Hydrolysis Of Methyl Acetate Research Articles

Structure of proton disolvates formed in the acid hydrolysis of ethyl formate and methyl acetate

By the density functional method (B3LYP/6-31++G(d,p)) optimal structures of proton hetero and homo disolvates involving water molecules, ethyl formate, methyl acetate and products of their hydrolysis are calculated. The data on the structure of these ions and the strength of their H bonds are analyzed together with the results of a similar calculation previously performed for methyl formate. It is shown that in proton solvation by two molecules present in the solution during the hydrolysis of ethyl formate, methyl acetate, and methyl formate stable (X…H…X)+ or (X…H…Y)+ particles form. Structural and energy parameters of their O…H…O bridges obey the same regularities and are mainly determined by a difference in the proton affinity of X and Y molecules. Calculation results are compared to the data of a number of experimental studies of the acid hydrolysis of esters.

Mixed Ligand Co (II) Complexes: Use as Catalysts in the Hydrolysis of Esters

Mixed ligand metal complexes of the type MLL’xH2O (x=1), where M is Co(II)/Ni(II), L is deprotonated 8-hydroxyquinoline and L’ is a deprotonated amino acid have been synthesized. The metal complexes have been characterized on the basis of elemental analysis and various physicochemical techniques. Hydrolysis of methyl acetate and ethyl acetate was studied by using the complexes as homogeneous catalysts. The rate constants have been obtained by using different catalysts at various temperatures. The activation energy (E) was calculated from the Arrhenius plots. The changes in the enthalpy of activation (∆H), entropy of activation (∆S) and free energy of activation (∆G) were also calculated. A probable reaction mechanism has also been suggested.

Simulation study on a reactive distillation process of methyl acetate hydrolysis intensified by reaction of methanol dehydration

Methyl acetate (MeOAc) recovery from the polyvinyl alcohol (PVA) production is a difficult and heavy energy consuming process. In this work, a reactive distillation (RD) process of MeOAc hydrolysis intensified by methanol (MeOH) dehydration, as an auxiliary reaction, was proposed. Two different feeds with the mole ratio of MeOAc to MeOH at 1:1 and 1:9 were studied, and the effect of the operating pressure, the feed location and the reflux ratio on the RD column was analyzed. The simulations of reactive distillation were performed using a three phase non-equilibrium model implemented by gPROMS. As the limit of the reaction rate of MeOH dehydration, it is impossible to get 100% conversion of MeOAc and MeOH by a single RD column. Therefore, two novel processes for recovery of methyl acetate in PVA production were developed. The simulation results show that the high purity of dimethyl ether (DME) could be achieved with a complete conversion of MeOAc, and a large amount of energy demand and equipment costs can be reduced.

Bifunctional Organorhodium Solid Acid Catalysts for Methanol Carbonylation

Robust, bifunctional catalysts comprising Rh(CO)(Xantphos) exchanged phosphotungstic acids of general formulas [Rh(CO)(Xantphos)]+n[H3–nPW12O40]n− have been synthesized over silica supports which exhibit tunable activity and selectivity toward direct vapor phase methanol carbonylation. The optimal Rh:acid ratio = 0.5, with higher rhodium concentrations increasing the selectivity to methyl acetate over dimethyl ether at the expense of lower acidity and poor activity. On-stream deactivation above 200 °C reflects Rh decomplexation and reduction to Rh metal, in conjunction with catalyst dehydration and loss of solid acidity because of undesired methyl acetate hydrolysis, but can be alleviated by water addition and lower temperature operation.

A systematic framework for the feasibility and technical evaluation of reactive distillation processes

This study presents a novel design methodology for the feasibility and technical evaluation of reactive distillation (RD), and discusses the applicability of various design methods of RD. The proposed framework for the feasibility evaluation determines the boundary conditions (e.g. relative volatilities, target purities, equilibrium conversion and equipment restriction), checks the integrated process constraints, evaluates the feasibility and provides guidelines to any potential RD process application. Providing that a RD process is indeed feasible, a technical evaluation is performed afterward in order to determine the technical feasibility, the process limitations, working regime and requirements for internals as well as the models needed for RD. This approach is based on dimensionless numbers such as Damkohler and Hatta numbers, as well as the kinetic, thermodynamic and mass transfer limits.The proposed framework for feasibility and technical evaluation of reactive distillation allows a quick and easy feasibility analysis for a wide range of chemical processes. In this work, several industrial relevant case studies – e.g. synthesis of di-methyl carbonate (DMC), methyl acetate hydrolysis, toluene hydro-dealkylation (HDA) process, fatty acid methyl esters (FAME) process and unsaturated polyesters synthesis – clearly illustrate the validity of the proposed framework.

Reactive Divided Wall Distillation Column: Simulation and Experiment of Methyl Acetate Hydrolysis

As a combination of divided wall column (DWC) and reactive-distillation column, the reactive divided wall distillation column is a highly complex technology that reaction and separation can occur simultaneously, which can reduce the energy consumption and decrease the costs of captial and operation. This new process was simulated with PROⅡ software and mini plant experiments were implemented. In addition, we investigated the influences of reflux ratio, liquid distribution ratio and molar ratio of ester in water on the conversion rate of methyl acetate and the purity of the product respectively. It could be seen that the trend from experiments was suitable with simulation results.

Hydrolysis of carboxylic acid esters catalyzed by a carbon-based solid acid

A carbon-based solid acid catalyst is prepared by incomplete carbonization of sulfonated naphthalene and used for the hydrolysis of carboxylic acid esters. XRD, FT-IR, TGA and acid density test are employed to characterize the structure and performance of the catalysts. The results show that the catalysts prepared under different synthesis temperature and time are amorphous carbon composed of small aromatic carbon sheets with –SO3H groups. The catalytic activities of catalysts for methyl acetate hydrolysis are closely related with their acid densities. The appropriate synthesis temperature and time for the catalyst are 230 °C and 12 h and the acid density of catalyst under the optimized conditions can reach 4.49 mmol g−1. The carbon-based solid acid shows higher catalytic activity than Amberlyst-15 resin as a popular hydrolysis catalyst for a series of carboxylic acid esters hydrolysis. The catalyst has good thermal stability, which can bear 250 °C without decomposition. It also remains satisfactory catalytic activity for methyl acetate hydrolysis after six times recycling.

Control of Catalytic Divided Wall Column

A control strategy which is based on the Catalytic Divided Wall Column (CDWC) for hydrolysis of methyl acetate (MeAc) is studied and a feasible control structure is obtained. The manipulated variables and controlled variables are selected and paired. Two kinds of disturbances are employed to test this control configuration and the result shows that a simple PI control scheme with three temperature loops can obtain reasonable control performance and maintains the desired purity of two products and stoichiometric balance between reactants.

Design of Catalytic Divided Wall Column

The Catalytic Divided Wall Column (CDWC) for hydrolysis of methyl acetate (MeAc) is designed and optimized. Distillate rate and side rate of CDWC are used to maintain the desired product purities, and the minimum reboiler duty is obtained by changing the reflux ratio and vapor split ratio. The result shows that the new process can save energy consumption by 20.1%.

A Novel Route for Conversion of Free Fatty Acids in Acidic Oils to Methyl Esters by In-Situ Hydrolysis of Methyl Acetate

Biodiesel from clean oils is comparatively easier than production from crude and non-edible oils. To achieve maximum yield of biodiesel, a two stage process is adopted in which non-edible oils are used as feed-stock: an acid catalyzed esterification of free fatty acids followed by base catalyzed transesterification. Presence of water formed during esterification reaction is detrimental to a viable transesterification process. In the present work, an alternate method for removal of water by in situ hydrolysis reaction of methyl acetate is introduced. The dehydration using methyl acetate during esterification has yielded good results as the soap formed during transesterification was minimal. The results indicated high conversion of triglycerides to methyl ester for lower oil to methanol ratio and at a lower temperature. For 1:3 molar ratio of oil to methanol, the conversion obtained was less than 90 percent and is equivalent to conversions with higher alcohol ratios during esterification in the absence of methyl acetate. These results are indicative of the fact that use of methyl acetate reduces the alcohol to oil ratio without affecting the conversions. Moreover, higher conversions are possible at lower temperatures in the presence of methyl acetate. It is further observed that the oils that are subjected to free fatty acid conversions in the presence of methyl acetate record very little soap formation during the transesterification reactions, thereby resulting in higher grade of biodiesel.

A Novel Route for Conversion of Free Fatty Acids in Acidic Oils to Methyl Esters by In-Situ Hydrolysis of Methyl Acetate

Biodiesel from clean oils is comparatively easier than production from crude and non-edible oils. To achieve maximum yield of biodiesel, a two stage process is adopted in which non-edible oils are used as feed-stock: an acid catalyzed esterification of free fatty acids followed by base catalyzed transesterification. Presence of water formed during esterification reaction is detrimental to a viable transesterification process. In the present work, an alternate method for removal of water by in situ hydrolysis reaction of methyl acetate is introduced. The dehydration using methyl acetate during esterification has yielded good results as the soap formed during transesterification was minimal. The results indicated high conversion of triglycerides to methyl ester for lower oil to methanol ratio and at a lower temperature. For 1:3 molar ratio of oil to methanol, the conversion obtained was less than 90 percent and is equivalent to conversions with higher alcohol ratios during esterification in the absence of methyl acetate. These results are indicative of the fact that use of methyl acetate reduces the alcohol to oil ratio without affecting the conversions. Moreover, higher conversions are possible at lower temperatures in the presence of methyl acetate. It is further observed that the oils that are subjected to free fatty acid conversions in the presence of methyl acetate record very little soap formation during the transesterification reactions, thereby resulting in higher grade of biodiesel.

Coupled Reaction/Distillation Process for Hydrolysis of Methyl Acetate

A process composed of a fixed-bed and a distillation column with a side withdraw, mainly methanol, is developed to hydrolyze methyl acetate (MA) as a typical byproduct in polyvinyl alcohol (PVA) and pure terephthalic acid (PTA) factory. The process is simulated by employing the equilibrium stage model RadFrac and plug flow model Rplug in Aspen Plus. Experiments are also carried out in a lab-scale to evaluate the process. The results show that at the molar ratio of water to methyl acetate about 4.0-5.0 in the feed stream and the volume ratio of distillate to feed MA above a critical value, the side product contains more than 80% (by mass) (MeOH) and less than 2% (by mass) MA, while the bottom contains more than 46% (by mass) acetic acid (HAc) and less than 0.5% (by mass) methanol with almost complete conversion of MA. Compared with the old catalytic distillation process we proposed before, this process can cut down 47.6% energy consumption and a distillation column.

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 350kPa, 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.

Numerical Investigation of the Reactive Dividing Wall Column Exemplified by Methyl Acetate Hydrolysis

AbstractReaktive Trennwandkolonnen bieten eine Möglichkeit, die Vorzüge der Trennwandkolonnen und der Reaktivrektifikation in einem Apparat zu kombinieren. Aufgrund der Neuartigkeit dieses komplexen Verfahrens sind ausgiebige, numerische Untersuchungen unabdingbar. Zu diesem Zweck wurde ein auf dem rigorosen Stoffaustauschmodell basiertes Simulationstool entwickelt. Die erfolgreiche Validierung des Modells und des Simulationstools anhand von Experimenten wird vorgestellt.

Design and Control of a Heat-Integrated Reactive Distillation System for the Hydrolysis of Methyl Acetate

There is increasing interest in the heat-integrated reactive distillation systems, lately. In this Article, two types of heat-integrated reactive distillation systems for the hydrolysis of methyl acetate are investigated. One type is to use the concept of internally heat-integrated distillation column (HIDiC) as applied to the reactive distillation system. Another type for the heat integration is to use a multieffect distillation concept by splitting the feed to enter into two smaller reactive distillation columns operated at different pressures. Rigorous simulation study has been conducted to compare the optimal flowsheet of the above two designs. It is found that, although the first design can save operating costs by 8.05%, due to the high cost of the compressor needed in the system, the total annual cost is 33.13% higher than that of the base design without heat integration. On the contrary, the multieffect distillation design not only saves operating cost by 15.19%, but also saves the total annual cos...

Control of plantwide reactive distillation processes: Hydrolysis, transesterification and two-stage esterification

General design principles for controlling plantwide reactive distillation processes are developed in this work. Three cases of plantwide RD processes with large recycle flow rates are used to illustrate the application of the design principals. The cases are hydrolysis of methyl acetate, transesterification of methyl acetate and esterification of adipic acid. The design principles produce workable control structures for the three systems. Temperature and temperature-composition control structures can deal with the two major disturbances: changes in the feed flow rates and reactant composition. Results show that the control structures offer good robustness and acceptable dynamic performances.

The neutral hydrolysis of methyl acetate — Part 1. Kinetic experiments

The neutral hydrolysis of methyl acetate and catalysis of the reaction by the acetic acid product have been studied in the temperature range 90–110 °C. Extrapolated to 25 °C, the rate constants are 0.17 × 10−8 s–1 for the uncatalyzed reaction and 1.4 × 10−4 (mol/L)–1s–1 for the catalyzed reaction. The acid catalysis is specific not general: at 90 °C the rate constants for hydrochloric acid catalysis and catalysis by ionized acetic acid are the same as the rate constant, kH = 1.4 × 10−2 (mol/L)–1s–1, determined in the neutral reaction.

The neutral hydrolysis of methyl acetate — Part 2. Is there a tetrahedral intermediate?

A computational strategy that reproduces the experimental rates of hydration of formaldehyde, acetaldehyde, acetone, and cyclohexanone and the rates of acetic acid and 2-hydroxypyridine-catalyzed hydration of acetone has been extended to the results of the neutral hydrolysis of methyl acetate reported in Part 1. Calculations have been performed for one-step and two-step mechanisms, with cooperative assistance from one to three additional water molecules in the presence and absence of the acetic acid product. The calculations predict that, for the neutral reaction, a one-step mechanism will be favoured if tetrahedral intermediates have a short lifetime and do not interconvert prior to breakdown (case A), and a two-step mechanism will be operative if tetrahedral intermediates are allowed to interconvert prior to breakdown (case B). The experimental results are consistent with the predictions of case A. In the presence of acetic acid, case A predicts that the acid will contribute only 1.6% to the overall rate, a negligible acceleration over the noncatalytic process, and case B predicts general acid catalysis to be an order of magnitude greater than the experimental result. It is concluded that the neutral hydrolysis of methyl acetate is mainly a cooperative one-step process, and that general acid catalysis by the acetic acid product does not occur.

Catalytic distillation for simultaneous hydrolysis of methyl acetate and etherification of methanol

A catalytic distillation process was developed for the treatment of a methyl acetate/methanol byproduct stream typically encountered in polyvinyl alcohol manufacture. A two-step reaction scheme (hydrolysis + etherification) with separation is modeled in a catalytic distillation column to produce dimethyl ether (DME) and acetic acid. Simulations are performed using Aspen Plus ® and assume both physical and reaction equilibrium. A batch catalytic distillation test with only methyl acetate and methanol as feed, showed DME to be the sole distillate product, whereas, the bottoms product contained acetic acid, water, methanol, and DME. Simulation results show that this “self-feeding” reaction sequence can be used to produce a high purity DME product with complete conversion of water and methanol. The effect of pressure, water, molar feed ratio of methyl acetate/methanol, and feed location were examined. Even with no additional water fed, the hydrolysis reaction proceeds to completion and is only dependent on the molar feed ratio of methyl acetate/methanol. All possible azeotropes (methyl acetate/water, methyl acetate/methanol) are eliminated by completely reacting away water and methanol.

Process alternatives for methyl acetate conversion using reactive distillation. 1. Hydrolysis

In a polyvinyl alcohol (PVA) plant, reaction stoichiometry indicates that equal molar of methyl acetate is generated for every mole of PVA produced. This work explores an alternative to convert methyl acetate back to acetic acid (raw materials of PVA plant), methyl acetate (MeAc) hydrolysis. The design and control of methyl acetate hydrolysis using reactive distillation is studied. Because of the small chemical equilibrium constant ( ∼ 0.013 ) and unfavorable boiling point ranking (MeAc being the lightest boiler), the reactive distillation exhibits the following characteristics: (1) total reflux operation and (2) excess reactant (water) design. The proposed flowsheet consists of one reactive distillation column with a reactive reflux drum, two separation columns, and one water-rich recycle stream. A systematic design procedure is used to generate the flowsheet based on the total annual cost (TAC). Two dominate design variables are: recycle flow rate (for the degree of excess in water) and the overhead impurity level of acetic acid in the product column (to avoid tangent pinch). Finally, the operability of the hydrolysis plant is evaluated. A plantwide control structure is developed followed by process identification and controller tuning. The results show that reasonable control performance can be achieved using simple temperature control for feed flow and feed composition disturbances.