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The process of perfluoro(7-methylbicyclo[4.3.0]nonane) (MBCN) purification from an industrial mixture of decalin or naphthalene fluorination products is considered. According to experimental data, distillation separation allows us to concentrate MBCN to a fraction with the target-component content of more than 0.950 wt. fr., after which the process efficiency begins to decrease quickly; upon reaching a concentration of 0.975 wt. fr., separation practically breaks down (the value of the separation coefficient → 1). The process of purification of MBCN by the method of heteroazeotropic distillation using acetone (Aс) as a separating agent is proposed, the process being realized on a batch semi-industrial distillation column. The method makes it possible to intensify significantly the final stage of purification and to increase the MBCN content from 0.950 to more than 0.998 wt. fr., the mass fraction of the enriched fraction sampling comprises more than 0.85 of the load and the product yield being above 88%. The values of the separation coefficients between the distillate and the bottom product and the coefficients of enrichment for the target and impurity components are given; for the MBСN–Aс binary system, data on the liquid–liquid phase equilibrium and heteroazeotrope characteristics are determined. [ABSTRACT FROM AUTHOR]

The purification of perfluoro(7-methylbicyclo[4.3.0]nonane) industrial fractions with a component content above 0.950 in mass fraction is not effective and requires the use of special separation methods. According to experimental data, the separation factor of the initial mixture during distillation with no additional substances is close to 1. At the same time, the addition of acetone (Ac) makes it possible to significantly intensify the process. Ac allowed for obtaining MBCN with a purity higher than 0.998 in mass fraction in one separation cycle, and the degree of recovery was more than 0.85 by weight. The paper presents data on the distribution of components (target product, identified and unidentified impurities of electrochemical fluorination of decalin) between the distillate and bottom product fractions, separation factor, liquid–liquid phase equilibrium in the MBCN-Ac system, and characteristics of the MBCN-Ac heteroazeotrope. [ABSTRACT FROM AUTHOR]

[Display omitted] • Several operation policies in batch distillation are evaluated. • The total reflux start-up is found to be an unnecessary step in most cases. • An efficient decanter is essential for a single-batch approach. • A moderate decanter performance is adequate for a sequential-batch approach. • Distillation with no reflux is preferred over 70% aqueous phase return fraction. Heteroazeotropic batch distillation of methyl isobutyl ketone-water binary mixture is investigated, seeking a reliable operation for dehydration of methyl isobutyl ketone (MIBK). The dynamic batch distillation module (BatchSep) of the commercial package Aspen Plus V.12.1® is applied for simulations. An initially fed unit at atmospheric pressure is simulated from the heating-up step until it reaches the desired MIBK purity of 99.8 wt%. Three configurations, namely conventional batch distillation unit (Mode I), batch distillation unit with decanter (Mode II), and a simple distillation unit (Mode III), are compared in a wide range of operating conditions. The effects of condenser temperature and the number of theoretical stages are also examined. According to the results, applying a decanter (Mode II) with a return fraction of over 0.75 for the MIBK-rich phase and below 0.4 for the aqueous phase provides higher MIBK recovery than the maximum achievable value in a conventional unit (Mode I), with almost no increase in process time. A perfect decanter offers an almost complete MIBK recovery, which is about 5% over the maximum value by conventional units (Mode I). Moreover, cutting the reflux (Mode III) offers the fastest way to the desired product but provides the lowest MIBK recovery value. The aqueous phase return fraction does not significantly impact MIBK recovery, but if it exceeds 0.5, it remarkably affects the process time/energy cost. When maximum MIBK recovery rate/minimum energy cost is desired, applying a decanter (Mode II) with a return fraction above 0.5 for the MIBK-rich phase and below 0.55 for the aqueous phase yields a higher production rate and a lower energy cost per unit quantity of product compared to the best achievable values for a conventional unit (Mode I). A perfect decanter improves production rate and energy efficiency by 8 % over the best case in a conventional unit (Mode I). Also, operation without reflux (Mode III) is preferred over a conventional operation (Mode I) with a total return fraction over 0.7 due to its superior energy efficiency and production rate. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The purification of perfluoro(7-methylbicyclo[4.3.0]nonane) industrial fractions with a component content above 0.950 in mass fraction is not effective and requires the use of special separation methods. According to experimental data, the separation factor of the initial mixture during distillation with no additional substances is close to 1. At the same time, the addition of acetone (Ac) makes it possible to significantly intensify the process. Ac allowed for obtaining MBCN with a purity higher than 0.998 in mass fraction in one separation cycle, and the degree of recovery was more than 0.85 by weight. The paper presents data on the distribution of components (target product, identified and unidentified impurities of electrochemical fluorination of decalin) between the distillate and bottom product fractions, separation factor, liquid–liquid phase equilibrium in the MBCN-Ac system, and characteristics of the MBCN-Ac heteroazeotrope.

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. [ABSTRACT FROM AUTHOR]

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.

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. Wood hydrolysates must be concentrated and detoxified before they can be used in fermentation processes. This can be achieved by partial evaporation. Evaporation can be integrated with heteroazeotropic distillation to recover the important inhibitor furfural with high yield and purity without additional energy costs. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A process flowsheet for dehydration of the ethanol-propan-1-ol-butan-1-ol-water mixture has been developed using a thermodynamic and topological analysis of the phase diagram of the system. The operating parameters of the distillation columns involved in the process have been determined, and an energy-efficient flowsheet has been chosen. [ABSTRACT FROM AUTHOR]

Model-based design of separation processes for heterogeneous azeotropic mixtures is a challenging task. The multiplicity of the solutions of equilibrium calculations and the discontinuity due to the potential switching between homogeneous and heterogeneous mixtures on a tray severely complicate the application of deterministic optimization. This paper presents a novel computational approach to reliably determine phase stability and the correct equilibrium solutions in every iteration of the optimization. The approach builds on the decomposition of the optimization problem into a generic superstructure model and an implicit model for equilibrium and enthalpy calculations, which is integrated into the optimization problem by means of an external function. The phase states and equilibrium solutions are determined by means of a reliable homotopy continuation algorithm. An additional reformulation of equilibrium solutions and enthalpy calculations allows overcoming the discontinuity problems. Different case studies illustrate the applicability and show the potential of the proposed method. [ABSTRACT FROM AUTHOR]

This paper studies the separation of an ethyl acetate-isooctane mixture by heterogeneous azeotropic distillation in a batch rectifying column. An initial list of 60 candidates was studied but only methanol and acetonitrile were obtained as potential heterogeneous entrainers. These entrainers form a low boiling heterogeneous azeotrope with isooctane. Experimental verification of the miscibility gap with isooctane was performed at 25 °C for each entrainer giving a smaller region for methanol than for acetonitrile. Feasibility of the heterogeneous azeotropic batch distillation was carried out experimentally in a laboratory batch distillation column having 44 theoretical equilibrium stages and using a high reflux ratio. Several distillate fractions were taken as a function of the temperature at the top of the column. For both methanol and acetonitrile, the main fraction was defined by the condensed vapor providing a liquid-liquid split of the isooctane/entrainer heteroazeotrope into the decanter. Ethyl acetate impurity was detected in both decanted phases, but in much lower amount when using acetonitrile as entrainer. The process with acetonitrile also resulted in a shorter operating time and higher purity and recovery yield of isooctane as the main distillate product. Pure ethyl acetate remained into the boiler at the end of each process. [ABSTRACT FROM AUTHOR]

Shortcut methods are valuable tools in the early stages of chemical process design, where numerous flowsheet alternatives need to be evaluated to determine the most energy-efficient, feasible flowsheet. Various shortcut methods based on tray-to-tray or pinch point analysis for the inspection of feasibility and the determination of the minimum energy demand (MED) for homogeneous azeotropic distillation have been published. For multicomponent heteroazeotropic distillation, however, no generally applicable shortcut methods are available yet. In this work, various shortcut methods for heteroazeotropic multicomponent distillation are assessed. Two novel thermodynamically sound shortcut methods, the feed pinch method (FPM) and the feed angle method (FAM), are proposed to resolve the limitations of existing methods. In particular, the fully algorithmic FAM is applicable to direct, indirect, and intermediate splits for heterogeneous azeotropic mixtures of any number of components. The novel methods are illustrated by four sample separations involving ternary, quaternary and quinternary heterogeneous mixtures. The performance of the FAM is highlighted by an industrial case study, where the effectiveness of an optimization-based conceptual design of a heteroazeotropic column sequence is demonstrated. The computational efficiency of the FAM allows a numerical optimization of the operating points of flowsheet alternatives in order to determine the most energy-efficient variant. [ABSTRACT FROM AUTHOR]

Increasing regulations and constraints have renewed interest for more efficient distillation process in separating azeotropic mixtures and close boiling components. We investigate the feasibility of heterogeneous extractive distillation process in a continuous column considering several feed point strategies for the entrainer recycle stream and for the main azeotropic feed. Depending on these choices, the heterogeneous distillation column is composed of one, two, or three column sections. A differential mass balance model enables to compute continuous liquid composition profiles of the rectifying, extractive, and stripping sections. Unlike homogeneous extractive distillation, reflux policy composed by a single or both decanted liquid phases is considered as well as the external feeding influence on the composition of the top column liquid stream. Limiting operating conditions of key parameters like the entrainer/feed flowrate ratio and reflux ratio required to obtain a target top and bottom product compositions are obtained. For illustration, separation of acetonitrile-water mixture using butyl acetate as a heavy heterogeneous entrainer is selected. In this case, withdrawal of a saddle binary heteroazeotrope is the main difference of this process compared with the well-known heterogeneous azeotropic distillation process where the top vapor product is the lower boiling point of the ternary system. [ABSTRACT FROM AUTHOR]

In this work, the use of heteroazeotropic distillation for separation of thermally unstable substances is discussed. A new process has been developed and analysed, which makes use of the fact that the boiling temperature of a heteroazeotrope is always lower that that of its constituents. Three-phase distillation is characterized by the fact that two liquid phases and a vapour phase coexist in the entire column which ensures low temperatures in the entire apparatus. The process is an alternative or addition to state of the art processes like vacuum distillation. Experiments were carried out in a continuous laboratory scale distillation column equipped with structured gauze wired packing. The experiments prove the feasibility and operability of the new process and provide a sound data base for the development and the validation of process models. It is shown that the process can be successfully modelled using an equilibrium stage approach that accounts for the presence of two liquid phases. Convergence of the simulation model is not trivial. The homotopy continuation method was used for solving the model equations. [ABSTRACT FROM AUTHOR]

• Process feasibility studies should consider a wide range of operating conditions if disturbances are likely to occur. • Combining residue curves and LLE diagrams allows a better understanding of the heteroazeotropic distillation unit. • The top vapor overcooling in the condenser and downstream decantation enhance the separation thermodynamic flexibility. 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. [ABSTRACT FROM AUTHOR]

• Downstream isopropanol separation is studied to achieve cleaner production. • A heteroazeotropic and pressure-swing coupling distillation process is proposed. • Heat pump-assisted dividing wall column is employed to enhance energy efficiency. • A dual-staged sequential iterative method is used in the parameter optimization. • Simultaneous use of DWC and VRC significantly reduced TAC and energy consumption. The isopropanol stream obtained by direct hydration of propylene is mainly the diisopropyl ether-isopropanol-water ternary mixture with a low concentration and multiple azeotropes that leads to high energy usage for downstream isopropanol processing. For this, a new three-column heteroazeotropic and pressure-swing coupling distillation process (TCHPSD) is proposed and further intensified by employing dividing-wall column (DWC) and vapor recompression (VRC) technologies, resulting in two energy-efficient processes (TCHPSD-DWC, TCHPSD-DWC-VRC). Rigorous simulations and a dual-staged sequential iterative method are used in the design and optimization of processes. The results show that the TCHPSD-DWC-VRC process achieves a significant reduction in total annual costs (12.0%) and energy consumptions (63.8%) in comparison with the TCHPSD process. Furthermore, thermodynamic and environmental evaluations based on exergy efficiency, pinch analysis and CO 2 emissions display that this double-effect intensified process is industrially sustainable, especially for industrial sites without access to cheap heat sources. [ABSTRACT FROM AUTHOR]

• A heteroazeotropic and pressure-swing distillation hybrid process is developed. • Intensified models by dividing-wall column and vapor recompression are explored. • All proposed processes are economically viable compared to available treatments. 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. [ABSTRACT FROM AUTHOR]

• Optimization-based design of extractive and heteroazeotropic distillation processes. • Automatic initialization and polylithic modeling and solution approach. • Evaluation of heat integration, vapor recompression and dividing wall columns. • Integration of solvent selection and energy integration. • Efficient comparison of competing process options in three complex case studies. 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. [ABSTRACT FROM AUTHOR]