Dual Solvent-catalyst Research Articles

Ionic liquids: green organic transformation with dual solvent-catalyst strategy and its multidisciplinary applications

Ionic liquids: green organic transformation with dual solvent-catalyst strategy and its multidisciplinary applications

Acidic natural deep eutectic solvents as dual solvents and catalysts for the solubilization and deglycosylation of soybean isoflavone extracts: Genistin as a model compound

This study investigated the possibility of using green solvent natural deep eutectic solvents (NADESs) as dual solvent-catalysts for the solubilization and deglycosylation of soybean isoflavones. The deglycosylation behavior of genistin as a model compound in NADESs was compared. Acidic NADESs showed moderate solubility for genistin and could hydrolyze it to form genistein. The onset temperature of deglycosylation in the choline chloride/malic acid (Ch-Ma) was 60 °C. The solubilities of genistin in the Ch-Ma system were modeled. The dissolution process was endothermic and mainly enthalpy-driven. The deglycosylation followed first-order kinetics with a half-life (t1/2) of 40 min at 90 °C. The method was validated using soybean isoflavone extracts as a substrate and the ratio of glycoside to aglycone in the extracts could be adjusted by changing the conditions. The methods have great potential in the extraction and preparation of ready-to-use isoflavone extracts from soybean and other legumes.

Toward reactive extraction processes for synthesizing long-chain esters: A general approach by tuning bifunctional deep eutectic solvent

The synthesis of long-chain esters in reactive extraction using bifunctional deep eutectic solvent (DES) demands a wide solvent selection range and optimal solvent choice. In this work, a general approach towards rational DES selection is presented. First, novel halogen-free DESs based on triazole and p-toluenesulfonic acid (PTSA) or benzenesulfonic acid (BSA) are prepared to expand the selection range of Brønsted acidic DESs, whose binary solid–liquid phase diagrams are measured to confirm the DES formation. Then, the triazole-PTSA/BSA DESs together with the imidazole (Im)-PTSA/BSA DESs are characterized by pH measurement, 1H-NMR characterization, and COSMO-RS interaction energy analysis, which reflect a two-step formation mechanism. The Im-PTSA/BSA DESs are acid-base tunable while the triazole-PTSA/BSA DESs are tunable from weak acid to strong acid. Afterwards, four strong acidic DESs at the eutectic compositions namely [Im:2BSA], [Im:2PTSA], [triazole:4BSA] and [triazole:4PTSA] are determined as dual solvent-catalyst for the intensified esterification with ester carbon chain length changing from C6 to C11. Combining σ-potential thermodynamic analysis with experimental results, the applicable boundary and change rule of carbon chain length versus different DESs are clarified. On this basis, a rational DES selection strategy is formulated aiming to the development of reactive extraction for synthesizing different long-chain esters.

Biocompatible anions-derived ionic liquids a sustainable media for CO2 conversion into quinazoline-2,4(1H,3H)-diones under additive-free conditions

Based on an one-step acid-base neutralization method, several biocompatible anions-derived ionic liquids (bio-AILs) were prepared and characterized. They were first used as dual solvent-catalyst for cyclization of CO2 and 2-aminobenzonitriles to synthesize quinazoline-2,4(1H,3H)-diones. The influence of different bio-AILs structures on the cyclization reaction were studied, and [HTMG][Lae] was confirmed to be an excellent medium. By optimizing the reaction conditions, the [HTMG][Lae]-mediated cyclization reaction could afford a 96 % quinazoline-2,4(1H,3H)-dione yield at 70 °C, 1.0 MPa CO2 pressure for 6 h without other additives. The catalytic activities of various homogeneous media for transformation of CO2 into quinazoline-2,4(1H,3H)-dione were analyzed and compared. In addition, the reusability and general applicability of the [HTMG][Lae] medium were examined, the [HTMG][Lae] could show comparable activity in the fifth experiment, and it had good versatility for cyclization of CO2 with various 2-aminobenzonitriles. Finally, an insight into the activation behaviors of [HTMG][Lae] to reactants were further investigated, and based on this, a feasible reaction mechanism was proposed.

4,4'-trimethylenedipiperidine as a nitrogen heterocycle solvent and/or catalyst: Liquid phase tandem Knoevenagel-Michael condensation.

Liquid phase tandem Knoevenagel–Michael condensation of various aromatic and heteroaromatic aldehydes with barbituric acid or 2-thiobarbituric acid and malononitrile was studied in a one-pot three-component reaction. For the first time, TMDP was employed as a safe and efficient solvent and/or catalyst in the liquid and aqueous ethanol medium, respectively, for the practical and eco-friendly Knoevenagel–Michael condensation. The reactions were carried out by using greener procedures, including a) the use of TMDP as an N-heterocycle organocatalyst in a green medium including water and ethanol (1:1 v/v) at reflux temperature, and b) the use of TMDP as a dual solvent-catalyst at 65 °C in the absence of any solvent. High to excellent yields of the desired pyrano[2,3- d ]pyrimidinones were obtained under the two earlier mentioned conditions. The current methodologies have advantages, including (a) avoiding hazardous, toxic, volatile, and flammable materials and solvents, (b) avoiding tedious processes, harsh conditions, and multiple steps for the preparation of catalysts, (c) using a less toxic and noncorrosive catalyst, (d) minimizing hazardous waste generation and simple workup process, and (e) high recyclability of TMDP. Another important result of this work is that the TMDP can be a promising alternative for toxic, volatile, and flammable base reagents such as piperidine and triethylamine in liquid phase organic syntheses owing to its unique properties such as being less toxic, nonflammable, and nonvolatile, and having a low melting point, broad liquid range temperature, high thermal stability, and safe handling and storage.

Reactive extraction for intensifying 2-ethylhexyl acrylate synthesis using deep eutectic solvent [Im:2PTSA

2-Ethylhexyl acrylate (2-EHA) is one of the most widely used acrylates in the polymer industry, which is synthesized via Fisher esterification that is limited by chemical equilibrium. To intensify the esterification process, in this work, reactive extraction concept is proposed, with halogen-free deep eutectic solvent (DES [Im:2PTSA]) as dual solvent-catalyst that consists of imidazole (Im) and p-toluenesulfonamide (PTSA). The bifunctional effects of the DES [Im:2PTSA] are evaluated by thermodynamic analysis and experimental study. Favorable phase splitting is verified by σ-potential analysis predicted by COSMO-RS theory, combined with experiments, and the optimal acid-to-alcohol molar ratio is set to 1.2. The esterification kinetics is then experimentally determined and fitted using the molar-based and activity-based pseudo-homogeneous (PH) models, respectively. The activity-based PH model, that considers the bifunctional roles of the DES, proves to be more accurate with small RMSD of 0.0344. The stability of DES after recycling is validated to further confirm the industrial prospects of DES [Im:2PTSA] in 2-EHA production.

Reactive extraction for synthesizing long chain ester butyl hexanoate intensified by deep eutectic solvent

Butyl hexanoate (BuHE) is an important long-chain ester that is widely used in the food, beverage and cosmetic industries. In this work, reactive extraction concept was proposed to intensify the BuHE formation in a biphasic system, in which deep eutectic solvent (DES) comprising 2-methylimidazole (2-MIm) and p-toluenesulfonic acid (PTSA) was used as dual solvent-catalyst. First, the effect of 2-MIm to PTSA molar ratio on esterification was investigated to determine the optimum DES of [2-MIm:2PTSA], which was characterized by FT-IR and TGA. Then, the liquid–liquid equilibrium (LLE) and esterification experiments were carried out to confirm the extraction and catalytic effect of [2-MIm:2PTSA], respectively. Afterwards, the pseudo-homogeneous kinetic model was employed to describe the esterification kinetics. Finally, the intensification mechanism of reactive extraction for BuHE formation was proposed according to the experiments and interaction effect analysis.

Reactive Extraction Strategy for Synthesizing Dioctyl Phthalate Intensified by Bifunctional Deep Eutectic Solvent [Im:2PTSA

Dioctyl phthalate (DOP) is a widely used efficient plasticizer with great stability to heat and ultraviolet light, as well as the compatibility to use with PVCs resin. In this work, the process intensification of reactive extraction strategy is proposed to promote DOP synthesis in a biphasic system, with the halogen-free deep eutectic solvent (DES) [Im:2PTSA] as dual solvent-catalyst. First, the bifunctional effects of DES, which consists of imidazole (Im) and p-toluenesulfonic acid (PTSA), are experimentally demonstrated. Afterwards, the reactive extraction process is illustrated from both thermodynamic and kinetic aspects: (1) the thermodynamic analysis of σ-profiles that are derived from COSMO-RS theory is performed, and DES can intensify the phase splitting by forcing DOP and water into different phases, confirming the feasibility of conducting such an intensified process; (2) the esterification kinetics are investigated and fitted using the pseudo-homogeneous (PH) model, suggesting that the DES can efficiently catalyze the DOP formation. Finally, based on the liquid-liquid equilibrium predicted by COSMO-RS and the fitted kinetic model, the three-stage reactive extraction scheme is developed, with the DOP yield and purity at a high level, i.e., 98.61 % and 99.01 wt%, respectively.

1H,4H-Piperazine-diium Dichlorosulfonate: Structure Elucidation and its Dual Solvent–Catalyst Activity for the Synthesis of New Dihydro-[1,2,4]triazolo[1,5-a]pyrimidine Scaffolds

A new ionic liquid containing a 1H,4H-piperazine-diium ring and chlorosulfonate as a 1,4-dicationic core and counter ion, respectively, was designed and synthesised. The structure elucidation of this ionic liquid was conducted by 1D and 2D NMR, FT-IR, Raman, and mass spectrum analysis. The physical properties of this ionic liquid were determined and reported. Furthermore, the dual solvent–catalyst activity of piperazine-1,4-diium dichlorosulfonate was investigated for the synthesis of new dihydro[1,2,4]triazolo[1,5-a]pyrimidines through a one-pot three-component reaction. The ionic liquid was retrieved and reused several times without reducing its catalytic efficiency.

Succinimide-Based Ionic Liquids: An Efficient and Versatile Platform for Transformation of CO2 into Quinazoline-2,4(1H,3H)-diones under Mild and Solvent-Free Conditions

Multifunctional succinimide-based ionic liquids (SIILs) were well-designed and synthesized, and they were used as a dual solvent–catalyst for efficient transformation of CO2 and 2-aminobenzonitriles into quinazoline-2,4(1H,3H)-diones under mild conditions. The catalytic behaviors, including the effects of anion–cation structures and reaction parameters, catalyst recyclability, and versatility were thoroughly studied. The optimum [HTMG][Suc] comprising a tetramethylguanidine cation and a succinimide anion showed excellent activity toward various substituted 2-aminobenzonitrile substrates. [HTMG][Suc] was easily recyclable with superior structural integrity. The possible pathways of CO2 and 2-aminobenzonitrile activated by [HTMG][Suc] were investigated in depth, which supported the reaction mechanism well. In comparison with reported catalysts, the protocol herein exhibited comparable catalytic performance under milder and greener conditions without any additional organic solvents.

4-Imidazol-1-yl-butane-1-sulfonic acid ionic liquid: Synthesis, structural analysis, physical properties and catalytic application as dual solvent-catalyst

4-Imidazol-1-yl-butane-1-sulfonic acid (ImBu-SO3H) has been successfully synthetized and fully characterized by FT-IR and high-resolution NMR spectroscopy (1H, 13C). The “plausible” alternative structures of ImBu-SO3H were discussed on the basis of its NMR data. The ionic liquid showed interesting dual solvent-catalyst property, which was studied experimentally for the acetylation of a variety of functionalized alcohols, phenols, thiols, amines and α-tocopherol (α-CTP) as the most active form of vitamin E with acetic anhydride and which provided good yields within a short reaction time. ImBu-SO3H was successfully recycled by product extraction with an average recovered yield of 82% for 5 subsequent runs. The catalytic activity of the recycled ImBu-SO3H showed almost no loss even after five consecutive runs.

Towards an understanding of the microstructure and interfacial properties of the ionic liquid/sulfuric acid catalyst in liquid-liquid reactions

Sulfonic-acid-functionalized Brønsted acidic ionic liquids (SFILs) have been considered as a promising dual solvent-catalyst for numerous applications. The bulk microstructure and interfacial characteristics of different kinds of SFILs and the corresponding SFIL/H2SO4 systems were investigated in this work using molecular dynamics (MD) simulations in terms of the SFILs possessing three anions (e.g. bisulfate, triflate, and bis(trifluoromethylsulfonyl)imide), different alkyl chain lengths, and different introduced position of the sulfonic acid groups (-SO3H). The introduction of the sulfonic acid groups is found to provide a strong hydrogen-bonding interaction site with both the HSO4− and H2SO4, making almost two order of magnitudes larger for average numbers of hydrogen bonds between different pairs. The introduction of sulfonic acid groups onto the shorter side chains contributes to stronger hydrogen-bonding interactions with both the HSO4− and H2SO4 than when introduced onto the longer side chains. The coordination numbers of the equivalent terminal carbon atoms of octyl chain and equivalent sulfur atoms of sulfonic acid groups are more than 4.5 and 2.5, respectively, which suggests that obvious nanostructured aggregation of the polar sulfonic acid groups, as well as nonpolar longer alkyl chains, exists in the pure SFILs and SFIL/H2SO4 systems. In addition, it is found that the ordering preference and interfacial orientation of the side chains and imidazole rings at gas-liquid interfaces are sharply changed following the addition of the sulfonic acid groups. The insights into the bulk structural and interfacial characteristics of the SFIL/H2SO4 systems obtained in this work may inform the design and optimization of novel SFILs for specific catalytic applications.

Synthesis of Quinoline Derivatives via the Friedländer Annulation Using a Sulfonic Acid Functionalized Liquid Acid as Dual Solvent-Catalyst

4-Imidazol-1-yl-butane-1-sulfonic acid (ImBu-SO3H) has been synthesized and completely characterized by FT-IR, one-dimensional NMR spectroscopy (1H, 13C). The “plausible” alternative structures of ImBu-SO3H were discussed by NMR. The title liquid acid showed interesting dual solvent-catalytic property, which was studied experimentally in the synthesis of quinoline derivatives via the Friedländer annulation and provided good yield within short reaction time. ImBu-SO3H was successfully recycled by water extraction, instead of organic solvent extraction, with an average recovered yield of 82% for five subsequent runs. The recycled liquid acid showed almost no loss of the catalytic activity even after five consecutive runs.

Experimental and modeling study of isobutane alkylation with C4 olefin catalyzed by Brønsted acidic ionic liquid/sulfuric acid

As a dual solvent-catalyst, sulfonic-acid-functionalized ionic liquids (SFILs) are promising catalysts for the C4 alkylation. In the present work, the effect of the SFILs with different ratios to the H2SO4 on the catalytic performance and interfacial properties for the H2SO4-catalyzed alkylation was investigated by the combination of experiments and MD simulation. Experimental results indicated that compared to pure H2SO4, the introduction of the SFILs can contribute to a higher selectivity of C8-alkylates as well as Research Octane Number (RON), suggesting a higher quality of alkylate. Moreover, the catalytic performance of the SFIL/H2SO4 catalyst is improved with the increased addition ratio of the SFIL into the H2SO4 within the range of 10 wt%. MD simulation results revealed that the obvious density enrichment of the cations of the SFILs at the interface results in a larger interface width, and higher interface number and better dispersion of C4 hydrocarbons at the interface, which can be ascribed to the location of the alkyl chains close to the C4 hydrocarbon phase with the extended and perpendicular behaviors. The improvement of interfacial properties due to the addition of the SFILs is favorable to the enhancement of the quality of alkylate, which is in excellent agreement with experimental results. Hopefully, the useful information in this work can provide a reference to the design of the SFILs and the optimization of the C4 alkylation process.

Liquid-liquid equilibrium for the system of ionic liquid [BMIm][HSO 4 ] catalysed isobutyl isobutyrate formation

Isobutyl isobutyrate is an important chemical which can be formed in a reactive extraction process with ionic liquid as dual solvent-catalyst. To design such an intensified process, the liquid-liquid equilibria (LLE) data for the esterification system involving ionic liquid are essential. In this work, the LLE of ternary systems {isobutyl isobutyrate (IBIBE) + isobutyric acid (IBAc) or isobutanol (IBOH) + 1-butyl-3-methylimidazolium hydrogen sulfate ([BMIm][HSO4])} and the quinary system {IBAc + IBOH + IBIBE + H2O + [BMIm][HSO4]} were measured at temperature T = (298.2, 323.2 and 353.2) K, T = (323.2, 333.2, 343.2 and 353.2) K and atmospheric pressure, respectively. Based on the experimental data, the solute distribution coefficient and the selectivity were determined, which confirms the feasibility of the ionic liquid for isobutyl isobutyrate formation. The phase behaviour was explained by the molecular interaction using σ-potential analysis. Moreover, the binary parameters of the NRTL model for [BMIm][HSO4] catalysed isobutyl isobutyrate formation system were fitted.

Conversion of Biomass and Its Derivatives to Levulinic Acid and Levulinate Esters via Ionic Liquids

Biomass has emerged as an abundant and relatively low cost carbon resource alternative to fossil fuel resources in the sustainable production of specialty chemicals and biofuel. Levulinic acid is an attractive platform chemical. Upgrading of levulinic acid produces levulinate esters, which serve as a transportation fuel and fuel additive. The present review focuses on the development of sustainable conversion of biomass into levulinic acid and levulinate esters via ionic liquids dual solvent–catalysts. The synthesis routes of levulinic acid and levulinate esters and the corresponding ionic liquids are introduced. The biomass pretreament, as well as the conversions of lignocellulosic biomass and their derivatives into levulinic acid and levulinate esters, are detailed in relation to the catalytic role, properties, and performance of acidic ionic liquids. Finally, the operating conditions affecting the ionic liquids catalytic conversions are discussed as part of a comprehensive review of this topic.

Application of Green Catalysts for the Esterification of Benzoic Acid with Different Alcohols

In this study, three different catalysts were applied as catalysts for esterification of benzoic acid with ethanol, butanol and hexanol. These catalysts are ionic liquid, deep eutectic solvent, ion exchange resin. Amberlyst 15, ion exchange resin, was used as control catalyst to observe the catalytic activity of new generation solvent, deep eutectic solvent. Deep eutectic solvents show the similar properties with ionic liquids and have great attraction due to ease of preparation, low cost and environmentally friendly nature. They have many advantages such as reusability, stability, catalytically activity and removal of the reaction mixture. Deep eutectic solvents (DES) are composed hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA). It has lower freezing point than that of individual constituents. In this study, p -toluene sulfonic acid (p-TSA) was used as HBD, benzyl tri-ethyl ammonium chloride (BTEAC) was used as HBA. DES formed by p-TSA and BTEAC was used as dual solvent-catalyst for esterification of benzoic acid with different alcohols. DES gave high catalytic activity among three different catalysts, 88.3, 87.8 and 67.5% conversion of benzoic acid for ethanol, butanol and hexanol, respectively. The effects of time, temperature, alcohol type and catalyst type were investigated in a batch reactor at specified conditions. It was found that DES provided the simple, efficient and environmentally friendly method for the synthesis of benzoic acid ester.

Quaternary Ammonium Ionic Liquid as a Dual Solvent-Catalyst in Biginelli Reaction

Multi-component reactions (MCRs) utilizing unconventional solvents like ionic liquids have become a new research direction that has emerged as an important facet of green chemistry. The present work deals constructively with the MC one pot synthesis of 4-aryl-5-ethoxycarbonyl-3,4-dihydro-6- methylpyrimidin-2(1H)-ones using L-valine sulfate 1:1 [H-Val][HSO4], a cheap, non-corrosive, and eco-friendly ionic liquid as a dual solvent-catalyst. Keywords: 4-Aryl-5-ethoxycarbonyl-3, 4-dihydro-6-methylpyrimidin-2(1H)-ones, Biginelli compounds, Brønsted acidic ionic liquid, dual solvent-catalyst, L-valine sulfate 1:1, multi-component reactions.

Simultaneous synergistic microwave–ultrasonic extraction and hydrolysis for preparation of trans-resveratrol in tree peony seed oil-extracted residues using imidazolium-based ionic liquid

Imidazolium-based ionic liquid-based microwave–ultrasonic synergistic simultaneous extraction and hydrolysis (IMUSEH) method was developed to obtain trans-resveratrol from tree peony (Paeonia rockii (S.G. Haw & Lauener) T. Hong & J.J. Li) seed oil-extracted residues, in which the basic ionic liquid aqueous solution was used for extraction and transformation of trans-resveratrol glycosides to free trans-resveratrol. Through comparison, 1-butyl-3-methylimidazolium imidazolide ([C4C1im]Im) was selected as a dual solvent–catalyst, which showed an excellent solvent effect and catalytic activity. After optimization by a factorial design and response surface methodology, a higher yield of trans-resveratrol (3.06±0.12μmol/g) was obtained under optimal conditions (0.5M [C4C1im]Im, 24mL/g liquid–solid ratio, 25min time, and 396W microwave irradiation power). The developed technique was compared with ionic liquid-based microwave-assisted extraction and ionic liquid-based ultrasonic-assisted extraction based on first-order kinetic model and scanning electron microscopy, which highlighted the mechanism of the microwave–ultrasonic synergistic apparatus. Method validation studies showed that the proposed method can be used to prepare trans-resveratrol. The developed method showed promise in transforming glucoside to aglycone in plant materials.

Using imidazolium-based ionic liquids as dual solvent-catalysts for sustainable synthesis of vitamin esters: inspiration from bio- and organo-catalysis

An efficient and sustainable approach using imidazolium-based ionic liquids as dual solvent-catalysts for synthesis of vitamin E ester was developed.