Task Specific Ionic Liquids for Cellulose Technology

Abstract

Design of ionic liquids for dissolution, depolymerization, and energy conversion of cellulose and their derivatives is described. Importance of physicochemical properties such as polarity and hydrogen-bonding ability of the ionic liquids is described, and some practical approaches to prepare novel ionic liquids as solvents for cellulose technology are reviewed with latest results. Ç IntroductionThe energy crisis is a major concern. There have been many discussions of substitute materials to replace petroleum and other decreasing natural fuel resources. These natural resources derive from plants, namely, sugar derivatives have been synthesized by plants with the aid of solar energy. Biomass can then be converted into hydrocarbon fuel under the ground. However, we cannot wait for plants to be turned spontaneously but slowly into hydrocarbons. An excellent strategy for providing a new energy source is the immediate use of the biomass. It is, however, ridiculous to convert edible crops or vegetables into energy materials. We do not want to go into details, but energy should be extracted from inedible biomass, such as cereal straws, corn bagasse, cotton, and even used papers. Cellulose is the major component of such biomass, and it can be depolymerized into glucose. Furthermore, energy can be taken from glucose with the aid of enzymes. For efficient energy conversion, it is necessary to dissolve and depolymerize cellulose under mild reaction conditions. Accordingly, it is essential to design solvents for cellulose and to propose a system with minimum energy.Cellulose is stabilized by intra-and inter-molecular hydrogen bonds so as to form tough bundles. Multiple hydrogen-bonding between cellulose molecules results in the formation of highly ordered crystalline regions; furthermore, these are mixed or covered by lignin. It is almost impossible to solubilize cellulose with water and common organic solvents. Some mixed systems composed of organic solvents, water, and salts have been proposed. In spite of the utility of these mixed solvent systems for cellulose, there remain some drawbacks such as volatility, generation of poisonous gas or waste, and difficulty of solvent recovery with small energy. It is not so difficult to combine the above requirements for a classical solvent system for cellulose, i.e., charge and organic compounds, and hydrogen-bonding ability. Organic salts typically fit this combination. In particular, organic salts with very low melting point should be good starting materials for the design of solvents for cellulose. In this review, we discuss the use of ionic liquids in cellulose processing.

Efficient biomass pretreatment using ionic liquids derived from lignin and hemicellulose

“…A slight shielding of the methylene carbons in the α position were also observed when converting the amine δ = 45.9 ppm (2C) and δ = 54.8 ppm (1C) to the IL δ = 45.3 ppm (2C) and δ = 54.6 ppm (1C PO 4 ] were also selected based on their subtle differences in polarity and substituent effects. The polarity of an IL has been correlated with its ability to solubilize both lignin (42,43) and cellulose (44)(45)(46) PO 4 ] were used to dissect the role of these substituents on the relative acidity of the cation and relate these effects to biomass pretreatment.…”

Structural effects of polyethers and ionic liquids in their binary mixtures on lower critical solution temperature liquid-liquid phase separation

“…[8][9][10][11] Furthermore, many liquid-liquid phase equilibrium systems such as IL/water and IL/ organic solvent systems have been presented; this indicates the possibility of utilizing ILs as reaction or extraction solvents. [12][13][14][15] For example, it has been shown that 1-alkyl-3-methylimidazolium bis(trifluoromethane sulfonyl)amide ([C n mim][NTf 2 ]), a typical hydrophobic IL, can be used for the extraction of aromatic compounds from aliphatic hydrocarbons.…”

Observation of Electrochemical Reaction and Biological Specimen by Novel Analytical Technique Combined with Room-Temperature Ionic Liquid and Scanning Electron Microscope

“…First article on the cellulose depolymerization in ionic liquids was reported by Rogers et al 25 Ohno et al proposed a cellulose-based energy conversion process using the RTIL treatment in order to generate electrical energy from cellulose that cannot be decomposed under a mild chemical process. 26 Recent years, several research groups have attempted to directly liquefy wood in RTILs so as to yield glucose. 27,28 However, there is a limited number of articles on the liquefaction mechanism of wood.…”

“…It is well-known that RTILs showing the high ¢ value can dissolve cellulose with ease. 26 The liquefaction experiment of the wood (Cryptomeria japonica) was conducted at less than 393 K. Figure 5 shows SEM images of the cross-sectional wood sample pretreated with the Scheme 1(b) before and after the liquefaction process of the wood. Before the liquefaction process, two different parts, earlywood and latewood, were observed clearly [ Fig.…”