Production Of Methyl Acetate Research Articles

Experimental analysis in different batch operating units for process intensification: methyl acetate production case study

In the present study, different process intensification options in batch mode are considered for a class of reactions, and are evaluated with respect to enhancement in conversion and product purity considering methyl acetate formation reaction as an experimental case study. The options explored include operation in different batch operating units and use of different molar ratios of reactants. Integrated reaction and separation is considered in two ways, namely by simple reactive batch distillation, and by multi-stage reactive batch distillation with partial reflux. It is observed that conversions beyond equilibrium conversion are achieved by process intensification, and relatively purer products are obtained compared to the base case. The purity and conversions in the multi-stage column are found to be higher than with simple distillation. Increasing the molar ratio of methanol in the reaction feed mixture is found to yield high conversions at the expense of purity of methyl acetate in the product. The present study considers a typical case of an esterification reaction with azeotropic mixtures, and the analysis is applicable to a class of reactions satisfying the criteria mentioned.

A process synthesis-intensification framework for the development of sustainable membrane-based operations

In this paper a multi-level, multi-scale framework for process synthesis-intensification that aims to make the process more sustainable than a base-case, which may represent a new process or an existing process, is presented. At the first level (operation-scale) a conceptual base case design is synthesized through the sequencing of unit operations and subsequently analyzed for identifying process hot-spots using economic, life cycle and sustainability metrics. These hot-spots are limitations/bottlenecks associated with tasks that may be targeted for overall process improvement. At the second level (task-scale) a task-based synthesis method is applied where one or more tasks representing unit operations are identified and analyzed in terms of means-ends for generating intensified flowsheet alternatives. At the third level (phenomena-scale) a phenomena-based synthesis method is applied, where the involved phenomena in various tasks are identified, manipulated and recombined to generate new and/or existing unit operations configured into flowsheet alternatives that target the tasks associated with hot-spots. Every lower-scale or higher-level, generates more alternatives than their corresponding larger-scale. Those alternatives that are able to address the identified hot-spots therefore give innovative and more sustainable process designs that otherwise could not be found from the larger-scales. In this paper, membrane-based operations identified through this framework are highlighted in terms of extension of the combined intensification-synthesis method and its application to generate membrane-based operations. Also, application of the framework is illustrated through a case study involving the production of methyl acetate where membrane-based intensified operations play a major role in determining more sustainable process design alternatives.

Comparative kinetics of esterification of methanol–acetic acid in the presence of liquid and solid catalysts

ABSTRACTEsterification of acetic acid with methanol to produce methyl acetate in an isothermal stirred batch reactor has been studied. Sulfuric acid was used as a liquid catalyst, and Indion‐180, Indion‐190 and Amberlyst‐16wet ion exchange resins were used as solid catalysts. The feed mole ratio was varied from 1 : 1 to 1 : 4. The reaction temperatures were varied from 305.15 to 333.15 K for sulfuric acid as catalyst and 323.15 to 353.15 K for the solid catalysts. The catalyst concentrations were used in the range of 1% to 5%, for the sulfuric acid catalyst, and 0.01 to 0.05 g/cc, for the solid catalysts. The effect of temperature, catalyst concentration, agitation speed, size of catalyst particle and reactant concentration on the acetic acid conversion was investigated. A second‐order kinetic rate equation was proposed to fit the experimental data. For both forward and backward reactions, the activation energies were estimated from Arrhenius plots. The reaction rate increased with catalyst concentration and temperature for both the liquid and solid catalysts. The acetic acid conversion was found to increase with increases in acetic acid to methanol ratio in the feed. The developed kinetic rate equation was used for the simulation of reactive distillation process, in our laboratory column. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.

Reactive Distillation Using an Ion-Exchange Catalyst: Experimental and Simulation Studies for the Production of Methyl Acetate

In this study, the performance of a packed-bed reactive distillation (RD) column for the production of methyl acetate (MeOAc) using an ion-exchange catalyst and simulation of the same using CHEMCAD were analyzed. An ion-exchange catalyst, Indion 190, was used in this study. The performance of the RD column was evaluated based on the MeOAc concentration in the top product. Both steady- and unsteady-state behavior of the column was simulated using CHEMCAD, and the results were experimentally validated. The process parameters, viz., reboiler temperature, enriching temperature, reactor temperature, catalyst loading, molar ratio of the reactant, and flow rate of reactants, were studied, and the optimal values were found to be 73 °C, 56 °C, 72 °C, 100 g, 1:2, and 15 mL/min, respectively. Feed locations of acid and alcohol to the reactor that gave maximum MeOAc concentration in the top product were determined. A mathematical model based on the rigorous calculation using SCDS (used to calculate the nonideal K val...

Pervaporation membrane reactor design guidelines for the production of methyl acetate

Design guidelines were applied for the production of methyl acetate in a pervaporation membrane reactor. The limits of operation were determined. The shift in equilibrium is evaluated by a simple model involving simultaneously chemical equilibrium and transport across the membrane. This analysis establishes possibilities and limitations of a pervaporation membrane reactor. The performance of a continuous stirred tank reactor with a pervaporation membrane (PV-CSTR) is analyzed. To achieve conversions higher than 90%, conditions must satisfy Da > 150 and 0.01 < Pe < 100. Increasing temperature has a negative effect on membrane reactor conversion. The effect of sweep is important at high-permeate pressures. Two design charts were created to illustrate dynamics between permeation rates, reaction rates, and selectivity with conversion. The three powerful tools proposed for the analysis of a pervaporation membrane reactor described the system in a systematic way.

Conceptual Design of Double‐Feed Reactive Distillation Columns

AbstractThe feasibility and feasible range of operating parameters for double‐feed reactive distillation columns are evaluated, based on the combination of pinch point map analysis for the middle‐section in the compositional space and the feed angle method as an efficient shortcut design method. Limiting bounds for operating parameters are determined where the properties of singular points change. The existence and values of such bounds may vary in double‐feed reactive distillation columns depending on the nature of the system under study. The methodology is illustrated by production of methyl acetate and ethyl acetate. An efficient method is described to identify the most promising candidates of double‐feed reactive distillation columns and to study the design flexibility in terms of operating parameters.

Catalyst dilution to improve dynamic controllability of cooled tubular reactors

The dynamics of cooled tubular reactors are strongly affected by the overall heat-transfer coefficient U, which depends primarily on the velocity through the tubes. Higher velocities produce larger U's but increase pressure drops. Design involves trade-offs among tube diameter, tube length and number of tubes to achieve a specified pressure drop and per-pass conversion. This paper points out that another design optimization variable is available to improve the dynamic stability of cooled tubular reactors. If the catalyst activity is high, the size of the required reactor is small, which implies small heat-transfer area, and the reactor can be uncontrollable. If the catalyst is diluted with an inert solid, a bigger reactor will be required that will have more heat-transfer area and provide improved dynamic stability. This catalyst dilution strategy is explored for two reaction systems: a hypothetical chemical process and the carbonylation of dimethyl ether to produce methyl acetate.

Adiabatic operation of chromatographic fixed-bed reactors

Adiabatic operation of single column chromatographic reactors was investigated experimentally and using numerical simulations. Esterification of acetic acid with alcohols to produce methyl acetate and ethyl acetate was carried out under isothermal and adiabatic conditions. Higher conversions of the acids, as well as higher ester/water mole ratio in the product fraction, were obtained in the adiabatic reactor than in the isothermal reactor. Improved performance was attributed to a thermal wave that travels through the reactor together with the reaction front. It was shown that thermal effects in such systems originate from reaction heat, adsorption enthalpies, as well as the enthalpy of mixing. Numerical simulations were carried out to investigate under which conditions adiabatic operation of a fixed-bed chromatographic reactor is potentially beneficial. The influence of physical properties of the reaction system (heat capacities of the liquid and solid phases, reaction rate, and separation factor) and operating parameters (injection volume of reactant and residence time) on the process performance was demonstrated.

Design and Control of a Methyl Acetate Process Using Carbonylation of Dimethyl Ether

The production of methyl acetate from the raw materials of methanol and carbon monoxide offers a potentially attractive alternative to other routes. The process has two distinct reaction and separation steps. First, methanol is dehydrated to form dimethyl ether (DME). Then carbon monoxide is combined with DME to produce methyl acetate. Each section involves reactors and distillation columns with either liquid or gas recycle. The purpose of this paper is to develop the economically optimum design of the two-step process and to study its dynamic control. The economics consider capital costs (reactors, distillation columns, heat exchangers, and compressors), energy costs (compressor work, reboiler heat input, and condenser refrigeration), the value of steam produced from the exothermic reactions, the cost of the carbon monoxide, and the heating value of a vent stream that is necessary for purging off the inert hydrogen that enters in the fresh carbon monoxide feed. The process illustrates a number of important design trade-offs among the many design optimization variables: reactor temperatures, reactor pressures, distillation column pressures, reactor sizes and purge composition. A plantwide control structure is developed for the entire two-section process that is capable of effectively handling large disturbances in production rate and fresh feed compositions.

Study of the Performance of Batch Reactive Distillation Column

Batch reactive distillation was studied in packed bed column. Esterification of methanol with acetic acid to produce methyl acetate and water with homogenous sulfuric acid as a catalyst was considered. This system was chosen because the reaction is reversible and the boiling point of reactant and products are different.The reaction was carried out with and without distillation column and shows that the reactive distillation is more efficient from the conventional process (reactor and then separation). The conversion of acetic acid and concentration of methyl acetate increase by (30.43% and 75.14%) respectively at the best condition (reflux ratio 2, feed mole ratio 2 and batch time 90 minute).The influence of various parameters, such as batch time, reflux ratio, and feed mole ratio (methanol to acetic acid) on the performance of the batch reactive distillation column was studied, through the effect of the concentration of product and conversion of reactant.The results obtained for the non-ideal packed bed reactive batch distillation column show that the conversion of acetic acid is 90% at the best condition reflux ratio 2, feed mole ratio 2, and batch time 90 minute

Non-equilibrium Model and Experimental Validation for Reactive Distillation

Firstly, a non-equilibrium model is implemented in order to simulate non-ideal multi-component reactive separation processes. This model is characterised by mass and energy transfer description and is completed up by considering hydrodynamics using the film theory model. The Maxwell Stefan approach is used for the description of mass transfer without restrictive hypotheses. Moreover, there are no restrictive hypotheses about the type and localisation of the chemical reactions. Secondly, the numerical analysis of this model ends in setting up a sure and stable strategy, especially to the differentiation index and the initialisation coherence. Thirdly, an experimental apparatus is set up in order to validate the numerical results. It represents a section of a packing distillation column fed by two fully controlled flows. The experiments were performed for the homogeneously catalysed etherification of acid acetic and methanol to produce methyl acetate and water. Several runs have been realised by varying the flow rates and compositions of the feeds, as well as the concentration of the catalyst. For each one, the simulation results are in good agreement with the vapour composition and the liquid temperature profile, without any parameter adjustments. In addition, the need of taking into account the reaction contribution in the diffusional layers is clearly shown.

New Insights into Acetone Metabolism ▿

New Insights into Acetone Metabolism ^▿

Process Chemistry and Design Alternatives for Converting Dilute Acetic Acid to Esters in Reactive Distillation

This work explores the recovery of acetic acid aqueous solution with different acid concentrations. Instead of separating acid from water using azeotropic distillation, acetic acid is converted to acetate via esterification. Two questions then arise. First, what is a better choice of alcohol (e.g., ranging from methanol to pentanol, C1−C5) for the esterification? This is a solvent selection problem. Second, what is the more economical process flowsheet (e.g., a stand-alone reactive distillation versus a pretreatment unit followed by a reactive distillation)? For the solvent selection problem, an earlier study [Tang et al., AIChE J. 2005, 51, 1683−1699] has indicated that the esterifications using methanol or pentanol is much more economical as compared to other choices (e.g., ethanol, 2-propanol, or butanol). Quantitative analysis reveals that the production of methyl acetate (from methanol and acetic acid) is not tolerant to acid concentration variation, and a very-high-purity acid feed is needed to achieve product specification. Thus, methanol is ruled out for esterification and pentanol is selected to convert acid to the ester. Next, a systematic design procedure is taken to design the process flowsheets and the total annual cost (TAC) is used to discriminate between different flowsheets, with and without pretreatment unit. A range of acetic acid concentration is explored, varying from 100 wt %, to 75 wt %, to 50 wt %, and then to 30 wt %. The TAC analysis shows that a stand-alone reactive distillation is more economical than the flowsheet with a pretreatment unit.

Reactive distillation for methyl acetate production

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, (2) 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].

Distillation column with reactive pump arounds: an alternative to reactive distillation

The hardware design of reactive distillation (RD) columns pose severe challenges with respect to the choice and design of the hardware; the requirements of reaction (i.e. high liquid or catalyst holdup) is not in consonance with the requirement of separation (high interfacial area). In this paper, we examine an alternative to the RD concept, namely a distillation column networked with a number of side (external) reactors. If each distillation stage is linked to a side reactor, the performance of the RD column is matched exactly. From a practical point of view, it is desirable to reduce the number of side reactors to below, say, six. The precise location of the chosen number of side reactors and the manner in which the liquid draw-offs and reactor effluent re-entry to the distillation column needs to be chosen carefully. We have developed an algorithm to determine an optimum configuration of the side-reactor concept in order to maximise conversion. For the case study of methyl acetate production, we see that it is possible to match the conversion level of an RD column by appropriate choice of the number of side reactors and the pump around ratio. The higher the conversion target the larger the number of side reactors and pump around ratios. For modest conversion levels, say <90%, even a 3-side-reactor configuration will be able to match the performance of the RD column. The study presented here reveals the potential, and limitations, of the side-reactor concept for use as an alternative to RD technology.

Widening the Applicability of Reactive Distillation Technology by Using Concurrent Design

In this paper the concurrent design method based on partial control, which was developed by Shinnar and co-workers [(Ind. Eng. Chem. Res. 1995, 34, 1228; 1995, 34, 3014; 1996, 35, 2215; 1997, 36, 747; 2000, 39, 103) (AIChE J. 2000, 46, 2456)] is applied to reactive distillation systems. It is shown that this approach provides important insights on the design and control of such processes. One main advantage of the method is that the design and scale-up of complex processes are based on the identification of the process dominant variables using learning models such as literature, pilot plants, and simulation models. While we use the methyl acetate production system as our prime example, the results could be of general interest. Our results also explain what are the limitations in the current application of reactive distillation and what could be done to increase its applicability to a wider set of problems.

Distillation column with reactive pump arounds: an alternative to reactive distillation

The hardware design of reactive distillation (RD) columns pose severe challenges with respect to the choice and design of the hardware; the requirements of reaction (i.e. high liquid or catalyst holdup) is not in consonance with the requirement of separation (high interfacial area). In this paper we examine an alternative to the RD concept, viz. a distillation column networked with a number of side (external) reactors. If each distillation stage is linked to a side reactor, the performance of the RD column is matched exactly. From a practical point of view it is desirable to reduce the number of side reactors to say 3–6. The precise location of the chosen number of side reactors and the manner in which the liquid draw-offs and reactor effluent re-entry to the distillation column needs to be chosen carefully. We have developed an algorithm to determine the optimum configuration of the side reactor concept in order to maximize conversion. For the case study of methylacetate (MeOAc) production, we see that it is possible to match the conversion level of an RD column by appropriate choice of the number of side reactors and the pump around ratio. The higher the conversion target the larger the number of side reactors and pump around ratios. For modest conversion levels, say <90%, even a three-side reactor configuration will be able to match the performance of the RD column. The study presented here reveals the potential, and limitations, of the side reactor concept for use as an alternative to RD technology.

Analysis of Complex Separation Schemes in the Presence of Chemical Reactions

A key feature in the analysis of extractive distillation columns is the use of difference points representing the flow rate and composition difference between the cascade section end-product and the extractive side feed(s). Also referred to as a Δ-point, it may be used to assess feasibility for complex cascades with highly non-ideal VLE behavior. We have recently generalized the concept of difference points to systems where chemical reactions take place. We have also shown that the analytical insights are independent of the actual configuration of physical equipment and apply to any partial or complete flowsheet. This paper will demonstrate how the theory of generalized difference points may be applied to the design of complex separation cascades with reaction. Two example designs with integrated reaction and separation will be presented and analyzed for 3 and 4 components, respectively: (a) reactive distillation for the production of acetic acid from acetic anhydride and water and (b) reactive extractive distillation for the production of methyl acetate from acetic acid and methanol with water as a side product. The acetic acid example will illustrate how composition space can be divided into regions where feasibility with respect to distillate placement and internal reaction distribution can be performed using difference point theory. The methyl acetate design will show how a complex column can be divided into sections and analyzed using difference points to expose the role each section plays in making a feasible design.

Comparative control study of ideal and methyl acetate reactive distillation

The control of an ideal reactive distillation column is compared with that of a similar, but somewhat different, real chemical system, the production of methyl acetate. Similarities and differences are observed. Three control structures are evaluated for both systems. A control structure with one internal composition controller and one temperature controller provides effective control of both systems for both high and moderate conversion designs. A two-temperature control structure is effective when the system is overdesigned in terms of number of reactive trays, holdup and/or catalyst load. Direct control of product purity for the high-conversion/high-purity design is difficult because of system nonlinearity and interaction. Tray temperature control avoids the nonlinearity problem.

Water and chemicals recovery in the German automotive industry

A reactive dividing-wall column (RDWC) is developed for the production of methyl acetate (MeAc) in this work. Both design and control of the RDWC are investigated by using commercial chemical simulator Aspen Plus and Aspen Dynamics. The optimum RDWC design in terms of total annual costs (TAC) is screened based on the proposed optimization procedure. The results show that about 7.7% savings in energy consumption, 8.3% reduction in operating cost and 15.5% decrease in capital investment can be achieved by the RDWC design compared to the corresponding two-column design. Two control structures (i.e., basic control structure and improved control structure) for the RDWC are presented. The results indicate that the improved control structure can handle disturbances in ±20% feed flow rate and −5 wt% feed composition effectively.