(86c) Unlocking Biomass Recalcitrance Using Lignin Based Ionic Liquids

Certain types of ionic liquids (ILs) have shown great solvation power for biopolymers, resulting in remarkable biomass pretreatment efficiency for production of renewable fuels and chemicals. To date, the best performing IL cations such as imidazolium and cholinium, are derived from petroleum and/or natural gas. ILs derived from inexpensive and renewable sources are thus highly desirable. Lignin is Earth’s most abundant, naturally-occurring aromatic polymer, and replacement of petroleum-based platforms with those derived from lignin represents a virtuous challenge for chemists.

Protic ILs prepared from benzaldehydes and furfural have demonstrated efficacy as pretreatment solvents, yielding over 85% fermentable sugars from switchgrass. We herein present the first synthesis and evaluation of quaternary benzylammonium ILs from vanillin and syringaldehyde, two major products of oxidative lignin depolymerization. Reductive amination with dialkylamines (C₁-C₆) followed by methylation with dimethyl carbonate was used to prepare a series of ILs, which were characterized and evaluated for their ability to pretreat switchgrass. Under mild and dilute conditions, certain ILs gave excellent pretreatment yields of fermentable sugars.