Poster

P2.3 – Mechanistic evaluation of acidic thiourea fractionation with lignan-based tetramer model compound

Andreas Schröder

Åbo Akademi University

Co-author(s):
Ruijie Wu, Åbo Akademi University
Mathias Herrlin, Åbo Akademi University
Veronika Badazhkova, Åbo Akademi University
Juho Sirviö, University of Oulu
Patrik Eklund, Åbo Akademi University
Chunlin Xu, Åbo Akademi University

Lignin valorization remains a key challenge in the development of sustainable biorefineries. However, the inevitable condensation of lignin during the fractionation of lignocellulosic biomass results in lower lignin yield and increased heterogeneity, thereby limiting its applications. Acidic thiourea fractionation has been shown to produce high-yield, light-colored lignin under relatively mild conditions. To investigate lignin reactivity and fractionation behavior, two model compounds (a β-O-4’ dimer and a lignan-based tetramer with four aromatic rings) were synthesized, and both model compounds were then subjected to an acidic thiourea fractionation process. Unlike the traditional use of lignin dimer models, we incorporated a lignan structure into the model to develop a lignin tetramer featuring both lignan and β-O-4 linkages. The successful synthesis of the model compound with a lignan structure was confirmed using various characterization methods, including nuclear magnetic resonance (NMR) and Ultra-performance liquid chromatography-mass spectrometry (UPLC-MS). The mechanistic evaluation indicated that thiourea did not cleave the β-O-4’ ether linkage but influenced the chemical environment of the α- and γ-positions. Significant shifts in the α-, β-, and γ-protons suggest that thiourea interacts with hydroxyl-containing structures, leading to possible modifications in these regions. The development of new lignin-structured model compounds has significantly advanced research in lignin chemistry. It not only enhances the understanding of lignin degradation, separation, and conversion mechanisms but also provides theoretical support and an experimental foundation for its efficient utilization.

References:Sirviö, J. A.; Mikola, M.; Ahola, J.; Heiskanen, J. P.; Filonenko, S.; Ämmälä, A. Highly Effective Fractionation Chemistry to Overcome the Recalcitrance of Softwood Lignocellulose. Carbohydrate Polymers 2023, 312, 120815.

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