1. A Study of Kinetics ofBatch and Continuous Stirred Tank Reactor Reaction ofSodium
Hydroxide with Ethyl Acetate
The objective of this experiment is to determine
the reaction rate constant k and activation energy
Ea using the kinetics of a reaction in a batch and
continuous stirred tank reactor (CSTR). The
reaction of sodium hydroxide (NaOH) with ethyl
acetate (EtOAc) is irreversible and second order
overall.
The schematic of the reactor unit is shown in
Figure 1. The reactants are pumped and fed into
the reactor at different set flow rates,which is 39
mL/min for NaOH and 32 mL/min for EtOAc in
this experiment. The water circulator is used to
change the temperature setting of the reactor.
When conducting the batch reaction, only the
reactor and agitator are used. All reactants are
added into the reactor at the beginning of the
reaction. The temperature and conductivity data is
measured and recorded on the computer. With the
reaction rate law and design equations for batch
and CSTR reactors,the concentrations of different species and fractional conversion X can be calculated.
The fractional conversion X and concentrations of both reactants and desired product sodium acetate
(NaOAc) are plotted versus time in Figure 2. The reactant concentrations should approach zero slowly for
an irreversible second-order reaction. The observed concentration data results in an exponential line that
meets the expectation. The concentration of NaOAc increases with time but the final value does not get
very high because EtOAc is limiting the conversion.
Figure 1: Schematic ofCSTR Reaction Unit
containing temperature and flow rate control. The
same reactor is used for both batch and CSTR
reactions.
Figure 2: Fractional Conversion Xand
Species Concentrations versus Time for the
Batch Reaction. The system reaches a high
final conversion.
0
0.02
0.04
0.06
0.08
0
0.2
0.4
0.6
0.8
1
0 500 1000 1500 2000
Concentration(M)
FractionalConversionX
Time (s)
NaOH
EtOAc
NaOAc
0
0.2
0.4
0.6
0.8
1
0.00
5.00
10.00
15.00
0 500 1000 1500 2000
FractionalConversionX
Conductivity(mS)
Time (s)
Conductivity
Conversion
Figure 3: Solution Conductivity Λm and
Fractional Conversion Xversus Time for the
Batch Reaction.As the reaction proceeds,the
measured conductivity goes down because of the
decreasing amount of [CH3COO-
] ions.

2. The exponential decay of the solution conductivity is shown in Figure 3, with the fractional conversion
versus time for comparison. At the same temperature, [OH-
] ions have much higher mobility than
[CH3COO-
] and conduct charges with the surrounding better.1
Therefore,as the isothermal batch reaction
proceeds,the solution conductivity will decrease because the amount of [CH3COO-
] ions increases and
that of [OH-
] ions goes down. Based on this fact,the measured solution conductivity can be used to
calculate the concentrations of reactants and products, which have different conductivity values. Then the
fractional conversion X can be determined. Among all 4 species, NaOH has the highest conductivity.
With the calculated values of conversion X, the rate constant k can also be achieved using an equation
derived from the balance equation of a batch reactor—
ln (
𝐶 𝑎𝑜
𝐶 𝑏𝑜
−𝑋
1−𝑋
) = ln (
𝐶 𝑎𝑜
𝐶 𝑏𝑜
) + (C 𝑎𝑜 − C 𝑏𝑜) × kt (Equation 1)
where Cao and Cbo are the concentrations of NaOH and EtOAC respectively. The slope of Equation 5
gives the value of k times a constant, (Cao - Cbo). The kinetics data is plotted as in Figure 4. The plotted
data is linear from t=0s to t=500s, when the reaction is reaction limited. After this time range, the reaction
turns to be diffusion limited and gives a curved line. The linear data is used to calculate for the slope and
the intercept ln(Cao/Cbo). The trendline gives the value of k=0.0664 L/mol s and the actual
intercept=0.4516, which is very close to the literature intercept value 0.440.
The measured reactor temperature change is
0.3K and smaller than the theoretical value
0.756K. However the theoretical value is
calculated under the assumption that the
reaction is adiabatic and the actual reaction
is isothermal. Such a difference leads a
smaller temperature change than the
theoretical value.
A water circulation unit is used to heat up the reacting
solution in the CSTR in order to reach different steady states.
In such a situation, the solution conductivity increases with
fractional conversion as plotted in Figure 5. The temperature
increments cause the particles inside the fluid move faster
and exchange charges more easily. The temperature also
affects the rate constant of the CSTR reaction. According to
the Arrhenius equation, the rate constant k increases with the temperature.
𝑘 = 𝐴𝑒−
𝐸 𝑎
𝑅𝑇 (Equation 2)
y = 0.0015x + 0.4516
0
0.5
1
1.5
2
0 500 1000 1500 2000
A=ln(Cao-Cbo)+(Cao-Cbo)*kt
Time (s)
Figure 4: Batch Reaction Kinetics. The plotted data
shows that the reaction is reaction limited at first, then
turns to be diffusion limited after t=500s.
Figure 5: Solution Conductivity Λm and
Fractional Conversion Xversus Time for the
CSTR Reaction. The conductivity increases
with conversion in the CSTR reactor, while it
decreases in the batch.
0.75
0.8
0.85
0.9
6.60
6.80
7.00
7.20
7.40
7.60
292 297 302 307
FractionalConversionX
Conductivity(mS)
Temperature (K)
Conductivity
Conversion

3. At each steady state,the solution conductivity is measured to calculate the fraction conversion X using
Equation 1. The data is taken a few minutes after the solution first reaches the set temperature and the
conductivity versus time graph shows a line parallel to the x-axis, which indicates the true steady state.
Data recorded at true steady states will give more accurate values of reaction constant k and activation
energy Ea.
Once the activation energy is achieved using the conductivity data at steady states for the CSTR, the rate
constant at the same temperature as the batch reaction can be calculated using the Arrhenius equation for
comparison. Since the rate constant k is dependent on the temperature and the activation energy, the k
values for two reactions should be similar. However at T=292.85 K, kbatch=0.065 L/mol s and kCSTR=
0.160 L/mol s. Two calculated k values are largely different. A reasonable explanation for this
discrepancy is the flow rate calibration. For the CSTR reaction, reactants are pumped from the vessel
tanks to the reactor through separate pumps. Mistakes in pump flow rate calibrations or air bubbles left in
the tubes will change the actualmolar concentrations of two reactants entering the reactor,and affect the
fractional conversion of the reaction. Another possible factor is the reactor volume. The actualreactor
used in the experiment is much larger than 1L. The temperature setting is changed after the volume of
reacting solution reaches approximately 1L, which is the volume used to calculate fraction conversion X
for the CSTR. Since there is no volume scale on the reactor,the actualreacting volume may have an
offset and cause errors in calculations. The literature value of activation energy for the saponification of
ethyl acetate2
is 14700 cal/mol=61504.8 J/mol, while the calculated activation energy value for the CSTR
reaction is 80723.798 J/mol. The huge difference between two values of activation energy Ea also implies
the possibility of having a wrong volume.
The data shows the experiment results partially meet the expectations of batch and CSTR reaction
kinetics. The calculated values of reaction rate constant k confirm the dependence of k on the reaction
temperature: the rate constant increases with temperature. But the calculated activation energy is far
distinct from the literature value and gives different values of rate constant k at the same temperature for
batch and CSTR reactions. For improvements, the isothermal batch reaction should be conducted at an
environment without much disturbing heat transfer. A reactor with measuring scale is also important for
determining the actual reacting volume of the solution for the CSTR.
Group W
Group Members: Wanying Chia, Matthew Liu, Ahmad Alhazeem, Rashid Alsuwaidi.

4. Reference
1. Moore, W.J. Physical Chemistry,4th
Ed.; Prentice Hall Inc: London, 1962; pp 435.
2. Smith, H.A.; Levenson, H.S. J. Am. Chem. Soc., 1939,61(5),pp 1172-1175.