Lignocellulosic Biomass Dissolution and Fractioning Using Ionic Liquids as a Solvent

Abstract

Lignocellulosic biomass is a promising renewable resource for many different applications such as second-generation biofuels, chemicals and biomaterials. Its main components are cellulose, hemicelluloses (e.g., xylan), and lignin; they are combined in a complex fibre structure that is remarkably recalcitrant against decomposition. To disrupt this complex network and release single components, the conventional technologies apply high temperature, high pressure, and/or aggressive chemicals. In a new alternative method, an "ionic liquid" facilitates the dissolution of lignocellulosic biomass at comparatively mild conditions. Ionic liquids (IL) are a new class of salts with unique properties, such as low melting point (liquid at room temperature), negligible vapour pressure, and thermal stability. This work deals with the dissolution of synthetic cellulose, xylan and lignin as well as wheat straw in the ionic liquid EMIM-OAc. It further presents near infrared spectroscopy as promising analytical method to quantify dissolved components in ionic liquids. In addition, it introduces a stepwise procedure to fraction cellulose, xylan, and lignin from mixtures with ionic liquid. Based on these results, a promising procedure for fractioning the complex chemical components in lignocellulosic biomass can be derived.