Junli Xu, Qing Zhou, Xinxin Wang, Xingmei Lu, and Suojiang Zhang

Abstract Ionic liquids (ILs) are composed of cations and anions that exist as liquids at relatively low temperatures (<100 °C). They have many attractive properties, such as chemical and thermal stability, low flammability, and immeasurably low vapor pressures. This review provides a summary of the fundamental structural features of ionic liquids, the physical properties, and their applications as solvents for biomass.

Keywords ILs • Properties • Cellulose • Biomass

1.1 Introduction

The energy crisis has caused great pressure on the economic development and environmental sustainability worldwide, resulting in renewable energy, such as, solar, wind, and biomass, receiving significant attention [1]. Especially, as a resource of fuel and chemicals, biomass is developed greatly due to its large potential and universality as an energy resource. Biomass pretreatment is a key procedure for efficient processing. Biomass pretreatment was first conducted with acid or alkali, as well as some organic solvents. Gradually, considering the envi­ronmental and economic influence, ionic liquids (ILs) were introduced for biomass

J. Xu

Beijing Key Laboratory of ILs Clean Process, Key Laboratory of Green Process

and Engineering, State Key Laboratory of Multiphase Complex Systems, Institute of Process

Engineering, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China

College of Chemistry and Chemical Engineering, University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China

Q. Zhou • X. Wang • X. Lu (*) • S. Zhang (*)

Beijing Key Laboratory of ILs Clean Process, Key Laboratory of Green Process and Engineering, State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China e-mail: xmlu@home. ipe. ac. cn; sjzhang@home. ipe. ac. cn

Z. Fang et al. (eds.), Production of Biofuels and Chemicals with Ionic Liquids, Biofuels and Biorefineries 1, DOI 10.1007/978-94-007-7711-8_1,

© Springer Science+Business Media Dordrecht 2014

pretreatment and biomass conversion with ILs was followed since ILs have many unique and excellent properties.

This part aims to briefly introduce the definition of ILs, the structures and classi­fication of ILs, meanwhile, the properties of ILs will be discussed in detail, including melting point, viscosity, density, and thermal stability. Then the history, advantage and current status of ILs applied to cellulose/biomass, the quantities and kinds of ILs are used in dissolution and separation of cellulose from biomass are also summarized.