Preparation and characterization of tubular carbon molecular sieving membrane by vacuum-assisted dip-coating method and their gas separation properties

管柱式碳分子篩選薄膜因易與觸媒整合且具有高比表面積、高氣體選擇率、優異的熱和化學穩定性，是適合應用在薄膜反應器中的膜材料。 浸塗法是最常被使用在製備管柱式薄膜的方法，此方法僅需將基材透過浸沒、浸滯、抽出、乾燥程序即可完成。然而，浸塗過程中，因受毛細作用力雖可使塗佈液滲入基材而達到修飾粗糙度的目的，但受重力、黏滯阻力的影響，會使薄膜下端膜厚增加，整體膜厚均勻度下降。 本研究利用真空輔助浸塗法來製備管柱式高分子薄膜，選用聚醚醯亞胺（Polyetherimide,PEI）作為高分子前趨物，N-甲基?咯酮(N-methyl-2-pyrrolidone,NMP)與三氯甲烷(Trichloromethane, TCM)作為溶劑，塗佈於多孔管柱式氧化鋁基材上，再藉由高溫裂解得到管柱式碳分子篩選薄膜。探討參數為：基材浸沒與抽出速度、真空輔助系統的影響、塗佈液組成、塗佈次數。 研究結果顯示，真空輔助系統能避免鑄膜液因毛細作用力而滲入基材孔隙，提升選擇層結構平整度；使用三氯甲烷作為溶劑能減緩塗佈液受重力影響，使薄膜整體膜厚值較為均ㄧ；最佳條件為塗佈液濃度10 wt.%、基材浸沒與抽出速度為1 mm/s、塗佈6次，其H2/N2及CO2/N2的選擇係數為8.8與6.7，H2的滲透率為464 Barrer、CO2的滲透率為356 Barrer。Carbon molecular sieve (CMS) tubular membrane is regarded as the promising material for gas separation in membrane reactor due to its advantages such as can be combined with the catalyst easily, high specific surface area, high gas selectivity, and superior heat and chemical stability. Dip-coating is a common method for tubular membrane preparation. The process of dip-coating just includes immersion, retention, withdrawal, and drying steps. However, although the roughness of tubular membrane would be decrease by filling with casting solution through capillary force, the bottom width of tubular membrane would be increased owing to the gravity, resulting in decreased uniformity of membrane. In this study, the CMS tubular membranes were obtained by one step of vacuum-assisted dip-coating and pyrolysis procedure. Porous alumina tube was chosen as supporting material; polyethyleneimine (PEI) was chosen as membrane precursor; N-methyl-2-pyrrolidone (NMP) and Trichloromethane (TCM) were chosen as casting solutions. The effects of vertical immersion velocity, vertical withdrawal velocity, casting pressure, casting solution composition, and coating times on the membrane structure and gas separation performance were discussed in this study sequentially. The results indicated that coating membrane on the porous alumina tube surface by vacuum-assisted dip-coating method could enhance the flatness of CSM tubular membrane surface, resulting in higher gas pair selectivity. Moreover, using TCM as the casting solution could diminish the gravity force effect, resulting in uniform membrane thickness. When control the casting solution concentration = 10 wt.% (TCM as solvent); vertical immersion velocity and vertical withdrawal velocity = 1 mm/s; coating times = 6, the as-prepared CMS tubular membrane exhibited the best gas selectivity of H2/N2 =8.8 and CO2/N2 =6.7 and permeability of H2 464 Barrer and CO2 356 Barrer.摘要 i Abstract ii 總目錄 iv 圖目錄 vii 表目錄 ix 第一章 前言 1 1-1 研究緣起 1 1-2 研究動機 2 1-3 研究目的 4 1-4 研究架構 5 第二章 文獻回顧 8 2-1 氣化複循環發電系統 8 2-2 氣體薄膜分離技術 12 2-2-1 氣體薄膜種類 13 2-2-2 氣體薄膜分離機制與原理 14 2-3 碳分子篩選薄膜 22 2-3-1 碳分子篩選薄膜的孔洞結構 24 2-3-2 碳分子篩選薄膜的製備程序 25 2-3-3 碳分子篩選薄膜分選效能的提升 30 2-3-4 管柱式碳分子篩選薄膜 31 2-4 浸塗法(Dip-coating) 37 2-4-1 浸塗法作用機制 38 2-4-2 浸塗法製程參數 39 2-4-3 浸塗法膜厚公式 53 2-5 文獻總結 56 第三章 研究設備與方法 57 3-1 實驗藥品及氣體 57 3-2 實驗儀器 58 3-3 薄膜製備流程 58 3-4 薄膜特性分析 59 3-5 薄膜氣體滲透試驗 61 3-6 實驗試程 63 第四章 結果與討論 64 4-1 管柱式氧化鋁基材之選擇 64 4-2 浸塗法作用機制對膜厚均勻度的影響 70 4-2-1 毛細作用力、黏性阻力與重力的綜合效應-浸沒與抽出速度之影響 70 4-2-2 毛細作用力-浸沒速度的影響 76 4-3 塗佈液揮發速率與真空輔助系統改善膜厚均勻度 82 4-3-1 塗佈液揮發速率 82 4-3-2 真空輔助系統 84 4-3-3 綜合評估 89 4-4 塗佈次數的影響 94 4-5 塗佈液濃度的影響 97 第五章 結論與建議 101 5-1 結論 101 5-2 未來建議 103 參考文獻 105 附錄 11