Lignin Hydrogenolysis: Improving Lignin Disassembly through Formaldehyde Stabilization

Abstract

Lignocellulosic biomass is available in large quantities and constitutes an attractive feedstock for the sustainable production of bulk and fine chemicals. Although methods have been established for the conversion of its cellulosic fractions, valorization of lignin has proven to be challenging. The difficulty in disassembling lignin originates from its heterogeneous structure and its propensity to undergo skeletal rearrangements and condensation reactions during biorefinery fractionation or biomass pretreatment processes. A strategy for hindering the generation of these resistive interunit linkages during biomass pretreatment has now been devised using formaldehyde as a stabilizing agent. The developed method when combined with Ru/C‐catalyzed hydrogenolysis allows for efficient disassembly of all three biomass fractions: (cellulose, hemicellulose, and lignin) and suggests that lignin upgrading can be integrated into prevailing biorefinery schemes.

Bright Side of Lignin Depolymerization: Toward New Platform Chemicals

“…As mentioned in section 1.2 , lignocellulose pretreatment inevitably modifies the native structure of lignin, by formation of robust C–C linkages. 158 To minimize this structural modification Luterbacher and co-workers 105 devised an elegant strategy that involved addition of formaldehyde during biomass pretreatment, leading to a soluble lignin fraction that could be subsequently converted by reductive treatment to a mixture of guaiacyl and syringyl monomers at near theoretical yield. As shown in Figure 7 , the role of the formaldehyde was to stabilize the native lignin structure via the formation of a 1,3-dioxane moiety.…”

“… Highly efficient catalytic conversion of lignin through formaldehyde stabilization (top) and product distribution for beech wood and F5H poplar lignin with or without formaldehyde stabilization (bottom). Reprinted with permission from ref ( 158 ). Copyright 2017 Wiley-VCH.…”

Technoeconomic Assessment of Hybrid Organosolv–Steam Explosion Pretreatment of Woody Biomass

“…For example, applications as binding agent or thermoplastics would favor lignin prices towards the high-end of the range used in the sensitivity analysis. Moreover, hydrogenolytic depolymerization of lignin is an active research area pursued by many researchers and institutions in the context of value-added biochemicals and biofuels, e.g., References [16,[29][30][31].…”

Valorisation of plastic waste via metal-catalysed depolymerisation

“…The excess of H 2 reagent can also be easily removed from the reaction mixture. The approach, referred to as hydrodeoxygenation [ 95 – 96 ], is already in use for the valorisation of naturally-occurring polymeric waste, i.e., lignocellulosic biomass [ 97 – 98 ], particularly lignin [ 99 – 100 ] and cellulose [ 101 ], to monomers or added-value platform molecules [ 102 – 103 ]. Here the main drawbacks concern safety hazards, supply, transport and storage costs of hydrogen.…”