Ionic Liquids Provide Effective Biomass Pretreatment
Ionic liquids (ILs) have been shown to be an excellent pretreatment solvent for biomass in preparation for hydrolysis into its component sugars. However, IL availability and high cost remain an issue. Researchers from the Department of Energy’s Joint BioEnergy Institute sought to decrease the cost of ILs by synthesizing new ILs directly from lignin monomers and hemicellulose, which are found in the biomass. Tertiary amine-based ILs were synthesized from aromatic aldehydes derived from lignin and hemicellulose. Molecular modeling was used to compare IL solvent parameters with experimentally obtained compositional analysis data.
Effective pretreatment using these new ILs of switchgrass was investigated by powder X-ray diffraction showing structural changes in cellulose and glycome profiling showing changes in the extractability of hemicellulose epitopes. Deriving ILs from lignocellulosic biomass shows significant potential for the realization of a “closed-loop” process for future lignocellulosic biorefineries and has far-reaching economic impacts for other IL-based conversion technology currently using ILs synthesized from petroleum sources. IL synthesis by reductive animation of aromatic aldehydes, followed by treatment with phosphoric acid, provided three biomass-derived ILs in excellent yields without the need for chromatographic purification. When these renewable biomass-derived ILs were used in pretreatment of switchgrass biomass, comparable high yields of sugar were generated and saccharification was comparable to current imidazolium-based ILs. Cost projections of renewable ILs are $4/kg, much lower than top performing conventional ILs, improving the economic viability of lignocellulosic-derived sugars.
Socha, A. M., R. Parthasarathia, J. Shia, S. Pattathil, D. Whyte, M. Bergeron, A. George, K. Tran, V. Stavila, S. Venkatachalam, M. G. Hahn, B. A. Simmons, and S. Singh. 2014. “Efficient Biomass Pretreatment Using Ionic Liquids Derived from Lignin and Hemicellulose,” Proceedings of the National Academy of Sciences (USA) 111(35), E3587-95.