Hydrolysis Of Acetic Anhydride Research Articles

Use of isoperibolic reaction calorimeter for the study of reaction kinetics of acetic anhydride hydrolysis reaction: Effect of acetic anhydride and water ratio

Use of isoperibolic reaction calorimeter for the study of reaction kinetics of acetic anhydride hydrolysis reaction: Effect of acetic anhydride and water ratio

Development of an optimal bilayered back propagation neural network (BPNN) to identify thermal behaviors of reactions in isoperibolic semi-batch reactors

It is very important to identify the thermal behaviors of semi-batch reactors (SBRs) in isoperibolic operating mode. First, a default bilayered back propagation neural network (BPNN) is selected from multiple recognition algorithms to achieve this task, which is suitable for three kinds of reactions with arbitrary reaction orders: homogenous, kinetically−controlled, and diffusion−controlled liquid−liquid heterogeneous reactions. Then, it is further optimized by Bayesian regularization and genetic algorithm (GA). The result shows that the optimal bilayered BPNN undoubtedly has better recognition accuracy and generalization performance. It is found that the accuracy of the two test sets are 98.8% and 100%, respectively. Subsequently, a simple and user-friendly standalone desktop application program (app) is designed to easily use the developed optimal bilayered BPNN. Finally, a case of acetic anhydride hydrolysis reaction with acetic acid solvent is studied to prove the good validity of the bilayered BPNN and the great reliability of the standalone desktop app.

Data Management of Microscale Reaction Calorimeter Using a Modular Open-Source IoT-Platform

Unifying research data collection methods and capturing data streams in an organized and standardized manner are becoming increasingly important in laboratories as digital processes and automation progressively shape the laboratory workflows. In this context, the Internet of Things (IoT) not only offers the opportunity to minimize time-consuming and repetitive tasks by delegating them to machines, but it also supports scientists in curating data. As a contribution to the establishment of IoT tools in academic research laboratories, a microscale reaction calorimeter is exemplarily connected to a modular open-source IoT-platform. The microcalorimeter’s process data is streamed to the data platform for data repository and analysis. Advantages of the platform from academia’s point of view are presented. Finally, the application of the platform was successfully tested with the hydrolysis of acetic anhydride. The data were accessed and analyzed exclusively via the IoT-platform, which provided important advantages for the operator in terms of standardized evaluation in just a few steps.

Identification of Kinetics and Autocatalytic Behavior in Acetic Anhydride Hydrolysis Reaction via Reaction Calorimetry

In the fine and pharmaceutical chemical industries, the operation of highly exothermic reactions with the autocatalytic feature needs great caution. Identification of the autocatalytic behavior for a given reaction is of signification importance. In this work, first, an autocatalytic mathematic model for the acetic anhydride hydrolysis reaction is established. Then, a series of experiments at an approximate mole ratio of acetic anhydride to water with the solvent of acetic acid are designed to study this reaction by reaction calorimetry. Third, the six isothermal experiments are used to fit the kinetic constants, and the fitting result is very good and reasonable when compared to the published literature. Besides, it is proven that this reaction also has an autocatalytic feature at an approximate mole ratio of acetic anhydride to water. Last, the determined kinetic constants are also verified by two experiments operating under isoperibolic conditions.

Comparison of runaway criteria for prediction of different thermal behaviors in the acetic anhydride hydrolysis reaction performing in batch or semi-batch reactors

In this paper various runaway criteria for batch reactors (BRs) and semi-batch reactors (SBRs) have been used and compared to study the boundaries of different thermal behaviors for the acetic anhydride hydrolysis reaction with the solvent of acetic acid carried out in BRs and SBRs. It is shown that the majority of criteria for BRs could give relatively precise results, but the remaining minority are less accurate due to they all have some specific assumptions. Besides, the simulated results indicated that all the criteria for SBRs could accurately identify the transition point from TR to QFS behaviors in spite of that they give slight different results of transition point corresponding to NI and TR behaviors. The results can give an effective instruction for selection and usage of runaway criteria, especially in terms of effectiveness and applicability, to easily identify thermal behaviors in chemical industry.

Thermokinetic analysis of the stability of acetic anhydride hydrolysis in isothermal calorimetry techniques

Thermokinetic analysis of the stability of acetic anhydride hydrolysis in isothermal calorimetry techniques

Kinetics Modelling of Uncatalyzed Esterification of Acetic Anhydride with Isoamyl Alcohol in a Microreactor System

Uncatalyzed esterification of acetic anhydride and isoamyl alcohol has been carried out in a miniaturized intensified reactor (MIR) to develop a kinetic equation using an ideal homogenous model. The effect of reaction temperature (65℃-85℃) and residence time (7.9–180.3 min) at constant molar ratio 2:1 of isoamyl alcohol to acetic anhydride were studied. The results showed that isoamyl acetate concentration production increased from 0.80 mol/L to 2.64 mol/L with residence time from 7.9 min to 180.3 min and also increased from 1.6 mol/L to 2.0 mol/L when reaction temperature increase from 65℃ to 85 ℃. High conversion (>97%) of acetic anhydride was obtained in the absence of a catalyst in a microreactor system in a short residence time of 90 min as compared to days in a traditional batch reactor. This is because of the high surface-to-volume ratio of a microreactor system which promotes excellent proximate contact between reactants to allow efficient heat and mass transfer for esterification and effective mixing. Three different kinetic equations which are the second-order model, autocatalytic and reversible reaction were used to fit the experimental data. The latter kinetic model represented well for the esterification reaction between acetic anhydride and isoamyl alcohol with a good fit of 0.38 average standard error of regression between predicted concentration compare to experimental result. From the simulation result, hydrolysis of isoamyl acetate was found to be more favorable compared to acetic anhydride. This can be seen from the rate constant of reverse reaction of isoamyl acetate, where k3=0.008530Lmol.s which is significantly higher compare to hydrolysis of acetic anhydride, where k4=3.983×10−8Lmol.s at initial water concentration of 0.2 M. Even at different simulated initial water concentration, rate constant of hydrolysis of isoamyl acetate, k3 was always greater than the hydrolysis of acetic anhydride, k4. The parameter of initial water concentration was important to be determined in which it allows to improve the fitness of the kinetic model.

Analysis and experimental demonstration of forced periodic operation of an adiabatic stirred tank reactor: Simultaneous modulation of inlet concentration and total flow-rate

It is well known, that forced periodic operation possesses the potential for process improvements. Nevertheless, only a small number of applications is reported, due to complex realization, limited predictability and high inertia of larger units.Nonlinear frequency response (NFR) analysis has proven to predict efficiently time-averaged performance of reactor effluent streams originating from forced periodic changes of one or several input(s).Focus of this paper was an experimental demonstration of forced periodic operation applied to the hydrolysis of acetic anhydride carried out in an adiabatic CSTR. Theoretical results provided a guideline for experiments exploiting simultaneous sinusoidal modulations of the anhydride inlet concentration and the total volumetric flow-rate. Influences of the forcing parameters (amplitudes and the phase difference) were also studied. Confirming the predictions of NFR analysis a significantly higher time-averaged product yields were experimentally achieved compared to conventional steady-state operation with simultaneous modulation of two inputs using an optimized phase shift.

Kinetics of the hydrolysis of acetic anhydride using reaction calorimetry: effects of strong acid catalyst and salts

The effect of strong acid (hydrochloric acid) catalyst and salts (sodium chloride and potassium chloride) on the kinetics of the hydrolysis of acetic anhydride was studied using a simple isoperibolic calorimetric technique. The apparent second-order rate constant was observed to increase linearly with the increase in the strong acid concentration, suggesting the occurrence of a non-catalytic and an acid-catalyzed reaction route. The kinetic parameters for the non-catalytic route and for the acid-catalyzed route were determined. The effect of salt concentration causes a decrease in the effective rate constant over the range of variables studied. Sodium and potassium chloride presented practically the same negative effect on the hydrolysis kinetics.

A simulated annealing optimization algorithm based nonlinear model predictive control strategy with application

Batch reactors are widely used in the production of fine chemicals, polymers, pharmaceuticals and other specialty products. For certain exothermic reactions, the transient operation of the reactor with respect to small changes in critical parameters like coolant temperature and initial composition of the reactants can lead runaway condition of the reactor. In order to avoid the hazards associated with runaway situations, it is imperative to operate the reactor by means of an efficient controller. This work presents a nonlinear model predictive control (NMPC) strategy based on simulated annealing (SA) for the temperature control of a batch reactor involving a highly exothermic runaway reaction. The efficacy of the proposed strategy is studied through simulation for the temperature control of the reactor in which a highly parametric sensitive exothermic reaction of hydrolysis of acetic anhydride with sulfuric acid as catalyst and acetic acid as a solvent is carried out. The controller is found effective in averting the runaway behavior with the smooth and quick attainment of the desired operating condition. The results demonstrate the better performance of the SA based NMPC over the linear model predictive controller (LMPC).

Analyses of reaction rate data for the simple hydrolysis of acetic anhydride in the acetonitrile/water and acetone/water cosolvent systems using recently developed thermodynamic rate equations

AbstractThis article presents reaction rate data for the simple hydrolysis of acetic anhydride in the acetonitrile/water and acetone/water cosolvent systems and regression analyses using recently developed thermodynamic rate equations that contain electrostatic and solvent‐solute terms. The isomole fraction plots for these reaction systems are linear, and previous theoretical work has shown that the electrostatic term is negligible for such systems. On the other hand, the reaction rates are dependent upon the cosolvent mole fraction, indicating that the solvent‐solute term, which is modeled empirically, is significant. The results of the analyses provide the foundation for a paradigm shift away from the emphasis on electrostatic effects to more tenable explanations of kinetic behavior in solvent systems.

Hydrolysis of acetic anhydride: In situ, real-time monitoring using NIR and UV–Vis spectroscopy

Hydrolysis of acetic anhydride is a fast and very exothermic reaction that has been studied with different analytical techniques to account for the reaction progress. This work presents the real-time monitoring of the hydrolysis of acetic anhydride using in situ NIR and UV–Vis spectroscopy, under non-isothermal and non-adiabatic conditions. The experimental apparatus consists of a reaction vessel equipped with a magnetic stirrer, NIR and UV–Vis immersion probes and a thermocouple. Two multivariate models are proposed to account for the conversion of acetic anhydride as a function of time, one for NIR and other for UV–Vis. The calibration data were generated by calorimetry. The external validation permits the assessment of the adherence of the model to data not used for calibration. The results show that both models can be useful to monitor this hydrolysis, employing a simple and intuitive apparatus.

Kinetic modeling using temperature as an on-line measurement: Application to the hydrolysis of acetic anhydride, a revisited kinetic model

The use of calorimeter in chemical reaction engineering is a powerful tool to estimate kinetic constants. Indeed, reaction temperature is used as an online analytical signal. Nevertheless, the thermal characterization of the calorimeter must be done to avoid wrong estimation. The hydrolysis of acetic anhydride was used as a reaction model in a handmade calorimeter, because it is a fast and exothermic reaction. Several research groups have studied this reaction without taking into account the autocatalytic effect due to the production of acetic acid. To fill this gap, a kinetic model was developed by taking this phenomenon and in a thermally characterized handmade calorimeter. The estimated kinetic constants in the handmade calorimeter were found to be similar than in the established calorimeter Mettler Toledo RC1.

Mathematical modeling of the dynamics of homogeneous reactions in the cascade of perfect mixing reactors

Present study tackles theoretical analysis and mathematical modeling of the process of homogeneous first-order reaction in the cascade of perfect mixing reactors of continuous action (PMR-C). The modeling of chemical reactors is based on the thermal and material balances in combination with chemical kinetics. The mathematical model of the dynamics of the process of homogeneous first-order reaction in the PMR-C cascade is represented in the form of equations of change in the molar fraction of substance over time and a change in the inner energy of the ideal flow of substance. In the present work, we calculated, by the mathematical model, the process of acetic anhydride hydrolysis in 5 sequentially connected PMR-C. Calculation by the model is performed by the Runge-Kutta method of third order. We obtained temperature profiles for the dynamics of the process of acetic anhydride hydrolysis for a cascade of PMR-C. The temperature gradient in reactor grows over time; consequently, it takes on a constant value. We analyzed the impact of the volume of reaction mixture on the depth of the course of the process both for the separate perfect mixing reactors and for the cascade of perfect mixing reactors. With an increase in the volume of mixture, the reaction rate increases, while the speed of reaching the necessary degree of conversion decreases. The speed of reaching the maximum degree of conversion for the cascade of reactors compared with one perfect mixing reactor of the same volume is considerably higher. Recommendations regarding the course of the process are formulated. We calculated the value of cost for conducting the process of acetic anhydride hydrolysis depending on the change in temperature. Minimum cost is attained at temperature 341 K and amounts to UAH 1.70 million per year.

A comparative study on the hydrolysis of acetic anhydride and N,N-dimethylformamide: Kinetic isotope effect, transition-state structure, polarity, and solvent effect

A comparative study on the hydrolysis of acetic anhydride and N,N-dimethylformamide: Kinetic isotope effect, transition-state structure, polarity, and solvent effect

Periodic Operation with Modulation of Inlet Concentration and Flow Rate Part II: Adiabatic Continuous Stirred‐Tank Reactor

AbstractThe nonlinear frequency response (NFR) method, which is an analytical, fast, and easy method for evaluating the performance of forced periodically operated chemical reactors, was used to investigate possible improvements to a nonisothermal continuous stirred‐tank reactor (CSTR) when inlet concentration and/or flow rate are periodically modulated. The product yield was used for evaluating the performance improvements. Part I of this paper considered the general nonisothermal case. In this part, the results are applied to an adiabatic CSTR. A laboratory‐scale adiabatic CSTR was analyzed by applying kinetic parameters for the hydrolysis of acetic anhydride. It is shown that improvement can be obtained for simultaneous modulation of the two inputs with appropriately chosen forcing parameters.

Hydrolysis of Acetic Anhydride in a CSTR

To find the optimal reactor volume and temperature for the hydrolysis of acetic anhydride at the lowest possible cost with a 90% conversion of acetic anhydride, a formula for the total cost of the reaction was created. Then, the first derivative was taken to find a value for the temperature. This value was then inputted into the second derivative of the equation to find the sign of the value which would indicate whether that point was a minima or maxima value. The minima value would then be the lowest total cost for the optimum reaction to take place.

Thermal stability and dynamic analysis of the acetic anhydride hydrolysis reaction

In this work, a rigorous dynamic analysis was performed for the acetic anhydride hydrolysis reaction. It allowed identifying its safe operational conditions in a Continuous Flow Stirred-Tank Reactor (CSTR). Some parameters were introduced and the dimensionless variables and model equations (material and energy balances) were defined. The temperature and conversion profiles were calculated using the experimentally validated kinetic expression and typical operating conditions. Subsequently, thermal and bifurcation diagrams were obtained. All thermal states were recognized: stability (unique and multiple solutions) and instability, bifurcation points, saddle-node bifurcations, turning points (limit points) and oscillatory behavior. The obtained results demonstrated high sensitivity of reactive system (thermal runaway) and predominant oscillatory instability.

Acetic Anhydride Hydrolysis at High Acetic Anhydride to Water Ratios

ABSTRACTThe hydrolysis of acetic anhydride in the presence of water is an exothermic reaction that produces acetic acid. Most of the research has focused on low ratios of acetic anhydride to water. The major concern in the industry is the accidental addition of a small amount of water to large quantities of acetic anhydride stored in tanks, or as handled in a manufacturing process. This paper focuses on isothermal and adiabatic experiments that were conducted to understand the effect and rate of hydrolysis at high ratios of acetic anhydride to water. The acetic acid produced in the reaction also affects the rate of reaction. Detailed calorimetric data and specific rate expressions that have been developed are presented in this paper.

New insight on an old reaction – the aqueous hydrolysis of acetic anhydride

Studies have shown that aqueous reactions generating a change in pH can be accurately monitored using a fast‐response pH electrode. This technique has been successfully applied in this work to the aqueous hydrolysis of acetic anhydride, which is a reaction that has been studied using a variety of techniques for nearly one hundred years. Many of these techniques involve elaborate equipment and sophisticated analyses, making the pH technique an attractive alternative. Studies here have focused on the temperature effects of the simple hydrolysis and acetate‐catalyzed hydrolysis reactions. Data analyses suggest the notion that if simple hydrolysis occurs by a two‐step mechanism, it does so only at low temperatures, whereas acetate‐catalyzed hydrolysis occurs almost assuredly by a single step mechanism. Results of this work yield the following values for the activation parameters for simple hydrolysis (subscripted with a “w”) and acetate‐catalyzed hydrolysis (subscripted with an “a”) at atmospheric pressure: and . Implications of these results are discussed in this article. Copyright © 2012 John Wiley & Sons, Ltd.