Mesoscale Reaction-Diffusion Phenomena Governing Lignin-First Biomass Fractionation

Area of Science:

• Biomass Fractionation
• Chemical Engineering
• Sustainable Chemistry

Background:

• Lignin solvolysis is crucial for biomass depolymerization but its kinetics are poorly understood.
• Coupled reaction kinetics and transport phenomena governing lignin extraction rates remain largely unknown.

Purpose of the Study:

• To develop and validate a simulation framework for determining intrinsic kinetic parameters of lignin, hemicellulose, and cellulose solvolysis.
• To incorporate feedstock characteristics into a model for methanol-based lignin extraction from poplar biomass.
• To elucidate the interplay between reaction kinetics and mass transfer limitations in biomass fractionation.

Main Methods:

• Developed a validated simulation framework to analyze solvolysis kinetics.
• Incorporated feedstock characteristics, specifically for methanol-based extraction of poplar.
• Investigated the influence of particle size on lignin fragment diffusion and reaction rates.

Main Results:

• Lignin fragment diffusion competes with reaction kinetics within cell walls and pores.
• Mass transfer resistances dominate solvolysis for poplar particles > 2 mm.
• Effectiveness factors drop below 0.25 for particles > 2 mm, indicating significant pore diffusion limitations.

Conclusions:

• Biomass particle size critically affects observed lignin solvolysis rates.
• Researchers should use biomass particles < 0.2 mm for kinetic studies to avoid mass transfer limitations.
• Findings provide actionable kinetic data to guide biorefinery design and scale-up, suggesting potential for genetic engineering to improve lignin solvolysis.