Department of Catalysis and Chemical Reaction Engineering, National Institute of Chemistry, Hajdrihova 19, 1000, Ljubljana, Slovenia.
Sci Rep. 2020 Jul 6;10(1):11037. doi: 10.1038/s41598-020-67787-9.
The selective lignin conversion into bio-based organic mono-aromatics is a major general challenge due to complex structure itself/additional macromolecule modifications, caused by the cleavage of the ether chemical bonds during the lignocellulosic biomass organosolv pulping in acidified aqueous ethanol. Herein, the acido-lysis of connected benzyl phenyl (BPE), being a representative model compound with α-O-4 linkage, was investigated in methanol, EtOH and 75 vol% EtOH/water mixture solutions, progressing each time with protonating sulfuric acid. The effect of the physical solvent properties, acidity of the reaction process media and temperature on rate was determined. Experiments suggested BPE following S1 mechanism due to the formation of a stable primary carbocation/polarity. The product species distribution in non-aqueous functional alcohols was strongly affected. The addition of HO was advantageous, especially for alkoxylation. Yield was reduced by a factor of 3, consequently preserving reactive hydroxyl group. Quantitative experimental results indicated key performance parameters to achieve optimum. Organosolv lignins were further isolated under significantly moderate conditions. Consecutive structural differences observed supported findings, obtained when using BPE. HO presence was again found to grant a higher measured -OH content. Mechanistic pathway analysis thus represents the first step when continuing to kinetics, structure-activity relationships or bio-refining industrial resources.
由于在酸性乙醇水溶液中木质纤维素生物质有机溶剂法制浆过程中醚化学键的断裂会导致复杂的结构本身/额外的大分子修饰，因此将木质素选择性转化为基于生物的有机单芳烃是一个主要的一般性挑战。在此，通过质子化硫酸，研究了连接的苄基苯基（BPE）的酸解，BPE 是具有α-O-4 键的代表性模型化合物。考察了物理溶剂性质、反应过程介质酸度和温度对反应速率的影响。实验表明，由于形成稳定的初级碳正离子/极性，BPE 遵循 S1 机制。非水功能醇中的产物种类分布受到强烈影响。HO 的加入是有利的，特别是对于烷氧基化。产率降低了 3 倍，因此保留了反应性羟基。定量实验结果表明，实现最佳性能需要关键性能参数。在明显温和的条件下进一步分离了有机溶剂木质素。观察到的连续结构差异再次支持了使用 BPE 时获得的结果。HO 的存在再次被发现可以赋予更高的测量-OH 含量。因此，当继续进行动力学、结构-活性关系或生物精炼工业资源研究时，机理途径分析代表了第一步。
