Search Results (70)

Industrial effluents often contain azeotropic mixtures that are difficult to separate by conventional distillation. An illustrative case is the methanol/methyl acetate/ethyl acetate (MA/ME/EA) mixture. To address these challenges, this work studies the conceptual design and optimization of the reactive distillation-based hybrid processes for separating the MA/ME/EA mixture with an EA-rich feed composition (0.25/0.20/0.55 mol fraction). An improved triple-column extractive–reactive distillation with a side-draw product (TCERD-SP) and its heat-integrated variant (TCERD-SP-HI) have been developed. In the TCERD-SP process, EA is strategically withdrawn as a side product, reconfiguring the extractive column into integrated pre-separation and entrainer-recovery sections, thereby reducing entrainer and energy demands. A four-step process design methodology is applied, including thermodynamics analysis, conceptual design, rigorous optimization via Aspen Plus integrated with the genetic algorithm to minimize total annual cost (TAC), and comparative evaluation of economic and environmental performance. The results show that the basic double-column pre-separation-reactive distillation (DCPSRD) process, optimal for a previous feed composition, exhibits unsatisfactory TAC performance for this EA-rich feed composition. Among the configurations studied, the TCERD-SP process exhibits superior performance, saving TAC by 8.4% and 14.4% compared to the TCERD and DCPSRD processes, respectively. In addition, based on the advantage of convenient heat integration between the side reboiler and the reactive distillation column condenser, the heat-integrated TCERD-SP-HI process achieves a further 10.7% TAC reduction. Thus, for this EA-rich feed examined in this work, the TCERD-SP and TCERD-SP-HI processes are demonstrated as effective solutions for recovering these valuable chemicals. Full article

The integration of bioethanol into transportation fuels requires efficient purification methods to overcome the ethanol–water azeotrope, which cannot be separated by conventional distillation. Pervaporation has become an attractive alternative, offering high selectivity while minimising energy consumption. To further improve membrane performance, this study analyses sodium alginate-based hybrid membranes containing binary mixtures of chromite selenides with varying magnetic properties (ZnCr₂Se₄, CdCr₂Se₄, and CuCr₂Se₄). Pairwise combinations of these fillers were introduced to create complex magnetic structures that can influence polymer–filler interactions and molecular transport. Structural, magnetic, and functional characterisation showed that membrane properties were strongly dependent on the type and proportion of fillers. In particular, the CdCr₂Se₄ with CuCr₂Se₄ combination exhibited the most favourable balance between permeation flux and selectivity, achieving the highest parameters, including pervaporation separation index (PSI) reaching 747 kg·m⁻²·h⁻¹. This superior performance is attributed to the synergistic interaction of these two magnetic fillers, which enhances membrane selectivity while maintaining its integrity. This work presents a novel approach to membrane-based separation, advancing the development of energy-efficient, environmentally sustainable bioethanol purification technologies. Full article

Extractive Heterogeneous Azeotropic Distillation (EHAD) is a highly efficient method for separating strongly non-ideal mixtures that exhibit azeotropy. EHAD employs an autoentrainer, typically water, which enables the separation of both ternary and quaternary azeotropic systems. A distinctive feature of EHAD is the relatively small temperature difference between the top and bottom of the distillation column. This unique thermal profile not only simplifies column operation but also creates opportunities for efficient energy integration strategies. This work investigates the impact of energy integration on the applicability and performance of EHAD. Specifically, the study evaluates process intensification through heat integration and heat pump coupling to reduce the overall energy demand of the process. Simulation results demonstrate that, with proper integration, the energy requirement of EHAD can be lowered to 30–40% of that of non-integrated operation. Furthermore, experimental measurements are used to validate the accuracy of the models, confirming the robustness of the proposed approach. The results highlight the capability of EHAD to achieve energy efficient separation of complex azeotropic mixtures. By combining separation principles with sustainable energy utilization, EHAD demonstrates strong potential for industrial applications in the chemical and pharmaceutical sectors. Full article

The decarbonisation of energy-intensive separation processes is critical for achieving net-zero goals in the chemical industry. While widely used for separating azeotropic mixtures, pressure swing distillation (PSD) remains highly energy-intensive due to significant thermal demands. This work presents a comprehensive systems-based assessment of electrified distillation designs, with a specific focus on tetrahydrofuran–water separation as a case study. Using Aspen Plus and Aspen Plus Dynamics, key performance indicators, including controllability, thermal and exergy efficiencies, and CO₂ emissions reduction potential, are evaluated. The electrified configurations employed heat pumps as substitutes for conventional steam heating. Disturbance rejection was applied to compare the input–output pairings and select pairings with the best controllability and disturbance rejection indices. Results showed that the conventional PSD (CPSD) exhibited higher Morari Resiliency Index (MRI) and acceptable Condition Number (CN) values, indicating better robustness and disturbance rejection than the heat pump-assisted PSD (HPAPSD). Despite this, HPAPSD achieved a 59% reduction in primary energy demand, a 23% increase in exergy efficiency, and an 82% reduction in CO₂ emissions. This study demonstrates the potential of electrification to transform PSD systems from rigid, energy-intensive operations into flexible and sustainable processes. The findings support a shift towards integrated, systems-driven design strategies in chemical separation, aligning with broader goals in process electrification, circularity, and net-zero manufacturing. Full article

A techno-economic and environmental evaluation of dehydrating five industrially relevant solvents (isopropanol, acetonitrile, tetrahydrofuran, acetic acid, and n-methyl-2-pyrrolidone) using pervaporation-based processes was performed and compared to their respective traditional distillation processes. A standalone pervaporation and two hybrid processes (i.e., distillation-pervaporation and distillation-pervaporation-distillation) employing HybSi^® AR membranes were simulated in Aspen Plus, where the pervaporation module was modeled as a separator block that followed the experimental data. The experiments were performed at a vacuum pressure of 20 mbar and a temperature of 130 °C. The performance was compared based on several technical, economic, and environmental measures, of which key metrics are the levelized cost of separation (LCOS) and CO₂ footprint reduction. From the economic perspective, the pervaporation-based processes are much more economical than the distillation processes for isopropanol (up to 42% reduction in LCOS) and acetonitrile (up to 39% reduction in LCOS), while their economic performance is similar to the benchmark process in the case of tetrahydrofuran (only up to 4% reduction in LCOS). For acetic acid (9% higher LCOS) and n-methyl-2-pyrrolidone (124% higher LCOS), the pervaporation-based processes do not perform better than the distillation processes under the current technical and economic considerations. However, a sensitivity analysis showed the potential to make the pervaporation-based processes more economical by improving the permeate flux and membrane module cost. On the other hand, the pervaporation-based processes are much more environmentally friendly for all the solvents studied compared to their respective benchmark processes. The reduction in CO₂ footprint is in the order of 86%, 82%, 73%, 82%, and 65%, respectively, for the aforementioned solvents. Full article

Pervaporation is a compelling alternative to azeotrope-breaking and solvent dehydration due to lower energy demand and strong selectivity compared with distillation. FAU-type zeolite membranes combine large pore openings and hydrophilic frameworks with robust chemical stability, enabling water-selective separations from alcohols such as isopropanol and ethanol. Despite numerous synthesis routes, the role of seed crystal size in secondary growth, controlling nucleation density, intergrowth, and defect formation remains insufficiently quantified for FAU membranes under identical growth conditions. Here, FAU layers were fabricated on α-Al₂O₃ supports via secondary growth with varying seed sizes in the nanometer-to-micrometer range (72 nm to 6 μm). Zeolite crystal phase purity and morphology of membranes were assessed by XRD and SEM, with pervaporation of IPA/water 80 wt% at 75 °C quantified flux, separation factor, and permeance. We show that smaller seeds (95.51 nm) increase nucleation density, yielding thinner, more intergrown FAU layers with a higher separation factor but a modest trade-off in flux. Full article

The global demand for sustainable fuels has intensified interest in bioethanol production. Conventional distillation is limited by the ethanol–water azeotrope at ~95.8 wt.% ethanol, necessitating alternative separation methods. This study presents a technical and economic comparison of bioethanol dehydration via azeotropic distillation using cyclopentane as a novel entrainer and extractive distillation with ethylene glycol. Steady-state simulations were conducted in AVEVA PRO/II v.2024 under identical feed conditions, targeting a final ethanol purity of 99.94 wt.%. Cyclopentane proved effective, producing high-purity ethanol and water streams free of entrainer, while ethylene glycol also achieved comparable purity. Economically, the azeotropic process required ~36.5% higher capital investment due to taller columns, larger condensers, and the entrainer cost, resulting in a total annual cost (TAC) ~25.6% higher than the extractive process. Nevertheless, the azeotropic configuration offers lower operating costs, relying solely on low-pressure steam, and residual cyclopentane in ethanol does not compromise fuel quality, unlike ethylene glycol. The study demonstrates that cyclopentane-based azeotropic distillation is technically viable for fuel-grade ethanol production and provides a quantitative framework for evaluating entrainer selection and process economics, particularly in regions where cyclopentane is available or cost-effective. Full article

Since H₂O and Ethylene Glycol Monomethyl Ether (EM) form a minimum-boiling azeotrope, 1-pentanol, 1-hexanol, and 1-heptanol are selected as entrainers to separate the azeotropic mixture (H₂O/EM) using azeotropic distillation. The binary vapor liquid equilibrium (VLE) data were determined at 101.3 kPa, including H₂O/EM, EM/1-pentanol, EM/1-hexanol, EM/1-heptanol, H₂O/1-pentanol, H₂O/1-hexanol and H₂O/1-heptanol. Meanwhile, the Herington area test was used to validate the thermodynamic consistency of the experimental binary data. The VLE data for the experimental binary system were analyzed using the NRTL, UNIQUAC, and Wilson activity coefficient models, showing excellent agreement between predictions and measurements. Finally, molecular simulations were employed to calculate interaction energies between components, providing insights into the VLE behavior. The azeotropic distillation process was simulated using Aspen Plus to evaluate the separation performance and determine the optimal operating parameters. Therefore, this study provides guidance and a foundational basis for the separation of H₂O/EM systems at 101.3 kPa. Full article

Tetrahydrofuran (THF) and methanol (MeOH) are widely used as organic solvents in chemical, pharmaceutical, and other industrial fields. The wastewater from producing 1,4-butanediol contains THF, MeOH, and water ternary azeotropic mixture. In this study, to protect the environment and improve economic feasibility, THF and MeOH from the wastewater must be recovered. Triple-column extractive distillation (TED), pressure-swing azeotropic distillation (PSAD) and reactive extractive dividing-wall column (REDWC) are introduced to separate this ternary system, and the NSGA-III algorithm is introduced to optimize the processes, taking the total annual cost (TAC), CO₂ emissions, and process route index (PRI) as objective functions. The results indicate that in comparison with TED process, TAC of PSAD and REDWC is reduced by 29.92% and 24.25%, respectively, and CO₂ emissions decreased by 18.01% and 25.13%, while PRI increased by 150.25% and 100.50%. This study can provide an insight for the design of ternary azeotropic system separation. Full article

This study presents the first combined techno-economic and environmental analysis of IPA dehydration using HybSi^® membranes across three configurations, offering a low-emission alternative to conventional azeotropic distillation. The processes are simulated in Aspen Plus, and include two hybrid separation processes (i.e., distillation–pervaporation and distillation–pervaporation–distillation) and one standalone pervaporation process. The pervaporation module uses data from experiments that were performed using HybSi^® AR membranes at 130 °C and two vacuum pressures (20 and 50 mbar). The separation processes were systematically compared using a comprehensive set of performance indicators covering technical, economic, and environmental aspects. A new cost-efficiency metric, COPCO, is introduced, alongside updated modeling under 2024 market conditions. The isopropanol recovery and water selectivity were >99.5% and >98.7%, respectively, in all pervaporation-based processes. It was found that the hybrid distillation–pervaporation process resulted in a 42% reduction in the levelized cost of the benchmark azeotropic distillation process, while standalone pervaporation resulted in a 38% reduction. The CO₂ footprint was also reduced significantly in all cases, up to 86% in the case of standalone pervaporation compared to azeotropic distillation. The COPCO analysis revealed that the distillation–pervaporation configuration offers the highest cost-efficiency among the evaluated systems. Sensitivity analysis revealed that feed flow rate, average water flux, membrane module price, membrane lifetime, and steam price significantly impact the levelized cost. Lower vacuum pressure and feed water near the azeotropic composition enhance economic performance. Full article

Separating azeotropes is an important, difficult, and expensive task, in particular for the 2-propanol–water mixture. The literature on the problem is rich in modeling studies but often lacking even the simplest experimental confirmation. In this paper, extractive distillation, liquid–liquid equilibrium-based extraction, and salting-out were experimentally tested for the desired separation. Among the four tested extractive distillation entrainers, none was able—in the investigated experimental setup—to push the system over the azeotropic composition threshold. Four novel hydrophobic deep eutectic extraction media were tested for the desired separation, and those based on menthol or thymol with decanoic acid were found most promising. Among 16 tested salting-out agents, 5 of them produced two-liquid phases, and only 4 hydrophilic inorganic salts promoted 2-propanol separation, with sodium carbonate being the most promising candidate. The purity of the products was tested with FTIR and ¹H-NMR. The experimental findings were compared with COSMO-RS model predictions, with moderate success. Full article

Pervaporation is a proven technology that overcomes distillation to produce high-quality ethanol. The process is modeled and simulated in the literature, but the model’s accuracy with industrial data is rarely discussed. In this work, a commercial pervaporation membrane was modeled and simulated in UniSIM^® (R490) to purify ethanol from water after the azeotrope point of distillation. The pervaporation system was developed manually using a component splitter, adjust functions, and a spreadsheet. Results show that the simulation calculations were acceptable and differed from pilot-plant data by 4.6%. A correction factor was used to reduce the error further to 0.7%. Full article

This study explores the production of anhydrous ethanol from discarded fruits, aiming to determine optimal fermentation conditions and evaluate the feasibility of a green separation technology. Fermentation experiments were performed using juices from Psidium guajava (S1), Carica paapaya (S2), and mucilage residues of Coffea arabica (S3). All fermentations were carried out at a pH of 4.5 for 7 days in 1 L bioreactors. A full 2² factorial design was applied to evaluate the effects of two variables: yeast type (commercial Saccharomyces cerevisiae [CY] vs. native yeast [NY]) and temperature (21 °C vs. 30 °C). Higher ethanol concentrations were achieved with CY at 30 °C, yielding 6.79% ethanol for S3. A multi-criteria matrix prioritized coffee residues due to their high ethanol yield, biomass availability, and economic viability. The ethanol was dehydrated using a packed-bed bioadsorption system with crushed corn, which increased purity from 6.7% v/v to 98.9% v/v in two stages, while avoiding azeotropic limitations. Energy analysis revealed low specific consumption (3.68 MJ/kg), outperforming conventional distillation. The results of this study, obtained at operating temperatures of 30 °C and 21 °C, a pH of 4.5, and an operating time of 7 days in a 1L bioreactor, demonstrate ethanol concentrations of 6.79%, confirming the technical feasibility of using agricultural waste as a raw material and validating the efficiency of a bioadsorption-based dehydration system. These findings address the current gap in integrating green ethanol separation with low-cost agricultural residues and highlight a sustainable alternative for decentralized bioethanol production. Full article

In recent decades, the attention of researchers has been directed towards the study of the dehydration of isopropanol (IPA) through different techniques. Besides its multiple uses in the chemical industry, IPA is also a potential bio-component in eco-friendly gasolines. Extractive distillation is a successful technique for separating IPA from a minimum boiling azeotrope with water. However, the major challenge is the production of fuel-grade IPA (minimum 99.92 mol%) with low expenses. As a consequent step in the investigation of IPA dehydration with propylene glycol as extractive solvent, the present study compares its efficiency and economic viability with two other extractive solvents, namely ethylene glycol (EG) and dimethyl sulfoxide (DMSO). A systematic and comprehensive methodology was developed to design a three-column extractive distillation (TCED) for each investigated solvent. A techno-economic assessment of all the investigated processes concluded that ethylene glycol, followed by propylene glycol, seems to be the most promising solvent in the IPA dehydration process. Further, the heat integration of hot streams (SH flowsheets) demonstrated improvements over 17% in the case of ethylene glycol solvent, around 16% in the case of propylene glycol (PG) solvent, and only 10% (in the case of DMSO solvent) reduction in utility consumption, improving the energy efficiency of TCED processes. Furthermore, SH flowsheets yield a 14% cost saving obtained in terms of total annualized cost (TAC) and, respectively, 8.69%, by comparison with TCED processes. In the case of DMSO solvent, the TAC reduction is only 3.54% due to the capital cost, which has an increase of 3% mainly due to the high solvent cost. Full article

2-Methyl-2-cyclopentenone (MCP) is the main by-product of the newly developed heterogeneous catalysis process for producing crotonaldehyde, which serves as an important intermediate for drug synthesis. However, how to recover and purify MCP from the product mixture is not known. To decipher this, a computer-aided process based on the measured phase-equilibrium data was developed. The improved Rose–Williams equilibrium kettle was used to measure the vapor–liquid equilibrium data for MCP–crotonaldehyde and MCP–water. Surprisingly, MCP and water formed a minimum azeotrope, which aided its own recovery from its dilute solution. The mole fraction of MCP in the azeotrope was 9.1%, the mole fraction of water was 90.9%, and the azeotropic temperature was 96.8 °C. Equilibrium data from the two binary systems were correlated using the Wilson and NRTL activity coefficient models. The NRTL-RK model was selected to simulate the process for recovering and purifying MCP. A two-column process was developed and optimized in this study, and the aim of effectively utilizing the by-product MCP was achieved with this process. Full article