Kinetics of Alkaline Hydrolysis of Ethyl Acetate by Conductometric Measurement Approach Over Temperature Ranges (298.15-343.15K)

Research Article

Austin Chem Eng. 2017; 4(1): 1046.

Kinetics of Alkaline Hydrolysis of Ethyl Acetate by Conductometric Measurement Approach Over Temperature Ranges (298.15-343.15K)

Mukhtar A¹*, Shafiq U¹, Qazi MO², Qadir HA¹, Qizilbash M² and Awan BA¹

¹Department of Chemical Engineering, NFC IE & FR Faisalabad, Pakistan

²Department of Chemical Engineering, Universitat Politecnica de Catalunya-UPC, Spain

³Institute of Chemical Engineering and Technology, University of the Punjab, Lahore, Pakistan

*Corresponding author: Ahmad Mukhtar, Department of Chemical Engineering, NFC IE & FR Faisalabad, Pakistan

Received: December 21, 2016; Accepted: January 30,2017; Published: February 01, 2017


Industrial significance of the reaction product sodium acetate and ethanol demands for the process improvements in terms of maximum conversion and economical & environmental friendly usage of raw material. This research aims the kinetic study of ethyl acetate hydrolysis with sodium hydroxide at different temperatures and development of mathematical model for holding time in batch reactor. For this purpose the experiment is carried out in a batch type stirred tank reactor over different temperatures and change in concentrations (in terms of electrical conductivity) measured with time. Detail kinetic study has been investigated and concluded that this reaction is shifting order and cannot be expressed as 2nd order reaction kinetics also it has been found that the reaction is exothermic in nature and low reaction temperature favors the high conversion and high reaction rate. The average values of rate constant and activation energy are found to be 4.409 KJ/mole and 0.0243μs 0.3118s-1 respectively which are agreed well with those of previous studies.

Keywords: Hydrolysis; Reaction Kinetics; Order of Reaction; Rate Constant; Conversion; Activation Energy


The chemical reactions taking place in a chemical reactor are considering the heart of a chemical process. Reaction kinetics is the translation of our understanding about chemical process into a mathematical rate expression that can be used in reactor design and rating. Because of the importance of the development of performance models to stimulate the reactor fundamental parameters, comprehensive reactor design chemical kinetics is a key aspect of research and development (R&D) in chemical process industries [1]. Chemical Kinetics is actually a part of physical chemistry deals with the study of reaction rates. Reaction rate can be defined as the changes in the number of molecules of reacting species per unit volume per unit time or how fast a reaction takes place [2]. The rate of chemical reactions is affected by a number of factors like greater the surface area of solid reactants greater will be the rate of reaction, high concentration of reactants high will be the rate of reaction, in case of gaseous reactants and products the rate of reactions directly proportional to the pressure, catalysts also increase the rate of reaction however negative catalysts can decrease the rate of chemical reactions, and high temperature usually favors high rate of reaction Saponification is the hydrolysis of carboxylic acid under alkaline conditions. Hydrolysis is the chemical decomposition involving the breaking of ester bond and releasing the fatty acid and glycerol in the presence of an alkali. Commercial importance of the reaction product sodium acetate which is not used specifically for cleaning purposes but has a wide range of industrial applications such as in pharmaceutical, paint and dying industry, as food additive, in electroplating industry, as meat preservative, photography and purification of glucose etc. whereas ethanol as a by-product can be used as a bio fuel. Despite the commercial importance of no study has been found on the process improvements in terms of maximum conversion and economical & environmental friendly usage of raw material for this saponification reaction [3-6]. Saponification of ethyl acetate with sodium hydroxide proceeds through the direct attack of nucleophile (OH-1) on carbon atom of ethyl acetate [7-12]. Saponification of ethyl acetate with sodium hydroxide is the 2nd order overall, 1st order with respect to reactants furthermore reaction order decreases and become sequential rather than 2nd order when equimolecular concentrations of both reactants are used. This is a non-catalytic, homogeneous phase (liquid/liquid) and constant density system reaction. This reaction is mild exothermic in nature.


The hydrolysis of ethyl acetate with sodium hydroxide is one of the most well-known reactions in chemistry and it is represented as a model example of the 2nd order reaction in the literature dealing with chemical kinetics [13-15].

Previous research shows that equimolecular concentration of both reactants yield high conversion this can be also seen from the reaction stoichiometry. The addition of products actually retarded the overall reaction rate, but it is too much small to illustrate the deviation from 2nd order kinetics. Experimentally the deviation is more remarkable when the concentrations of ester and base are close. All the previous study shows that in continuous process increase in reactant flow rates cause decrease in residence time and due to which overall conversion decrease. On the other hand rate constant initially increase and then shows decline with the reactant flow rate. The dramatically decrease in conductivity can be observed with stirrer rate and results in achieving higher conversion as reaction proceeds. Therefore agitation is necessary to provide efficient mixing and uniform temperature distribution in reactor. The reaction conversion increases from 50.2% to 58.8% corresponding to a temperature change from 25°C to 30°C but for a reaction temperature more than 30°C a more sluggish behavior of change in reaction conversion can be observed [16-19]. As the previous research shows that the hydrolysis of ethyl acetate under alkaline conditions is 2nd order reaction, however during the experiments, we found that saponification of ethyl acetate with sodium hydroxide does not satisfy the 2nd order reaction kinetics. It was necessary to analyze the reaction more carefully. The previous works on this reaction did not analyze the reaction rate in details. Usually only the mean initial rate constant has been obtained. The deviation from the 2nd order rate equation has never been analyzed in detail kinetically. Therefore we study the kinetics and reaction rate of this reaction at different temperature careful in order to analyze the reaction kinetics.

This reaction has been studied by several researchers at different temperatures using a variety of measurement techniques in order to estimate the reaction order and activation energies [14,20]. Daniels et al [21]. And Levenson [22] use a volumetric titration method independently in which the composition of reaction mixture is analyses by withdrawal of samples after equal interval of time. The main disadvantages are the errors associated with the titration using color indicators. The 2nd technique is reported by Walker [15] based upon the composition measurement at any time using Conductometric measurement method. These measurements are carried out manually. However the accuracy of results strongly depends upon the response time in Conductometric measurement. Another technique reported by Stead et al [23]. This is based upon the continuous flow systems and usually for large volumes of fluids. In this method the reactants are fed continuously to a stirred tank reactor at constant temperature. Jensen et al [24]. Used high frequency titrimetry. This method does not need the introduction of any electrodes or external indicator in the reaction vessel. But the precaution about the calibration of the equipment must be taken for the nonlinearity of the equipment. This method involves a number of manual operations in methodology as compared with the proposed method. Shui-Yuan et al. and Ge-Li et al. [25,26] used acidometry and micro calorimetry techniques respectively in order to estimate the rate constant of saponification of ester. However these latest techniques are not so simple as compared to proposed methods. Zhanjun et al. and Young-Tao et al. [27,28] focused their attention to online data using a Conductometric measurement technique in order to make the methodology much simpler.

Experimental Work

For the batch experimentation equimolecular amounts of both reactants 0.1M of ethyl acetate (CH3COOC2H5) purchased from E. Merck KG and 0.1M of sodium hydroxide (NaOH) purchased from RdH Chemicals are introduced in a batch type stirred tank reactor. Agitation is provided with the help of a magnetic stirrer with a speed of (438rpm). Both reactants should be as close to same temperature as possible before starting the experiment. As the reaction proceeds to the forward direction hydroxide ions (OH-1) are consumed and acetate ions (CH3COO-1) are produced. This change in ion concentration results in a conductivity change in the solution that is continuously measured by a conductivity meter and by the measurement of this conductivity we could ascertain the degree of hydrolysis. Note the conductivity of the reaction mixture after equal interval of times until the conductivity becomes constant. Repeat the experiment at different temperatures from (25°C-70°C). Heating is providing with the hot water circulation. The data obtained on the basis of key Component (NaOH) from the experiments are given in Table 1. The experimental setup is shown in Figure 1.