Dissolution Of Ionic Liquids Research Articles

Imidazolium-Based Ionic Liquid Dissolution Influence on Crystallinity of Oil Palm Frond, Oil Palm Trunk and Elephant Grass Lignocellulosic Biomass

Ionic liquid (IL) has been shown to affect cellulose crystalline structure in lignocellulosic biomass (LB) during pretreatment. This research was carried out with two different experimental design involving IL to observe the effect of dissolution in IL on: (A) the crystallinity of cellulose and (B) the dissolution efficiency of LB. For experiment A, the types of IL used in this research were 1-ethyl-3-methylimidazolium Acetate [EMI[A, 1-allyl-3-methylimidazolium Chloride [AMI[C, 1-butyl-3-methylimidazolium Chloride [BMI[C and 1-ethyl-3-methylimidazolium Chloride [EMI[C. The crystallinity degree of LB was investigated before and after pretreatment with IL. The microcrystalline cellulose (MCC) was used as the simulated LB (cellulose content) was dissolved in IL and the crystallinity after the dissolution was analyzed. The temperature (70°C, 80°C, 90°C, 99°C) and concentration ratio of IL with volume/volume (v/v: 10%, 25%, 50%) were varied while the dissolution time remained constant. The crystallinity was analyzed by using Fourier Transform Infrared Spectroscopy (FTIR). The results showed that the dissolution temperature and IL concentration ratio affects the intensity of the FTIR peaks. In experiment B, the dissolution of LB with 1-butyl-3-methylimidazolium Chloride [BMI[C and 1-Ethyl-3-methylimidazolium Chloride [EMI[C as ILs were investigated. Four types of LB involved were Elaeis guineensis species of Oil Palm Trunk (OPT) and Oil Palm Frond (OPF) and Pennisetum purpureum species (elephant grass) originated from Taiwan and India. From the results obtained, the [BMI[C gave better dissolution to biomass.

Influence of organic solvent on the separation of an ionic liquid from a lignin–ionic liquid mixture

Sixteen solvents added in lignin-ionic liquid mixture provide four types of solubility characteristics. The distinct characteristics can be classified by considering solubility parameters including ET Scale, Kamlet-Taft parameters and solubility parameters. Group 1 solvent shows promising solvents for lignin-ionic liquid separation, contributing full dissolution of ionic liquid with lignin precipitation. Isopropanol, the most potential solvent has solubility properties as following normalized molar electronic transition energies (ET(N))=0.57, hydrogen-bond acidity (α)=0.76 and Hildebrand solubility parameter (δT)=23.58. This study examines potential solvents for ionic recovery, provides simple method of separation and leads to the feasibility of using ionic liquids in industrial applications.

Structure and Properties of Natural Cellulose Extracted from Pineapple Leaf

Utilization of agriculture waste has been an issue around the world. In this study, the natural cellulose was extracted from pineapple leaf. Under the optimal pretreatment conditions of 25 g/L, 368 K and 6 h, the ratio of obtained cellulose was above 85 wt%. The structure of obtained cellulose at different stage was confirmed by XRD results. Origin cellulose (OC) and pretreated cellulose (PC) belong to be cellulose I, while regenerated cellulose possessed cellulose II structure, attributed to the dissolution of ionic liquid which destroyed the hydrogen bonds between the cellulose molecules. On the other hand, the structure could be explained by the morphology analysis of OC, PC and RC. The porous network structure of RC led to the reduction of ordered crystalline region and the decrease of crystallinity (CrI), which was proved by BET results. However, the dissolution was testified to be a physical process through FTIR analysis, the existence of characteristic absorption peaks of cellulose. The thermal stability was decreased through pretreatment, dissolution processes, corresponding to the decrease of CrI. The disordered amorphous region of RC decides convenient for production and broad applications.

Effects of pretreatments on crystalline properties and morphology of cellulose nanocrystals

Cellulose nanocrystals (CNCs) have drawn tremendous attention because of their extraordinary physical and chemical properties as well as renewability and sustainability. In this work, after a range of pretreatments, such as freeze-drying, ball-milling, mercerization, N-methylmorpholine-N-oxide dissolution and ionic liquid dissolution, various CNCs with different crystalline properties and morphologies were obtained by hydrolysis or oxidation. XRD and AFM were used to determine the influences of pretreatments on the crystalline properties and morphologies of CNCs. New methods, i.e., specific pretreatments followed by sulfuric acid hydrolysis or 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) oxidation, were developed to obtain sphere-like CNCs. It was found that sphere-like CNCs were more likely to be obtained from cellulose materials possessing high accessibility. Pretreatments produced cellulose with various crystallinities and polymorphs, and therefore changed the yields of CNCs and influenced their morphology. CNCs prepared by TEMPO oxidation generally had smaller size than the corresponding products obtained by sulfuric acid hydrolysis. In addition, for the dissolved/regenerated cellulose, TEMPO oxidation was a better method to yield sphere-like CNCs than sulfuric acid hydrolysis.

Molecular Dynamics Simulation Study on the Absorption of Ethylene and Acetylene in Ionic Liquids

As environmentally friendly and designable solvents, ionic liquids (ILs) have great potential in the separation of C2H4 and C2H2, which is quite important in chemical industry. The microscopic insight into the intermolecular interaction and the diffusion dynamics at a molecular level is crucial for designing more efficient ILs. In this work, the interaction mechanism and diffusion dynamics for C2H4/C2H2 absorption and separation with five ILs, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), 1-butyl-3-methylimidazolium acetate ([bmim][OAc]), 1-butyl-3-methylimidazolium trifluoroacetate ([bmim][TFA]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf2N]), and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([bmpyrr][Tf2N]), were investigated by molecular dynamics (MD) simulation. The result suggests that the van der Waals interaction between C2H4 and cation plays an important role in C2H4 dissolution in ILs, but the hydrogen bonding interaction between C2H...

Ionic liquids as a tool for lignocellulosic biomass fractionation

AbstractLignocellulosic biomass composes a diversity of feedstock raw materials representing an abundant and renewable carbon source. In majority lignocellulose is constituted by carbohydrate macromolecules, namely cellulose and hemicellulose, and by lignin, a polyphenilpropanoid macromolecule. Between these biomacromolecules, there are several covalent and non-covalent interactions defining an intricate, complex and rigid structure of lignocellulose. The deconstruction of the lignocellulosic biomass makes these fractions susceptible for easier transformation to large number of commodities including energy, chemicals and material within the concept of biorefinery. Generally, the biomass pre-treatment depends on the final goal in the biomass processing. The recalcitrance of lignocellulose materials is the main limitation of its processing once the inherent costs are excessively high for the conventional pre-treatments. Furthermore, none of the currently known processes is highly selective and efficient for the satisfactory and versatile use, thus, new methodologies are still studied broadly. The ionic liquid technology on biomass processing is relatively recent and first studies were focused on the lignocellulosic biomass dissolution in different ionic liquids (ILs). The dissolution in IL drives to the structural changes in the regenerated biomass by reduction of cellulose crystallinity and lignin content contrasting to the original biomass. These findings provided ILs as tools to perform biomass pre-treatment and the advantageous use of their specific properties over the conventional pre-treatment processes. This review shows the critical outlook on the study of biomass dissolution and changes occurred in the biomass during this process as well as on the influence of several crucial parameters that govern the dissolution and further pre-treatment process. The review of currently known methods of biomass fractionation in IL and aqueous-IL mixtures is also discussed here and perspectives regarding these topics are given as well.

The effect of deuteration on the structure of bacterial cellulose

In vivo generated deuterated bacterial cellulose, cultivated from 100% deuterated glycerol in D2O medium, was analyzed for deuterium incorporation by ionic liquid dissolution and 2H and 1H nuclear magnetic resonance (NMR). A solution NMR method of the dissolved cellulose was used to determine that this bacterial cellulose had 85% deuterium incorporation. Acetylation and 1H and 2H NMR of deuterated bacterial cellulose indicated near equal deuteration at all sites of the glucopyranosyl ring except C-6 which was partly deuterated. Despite the high level of deuterium incorporation no significant differences in the molecular and morphological properties were observed for the deuterated and protio bacterial cellulose samples. The highly deuterated bacterial cellulose presented here can be used as a model substrate for studying cellulose biopolymer properties via future small angle neutron scattering (SANS) studies.

Molecular weight distributions of acetylated lignocellulosic biomasses recovered from an ionic liquid system

Abstract Recently, a method was presented for the dissolution and nuclear magnetic resonance analysis of cell wall components in lignocellulosic biomass, which involves cell wall ball-milling, dissolution in ionic liquids (ILs), in situ acetylation, and the recovery of acetylated materials. However, the dissolution in ILs and the relatively long ball-milling times may partially degrade the plant cell wall components. In the present study, the molecular weight (MW) distributions of acetylated biomasses from fir (Abies sachalinensis), birch (Betula platyphylla), and bamboo (Phyllostachys nigra) recovered from IL systems were examined by size exclusion chromatography. The effects of IL types, cosolvents, dissolution temperatures and times, and ball-milling times were evaluated. The MW of acetylated fir woods recovered from 1-allyl-3-methylimidazolium chloride at 30–80°C or from 1-butyl-3-methylimidazolium chloride at 100°C for 2 h were similar to those materials that were recovered from the N-methylimidazole/dimethyl sulfoxide system. In contrast, a significant decrease in MW was observed with 1-ethyl-3-methylimidazolium acetate ([Emim]OAc) even at 30°C. The degradation of cell wall components in [Emim]OAc was reduced to some extent in the presence of N,N-dimethylacetamide or pyridine. The MW decreased gradually with increased ball-milling time.

Relation between differential solubility of cellulose and lignin in ionic liquids and activity coefficients

In this work, the excess enthalpies and activity coefficients were evaluated as reference parameters of the solubility of cellulose and lignin in ionic liquids (ILs) using COSMO-RS. Guided by experimental tests, a variety of solubility behaviours of these compounds in 12 ILs with different anions was reported. Appropriate molecular models able to simulate the behaviour of real cellulose and lignin compounds were selected with the aid of experimental data on their dissolution in ILs. The aim was to develop a reliable COSMO-RS computational approach to predict the ability of an IL to dissolve cellulose and/or lignin. A 3 × 3 cellulose structure was optimized in order to achieve an adequate model for describing cellulose solubility, and nine different models were obtained. Several molecules were evaluated as lignin models in COSMO-RS calculations, such as pinoresinol, guaiacylglycerol-2-coniferyl ether, and p-coumaryl, coniferyl and sinapyl alcohols. The results showed that the activity coefficient was the most consistent property to predict the ability of ILs to dissolve these compounds, allowing a tentative classification of the cellulose and lignin differential solubility in ILs in terms of this parameter value. In addition, the study of the differential solubility of cellulose and lignin, based on the developed COSMO-RS approach, was extrapolated to a wide sample of 750 ionic liquids, including 25 cations and 30 anions.

Process optimization and performance evaluation on sequential ionic liquid dissolution–solid acid saccharification of sago waste

The production of reducing sugars from sago waste via sequential ionic liquid dissolution–solid acid saccharification was optimized in this study. Ionic liquid dissolution of sago waste with 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) was conducted prior to the solid acid saccharification with Amberlyst 15 (A15). The effect of time, temperature and substrate loading during dissolution reaction; and the effect of time, temperature and catalyst loading during saccharification reaction were examined by applying central composite design (CCD) separately. Both dissolution and saccharification reactions were respectively modeled into quadratic polynomial equations with good predictive accuracies. A high reducing sugars yield of 98.3% was obtained under the optimized conditions, i.e. dissolution at 1.75h, 160°C, 1.5% substrate loading, and saccharification at 0.5h, 130°C, 4% catalyst loading. From comparison studies of different saccharification schemes, the sequential ionic liquid dissolution–solid acid saccharification has proven to be a potential method in reducing sugars production from the lignocellulosic biomass.

The dissolution of lignite in ionic liquids

A Xianfeng lignite (XL) was dissolved in a series of ionic liquids (ILs) at 200 °C. It was found that the anions of the imidazolium-based ILs are one significant factor to affect the extraction yield of XL and the chemical characteristics of extracts obtained from ILs extraction. The dissolution of ILs to lignite is related to the destructive ability of ILs to hydrogen bonds widely existing in lignite. The analyses of residues by in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFT) indicate that the nature of ILs has a significant effect on the disruption of hydrogen bonds existing in lignite. The effective extraction of lignite results from the fracture of the hydrogen bonding network in lignite during lignite dissolving in ILs. Ionic liquid 1-butyl-3-methyl-imidazolium chloride [Bmim]Cl can dissociate significantly almost all of hydrogen bonds existing in lignite.

An Orthogonal Experiment of Bagasse Cellulose Dissolution in Ionic Liquid by Microwave Heating

In this paper, bagasse cellulose was dissolved in ionic liquid (1-butyl-3-methylimidazolium chloride) by microwave heating. The orthogonal test and variance analysis were applied to obtain the optimum dissolution condition of bagasse in ionic liquid. The effects of microwave power, temperature and the mass fraction of cellulose were examined by an orthogonal experiment designed through the different dissolution time and the yield of regeneration bagasse. Results showed that the optimal dissolution condition for faster dissolution time was 1% of bagasse cellulose in ionic liquid at 140°C, 500W; while, to get the most yield of cellulose, the condition was 2% of bagasse cellulose at 130°C, 500W.

Specific features of cellulose and chitin dissolution in ionic liquids of varied structure and the structural organization of regenerated polysaccharides

Solubility of cellulose, chitin, and chitosan in seven ionic liquids of varied structure was studied. It was found that pressure, temperature, and amount of an aprotic diluent (dimethyl sulfoxide) affect the dissolution of cellulose and chitin in an ionic liquid. The variation of the degree of polymerization of cellulose and chitin in ionic liquid solutions was studied. IR Fourier spectroscopy and X-ray diffraction analysis were used to examine the structural organization of hydrated cellulose and chitin films obtained.

Dissolution of Cellulose in Ionic Liquids Assisted with Ethanol Pretreatment

One of the major current challenges to the chemical industry is the efficient use of renewable lignocellulosic biomass for the production of performance materials, platform chemicals, and biofuels. Dissolution of natural polymers including cellulose in ionic liquids has attracted much more attention around all over the world. However, the time for complete dissolution of cellulose in ionic liquids was too long for processing and derivatization to produce industrial materials. Herein, ethanol pretreatment was introduced to improve cellulose dissolution in ionic liquids. The pretreated cellulose was easily wetted and penetrated for dissolution in ionic liquids, which efficiently avoided the formation of the agglomerates of cellulose mixed with air wrapped with viscous ionic liquids. The dissolution time of pretreated cellulose could decrease to 75 min under the given conditions. FT-IR and CP/MAS 13C-NMR analyses indicated that ethanol pretreatment and dissolution in ionic liquid did not lead to any functionalization of cellulose. It was also found that the crystalline structure of native cellulose was destroyed and the regenerated cellulose was mainly composed of amorphous structure. The thermal stability of cellulose decreased and the pyrolysis residues increased after dissolution and regeneration.

Impact of Anti-Solvents on the Structural Features and Enzyme Digestibility of Regenerated Cellulose from Ionic Liquid Dissolution

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Increased Dissolution of Lignocellulosic Biomass in Ionic Liquid 1-Butyl-3-Methylimidazolium Chloride at High Temperature

The increased dissolution of ball-milled lignocellulosic biomass including sugarcane bagasse, Eucalyptus, and Masson pine was investigated in ionic liquid 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) at relatively high temperature. The dissolution time of bagasse in [C4mim]Cl decreased from 13.5 h at 90oC to 2.0 h at 140oC, and further decreased to 0.5 h at 170oC, 0.33 h at 180oC, and 0.28 h at 190oC. Similarly, the dissolution of ball-milled Eucalyptus and Masson pine in [C4mim]Cl was achieved under same conditions within 0.75 h and 0.25 h, respectively. The order of the dissolution efficiency of the ball-milled lignocellulosics in [C4mim]Cl at 170oC was Masson pine > bagasse > Eucalyptus, which was probably related to the more compact and complicated cell wall structure of Eucalyptus than bagasse and Masson pine. The physicochemical properties of the regenerated lignocellulosics were characterized with FT-IR, CP/MAS 13C-NMR and wide-angle X-ray diffraction as well as thermal analysis. The results indicated that no derivatization occurred in dissolution in ionic liquid even at high dissolution temperature. The crystalline structure in native bagasse was destroyed and converted from cellulose I to amorphous structure at low dissolution temperature and to cellulose II at high dissolution temperature after regeneration. Thermal stability of lignocellulosics was slightly decreased after dissolution and regeneration in [C4mim]Cl.

Ionic liquids-based hydrolysis of Chlorella biomass for fermentable sugars

An ionic liquids-based chemical hydrolysis strategy was developed to obtain high-yielding soluble sugars from Chlorella biomass. Initial ionic liquids dissolution and subsequently HCl catalyzed hydrolysis could dissolve 75.34% of Chlorella biomass and release 88.02% of total sugars from Chlorella biomass. The amount of HCl loading was 7wt.% relative to Chlorella biomass weight, which was much lower (only 14.6%) than that in HCl/MgCl2-catalyzed system with similar sugars release (Zhou et al., 2011). Ionic liquids in the hydrolysates were recycled and fermentable sugars were evaluated by converting to bioethanol after separated by ion-exclusion chromatography. This ionic liquids-based hydrolysis strategy showed the great potential to produce fermentable sugars from algal biomass.

All-cellulose composites prepared from flax and lyocell fibres compared to epoxy–matrix composites

All-cellulose composites (ACCs) were prepared by partial dissolution in ionic liquid and compared to composites with epoxy matrix. Wide-angle X-ray diffraction and scanning electron microscopy were used to reveal differences in the structure of the composites. In tensile tests, lyocell-fibre based ACCs showed similar strength and stiffness, yet superior extensibility compared to lyocell-epoxy composites. However, when flax fibres were used, tensile properties clearly inferior to flax-epoxy were observed. Dynamic-mechanical and thermogravimetric analysis revealed a favourable behaviour for ACC in terms of more diffuse thermal softening and increased resistance to thermal degradation.

Dialkylimidazolium Ionic Liquids Hydrolyze Cellulose Under Mild Conditions

The average molecular weight of cellulose derived from filter paper, poplar, and Avicel decreases by up to two orders of magnitude during typical mild dissolution protocols using ionic liquids (ILs). About an order of magnitude greater cellulose depolymerization rate during ionic liquid dissolution occurs in 1-butyl-3-methylimidazolium chloride (BmimCl) and 1-ethyl-3-methylimidazolium chloride (EmimCl) compared to 1-ethyl-3-methylimidazolium acetate (EmimOAc), and, unintuitively, greater IL purity results in greater cellulose depolymerization. The following data support the mechanism of cellulose hydrolysis to be acid-catalyzed: (i) increase in number of reducing ends following cellulose dissolution in IL; (ii) addition of N-methylimidazolium base suppresses cellulose depolymerization during dissolution in IL; (iii) small amounts of glucose and traces of hydroxymethyl furfural are present following cellulose dissolution in IL. The acid is presumably synthesized via IL decomposition to generate a carbene and proton, consistent with hypothesis derived from molecular modeling. Titration experiments conducted here measure the amount of acid synthesized to be in the 4000 ppm range for high-purity BmimCl IL during mild processing conditions for cellulose dissolution. This data is relevant for understanding the extent of IL decomposition during biomass dissolution.

Pretreatment of rice hulls by ionic liquid dissolution

As a highly available waste product, rice hulls could be a starting block in replacing liquid fossil fuels. However, their silica covering can make further use difficult. This preliminary study investigates effects of dissolving rice hulls in the ionic liquids 1-ethyl-3-methylimidazolium acetate (EMIM Ac), 1-hexyl-3-methylimidazolium chloride, (HMIM Cl), and 1-allyl-3-methylimidazolium chloride (AMIM Cl), and what lignocellulosic components can be precipitated from the used ionic liquid with water and ethanol. EMIM Ac dissolution at 110°C for 8h was found to completely remove lignin from rice hulls, while ethanol was capable of precipitating lignin out of the used EMIM Ac. With 8h dissolution at 110°C using HMIM Cl, approximately 20% of the cellulose in the rice hull sample can be precipitated out using water as co-solvent, while more than 60% of the hemicellulose can be precipitated with ethanol.