward the steam assisted conversion coating method, containing seed dry gel slurry is coated on the surface of the macroporous carrier, after the effect of steam reforming of gel layer crystallization into the seed layer, and investigated the effect of doping the crystal size and dry gel coating times on SAPO-34 zeolite membrane. The study found that the coating containing 2 500nm seed seed dry gel slurry prepared thin and continuous, SAPO-34 molecule on the basis of preparation of zeolite membranes showed good gas molecular sieving effect, the H2 flux is 6.96 * 10-6mol, m-2s-1Pa01, H2 on CH4, C3H8 and i-C4H10 ideal selectivity were 14.8,26.5 and 53.0.
(2) to simplify the membrane preparation process of SAPO-34 molecular sieve membrane, the effective use of organic template, the seed induced by the dry gel conversion method. Through the optimization of preparation conditions were investigated, the concentration of gel coating dry gel size and vapor doping seed phase composition on the influence of the film, so as to get the SAPO-34 zeolite membrane with high quality, gas permeability characterization of the membrane flux is 7.04 * 10-6mol, H2, m-2s-1Pa-1, H2/C3H8 and H2/i-C4H10 and 50.6. ideal selectivity up to 25.4 of the film forming mechanism of the method, when the vapor phase contains the template, the template interaction with dry gel, is conducive to the gel layer MICROTEK nuclear generation, thus effectively fill the intergranular defects.
(3) to improve the nucleation density of crystal macroporous carrier surface prepared by continuous and twin well AlPO-34 molecular sieve membrane, using ionic liquid as solvent green can be recycled two times, using the method of growth, in the absence of template N- methyl imidazole (N-MIm) conditions respectively for HF content of to investigate the seed layer type and water content. In the interaction of water and seed layer, prepare AlPO-34 zeolite membrane with high quality, and achieved good gas permeability, H2 flux is 9.74 * 10-8mol, m-2s-1Pa1, H2/CO2, H2/CH4, H2/C3H8 and H2/i-C4H10 ideal selectivity were 7.49,14.6,39.3 and 65.8, better than the ion thermal for other molecular sieve membrane preparation.
(4) for the induction period of Si-DD3R molecular sieve, using microwave assisted method in fluorine ion and ethylenediamine (EDA) of the two additives, can be obtained with the nucleation precursor by dry gel conversion after preparation of the size of Si-DD3R 30nm molecular sieve, the synthesis time is shortened from 25 days to 4 days. Using the induction effect of the precursor of MICROTEK core seed induced by ball milling, dry gel conversion coating method, improve the nucleation point on the surface of the carrier, the dry gel conversion time of seed layer and coating effects, including 3 days of the seed layer can induce the crystallization degree is high and continuous film the H2/i-C4H10 ideal selectivity for 43.8. to further improve the performance of the membrane, the two repair method, basement membrane to membrane Si-DD3R defects, grinding processing, so that a large number of nuclei exposed, increase the nucleation density of the surface of the carrier. The two optimal growth conditions in the synthesis of high concentration gel Si-DD3R molecular sieve prepared under membrane has good separation performance, H2 flux is 7.35 * 10-8mol, m-2s-1Pa-1, H2 on CH4, C3H8 and i-C4H10 were respectively 8.77,29.2 and 57.4. ideal selectivity of the temperature dependence of the test, and sieve membrane compared with SAPO-34 and AlPO-34 molecules, Si-DD3R molecular sieve membrane in more demanding the conditions can still maintain a high separation performance, showing the small molecular sieve membrane separation in some practical application value.

【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ051.893

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