Armfield CEM-MKII, Instruction Manual

Page: 28 / 37

24
Exercise A - To find the reaction rate constant in a
Continuous Stirred Tank Reactor
Theory
The reaction:
NaOH + H
3
COOC
2
H
5
→ CH
3
COONa + C
2
H
5
OH
Sodium Hyd Ethyl Acetate → Sodium Acetate + Ethyl Alcohol
can be considered equi-molar and first order with respect to both sodium hydroxide
and ethyl acetate, i.e. second order overall, within the limits of concentration (0 -
0.1M) and temperature (20 - 40°C) studied.
The reaction carried out in a Continuous Stirred Tank Reactor or Tubular Reactor
eventually reaches steady state when a certain amount of conversion of the starting
reagents has taken place.
The steady state conditions will vary depending on concentration of reagents,
flowrate, volume of reactor and temperature of reaction.
Method
Make up 2.5 litre batches of 0.1M sodium hydroxide and 2.5 litres of 0.1M ethyl
acetate.
IMPORTANT:
It is essential when handling these chemicals to wear protective
clothing, gloves and safety spectacles.
Remove the caps of the reagent bottles and carefully fill with the reagents to a level
approximately 50mm from the top using a funnel if necessary. Refit the caps.
Start the software using the option of the experiment with heater.
Click the ‘Power on’ button on the mimic diagram, click the ‘Hot Water Circulator’
button and water will start to recirculate through the hot water circulator and coil in
the reactor.
Adjust the set point of the PID controller to 30°C.
Change the PID ‘mode of operation’ to ‘Automatic’
Collection of conductivity data should continue until a steady state condition is
reached in the reactor and this takes approximately 30 minutes. It is advisable to set
the data collection period to, say, 45 minutes.
Set the pump speed controls to 40ml/min flowrate in the software.
Fill the concentration of both solutions in their respective boxes in the software.
Fill the volume of the reactor in the box on the software. Set the stirrer speed to 50%
in the software.
It has been determined that the degree of conversion of the reagents affects the
conductivity of the reactor contents so that recording the conductivity with respect to