Reactive Distillation Research Papers - Academia.edu (original) (raw)

2011, Industrial & Engineering Chemistry Research

The economic optimum design and plantwide control of two alternative processes for cumene manufacture, a conventional process using a vapor-phase packed bed reactor and a reactive distillation (RD) process, are compared in this work. In terms of the total annualized cost (TAC), the RD process is a significant 47% cheaper than the conventional process. This is attributed to the lower capital and energy costs due to process integration. The RD process yield to desired product is also higher. Effective decentralized plantwide regulatory control structures exhibiting good load rejection characteristics are developed for the two processes. A two-point temperature inferential control structure on the RD column is found to work well. The RD process thus appears a promising alternative to the conventional process.

2002, Chemical Engineering and Processing: Process …

A comparison of computer simulation results of reactive distillation obtained by ASPEN PLUS and HYSYS software was done. Esterification of acetic acid and 1-butanol was chosen as the model reaction proceeding in a reactor and reactive distillation column (RD) system. A nearly equimolar reaction mixture was fed into the equilibrium fixed bed reactor and the liquid product was continuously fed into reaction zone of the reactive distillation column. The same mass balance in the reactor and reactive distillation column was used to compare the adequacy of chosen simulation systems. The results of computer simulation have been consequently compared with pilot plant experimental data. A good agreement was reached.

2007, Control Engineering Practice

1988, Chemical Engineering Science

A new set of transformed composition variables is introduced to simplify the design equations for single-feed, multicomponent reactive distillation columns. Based on these equations. a general method of calculating minimum refiux ratios for reactive distillation columns is presented. The new composition variables are also used to derive simple relationships between the dependent design variables which are not evident when the design equations are written in terms of mole fractions.

2003, Chemical Engineering and Processing Process Intensification

In the last years chemical process industries have shown permanently increasing interest in the development of reactive separation processes (RSP) combining reaction and separation mechanisms into a single, integrated unit. Such processes bring several important advantages among which are increase of reaction yield and selectivity, overcoming thermodynamic restrictions, e.g. azeotropes, and considerable reduction in energy, water and solvent consumption. Important examples of reactive separations are reactive distillation (RD) and reactive absorption (RA). Due to strong interactions of chemical reaction and heat and mass transfer, the process behaviour of RSP tends to be quite complex. This paper gives an overview of up-to-date reactive separation modelling and design approaches and covers both steady-state and dynamic issues. These approaches have been applied to several different RA and RD processes including the absorption of NO x , coke gas purification, methyl acetate synthesis and methyl tertiary butyl ether (MTBE) synthesis. #

Distilasi reaktif merupakan salah satu pengembangan proses yang sangat mempengaruhi industri kimia. Pada distilasi reaktif terjadi reaksi kimia dan pemisahan difusional yang terjadi secara simultan. Pada penelitian ini dilakukan evaluasi tray column yang dibandingkan dengan model matematika yang telah dibangun. Penelitian dilakukan dengan melakukan distilasi reaktif menggunakan kolom distilasi dengan umpan etanol-asam asetat. Distilasi reaktif dilakukan dengan variasi konsentrasi umpan masuk dan laju pemanasan pada refluks total. Pengambilan sampel dilakukan setelah keadaan tunak dan dianalisis menggunakan gas chromatography. Profil temperatur diukur setelah keadaan tunak. Hasil pengukuran komposisi dan temperatur dibandingkan dengan model yang telah dibangun dengan asumsi terjadinya kesetimbangan kimia dan kesetimbangan fasa di dalam kolom. Hasil penelitian menunjukkan bahwa konsentrasi umpan memengaruhi konsentrasi etil asetat dan etanol pada distilat, serta asam asetat dan etanol pada produk bawah. Profil temperatur kolom juga turut dipengaruhi di mana semakin tinggi konsentrasi asam asetat pada umpan semakin tinggi temperatur pada titik yang diamati. Ditemukan juga bahwa laju pemanasan tidak begitu berpengaruh terhadap konsentrasi distilat, konsentrasi produk bawah, maupun profil temperatur. Selain itu, diamati bahwa kolom memberikan kinerja yang mirip dengan model yang telah dibangun dengan beberapa penyimpangan kecil. Kata kunci : Distilasi reaktif, etil asetat, kesetimbangan kimia, kesetimbangan fasa

2004, Computers & Chemical Engineering

The potential benefits of applying reactive distillation (RD) processes are taxed by significant complexities in process development and design. The design problem is formulated in the wider context of process development and engineering. From that perspective design methods for RD units developed over the last decades are classified and described. A fingerprint of the most representative work in the three categories, graphical, optimisation-and heuristic-based, is presented and deficiencies are identified. In response to a need for a more integrated design methodology, a conceptual model is offered which uses a hierarchy of embedded design spaces of increasing refinement and conjugates the strengths of both the graphical-and optimisation-based methods. analysis methods evaluation methods good enough models DESIGN DESCRIPTION PHYSICAL BEHAVIOUR PREFERED ALTERNATIVE BUILDING BLOCKS Abstract description Refined description definition/ specification

The production of ethyl acetate is gaining lot of attention because of the growing needs of the greener fuel in the world. Reactive distillation (RD) is a column in which reactor and separator work simultaneously. Ethyl acetate is an ester produced through the reversible reactions such as esterification and etherification in reactive distillation column. In the proposed work modeling of the reactive distillation column for the production of ethyl acetate is given. The model incorporates reaction kinetics and vapor liquid non idealities balanced through MESH (Material Balance, Equilibrium Relationships, Summation equation and energy balance). Present study discussed the current modeling techniques and its importance.

2009, Chemical Engineering Journal

Please cite this article in press as: Q. Smejkal, et al., Ethyl acetate synthesis by coupling of fixed-bed reactor and reactive distillation column-Process integration aspects, Chem. Eng.

2006, Separation and Purification Technology

The possibility of manufacturing a biodegradable polymer from lactic acid has led to extensive research in recovery of lactic acid produced by fermentation, by different downstream processing routes. This paper assesses the suitability of different downstream processing options such as reactive extraction, adsorption, electrodialysis, esterification and reactive distillation. It compares the costs of different process routes. The assessment indicates that the conventional precipitation of calcium lactate, followed by acidification, esterification and hydrolysis will be the most economical route although it generates large quantity of gypsum sludge.

2007, Industrial & Engineering Chemistry Research

In this paper, a novel rate-based description of nonreactive and reactive dividing wall columns is presented. These highly integrated units promise advantages in the context of process intensification. Until now, published studies have been focused on the nonreactive columns, based on equilibrium stage models, whereas the modeling of both dividing wall columns and reactive dividing wall columns, using the rate-based approach, has not been done yet. In the presented model, special attention is given to phenomena that have not been considered in previous publications (e.g., heat transfer through the dividing wall). The model has been applied to a nonreactive, ternary alcohol mixture and successfully validated. The transesterification of carbonates has been identified as an interesting system for the reactive dividing wall column. This reaction system is equilibrium limited and characterized by high conversion, yet low selectivity. Initial simulation studies demonstrate that the selectivity can be significantly increased by means of the reactive dividing wall column. Besides, this highly integrated unit enables a more efficient separation of products and nonconverted reactants, resulting in a reduction in the separation unit number.

The object of this,work is to, determine how the mathematical model would predict the dynamic response of a pilot plant scale distillation column under extreme transient conditions, and to demonstrate the usefulness of the model in... more

2007, Chemical Engineering Science

A hybrid reactive distillation system with high selectivity pervaporation was examined to produce butyl acetate and methanol via transesterification of methyl acetate with butanol. High selectivity pervaporation was combined with reactive distillation to eliminate a hitherto required column for the separation of a methanol and methyl acetate azeotrope. The polyamide-6 membrane was used for this purpose because of its high selectivity for methanol while also allowing sufficient permeate flux. The high purity methyl acetate recovered in the retentate stream leads to high conversion in the reactive distillation column, which enhances the energy savings (up to 71%) of this process. The feasibility of the proposed hybrid processes and several alternative designs were evaluated by rigorous simulation and optimization using the Aspen Plus software package. The effects of several designs and operating variables were also investigated for the proposed design. The high potential of the hybrid reactive distillation and pervaporation system for butyl acetate production is very promising; it may not only reduce the total annual costs relative to conventional systems but may also provide an attractive strategy to address problems associated with methanol and methyl acetate azeotropes in the effluent generated in the polyvinyl alcohol industry.

2007, Chemical Engineering Science

This paper reports on the development of a new industrial process for the production of trioxane (C 3 H 6 O 3 ), the cyclic trimer of formaldehyde (CH 2 O). Trioxane is synthesized from concentrated aqueous formaldehyde solutions, which are inherently reactive complex multicomponent mixtures. Based on the knowledge on the physical chemistry of these complex solutions, reliable modeling of processes containing formaldehyde solutions has recently become possible. This was the key to the process development of the present work. The new trioxane process uses solely distillations for the purification. This is a great advantage compared to the existing process in which an extraction step with tedious solvent recovery is necessary. Conceptual process design was carried out with ∞/∞-analysis using reactive distillation line diagrams. They show the possibility of a pressure swing distillation. Distillation experiments were carried out to validate the results. They prove the feasibility of all distillation cuts and, hence, of the entire process. The resulting new process, including all recycles, was successfully simulated based on a rigorous physico-chemical equilibrium stage model using Chemasim. Moreover, quantitative 1 H NMR experiments were carried out, in which the trioxane formation as well as the formation of important side products in highly concentrated formaldehyde solutions containing up to 0.10 g g −1 sulfuric acid was studied at temperatures up to 338 K to gain reliable information on reaction kinetics, needed for process design. ᭧

2006, Journal of Chemical Technology & Biotechnology

Lactic acid, being virtually a non-boiling compound, is difficult to separate from its aqueous solution by conventional methods such as distillation. It is necessary to convert it to the relatively volatile ester and the separation of the ester, followed by hydrolysis, is recommended as an appropriate method of recovery. In the present work, we explore and investigate a novel reactive distillation strategy to perform esterification, distillation and hydrolysis in a single unit. The experiments were performed in a batch reactive distillation set-up and the results have been explained with the help of an appropriate model. An unsteady state mathematical model based on an equilibrium stage concept was developed for batch reactive distillation. A pseudo-homogeneous model was used for the determination of reaction kinetics. The effect of operating parameters such as feed concentration, mole ratio, catalyst loading, boil-up rate, etc. on the recovery of lactic acid was studied with the help of simulation and experimental results. The feasibility issue of reactive distillation has been discussed based on the results obtained.

2004, Chemical Engineering and Processing: Process Intensification

The ethyl acetate synthesis via reactive distillation is studied theoretically and experimentally using different catalytic packings. Experiments are carried out in laboratory scale in a 50 mm diameter column, packing height of 3 m, and in semiindustrial scale in a 162 mm diameter column, packing height of 12 m. The experimental set-up is similar for both cases. The commercially available packings studied are Sulzer KATAPAK  -S and Montz MULTIPAK  -1.

Biodiesel is a clean burning alternative fuel derived from domestic and renewable resources, which can be used pure or mixed without carrying out major changes in conventional engines. Biodiesel is usually produced by a transesterification reaction. This process requires an alcohol excess to be carried out completely. These excess should be recovered in order to purify the biodiesel and recycle it to the transesterification reactor, resulting in additional demand of energy and operating costs. Reactive distillation is the simultaneous implementation of reaction and separation within a single unit operation. This combined operation is especially suited for liquid phase reactions that must be carried out with a large excess of one reactant. In this study, the surface response methodology and the Aspen Plus software were used for simulating the castor oil biodiesel production by reactive distillation with the aim of obtaining a deep understanding about the process, finding the best conditions for producing the largest amount of fatty acid esters and assess its viability.

In this paper, a reactive distillation (RD) column was applied for synthesis n-butyl acetate from n-butanol and acetic acid. The Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetic model and an equilibrium stage model for separation were employed to study the RD process. The results obtained from the equilibrium stage model agreed well with the experiments. The effects of operating variables on the n-butanol conversion and n-butyl acetate purity were further investigated. The optimal column configuration for the production of n-butyl acetate was designed with 5 rectifying stages, 8 reaction stages and 13 stripping stages by the simulation study. According to the simulation results, n-butanol conversion and n-butyl acetate purity all reached greater than 96%.

This paper presents a novel hybrid process combining thermally coupled reactive distillation with membrane-based pervaporation for enhanced production of n-butyl acetate. A conventional reactive distillation process was used as the base case and first optimized for the transesterification of methyl acetate with n-butanol to produce n-butyl acetate. It was observed that methyl acetate recovered in the recycle stream significantly affects the con-version in the reactive distillation column and overall energy efficiency of the whole process. The existing and proposed configurations were evaluated and optimized by simulation in Aspen Plus. The integration of thermally coupled reactive distillation and pervaporation improved the energy efficiency of the reactive distillation process by preventing remixing effect in the reactive distillation column and eliminating the azeotropic nature of the methanol and methyl acetate in the recycle stream, respectively. Finally, integration of the thermally coupled reactive distillation with a commercial pervaporation membrane was explored to take synergistic advantage of the thermally coupled reactive distillation and pervaporation hybrid configuration. As a result, the proposed hybrid design showed remark-ably improved energy efficiency and economics. The total reboiler duty and total annual cost reduced to 63 and 43%, respectively, compared to those of the base case.

2011, ISA transactions

In this paper, an artificial neural network (ANN)-based nonlinear control algorithm is proposed for a simulated batch reactive distillation (RD) column. In the homogeneously catalyzed reactive process, an esterification reaction takes place for the production of ethyl acetate. The fundamental model has been derived incorporating the reaction term in the model structure of the nonreactive distillation process. The process operation is simulated at the startup phase under total reflux conditions. The open-loop process dynamics is also addressed running the batch process at the production phase under partial reflux conditions. In this study, a neuro-estimator based generic model controller (GMC), which consists of an ANN-based state predictor and the GMC law, has been synthesized. Finally, this proposed control law has been tested on the representative batch reactive distillation comparing with a gain-scheduled proportional integral (GSPI) controller and with its ideal performance (ideal GMC).

2009, Chemical Engineering and Processing: Process Intensification

We performed steady state and dynamic simulations of a reactive Petlyuk column through an equivalent reactive dividing wall column (RDWDC). In the case of the reaction between ethanol and acetic acid catalyzed by sulfuric acid to produce ethyl acetate and water, we have found that the reactive Petlyuk column can achieve set point changes in two control loops of temperature. Also, for load rejection, the control loops can eliminate the effect of the disturbances in the feed composition. These results and previous knowledge reported about thermally coupled distillation columns and reactive distillation were considered to design and implement a RDWDC.

2006, Separation and …

Lactic acid is a simple compound containing both the hydroxyl and carboxylic acid groups, which permit it to participate in many interesting and valuable chemical reactions. Among the known reactions of lactic acid the dehydration to... more

2011, Chemical Engineering Journal

Hydrolysis of methyl lactate to lactic acid in a reactive distillation column is widely used in the purification of lactic acid. In this work, optimal operations of conventional and inverted batch reactive distillation columns undergoing the hydrolysis reaction are presented. Minimum time optimisation problem is formulated incorporating a process model within gPROMS software and is solved for different range of lactic acid purity and the amount of product using both columns. For a given column type and configuration the minimum operation time is obtained by optimising the reflux ratio profile. For conventional column, the lactic acid being the heaviest in the reaction mixture, reflux ratio policy plays an important role in removing the light product methanol from the top of the column while ensuring the presence of both reactants in the reaction zone to maximise the conversion to lactic acid. For inverted column, reboil ratio policy plays an important role in removing the lactic acid from the bottom of the column while ensuring the presence of both reactants in the reaction zone to maximise the conversion to lactic acid. For some cases (although limited) it is observed that for low lactic acid product purity the conventional column outperforms the inverted column while for high product purity the inverted column outperforms the conventional column in terms of batch time.

2008, Industrial & Engineering Chemistry Research

The impact of altering feed tray locations (for the purpose of saving energy) on the controllability of double feed reactive distillation (RD) columns is evaluated for two case studies: a hypothetical ideal RD column and a methyl acetate RD column. Energy savings of 18.3% and 36.4% over the conventional design (feed immediately above and below the reactive zone) is achieved for the ideal and methyl acetate systems, respectively. A steady-state bifurcation analysis shows that, for both systems, output multiplicity, with respect to reboiler duty, occurs at a fixed reflux rate for the different designs (conventional/altered feed tray location). The output multiplicity is eliminated at a fixed reflux ratio. Closed-loop dynamic simulation results show that the controllability of the internally heat integrated ideal RD column deteriorates, compared to the conventional design. Unlike the conventional design, temperature-based inferential control is infeasible and compositionbased control structures must be used. For the methyl acetate column, on the other hand, heat integration by altering the feed locations entails no loss in controllability using two-point temperature inferential control.

2011, 2011 IEEE International Conference on Control System, Computing and Engineering

Methyl Tert-butyl Ether (MTBE) is usually used as solvent, chemical reagent and antiknock additive to improve octane number of gasoline and can be efficiently produced using reactive distillation column. Maximum production of the MTBE can be achieved if the reaction can be kept at optimum operating conditions and column configuration. In practice, changing the column configuration such as tray or catalyst location always incurs high cost. Therefore, the development of the MTBE reactive distillation model can serve as an important tool in predicting and investigating the optimum production for MTBE without the need to run the actual experiment. Therefore, the development of the MTBE reactive distillation model is essential to simulate the process which can lead to high yields of MTBE production. In this work, a detailed equilibrium (EQ) model for continuous reactive distillation (RD) processes is developed using Aspen Plus™ and Matlab TM software. The simulation results achieved is compared with data available in the literature. The validated model is then further used to study the interaction of various inputs and output variables of the MTBE process which can be used for future empirical model development and control studies.

2006, Journal of Chemical Technology & Biotechnology

Separation and purification of lactic acid from the fermentation broth are difficult because of its nonvolatile nature and the presence of other organic acids. Esterification of lactic acid with methanol followed by hydrolysis of the separated methyl lactate is an effective technique for this purpose. A continuous process for recovery is proposed and various aspects are evaluated through simulation and experiments. In the proposed route, a vapor stream containing methyl lactate is removed from a two-phase CSTR, used for esterification, operated under boiling conditions. The ester thus separated from the aqueous solution is further hydrolyzed in a reactive distillation column. Continuous removal of the volatile component (i.e. methanol) from the reaction zone increases conversion, thus pure lactic acid is obtained from the bottom of reactive distillation column. The results obtained in the experiments are compared with the simulation results. Further simulation studies were performed to obtain the suitable operating conditions for higher conversion and concentration of lactic acid.

2003, Chemical Engineering and Processing: Process Intensification

2005, Chemical Engineering Research and Design

A procedure that combines feasibility analysis, synthesis and design of reactive distillation columns is introduced. The main interest of this methodology lies on a progressive introduction of the process complexity. From minimal information concerning the physicochemical properties of the system, three steps lead to the design of the unit and the specification of its operating conditions. Most of the methodology exploits and enriches approaches found in the literature. Each step is described and our contribution is underlined. Its application is currently limited to equilibrium reactive systems where degree of freedom is equal to 2 or less than 2. This methodology which provides a reliable initialization point for the optimization of the process has been applied with success to different synthesis. The production of methyl-tert-butyl-ether (MTBE) and methyl acetate are presented as examples.

2009, Computers & Chemical Engineering

Catalytic reactive distillation offers new opportunities for manufacturing fatty acid esters, involved both in biodiesel and specialty chemicals. A key problem is the effective water removal in view of protecting the solid catalyst and avoiding costly recovery of the alcohol excess. This work proposes a novel approach based on dual esterification of fatty acid with light and heavy alcohols, namely methanol and 2-ethylhexanol. These two complementary reactants have an equivalent reactive function but synergistic thermodynamic features. The setup behaves rather as reactive absorption combined with reactive azeotropic distillation with heavy alcohol as co-reactant and water-separation agent. Another element of originality is the control of the inventory of alcohols by fixing the reflux of heavy alcohol and the light alcohol column inflow. This strategy allows achieving both stoichiometric reactant feed rate and large flexibility in ester production. The distillation column for recovering light alcohol from water is not longer necessary. The result is a compact, efficient and easy-to-control multi-product reactive setup.

2004, Industrial & Engineering Chemistry Research

This work proposes a simplified methodology for the analysis and design of reactive batch distillation columns based on the McCabe-Thiele method for reactive continuous columns and on the concept of a reactive difference point. To extend the application of the concept of a reactive difference point for reactive batch distillation columns, expressions for the McCabe-Thiele operating line and for the dynamics of the reboiler in the reactive case have been derived; two cases are considered depending upon the phase in which reactions occur (i.e., liquid or vapor). We also provide an approach to the derivation of an expression to calculate the molar turnover flow rate by considering each reactive distillation plate as a combined system of a conventional equilibrium stage linked to a chemical reactor (phenomena decomposition). Furthermore, we present our derivation of the Underwood equations (minimum reflux) for continuous and batch reactive distillation columns. Finally, five illustrative examples allow us to show that our results present reasonable agreement with those obtained through BatchFrac of AspenPlus.

2007, Chemical Engineering Research & Design

First steps of the development of a catalytic reactive distillation process for the production of n-propyl acetate based on experiments and simulations are proposed. The kinetics for homogeneously (sulphuric acid) and heterogeneously (Amberlyst 15) catalysed reaction were investigated and the constants for a pseudo-homogeneous model are presented. Pilot plant experiments were performed using a homogeneous strong acid catalyst in a

1997, Reactive & Functional Polymers

Diethoxymethane was prepared in batch mode as well as in continuous Reactive Distillation Column (RI@) from ethanol and aqueous formaldehyde in the presence of a macroporous cation-exchange resin Indion-130. The batch reaction was studied for the effect of catalyst loading, mole ratio, concentration, temperature, etc. A pseudo homogeneous model was used to explain the batch kinetics and the kinetic parameters were evaluated. In the case of RDC, the effect of various parameters such as residence time, reflux ratio, mole ratio, feed concentration, feed configuration, etc. on the conversion and product purity was studied and evaluated.

2010, Applied Biochemistry and Biotechnology

Biodiesel is a clean burning fuel derived from a renewable feedstock such as vegetable oil or animal fat. It is biodegradable, non-inflammable, non-toxic, and produces lesser carbon monoxide, sulfur dioxide, and unburned hydrocarbons than petroleum-based fuel. The purpose of the present work is to present an efficient process using reactive distillation columns applied to biodiesel production. Reactive distillation is the simultaneous implementation of reaction and separation within a single unit of column. Nowadays, it is appropriately called "Intensified Process". This combined operation is especially suited for the chemical reaction limited by equilibrium constraints, since one or more of the products of the reaction are continuously separated from the reactants. This work presents the biodiesel production from soybean oil and bioethanol by reactive distillation. Different variables affect the conventional biodiesel production process such as: catalyst concentration, reaction temperature, level of agitation, ethanol/soybean oil molar ratio, reaction time, and raw material type. In this study, the experimental design was used to optimize the following process variables: the catalyst concentration (from 0.5 wt.% to 1.5 wt.%), the ethanol/soybean oil molar ratio (from 3:1 to 9:1). The reactive column reflux rate was 83 ml/min, and the reaction time was 6 min.

In this paper the detailed mathematical dynamic model of semi-batch reactive distillation is formulated for ethyl acetate synthesis (estrefication reaction). The model is composed of material balance, heat balance, and equilibrium equations. The set of nonlinear ordinary differential equations governing the unsteady state composition profile in a semi-batch reactive distillation column were solved by using fourth order Runge-Kutta integration method with the aid of the powerful MATLAB 6.5 program which used to simulate and optimize the semi-batch reactive distillation column. The simulation provides compositions, temperatures and holdups profiles along the column as a function of time. Also the reactant conversion and ethyl acetate purity in distillate are calculated. Finally, the simulation results are analyzed to find the optimum operating policy of reflux ratio, Ethanol/Acetic acid and catalyst weight.

2008, Chemical Engineering Science

1997, Reactive & Functional Polymers

1,3-Dioxolane was prepared from ethylene glycol and formaldehyde in the presence of a cation-exchange resin. The reaction was studied in batch mode, semi-batch reactive distillation mode and in a continuous reactive distillation column. A pseudohomogeneous model explains the batch kinetics. Higher than 98% conversion of formaldehyde was achieved in semi-batch reactive distillation. Recovery of ethylene glycol from aqueous solutions via reaction kith solid paraformaldehyde in a semi-batch reactive distillation mode was also studied.

2011

Methyl Tert-butyl Ether (MTBE) is usually used as solvent, chemical reagent and antiknock additive to improve octane number of gasoline and can be efficiently produced using reactive distillation column. Maximum production of the MTBE can be achieved if the reaction can be kept at optimum operating conditions and column configuration. In practice, changing the column configuration such as tray or catalyst location always incurs high cost. Therefore, the development of the MTBE reactive distillation model can serve as an important tool in predicting and investigating the optimum production for MTBE without the need to run the actual experiment. Therefore, the development of the MTBE reactive distillation model is essential to simulate the process which can lead to high yields of MTBE production. In this work, a detailed equilibrium (EQ) model for continuous reactive distillation (RD) processes is developed using Aspen Plus™ and Matlab™ software. The simulation results achieved is compared with data available in the literature. The validated model is then further used to study the interaction of various inputs and output variables of the MTBE process which can be used for future empirical model development and control studies.

2014, Chemical Engineering Research and Design

Available at: https://works.bepress.com/adrian_bonilla_petriciolet/287/ chemical engineering research and design 9 2 ( 2 0 1 4 ) 1-12 a b s t r a c t Until now, few studies have proposed analytical short-cut methods for reliably designing multicomponent reactive distillation columns. Therefore, in this study we have improved and extended a design methodology for the design of RD columns of multicomponent systems. We have developed a graphical design method, based on distillation lines and tray-by-tray calculations defined in terms of reaction-invariant composition variables, to determine RD design parameters such as the number of theoretical stages, operating reflux ratio, the feed tray location and the top or bottom flow. In this note, we report our extended and improved method, which is analytical and useful for reliably determining the design parameters of multicomponent RD systems. We study the synthesis of TAME with inert components (with different feed thermal conditions) as case of study to show the effectiveness of the proposed strategy. Results obtained with our strategy show a significant agreement with those obtained using a rigorous model of commercial simulator AspenONE Aspen Plus ® . literature, the commercial applications of RD are still limited because of the partial knowledge about the control performance and operation complexity of these separation systems. Many of the current design strategies are often tedious from the point of view of their implementation and imply iterative procedures, which do not necessarily guarantee an optimal design of distillation system . As a consequence, an increasing interest in the development of effective and robust methods and simulation tools for the determination of optimum column configuration has been turned into a great design challenge. Until now, robust shortcut methods have been reported especially for the modeling of non-reactive separation systems involving homogeneous and heterogeneous azeotropic multicomponent mixtures. These methods are based on tray-to-tray calculations, pinch 0263-8762/$ -see front matter

2004, Chemical Engineering and Processing: Process Intensification

The scale-up of reactive distillation columns with catalytic packings requires the knowledge of reaction kinetics, phase equilibrium and packing characteristics. Therefore, pressure drop, liquid holdup and separation efficiency have been determined for the catalytic packing MULTIPAK ® . A new hydrodynamic model that describes the counter-current gas-liquid flow for the whole loading range and considers the influence of the column diameter has been implemented into a ratebased column model. Simulation results for the methyl acetate synthesis are compared with pilot plant experiments that cover a wide range of different process conditions. The experiments are in good agreement with the simulation results and confirm the applicability of the modelling approach for reactive distillation processes with catalytic packings.

2011, Energy

Biodiesel can be produced from a number of natural, renewable sources, but vegetable oils are the main feedstocks. The current manufacturing biodiesel processes, however, have several disadvantages: expensive separation of products from the reaction mixture, and high costs due to relatively complex processes involving one to two reactors and several separation units. Therefore, to solve these problems, in recent years several researchers have developed a sustainable biodiesel production process based on reactive distillation. In this paper the production of biodiesel using feedstock mixtures of fatty acids is explored using reactive distillation sequences with thermal coupling. The results indicate that the complex reactive distillation sequences can produce a mixture of esters as bottoms product that can be used as biodiesel. In particular, the thermally coupled distillation sequence involving a side rectifier can handle the reaction and complete separation in accordance with process intensification principles.

2010, Chemical Engineering and Processing: Process Intensification

Successful process intensification (PI) stories applied broadly are the reactive distillation (RD) processes used in esterification syntheses. One application is developed here with the heterogeneously catalyzed synthesis of n-propyl propionate (ProPro) from 1-propanol (ProOH) and propionic acid (ProAc). In this investigation, conventional RD of ProPro was further improved. With the objective to recover product and reactant, an experimental column set-up was equipped with a decanter on top enabling to separate the distillate product into two main streams. The aqueous phase was discharged and part of the organic phase was refluxed back to the column. Experimental results comprising temperature and composition column profiles were obtained in a pilot-scale column (DN-50), equipped with structured packings (Sulzer BX and Katapak-SP 11 with Amberlyst 46 TM for the reactive part). For simulation studies a non-equilibrium stage model (NEQ model) was applied which shows satisfactory agreement with the performed experiments. Further theoretical investigations of relevant operating parameters (total feed, molar feed ratio, reflux ratio and heat duty) and their effect on the overall process performance were realized. Studies with the given column configuration showed that product purity in the bottom stream could be increased to w ProPro,bottom = 91.0% and maximum ProAc conversions to X ProAc = 94.5%.

The ethyl acetate synthesis via heterogeneous reactive distillation is studied experimentally using ethanol and acetic acid. Three types of cation exchanging resins were used as catalysts: Zerolit 225, Zerolit 226 and Ambylite 400. Experiments were carried out in two units of the same dimensions. Each unit consisted of three sections: rectifying, reactive and stripping sections of heights (60+25+20) cm respectively and 2.5cm column diameter. The first unit (column-A-) was a fractionation type and the second unit (column-B-) was packed column. The packing type was hollow glass cylinders with 10 mm height, and 4, 5 mm inner and outer diameter respectively. The experiments were carried out by using two operation modes. The semi-batch and continuous operation mode. In the first part of present investigation, the semi-batch mode was used to evaluate the catalyst type and to evaluate the performance of reactive distillation unit configuration (Fractionation and packed column). Results show that, the column-B-gave higher conversion rates than column-A-. This is attributed to the high surface area available for liquid vapour contact in packed type column, which leads to increasing mass transfer rates. On the other hand, Ambylite 400 catalyst showed higher activity for esterification reaction than other two types of catalysts. The second part of work continued with column-B-only. It is well known that, the esterification process is regarded one of exothermic reactions. Therefore, the monitoring of the temperature distribution along column axial for all three types of catalysts showed that the temperature distribution was essentially the same due to steady state operation in continuous operation mode. On the other hand, the effect of reflux ratio on temperature distribution was clearly noted, that is as the reflux ratio increased the temperature distribution along the column was reduced for each type of catalysts. On the other hand, the experimental results point that, as a reflux ratio increases the conversion rates of acetic acid is increased too because such increasing is related to high mass transfer rates between vapour and liquid along reactive distillation column.

– The development and optimization of an empirical model of a reactive distillation process producing palmitic acid methyl ester (PAME), with the aid of Minitab, have been carried out in this work. In order to achieve these, Box-Behnken technique of response surface methodology was used to design experiments that were carried out in a prototype plant of the process developed with the aid of Aspen HYSYS using Distillation Column Sub-Flowsheet as the column type and Wilson model as the fluid package. The results obtained from the analysis of the developed full quadratic model revealed that reboiler duty was not having any significant effect on the process as its probability value (P-value) was obtained to be greater than 0.05 that was chosen, based on the confidence level of 95%.This was found to justify the fact that no reaction was occurring in the reboiler section of the column. Based on this, the full quadratic model developed was modified. Although the R-squared value of the full quadratic model was found to be better than that of the modified one, the latter was found to be better in prediction because its predicted R-squared value was discovered to be greater than that of the former. In addition, the optimum values of the factors estimated with the aid of Minitab were found to be valid ones because the measured optimum mole fraction of palmitic acid methyl ester was found be in good agreement with the predicted one given by the Box-Behnken technique of response surface methodology.

We describe a hierarchy of methods, models, and calculation techniques that support the design of reactive distillation columns. The models require increasingly sophisticated data needs as the hierarchy is implemented. The approach is illustrated for the production of methyl acetate because of its commercial importance, and because of the availability of adequate published data for comparison. In the limit of reaction and phase equilibrium, we show (1) the existence of both a minimum and a maximum reflux, there is a narrow range of reflux ratios that will produce high conversions and high purity methyl acetate, and (3) the existence of multiple steady states throughout the entire range of feasible reflux ratios. For finite rates of reaction, we find (4) that the desired product compositions are feasible over a wide range of reaction rates, up to and including reaction equilibrium, and (5) that multiple steady states do not occur over the range of realistic reflux ratios, but they are found at high reflux ratios outside the range of normal operation. Our calculations are in good agreement with experimental results reported by Bessling et al., [Chemical Engineering Technology 21 (1998) 393].

2007

The paper presents a detailed analysis of the dynamic behavior of a reactive distillation column. A control relevant dynamic model is derived using firstprinciples modeling and it is used to study the dynamic behavior of the process at high and low purity operating regimes. The results are used to analyze the performance of linear and nonlinear model predictive control in comparison to coupled PID control.

2015

Ethyl acetate (EtAc) is mainly used as solvent in paints, adhesives and coatings, eliminating the use of aromatic compounds. Reactive distillation is a type of process intensification in which the separation and reaction is combined in one vessel. In this work, reactive distillation (RD) process for EtAc was implemented using process simulator Aspen HYSYS by applying the data obtained from the bibliography. A sensitive analysis was performed to determine the effects of key design and operating variables on column performance and, subsequently, an optimal column configuration was obtained

2011, Fuel

Deoxygenation of methyl esters and triglycerides was studied for production of either a-olefins or diesel components. The reactions were carried out in a reactive distillation fashion in which products are quickly removed from the reaction mixture in flowing He. The effects of He flow rate, reaction temperature, active component and support were studied. PtSnK supported on silica was found to be the best catalyst for selective production of a-olefins. Palm kernel oil and coconut oil were also deoxygenated to produce aolefins or diesel components, depending on reaction conditions.