Predicting Cellulose Solvating Capabilities of Acid-Base Conjugate Ionic Liquids (original) (raw)
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Towards Ionic Liquid Fractionation of Lignocellulosics for fermentable sugars
Cellulose Chemistry and Technology
The present study investigates wood fractionation through ionic liquid (IL) mediated pretreatment, for obtaining simple fermentable sugars, namely oligo- and monosaccharides, and in particular hexoses (and pentoses). The study focuses on softwood, Scots Pine (Pinus sylvestris) and Norway Spruce (Picea abies), exposed to ionic liquid 1-ethyl-3-methylimidazolium chloride (EmimCl). Since both EmimCl and the monosaccharides are water-soluble and dissolve readily in similar solvents, the separation of this hydrophilic IL from sugars is difficult. Moreover, the analytics of monosaccharides released from lignocellulosics with the help of EmimCl is challenging. Sufficiently diluted samples, with low enough EmimCl concentrations, tolerated by GC sugar columns, can be also analyzed by GC. The results obtained suggest that some IL-tolerating HPLC columns can be utilized for a quantitative determination of monosaccharides. However, frequently, these columns have low separation ability for monos...
Recovery of Sugars from Ionic Liquid Biomass Liquor by Solvent Extraction
BioEnergy Research, 2010
The dissolution of biomass into ionic liquids (ILs) has been shown to be a promising alternative biomass pretreatment technology, facilitating faster breakdown of cellulose through the disruption of lignin and the decrystallization of cellulose. Both biological and chemical catalysis have been employed to enhance the conversion of IL-treated biomass polysaccharides into monomeric sugars. However, biomass-dissolving ILs, sugar monomers, and smaller carbohydrate oligomers are all soluble in water. This reduces the overall sugar content in the recovered solid biomass and complicates the recovery and recycle of the IL. Nearcomplete recovery of the IL and the holocellulose is essential for an IL-based pretreatment technology to be economically feasible. To address this, a solvent extraction technique, based on the chemical affinity of boronates such as phenylboronic acid and naphthalene-2-boronic acid for sugars, was applied to the extraction of glucose, xylose, and cellobiose from aqueous mixtures of 1-ethyl-3-methylimidazolium acetate. It was shown that boronate complexes could extract up to 90% of mono-and disaccharides from aqueous IL solutions, 100% IL systems, and hydrolysates of corn stover containing IL. The use of boronate complexes shows significant potential as a way to recover sugars at several stages in ionic liquid biomass pretreatment processes, delivering a concentrated solution of fermentable sugars, minimizing toxic byproducts, and facilitating ionic liquid cleanup and recycle.
Ionic liquid fractionation of woody biomass for fermentable monosaccharides
2011
The goal of the present study, devoted to wood fractionation, was to obtain monosaccharides, hexoses and pentoses by means of an ionic liquid (IL) based pre-treatment procedure. Softwood sawdust (maximum particle size of 2 mm) of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) were exposed to ionic liquids – 1-ethyl-3-methylimidazolium acetate (C2mimAce) and 1-ethyl-3-methylimidazolium chloride (C2mimCl) – and thermal treatment (80-150 °C), for various time intervals (0-72 h). Furthermore, cellulose of various origins (plants, wood pulps) was dissolved in C2mimAce and 1-butyl-3-methylimidazolium chloride (C4mimCl) for the study of the dissolved fractions, stress being laid on monosaccharides and possible by-products, 5-hydroxymethylfurfural and furfural. Knowing the challenges in analysis techniques when ILs and sugars are involved, the present work focuses on the development of suitable analysis methods. To this end, a Hewlett Packard 1100 series HPLC equipped with a refractive index (RI), detector model HP1047 A and a diode array UV detector (DAD) fitted with a carbohydrate column HPX-87K was utilized. Challenges and improvements are discussed.
Journal of agricultural and food chemistry, 2015
Ionic liquids (ILs) can play multiple roles in lignocellulose biorefineries, including utilization as agents for the separation of selected compounds, or as reaction media for processing lignocellulosic materials (LCM). Imidazolium-based ILs have been proposed for separating target components from LCM biorefinery streams, for example the dehydration of ethanol-water mixtures, or the extractive separation of biofuels (ethanol, butanol) or lactic acid from the respective fermentation broths. As in other industries, ILs are potentially suitable for removing Volatile Organic Compounds or carbon dioxide from gaseous biorefinery effluents. On the other hand, cellulose dissolution in ILs allows to carry out homogeneous derivatization reactions, opening new ways for product design and/or for improving the quality of the products. Imidazolium-based ILs are also suitable for processing native LCM, allowing the integral benefit of the feedstocks via separation of polysaccharides and lignin. Ev...
Journal of Solution Chemistry, 2015
This work reports on the ionic liquid (IL) based separation of cellulose/ hemicellulose from lignocellulosic biomass, by means of macroscale predictions using the COnductor like Screening MOdel for Real Solvents (COSMO-RS) model that is based on a statistical mechanical framework. For the benchmarking studies the experimental infinite dilution activity coefficient values for 13 components were predicted in 1-alkyl-3-methylimidazolium bis{(trifluoromethyl)sulphonyl}imide with an average absolute deviation (%AAD) of 15 %. Further, the solid-liquid equilibria of glucose, fructose, galactose, and xylose in [EMIM][EtSO 4 ] and Aliquat Ò 336 were predicted successfully with 15 % rootmean-square deviation. Afterwards, the selectivities were predicted at infinite dilution for cellulose/hemicellulose in 1,156 ILs with a combination of 34 cations and 34 anions. Based on these values, the ammonium-based ILs 1-methyl-4-aminotriazolium hexafluorophosphate [14MATAZ] [PF 6 ] and 4-aminotriazolium bis(oxalato(2)borate) [4ATAZ] [BOB] were found to be good candidates for cellulose and hemicellulose extraction, respectively. The ILs selected using the COSMO-RS methodology were then studied qualitatively in terms of interaction energies and HOMO-LUMO energy gap. The binding energy for [1-methyl-4-aminotriazolium][PF 6 ] ? cellulose and [4-aminotriazolium][BOB] ? cellulose systems are higher as compared with IL ? cellulose ? hemicellulose, indicating greater stability. Keywords Ionic liquid Á COSMO-RS Á Cellulose Á Hemicellulose Á HOMO-LUMO Electronic supplementary material The online version of this article (
Fractionation of Lignocellulosic Biomass by Selective Precipitation from Ionic Liquid Dissolution
Applied Sciences
We propose the treatment of barley straw with 1-ethyl-3-methylimidazolium acetate [EMIMAcO] ionic liquids (ILs) and subsequent precipitation with antisolvent mixtures, thus allowing the separation of the sugar-rich fractions (cellulose and hemicellulose) from the lignin fraction. For this purpose, different concentration ranges of acetone:water antisolvent mixtures were studied. In all cases, a high recovery percentage and a high and effective separation of fractions was achieved for 1:1 acetone:water. The fractionated lignocellulosic compounds were studied by using infrared spectroscopy, scanning electron microscopy and 1H nuclear magnetic resonance characterization techniques. This method allows the possibility of reusing IL, confirming the versatility of the established method. The fraction rich in cellulose and hemicellulose was subjected to acid hydrolysis (0.2 mol/L H2SO4) for 5 h at 140 °C, obtaining a yield of total reducing sugars of approximately 80%, much higher than thos...
Catalysis Today, 2014
Processing of woody lignocellulosic biomass, under heating in combination with ionic liquids (ILs) was studied in order to obtain simple (fermentable) sugars. Due to the new environmental challenges, finding greener ways to produce platform chemicals and/or bio-fuels has become a popular research area. Various industrial, pilot or laboratory scale technologies for the depolymerization or fractionation of lignocellulosic polysaccharides to monomers are known. One of the new, interesting, methods is to utilize ILs in biomass pre-treatment procedures with an aim to bypass other pre-treatment methods. Furthermore, in order even to initiate studies whether ILs can contribute to catalytic depolymerization, there has to be a robust way to analyze the IL-treated lignocellulosics. This is a major issue since woody samples that contain any salts such as ILs can indeed be quite challenging from the analytic point of view. The applied capillary electrophoresis was found to be an excellent analytical method providing substantial improvements compared to the earlier used chromatographic methods.
Ionic liquids as a tool for lignocellulosic biomass fractionation
Sustainable Chemical Processes, 2013
Lignocellulosic 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.
Chemical Communications
A novel physical (non-reactive) separation of cellulose from an ionic liquid (IL) / cosolvent mixture by compressed carbon dioxide is presented. The precipitation is completely reversible and rapid within small changes of pressure i.e. liquid phase CO 2 composition. High pressure phase equilibrium, high pressure NMR, and solid state NMR have been utilized to understand the separation phenomena. Cellulosic biomass is a potential sustainable alternative to petroleum-based feedstocks for fuels and chemicals provided that it is renewable, abundant, and inexpensive with lowenergy input and without significantly impacting food sources. However, processing cellulosic biomass is challenging due to its relative recalcitrance to conventional heterogeneous solid-liquid reactions which are mass-transfer limited especially for crystalline biomass types. Only a small number of organic solvents have been discovered that can dissolve even measurable quantities of cellulose. 1 The ability to dissolve biomass can significantly aid in separations of the constituent components (e.g. cellulose, lignin, etc.) and can significantly decrease the reaction time or reactor size required to transform biomass to various chemicals and fuels. Some ionic liquids (ILs) have the highest known solubilities of cellulose at any given temperature. 1a Furthermore, select ILs including 1-ethyl-3methylimidazolium diethyl phosphate ([EMIm][DEP], see Figure 1) have demonstrated success for cellulose dissolution and pretreatment using antisolvent precipitation. 1a, 2 The precipitated cellulose product is highly amorphous which has been correlated to superior chemical and biochemical conversion rates to glucose or other chemicals even despite the heterogeneous reaction scenario. 3 While significant interest has been given to cellulose dissolution, only limited work has investigated the ensuing biomass precipitation step and necessity for IL recycling. The majority of aqueous and organic solvents have no intrinsic cellulose solubility and most act as "antisolvents" when added to IL/cellulose mixtures leading to cellulose precipitation. Typical antisolvents in the literature are chosen among polar protic liquids (H 2 O, EtOH, etc.
RSC Advances, 2014
Ionic liquids (ILs) have proven effective solvents for pretreating lignocellulose, leading to the fast saccharification of cellulose and hemicellulose. However, the high cost of most ILs remains a major barrier to commercializing this recent approach at a practical scale. As a strategic detour, aqueous solutions of ILs are also being explored as less costly alternatives to neat ILs for cellulose pretreatment. However, limited studies on a few select IL systems are known and there remains no systematic survey of various ILs, eluding an in-depth understanding of pretreatment mechanisms afforded by aqueous IL systems. As a step toward filling this gap, this study presents results for Avicel cellulose pretreatment by neat and aqueous solutions (1.0 and 2.0 M) of 20 different ILs and three deep eutectic solvents, correlating enzymatic hydrolysis rates of pretreated cellulose with various IL properties such as hydrogen-bond basicity, polarity, Hofmeister ranking, and hydrophobicity. The pretreatment efficiencies of neat ILs may be loosely correlated to the hydrogen-bond basicity of the constituent anion and IL polarity; however, the pretreatment efficacies for aqueous ILs are more complicated and cannot be simply related to any single IL property. Several aqueous IL systems have been identified as effective alternatives to neat ILs in lignocellulose pretreatment. In particular, this study reveals that aqueous solutions of 1-butyl-3-methylimidazolium methanesulfonate ([BMIM][MeSO 3 ]) are effective for pretreating switchgrass (Panicum virgatum), resulting in fast saccharification of both cellulose and