SGER - Fundamental Understanding of Catalytic Cleavage of Lignin in Ionic Liquids

木质素是木质纤维素生物质中的主要组分之一。木质素对微生物分解的抑制性质是保护天然林业免受自然本身快速降解的非常有益的特征。尽管自然界已经进化出许多酶，这些酶共同有效地将纤维素和半纤维素水解裂解成它们的结构单元，但已知木质素的存在严重抑制这种活性。这项研究解决了生物质转化中最紧迫的问题，并寻求开发工艺和深入了解木质素解聚的关键步骤，这是有效生物质转化的第一步。这项研究建立在以前的研究和文献的基础上，这些研究和文献表明木质素可以溶解在离子液体中，并且木质素会受到碱的攻击。木质素具有复杂但表征不佳的组成和结构，其还取决于植物种类和产生木质纤维素生物质的条件。为了避免分析复杂的目的，了解碱催化水解的木质素氧键的机制，本研究将研究模型化合物，含有在木质素中发现的氧键。该研究调查了中性离子液体和碱性离子液体，每种离子液体都具有优化的水量，并且使用和不使用催化剂。将控制并遵循试验培养基的pH值和温度。反应时间、工艺压力、碱催化剂类型和浓度的影响都将被检查。研究将使用芳香碱，其碱性可以通过金属离子的碱性、芳香部分的类型和大小以及多碱性来调节。碱性芳香族羧酸盐将被包括在研究中，以利用它们在合适的载体溶剂（如离子液体）中对木质素结构的强亲和力。通过选择不同碱性的催化剂和不同的操作条件，我们建议选择性地靶向不同键合网络中不同键强度的氧键。更广泛的影响通过与一些模拟木质素中氧键的模型化合物合作，本研究旨在对木质素水解裂解所涉及的机制有一个基本的了解。溶解木质素的离子液体溶剂将用作进行反应的介质。具有不同碱度的碱催化剂将用于研究碱强度在其活性中对离子液体溶剂中的氧键的水解裂解的影响。模型木质素化合物中的氧键的类型将根据它们在离子液体中碱存在下裂解的容易程度进行排序。通过这项研究获得的知识将有助于设计离子液体中木质素快速碎片性质的工艺。此外，基于对木质素中氧键水解裂解的理解，将在离子液体中进一步研究模型木质素化合物，以选择性裂解产生作为潜在燃料和化学品的芳族分子。

0849342EkerdtIntellectual Merit Lignin is one of the major components in lignocellulosic biomass. The recalcitrant nature of lignin toward microbial breakdown is a highly beneficial feature in guarding natural forestry from rapid degradation by nature itself. Even though nature has evolved a number of enzymes that collectively are efficient in hydrolytically cleaving cellulose and hemicelluloses into their building units, the presence of lignin has been known to severely inhibit such activities. This research addresses this most pressing of issues in biomass conversion and seeks to develop processes and insight into key steps in lignin depolymerization, which are first steps in efficient biomass conversion. The research builds on previous studies and literature that demonstrate lignin can be dissolved in ionic liquids and that lignin is attacked by bases. Lignin has a complicated but poorly characterized composition and architecture, which also depend on the plant species and conditions in which the lignocellulosic biomass are produced. To avoid analytical complication for the purposes of understanding the mechanisms involved in base catalyzed hydrolysis of lignin oxygen linkages, this research will study model compounds that contain oxygen linkages found in lignin. The research investigates neutral ionic liquids and basic ionic liquids, each with an optimized amount of water, and with and without using a catalyst. The pH and the temperature of the test media will be controlled and followed. The effects of reaction time, process pressure, base catalyst type and concentration will all be examined. The research will employ aromatic alkali, of which the basicity can be tuned by the alkalinity of the metal ion, the type and the size of aromatic moiety, and polybasicity. Basic aromatic carboxylates will be included in the study to leverage their strong affinity toward lignin structure in a suitable carrier solvent, such as ionic liquids. By selecting catalysts of varying basicity and by varying operating conditions, we propose to target selectively oxygen linkages of different bond strength in different bonding networks. Broader Impacts By working with a number of model compounds that simulate the oxygen linkages in lignin, this research seeks to achieve a fundamental understanding of the mechanisms involved in lignin hydrolytic cleavage. Ionic liquid solvents that dissolve lignin will be used as media to carry out the reactions. Base catalysts with varying basicity will be used to study the effect of base strength in their activity toward the hydrolytic cleavage of oxygen linkages in ionic liquid solvents. The types of oxygen linkages in the model lignin compounds will be ranked according to their ease of cleavage in the presence of a base in ionic liquids. The knowledge to be gained through this research will help design processes for the rapid fragmentation nature of lignin in ionic liquids. Further, building upon an understanding in the hydrolytic cleavage of oxygen linkages in lignin, the model lignin compounds will be further studied in ionic liquids for selective cracking to produce aromatic molecules as potential fuels and chemicals.