Fractionation of lignocellulosic biomass to produce uncondensed aldehyde-stabilized lignin

Abstract

Lignin is one of the most promising sources of renewable aromatic hydrocarbons. Current methods for its extraction from lignocellulosic biomass-which include the kraft, sulfite, and organosolv processes-result in the rapid formation of carbon-carbon bonds, leading to a condensed lignin that cannot be effectively depolymerized into its constituent monomers. Treatment of lignocellulosic biomass with aldehydes during lignin extraction generates an aldehyde-stabilized lignin that is uncondensed and can be converted into its monomers at near-theoretical yields. Here, we outline an efficient, reproducible, and scalable process for extracting and purifying this aldehyde-stabilized lignin as a solid, which can easily be re-dissolved in an organic solvent. Upon exposure to hydrogenolysis conditions, this material provides near-theoretical yields of aromatic monomers (~40-50% of the Klason lignin for a typical hardwood). Cellulose and hemicellulose are also efficiently fractionated. This protocol requires 6-7 h for the extraction of the stabilized lignin and a basic proficiency in synthetic chemistry.

Recent Advances in the Catalytic Depolymerization of Lignin towards Phenolic Chemicals: A Review

“…Afterwards, they compared different protecting reagents (aldehydes, ketones, dimethyl carbonate, phenylboronic acid), with formaldehyde giving the highest yield (46 wt %) of phenolic monomers, followed by propionaldehyde (42 wt %) and acetaldehyde (37 wt %) . The aldehyde‐stabilized lignin could be readily selectively dissolved in an organic solvent and catalytically depolymerized to a near‐theoretical yield of phenolic monomers (40–50 wt % for a typical hardwood) …”

Selective electrocatalytic hydrogenation of bio-oil to oxygenated chemicals via suppression of deoxygenation

“…6c and Fig. S29) 28 . This lignin-derived oil was then selectively hydrogenated to the oxygenated 2-methoxy-4propylcyclohexanol (1, having -OH and -OCH 3 retained) with suppressed deoxygenation using PtRhAu catalyst.…”

“…We further demonstrate the versatility of PtRhAu catalysts in an integrated lignin biore nery to obtain oxygenated chemicals directly from lignocellulosic biomass. We rst converted birch wood to ligninderived oils containing 4-propylsyringol (4PS) and/or 4-propylguaiacol (4PG) using aldehyde-assisted fractionation (AAF) followed by hydrogenolysis 5,28 . These lignin-derived oils were then selectively hydrogenated and funneled to a single OFG-rich chemical 2-methoxy-4-propylcyclohexanol for synthetic perfumes using our novel electrocatalysts under ambient conditions.…”

Lignin Functionalization for the Production of Novel Materials

“…Although this functionalization was first reported with formaldehyde, it has since been shown that this reaction works efficiently with a large array of aldehydes. It was also notably shown that, by using a variety of multiple aldehydes, the solubility of the resulting lignins could be tuned, making them soluble in vastly different solvents from water to toluene [97][98][99]. This range of solubility could be further used to tailor lignin incorporation into several polymers.…”