SusCHEM: Mixtures of Ionic Liquids with Compressible Fluids for Biopolymer Separations and Processing of Lignocellulosic Materials

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

1509390 Kiran VA Polytechnic Inst The proposed research program will explore a novel approach for separation of the biopolymers of lignocellulosic materials or woody biomass. The successful outcomes are expected to lead to purified cellulose and hemicellulose fractions that are free of extractives and lignin; or to purified lignin fractions that are free of carbohydrates. The possibility of generating uniform cellulose resources that are free of extractives and lignin is of high technological significance. Such a resource would greatly improve the efficiency and the sustainable production of biofuels such as bioethanol; or may be used as advanced fiber source for paper manufacture, or for production of cellulosic aerogels or scaffolds. The possibility of generating a uniform lignin resource is also of high significance. If it were available, such a resource could be used for possible conversion to nonpetroleum-based, hydrocarbon-like transportation fuels, or for conversion to advanced materials such a carbon fibers or porous adsorbents. As solvent media, the project will explore mixtures of selected ionic liquids with a supercritical or compressible fluid such as carbon dioxide plus an organic solvent. The approach is non-traditional in that the focus will be on using the ionic liquids not as the major, but as a minor component of the mixtures. The objective is to incorporate the functionality or solvating power of the ionic liquids to mixtures of an organic solvent with a more compressible supercritical fluid at a level that would be just sufficient for separation and processing of biopolymers. The methodology is to combine the pressure-tunability of compressible fluids with the solvating power of ionic liquids while at the same time lowering the viscosity of the medium for easier processability. The goal is to develop solvent-antisolvent combinations that can be tuned for selective dissolution and precipitation of target polymers with manipulations of pressure and /or temperature, while at the same time facilitating the recovery and the recycle of the ionic liquids employed. Towards these objectives, the project will generate fundamental data on the high-pressure miscibility, volumetric properties, solubility parameters and viscosity of mixtures of selected ionic liquids with compressible fluids and their mixtures with the biopolymers of interest as a function of the fluid composition, pressure and temperature. The proposed combination of ionic liquids with compressible or supercritical fluid mixtures at high pressures are expected to provide new process flexibilities in terms of pressure, temperature, or compositional tuning of (a) the thermodynamic conditions for miscibility and phase separation, or (b) the transport properties such as viscosity, or (c) the kinetics with respect to either chemical reactivity and transformations, or (d) the thermophysical transitions and morphological modifications.