矽/鋁基材結構對碳分子篩選薄膜進行氫分離與二氧化碳捕獲之影響

Effects of Si/Al support texture on H2 separation and CO2 capture properties of CMS membrane

江建楷(Chien-kai Chiang)

指導教授 ： 曾惠馨

中山醫學大學/健康管理學院/職業安全衛生學系碩士班/碩士(2012年)

摘要

一般而言，當碳膜孔徑小於5Å時，小分子維度氣體，如H2 (2.8 Å)、CO2 (3.3 Å)、O2 (3.46 Å)、N2 (3.64 Å)及CH4 (3.8 Å)的分離表現將由分子篩選為主要的作用機制。因此，為能獲得次微米孔徑分佈之碳分子篩選薄膜，熱裂解高分子膜成為最被廣泛使用的製備程序。
然而，碳膜與鋁基材所形成之碳/鋁複合薄膜，因有機-無機材料的性質不同，在兩相間會有界面的產生，即應力集中的地方；經熱裂解後，此一應力集中的地方可能因收縮而產生相分離，進而斷裂形成裂縫，影響碳膜之氣體通透分選行為。因此，在本研究中將探討氧化鋁基材的物化特性對碳薄膜之孔洞結構及氣體分選能力的影響。
實驗將使用氧化鋁為碳膜之基材，藉由不同燒結條件與水熱合成處理後，改變氧化鋁基材的孔洞結構、表面粗糙係數及化學官能基。研究所用之碳膜亦將利用熱重分析儀(TGA)、X光繞射儀(XRD)、原子力顯微鏡(AFM)、比表面積分析儀(BET)、紅外線吸收光譜儀(FTIR)及單一氣體滲透測試，來探討使用不同基材所製備之碳分子篩選薄膜的氣體分選特性。
實驗結果發現，氧化鋁基材S1400-2-2因孔隙率及表面粗糙度的綜合效應，使其所支撐之碳膜擁有最佳的氣體分選效率，H2的滲透率為1300 Barrer，H2/CH4的選擇率為174。而矽/鋁基材1100-MFI-1因植種矽晶核後修飾了原氧化鋁的孔洞結構，且因高分子鏈與Si-O及Si-O-Si官能基產生交聯作用，故其所支撐之碳膜的滲透率及選擇率皆明顯增加，H2的滲透率為2223 Barrer，H2/CH4的選擇率為260。不同基材所支撐之碳膜的滲透分選效能大多都超越Robeson’s 2008 upper bound。此結果顯示，本研究所探討的基材改質方法可有限地改善薄膜應用於氣體分離時，滲透率與選擇率平衡得失之限制。

關鍵字

燒結 ； 矽/鋁基材 ； 碳分子篩選薄膜 ； 氣體分離 ； 粗糙係數

並列摘要

In general, carbon materials with a very narrow micropore distribution below 5 A makes possible to separate gas pairs with very similar molecular dimensions via molecular sieving mechanism, such as H2 (2.8 A), CO2 (3.3 A), O2 (3.46 A), N2 (3.64 A) and CH4 (3.8 A). Therefore, to obtain the carbon molecular sieve membrane (CMSM) with ultra-microporous structure, pyrolysis of polymer precursor becomes a main preparation procedure.
However, the selective layer (carbon) cannot be bond well to the Al2O3 support due to the different properties between them. In general, After the composite polymer membrane were formed by the spin coating procedure, there exist interfacial stresses between polymer and support, which builds up and finally are relaxed by forming interfacial gap due to the shrinkage of organic phase during the carbonization process. Thus, in this project, the effect of support physic-chemical characterization on the texture and the gas separation performance of the CMS membrane were investigated.
In this research, alumina disk was selected as substrate material; it’s porous structure, surface roughness and chemical functional groups was modified with different sintering conditions and MFI silica. The characterization of support materials and CMS membrane were investigated by TGA, FTIR, XRD, BET, AFM and SEM.
The results indicated that the CMSM supported on S1400-2-2 substrate shows the best separation performance with PH2= 1300 Barrer [1 Barrer = 1x10-10 cm3 (STP) cm/(cm2 s cmHg)], αH2/CH4 = 174. After modification with MFI silica, the CMSM supported on 1100-MFI-1 substrate shows better H2 permeability of 2223 Barrer and an ideal H2/CH4 selectivity of 260 due to the crosslinking reaction between polymer chain and Si-O, Si-O-Si groups. The results indicated that the permselectivity of carbon molecular sieving (CMS) membrane fabricated in this study can exceed the 2008 Robeson’s trade-off line.

並列關鍵字

Sintering ； Si/Al substrate ； Carbon molecular sieving membrane ； Gas separation ； Surface roughness

參考文獻

[1] H.C. Foley, Carbogenic molecular sieves: synthesis, properties and applications, Microporous Materials, 4 (1995) 407-433.

[2] A.A. Olajire, CO2 capture and separation technologies for end-of-pipe applications A review, Energy, 35 (2010) 2610-2628.

[3] T. Bein, Synthesis and applications of molecular sieve layers and membranes, Chemistry of materials, 8 (1996) 1636-1653.

[4] Y. Xiao, B.T. Low, S.S. Hosseini, T.S. Chung, D.R. Paul, The strategies of molecular architecture and modification of polyimide-based membranes for CO2 removal from natural gas--A review, Progress in Polymer Science, 34 (2009) 561-580.

[5] G. Lu, J. Diniz da Costa, M. Duke, S. Giessler, R. Socolow, R. Williams, T. Kreutz, Inorganic membranes for hydrogen production and purification: A critical review and perspective, Journal of colloid and interface science, 314 (2007) 589-603.