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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)/H 2 O 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. [ABSTRACT FROM AUTHOR]

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)/H 2 O 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. [ABSTRACT FROM AUTHOR]

• A novel cryogenic distillation-based CO 2 capture method in LNG process is proposed. • The azeotropic characteristics of CO 2 -C 2 H 6 is utilized to avoid CO 2 freeze-out. • The proposed process can remove up to 17 % of CO 2 to less than 50 ppm. • The integrated "LNG + C 2 H 6 recovery + CO 2 removal" minimizes energy consumption. • The exergy efficiency of the system is higher than 50%. Cryogenic CO 2 capture technique is superior to other CO 2 capture methods in terms of potential environmental protection, because it uses no chemical solvent or membrane materials that need regular replacement. However, the freezing problem of CO 2 makes it difficult to achieve CO 2 capture through simple gas–liquid separation, and the existing cryogenic CO 2 capture techniques often require a specially designed separation equipment. In addition, cryogenic CO 2 capture is generally considered a method with high energy consumption due to the need for refrigeration. This study proposes a cryogenic distillation-based CO 2 capture method for natural gas with high ethane content, such as shale gas and oilfield associated gas. This method utilizes the azeotropic characteristics of CO 2 and ethane to avoid CO 2 freeze-out and the energy consumption for CO 2 capture is minimized through process integration with natural gas liquefaction and ethane recovery. The proposed system uses the propane precooled mixed refrigerant process to provide the required refrigeration, and it is simulated in Aspen HYSYS and optimized by a combined method of a genetic algorithm and sequential optimization. The results show that the proposed process can remove up to 17 mol% of CO 2 to less than 50 ppm. With extractive distillation, 99.50 % of the ethane in the feed gas is recovered with a purity of 99.50 mol%. The optimal results corresponding to the maximum allowable CO 2 content to avoid its freeze-out (with a solubility margin of 500 ppm) show that when ethane content is 2–20 mol%, the specific power consumption of the system is about 0.43 kWh/Nm3(NG) with an exergy efficiency higher than 50 %. The proposed process achieves energy-saving and efficient CO 2 capture method for natural gas with high ethane content. [ABSTRACT FROM AUTHOR]

• Energy-saving extractive distillation for separating dimethyl carbonate/methanol presented. • O-Xylene is selected as suitable entrainer for its relative low boiling point, price, and toxicity. • A lab-scale extractive distillation is modeled, analyzed, validated and further be scale-upped. • The optimized extractive distillation offers marked economic benefit and CO 2 emission reduction. The pressure-swing distillation traditionally used in the industry for separating dimethyl carbonate/methanol (DMC/MeOH) commonly suffers from high energy consumption and challenges in achieving high-purity separation due to the existence of pinch zone. Hence, energy-saving extractive distillation system is explored to achieve the high-purity separation of DMC/MeOH azeotrope. With the analyses of isovolatility and residue curve maps based on Wilson model calibrated by vapor–liquid equilibrium experimental data, an extractive distillation process using O-Xylene (OX) as the most suitable entrainer were modeled and experimentally validated. Furthermore, design, optimization, and comparison of an extractive distillation process and a pressure-swing distillation process for producing 10000 t DMC/a are investigated. It is demonstrated that the extractive distillation process presents significant economic and emission advantage, specifically with 34.66 % and 26.95 % reductions in operating cost (OC) and in total annual cost (TAC) respectively, as well as 42.53 % reduction in CO 2 emissions. This work should provide a feasible and promising approach to energy saving, low-carbon, and high-purity separation of DMC/MeOH azeotrope. [ABSTRACT FROM AUTHOR]

• Heat pump-assisted (reactive) dividing-wall column for propionic acid recovery. • Cost-effective and energy-efficient recovery of carboxylic acids from fermentation. • Large-scale downstream processing of propionic, acetic and succinic acid. Propionic acid is a valuable platform chemical that is usually produced via fossil routes. As these are energy-intensive and eco-unfriendly processes, fermentative production of propionic acid is becoming more attractive. However, the complex downstream processing (due to low achievable product concentrations, high water content, presence of by-products and thermodynamic constraints), presents a potential barrier to scale-up this technology. This original research proposes a novel intensified large-scale (production capacity of ∼ 20 ktonne/y) process for the final recovery of propionic acid after the initial biomass and counterion removal. Vacuum distillation steps ensure the recovery of a high-purity succinic acid product (>99.9 wt%) and a water stream that may be recycled to the fermentation to reduce the fresh water requirements. The main unit that follows is a highly integrated heat pump-assisted dividing-wall column (DWC), which allows the effective separation of propionic (>99.9 wt%) and acetic acid (99.4 wt%) products. Alternatively, it can serve as a reactive DWC that performs the esterification and separation of methyl propionate (99.8 wt%), methyl acetate (91.0 wt%) as higher added value products, and water by-product. If needed, extractive distillation can be implemented additionally to recover methyl acetate at higher purity (99.9 wt%). Overall, both options are proven to be economically interesting (recovery costs of 0.399 – 0.469 $/kg considering the product price of 1.349 – 1.802 $/kg) and environmentally attractive (3.206 – 3.678 kW th h/kg). [ABSTRACT FROM AUTHOR]

[Display omitted] • Propose three reactive distillation-based processes to separate Serafimov's class 2.0–2b mixtures containing methanol/methyl acetate. • Methyl acetate transesterification eliminates methyl acetate and coproduces high-value products. • Integrate extractive/pre-separation distillation and reactive distillation. • Two-column pre-separation-reactive distillation is preferred. • Use parallel genetic algorithms to optimize processes. The treatment of waste streams is an important research topic for the sustainable development of chemical process. Recently, reactive distillation-based (RD) processes with ethylene oxide hydrolysis have been developed to separate water-containing azeotropic mixtures. To separate Serafimov's class 2.0–2b mixtures containing methanol/methyl acetate, a methyl acetate transesterification reaction between propylene glycol monomethyl ether is introduced to convert methyl acetate to methanol and coproduce produce propylene glycol monomethyl ether acetate as advanced solvents. Three-column reactive-extractive distillation (TCRED) and extractive-reactive distillation (TCERD), and double-column pre-separation-reactive distillation (DCPSRD) processes, are proposed. Then, we use a parallel genetic algorithm to optimize processes to maximize total net revenue. The case study is methanol/methyl acetate/ethyl acetate. Though TCRED is not suitable due to the occurrence of ethyl acetate transesterification reactions, to compare economic performances of three RD-based processes, TCRED is regarded as a pseudo process. The total net revenue of three RD-based processes is relatively larger than (∼20 % increase) that of the conventional extractive distillation process. Compared with TCRED process, TCERD and DCPSRD can achieve $582336 and $1045995 increase in TNR, 27.43 % and 49.99 % TAC reduction, respectively. In summary, proposed RD-based processes are promising to separate Serafimov's class 2.0–2b mixtures containing methanol/methyl acetate, especially TCRED and DCPSRD. [ABSTRACT FROM AUTHOR]

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, H 2 O, 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/H 2 O 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 H 2 O/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. [ABSTRACT FROM AUTHOR]

• Recovering 2-Methoxyethanol from wastewater has environmental and economic benefits. • Mixed solvents based on ionic liquids are used for extractive distillation. • The interaction mechanism is analyzed from the microscopic perspective. • Research process strengthening technology to save energy and reduce consumption. • The processes are considered from economic, environmental, and exergy. 2-Methoxyethanol is an important solvent with wide application prospects. Recovering 2-Methoxyethanol from wastewater has significant environmental and economic benefits. In this work, quantum chemistry methods are used to calculate the surface electrostatic potential, mutual penetration analysis, and reduced density gradient-independent gradient model of solvents and azeotrope. From the perspective of the mechanism of action, suitable extractants are selected. With the minimum total annual cost as the goal, the splendid process parameters and the excellent ratio of mixed solvents (30 % 1-ethyl-3-methylimidazole acetate + 70 % N, N-dimethyl acetamide) are acquired. Moreover, two reinforcing processes for energy saving and consumption reduction are also researched. All processes are appraised from three aspects: economy, environment and exergy. The results show that the total annual cost and gas emission of mixed solvent extraction distillation are reduced by 26.79 % and 35.45 %, respectively, compared with the process with NMP as an entrainer. Compared with the process with [EMIM][AC] as an entrainer, the total annual cost and gas emissions are reduced by 44.99 % and 25.04 %, respectively. Relative to mixed solvent, the total annual cost and gas emissions of the heat pump combined with mixed solvent extractive distillation technology decreased by 6.77 % and 21.78 % respectively, while that of the heat integration process decreased via 9.93 % and 12.30 % respectively. From the point of view of environmental sustainability, the process effect combined with the heat pump is better, and from the point of view of economic benefits, the heat integration process has better performance. This study reveals the intrinsic relationship between the structure of mixed solvents and explores the intensification of the process, which provides a theoretical basis for the industrial separation of 2-Methoxyethanol/water azeotrope. [ABSTRACT FROM AUTHOR]

Ethyl tert -butyl ether is a green gasoline additive that enhances fuel efficiency and can play an essential role in improving fuel performance. This study explored the separation of wastewater containing ethyl tert -butyl ether and ethanol by changing the pressure and adding reactions based on extractive distillation, using the synergistic effect of the entrainer, pressure, and chemical reaction. By utilizing coupling technology and process intensification concepts, developed a comprehensive series of intensified processes that have clarified the interaction mechanisms between the extractive distillation process (EDP), pressure swing extractive distillation process (PSEDP), and reactive extractive distillation process (REDP). Studying the separation and purification mechanisms of products and intermediates during the reaction process provides theoretical and practical support for optimizing chemical processes. Comparative analysis showed that the reactive extraction pressure swing distillation process (REPSDP) had preeminent economic and environmental benefits. The total annual cost of PSEDP, REDP, and REPSDP was reduced by 5.88 %, 1.68 %, and 10.08 %, respectively, compared with EDP. The gas emissions of PSEDP, REDP, REPSDP, and REPSDP with heat integration process (HI-REPSDP) are all lower than those of EDP. HI-REPSDP saves 47.59 % of gas emissions compared to EDP, highlighting its environmental benefits. HI-REPSDP has the best energy efficiency, reducing energy consumption by 47.58 % compared to EDP, significantly improving the energy utilization rate. It was found that the introduction of heat integration technology had a significant improvement effect. This research has crucial theoretical and practical value and provides guidance and reference for achieving a clean and efficient production process. [ABSTRACT FROM AUTHOR]

[Display omitted] The separation of the ternary azeotrope system is still a topic worth studying. An effective method based on a mixed ionic liquids (ILs) extractant was proposed and applied to the separation of isopropanol (IPA), n-hexane (NH) and water (H 2 O) systems. Firstly, the organic solvent and ILs with better separation effects for the two components of the ternary azeotropic system were screened out by relative volatility calculation, quantum chemistry and molecular dynamics calculation. Based on the synergistic effect of dimethyl sulfoxide (DMSO) and 1-ethyl-3-methylimidazolium thiocyanate ([EMIMSCN]), a mixed ILs extractant was designed. It was then applied to three extractive distillation (ED) processes. Aiming at the minimum total process cost and gas emission, an optimization strategy was designed to achieve multi-objective optimization of process flow, the optimal composition and dosage of the mixed extractant were determined. The process results showed that the total annual cost (TAC) and gas emissions from mixed extractive distillation (MED) were 795406.85 $/y and 1536.84 kg/y, and the process energy consumption was 1987.99 kW. Compared with the ED process with DMSO as an extractant, the MED process can save 40.05 % TAC and reduce 30.39 % gas emission and energy consumption. The mixed extractant was carefully studied, and the addition of ILs was analyzed to increase the relative volatility between IPA and H 2 O separated by the extractant. The sensitivity analysis of the key variables of the MED process was carried out. The results show that the feed position of the extractant has the greatest influence on the objective function. Finally, the MED and the mixed extractive distillation under reduced pressure (RPMED) process were intensified, and the heat pump coupled thermal integrated Heat-integrated mixed extractive distillation (HPH-MED) process was determined to be the best process based on environmental pollution and energy consumption considerations. The TAC of the process is 767298.474 $/y, the gas emission is 753.84 kg/y, and the energy consumption of the process is 975.13 kW. Compared with the MED process, TAC is reduced by 3.53 %, and total gas emissions and energy consumption are reduced by 50.95 %. [ABSTRACT FROM AUTHOR]

[Display omitted] • Proposes a mixed solvent with a 6:4 ratio of methyl salicylate to [BMIM][NTf 2 ]. • Analyzes synergistic effects of thermodynamics and kinetics. • Compares transfer efficiency and TAC across four process configurations. • Direct extractive distillation outperforms indirect sequences. • Mixed solvent enhances transfer efficiency and reduces TAC versus pure solvents. The low selectivity of traditional organic solvents and the limited mass transfer efficiency caused by the high viscosity of ionic liquids (ILs) pose challenges in separating of dimethyl carbonate (DMC)/methanol/water mixtures. Therefore, a novel mixed solvent is proposed with a mass ratio of methyl salicylate to 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide of 6:4. The synergistic effects of thermodynamic, kinetic, and economic performance using the mixed solvent are investigated. Comparisons of overall efficiency and total annual cost (TAC) for four process configurations using direct and indirect extractive distillation sequences to produce industrial and battery-grade DMC products are conducted. The results indicate that direct extractive distillation outperforms the indirect sequence, reducing TAC by 6.1–14.3 % for producing industrial-grade DMC and 6.6–15.8 % for battery-grade DMC. Additionally, using mixed solvents in direct extractive distillation is more effective than using pure solvents, enhancing mass transfer coefficients by 2.8–20.9 % for industrial-grade DMC and 1.8–17.8 % for battery-grade DMC. This approach also reduces TAC by 3.2–3.6 % for industrial-grade DMC and 4.7–5.7 % for battery-grade DMC. [ABSTRACT FROM AUTHOR]

Tetrahydrofuran (THF) and methanol (MeOH) are commonly used raw materials and reagents in the chemical industry, but the azeotropic phenomenon between the two components makes it challenging to achieve high-purity separation. This study separated THF/MeOH/H 2 O mixtures by heat-integrated extractive distillation using an ionic liquid-based mixed entrainer (ILME). The dimethyl sulfoxide (DMSO) was determined by relative volatility analysis, and IL [EMIM][AC] was screened from 240 ionic liquids according to the COSMOtherm 2021 software. The separation mechanism was investigated at the molecular level (i.e., IGM analysis, polarisation charge density (σ-profile), electrostatic potential (ESP), interaction energy, and quantum chemical theory), which demonstrated that the rationality and strength of the interaction between the entrainer and the separated system were conducive for the separation to proceed. Single DMSO, ILME indirect extractive distillation (IED) and direct extractive distillation (DED) were designed and optimized, and further heat-integrated optimization (HI-DED) was performed on the ILME direct extractive distillation process. The results showed that HI-DED reduced the average annual total energy consumption, energy utilization and CO 2 emissions by 23.23%, 26.24% and 26.24%, respectively, compared to the conventional direct extraction distillation process. The HI-DED process using ILME significantly reduces economic, energy consumption and CO 2 emissions compared to conventional extractive distillation and has great potential for industrial applications. [ABSTRACT FROM AUTHOR]

It is of great significance and necessity to develop a sustainable and efficient separation scheme of butanone (MEK), ethanol (EtOH), and water, which are usually formed during the cinepazide maleate synthesis process. To the best of our knowledge, the systematic separation of this ternary multi-azeotropic mixture remains comparatively less studied, compounded by the significant challenges posed by its intricate composition comprising four azeotropes and three distillation boundaries. Therefore, a systematic approach by integrating the process design, multi-objective optimization, and multi-criteria decision-making (MCDM) methods was proposed to achieve the sustainable separation. Initially, three separation schemes, i.e., triple-column extractive distillation (TCED), double-column reactive extractive distillation (DCRED), and side stream intensified double-column reactive extractive distillation (SS-DCRED), were mainly explored via the thermodynamic and kinetic analysis. Subsequently, the multi-objective particle swarm optimization (MOPSO) algorithm was employed to optimize the process based on three objectives namely the total annual cost (TAC), CO 2 emissions, and process route index (PRI). Finally, an efficient MCDM method combining CRITIC and TOPSIS was employed to rank the Pareto front solutions of the corresponding process design. Based on the comparison results, the optimal TCED process exhibits the lowest PRI with a decrease of 50.61% and 55.06% compared to that of the SS-DCRED and the DCRED, respectively. It also shows the best performance simultaneously considering economic, environmental, and safety criteria. Of note, the SS-DCRED separation process exhibited the lowest TAC, with a decrease of 60.67% and 11.45% compared to that of the TCED and the DCRED, respectively. [ABSTRACT FROM AUTHOR]

This study reported a conceptual design of dimethyl carbonate/methanol (DMC/MET) separation via an azeotropic distillation (AD) process with water as the entrainer. Water can form a minimum azeotrope with DMC, stripping DMC from MET via a distillation column. Meanwhile, the liquid–liquid equilibrium can lift the DMC fraction from the azeotropic composition to a much higher level with a decanter. It enables the subsequent distillation column to produce pure DMC. The techno-economic analysis after process optimization demonstrated that the total annualized cost (TAC) of the AD process is 13.8 % lower than the conventional extractive distillation (ED) process. Subsequently, heat integration and double-effect distillation were introduced to further increase the energy efficiency. The improved AD process is also superior to the improved ED process (31.7 % energy cost and 4.1 % TAC saved). Moreover, the moderate temperature of the reboilers of the AD process with water as the entrainer further elevates its superiority since industrial waste heat can be applied in this case. [ABSTRACT FROM AUTHOR]

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][HSO 4 ]) 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 CO 2 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%. [ABSTRACT FROM AUTHOR]

The extractive dividing-wall column (EDWC) exhibits superior energy-saving effects, while the structure of liquid-only transfer configuration increases the potential for industrial applications. Therefore, a study on the dynamic control of liquid-only transfer extractive dividing-wall column (LTS-EDWC) separating isopropanol-water-dimethyl sulfoxide system was conducted. Initially, a multi-objective genetic algorithm was employed to economically optimize the LTS-EDWC with the total number of stages and reboiler duty as objectives. Subsequently, a basic control structure (CS1) for LTS-EDWC was proposed. Dynamic responses indicated that CS1 could recover to near the setpoint within ±10% feed flow rate and composition disturbances but failed to achieve stability within 10 h. An improved control structure (CS2) was then proposed, showing that product purity could rapidly return to the setpoint under ±20% feed disturbances. Based on CS2, to further enhance the dynamic control performance and address the nonlinear and strong coupling challenges in LTS-EDWC, the adaptive neuro-fuzzy inference system (ANFIS)-PID control structure (CS3) was designed. CS3 exhibits a total reduction of 8.6% in the time required for product recovery to the setpoint under all disturbance scenarios compared to CS2. However, the generality of model-based control is not as robust as PID control structures. To evaluate the universality of CS2, dynamic responses were investigated in two classic extractive distillation systems, namely n-heptane-toluene-aniline and acetone-methanol-water. Results demonstrated that under ±20% feed disturbances, the product purity of both systems could be restored to stable setpoints within 10 h. [ABSTRACT FROM AUTHOR]

The integration of preconcentration and solvent recovery functions is one of the effective ways to save energy consumption of extractive distillation processes for separating ternary azeotropic mixtures with a high content of one composition. However, the integration of various functions inevitably increases the difficulty of constructing robust control structures. In this paper, different proportion-integration (PI) control structures are investigated for the four-column extractive distillation with preconcentration process, while different PI and PI with model prediction controller (MPC) hybrid control structures are proposed for the three-column extractive distillation with integrated distillation column (TCED-IDC) process to deal with feed disturbances via taking the separation of ternary azeotropic mixture ethyl acetate-ethanol–water as a case study. The control structures are tested via introducing multiple feed disturbances including one feed flowrates disturbance and three feed compositions disturbances. The dynamic test comparison results show that the integration of preconcentration and solvent recovery functions causes a larger transient deviation in terms of dynamic responses of the individual optimal control structures. In addition, the integral of squared error of the TCED-IDC process are reduced by about 22 times after introducing the MPC in the face of feed disturbances. [ABSTRACT FROM AUTHOR]

• Dynamic control of the double-thermally coupled extractive distillation process is studied. • Newly robust control schemes are developed for this highly integrated configuration. • Dynamic performance is improved by robustly manipulating the splitting vapor flowrate. • ±20 % large disturbances in throughput and feed composition are effectively handled. • Oscillations are eliminated by adjusting position of temperature-composition cascade control. Currently, little literature has focused on the dynamic control of the economic and energy-saving double-thermally coupled ternary extraction distillation (DTCTED) systems, which demonstrates difficulties due to complex interactions between the main column and two rectifiers. The novel contribution of this paper is proposing effective and robust control structures to improve the dynamic controllability of the DTCTED process. To maintain the product purities more precisely, the key control loops employ composition-temperature cascade controls to regulate the side-vapor flowrates because the reliance on temperature control alone (CS1) is insufficient. Although this structure (CS2) can achieve the control of product purity, there could be severe oscillation in the control process. Therefore, one of the composition-temperature cascade controls is paired with the reflux ratio of the side rectifier to relax the operating freedom of the main column. The obtained structure (CS3) can brilliantly handle ±20 % throughput and various feed composition disturbances, which ensures the product purities and reduces oscillation. Additionally, control strategies based on the relative gain array (RGA) pairing criterion are explored and compared with the empirical ones. The proposed structures significantly enhance the controllability and stability of the DTCTED process, making it highly suitable for industrial applications. [ABSTRACT FROM AUTHOR]

• A novel extractive distillation process with vapor recompression and feed preheating was designed to separate xylene isomers. • Process parameters were optimized by multi-objective genetic algorithm with superior economic and environmental benefits. • The TAC and E CO2 can be reduced by 14.2% and 30.2% respectively compared with the existing distillation process. The focus of the chemical industry on environmental protection and energy conservation has driven the development of green distillation technology. Xylene isomers are extensively utilized industrial raw materials, whose separation is challenging and energy-intensive due to their closely similar boiling points. Therefore, it is urgent to develop energy-saving and environmental protection technology. In this paper, an energy-saving and environmental protection process for separating the xylene isomers by extractive distillation was designed combing the vapor recompression process with feed preheating (VRAPFP). The parameters of extractive distillation processes were synthetically optimized by multi-objective genetic algorithm (MOGA) with total annual cost (TAC), CO 2 emission (E C O 2 ) and separation efficiency (E ext) as the objective evaluation indexes. The economical optimal process was used further for VRAPFP design through heat integration to reduce energy consumption, and all the designed candidate processes were synthetically analyzed, compared and evaluated with performance indexes. Results show that the VRAPFP process has superior economic efficiency and ecological sustainability compared with the existing distillation process, wherein the TAC and E C O 2 are reduced by 14.2 % and 30.2 %, respectively. This work provides a new reference and idea for separating xylene isomers with the economy and developing new processes for energy conservation and environmental protection. [ABSTRACT FROM AUTHOR]

• A novel extractive distillation process with vapor recompression and feed preheating was designed to separate xylene isomers. • Process parameters were optimized by multi-objective genetic algorithm with superior economic and environmental benefits. • The TAC and E CO2 can be reduced by 14.2% and 30.2% respectively compared with the existing distillation process. The focus of the chemical industry on environmental protection and energy conservation has driven the development of green distillation technology. Xylene isomers are extensively utilized industrial raw materials, whose separation is challenging and energy-intensive due to their closely similar boiling points. Therefore, it is urgent to develop energy-saving and environmental protection technology. In this paper, an energy-saving and environmental protection process for separating the xylene isomers by extractive distillation was designed combing the vapor recompression process with feed preheating (VRAPFP). The parameters of extractive distillation processes were synthetically optimized by multi-objective genetic algorithm (MOGA) with total annual cost (TAC), CO 2 emission (E C O 2 ) and separation efficiency (E ext) as the objective evaluation indexes. The economical optimal process was used further for VRAPFP design through heat integration to reduce energy consumption, and all the designed candidate processes were synthetically analyzed, compared and evaluated with performance indexes. Results show that the VRAPFP process has superior economic efficiency and ecological sustainability compared with the existing distillation process, wherein the TAC and E C O 2 are reduced by 14.2 % and 30.2 %, respectively. This work provides a new reference and idea for separating xylene isomers with the economy and developing new processes for energy conservation and environmental protection. [ABSTRACT FROM AUTHOR]

The bottom flash heat pump (BFHP) technology has been recognized as an effective approach to improve the thermodynamic efficiency of the distillation processes with a relatively large temperature difference between the condenser and reboiler. However, although the BFHP-assisted extractive distillation (BFHP-ED) processes have been extensively studied in the literature, the dynamic controllability of the BFHP-ED processes is still to be explored. In this study, the controllability of the BFHP-ED process for separating the azeotropic mixture of n -hexane and 1,2-dichloroethane is investigated by presenting three temperature control schemes and two temperature difference control schemes. The dynamic simulation results demonstrate that the integration with the feed-forward structure and pressure-compensation action can significantly enhance the performance of the temperature control schemes to resist disturbances in feed flow rate. The temperature difference control structures are effective in resisting disturbances in feed composition, and the performance can be further improved by regulating the flow rate ratio of the entrainer to the feed stream (S / F) using a temperature controller that is cascaded with a high selector. Consequently, the temperature difference control schemes in the extractive distillation column with pressure compensation action and a high selector for regulating S/F exhibit the best performance by achieving smaller transient deviations, setting times and integral absolute errors, and maintaining the purities of the two products around the desired values with a maximum steady-state offset of ± 0.08 %. [ABSTRACT FROM AUTHOR]

• The structural distribution and phase behavior of the mix system from the initial state to the equilibrium state are studied. • The mechanism of ionic liquid solvent to improve the separation efficiency was studied. • The separation of azeotropic systems was simulated at multiple scales by combining QC, MD and process simulation. The selection of efficient and environmentally friendly extractants is crucial for extractive distillation (ED), and the microscopic mechanism of extractants in ED is still unclear. For the benefit of interpreting the microstructure distribution and phase behavior of the mixed system, this paper studied it by quantum chemical (QC) calculation and molecular dynamics (MD) simulation. Firstly, 1,3-dimethylimidazolium hexafluorophosphate [Mmim][PF 6 ], 1-ethyl-3-methylimidazolium hexafluorophosphate [Emim][PF 6 ] and organic solvent DMSO were screened based on COSMO-RS model and relative volatility. The bond length, bond energy, total electron density and deformation charge density of [Mmim][PF 6 ], [Emim][PF 6 ], DMSO extractant and ethyl acetate were analyzed by QC, the intrinsic properties of the chosen extractant and azeotropic system, as well as the interactions among the three extractants and ethyl acetate, were investigated. Then, the effect of extractant on the separation performance of cyclohexane ethyl acetate azeotrope in solvent environment was further studied by MD simulation. The two-dimensional mass density distributions (ANDDs) visualized the mixing behavior and structural distribution of the three extractants with the azeotropic system in the ternary system respectively, and the hydrogen bonding statistics indicated a high number of hydrogen bonds between [Mmim][PF 6 ] and ethyl acetate. The radial distribution function (RDF) indicated that the extraction effect of [Mmim][PF 6 ] was better and [PF 6 -] played a dominant role in the separation of azeotropic system. The strong interaction between [Mmim][PF 6 ] extractant [PF 6 -] and ethyl acetate was further verified by the spatial distribution function (SDF). Ultimately, through Aspen Plus software simulation, it was found that the [Mmim][PF 6 ] extractive distillation process was superior to the traditional solvent DMSO process, TAC was reduced by 8 %, and gas emissions were reduced by 5 %. Through the combination of QC, MD, and process simulation offer theoretical guidance for the efficient separation of the cyclohexane-ethyl acetate system and provide a specific reference value for the selection of the optimal extractant. [ABSTRACT FROM AUTHOR]

• The separation of ternary azeotropic mixture is investigated. • Side-stream extractive distillation schemes are optimized using genetic algorithm. • Temperature differences between top and bottom of different columns are analyzed. • The heat integration and vapor recompression heat pump schemes are designed. • Economy, environment, energy, and thermodynamic indexes are quantified. The side-stream extractive distillation (SSED) process is attracting extensive attention due to its high energy efficiency for separating ternary azeotropic mixture. However, the correlation between the bottom temperature level of distillation columns depending on the flowrates and compositions of side streams and the introduction of heat integration (HI) and vapor recompression heat pump (VRHP) technology is ignored. In the work, a range of initialization extractive distillation processes including one conventional extractive distillation (CED) process and five SSED processes considering different flowrates, compositions, and feed locations of side streams are proposed for separating acetonitrile/isopropanol/water ternary azeotropic system. The optimization results with the minimum the total annual costs (TAC) as the optimization objective show that not all SSED schemes are superior to the CED separation process, and the SSED separation schemes can achieve up to a 2.72 % reduction in the TAC. Following that, the HI and VRHP assisted extractive distillation schemes are proposed based on the temperature levels between the top and bottom of different distillation columns and compressor restraints for the initialization extractive distillation schemes mentioned after optimization. Moreover, sustainable evaluations covering economy, energy consumption, environment, and energy utilization are implemented for the extractive distillation schemes proposed. The evaluation results indicate that the CED-HI scheme overcomes all SSED-HI and SSED-VRHP schemes in terms of economic costs, but the optimal SSED-HI processes can reduce 8.77 % of energy consumption and 4.73 % of CO 2 emissions, while the energy utilization raised from 1.70 % to 1.78 % compared to the CED-HI process. [ABSTRACT FROM AUTHOR]

• SWM system is designed with the combination of water and porous PTFE membrane. • SWM-based strategy for DMC/MeOH separation in a high-flux manner. • Membrane module composed of SWM and PV for practical DMC production. Dimethyl carbonate (DMC) produced through transesterification, which involves the reaction of methanol (MeOH) with a suitable ester, has been considered as an attractive route for industrial production. Although high-purity DMC can be obtained from DMC/MeOH mixture by energy-intensive extractive distillation or time-consuming pervaporation (PV), it is still challenging to produce pure DMC in an energy-saving and high-efficiency manner. Here we demonstrate an energy-economy yet efficient superwetting membrane (SWM)-based strategy to produce pure DMC by combining porous polytetrafluoroethylene (PTFE) as the solid membrane and eco-friendly water molecules as the liquid inductive agent. The relatively low polar DMC can rapidly and selectively permeate the nonpolar PTFE membrane by nonpolar interaction between PTFE and DMC. Meanwhile, the high polar water molecules generate strong hydration with MeOH, which makes the relatively high polar MeOH/H 2 O being blocked by the nonpolar PTFE membrane. The SWM system exhibits outstanding separation flux of 1090 L m−2 h−1, with DMC purity higher than 93 wt%. Furthermore, taking advantage of the easy assembly of this SWM with conventional PV, we can produce DMC with purity of 99.4 wt%, showing great potential in practical DMC production. [ABSTRACT FROM AUTHOR]

• An innovative technique for the efficient separation of EG/1,2-BDO azeotrope was proposed. • VLE, COSMO-SAC, and quantum chemistry calculations was used for determination of the optimal entrainer for the separation of EG/1,2-BDO from various angles. • EDWCP process demonstrates the optimal performance in terms of economic, environmental, and thermodynamic efficiency. In the synthesis of ethylene glycol (EG) from syngas, the inevitable by-product, 1,2-butanediol (1,2-BDO), is generated. Additionally, EG and 1,2-BDO form minimum boiling homoazeotrope, which is a challenge for conventional distillation method. To address this, four processes, extractive distillation process (EDP), extractive distillation with heat integration process (HI-EDP), side-stream extractive distillation process (SSEDP), and extractive dividing wall column process (EDWCP), are used for the separation of EG/1,2-BDO binary system. Firstly, a combination of VLE analysis and COSMO-SAC model analysis was employed to select appropriate entrainers (eugenol). Subsequently, interaction region indicator (IRI) was utilized to reveal the extractive distillation mechanism at the molecular level, demonstrating the feasibility of eugenol as an entrainer for separating EG/1,2-BDO mixture. Next, simulations of the EDP, HI-EDP, SSEDP, and EDWCP processes were conducted through Aspen Plus V11. The optimal process parameters for each flowsheet were determined by the minimum Total Annual Cost (TAC). Furthermore, the process performance was evaluated from economic, energy, and environmental aspects. The EDWCP process demonstrates superior performance compared to the EDP process, with reductions of 16.79% in TAC, 17.6% in TOC, and 14.8% in TCC. Additionally, emissions of acidic gases of decreased by 19.78%, while thermal efficiency improved by 32.91%. EDWCP process represent enormous potential in the field of energy efficiency, economy and environment. [ABSTRACT FROM AUTHOR]

• A new distillation process for purifying MMA from azeotrope is proposed. • The feasibility of separation are assessed using ternary phase diagram analysis. • Extractive distillation and pressure-swing distillation are coupled for new process. • Heat integrated extractive pressure-swing distillation is used to save more energy. • Evaluate the processes from the economy, environment, energy and exergy. Methyl methacrylate is a new polymer material monomer, which is often used in the manufacture of plexiglass, and has very high industrial application value. Producing high purity methyl methacrylate requires a clean and effective separation process. In this work, an efficient separation method of methyl methacrylate/water/methanol azeotrope based on pressure swing distillation coupled extractive distillation is established. The best entrainer in terms of both environmental impact and effectiveness is chosen by examining the impact of relative volatility. The feasibility of pressure swing distillation and the best separation order are determined by ternary phase diagram analysis. A multi-objective optimization method is used to optimize the three designed processes, targeting gas emissions and total annual costs, thereby obtaining the best process plans and parameters. On this basis, the optimal thermal integration design of the three processes is carried out. The analysis of the four processes is conducted from the viewpoints of the energy, economy, environment and exergy. The findings demonstrate that the pressure swing extractive distillation process when combined can significantly increase economy and lessen mixture separation difficulty. Compared with the traditional process, the total annual cost, gas emission and energy loss are reduced by 8.20%, 10.46%, 11.69%, and the effective energy utilization rate is 50.31%. The development of this process is of great significance for the recovery of wastewater containing methyl methacrylate and methanol and the separation of high-purity methyl methacrylate. [ABSTRACT FROM AUTHOR]

• An innovative extractive distillation process combining prefractionator with extractive distillation column for separating high-concentration azeotropic mixtures. • Multi-objective optimization is conducted with the minimization of TAC, CO 2 emissions, and entropy generation as the objective functions. • Entropy generation analyses highlights areas of irreversibility. • Heat pump technology and heat integration technology have obvious energy-saving effects. The process design and optimization of separating azeotropic mixtures by extractive distillation (ED) has been a hot problem in recent years. Conventional ED process often faces challenges of high energy consumption and high costs when dealing with azeotropic mixtures containing a high content of a certain component. Therefore, an energy-efficient innovative three-column extractive distillation process (ITCED) that is capable of simultaneously performing preconcentration and extractive distillation functions within a complex distillation column for separating ethyl acetate/n-propanol/water azeotropic mixture containing a large amount of n-propanol is developed. Multi-objective optimization is conducted with the minimization of total annual cost (TAC), CO 2 emissions, and entropy generation as the objective functions. According to the optimization results, the ITCED process exhibits substantial advantages compared to the conventional three-column extractive distillation process (TCED), with reductions of 34.95% in TAC, 35.84% in CO 2 emissions, and 38.91% in entropy generation. Subsequently, heat pump and heat integration technologies are employed to enhance the ITCED process for the further energy conservation. As a result, compared with the TCED process, the DHP-HI-ITCED process achieves savings of 48.18% in TAC, 67.5% in CO 2 emissions and 72.96% in entropy generation. [ABSTRACT FROM AUTHOR]

• Efficient separation technology for the fermentation mother liquor to n-butanol was proposed. • Molecular polarity and weak interaction analysis revealed the extractive separation mechanism. • TCEDP is a typical process intensification strategy with economic, energy and environmental benefits. To solve the problems of difficult separation of azeotropes and high energy consumption in the preparation of n-butanol from the fermented mother liquor, this study focused on the separation process integration of water/acetone/ethanol/n-butanol mixture based on the combination of mixed entrainer and thermally coupled distillation technology. Based on quantum chemical calculations, the molecular polarity and weak interaction between the entrainer and the mixture to be separated were studied at the molecular scale, and the separation mechanism of extractive distillation was revealed. Based on the simulation results, the three different configurations' process performance was evaluated and compared to the benchmark conventional extractive distillation process with ethylene glycol as the entrainer. The thermally coupled extractive distillation process with mixed entrainers can reduce the total annual cost by about 39.87%, reduce energy consumption and acid gas emissions by 46.53%, and improve the thermodynamic efficiency by 47.57%. The thermally coupled extractive distillation process with mixed entrainers is an economical, energy-saving, and environmentally friendly production scheme superior to the conventional extractive distillation process. The thermally coupled extractive distillation process, as an essential energy-saving technology for producing n-butanol from fermentation mother liquor, has broad development prospects. [ABSTRACT FROM AUTHOR]

• A natural decantation assisted extractive distillation enhanced process with heat integration and vapor recompression heat pump is proposed. • Multi-objective genetic algorithm is used to find trade-off solution in terms of economic and environmental benefits. • A systematic approach is demonstrated in the optimum design of extractive distillation process. Isobutanol (i -BuOH) and n -butanol (n -BuOH) are widely used as solvents and organic raw materials in fine chemical and pharmaceutical fields. Hence the recovery of high-purity products from chemical industrial effluent containing i -BuOH and n -BuOH is of great significance to improve economic and environmental benefits. In this article, two extractive distillation processes with or without natural decantation are developed with 1,4-butanediol as entrainer, namely CED and NDED. In order to obtain the optimal process parameters under the trade-off between economic and environmental benefits, the two processes are optimized with total annual cost (TAC) and CO 2 emissions as objective functions by a non-sorting genetic algorithm. Further, a heat integrated extractive distillation process with natural decantation and vapor recompressed heat pump is designed and investigated, namely HI-NDED-VRHP. Finally, a fair multi-criteria evaluation is conducted on all three optimal processes in terms of TAC, CO 2 emissions, and total energy consumption (TEC). The results show that the HI-NDED-VRHP process is highly eco-efficient, which can reduce TAC by 18.9%, CO 2 emissions 44.2% and TEC 44.7% than the CED process and decrease TAC by 12.4%, CO 2 emissions 36.7% and TEC 37.1% than the NDED process. [ABSTRACT FROM AUTHOR]

[Display omitted] • A efficient and environmentally friendly extractant for separating toluene-methanol-water azeotrope. • Three feasible schemes were designed by changing solvent and optimized by multi-objective genetic algorithm. • The proposed double-column extractive distillation process with a decanter presents superior performance. • The TAC and CO 2 emissions were reduced by 33.1 % and 50.5 %, respectively, compared with the existing process. Cleaner production and sustainable development are still hot topics for modern industry. Developing green technology with low energy consumption, low pollution, and low cost has always been the common pursuit of chemical, petroleum, pharmaceutical, and other industries. This article proposes an environmentally friendly and efficient solvent, glycerol, for the separation of the ternary azeotrope of toluene-methanol-water. Three feasible extractive distillation schemes were designed and optimized, while the double-column extractive distillation process with a decanter demonstrated superior performance when glycerol was used as the solvent. Additionally, the multi-objective genetic algorithm was employed to optimize these separation processes and determine the optimal operating conditions, taking total annual cost (TAC), CO 2 emissions (E CO2), and separation efficiency (E ext) as target performance indicators to achieve the objectives of energy conservation, consumption reduction, and emission reduction. Results demonstrated that the newly proposed scheme can significantly reduce the total annual cost by up to 33.1 % and CO 2 emissions by 50.5 % compared with the existing separation process. This work provides a new insight to separate and purify the multiple systems by extractive distillation in industry. [ABSTRACT FROM AUTHOR]

• New arrangement of reactive-extractive distillation (RED) for energy-saving. • Rearrange double column RED (DCRED) to extractive-reactive distillation (ED-RD). • New intensified ED-RD provides significant energy-saving. • Old intensified DCRED cannot provide any energy-saving. • Thermally couple ED-RD provides 28 and 27% lower energy and cost relative to DCRED. The concept of reactive-extractive distillation (RED) is not new and has gained significant attention as an innovative approach for separating azeotropic mixtures. Presently, there have been at least 18 studies on RED, exploring variations such as triple column RED (TCRED), double column RED (DCRED), and their intensified configurations like dividing-wall DCRED (DW-DCRED) or side-stream DCRED (SS-DCRED). However, a major drawback observed in all existing intensified RED studies is the inability to achieve energy savings, which contrasts with the outcomes of most conventional distillation system studies. To address this, we propose a new alternative configuration called extractive-reactive distillation (ED-RD) by rearranging the column sequence in DCRED. The ED-RD configuration achieves a substantial 7 % reduction in the total annual cost (TAC) compared to DCRED, primarily due to a reduced number of stages and the utilization of relatively cheaper low-pressure steam in the extractive distillation column (EDC). Furthermore, the intensified thermally coupled ED-RD (TC-ED-RD) configuration demonstrates superior performance, achieving an impressive 21 % reduction in TAC compared to the proposed ED-RD configuration, mainly driven by a significant decrease in total reboiler energy consumption. Overall, the TC-ED-RD configuration excels with a remarkable 28 % reduction in total reboiler energy consumption and a 27 % decrease in TAC compared to DCRED. This reflects the potential of incorporating process intensification techniques to the proposed configuration to achieve substantial energy and cost savings, in contrast to the limitations observed in the conventional RED systems. [ABSTRACT FROM AUTHOR]

• Reaction distillation processes to separate ethanol/1,4-dioxane/water mixture. • MOGA optimize with economy and entropy generation as the objective functions. • Novel side-stream reactive-extractive distillation process with intermediate reboiler. • Performance comparison with existing extractive distillation process. Conventional distillation methods cannot separate ternary mixtures containing multiple azeotropes. This article designs two reaction distillation processes to recovery ethanol and 1,4-dioxane from wastewater, and a novel side-stream reactive-extractive distillation process with intermediate reboiler (SREDIR) process for the first time is proposed to separate this mixture. Taking economy and entropy generation as objective functions, multi-objective genetic algorithm is used to optimize the processes. It is concluded that all the proposed reaction distillation processes are energy-saving than the existing extractive distillation process for recoverying ethanol and 1,4-dioxane from wastewater. This existing process is an indirect extractive distillation process with DMSO as entrainer with heat integration (IED-DMSO-HI) process. Compared with IED-DMSO-HI process, the SREDIR process is economic since its total annual cost is reduced by 64.30%. However, the total entropy generation of SREDIR process is increased by 16.06%. Therefore, if there are high thermodynamic requirements for the separation process, reactive distillation requires careful consideration. [ABSTRACT FROM AUTHOR]

• Extractive distillation and pressure-swing distillation are coupled for new process. • Azeotrope with special phase behavior is separated by the proposed process. • Normal distance based on quaternary phase diagram is studied to evaluate processes. • Heat integrated extractive pressure-swing distillation is used to save more energy. Special azeotropic behaviors of complex mixtures can be used to develop distillation processes to realize energy-saving separation. Based on the residual curves of the system at different pressures and an examination of the impact of several extractants on the relative volatility, the pressure-swing distillation (PSD) process and the extractive distillation (ED) process were proposed to separate benzene/ethanol/butanone azeotrope. According to the characteristic of the azeotropic disappearance of ethanol/butanone with increasing pressure, two new extractive pressure-swing distillation (EPSD) processes were developed and compared with PSD as well as ED. To be able to determine the optimal operating parameters for various processes, the non-dominated sorting genetic algorithm II (NSGA-Ⅱ) was utilized. Heat integration was designed for the EPSD processes to reduce energy consumption. The above processes were evaluated in four aspects of the economy, energy, environment and exergy. The relationship between the four performances of different processes and the normal distance was discussed. The results indicate that the EPSD processes show better performance than the ED and PSD processes. Compared with the two EPSD processes, the total annual cost (TAC) of the heat integrated EPSD processes (HI-EPSD) was reduced by 13.2% and 14.4%, the total gas emissions of CO 2 , SO 2 and NO X were also reduced by 23.6% and 27.2%, respectively. Hence, coupling the ED process with the PSD process and heat integration can both better improve the separation performance of distillation. [ABSTRACT FROM AUTHOR]

• Effect of different water content on reactive-extractive distillation (RED). • Performance comparison between RED and conventional extractive distillation. • Separation of ethyl acetate (EA), 1,4-dioxane (DIO), and water as case study. • Different configurations perform differently under various water content conditions. Reactive-extractive distillation (RED) has gained significant attention as an innovative approach for separating azeotropic mixtures. Although many studies have reported its positive benefits, no studies have explored the impact of varying water content on RED performance, a domain that has seen exhaustive exploration in conventional extractive distillation. In this study, we investigate how water content affects RED performance using the separation of ethyl acetate (EA), 1,4-dioxane (DIO), and water as a case study. We design diverse configurations tailored for feed compositions ranging from 0.35 to 0.8 water mole fractions using a double column reactive-extractive distillation (DCRED). These configurations are globally optimized and the performance is compared against the triple-column conventional extractive distillation (TCCED) based on economic, environmental, and thermodynamic efficiency considerations. The TAC and CO 2 emission of TCCED schemes exhibit the linear decreases, reaching its lowest point at 50 mol.% water content. Beyond this threshold, both indicators increase significantly, even surpassing the reference case (20 mol.% water) at 80 mol.% water content. The thermodynamic efficiency of TCCED behaves inversely due to the intrinsic exergy destructions. Interestingly, the DCRED schemes show almost linear decreases in the trends of both economic and environmental indicators, and the notable deviations are then observed at 65 mol.% water content, accompanied with a slight decrease up to 80 mol.%. The thermodynamic efficiency of DCRED scheme gives an inverse trend, identical to those observed in TCRED. Overall, TCCED performs best at 50 mol.%, in which DCRED excels at 80 mol.% water content. This comprehensive study bridges a significant knowledge gap, offering insights into optimizing RED processes for varying water content, an unexplored topic despite widespread application of RED. [ABSTRACT FROM AUTHOR]

• An interaction energy difference method was proposed to screen extractant for azeotrope separation. • The first separated component is determined by the magnitude of the interaction energy. • The molecular mechanism is explained by EDA-FF and AIM analysis. • An extractive distillation process using DMSO as extractant was designed for MeOH/DMC azeotrope. The separation of methanol/dimethyl carbonate azeotrope is an important process in the industrial production of dimethyl carbonate. Extractive distillation is an effective separation method, which can ensure the full utilization of resources and achieve sustainable development. In this work, an extractant screening method based on density functional theory (DFT) was proposed. By comparing the interaction energy difference, the optimal extractant (dimethyl sulfoxide, DMSO) was obtained. The molecular mechanism of action between the extractant and the separated components was explained. The separation order of the components of the extraction distillation process was obtained by the magnitude of the interaction energy. The σ -profile curve and isovolatility curves method were used to verify the effectiveness of the proposed method. A new separation process with DMSO as an extractant was designed. With the lowest total annual cost (TAC) as the goal, sensitivity analysis and cyclic iteration method is used to optimize the parameters involved in the process to determine the best process parameters. Heat integration technology is introduced to further reduce energy consumption. TAC, energy utilization efficiency, and global warming potential (GWP) were used to evaluate the process. Compared with the reported optimal extractant methyl salicylate, the TAC of the simple process using DMSO as the extractant was reduced by 9.08%. The heat-integrated process with DMSO shows a TAC reduction of 17.17% compared to the simple process. And the energy utilization efficiency and GWP were increased by 40.90% and decreased by 31.88%, respectively. The results show that the extractant screened by DFT method is applied to the azeotrope separation, which makes the process have good economic benefits, low energy consumption, and less environmental impact. [ABSTRACT FROM AUTHOR]

• A quaternary low-boiling solvent mixtures is separated efficiently by extractive distillation. • Four extractive distillation designs with ethylene glycol or aniline entrainer are proposed and optimized by simulated annealing method. • Multi-criterion comparison among all designs is made from four aspects of economy, environment, energy consumption and inherent safety. 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, CO 2 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 , CO 2 emission and process route index (PRI). It can reduce TAC by 9.38%, CO 2 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 CO 2 emissions and inherent safety. [ABSTRACT FROM AUTHOR]

• Ionic liquid is used as entrainer for ternary extractive distillation. • Thermally coupled technology is used to reduce energy consumption. • Multi-objective generic algorithm is performed to determine operating parameters. The major intrinsic obstacle of extractive distillation (ED) is high energy consumption. Thus it is significant to reduce the energy consumption of ED processes as low as possible. In this work, using green solvent ILs which have high selectivity, process intensification and optimizing operation parameters are adopted in the ED of ethyl acetate-ethanol-water mixture. For high-selective entrainers, ionic liquid (IL) 1-butyl-3-methylimidazolium acetate ([bmim][OAc]) is used as the solvent for the ED process of ethyl acetate-ethanol-water, and the physical properties of [bmim][OAc] are accurately defined in Aspen Plus by correlating the experimental data. To optimize the distillation sequence for process intensification, thermally coupled ternary extractive distillation (TCTED) process is adopted for the separation of the ternary mixture. Moreover, multi-objective generic algorithm with total annual cost (TAC), CO 2 emissions (E CO2) and thermodynamic efficiency (η) as objective functions is used to optimize the operation parameters in order to evaluate the economy, the energy efficiency and environmental impact of alternative ternary extractive distillation processes. The result shows that the TCTED process can result in the reduction of both TAC and E CO2. So, this study can provide a reference for the separation of ethyl acetate-ethanol-water mixture in industry. [ABSTRACT FROM AUTHOR]

• Basic control structure of double side-stream extractive distillation is designed. • F/SS and Q R /F feedforward structures are explored for better control performances. • A robust control strategy CS4 is proposed to obtain the desired product purities. The investigation of dynamic controllability for the double side-streams ternary extractive distillation (DSTED) is necessary due to its advantages in energy-efficient. However, the control strategy of the energy-saving DSTED scheme is unique and complex issues owing to the wobbly of side-stream flow rate. Herein, control strategy of the energy-saving DSTED scheme is explored for separating ternary azeotropic mixtures acetonitrile/methanol/benzene. Inspiring from the control strategy of the ordinary triple-column extractive distillation scheme, the fundamental control structure CS1 is firstly designed. The control scheme CS2 with feed/side-stream (F/SS) ratio and control structure CS3 with feedforward and F/SS are then investigated to achieve higher efficiency of process control. Finally, a robust control strategy CS4 with the ratio of reboiler duty and feed flow rate and without F/SS ratio is proposed to well maintain the product purities. Moreover, additional ±15% feed flow rate and composition disturbances are added in the CS4 to assess the stability and controllability of the energy-saving DSTED. Dynamic performances illustrate that the structure CS4 can handle as well as that of confronted ±10% disturbances when the large disturbances are occurred in the real chemical process. [ABSTRACT FROM AUTHOR]

• A systematic design procedure is proposed for the four-azeotrope mixture separation. • The conceptual design including residue curve maps on two schemes is investigated. • The control strategies is proposed for the DEDP process with economic superiority. • An improved control structure combining proportion with "HiLoSelect" is developed. The separation of ternary mixtures with homogeneous or heterogeneous multi-azeotropes has received increasing attention. In this work, a systematic design, optimization and control procedure is proposed for extractive distillation of heterogeneous mixtures with four azeotropes. Herein, the ternary system isopropyl alcohol/isopropyl acetate/water is taken as a case study. The suitable entrainer is first obtained through a proposed approach combining the vapor–liquid equilibrium (VLE) curves and infinite dilution activity coefficient ratios. Conceptual design of two alternative separation sequences involving double-column extractive distillation with a pre-concentrator (DEDP) and triple-column extractive distillation (TED) are then investigated based on thermodynamic insights. With the method of sequential iterative optimization and taking total annual cost (TAC) as the objective function, the two processes are optimized. The optimal results indicate that the DEDP process with dimethyl sulfoxide as entrainer can save 6.43% TAC than that of TED. Finally, a new control structure combining reflux flowrate-to-feed (R/F) and adjustable reboiler duty-to-feed (Q R /F) with "HiLoSelect" strategy is proposed to better handle three product purities than that of the basic control structure while feed flowrate and composition disturbances are introduced in the studied DEDP process. [ABSTRACT FROM AUTHOR]

• Dynamic control of nonconventional ternary extractive distillation is conducted. • Ethanol composition controlled by adjusting reflux ratio works better than that with regulating solvent flowrate. • Controllability of non-conventional ternary extractive distillation is also robust. • The dynamic controllabilities of different processes are compared. This paper explores the dynamic control of thermally coupled ternary extractive distillation process containing two extractive columns with recycle splitting of mixed separating agent by taking the separation of tetrahydrofuran/ethanol/water as a demonstrating example. A series of control structures are devised and assessed by the large (20%) perturbations of throughput and feed composition, and the robust regulatory control is achieved since the purities of all three products are closely going back to their initial steady-state design specifications when facing the large (20%) feed flowrate and composition disturbances. Besides, the dynamic response performance for control strategy with product ethanol purity controlled by manipulating the reflux ratio is superior to that with manipulating solvent flowrate in terms of peak dynamic transients, settling time and steady-state offsets when facing the large (20%) throughput and feed composition disturbances for extractive rectifier column C 2. The direct dynamic response performance comparisons for conventional and thermally coupled processes with mixed entrainer are also investigated and showed that there is no conflict (tradeoff) between the steady-state economics and dynamic controllability for this system. [ABSTRACT FROM AUTHOR]

• Separation alternatives of ethyl acetate/water/ethanol mixture are investigated. • Four methods, based on distillation techniques and pervaporation are modelled. • The distillation and pervaporation models are experimentally verified. • The methods are optimized by economic evaluation based on the total annual cost. • The heat integrated EHAD + PSD with D + HPV method is found as optimum. Ethyl acetate and ethanol are important organic solvents in fine chemical industry, which form with water ternary minimum-boiling azeotrope and three binary azeotropes, including heterogeneous-azeotrope. In this article, different distillations and pervaporation methods are studied to separate sharply the ternary mixture. In the case of separation of highly non-ideal mixtures the distillation based separation methods can be extraordinarily complex. The extractive heterogeneous-azeotropic distillation (EHAD) as new improvement can be a promising tool for splitting the ternary mixture. This process contains the preferences of heterogeneous-azeotropic- and extractive distillations in one unit without extra material addition. Four advanced separation methods are compared: Method I (pressure swing distillation (PSD) for ethyl acetate purification with extractive distillation (ED) for ethanol purification), Method II (PSD with distillation-hydrophilic pervaporation (D + HPV) for ethanol purification), Method III (EHAD + PSD with ED) and Method IV (EHAD + PSD with D + HPV). The different alternatives are rigorously modelled in ChemCAD simulator and optimized with the dynamic programming optimization method first in the literature. In the case of distillation operations, heat integration is also considered, the feed is preheated with its bottom stream. Such ternary pervaporation separation with new semi-empirical model has not been published in this professional flowsheet environment yet. The distillation and pervaporation models are experimentally verified. Separation factor values are compared to those of other published membranes in the recent literature and it is found that PERVAP™ 1510 has the highest separation factor value. It can be determined that every method is capable for the separation of ethyl acetate-ethanol-water ternary mixture. The methods are optimized by economic evaluation based on the total annual cost (TAC) and the EHAD + PSD with D + HPV is found the optimum, because it has the lowest heat duties. [ABSTRACT FROM AUTHOR]

Highlights • Conventional triple column extractive distillation with multi binary azeotropes. • Extractive dividing wall column with single- and double-partition are proposed. • Heat transfers through the dividing wall. • Illustrated through tetrahydrofuran-methanol-water system with ethylene glycol. • Performance evaluation is made in terms of energy and cost savings. Abstract In this work, we propose the development of a dividing wall column (DWC) for the separation of ternary azeotropic mixture using an entrainer. Traditionally, this type of complex ternary system is traditionally separated in a triple column extractive distillation (TCED), among which, the first column is served as an extractive distillation. For this, at first, the first two towers are proposed to transform into a single column with a dividing wall. The resulting scheme is called here as extractive single-partitioned dividing wall column (ESPDWC). Subsequently, further intensification is made by merging all three columns of TCED into a single unit with two dividing walls, from which, one can get three products and the entrainer simultaneously with reasonably high purity. This proposed configuration is named as extractive double-partitioned dividing wall column (EDPDWC). To make the proposed extractive DWCs more practical, the heat transfer through the internal dividing wall is taken into account. For the separation of a ternary azeotropic mixture (tetrahydrofuran-methanol-water) with the use of an entrainer (ethylene glycol), the performance improvement of the proposed DWCs is quantified over the conventional TCED in terms of energy and cost savings. It appears that the proposed double-partitioned extractive DWC secures a better performance than its single-partitioned counterpart for the sample multiple binary azeotropes case. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • ChCl/Urea (1:2) is selected as the entrainer for the ethanol dehydration process. • Five control schemes, including the proportional-integral and model predictive control strategies, are developed for the proposed separation process. • The integral absolute error and destroyed exergy are applied as evaluation criteria to test the control system. Abstract With the development and improvement of solvents (or entrainers), the extractive distillation process has been significantly enhanced, and the energy consumption of the separation process has been effectively reduced. In this work, the energy-efficient separation process for extractive distillation with deep eutectic solvent ChCl/Urea (1:2) is designed. The ethanol dehydration process is selected as a case study to evaluate the practical utility of this novel solvent in large-scale production. The multi-objective genetic algorithm is used to optimize the extractive distillation process, and the waste heat is recovered through the heat intensification strategy to achieve the optimal design. Five control schemes, which include proportional-integral (PI) and model predictive control strategies (MPC), are developed for the proposed separation process. According to the nonlinear relationship between manipulated variables and controlled variables, the improved control structures are designed to enhance the dynamic performance. Integral absolute error (IAE) and destroyed exergy are applied as evaluation criteria to test the controllability and energy efficiency of the system. The results show that both CS4 and MPC control schemes have good controllability, and the MPC control scheme displays better energy efficiency than the CS4 control scheme. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Comparison of alternative separation techniques for Dichloromethane-Methanol. • Simple design flow sheet synthesis using ED and AD techniques. • TAC has been reduced by 24.2% in ED in comparison to a recently published work. • Control synthesis does not require any costly continuous composition analyzer. Abstract Design and control of an energy and cost efficient separation process is deduced amongst several evaluated separation alternatives for Dichloromethane-Methanol binary mixture. Separation process evaluation for this specific binary mixture has not received much attention in the open literature so far. In the present study, several other significant alternatives (Pressure swing distillation, Extractive distillation and Azeotropic distillation) for the separation of the mixture have been explored and compared with the single reported work published earlier wherein separation using pressure swing batch distillation method has been discussed. Steady state analysis reveals that out of these evaluated alternatives; Extractive distillation is the best method in terms of economics and energy efficiency. The TAC of the extractive distillation method (best amongst four alternatives studied including the published work of PSBD method) was found to be 27.62% less than that of the second best from the list, which is Pressure Swing Batch Distillation method (Heat integration variant). The saving by extractive distillation method will result in significant benefits based on the futuristic surge in compound annual growth rate in the production of Dichloromethane-Methanol. Further, a plantwide control structure is designed for the recommended extractive distillation flow sheet which is further evaluated for throughput and composition disturbances. The present study will be helpful in designing the real process plants for the separation of Dichloromethane-Methanol binary mixture. [ABSTRACT FROM AUTHOR]

Highlights • A systematic method exploring organic and ionic liquid entrainers has been developed. • The toxicity and physical properties of two types of entrainers are first considered. • The separation performance are further evaluated with the process restrictions. • The result of process optimization agrees well with that of screening procedures. Abstract A systematic strategy for the screening of organic solvents and ionic liquids as entrainers along with the design of the corresponding homogeneous extractive distillation processes has been developed. The proposed approach is illustrated by an example of the entrainer screening in the dehydration of tert -butanol. The toxicity and the physical properties of two types of entrainers (e.g., 19 organic solvents and 289 ionic liquids) are first considered. Then, the properties related to separation performance are further evaluated and three organic solvents and 11 ionic liquids are found to conform to the process feasible restrictions. In the third step, glycerol, triethylene glycol, 1-butyl-3-methylimidazolium thiocyanide [C 4 MIM][SCN], and 1-pentyl-3-methylimidazolium thiocyanide [C 5 MIM][SCN] are chosen as the representatives to perform thermodynamic topological analysis. Finally, the process design and optimization with four entrainers are performed using the minimization of total annualized cost as the objective function. And the process economic evaluation proves that the ability of glycerol in separating tert -butanol-water system is superior to those of 18 organic solvents candidates while that of [C 4 MIM][SCN] is the most advantageous entrainer among 289 ILs in terms of saving energy. [ABSTRACT FROM AUTHOR]

Highlights • The control strategies were proposed for side-stream extractive distillation. • ±10% and ±20% disturbances were introduced to test the control strategies. • The dynamic controllabilities of different processes were compared. Abstract It is important to study the dynamic controllability for the side-stream extractive distillation due to its superiority of energy saving. Control structures of the side-stream extractive distillation process are special and complex due to the instability of side-stream flow rate. In this work, the dynamic control of the side-stream extractive distillation was explored for separating azeotropic mixture of acetone and methanol. The detailed control structures were used to investigate the control strategies of side-stream extractive distillation. During the whole design process, the control of flow rate on side stream is a key factor for achieving this process efficient control. A new control structure combining a component controller and a side-stream throughput valve was proposed to achieve good dynamic performance for the side-stream extractive distillation process when ±10% disturbances were introduced, but it is difficult to control the ±20% feed disturbances. In addition, the side-stream extractive distillation takes about a longer time to reach a steady state while maintaining the purity of products, compared with conventional process. Research on control performance is of great significance to the development of energy saving technology for side-stream extractive distillation. [ABSTRACT FROM AUTHOR]

• Separation of different components of ACN/EtOH/water by EDP. • Purification process based on multi-objective optimization. • Use heat integration to enhance processes. • Recovery of extractant by pervaporation technology. In order to separate and purify the reaction raw material ethanol (EtOH) and product acetonitrile (ACN) from the azeotrope of ACN / EtOH / water, an efficient extractive distillation by varying pressure process (EDP) was designed to separate them. Because the feed composition in industrial production was constantly changing, processes of different feed compositions was simulated. Taking into account both economic and environmental factors, the non-dominated sorting genetic algorithm comprehensively optimizes the parameters. The azeotrope was pressure sensitive and the pressure parameter was also optimized in order to improve the efficiency of process energy utilization. Heat exchange network optimization technology was used to fully utilize excess heat in the process. The distillation coupled pervaporation technology has also been designed to explore emerging technologies. Among the three different coupling processes, the performance of EDP-pervaporation (EDPV) was better. Compared with EDP, EDPV under different schemes reduce the total annual cost (TAC) and gas emissions by more than 15% and 21 %, respectively. It was found that the energy consumption was related to the normal distance from the feed composition to the distillation boundary and isovolatility curve. [ABSTRACT FROM AUTHOR]

• Integration of a green biorefinery with ethanol fermentation was evaluated. • 90% of the green juice crude protein was recovered in the protein concentrate. • Nanofiltration raised the sugar composition in the brown juice from 2.4 to 13.6 %. • Purification of ethanol from concentrated brown juice used up to 45% less energy. • DWC was the best choice to purify ethanol among the tested extractive distillations. The objective of this study is to propose the integration of a green protein biorefinery with ethanol production and to highlight the potential of nanofiltration membrane technologies and extractive distillation in the separation and purification of valuable substances. Depending on the product and its purity, the nanofiltration membrane can help in decreasing energy expenditure and greenhouse gas emissions while extractive distillation overcomes the water–ethanol azeotrope formation. The aim is to enhance the sustainability of biorefinery processes by integrating new separation techniques and adopting process intensification. The concentration of the residual brown juice using nanofiltration reduced its water content and favored the sugar conversion into ethanol while concomitantly decreasing the formation of byproducts. It has been shown that these configurations (with the presence of nanofiltration and intensified) have lower energy consumption compared to the proposed classical sequence. The results of the simulations indicate that better results are obtained with the extractive distillation using a dividing-wall column, achieving around a 50 % reduction in energy consumption and a 58 % reduction in CO 2 emissions. [ABSTRACT FROM AUTHOR]

• Analysis of trade-off between total annual cost (TAC) and flexibility index (FI). • Integrating TAC and FI as single objective function, TAC FI. • Introduction of penalty terms to compensate for unexpected offset. • Identified a cheaper optimum point for all configurations under same FI. • Ethylene glycol with penalty 10 yields cost-efficient & flexible process. In our previous work (Sep. Purif. Technol. 312 (2023) 123344), we incorporated flexibility index (FI) into steady-state extractive distillation (ED) design for binary azeotropic separation. We pointed out the significant trade-off between the cost and FI , whereby good operational flexibility (i.e., FI) is always accompanied by a higher cost. One shortcoming, however, was that we did not determine an optimum configuration that provides a compromise trade-off between the cost and flexibility. In this work, we address this by introducing a novel approach, i.e., integrated total annual cost and FI objective function (TAC FI), which combines cost and FI as a single objective function, to obtain the most economic configuration with the largest operational flexibility. Additional penalty terms based on values of 10, 100, and 1000, were also introduced to compensate for the unexpected offset when the system operates beyond its limit point. Using the same isopropyl alcohol (IPA) dehydration process with the same uncertainties of ±20% feed flowrate and ±20% IPA feed composition as before, the TAC FI with penalty terms enables a lower cost relative to the previous work by 39–41%. We also observe significant enhancement in operational flexibility, with a penalty value of 10, resulting in a 520-fold enhancement. However, there is no improvement for penalty values of 100 and 1000 due to the physical and thermodynamic constraints for producing electronic grade IPA. This approach allows us to locate a new optimum point with lower cost under the same FI value, and the IPA dehydration using ethylene glycol (EG) with a penalty value of 10 provides the most significant improvement in both FI and cost by about 520 times and 5%, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Design of ED with ionic liquids process is more reliable using rate-based models. • [C 2 C 1 im][SCN] ranks as the most promising IL for separating R-410A in an ED process. • Process layout and operating conditions are tuned for minimum energy consumption. • Solubility selectivity is the most influential IL property in the ED process design. 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 [C 2 C 1 im][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. [ABSTRACT FROM AUTHOR]