Reactive Extractive Distillation Research Articles

Performance analysis of reactive-extractive distillation for multi-azeotropic mixture based on the relationship between economy and conversion rate

The synthesis and purification of ethyl acrylate are of great importance in studying the coupling performance of reaction and separation. In this manuscript, reactive extractive distillation (RED), immiscible-assisted reactive extractive distillation (IRED), and high conversion rate process (HCP) were comprehensively studied. The conceptual design by quaternary phase diagram was demonstrated. The optimal extractant was selected based on relative volatility and quantum chemistry. Multi-objective algorithm was used to minimize gas emissions and total annual cost (TAC). Based on economic, environmental and profit etc., the RED, IRED, and HCP were evaluated. The results show that the TAC, gas emissions, exergy loss, energy consumption, and profit of IRED were decreased by more than 25 %, 21 %, 12 %, 14 %, and 26 % compared to RED. Besides, the profit of the IRED is better than that of the HCP, which indicates that higher conversion rate of the reaction cannot represent better economy of the reactive distillation process.

A more appropriate way to optimize the hybrid reactive-extractive distillation system

Existing studies on reactive-extractive distillation (RED) commonly misapply optimization variables by including reaction stages. Given the uncatalyzed nature of ethylene oxide (EO) hydration in RED, where it naturally occurs throughout the column, a more appropriate strategy is to optimize only the total stages, allowing the reactive stage to align accordingly. However, previous attempts to implement this approach faced challenges. Here we introduce an algorithm addressing the variable overlap issue in optimizing RED, exemplified in two case studies. In Case 1, we explored a distinct scenario where the original process designated a specific reaction zone. Adjustments were made to ensure the reaction occurred throughout the entire column but it leads to a 13 % total annual cost (TAC) increase compared to the base case. In Case 2, optimization was applied to a system where reaction were distributed throughout the column without prior optimization, yielding a marginal 3.87 % reduction in the TAC.

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.

A new hybrid reactive-extractive distillation configuration for ternary azeotropic separation with intensification opportunity

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.

Unfavorable process intensification of double column reactive extractive distillation system

This study evaluated the energy saving potential of process intensified double column reactive extractive distillation (DC-RED) through three case studies. The results showed that process intensified technologies, thermally coupled reactive extractive distillation (TC-RED) and dividing wall reactive extractive distillation (DW-RED), did not yield any energy savings compared to conventional DC-RED. Contrary to the expectation, the elimination of the remixing effect in the process intensified DC-RED did not lead to any energy savings. Further analysis revealed that the remixing effect was not significant enough to achieve energy savings through process intensification, and the strong reaction exotherm in DC-RED reduced the potential for energy saving. Additionally, the higher interconnection flowrate in TC-RED and DW-RED resulted in higher energy consumption due to the increased boil-up ratio. Moreover, the lower feed temperature to the solvent recovery column (SRC) led to less energy efficiency and larger reboiler duty. An alternative energy saving scheme was proposed by adding a heat exchanger (HEX). The addition of HEX led to energy savings of 37.23 % in Acetonitrile (ACN)/Isopropanol (IPA)/Water separation, 45.62 % in Ethyl Acetate (EA)/Ethanol (EtOH)/Water separation, and 39.21 % in IPA/EA/Water separation.

Exploration of different water content on the performance of reactive-extractive distillation for separating the ternary azeotropic mixture

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 CO2 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.

Novel hybrid reactive-extractive distillation for separation of tetrahydrofuran, ethanol, and water azeotropic system with rigorous side reactions consideration

This study builds upon our previous research work (Ind. Eng. Chem. Res. 2023, 62, 27, 10,601–10,610), which investigated the impact of considering the side reactions in the hybrid reactive-extractive distillation (RED). Our prior investigation revealed a significant challenge, as the inclusion of side reactions led to staggering spikes in energy consumption and total annual cost (TAC), seemingly rendering the performance of RED impractical. In this study, we present another possible scenario for considering side reactions in RED and highlight that RED with side reactions can still be a superior alternative to conventional distillation methods, even when side reactions are considered. This work was exemplified by using the recovering tetrahydrofuran (THF) and ethanol (EtOH) from waste effluent. We explore two different cases: Case 1 involves a side-reaction-free RED configuration reproduced as the base case, while the introduction of side reactions resulted in an increase in TAC by about 79.2% and a rise in total energy consumption by about 69%. Implementing a vacuum system (Case 2) substantially reduced the TAC by about 39% and energy consumption by about 20.5%. Although Case 2 outperformed Case 1 economically, it fell short of the base case due to additional capital costs. In contrast, Case 2 exhibited a lower TAC by 58% relative to the conventional pressure swing distillation.

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

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

Novel Process Development of Hybrid Reactive–Extractive Distillation System for the Separation of a Cyclohexane/Isopropanol/Water Mixture with Different Feed Compositions

Novel Process Development of Hybrid Reactive–Extractive Distillation System for the Separation of a Cyclohexane/Isopropanol/Water Mixture with Different Feed Compositions

Process intensification from conventional to advanced distillations: Past, present, and future

This perspective paper features the process intensification (PI) application for advanced distillation-based processes. Starting with the historical background of generic PI, we subsequently narrow down the discussion to extractive distillation (ED), reactive distillation (RD), and hybrid reactive-extractive distillation (RED). We categorize the existing PI techniques onto internal and external intensification, where the former does not involve altering the distillation configuration while the latter does. Instead of deliberating the technical aspects, we explicitly highlight the contribution of PI applied to ED, RD, and RED towards societal impact covering energy, economic, environmental, control, and safety perspectives. The future perspectives of PI are discussed in the last section, covering the development of hybrid PI technologies, exploring the energy efficiency of different PI configurations, prioritizing PI beyond energy by considering some other sustainability aspects, and linking PI with the ever-increasing Industry 4.0 applications.

Transesterification reactive extractive distillation process using ionic liquids as entrainers: From molecular insights to process integration

In this work, the transesterification reactive distillation coupled with extractive distillation process for n-propanol (PROH) and methyl acetate (MEAC) was developed based on pseudo homogeneous kinetic parameter model using ionic liquids (ILs) as entrainers. The COSMO-RS model was used for screening ILs entrainers. Here, 1-ethyl-3-methylimidazolium acetate [EMIM][AC] was selected as a potential entrainer due to its excellent solvent capacity and selectivity. Further, the COSMO-RS model was performed to calculate the polarization charge density (σ-profile) of methanol (MEOH), methyl acetate and [EMIM][AC], and to explore the molecular polarity. Based on quantum chemistry (QC) theory, the interaction energy between different molecular pairs is calculated. Independent gradient model (IGM) analysis identifies the interaction types of molecular pairs from the perspective of visualization. Owing to the strong hydrogen bond between anion [AC]− and MEOH, the extractive distillation process performance was significantly improved. Based on Aspen Plus platform, the effects of the theoretical stage number, reflux ratio, feed position and entrainer dosage on the cost and energy consumption of the new process was investigated. Based on the sensitivity analysis method, the operating conditions were optimized. Compared to the conventional process, the new reactive distillation coupled with extraction distillation process has higher energy efficiency and lower economic cost. The new process can save the total annual cost of about 3.42 × 105 $/year.

Economic, environmental, exergy (3E) analysis and multi-objective genetic algorithm optimization of isopropyl acetate production with hybrid reactive-extractive distillation

Isopropyl acetate (IPAC) is an important fine chemical intermediate with a great demand for industrial production. In view of the high energy consumption in the traditional reactive distillation (RD) process of IPAC production, this study further proposed three enhanced processes of reactive-extractive distillation (RED), reactive-extractive dividing wall column (REDWC) and reactive-extractive distillation coupled pervaporation (REDPV) process. Firstly, the surface charge density distribution between components is calculated by COSMO-SAC model to screen a variety of potential solvents. Combined with the empirical screening method, relative volatility is used to determine the optimal solvent. Then, the conceptual design of RD, RED and REDWC three processes are completed based on reaction kinetics, and the operating conditions of processes are optimized by multi-objective genetic algorithm. Furthermore, REDPV process using pervaporation module instead of solvent recovery column is proposed. Finally, the total annual cost (TAC), gas emissions and exergy efficiency are used to evaluate the proposed process. The results show that compared with RD process, the TAC and gas emission of RED process are reduced by 42.69% and 49.82%. While those of REDWC process are reduced by 45.06% and 52.93%. The thermodynamic efficiency of these two processes is increased by 63.28% and 62.67%. Compared with RED process, REDPV process further reduces the cost by 14.45% and the gas emissions by 34.55%, but obtain the lowest thermodynamic efficiency.

Recent progress on hybrid reactive-extractive distillation for azeotropic separation: A short review

The reactive-extractive distillation (RED) has the advantages of combining the beneficial features of both reaction and separation processes. Relative to the conventional reactive or extractive distillation-based processes, the RED is also less energy intensive as it relies on the reaction heat produced for the subsequent separation process. Therefore, the application of RED for ternary azeotropic separation has become the subject of popular interest, as evident by the increasing number of publications since 2020. This review paper is the first that puts together, in a chronological manner, all the existing studies on the RED to date, starting from the initial three column reactive-extractive distillation (TCRED) to the most recent dividing wall reactive-extractive distillation (DW-RED), for ternary azeotropic separation, so that the rapid progress in this area is summarised and any existing gaps in these studies become easier to identify for future work. The last part of this review provides three potential areas for future work, i.e. analysis of the sustainability of RED, combination of different process intensification strategies to improve the energy efficiency and separation performance, and further exploration on the control studies for the RED.

Process design and mechanism analysis of reactive distillation coupled with extractive distillation to produce an environmentally friendly gasoline additive

Ethyl tert-butyl ether is a high-octane gasoline blending component with excellent performance and has important industrial application value. When ethanol and isobutylene react to form ethyl tertiary butyl ether, there is an azeotrope system of ethyl tertiary butyl ether and ethanol. The efficient production of ethyl tert-butyl ether and the precise separation of the ethyl tert-butyl ether/ethanol azeotrope are the keys to the entire process. In this work, reactive extractive distillation process and reactive extractive dividing-wall process were designed to achieve high-quality production and separation of ethyl tert-butyl ether. By analyzing the relative volatility of the solvents and combining molecular dynamics simulation and quantum chemical calculations, ethylene glycol was selected as the extractant for the separation of ethyl tert-butyl ether/ethanol. Based on the total annual cost as the objective function, three different ethyl tert-butyl ether production and separation processes were optimized and obtained the best process parameters. Finally, the whole process was analyzed from the aspects of economy, environment and exergy loss efficiency. Compared with common process, the total annual cost of reactive extractive dividing-wall process was reduced by 14.56%. The global warming potential, acidification potential and abiotic depletion potential of the reactive extractive dividing-wall process were 28.38%, 29.03%, and 28.36% lower than those of common process respectively. The exergy loss efficiency of reactive extractive dividing-wall process was reduced by 10.9%. The results showed that reactive extractive dividing-wall process has obvious economic advantages and environmental benefits and the actual production of ethyl tert-butyl ether and the separation of ethyl tert-butyl ether/ethanol azeotrope system have certain guiding significance.

Molecular dynamics-assisted process design and multi-objective optimization for efficient production of N-butyl acetate by reactive-extractive distillation/pervaporation

At present, the market demand for methyl acetate (MEOAC) is small and there is the problem of overcapacity. As an important organic solvent, n-butyl acetate (nBuOAC) is widely used in industry. It is very important to explore the efficient transesterification synthesis and separation process of nBuOAC. In this work, the schemes of reactive-extractive distillation (RED), side-line reactive extractive distillation (SLRED) and reactive distillation-pervaporation (RDPV) were proposed for the transesterification of MEOAC and n-butanol (nBuOH) to synthesize nBuOAC and methanol (MEOH). Firstly, according to the relative volatility of MEOAC and MEOH azeotrope systems, and the interaction energy and radial distribution function (RDF) were calculated by molecular dynamics (MD) to complete the screening of extractants. Then the process design is completed based on reaction kinetics, and the established processes with optimal operating conditions were obtained by the multi-objective particle swarm optimization algorithm. Finally, the total annual cost (TAC) and gas emissions are used to assess the economic efficiency and environment performance of these processes and the optimal process was obtained. The calculation results show that among the three proposed processes, the RDPV process performs best economically and environmentally. The TAC of RDPV is 8.17% lower than that of RED and 6.46% lower than that of SLRED. Meanwhile, the TAC of SLRED is 1.83% lower than that of RED. The gas emissions of RDPV is 23.13% lower than that of RED and 23.51% lower than that of SLRED, and there is little difference between RED and SLRED process.

Intensified hybrid reactive-extractive distillation process for the separation of water-containing ternary mixtures

• Process intensification for separating water-containing ternary azeotropic mixtures. • Combine reactive distillation and extractive distillation into one column. • Systematic VLE analysis helps to screen for feasible ternary systems. • Three ternary systems including: TBA/EtOH/water, THF/EtOH/water, and ACN/IPA/water. • Significant reduction in total annual cost is achieved in all applications. Separation of ternary mixture is a challenging task if multiple azeotropes exist among the components, and special distillation techniques should be adopted. For water-containing ternary mixtures with multiple azeotropes, a dehydrating agent, ethylene oxide (EO), can be used to consume water with the production of ethylene glycol (EG) as the product, which can be utilized as entrainer for separating the remaining two components. In this work, systematic thermodynamic analysis was conducted to screen for the feasible ternary systems. After conducting suggested analysis without needing of rigorous process simulation, tert -butyl alcohol (TBA)/ethanol (EtOH)/water, tetrahydrofuran (THF)/EtOH/water and acetonitrile (ACN)/isopropyl alcohol (IPA)/water mixtures were chosen to be suitable for this application. Within the scope of using dehydrating agent, a process configuration of triple column reactive-extractive distillation (TCRED) is developed for three different ternary systems. Subsequently, an intensified process configuration - double column reactive-extractive distillation (DCRED), which combines both functions of reactive distillation and extractive distillation in a single unit, is constructed to significantly reduce capital cost and energy consumption. With the application of further energy-saving schemes in the systems, total annual cost and total operating cost of the final proposed design flowsheets can be considerably saved compared to respective separation systems recently published in open literature.

Economic and environmental assessment for purification of acetonitrile and isopropanol by reactive coupling extractive distillation

• The sustainable process of reactive extractive distillation for treatment wastewater is proposed. • The intensified configuration applied in processes are developed. • The calculation of σ-Profiles used for screening the entrainer. • Comparisons from economic and environmental for assessment the benefits of proposed processes. • The intensified process with heat-integrated and intermediate reboiler presents best economy and environmental-benefits. Large amount of high purity acetonitrile and isopropanol are required as the raw material to meet the growth requirements of rapidly the chemical industries development. The high demands for acetonitrile and isopropanol have created the need for an efficient sustainable process to reduce the energy consumption which satisfies the environment regulations. Thus, a sustainable process of reactive coupling extractive distillation to separate acetonitrile/isopropanol/water ternary mixture is proposed. The intensified processes of heat-integrated combination intermediate reboiler are explored to further reducing energy consumption. The comparisons from the views of 4E which contains energy, exergy, economic and environment are conducted to assessment proposed processes benefits. The advanced intensification process of reactive extractive distillation (RED-HI-IR) has the best energy saving potential and economic benefits which achieves the reductions on energy, total annual cost and gas emissions of approximately 54.16%, 39.02% and 54.16% respectively, and the total exergy efficiency is up to 97.52%. Thus, heat-integrated and intermediate reboiler technology used of distillation is of significance for the sustainable chemical process development.

Design and optimization of reactive dividing-wall extractive distillation process for dimethyl carbonate synthesis based on quantum chemistry and molecular dynamics calculation

• Selection of extractants based on quantum chemistry and molecular dynamics calculation. • The process of dimethyl carbonate production by transesterification was designed. • Economic and environmental optimization of several different production separation processes. The preparation of dimethyl carbonate by transesterification of ethylene carbonate and methanol has an important application in industry. The preparation of dimethyl carbonate by reactive distillation and the efficient separation of dimethyl carbonate and methanol are the inevitable requirements of the sustainable development of extractive distillation. Based on the quantum chemistry calculation and molecular dynamics calculation analysis, a better extractant (2-Furaldehyde) was selected. The simulated extractive distillation was designed to separate dimethyl carbonate methanol. The σ - profile was drawn by using COSMO-SAC model, and three different separation processes of dimethyl carbonate production were compared and optimized. Taking TAC as the objective function, the separation process of reactive dividing-wall extractive distillation can reduce about 21% and carbon dioxide emission by about 10% compared with the common reactive distillation process, which has obvious economic advantages and environmental performance. Through the economic and environmental optimization analysis of the production and separation process of dimethyl carbonate, it provides a certain guiding significance for the actual production of dimethyl carbonate and the separation of dimethyl carbonate methanol.

Exergy, economic and environmental assessment of sec-butyl acetate hydrolysis to sec-butyl alcohol using a combined reaction and extractive distillation system

Sec-butyl alcohol (SBA), an important chemical intermediate, is widely used in the synthesis of methyl ethyl ketone, herbicides and other products. However, there are some problems, such as high energy consumption and high equipment investment, in the traditional method of SBA production. With the mature application of the synthesis method of sec-butyl acetate (SBAC) in industry, the excess capacity of SBAC gradually appears. The synthesis of SBA from SBAC has become a research hotspot. SBA synthesized via the hydrolysis of SBAC has the advantages of fewer byproducts and wide sources of raw materials, but it has the limitation of a low degree of hydrolysis. In this study, based on Douglas’s economic optimization model, taking the total annual cost (TAC) as the objective function, the influencing factors and suitable operating conditions of the SBAC hydrolysis reactive extractive distillation process were explored, and TAC was obtained under the optimal operating conditions. The environmental performance of the process was studied according to life cycle analysis. The exergy efficiency was obtained based on thermodynamic analysis. The process was analyzed from the aspects of exergy, environment and economy, which provided theoretical guidance for the industrial design of the new SBA process.

Investigation on ternary system tetrahydrofuran/ethanol/water with three azeotropes separation via the combination of reactive and extractive distillation

In this work, a systematic method for conceptual design and multi-objective optimization of an energy-efficient and sustainable reactive/extractive distillation (RED) process is proposed to separate a ternary wastewater mixture with multi-azeotrope tetrahydrofuran/ethanol/water. Conceptual design of the proposed scheme is carried out by the analysis of thermodynamic feasibility (e.g., residue curve maps and iso-volatility line). In the proposed process, the component of water in the ternary system is firstly removed by adding the reactant in a reactive distillation column and the remaining binary azeotropic mixture is then separated via ED. During the ED process, the best entrainer dimethyl sulfoxide could be determined via the comparison of iso- and uni-volatility. An improved multi-objective genetic algorithm is employed for optimizing the established process with some key decision variables (e.g., feed locations and distillate rate). The results illustrated that the economic and environmental benefits of the proposed RED process will be greatly improved.