CHEMICAL REACTORS – BATCH
PROC2083 Reaction Engineering (2019) – Reaction Engineering Laboratory
PROC2083 Reaction Engineering (2019)
Reaction Engineering Laboratory – batch and continuous reactors
Aims
There are two components to these laboratory experiments. The aims of these are:
I. To determine the overall reaction order and the reaction rate constant for the saponification of ethyl
acetate by measuring the reaction conversion in a batch reactor.
II. To determine the overall reaction order and the reaction rate constant for the saponification of ethyl
acetate by measuring the reaction conversion in a continuous sti
ed tank reactor (CSTR).
Report and group organisation
This laboratory will be performed by two groups (max. 5 students/group) in parallel. One group will perform
the experiments required for aim (i) using the batch reactor. The other group will perform the experiment
equired for aim (ii) using the CSTR. The experiments should take no longer than 2 hours to perform. At the
end of the laboratory session each group will exchange their results with the other group. Each group must
submit an independent group report that covers all three aims. You have two weeks (on 11:59 pm 14 days
after the laboratory) to submit your group report as a soft copy via blackboard.
Note that if you perform the laboratory before the mid semester
eak then you will have three weeks to
complete the assignment.
The laboratory report should be extensive and include a literature review. A ru
ic detailing the marking
procedure is available on blackboard, as is a report template that may be used for preparing the report. The
group report mark is given to all individuals of the group so it is the responsibility of all individuals within the
group to ensure they are happy with the report prior to its submission.
IMPORTANT:
• You MUST attend the laboratory session to be eligible for report submission.
• There are only a fixed number of laboratory sessions available for this course and
there will be NO make-up session. If you miss the opportunity to attend any one of
these timetabled laboratory sessions, you will not be able to complete this
laboratory-based assessment task and will not be provided an alternative task for
assessment.
PROC2083 Reaction Engineering (2019) – Reaction Engineering Laboratory
Aim I – Measurement of the reaction kinetics of the saponification of ethyl acetate in a
atch reactor
Introduction
Chemical reactors are key equipment items in many chemical process plants. Batch reactors are used in
industry for non-continuous, relatively small-scale specialist reactions usually involving liquid phase reactions.
In the laboratory, batch reactors represent a convenient method of investigation of chemical kinetics.
This experiment explores the chemical kinetics of a well-documented homogeneous liquid reaction: viz the
saponification of ethyl acetate by sodium hydroxide to sodium acetate and ethyl alcohol. The reaction ca
ied
out in a batch reactor is allowed to proceed close to completion. The conductivity of the reaction solution in
the reactor changes with the degree of conversion, and this provides a convenient method for monitoring the
progress of the reaction.
Theory
The saponification of ethyl acetate by sodium hydroxide is generally considered first order reaction with
espect to both sodium hydroxide (reactant A) and ethyl acetate (reactant B) within the limits of concentration
(0 – 0.1 M) and temperature (20 – 40 °C). For an equimolar feed of sodium hydroxide and ethyl acetate, the
eaction is second order overall (Note: in your report you should seek to find literature to support this
assertion).
Stoichiometry
The stoichiometric equation can be written as:
???????????? ℎ???????????????? (??) + ????ℎ???? ?????????????? (??) ⟶ ???????????? ?????????????? (??) + ????ℎ???? ????????ℎ???? (??)
Rate of reaction
The rate of reaction is defined as
−???? = −???? = ???? = ???? = −
??????
????
(1)
For an i
eversible reaction the general form of the rate law is often given as:
−???? = ?????????????? (2)
where −???? is the reaction rate with respect to species ??
?? is the reaction rate constant
???? is the molar concentration of species ??
?? & ?? are reaction orders (with respect to the co
esponding species in the rate equation)
For equal feed concentrations, ????0 = ????0, and since the reaction stoichiometry is 1:1, the reaction rate may
e simplified to:
−???? =
??????
????
= ????????′
(3)
where ??′ = ?? + ??
Differential Method of Analysis
A natural plot of log reaction rate versus log concentration will give a straight line of slope equal to the power
of the relationship.
Integral Method of Analysis
Integration of the second order reaction equation gives:
PROC2083 Reaction Engineering (2019) – Reaction Engineering Laboratory
???? =
1
????
−
1
????0
(4)
where ?? is the reaction rate constant and ?? is the time of reaction.
Equipment, materials and safety
This experiment employs the following pieces of equipment.
• The CEB batch reactor
• The IFD3 unit and its connecting cables
Sodium hydroxide is a highly caustic chemical and ethyl acetate is flammable. It is essential
when handling these chemicals to wear protective clothing, gloves and safety spectacles.
Procedure
It has been determined that the degree of conversion of the reagents affects the conductivity of the reactor
contents. So by recording the conductivity with respect to time using the Armfield Data Logger (the IFD3
Interface) the data can be used to calculate the amount of conversion.
Collection of conductivity data will be until the reaction is effectively complete, and this takes approximately
XXXXXXXXXXminutes. Set the sampling rate of the software to 10 seconds and either set the time period for 25
minutes or elect to sample continuously.
1. Make up 0.5 lite batches of 0.1 M sodium hydroxide in water, and 0.5 litre batches of 0.1 M ethyl acetate
in water.
2. Ensure the conductivity probe and temperature sensors have been installed.
3. Charge the batch reactor with 0.5 litre of the sodium hydroxide solution.
4. Switch on the reactor agitator and adjust the speed setting to “7.00”
5. Carefully add to the reactor 0.5 litre of ethyl acetate solution and start the collection of data.
6. Use the IFD channel history window to monitor the progress of the reaction.
Calculations
Differential Analysis
1. Plot the concentration of sodium hydroxide/ethyl acetate versus time.
2. Using time intervals of 20 seconds, calculate by finite difference the reaction rate as a function of
time
eactant concentration – plot the reaction rate versus reactant concentration data.
3. Plot the natural log of −???? versus natural log of ????. Determine the overall order of the reaction, ??, from
the slope of the curve. How close was your value to 2? Determine the rate constant ??.
4. Write the rate law for the reaction of sodium hydroxide and ethyl acetate when fed in equimolar amounts.
Integral Analysis
1. Rea
ange equation (4) and plot appropriate variables to obtain ??. Express the rate equation in the form
of equation (3).
Report
Report on the differential and integral methods of analysis, and compare the two methods. You should
perform a literature search and seek to compare your results of the chemical parameters with other
esearchers.
PROC2083 Reaction Engineering (2019) – Reaction Engineering Laboratory
Aim II – Measurement of the Reaction Kinetics of the Saponification of Ethyl Acetate in
a CSTR
Introduction
The use of a CSTR to measure reaction kinetics has an advantage over batch experiments as the data allows
direct measurement of the rate of reaction.
Theory
Refer to the previous pages for information on the saponification reaction of ethyl acetate.
According to the model of the ideal CSTR, the relationship between reaction rate (−????) and space time (??) is
given by the relationship:
?? =
????0??
−????
(5)
where τ = ?? ??0�
?? is the total volume of the reactor
??0 is the volumetric flow rate of entering reactants
−???? is the reaction rate at exit concentration of reactant CA
????0 is the concentration of reactant entering the reactor
?? is the conversion od reactant A
Equation (5) may be rea
anged as:
−???? =
????0??
??
(6)
Equipment, materials and safety
This experiment employs the following pieces of equipment.
• The CEM MkII CSTR
• The IFD3 unit and its connecting cables
Sodium hydroxide is a highly caustic chemical and ethyl acetate is flammable. It is essential
when handling these chemicals to wear protective clothing, gloves and safety spectacles.
Procedure
Fill the feed vessels (to about 50mm from the top) with the 0.1M sodium hydroxide and 0.1M ethyl acetate
solutions
• Ensure the conductivity probe and temperature sensors have been installed.
• Switch on the reactor agitator and adjust the speed setting to “7.00”
• Switch on the feed pumps and set the flow rate to 80 ml/min on each pump.
It has been determined that the degree of conversion of the reagents affects the conductivity of the reactor
contents.
Collection of conductivity data will be until the reaction is effectively at steady state, and this takes
approximately 15 minutes. Set the sampling rate of the software to 10 seconds and set the time period to
sample continuously.
PROC2083 Reaction Engineering (2019) – Reaction Engineering Laboratory
• Use the IFD channel history window to monitor the progress of the reaction
• After the reaction has reached steady state reduce the flow rate to 70 mL/min and again wait about 15
minutes for steady-state to occur.
• Continue reducing the flow rate by 10 mL/min and waiting for steady state until reactant tanks are empty.
Calculations
1. Plot the outlet concentration (at steady-state) versus total volumetric flow rate used.
2. Calculate the reaction rate (−????) versus outlet reactant concentration – again at steady state – and plot.
3. Plot the natural log of −???? versus natural log of ????. Determine the overall order of the reaction, ??′, from
the slope of the curve. How close was your value to 2? Determine the rate constant ??.
Report Writing Template
2
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