Haibo Xie and Zongbao Kent Zhao

Abstract In consideration of unique properties of ionic liquids, the research into using ionic liquids as solvents and catalysts for lipids extraction, biodiesel produc­tion and purification, as well as bioalcohol extraction from fermentation booth have been investigated to develop clean and cost-competitive new technologies. This review summarizes up-to-date progress in these areas and analyzes examples with the aim to provide an in-depth understanding of how to integrate ionic liquids-based technologies into traditional biofuel production processes.

Keywords Ionic liquids • Lipids • Extraction • Transesterification • Biodiesel • Bioethanol • Biobutanol • Catalysis

7.1 Introduction

The search for alternative resources for transportation fuel production is driven by the increasing concerns on global warming and fossil resources depletion. Biomass refers to all organic matters derived from the process of photosynthesis. It is produced in large quantity, with an estimated 140 billion metric tons per year. Thus, sugar, starch, vegetable oils, agricultural wastes, forest residues, and dedi­cated industrial materials from plants, all belong to biomass by definition. Ligno — cellulose, is mainly consisted of cellulose, hemicellulose and lignin, is by far the most abundant form of biomass. Biomass has been considered as the most impor­tant alternative feedstock for the production of fuels, chemicals and materials [1].

Ionic liquids (ILs) are specifically referred to salts that melt below 100 °C. ILs are usually organic salts comprised of cations and anions. Some ILs exist as liquids

H. Xie (*) • Z. K. Zhao (*)

Division of Biotechnology, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences (CAS), 457 Zhongshan Road,

Dalian 116023, People’s Republic of China e-mail: hbxie@dicp. ac. cn; zhaozb@dicp. 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_7,

© Springer Science+Business Media Dordrecht 2014 at relatively low temperatures, even below room temperature, so they are usually called as room temperature ILs. Due to their unique structural properties, ILs may have some of the following properties, such as non-detectable volatile under atmosphere pressure, good solubility to most of inorganic and organic compounds, high thermal stability, high ionic conductivity, tunable miscibility with traditional solvents, etc. Notably, the chemical and physical properties of ILs can be tuned by combining different cation and anion [2]. These unique properties suggest their important roles in green chemical processes, especially in the topic of biomass processing and conversion towards a foundation of sustainable biorefinery process [3, 4]. Up to date, the use of ILs for biomass processing and conversion mainly focuses on the following subjects:

• Dissolution, derivation, and regeneration of biopolymers

• Catalytic conversion of biopolymers and their monomers into platform

chemicals

• Biomass pretreatment, components fractionation and structural elucidation

• Separation, production of biofuels

Currently, biodiesel, bio-alcohols (e. g. ethanol, butanol) and bio-oil from pyrol­ysis are among the most extensively studied biofuels [5]. Biodiesel is produced mainly from vegetable oils and animal fats via transesterification process. These kinds of oils (lipids) are regarded as important energetic biorenewable resources and chemical raw materials [6, 7]. Bio-alcohols are normally made by microbial fermentation of sugars produced from carbohydrates or starch crops such as sugar­cane or corn [8,9]. With the significant progress in the conversion and utilization of biomass, it is well-recognized that clean and efficient technologies are in high demand to develop a cost-effective bioenergy production system, such as extraction of lipids and bio-alcohols, biodiesel preparation and purification [10].

The applications of ILs as a solvent and/or catalyst in conversion of biomass in a wide perspective have been covered in other chapters of this book or being reviewed elsewhere [11—13]. Especially, with ILs-based pretreatment technology, lignocellulosic biomass is also being developed as a feedstock for the production of bio-alcohols and biodiesel [14, 15]. This chapter focuses on those areas, in which ILs are used for the production of biofuel molecules in a more direct way. Specif­ically, the chapter will provide an up-to-date overview on how to apply ILs in the following areas: lipids separation, biodiesel production, bio-alcohols extraction, and bio-oil production through pyrolysis and upgrading.