(6o) A Practical Way to Separate Uncondensed Lignin during Biomass Pretreatment and Quantitatively Depolymerize It at a Low Temperature of 120°C with a Cheap Ni/Al2O3-SiO2 Catalyst

High-yield lignin monomer production from separated
lignin in practical ways could greatly increase biorefinery
productivity and profitability. However, lignin condensation caused by the
formation of inter-unit carbon-carbon linkages during biomass pretreatment
dramatically reduces lignin monomer yields; besides, high temperatures and
noble-metal catalysts used in lignin hydrogenolysis depolymerization further increase the impracticality.

Recently, we have two significant findings which can
largely drive the valorization of lignin. First, adding formaldehyde during
biomass pretreatment produces a soluble lignin liquor that can be converted to guaiacyl and syringyl monomers at
near-theoretical yields during subsequent hydrogenolysis;
second, separated lignin can be readily depolymerized at a low temperature of
120°C with a cheap Ni/Al₂O₃-SiO₂ catalyst.
 We achieved a yield of 45% for beech wood, and a yield of 78% for
transgenic poplar wood with low levels of carbon-carbon linkages in native
lignin (yields were on the basis of native lignin). These yields were 3-7 times
those obtained without formaldehyde. Formaldehyde reacted with lignin
side-chain alpha- and gamma- hydroxyl groups to form stable 1,3-dioxane
structures and with lignin aromatic rings to block the active positions, which
completely quenched the condensation of lignin and facilitate its depolymerization under mild catalytic conditions.

Research
Interests: Catalytic conversion of biomass into fuels, chemicals and
materials.

Teaching Interests:
 Biomass conversion