Solvent Recycling Research Articles

Decoupling of ion pairing and ion conduction in ultrahigh-concentration electrolytes enables wide-temperature solid-state batteries

The S-LHCE strategy with the decoupling of ion pairing and ion conduction is proposed via a freeze-drying method, which realizes the recycling of solvents used and enables solid-state lithium-metal batteries with excellent electrochemical performance.

The Mechanics of Forming Ideal Polymer-Solvent Combinations for Open-Loop Chemical Recycling of Solvents and Plastics.

The inherent value and use of hydrocarbons from waste plastics and solvents can be extended through open-loop chemical recycling, as this process converts plastic to a range of non-plastic materials. This process is enhanced by first creating plastic–solvent combinations from multiple sources, which then are streamlined through a single process stream. We report on the relevant mechanics for streamlining industrially relevant polymers such as polystyrene (PS), polypropylene (PP), high-density polyethylene (HDPE), and acrylonitrile butadiene styrene (ABS) into chemical slurries mixed with various organic solvents such as toluene, xylene, and cyclohexane. The miscibility of the polymer feedstock within the solvent was evaluated using the Relative Energy Difference method, and the dissolution process was evaluated using the “Molecular theories in a continuum framework” model. These models were used to design a batch process yielding 1 tonne/h slurry by setting appropriate assumptions including constant viscosity of solvents, disentanglement-controlled dissolution mechanism, and linear increase in the dissolved polymer’s mass fraction over time. Solvent selection was found to be the most critical parameter for the dissolution process. The characteristics of the ideal solvent are high affinity to the desired polymer and low viscosity. This work serves as a universal technical guideline for the open-loop chemical recycling of plastics, avoiding the growth of waste plastic by utilising them as a carbon feedstock towards a circular economy framework.

γ-Valerolactone/water system for lignin fractionation to enhance antibacterial and antioxidant capacities

• A simple and green method for fractionating lignin by γ-valerolactone was proposed. • Lignin fractionation mechanism was investigated through solvatochromic parameters. • Mechanisms of improving antibacterial/antioxidant activities were proposed. • The low molecular weight lignin had excellent antibacterial/antioxidant properties. • The recovered γ-valerolactone had excellent lignin fractionation performance. In this study, γ-valerolactone, a green and recyclable organic solvent, was applied to fractionate organosolv lignin. The original lignin was dissolved in 60% γ-valerolactone/water solution, and sequentially sedimentated in 50%, 40%, 30%, and 1% γ-valerolactone aqueous solution with the addition of water afterwards, producing four fractions (L1, L2, L3, and L4). Multiple analytical methods were used to characterize the lignin fractions in detail. Results manifested that weight average molecular weight of lignin decreased gradually from 7900 (L1) to 1890 g/mol (L4), and the total phenolic hydroxyl content increased from 2.18 (L2) to 2.80 mmol/g (L4). Here, due to the increase of water content in the solvent system, the hydrogen bond capacity with lignin decreased and the solvent polarizability increased. Therefore, the solubility of high molecular weight lignin with low polar groups (hydroxyl and carboxyl) decreased, thus realizing the sequential fractionation of lignin. DPPH and agar diffusion test results indicated that low molecular weight lignin exhibited good antimicrobial/antioxidant activities, which was mainly due to the positive effects of the phenolic hydroxyl content and side chain structure of lignin. The mechanisms of improving antibacterial/antioxidant activities of lignin were proposed for potential practical applications.

The Effect of Temperature on Solvent Recycle Process using Stripping of CO2 from MDEA, Ethylene Glycol, and Water

Stripping is a process to separate dissolved gas in the saturated solvent to regenerate the absorption solvent. In this study, N2 gas was used to strip dissolved CO2 gas in MDEA, ethylene glycol, and water. The experiment was conducted with three variations of temperature, namely 28°C, 35°C, and 50°C, to determine the effect of solvent’s temperature entering the stripper column on the value of the mass transfer coefficient (Kla). The stripper effluent was connected to the KANE 457 Flue Gas Analyzer to measure the concentration of CO2. Data retrievals were carried out at the 0; 30; 60; 90; 120; 150; 180th second. The experimental results show the trend of mass transfer coefficient of CO2 (Kla) is higher with the increase of solvent’s temperature entering the stripper.

Nenitzescu Synthesis of 5‐Hydroxyindoles with Zinc, Iron and Magnesium Salts in Cyclopentyl Methyl Ether

AbstractIn this work, mild Lewis acids and low environmental impact solvents were investigated for Nenitzescu synthesis. Cyclopentyl methyl ether can be used at room temperature in substitution of halogenated solvents with zinc, iron and magnesium salts as homogeneous catalysts to give 5‐hydroxyindoles in fair to good yields. The reaction features a straightforward workup and excellent solvent recycle.

Short Alternative Route for Nuclear Fuel Reprocessing Based on Organic Phase Self-Splitting.

A more sustainable management of natural resources and the establishment of processes allowing a joint management of nuclear materials to avoid their diversion from their civilian use are two issues for the nuclear industry. Short alternatives to existing processes have therefore been proposed based on known systems available, tributylphosphate (TBP), for the separation of actinides by liquid/liquid extraction. Proof of concept of such alternative has been established on the uranium(VI)/thorium(IV) system. From an organic phase consisting of a mixture of TBP/n-dodecane loaded with uranium and thorium, two fluxes have been obtained: the first contains almost all of the thorium in the presence of uranium in a controlled ratio, the second contains surplus uranium. Two levers were selected to control the spontaneous separation of the organic phase: the addition of concentrated nitric acid, or the temperature variation. Best results have been obtained using a temperature drop in the liquid/liquid extraction process, and variations in process conditions have been studied. Final metal recovery and solvent recycling have also been demonstrated, opening the door for further process development.

Simultaneous transformation and extraction of resveratrol from Polygonum cuspidatum using acidic natural deep eutectic solvent

Resveratrol, as a natural antioxidant, has been studied widely for its antioxidant, anti-inflammatory, anti-apoptotic, and anticancer properties. In this study, a strategy was developed to transform and extract resveratrol from Polygonum cuspidatum on the basis of NADES (natural deep eutectic solvent). In the series of adjustments and optimizations by single-factor experimental, the optimum NADES system (choline chloride to oxalic acid was 1:1) and other experimental conditions were determined, including water content of NADES, solid-liquid ratio, extraction time, extraction temperature and ultrasonic power. At the same time, RSM combined with BBD further optimized the experimental process, the results obtained by RSM optimization showed that the resveratrol yield of 12.31 mg/g was achieved when solid-liquid ratio was 1:50, temperature was 75℃ and time was 80 min. Meantime, the conversion efficiency of polydatin was 96.11 % and the content of resveratrol increased 6-fold higher than that of untreated sample. The kinetic of extraction and thermodynamic analysis were performed at different extraction temperatures to examine the temperature on the impact of the resveratrol extraction from P. cuspidatum. Ethyl acetate was used for back extraction in order to achieve the recycling of solvent and the recovery of resveratrol from NADES. The results showed that ethyl acetate had a good extraction effect and NADES still had a high capacity to convert and extract resveratrol after three cycles. In addition, the extracts exhibited superior antioxidant activity with higher content of recovered resveratrol. This established process can therefore be used to extract and recover resveratrol from plants as an environmental, pollution-free alternative approach.

Carboxylate functionalized imidazolium-based zwitterions as benign and sustainable solvent for cellulose dissolution: Synthesis and characterization

Cellulose is most abundant biopolymer on earth and can be utilized as sustainable resources for many applications, however, their utilization at great extent is limited due to lack of benign and recyclable solvent. While N-methylmorpholine-N-oxide (NMMO), used in Lyocell process, is thermally unstable and may undergoes runaway conditions, commercialization of ionic liquid as solvent still suffers from recyclability issues. Herein, we present the synthesis of a series of zwitterions, composed of tethered alkyl imidazolium cation and carboxylate anion, and investigated their cellulose dissolution characteristics. Effect of alkyl chain length of imidazolium ring on its dissolution efficiencies was studied and amongst synthesized zwitterions, the hexanoate derivatives exhibited 13% (w/w) cellulose dissolution at 100–125 °C. Thermal stability of zwitterions and their cellulose solution was characterized by DSC-TGA and found to be more stable than the NMMO and Lyocell solution. Rheological studies indicate that cellulose solution in zwitterions are viscoelastic and in spinnable range of fibre processing. Structural and morphological characterization of regenerated cellulose using elemental analysis, FTIR, DSC-TGA, GPC, XRD and SEM showed that zwitterions have no adverse effect on its physicochemical and morphological properties. A method for recovery and purification of solvent after cellulose dissolution and regeneration is also presented.

Cover Feature: Potential Degradation of 4‐Methyltetrahydropyran (4‐MeTHP) under Oxidation Conditions (Asian J. Org. Chem. 10/2021)

4-Methyltetrahydropyran is a new recyclable ether solvent that can be applied to bench-scale oxidative reactions. During oxidation, however, trace degradation of solvent occurs. Slight amounts of solvent-derived oxidative products were characterized by 1H NMR analyses. The picture shows that the solvent used in the epoxidation reaction contains some degradation products that could be detected in microanalysis. More information can be found in the Full Paper by Shoji Kobayashi and Tomoki Tamura.

Rapid and efficient microwave-assisted guanidine hydrochloride deep eutectic solvent pretreatment for biological conversion of castor stalk

Microwave-assisted guanidine hydrochloride deep eutectic solvents (DESs) was developed for rapid and efficient pretreatment of castor stalk. The DES synthesized with guanidine hydrochloride and lactic acid showed a better delignification (92.02%) and enzymatic saccharification yield (96.3%) than choline chloride and lactic acid DES resulted. In addition, high-purity (up to 98%) lignin was recovered from the pretreatment liquor. The good recyclability of the guanidine hydrochloride-based DES was also proven with up to 90% cellulose hydrolysis with third-time recycled DES without post purification. The proposed microwave-assisted guanidine hydrochloride/lactic acid DES showed its great potentials as a highly effective and recyclable pretreatment solvent for future biorefinery strategies.

Viscosity-temperature characteristics of high-concentration coal-oil slurry preheated by light solvent

The viscosity and stability of coal-oil slurry (COS) with different concentrations prepared by recycle solvent and low-rank coal were investigated. The effect of light solvent naphtha preheating treatment on the viscosity-temperature characteristics of high-concentration COS and properties of pulverized coal was studied. Results show that when the concentration is higher than 48 wt%, the viscosity and swelling viscosity peak value of conventional COS increase exponentially, resulting in the significant deterioration of the stability of COS. The concentration of COS can be increased to 50 wt% by preheating with light solvent. With the increase of preheating temperature and time, the viscosity of COS decreases as a whole. The viscosity of high-concentration COS with the optimum preheating temperature of 375 °C and time of 4 h is 383 mPa·s (60 °C), which is 30% lower than that of conventional COS (543 mPa·s (60 °C)) with 50 wt%. Due to the influence of the full swelling, irreversible swelling, and primary pyrolysis of pulverized coal, the physical structure and chemical composition of pulverized coal changes, the swelling viscosity peak no longer appears, and the stability of COS is improved.

Potential Degradation of 4‐Methyltetrahydropyran (4‐MeTHP) under Oxidation Conditions

Abstract4‐Methyltetrahydropyran (4‐MeTHP) is a next‐generation recyclable ether solvent that can be applied to a wide variety of synthetic reaction methods. Previous studies indicated that 4‐MeTHP could degrade to some extent with certain oxidants, while the oxidation reactions themselves proceeded in good yields. Here we disclose the potential oxidative degradation pathways of 4‐MeTHP when exposed to selected organic‐based and metal‐based oxidants. Crude NMR analyses revealed that degradation of 4‐MeTHP was initiated by C2−H abstraction, giving rise to C2‐ or C4‐oxidized products or the C−C bond cleavage product depending on the oxidants used. This study therefore illustrates possible degradation products of 4‐MeTHP under oxidative conditions, which is particularly helpful in predicting and analyzing trace impurities when adopting 4‐MeTHP or other ethereal solvents in industrial processes.

Fabrication of rGO/Fe3O4 Magnetic Composite for the Adsorption of Anthraquinone-2-Sulfonate in Water Phase

In the last few decades, anthraquinone and its derivatives (AQs) have been intensively applied to electrochemical, textile and dye, and photovoltaic industries. This has increased the levels of AQs in the natural environment and threatens human health. To remove AQs from the aqueous phase and recover these multi-functional molecules, a binary magnetic adsorbent, reduced graphene/Fe3O4 (rGO/Fe3O4), was synthesized via a hydrothermal method. Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman spectra, and thermogravimetric analysis (TGA) were then used to characterize the samples. The adsorption capacities of rGO/Fe3O4 to AQs were investigated by selecting anthraquinone-2-sulfonate (AQ2S) as a model molecule. The adsorption process followed the Langmuir adsorption isotherm and the second-order kinetics. The regeneration of adsorbents and the recycling of AQ2S and solvent were simultaneously achieved by Soxhlet extraction and rotary evaporation. These results confirm the high adsorption efficiency of rGO/Fe3O4 for removing AQs from water and provide a promising approach to recover the valuable molecules from the aqueous phase.

Recovery and recycling of deep eutectic solvents in biomass conversions: a review

Recovery and recycling of deep eutectic solvents in biomass conversions: a review

Practical Online Monitoring of Ionic Liquid Fiber Welding Solvent.

Ionic liquids (ILs) are becoming important solvents in commerce, but monitoring their purity and performance in industrial applications presents new challenges. Fiber welding technology utilizes ILs to mold and shape natural fibers (cotton, hemp, flax, silk, and wool) into morphologies that are typically attained only using synthetic, petroleum-based non-biodegradable plastics. The result is an atom-efficient process that up-converts fibrous substrates to value-added products and materials. A key aspect of bringing this and other IL-enabled technologies to market relies on efficient monitoring and recycling of IL-based solvents. Implementing online IL quality monitoring enhances the unit economics of these processes. Here, we characterize and report conductivity measurements, refractometry, and ATR–FTIR spectroscopy techniques for online IL monitoring during an industrial fiber welding process. The online analysis enables more efficient recycling of the IL solvent, increasing the process efficiency and product quality.

Development of Methanol Permselective FAU-Type Zeolite Membranes and Their Permeation and Separation Performances.

The separation of non-aqueous mixtures is important for chemical production, and zeolite membranes have great potential for energy-efficient separation. In this study, the influence of the framework structure and composition of zeolites on the permeation and separation performance of methanol through zeolite membranes were investigated to develop a methanol permselective zeolite membrane. As a result, the FAU-type zeolite membrane prepared using a solution with a composition of 10 SiO2:1 Al2O3:17 Na2O:1000 H2O showed the highest permeation flux of 86,600 μmol m−2 s−1 and a separation factor of 6020 for a 10 wt% methanol/methyl hexanoate mixture at 353 K. The membrane showed a molecular sieving effect, reducing the single permeation flux of alcohol with molecular size for single-component alcohols. Moreover, the permeation flux of methanol and the separation factor increased with an increase in the carbon number of the alcohols and methyl esters containing 10 wt% methanol. In this study, the permeation behavior of FAU-type zeolite membranes was also discussed based on permeation data. These results suggest that the FAU-type zeolite membrane has the potential to separate organic solvent mixtures, such as solvent recycling and membrane reactors.

Dissolution behavior of hydrogen in the model recycle solvent of mild direct coal liquefaction

Direct coal liquefaction (DCL) at mild conditions (about 693 K and less than 10 MPa) is an important and efficient way for the conversion of coal to high value-added chemicals and fuel oil. In the process of DCL, the pre‑hydrogenation of a recycle solvent is an important step and the recycle solvent is always heated from low temperatures to high temperatures. So, it important to study the dissolution behavior and the migration of hydrogen in the recycle solvent for DCL processes, especially for mild DCL processes. First, physical solubility of hydrogen in a model recycle solvent of naphthalene and 1,2,3,4-tetrahydronaphthalene was measured, and the Henry's constants at different temperatures were obtained. Then, the chemical solubility of hydrogen (chemical bonded hydrogen via hydrogenation of naphthalene to 1,2,3,4-tetrahydronaphthalene) in the recycle solvent was measured simultaneously. The equilibrium constants of the hydrogenation reaction at different temperatures were obtained. Finally, through the physical solubility of hydrogen and chemical solubility of hydrogen, the dissolution and migration of hydrogen in the recycle solvent were analyzed. When the temperature is increased, the physical solubility of hydrogen increases, the chemical solubility of hydrogen decreases, the total solubility of hydrogen decreases due to the dominant contribution of chemical solubility of hydrogen, and interestingly a small part of hydrogen released from 1,2,3,4-tetrahydronaphthalene is transferred to physical solubility. When the pressure is increased, the chemical solubility of hydrogen, the physical solubility of hydrogen and the total solubility of hydrogen all increase

Room temperature dissolving cellulose with a metal salt hydrate-based deep eutectic solvent

Abundant and renewable cellulose is a potential candidate for petroleum-derived synthetic polymers. However, the efficient dissolution of this material is problematic because of the high cost, severe reaction condition (e.g., high temperature) and environmentally unfriendly (e.g., toxic reagents, and solvent recyclability). Herein, to realize the room temperature dissolution of cellulose with an inexpensive and eco-friendly solvent, we design a novel low-cost deep eutectic solvent that is composed of zinc chloride, water and phosphoric acid for the efficient dissolution of cellulose. This solvent is featured as having both the superior hydrogen bonding acidity and the hydrogen bonding basicity, and thus can act as a hydrogen bond molecular scissors to cleave the hydrogen bonds within cellulose. In this process, microcrystalline cellulose can be easily dissolved in the solvent at room temperature with a dissolution ratio up to 15 wt%. The dissolved cellulose can also be recovered without any derivatization. The universality, recyclability and pilot production of dissolving cellulose using this solvent are also demonstrated. This work provides a new strategy for the design of novel deep eutectic solvent capable of disrupting the hydrogen bonds of cellulose under mild conditions.

Effect of Novel Deep Eutectic Solvents on the Endo/Exo Ratio of Diels-Alder Reactions at Room Temperature.

The Diels–Alder reaction is a prototypical example of a thermally allowed [4 + 2] cycloaddition with good control over the regio- and stereochemical outcomes. Therefore, Diels–Alder reactions in which adjacent stereocenters are generated at the two ends of the newly formed single bonds imply two different possible stereochemical outcomes. In cases where the dienophile has a single electron-withdrawing substituent, the outcome can often be predicted by applying the known “endo rule”. Furthermore, the use of chiral eutectic solvents in asymmetric synthesis has become a novel tool to maintain sustainability in organic synthesis. In the present work, a set of recyclable and sustainable bio-based deep eutectic solvents (DESs) was designed using hydrogen bond acceptors (HBAs) with a chiral center. These compounds were used in their racemic and enantiomerically enriched forms to prepare DESs with lactic acid (LA), glycerol (Gly), and ethylene glycol, which act as hydrogen bond donors (HBDs) in the corresponding eutectic mixture. These DESs were used as solvents to study the reaction between cyclopentadiene and ethyl acrylate or butyl acrylate in typical [4 + 2] cycloadditions. The best yields and endo-selectivity were achieved using LA as the HBD in the eutectic mixtures. The results and adduct ratios obtained show that these DESs were able to improve both reaction yields and selectivity when compared to those observed in organic solvents or ionic liquids. Moreover, the reaction products (adducts) were easily recovered with diethyl ether from the reaction mixture, where they appeared as an upper layer.

A comparison of chiral separations by supercritical fluid chromatography and high-performance liquid chromatography

The supercritical fluid chromatography technique is one of the most promising and innovative technologies used in the analysis as well as the separation of various racemates. The various enantiomers have been separated using SFC due to its several merits over conventional HPLC methods such as low cost, wide polarity compatibility, higher column efficiency, and fast analyzing capability, which are desirable features for the pharmaceutical industry. Therefore, it was considered worthwhile to review the applications of SFC in achiral and chiral separations. This review encompasses the latest literature exploration of various practical aspects of SFC for enantiomeric separation, purification, and applications to the pharmaceutical industry. A detailed discussion of SFC was made in terms of productivity, stacked injections, sample solubility, particle size, green incentive, organic solvent, recycle solvents, and economical aspects. Besides, future perspectives of SFC have also been highlighted. A comparison was also made between SFC and HPLC. SFC has been found better technique than HPLC for the chiral separations on a preparative scale. This article will be highly useful for chiral chromatography in pharmaceutical industries and research laboratories.