Reactive Distillation Technology Research Articles

A green synthesis route of cyclohexanol via transesterification reaction intensified by reactive distillation technology

With the increasing demand of cyclohexanol in nylon industry, it is significant to develop a safe, green and economical process to produce cyclohexanol. For this purpose, a novel reactive distillation process through cyclohexyl acetate transesterification with methanol was proposed in this work. The NKC-9 catalyst was preferred to establish the reaction kinetic model based on pseudo-homogeneous model. Seven reactive distillation experiments with pilot-scale for cyclohexanol synthesis were explored to prove feasibility of reactive distillation processes and accuracy of model by comparing simulated results, which ensured the establishment of the process simulation. Furthermore, three reactive distillation processes of cyclohexanol production were designed and optimized by the sequential iterative algorithm based on minimum total annual cost. After optimization of pressure and recycled stream flow, a novel double column of reactive and pressure-swing hybrid distillation process showed the minimized total annual cost per ton product, which was 170.90 $/kg. Finally, total annual cost of transesterification, hydrolysis and hydrogenation processes were compared, and transesterification process demonstrated economic advantage. This work would provide a guidance for cyclohexanol green production by reactive distillation through cyclohexyl acetate transesterification, while a whole, economical and atomic economical reactive distillation process of cyclohexanol production could be established in the future.

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.

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.

Novel intensified process for di-isopropyl ether production from isopropanol etherification using reactive distillation technology

The preparation of di-isopropyl ether (DIPE), as an important chemical solvent, by isopropanol (IPA) etherification is limited by chemical equilibrium and azeotropic formation in its production processes. A novel sustainable etherification process based on reactive distillation (RD) coupled with extractive distillation is proposed. The reaction of IPA etherification was carried out by cation exchange resin NKC-9 in a 250 mL autoclave and fitted by a pseudo-homogeneous model. According to the reaction kinetic, the IPA etherification RD model was established. To confirm the viability of RD and the accuracy of the model, pilot-scale RD experiments for generating DIPE were investigated. Based on the established model matching the pilot scale experiments, the operating conditions of the etherification RD column were optimized by sensitivity analysis. The simulation results show that the conversion of IPA in the RD column can be increased from 18.2 % to 77.9 % compared with autoclave and the yield of DIPE in the whole process flowsheet can reach 99.9 %, which demonstrates that combining reactive distillation with extractive distillation technology is a feasible and advantageous solution for DIPE production.

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.

Determining catalyst loading in reactive distillation column

The widespread industrial application of reactive distillation technology is inseparable from the development of catalytic packing. However, systematic research on the heterogeneous catalyst loading in the reactive distillation column is vacant, and existing studies about catalyst loading on each stage and their distribution ignore the physical structure of the reactive distillation column. In this work, Modular Catalytic Structured Packing combining catalyst bags and structured packing sheets is applied in the modeling and optimization of reactive distillation processes. The catalyst loading on each stage is obtained from three parameters: the catalyst volume fraction of catalytic packing, the catalytic distillation column diameter, and the height of the theoretical stage. Using the effective diffusivity method, a simplified non-equilibrium stage model is chosen to simulate the reactive distillation process, and the bubble-point method for solving the non-equilibrium stage model’s equation system is introduced. The genetic algorithm optimizes both catalyst volume fraction and the number of theoretical stages in the reactive section. Case studies of methyl acetate esterification and ethyl tert-butyl ether (ETBE) synthesis show that greater theoretical stages of the reactive section and enough reflux ratio will reduce the demand of catalysts. Redistribution of catalyst is implemented by dividing the reactive section into several. The non-uniform distribution of catalyst will reduce both energy consumption and catalyst amount for the methyl acetate system, but insignificant for ETBE synthesis, due to different interactions of reaction and separation.

Investigation of sustainable reactive distillation process to produce malonic acid from dimethyl malonate

The new energy battery is currently a hot research topic, leading to an increase in the demand for malonic acid (MA) as a raw material. The objective of the present work is to find a potential reactive distillation (RD) process to solve the problem of low conversion and high energy consumption in hydrolytic system. In the meantime, the RD technology still faces the problem of how to distribute water in the RD column. Aiming at the problem, four different RD processes are proposed: RD combined water separation process (RDWS), RD combined with MA concentration process (RDMC), RD combined methanol separation process (RDMS), and single RD process (SRD). Beforehand, reaction kinetic of dimethyl malonate (DM) hydrolysis was investigated using the ion exchange resin catalysts, and the developed RD model was verified via pilot-scale RD experiments. Finally, the proposed RD process is analyzed from the aspects of economic and environmental and compared with the traditional reaction + distillation (R + D) process. Consequently, the proposed SRD process is a better economy-saving and environment-friendly technology, and has certain directive significance for the industrial production of MA.

A Systematic Methodology for the Synthesis of Advanced Reactive Distillation Technologies

A Systematic Methodology for the Synthesis of Advanced Reactive Distillation Technologies

Structured Data Management for Investigating an Optimum Reactive Distillation Design

Reaction and separation are the two most important processes in the chemical industry that significantly affect the overall energy and cost requirements. Therefore, the operation of integrated reactive separation in a single equipment, such as reactive distillation, potentially increases the chemical process efficiency remarkably. To achieve that advantage, it is vital to design an optimum reactive distillation configuration in the preliminary evaluation. This paper proposes structured data management that can be used to encounter an optimum reactive distillation design. The approach simplified and reduced the data necessity from thousands to dozens by applying a systematic data sorting for the simulation results obtained from the Aspen Plus simulator. Using a case study that is highly relevant to the real chemical processes, i.e., the metathesis of 2-pentene, this study showed that the rule of thumb for determining the optimum design of conventional distillation can be adapted for reactive distillation technology.

Operating windows for early evaluation of the applicability of advanced reactive distillation technologies

Advanced reactive distillation technologies (ARDT) are often overlooked during process synthesis due to their complexity. This work proposes the use of operating windows with additional features to identify suitable operating limits for ARDT. Data needed to construct the operating windows are thermodynamic properties, kinetic parameters, constraints of materials and experimental methods, and heuristics. In addition, two new concepts are proposed to represent complex features: representative components and a sliding window. Results include the identification of suitable operating limits for ARDT to help assess their feasibility early in process design. The proposed approach is demonstrated by case studies. Methyl acetate production can be carried out at low pressures (0.5–3.6 atm), while lactic acid purification requires vacuum conditions (0.3–0.8 atm) to avoid thermal degradation. Tert-amyl methyl ether production was evaluated in two scenarios where the effect of side reactions is evidenced in a reduction of the reaction window due temperature limits to favour the main reaction over side reaction. This study is the first to evaluate advanced reactive distillation technologies using a graphical representation in an operating window to aid process synthesis, where the results provide key selection insights.

Classical vs. reactive distillation technologies for biodiesel production: An environmental comparison using LCA methodology

Sustainable fuels and technologies are expected to significantly contribute towards climate change mitigation considering that the transportation sector provides a 23% share out of the total CO2 emissions. Biodiesel is a green fuel produced by transesterification of triglycerides with an alcohol in the presence of a catalyst. The current study entails modelling and simulation of biodiesel production, through an acid transesterification process, using both classic and intensified methods, coupled with an environmental impact analysis performed following the Life Cycle Assessment methodology. The traditional biodiesel production consists in the synthesis and separation sections, while the intensified method is based on reactive distillation. ChemCAD software was used to simulate and evaluate the processes from a technical point of view. Methanol is generated using CO2 and H2, this method being considered as a new approach for CO2 utilization. Water electrolysis is employed for H2 generation, with either biomass or natural gas as power source. A cradle-to-gate environmental analysis is performed within the current research by means of GaBi software, considering the following system boundaries: i) upstream processes: catalyst supply chain, sunflower oil supply chain, natural gas supply chain, limestone extraction and decomposition, ii) main-processes: methanol and biodiesel production, iii) downstream processes: disposal of wastes. ReCiPe method was chosen as the impact assessment method. High purities for the main product and by-product are obtained (i.e., purities higher than 99%). The outcome of the process simulation points to the conclusion that the intensified path gives better performances from technical point of view. The environmental results show that the classic approach performs better when CO2 and H2 are used as raw materials, while reactive distillation displays a higher efficiency when natural gas is used as feedstock.

Innovative reactive distillation process for the eco-friendly Poly(oxymethylene) dimethyl ethers synthesis from methylal and trioxane

• Improved performance of PODEn selectivity by reactive distillation technology. • A rigorous simulation model of the RD process was developed for the plant design. • The RD process for PODEn synthesis is assessed from techno-economic views. • Proposed the regulation mechanism of the parameters on the polymerization degree. Poly(oxymethylene) dimethyl ethers (PODE n ) is a promising excellent additive for diesel fuels. The PODE n production by traditional reactor conform to Schulz − Flory distribution resulting in low product yield and large circulating material flow, which leads to high energy consumption and cost. This study presents a novel reactive distillation (RD) process for the PODE n synthesis by polymerization reaction from trioxane and methylal. A rigorous simulation model of the RD process was developed for the plant design and scale-up. Also, a sensitivity analysis was performed to determine the influence of key operating parameters on the RD process performance. The production composition analysis indicates that the RD process can effectively control the degree of polymerization and obtain high selectivity for any target product(s). The techno-economic analysis shows that the process is feasible, with over 96% and 13% reduction in CapEx and OpEx, over 68% savings in total annual costs as compared to the reaction-separation technology. Higher conversion and selectivity can be obtained by RD, within lower recirculation rate (only 12281 kg/h instead of 2950 kg/h) as compared to the conventional process.

Review of Neural Network Algorithm and Its Application in Reactive Distillation

Artificial Neural Networks (ANN) can accurately identify and learn the potential relationship between input and output, and have self-learning capabilities and high fault tolerance, which can be used to predict or optimize the performance of complex systems. Reactive distillation integrates reaction and rectification into one device, so that the two processes occur at the same time and at the same place, but at the same time it also produces highly nonlinear robust behavior, making its process control and optimization unable to use conventional methods. Instead, neural network algorithms must be used. This paper briefly describes the research progress of neural network algorithms and reactive distillation technology, and summarizes the application of neural network algorithms in reactive distillation, aiming to provide reference for the development and innovation of industry technology.

Reactive Distillation: Stepping Up to the Next Level of Process Intensification

Reactive distillation (RD) is an efficient process intensification technique that integrates chemical reaction and distillation in a single apparatus. The process is also known as catalytic distillation when a solid catalyst is used. RD technology has many key advantages such as reduced capital investment and significant energy savings, as it can surpass equilibrium limitations, simplify complex processes, increase product selectivity, and improve separation efficiency. However, RD is also constrained by thermodynamic requirements (related to volatility differences and heat of reaction), the need to align the reaction and distillation operating conditions, and the availability of catalysts that are active, selective, and with sufficient longevity. This paper is the first to provide an overview and insights into novel integrated reactive distillation technologies that combine RD principles with other intensified distillation technologies—e.g., dividing-wall column (DWC), cyclic distillation, HiGee distilla...

Improvement of the butyl acetate process through heat integration: A sustainability-based assessment

The heat integration of a conventional and a reactive distillation technologies for butyl acetate production is studied in this work. Different configurations were evaluated and compared to the original designs in terms of their sustainable performances. The comparison was carried out through the Eco-efficiency Comparison Index method by determining six ecological indicators (raw materials consumption, fuel consumption, energy consumption, CO2 emissions, water consumption and wastewater generation), five economic indicators (specific raw materials cost, specific energy cost, specific water cost, liquid waste cost fraction and yield factor) and three safety indicators (safety hazard fire/explosion, chemical exposure index and chronic toxicity factor). The heat integration proved to be a convenient strategy since it significantly improved the conventional and reactive distillation processes’ eco-efficiencies. While the reactive distillation technology has a 53% higher environmental performance than the conventional route, the former’s integrated arrangement increases its eco-efficiency up to 62% when compared to the latter. Finally, we propose new intensified flowsheets for both the conventional and reactive distillation schemes, being the latter approximately 49% more sustainable than the former.

Taking Reactive Distillation to the Next Level of Process Intensification

Reactive distillation (RD) is an efficient process intensification technique that integrates catalytic chemical reaction and distillation in a single apparatus. The process is also known as catalytic distillation when a solid catalyst is used. RD technology has many key advantages such as reduced capital investment and significant energy savings, as it can surpass equilibrium limitations, simplify complex processes, increase product selectivity and improve the separation efficiency. But RD is also constrained by thermodynamic requirements (related to volatility differences and heat of reaction), overlapping of the reaction and distillation operating conditions, and the availability of catalysts that are active, selective and with sufficient longevity.This paper is the first to provide insights into novel reactive distillation technologies that combine RD principles with other intensified distillation technologies – e.g. dividing-wall columns, cyclic distillation, HiGee distillation, and heat integrated distillation column – potentially leading to new processes and applications.

Novel Catalytic Reactive Distillation Processes for a Sustainable Chemical Industry

Reactive distillation (RD) is a great process intensification concept taking advantage of the synergy created when combining (catalyzed) reaction and separation into a single unit, which allows the concurrent production and removal of products. This feat improves the productivity and selectivity, reduces the energy usage, eliminates the need for solvents, and leads to highly-efficient systems with improved sustainability metrics (e.g. less waste and emissions). This paper provides an overview of the key features of RD processes, with emphasis on novel catalytic/reactive distillation processes that can make a difference at large scale and pave the way for a more sustainable chemical process industry that is more profitable, safer and less polluting. These examples include the production of: acrylic and methacrylic monomers, unsaturated polyesters resins, di-alkyl ethers, fatty esters, as well as other short alkyl esters (e.g. by enzymatic reactive distillation). The main drivers for such new RD applications are: economical (large reduction of costs and energy use), environmental (lower CO2 emissions, no or reduced waste) and social (improved safety and health due to lower reactive content, reduced footprint and run away sensitivity). Hence RD technology strongly contributes to all three pillars of sustainability in the chemical process industry. Nonetheless, the potential of RD technology has not been fully tapped yet, and there is still undergoing research to improve it further by various means: e.g. ultrasound or microwave assisted RD, use of high-gravity fields (HiGee), internally heat integration, cyclic operation, or coupling RD with other operations such as membrane separations.

Hydrodesulfurization of Dibenzothiophene in a Micro Trickle Bed Catalytic Reactor under Operating Conditions from Reactive Distillation

Abstract The hydrodesulfurization (HDS) of dibenzothiophene (DBT) is investigated over a commercial NiMoP/γ-Al2O3 catalyst in a micro trickled bed reactor (Micro-TBR) at operating conditions of a reactive distillation (RD) column. An analysis with and without reaction is carried out to have a first understanding on the complex interaction between kinetics and transport phenomena. A set of well-accepted criteria is evaluated to elucidate the presence of heat and mass transport limitations. Residence time distribution (RTD) experiments are performed to evaluate axial dispersion through the estimation of axial dispersion coefficient (Daxial,L) from a convection-dispersion model. Experiments with reaction are carried out using hydrogen and DBT as feedstock at reaction temperatures from 533 to 599 K, pressures from 1.5 to 2.5 MPa and inlet molar flow of DBT from 4 to 12×10–8 mol.s–1. A pseudo heterogeneous model accounting for mass transport limitations is used to describe experiments under reaction conditions. The main findings can be summarized as follows: most of RD operating conditions lead to the presence of interfacial mass transport limitations at both interfaces L-S and G-L; convection-dispersion model is able to describe satisfactorily RTD observations, suggesting that axial dispersion phenomena are negligible; conversion of DBT ranges from ca. 22 to 90% having a selectivity to by-product molecules from 30 to 80%, respectively; and the pseudo heterogeneous reaction model describes observations adequately obtaining activation energies ranging from 49 to 62 kJ mol–1 at pressures from 1.5 to 2.5 MPa, respectively. Estimated activation energies are comparatively lower than the activation energies reported in literature for the conventional HDS process, i.e. 40–160 kJ.mol–1, thereby suggesting an apparent catalytic energy savings by using RD technology.

A Novel Non-Phosgene Process for Polycarbonate Production from CO2: Green and Sustainable Chemistry in Practice

This paper focuses on the world’s first non-phosgene process using CO2 as starting material succeeded in development and industrialization by Asahi Kasei Corp. The Asahi Kasei Process enables high-yield production of high-quality PC having excellent properties and high-purity monoethylene glycol (MEG), starting from ethylene oxide (EO), by-produced CO2 and bisphenol-A without waste and waste water. The innovative reactive distillation technologies in the monomer production and the innovative gravity-utilized, non-agitation polymerization reactor in the melt polymerization, led the new process to success. The monomer process consists of 3 production steps, ethylene carbonate (EC) from CO2 and EO, dimethyl carbonate (DMC) and MEG from EC and MeOH, and diphenyl carbonate (DPC) and MeOH from DMC and PhOH. All intermediates are recycled. The new type polymerization reactor perfectly overcomes the difficulty based on the extremely high viscosity in the melt polymerization of DPC with Bis-A. The by-produced PhOH is recycled to the monomer process. The reduction of CO2 emissions (0.173t/PC 1t) is also achieved, because CO2 used as raw material is utilized as the main chain components of the products. Four commercial plants (Taiwan: 150,000 t/y, Korea: 2 plants of 65,000 t/y, Russia: 65,000 t/y) using the Asahi Kasei Process are now successfully operating, and the plant of 260,000 t/y in Saudi Arabia will start in 2010.

Biodiesel by Catalytic Reactive Distillation Powered by Metal Oxides

The properties and use of biodiesel as a renewable fuel as well as the problems associated with its current production processes are outlined. A novel sustainable esterification process based on catalytic reactive distillation is proposed. The pros and cons of manufacturing biodiesel via fatty acid esterification using metal oxide solid acid catalysts are investigated. Finding catalysts that are active, selective, and stable under the process conditions is the main challenge for a successful design. The best candidates are metal oxides such as niobic acid, sulfated zirconia, sulfated titania, and sulfated tin oxide. Rigorous process simulations show that combining metal oxide catalysts with reactive distillation technology is a feasible and advantageous solution for biodiesel production.