Lignin depolymerization to monophenolic compounds in a flow-through system

Abstract

A reductive lignocellulose fractionation in a flow-through system in which pulping and transfer hydrogenolysis steps were separated in time and space has been developed.

Lignin Valorization by Cobalt‐Catalyzed Fractionation of Lignocellulose to Yield Monophenolic Compounds

“…Thus, Co‐phen/C performs reductive cleavage of lignin fragments/oligomers provided by organosolv pulping and simultaneously plays a key role in stabilizing reactive monomers by catalyzing‐transfer hydrogenolysis/hydrogenation reactions (Table ). Both these actions further increase the yield of monophenolic compounds …”

“…To avoid this issue the use of hydrogen donors such as alcohols has been studied . In addition, efficient hydrogenolysis of lignocellulose was recently reported by using Pd/C without an added hydrogen source and employing part of the lignocellulose as a hydrogen donor . Nickel‐based catalysts have also been reported as an alternative to expensive noble‐metal catalysts for lignin valorization.…”

“…Untreated birch sawdust (Vanhälls Såg AB, see Ref. for analysis) was selected as the substrate for the fractionation experiments. Owing to its high syringyl content, native birch lignin is abundant in β‐ O ‐4′ moieties, which is crucial for achieving high monomer yields .…”

“…Model compound 5 with the β‐ O ‐4′ interlinkage was treated under organosolv conditions, which transformed model compound 5 into aldehyde ( 9 ), syringol ( 10 ), and some oligomeric species (Table , entry 1). As reported, mildly acidic organosolv pulping of lignocellulose can release up to 20 wt % of reactive monomeric species such as sinapyl alcohol ( 6 ) and coniferyl alcohol ( 7 ) through solvolysis of lignin . Therefore, 6 and 7 were selected as model compounds for transfer hydrogenation/hydrogenolysis using Co‐phen/C under fractionation conditions.…”

Catalytic Transfer Hydrogenolysis as an Effective Tool for the Reductive Upgrading of Cellulose, Hemicellulose, Lignin, and Their Derived Molecules

“…In 2017, the same authors presented for the first time a method to fractionate the lignin in high yield to monophenolic products by a flow system in CTH conditions using the Pd/C catalyst and hemicellulose as an internal H-source and reducing agent at 160-220 • C for 3-6 h. Furthermore, the cellulose fraction was found as solid residue in 92 wt% [135].…”