Lignin solubility is a varying property, as depending on the type of lignin and its origin, its solubility in different solvents will differ. This is due to the highly heterogeneous nature of lignin. Solubilizing lignin could improve its potential valorization by making it more conducive to chemical reactions. Solvent fractionation could be utilized as the first step in lignin refining to adjust some of its properties before further processing. It is known that kraft lignin is completely soluble in alkaline solvents such as aqueous NaOH. The purpose of this study was to assess the solubility of Indulin AT lignin in aqueous ethanol solvents and to determine the useful properties of the resulting fractions: namely, molar mass distribution and phenolic hydroxyl groups. The highest concentration of lignin was achieved in 60 wt% ethanol solution with 235.89 g/L at a solid-to-liquid ratio of 300 g_Lignin/L_Solvent. The original lignin had a mass average molar mass of 4.7 kDa. When only water was utilized, the average molar mass of the dissolved fraction was between 1 and 2 kDa and the molecular size distribution was mostly between 0.1 and 1 kDa. When using pure ethanol, the molecular size distribution ranged from 0.1 kDa to 10 kDa, with a mass average molar mass between 1 and 1.3 kDa. With an ethanol content in the solvent higher than 90 wt%, the bigger molar mass molecules (>10 kDa) could be separated as the insoluble fraction. Additionally, the polydispersity of both fractions decreased with an ethanol concentration above 80 wt%. The hydroxyl group content of the insoluble fraction was higher when fractionating with less than 20 wt% ethanol, whereas with 20 wt% ethanol and higher, the soluble fraction retained most of the phenolic hydroxyls. Fractionating lignin prior to use or further processing may be potentially beneficial if the lower molar mass molecules can be used as they are, leaving only the higher molar mass molecules to be further processed or burned for energy.

木质素溶解度是一个变化的特性，因为根据木质素的类型及其来源，其在不同溶剂中的溶解度会有所不同。这是由于木质素的高度异质性。溶解木质素可以通过使其更有利于化学反应来提高其潜在的价值。溶剂分馏可以用作木质素精炼的第一步，以在进一步加工之前调整其一些特性。众所周知，硫酸盐木质素完全溶于碱性溶剂，例如NaOH水溶液。本研究的目的是评估 Indulin AT 木质素在乙醇水溶液中的溶解度，并确定所得馏分的有用特性：即摩尔质量分布和酚羟基。在固液比为 300 g_木质素/L_溶剂时，60 wt% 乙醇溶液中木质素的浓度为 235.89 g/L 。原始木质素的质量平均摩尔质量为4.7 kDa。当仅使用水时，溶解部分的平均摩尔质量在1至2kDa之间，分子尺寸分布大多在0.1至1kDa之间。当使用纯乙醇时，分子大小分布范围为 0.1 kDa 至 10 kDa，质量平均摩尔质量在 1 至 1.3 kDa 之间。当溶剂中乙醇含量高于 90 wt% 时，较大摩尔质量的分子 (>10 kDa) 可以作为不溶部分分离。此外，当乙醇浓度高于 80 wt% 时，两种组分的多分散性都会降低。当乙醇含量低于 20 wt% 时，不溶性馏分的羟基含量较高，而乙醇含量为 20 wt% 或更高时，可溶性馏分保留了大部分酚羟基。如果较低摩尔质量的分子可以按原样使用，而仅留下较高摩尔质量的分子进行进一步加工或燃烧以获取能量，那么在使用或进一步加工之前分馏木质素可能是潜在有益的。