Rajbangshi Juriti, Sener Canan, Van Lehn Reid C
Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States.
DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin 53726, United States.
J Phys Chem B. 2025 Sep 11;129(36):9175-9189. doi: 10.1021/acs.jpcb.5c02943. Epub 2025 Aug 27.
Lignin, an essential building block of lignocellulosic biomass, is a potential abundant source of aromatic monomers for the polymer and chemical industry. Reductive catalytic fractionation (RCF) is one promising process that can produce high yields of phenolic monomers and oligomers from lignin under different catalytic conditions. An important choice in optimizing RCF is the selection of solvent; however, detailed insights into the effects of solvent on lignin behaviors and interactions remain limited. In this work, we perform all-atom molecular dynamics simulations to study the solvation of lignin, solvent-mediated conformational changes, and the interaction of solvated lignin oligomers with model surfaces. We focus on the behavior of an oligomeric lignin model compound in methanol, ethanol, a binary mixture of ethanol and water, and water at both the RCF reaction temperature (473 K) and room temperature. Analysis of structural features of lignin suggests that these three organic solvent systems favorably solvate lignin, resulting in a more extended conformation suitable for catalytic conversion to valuable chemicals. We further introduce model palladium (Pd) and carbon (C) surfaces to understand how solvent choice impacts adsorption onto a representative catalytic surface and support and to quantify the competition among the reactant and solvent molecules for the surface. Unbiased simulations suggest strong adsorption of lignin on both Pd and C surfaces at 473 K, with notable solvent-mediated differences in adsorption energies. Additionally, our findings indicate that lignin adsorption is promoted by the entropy change resulting from the displacement of the solvent molecules from the surface. This study provides a molecular perspective of adsorption of lignin onto varying surfaces, which is a step toward understanding and optimizing the catalytic conversion of lignin into valuable chemicals.
木质素是木质纤维素生物质的重要组成部分，是聚合物和化学工业潜在的丰富芳香单体来源。还原催化分馏（RCF）是一种很有前景的工艺，在不同催化条件下可从木质素中高产率地生产酚类单体和低聚物。优化RCF的一个重要选择是溶剂的选择；然而，关于溶剂对木质素行为和相互作用影响的详细见解仍然有限。在这项工作中，我们进行全原子分子动力学模拟，以研究木质素的溶剂化、溶剂介导的构象变化以及溶剂化木质素低聚物与模型表面的相互作用。我们重点研究了一种低聚木质素模型化合物在甲醇、乙醇、乙醇和水的二元混合物以及水（在RCF反应温度473 K和室温下）中的行为。对木质素结构特征的分析表明，这三种有机溶剂体系有利于木质素的溶剂化，从而产生更适合催化转化为有价值化学品的伸展构象。我们进一步引入模型钯（Pd）和碳（C）表面，以了解溶剂选择如何影响在代表性催化表面和载体上的吸附，并量化反应物和溶剂分子在表面上的竞争。无偏模拟表明，在473 K时，木质素在Pd和C表面上均有强烈吸附，吸附能存在显著的溶剂介导差异。此外，我们的研究结果表明，溶剂分子从表面的位移所导致的熵变促进了木质素的吸附。这项研究提供了木质素在不同表面上吸附的分子视角，这是朝着理解和优化木质素催化转化为有价值化学品迈出的一步。
