Dissolution in Ionic Liquids (and Deep Eutectic Solvents?): an Environmentally Sustainable Approach for the for the Pretreatment of Lignocellulosic Biomass
Hayes, D. G.  2019.  International Palm Oil Congress (PIPOC), Kuala Lumpur, Malaysia, 19-21 November 2019.  (invited)

lignocellulosic biomass is an abundant but underutilized coproduct from oil palm (e.g., empty fruit bunches, mesocarp fibre, palm shell, fronds, roots and trunks) , available at ~40 million metric tons per year. Lignocellulosics can serve as feedstocks for the preparation of biofuels, chemical intermediates, materials, and other value-added products; yet, most biomass is inefficiently burned to provide energy, or placed in landfills, or improperly discarded. For efficient utilization, the recalcitrance of biomass should be reduced through reduction of crystallinity and perhaps partial depolymerization, and the major components of biomass (cellulose, hemicellulose, and lignin) should be isolated in separate fractions. Fifteen years ago, it was discovered that whole biomass can be dissolved into ionic liquids (ILs), which are salts that exist as liquids at moderate temperatures (~25-100 C). ILs comprise a versatile family of solvents that can be tailor-made through control of the cationís and anionís chemistry to control solvent-related properties such as polarity. Biomass dissolvent in ILs (at typical loading of ~1-5%) can be fractionated into its polymeric constituents through the sequential addition of antisolvents that selectively promote precipitation of hemicellulose, lignin, and cellulose. Biomass recovered from ILs possesses lower crystallinity and is de-acetylated, thereby being more readily processed and reacted. This presentation will review research and development of IL-based biomass pretreatment and the use of ILs in the chemical analysis of lignocellulosics.