Showing papers on "Solvent published in 2014"
TL;DR: In this article, the chemistry of different solvent extractants and typical configurations for rare earth separations are reviewed. But the choice of extractants is influenced by both cost considerations and requirements of technical performance.
947 citations
TL;DR: This review gives a brief overview of single-crystal X-ray diffraction studies and single-Crystal transformations of porous coordination polymers under various chemical and physical stimuli such as solvent and gas sorption/desorption/exchange, chemical reaction and temperature change.
Abstract: X-Ray single-crystal diffraction has been the most straightforward and important technique in structural determination of crystalline materials for understanding their structure–property relationships. This powerful tool can be used to directly visualize the precise and detailed structural information of porous coordination polymers or metal–organic frameworks at different states, which are unique for their flexible host frameworks compared with conventional adsorbents. With a series of selected recent examples, this review gives a brief overview of single-crystal X-ray diffraction studies and single-crystal to single-crystal transformations of porous coordination polymers under various chemical and physical stimuli such as solvent and gas sorption/desorption/exchange, chemical reaction and temperature change.
367 citations
TL;DR: In this article, reaction kinetics were studied to quantify the effects of polar aprotic organic solvents on the acid-catalyzed conversion of xylose into furfural.
Abstract: Reaction kinetics were studied to quantify the effects of polar aprotic organic solvents on the acid-catalyzed conversion of xylose into furfural. A solvent of particular importance is g-valerolactone (GVL), which leads to signifi- cant increases in reaction rates compared to water in addition to increased product selectivity. GVL has similar effects on the kinetics for the dehydration of 1,2-propanediol to propanal and for the hydrolysis of cellobiose to glucose. Based on results obtained for homogeneous Bronsted acid catalysts that span a range of pKa values, we suggest that an aprotic organic solvent affects the reaction kinetics by changing the stabiliza- tion of the acidic proton relative to the protonated transition state. This same behavior is displayed by strong solid Bronsted acid catalysts, such as H-mordenite and H-beta. The use of organic solvents is pervasive in the chemical industry, and recently it has been shown that organic solvents are beneficial in the chemical conversion of lignocellulosic biomass. (1-3) One such solvent is g-valerolactone (GVL), which can be produced from biomass and displays significant improvements in reaction performance for biomass conver- sion reactions compared to conversion in aqueous media, such as increased catalytic activity and higher selectivity to desired reaction products. (2, 3) Furthermore, we have reported that the simultaneous conversion of hemicellulose and cellulose can be achieved using GVL as a solvent in a single reactor, eliminating the need for pretreatment and/or sepa- ration steps. (4) Recently, we have taken advantage of accel- erated rates of cellulose and hemicellulose deconstruction in GVL-H2O solvent mixtures to develop a processing strategy to produce streams of C5 and C6 sugars (e.g., 130 g l � 1 ) from biomass. (5) Other polar aprotic solvents, such as g-lactones and tetrahydrofurans, have also shown comparable benefits to GVL in biomass conversion processes. (3) Herein, we report the effects of GVL and other polar aprotic solvents on acid-catalyzed biomass conversion reac- tions using acid catalysts that span a range of pKa values. The liquid-phase dehydration of xylose to furfural is catalyzed by Bronsted acids and serves as a probe reaction in the present study. We compare the reactivity trends displayed by these homogeneous acid catalysts in the liquid phase with the performance of solid acid catalysts, the latter of which have been shown to span a range of catalytic activities for the gas-
361 citations
TL;DR: Well-established principles of coordination chemistry provide an explanation for the remarkable strengths and selectivities shown by most of these solvent extractants used in extractive hydrometallurgy.
Abstract: The modes of action of the commercial solvent extractants used in extractive hydrometallurgy are classified according to whether the recovery process involves the transport of metal cations, Mn+, metalate anions, MXxn−, or metal salts, MXx into a water-immiscible solvent. Well-established principles of coordination chemistry provide an explanation for the remarkable strengths and selectivities shown by most of these extractants. Reagents which achieve high selectivity when transporting metal cations or metal salts into a water-immiscible solvent usually operate in the inner coordination sphere of the metal and provide donor atom types or dispositions which favour the formation of particularly stable neutral complexes that have high solubility in the hydrocarbons commonly used in recovery processes. In the extraction of metalates, the structures of the neutral assemblies formed in the water-immiscible phase are usually not well defined and the cationic reagents can be assumed to operate in the outer coordination spheres. The formation of secondary bonds in the outer sphere using, for example, electrostatic or H-bonding interactions are favoured by the low polarity of the water-immiscible solvents.
328 citations
TL;DR: In this paper, the phase behavior of high-concentrated electrolytes containing carbonate solvents with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) have been investigated to determine the influence of eliminating bulk solvent on electrolyte properties.
Abstract: Highly concentrated electrolytes containing carbonate solvents with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) have been investigated to determine the influence of eliminating bulk solvent (i.e., uncoordinated to a Li+ cation) on electrolyte properties. The phase behavior of ethylene carbonate (EC)–LiTFSI mixtures indicates that two crystalline solvates form—(EC)3:LiTFSI and (EC)1:LiTFSI. Crystal structures for these were determined to obtain insight into the ion and solvent coordination. Between these compositions, however, a crystallinity gap exists. A Raman spectroscopic analysis of the EC solvent bands for the 3–1 and 2–1 EC–LiTFSI liquid electrolytes indicates that ∼86 and 95%, respectively, of the solvent is coordinated to the Li+ cations. This extensive coordination results in significantly improved anodic oxidation and thermal stabilities as compared with more dilute (i.e., 1 M) electrolytes. Further, while dilute EC–LiTFSI electrolytes extensively corrode the Al current collector at high potential, the concentrated electrolytes do not. A new mechanism for electrolyte corrosion of Al in Li-ion batteries is proposed to explain this. Although the ionic conductivity of concentrated EC–LiTFSI electrolytes is somewhat low relative to the current state-of-the-art electrolyte formulations used in commercial Li-ion batteries, using an EC–diethyl carbonate (DEC) mixed solvent instead of pure EC markedly improves the conductivity.
318 citations
TL;DR: In this article, poly lactic acid (PLA) solutions were prepared in various pure solvents and binary-solvent systems to investigate the effect of different solution properties on nanofibre morphology and diameter.
266 citations
TL;DR: The activated desolvated material SOF-7a shows high CO2 adsorption capacity and selectivity compared with other porous organic materials assembled solely through hydrogen bonding.
Abstract: A robust binary hydrogen-bonded supramolecular organic framework (SOF-7) has been synthesized by solvothermal reaction of 1,4-bis-(4-(3,5-dicyano-2,6-dipyridyl)dihydropyridyl)benzene (1) and 5,5′-bis-(azanediyl)-oxalyl-diisophthalic acid (2). Single crystal X-ray diffraction analysis shows that SOF-7 comprises 2 and 1,4-bis-(4-(3,5-dicyano-2,6-dipyridyl)pyridyl)benzene (3); the latter formed in situ from the oxidative dehydrogenation of 1. SOF-7 shows a three-dimensional four-fold interpenetrated structure with complementary O–H···N hydrogen bonds to form channels that are decorated with cyano and amide groups. SOF-7 exhibits excellent thermal stability and solvent and moisture durability as well as permanent porosity. The activated desolvated material SOF-7a shows high CO2 adsorption capacity and selectivity compared with other porous organic materials assembled solely through hydrogen bonding.
246 citations
TL;DR: The most recent advances in the use of glycerol and glycerols as solvents are reviewed in this paper, where new synthetic methods, physico-chemical properties and application examples are revised.
231 citations
TL;DR: In this paper, the dissolution of microcrystalline cellulose in 1-butyl-3-methylimidazolium acetate [C4C1Im][OAc] was studied using a solid-liquid equilibrium method based on polarized-light optical microscopy from 30 to 100 °C.
222 citations
TL;DR: The method has a broad scope and shows high functional group compatibility and Toluene derivatives can be used as the coupling partner in an unreactive solvent.
Abstract: Oxidative coupling between C(sp2)–H bonds and C(sp3)–H bonds is achieved by the Ni(II)-catalyzed reaction of benzamides containing an 8-aminoquinoline moiety as the directing group with toluene derivatives in the presence of heptafluoroisopropyl iodide as the oxidant. The method has a broad scope and shows high functional group compatibility. Toluene derivatives can be used as the coupling partner in an unreactive solvent.
216 citations
TL;DR: It was found that when cellulose is dissolved in DMAc/LiCl cosolvent system, the hydroxyl protons of cellulose form strong hydrogen bonds with the Cl(-), during which the intermolecular hydrogen bonding networks of cellulOSE is broken with simultaneous splitting of the Li(+)-Cl(-) ion pairs.
Abstract: Understanding the interactions between solvent molecules and cellulose at a molecular level is still not fully achieved in cellulose/N,N-dimethylacetamide (DMAc)/LiCl system. In this paper, cellobiose was used as the model compound of cellulose to investigate the interactions in cellulose/DMAc/LiCl solution by using Fourier transform infrared spectroscopy (FTIR), 13C, 35Cl, and 7Li nuclear magnetic resonance (NMR) spectroscopy and conductivity measurements. It was found that when cellulose is dissolved in DMAc/LiCl cosolvent system, the hydroxyl protons of cellulose form strong hydrogen bonds with the Cl–, during which the intermolecular hydrogen bonding networks of cellulose is broken with simultaneous splitting of the Li+–Cl– ion pairs. Simultaneously, the Li+ cations are further solvated by free DMAc molecules, which accompany the hydrogen-bonded Cl– to meet electric balance. Thereafter, the cellulose chains are dispersed in molecular level in the solvent system to form homogeneous solution. This work ...
TL;DR: In this article, the authors described the direct conversion of chitin into a nitrogen-containing (N-containing) furan derivative (3A5AF) for the first time under optimized conditions, the yield of 3A5F reached 75% with ca 50% chitIN conversion by using boric acid and alkaline chlorides as additives, and NMP as a solvent.
15 Jun 2014
TL;DR: New information is provided about the role of the solvent in the synthesis process of nanoZIF-8, which can be useful for controlling the crystallization rates and nanocrystal sizes of this material.
Abstract: The effect of the solvent on the synthesis process and on the nanocrystal characteristics of the zeolitic imidazolate framework-8 (ZIF-8) was investigated. A synthesis protocol at room temperature employing a series of aliphatic alcohols, water, dimethylformamide and acetone was employed. The results show that the solvent modifies the evolution of the reaction, altering the crystallization rates and nanocrystal sizes. Its hydrogen bond donation ability is the main factor that governs this effect. More precisely, the solvent modulates the formation of ZIF-8 nanocrystals with sizes in the range between 15 and 42 nm. When synthesized in alcohol and acetone, these nanocrystals form globular aggregates with sizes between 130 and 420 nm. In contrast, under the same synthesis conditions, when using water or dimethylformamide the ZIF phase is not developed. In alcohols other than methanol, the crystals develop pill-shaped morphologies with poorly defined facets. Moreover, a markedly fast growing kinetics is verified in these alcohols, leading to an ultra-fast crystallization of ZIF-8 in about 60 s. These findings provide new information about the role of the solvent in the synthesis process of nanoZIF-8, which can be useful for controlling the crystallization rates and nanocrystal sizes of this material.
TL;DR: The use of solvents for the extraction of lipids from algal biomass has been a method of choice for many years as mentioned in this paper, and the soxhlet extraction method was chosen because of its simplicity in operation, relative safety and potential for upscaling to industrial plant level.
TL;DR: The radical intermediates formed upon UVA irradiation of titanium dioxide suspensions in aqueous and non-aqueous environments were investigated applying the EPR spin trapping technique and the character and origin of the carbon-centered spin-adducts was confirmed using nitroso spin trapping agents.
Abstract: The radical intermediates formed upon UVA irradiation of titanium dioxide suspensions in aqueous and non-aqueous environments were investigated applying the EPR spin trapping technique. The results showed that the generation of reactive species and their consecutive reactions are influenced by the solvent properties (e.g., polarity, solubility of molecular oxygen, rate constant for the reaction of hydroxyl radicals with the solvent). The formation of hydroxyl radicals, evidenced as the corresponding spin-adducts, dominated in the irradiated TiO2 aqueous suspensions. The addition of 17O-enriched water caused changes in the EPR spectra reflecting the interaction of an unpaired electron with the 17O nucleus. The photoexcitation of TiO2 in non-aqueous solvents (dimethylsulfoxide, acetonitrile, methanol and ethanol) in the presence of 5,5-dimethyl-1-pyrroline N-oxide spin trap displayed a stabilization of the superoxide radical anions generated via electron transfer reaction to molecular oxygen, and various oxygen- and carbon-centered radicals from the solvents were generated. The character and origin of the carbon-centered spin-adducts was confirmed using nitroso spin trapping agents.
TL;DR: In this article, three industrial lignins (Indulin AT Kraft softwood, Protobind 1000, and corn stover) were fractionated in methanol to obtain soluble and insoluble fractions.
TL;DR: In this review, various immobilization methods of the polysaccharide derivatives are described and enantioseparations of various racemates on the immobilized commercial columns using the non-standard eluents are briefly summarized.
TL;DR: Changing the dye concentration provides tunability between ∼550 nm in the dilute case and ∼620 nm at high concentration, at which point the fluorescence spectrum indicates the formation of R6G aggregates.
TL;DR: This is the first study in which the microstructural properties of a macromolecule are examined in a deep eutectic solvent and it was found that urea molecules denature the enzyme by interrupting the intra-chain hydrogen bonds in a "direct denaturation mechanism".
Abstract: Deep eutectic solvents (DESs) are utilized as green and inexpensive alternatives to classical ionic liquids. It has been known that some of DESs can be used as solvent in the enzymatic reactions to obtain very green chemical processes. DESs are quite poorly understood at the molecular level. Moreover, we do not know much about the enzyme microstructure in such systems. For example, how some hydrolase can remain active and stable in a deep eutectic solvent including 9 M of urea? In this study, the molecular dynamics of DESs as a liquid was simulated at the molecular level. Urea : choline chloride as a well-known eutectic mixture was chosen as a model DES. The behavior of the lipase as a biocatalyst was studied in this system. For comparison, the enzyme structure was also simulated in 8M urea. The thermal stability of the enzyme was also evaluated in DESs, water, and 8M urea. The enzyme showed very good conformational stability in the urea : choline chloride mixture with about 66% urea (9 M) even at high temperatures. The results are in good agreement with recent experimental observations. In contrast, complete enzyme denaturation occurred in 8M urea with only 12% urea in water. It was found that urea molecules denature the enzyme by interrupting the intra-chain hydrogen bonds in a “direct denaturation mechanism”. However, in a urea : choline chloride deep eutectic solvent, as a result of hydrogen bonding with choline and chloride ions, urea molecules have a low diffusion coefficient and cannot reach the protein domains. Interestingly, urea, choline, and chloride ions form hydrogen bonds with the surface residues of the enzyme which, instead of lipase denaturation, leads to greater enzyme stability. To the best of our knowledge, this is the first study in which the microstructural properties of a macromolecule are examined in a deep eutectic solvent.
TL;DR: In this article, the authors provided two feasible methods to prepare stable organic solvent nanofiltration (OSN) membranes by chemically cross-linking the polybenzimidazole (PBI) membranes fabricated from environmentally benign ionic liquids for the first time.
TL;DR: In this paper, an acetylated softwood kraft lignin was dry-spun into precursor fibers and successfully processed into carbon fibers with a tensile strength exceeding most values reported in prior studies on Lignin-based carbon fibers.
TL;DR: In situ grazing-incidence small-angle X-ray scattering experiments on thin films of block copolymers during annealing in neutral solvent vapors are reported, finding the period of the microphase separated morphology is found to increase with increasing blockCopolymer concentration in a power law manner.
Abstract: In situ grazing-incidence small-angle X-ray scattering experiments on thin films of block copolymers during annealing in neutral solvent vapors are reported. By removing the solvent in a controlled manner, the period of the microphase separated morphology is found to increase with increasing block copolymer concentration in a power law manner with an exponent ∼ 2/3. By venting the systems at different rates during the solvent removal process, kinetically arresting the system, the period of the microphase separated morphology in the dried film can be varied.
TL;DR: A new process for the efficient conversion of cellulose into 5-hydroxymethylfurfural (HMF) was developed by the use of AlCl3 as the catalyst in DMSO-ionic liquid ([BMIM]Cl) mixtures.
TL;DR: An accurate and general solvation model that includes a cavity that is a nonlocal functional of both solute electron density and potential, local dielectric response on this nonlocally determined cavity, and nonlocal approximations to the cavity-formation and dispersion energies is developed.
Abstract: Many important applications of electronic structure methods involve molecules or solid surfaces in a solvent medium. Since explicit treatment of the solvent in such methods is usually not practical, calculations often employ continuum solvation models to approximate the effect of the solvent. Previous solvation models either involve a parametrization based on atomic radii, which limits the class of applicable solutes, or based on solute electron density, which is more general but less accurate, especially for charged systems. We develop an accurate and general solvation model that includes a cavity that is a nonlocal functional of both solute electron density and potential, local dielectric response on this nonlocally-determined cavity, and nonlocal approximations to the cavity-formation and dispersion energies. The dependence of the cavity on the solute potential enables an explicit treatment of the solvent charge asymmetry. With only three parameters per solvent, this `CANDLE' model simultaneously reproduces solvation energies of large datasets of neutral molecules, cations and anions with a mean absolute error of 1.8 kcal/mol in water and 3.0 kcal/mol in acetonitrile.
TL;DR: The gel material shows a highly selective visual response to a commonly used nitroexplosive, picric acid among a set of 19 congeners and the preferred selectivity has been mechanistically interpreted with density functional theory-based calculations.
Abstract: Thiourea (TU), a commercially available laboratory chemical, has been discovered to introduce metallogelation when reacted with copper(II) chloride in aqueous medium. The chemistry involves the reduction of Cu(II) to Cu(I) with concomitant oxidation of thiourea to dithiobisformamidinium dichloride. The gel formation is triggered through metal–ligand complexation, i.e., Cu(I)-TU coordination and extensive hydrogen bonding interactions involving thiourea, the disulfide product, water, and chloride ions. Entangled network morphology of the gel selectively develops in water, maybe for its superior hydrogen-bonding ability, as accounted from Kamlet–Taft solvent parameters. Complete and systematic chemical analyses demonstrate the importance of both Cu(I) and chloride ions as the key ingredients in the metal–organic coordination gel framework. The gel is highly fluorescent. Again, exclusive presence of Cu(I) metal centers in the gel structure makes the gel redox-responsive and therefore it shows reversible gel–...
TL;DR: In this article, the authors investigated the effect of ionic liquids (IL) pretreatment of switchgrass with mixtures of 1-ethyl-3-methylimidazolium acetate, [C2mim][OAc], and water at 160 °C.
TL;DR: In this article, a pre-biodiesel-production lipid extraction from microalgae (Chlorella vulgaris) was performed, and the yield was compared with the yield obtained with organic solvents and ionic liquid mixtures.
TL;DR: In this paper, the authors investigated the antioxidant capacity (AC) of ethanol and ethanol/water extracts of selected spices, using cyclic voltammetry (CV), spectrophotometric and photochemiluminescence (PCL) methods.
Abstract: The present study investigates the antioxidant capacity (AC) of ethanol and ethanol/water (1:1, v/v) extracts of selected spices, using cyclic voltammetry (CV), spectrophotometric and photochemiluminescence (PCL) methods. The ABTS test was used for the measurement of the scavenging capacity of the extracts against 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonate) radical cations whilst a photochemiluminescence technique was employed to measure the scavenging capacity against superoxide anion radicals (O 2 − ). The cyclic voltammetry (CV) method provided the reducing capacity values of spices. The total phenolics (TPC) and total flavonoids (TF) were determined in both types of spice extracts. With the exception of vanilla, ethanol/water (1:1, v/v) was a better extraction solvent of TPC and TF in all spices when compared to ethanol alone. The order of AC values of spices determined by the applied methods was as follows: ABTS test > PCL assay > CV method. The obtained results were useful for classification of the tested spices into groups with high antioxidant capacity (clove, cinnamon and allspice), middle (star anise and nutmeg) and low AC (anise, ginger, vanilla, fennel, cardamom, white pepper and coriander). In conclusion, these findings may be useful for the selection of spices for further applications in different food formulations to support their function as antioxidants.
TL;DR: The CNFs obtained using the DES as a solvent were used to prepare calcium alginate bio-nanocomposite gel beads having enhanced elasticity in comparison to Ca-alginate beads to study slow release of 5-fluorouracil, an anticancer drug.
TL;DR: Self-organization of colloidal Pt nanocubes into two types of distinct ordered superlattices, simple-cubic and body-centered-tetragonal structures, has been achieved using a home-built setup and provides important insights into the effects of ligand-solvent interactions on superlATTice formation from nonspherical nanoparticles.
Abstract: Self-organization of colloidal Pt nanocubes into two types of distinct ordered superlattices, simple-cubic and body-centered-tetragonal structures, has been achieved using a home-built setup. Detailed translational and orientational characteristics of these superstructures were determined using a transmission electron microscopy tomographic technique with 3D reconstruction analysis. The formation of these distinct superlattices is the result of a delicate choice of solvent (i.e., aliphatic hexane or aromatic toluene hydrocarbons), which serves as a dispersion medium to fine-tune the relative strengths of ligand–ligand and ligand–solvent interactions during the self-assembly process. This work provides important insights into the effects of ligand–solvent interactions on superlattice formation from nonspherical nanoparticles.