阿拉伯木聚糖在咪唑型离子液体中的溶解规律及溶解机理

Hemicellulose, cellulose and lignin are the three main components of lignocellulosic biomass. In-depth knowledge of dissolution law and dissolution mechanism of the three main components of lignocellulosic biomass in ionic liquid is crucial for the design of ionic liquids to efficiently pretreat biomass and fractionate its three main components. However, the dissolution rule and dissolution mechanism of hemicelluose in ionic liquid medium are still not clear today. In the present study, arabinoxylan from bamboo and imidazolium-based ionic liquid are employed as model of hemicellulose and solvent, respectively. The dissolution law of arabinoxylan in imidazolium-based ionic liquid will be elucidated through analyzing the influence of ionic liquids with different anionic and cationic structure on the dissolubility of arabinoxylan. Furthermore, the details about the influence of ionic liquids with different anionic and cationic structure on the interaction position and strength of hydrogen bond formed between ionic liquid and arabinoxylan will be studied. An overall comprehension of the effect of ionic liquids with different anionic and cationic structure on the chemical structure and aggregate properties of arabinoxylan dissolved in ionic liquid medium will form. On the other hand, the knowledges about the influence of ionic liquids with different anionic and cationic structure on the chemical and physical properties of arabinoxylan regenerated from the ionic liquids will also be obtained. At the same time, the effect of ionic liquids with different anionic and cationic structure on the possible degradation of arabinoxylan catalyzed by ionic liquids and on the dissolubility of arabinoxylan will be analyzed in detail. The influence of the concentrations of arabinoxylan and ionic liquid on the interactions between arabinoxylan and ionic liquid will obtained. Finally, the relationships between the solubility of arabinoxylan and acidity, alkalini, and polarity of ionic liquids will be established. Based on these seven aspects, the dissolution mechanism of arabinoxylan in imidazolium-based ionic liquid will be deeply understood.

对木质纤维生物质中三大组分半纤维素、纤维素和木素在离子液体中溶解机制的全面认知是合理设计用于高效预处理该类生物质的离子液体的前提条件之一。但迄今为止，对半纤维素在离子液体中的溶解规律和溶解机理尚不明确。本研究以阿拉伯木聚糖为半纤维素模型物、以咪唑型离子液体为溶剂，通过分析离子液体的阴阳离子结构对阿拉伯木聚糖溶解度的影响规律阐明阿拉伯木聚糖在咪唑型离子液体中的溶解规律；通过分析离子液体的阴阳离子结构对离子液体与阿拉伯木聚糖之间形成氢键的影响规律、对阿拉伯木聚糖在离子液体中的化学结构和聚集形态的影响规律、对再生阿拉伯木聚糖的物理化学特性的影响规律、对离子液体可能催化降解阿拉伯木聚糖的影响规律、对阿拉伯木聚糖溶解度的影响规律，并结合阿拉伯木聚糖和离子液体浓度对二者之间形成氢键的影响规律、溶解度与离子液体的氢键酸碱度和极性的关系，从七个角度深入理解阿拉伯木聚糖在咪唑型离子液体中的溶解机理。

对木质纤维生物质中三大组分半纤维素、纤维素和木素在离子液体中溶解机制的全面认知是合理设计用于高效预处理该类生物质的离子液体的前提条件之一。但迄今为止，对半纤维素在离子液体中的溶解规律和溶解机理尚不明确。本研究以从毛竹中提取的阿拉伯木聚糖为半纤维素模型物、以咪唑型离子液体为溶剂，通过测定阿拉伯木聚糖在阴阳离子结构不同的离子液体中的溶解度，深入分析了阿拉伯木聚糖在咪唑型离子液体中的溶解规律；并从多方面深入分析了阿拉伯木聚糖在离子液体中的溶解机理，包括借助1H NMR和13C NMR技术确定了离子液体与阿拉伯木聚糖之间形成氢键的位置、分析了离子液体的阴阳离子结构、以及阿拉伯木聚糖浓度（相对于离子液体）和离子液体浓度（相对于阿拉伯木聚糖）对离子液体与阿拉伯木聚糖之间形成氢键作用的影响规律等。.阿拉伯木聚糖在咪唑型离子液体中溶解规律的研究表明：阿拉伯木聚糖在离子液体中的溶解度受阴阳离子的电负性、空间位阻、关键基团的给/吸电子诱导效应的影响，同时又遵循阴阳离子上关键基团中碳原子数目的奇偶效应影响；温度也对阿拉伯木聚糖的溶解度有重要影响。.阿拉伯木聚糖在咪唑型离子液体中溶解机理的分析表明：阴离子和咪唑阳离子上的酸性质子分别与阿拉伯木聚糖中木糖单元上的羟基氢和羟基氧形成氢键而协同促进阿拉伯木聚糖的溶解，但阴离子对阿拉伯木聚糖的溶解起主导作用；离子液体与阿拉伯木聚糖中木糖单元上XC2−OH形成氢键能力强于与XC3−OH形成氢键的能力；离子液体与阿拉伯木聚糖之间形成氢键的强度大小与咪唑阳离子和阴离子的电负性、空间位阻和关键基团的给/吸电子诱导效应息息相关，并受离子液体和阿拉伯木聚糖之间的相对浓度影响；在阿拉伯木聚糖溶解过程中，离子液体只是起溶剂作用，不会明显催化阿拉伯木聚糖的降解。.研究结果对将来设计新型高效的预处理木质纤维生物质的离子液体提供重要理论依据。