一种简单组装纳米沸石粒子层的方法及其二次法成膜研究

使用一种简单、新颖的纳米沸石晶体自组装方法, 以γ-氨丙基三甲氧基硅烷(AP-TMS)为偶联剂, 成功地实现了纳米A型沸石粒子在多孔不锈钢、陶瓷以及单晶硅表面的沉积组装, 获得了覆盖度高的续、均匀的沸石粒子层. 组装过程在合成釜内分为载体功能化和晶种化两步. 以该沸石粒子层为晶种二次法成膜, 形成了交织生长的连续、均匀的沸石膜, 并用含少量水的苯甲醛混合液评价了微型膜的渗透蒸发性能, 水-苯甲醛分离系数超过10 000以上. 考察了使用γ-氨丙基三甲氧基硅烷(AP-TMS)、γ-氯丙基三甲氧基硅烷(CP-TMS)和γ-巯丙基三甲氧基硅烷(SP-TMS)三种不同偶联剂时, 纳米A型沸石晶体在多孔不锈钢、陶瓷以及单晶硅表面的自组装效果. 研究发现, 使用CP-TMS作为偶联剂时, 只在不锈钢载体上形成较为连续的粒子层, 而使用SP-TMS作为偶联剂时, 在三种载体上纳米A型沸石粒子均不能沉积形成粒子层. 对偶联剂的作用和粒子组装机制进行了讨论和预测.

A Simple Method of Nano-zeolite Crystals Self-assembly and Its Application to Zeolite Membrane Synthesis by Secondary Growth

Zeolite A nano-crystals were readily self-assembled into uniform zeolite layers with high degrees of coverage on the surfaces of different substrates such as porous stainless steel(SS), ceramic and silicon wafer by a simple method employing 3-aminopropyltriethoxysilane(AP-TMS) as linker reagent. The fabrication process involves two steps: (1) surface functionalization by immersion of the substrate into the ethanol solution with linker reagent in an autoclave at 373 K for 3 h; (2) zeolite deposition assembly by immersion of the functionalized substrate into the nano-zeolite suspension in ethanol under the same condition as above step. A continuous, intergrown, uniform zeolite membrane was obtained on the assembled substrate by the secondary growth. The membrane pervaporation was carried out to evaluate the performance of NaA membrane for the separation of water-benzaldehyde mixture in the microreactor assembly at room temperature and 16.7 kPa vacuum pressure. It is shown that the membrane has an excellent selectivity for water. The separation factors for H_ 2 O/benzaldehyde as high as 31 033 and 11 018 were obtained for benzaldehyde feed mass fraction of 99.5% and 97.0%, respectively. Influence of three linkers including AP-TMS, 3-chloropropyltriethoxysilane(CP-TMS), and 3-mercaptopropyltriethoxysilane(SP-TMS) for the zeolite crystals assembly on the substrates was investigated. It is found that using CP-TMS as linker, only a closely packed zeolite layer can be formed on the SS, while SP-TMS as linker, a zeolite layer can not be formed on any of these substrates. The reaction mechanism of the self-assembly and role of the linker were discussed.