Extractive Distillation Process Research Articles

Extractive distillation of tetrahydrofuran–ethanol azeotropic mixture with ionic liquid as extractant

AbstractBACKGROUNDThe tetrahydrofuran–ethanol azeotrope cannot be separated by common distillation, but can be effectively separated by extractive distillation. Extractive distillation can be simulated by Aspen Plus software. The minimum annual cost of the process can be calculated to assess ionic liquid separation ability. The interaction energy can be used to explain the separation mechanism.RESULTSThe non‐random two‐liquid model parameters of ternary mixtures for tetrahydrofuran and ethanol containing tributylmethylammonium acetate or 1‐octyl‐3‐methylimidazolium acetate were obtained. Thermodynamic property databases of tributylmethylammonium acetate, 1‐hexyl‐2,3‐dimethylimidazolium acetate and 1‐octyl‐3‐methylimidazolium acetate were established. Based on the thermodynamic model parameters and properties, the sequential iterative method was used to determine the best operating conditions and minimum total annual cost the of extractive distillation process. The interaction energy was calculated to explain the separation mechanism.CONCLUSIONSThe separation performance of tributylmethylammonium acetate is better than that of 1‐hexyl‐2,3‐dimethylimidazolium acetate or 1‐octyl‐3‐methylimidazolium acetate. The selection and design of the ionic liquids can be conducted in terms of the interaction energy. © 2023 Society of Chemical Industry (SCI).

Flowsheets for hydroxyacetone–phenol binary mixture separation: The use of special distillation methods

Objectives. To study the possibility of hydroxyacetone–phenol binary mixture (a constituent of a mixture of phenol production by the cumene method) separation in flowsheets based on the use of distillation special methods. This is the addition of separating agents to increase the relative volatility of the components of the original mixture, and the variation of pressure in the columns.Methods. A computational simulation in Aspen Plus® was used as the research method. Mathematical modeling of the vapor–liquid equilibrium was carried out using a local compositions model Non-Random Two Liquid. The viability of the latter was confirmed by comparing experimental and calculated on phase equilibrium data, and azeotropic data. The average relative error does not exceed 3%.Results. The dependence of the composition and boiling point of the hydroxyacetone–phenol azeotrope on pressure was determined in a computational experiment (as the pressure increases, the azeotrope is enriched with phenol). The possibility of using a complex of columns operating under different pressures to separate the mixture was shown (the shift of the azeotrope is about 9%). The change in the relative volatility of components of the original mixture in the presence of a high(diethylene glycol) and a low-boiling (acetone) separating agent was investigated. Both solvents are selective agents used in extractive and re-extractive distillation processes. Three technological separation flowsheets containing two distillation columns were proposed.Conclusions. The study established the operation parameters of the columns (number of theoretical stages, feed stages of the original mixture and separating agent, and reflux ratio) and energy consumption (total heat supplied to the columns boiler) of three separation flowsheets ensuring the production of products of a given quality (not less than 0.99 mol fractions). The flowsheet with diethylene glycol is characterized by the lowest energy consumption. It is recommended that complexes of extractive and re-extractive distillation be further optimized. This enables the second product of cumulus production—acetone—to be involved in the technological cycle.

Extractive distillation for separation of isopropanol-n-propanol-water ternary system: Mechanism analysis and process design

In the process of producing isopropanol (IPA) by direct hydration of propylene, a mixture of IPA, n-propanol (NPA) and H2O is formed. In order to obtain high purity IPA and NPA, extractive distillation technology can be used to separate these three components. In this paper, Based on the COSMO-RS model, 1-ethyl-3-methylimidazolium dicyandiamide ([EMIM][DCA]) was selected as the extractant for extractive distillation in ionic liquids. The extractive distillation process for the separation of IPA-NPA-H2O system with ethylene glycol (EG) or [EMIM][DCA] as extractant was designed and optimized by multi-objective genetic algorithm. Process simulation results show that the process using [EMIM][DCA] can reduce total annual cost by 44.635% and total gas emission by 29.873% compared with the traditional organic solvent EG as extractant. These results show that [EMIM][DCA] is a good extractant, which can reduce the gas emission and energy consumption of the distillation process. In addition, we further explored the separation mechanism of the system at the molecular level by analyzing the σ-curve and the intermolecular interaction energy.

Efficient Single-Column Extractive Distillation Process Achieved through Vapor–Liquid Separation of Feed

Efficient Single-Column Extractive Distillation Process Achieved through Vapor–Liquid Separation of Feed

Optimal design and multicriteria comparison of extractive distillation processes for separating of a quaternary low-boiling solvent mixture

This article mainly explores the eco-efficient separation of a complex quaternary azeotropic mixture of methanol, n-hexane, ethyl acetate and ethanol from a pharmaceutical enterprise via extractive distillation. To this end, aniline (AN) and ethylene glycol (EG) are selected as two alternative entrainers based on the relative volatility curve. Two conventional processes with AN and EG (AN-CED and EG-CED) are proposed and optimized with total annual costs (TAC) as a goal by simulated annealing algorithm. To improve energetic and economic performance, two optimal strengthening processes, that is, low-pressure side-stream extractive distillation process with AN (AN-SSED) and dividing-wall extractive distillation process with EG (EG-EDWC) are also developed for the first time. Finally, the four processes are compared in terms of economics, CO2 emissions and inherent safety. The results show that the AN-SSED process is recommended due to the best economic, environmental and inherent safety properties, as reflected by the lowest TAC, CO2 emission and process route index (PRI). It can reduce TAC by 9.38%, CO2 emission by 26.34% and PRI by 38.02% relative to the EG-EDWC process. Remarkably, the EG-EDWC process can reduce TAC by 11.12% than AN-CED process and 6.9% than the EG-CED process, but it is inferior to the two conventional processes in terms of CO2 emissions and inherent safety.

Molecular dynamics investigation on the interaction of nitrile-based ionic liquids in the separation of azeotropic refrigerant R-513A

The reclamation of mixed refrigerants stands as a potent measure to substantially mitigate the emission of fluorinated gases (F-gases). In the separation of the azeotropic refrigerant R-513A (comprising 56 wt% R-1234yf, 2,3,3,3-Tetrafluoropropene, and 44 wt% R-134a, 1,1,1,2-Tetrafluoroethane), the extractive distillation process using ionic liquids (ILs) was employed. The molecular structure of nitrile-based ILs ([C4C1im][SCN], [C4C1im][N(CN)2], [C4C1im][C(CN)3], [C4C1im][B(CN)4]) exerts a regular impact on the solubility of refrigerants, thereby necessitating molecular dynamics simulation to ascertain the law of refrigerant solubility in ILs concurrent with the augmentation in the number of –CN in the anion. Additionally, an analysis was conducted to elucidate the mechanism underlying the high selectivity of nitrile-based ILs. The results revealed pronounced interactions between R-1234yf and R-134a, predominantly occurring between carbon atoms (-CF3 groups in R-134a and R-1234yf), and chiefly van der Waals interactions. An enhancement in the number of –CN in anion led to the fortification of the van der Waals interaction between R-134a/R-1234yf and the anion. The stronger nonbonding interaction energy between R-134a and the anion, as well as the higher radial distribution function (RDF) peak height between R-134a and the anion, signified a more robust interaction between R-134a and the anion compared to R-1234yf and the anion. Concurrently, the variance in the RDFs in the anion-C atom (-CH2F group in R-134a and -CF group in R-1234yf) revealed the selectivity of the four ILs to R-134a and R-1234yf. Among the four anions, [B(CN)4]− exhibited the most interaction sites with R-134a. This investigation contributes significantly to comprehending the interaction mechanism of azeotropic refrigerants and the interaction mechanism between refrigerants and nitrile-based ILs.

Solubility of difluoromethane (R-32) and pentafluoroethane (R-125) in 1-alkyl-3-methylimidazolium tricyanomethanide ionic liquids

The recovery of refrigerant blends and the subsequent separation of value-added hydrofluorocarbons (HFCs) for reuse would help to meet the phase-down in the production of virgin HFCs established by the Kigali Amendment to the Montreal Protocol. The use of ionic liquids (ILs) in extractive distillation processes has become particularly relevant. In this process, the selection of the IL is the core element for a technically and economically feasible design. For this purpose, the absorption of the HFCs difluoromethane (R-32) and pentafluoroethane (R-125), components of the equimassic mixture R-410A, in 1-alkyl-3-methylimidazolium tricyanomethanide ILs was studied. The isochoric saturation method was applied to report vapor-liquid equilibrium data over a temperature range of 283.15–323.15 K and up to 0.9 MPa. These data were fitted accurately to the NRTL activity coefficient model and the Henry's law constants, the activity coefficients at infinite dilution, the enthalpies and entropies of solvation and the thermodynamic mixing properties were calculated. Finally, [C2C1im][tcm] ranked as one of the most selective ILs to date, exhibiting a good R-32 absorption capacity that could make it a valuable solvent for the separation of R-410A by extractive distillation.

Economic, environmental, exergy (3E) evaluations of recovering n-propyl acetate and n-propanol from wastewater via distillation coupled pervaporation

This work investigates an efficient and sustainable process for recovering n-propyl acetate and n-propanol from wastewater via extractive distillation coupled with pervaporation (PV). The selection of potential extractants is based on the equilibrium data between the system and the extractants in vapor-liquid phase. For the ternary extractive distillation process, we optimize it using the Non-Dominated Sorting Genetic Algorithm II with the objectives of minimizing the total annual cost and gas emissions. The PV model is integrated with the distillation process to enhance solvent recovery, while an energy-efficient scheme combined with heat integration technology and heat pump improves separation efficiency. Economic, environmental and exergy analyses are conducted to evaluate feasibility, revealing that coupling extractive distillation with PV enhances economic and environmental benefits compared to basic processes. The combination of heat pump assisted heat integration technology further improves the economy performance, environmental protection and thermodynamic efficiency, and the process selection needs to be balanced according to the actual industry.

Conceptual Design and Simulation-Based Optimization of Indirect Extractive Distillation Processes Considering Preconcentration for Separating Ternary Azeotropic Systems

Conceptual Design and Simulation-Based Optimization of Indirect Extractive Distillation Processes Considering Preconcentration for Separating Ternary Azeotropic Systems

Insights on the sustainable design of extractive distillation processes for separating the isopropanol/1,4-dioxane/water mixture considering economic and entropy generation indicators

Several extractive distillation processes with DMSO as extractant are proposed to separate isopropanol/1,4-dioxane/water azeotropic mixtures in this study, including direct extractive distillation (DED), indirect extractive distillation (IED), DED process with dividing wall column (DED-DWC), IED process with dividing wall column (IED-DWC) and IED process with heat integration (IED-HI). The multi-objective genetic algorithm employs total annual cost (TAC) and entropy generation as the objective functions to optimize processes. The TOPSIS entropy weight method has invested to identify the appropriate optimal solution. DWC and heat integration technologies are proposed to decrease the irreversibility of DED and IED processes. The results showed that the best option to perform the separation of the mixture was the IED-HI process. It is gratifying to note that the TAC and entropy generation of IED-HI process is decreased by 15.36 % and 28.84 %, respectively, in relation to the IED process.

Economic, environmental, exergy (3E) analysis and multi-objective genetic algorithm optimization of efficient and energy-saving separation of diethoxymethane/toluene/ethanol by extractive distillation with mixed extractants

Diethoxymethane, toluene, ethanol are important organic solvents with excellent performance and are widely used in the industrial fields. In this study, extractive distillation with mixed extractants was used to separate the mixture. The separation process of diethoxymethane, toluene and ethanol azeotrope system with different extractant agents was designed. The multi-objective optimization was carried out with the objective of total annual cost and gas emission, and the optimal process parameters were obtained by coordinating the two objectives. Based on the best extractive distillation process with mixed extractants, the intensification of process was performed by adding heat pump and heat integration technology, to improve the economy and energy consumption of the process. By comparing the results of economic, environmental and exergy efficiency analysis calculations, it was found that the intensification of the heat integration technology was better than the intensification of the heat pump. As for the intensification effect of heat integration technology saved about 5.5% more economical than primary mixed extractants process, the gas emission had been reduced by about 14.8% in terms of environment, and exergy loss decreased by 33.8%. This study provides theoretical guidance for the design and optimization of extractive distillation processes using the mixed extractants.

Control structure selection of increased‐pressure extractive distillation process for DMC‐MeOH azeotropic mixture

AbstractProducing dimethyl carbonate (DMC) as a green chemical with the desired purity is important in the industry. Although studies on the steady‐state design of energy‐efficient extractive distillation processes are important for the purification of DMC‐methanol (DMC‐MeOH) azeotropic mixtures, the dynamic controllability of these processes is also critical in the case of feed condition changes, and it should be investigated carefully. Results of the limited studies in the literature show that changing the operating pressures in extractive distillation processes might have different effects on the dynamic controllability of different systems. Thus, in this study, alternative control strategies are developed for a recently proposed increased‐pressure extractive distillation process to separate DMC‐MeOH mixture. All control structures are designed using inferential temperature controllers, which have a general acceptance in industrial applications. Effects of different ratio controllers are investigated by evaluating the dynamic responses of control structures for disturbances in feed flowrate and composition. Two metrics including integral absolute error and steady‐state deviation of purities are used in the evaluation of alternatives. Results of dynamic simulations show that a control structure including reflux ratio controller is not a suitable strategy for this process. It is demonstrated that a control structure including reflux to feed ratio controller for both distillation columns is necessary for the robust and efficient control of a pressure‐increased extractive distillation process. These efficient dynamic results support the economic advantage of increased‐pressure extractive distillation process separating DMC‐MeOH azeotropic mixtures.

Data‐driven integrated design of solvents and extractive distillation processes

AbstractAs property and process models with many variables need to be considered, integrated computer‐aided molecular and process design (CAMPD) problems are computationally expensive. An efficient CAMPD approach is proposed for the simultaneous design of solvents and extractive distillation (ED) processes based on a data‐driven modeling strategy. First, artificial neural network (ANN)‐based process models are trained to replace the physical models conventionally used in CAMPD. Subsequently, optimization is performed to maximize process performance, through which optimal solvent properties and corresponding optimal process parameters are obtained. Then, real solvents approximating the optimal property values are identified from a large solvent database. Rigorous simulations of the ED process are performed to evaluate the performance of the optimal solvents and corresponding process parameters. Further economic evaluation (6.11% lower annual cost compared to the benchmark process) and chemical hazard assessment confirm that acetylacetone is a promising solvent for the ED separation of 1‐butene from 1,3‐butadiene.

Environmental, economic and exergy analysis of separation of ternary azeotrope by variable pressure extractive distillation based on multi-objective optimization

In this work, the ternary azeotrope of tert-butyl alcohol/ethyl acetate/water is separated by extractive distillation (ED) to recover the available constituents and protect the environment. Based on the conductor like shielding model and relative volatility method, ethylene glycol was selected as the extractant in the separation process. In addition, in view of the characteristic that the relative volatility between components changes with pressure, the multi-objective optimization method based on nondominated sorting genetic algorithm II optimizes the pressure and the amount of solvent cooperatively to avoid falling into the optimal local solution. Based on the optimal process parameters, the proposed heat-integrated process can reduce the gas emissions by 29.30%. The heat-integrated ED, further coupled with the pervaporation process, can reduce gas emission by 42.36% and has the highest exergy efficiency of 47.56%. In addition, based on the heat-integrated process, the proposed two heat pump assisted heat-integrated ED processes show good economic and environmental performance. The double heat pump assisted heat-integrated ED can reduce the total annual cost by 28.78% and the gas emissions by 55.83% compared with the basis process, which has a good application prospect. This work provides a feasible approach for the separation of ternary azeotropes.

Energy-saving investigation of ester hydrolysis to alcohol by reaction extractive distillation process: From molecular insight to process integration

Sec-butyl alcohol (SBA), a common chemical intermediate, is used as an anti-emulsion, dye dispersant, industrial detergent, and raw material to produce methyl ethyl ketone. To further reduce the energy consumption and production cost of the hydrolysis of sec-butyl acetate (SBAC) to SBA, a reactive distillation coupled with extractive distillation using a mixed entrainers process was proposed in this study. Based on the relative volatility curve and quantum chemical calculations, EG and DMSO were selected as potential entrainers. Based on the total annual production cost, the appropriate ratio of mixed solvent is obtained (EG: DMSO = 9:1). The thermal coupling distillation technology is introduced into the proposed process to achieve energy-saving further. The results showed that the thermodynamic efficiency of the thermal coupling process using mixed entrainers increased by 18.02%, the total annual cost is saved by 15.18%, and CO2 emissions were reduced by 391.82 kg/h compared to the process using single DMSO entrainers process.

Design and multiple performance evaluation of green energy saving process for ethyl acetate/ethanol/water azeotrope separation by extractive distillation based on mixed solvent

The clean and efficient separation of ethyl acetate/ethanol/water azeotrope is of great significance for the production of high-purity ethyl acetate. In this study, a highly efficient separation of ethyl acetate/ethanol/water azeotrope by extractive distillation based on mixed solvent was developed. The relative volatility and quantum chemistry calculation were used to determine the alternative entrainer of mixed solvent. The multi-objective optimization based on genetic algorithm was carried out to obtain the optimal process scheme which considered both economy and environment. Three energy-saving process schemes were developed based on the conventional extractive distillation process, and the economic, environmental, energy and exergy properties of each process were investigated. The results show that the heat pump-assisted extractive distillation process may yield a significant reduction in gas emission and process energy consumption, showing an obvious advantage over the conventional extractive distillation process and the process proposed by previous researchers. The results of this study have important significance for the separation of high purity ethyl acetate and the recovery of wastewater containing ethyl acetate and ethanol. The research approach can be applied to further systems and serve as a reference for the creation of extractive distillation with mixed solvent.

An efficient multi-criteria decision making for assessing the optimization of reactive extractive distillation in terms of economy, environment and safety

In order to effectively separate complex azeotropic mixtures, it is crucial to consider economic, environmental, and safety factors during the process design and optimization. This study presents a systematic approach to separate a ternary azeotropic mixture of tetrahydrofuran, methanol, and water by employing multi-objective optimization and multi-criteria decision making. Two energy-efficient configurations, i.e., double-column reactive extractive distillation and reactive-extractive dividing wall column, are proposed by integrating reaction and extractive distillation in a single unit. The developed processes are then optimized using a multi-objective particle swarm optimization algorithm, considering the aforementioned factors. Finally, a multi-criteria decision making technique is applied to rank the Pareto frontier solutions obtained from the optimization process, using a combination of gray relational analysis and entropy weight method. Compared to the base case, the double-column reactive extractive distillation process exhibits a significant reduction in total annual cost (59.39 %) and CO2 emissions (61.75 %). Through comprehensive evaluation, the double-column reactive extractive distillation process is found to be the most effective separation solution among the proposed and existing processes. This systematic approach can be extended to other complex aqueous azeotropic systems for their design, optimization, and decision making.

Extractive distillation process using organic and ionic liquids for the separation of high-GWP refrigerant R410A: A thermodynamic and techno-economic assessment

Reclamation of mixed refrigerants can effectively reduce high global warming potential (GWP) fluorinated gases (F-gases) emissions. Two organic liquids (OLs), Dimethylformamide (DMF) and N, N-Dimethylacetamide (DMAC), were proposed to explore the possibility of separating high GWP and near-azeotropic mixture R410A (50 wt% R32 (difluoromethane) + 50 wt% R125 (pentafluoroethane)) by absorption. Solubilities of R125 in DMF and DMAC were measured from 283.15 to 333.15 K and well correlated with the five-parameter non-random two-liquid (NRTL) activity coefficient model. Ideal selectivity for R32 + R125 of DMAC were higher than that of DMF. Five ionic liquids (ILs) and DMAC on the Pareto front showed good overall performance (integration of capacity and selectivity) for separating R410A, and in the area below the Pareto front, the overall performances of the other solvents were not as good as those from the Pareto front. Subsequently, based on DMAC, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([EMIM][Tf2N]) and 1-ethyl-3-methylimidazolium thiocyanate ([EMIM][SCN]), the extractive distillation processes for R410A separation were simulated and evaluated in Aspen Plus. Results showed DMAC was a suitable choice of extractant nowadays due to the lower viscosity and consumption than ILs and the mature corresponding R410A separation process. ILs may be the mainstream extractant for R410A separation in the future, once the price of some ILs such as [BMIM][PF6] can be reduced to $30/kg, the separation process using ILs as extractants will cost less than that of DMAC. Heat pump technology can be further applied for energy integration in the corresponding process of ILs with high ideal selectivity such as [EMIM][SCN]. Thermodynamic and economic analysis of OLs and ILs could provide the key information for the separation of commercial refrigerant R410A, which can also be used as a benchmark to screen more efficient extractants.

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.

Sustainable design and multi-objective optimization of heat pump assisted extractive distillation process for separating a ternary mixture of methyl acetate, tetrahydrofuran and methanol

The separation of a ternary mixture of methyl acetate (MeAc), tetrahydrofuran (THF), and methanol (MeOH) produced from chemical or pharmaceutical plants can not only recover the valuable chemicals but also reduce the environmental pollution caused by the emission of waste organics. In this study, a two-step extractive distillation process with four columns (FCED) with dimethyl sulfoxide and p-xylene serving as the entrainers was firstly proposed to separate the ternary mixture by using Aspen Plus simulation. The vapor recompression heat pump (VRHP) technology was introduced to improve the thermodynamic efficiency of the proposed FCED process. Subsequently, a multi-objective optimization using the non-dominated sorting genetic algorithm-II was employed to optimize the designed processes to accomplish a Pareto front trade-off in three crucial indicators, i.e., total annual cost (TAC), CO2 emission, and exergy efficiency. A Pareto ranking method, i.e., the technique for order of preference by similarity to ideal solutions combined with entropy weighting approach, was used to choose the best solution from the Pareto front. The results indicate that, compared to the FCED process, TAC (8-year payback period) and CO2 emissions of the VRHP-assisted FCED are reduced by 8.75% and 33.26%, respectively, while the exergy efficiency is increased by 8.06% from 3.67% to 3.96%, demonstrating that the introduction of VRHP can significantly improve the performance of the FCED process.