Thomas Heinze and Martin Gericke

Abstract The chapter provides a comprehensive overview of the chemical deriv­atization of cellulose in ionic liquids (ILs). Different types of chemical reactions, including esterification, etherification, and grafting reactions, that have been performed in these novel type of polysaccharide solvents are discussed separately regarding efficiencies and unique characteristics. With respect to the use of ILs in technical scale, specific limitations and open questions are discussed such as the chemical reactivity of certain ILs, their high viscosity and hydrophilicity, and the need to develop efficient recycling strategies. Finally, an outlook on the develop­ment of task-specific ILs and IL/co-solvent systems as reaction media for cellulose is presented.

Keywords Cellulose • Ionic liquids • Homogeneous synthesis • Polysaccharide derivatives • Side reactions • Co-solvents • Task-specific solvents

5.1 Introduction

In recent years, ILs have received enormous interest in different areas of polysac­charide research. They are intensively studied in different areas for processing of cellulose and cellulosic biomass:

1. Cellulose is the most abundant bioresource worldwide and ILs can find use in the extraction of cellulose from lignocellulosic biomass and/or the selective sepa­ration from other plant components, such as hemicelluloses and lignin [1—3].

T. Heinze (*) • M. Gericke

Institute of Organic Chemistry and Macromolecular Chemistry,

Centre of Excellence for Polysaccharide Research, Friedrich Schiller University of Jena, HumboldtstraBe 10, D-07743 Jena, Germany e-mail: thomas. heinze@uni-jenna. de

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_5,

© Springer Science+Business Media Dordrecht 2014

2. ILs can also be used for the conversion of biomass into monosaccharides or platform chemicals. They may act either as reaction medium for cellulose hydrolysis or as efficient pretreatment agents to improve saccharification of the polysaccharide [2—4].

3. With respect to the environmental and safety concerns of the viscose and NMMO process, ILs are studied as alternative solvents for shaping of cellulose into fibers, sponges, beads, and other cellulosic objects [5—7].

4. Several ILs could be exploited as efficient homogeneous reaction media for the chemical modification of cellulose [8].

Regarding the complexity of all these topics, the present chapter is only devoted to the latter issue. It should be noted at this point that the ability to dissolve cellulose is not an inherent property of ILs but merely limited to a small fraction of this group with specific structural features. If not explicitly stated otherwise, however, the term ‘IL’ used in the chapter refers to ones that act as cellulose solvents.