利用固態核磁共振光譜對含胺基中孔SBA-15氧化矽之二氧化碳捕捉效能與吸附機制探討

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Title:	利用固態核磁共振光譜對含胺基中孔SBA-15氧化矽之二氧化碳捕捉效能與吸附機制探討
Other Titles:	Capture and sorption mechanism of CO2 on amine-incorporated SBA-15 mesoporous silica studied by solid-state NMR spectroscopy
Authors:	林仁山;Lin, Jen-Shan
Contributors:	淡江大學化學工程與材料工程學系碩士班張裕祺;Chang, Yu-Chi
Keywords:	胺;二氧化碳;核磁共振;amine;CO2;NMR
Date:	2013
Issue Date:	2013-04-13 11:50:42 (UTC+8)
Abstract:	大氣中二氧化碳含量的增加被認為是造成地球暖化現象的主要元兇之一。因此，高效能且符合經濟效益的二氧化碳捕捉或隔離技術的研發是一重要且刻不容緩的議題。在本研究中，吾人利用中孔洞氧化矽所具備的高比表面積、高孔體積、可調控孔徑以及豐富的表面氫氧基可供官能化修飾等特點，探討並比較以後合成法製備不同含胺化合物中孔洞氧化矽樣品，並利用各種物化光譜與分析實驗技術，如傅立葉紅外線光譜、氮氣等溫吸附/脫附、粉末X-光繞射、元素分析、熱重分析及穿透式電子顯微鏡等，對各種樣品之物化特性詳加鑑定。隨後利用熱重分析儀測試比較各種樣品之二氧化碳吸附效能，並利用一維、二維及偶極回耦等固態核磁共振光譜探討可能的CO2吸附機理。吾人首先合成中孔洞二氧化矽SBA-15做為擔體，而後將各種胺官能基含浸在其孔道中，並探討不同胺基結構、鏈長與負載量之聚乙烯聚胺類，如三乙烯四胺(TETA；含4N)、四乙烯五胺(TEPA；含5N)、五乙烯六胺(PEHA；含6N)等對 CO2吸附效能之影響。實驗結果發現，所合成修飾之吸附劑在未去除模板劑時(樣品以PxN命名；x = 4-6)，由P4N、P5N、P6N所測得之CO2吸附量分別為5.8、5.2和4.7 mmol-CO2/g-adsorbent，其效能遠超過一般公認商業化所需的最低標準(~ 2 mmol/g)。此外，吾人亦發現此類固態吸附劑在經過多次重複吸/脫附之後，其CO2吸附效能並無明顯衰退。在CO2吸附機理方面，吾人由1H MAS、13C與15N CP-MAS以及13C{14N} SPI-R3 RESPDOR等固態核磁共振光譜研究CO2與胺基之間的交互作用與吸附反應產物氨基甲酸酯(carbamate)。吾人由實驗結果可發現SBA-15擔體中P123模板劑的存在與否對CO2之吸附效能並無顯著影響。此外，吾人亦使用二維相關譜(29Si{1H} FSLG-CP HETCOR) NMR技術，探討矽表面在胺官能基擔載前後之變化情形。 The progressive increase in atmospheric carbon dioxide (CO2) content has been held responsible for the global warming phenomena, which has becoming a vital ecological issue. Thus, the R&D of highly efficient and cost-effective technologies for CO2 capture and separation is a demanding task in carbon sequestration. Utilizing the unique characteristics possessed by mesoporous silicas, viz. high surface areas, high total pore volume, controllable pore sizes, and enriched surface hydroxyls available for functionalization etc., this study aims to use them as supports to fabricate various amine-incorporated adsorbents for CO2 capture. These amine-incorporated porous adsorbents were characterized by a variety of different analytical and spectroscopic techniques, such as Fourier-transformed infrared (FT-IR), N2 adsorption/desorption isotherm, powdered X-ray diffraction (PXRD), elemental analysis (EA), Thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). The CO2 uptake capacities and adsorption/desorption kinetics of various solid adsorbents were evaluated by thermogravimetric apparatus. The adsorption mechanism invoked for CO2 adsorption was also explored by solid-state nuclear magnetic resonance (SS-NMR) spectroscopy. The amine-incorporated porous adsorbents were prepared by post-synthesis modification method by loading varied amounts of different polyethylenepolyamines, viz. triethylenetetramine (TETA; 4N), tetraethylenepentamine (TEPA; 5N), and pentaethylenehexamine (PEHA, 6N), onto the as-synthesized mesoporous SBA-15 silica without removing the surfactant (P123) template. The solid adsorbents so fabricated (denoted as PxN; x = 4-6), namely P4N, P5N, and P6N were found to have a maximum CO2 uptake capacity of 5.8, 5.2, and 4.7 mmol-CO2/g-adsorbent, respectively, surpassing the minimum benchmark value (ca. 2 mmol/g) proposed for commercialization. These amine-incorporated solid adsorbents were also found to exhibit excellent durability. Further experiments by solid-state nuclear magnetic resonance (SS-NMR) techniques, such as 1H magic-angle-spinning (MAS), 13C and 15N cross-polarization magic-angle-spinning (CP-MAS) and 13C{14N} Synchronous Phase Inversion Rotary Resonance Recoupling Resonance Echo Saturation Pulse DOuble Resonance (SPI-R3 RESPDOR) NMR, revealed the presence of the carbamate species and verified that the presence of the P123 surfactant template in the SBA-15 silica support has negligible effect on the CO2 uptake. Additional studies by 29Si{1H} FSLG-CP HETCOR NMR spectroscopy further revealed changes in the proximity of the silica surface upon impregnating the amine moieties and during CO2 uptake.
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