Reactive Distillation Research Articles

Reactive Distillation Process Using a Solid-Solid Reaction for the Separation of Strontium from Spent Nuclear Fuel

Reactive Distillation Process Using a Solid-Solid Reaction for the Separation of Strontium from Spent Nuclear Fuel

Economical process design of reactive-extractive distillation combining variable pressure and heat integration for separating a ternary azeotropic mixture

Research and development of environmentally friendly processes that can generate significant profits has always been a focus of attention in pharmaceutical and chemical fields. In this study, a novel reactive-extractive pressure-swing distillation (REPSD) process was designed to separate tetrahydrofuran (THF)-methanol-water (TMW) ternary azeotropic mixtures. Ethylene oxide (EO) is reacted with water to form ethylene glycol (EG) in a reactive distillation (RD) column, which removes the water from the mixture. Then, the THF-methanol (TM) mixture is separated by extractive distillation (ED) and pressure-swing distillation (PSD). A multi-objective genetic algorithm (MUOGA) with total annual cost (TAC) and total capital cost (TCC) as objective functions, along with heat integration techniques were used to optimise the designed REPSD process. Optimal operating conditions to achieve maximum economic benefits were obtained for the process. Subsequently, the environmental benefits of the process were evaluated. The results showed that the proposed REPSD with heat integration can significantly reduce the TAC and CO2 emissions by 29.1 and 26.9 %, respectively, compared to existing optimal heat integration extractive distillation (HIED) processes. This study provides a new perspective on the separation and purification of ternary azeotropic mixtures.

Preserving precise choreography of bonds in Z-stereoretentive olefin metathesis by using quinoxaline-2,3-dithiolate ligand

The Z-alkene geometry is prevalent in various chemical compounds, including numerous building blocks, fine chemicals, and natural products. Unfortunately, established Mo, W, and Ru Z-selective catalysts lose their selectivity at high temperatures required for industrial processes like reactive distillation, which limits their synthetic applications. To address this issue, we develop a catalyst capable of providing Z-alkenes with high selectivity under harsh conditions. Our research reveals a dithiolate ligand that, stabilised by resonance, delivers high selectivity at temperatures up to 150 °C in concentrated mixtures. This distinguishes the dithioquinoxaline complex from existing Z-selective catalysts. Notably, this trait does not compromise the new catalyst’s usability under classical conditions, matching the activity of known stereoretentive catalysts. Density Functional Theory calculations were employed to understand the reaction mechanism and selectivity, and to investigate the poisoning that the catalyst may undergo and how it competes with catalytic activity. Furthermore, the quinoxaline-based catalyst enables the valorisation of bio-sourced alkene feedstocks and the production of agricultural sex pheromones for pest control.

Alkyl-Substituted Polycaprolactone Poly(urethane-urea)s as Mechanically Competitive and Chemically Recyclable Materials.

We report the mechanical performance and chemical recycling advantages of implementing alkyl-substituted poly(ε-caprolactones) (PCLs) as soft segments in thermoplastic poly(urethane-urea) (TPUU) materials. Poly(4-methylcaprolactone) (P4MCL) and poly(4-propylcaprolactone) (P4PrCL) were prepared, reacted with isophorone diisocyanate, and chain-extended with water to form TPUUs. The resulting materials' tensile properties were similar or superior to a commercially available polyester thermoplastic poly(urethane) and had superior elastic recovery properties compared to a PCL analogue due to the noncrystalline nature of P4MCL and P4PrCL. Additionally, monomers were recovered from the TPUU materials in high yields via ring-closing depolymerization using a reactive distillation approach at an elevated temperature and a reduced pressure (240-260 °C, 25-140 mTorr) with zinc chloride (ZnCl2) as the catalyst. The thermodynamics of polymerization were estimated using Van't Hoff analyses for 4MCL and 4PrCL; these results indicated that the propyl group in 4PrCL results in a lower practical ceiling temperature (Tc) for P4PrCL.

Catalytic disproportionation of trimethoxysilane to monosilane: Studies on catalyst, kinetics and reactor modeling

Monosilane is an indispensable special gas used in semiconductor, photovoltaic, LED, TFT, and lithium-ion battery industries. In this work, a chlorine-free route for monosilane by the disproportionation of trimethoxysilane (TMS) was investigated with a novel efficient and stable solid alkaline catalytic system composed of γ-Al2O3 supported K2CO3. TMS conversion of 71.6 % and silane selectivity of 97.6 % were obtained on the 15K2CO3/γ-Al2O3 catalyst with a high WHSV of 8 h−1, which could be operated stably over 300 h. Furthermore, the reaction kinetic model was established based on the E-R mechanism and a catalytic pathway was proposed according to kinetic results and DFT calculation. A novel reactive distillation reactor with cascaded condensers for silane production was simulated by using Aspen Plus. The results showed that the energy consumption of TMS disproportionation is much lower than that in TCS disproportionation.

Decentralized control of ideal ternary reactive distillation column with inert

Decentralized control of an ideal hypothetical ternary reactive distillation column with an inert component is explored. Both composition measurement based and temperature inferential control structures are designed using simple heuristic approaches (two and three-point). The three-point composition control structure is proposed for the example RD column for the first time in this work. Although stable closed loop responses are seen for the throughput changes for all, the two-point structures have failed to achieve tight control of the product purity in the bottoms or purity of inert in the distillate for the inert composition changes due to fixed reflux ratio. The performances of the three-point control structures for the inert composition changes are quite satisfactory due to the indirect manipulation of the reflux ratio. The independent manipulation of the reflux rate and distillate (instead of fixed reflux ratio policy) is an important control decision for the successful regulation of the example RD column.

Rigorous design and economic optimization of reactive distillation column considering real liquid hold-up and hydraulic conditions of industrial device

The liquid hold-up in a reactive distillation (RD) column not only has a significant impact on the extent of reactions, but also affects the pressure drop and hydraulic conditions in the column. Therefore, the liquid hold-up would be a critical design factor for RD columns. However, the existing design methods for RD columns typically neglect the influence of considerable amount of liquid hold-up in downcomers owing to the difficulties of solving a large-scale nonlinear model system by considering downcomer hydraulics, resulting in significant deviations from actual situation and even operation infeasibility of the designed column. In this paper, a pseudo-transient (PT) RD model based on equilibrium model considering tray hydraulics was established for rigorous simulation and optimization of RD plate columns considering the liquid hold-up both in downcomers and column trays, and a steady-state optimization algorithm assisted by the PT model was adopted to robustly solve the optimization problem. The optimization results of either ethylene glycol RD or methyl acetate RD demonstrated that assuming all the liquid hold-up of a stage belonged to the tray will cause significant deviations in the column diameter, weir height, and the number of stages, which leads to not meeting the separation requirements and even operation hydraulic infeasibility. The rigorous model proposed in this study which considers the liquid hold-up both on trays and in downcomers as well as hydraulic constraints can be applied to systematically design industrial RD plate columns to simultaneously obtain optimal operating variables and equipment structure variables.

Exploration and multi performance evaluation of process intensification for separation of ethyl tert-butyl ether/ethanol from wastewater

Ethyl tert-butyl ether is a green gasoline additive that enhances fuel efficiency and can play an essential role in improving fuel performance. This study explored the separation of wastewater containing ethyl tert-butyl ether and ethanol by changing the pressure and adding reactions based on extractive distillation, using the synergistic effect of the entrainer, pressure, and chemical reaction. By utilizing coupling technology and process intensification concepts, developed a comprehensive series of intensified processes that have clarified the interaction mechanisms between the extractive distillation process (EDP), pressure swing extractive distillation process (PSEDP), and reactive extractive distillation process (REDP). Studying the separation and purification mechanisms of products and intermediates during the reaction process provides theoretical and practical support for optimizing chemical processes. Comparative analysis showed that the reactive extraction pressure swing distillation process (REPSDP) had preeminent economic and environmental benefits. The total annual cost of PSEDP, REDP, and REPSDP was reduced by 5.88 %, 1.68 %, and 10.08 %, respectively, compared with EDP. The gas emissions of PSEDP, REDP, REPSDP, and REPSDP with heat integration process (HI-REPSDP) are all lower than those of EDP. HI-REPSDP saves 47.59 % of gas emissions compared to EDP, highlighting its environmental benefits. HI-REPSDP has the best energy efficiency, reducing energy consumption by 47.58 % compared to EDP, significantly improving the energy utilization rate. It was found that the introduction of heat integration technology had a significant improvement effect. This research has crucial theoretical and practical value and provides guidance and reference for achieving a clean and efficient production process.

Homogeneous reactive distillation: The influence of pressure drop on separation and reaction kinetics

This study investigates the Total Annual Cost (TAC) optimization of a reactive distillation (RD) process for methyl acetate (MA) production as a function of tray pressure drop, focusing on the trade-off between chemical reaction kinetics and separation efficiency. The analysis examines how variations in column diameter and weir height influence the TAC across different liquid hold-ups with and without incorporating a tray pressure drop in the simulations. Results indicate that for larger liquid hold-ups, the decrease in separation efficiency predominates over kinetic advantages, leading to higher energy costs when pressure drop is considered. Despite the loss in separation efficiency with a high weir height, a pressure drop-incorporated column design featuring a high weir height and small diameter is shown to achieve lower TAC due to the comparatively lower installed costs. A reduction of tray liquid hold-up of more than 50 % is found for the optimal column design in the considered case study when the tray pressure drop is considered. A sensitivity analysis towards a hypothetical infinite fast reaction is conducted to illustrate how the energy costs are affected by the kinetic rate of the chemical reaction.

Kinetic modelling and mechanism elucidation of catalyst-free dimethyl terephthalate hydrolysis process intensification by reactive distillation

Polyethylene terephthalate (PET) is a widely used thermoplastic polymer in the packaging and materials industries, and is predicted to have continuous market growth in the future. Methods such as glycolysis and methanolysis of PET have been identified as promising approaches in sustainable chemical recycling of PET. The latter produces dimethyl terephthalate (DMT), which can be easily hydrolyzed to terephthalic acid (TPA) at elevated temperatures and pressures, and further reused for PET production. The aim of this study was to develop a kinetic model for the hydrolysis of dimethyl terephthalate, using the experimental data. Various reaction conditions (temperature, pressure, time) have been investigated and used to calculate the activation energies and reaction rate constants, while the variation in reactor setup with methanol (MeOH) removal was conducted to show its detrimental effect on the efficiency of the reaction and selectivity towards terephthalic acid. The first reaction step of DMT to monomethyl terephthalate (MMT) is relatively irreversible, while the second reaction step of MMT to TPA ceases, as soon as the equilibrium is reached. Highest yields of TPA (76.7 %) were obtained after 40 min at 265 °C, with MeOH removal, and the activation energy was calculated to be 95 and 64 kJ mol−1 for the first and second hydrolysis reaction step, respectively.

Optimization of operating parameters for furfuryl alcohol production in a reactive distillation column using response surface methodology

Furfuryl alcohol is an important platform chemical with a wide range of industrial applications. In this study, the optimization of operating parameters for the production of furfuryl alcohol in a reactive distillation column was investigated using response surface methodology (RSM). The key operating parameters, such as pressure, reflux ratio, feed ratio, and residence time, were examined to determine their influence on the yield of furfuryl alcohol. A Box–Behnken design (BBD) was employed to model the relationships between the process variables and the responses. The optimal operating conditions were determined by maximizing the furfuryl alcohol yield. The results showed that feed ratio and reflux ratio had the most significant impact on the process performance. The optimal operating conditions were found to be a pressure of 0.4 bar, reflux ratio of 5.6 feed ratio of 1, and residence time of 14. Under these conditions, the furfuryl alcohol yield is 99 %.

A new strategy to design the purification process of ethyl tertiary butyl ether gasoline additive via hybrid extractive-reactive distillation

Here we propose a new strategy for designing the purification process of ethyl tertiary butyl ether (ETBE) gasoline additive. Our proposal suggests replacing the last two columns of the triple-column extractive distillation process from previous work with a single reactive distillation column. This column incorporates an ethylene oxide hydration reaction, yielding ethylene glycol, which can be utilized as a solvent for extractive distillation. This replacement is able to reduce the total number of columns, the amount of solvent needed, and significantly decreases total energy consumption up to 32% compared to the original process. Furthermore, it benefits from the redistribution of energy between different steam-grade utilities, enabling significant reduction in operational costs. These advantages result in a 3−22% cost decrease compared to the original process. Overall, the proposed process exhibits significant improvements in energy efficiency and cost reduction with respect to the original process with and without heat integration from previous research.

Circulation of self-supplied water for significant energy recovery through heat integration

This study introduces an overhead heat-integrated distillation column (OHIDiC), a novel approach that maximizes heat recovery by multiple heat exchanges and product circulation. By utilizing the overhead vapor as a direct heat source, low-temperature feed and product water were used as cooling agents, thereby significantly reducing the condenser duty and reliance on cooling utilities. Additionally, the heated feed transfers heat to the column, leading to a substantial reduction of reboiler heat duty. Some of the heated product water is recycled back to the decanter for product cycling, while the rest is released as the final product. This circulation process ensures a continuous coolant supply, which contributes the reduction of condenser duty. Two processes were considered in this study, utilizing the water product from a non-reactive, and from a reactive separation within the system. When applied to the separation of a water-dodecanol mixture, OHIDiC reduced the condenser duty by 69.21% compared to a traditional distillation column, with a 31.46% reduction in the total utility consumption. When reactive distillation was incorporated into the OHIDiC, the higher overhead vapor temperature facilitated high heat transfer in the multiple heat exchange sections, thereby significantly reducing the total thermal load. This resulted in a reduction of up to 46.96% in total heat duty and a 36.06% decrease in CO2 emissions. These findings confirm that the OHIDiC achieves significant energy savings through the utilization of process-derived substances, with pronounced benefits when the temperature of the overhead vapor becomes higher.

Sustainable and efficient separation of ternary multi-azeotropic mixture butanone/ethanol/water based on the intensified reactive extractive distillation: process design, multi-objective optimization, and multi-criteria decision-making

It is of great significance and necessity to develop a sustainable and efficient separation scheme of butanone (MEK), ethanol (EtOH), and water, which are usually formed during the cinepazide maleate synthesis process. To the best of our knowledge, the systematic separation of this ternary multi-azeotropic mixture remains comparatively less studied, compounded by the significant challenges posed by its intricate composition comprising four azeotropes and three distillation boundaries. Therefore, a systematic approach by integrating the process design, multi-objective optimization, and multi-criteria decision-making (MCDM) methods was proposed to achieve the sustainable separation. Initially, three separation schemes, i.e., triple-column extractive distillation (TCED), double-column reactive extractive distillation (DCRED), and side stream intensified double-column reactive extractive distillation (SS-DCRED), were mainly explored via the thermodynamic and kinetic analysis. Subsequently, the multi-objective particle swarm optimization (MOPSO) algorithm was employed to optimize the process based on three objectives namely the total annual cost (TAC), CO2 emissions, and process route index (PRI). Finally, an efficient MCDM method combining CRITIC and TOPSIS was employed to rank the Pareto front solutions of the corresponding process design. Based on the comparison results, the optimal TCED process exhibits the lowest PRI with a decrease of 50.61% and 55.06% compared to that of the SS-DCRED and the DCRED, respectively. It also shows the best performance simultaneously considering economic, environmental, and safety criteria. Of note, the SS-DCRED separation process exhibited the lowest TAC, with a decrease of 60.67% and 11.45% compared to that of the TCED and the DCRED, respectively.

Plant Design for the Production of Propylene Oxide by Isopropylbenzene 2-phenylpropane, or (1-Methylethyl) Benzene (Cumene)

Cumene is a colorless, volatile liquid with a gasoline-like odor. It’s also known as isopropylbenzene, 2-phenylpropane, or (1-methylethyl) benzene. It’s a natural component of coal tar and crude oil, and it can also be employed in gasoline as a blending component. Cumene hydroperoxide is produced by oxidizing cumene with benzene and propylene in the presence of air. As a result, the cumene hydroperoxide is changed to cumyl alcohol, which is then transformed to propylene without the use of oxygen. Propylene oxide is an organic compound produced through various methods such as the cumene process and the hydroperoxide process. The cumene method is preferred due to its low by-product production and high market value of co-products. The reactive distillation process is a feasible method for producing propylene oxide with high purity and reduced costs. Future work includes optimizing processes, developing new catalysts, and improving efficiency. Propylene oxide has practical applications in the production of polyurethane foams, coatings, adhesives, polyether polyols, and propylene glycols.

A CHEMCAD Software Design Approach for Non-Conventional Biodiesel Production Using Methyl Acetate as Feedstock

Biodiesel is a sustainable and renewable fuel generated from renewable resources, including vegetable oil or animal fats. It is thought to be a non-toxic fuel that degrades gradually and causes no harm to the environment. In the present study, a non-conventional supercritical method for industrial biodiesel production is investigated. The non-conventional method refers to a single-step interesterification reaction between triglycerides and methyl acetate resulting in methyl esters of fatty acids and triacetin as a secondary product. Process flowsheet modeling, using CHEMCAD chemical engineering software, was used as an investigation tool. The production capacity was set to 25,000 kg/h biodiesel. Methyl acetate requested in the biodiesel production is produced from methanol esterification with acetic acid using an intensified reactive distillation unit. Methanol, in turn, is obtained using synthetic gas derived from biomass as a raw material, the process representing a new method at the industrial level to solve problems related to the energy that is required, storage and disposal of residual materials, and pollution through the release of pollutants into the air. The methanol synthesis process is similar to the one based on natural gas, consisting of three main steps, namely: (i) synthesis gas production, followed by (ii) methanol production, and (iii) methanol purification. Acetic acid is an essential chemical product, generated in the proposed approach by a sustainable method with low energy consumption and low air emissions, more exactly methanol carbonylation. All the processes previously mentioned: (i) biodiesel production, (ii) methyl acetate production, (iii) acetic acid production, and (iv) methanol production were modeled and simulated, leading to the desired biodiesel productivity (e.g., 25,000 kg/h) with the obtained purity being higher than 99%. Relevant discussions regarding the design assumptions used, the simulation and validation results, as well as other technical issues (i.e., electricity and thermal energy consumption) for the system being simulated, are provided, leading to the conclusion that the proposed route is well suited for the desired application and can deliver significant results. The simulation outcomes have provided confidence in the feasibility and effectiveness of the chosen process design, making it a viable option for further development and implementation.

Optimized energy efficient reactive distillation for octane upgrading with economic and environmental considerations

Advancing fuel efficiency and production technologies can significantly reduce “Well to Wheels” and “Octane on Demand” emissions. This has been accomplished by integrating intensified technologies in fuel refineries. However, maintaining low energy consumption and high octane number while considering the impact of operating conditions under uncertainty on the process feasibility remains a challenge. Therefore, this article proposes a novel absorption heat pump reactive distillation (AHPRD). Aiming to maximize the economic potential of the AHPRD, an optimization framework that considers operating conditions under uncertainty (i.e. temperature (T), pressure (P), reflux ratio (RR), and feed stage (FS)) is developed. The optimization framework synchronizes Monte Carlo simulation and particle swarm optimization (PSO) to maximize the net present value (NPV). The framework used a hybrid Python-DWSim interface platform. The AHPRD was further investigated and compared against existing processes, namely, a conventional process refinery (CP) and reactive distillation (RD), to improve energy saving, increase financial return, and cut CO2 emissions. Attractively, the AHPRD outperforms existing processes, both economically and environmentally, doubling profit values and avoiding 52.2% − 77.4% of CO2 emissions. This study believes that the future direction will be to build an artificial intelligence model for process optimization and economic prediction.

Kinetic insights into energy-saving and low-carbon reactive distillation processes for the transesterification to dimethyl carbonate

The transesterification of propylene carbonate (PC) or ethylene carbonate (EC) to dimethyl carbonate (DMC) by using catalytic reactive distillation (RD) is a promising approach for carbon dioxide utilization. However, there is still scarcity of comprehensive comparison between the two RD processes. Hence, using the UNIQUAC model and kinetics calibrated by literature and our experiments, we conduct an extensive comparison of the two RD processes. Based on the kinetic insights, laboratory RD processes for both reactions are modeled, analyzed, and experimentally validated. Consequently, two RD processes designed to produce 60 ktpy of DMC are optimized and compared. The interplay and control factors between reaction and separation are elucidated and clarified via investigating variations of the actual chemical equilibrium constant profile compared with theoretical values along the reactive section at various pressures, liquid holdups, etc. The results reveal that the optimized EC RD process achieves almost 50 % reductions in both total annual cost and carbon dioxide emission compared to the PC RD process. This work facilitates the carbon neutrality and provides an essential guide for quantitatively assessing the two routes.

Insights on the separation process of the diethyl carbonate plant obtained by ethanol and CO2

This paper presents the techno-economics insights of projects of diethyl carbonate (DEC) production from ethanol and CO2 in which the raw materials are proposed to be obtained from existing plants such as the bioethanol industry. The complete DEC plant was simulated using Aspen Plus®. The exothermic reaction system was modeled in multitubular PFR with CeO2 catalyst and dehydrating agent 2-cyanopyridine (2-CP), achieving an EtOH conversion of 86.04 % and a yield of DEC of 83.34 %. Three different configurations were evaluated in the DEC separation stage aiming to intensify the plant with the use of a sidestream distillation column and reactive distillation column. The integration of the DEC plant with ethanol and sugar biorefineries, offering lower-cost acquisition of raw materials, is the key to making the process economically profitable. The process has the potential to capture 0.088–0.204 kg CO2/kg DEC, demonstrating a promising pathway to extend the life cycle of renewable carbon.

Adaptive fault diagnosis for high-purity carbonate process based on unsupervised and transfer learning

Reactive distillation integrates reaction and distillation to achieve process intensification. And the increasing process complexity urgently requires fault diagnosis system to ensure its safe and efficient operation. However, establishing fault diagnosis model is facing intractable challenges, e.g. scarce labeled data, operating mode changeover due to product proportion variation. To tackle absent labeled data problem, pseudo-labeled database is established by integrating data mining, density-based spatial clustering of applications with noise algorithm and process knowledge, based on which unsupervised deep learning is developed. Besides, to make intelligent fault diagnosis system adaptive for multimode operation changeover, transfer learning with domain adaptation strategy is adopted, which could mitigate different data distributions in various operating states and transfer knowledge learned from source domain to target domain. Taking carbonate ester process with reactive distillation as benchmark, the performance and superiority of unsupervised learning and transfer learning is verified and demonstrated in solving the corresponding puzzle.