Biorefinery Processes Research Group, Chemical and Environmental Engineering Department, Engineering Faculty of Gipuzkoa, University of the Basque Country UPV/EHU, Plaza Europa 1, 20018 Donostia, Spain.
Biorefinery Processes Research Group, Department of Applied Mathematics, University of the Basque Country UPV/EHU, Rafael Moreno "Pichichi" 3, 48013 Bilbao, Spain.
Int J Biol Macromol. 2024 Apr;264(Pt 2):130518. doi: 10.1016/j.ijbiomac.2024.130518. Epub 2024 Feb 28.
Lignin has been overlooked and used as a waste for long due to its complex and partially hydrophobic structure. Many efforts have been carried out to overcome these deficiencies and apply it as a high-value product, which are insufficient to reach the full potential of lignin in various advanced applications, since they require with procedures for the obtaining of more specific and fine-tuned chemical structures. This work focuses on the obtaining of differently structured hydrophilic lignins derived both from Kraft and organosolv isolation processes. The chemical structures of the different lignin types were studied, and the effect of the structural differences in the modification processes and their subsequent properties analyzed, valorizing their potential application for diverse purposes. The carboxymethylation and sulfomethylation reactions were carried out with the aim of enhancing the polarity of the lignin samples, while the methylation reaction aimed to obtain lignins with higher stability. The physicochemical analyses of the samples, carried out by FTIR, GPC, P NMR, C NMR, and HSQC NMR, verified the effectiveness of the chemical reactions and conditions selected, obtaining lignins with lower hydroxyl content, due to their substitution and insertion of carboxymetyl, sulfomethyl and methyl groups, therefore obtaining more condensed, aromatic and oxygenated aromatic carbon structures. While the methylation reaction was the most efficient in substituting the OH groups, due to its non-selectivity, OL showed higher modification yields than KL. In terms of the thermal and morphological properties, analyzed by DLS and TGA respectively, it was observed that the modified samples showed lower Z potential values, along with higher conductivity, being the sulfomethylated organosolv lignin the one showing the best results, which was also the one with the smallest particle size and polydispersity index. Finally, all the modified samples showed higher T values, suggesting a better stability towards degradation.
由于其复杂且部分疏水性的结构，木质素长期以来一直被忽视和作为废物使用。为了克服这些缺陷并将其作为高价值产品应用，已经进行了许多努力，但这些努力还不足以充分发挥木质素在各种先进应用中的潜力，因为它们需要更具体和精细的化学结构的获得程序。本工作重点研究了从 kraft 和有机溶剂分离过程中获得的具有不同结构的亲水性木质素。研究了不同木质素类型的化学结构，并分析了结构差异对改性过程及其后续性能的影响，以实现其在各种用途中的潜在应用价值。进行了羧甲基化和磺甲基化反应，旨在提高木质素样品的极性，而甲基化反应旨在获得具有更高稳定性的木质素。通过 FTIR、GPC、P NMR、C NMR 和 HSQC NMR 进行的样品物理化学分析验证了所选化学反应和条件的有效性，获得了羟基含量较低的木质素，因为它们取代和插入了羧甲基、磺甲基和甲基，因此获得了更浓缩、芳构化和含氧芳构化的碳结构。虽然甲基化反应由于其非选择性而在取代 OH 基团方面最有效，但由于其非选择性，OL 比 KL 具有更高的修饰产率。就热和形态特性而言，分别通过 DLS 和 TGA 进行分析，观察到改性样品的 Z 电位值较低，同时导电性较高，磺甲基化有机溶剂木质素的性能最佳，其粒径和多分散指数也最小。最后，所有改性样品的 T 值均较高，表明其在降解方面具有更好的稳定性。
