Reactive Distillation

Abstract The formation of methyl decanoate (MeDC) by esterification reaction of decanoic acid with methanol through batch/continuous reactive distillation columns is operationally challenging, energy intensive and thus cost intensive operation due to complex thermodynamic behaviour of the reaction scheme. Aiming to overcome the equilibrium restriction of the decanoic acid (DeC) esterification operation, to improve the process efficiency and to reduce the total annualised cost (TAC), the semi-batch distillation column (SBD) and the recently proposed integrated semi-batch distillation column configuration (i-SBD) are investigated here. The performances of each of these column operations are evaluated in terms of minimum TAC for a given separation task. In both column configurations, additional operating constraints are considered into the optimization problem to prevent flooding of still pot due to the continuous charging of methanol into it. This study shows the superiority of i-SBD mode of operation over SBD operation in terms of TAC. Also, the optimization results for a defined separation task indicate that the performance of multi-interval control policy is overwhelmingly superior to the single-interval control operation in terms of operating batch time, and overall annual cost in the i-SBD system providing about a time saving of 82.75%, and cost (TAC) saving of 36.61% for a DeC (product) concentration of 0.945 molefraction.

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 acrylic acid, the polymerization to poly(lactic ...

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

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.

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

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.

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%.

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.

The separation of 2-Methoxyethanol-toluene azeotropic mixture has high practical significance in both industry and the laboratory because of their multipurpose solvating properties. However, both 2ME and toluene have adverse effects on human and animal health; therefore, researchers have become interested in their separation. A significant amount of 2-methoxyethanol-toluene forming a minimum-boiling azeotrope is discharged by the electrochemical industry. The presence of this azeotrope renders separation a challenging task. Separation techniques, namely pressure swing distillation (PSD) and azeotropic distillation (AD), have not yet been explored. In this study, these separation techniques are evaluated economically and dynamically using a wellknown commercial simulator Aspen Plus®. This study includes the development of process schematics for these alternative separation processes and economic analysis involving total annual cost (TAC) calculations. It is concluded that the heat-integrated PSD technique leads to 21.35% savings in TAC compared to previously reported techniques. Furthermore, a decentralized plant-wide control structure for a suitable separation technique is also developed and tested for ±10% throughput manipulations in fresh feed flow rate and ±5% disturbances in feed composition. This study will significantly help the process engineers overcome the challenges of handling the electrochemical industry's hazardous effluent in environmentally and economically ways.

A conceptual design methodology for the synthesis of reactive distillation columns is presented. The method assesses feasibility of a proposed reactive distillation column, designs the column and allows evaluation of the design for both fully reactive and 'hybrid' column ...

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 feed-forward control of 'the column. The data from the column will be compared with the calculated results. The comparison serves as a test for the mathematical model and its computer program. The control of distillation columns has received a considerably large interest in recent years. Because the separation processes by distillation are found an almost every phase of the chemical and petroleum industries. In order to ensure smooth and economic operation of the distillation column, flows of cooling, heating media and intermediate product should be disturbed as little as possible. Thus, an accurate control of product compositions and column performance is very important. A computer program· is developed for dynamic simulation of the column. The nonlinear equations of the dynamic model are solved numerically. This model requires simultaneous solution of over-all material balances, heat balances, equilibrium and efficiency relationships for each plate. condenser and the reboiler of the column. The component mole balance establishes the liquid flowrate. The vapor liquid relationships establish the vapor composition where
as the overall heat balance defines the vapor flow leaving the plate. The binary system of methanol-tertiary butyl alcohol is distilled in,twentyplate, which 10 cm internal diameter bubble cap distillation column which is made of glass.

Turkish

Bu calışmanın amacı pilot· tesis düzeyinde gecici durum şartlarındaçalışan bir damıtma kulesinin· dinamik tepkilerinin matematiksel model ile tahminini hesaplamaktır. Bir ikinci amacı da bu modelin ileri-beslemeli kule kontrolündak faydasını saptamaktır. Bu amaç için bir damitma kulesinde elde edilen veriler matematiksel model icin yazılan bilgisayar programı sonuclarıyla karılaştırılmıştır. Damıtma kulelerinin koritrolu son yıllarda büyük önem kazanmıştır. Çünkü damıtma ile ayırma işlemleri bütün kimya ve petrol sanayiinde geniş bir şekilde kullanılmaktadır. Damıtma kulelerinin düzenli ve ekonomik calışmaları için soğutma ve ısıtma ayrıca ara ürünlerinin sıcaklığı ve derişimlerinin öngörülen belli sınırlar içinde kalması gerekir. Bu nedenle damıtma kulelerinin iyi bir şekilde kontrol edilmesi önemlidir. Damıtma kulesinin çalışması hakkındaki dinamik model icin bir bilgisayar programı yazılmıştır. Bu·programdaki doğrusal olmayan denklemler nümerik metodla çözülmüştür. Bu cözümde her bir tepsi ve yoğuşturucu ile kazan için genel madde denkliği, ısı denkliği ve verim bağıntıları yer almaktadır. Sıvı akım hızları her bir bileşen için yazılan molar denkliklerle bulunmuştur. Buhar deişimleri buhar-sıvı denge bağıntısıyla, bir tepsiyi terkesen buharın hızıda genel ısı denkliğiyle bulunmuştur. Bu çalışmada deneysel veriler methanol-tersiyer bütül alkol karışımı ile, 10 cm çapındaki yirmi tepsili camdan yapılmış bir damıtma kulesinde elde edilmiştir.