(365b) An Assessment of The Recovery and Recycle of Ionic Liquids (ILs) Following Lignocellulosic Biomass Pretreatment

Many technical challenges exist in the development of commercially viable biorefining processes for plant (lignocellulosic) biomass, although it is an abundant, inexpensive and sustainable source of organic carbon for the production of fuels and chemicals. Pretreatment of biomass and enzymatic hydrolysis are critical steps, and most of the current pretreatment methods fail to effectively disrupt the crystallinity of cellulose, which is a major barrier for efficient enzymatic hydrolysis. Ionic liquids (ILs) being non volatile, non-flammable, recyclable and designer friendly, are gaining wide recognition as green solvents, and their unique solvating properties make them ideal for pretreating lignocellulosic substrates. IL pretreated lignocellulosic substrates like corn stover (softwood) and poplar (hardwood) are shown to produce enhanced enzymatic hydrolysis yields of glucan to glucose and xylan to xylose. However, economic viability of this promising pretreatment technique materializes only when the process solvent (IL) is completely recovered and recycled. After incubation with biomass, the IL is separated from the latter via dissolution in a suitable anti-solvent (water/ethanol). Subsequently, IL can be recovered from the anti-solvent via evaporative and/or membrane based separations. It is of importance to quantify the residual anti-solvents in the recovered IL, to establish their permissible levels.

This study reports: (1) the use of ILs as non-derivitizing green solvents for the pretreatment of lignocellulosic biomass for subsequent bio-ethanol production, (2) the recovery of ILs using an evaporative separation scheme, along with a concomitant assessment of the efficiency of the recycled IL for biomass-pretreatment over several cycles of recovery and reuse, and (3) the establishment of acceptable levels of anti-solvent in the recycled IL (without compromising on its effectiveness as a pretreatment agent), and the development of analytical methods to accurately measure these concentrations.