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標題: | 於共溶劑微流道系統中應用電化學高級氧化法降解脫鹼性木質素 Depolymerization of Dealkaline Lignin in the Co-solvent System by Electrochemical Advanced Oxidation in a Microreactor |
作者: | 韋麗音 Lalida Waura-angkura |
指導教授: | 吳嘉文 Kevin Chia-Wen Wu |
關鍵字: | 脫鹼木質素,木質素模型化合物,電化學高級氧化過程,微反應器,共溶劑, Dealkaline lignin,Lignin model compound,Electrochemical advanced oxidation process,Microreactor,Co-solvent, |
出版年 : | 2023 |
學位: | 碩士 |
摘要: | 目前燃料和化學品的生產主要依賴不可再生的石油資源,預計2050年石油將被耗盡。木質素包含羧基和羥基官能團,因此被視為可再生芳香化合物的重要來源,可作為可再生能源生產高價值化學品的替代品。鑒於從木質素中回收芳香族化合物,本研究的重點是在連續微流道系統中應用電化學高級氧化法 (EAOP) 降解脫鹼性木質素。由於陽極處的水產生的羥基自由基是 EAOP 的關鍵,且脫鹼性木質素在水中的溶解度極低,因此與水混溶的共溶劑,例如:四氫呋喃 (THF)、二甲基甲酰胺 (DMF) ,對脫鹼性木質素在水中的溶解度有影響。本研究發現乙腈 (MeCN)、甲醇 (MeOH) 和乙醇 (EtOH) 對脫鹼性木質素在水中的溶解度和反應效率有重要影響。雖然脫鹼性木質素在共溶劑的溶解度順序為: THF > DMF > MeCN > MeOH > EtOH,但是根據電子自旋共振 (EPR)分析,具有較強清除能力的共溶體系產生的羥基自由基濃度較低,從而導致脫鹼性木質素的轉化較小。根據三種選定共溶劑的化學動力學分析,脫鹼性木質素的降解遵循擬一級反應動力學模型,其中使用MeCN當共溶劑的速率常數 (k) 是3.3 x 10-3 s-1,DMF 是1.2 x 10-3 s-1 以及 EtOH 是0.1 x 10-3 s-1。在代表β-O-4 連接木質素模型化合物 (即2-苯氧基-1-苯基乙醇 (PPE)) 中也觀察到相同的趨勢,其中 PPE、共溶劑和水造成這一現象的主要原因。在共溶劑體系中,水跟MeCN體系中的脫鹼性木質素在100秒停留時間和1 mA以下表現出最高轉化率,達到 72%。根據PPE 模型化合物的降解產物,證實了β-O-4在水跟EtOH中的降解主要是遵循Cα-OH/Cα-H的活化和Cα-OH的氧化途徑。 Currently, the production of fuels and chemicals heavily relies on non-renewable petroleum oil, which is projected to be depleted by 2050. Lignin is the largest source of renewable aromatic compounds rich in carboxylic and hydroxyl functional groups, thus potentially being used as a renewable alternative for the production of valuable chemicals. In light of aromatic compounds’ recovery from lignin, this work focuses on the efficient depolymerization of dealkaline lignin using the electrochemical advanced oxidation process (EAOP) under ambient conditions in a continuous-flow microreactor system. As hydroxyl radicals generated from water at the anode are the key to the EAOP and dealkaline lignin has extremely low solubility in water, the effects of water-miscible co-solvents, e.g., tetrahydrofuran (THF), N, N-dimethylformamide (DMF), acetonitrile (MeCN), methanol (MeOH), and ethanol (EtOH), on the solubility of dealkaline lignin in water and the efficiency of the reaction were investigated. While the solubility of dealkaline lignin in THF > DMF > MeCN > MeOH > EtOH, the co-solvent system with a stronger scavenging ability (based on electron spin resonance (EPR) analysis) gave a lower concentration of hydroxyl radicals and subsequently led to the smaller conversion of dealkaline lignin, vice versa. From the kinetic analysis in three selected co-solvents, e.g., MeCN, DMF, and EtOH, the degradation of dealkaline lignin followed a pseudo-first-order kinetic model, where the rate constant (k) in MeCN (3.3x10–3 s–1) > DMF (1.2x10–3 s–1) > EtOH (0.9x10–3 s–1). The same trend was also observed in the lignin model compound representing β-O-4 linkage, i.e., 2-phenoxy-1-phenyl ethanol (PPE), where the stabilization of transition state (TS) between PPE, co-solvent, and water was the one responsible for such trend. Among the co-solvent systems, dealkaline lignin in the water/MeCN system showed the highest conversion of 72% within 100 s of residence time and under 1 mA. Based on the degradation products of the PPE model compound, it was elucidated that the depolymerization of β-O-4 in water/EtOH primarily followed Cα-OH/Cα-H activation and Cα-OH oxidation pathways. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/91559 |
DOI: | 10.6342/NTU202301466 |
全文授權: | 同意授權(限校園內公開) |
顯示於系所單位: | 化學工程學系 |
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