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.

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 speudoternary 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. Incomparison 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.

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.

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.

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.

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.

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.

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.

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.

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.

Despite the huge efforts devoted to the development of the electrochemical reduction of CO2 (ECO2R) in the past decade, still many challenges are present, hindering further approaches to industrial applications. This paper gives a perspective on these challenges from a Process Systems Engineering (PSE) standpoint, while at the same time highlighting the opportunities for advancements in the field in the European context. The challenges are connected with: the coupling of these processes with renewable electricity generation; the feedstock (in particular CO2); the processes itself; and the different products that can be obtained. PSE can determine the optimal interactions among the components of such systems, allowing educated decision making in designing the best process configurations under uncertainty and constrains. The opportunities, on the other hand, stem from a stronger collaboration between the PSE and the experimental communities, from the possibility of integrating ECO2R into existing industrial productions and from process-wide optimisation studies, encompassing the whole production cycle of the chemicals to exploit possible synergies.

Ethyl acetate is a platform chemical conventionally obtained through fossil fuel routes, but more recently its production by fermentation from carbohydrates has been scaled up to a pilot scale. Yet, the complexity of downstream processing (low product concentrations in liquid broth and in off-gas, azeotrope formation, and the presence of microorganisms) may complicate industrial application. This original theoretical study is the first to develop advanced downstream processing, based on process intensification principles, for large-scale recovery (~10 kton/year) of ethyl acetate after fermentation. To minimize product losses, ethyl acetate is separated from both the liquid broth and off-gas. The final purification is performed in a highly integrated azeotropic dividing-wall column. The economic and sustainability analysis shows that using refrigeration for initial product separation from the gas phase is more cost-effective (~0.61 $/kg) and less energy-intensive (2.20–2.40 kW_thh/kg) than compression combined with high-pressure condensation using chilled water (1.09 $/kg and 9.98 kW_thh/kg).

Valorization of carbon dioxide towards value added chemicals can drastically mitigate the increased CO2 levels in the atmosphere. In this context, formic acid is a versatile bulk chemical with promising market potential. The novel process design proposed in this work involves a sustainable thermochemical synthesis of formic acid from CO2, which is rigorously simulated using Aspen Plus V12 as a CAPE tool. The process relies on the reverse water-gas shift reaction (RWGS) to synthesize CO from green H2 and CO2. The purified CO is used for the synthesis of methyl formate, which is then hydrolyzed to produce formic acid. To address downstream processing energy intensity, a distillation column with a dividing wall (DWC) is employed. The 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 formic acid. The new process achieves a substantial reduction of 51% in the CO2 emissions, 64% in electricity consumption and 20% in steam usage as compared to conventional fossil fuel-based FA production plants (reference case).

This chapter focuses on the design and control of reactive distillation (RD) columns, which are seen as an integral part of an intensified chemical process. While most of the published literature presents analyses of the RD columns as standalone process units, this work frames the RD columns within a process where recycle streams (to these columns) are present, as typical to industrial practice. These recycle streams originate from the incomplete conversion of reactants or their conversion to undesired by-products. Therefore, the unreacted reactants need to be recovered and recycled, while the by-products need to be recovered and reconverted into reactants followed by their recycle to the RD columns.

A case study of industrial importance is used to illustrate key aspects of design and control of such reactive distillation systems with recycles. The design is focused on developing the topology of the entire process and solving the mass and energy balance based on which key process performance indicators (e.g. reactant utilization, energy efficiency, material and energy intensity, and carbon dioxide emissions) can be analyzed. The control is focused on developing a plantwide strategy to achieve the material inventory (in other words, balancing the reactions' stoichiometry), along with achieving the desired production rate and product purity. Several key process changes (e.g. flowrate and composition changes) are implemented to test the proposed control structure of the plant. All this work makes use of both steady-state and dynamic, rigorous process simulations.

In industrial processes there are instances where heat pump assisted distillation falls short of full electrification, necessitating an auxiliary reboiler. To solve this limiting issue, this short communication proposes a new method using flash vapour circulation (FVC) to recuperate the waste heat within the heat pump cycle. This method incorporates a flash drum after the throttling valve to generate flash vapour. Rather than employing an auxiliary cooler for condensing the mixed vapour-liquid in a conventional heat pump system, the produced flash vapour is circulated back to the compressor inlet to enhance the recycled heat in the reboiler. With proper energy match, this approach has the potential to realise full electrification of distillation. The distillation of methanol/water serves as an illustrative case study, showcasing the viability of FVC which allows additional 22% energy savings, as compared to mechanical vapour recompression. Yet, this strategy may not be advantageous if the waste heat is already maximally utilised in preheating both the compressor and column inlet feed. The separation of tetrahydrofuran/water is used as case study to demonstrate the limitations of this approach.