(669f) Evaporative Separation of Ionic Liquid Following Biomass Pretreatment: Generation of Required Thermodynamic Data

Plant (lignocellulosic) biomass is an abundant, inexpensive and sustainable source of organic carbon, for the production of renewable fuels and chemicals. However, many technical and environmental challenges exist in developing commercially viable processes for producing sugars from biomass that serve as precursors for fuel and chemical production. Pretreatment and enzymatic hydrolysis are critical steps, and most of the current pretreatment methods do not effectively disrupt the biomass structure, especially 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. Enhanced enzymatic hydrolysis yields of glucan to glucose and xylan to xylose are observed for ionic liquid pretreated ligocellulosic substrates like corn stover and poplar. In IL-pretreatment, the IL is displaced from the biomass by washing the pretreated biomass with an anti-solvent (water/ethanol). The IL preferentially dissolves in the anti-solvent and hence can be completely recovered. However, from an economic stand-point it is important that the IL is separated from the IL/water mixture. This is also desirable to avoid any ecological consequences associated with the presence of IL in wash streams and be able to reuse the process water. This work addresses: (1) the pretreatment of lignocellulosic biomass using suitable ionic liquids, and (2) a facile thermo gravimetric method for efficiently generating the required thermodynamic (vapor liquid equilibrium) data needed for designing evaporative separation of IL from the anti solvent.