In extractive distillation for the separation of azeotropic mixtures, eco-friendly solvents have demonstrated potential as greener alternatives to conventional entrainers. However, the absence of thermodynamic data for mixtures that include green solvents presents a significant hurdle to their practical application. This work explores, for the first time, vapor-liquid equilibrium (VLE) data for the azeotropic mixture of n-hexane and ethanol in the presence of the biobased entrainers guaiacol and dimethyl isosorbide (DMI). The VLE measurements were conducted using a Fischer Labodest VLE 502 ebulliometer with varying pressures and entrainer-to-feed ratios (E/Fs). The VLE data met the criteria of the Van Ness method and thereby pass the thermodynamic consistency test. The results confirm that the relative volatility of n-hexane to ethanol is increased by the addition of guaiacol and DMI to the mixture. Moreover, the azeotrope has been successfully removed. The VLE data were well regressed using the Non-Random Two Liquid (NRTL) thermodynamic model, which provided accurate binary interaction parameters (BIPs). The thermodynamic modeling verifies the reliability of the experimental data and its relevance for effective process design, emphasizing the viability of guaiacol and DMI as biobased entrainers for more sustainable and greener extractive distillation.

The electrification of chemical processes and CO₂ utilization are key approaches to improving efficiency and reducing CO₂ emissions in the process industry. The development of electrolyzers has gathered momentum, enabling the potential introduction of renewable electrons into the manufacture of CO₂-based chemicals. While the performance of electrolyzers is subject to improvements driven by the experimental community, the generation of waste heat is unavoidable due to electrical resistances and process inefficiencies within the electrochemical cells. Nonetheless, reusing this waste heat has yet to be investigated for CO₂ electrolyzers. This novel work shows the potential for upgrading the electrolyzer waste heat by means of a heat pump, enabling its utilization in the separation processes downstream of the carbon dioxide electrolyzer. The product chosen is formic acid (60 kt/y), and for our system, the waste heat represents approximately 60 % of the power input to the electrochemical cells, and it can be upgraded from 50 °C to 120 °C to drive the azeotropic distillation of formic acid and water. This integration results in the electrification of 76 % of the separation energy duty, yielding a decrease in CO₂ emissions of 29–84 % compared to the conventional production, depending on the source of electricity. The results demonstrate that the use of traditional heating media in thermal separation processes can be offset and substituted with (renewable) electrical energy, allowing for an increased overall system efficiency. This approach can be readily extended to different productions based on carbon dioxide electroreduction, for example for methanol and ethanol manufacture. This eco-efficient process design leads to a deeper penetration of renewable energy into chemical manufacturing, as both reaction and separation are driven by electricity.

This study investigates the dynamics and control of discretely heat integrated distillation columns, focusing on two configurations: one utilizing a liquid pumparound loop and the other employing liquid injection for waste heat recovery in a multi-stage vapor recompression cycle. These innovative designs eliminate the need for vapor splitters, simplifying operation and enhancing control robustness. As case study, the methanol/water separation process was modelled to achieve 99.99 mol % purity for both products. Dynamic simulations were conducted in Aspen Dynamics to evaluate the control performance for ± 20 % throughput and composition disturbances. Results demonstrated that the proposed control structures, which rely on inferential temperature-based strategies, effectively maintain product specifications and ensure stable operation. This work provides valuable insights into the practical implementation of discretely heat integrated distillation columns, offering a pathway toward energy-efficient and operationally flexible distillation systems.

Gravitation dictates the allowable flow phases and the achievable mass transfer rates in classic distillation columns, which are tall for that exact reason. High-gravity (HiGee) devices use a high centrifugal field to increase the interfacial area through high-speed rotating packing, resulting in a large enhancement of gas–liquid mass transfer and thus smaller equipment volumes. HiGee is an effective process intensification approach to enhance both reaction and separation efficiency. Combining reaction and distillation in a HiGee equipment (R-HiGee) is a topic that attracts significant attention. This paper summarises recent developments in HiGee (reactive) distillation technologies, including process synthesis and design, modelling and analysis of rotating packed bed systems, and equipment design. It also highlights future directions for developments in order to facilitate the systematic evaluation and application of high-gravity (reactive) distillation technologies.

Fermentation can be used to obtain a wide variety of valuable high-boiling components. Among these components, microorganisms can produce aliphatic diols (e.g. propanediols, butanediols, etc.) in significant concentrations (e.g. 5–15 wt.%). Nonetheless, the high boiling points of these components, presence of microorganisms, and formation of by-products complicate recovery after fermentation. Hence, this perspective offers valuable insights into downstream processing options. A novel methodology was developed for recovering high-boiling components from dilute aqueous solutions, whereby both light and heavy impurities are present. The main steps in the proposed methodology are heat pump-assisted preconcentration and final purification in a dividing-wall column. These steps allow effective separation of high-purity product from water, light and heavy impurities. Furthermore, processes for recovery of 1,3-propanediol, 2,3-, 1,4- and 1,3-butanediol, designed according to the proposed methodology, were compared. Downstream processing performance is mainly determined by the product concentration in the fermentation broth, but is also influenced by the amount of impurities in the broth.

Electrification of distillation processes through discretely heat integrated distillation columns (D-HIDiC) is an effective approach to enhance energy efficiency and lower carbon emissions. For separating systems with high temperature lift, multi-stage compression and inter-stage cooling are necessary to link the high-pressure rectifier and low-pressure stripper. Traditionally, heat recovery employs pumparound loops, but this study introduces liquid injection as a more efficient and innovative alternative. Simulation results using methanol/water separation indicate that liquid injection reduces both reboiler duty and compression power, achieving up to 50% primary energy savings compared with conventional distillation columns. Unlike continuous heat exchange in conventional HIDiC (C-HIDiC), D-HIDiC simplifies heat integration, avoiding complex hardware and energy penalties. Comparative analysis across multiple configurations, including SuperHIDiC, confirms the potential of D-HIDiC with liquid injection to fully electrify distillation, eliminate steam utility, and significantly support sustainable industrial operations.

In this work, dimethyl isosorbide (DMI) and 1-butylpyrrolidin-2-one (NBP), as biobased and greener organic solvents, were used for the first time as entrainers in extractive distillation to separate a close-boiling mixture of methylcyclohexane and toluene. Vapor–liquid equilibrium (VLE) data were collected for pseudoternary mixtures consisting of methylcyclohexane and toluene in the presence of DMI and NBP at various entrainer-to-feed ratios (E/F) and pressures. The VLE measurements were conducted by using a Fischer Labodest VLE602 ebulliometer, and the thermodynamic consistency of the data was verified by using the Van Ness test. Both DMI and NBP were found to increase the relative volatility of methylcyclohexane to toluene, successfully eliminating close-boiling behavior. Compared to benchmark entrainers, both outperformed 1-methylpyrrolidin-2-one (NMP) and sulfolane under certain conditions. In comparison with other green entrainers, DMI and NBP showed similar performance to gamma-valerolactone (GVL) and Cyrene under specific conditions. The VLE data were accurately correlated by using the nonrandom two-liquid (NRTL) model.

The butanediols (BDOs), 2,3-, 1,4- and 1,3-butanediol, are platform chemicals that are mainly produced from fossil hydrocarbons but may be obtained through fermentation. However, low product concentration, by-product formation and high boiling temperatures of BDOs hinder downstream processing and increase overall fermentation costs. This study increases the competitiveness of industrial biotechnology by designing a large-scale process (broth processing capacity of 160 ktonne/y) for the final purification of BDOs after fermentation (recovery >99 %). It includes an initial preconcentration step in a vacuum distillation column to remove most water and light impurities. The initial removal of most of the water and the use of a heat pump system allowed significant energy reduction. At the heart of the process is an integrated dividing-wall column that can efficiently purify BDO from the remaining light and heavy impurities. Moreover, a single process design was proven effective in purifying different BDOs to > 99.4 wt%. This was cost-effective (total purification costs of 0.208 – 0.243 $/kgBDO) and energy-efficient (with primary energy requirements of 1.854 – 2.176 kWthh/kgBDO). The proposed purification sequence can be used for each BDO type, which offers flexibility in developing sustainable bioprocesses for BDO production.

The isobaric vapor–liquid equilibrium (VLE) data of the binary mixture of methylcyclohexane (1) + toluene (2) at 101.3 kPa; the pseudoternary mixture of methylcyclohexane (1) + toluene (2) + gamma-valerolactone (GVL) (3) with the entrainer-to-feed ratio (E/F) = 1 (mass basis) at 50, 80, and 100 kPa, and E/F = 2 and 3 at 100 kPa; and the pseudoternary mixture of methylcyclohexane (1) + toluene (2) + 1-methylpyrrolidin-2-one (NMP) (3) with E/F = 1 at 100 kPa were measured using a Fischer Labodest VLE602 ebulliometer. The reliability of the experimental VLE data was tested and confirmed by Van Ness and Fredenslund thermodynamic consistency tests. The experimental results indicate that the presence of GVL and NMP increases the relative volatility of methylcyclohexane to toluene; therefore, both entrainers remove a close-boiling behavior in the mixture. Non-random two-liquid (NRTL) and universal quasi chemical (UNIQUAC) thermodynamic models were applied in the experimental data correlation to obtain the optimum binary interaction parameters. For the mixture involving GVL, the experimental VLE data were accurately correlated by NRTL and UNIQUAC. However, NRTL has more accurate results compared with UNIQUAC. For the mixture containing NMP, both the UNIQUAC and NRTL models show favorable regression results.

BACKGROUND
2-Phenylethanol (2-PE) and 2-phenylethyl acetate (2-PEAc) are valuable aroma compounds with growing market demands. As an alternative to conventional petrochemical production, more valuable natural forms of these chemicals can be obtained by biotransformation. Low product concentrations, resulting from significant product toxicity to microorganisms, and high boiling points of products complicate recovery process. In situ product recovery by liquid–liquid extraction can be used to increase bioprocess yield and productivity. However, the subsequent purification of 2-PE and 2-PEAc is challenging as a consequence of the multiple phases, high-boiling temperatures of main products, occurrence of remaining substrate and byproducts, and presence of microorganisms.

RESULTS
The main goal of this original work is to improve the competitiveness of the biotechnological production of 2-PE by using in silico methods to develop an advanced industrial process for the final purification after centrifugation. An adaptable dividing-wall column was designed to remove 2-PE with 2-PEAc from organic phase or to esterify 2-PE to pure 2-PEAc. The production flexibility of the developed process allows adjustability to market demand. Additionally, recovery of co-produced ethanol from aqueous phase can increase the economic and environmental performance of the developed process. As confirmed by detailed techno-economic analysis, the proposed processes can cost-effectively (total recovery costs of 0.64–0.72 US$/kg2-PE/2-PEAc) and energy-efficiently (primary energy requirements of 1.83–2.05 kWthh/kg2-PE/2-PEAc) recovery of 2-PE or 2-PEAc after biotransformation.

CONCLUSION
The developed process enhances economic and environmental viability of biotechnological 2-PE production by reducing costs and energy requirements, while ensuring flexibility to adapt to market demands.

This study investigates the dynamics and control of a fully electrified heat pump assisted distillation system based on the flash vapor circulation (FVC) concept. The proposed configuration enables complete electrification without auxiliary steam. Two control structures are developed and evaluated in Aspen Dynamics under ± 20 % disturbances in throughput and composition. The first structure CS1 employs single-end temperature control with fixed reflux ratio and demonstrates satisfactory performance in most cases. However, it shows minor deviations in product purity under large composition changes. To address this, a second structure CS2 incorporates an additional composition controller to adjust the reflux ratio, achieving improved purity regulation and energy flexibility. The results confirm the dynamic feasibility and controllability of FVC-based distillation, supporting its integration in future sustainable and flexible separation systems.

BACKGROUND: 2-Phenylethanol (2PE) is a valuable aroma component that can be obtained through de-novo fermentation from glucose. However, its toxicity at very low concentrations (<2.5 g L⁻¹) limits the fermentation titer, rate and yield. To address these limitations, in-situ product removal has been explored, leading to a recent scale-up to pilot scale. Nonetheless, an industrial scale has yet to be achieved. RESULTS: This original research pioneers conceptual development of two large-scale (2 ktonne_2PE/y) production processes for 2PE via de-novo fermentation from glucose. Liquid–liquid extraction with oleyl alcohol and adsorption by hydrophobic resins followed by ethanol desorption, were alternatives considered for in-situ 2PE removal. For either design, solvent recovery and final purification were performed using advanced distillation techniques, including a heat pump-assisted distillation and a dividing-wall column. A fermentation titer of approximately 1.5 g_2PE/L_broth minimized production costs by achieving balance between upstream and downstream processing costs. This resulted in a cost-effective 2PE production for both designs of the recovery process (9.03–9.40 $/kg_2PE). Sensitivity analysis revealed that glucose, oleyl alcohol, and ethanol costs strongly impact total production costs. CONCLUSION: This novel study provides a comprehensive and scalable process framework for the large-scale production of 2PE through de-novo fermentation. Integrating in-situ product removal and energy-efficient purification strategies, it marks a significant step forward in industrial biotechnology.

Green solvents have emerged as promising green entrainers to substitute conventional entrainers in extractive distillation to separate azeotropic mixtures. However, the limited availability of thermodynamic data for green-solvent-containing mixtures continues to hinder their practical implementation in this process. This study is the first to report experimental vapor–liquid equilibrium (VLE) data for the n-hexane + ethanol azeotropic system containing the greener entrainer 1-butylpyrrolidin-2-one (NBP) alongside the benchmark entrainer 1-methylpyrrolidin-2-one (NMP). Using a Fischer Labodest VLE602 ebulliometer, VLE measurements were performed at pressures of 50.0 and 100.0 kPa and various entrainer-to-feed ratios (E/F). The reliability of the reported VLE data was tested and confirmed using the Van Ness thermodynamic consistency test. The results show that NBP enhances relative volatility and effectively eliminates the azeotrope, performing comparably to the benchmark entrainer NMP. The nonrandom-two-liquid (NRTL) model was utilized to regress the investigated VLE data and determine the optimum binary interaction parameters (BIPs). As a result, the NRTL model demonstrates good agreement with the experimental data. This thermodynamic modeling confirms the data’s reliability and suitability for process design, highlighting NBP’s potential as an environmentally friendly alternative entrainer in extractive distillation.

Steel mill off gas fermentation presents a promising green alternative to petrochemical isopropyl alcohol (isopropanol, IPA) and acetone production while potentially reducing greenhouse gas emissions. A pilot-scale study stated negative global warming potential (GWP) at 85% gas conversion and 90% product selectivity. However, industrial-scale plant design including detailed techno-economic assessment (TEA) and life cycle assessment (LCA) remain undescribed. Therefore , this study modelled a heat-integrated 47.5 kton/ year gas fermentation process to IPA and acetone, based on pilot-scale data. The downstream processing was designed using vacuum distillation and heat-pump integrated (extractive) distillation to purify the 50 gproduct/ L broth with bi-omass and acetate as byproducts, to obtain 41.8 kton/ year of 99.6 wt. % IPA and 5.64 kton/ year of 99.0 wt. % acetone. Notably, no steam is consumed and 2.6 MWh of electricity is generated by utilising the energy from the steel mill off gas. The estimated unit production cost (UPC; 0.57 /kgproduct)issignificantlybelowmarketprices(1.65/ kgIPA and 1.45 $/ kgacetone). Moreover, the cradle-to-gate LCA gave GWPs of-1.42 kgCO2-eq/ kgIPA and-1.25 kgCO2-eq/ kgacetone, mainly due to avoided steel mill emissions. Other environmental impacts studied were also lower than for petrochemical production. Only the freshwater use is higher (70 L/ kgIPA and 62 L/ kgacetone) compared to petrochemical production (16 L/ kgIPA and 28 L/ kgacetone). Future research should study the impact of IPA and acetone selectivity and titer on the economic and environmental sustainability of steel mill off gas fermentation to IPA and acetone.

Many fermentation products inhibit their own microbial production, which complicates industrial-scale fermentation development for these products. When a product is volatile, this inhibition can be circumvented by removing product during fermentation through evaporation in a loop around the bioreactor. Microbes can survive this loop if its temperature is reduced using vacuum. Then, regrowing of microbes is not required. From a separation efficiency viewpoint, the evaporation loop should not use a single equilibrium stage, but a multistage vacuum distillation column. Such in situ product removal (ISPR) by vacuum distillation has hardly been recognized as an option, however. Costs for this product removal with subsequent purification are modest, even when product titers are low. A prerequisite is the use of advanced energy integration and heat pumping methods.

Distillation is widely used for separating liquid mixtures, but its high heating demand poses challenges for achieving net-zero emissions. This study presents an innovative approach to electrifying distillation for load adaptability and flexible operation, aligning with dynamic electricity markets driven by renewables. The approach integrates flash vapor circulation and thermal storage into the distillation to optimize power usage and capitalizes on economic opportunities from load-flexible operation in response to fluctuating electricity pricing. A methanol/water distillation case study, using two typical electricity pricing scenarios, demonstrates that the proposed approach is more economically efficient than mechanical vapor recompression distillation, especially in lowering operational costs when the latter operates under fixed electricity pricing. However, compressor capital costs significantly impact overall costs, with sensitivity analysis examining different cost models. This approach can be applied to general distillation, allowing integration with the power sector and demand response programs, while enhancing flexibility, decarbonization, and efficiency.

The valorisation of green hydrogen and captured CO2 to produce chemicals or energy carriers holds immense potential to reduce GHG emissions. Among them, formic acid (FA) is an essential chemical with diverse applications and a growing market demand. Furthermore, due to liquidity at ambient conditions and its chemical stability, it is a promising hydrogen carrier. However, its direct thermochemical synthesis from CO2 hydrogenation still faces significant challenges due to a high thermodynamic barrier. This study presents a novel and eco-efficient process design for a 50 kta FA production from CO2 and green H2. Initially, CO2 is converted to CO as an intermediate compound that undergoes a carbonylation reaction with methanol to form methyl formate, which is then hydrolysed into FA. The major challenges of this new proposed process lie in the purification of CO and the energy-intensive downstream separation of FA. The former is addressed by using the COPure™ technology, which combines chemical and physical absorption, while the latter requires the use of process intensification techniques to minimize the energy and capital expenses. The newly designed process achieves high molar yields of 95 % for CO2 and 96 % for H2 with a specific energy intensity of 21.8 MJ/kg of FA. Notably, the CO2 emissions can be reduced by almost half as compared to the existing FA synthesis from fossil fuels, coupled with a 64 % reduction in electricity usage and 20 % decrease in steam requirements.

Propionic acid is a valuable platform chemical that is usually produced via fossil routes. As these are energy-intensive and eco-unfriendly processes, fermentative production of propionic acid is becoming more attractive. However, the complex downstream processing (due to low achievable product concentrations, high water content, presence of by-products and thermodynamic constraints), presents a potential barrier to scale-up this technology. This original research proposes a novel intensified large-scale (production capacity of ∼ 20 ktonne/y) process for the final recovery of propionic acid after the initial biomass and counterion removal. Vacuum distillation steps ensure the recovery of a high-purity succinic acid product (>99.9 wt%) and a water stream that may be recycled to the fermentation to reduce the fresh water requirements. The main unit that follows is a highly integrated heat pump-assisted dividing-wall column (DWC), which allows the effective separation of propionic (>99.9 wt%) and acetic acid (99.4 wt%) products. Alternatively, it can serve as a reactive DWC that performs the esterification and separation of methyl propionate (99.8 wt%), methyl acetate (91.0 wt%) as higher added value products, and water by-product. If needed, extractive distillation can be implemented additionally to recover methyl acetate at higher purity (99.9 wt%). Overall, both options are proven to be economically interesting (recovery costs of 0.399 – 0.469 $/kg considering the product price of 1.349 – 1.802 $/kg) and environmentally attractive (3.206 – 3.678 kWthh/kg).

PDO (1,3-propanediol) is a platform chemical that is obtained by petrochemical routes and by fermentation. The latter needs relatively complex downstream processing after fermentation, due to the modest concentration of the high-boiling product, and the presence of microorganisms and many impurities in the fermentation medium. This novel research proposes an original large-scale (production capacity of 23 – 32 ktonne/y) process for the final purification of PDO and dominant by-products, from the fermentation of glucose or glycerol. Following the initial microfiltration, diafiltration, ultrafiltration and ion exchange steps, heat pump-assisted vacuum distillation was implemented to remove most of the water from the broth. Afterwards, an advanced highly-integrated dividing-wall column was designed to allow the final purification of PDO (product purity > 99.9 wt%) from light and heavy by-products. Fermentation by-products that are present in significant amounts can also be recovered and valorized. Overall, the developed final purification processes demonstrate cost-effectiveness (0.150 – 0.274 $/kg) and energy-efficiency (1.258 – 3.175 kWthh/kg) which contributes to the competitiveness of the overall downstream processing (0.256 – 0.384 $/kg and 1.487 – 3.496 kWthh/kg).