Heteroazeotropic Distillation Research Articles

Hybrid process for separation of morpholine−water mixture: A rigorous design with experimental confirmation based on LLE and VLE data

The separation of morpholine from the aqueous effluent stream is carried out using an efficient hybrid extraction-distillation (HED) system using commercially viable solvents 2-ethyl hexanol and toluene, which makes heteroazeotrope with water. This paper investigated the tie-line, mutual solubility and VLE measurements, and thermodynamic modeling. On comparing the two solvents, 2-ethyl hexanol emerged as an appropriate extractant. The experimental tie-line data regressed by the NRTL model and a deviation of 0.8 indicates a good correlation between experimental and predicted data. Further, the process is designed, simulated, and optimization is performed by minimizing total annual cost (TAC) as the objective function. At extract/solvent to feed ratio S/F of 0.78 mol fraction, number of stages, NT of 28, 99.8% morpholine recovered in the extract phase with TAC of $23.3×104/y. Subsequently, the extract phase is fed to the heteroazeotropic distillation column to remove moisture followed by the final recovery column. Finally, a laboratory-scale experiment was conducted to verify the separation performance in the downscaled (3.5×50 cm) counter-current extraction column.

The phase behavior of Isopropanol/Water/NaCl mixtures at atmospheric pressure and temperatures from 294.15 K up to the boiling point

Branched-chain higher alcohols (BCHAs) have potential applications in the preparation of biofuels as they have properties similar to those of gasoline. Isopropanol is the simplest member of the BCHA family and is produced by either a catalytic process or fermentation of biomass. Regardless of the process, the isopropanol is produced as a component of a mixture with water content as high as 80%; therefore, purification is needed to produce fuel-grade isopropanol. Azeotropic and heteroazeotropic distillation are currently used to purify the isopropanol but they are carbon-intensive and costly. The addition of NaCl to an isopropanol/water mixture has two effects: could trigger a liquid–liquid phase split; and increases the relative volatility of the alcohol. These effects could potentially be used as the departure for the design of low-carbon and less expensive purification operations.The phase behavior of isopropanol/water/NaCl mixtures was experimentally mapped at temperatures up to the boiling point at atmospheric pressure. The liquid–solid, liquid–liquid, liquid–liquid–solid, liquid–vapor, liquid–liquid–vapor, liquid–liquid–solid–vapor and liquid–solid–vapor regions were experimentally detected and located in the phase diagram. The equilibrium compositions within the liquid–liquid, liquid–vapor and liquid–liquid–solid–vapor regions were measured. Three well-known methods were employed to assess the reliability of the measured liquid–liquid phase compositions. The temperatures and the composition of the vapor phase in the liquid–liquid–vapor region were also experimentally measured. The collected experimental data was used to construct the phase diagram of isopropanol/water/NaCl mixtures at 5, 10 and 20 wt% NaCl content, at atmospheric pressure, and temperatures from 294.15 K to the boiling point.

Separation of an Industrial Mixture of Decalin or Naphthalene Fluorination Products. Purification of Perfluoro(7-methylbicyclo[4.3.0]nonane) from Close-Boiling Impurities by Heteroazeotropic Distillation

Separation of an Industrial Mixture of Decalin or Naphthalene Fluorination Products. Purification of Perfluoro(7-methylbicyclo[4.3.0]nonane) from Close-Boiling Impurities by Heteroazeotropic Distillation

Separation of an Industrial Mixture of Decalin or Naphthalene Fluorination Products. Purification of Perfluoro(7-methylbicyclo[4.3.0]nonane) from Close-Boiling Impurities by Heteroazeotropic Distillation

Separation of an Industrial Mixture of Decalin or Naphthalene Fluorination Products. Purification of Perfluoro(7-methylbicyclo[4.3.0]nonane) from Close-Boiling Impurities by Heteroazeotropic Distillation

Process design, simulation and experimental studies of heteroazeotropic batch distillation for phenol dehydration

Phenolic compounds are important groups of chemicals with many applications. Due to the strong affinity between phenols and water, the dehydration of phenolic compounds is often necessary and inevitable. The conventional method for phenol dehydration is the direct distillation without entrainers, leading to high phenol concentration (2–5 wt%) in wastewater and significant difficulty in subsequent wastewater treatment. In this work, heteroazeotropic batch distillation was studied by simulations and experiments to remove water from water-bearing phenols. By simulation, effects of entrainer type, operating pressure, number of theoretical stages, entrainer amount and decanter hold-up on dehydration efficiency were studied in detail. The results showed that the heteroazeotropic batch distillation using ethylbenzene as the entrainer yielded desirable dehydration results with many advantages. The wastewater generated in the dehydration process showed a much lower content of phenolic compounds than the direct distillation, greatly reducing the cost and difficulty of wastewater treatment. The energy consumption of heteroazeotropic distillation was also lower than the direct distillation. Batch distillation experiments were performed to validate the reliability of simulation results. The experimental results were in high agreement with simulations. The produced phenol products showed a water content of 470 ppm, and the content of phenolic compounds in wastewater was reduced to as low as 5.0 ppm. The heteroazeotropic batch distillation proposed in this study suggested an ideal strategy for phenol dehydration which is economically feasible and environmental-friendly.

Comparison of Extractive and Heteroazeotropic Distillation of High-Boiling Aqueous Mixtures

The processes of extractive distillation and heteroazeotropic distillation of mixtures containing water and a high-boiling component (propionic acid, acetic acid, 1-methoxy-2-propanol) are compared. Entrainers declared in the literature as effective agents for these processes were selected as separating agents. A distillation process simulation in AspenPlus V.11.0 is made. Parametric optimization is carried out and the column operation parameters (number of stages, feed stage, reflux ratio) that meet the minimum energy consumptions and ensure the production of marketable substances are determined. It is shown that the process of heteroazeotropic distillation is more energy-efficient compared to extractive distillation by more than 50%, due to the introduction of an entrainer that lowers the boiling point of process. In addition, in some cases (acetic acid + water with vinyl acetate, propionic acid + water with hexane, cyclohexane, cyclohexanol), one of the columns in the separation flowsheet can be abandoned due to the significantly limited mutual solubility.

Topology-Based Initialization for the Optimization-Based Design of Heteroazeotropic Distillation Processes

Distillation-based separation processes, such as extractive or heteroazeotropic distillation, present important processes for separating azeotropic mixtures in the chemical and biochemical industry. However, heteroazeotropic distillation has received much less attention than extractive distillation, which can be attributed to multiple reasons. The phase equilibrium calculations require a correct evaluation of phase stability, while the topology of the heterogeneous mixtures is generally more complex, comprising multiple azeotropes and distillation regions, resulting in an increased modeling complexity. Due to the integration of distillation columns and a decanter, even the simulation of these processes is considered more challenging, while an optimal process design should include the selection of a suitable solvent, considering the performance of the integrated hybrid process. Yet, the intricate mixture topologies largely impede the use of simplified criteria for solvent selection. To overcome these limitations and allow for a process-based screening of potential solvents, the current work presents a topology-based initialization and optimization approach for designing heteroazeotropic distillation processes. The systematic initialization enables an efficient evaluation of different solvents with different mixture topologies, which is further exploited for optimization-based sensitivity analysis and multi-objective optimization. Three case studies are analyzed with about 170 individually optimized process designs, including stage numbers, feed locations, phase ratios, and heat duties.

Separation of a water/MIBK mixture by batch heteroazeotropic distillation: A self-entrained case

In this work, we present a study on the dehydration of methyl isobutyl ketone (MIBK) by batch distillation, using the dynamic module for batch distillation (BatchSep) provided by the commercial chemical process simulator Aspen Plus V11®. A 98 wt.% MIBK/water mixture was initially fed to the column. The scope of the separation was set at 99.8 wt.%, as a standard purity for solvent reuse. Taking advantage of the heteroazeotropic behaviour of the mixture water/MIBK (self-entrained), an alternative configuration with a decanter, which allowed selective reflux of the organic phase, was studied and compared with the conventional batch distillation configuration at 1 atm. This alternative configuration presented clear operating advantages compared to the conventional case, i.e. reduction of both operational time and energy demand by 50% and increase in specific production by 100%. Finally, the distillation-decanter configuration was studied at reduced pressures (50–400 mbar), registering further operating improvements.

Enhancing heteroazeotropic distillation thermodynamic flexibility boundaries by means of condenser overcooling

When chemical processes involve the treatment of raw materials characterized by unstable properties over the year’ s seasons, upstream perturbations could affect the downstream operation feasibility. This research work discusses how non-idealities can be exploited to enhance the flexibility of the operation for an ABE/W purification section. In particular, the effects of condenser overcooling on the allowed feed composition perturbations are analyzed in case of distillation process. For this purpose, an innovative methodology based on residue curve maps coupled with liquid-liquid equilibrium is presented. Calculations have been performed by means of an interface between the Simulis Thermodynamics®software for components characterization and Matlab. A graphical tool for mixtures up to four components is provided as well. This procedure extends the available methodology for the conventional distillation feasibility study by including specifications in terms of recovery ratio and by its generalization to distillation trains and Dividing Wall Columns as well.

Dehydration of a Dilute Acetic Acid‐Water Mixture via Batch Heteroazeotropic Distillation

AbstractDehydration via batch heteroazeotropic distillation emerges as a promising technology for the recovery of acetic acid (HAc) from dilute aqueous solutions. In this preliminary work, this process was studied with the aid of Aspen Batch Modeler®, using an acetic acid aqueous solution as the model feed instead of wood vinegar from biorefineries andn‐butyl acetate as the azeotropic entrainer. The non‐random two liquids (NRTL)‐virial Hayden‐O'Connell model (HOC) model was chosen to calculate the thermodynamic properties. The response surface methodology with Box‐Behnken design was successfully applied to obtain optimum process conditions, providing a dehydrated HAc product from the pot with high purity and recovery.

Development and intensification of a four-column hybrid process of heteroazeotropic distillation and pressure-swing distillation

This article develops a four-column hybrid process of hetero-azeotropic distillation and pressure-swing distillation (HAD-PSD) for separating a ternary multi-azeotropic mixture i.e., an organic aqueous solution with a low concentration of isopropanol (IPA) and diisopropylether (DIPE). For improving its economic and energetic performances, an intensified process by heat pump and dividing wall column is proposed, namely HAD-DWC-VRC-PSD. The quantified performance improvement over the HAD-PSD process reveals that the annual energy cost is drastically reduced by 39.7 % from 45.5–27.4 $ per tonne of IPA and DIPE while the total annual cost is cut by 11.7 % from 92.0–81.3 $ per tonne of IPA and DIPE. Besides, the thermodynamic efficiency is increased from 19.80 % to 25.96 %, and the carbon footprint as an indicator of unsustainable energy use is abated by 59 %. Overall, the HAD-DWC-VRC-PSD process is economically viable and eco-sustainable in a way.

Efficient optimization-based design of energy-integrated azeotropic distillation processes

The separation of azeotropic mixtures is frequently performed by extractive or heteroazeotropic distillation processes. The design of these processes requires careful selection of a suitable solvent and is specifically challenging since feasibility and optimality of the processes require consideration of the closed loop design including solvent recovery. Consideration of energy integration further complicates the design task and is usually conducted as post-evaluation step. The current publication proposes an efficient optimization-based design approach, which allows for the direct evaluation of several energy-integrated process concepts, while significantly reducing manual effort and computational time through a polylithic modeling and solution approach. The developed approach allows for a simultaneous evaluation of solvent selection and energy integration and is illustrated for different case studies, including the evaluation extractive and heteroazeotropic distillation for the dehydration of ethanol, as well as the evaluation of multiple solvent candidates for the extractive distillation of acetone and methanol.

Comparison of batch heteroazeotropic distillation operational strategies for the dehydration of isopropanol

The dehydration of isopropanol (B) from a mixture containing methyl ethyl ketone (A) and toluene (E) as pollutants by batch heteroazeotropic distillation (BHAD) is studied by dynamic simulation. The water (C) content of the feed is much lower than that of the BC azeotrope. Isopropanol can be obtained by conventional batch distillation under high reflux ratio and considerable loss. Toluene is a potential entrainer forming a ternary heteroazeotrope BCE.Dehydration is feasible by Mode II, Strategy A of BHAD, by which the whole amount of E-rich phase is refluxed, that of E-lean phase is withdrawn as distillate. Since the production is very slow due to the high (E-rich/E-lean) phase ratio, different operational strategies are studied in order to make the production faster without significant decrease in isopropanol recovery. These include taking a homogeneous fore-cut to remove methyl ethyl ketone, and Strategy B of Mode II, where one part of the E-rich phase is also withdrawn as distillate.A novel operational policy is proposed, as well, that is a combination of Strategies A and B. The application of cyclohexane (D) as entrainer and batch extractive distillation with dimethyl sulfoxide (F) are also studied.

Influence of entrainer recycle for batch heteroazeotropic distillation

Dehydration of isopropanol applying batch heteroazeotropic distillation with toluene as entrainer (E) is investigated. The composition of the feed is near to that of the isopropanol (A)-water (B) azeotrope. The effects of recycling the entrainer and the off-cut are studied by dynamic simulation with a professional flow-sheet simulator. Three consecutive batches (one production cycle) is studied. Both operational modes (Mode I: decantation after distillation and Mode II: decantation during distillation) are simulated. For Mode II, calculations are performed both for Strategy A (distillate from the aqueous (E-lean) phase only) and Strategy B (partial withdrawal of the organic (Erich phase), as well). The E-rich phase, the final column hold-up and the off-cut (Mode II only) are recycled to the next batch. The influence of the following parameters are determined: quantity of entrainer, reflux ratios of the steps. The variations caused by the recycling in the 2nd and 3rd batches are also shown. The best results (lowest specific energy demand and highest recovery of A) are obtained by Mode II, Strategy A. Recycling increases the recovery, and drastically diminishes the entrainer consumption. However, it makes the production slower and decreases the quantity of fresh feed that can be processed.

Recovery of Furfural and Acetic Acid from Wood Hydrolysates in Biotechnological Downstream Processing.

Wood hydrolysates contain sugars that can be used as feedstock in fermentation processes. For that purpose, the hydrolysate must be concentrated and inhibitors that harm fermentation must be removed. Herein, the integration of these tasks with the recovery of inhibitors is studied. The wood hydrolysate is represented as a mixture of water, xylose, acetic acid, and furfural. Acetic acid and furfural are two frequently occurring inhibitors and valuable chemicals, and thus, their recovery is studied. Furfural is recovered from the vapors by heteroazeotropic distillation. It is shown that this can be achieved without additional energy. The recovery of acetic acid by distillation is also possible, but not attractive. The new process is simulated by using a thermodynamic model based on experimental data.

Development of a flowsheet for sec-butyl acetate production based on a complex analysis of the reaction and distillation components

The vapor–liquid and liquid–liquid phase equilibria in the reaction system of sec-butyl acetate production from n-butenes and acetic acid were simulated. The simulation made it possible to develop two variants of principal technological flowsheets of the process organization. The both variants are based on the principle of redistribution of the concentration fields between the separation regions: in the first case, due to the chemical reaction; in the second case, owing to the splitting phenomenon. The material balances of the schemes were calculated, and the static operating parameters were determined. The first variant of the flowsheet does not enable one to obtain sec-butyl acetate of the required quality and, therefore, heteroazeotropic distillation for the separation of sec-butyl acetate from acetic acid was proposed in the second variant. The use of water as a heteroazeotrope-forming agent in the separation block allows the quality of sec-butyl acetate satisfying the environment standard requirements (GOST) to achieve at technologically appropriate operating parameters.

Dehydration of Isopropanol by Batch Heteroazeotropic Distillation with Toluene as Entrainer

The dehydration of isopropanol (B) by batch heteroazeotropic distillation (BHAD) is studied by dynamic simulation. The mixture also contains methyl ethyl ketone (A) and toluene (E) as pollutants. The water (C) content of the feed (ca. 2 mass%) is much lower than that of the B-C azeotrope. B can be obtained as residue by conventional batch distillation (BD) under a very high reflux ratio and considerable loss of B, only. The loss of B can be considerably decreased by BHAD. Toluene, already present in the mixture, can be a suitable entrainer (E), since it forms a ternary heteroazeotrope with isopropanol and water.Dehydration is feasible by Mode II, Strategy A of BHAD, that is, the two liquid phases of the condensate are separated in a decanter, and the whole amount of E-rich phase is refluxed, while that of E-lean phase is withdrawn as distillate. As the production is very slow because of the high (E-rich/E-lean) phase ratio, several operational strategies are studied in order to make it faster. These include taking a homogeneous fore-cut to remove methyl ethyl ketone, and Strategy B of Mode II, where part of the E-rich phase is also taken as distillate.

SYNTHESIS OF FLOWSHEETS FOR SEPARATION OF MULTIPHASE MIXTURES: STATE OF THE ART

The paper presents an analysis of the current state of research on separation flowsheets based on the combination of distillation and phase separation processes, as well as heteroazeotropic distillation. It is shown that the works of foreign researchers devoted to the study of flowhseets with decanters are more focused on finding ways to reduce energy consumption by introducing additional separators, a combination of several methods (extractive and heteroazeotropic complex columns with external decanters. The task of synthesizing all possible separation flowsheets is not considered in these works. In this paper, a complete set of flowsheets of different structures based on the combination of distillation and phase separation processes, including the use of columns with an external decanter, is proposed for water - butyl acetate - methanol and methanol - heptane-water ternary mixtures separation. Aspen Plus and NRTL model were used for mathematical modelling of phase equilibrium (the relative error of describing liquid-vapor and liquid-liquid equilibrium is less than 5%) was chosen as a method of research. Operating parameters for distillation columns (the number of theoretical plates, feed plate, reflux ratio) and the total energy consumption were obtained for each case. The necessity of using a double feed-plate column for separating of propanol-1 - water - butanol-1 and ethyl acetate - water - butyl acetate ternary systems was explained by the presence of extractive effect. Analytical review of modern publications and results of own research allowed to formulate a number of recommendations for the synthesis of energy effective flowsheets based on a combination of distillation and phase separation processes.

Investigation of Process Alternatives for the Separation of Ethanol, N-Butanol and Water Ternary Mixture

Biofuel production is an ever current topic, as bioethanol and biobutanol have a great potential to partially or completely replace fossil fuels in the automotive industry due to their attractive characteristics. They are usually produced by fermentation resulting in a highly diluted mixture, which poses a challenge to the downstream processing and the production of pure alcohols.In the course of this work, conventional separation systems of simple, extractive and heteroazeotropic distillation are compared with hybrid distillation-pervaporation systems for the separation of a ternary ethanol-n-butanol-water (EBW) mixture. Pervaporation (PV) is studied as an option for the final dehydration of the alcohol-water mixtures due to its great industrial potential in the separation of azeotropes. Simulations are carried out in ChemCAD® flowsheeting software, and the process alternatives are evaluated in an economic point of view, revealing the potentials and drawbacks of PV in a complex separation task.

Liquid–liquid phase equilibria of the quaternary system {water (1) + acrylic acid (2) + acetic acid (3) + cyclopentyl methyl ether (4)}: Measurement, correlation, and comparative study

Extraction followed by heteroazeotropic distillation is considered to be a potentially energy-saving method for purifying acrylic acid. Based on our previous work, cyclopentyl methyl ether is an excellent solvent that can be used as extractive an agent as well as an entrainer. In this work, liquid–liquid equilibria (LLE) data of the quaternary system {water (1)+acrylic acid (2)+acetic acid (3)+cyclopentyl methyl ether (4)} were determined at T=(293.15, 303.15, and 313.15)K and p=100.25kPa. The reliability of the experimental data was evaluated using the Othmer–Tobias and Hand equations. The NRLT and UNIQUAC activity coefficient models were used to correlate the LLE data of the quaternary system. The UNIFAC-Dortmund model was used to predict the observed LLE data with a average root-mean-square deviation value of 3.41%. Additionally, the physical properties and extraction capabilities of cyclopentyl methyl ether, cyclohexane, and toluene were compared.