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Aldehyde-Assisted Fractionation Enhances Lignin Valorization in Endocarp Waste Biomass

Jean Thierry C Behaghel de Bueren, Raymond Gérard Buser, Graham Reid Dick, Florent Emmanuel Héroguel, Jeremy Luterbacher, Chloé Wegmann

Endocarp biomass, which forms much of the inedible portion of nuts and stone fruits, is a promising feedstock for aromatic chemical production due to its high lignin content and because it is a food industry waste. Here, we tested the nut shells and fruit kernels of seven species and report that their aromatic monomer yields can surpass those obtained using wood chips by up to 30% on a dry biomass basis due to their high lignin content. We also observed that acid-catalyzed aldehyde-assisted fractionation (AAF) facilitates lignin valorization when using industrially relevant particle sizes (3-5 mm) with monomers yields that are 80% to 170% higher than those obtained with reductive catalytic fractionation (RCF) for similarly sized particles. This difference was highly correlated with the feedstock surface area, demonstrating the importance of acidic pretreatment for substrates with low accessibility and/or large particles.

AMER CHEMICAL SOC2020

Aldehyde-Assisted Lignocellulose Fractionation Provides Unique Lignin Oligomers for the Design of Tunable Polyurethane Bioresins

Jean Thierry C Behaghel de Bueren, Raymond Gérard Buser, Florent Emmanuel Héroguel, Jeremy Luterbacher, Chloé Wegmann

Thanks to chemical stabilization, aldehyde-assisted fractionation (AAF) of lignocellulosic biomass has recently emerged as a powerful tool for the production of largely uncondensed lignin. Depolymerization of AAF lignin via ether deavage provides aromatic monomers at near theoretical yields based on ether cleavage and an oligomeric fraction that remains largely unexploited despite its unique material properties. Here, we present an in-depth analytical characterization of AAF oligomers derived from hardwood and softwood in order to elucidate their molecular structures. These bioaromatic oligomers surpass technical Kraft lignin in terms of purity, solubility, and functionality and thus cannot even be compared to this common feedstock directly for material production. Instead, we performed comparative experiments with Kraft oligomers of similar molecular weight (Mn similar to 1000) obtained through solvent extraction. These oligomers were then formulated into polyurethane materials. Substantial differences in material properties were observed depending on the amount of lignin, the botanical origin, and the biorefining process (AAF vs Kraft), suggesting new design principles for lignin-derived biopolymers with tailored properties. These results highlight the surprising versatility of AAF oligomers towards the design of new biomaterials and further demonstrate that AAF can enable the conversion of all biomass fractions into value-added products.

AMER CHEMICAL SOC2020