Extractive Distillation Process Research Articles

Mechanism analysis and performance evaluation of clean and efficient recovery of N-heptanol/N-hexanol from wastewater via extractive distillation with green mixed entrainer

A clean and sustainable process for separating n-heptanol/n-hexanol/water industrial mixing system by extractive distillation via mixing organic solvent with ionic liquid as an entrainer was proposed. The mechanism of intermolecular microscopic interaction was explored by quantum chemistry calculation. By using multi-objective optimization, the optimal operating parameters of the process were obtained. In addition, process intensification technology was introduced, which improved the problems of high cost and high energy consumption in the conventional extractive distillation process. Finally, multiple performances were evaluated and analyzed for different processes. It was found that the coupled heat integration and heat pump technology to assist the extractive distillation process saved 10.45% in terms of economy, reduced gas emissions by 49.00%, and reduced energy consumption by 48.99% compared to the basic extractive distillation process. This confirmed the reliability and feasibility of implementing the process intensification technology. This work demonstrates the application of organic solvent mixed with ionic liquid as entrainer and process intensification technology in the extractive distillation process, providing guidance and reference for the design of the extractive distillation process.

Energy-saving extractive distillation system using o-xylene as an entrainer for the high-purity separation of dimethyl carbonate/methanol azeotrope

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 CO2 emissions. This work should provide a feasible and promising approach to energy saving, low-carbon, and high-purity separation of DMC/MeOH azeotrope.

Design and optimization for the separation of xylene isomers with a novel double extractants-based extractive distillation

Xylene is a crucial chemical raw material, serving as a synthetic monomer and solvent extensively employed in coating, medicine, rubber and other industries. It contains of three isomers: o-xylene (OX), m-xylene (MX), and p-xylene (PX), their separation is considered a worldwide challenge due to their extremely close boiling points. A novel extractive distillation based on double extractants is first proposed to separate these isomers in this paper, while it was considered impractical to separate these isomers by distillation technology alone in the past. Through the analysis of residual curve and extractant screening, two potential solvents, i.e., N-Methylpyrrolidone (NMP) and Tetramethylene sulfone (Sul) were used as extractants, and then the separation sequences were designed and optimized. The extractive distillation processes were optimized by sequential iterative method according to the minimum total annual cost (TAC), and the best separation sequence and process parameters were determined. For comparison, it was found that the optimized double extractant-based extractive distillation (DEED) process has the best economic performance with TAC of 5.72×106$, and the energy consumption was greatly reduced by 41.2% compared to the single extractant-based extractive distillation (SEED). This article provides a new perspective on energy-efficient distillation technology for industrial xylene separation and purification production.

Ionic Liquids for the Separation of Fluorocarbon Refrigerant Mixtures.

This review discusses the research being performed on ionic liquids for the separation of fluorocarbon refrigerant mixtures. Fluorocarbon refrigerants, invented in 1928 by Thomas Midgley Jr., are a unique class of working fluids that are used in a variety of applications including refrigeration. Fluorocarbon refrigerants can be categorized into four generations: chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, and hydrofluoroolefins. Each generation of refrigerants solved a key problem from the previous generation; however, each new generation has relied on more complex mixtures that are often zeotropic, near azeotropic, or azeotropic. The complexity of the refrigerants used and the fact that many refrigerants form azeotropes when mixed makes handling the refrigerants at end of life extremely difficult. Today, less than 3% of refrigerants that enter the market are recycled. This is due to a lack of technology in the refrigerant reclaim market that would allow for these complex, azeotropic refrigerant mixtures to be separated into their components in order to be effectively reused, recycled, and if needed repurposed. As the market for recovering and reclaiming refrigerants continues to grow, there is a strong need for separation technology. Ionic liquids show promise for separating azeotropic refrigerant mixtures as an entrainer in extractive distillation process. Ionic liquids have been investigated with refrigerants for this application since the early 2000s. This review will provide a comprehensive summary of the physical property measurements, equations of state modeling, molecular simulations, separation techniques, and unique materials unitizing ionic liquids for the development of an ionic-liquid-based separation process for azeotropic refrigerant mixtures.

A systematic approach for screening green entrainers combining the environmental-health-safety indexes and separation performance

Here we propose a new approach for extractive distillation (ED) process design, integrating environmental-health-safety (EHS) indexes as early as during the entrainer screening phase. Typically, safety and environmental factors are addressed later in the design process, often during optimization or in a sequential evaluation after cost-based optimization. However, in this study, we propose for the early incorporation of EHS considerations during the entrainer screening phase. This involves assessing the entrainer suitability using traditional metrics alongside additional EHS criteria, such as lethal dose (LD50) and flash point. Two azeotropic mixtures, i.e., tetrahydrofuran (THF)/ethanol (EtOH) and THF/methanol (MeOH), are chosen to exemplify our proposed methodology. Among the 1432 screened entrainers, the top 10 entrainers were identified based on separation index. These candidates were then subjected to further evaluation based on EHS criteria. Ethylenediamine (EDA) emerged as the optimal choice for the separation of THF/MeOH and THF/EtOH mixtures, demonstrating commendable EHS performance. Both separation processes were successfully simulated using Aspen Plus, which confirms the validity and suitability of the screened entrainer.

Novel energy-efficient design of side-stream extractive distillation process with intermediate reboiler for separating multi-azeotropic mixture based on multi-objective optimization

Side-stream extractive distillation is extensively employed to separate azeotropic mixtures since its energy-efficient benefits. Nevertheless, its economic effect is not always obvious due to the introduction of expensive high-pressure steam. In this article, a conventional triple-column extractive distillation process is firstly researched for separating n-hexane/ethyl acetate/acetonitrile mixture. To effectively decrease the requirement for high-pressure steam and achieve a reduction in economic costs of side-stream extractive distillation, three innovative side-stream extractive distillation processes with intermediate reboiler are proposed. A multi-objective genetic method is applied to optimize the four processes with total annual cost (TAC) and entropy production as two objective functions. Additionally, due to the presence of intermediate reboiler, heat integration design is implemented to the three side-stream extractive distillation processes with intermediate reboiler. Compared to the triple-column extractive distillation process, the heat integration of the three side-stream extractive distillation processes with intermediate reboiler exhibit better performance considering economy, energy-efficient, and entropy production. It indicates that the heat integration of the double side-stream extractive distillation process with intermediate reboiler can reduce 20.10% of TAC, 29.65% of energy consumption, and 35.63% of entropy production, respectively.

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

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

Investigation of side-stream extractive distillation for separating multi-azeotropes mixture based on multi-objective optimization

In this study, a conventional triple-column extractive distillation process and three side-stream extractive distillation processes are investigated for separating a ternary mixture of n-hexane/ethyl acetate/acetonitrile. A multi-objective genetic optimization method is applied to optimize the four processes with the minimum total annual cost (TAC) and entropy production as two objective functions. The results indicate that the three side-stream extractive distillation processes can effectively reduce the remixing phenomenon, achieving a reduction in energy consumption. In addition, the three side-stream extractive distillation processes exhibit better economic advantages and significantly decrease entropy production compared to the conventional triple-column extractive distillation process. Among the processes, the single side-stream extractive distillation process presents the optimal performance considering economy, energy-efficient and entropy production. Specifically, it can reduce 6.17% of TAC, 7.85% of energy consumption and 15.54% of entropy production in comparison to the conventional triple-column extractive distillation process, respectively.

Enhanced reaction extraction distillation via multi-objective optimization and 4E analysis for sustainable recovery of organic compounds from wastewater

Resource utilization and sustainable treatment of wastewater, which can achieve efficient energy utilization and environmental protection, have received hot social attention. Tetrahydrofuran and methanol are the two most common substances in pharmaceutical wastewater. It is very necessary to explore the wastewater treatment process containing these two substances. In this study, extractive distillation and reactive distillation were proposed to effectively separate the tetrahydrofuran-methanol-water component of pharmaceutical wastewater. To further reduce energy consumption, two strengthening processes, double-column reactive-extractive distillation and reactive-extractive dividing wall column distillation were designed. Taking the minimum operating and equipment cost as the objective function, the processes were optimized by using the multi-objective genetic optimization algorithm to obtain the best process parameters. Four processes were evaluated in terms of total annual cost, energy consumption, gas emissions and thermodynamic efficiency. Compared to the traditional three-column extractive distillation process, the above-mentioned four aspects of the reactive-extractive dividing wall column process was reduced by 40.63%, 43.13%, 43.14% and 17.71%, respectively. The reactive-extractive dividing wall column distillation process is of great significance for the efficient purification of valuable organic matter in wastewater and environmental protection.

Energy-saving extractive distillation process for the separation of close-boiling 2, 6-xylenol and p-cresol mixture

1) Background2,6-xylenol and p-cresol are widely used in medicine synthesis, which are both important raw materials in chemical engineering. It is shown significant economic benefits to separate 2,6-xylenol and p-cresol. Owing to the extremely relative volatility between 2,6-xylenol and p-cresol, it is difficult to separate the two phenolic compounds through conventional distillation. 2) MethodsThe results of vapor–liquid equilibrium analysis, COSMO-SAC and reduced density gradient result are used to investigate molecular interaction in the separation system, indicating diethylene glycol (DEG) as the optimal solvent. Accordingly, we propose an energy-saving extractive distillation process with DEG as an efficient entrainer for the separation of 2,6-xylenol and p-cresol. Total annual cost (TAC) and CO2 emission are investigated for optimization and estimation of the proposed process. In addition, three energy-saving scenarios for further reductions in TAC and CO2 emission are proposed. 3) Significant FindingsCompared with the benchmark process, the TAC and CO2 emission of the energy-saving design vapor recompression heat pump assisted extractive distillation separation sequence B are reduced by 26.18 % and 49.18 %, respectively, which indicates that the considerable industrial potential of the proposed design.

The Impact of Feed Composition on Entrainer Selection in the Extractive Distillation Process

The selection of entrainers primarily focuses on their ability to alter the relative volatility. However, the impact of feed composition on entrainer selection has often been overlooked. In this study, we conducted two case analyses of the minimum azeotropic mixtures in the ethyl acetate–ethanol and acetone–methanol systems to explore how the feed composition influences the entrainer selection when aiming for maximum economic efficiency. Additionally, the impact of the entrainer type (positive or reverse) on the economic benefits was also investigated. The cases revealed that economic benefits will be notably enhanced when the selected entrainer preferentially targets and removes the low-content component as the light key component. For the two cases studied, when the feed composition was 0.2–0.8, compared to preferentially separating the high-content component, preferentially separating the lower-content component resulted in a reduction in energy consumption by more than 24.14% and 22.72%, respectively. The results show that the ideal entrainer should be capable of converting the higher-content component in the feed into the heavy key component.

Applicability exploration and sustainable assessment of heat integration and vapor recompression heat pump to side-stream extractive distillation processes for separating ternary azeotropic system

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 CO2 emissions, while the energy utilization raised from 1.70 % to 1.78 % compared to the CED-HI process.

Study on the separation of methyl-ethyl-ketone / isopropanol / water ternary mixture by energy-efficient extractive distillation processes

The separation of ternary mixtures of methyl-ethyl-ketone (MEK)/isopropanol (IPA)/water, which are produced through chemical processes, is an imperative task aimed at reducing energy expenditures and mitigating environmental contamination. In the industry, Ethylene glycol (EG) and dimethyl sulfoxide (DMSO) are commonly employed as extractants. The selection of EG as the extractant was based on an investigation into the impact of relative volatility. Three distinct processes, namely conventional extractive distillation (CED), side-stream extractive distillation (SED), and heat pump extractive distillation (HPED), were evaluated by total annual cost (TAC), total energy consumption (TEC) and carbon dioxide emissions (CO2 emissions). The results demonstrate that both the enhanced SED and HPED processes effectively decrease energy consumption. Specifically, the TEC for the SED process exhibits a reduction of 15.36% compared to the CED process, resulting in a TAC saving of 9.06% and a decrease in CO2 emissions by 12.37%. Similarly, the HPED process surpasses the CED process by achieving a TAC saving of 15.41% and a CO2 emissions reduction of 22.61%. Consequently, this research presents a novel approach for the separation of MEK/IPA/water, offering significant practical implications.

Energy-saving exploration of separation for EG/1,2-BDO binary azeotrope based on energy, environmental and economic analysis

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.

Novel process development and mechanism analysis of purification of polymer monomers by combining pressure swing distillation and extraction distillation

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.

Improved extractive distillation process using dual decanters

Novel distillation configurations continue to appear in the literature despite the predictions made many decades ago that distillation had attained the status of a mature and stagnant technology needing no further research and development. The driving force for improvement has traditionally been energy conservation, but political decisions related to environmental and sustainability issues have provided additional motivation for improving the efficiencies of chemical and petroleum processes. Since distillation columns require a large fraction of the total energy used in these processes, there is a significant incentive to improve process efficiency.An excellent example of this activity is a paper in which a conventional three-column extractive distillation configuration is compared with a novel two-column process that includes a single decanter. The chemical separation system is a ternary mixture of methanol, water and toluene, which is important in the pharmaceutical industry. The new configuration reduces total annual cost by 50%.The purpose of this paper is to propose a simple modification of the two-column configuration that reduces energy costs by an additional 14% by using two decanters in series operating at different temperatures.

A novel reactive-extractive distillation process for separation of water/methanol/tetrahydrofuran mixtures

The design of separation systems for the purification of azeotropic mixtures is of great importance in the chemical industries from economic and environmental points of view. Two novel reactive-extractive distillation (RED) processes, new design (I) and new design (II), were proposed for separating the azeotropic mixture of water/methanol/tetrahydrofuran (THF). These processes were compared to a conventional extractive distillation (ED) process. New design (I) employs dimethyl sulfoxide as a solvent, while new design (II) utilizes ethylene glycol. Ethylene oxide was introduced to the first column in both designs, enabling the in-situ production of ethylene glycol, a valuable byproduct. This is a novel solution to separate water from the azeotropic mixture by reaction between ethylene oxide and water. Aspen Plus software was used to simulate and design the processes. Both suggested designs were compared economically with the base design which is an ED process. According to the results, the new design (I) is more cost-effective and environmentally friendly alternative to the base design and the new design (II). It has a lower total capital cost and produces less carbon dioxide. Additionally, it generates a valuable by-product, ethylene glycol, which can be sold for substantial revenue. As a result, the new design (I) is the preferred choice for replacing the conventional extractive distillation method.

Separation of the cyclohexane-benzene mixture by the extractive distillation process using ethylene glycol as a solvent

The importance of cyclohexane lies in the fact that it is the main precursor for the production of Nylon 6 and Nylon 6.6, two of the most important synthetic fibers. Cyclohexane (CHX) is produced by catalytic hydrogenation of benzene (BZ), where cyclohexane with benzene is obtained as a product. Since CHX and BZ have close boiling temperatures, and similar molecular structures, their separation by conventional binary distillation is complicated. Thus, ethylene glycol (EG) was selected as a solvent in an extractive distillation (ED) process for the separation of the CHX-BZ mixture in Aspen Plus V9®; where the use of ethylene glycol as a solvent allowed us to obtain cyclohexane and benzene with purities of 99.91 mol%. In addition, compared to the extractive distillation with heat integration (EDHI) process that uses [C5(MIM)2][NTf2]2 + H2O as a mass separation agent; the use of EG as a solvent promotes an energy decrease of 41.14%, a saving of 55.07% in the Total Annual Cost (TAC), and a decrease of 72.38% in CO2 emissions. These outcomes underscore the efficacy of ethylene glycol as a suitable solvent in the purification of the cyclohexane-benzene mixture.

Efficient purification of n-butanol by thermally coupled extractive distillation with mixed entrainer

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.

Dual-objective optimization and energy efficiency enhancement of natural decantation assisted extractive distillation process for n-butanol/isobutanol/water separation

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 CO2 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, CO2 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%, CO2 emissions 44.2% and TEC 44.7% than the CED process and decrease TAC by 12.4%, CO2 emissions 36.7% and TEC 37.1% than the NDED process.