碳質材料的表面改質與鑑定及其應用於水解生物質衍生之葡聚醣的研究

Surface Modification and Characterization of Carbonaceous Materials and its Application on Catalytic Hydrolysis of Biomass-derived Polysaccharides

王家惠(Wang Jia-Hui)

指導教授 ： 鍾博文

國立臺灣師範大學/理學院/化學系/碩士(2018年)

https://doi.org/10.6345/THE.NTNU.DC.066.2018.B05

摘要

本研究利用石油精煉所產出之廢棄碳質材料，介相瀝青(Mesophase pitch)，經由各種化學表面修飾可以將酸性官能基團集中在其層狀結構邊緣上，已達到高的酸表面覆蓋率，且空間上鄰近的官能基可以仿纖維素水解酶上鄰近的羧酸基一般，有效水解纖維素的醣苷鍵斷鍵進而提高葡萄糖產率。以下本研究將使用四種不同的化學改質方式：(1)硫酸修飾(MP-SO3H)、(2)硫酸修飾再經水熱處理(MP-SO3H-HT)、 (3)硝酸修飾(MP-COOH)、(4)次氯酸鈉修飾(MP-Oxy)來合成酸性官能基化的碳質觸媒，並藉由表面分析來鑑定改質後之材料結構穩定度、酸性官能基團的組成等。由酸鹼反式滴定及元素分析計算表面的總酸量及不同酸性官能基團的組成，再藉由粉末X射線衍射計算材料的層間距離以及利用氮氣吸脫附測量材料的比表面積。另外，13C DP-MAS固態核磁共振光譜的分析中觀察到大部分的酸性官能基團位於sp2的碳上，因此可推論主要是在石墨納米結構邊緣上被改質。進一步將此一系列改質後的碳材用來做為水解纖維素的觸媒使用，在與纖維素(分子量約莫7,370 Da)的水解實驗中僅使用酸與纖維素的比例約4.8 mol%的催化劑(MP-SO3H)即可達到約44 mole %的高葡萄糖產率，再者由此催化劑上之酸性官能基團在水溶液中浸出(leaching)所造成的葡萄糖產率低於3 mole %，證實本研究設計之催化劑具有良好的穩定度以致於整個催化反應兼具環保與效率。
除此之外，本研究意外發現在二氧化碳吸附的分析結果中，MP-SO3H-HT具有特別顯著的二氧化碳吸附量約為28 wt% (273K)，由於本碳質材料為一層狀結構，有別於先前文獻所提到需具有孔洞及特定官能基之材料始具有的吸附能力，因此推論此一催化劑未來將有助於應用在二氧化碳吸附及封存。

關鍵字

碳質材料 ； 表面改質 ； 纖維素 ； 水解 ； 二氧化碳吸附

並列摘要

Herein, this study has discovered mesophase pitch (MP) carbonaceous material derived from petroleum waste, can be modified with high surface coverage of acid functional groups on the edges of layered structure, which could be further used as hydrolytic catalysts for hydrolyzing cellulose. This close proximity of acid moiety on aforementioned carbon materials resembles the center of hydrolysis enzymes, which composes of two close carboxylate groups, such as glycosidase. Chemical modification on carbon materials was listed as following: (1) sulfonic acid modification (MP-SO3H), (2) hydrothermal treatments of MP-SO3H (MP-SO3H-HT), (3) nitric acid modification (MP-COOH), and (4) sodium hypochlorite modification (MP-Oxy) and surface properties were characterized both qualitatively and quantitatively. Quantification of acid functionality was determined by the acid-base back-titration and the distance between layered structure was calculated from the powder X-ray diffraction pattern, and surface area can be characterized from nitrogen sorption study. Furthermore, acid groups were observed to be mainly modified on the edge of the graphitic nanostructure for MP structure owing to the diminishing of aliphatic carbon in spectra of 13C DP/MAS solid-state NMR analysis. In addition, hydrolytic performance was carried out by using MP-SO3H with a catalytic ratio of 4.8 mol% (acid groups/cellulose) for hydrolyzing cellulosic polymer of peak molecular weight (7,374 Da) and the results have shown the glucose yield can reach up to 44 mol%. On the other hand, only lower than 3 mol% of glucose yield could be observed during the hydrolytic reaction of leaching sulfonic groups and it further suggested that MP-based catalysts with acidic functionalities exhibited hydrolytically stable, which could lead the entire catalytic processes more effectively and eco-friendly.
In addition, we serendipitously discovered that MP-SO3H-HT exhibited high carbon dioxide uptake upto 28 wt% and it might be attributed to layered structure of carbonaceous material, which was different from the adsorption energetics of porous materials reported previously. Hence, it suggested that this aforementioned carbon material can be potentially employed for the capture and storage of carbon dioxide in the future.

並列關鍵字

carbonaceous materials ； surface modification ； cellulose ； hydrolysis ； carbon dioxide adsorption

參考文獻

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