Ionic liquids and their interaction with cellulose (original) (raw)
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Ionic Liquids as Environmental Benign Solvents for Cellulose Chemistry: A Review
Solvents, Ionic Liquids and Solvent Effects
The application of cellulose and its derivatives is restricted because of their limited solubility in water and many organic solvents. Recently, several attempts are being made to dissolve them in inorganic and organic solvents. The solubility of these polymeric materials mainly depends upon their molecular weight, pH, and source of origin. Nowadays, there has been a new breakthrough of applying ionic liquids (ILs; designer solvents) in the field of cellulose solvent chemistry. Association of ionic liquids with several salient features such as high thermal, chemical and low vapor pressure, and so on makes them ideal environmentally green solvents to be used for cellulose. The present chapter deals with a collection of some major works in which ionic liquids have been used as solvents for cellulose dissolution. The articles also describe the works illustrating the use of ionic liquids as cosolvents (organic aprotic solvents) for the better increase of the solvent activity (solubility).
2010
Cellulose is one of the most abundant biological and renewable materials in the world. The application of cellulose is widely distributed among various industries such as fiber, paper, pharmaceutical, membrane, polymer and paint. However, the utilization of cellulose or cellulosic materials has not been developed entirely because of its poor solubility in common organic solvents. Ionic liquids (ILs) are relatively new family of solvents for dissolution of cellulose. They are organic salts contain only cations and anions with low melting temperature, which make them suitable for the solubilization of cellulose. Moreover, ILs are non-volatile, non-toxic, non-flammable and thermally and chemically stable. Cellulose dissolved in ILs can be regenerated with anti-solvents as water, ethanol and acetone. In this study, both the dissolution and regeneration of hardwood and softwood dissolving pulps with and from two ILs ([C mim + ]CH 3 COOand [C4mim + ]Cl-) were investigated. Furthermore, the impact of treating cellulose with ILs was also evaluated by using different analytical techniques, such as size exclusion chromatography (SEC), thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM).
Dissolution of cellulose in ionic liquids and their mixed cosolvents: A review
Sustainable Chemistry and Pharmacy, 2019
Because of increasing environmental awareness and over-extrapolation of non-renewable materials, the application and processing of carbohydrate polymers (polysaccharides) have attracted immense courtesy as they are most abundant natural and biorenewable materials on the Earth. However, insolubility of the most of the polysaccharides in most of the common solvents including water limits their applications. Limited solubility of the polysaccharides is attributed because of the strong intermolecular interactions between polymeric chains that offer them high degree of crystallinity. More so, some organic solvents such as morpholine, N-methylmorpholine-N-oxide (NMMO), N-methylmorpholine (NMM), urea and thiourea in association with sodium hydroxide etc. were used to solubilise carbohydrate polymers with particular emphasis of cellulose. However, processing of the polysaccharides with these solvents is not only toxic to surrounding environment and living beings but also release several environmental malignant chemicals that can cause several side reactions and adversely affect their physiological properties. Present review paper features the collection of some major works that have been carried out in the area of cellulose dissolution in ionic liquids with and without co-solvents (DMSO, DMF, DMAc etc.).
Dissolution of cellulose in ionic liquid: A review
AIP Conference Proceedings
Dissolution of cellulose with ionic liquids (IL) and deep eutectic solvent (DES) lets the comprehensive dissolution of cellulose. Basically, cellulose can be dissolved, in some hydrophilic ionic liquids, such as 1-butyl-3-methylimidazolium chloride (BMIMCl) and 1-allyl-3-methylimidazolium chloride (AMIMCl). Chloride based ionic liquids are suitable solvents for cellulose dissolution. Although the ILs is very useful in fine chemical industry, its application in the pharmaceutical and food industry have been very limited due to issues with toxicity, purity, and high cost. Seeing to these limitations, new green alternative solvent which is DES was used. This green solvents, may be definitely treated as the next-generation reagents for more sustainable industrial development. Thus, this review aims to discuss the dissolution of cellulose either with ionic liquids or DES and its application.
Direct analysis of cellulose in polar ionic liquids
2015
A novel method for cellulose hydrolysis catalyzed by mineral acids in the ionic liquid 1butyl-3-methylimidazolium chloride ([C4mim]Cl) has been developed that facilitates the hydrolysis of cellulose with dramatically accelerated reaction rates at 100 8C under atmospheric pressure and without pretreatment.
Mixtures of ionic liquids as more efficient media for cellulose dissolution
Carbohydrate Polymers, 2017
Highlights The ability of ionic liquids eutectic mixture to dissolve cellulose was studied. Addition of DMSO to the ionic liquid mixture improves the cellulose dissolution. Up to 43 g of cellulose per 100 g of used solvent mixture could be dissolved. Anisotropy was observed in the solutions with highest cellulose concentration. The dissolved cellulose could be easily reconstituted from the solutions. The IR spectroscopy can be used to assess the purity of the regenerated cellulose.
True molecular solutions of natural cellulose in the binary ionic liquid-containing solvent mixtures
Amorphous amphiphilic cellulose Binary solvent mixture Small-angle neutron and X-ray diffraction a b s t r a c t Evidence is presented for the first time of true molecular dissolution of cellulose in binary mixtures of common polar organic solvents with ionic liquid. Cryogenic transmission electron microscopy, smallangle neutron-, X-ray-and static light scattering were used to investigate the structure of cellulose solutions in mixture of dimethyl formamide and 1-ethyl-3-methylimidazolium acetate. Structural information on the dissolved chains (average molecular weight ∼5 × 10 4 g/mol; gyration radius ∼36 nm, persistence length ∼4.5 nm), indicate the absence of significant aggregation of the dissolved chains and the calculated value of the second virial coefficient ∼2.45 × 10 -2 mol ml/g 2 indicates that this solvent system is a good solvent for cellulose. More facile dissolution of cellulose could be achieved in solvent mixtures that exhibit the highest electrical conductivity. Highly concentrated cellulose solution in pure ionic liquid (27 wt.%) prepared according to novel method, utilizing the rapid evaporation of a volatile co-solvent in binary solvent mixtures at superheated conditions, shows insignificant cellulose molecular aggregation.
Distillable Acid-Base Conjugate Ionic Liquids for Cellulose Dissolution and Processing
Angewandte Chemie International Edition, 2011
Future biorefinery concepts are seriously entertaining the use of ionic liquids (ILs) as a platform media for the processing of woody material as a second-generation biomass feedstock. The main motivation is the demonstrated efficiency of some molten salts in the dissolution of cellulose, a major structural and solvolytically resistant component of lignocellulosic materials.