Reactive Distillation Process Research Articles

Performance analysis of reactive-extractive distillation for multi-azeotropic mixture based on the relationship between economy and conversion rate

The synthesis and purification of ethyl acrylate are of great importance in studying the coupling performance of reaction and separation. In this manuscript, reactive extractive distillation (RED), immiscible-assisted reactive extractive distillation (IRED), and high conversion rate process (HCP) were comprehensively studied. The conceptual design by quaternary phase diagram was demonstrated. The optimal extractant was selected based on relative volatility and quantum chemistry. Multi-objective algorithm was used to minimize gas emissions and total annual cost (TAC). Based on economic, environmental and profit etc., the RED, IRED, and HCP were evaluated. The results show that the TAC, gas emissions, exergy loss, energy consumption, and profit of IRED were decreased by more than 25 %, 21 %, 12 %, 14 %, and 26 % compared to RED. Besides, the profit of the IRED is better than that of the HCP, which indicates that higher conversion rate of the reaction cannot represent better economy of the reactive distillation process.

Optimal design and operation of reactive distillation systems and reactive dividing wall systems with pressure swing distillation and hybrid distillation-pervaporation

Process intensification is essential in exploring more energy-efficient processes, and key examples related to fluid separations are reactive distillation and hybrid distillation-pervaporation processes. This work will consider the reaction and separation of a general quaternary reactive system with a minimum boiling binary azeotrope AC, in a reactive distillation column where, given the thermodynamics limitations, further downstream separation is required. Low and high chemical equilibrium is considered for the reaction. For the downstream purification, both pressure swing distillation and a hybrid distillation-pervaporation process are considered. For each of the structures, their intensified equivalent dividing wall structures are also considered, including a hybrid reactive dividing wall system. It is shown that reactive distillation followed by a hybrid distillation-pervaporation system can save up to 24% energy compared to reactive distillation with pressure swing separation, and that the dividing wall column counterpart structures have lower production-based total annualised costs than the corresponding base systems.

A Study of ZSM-5 Molecular Sieve Shaping for an Innovative Cyclohexene Hydration Process

The development of the zeolite molecular sieves (ZSM-5) molding technique is essential for the cyclohexene hydration reaction distillation process in both industrial and research settings. The reactive distillation process can solve many of the drawbacks associated with the existing technique of manufacturing cyclohexanol via cyclohexene hydration, such as high catalyst digestibility, low conversion rate, and operational challenges. This study developed a series of molded ZSM-5 catalysts with various binder types and contents were constructed. The suggested pseudo-boehmite and hydroxypropyl methylcellulose were chosen as binders for extrusion molding of ZSM-5. The effects of binders on the strength reliability were investigated by strength tests and statistical analysis of the Weibull function. The effects of binders on the physical structure, acidity, and catalytic performance of ZSM-5 were investigated by X-ray diffraction, scanning electron microscopy, physical adsorption of N2, and desorption of NH3. The findings demonstrate that the addition of binder has no effect on ZSM-5's crystal structure. The experiment's results showed that the molded catalyst could be used for the hydration process with over 95% selectivity and a yield of 10.45% cyclohexanol. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Novel dynamic control structure of reactive distillation process for isopropanol production via transesterification

Due to the complicated interaction between reaction and separation in a column, it was inherently challenging to design a control structure for the reaction distillation process. In this research, the control structures of the hybrid reactive distillation process combining pressure-swing distillation (RDC-HDC) and its thermal coupling (RDWC-HDC) processes, were explored for producing isopropanol (IPA) by isopropyl acetate (IPAC) with methanol (MeOH) transesterification. The control performances of only temperature control and temperature difference control schemes for RDC-HDC process were first investigated. The research results displayed that double temperature control (CS3) and temperature difference control schemes (CS4–1, CS4–2 and CS5) for the RDC-HDC process could shorten the maximum transient deviation, amplitude of oscillations and setting time in face with ±20% throughout and ±5% feed composition disturbances. To further improve control characteristics and make control structures concise, a novel control strategy (CS6) by a proportional controller adjusted by reverse action of an IPAC component controller in 34 trays for keeping IPAC composition at a certain range in the RDC-HDC process was developed based on the closed loop analysis before and after disturbance. The application of the innovative control structures (CST4) to the RDWC-HDC process was equally feasible in face of ±10% throughout and ±5% feed composition disturbances. The analysis of integral of squared error (ISE) indicated that a novel control strategy (CS6 and CST4) had better robustness and dynamic performance. These studies contributed to the development of controllability for hybrid reactive distillation processes to produce chemicals for reaction and separation.

Conceptual methods for synthesis of reactive distillation processes: recent developments and perspectives

AbstractReactive distillation (RD) is a process intensification technique that offers major advantages over conventional technologies by enabling the integration of reaction and separation into a single apparatus. This integration introduces and exploits complex interaction between mass transfer, chemical reaction and hydrodynamics within an RD column; however, these complexities can hinder the adoption of RD by industry. Many approaches have been developed by the scientific community to advance understanding and to expedite the initialization of RD design at the conceptual level. This paper critically discusses recent developments in conceptual methods for synthesizing RD processes. This review paper is the first to consider the range of available approaches for assessing the technical feasibility, controllability, economic viability, and sustainability of RD units by taking into account various configurations in which RD is treated as a new unit operation, and as part of process synthesis in a different way of designing processes based on functions. The review also addresses complex configurations, such as advanced RD technologies. Special attention is paid to process modeling and simulation as well as to education. Knowledge gaps to be filled by further research are indicated. © 2024 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Parametric Optimization of a Reactive Distillation Column for the Ethyl Tert-Butyl Ether Production

Combined processes in chemical industry are of current increasing interest, since they present a feasible solution for capital and operating expenses optimization. Multiplicities, which are specific to combined processes, cause certain control and design difficulties, thus, parametric sensitivity analysis and defining the range of existing multiplicities are the necessary part of the sustainable design and development of the combined process. Parametric and design optimization is the way of decreasing capital and operational costs. The paper discusses optimization of the design and operating parameters of an ethyl-tert-butyl ether synthesis reactive distillation column. The research aims to perform a parametric sensitivity analysis and explore existent multiple steady states of the process. The areas of multiple steady states are established, the optimal column design is developed, the optimal operation modes are determined. The procedure suggested in the study is universally applicable for design and optimization of other reactive distillation processes.

Partial heat-integrated reactive distillation process for producing n-propyl acetate using a heat exchanger network

ABSTRACT In this work, a partial heat-integrated reactive distillation process was studied to yield n-propyl acetate. To optimize the operating parameters of two distinct processes, the sequential iteration optimization method was employed. The heat exchanger network (HEN) is an effective approach for the heat-integrated design of a distillation process. Compared with the conventional reactive distillation process, the total annual cost, CO2 emissions and total energy consumption of the partial heat-integrated reactive distillation process decreased by 20.7%, 31.1%, and 32.2%, respectively. The thermodynamic efficiencies of reactive distillation process and partial heat-integrated reactive distillation process were 4.33% and 9.86%, respectively. The significance of this paper is crucial in guiding the process of partial heat-integrated reactive distillation for the production of n-propyl acetate.

Development of a superstructure optimization framework with heat integration for the production of biodiesel

Abstract This work presents a superstructure for maximizing the annual profit of biodiesel production with Advanced Interactive Multidimensional Modeling System (AIMMS). The novelty features are the combination of pinch-based heat integration with a wide range of biodiesel feedstocks and the application of superstructure to evaluate the effect of uncertainties on the optimized design. The case study is a pilot refinery with the infeed capacity of 8000 tonnes feedstock per year. The biodiesel production route from tallow with reactive distillation technology and a heterogeneous acid catalyst has the highest total annual profit of 3.5 million USDs. The heating and cooling utilities can be reduced by 30 % with the heat integration. The result from the sensitivity analysis shows that the biodiesel and feedstock prices, and the production capacity have the most pronounced effects. From technical assessment, the reactive distillation process is the best choice for biodiesel production from different feedstocks.

Simulation study of reactive distillation process for synthesis of dimethyl maleate

Abstract Conventional dimethyl maleate (DMM) synthesis relies on the use of sulfuric acid as a catalyst which requires water washing and produces a large amount of wastewater that harms the environment. The use of this method is expensive since it involves numerous processes such as neutralization of sulfuric acid, washing with water, distillation etc. and the yield of dimethyl maleate is not very high. Reactive distillation integrates the two important industrial processes such as reaction and distillation into a single unit which shortens the overall process, reduces capital and operating costs, and maintains the reaction in a forward direction to enhance the conversion of maleic anhydride by continuously removing of the products. In this work, simulation study based on experimental investigation of reactive distillation process for the synthesis of dimethyl maleate was carried out using Aspen Plus V11. DZH strong cation exchange resin was used as catalyst for esterification reaction of maleic anhydride with methanol. A reactive section of column was packed with Katapak SP type packing loaded with DZH catalyst while non-reactive sections consist of wire gauze packing. In order to describe a reactive distillation process for synthesis of dimethyl maleate, RAD-FRAC equilibrium stage model was employed. The NRTL activity model and RK equation of state model were selected to describe vapor-liquid equilibrium of the system. The reliability of the developed simulated model was verified by validating the simulation results with the experimental ones. The effect of various design and operating parameters on the conversion of maleic anhydride and purity of dimethyl maleate has been studied. It was found that the optimal condition for RD, were as follow: total number of theoretical stages 17, rectifying stages 3, reactive stages 7, stripping stages 5, reflux ratio 0.25, operating pressure 0.1 MPa, reboiler duty 250 Cal/Sec, feed mole ratio 1:5. Under optimized condition the water formed as a results of esterification reaction was constantly removed from the reactive section of the column to maintain reaction balance, the conversion of maleic anhydride was 99.95 %, purity of dimethyl maleate achieved was 0.997 and the reactive distillation process was feasible to produce dimethyl maleate without any wastewater.

General Construction of Asymmetric Amine Ethers via Efficient Transesterification.

A novel method to prepare asymmetric amine ethers is reported. Tertiary amine alcohol hydrogen sulfate intermediates are prepared through a reactive distillation process, followed by the transesterification process to afford eventually asymmetric amine ethers. Experiments and DFT calculations revealed the essential roles the sulfate group plays in the highly selective monoesterification process. This clean method is tolerant towards various functional groups with good yields under mild condition, which is obviously superior compared to the conventional processes.

Entrainer assisted production of high purity 2-phenyl ethyl acetate by reactive distillation

Reactive distillation (RD) is a promising alternative for the processes involving reversible reactions. In this work, we examine its potential for the esterification of a heavy alcohol (2-phenyl ethyl alcohol) with acetic acid in the presence of an ion exchange resin (Amberlyst-15) as the catalyst. The proposed RD process facilitates separation of the desired product, 2-phenyl ethyl acetate, in the pure form and provides a cost-effective and compact alternative to the conventional batch process. We determine the feasibility of this approach by conducting experiments in a laboratory-scale hybrid reactive distillation column having structured packings filled with Amberlyst-15. The experimental results are compared with the predicted values from an equilibrium-staged RD model. The model uses reaction kinetics developed in our earlier studies and the vapor–liquid equilibrium model is based on the experimental data generated in the present work and data available in literature. The experimentally validated model is further used to identify the best possible operating and design parameters to achieve high purity, high conversion and longer catalyst life. All in all, entrainer-based reactive distillation was found to be feasible in this case. The methodology followed here can be easily extended to similar reactions of heavy alcohols with lower carboxylic acids like acetic acid.

Heteropoly acid supported on hierarchical Y zeolite decorated SiC foam as the structured catalytic packing for reactive distillation synthesis of ethyl lactate

Rational design of catalytic packing is crucial in developing reactive distillation (RD) processes as efficient in-situ coupling of reaction and separation is required. Structured catalytic packings are advantageous than the conventional packings (e.g., inert packing + catalyst ‘tea bags’), due to the integration of the catalysis and separation function in one unit, mitigating mass/heat transfer limits. Herein, we present one of the latest developments in the field of structured catalytic packings, which was applied to a pilot-scale RD process of ethyl lactate (EL) synthesis via acid-catalyzed esterification and showed the advantages. The tungstophosphoric acid and hierarchical Y zeolite were uniformly decorated on corrugated silicon carbide (SiC) foam sheets via new preparation method (of ultrasound-assisted impregnation and microwave-assisted drying). The activity of the resulting materials was first assessed in a batch reactor, then the best candidate was employed by the pilot process. Findings from the pilot-scale RD experiments show that the developed structured SiC foam catalytic packing (SSFCP) exhibited an excellent performance (with the normalized conversion of 0.155 mol/gcatalyst), outperforming the conventional seepage catalytic packing internal (0.002 mol/gcatalyst). The influence of various variables (including molar feed ratio, feed position and reflux ratio) on the process performance of the pilot RD rig was also investigated and optimized, achieving a lactic acid conversion of 46.9 % and EL purity of 44.9 % (bottom). The good performance was attributed to the improved mass transfer thanks to SiC foam corrugated sheet (which encourage the vortex formation), thereby enabling more efficient coupling with the reaction. The SSFCP demonstrated reasonable stability, making it a promising candidate for relevant practical RD applications.

Design and multi-objective optimization of reactive pressure-swing distillation process for separating tetrahydrofuran-methanol-water

The low-energy and low-cost process development and design has always been a hot topic and challenge in separating azeotropic systems in the world. In this paper, a novel, energy-saving reactive pressure-swing distillation (RPSD) was, for the first time, designed for separating the ternary mixture of tetrahydrofuran (THF)-methanol–water. In the reactive distillation column, the process of reacting water with ethylene oxide to produce ethylene glycol for the first time was used to separate THF-methanol–water mixture, then the residual mixtures were separated by two pressure-swing distillation columns. Two feasible RPSD separation processes were investigated in terms of thermodynamic modeling and T-xy phase diagram analysis to achieve optimal separation sequence. The two designed separation processes were optimized by a multi-objective genetic algorithm and heat integration to maximize economic benefit. Results demonstrated that, compared to the conventional pressure-swing distillation process, the total annual cost of the designed two heat-integrated processes based on the RPSD-B process were greatly reduced, i.e., 45.9% and 52.2%, respectively. This paper has important guiding significance for the separation and purification of multicomponent azeotropes.

Photocatalytic reactive distillation - A novel process intensification approach for purification of electronic-grade silicon tetrachloride

In order to remove the hydrogen-containing impurities in silicon tetrachloride which are difficult to remove because of the exceptionally low content, a photochlorination reactive distillation process has been proposed to obtain the electronic-grade silicon tetrachloride in this paper. The photochlorination reaction kinetics of C-H compound impurity was studied to verify the photochlorination reactive distillation process. The influence of the key factors in the photochlorination process, such as structure of tubular reactor and the layout of the ultraviolet light, on the content of methylchlorosilane (CH3SiCl3) was investigated in tubular reactor. The industrial production experiments and corresponding simulation of the photochlorination reaction followed by distillation process to conduct deep separation of trace amounts of CH3SiCl3 in silicon tetrachloride raw material were studied to verify the feasibility of process and the accuracy of model. Furthermore, the photochlorination reactive distillation process was proposed to execute further process intensification of purification process of silicon tetrachloride. Finally, after sensitivity analysis and optimization, the photochlorination reactive distillation process achieved 1626.82 $/year TAC savings compared with the photochlorination reaction followed by distillation process.

Process intensification in bio-jet fuel production: Design and control of a catalytic reactive distillation column for oligomerization

Biojet-fuel represents a promising avenue for decreasing CO2 emissions within the aviation industry. Among different biojet-fuel production processes, the Alcohol-to-Jet (ATJ) process stands out as highly promising. Despite its potential, the ATJ process currently faces economic challenges due to low yields and high energy usage. This study introduces a strategy for enhancing the economic feasibility of the ATJ process through process intensification, specifically by incorporating a novel reactive distillation column in the oligomerization stage. This innovative process was evaluated and compared with its conventional counterpart. The total annual cost, eco-indicator 99, and individual risk were chosen as critical parameters for assessing the improvements in cost, environmental impact, and safety brought about by the reactive column. Additionally, control studies were conducted using both Proportional-Integral (PI) and Model Predictive Control (MPC) controllers to determine the feasibility of operating the reactive distillation column. The results suggest that the reactive distillation process offers 20 % cost savings, reduces environmental impact by 50 %, and lowers risk by 22 % when compared to the conventional process. In terms of control strategies, the study found that the catalytic column can be successfully operated using both traditional feedback control and more advanced techniques, such as model predictive control.

An efficient multi-criteria decision making for assessing the optimization of reactive extractive distillation in terms of economy, environment and safety

In order to effectively separate complex azeotropic mixtures, it is crucial to consider economic, environmental, and safety factors during the process design and optimization. This study presents a systematic approach to separate a ternary azeotropic mixture of tetrahydrofuran, methanol, and water by employing multi-objective optimization and multi-criteria decision making. Two energy-efficient configurations, i.e., double-column reactive extractive distillation and reactive-extractive dividing wall column, are proposed by integrating reaction and extractive distillation in a single unit. The developed processes are then optimized using a multi-objective particle swarm optimization algorithm, considering the aforementioned factors. Finally, a multi-criteria decision making technique is applied to rank the Pareto frontier solutions obtained from the optimization process, using a combination of gray relational analysis and entropy weight method. Compared to the base case, the double-column reactive extractive distillation process exhibits a significant reduction in total annual cost (59.39 %) and CO2 emissions (61.75 %). Through comprehensive evaluation, the double-column reactive extractive distillation process is found to be the most effective separation solution among the proposed and existing processes. This systematic approach can be extended to other complex aqueous azeotropic systems for their design, optimization, and decision making.

Dynamic modeling and optimal control of reactive batch distillation: An experimental case study

In the present study, dynamic modeling, optimal operation and control of a reactive batch distillation process is illustrated based on experimental and simulation studies using methyl acetate production case study. An equilibrium stage model, incorporating non-ideal VLE and start-up region of heating, is developed based on data generated on an experimental unit by identifying five input parameters representing uncertainties. The optimal control problem is solved using genetic algorithm, considering the objective function identified on the basis of trend analysis using the developed dynamic model, to find the optimal reflux ratio, heat input to the reboiler, and mole ratio of methanol to acetic acid in the initial reaction mixture. Open-loop and closed-loop implementations clearly illustrate the improved performance with respect to the quantity of methyl acetate in the distillate product with a reasonably high conversion and product purity within reasonably short batch duration, illustrating the successful optimal control implementation experimentally.

Research progress in reactive distillation

As a special distillation process, reactive distillation technology has been widely used in the petrochemical field due to its outstanding advantages such as high efficiency and energy saving. It has been paid more and more attention from researchers in the field of chemical process enhancement since the 1920s. With the progress of social development level, resource conservation and environmental friendliness have become the general trend. In order to pursue the maximization of energy utilization and higher economic benefits, scientific researchers have developed a variety of new reactive distillation processes suitable for various occasions considering the advantages and limitations of traditional reactive distillation technology. The biggest difference from traditional reactive distillation is that the new processes have the characteristics of saving equipment investment, low reaction energy consumption, improving mass transfer, heat transfer efficiency and energy utilization rate. In order to fully understand and apply the technology, this paper describes the process flow of traditional and new reactive distillation technologies in detail, and focuses on analyzing and summarizing the latest developments in the industrial application of reactive distillation technologies in various fields. Finally, it points out that reactive distillation technologies issues that need attention and future development directions.

Understanding the Quantitative Matching Principle of Reaction and Distillation for the Reactive Distillation Process of Cyclohexyl Acetate Synthesis

The matching problem of reaction and separation in reactive distillation (RD) is an urgent problem, and the main reason for little relevant research is that there is no suitable RD for experiments. To understand the matching principle, this work designed KRD001#SCPI and HY@SiC catalytic packings, which tend to different coupling ratios of reaction and separation. The pilot-scale RD experiments and corresponding simulation of cyclohexyl acetate production were studied to verify matching coupling of different reaction RD requirements. Upon verification of this, conventional RD processes were considered from economic, environmental, and energy perspectives, and a new matching form of RD was further proposed based on uneven product distribution. For a ternary reaction system where product was heavy, product concentration moved downward, catalytic packings with high reaction rates were needed at lower reaction sections to avoid a reverse reaction, and those with high separation efficiency are needed at the upper section to separate product and reactants better.

Effect of ethanol on selective oligomerization of isobutene and the simulation of reactive distillation process

AbstractThis paper investigates the selective oligomerization of isobutene in mixed C4 using ethanol as an inhibitor. The effects of ethanol/isobutene, reaction temperature, and reaction space velocity on isobutene oligomerization were examined using two β molecular sieve catalysts. The results indicate that the optimal reaction conditions, at the same calcination temperature, are as follows: The mass ratio of ethanol to isobutylene is 20%, the reaction pressure is 1 MPa, the reaction temperature is 65°C, the reaction space velocity is 2 h−1, the dimerization product C8 has fewer types, and the selectivity can reach over 15%. After adding ethanol, there is a significant inhibitory effect on n‐butene. Furthermore, we used reactive distillation technology to simulate isobutene oligomerization. By optimizing the sensitivity of the tower's operating conditions, we obtained the optimal operational parameters of the tower. Under optimal operating conditions, the conversion rate of isobutene can reach over 80%. The mass fraction of C8 in the oligomerization product accounted for 57.44%, C12 accounted for 8.29%, and ETBE accounted for 34.23%. The reactive distillation technology can improve product selectivity.