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CPE554 Universiti Teknologi MARA 1 OPERATING & EXPERIMENTAL MANUAL CONTINUOUS STIRRED TANK REACTOR MODEL: BP 143

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manual

Transcript of CSTR

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    OPERATING & EXPERIMENTAL

    MANUAL

    CONTINUOUS

    STIRRED TANK

    REACTOR

    MODEL: BP 143

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    OPERATING PROCEDURES General Start-Up Procedures

    1. Prepare the following solutions: a) 40 L of sodium hydroxide, NaOH (0.1M) b) 40 L of ethyl acetate, Et(Ac) (0.1M) c) 1 L of hydrochloric acid, HCL (0.25M), for quenching

    2. Ensure that all valves are initially closed.

    3. Charge the feed vessels as follows:

    a) Open the charge port caps for vessels B1 and B2. b) Carefully pour the NaOH solution into vessel B1 and the Et(Ac) solution into vessel B2. c) Close the charge port caps for both vessels.

    4. Turn on the power for the control panel. 5. Check that there is sufficient water in the thermostat T1 tank. Refill as necessary.

    6. Open cooling water valve V13 and let the cooling water flow through the condenser W1. (Only for

    Experiment 2)

    7. Adjust the overflow tube to give a working volume of 10 L in the reactor R1.

    8. Open valves V2, V3, V7, V8 and V11.

    9. The unit is now ready for experiment. General Shut-Down Procedures

    1. Keep the cooling water valve V13 open to allow the cooling water to continue flowing. 2. Switch off both pumps P1 and P2. Switch off stirrer M1.

    3. Switch off the thermostat T1. Let the liquid in the reaction vessel R1 cool down to room

    temperature.

    4. Close cooling water valve V13.

    5. Close valves V2, V3, V7 and V8. Open valves V4, V9 and V12 to drain any liquid from the unit.

    6. Turn off the power for the control panel.

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    EXPERIMENTAL PROCEDURES

    Preparation of Calibration Curve for Conversion vs. Conductivity The reaction to be studied is the saponification reaction of ethyl acetate Et(Ac) and sodium hydroxide NaOH. Since this is a second order reaction, the rate of reaction depends on both concentrations of Et(Ac) and NaOH. However, for analysis purposes, the reaction will be carried out using equimolar feeds of Et(Ac) and NaOH solutions with the same initial concentrations. This ensures that both concentrations are similar throughout the reaction.

    NaOH + Et(Ac) Na(Ac) + EtOH The following procedures will calibrate the conductivity measurements of conversion values for the reaction between 0.1 M ethyl acetate and 0.1 M sodium hydroxide: PROCEDURES: 1. Prepare the following solutions:

    a) 1 liter of sodium hydroxide, NaOH (0.1 M) b) 1 liter of sodium acetate, Et(Ac) (0.1 M) c) 1 liter of deionised water, H2O

    2. Determine the conductivity and NaOH concentration for each conversion values by mixing the following solutions into 100 ml of deionised water: a) 0% conversion : 100 ml NaOH b) 25% conversion : 75 ml NaOH + 25 ml Et(Ac) c) 50% conversion : 50 ml NaOH + 50 ml Et(Ac) d) 75% conversion : 25 ml NaOH + 75 ml Et(Ac) e) 100% conversion : 100 ml Et(Ac) ANALYSIS AND DISCUSSION: 1. Record all data in the sample table in Appendix A. 2. Plot the calibration curve of conductivity vs conversion. Determine the slope and y-axis intercept.

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    Back Titration Procedures for Manual Conversion Determination It is advisable to carry out manual conversion determination on experiment samples to verify the conductivity measurement values. The following procedures will explain the method to carry out back titration on the samples. It is based on the principle of quenching the sample with excess acid to stop any further reactions, then back titrating with a base to determine the amount of unreacted acid. PROCEDURES: 1. Fill up a burette with 0.1 M NaOH solution.

    2. Measure 10 ml of 0.25 M HCl in a flask. 3. Obtain a 50 ml sample from the experiment and immediately add the sample to the HCl in the flask to

    quench the saponification reaction. 4. Add a few drops of pH indicator into the mixture. 5. Titrate the mixture with NaOH solution from the burette until the mixture is neutralized. Record the

    amount of NaOH titrated. ANALYSIS AND DISCUSSION:

    NaOH + HCl NaCl + H2O

    Unknown quantity:

    Concentration of NaOH in the reactor = CNaOH mol/L Known quantities: Volume of sample = Vs ml Concentration of NaOH in the feed vessel = CNaOH,f mol/L Volume of HCl for quenching = VHCl,s ml Concentration of HCl in standard solution = CHCl,s mol/L Volume of titrated NaOH = V1 ml Concentration of NaOH used for titration = CNaOH,s mol/L

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    Calculations: Conc. of NaOH entering the reactor, CNaOH,0 = (CNaOH,f)/2 mol/L

    Volume of unreacted quenching HCl, V2 = 1sHCl,

    sNaOH,

    C

    CV ml

    Vol. of HCl reacted with NaOH in sample, V3 = VHCl,s V2 ml Moles of HCl reacted with NaOH in sample, n1 = (CHCl,s V3)/1000 mol Moles of unreacted NaOH in sample, n2 = n1 mol Conc. of unreacted NaOH in the reactor, CnaOH = n2 / (Vs 1000) mol/L

    Conversion of NaOH in the reactor, X = %10010,

    xC

    C

    NaOH

    NaOH

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    EXPERIMENT 1: Effect of Residence Time of the Reaction in a CSTR OBJECTIVE: To carry out a saponification reaction between NaOH and Et(Ac) in a CSTR To determine the effect of residence time onto the reaction extent of conversion To determine the reaction rate constant PROCEDURES:

    1. Perform the general start-up procedures as in Section 4.1.

    2. Switch on both pumps P1 and P2 simultaneously and open valves V5 and V10 to obtain the highest possible flow rate into the reactor.

    3. Let the reactor fill up with both the solution until it is just about to overflow.

    4. Readjust the valves V5 and V10 to give a flow rate of about 0.1 L/min. Make sure that both flow

    rates are the same. Record the flow rate.

    5. Switch on the stirrer M1 and set the speed to about 200 rpm.

    6. Start monitoring the conductivity value at QI-401until it does not change over time. This is to ensure that the reactor has reached steady state.

    7. Record the steady state conductivity value and find the concentration of NaOH in the reactor and

    extent of conversion from the calibration curve.

    8. Open sampling valve V12 and collect a 50 mL sample. Carry out a back titration procedure to manually determine the concentration of NaOH in the reactor and extent of conversion (Section 5.2).

    9. Repeat the experiment (steps 5 to 9) for different residence times by adjusting the feed flow rates

    of NaOH and Et(Ac) to about 0.15, 0.20, 0.25 and 0.30 L/min. Make sure that both flow rates are the same.

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    ANALYSIS AND DISCUSSION:

    1. Use the sample table in Appendix B for data collection. 2. Plot a graph of conversion vs. residence time. The reactors residence time is defined as the

    reactor volume divided by the total feed flow rates.

    Residence time, 0

    CSTRV

    3. For a second order equimolar reaction with the same initial reactants concentration ( CA0 = CB0 ) , the rate law is shown to be:

    2

    00

    2

    0

    0

    2

    )(

    A

    AA

    A

    ATFR

    A

    ACSTR

    ABAA

    kC

    CCF

    kC

    FV

    r

    XFV

    kCCkCr

    where: X = extent of conversion

    CA = exit concentration of reactant NaOH [M] v0 = total inlet flow rate of solutions [ml/min] CA0 = inlet concentration of reactant NaOH in the reactor [M]

    4. For different reactor residence times, calculate the value of the reaction rate constant, k and the rate of reaction, -rA.

    Reaction rate constant,

    2

    0

    A

    AA

    C

    CCk

    Rate of reaction, 2AA kCr

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    EXPERIMENT 2: Effect of Temperature on the Reaction in a CSTR OBJECTIVE: To determine the effect of temperature onto the reaction extent of conversion To determine the reactions activation energy PROCEDURES:

    1. Perform the general start-up procedures as in Section 4.1.

    2. Switch on both pumps P1 and P2 simultaneously and open valves V5 and V10 to obtain the highest possible flow rate into the reactor.

    3. Let the reactor fill up with both the solution until it is just about to overflow.

    4. Readjust the valves V5 and V10 to give a flow rate of 0.20 L/min. Make sure that both flow rates

    are the same. Record the flow rate.

    5. Switch on the stirrer M1 and set the speed at about 200 rpm.

    6. Switch on the thermostat T1 and set the water temperature to 40 C.

    7. Start monitoring the conductivity value at QI-401 and temperature value at TI- 101 until they do not change over time. This is to ensure that the reactor has reached steady state.

    8. Record the steady state conductivity and temperature values and find the concentration of NaOH in

    the reactor and extent of conversion from the calibration curve.

    9. Open sampling valve V12 and collect a 50 mL sample. Carry out a back titration procedure to manually determine the concentration of NaOH in the reactor and extent of conversion (Section 5.2).

    10. Repeat the experiment (steps 7 to 10) for different reactor temperatures by setting the thermostat

    temperature to 50, 60, 70, and 80 C. Make sure that the flow rates of both solutions are maintained at 0.20 L/min.

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    ANALYSIS AND DISCUSSION:

    1. Use the sample table in Appendix B for data collection.

    2. Plot a graph of conversion, X vs. reactor temperature, T.

    3. For different reactor temperatures, calculate the value of the reaction rate constant, k.

    Reaction rate constant,

    2

    0

    A

    AA

    C

    CCk

    4. Plot the graph of ln k vs 1/T and evaluate the slope and y-axis intercept.

    5. Calculate the saponification reactions activation energy, E and Arrhenius constant, A from the slope and intercept values using the Arrhenius equation.

    RTE

    T Aek

    )( , R = universal gas constant (8.314 J/mol.K)

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    APPENDIX A SAMPLE TABLE FOR PREPARATION OF CALIBRATION CURVE

    APPENDIX B SAMPLE TABLE FOR EXPERIMENTS 1 & 2 Reactor volume = _____ L Concentration of NaOH in feed vessel = _____ M Concentration of Et(Ac) in feed vessel = _____ M

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    APPENDIX C PHYSICAL PROPERTIES OF COMPONENTS