乳酸类低共熔溶剂分离油茶壳木质素及结构特性分析

Structural and functional specificity of lignin from camellia oleifera shell obtained by lactic acid-based deep eutectic solvent (DES)

摘要:

以油茶壳为原料，利用两种乳酸类低共熔溶剂（DES）分离木质素，并对其结构、热解特性和抗氧化活性进行分析和评价。结果表明:三乙基苄卡基氯化铵/乳酸（TEBAC/LA）和甜菜碱/乳酸（Bet/LA）DES均表现出良好的木质素分离能力，在固液比1∶20，120 ℃，5 h的反应条件下，木质素提取率分别为77.87%和59.49%。紫外和红外光谱分析结果表明油茶果壳木质素结构保留完整，主要由紫丁香基和愈创木酚基单元结构组成。与TEBAC/LA相比，Bet/LA分离得到的木质素具有相对分子量低和分布窄的特性。此外，从热解特性方面分析，两种木质素的失重速率、失重温度和热解产物均存在显著差异。同时，两种木质素均表现出良好的抗氧化活性，其中Bet/LA对DPPH清除率最高可达84.57%。

Abstract:

Lignin was isolated from Camellia oleifera shell by lactic acid-based deep eutectic solvent (DES). The structure, thermal stability and antioxidant activity of lignin samples were investigated. The results showed that TEBAC/LA and Bet/LA DES exhibited excellent capability of solubilizing lignin from biomass. The yield of lignin was 77.87% and 59.49% after pretreatment at 120 ℃ for 5 h, respectively. UV and FTIR analyses show that the benzene ring structure of lignin remains complete and with syringl and guaiacyl units. Compared to TEBAC/LA, the lignin samples extracted by Bet/LA presented low relative molecular mass, low polydispersity index and homogeneous structure. The weight loss rate, weight loss temperature and pyrolysis product of the two lignin are different, indicating that there are significant differences in the thermal stability of different lignin. Moreover, the two lignin samples showed distinct antioxidant activity. The capability of Bet/LA sample to scavenge DPPH radical were up to 84.57%.