Acetate-based Ionic Liquids Research Articles

Vapor–Liquid Equilibrium for Ethyl Acetate + Acetonitrile with Acetate-Based Ionic Liquids as Entrainers at 101.3 kPa and Analysis of the Separation Mechanism

Vapor–Liquid Equilibrium for Ethyl Acetate + Acetonitrile with Acetate-Based Ionic Liquids as Entrainers at 101.3 kPa and Analysis of the Separation Mechanism

Biomass pretreatment with distillable ionic liquids for an effective recycling and recovery approach

Ionic liquid (IL) pretreatment methods show incredible promise for the efficient conversion of lignocellulosic feedstocks to fuels and chemicals. Given their low vapor pressures, distillation-based methods of extracting ionic liquids out of biomass post-pretreatment have historically been ignored in favor of alternative methods. We demonstrate a process to distill four acetate-based ionic liquids ([EthA][OAc], [PropA][OAc], [MAEthA][OAc], and [DMAEthA][OAc]) at low pressure and high purity that overcome some disadvantages of “water washing” and “one pot” recovery methods. Out of four tested ILs, ethanolamine acetate ([EthA][OAc]) is shown to have the most agreeable conversion metrics for commercial bioconversion processes achieving 73.6 % and 51.4 % of theoretical glucose and xylose yields respectively and >85 % recovery rates. Our process metrics are factored into a techno-economic analysis where [EthA][OAc] distillation is compared to other recovery methods as well as ethanolamine pretreatment at both milliliter and liter scales. Although our TEA shows [EthA][OAc] distillation underperforming against other processes, we show a step-by-step avenue to reduce sugar production cost below the wholesale dextrose price at scale.

Biocompatible ammonium-based ionic liquids/ZIF-8 composites for CO2/CH4 and CO2/N2 separations

The development of sorbent materials with high carbon dioxide (CO2) selectivity is of vital importance to minimize the impact of global warming by separating and capturing this major greenhouse gas. In this work, for the first time five ammonium-based ionic liquids (ILs) were impregnated into the metal-organic framework (MOF) ZIF-8 for gas sorption applications. Characterization results showed that the produced IL@ZIF-8 composites are thermally stable and of microporous nature. IL impregnation was successfully accomplished and did not affect the crystalline structure of ZIF-8. Sorption-desorption equilibrium isotherms of different gases, including CO2, methane (CH4) and nitrogen (N2) were measured at 303 K for the pristine MOF and the composites. Given the careful choice of the ILs, the anion and cation effects were studied in terms of their impact on the sorption capacity and selectivity performance of each composite. Acetate-based composites showed high CO2 selectivity when compared to ZIF-8; specifically, the composite [N2 1 1 4][Ac]@ZIF-8 showed 51% increase, at 1 bar and for flue gas conditions. Because of the good CO2/N2 selectivity of the acetate-based composites, sorption-desorption equilibrium isotherms of the above-mentioned gases were also measured at 323 K, along with ZIF-8. Ideal selectivities were thus calculated to study the temperature impact on the selectivity performance of the materials. It can be observed that the higher the temperature, the less selective the materials are. Nevertheless, at 323 K and when compared to ZIF-8, the composite [N2 1 1 4][Ac]@ZIF-8 showed 56% increase, at 1 bar and for flue gas conditions. Finally, the isosteric heats of adsorption of ZIF-8 and the acetate-based ILs were calculated revealing that all gases are physisorbed by the three materials.

From biopolymer dissolution to CO2 capture under atmospheric pressure - A molecular view on biopolymer@Ionic liquid materials

Finding a cheap and easily recycling material that can capture CO2 under atmospheric pressure (1 atm) is of paramount importance. In this context, combining ionic liquids (ILs) with abundant and natural materials, such as chitin-based biopolymers, appears as an interesting alternative. In this work, four acetate-based ILs were selected to explore the solubility of chitin, chitosan, and carboxymethyl-chitosan. Using carboxymethyl-chitosan and biopolymer monomer units as models, different Nuclear Magnetic Resonance (NMR) techniques, namely, 1H, 13C, nuclear Overhauser effect spectroscopy, and spin-lattice relaxation, were performed to evaluate the dissolution. Shrimp shells were used as a chitin source. Through a simple acid/base treatment, it was possible to remove minerals and proteins, and use it to prepare biopolymer@IL materials for CO2 capture tests. Efficient CO2 sorption capacity was observed upon bubbling CO2 with a maximum of 2.32 mmolCO2/gsorbent. Under N2 bubbling, the system demonstrated excellent recycling capacity using a room temperature procedure that outperformed aqueous amine solutions recycling. The absence of heating and vacuum recycling procedures, combined with the use of N2 or compressed air is much more appealing for industrial applications.

A comparative study of ionothermal treatment of rice straw using triflate and acetate-based ionic liquids

Ionic liquids (ILs) have found applications in the pretreatment of waste lignocellulosic biomass by interacting with the carbohydrate molecules present in the biomass materials. Pretreatment is essential before biomass conversion into valuable chemicals, fuels, and many other value-added products. This comparative study mainly focused on the pretreatment ability of four ILs having acetate or triflate as a common anion with different cations. Among various studied ILs, diazabicyclo[5.4.0]undec-7-ene (DBU)-based acidic ionic liquid when used as a dual solvocatalyst showed significant structural modifications of the rice straw (RS) sample, through C6-O bond breakage assisted by the tertiary nitrogen in DBU cation. Structural modifications due to the pretreatment were confirmed through SEM, PXRD, and FTIR analysis. The elemental analysis confirmed that carbon content in original RS is reduced to 29% and 20% upon ionothermal treatment of RS with IL at 90 °C and 120 °C, respectively. Additionally, TGA indicated that further pyrolysis could be easier with the pretreated rice straw yielding biochar up to 9% thereby reducing wastes. Conversion of RS was found to be 60% which reduced marginally to 50% after three cycles of recycling the IL. The findings of this work provide the proof of concept that studied IL with high thermal stability and recyclability should act as a potential solvocatalyst in sustainable pretreatment and other biomass applications.

Isobaric vapor-liquid equilibrium for 2-butanone + ethanol + acetate-based ionic liquids at 101.3 kPa

Three acetate-based ionic liquids (ILs) (tetraethylammonium acetate, [N2,2,2,2][AC]; 1‑butyl‑2,3-dimethylimidazolium acetate, [BMMIM][AC]; or tributyl-methylammonium acetate, [N4,4,4,1][AC]) were used to separate the 2-butanone-ethanol azeotropic mixture as entrainer. The separation abilities of the three ILs were compared by measuring isobaric vapor-liquid equilibrium (VLE) data of the 2-butanone + ethanol + IL ternary systems at 101.3 kPa. The VLE data were well correlated through the use of the nonrandom two-liquid (NRTL) model. The azeotrope of 2-butanone + ethanol binary system is entirely eliminated when the concentration of IL achieves a certain value. The minimum mole fractions of the three ILs to completely eliminate azeotropic phenomena are 0.0146, 0.0166 and 0.0240, respectively. The breaking azeotropic capacities of the three ILs are better than that previously reported in the literatures. According to the average relative volatility, after the azeotropic point is thoroughly eliminated, the order of the separation capability of the three ILs is as below: [N2,2,2,2][AC] > [BMMIM][AC] > [N4,4,4,1][AC]. The σ-profiles were used to further explore the separation mechanism.

Solubility measurement, modeling and mixing thermodynamic properties of R1243zf and R600a in [BMIM][Ac

3,3,3-Trifluoropropene (R1243zf) and isobutane (R600a) are considered as prominent environmentally-friendly refrigerants, and acetate-based ionic liquids are potential absorbents used in absorption refrigeration cycles. In this work, the dissolving capacities of R1243zf and R600a in one of the acetate-based ionic liquids (1-butyl-3-methylimidazolium acetate, [BMIM][Ac]) were investigated. The measurements were based on isochoric saturation method and the experimental temperature range was from 283.15 K to 343.15 K. The non-random two liquid (NRTL) model and Krichevsky-Kasarnovsky (K-K) model were utilized to model the experimental results, and both models exhibited reasonable deviations. On the basis of solubility data and correlation results, the Henry’s law constants and the mixing thermodynamic properties (mixing enthalpy, mixing entropy and Gibbs energy) for the two mixtures were determined. In addition, the dissolving abilities of R1243zf and R600a in [BMIM][Ac] were compared with the reported results of R1234yf in the literature.

Technoeconomic Assessment of a Biomass Pretreatment + Ionic Liquid Recovery Process with Aprotic and Choline Derived Ionic Liquids

Ionic liquids have shown promising results in biomass pretreatment; however, an extensive water washing step is necessary. This fact increases not only the processing costs but also those associated with the ionic liquid recovery step. In this work, Eucalyptus globulus wood pretreated with two acetate-based ionic liquids, namely 1-ethyl-3-methylimidazolium acetate and choline acetate, has been washed with increasing volumes of water in order to analyze the influence of the amount of washing water used on the subsequent enzymatic hydrolysis stage and on the IL recovery costs. Vapor–liquid equilibria data of recovered ionic liquid/water mixtures have been determined to simulate the IL recovery step with Aspen Plus, calculating the operating costs using the Aspen Plus Economics Analyzer afterward. [Emim][OAc] was more efficiently washed and more effective toward wood pretreatment than [Ch][OAc]. Both IL/water systems were successfully modeled, and simulation studies showed that incremental volumes of water led to higher operating costs in the IL recovery step that are compensated with less IL makeup costs. Therefore, this work offers a technoeconomical analysis of the IL recovery step in a real biorefinery pretreatment process as a function of the volume of water used in the pretreated wood washing stage.

Simulation of H2S solubility in three acetate-based ionic liquids using PC-SAFT EoS together with RETM

In current work, Perturbed Chain- Statistical Associating Fluid Theory (PC-SAFT) EoS together with the Reaction Equilibrium Thermodynamic Model (RETM) was employed to correlate H2S solubility in three carboxylate ionic liquids including [emim][Ace], [bmim][Ace] and [hmim][Ace]. The RETM proposes a chemical reaction approach between IL (B) and H2S (A) in the liquid phase. Moreover PC-SAFT EoS contributes for VLE calculations. All the H2S and the investigated ILs, as self-associating components, assumed to follow 2B association scheme.Five adjustable variables of PC- SAFT EoS for pure components were calculated using experimental data of liquid density and vapor pressure. Afterwards, the binary systems were investigated applying RETM. Indeed, two nested loops calculate the liquid phase, total pressure and vapor phase concentrations, respectively. For these systems, AAD% equal to 2.29, 3.09 and 7.65 were obtained for all ILs respectively.

Fast Track to Acetate-Based Ionic Liquids: Preparation, Properties and Application in Energy and Petrochemical Fields.

Acetate-based ionic liquids (AcILs), as a kind of typical carboxylate-based ILs, display excellent structure tunability, non-volatility, good solubility to biomass, and favorable adsorption capacity, etc. These unique characteristics of AcILs make them important candidates for a range of applications in the field of energy and in the petrochemical industry. This paper intends to provide a comprehensive overview of recent advances in AcILs, including pure AcILs, AcIL-based multi-solvents, and AcIL-based composites, etc. Preparation methods, with one- and two-step synthesis, are reviewed. The relationship between properties and temperature is discussed, and some physical and thermodynamic properties of different AcILs are summarized and further calculated. The applications of AcILs in the fields of biomass processing, organic synthesis, separation, electrochemistry, and other fields are reviewed based on their prominent properties. Thereinto, the dual functions of AcILs as solvents and activators for biomass dissolution are discussed, and the roles of AcILs as catalysts and reaction mediums in clean organic synthesis are highlighted. Meanwhile, the reaction mechanisms of AcILs with acid gases are posed by means of molecular simulation and experimental characterization. Moreover, AcILs as electrolytes for zinc batteries, supercapacitors, and electrodeposition are particularly introduced. Finally, the future research challenges and prospects of AcILs are presented.

Selective adsorption of acidic gases from ternary mixture by acetate- and sulfonate-based ionic liquids at molecular level.

This paper attempts to elucidate the competitive adsorption mechanism of thin films of ionic liquids (ILs) on the surface of porous materials for acidic gases at a molecular level in order to design a proper material for the diminishment of gas emissions. Thin film 1-butyl-3-methylimidazalium ([BMIM]+) cation-based IL systems composed of four different anions such as [CH3CO2]- and [CF3CO2]- (acetate-based), and [CH3SO3]- and [CF3SO3]- (sulfonate-based) are created in contact with the gas phase containing ternary H2S/CO2/CH4:1/25/74 mixture. To define gas adsorption performance at gas-liquid interface and bulk liquid phase, classical molecular dynamics simulations are carried out. Adsorption of acidic gases is governed by the formation of an adsorbed gas layer on the surface of the ionic liquid based on thermodynamics aspects, and then the partial dissolution of gases in the bulk liquid phase is accompanied by the transport of gases. These behaviors are followed by several analysis methods in simulation approaches such as radial distribution function (RDF) of gases around specific atoms of ILs, lateral displacement of gas molecules, radial distance between gas and ILs, interaction energy between gases and ILs, and average number of hydrogen bonding between ions with and without adsorbed gases. Acetate-based ILs performed twice as good in CO2 adsorption capacity than sulfonate-based ILs. However, the one having -CF3 group in acetate-based ILs has short CO2 retention time and high CH4 adsorption capacity, diminishing the H2S+CO2/CH4 adsorption selectivity. High CO2 adsorption performance of acetate-based ILs is related to their strong anion-cation interaction and less hydrogen-bonding ability between cation tail and anion, which is the source for free space between anion and cation. Those with high adsorption capacities and long retention times are those that can ensure that CO2 molecules are coordinated in these free volumes between cation tails and anions. Therefore, here, the effect of different parameters on the CO2 and H2S adsorption over CH4 is revealed via atomistic design, and the importance of selection of suitable anions in IL for identifying potential nanocomposite adsorbent materials for acidic gas removal is highlighted.

A Comparative Study of Ionothermal Treatment of Rice Straw Using Triflate and Acetate-Based Ionic Liquids

A Comparative Study of Ionothermal Treatment of Rice Straw Using Triflate and Acetate-Based Ionic Liquids

Insight into the interaction between arabinoxylan and imidazolium acetate-based ionic liquids

Herein, six ionic liquids (ILs) with different cations and the same anion of acetate (Ac−) were used to dissolve arabinoxylan. These ILs included N-methylimidazolium acetate (HmimAc), 1-ethyl-3-methylimidazolium acetate (EmimAc), 1-hydroxyethyl-3-methylimidazolium acetate (HOemimAc), 1-propyl-3-methylimidazolium acetate (PrmimAc), 1-allyl-3-methylimidazolium acetate (AmimAc), and 1-butyl-3-methylimidazolium acetate (BmimAc). The solubilities of arabinoxylan in these ILs were determined, and the dissolution mechanism was explained using 1H and 13C NMR techniques. The solubilities of arabinoxylan in the ILs were in the order: BmimAc > EmimAc > AmimAc > PrmimAc > HOemimAc > HmimAc. Both the cation and Ac− played an important role in the solubilization of arabinoxylan, but Ac− performed the major factor. The structure of cation greatly affected the hydrogen bond accepting ability of Ac−. Increasing the mass ratio of arabinoxylan to ILs resulted in stronger hydrogen bond between arabinoxylan and the ILs. Both the solubility and the strength of hydrogen-bonding interaction between arabinoxylan and the ILs decreased in the recycled ILs because of the impurities remained.

Evaluating Protic Ionic Liquid for Woody Biomass One-Pot Pretreatment + Saccharification, Followed by Rhodosporidium toruloides Cultivation

Woody biomass feedstocks pose challenges in their use as sustainable carbon sources due to their recalcitrance. One-pot ionic liquid-based processes are a promising bioproduction strategy to reduce water consumption (removing the washing of biomass), reduce costs, and minimize the presence of inhibitory compounds. We evaluated the one-pot ionic liquid pretreatment + saccharification configuration as a scheme for the deconstruction and conversion of two different woody feedstocks, eucalyptus, and pine. A comparative study of protic ionic liquids 2-hydroxylethylammonium acetate-based ionic liquids, bis-2-hydroxyethylammonium acetate, and cholinium lysinate for pretreatment of eucalyptus and pine was conducted. The impact of ionic liquids at 11% w/w on the saccharification and toxicity of hydrolysates containing the ionic liquid for downstream use for microbial cultivation was evaluated. Protic ionic liquids were more effective in eucalyptus than in pine pretreatment and less toxic than cholinium lysinate at concentrations ≤10% w/w. 2-hydroxylethylammonium acetate yielded the highest digestibility, of up to 75% in eucalyptus. As a proof of concept of an integrated feedstocks-to-biofuels process, we tested the growth of the fungal strain Rhodosporidium toruloides in hydrolysates with low amounts of ionic liquids and phenolic compounds. The proof of concept demonstrated the ability of Rhodosporidium toruloides to grow in the presence of 2-hydroxyethylammonium acetate (5% w/w), the importance to adjust the pH after saccharification, and the ability to consume lignin monomers. This work offers a valid starting point for further studies aimed at increasing cellulose digestibility in a one-pot configuration in the presence of protic ionic liquids.

Investigation of CO2 capture using acetate-based ionic liquids incorporated into exceptionally porous metal–organic frameworks

The potential advantage of using supported ionic liquids (SILs) for CO2 capture applications has been investigated in this work. The impregnation of 1-ethyl-3-methylimidazolium Acetate [emim][Ac] into two voluminous metal–organic frameworks (MOF-177 and MIL-101) is evaluated using different synthesis methods. The performance of the composite sorbents for CO2 capture has been evaluated using various characterization techniques. The successful incorporation of [emim][Ac] into the pores of MOF-177 and MIL-101 have been confirmed using thermogravimetric analysis and Fourier transform infrared spectroscopy results. Furthermore, the porosity of the as-synthesized samples using different synthesis methods have been measured using N2 adsorption experiments to evaluate the changes in the specific surface areas and pore volumes upon the introduction of [emim][Ac] to the support materials. A significant decrease in the porosity was realized for the [emim][Ac]-confined samples especially when using wet impregnation synthesis method compared to the dry mixing approach. The crystal structures of the MOF-177 and MIL-101 were found to be maintained after the synthetic steps, with some reductions in the X-ray diffraction peak intensities. No improvements in the CO2 uptakes could be achieved for the MIL-101 samples using both synthesis strategies, whereas the [emim][Ac]@MOF-177 samples prepared using wet impregnation method, has shown a remarkable enhancement in the CO2 capacity up to 0.3 mmol/g at 0.15 bar and 303 K. Moreover, the adsorption kinetics in MOF-177 based samples was found to be significantly fast as depicted from the first order rate constant values. The [emim][Ac]@MOF-177 samples exhibited a substantially stable cyclic adsorption–desorption performance up to 10 successive cycles with a considerably fast desorption kinetics.

Separation abilities of three acetate-based ionic liquids for benzene-methanol mixture through vapor-liquid equilibrium experiment at 101.3 kPa

Three ionic liquids (ILs) with acetate anion (1-hexyl-3-methylimidazolium acetate, [HMIM][OAC]; 1-octyl-3-methylimidazolium acetate, [OMIM][OAC]; and 1-decyl-3-methylimidazolium acetate, [DMIM][OAC]) were studied as entrainers for separating the benzene-methanol binary azeotrope. Isobaric vapor-liquid equilibrium (VLE) data for the ternary systems of benzene + methanol + IL were measured at 101.3 kPa. The VLE data were well correlated by using the nonrandom two-liquid (NRTL) model. The relative volatility of benzene to methanol is enhanced with the increase in IL content. The azeotropic phenomenon of benzene-methanol mixture can be completely eliminated when IL content reaches a specific value. After the azeotropy of benzene-methanol mixture is completely eliminated, the separation ability of the three ILs follows the order [HMIM][OAC] > [OMIM][OAC] > [DMIM][OAC]. The separation abilities of the three ILs were further analyzed with the help of their σ-profiles.

Molecular dynamics of acetate-based ionic liquids

A radial distribution analysis of pairs between the constituent atoms of protic ionic 2-(hydroxy)ethylammonium acetate was performed with molecular dynamics technique (MDT). The ionic liquid structure will help us in different engineering applications, as emulsification process (petroleum industry). The results presented here show that the development of force field to predict the high interaction behaviour between the cation and the anion, as well as the formation of ion-pair dispersed aggregates. These results can contribute to help the different applications of ionic liquids.

Waste Recycling: Ionic Liquid-Catalyzed 4-Electron Reduction of CO2 with Amines and Polymethylhydrosiloxane Combining Experimental and Theoretical Study

The acetate-based ionic liquids (ILs), e.g., [nBu4N]OAc, have been developed for challenging 4-electron reduction of CO2 with amines and hydrosilane to afford aminals. Notably, polymethylhydrosiloxane, a cheap byproduct of the silicone industry, also works well as a reductant. Furthermore, an alternative pathway is rationally proposed via thorough density functional theory (DFT) study. In addition, the ILs play a surprisingly significant role through decreasing activation free energy. More importantly, the essence of being kinetically favorable with 4-electron reduction and thermodynamically favorable with 6-electron reduction is unveiled by DFT study, which guides us to successfully get 6-electron reductive products of CO2, i.e., methylamine. This work represents upgrading usage of both carbon and silicon wastes to valuable chemicals via IL catalysis.

Isobaric Vapor–Liquid Equilibrium for 2-Butanone + Ethanol System Containing Different Ionic Liquids at 101.3 kPa

In this work, ionic liquids (ILs) were selected as extractive distillation entrainers to separate the 2-butanone + ethanol binary azeotropic mixture because of their remarkable molecular designability, high selectivity, low volatility, and other excellent characteristics. The isobaric vapor–liquid equilibrium (VLE) data for the ternary systems of 2-butanone + ethanol + acetate-based ILs (1-ethyl-3-methylimidazolium acetate [EMIM][OAC], 1-butyl-3-methylimidazolium acetate [BMIM][OAC], and 1-hexyl-3-methylimidazolium acetate [HMIM][OAC]) were measured at 101.3 kPa in an all-glass dynamic recirculating still. The addition of ILs can significantly enhance relative volatility of 2-butanone to ethanol, and the azeotropy of the 2-butanone + ethanol binary mixture is eventually eliminated by increasing the IL content to a certain value. The separation efficiency of the three ILs follows the order [EMIM][OAC] > [BMIM][OAC] > [HMIM][OAC]. Additionally, the binary and ternary VLE data are well-correlated with the no...

Incorporation of acetate-based ionic liquids into a zeolitic imidazolate framework (ZIF-8) as efficient sorbents for carbon dioxide capture

Tuning the interior pores of solid sorbents to improve their adsorption characteristics is considered an effective approach to enhance gas separation performance. Herein, we examine the improvement of carbon dioxide (CO2) capture performance of a ZIF-8 impregnated with ionic liquid 1-Butyl-3-methylimidazolium Acetate [Bmim][Ac] and 1-Ethyl-3-methylimidazolium Acetate [Emim][Ac]. The synthesis and detailed characterizations of the developed composite materials are reported, and the impact of ionic liquid (IL) loading is studied. Fourier transform infrared (FTIR) spectroscopy was used to confirm the impregnation of the ILs into the pores of ZIF-8 and thermogravimetric analysis (TGA) was carried out to study the thermal stability of the composite materials. The powder X-ray diffraction (XRD) pattern of the ILs@ZIF-8 samples revealed that the crystal structure of ZIF-8 remained intact after the impregnation process. The Brunatuer–Emmett–Teller (BET) surface area and pore volumes have significantly decreased up to 80% for [Bmim][Ac]@ZIF-8 with 30 wt% IL loading confirming the presence of ILs inside the internal pores of ZIF-8. CO2 and N2 adsorption isotherms of the ILs@ZIF-8 composites were evaluated gravimetrically at (303, 313, and 323) K. The impregnated samples exhibited substantially higher CO2 uptake and CO2/N2 selectivity at all studied temperatures of up to 7 times higher the CO2 capacity at 0.2 bar and 303 K for [Bmim][Ac]@ZIF-30 as compared to the pristine ZIF-8. Findings from this work provide insights into the synthesis, structure, and sorption capacity of these novel composite materials, which could be utilized for the design of sorbents with outstanding properties to meet the environmental challenges.