侧反应器反应精馏方法生产醋酸甲酯的模拟

采用强酸性阳离子交换树脂催化醋酸与甲醇反应精馏生成醋酸甲酯,可避免硫酸作为催化剂的不足。但该非均相催化反应受平衡限制,且达到平衡时间较长,采用传统反应精馏塔难以提供足够反应空间。文中设计侧反应器与精馏塔耦合新工艺,采用Aspen Plus软件模拟研究了侧反应器数量、位置,原料进料位置,回流比,醇酸比等对反应精馏过程的影响。结果表明,当装置具有7个侧反应器,反应器间隔4块板,在优化的操作条件下,醋酸甲酯质量分数可达99.1%。     

Recovery of lactic acid by batch reactive distillation

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. Copyright © 2006 Society of Chemical Industry     

C_4和醋酸合成醋酸仲丁酯的动力学

为了给醋酸仲丁酯的工业生产提供动力学支持,研究了醋酸和丁烯在液相中直接酯化合成醋酸仲丁酯的本征动力学。在间歇搅拌釜式反应器中,以阳离子交换树脂为催化剂,采用MTBE后续工段中除去异丁烯后的C4混合组分和醋酸发生酯化加成反应生成醋酸仲丁酯。在消除内外扩散的影响下考察了催化剂用量、反应温度对反应速率的影响。得到其酯化反应正反应速率常数及活化能分别为65.23 L/(mol.min)和325.17 J/mol;其酯化反应负反应速率常数及活化能分别为0.239 L/(mol.min)和900.47 J/mol。得到了合成醋酸仲丁酯的反应动力学方程,为反应精馏的模拟优化提供了基础数据。     

An integrated reactive distillation process for biodiesel production

An integrated reactive distillation process for biodiesel production is proposed. The reactive separation process consists of two coupled reactive distillation columns (RDCs) considering the kinetically controlled reactions of esterification of the fatty acids (FFA) and the transesterification of glycerides with methanol, respectively. The conceptual design of the reactive distillation columns was performed through the construction of reactive residue curve maps in terms of elements. The design of the esterification reactive distillation column consisted of one reactive zone loaded with Amberlyst 15 catalyst and for the transesterification reactive column two reactive zones loaded with MgO were used. Intensive simulation of the integrated reactive process considering the complex kinetic expressions and the PC-SAFT EOS was performed using the computational environment of Aspen Plus. The final integrated RD process was able to handle more than 1% wt of fatty acid contents in the vegetable oil. However, results showed that the amount of fatty acids in the vegetable oil feed plays a key role on the performance (energy cost, catalyst load, methanol flow rate) of the integrated esterification–transesterification reactive distillation process.     

离子液体催化反应精馏合成乙酸乙酯工艺模拟

为研究离子液体在反应精馏中的作用,采用离子液体1-丁基-3-甲基咪唑硫酸氢盐（[BMIM]HSO₄）作为催化剂,对乙酸和乙醇合成乙酸乙酯的反应精馏流程进行了计算模拟。在确定了参数的酯化反应动力学的基础上,用Aspen Plus软件建立了反应精馏流程,研究了催化剂用量、精馏段理论板数、反应段理论板数、乙醇进料位置、进料摩尔比、持液量及回流比等参数对反应精馏过程的影响。研究结果表明,塔顶乙酸乙酯的质量分数随催化剂用量、精馏段理论板数、反应段理论板数和持液量增大而增大,工艺流程存在最佳回流比以及最佳进料酸醇摩尔比。得到的优化条件如下：离子液体与乙酸摩尔比为1：2.5,进料酸醇摩尔比为4：1,理论塔板数为21块,乙酸和催化剂在第7块理论塔板进料,乙醇在第19块理论塔板进料,塔板持液量0.1L,回流比为4,塔顶乙酸乙酯的质量分数可以达到98.73%。     

用阳离子交换树脂催化酯化合成乙酸异丙酯动力学研究

在间歇反应釜中,采用强酸型阳离子交换树脂(Amberlyst 15-Wet)作催化剂,在液-固两相体系中对乙酸异丙酯合成反应过程进行了研究,系统地考察了搅拌速度、催化剂粒径、温度、催化剂浓度、酸醇比对酯化反应速率的影响。同时通过拟均相动力学模型对反应过程进行了模拟,计算得到了相关的动力学参数。计算结果与与实验值吻合良好,能较好地描述乙酸和异丙醇合成乙酸异丙酯的酯化反应过程。     

Hydrolysis of methyl acetate via catalytic distillation: Simulation and design of new technological process

An equilibrium stage model was developed for the simulation of the catalytic distillation process of methyl acetate (MeOAc) hydrolysis. In the model, the influences of the reactive kinetics, residence-time, liquid holdup, and separation efficiency of the catalytic packing were considered. The model predicted the conversion of MeOAc and the mass ratio of acetic acid to water in the hydrolysis mixture. The predictions were in good agreement with experimental data. A novel process was designed based on the results of theoretic analysis and the simulation research. This new process had a higher conversion of MeOAc compared with the results in previous research and was found to be energy efficient. Optimal effect parameters and design factors of new technology on energy consumption and conversion were also determined and summarized as the following: the position of side draw is 18th to 19th stages, the catalytic distillation (CD) column pressure is at 350 kPa, the volume ratio of reflux to feed is 6–8, mole ratio of feed water to MeOAc is 3.5–4.5, and the mass ratio of side withdrawal to feed is 0.32–0.34.     

矿物均相酸催化剂催化甲醇和乙酸酯化反应动力学(英文)

In this work, esterification of acetic acid and methanol to synthesize methyl acetate in a batch stirred reactor is studied in the temperature range of 305.15–333.15 K. Sulfuric acid is used as the homogeneous catalyst with concentrations ranging from 0.0633 mol·L?1 to 0.3268 mol·L?1. The feed molar ratio of acetic acid to methanol is varied from 1:1 to 1:4. The influences of temperature, catalyst concentration and reactant concentration on the reaction rate are investigated. A second order kinetic rate equation is used to correlate the experimental data. The forward and backward reaction rate constants and activation energies are determined from the Arrhenius plot. The developed kinetic model is compared with the models in literature. The developed kinetic equation is useful for the simulation of reactive distillation column for the synthesis of methyl acetate.     

Kinetics of acetic acid esterification over ion exchange catalysts

Computer simulation showed that catalytic distillation is an attractive process for the removal of dilute acetic acid from wastewater. Selection of catalysts and kinetic data have been obtained for the design of the catalytic distillation column. Kinetic measurements were conducted in a batch reactor. Methanol was added to the dilute acetic acid solutions and reacted with the acid in water to form methyl acetate and water. The reaction can be catalyzed by solid acid catalysts. It was found that Amberlyst 15 was an effective catalyst for this reaction. The effects of stirrer speed, reaction temperature, reactant concentration and catalyst loading on reaction rate were investigated. A complete kinetic equation for describing the reaction catalyzed by Amberlyst 15 was developed. This equation can be used in the simulation and design of the catalytic distillation column for removing acetic acid from wastewater.     

离子液体催化反应精馏合成乙酸乙酯

利用1-己基吡啶四氟硼酸盐离子液体作溶剂和催化剂,在催化反应精馏塔内合成乙酸乙酯。结果表明该离子液体具有催化活性,反应的选择性为100%,分离后的1-已基吡啶四氟硼酸盐离子液体重复使用5次,其活性没有明显变化。考察了回流比、进料比、溶剂和催化剂用量对酯化反应结果的影响,优化了反应的工艺条件,适宜的反应条件为:物料比n(乙酸):n(乙醇)=1.1:1,离子液体用量n(乙酸):n(离子液体)=8:1,回流比为3。     

Analysis of reactive distillation using the esterification of acetic acid as an example

The uncatalyzed esterification of acetic acid is described in the literature as a typical example of reactive distillation. Many rigorous models were validated using this esterification as an example. Process proposals for the production of pure ethyl acetate from ethanol and acetic acid have been determined using short-cut methods with the assumption of chemical equilibrium only. In this publication, the limitations of this esterification are clarified, using a rigorous model that was developed. The reasons why reactive distillation appears to be unfavorable for this esterification are explained. It is, however, theoretically possible to obtain ethyl acetate in high purity with different variants of the process. Different process variants are examined in this work. Construction variables that are important for the design of reactive columns, such as the number of reactive separation stages and the holdup in the column, are analyzed. Furthermore, the influence of variables dependent on the component system, such as the phase equilibrium of the reactive system and the reaction kinetics on the conversion in the column, are described. It can be shown that the short-cut methods published so far for reactive distillation, which assume chemical equilibrium, are inadequate.     

Production of ethyltert-butyl ether fromtert-butyl alcohol and ethanol catalyzed byβ-zeolite in reactive distillation

The synthesis of ethyl tert-butyl ether (ETBE) from a liquid phase reaction between tert-butyl alcohol (TBA) and ethanol (EtOH) in reactive distillation has been studied.β-Zeolite catalysts with three compositions (Si/Al ratio=13, 36 and 55) were compared by testing the reaction in a semi-batch reactor. Although they showed almost the same performance, the one with Si/Al ratio of 55 was selected for the kinetic and reactive distillation studies because it is commercially available and present in a ready-to-use form. The kinetic parameters of the reaction determined by fitting parameters with the experimental results at temperature in the range of 343–363 K were used in an ASPEN PLUS simulator. Experimental results of the reactive distillation at a standard condition were used to validate a rigorous reactive distillation model of the ASPEN PLUS used in a simulation study. The effects of various operating parameters such as condenser temperature, feed molar flow rate, reflux ratio, heat duty and mole ratio of H₂O : EtOH on the reactive distillation performance were then investigated via simulation using the ASPEN PLUS program. The results were compared between two reactive distillation columns: one packed withβ-zeolite and the other with conventional Amberlyst-15. It was found that the effect of various operating parameters for both types of catalysts follows the same trend; however, the column packed withΒ-zeolite outperforms that with Amberlyst-15 catalyst due to the higher selectivity of the catalyst.     

2-Methylpropylacetate synthesis via catalytic distillation

The paper deals with a 2-methylpropylacetate synthesis process development. The process is based on esterification of acetic acid with 2-methylpropanol by the reactive distillation method. A column in which separation of the reaction products takes place together with esterification in catalytic active separation packing is utilized in this process. Computer simulation of catalytic distillation has been performed to study the process and to evaluate the pilot plant experimental data. KATAPAK^® S structural packing was used in the reaction zone, while stripping and rectifying sections of the column were packed by CY^® packing. A good agreement between the simulation results and pilot plant data has been achieved.     

Experiments and dynamic modeling of a reactive distillation column for the production of ethyl acetate by considering the heterogeneous catalyst pilot complexities

Great effort has been applied to model and simulate the dynamic behavior of the reactive distillation as a successful process intensification example. However, very little experimental work has been carried out in transient conditions. The work presents a series of experiments for the production of ethyl acetate from esterification of acetic acid and ethanol in a reactive distillation pilot column. The steady-state approach performed experiments with both excess of alcohol and stoichiometric feed configuration. Predicted and measured results show good agreement and reveal a strong dependency of the structured packing catalyst activity on the pilot geometry and its operating conditions. The transient process behavior of the heterogeneously catalyzed system was deeply investigated and continuous and dynamic data were collected for an equilibrium model validation, after different perturbations on parameters. The experimental validation is shown to be essential to provide realistic hydrodynamic parameters, to understand the sensitive parameters such as heat losses and to adapt values for the catalyst holdup as a function of the system.     

Reactive Chromatography for the Synthesis of 2-Ethylhexyl Acetate

Abstract

Reactive chromatography (RC) combines reaction and chromatography in a single unit. Due to simultaneous separation of products it can be advantageously used for reversible reactions to obtain the enhanced performance. It is a promising alternative to reactive distillation when the components are temperature sensitive and less volatile. In the present work, we study the application of RC for the synthesis of 2-ethylhexyl acetate through esterification of acetic acid with 2-ethylhexanol. Amberlyst-15 has been used as a catalyst/adsorbent. Several aspects such as reaction kinetics, multicomponent adsorption equilibria, and reaction-separation study using fixed bed chromatographic reactor are covered. The kinetics was studied in a stirred batch reactor. The effects of various parameters such as speed of agitation, particle size, temperature, mole ratio of reactants, and catalyst loading have been investigated. Kinetic modeling was performed using modified activity based Langmuir-Hinshelwood-Hougen-Watson (LHHW) model. Non-reactive binary adsorption experiments were performed to determine the parameters of Langmuir adsorption isotherm by minimizing the errors between the experimental and predicted breakthrough curves. Further, the reactive chromatography experiments were performed to obtain the reactive breakthrough curves which indicate a clear potential for the use of reactive chromatography for this reaction. The obtained data has been compared with the predictions of mathematical model of the chromatographic reactor.     

固体酸催化剂反应精馏法合成乙酸正丙酯的研究

研究了以阳离子交换树脂作为催化剂进行反应精馏合成乙酸正丙酯,分别考察了不同回流比、酸醇摩尔比以及不同固体酸催化剂类型对酯化反应的影响,并结合工艺条件进行催化剂的筛选,确定反应的较佳工艺条件。实验结果表明,回流比为1∶2,酸醇摩尔比为1∶2,乙酸正丙酯的收率为51.49%。     

Hybrid reactive distillation systems for n-butyl acetate production from dilute acetic acid

The recovery of dilute acetic acid, regarding as a waste stream in many chemical and petrochemical processes, becomes an important issue due to economic and environmental awareness. In this work, a simulation study on the direct utilization of dilute acetic acid to produce n-butyl acetate via esterification with butanol in a reactive distillation is presented by using Aspen Plus. The performance of a hybrid reactive distillation with a pretreatment unit, i.e., a conventional distillation or a pervaporation, is investigated. For a single reactive distillation system, it is found that higher overall energy of the system is required when the concentration of acetic acid is lowered. By considering the enrichment of acetic acid in the reactive distillation column feed from 35 to 65 wt.%, a hybrid pervaporation–reactive distillation requires lower energy than both the conventional distillation–reactive distillation system and the single reactive distillation.     

反应精馏法制备醋酸甲酯的研究

以醋酸、甲醇为原料,以浓硫酸为催化剂,对反应精馏法制备醋酸甲酯的过程进行了实验研究。着重考察了回流比、进料中醋酸摩尔分率、塔板数及混酸进料位置等因素对反应转化率和塔顶产品中醋酸甲酯含量的影响,并得出最佳的工艺条件。     

Effects of operation variables on the recovery of lactic acid in a batch distillation process with chemical reactions

In this study, the feasibility of recovery of lactic acid by batch reactive distillation using cation exchange resin as a catalyst was investigated. For the recovery of lactic acid, two reactions, esterification and hydrolysis, are involved and hence, an apparatus with two distillation columns was developed and operated in a batch mode to ensure enough residence time in the reboiler and column. The effects of operation variables such as catalyst loading, reactant mole ratio, feed concentration, type of alcohols and partial condenser temperature on the yield were studied. In this study, the reaction products of the esterification (methyl lactate and water) were distilled to the hydrolysis part to be recovered into pure lactic acid. The yield of lactic acid increased as catalyst loading in the esterification part increased and reactant mole ratio and feed lactic acid concentration decreased. Methanol as a reactant gave higher yield than any other alcohols. The yield of recovered lactic acid was as high as 90%. The yield of lactic acid was closely related to the boiling temperature of the reaction mixture in the esterification part     

Design of entrainer-enhanced reactive distillation for the synthesis of butyl cellosolve acetate

An innovative entrainer-enhanced reactive distillation (RD) process is presented, which aims to the production of high-purity butyl cellosolve acetate from butyl cellosolve and acetic acid via an esterification reaction. This entrainer-enhanced RD process can procure technical advantages from both heterogeneous azeotropic distillation and RD. Solvents such as cyclohexane, ethylene dichloride, toluene, and octane are considered as candidates in this esterification RD process. The function of entrainers is to simplify the separation between water and acetic acid. For this purpose, the proper entrainer to use is thus evaluated based on its mutual solubility with water in two liquid phases. Simulation results reveal that total annual cost can be substantially reduced when cyclohexane, toluene, and octane are used as entrainers in the RD column. The octane-enhanced RD provides the most economical design in this studied case.