(254b) Reaction Engineering in Planta? Tales of Mass Transfer Limitations and Their Kinetic Consequences at the Mesoscale

Between the molecular and reactor scales—familiar favorites to the chemical engineering community—lies an intermediate regime termed the “mesoscale” where chemical reaction kinetics and transport phenomena compete along similar time and length scales. However, little is known about the coupled chemistry and physics of biomass conversion at the mesoscale, which govern effective rates of component extraction from plant cell walls during condensed-phase fractionation processes. First, we will introduce an experimentally validated simulation framework that determines transport‐independent kinetic rate constants upon incorporating realistic feedstock characteristics for an exemplary hardwood solvolysis process. This generalizable mesoscale reaction–diffusion modeling approach will then be extended to validate and predict the alkaline deacetylation of corn stover, an emerging pretreatment system that removes acetyl moieties from hemicellulose prior to mechanical refining to improve downstream enzymatic sugar yields. Reaction–diffusion models are developed and validated for three major anatomical fractions (cobs, husks and stalks), and model findings categorize experimental feedstock performance into kinetic-controlled vs. diffusion-controlled regimes based on the particle size and microstructural attributes of each tissue type. Critically, we predict that typical corn stover particles as small as ~2.3 mm in length are entirely diffusion-limited for acetate extraction, with experimental effectiveness factors calculated to be 0.50 for such processes—size thresholds consistent with the unrelated hardwood solvolysis system first introduced. Researchers are therefore recommended to conduct kinetic evaluations of condensed-phase pretreatments using biomass particles smaller than ~0.2 mm in length to avoid feedstock‐specific mass transfer limitations, particularly when a catalyst phase is also present. Overall, this presentation highlights opportunities to improve biomass fractionation and conversion via reaction engineering and provides actionable kinetic information to guide the design and scale‐up of emerging biorefinery strategies.