LSRE-LCM - Laboratory of Separation and Reaction Engineering - Laboratory of Catalysis and Materials, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal; ALiCE - Associate Laboratory in Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.
LSRE-LCM - Laboratory of Separation and Reaction Engineering - Laboratory of Catalysis and Materials, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal; ALiCE - Associate Laboratory in Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.
Int J Biol Macromol. 2022 Aug 31;215:272-279. doi: 10.1016/j.ijbiomac.2022.06.067. Epub 2022 Jun 16.
This work aims to evaluate the structural characteristics and study the oxidative depolymerization of lignins obtained from hardwood and softwood sulfite liquors. Lignins were obtained after ultrafiltration and freeze-drying of the sulfite liquors and characterized based on inorganic content, nitrobenzene oxidation, C NMR, and molecular weight determination. The structural characteristics achieved allow evaluating the potential of each lignin through oxidative depolymerization to produce added-value phenolic monomers. Hardwood and softwood lignins were submitted to alkaline oxidation with oxygen and the reaction conditions optimized to obtain a final oxidation mixture with the maximum yield of phenolic monomers. Through oxidation with O, hardwood lignin generates mostly syringaldehyde while lignin from softwood biomass mainly produces vanillin; moreover, a lower reaction time and the interruption of O admission avoid the degradation of the oxidation products in the final mixture for both lignins, more evidenced to hardwood lignin due to its higher reactivity. From the results, it is possible to conclude that a phenolic aldehyde-rich oxidation mixture could be obtained, confirming the viability of lignin as raw material to produce added-value products as vanillin and syringaldehyde.
本工作旨在评估木质素的结构特性，并研究从硬木和软木亚硫酸盐液中获得的木质素的氧化解聚。木质素是通过亚硫酸盐液的超滤和冷冻干燥获得的，并根据无机含量、硝基苯氧化、C NMR 和分子量测定进行了表征。所获得的结构特征允许通过氧化解聚来评估每种木质素的潜力，以生产附加值酚类单体。硬木和软木木质素分别用氧气进行碱性氧化，优化反应条件以获得最终氧化混合物中酚类单体的最大产率。通过 O 氧化，硬木木质素主要生成丁香醛，而来自软木生物质的木质素主要生成香草醛；此外，较短的反应时间和中断 O 的供给避免了最终混合物中氧化产物的降解，这在两种木质素中更为明显，对于硬木木质素更为明显，因为其反应性更高。从结果可以得出结论，可以得到富含酚醛的氧化混合物，这证实了木质素作为生产香草醛和丁香醛等附加值产品的原料的可行性。
