Role of Solvents in Efficient Biomass Deconstruction

07/21/2020

(A) Small-angle neutron scattering (SANS) obtained from contrast-matched deuterated cellulose from experiments and simulations. (B) Surfaces of cellulose fiber classified as non-polar (red) and polar (blue). (C,D) Isosurfaces in which tetrahydrofuran (THF) (orange) concentration is 3x higher than bulk, viewed perpendicular (C) and parallel (D) to the cellulose fiber (green) axis. [Reused under a Creative Commons License (CC BY-NC-ND 4.0) from Pingali et al. 2020.]

Objective

Understand the effect of tetrahydrofuran (THF):water pretreatment on the nanoscale architecture of biomass and the role these co-solvents play in solubilizing lignin and cellulose.

Approach

In-situ small-angle neutron scattering (SANS) with contrast variation and molecular dynamics (MD) simulations were performed to characterize the biomass structure and the interactions of solvents with biomass components.

Results

In situ SANS determined temperature-dependent changes in biomass morphology. Lignin dissociates over a wide temperature range (>25°C), whereas cellulose disruption occurs only above 150°C.
SANS with contrast variation and MD simulations provide direct evidence for the formation of THF-rich nanoclusters (~0.5 nm) on the nonpolar cellulose surfaces and on hydrophobic lignin, and equivalent water-rich nanoclusters on polar cellulose surfaces.

Significance

Direct experimental and computational evidence of a simple physical chemical principle that explains the success of mixing an organic co-solvent, tetrahydrofuran, with water to overcome this recalcitrance. The hydrophilic and hydrophobic biomass surfaces are solvated by single-component nanoclusters of complementary polarity.

References

Pingali, S. V., et al. 2020. “Deconstruction of Biomass Enabled by Local Demixing of Cosolvents at Cellulose and Lignin Surfaces,” Proceedings of the National Academy of Sciences USA 17(29) 16776-781, [DOI:10.1073/pnas.1922883117]