Fractionation, characterization, and conversion of biorefinery process lignins to phenolic acids and aldehydes

Many biochemical conversion routes are envisioned that can effectively produce biofuels, biochemicals, and biomaterials from the polysaccharide fraction of lignocellulosic biomass. This will generate opportunities for the utilization of the process lignin fraction remaining after biochemical conversion as co-products. This proposed work will investigate the catalytic oxidation of several relevant process lignins to aromatic aldehydes and acids. In this work, we will generate and fractionate a range of industrially relevant lignins exhibiting a diverse spectrum of properties. Using these crude lignins or alkaline liquors, we propose to use solvent fractionation and a promising CO₂ fractionation process to generate a set of lignins with even more diverse properties and that may be enriched or depleted in select properties. Structural properties of these lignins will be characterized using a suite of analytical techniques and these properties will be related to the phase partitioning behavior of the lignins. Subsequently, these lignins will be subjected to various catalytic oxidation approaches. The yields of monomeric aromatic acids and aldehydes generated through these oxidation approaches will be determined, and the relationships between structural properties of the generated lignins, phenolic monomer yield, phenolic monomer distribution, and the molecular weight reduction will be correlated. Using this approach we propose that by understanding the lignin properties contributing most strongly to yields, it will be possible to fractionate the lignin to yield fractions with properties tailored for the specific conversion process.