A Novel Aqueous Counter Diffusion Seeding Method for the Preparation of Zeolitic Imidazolate Framework-8 (ZIF-8) Membranes on Ceramic Hollow Fiber Supports for Gas Separation

• Main Authors: Yu-Hsun Wu, 吳于勳
• Other Authors: 童國倫
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/6cbq4d

碩士 === 國立臺灣大學 === 化學工程學研究所 === 105 === Zeolitic imidazolate framework ZIF-8 is one of the best known ZIF structures due to its small aperture size (0.34 nm) which is suitable for the most concerned gas separations, such as H2/CH4 and CO2/N2. Tons of researchers have devoted to preparing the ZIF-8 membranes in the past five years, which makes the ZIF-8 membranes step up to commercialization stage. However, the absence of a reliable and practical preparation process results in a difficulty in commercializing the ZIF-8 membranes. In this study, we proposed a novel counter diffusion seeding method combining with an environment-friendly aqueous secondary growth to synthesize the ZIF-8 membranes on the alumina hollow fiber substrates, which is a scalable, economical and green process practically meeting the industrial requirement. A uniform seeded layer on the substrate, which has been considered as a crucial factor for making the defect-free ZIF-8 membranes by the secondary growth method, could be simply achieved by this novel counter diffusion seeding method. Besides, surface property of the substrate was also demonstrated to play an important role in forming a uniform seeded layer. The effects of the concentration of secondary growth solution and the synthesis temperature for secondary growth on the membrane quality were investigated to find out the optimum synthesis conditions which is using the secondary growth solution with zinc-hmin ratio of 1:50 and synthesizing it at 50 ºC. Additionally, activation drying process was performed to prevent the solvent filled ZIF-8 membranes from forming defects in traditional drying process. To examine the quality of the as-prepared ZIF-8 membranes, the single gas (He, CO2, N2, and SF6) permeation test was conducted. Finally, high quality ZIF-8 hollow fiber membranes can be obtained, achieving a CO2/N2 ideal separation factor as high as 9.14 with a quite high CO2 permeance (2.66 × 10-7 mol m-2 s-1 Pa-1) and the He/SF6 ideal separation factor of 50.57 (with He permeance 3.01 × 10-7 mol m-2 s-1 Pa-1), which demonstrates the scalable preparation process proposed in this study is promising and reliable.