Azeotropic Separation Research Articles

A Quest To Find a New Reactant To Replace Ethylene Oxide in Reactive–Extractive Distillation for Ternary Azeotropic Separation

A Quest To Find a New Reactant To Replace Ethylene Oxide in Reactive–Extractive Distillation for Ternary Azeotropic Separation

Vapor–Liquid Equilibrium Experiment and Process Simulation Study of Tetrahydrofuran–Methanol Azeotrope Separation from Wastewater Using Ionic Liquid Mixed Solvent

Vapor–Liquid Equilibrium Experiment and Process Simulation Study of Tetrahydrofuran–Methanol Azeotrope Separation from Wastewater Using Ionic Liquid Mixed Solvent

Separation of toluene-alcohol azeotropes by porous crystals of fluorinated leaning pillar[6]arene

Separation of toluene-alcohol azeotropes by porous crystals of fluorinated leaning pillar[6]arene

Thermoeconomic Evaluation of the Triple Pressure-Swing Distillation Process

Objective: Investigate distillation as a separation process based on the difference in volatility of components, focusing on the separation of azeotropic mixtures using Pressure-Swing Distillation (PSD). The study was applied to the ternary mixture water-acetonitrile-isopropanol (Water-ACN-IPA). Theoretical Framework: Based on previous studies that demonstrated the feasibility of PSD for separating this mixture using three columns operating at different pressures. However, challenges related to high energy consumption persist due to system irreversibilities. Method: Hydraulic analysis of the columns is proposed, including the implementation of variable diameter and thermal integration as optimization strategies. Results and Discussion: Results show a 47.5% reduction in the total annual cost (TAC), demonstrating greater economic efficiency and process viability. Research Implications: The study contributes to improving energy efficiency in azeotropic separation processes using PSD, providing practical solutions to minimize costs and environmental impacts. Originality/Value: This work introduces technical innovations in azeotropic distillation using PSD, offering an economically optimized and viable approach for the chemical, petrochemical, and pharmaceutical industries.

Energy-saving research on the separation of isopropyl acetate and isopropanol azeotrope using pressure-swing distillation based on phase equilibrium

In high purity thioglycolic acid production, isopropyl acetate is used to extract the acid from intermediates, but it hydrolyzes and forms azeotrope with isopropanol under acidic conditions. To achieve environmental conservation, resource utilization, and clean production goals, the design of economically profitable separation processes becomes imperative. Pressure-swing distillation (PSD) with process intensification is employed after derived binary interaction parameters from VLE data at lower pressures, and sequential iteration simplified optimization is performed. Further to overcome the high energy consumption encountered in traditional PSD, heat integration and steam recompression technology were incorporated, resulting in four energy-saving PSD designs. And temperature-enthalpy diagrams were utilized to assess their energy consumption. Based on evaluation indicators of total annual cost (TAC), total energy consumption (TEC), and CO2 emissions, all improved PSD processes significantly reduced TAC and CO2 emissions. Among them, heat pump (HP-PSD) demonstrating the highest economy and eco-friendliness with a 30.1 % and 82.4 % reduction in TAC and CO2 emissions. Heat pump assisted heat integration (HP-HIPSD) also attracted significant attention of reducing TAC by 16.3 %. A longer payback period is expected to yield higher cost savings from all enhanced designs. This study provides invaluable insights for the separation and sustainable development of alcohol ester azeotropes.

Efficient separation of methyl ethyl ketone and water azeotrope using hydrophobic amino acid ester ionic liquids

BackgroundMethyl ethyl ketone (MEK), an essential organic solvent, is commonly produced via the n-butene method, where water emerges as the principal impurity. The conventional distillation processes, which are necessitated by the azeotropic behavior between MEK and water, result in a substantial expenditure of energy. As a result, liquid-liquid extraction represents a promising alternative for energy-efficient separation. MethodsIn this work, three hydrophobic amino acid ester ionic liquids L-phenylalanine ethyl ester bis(trifluoromethylsulfonyl) imide ([Phe][NTf2]), L-leucine ethyl ester bis(trifluoromethylsulfonyl) imide ([Leu][NTf2]) and L-valine ethyl ester bis(trifluoromethylsulfonyl) imide ([Val][NTf2]) were utilized as extractants for separation of the binary azeotrope methyl ethyl ketone and water. The effects of extraction time, extraction temperature, mass ratio of MEK-water mixture to ionic liquid and initial concentration of MEK on extraction efficiency were investigated. Significant findingsThe results demonstrate that the ionic liquid [Phe][NTf2] exhibits superior extraction ability for the separation of the azeotrope methyl ethyl ketone and water. The maximum extraction yield of 99.86 % was achieved with the optimum extraction conditions of extraction time, 10 min, extraction temperature, 293.15 K, mass ratio of mixture to ionic liquid, 1:1 and initial concentration of MEK, 20 %. In addition, the relationship between the structure of ionic liquids and their extraction performance was revealed by quantum chemical calculations of ionic liquids with MEK and water. These ionic liquids were positioned as promising environmentally friendly alternatives to traditional organic solvents for the recovery of MEK from aqueous solutions, providing valuable insights for industrial applications.

Simulation and optimization of DMC synthesis process based on conventional and advanced exergy analyses

Dimethyl carbonate has received more and more attentions as an organic solvent in electrolytes. Aiming at the problem of high energy consumption in the process of dimethyl carbonate (DMC) production, the root of the problem was analyzed by using exergy analysis, which provides a theoretical basis for the construction of energy-saving process. Firstly, the overall process of DMC production was constructed, including propylene carbonate (PC) synthesis, DMC synthesis, azeotrope separation and propylene glycol (PG) purification processes. Secondly, the conventional and advanced exergy analyses of the four proposed processes were carried out. The distributions of exergy and exergy destruction were obtained through conventional exergy analysis. The exergy destructions were further divided through advanced exergy analysis, and the avoidable parts were focused on. Based on the above analyses, the corresponding heat integration processes were proposed. Finally, the conventional processes and the heat integration processes were evaluated with the performance indicators of the exergy destruction, total annual cost (TAC), total energy consumption (TEC) and CO2 emissions.

Efficient separation of diisopropyl ether and ethanol using green solvents: Thermodynamic analysis and process simulation

Ionic liquids (ILs) and deep eutectic solvents (DESs) were first proposed as green solvents to study and compare their azeotropic separation effects in diisopropyl ether (DIPE) and ethanol (EA). The COSMO-RS model was used to screen ILs/DESs, and the feasibility of the extractants were comprehensively analyzed in terms of viscosity, thermal stability, and toxicity. Experiments were carried out on selected ILs and DESs, and the results showed that the separation effect of ILs was significantly stronger than that of DESs. Quantum chemical calculations and molecular dynamics simulations were combined to comprehensively analyze and compare the microscopic mechanisms of extraction separation. Based on the experimental data, a DIPE-EA extraction-coupled separation process was designed. For the first time, life cycle analysis was used to comprehensively evaluate the impact of this process on human health and the environment from multiple perspectives, providing theoretical guidance for the separation of alcohol ethers in the industry.

Design and multiperformance evaluation of the ternary azeotrope separation process via extractive distillation based on different extractants

Resource utilization and sustainable wastewater treatment have received widespread attention because of their efficient use of energy. In this study, an ethanol (EtOH)/ethyl tert-butyl ether/water ternary azeotropic system was used to explore the separation efficiency of various extractants. The relative volatility, toxicity, and process modeling of extractants were analyzed to provide a theoretical basis and practical guidance for screening the optimal extractant among nine commonly used extractants. Extractive distillation (ED) was optimized for six processes with a focus on total energy consumption (TEC) and total annual cost (TAC). The ED-EtOH process was the most economical, whereas the extractive ED-DMSO process had the lowest TEC. After heat integration (HI) treatment, the TAC and TEC of each process were reduced, among which HI-ED-EtOH and HI-ED-glycerol (GLY) had the best and lowest economy, respectively. Although high-boiling point and high latent heat extractants (such as GLY and EtOH) increase the heat demand and operating costs, their high latent heat characteristics can effectively recycle heat energy during the HI process. The optimal balance between economy and energy consumption was determined through multi objective optimization considering the physical and chemical properties, environmental impact, and adaptability of extractants.

Ionic liquids based azeotropic separation of refrigerants R410A (R32+R125) and R508B (R23+R116) through hybrid extractive distillation

ABSTRACT The increment in GreenHouse Gases (GHGs) promotes high Global Warming Potential (GWP) due to the production and consumption of hydrofluorocarbons (HFCs) that diverts the aim toward the recycling and reclaiming of refrigerant gases. However, the presence of azeotrope in refrigerant mixtures restricts the recycling process. Therefore, in this work, the refrigerant R410A and R508B have been separated through the hybrid extractive distillation method by using [HMIM][TF2N] and [BMIM][BF4] as a solvent in ASPEN Plus. UNIFAC model has been used for the correlation of ionic liquid in ASPEN Plus. For thermodynamic properties, Cosmotherm has been used with the collaboration of TurbromoleX. The Vapor-liquid Equilibrium (VLE) data has been predicted by using the UNIFAC group contribution method. The Total Annual Cost (TAC) analysis with optimization has been performed. Besides that, the energy analysis has also been performed. In the overall separation process and (TAC) analysis, [BMIM][BF4] proves to be more efficient with high separation efficiency and minimal TAC requirements. Whereas, [HMIM][TF2N]/R508B provides less CO2 emission.

Mechanism analysis and performance comparison of extractive distillation with different extractants for separating methyl tert-butyl ether/methanol mixture

Methyl tert-butyl ether (MTBE) is an important chemical raw material and fuel additive commonly used in the chemical industry and can form minimum boiling azeotrope with methanol (MeOH). In this article, extractive distillation processes with common-extractant (diethylene glycol, DG), counter-extractant (chlorobenzene, CB) and ionic liquid ([MIM][HSO4]) for the separation of MTBE and MeOH binary azeotrope are investigated simultaneously for the first time. Moreover, five quantum chemical calculation methods of σ-profiles, electrostatic potential, interaction energy, Hirshfeld surface and weak interaction are used simultaneously for the first time to reveal the extractive distillation mechanism of different extractants in detail. Finally, three extractive distillation processes (CED-IL, CED-DG, CED-CB) are established and optimized with total annual costs (TAC) and CO2 emissions as objectives. Their performances are comprehensively compared from the aspects of economy, environment, energy, exergy and inherent safety under the optimal conditions. The results demonstrate that, in comparison to the CED-DG process, the CED-IL process reduces TAC by 31.0%, total energy consumption (TEC) and gas emissions by 27.7%, process route index (PRI) by 36.4% and increase thermodynamic efficiency by 46.4%, while the CED-CB process increases TAC by 29.1%, TEC and gas emissions by 23.2%, PRI by 22.1% and reduce thermodynamic efficiency by 11.4%.

Process comparison and performance evaluation of different entrainers for pressure swing extractive distillation refining gasoline additives based on multi-objective optimization and process intensification

As a new gasoline additive, methyl tertiary amyl ether (TAME) can improve the antiknock performance and quality of gasoline. This study uses an energy-saving process for separating TAME/methanol (MeOH)/H2O by pressure-swing extractive distillation with different entrainers based on multi-objective optimization and 4E analysis. The 1entrainers are screened by the difference in relative volatility of components under different entrainer conditions, and the electrostatic potential of the molecular surface of the system and entrainers are analyzed. Multi-objective optimization of the pressure swing extractive distillation process with 5 different entrainers is carried out based on the generation non-dominated sorting genetic algorithm (NSGA-Ⅱ) optimization scheme, and the Pareto frontier is optimized by the minimum distance method. The results indicate that the extraction schemes of 1,3-propanediol (PDO) and dimethyl sulfoxide (DMSO) have excellent economic and environmental benefits through comprehensive analysis. As an effective means of process intensification, the application of heat pump technology can further reduce process costs and environmental pollution. The coefficient of heating performance (COP) is used to find the most suitable pairing route for heat pump-assisted processes, achieving the goal of reducing gas emissions and energy use. Then, different processes are evaluated in terms of economy, energy consumption, environment, and exergy loss. The results show that the process intensification scheme based on heat pump technology can effectively improve the economic and environmental benefits of the process, reducing the annual total cost (TAC) and gas emissions by 9.19% and 23.55%, respectively. This study provides the selection and reference for azeotrope separation of TAME and recycling of wastewater.

Dehydration of Organic Solvents from Ternary Mixtures Containing Toluene/Methanol/Water by Pervaporation.

The separation of a toluene/methanol/water ternary mixture is a difficult task due to the toluene/water and toluene/methanol azeotropes. In this article, low-energy pervaporation is proposed for the separation of the ternary azeotrope toluene-methanol-water. This work investigates the effects of feed temperature, feed flow rate, and vacuum on pervaporation and compares the energy consumption of pervaporation with that of distillation. The results showed that at the optimized flow rate of 50 L/h and a permeate side vacuum of 60 kPa at 50 °C, the water and methanol content in the permeate was about 63.2 wt.% and 36.8 wt.%, respectively, the water/ methanol separation factor was 24.04, the permeate flux was 510.7 g/m2·h, the water content in the feed out was reduced from 2.5 wt.% to less than 0.66 wt.%, and the dehydration of toluene methanol could be realized. Without taking into account the energy consumption of pumps and other power equipment, pervaporation requires an energy consumption of 43.53 kW·h to treat 1 ton of raw material, while the energy consumption of distillation to treat 1 ton of raw material is about 261.5 kW·h. Compared to the existing distillation process, the pervaporation process consumes much less energy (about one-sixth of the energy consumption of distillation). There is almost no effect on the surface morphology and chemical composition of the membrane before and after use. The method provides an effective reference for the dehydration of organic solvents from ternary mixtures containing toluene/methanol/water.

A different strategy to reduce energy consumption for designing heterogeneous decanter-assisted advanced pressure-swing distillation process

In this work, we aim to explore the feasibility of integrating two strategies, i.e., (1) introducing a small quantity of solvent as a makeup stream and (2) employing a decanter, to develop an energy-efficient pressure swing distillation process for ternary azeotropic separation. The addition of a minor amount of solvent aims to facilitate the transition of the feed composition from outside the liquid–liquid equilibrium region to within it. This transition could enable the use of a decanter, thereby promoting a more energy-efficient separation process with reduced reliance on pressure-driven mechanisms. A systematic approach was proposed to explore this concept, involving the different thermodynamic features for conceptual design followed by process optimization and process evaluation. This approach was exemplified using a mixture containing chloroform, ethanol, and water. Two solvent and decanter-assisted triple-column pressure-swing azeotropic distillation (SD-TCPSAD) process were developed and evaluated against the conventional triple-column pressure swing distillation in terms of economic, energy, and environmental performance. Among the three configurations, SD-TCPSAD I exhibited the most favorable outcomes, achieving a 61 %, 69 %, and 69 % improvement in economic, energy, and environmental impact. These improvements were primarily attributed to the utilization of smaller column sizes, the utilization of different heating utilities, and a substantial decrease in overall energy consumption.

Experimental and mechanism study on the separation of isobutyl alcohol and water azeotrope using hydrophobic deep eutectic solvents

Isobutyl alcohol with good miscibility, high octane number and energy density has been paid more and more attention in the field of new biofuels, as it is an ideal alternative fuel for gasoline. However, isobutyl alcohol and water azeotrope need a clean and efficient separation method to realize the separation in isobutyl alcohol production process and industrial wastewater. Three hydrophobic deep eutectic solvents (DESs) were used to separate isobutyl alcohol. Decanoic acid was used as hydrogen bond donor and menthol, thymol and lidocaine were used as hydrogen bond acceptors to synthesize DESs. The liquid-liquid equilibrium experiment was carried out for the system containing DESs and MSD −water at 101.3 kPa and 303.15 K, and the separation effect of different DESs was indicated using distribution coefficient (β) and selectivity (S). The σ-Profile can be a good reflection of the strength of a substance's ability to accept and provide hydrogen bonds. The interaction energy and self-diffusion coefficient of the separation system were described quantitatively by molecular dynamics simulation. The relationship between DESs and the separation system was analyzed quantitatively by radial distribution function and spatial distribution function. The separation results show that the three DESs have good separation effect on isobutyl alcohol-water system, among which the DESs synthesized by thymol and decanoic acid has the best separation effect, and the interaction of isobutyl alcohol-water separation process is controlled by van der Waals forces. DESs plays an important role in the separation and treatment of isobutyl alcohol-containing wastewater, and promotes the sustainable development of wastewater treatment projects to save costs and increase production benefits.

Ionic liquid-assisted extractive distillation for separating of ethyl acetate/isopropanol from chemical wastewater: Molecular insights and process intensification

The effective separation of ethyl acetate (EAC)/isopropanol(IPA)/water azeotrope from industrial wastewater significantly reduces environmental risks and recycling resources. An azeotrope separation technique was proposed, combining ionic liquid mixed entrainer and dividing wall column extractive distillation (DWC-ED). The selectivity and solubility of 225 ionic liquids were calculated based on the COSMO-RS model. The molecular polarity of EAC, IPA, H2O, dimethyl sulfoxide (DMSO), and [EMIM][AC] was studied, and 1-ethyl-3-methylimidazolium acetate ([EMIM][AC]) was determined as the best solvent. In addition, the interaction mechanism between [EMIM][AC] (or DMSO) and EAC/IPA/H2O was studied using the quantum chemistry (QC) theory. Independent gradient model (IGM), interaction energy, and atoms in molecules (AIM) analysis showed that hydrogen bonds and vdW forces were formed between [AC]− anion and H2O/IPA/EAC, and the interaction energy was gradually weakened, which significantly improved the performance of extractive distillation process. The results showed that the total annual cost (TAC) and energy consumption of IL-based mixed solvent extractive distillation were reduced by 36.04 % and 37.72 %, respectively, compared to the single DMSO extractive distillation process. The TAC and energy consumption of the DWC-ED process were 44.61 % and 51.43 % lower than the benchmark processes.

Study on the mechanism of extractive distillation separation of cyclohexane/ethanol azeotrope based on ionic liquid and molecular liquid mixed solvent as extractant

The development of high-performance new extractants is crucial for the separation of azeotropes by extractive distillation (ED). In this paper, an effective method for the separation of azeotropes by ED using IL mixed extractants (ILMEs) is proposed. Based on the COSMO-SAC thermodynamic model and relative volatility, the optimal extractants [Dmim][Ac] and DMSO were selected respectively. The structure–activity relationship between single extractant and ILMEs was analyzed by quantum chemistry (QC) calculations. Molecular simulation results showed that compared with single extractant, the addition of DMSO increased the interaction sites between ethanol and extractant, which made ILMEs ([Dmim][Ac] + DMSO) easier to combine with ethanol to form H-bond, thus facilitating the separation of cyclohexane/ethanol. H in DMSO mainly forms C2–H5…O3 hydrogen bonds with O in ethanol, and O in [Ac]− mainly forms C1–O4…H4 H-bond with H in ethanol. Through molecular dynamics (MD) simulation, the phase behavior and structural distribution of ILMEs and azeotropes under different mixed solvent ratios were explored from the microscopic mechanism, so as to determine the optimal mixing ratio. The MD results showed that the interaction between [Dmim][Ac]+DMSO and ethanol was enhanced with the addition of DMSO. When the amount of [Dmim][Ac] is reduced to DMSO:[Dmim][Ac] = 4:1, the interaction between ethanol and the mixed extractant in the quaternary system is the strongest, and the ethanol molecule is completely immersed in the mixed extractant, cyclohexane and ethanol are completely separated and the aggregation behavior is maximized, indicating that the mixed solvent ratio DMSO:[Dmim][Ac] = 4:1, the separation effect is the best. Finally, the separation of ILMEs and DMSO cyclohexane/ethanol azeotrope was simulated by Aspen Plus V12, and the feasibility of ILMEs as extractant was verified. The results show that compared with the traditional organic extractant DMSO, ILMEs have potential environmental and economic advantages. The total annual cost (TAC) is reduced by 13.65 % and the gas emission is reduced by 23.04 %. This study provides theoretical guidance for the study of ED mechanism and the determination of solvent ratio of mixed extractants.

Study on separation of acetonitrile and methanol azeotropic system using tetraethylammonium chloride-based deep eutectic solvents

Large quantities of waste streams containing mixed acetonitrile (ACN) and methanol (MeOH) are generated during pharmaceutical and chemical production. The polarity of these two substances is extremely similar, resulting in the formation of an azeotrope at room temperature and atmospheric pressure. In this study, deep eutectic solvents (DESs) were selected as extractants for the separation of ACN-MeOH binary azeotrope. To obtain suitable DESs, the σ-profiles of ACN, MeOH, DESs were calculated using the COSMO-SAC model, and the results demonstrated that the DESs synthesized when tetraethylammonium chloride (TEAC) was chosen as the hydrogen bond acceptor (HBA) and acetamide as the hydrogen bond donor (HBD) could effectively break the azeotropy of ACN and MeOH. Therefore, four DESs were synthesized with molar ratios of TEAC: acetamide = 1: n (n = 1, 2, 3, 4) for subsequent ACN-MeOH-DESs ternary vapor–liquid phase equilibrium (VLE) experiments at 101.3 kPa to determine the optimal extractant. The measured VLE data revealed the higher separation of DES TEAC-2acetamide on the ACN-MeOH binary azeotrope compared with other DESs. Afterward, the NRTL model was adopted to calculate the binary interaction parameters between ACN/MeOH and DESs. The results of the fitting indicated agreement with the experimental data. Finally, the separation mechanism was further analyzed using the interaction energy analysis, improved independent gradient model (IGMH), and the theory of atoms in molecules (AIM). The results indicated that the strong interaction between DESs and MeOH is the primary factor in the ability of DESs to break the azeotrope of the system.

Dynamic control strategy of the ternary azeotrope separation process assisted by reactive-extractive distillation for ethyl acetate/isopropanol/water

The double-column reactive-extractive distillation (DCRED) process is a promisingly intensified compactness configuration for separating ternary water-containing azeotrope(s) by introducing the external reactions, such as the typical common adopted epoxy ethane (EO) hydration reaction. However, limited investigation has focused on the dynamic control analysis for the highly strong coupled DCRED process. In this paper, the efficient and robust control structure is proposed to achieve the dynamic operation of the DCRED process for the system of ethyl acetate/isopropanol/water. The composition controller is applied to precisely control the feed ratio of EO and water, thereby ensuring the qualified products when facing ± 10 % feed flowrate disturbances and ± 5 % feed composition disturbances. This work provides an alternative control strategy for the DCRED process, which is beneficial for its practical industrial applications.

Design and energy-saving strategy of sustainable pressure-swing distillation with thermally and electrically coupled intensification for separating ternary mixture with multiple azeotropes

The separation of ternary mixtures that form multiple azeotropes is frequently encountered in industry. Benefiting from the pressure-sensitive nature of the azeotropic mixture, the pressure-swing distillation (PSD) is promising to realise the separation without introducing foreign solvents. However, the wide application of PSD seems challenging from an energetic point of view. This work has developed a sustainable PSD process with thermally and electrically coupled intensification to decrease energy consumption, taking the separation of homogeneous acetonitrile/ethanol/water mixture as a demonstrating example. Two conventional PSD processes with different product sequences are designed through the ternary phase diagram and further optimised using the NSGA-II, considering multiple objectives, including total capital cost, total operating cost, and CO2 emissions. The optimal solution is selected by the TOPSIS analysis for each sequence and is then intensified with thermal heat integration and electricity-driven heat pump techniques. The results show that, in comparison to the non-heat-integrated PSD process, the proposed intensified design can dramatically reduce the total annual cost by up to 48%, simultaneously decreasing CO2 emissions by up to 60% and boosting energy efficiency. The present study can be of reference for designing a sustainable PSD process in ternary azeotropic separation.