Journal for Research|Volume3|
Issue1| March 2017 ISSN : 2395 - 7549
Kinetics of Esterification reaction using ion-exchange resin
catalyst
S. S Potdar U.S Patil
Lecturer, Department of chemical engineering (Polytechnic wing), Associate Professor and HOD, Department of chemical
E-mail: sumitpotdar3@gmail.com engineering (Degree wing), E-mail: unmeshp@gmail.com
Padmabhushan Vasantraodada Patil Institute of Technology Padmabhushan Vasantraodada Patil Institute of Technology
Budhgaon, Dist. -Sangli; Maharashtra; India. Budhgaon, Dist. -Sangli; Maharashtra; India.
Abstract
The reaction kinetics of esterification between n-butanol and acetic acid on acidic solid catalyst named SERALITE SRC-120 under
atmospheric pressure was investigated in this work. Reaction experiments were carried out in a stirred batch reactor at temperature
range of 353 to 356 K, under various catalyst loads and various starting reactants feed ratios. The experimental data were fitted to
estimate the kinetic parameters for reaction mechanisms. The chemical equilibrium composition was measured and kinetic
information was obtained at the same temperature range. The results show that the activation energy of n-butanol esterification
reaction was found to be 622.28 KJ/mol. Finally the results of produced reaction mechanisms were compared with Experimental
results to validate the reaction mechanism. Then it was conclude that the model results with the regressed kinetic parameters are in
excellent agreement with the experimental results.
Keywords: Esterification, Heterogeneous catalyst, n-butyl acetate, Reaction Kinetics, slurry reactor, catalyst loading, ion-exchange
resin.
1. INTRODUCTION
Esterification reaction is one of the most important Although homogeneous catalysts such as sulfuric acid, p-
industrial reactions. Esters are widely used in chemical toluene sulfuric acid, and hydrochloric acid have a strong
industry such as a solvent for plastics, liquors, resins, gums, catalytic effect, they can cause some issues such as the
and coatings. Butyl acetate is commonly synthesized through development of side reactions resulting in a corrosive
esterification of acetic acid with n -butanol in the presence of a environment by the discharge of acid-containing waste. . It
suitable acid catalyst by reversible and kinetically controlled also results in sulfur contamination of the final product, which
reaction. Several works have reported the kinetics of the is unacceptable. Further, the use of homogeneous catalyst
esterification reaction in the presence of ion exchange resin. requires neutralization with an alkali, which leads to severe
The kinetics of esterification in the presence of a strong cation effluent problems on industrial scale. In all kinetic studies
exchange resin is studied. The influence of various parameters done with ion-exchange resins as catalysts, acidic ion-
on reaction rate and proposed the rate equation is analyzed. exchange gel-type styrene-divinyl benzene (DVB) resins have
There is recovery of butyl acetate could be in very high purity. been used .Research in catalysis by ion exchange resins is
Conventional methods of recovery of 30% acetic acid by undeniably interesting, not only from a purely
reaction with n butanol and isoamyl alcohol in a reactive physicochemical point of view but also in terms of the
distillation column using macroporous ion-exchange resin as a advantages of these types of catalyst over the conventional
catalyst bed. They studied the esterification of acetic acid with ones. Ion exchange resins increase the product yield, keep
n-butanol in the presence of Amberlyst-15. They investigated their activity a long time, and do not pollute.
the influence of various parameters such as temperature, mole Ion exchange resins separate from reaction media
ratio, catalyst loading, and particle size and they proposed the easily and they regenerate easily for reuse. Heterogeneous
rate equation model. [1]. It was noted that, most of the catalysts such as zeolites, ion-exchange resins, and acidic clay
previous studies performed in the literature have focused on catalysts are gaining importance of high purity of products,
the modification of catalysts and only a rather limited number because they are easily removed from the reaction mixture and
of papers have focused on studying the influence of reaction have lower corrosive effects. The solid acid catalysts are non-
conditions and the type of catalysts on the activity and corrosive, easy to separate from the reaction mixture and a
selectivity. On the other hand, few studies were focused on variety of reactor types and configurations can be adopted on
production of butyl acetate [1]. industrial scale. They can also be used repeatedly over
The reaction progress is very slow in the absence of prolonged period of time without any difficulty in handling
acid catalysis. Therefore, both homogeneous and and storing. Most reactions catalyzed by ion exchange
heterogeneous catalysis can be used. resins can be classified as either quasi-homogeneous or
quasi-
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heterogeneous. acids react more readily than branched ones; particularly
The kinetics of this model reaction catalyzed by Amberlyst- branching in the β-position lowers the rate of esterification.
15 was described in previous investigations with both a Esterification of aromatic acids, e.g. benzoic acid, is
quasi- homogeneous and a quasi-heterogeneous model. A generally slow. Experiments with primary and secondary
common method of operating equilibrium-limited reactions alcohols have shown that the oxygen in the water formed
is to use an excess of one reactant in order to increase the during acid-catalyzed esterification originates from the
conversion of the limiting reactant. In reactive distillation acid, not from alcohol. The reactions of tertiary alcohols are
(RD), the continual separation of products from reactants more complex and do not proceed clearly via a tertiary
forces the reaction to surpass the equilibrium conditions. carbonium ion. Generally, in industrial processes refluxing
RD is a process where separation of the the reaction mixture until all the water has been split off
components of a reaction system is accompanied by a facilitates out esterification. The water or the esters formed
chemical reaction in a column. [6] are removed from equilibrium mixture by distillation. The
choice of a method to achieve complete esterification
ESTERIFICATION OF ACETIC ACID WITH depends on the boiling points of alcohols, acids, and esters.
With high boiling esters (esters of polyhydric alcohols), the
BUTANOL USING SERALITE SRC-120
water of reaction may either be removed by evaporation or
CATALYST
by means of inert gases. Esterification is usually carried out
in a batch or continues mode depending on the scale of
Esterification of carboxylic acids is an important class of operation. It can also be carried out in the vapor phase by
reactions, the kinetics and equilibrium of which have been heating a mixture of acid, alcohol, ester, and catalyst to the
investigated throughout the history of physical chemistry, desired temperature. [3]
the dating back to pioneering efforts of Berthelot and Gilles
(1863). In 1914 at the beginning of the World War I, amyl
2. EXPERIMENTAL
acetate in the form of fuel oil acetate was the best known
ester solvent. The demand for airplane dope and the 2.1 Materials
corresponding need for cellulose nitrate and cellulose
acetate solvents increased rapidly during the war period. The reactants butanol and acetic acid used were of A.R.
The only ester that was developed on a large scale during grade (99.8%) and were obtained from Fume Chemicals,
the war to replace amyl acetate was methyl acetate, thus Kolhapur (Maharashtra, India). The chemicals were
Esterification of acetic acid with methanol got a boost as an used without further purification.
important process. Esters can be produced by different
2.2 Catalyst
approaches on both laboratory and commercial scales.
The cation exchange resin Saralite 120 SC used as the
Among all these, the simplest route to produce esters with
catalyst before using for experiments, the resin was
high yield is the direct Esterification of acids with alcohol in
pretreated using standard procedures. First, the resin
presence of mineral acid or a heterogeneous catalyst.
was washed with water the catalyst was soaked in
distilled water for 15 minutes and then charged into the
CH3COOH + C4H9OH CH3COOC4H9 + H 2O column. Then, one liter of 0.1 M hydrochloric acid
Acetic Acid Butanol Butyl Acetate Water solution and 0.1 M sodium hydroxide solution was
passed through the catalyst bed to remove acid soluble
Esterification reactions are equilibrium processes and must and alkali soluble impurities. After acid and alkali
be displaced toward the desired ester by the use of excess treatment each time, the resin was washed with water to
of one of the free reactants or by continuous removal of ensure complete removal of chloride and sodium ions
water by azeotropic distillation. Removal of water by from the catalyst bed.
chemical or adsorptive binding is also possible in
preparative chemistry, while calcium carbide, calcium Table 1:- Range of operating conditions
hydride and calcium and magnesium sulfate have proved
Reaction temperature, K 353 K
successful in industrial application. The rate of ester
formation depends on the carboxylic acid and the alcohol
used. The lowest members, i.e. methanol and formic acid, Catalyst loading, (percentage) 3% , 4% , 5%
react most readily. Primary alcohols react faster than Butanol : acetic acid ratio 4:1, 3:1 and 2:1
secondary alcohols and the latter react faster than tertiary
ones. Within each series, the reaction rate generally Particle size, mm 0.458
decreases with increasing molecular mass. Straight-chain
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was negligible compared with the total volume of the
system. [6]
The esterification of acetic acid with butanol was carried
out in a glass reactor of 500 ml volume. The heating 2.4 Analysis
mental is used for heating purpose. The temperature in the The analysis of reactants and products was carried
reactor was maintained within 80-90oC using a out using simple titration with 1N NaOH solution and
thermometer. phenolphthalein as indicator. The end point of reaction is
colourless to faint pink.
2.5 Result and Discussion
Calculation for conversion of acetic acid
(NaOH) vs. (Acetic acid)
N1V1 = N2V2
2.3 Experimental Setup and Procedure
N2 = (1*11.1)/10
N2 =CA1= 1.11mole/lit
Now conversion is given by
XA= (CAO - CA1)/ CAO
XA= (2.8070 – 1.11)/ 2.8070
XA= 0.6046
Conversion = 0.6046 *100 = 60.46 %
As there is no side reaction present, hence
Yield = Conversion= 60.46 %
Table 2 – Calculation of conversion for different time
interval.
Sr. Time Burette Concentration Conversion
no (hour) reading (mol/lit) XA
(ml)
Fig. 1: Experimental setup of a batch slurry reactor for 1 1 23.5 2.35 0.1628
Esterification reaction 2 1.5 21.4 2.14 0.2376
3 2 19.6 1.96 0.3017
4 2.5 16.1 1.61 0.4264
In all the experiments, a known amount of butanol was
charged to the reactor and heated to the desired 5 3 12.1 1.21 0.5689
temperature. When the temperature remained constant, the 6 3.5 11.1 1.11 0.6046
required amount of acetic acid was added under constant
stirring. It was observed that the temperature fall as a result
3. KINETICS OF ESTERIFICATION REACTION
of this addition was not significant and the temperature
equilibrium was reached in a short time. A sample was A relation between the conversion of acetic acid and reaction
removed for analysis. This was taken as the starting point time is obtained by using Pseudo-homogeneous model. Order
of homogeneous (uncatalyzed) reaction. For the catalytic of reaction and rate constant is obtained as follows. Rate of
reaction, after attaining the desired temperature, a known esterification reaction can be determined thus:
quantity of ion exchange resin along with acetic acid was K1
added to the reactor. The moment of resin addition was CH3COOH + C4H9OH CH3COOC4H9 + H2O
K2
taken as the starting time of reaction. Samples were
The rate expression for this reaction is given by:
withdrawn at regular time intervals for analysis. The
volume of sample withdrawn from the reactor during a run
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-rCH3COOH = k1 CCH3COOH . CCH3 (CH2)2CH2OH - k2 CC5H11OOH. CH2O Forward and backward reaction rate constant of the
…….(1) esterification reaction between butanol and acetic acid
(catalyzed by seralite catalyst) were determined. Values are
The reaction equilibrium constant is given by calculated as
K=k1/k2 ΔG0 = -RT ln (K1)
The reaction equibrium constant is calculated from K1= 0.9998
K ΔHR 1 1 The equilibrium constant at optimum temperature of 830C can
ln = ( - ¿ Where, K° = exp be calculated by using Vant Hoff equation
K° R T1 T2
ΔGR
[ ] ΔH T 1 1
RT 1 ln ¿ ) = - ( − )
R T2 T 1
Esterification reactions are known to be second order
reversible reaction. Therefore, for the bimolecular type second K2 = 1.0036
order reaction,
A + B C + D Following fig2 a plot for concentration vs. time shows that the
acetic acid concentration decreases due to formation of butyl
acetate product. Acetic acid is consumed by butanol and hence
With reaction that, its concentration reduces. Finally line on the graph will be
constant due to completion of reaction.
CAO = CBO and CCO = CDO = 0
Fig2- Plot for Concentration vs. Time
The rate expression can be written as,
-rB = -dCA / dt = CAO. dXA / dt = k1 CA .CB - k2 CC. CD 2.5
= k1 C2AO (1- XA) 2 – k2 (CAO XA) 2 …………….(2) f(x) = − 0.53 x + 2.93
2 R² = 0.98
Where,
A = Acetic acid 1.5
B = Butyl alcohol
C = Butyl Acetate
1
D = Water 0.5
At the equilibrium, -rA = 0
Hence the above equation, we determine the fractional
0
conversion of A at equilibrium condition by following 0.5 1 1.5 2 2.5 3 3.5 4
equation:
K = CCe. CDe / CAe. CBe = X2Ae / (1 – XAe)2 ………(3)
The equilibrium constant is given by as,
K = k1 / k2 CONCLUSIONS
Combining equation (1), (2) and (3) in term the equilibrium Earlier studies of the esterification reaction between butyl
conversion, we obtain, alcohol and acetic acid considered it to be second order for
-dXA / dt = k1 CAO [ (1 –XA)2 - ( 1 – 1/ XAe ) . X2A] both the forward and reverse reactions. In this study, the
forward and reverse orders of reaction were found to be K 1
With conversion measured in term of XAe, this may be and K2, respectively. The relationships representing the effect
indicated as a Pseudo second order reversible reaction, which of temperature and catalyst concentration on the reaction-rate
on integration gives, [4] have also been developed. The esterification reaction between
butanol and acetic acid performed over an acidic ion exchange
ln[ Xae - (2 Xae – 1) Xe ]/Xae - Xa = 2k1[ 1/Xae - 1] resin Saralite SRC 120. The interaction between the solid
Cao t catalyst and the reactants will consider in the model. The rate
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Issue1| March 2017 ISSN : 2395 - 7549
constant and conversion increases with increasing the 2) M. Bengi TAYSUN, Emine SERT, Ferhan S.
temperature of the reaction at a certain mole ratio of reactants. ATALAY Esterification of Maleic Acid with Butanol
The use of excess reactants on the conversion is studied. Catalyzed by Environmentally Friendly Catalysts
Higher the amount of alcohol higher the conversion will Ege University, Department of Chemical
obtain. Engineering, İzmir, TURKEY
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