| 摘要: | 本研究目的為開發生物質來源之填料，改善聚醚/聚醯胺嵌段共聚物薄膜 (poly (ether-block-amide)，簡稱 Pebax) 分離二氧化碳之性能。生物質來源之含矽填料，係從稻殼中以環境友善之萃取回收程序製備。此外，本研究修飾生物質填料之表面官能基及孔洞特性，並評估其對Pebax薄膜分離CO2性能之影響。實驗結果顯示，葡萄糖酸浸出法可有效去除大部分非矽質成分，從稻殼中回收生物質含矽(biogenic silica, BSi）填料，約達89.91%。萃取回收之 BSi 主要以非晶質結構及中孔型態存在，相對而言，具有較低之表面積及較小之孔隙體積。此外，與現有前處理方法相比，葡萄糖酸浸出法具有較環境友善之特性與優勢，因此，葡萄糖酸可作為 BSi製備之萃取劑。
為進一步改善 BSi 作為 Pebax 薄膜填料之性能，本研究分別評估表面官能基功能及結構特性之修飾等兩種策略。首先，BSi以聚乙烯亞胺（polyethyleneimine，簡稱 PEI）、N-甲基氨基丙基三甲氧基矽烷（N-methylaminopropyl trimethoxysilane，簡稱 MAPS）及2-（2-吡啶基）乙基三甲氧基矽烷（2-(2-pyridyl) ethyl trimethoxy silane，簡稱 PETS）等三種物質與 Pebax薄膜混合，並成功達到薄膜之修飾與官能基功能化之目的。其中，胺基可在填料及聚合物之間，提供非選擇性空隙，並促進 CO2 分離之傳輸作用。整體而言，本研究開發含有胺基官能化BSi 之Pebax薄膜，展現出卓越之CO2分離性能，並超越Robeson 2008年研究結果之上限值。本研究開發之Pebax/BSi-MAPS-10薄膜，具有較佳之分離特性，其中CO2穿透率及CO2/N2選擇性，分別為90.05 Barrer及100.41。此外，Pebax/BSi-MAPS-10亦具有長期操作之穩定性能，深具未來工業應用之潛力。
調整BSi之結構特性，亦具有增強填料-聚合物之相容性，並提供選擇性擴散氣體之通道。本研究以具有環境友善性之溶膠-凝膠法，以葡萄糖酸作為催化劑，與聚乙烯醇 (polyvinylalcohol, PVA）、聚乙烯吡咯烷酮(polyvinylpyrrolidone, PVP）及可溶性澱粉等三種水溶性聚合物，作為結構定向劑(structure-directing agent, SDA)進行試驗。研究結果顯示，PVA/PVP混合物為製備具有均勻粒徑分布之球形中孔含矽奈米粒子(mesoporous silica nanoparticles, MSNs)之最佳SDA。MSNs顆粒與Pebax基質具有良好之界面作用，有助於提高其熱力及機械性能。此外，根據XRD之鑑定分析結果顯示，合成薄膜具有較小之晶面間距值(d-spacing)，有助於促進CO2/N2氣體之擴散。因此，添加10 wt%MSNs之Pebax薄膜，相較於僅有BSi填料之Pebax薄膜，具有更佳之CO2/N2分離性能，並接近Robeson 2008年的上限值。然而，分離性能仍較前述之Pebax/BSi-MAPS-10為差。因此，本研究在薄膜分離CO2/N2性能之試驗結果顯示，胺基官能化改質在改善Pebax薄膜之BSi填料性能，較調整BSi之結構特性有較佳之成效。
;This study aims to develop a biogenic filler to improve CO2/N2 separation performance of poly (ether-block-amide) or Pebax membranes. Biogenic silica filler was derived from rice husk through the eco-friendly recovery process. Its surface functionalities and pore characteristics were consequently modified and their impacts on the CO2/N2 perm-selectivity of Pebax membranes were evaluated.
Gluconic acid leaching could effectively remove majority of non-siliceous components, to recover biogenic silica (BSi) from rice husks with 89.91% efficiency. The recovered BSi was mainly in an amorphous structure and mesoporous profile, with relatively low surface area and small pore volume. In addition, gluconic acid leaching was environmentally preferable compared to the existing pre-treatment methods. In these regards, gluconic acid could be reasonably chosen for BSi preparation.
Two strategies (surface functionalities and textural properties modifications) for improving the BSi performance as a filler in poly(ether-block-amide)/Pebax membranes were investigated. First, BSi was perfectly functionalized with polyethyleneimine (PEI), N-methylaminopropyl trimethoxysilane (MAPS), and 2-(2-pyridyl) ethyl trimethoxy silane (PETS) and incorporated into Pebax matrices. Amines could provide non-selective voids between filler and polymer and enable facilitated transport for CO2 separation. As a result, the Pebax membrane comprising amine-functionalized BSi exhibited remarkable CO2/N2 perm-selectivity beyond Robeson′s upper bound 2008. Pebax/BSi-MAPS-10 became foremost, offering a CO2 permeability of 90.05 Barrer and CO2/N2 selectivity of 100.41. In addition, Pebax/BSi-MAPS-10 was found in a stable CO2/N2 performance for long-term operation, indicating good practicality in industrial applications.
Tuning the textural properties of BSi could enhance filler-polymer compatibility and provide a selective diffusional gas pathway. Thus, an eco-friendly sol-gel method was proposed, with gluconic acid as a catalyst and three water-soluble polymers including polyvinylalcohol (PVA), polyvinylpyrrolidone (PVP), and soluble starch as a structure-directing agent (SDA). The PVA/PVP mixture was the best SDA for preparing spherical mesoporous silica nanoparticles (MSNs) with homogenous particle size distribution. The MSNs particles were found in good interfacial interaction with the Pebax matrix, contributing good thermal and mechanical properties. Besides, a smaller d-spacing value was observed by XRD analysis, promoting a beneficial diffusional pathway for CO2/N2 gases. As a result, Pebax containing 10 wt% MSNs showed better CO2/N2 separation performance compared to Pebax membrane with BSi filler, approaching Robeson’s upper bound 2008. However, it was incomparable with Pebax/BSi-MAPS-10, indicating the eminence of amine functionalization towards the textural properties modification in improving the performance of BSi as a filler in Pebax membranes. |
