單步驟製備疏水性二氧化矽氣凝膠薄膜及其於二氧化碳捕捉之應用

Single-step synthesis of hydrophobic silica aerogel membranes for membrane contactors used for carbon dioxide capture

柯家傑(Chia-Chieh Ko)

指導教授 ： 童國倫 ； 林義峯

中原大學/工學院/化學工程研究所/碩士(2013年)

https://doi.org/10.6840/CYCU.2013.00156

摘要

中文摘要
本研究旨在以較低成本之單步驟改質方式製備出適用於薄膜接觸器之疏水性二氧化矽氣凝膠薄膜，並應用於燃燒後處理（Post-combustion）之二氧化碳捕捉，文中將探討薄膜合成條件對薄膜表面性質與二氧化碳捕捉效能之影響。
研究中先探討縮合反應中的鹼催化劑濃度對MTMS氣凝膠薄膜表面疏水程度之影響，結果發現在不同濃度範圍內，鹼催化劑濃度之增加對疏水程度有不同的影響，而藉由薄膜表面形態觀察，證實此疏水程度差異乃因表面氣凝膠之覆蓋情形所導致；接著再於鹼催化劑濃度17%下，嘗試改變縮合反應中的溶劑添加量，發現薄膜表面疏水程度隨溶劑量減少呈現上升趨勢，透過薄膜表面形態觀察與氣凝膠微結構分析，證實疏水程度差異乃因氣凝膠覆蓋均勻性及氣凝膠本身結構所造成。最後於鹼催化劑濃度17%、EtOH2nd/MTMS莫耳比值為1時，製備出具高疏水性與良好表面形態之MTMS氣凝膠薄膜。
隨後以不同合成條件下所製備出之MTMS氣凝膠薄膜進行二氧化碳吸收實驗，比較其穩定所需時間與穩定吸收通量，結果發現穩定所需時間受鹼催化劑濃度影響較小，反觀溶劑量之影響則較為明顯，最後於鹼催化劑濃度17%、EtOH2nd/MTMS莫耳比值為1之條件下，MTMS薄膜擁有極短的穩定所需時間與高達1.25 mmole/m2s的穩定吸收通量，證明具有良好結構之氣凝膠均勻覆蓋於表面能有效降低薄膜潤濕現象，進而大幅提升二氧化碳吸收效能。
最後，對MTMS氣凝膠薄膜進行耐久性測試，結果發現MTMS氣凝膠薄膜本身具有高耐熱性，且於長達四天的連續式操作吸收實驗下，仍保有相當高且穩定的吸收通量，此外，亦藉由氣體反覆沖洗之方式，證實其具有重複使用性，在在證明了經此縮孔後具疏水性陶瓷膜具備良好的耐用性，十分符合實廠應用之需求。

關鍵字

薄膜接觸器 ； 二氧化碳捕捉 ； 陶瓷薄膜 ； 甲基三甲氧基矽烷 ； 二氧化矽氣凝膠

並列摘要

Abstract
The purpose of this study is using a low-cost and single-step procedure to prepare a hydrophobic silica aerogel membrane to apply on membrane contactor for the removal of carbon dioxide in the post-combustion. In this paper, we would investigate the effect of synthesis conditions on the characteristic of membrane surface and the carbon dioxide removal efficiency.
First of all, the investigation about the effect of base-catalyst concentration used in condensation reaction on the degree of hydrophobic of membrane surface was proceeding. As the results, the increasing of base-catalyst concentration made different effects on the degree of hydrophobic of membranes in different ranges of base-catalyst concentration. After observing the surface morphology of membranes, we confirmed these hydrophobic degree differences were attributed to the existence of silica aerogel coverage. Next, based on the appropriate base-catalyst concentration (17%), we further investigated the effect of amount of solvent used in condensation reaction on the degree of hydrophobic of membrane surface. As the results, the hydrophobic degree generally increased with the decreasing of solvent amount. After the surface morphology observation of membranes and the microstructure analysis of aerogel, we confirmed these hydrophobic degree differences were attributed to the uniformity and structure of aerogel coverage. From the results above, we successfully prepared the methyltrimethoxysilane (MTMS)-derived silica areogel membrane with high hydrophobic degree and fine membrane surface morphology.
Subsequently, we did the carbon dioxide absorption test for all the membrane prepared above to compare the time to reach stable and the stable absorption flux. As the results, the time to reach stable was only slightly affected by the base-catalyst concentration, but obviously affected by the amount of solvent. Herein, the MTMS-derived silica aerogel membrane prepared under the appropriate synthesis conditions including base-catalyst concentration for 17% and EtOH2nd/MTMS molar ratio equal to one exhibited extremely short time to reach stable and high stable absorption flux approximately 1.25 mmole/m2s. The results confirmed that the coverage of silica aerogel with fine structure could effectively prevent the wetting of membrane pore and then greatly enhance the performance on carbon dioxide absorption.
Finally, under the optimal synthesis conditions, the MTMS-derived silica aerogel membrane exhibited high and quite stable CO2 absorption flux under continuous operation for four days. Also, the as-prepared MTMS-derived silica aerogel membrane could potentially be used during the post-combustion process in power plants since its excellent reusability.

並列關鍵字

carbon dioxide capture ； membrane contactor ； ceramic membrane ； silica aerogel ； Methyltrimethoxysilane (MTMS)

參考文獻

張昊崴，平板式氟碳薄膜親疏水性對二氧化碳回收效能影響之研究，私立中原大學化學工程學系碩士論文，中壢（2008）。

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