Promising Entrainer Research Articles

Selective absorption of ionic liquids in separating R-1243zf or R-161 from refrigerant blends

In order to recover and reuse pure refrigerants from the mixtures used in waste refrigeration facility, it is necessary to find a good way for separation. Due to the extremely low vapor pressure and good selectivity, ionic liquids (ILs) are regarded as promising entrainers for the extractive separation process of azeotropic or near-azeotropic mixtures. Phase behavior of refrigerant with ILs is the basic property in the design of selective absorption-separation process. In this work, the solubility of 3,3,3-trifluoropropene (R-1243zf) and ethyl fluoride (R-161) with trihexyltetradecylphosphonium chloride ([P6,6,6,14][Cl]) were measured based on the isochoric saturation method. The experimental temperature range was from 283.15 K to 343.15 K. Five activity coefficient models, including Margules, van Laar, Scatchard-Hamer, Wilson and non-random two-liquid (NRTL) model, were used to correlate the experimental data, and the results were discussed. In addition, based on the literature data, the separation capacities of different ILs for refrigerant blends composed of R-1243zf or R-161 were investigated.

Effect of glucose–citric acid deep eutectic solvent on the vapor–liquid equilibrium of an aqueous ethanol solution

Objectives. To study the effect of a deep eutectic solvent (DES) based on glucose and citric acid on the vapor–liquid equilibrium of an aqueous solution of ethanol.Methods. A qualitative and quantitative analysis of the conditions of vapor–liquid equilibrium in an ethanol–water–DES ternary mixture was performed based on the open evaporation method and the measurement of TPxy data using a Świętosławski ebulliometer. Since the volatility of the DES is negligible in comparison with that of water and ethanol, the composition of the vapor phase was measured by means of Karl Fischer titration. The conditions of vapor–liquid phase equilibrium were modeled using the UNIFAC model.Results. The open evaporation method was used to determine the curves of residual concentrations for the ethanol–water–DES mixture at various DES concentrations and compositions (glucose–citric acid ratios). TPxy data was obtained for the mixture produced by adding 30 wt % DES to an aqueous solution of ethanol at atmospheric pressure. Studies show that DES based on glucose and citric acid has a significant effect on the relative volatility of ethanol in aqueous solution, leading to the disappearance of the azeotropic point. This effect is due to only the presence of glucose. Citric acid does not change the composition of the equilibrium phases, but rather increases the solubility of glucose in aqueous ethanol solutions. This is especially important at high ethanol concentrations, since glucose is poorly soluble in ethanol.Conclusions. Addition of DES based on glucose and citric acid to an aqueous solution of ethanol leads to the disappearance of the azeotropic point. DES can thus be considered as a promising entrainer for extracting ethanol from aqueous solutions using extractive distillation. Modeling of the conditions of vapor–liquid equilibrium in the ethanol–water–DES system using the UNIFAC model showed a satisfactory level of accuracy. The error in the calculated data increases with increasing the glucose concentration, while remaining acceptable for practical use.

In the quest for ionic liquid entrainers for the recovery of R-32 and R-125 by extractive distillation under rate-based considerations

In line with the reduction targets imposed on the production of high global warming potential (GWP) hydrofluorocarbons by the Kigali Amendment to the Montreal Protocol, the recovery of refrigeration fluids at the end-of-life of refrigeration and air-conditioning equipment and the selective separation of the most valuable refrigerants is sought for recycling purposes and climate change mitigation. To that end, extractive distillation (ED) processes using ionic liquids (ILs) as entrainers is considered a promising technology to solve the difficulty of separating the typical close boiling or azeotropic behaviour of fluorinated hydrocarbon mixtures. This work provides insight into the design of ED processes evaluating the influence of both mass transfer phenomena (rate-based models) and IL properties (absorption capacity, solubility selectivity and viscosity) on the critical process variables (e.g., solvent-to-feed ratio, reboiler temperature, packing height) to separate the components of the binary mixture R-410A (50 wt% difluoromethane (R-32) + 50 wt% pentafluoroethane (R-125)) with minimum energy consumption and purity greater than 99.5 wt% of the two products. Results point to the solubility selectivity as the most influential IL property, and to [C2C1im][SCN], among all ILs assessed, as a promising entrainer because of its high R-32/R-125 solubility selectivity and low viscosity, which enables to operate the ED process at lower temperatures. The recovered R-32 can be used as a greener alternative to the high-GWP R-410A, as well as a main component in the formulation of new low-GWP mixtures.

Energy-efficient recovery of tetrahydrofuran and ethyl acetate by triple-column extractive distillation: entrainer design and process optimization

An energy-efficient triple-column extractive distillation process is developed for recovering tetrahydrofuran and ethyl acetate from industrial effluent. The process development follows a rigorous hierarchical design procedure that involves entrainer design, thermodynamic analysis, process design and optimization, and heat integration. The computer-aided molecular design method is firstly used to find promising entrainer candidates and the best one is determined via rigorous thermodynamic analysis. Subsequently, the direct and indirect triple-column extractive distillation processes are proposed in the conceptual design step. These two extractive distillation processes are then optimized by employing an improved genetic algorithm. Finally, heat integration is performed to further reduce the process energy consumption. The results indicate that the indirect extractive distillation process with heat integration shows the highest performance in terms of the process economics.

Cluster Formation and Its Role in the Elimination of Azeotrope of the Acetone–Methanol Mixture by Ionic Liquids

Ionic liquids (ILs) are promising entrainers in the separation of azeotropic systems with unique advantages, such as environmental benignity and flexible design. In this work, we carried out molecu...

Isobaric Vapor–Liquid Equilibrium for tert-Butyl Alcohol + Water + Propane-1,3-Diol + 1-Ethyl-3-Methylimidazolium Chloride at 101.3 kPa

In this study, we used a mixture of organic liquid propane-1,3-diol and ionic liquid 1-ethyl-3-methylimidazolium chloride ([emim]Cl) as the entrainer to separate tert-butyl alcohol (TBA) + water. We measured the isobaric vapor–liquid equilibrium (VLE) for the quaternary system TBA + water + propane-1,3-diol + [emim]Cl at 101.3 kPa, and found the VLE data to be well correlated with the nonrandom two-liquid model. These results show that the mixed solvent of propane-1,3-diol + [emim]Cl can increase the relative volatility of TBA to water and break the azeotropic point. We found no notable synergetic effect between them, and observed that the liquid mixed solvent of propane-1,3-diol and [emim]Cl had lower viscosity than [emim]Cl, which makes it a promising entrainer for separating the TBA + water azeotrope in industrial applications.

Extractive distillation of methylal/methanol mixture using the mixture of dimethylformamide (DMF) and ionic liquid as entrainers

Methylal is used as an important synthetic fuel blended with diesel oil to reduce the particulate emissions of toxic gas pollutants without affecting the energy density. The mixed entrainers (dimethylformamide (DMF) + ionic liquid (IL)) are proposed to replace conventional DMF for the separation of methylal and methanol by extractive distillation. [EMIM]+[Ac]− might be the most promising entrainer screened by COSMO-RS model considering relative volatility and solvent capacity together. Vapor–liquid equilibrium (VLE) experiments demonstrated that the relative volatility of methylal to methanol is obviously improved after the addition of [EMIM]+[Ac]− into DMF. Moreover, the UNIFAC-Lei model was extended to the methylal-methanol-DMF-IL system, and the corresponding interaction parameters were obtained and input into the equilibrium (EQ) stage model established in this work. Based on the thermodynamic study, process simulation was developed. It was found that the overall heat duty of reboilers decreased 9.25% using the proposed mixed entrainers when compared to pure DMF. In addition, the COSMO-RS model and DFT calculation provide some theoretical insights into the separation mechanism.

Liquid-liquid equilibrium data for water-ethanol-entrainer ternary system with entrainers: Cyclohexane, n-pentane, DEE (diethyl ether), DIPE (di-isopropyl ether), ETBE (ethyl tert-butyl ether)

The water-ethanol system was studied experimentally to find the liquid-liquid equilibrium (LLE) data at various temperature values by using five different entrainers: cyclohexane, n-pentane, DEE (diethyl ether), DIPE (di- isopropyl ether), and ETBE (ethyl tert-butyl ether). Ternary LLE data for water-ethanol-entrainer system was deter- mined based on an experimental procedure. Exact liquid activity coefficient parameters were found by experimental data and LLE data was predicted. For this purpose, two thermodynamic models, NRTL and UNIQUAC, were com- pared and contrasted with experimental data to probe into the better thermodynamic model for the azeotropic processes of ethanol system. The most promising entrainer was found through root mean square and average absolute deviations.

Measurement, correlation, and prediction of vapor pressure for binary and ternary systems containing an ionic liquid 1,3-dimethylimidazolium methylsulfate

Vapor pressure data for water, ethanol, 1-propanol, and 2-propanol, as well as the mixtures of {water+1-propanol} and {water+2-propanol}, were experimentally measured in the presence of an ionic liquid (IL) 1,3-dimethylimidazolium methylsulfate ([MMIM][MS]) at varying IL-contents and temperatures using a quasi-static ebulliometric method. The experimental vapor pressure data for binary systems containing IL were correlated using NRTL model with an overall relative root mean square deviation (rRMSD) of 0.0055, and the obtained binary NRTL parameters were employed to predict the vapor pressure for two ternary systems with an overall rRMSD less than 0.0234. Moreover, the inter-molecular interaction between [MMIM][MS] and volatile solvent was assessed theoretically in terms of the predicted activity coefficients of solvents for binary systems and quantum chemical calculations with polarizable continuum model. Finally, isobaric VLE data were predicted for three ternary systems containing [MMIM][MS] with IL mole fraction of 0.05, 0.15, and 0.25 at 101.325kPa, respectively. The results indicate that [MMIM][MS] might be applied as a promising entrainer to separate the azeotropic mixtures of {water+ethanol}, {water+1-propanol}, and {water+2-propanol} by extractive distillation.

Isobaric vapor–liquid equilibrium for binary and ternary systems with toluene, 2-methoxyethanol and dimethyl sulfoxide at 101.3 kPa

Isobaric vapor–liquid equilibrium (VLE) data for binary systems of toluene+2-methoxyethanol, 2-methoxyethanol+dimethyl sulfoxide (DMSO) and toluene+DMSO were obtained by using a Fischer VLE 602 equipment at 101.3kPa, as well as for the ternary system of toluene+2-methoxyethanol+DMSO. The binary VLE data were considered to be thermodynamically consistent according to the Wisniak's modification of the Herington test and the Wisniak's L–W test. It was determined that toluene and 2-methoxyethanol form binary azeotrope at 379.08K, 70.2mol% toluene at 101.3kPa. The binary VLE data were correlated by using Wilson, NRTL and UNIQUAC models with minor deviations. The ternary system was well predicted from binary interaction parameters and passed both the Wisniak–Tamir's modification of McDermott–Ellis test and the Wisniak's L–W test. Besides, the ternary VLE data were also satisfactorily correlated by using Wilson, NRTL and UNIQUAC models. Moreover, the change of phase equilibria behavior of toluene and 2-methoxyethanol due to the addition of DMSO is significant. Therefore, DMSO is recommended as a promising entrainer for the separation of toluene and 2-methoxyethanol azeotropic mixture by extractive distillation.

Study of Ionic Liquids as Entrainers for the Separation of Methyl Acetate–Methanol and Ethyl Acetate–Ethanol Systems Using the COSMO-RS Model

The separation of the nonaqueous azeotropic systems methyl acetate–methanol and ethyl acetate–ethanol was investigated with 13 cations and 27 anions as entrainers to identify suitable ionic liquids using the COSMO-RS model. It is observed that the cations best suited are imidazolium > pyridinium > methyl pyrrolidinium > octyl quinolinium. The lengthening of the alkyl chain of cations was also studied as well as whether the shorter the alkyl chain, the better is the separation. It was also noticed that the efficacy of the anions is in the order [OAc] > [Cl] > [DHP]. It was seen that the influence of anions is more significant on the behavior of ionic liquid solvation in alcohols. The effects of polarity, excess free energy, and excess enthalpy are addressed on nonaqueous systems containing ionic liquids. It is suggested that [EMIM][OAc], [EMIM][Cl], and [EMIM][DHP] can be used as promising entrainers for practical applications of ester–alcohol separation.

Effect of Mono- and Di-ethanolammonium Formate Ionic Liquids on the Volatility of Water, Ethanol, and Methanol

Vapor pressures were measured for six binary systems containing water, ethanol, or methanol with one of the two ionic liquids (ILs) at different component concentrations and temperatures using a quasi-static ebulliometer, with the ILs mono-ethanolammonium formate ([HMEA][HCOO]) and di-ethanolammonium formate ([HDEA][HCOO]). The vapor pressures of the IL-containing binary systems are well correlated using the NRTL model with an overall average absolute relative deviation (AARD) of 0.0062. The effect of ILs on the vapor pressure depression of solvents at 0.050 mole fraction of IL is that [HDEA][HCOO]>[HMEA][HCOO], and the vapor pressure lowering degree follows the order of water>methanol>ethanol. Further, the activity coefficients of three solvents (viz. water, ethanol, and methanol) for the binary systems {solvent (1)+IL (2)} predicted based on the fitted NRTL parameters at T=333.15 K indicate that the two ILs generate a negative deviation from Raoult's law for water and methanol and a positive deviation for ethanol to a varying degree, change the relative volatility of a solvent. [HMEA][HCOO] may be a promising entrainer to efficiently separate ethanol aqueous solutions by special rectification.

Isobaric Vapor–Liquid Equilibrium for the Ethanol + Water + 2-Aminoethanol Tetrafluoroborate System at 101.3 kPa

Isobaric vapor–liquid equilibrium (VLE) data for the ethanol (1) + water (2) system containing the ionic liquid (IL) 2-aminoethanol tetrafluoroborate ([MEA]+[BF4]−) (3) at atmospheric pressure (101.3 kPa) were measured with a modified Othmer still. The results showed that the azeotropic point can be broken at a specific IL mole fraction, indicating a significant salting-out effect following the order of x3 = 0.15 > x3 = 0.10 > x3 = 0.05. The IL [MEA]+[BF4]− may be a promising entrainer for the separation of ethanol and water with extractive distillation because it exhibits the highest separation ability when compared with other entrainers previously reported. The commonly used nonrandom two-liquid (NRTL) model was used for correlating the measured ternary VLE data.

Synthesis of Ternary Homogeneous Azeotropic Distillation Sequences: Entrainer Selection

This paper presents a methodology for automatic selection of entrainers for separating binary azeotropic mixtures using homogeneous azeotropic distillation. A new classification system for ternary mixtures based on the termini of distillation boundaries and the type (stability) of products and azeotropes is proposed. The new characterisation system is able to link candidate entrainers to flowsheet structures which can facilitate the separation. Existing entrainer selection criteria are extended to accommodate other promising entrainers, including light, intermediate and heavy-boiling entrainers.

Effect of alkanolammonium formates ionic liquids on vapour liquid equilibria of binary systems containing water, methanol, and ethanol

Vapour pressures were measured using a quasi-static ebulliometer for the pseudo-binary mixtures of (water+ethanol), (water+methanol), and (methanol+ethanol) containing an alkanolammonium-based ionic liquid (IL), namely, mono-ethanolammonium formate ([HMEA][HCOO]) and di-ethanolammonium formate ([HDEA][HCOO]), respectively, with fixed IL mass fraction of 0.30 and over the temperature ranges of (292.12 to 371.13)K. The vapour pressures of the IL-containing ternary systems were favourably correlated using the NRTL model with an overall average absolute relative deviation (AARD) of 0.0082. Further, the salt effects of [HMEA][HCOO] and [HDEA][HCOO] on isobaric vapour liquid equilibria (VLE) of azeotrope and close boiling mixture, especially for the mixtures of (water+ethanol) and (methanol+ethanol), were investigated and compared with other ILs in terms of the x′–y phase diagrams predicted with the binary NRTL parameters. It is demonstrated that the relative volatilities of ethanol to water and ethanol to methanol are enhanced, and [HMEA][HCOO] might be used as a promising entrainer for the efficient separation of ethanol aqueous solution by special rectification.

Isobaric vapor-liquid equilibrium for methanol+benzene+1-octyl-3-methylimidazolium tetrafluoroborate

Isobaric vapor-liquid equilibrium (VLE) data for {methanol (1)+benzene (2)+1-octyl-3-methylimidazolium tetrafluoroborate (3)} where 3 is an ionic liquid ([OMIM]+[BF4]−) at atmospheric pressure (101.32 kPa) were measured with a modified Othmer still. The results showed that the ionic liquid studied can transfer the azeotropic point and eliminate the azeotropic phenomena when its concentration is up to x3=0.30. This means that [OMIM]+[BF4]− can be used as a promising entrainer in the application of extractive distillation. The measured ternary data were correlated using the NRTL model.

Isobaric Vapor−Liquid Equilibrium for (Propan-2-ol + Water + 1-Butyl-3-methylimidazolium Tetrafluoroborate)

Isobaric vapor−liquid equilibrium (VLE) data for {propan-2-ol (1) + water (2) + 1-butyl-3-methylimidazolium tetrafluoroborate(3)} where 3 is an ionic liquid ([BMIM]+[BF4]−) at atmospheric pressure (101.32 kPa) were measured with a modified Othmer still. The results showed that the ionic liquid studied can transfer the azeotropic point and eliminate the azeotropic phenomena when its concentration is up to x3 = 0.20. This means that [BMIM]+[BF4]− can be used as a promising entrainer in the application of extractive distillation. However, the comparison of the salting-out effect of [BMIM]+[BF4]− with that of 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM]+[BF4]−) was conducted. The measured ternary data were correlated using the NRTL equation.

DESIGN STRATEGY FOR ACETIC ACID RECOVERY

Acetic add is recovered from dilute aqueous solutions by extraction followed by azeotropic distillation. The heat required for distillation accounts for the major proportion of the cost of the process. Therefore, the proper selection of the entrainer is of great importance. In this paper, a procedure for preliminary entrainer selection is developed combining the well proved heuristic approaches and the latest developments for the synthesis phase based on residue curve maps and liquid-liquid equilibria plots. The energy requirements for the most promising entrainers are calculated using a commercial process simulator. It was found that methyl tert-butyl ether is a promising entrainer for the acetic acid dehydration process.

Homogeneous azeotropic distillation: Analysis of separation feasibility and consequences for entrainer selection and column design

We present a method to assess the ranges of feasible separations in the distillation of ternary azeotrope-forming mixtures. The absolute boundaries for distillation in single- and multi-feed columns can be derived from a pinch curve analysis that locates the compositions of possible stationary points in each column section. The bifurcations of pinch trajectories explain the complex phenomena observable in homogeneous azeotropic distillation columns, in particular the crossing of boundaries for total reflux and the existence of a maximum reflux for such separations in single- and in multi-feed columns. These insights also lead to a simple new strategy to identify promising entrainers.