Metal-based ionic liquids: effective catalysts in aqueous media for the selective production of vanillin from alkali lignin at room temperature

Abstract

Catalytic depolymerization of lignin to value-added compounds is receiving increasing interest as part of the circular bioeconomy.

Ionic-Liquid-Mediated Deconstruction of Polymers for Advanced Recycling and Upcycling

“…154,155 With improvements in IL design, more examples of IL-mediated room-temperature deconstructions may be realized, as seen in the recent deconstruction of lignin to vanillin at 10−20 wt % yields in metal-containing ILs. 152,156 The release of solvents from industrial processes is estimated to result in 60% of global industrial emissions and 30% of VOC emissions. 157 Incorporating ILs in place of more volatile solvents for industrial processes, including in deconstruction methods, offers a pathway toward offsetting this environmental impact.…”

“…A key challenge in pyrolytic and solvent-based deconstructions is the need for extensive energy input to reach deconstruction temperatures and pressures (whether at high pressure to assist deconstruction or under vacuum to prevent byproduct formation) . ILs can enable significant energy savings by facilitating deconstruction under more benign conditions.…”

“…ILs can enable significant energy savings by facilitating deconstruction under more benign conditions. For example, IL catalytic behavior has been demonstrated to depolymerize epoxy thermosets and carbon fiber epoxy composites at 150 °C and atmospheric pressure, versus the 350–500 °C temperatures and 120–325 atm pressures typical of analogous solvent-mediated approaches. , With improvements in IL design, more examples of IL-mediated room-temperature deconstructions may be realized, as seen in the recent deconstruction of lignin to vanillin at 10–20 wt % yields in metal-containing ILs. , …”

Lignin Modification for Enhanced Performance of Polymer Composites

“…The reaction is carried out by lignin (20% by weight) in the presence of water and 5 wt % [BMIM] [FeCl 4 ] catalyst. The quantity of volatile aromatic compounds was 12.5 wt %, and 105 mg/g of vanillin can be isolated from 85% of that amount …”

“…Illustration of vanillin extraction from lignin using MBILs as a catalyst in water at room temperature. Reproduced from ref . Copyright 2022 Royal Society of Chemistry.…”