Lignin, a aromatic heteropolymer found within plant cell walls, is the second most abundant biopolymer on the planet. Due to its abundance and potential as a feedstock for high-value products, significant engineering effort has been undertaken to separate lignin from the cellulose and hemicellulose that it interacts with within a plant cell wall. A common approach is to use an organic solvent to selectively remove lignin from the underlying biomass. However, since lignin structure is highly heterogeneous, no systematic unified framework existed for directly comparing the solubility of lignins. Using a recently developed lignin modeling approach, we conduct systematic free energy perturbation calculations of monomeric and dimeric lignins to determine their solvation free energies within seven different industrially used lignin solvents, including methanol and acetone. In addition to the solvation free energies, the geometries of larger oligomers from extended simulations in these organic solvents are compared to the results of similar simulations in an aqeuous environment. The solvents tested are observed to increase the accessibility of the polymer by decreasing its compactness, which can be related to the autocatalytic degradation of lignin that has been observed for some of the solvents.

Determining differential lignin solvation and structural changes within industrial solvents

256th National Meeting (2018)

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