表面修飾規則中孔洞碳材吸附二氧化碳之研究

The CO2 adsorption on modified ordered mesoporous carbon

林誼真(Yichen Lin)

指導教授 ： 劉雅瑄

國立臺灣大學/理學院/地質科學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.01867

摘要

本研究以水熱法合成高比表面積之規則中孔洞碳材（OMC），以硝酸氧化修飾中孔洞碳材（OMCA），增加含氧之官能基，之後以迴流嫁接法接合不同胺基批覆量（5、10及20 wt%）及不同種類之胺基分子（四乙烯戊胺，Tetraethylenepentamine，TEPA；三（2-胺基乙基）胺，Tris（2-aminoethyl）amine，TAEA；聚乙烯亞胺，Polyethylenimine，PEI）進行胺基修飾。利用X光粉末繞射儀（XRD）、氮氣等溫吸附-脫附儀（BET）、場發射式掃描電子顯微鏡（FESEM）及穿透式電子顯微鏡（TEM）鑑定所製備的中孔洞碳材之結構及外觀形貌，以傅立葉轉換紅外光譜儀（FTIR）及元素分析儀（EA）探討材料之表面官能基及元素含量，並鑑定胺基修飾材料之表面接合胺基量及孔徑大小差異。在二氧化碳吸附測定方面，利用重量法及體積法評估材料的二氧化碳吸附量，並計算出胺基之氮原子利用效率（CO2/N ratio）。最後利用原位紅外光譜儀（In-situ FTIR）判斷二氧化碳吸附後之產物，以解釋反應機制。
實驗結果顯示，在TEPA及TAEA方面，10 wt%為最適批覆量，而OMCA-
TEPA-10有最高之吸附量，多於OMCA-TAEA-10及OMCA-PEI-10。體積法之結果顯示，OMCA-TEPA-10有最高之化學吸附量，13.23 μg/m2，多於OMCA-TAEA-10之12.96 μg/m2，及OMCA-PEI-10之7.03 μg/m2。然而在氮原子利用效率上，OMCA-TEPA-10卻為最低值0.027，低於OMCA-TAEA-10之0.037及OMCA-PEI-10之0.031，此因TEPA之長直鏈分子的立體障礙所導致。在原位紅外光譜儀的結果，則發現三種胺基有carbamic acid及carbamate的共同吸附產物，且吸附產物在不同溫度下的訊號強弱變化趨勢與化學吸附量之變化趨勢相同。1

關鍵字

中孔洞碳材 ； 二氧化碳吸附 ； 胺基修飾 ； 體積法 ； 原位紅外光譜儀

並列摘要

In this study, the ordered mesoporous carbon (OMC) with high surface areas and high pore volume was prepared by hydrothermal method, and then modified by nitric acid solution, which was named OMCA. OMCA materials were modified by grafting different amine separately, which were tetraethylenepentamine (TEPA) , tris（2-aminoethyl）amine (TAEA) and polyethylenimine (PEI), and loaded with varied amounts (5, 10 and 20 wt%). The textual, structural properties, and surface morphology of all prepared materials were characterized by powder X-ray diffraction (XRD), N2 sorption isotherms, transmission electron microscopy(TEM) and Fourier transform infrared (FTIR) spectroscopy. Carbon dioxide capture capacity of amine-modified mesoporous carbon was obtained by thermogravimetric analysis (TGA) and volumetric adsorption analyzer (BET); the latter was also used to investigate the adsorption performance on CO2/N ratio. The reaction mechanisms of CO2 adsorption on amine-grafted OMCA were confirmed by infrared spectroscopy.
The experimental results indicated that the optimal amine loaded amount is 10 wt% for OMCA-TEPA and OMCA-TAEA material. OMCA-TEPA-10 has highest adsorption amount. The results of the volumetric method showed that OMCA-
TEPA-10 also had the highest chemical adsorption amounts, 13.23 μg/m2,which was more than OMCA-TAEA-10, 12.96 μg/m2 and OMCA-PEI-10, 7.03 μg/m2. The CO2/N molar ratio were 0.027、0.037 and 0.031, respectively. OMCA-TEPA-10 had highest chemical adsorption amounts but lowest CO2/N ratio due to the steric hindrance. By in-situ FTIR spectroscopy, we showed that the amine groups reacted with CO2 and formed carbamic acids and carbamate under dry conditions. The intensities of ammonium carbamate, carbamic acids and carbamate changed with temperature, and the chemical adsorption intensities had the same trends.

並列關鍵字

mesoporous carbon ； CO2 adsorption ； amine-modified ； volumetric method ； in-situ FTIR

參考文獻

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