Reaction Kinetics Manual

Penn State Chemical Engineering

Revised Spring 2015

1

Table of Contents LEARNING OBJECTIVES............................................................................................................ 2

EXPERIMENTAL OBJECTIVES AND OVERVIEW ................................................................. 2

THEORY ........................................................................................................................................ 3

Background ................................................................................................................................. 3

PRE-LAB QUESTIONS(to be completed before coming to lab) .................................................. 4

EXCEL PREPARATION (Excel spreadsheet to be used for data processing in the lab must be

prepared before coming to the lab for the experiment) .................................................................. 7

DATA PROCESSING .................................................................................................................... 9

A. Batch Reaction Data Processing ................................................................................... 9

B. CSTR Reaction Data Processing ................................................................................... 9

KEY POINTS FOR THE REPORT ............................................................................................. 10

REFERENCES ............................................................................................................................. 11

APPENDIX A: EXPERIMENTAL SET-UP ............................................................................... 12

APPENDIX B: VARIABLE DEFINITIONS ............................................................................... 15

APPENDIX C: SAFETY NOTES ................................................................................................ 16

APPENDIX D: EXPERIMENTAL PROCEDURE ..................................................................... 17

Evening Preparation .................................................................................................................. 17

Reactor Operation ..................................................................................................................... 17

Conductivity Probe Preparation and Reactor Preparation ........................................................ 18

PART ONE - Batch Reactor ...................................................................................................... 18

PART TWO - CSTR ................................................................................................................... 20

Shutdown .................................................................................................................................. 24

2

LEARNING OBJECTIVES

1. Be able to set up and use batch reaction kinetics equations to calculate the reaction rate

constant.

2. Be able to use steady state kinetics of continuous stirred tank reactor (CSTR) to find the

reaction rate constant and activation energy.

3. Be able to design and conduct experiments to find the activation energy of reaction.

4. Understand the reaction rate limiting factors.

EXPERIMENTAL OBJECTIVES AND OVERVIEW

The main objective of this experiment is to study the reaction rate constant for the reaction of

sodium hydroxide with ethyl acetate to form sodium acetate and ethanol (called saponification

reaction) using both batch and CSTR reactors. Conductivity values will be used to determine the

concentration profiles of NaOH and sodium acetate.

PRE-LAB STUDY:

1) In this experiment, the concentration of the reacting species in the aqueous solution is

calculated from the electrical conductivity of the solution. Derive a calibration equation

that converts the solution conductivity to fractional conversion of the limiting reagent

using the calibration data provided in the manual.

2) Derive an integral form of the batch reaction rate equation to determine the reaction rate

constant from the fractional conversion measured as a function of time.

3) Predict the conversion as a function of time for an adiabatic batch reaction.

4) Predict the conversion as a function of temperature for a CSTR.

EXPERIMENTS IN THE LAB:

5) Run saponification reaction in a batch reactor and record the solution conductivity as a

function of time.

6) Run the same reaction in a CSTR mode at various temperatures and measure the solution

conductivity at each steady state.

CALCULATIONS IN THE LAB:

7) Convert the measured conductivity to fractional conversion

3

8) Calculate the reaction rate constant for batch and CSTR operations; compare the results

from these two different operation modes.

9) Calculate the activation energy for the saponification reaction and compare it with a

literature value.

THEORY

Background

In this experiment, an ArmfieldCEM Mk II CSTR will be utilized to study the

saponification reaction between ethyl acetate (EtAc) and sodium hydroxide (NaOH) as a means

of acquiring conductivity values to relate concentration to fractional conversion.

NaOH + CH3COOC2H5 CH3COONa + C2H5OH (eq 1)

The reaction of NaOH and EtAc to produce sodium acetate and ethanol is irreversible at low

concentrations and low temperatures. The saponification is first order with respect to both

reactants; therefore, the rate constant k will be second order overall. The heats of formation are

-112.193 kcal/mole for NaOH, -110.72 kcal/mole for EtAc, -175.45 kcal/mole for sodium

acetate, and -66.35 kcal/mol for ethanol.4

Our reactor is equipped with a conductivity probe. Since some of reactants and products exist in

ionic form in the reaction media, the solution conductivity (Λm) can be used to calculate the

concentration of species in real time. The equations below are the calibration equations that

provide a correlation between concentration and conductivity for the conductivity probe used in

the lab.

aa CT *))294(0184.01(195.0 (Eq2)

cc CT *))294(0284.01(07.0 (Eq3)

cam (Eq4)

where Ca and Cc are the molar concentrations of NaOH and sodium acetate, respectively; and Λa

and Λc are the conductivity in Siemens (-1

cm-1

) of NaOH and sodium acetate, respectively.

Note that Cc is the fractional conversion of the limiting reactant times its initial concentration.

4

Additional Theory Topics: (These are important learning points for prelab, prelab quiz,

conducting the experiment and for writing the report.)

Fractional conversion

Reaction rate constant, reaction rate law, reaction order

Design equation in differential form for batch reactor

Integral form of the batch reaction rate equation, in terms of fractional conversion of the limiting

reactant

Isothermal, liquid phase batch reaction design

CSTR design equation, derive starting from the mole balance

Arrhenius equation / plot

Heat of reaction, and total heat generated or released in a reaction

Temperature change due to reaction

They can be found in:

H. S. Fogler “Elements of Chemical Reaction Engineering”

In 4th

Edition: (TP157.F65 2006)

In 3rd

Edition: pp. 33-39, pp. 68-73, pp. 125-137 (TP157.F65 1999)

In 2nd

Edition: (TP157.F65 1992)

In 1st Edition: (TP157.F65 1986)

PRE-LAB QUESTIONS(to be completed before coming to lab)

Watch the theory video on ANGEL and read the theory section of the manual.

These sources will help you answer the pre-lab questions and will prepare you for

the quiz and the experiment on lab day.

Note: use the variable definitions on page 15 of the manual in all derivations (for

consistency)

1. You will need to make several solutions for this experiment. Determine how to make

each solution.

Note: Final volumes should be measured at the end after materials have been dissolved

and mixed in smaller volumes. Use a stir bar to mix thoroughly. Beaker markings are

5

only approximations. Always use a graduated cylinder for volume measurements (or

graduated pipette for small volumes).

a. If the desired feed concentration for the batch reactor is to be 0.064 M NaOH and

0.04 M EtOAc in 800 ml, calculate the concentrations required for the two

separate solutions used to make the desired final concentrations.

Concentration of 600 ml of EtOAc is: ___________M

Concentration of 200 ml of NaOH is :_____________M

b. Calculate the mass and/or volume of each reactant needed to make the solutions

determined in part a. Note that EtOAc comes as a concentrated liquid with

density of 0.90 g/cm3 and molecular weight of 88.11. Therefore a volume of

concentrate must be determined.

c. Explain in detail how you will make each solution. What will you do when you

cannot weigh out the exact mass of NaOH calculated in a above.

d. For the CSTR you will need to make 5L of each 0.1 M NaOH and 0.1 M EtOAc.

Explain in detail how you will make each.

2. What is the limiting reactant in this batch reaction?

3. Let’s look at the concentration profiles for reactions of different orders. Start with the

simple reaction A B.

Assume that the initial concentration of A is 1 mole/L and the rate constant for this

reaction is 0.1 with appropriate units (units will vary for each case).

a. Derive the equation for the concentration of A for zero order (Rate = k), first

order (rate= kCA), and second order (rate= kCA2). Graph all 3 cases on a single

graph. Note that for a batch reaction of constant volume, the change in moles of

A,𝜕𝑁𝐴

𝜕𝑡 , is equal to the rate of reaction, 𝑟𝐴, times the volume of the reactor, 𝑉𝑅.

(𝜕𝑁𝐴

𝜕𝑡= −𝑟𝐴𝑉𝑅)

b. Now calculate the fractional conversion of A for each case and graph all 3 cases.

Note that fractional conversion is 𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝐴

𝑖𝑛𝑖𝑡𝑖𝑎𝑙 𝐴

4. Derive the equation needed to determine the reaction rate constant for the batch

saponification reaction in this experiment. Use variables as defined on page 15 of the

6

manual. Start with a material balance, get it in terms of fractional conversion of the

limiting reactant and integrate. The slope of the resulting equation should give you k (or

k times a constant). The intercept should be a known constant. Your final equation

should be in the form:

g(X) = mt + b

where g(X) is a function of X, m is a slope and b is an intercept.

Note that

bax

qpx

aqbpqpxbax

dxln

1

))((

5. Calculate the heat of reaction for the saponification reaction. Is the reaction endothermic

or exothermic?

6. Calculate the expected temperature change of the reaction. (You may assume (1) the

reaction mixture has the heat capacity of water because you have a dilute solution, (2) the

reactor is adiabatic, and (3) you have complete conversion of the limiting reactant.) Set

this up in excel because you will do a very similar calculation at the end of your

experiment using the actual conversion.

7. For the batch reactor, make a sketch of what you expect fractional conversion as well as

the two reactant concentrations as a function of time to look like.

8. For the CSTR, make a sketch of what you expect fractional conversion as a function of

steady state temperature to look like for this irreversible second order reaction.

9. Which reactor, operating at the same temperature, will achieve a higher conversion (X)

after sufficiently long time?

10. Do you expect the reaction rate constant to be the same or different for the batch and

CSTR experiments? Why?

11. How do you expect the conductivity of the solution to change as the reaction proceeds in

the batch reactor (assume isothermal operation)? Explain in detail. (This can be

explained using the data shown in the “Mobility of ions in water solution at 298.15K” file

7

on ANGEL).

12. Will temperature affect the conductivity of a pure solution (NaOH for example)?

Explain.

13. Obtain the equation that can be used to calculate the fractional conversion (X) of the

limiting reactant in the reactor from the measured conductivity data. You need to

simultaneously solve equations 2-4 and two additional constraints (concentration

relations) to get an equation for X expressed in terms of TCC boaom ,,, . Use variable

definitions as defined on page 15 of the manual.

14. Starting with a steady state material balance on the CSTR reactor, derive the design

equation for the CSTR to determine k (rate constant) in terms of V (reactor volume), x

(fractional conversion), and initial concentrations. Use the variable definitions defined in

the manual on page 15.

15. What are Cao and Cbo for the CSTR if the feed tank concentrations and flow rates are 0.1

M and 150 ml/min and 0.1 M and 50 ml/min for NaOH and EtAc, respectively?

16. Describe what it means for a reaction to be reaction limited and what it means for a

reaction to be diffusion limited.

17. What are the objectives for this experiment?

18. Explain what data you will collect, how you will collect it, and what you will use it for.

EXCEL PREPARATION (Excel spreadsheet to be used for data processing in the lab must

be prepared before coming to the lab for the experiment)

1. Prepare a data processing excel spreadsheet to be used for the data processing in the lab. All

calculations will be done in excel. You may want to prepare separate spreadsheets: one for

batch calculations and one for cstr calculations.

a. Prepare a header section with your names and group ID.

8

b. Prepare a units section where you show unit conversions. Make it so that you can

reference the appropriate cell when a certain conversion is needed in later

calculations.

c. Prepare a section in which you will show initial concentrations. Prepare it so that

when you enter the measured mass and volume, and flow rate if used (one value

per cell), you get out the necessary initial concentration. Make sure to show units

clearly.

d. Show all needed formulas from the pre-lab calculations clearly explained in text

boxes

e. When using your spreadsheet in the lab, make sure that you use cell references

when using previously calculated values or constants (instead of copying them);

this will update the entire spreadsheet if/when a mistake is found early in the

spreadsheet. (no work required for 1.e)

2. Use the following “made-up” data to calculate conversion and reactant and product

concentrations for the batch reactor at 25 oC. You will replace this point with real data after

the TA checks your spreadsheet at the start of lab. Hint: use additional columns to break

lengthy calculations into parts. This limits formula error mistakes.

Batch Sample Data

Time Sample number

(reading taken every 10 seconds)

Conductivity (mS)

12:00:00 AM 1 13

12:00:10 AM 2 12

12:00:20 AM 3 11

12:00:30 AM 4 10

3. Use the following “made-up” data to calculate conversion and reactant and product

concentrations for the cstr reactor. Also calculate the reaction rate constant for this point.

You will replace this point with real data after the TA checks your spreadsheet at the start of

lab. Hint: use additional columns to break lengthy calculations into parts. This limits

formula error mistakes.

9

CSTR Sample Data

Temperature (oC) Conductivity (mS)

25 8

DATA PROCESSING

A. Batch Reaction Data Processing

1. Convert the measured conductivity to the fractional conversion of the limiting reactant

using the equation derived in the Pre-lab#13.

a. Plot the fractional conversion versus time. Also plot concentrations of reactants

and sodium acetate versus time.

b. Plot conductivity versus time. Include conversion on the same graph.

2. Graph the temperature versus time for the batch reaction.

3. Calculate k (rate constant) in M-1

s-1

using your derivation from the Pre-lab #4 calculation.

Show 2 plots of the linearized data: one with all data shown and one with only the initial

linear portion of the data. Make sure to calculate the standard error of k. Also clearly

indicate the temperature range and average temperature for this calculation.

4. Calculate the theoretical intercept value from the equation derived in the Pre-lab #4.

Give the actual intercept value from Post-lab #3 and calculate the error of the intercept

(choose the appropriate plot to use).

5. Is the reaction endothermic or exothermic? Calculate the expected temperature change of

the reaction by repeating pre-lab Q#6, but this time using the actual final fractional

conversion achieved in your experiment.

B. CSTR Reaction Data Processing

6. What is the feed concentration entering the reactor? This is the concentration at the point

of entry to the reactor that you would use in your subsequent calculations, not the

concentration in the feed tanks.

10

7. Plot the conductivity versus time data collected by the computer for the cstr reaction.

Clearly indicate the temperature at each steady state.

8. Using the equation obtained in the Pre-lab #13, determine the fractional conversions for

the reaction at each temperature. Organize the data (temperature, conductivity, fractional

conversion, and concentrations) in a table.

9. Construct a plot showing the relationship between conductivity and temperature and also

between fractional conversion and temperature. Plot on the same graph.

10. Calculate the rate constant k in M-1

s-1

at each temperature by utilizing the design equation

for the CSTR derived in pre-lab Q# 14.

11. Plot the natural logarithm of k versus reciprocal temperature and determine the activation

energy of the ethyl acetate saponification reaction. Make sure to calculate the standard

error of the activation energy.

12. Use the Arhenius equation (from CSTR data) to calculate the rate constant k at the

temperature from the batch reaction.

KEY POINTS FOR THE REPORT

If report requires a theory section, do further research on subjects included in “relevant theory”

section on page 2.

1. Include the process block flow diagram (BFD) or schematic of the CSTR system (make

your own and identify essential parts and connect them in a simple and easy-to-follow

way) in the methods section or appendix of your report.

2. Does the temporal profile of the fractional conversion and component concentrations for

the batch reaction follow what you would have expected for this irreversible, second

order overall (first order in each reactant) reaction?

3. Explain how monitoring the solution conductivity allows you to determine the

concentration of reactants and products in the mixture. Which component gives the

highest conductivity? Explain the reason.

11

4. Discuss the batch reaction kinetics (the slope and intercept of the kinetics plot).Is the

plotted data linear or curved? Explain the reason for the deviation from linearity. If the

plotted data is not linear, what region do you use for the slope and intercept calculation?

5. Compare the experimental temperature change in the batch reaction with theoretical

calculations. Comment on any difference.

6. Explain why conductivity increases with conversion in the CSTR (data processing #9)

but decreases with conversion in the batch (data processing #1b).

7. In the CSTR, comment on the effect of temperature on the rate constant.

8. In the CSTR, briefly comment on the steady states achieved. Was data taken at the true

steady state, or was it taken a bit early. If not truly at steady state, how will that affect the

calculations of k and activation energy?

9. Compare the rate constant from the batch reaction to that found from the CSTR reaction

at the same temperature. Are they the same/different? What might explain the

discrepancy, if any? Which data do you believe is more reliable? Why?

10. Compare the activation energy for the ethyl acetate saponification reaction determined

from your data with the literature value.

REFERENCES

1Fogler, Scott H. Elements of Chemical Reaction Engineering. 3

rd ed.

2 Hill, Charles G. An Introduction to Chemical Engineering Kinetics & Reactor Design. Wiley

& Sons, Inc. New York, 1977.

3Armfield. Engineering Teaching and Research Equipment. Armfield Ltd. England,

1999.

4Sandler, Stanley I. Chenical Engineering Thermodynamics. 2

nd ed. Wiley & Sons, Inc., New

York, 1989.

12

APPENDIX A: EXPERIMENTAL SET-UP

Figures 1 and 2 show a detailed schematic of the experimental setup for the kinetics

experiment. The Armfield CEM MKII continuous stirred tank reactor (1) rests on a base plate

(2) which is secured by thumbnuts (16) on four studs to the service unit. Three pillars (17)

support the reactor vessel above the base plate, making accessible the valves and connectors in

the reactor base. Inside the reactor, a coiled stainless steel heating element (5) provides the heat

transfer area to either heat or cool the reactants. For heating processes, the coil connectors (12

and 13) are connected to the flexible tubing of the hot water circulator that is part of the service

unit. The coil inlet, which draws water from the circulator, is located at the front of the reactor;

the coil outlet, which returns water to the circulator, is at the rear.

Figure 1. Schematic of Armfield CEM MKII CSTR System

(do not use in your report)

Do not copy

13

Figure 2. Detailed Schematic of Armfield CEM MKII CSTR

A turbine agitator (4) works in conjunction with a baffle arrangement (3) to ensure

efficient mixing and heat transfer. The agitation is driven by an electric motor (7) mounted on

the white lid of the reactor. The agitation from the motor is regulated by a variable speed unit in

the service bench and a jack plug (8) provides the electronic connection. The socket for the jack

plug is located at the rear of the main plate of the service unit.

The reactor lid contains glands to house temperature and conductivity probes (18 and 19).

The larger gland is designed for the conductivity probe. One may unscrew and re-tighten the

glands by hand if the probes need to be removed and then reinserted. The probes cannot be

wrongly connected to the sockets in the side of the console pod of the service unit because of the

difference in sizes.

During an experiment, the chemical reagents are pumped into the reactor from their

separate tanks through connectors (14 and 15) in the reactor base. Two feed pumps attached to

the front of the service unit work in conjunction with these connectors. As the pumps bring

reagents into the reactor, the reactor level increases until the stand-pipe (6) overflows and the

solutions travel to the drain. The height of this stand-pipe is adjusted by loosening the hexagon

backing nut (20), choosing the new position, and retightening. A stop prevents the stand-pipe

Do not copy

14

from being completely removed; when on the stop, the reactor operates at half-full volume.

When the reactor is not in use, it can be drained using a valve (11), which is shown offset from

center for diagrammatic purposes.

To load the reactor for batch mode, the temperature probe can be carefully removed. The

feed can be carefully added through this port using a funnel. When addition is complete, the

temperature probe can be re-attached.

15

APPENDIX B: VARIABLE DEFINITIONS

Use the following symbols to define variables in this experiment:

X Fractional conversion of the limiting reactant

ra Rate of reaction

k Rate constant (L/mol-min, for second order reaction)

T Temperature (Kelvin)

VR Reactor Volume (ml) = 1000 ml

Vo Overall volumetric flow rate (ml/min) = Fa + Fb

Fa Flow rate sodium hydroxide (ml/min)

Fb Flow rate ethyl acetate (ml/min)

Caµ Concentration sodium hydroxide in feed tank (mol/L) = 0.1 mol/L

Cbµ Concentration ethyl acetate in feed tank (mol/L) = 0.1 mol/L

Cao Initial sodium hydroxide concentration in or fed to the reactor (mol/L)

Cbo Initial ethyl acetate concentration in or fed to the reactor (mol/L)

Ca Concentration sodium hydroxide at time t (mol/L)

Cc Concentration sodium acetate at time t (mol/L)

Λm Conductivity of the solution in the reactor (Siemens)

Λa Conductivity of sodium hydroxide solution (Siemens)

Λc Conductivity of sodium acetate solution (Siemens)

16

APPENDIX C: SAFETY NOTES

NaOH – wear gloves when handling.

Ethyl Acetate – flammable liquid. Wear gloves when handling. Keep away from flames, hot

surfaces, and static charges. Handle in hood to avoid breathing vapors.

17

APPENDIX D: EXPERIMENTAL PROCEDURE

MAKE SURE YOU USE DISTILLED WATER WHEN PREPARING THE FEEDS. TAP

WATER HAS CONDUCTIVITY AND PREVENTS THE ACQUISITION OF PROPER

RESULTS!

Evening Preparation

Prepare solutions for the batch reactor (step 7.) and place in capped, clearly labelled

bottles. You can use these when you arrive on lab day. Use the remainder of the time to get

acquainted with the experiment set-up and computer data collection program. The conductivity

probe should be conditioning overnight (done by TA).

Reactor Operation

1.) ENSURE THAT THE REACTOR DRAIN VALVE IS CLOSED!!! This is the small,

black plastic valve located directly under the reactor vessel.

2.) On the left side at the base of the CSTR unit, the tube connected to the reactor tub drain

valve should empty into the bucket on the floor. Open the drain valve.

Do not copy

18

3.) On the front of the CSTR unit, verify that the silver toggle switches are in the follow

“Off” settings:

Switch Setting(s) “Off” Setting(s) “On”

Feed Pumps Remote (off) Manual (on)

Agitator Remote (off) Manual (on)

Temperature Control Heat; 0 Heat; 1

4.) Turn on power to the CSTR unit by flipping the white switch on the right hand side of the

unit by the Armfield logo.

Conductivity Probe Preparation and Reactor Preparation

1.) Before starting the experiment, the conductivity probe must be conditioned. The TA will

insert the conductivity probe into conditioning solution. Allow the probe to condition for

at least 30 minutes or overnight. You can make your batch solutions while the probe is

conditioning.

2.) While the probe is conditioning, add approximately 1L of distilled water to the batch

reactor – make sure the valve at the bottom of the reactor is closed. Turn on the agitator

to speed 7 and flip the remote switch to “manual”. Allow the water to stir while the

probe is conditioning and you are preparing solutions, or a minimum of 5 minutes. This

is to rinse the reactor and to warm the reactor to room temperature all the way through.

3.) When the probe has been conditioned, the TA will insert it into the reactor. Allow the

water to rinse the probe for about 1 minute, then turn off the agitator and drain the

reactor.

PART ONE - Batch Reactor

1.) Open up the Armfield program by going into the 480 Lab folder located on the desktop,

then double clicking the CEB-304 Batch Reactor icon.

2.) Choose Isothermal operation, and then proceed by clicking Load.

19

3.) Click the “View Diagram” icon located to the right of the paste icon.

4.) Do not bother to enter in the volumes or concentrations of the two reactants because you

only need the raw conductivity data recorded by the software.

5.) Ensure the software records the data every 10 seconds. Do this by clicking the Sample

drop down menu, choose configure. Sampling Operations should be set to Automatic,

and the Sampling Interval should be set to 10sec.

6.) Carefully remove the thermometer from the reactor. The batch feed will be added to the

reactor through this port using a funnel.

7.) You will need to make the feed solutions for the batch reaction. The goal is to have 800

ml final volume (assume no change on volume upon addition of two solutions) of 0.064

M in NaOH and 0.04 M in EtOAc. Remember that this is the final concentration. Make

200 ml of NaOH feed and 600 ml of EtOAc feed as per your pre-lab calculations. Do not

add the materials together yet because this will start the reaction. Make sure to cover

EtOAc solution because it evaporates quickly.

8.) Use the thermometer to measure the temperature of the 2 feed solutions. Record in your

notebook. If the temperatures vary, adjust the colder one with a warm water bath. Note

that the temperature may change some more after you add the EtOAc to the (cold)

reactor.

9.) Add the EtOAc feed solution to the reactor, turn on the agitator and set the agitation

speed to 7. The little pin on top of the knob locks to the right and unlocks in the 12

o’clock position. It is best to leave these pins unlocked while running the experiment.

Make sure you have good agitation.

10.) Measure the temperature of the EtOAc solution in the reactor and record in your

notebook. This is the starting reaction temperature. If the NaOH solution temperature is

more than 0.5 oC different from the EtOAc temperature, cool or warm it using a

cold/warm water bath, as appropriate.

20

11.) This step must be done carefully and quickly. Using a funnel, add the NaOH solution to

the reactor and immediately click the green “GO” icon on the computer screen.

Quickly, but carefully, insert the thermometer. Leave the bottom of the thermometer

about 1 cm from the reactor floor. Temperature must be recorded manually by clicking

the “Attach Note” button on the view diagram page (and recording in your notebook).

Enter in the temperature displayed on the thermometer (not the one on the computer

screen or the control unit) each time the temperature changes. Continue for 20-30

minutes until the conductivity no longer changes.

a. When using the “attach note” button, the information will be put into your data

table at the appropriate time. Look for it in the “notes” column.

b. You can watch the conductivity change in real time on the computer screen. Click

on the format graph button (all the way on the right of the tool bar) and choose

conductivity as the item to monitor. Then click on the view graph button.

12.) The batch experiment is complete. Set the agitator speed back to 0 and drain the

reactor.

13.) Save your data by going to File>Save As. Name your file, and ensure that it is saved as

an Excel 5.0 file (*.xls). This file can be found in the desktop folder 480 Lab Data.

Note that the Temp data collected in the file is only the set point temp. The actual

reactor temp is collected in the Notes column (which you entered). Also, you will have

to do your own calculations, as the default calibration equations are incorrect. Use the

time and conductivity data collected by the computer.

PART TWO - CSTR

Reactor Feed Preparation (use distilled water)

1.) Prepare 5L of a 0.1M solution of ethyl acetate for use in the reactor as determined in the

pre-lab. Note that beaker volume markings are only approximations. Use a graduated

cylinder to measure volumes. Make sure to stir using a stir bar. The ethyl acetate is in a

21

jug or bottle in the fume hood. It can be replenished from a 5 gal drum found under the

benches in the wet lab. Measure ethyl acetate in the fume hood. Add the ethyl acetate

solution to the feed vessel labeled ethyl acetate on the CSTR unit. MAKE SURE THAT

THE VALVE TO DRAIN THE FEED TANK IS CLOSED!!! It is the small black

plastic valve directly under the feed tank. Note: ethyl acetate is volatile and will

evaporate quickly if not kept covered.

2.) Prepare 5L of 0.1M sodium hydroxide. Again, beaker volume markings are only

approximations. Use a graduated cylinder or volumetric flask to measure the volume.

Stir the solution with a magnetic stirrer until the sodium hydroxide dissolves completely.

(It may take a while to dissolve.) Measure the final volume after the pellets have

dissolved in a smaller volume.

3.) Add the NaOH solution to the feed vessel labeled sodium hydroxide on the CSTR unit.

MAKE SURE THAT THE VALVE TO DRAIN THE FEED TANK IS CLOSED!!! It is

the small, black plastic valve located directly under the feed tank.

4.) Place the digital thermometer into the reactor. Ensure that the thermocouple which

displays on the Armfield unit is inserted into the hot water circulation priming vessel

(small vessel near back of unit containing water).

5.) Set flow rate of pumps.

Disconnect the tubing leading from the feed tank to the reactor at the quick disconnect for

both the NaOH and ethyl acetate. Disconnect the tubing coming from the feed vessel

from the disconnect fitting (the disconnect fitting has a valve that closes when

disconnected). Dial the sodium hydroxide feed pump to 39 ml/min and the ethyl acetate

pump to 32 ml/min. (To find the corresponding dial setting, refer to the NaOH/EtAc

pump calibration equations posted on the computer). Note that when disconnected, the

push connector will seal both ends of tubing. MAKE SURE THAT THE PUSH

CONNECTOR IS REMOVED FROM TUBING BEFORE MEASURING THE

FLOWRATE. Otherwise pressurized chemicals might burst out and cause an accident.

Work air bubbles out of the tubing. Discharge can be collected in the reservoir under the

reactor system, or it can be fed back into the appropriate feed vessel. (Make sure to

22

discard the first material out of the pump since this is likely left over material from the

previous group which was left in the tubing.) Verify the flow rate of each pump by

measuring the volume collected over a set time period. If off by more than 2 ml/min,

adjust the flow rate. Record the actual flow rate used in the experiment. Turn the flow

rate off, reconnect the fittings and tubing, then turn the flowrates back to the calibrated

settings and start filling the reactor.

6.) Set the agitator speed to 7. There should be good mixing.

7.) Open up the Armfield program by going into the 480 Lab folder located on the desktop,

then double click the CEB-304 CSTR Reactor icon.

8.) Click the “View Diagram” icon located to the right of the paste icon.

9.) Do not bother to enter in the volumes or concentrations of the two reactants because you

only need the raw conductivity data recorded by the software.

10.) Ensure the software records samples every 10 seconds. Do this by clicking the Sample

drop down menu, choose configure. Sampling Operations should be set to Automatic,

and the Sampling Interval should be set to 10 sec.

11.) Click on the format graph button (all the way on the right of the tool bar) and choose

conductivity as the item to monitor. Then click on the view graph button and wait until

the reactor fills up. You may not be able to do this until you actually start sampling.

12.) We now want to equilibrate the temperature of the water in the heating coil when there

is approximately 500 ml of solution in the reactor. Hold in the temperature button (with

the picture of the thermometer on it). Adjust the set point level up or down with the

black buttons on the right. Set the temperature 2 degrees below the actual temperature

in the reactor. This should prevent the heater from turning on. Flip the switch on the

temperature panel from 0 to 1. You will hear the water heater circulator start.

13.) The reactor volume is set at 1000 ml. It will take approximately 15-20 min for the

reactor to fill up to 1000 ml where it will be continuously drained by the overflow pipe.

23

When the reactor begins to overflow start monitoring the conductivity on the computer

program by clicking on the “go” button to start collecting data. Monitor the

conductivity manually. When it levels out you have achieved steady state. Record the

steady state conductivity and the reactor temperature. The temperature must be

recorded off the digital thermometer. The instrument panel temperature reads the

temperature of the recirculating water bath. The conductivity may be recorded off the

instrument panel or off the computer. Make sure to be consistent in which conductivity

you record as they are not identical. You can record the temperature manually or in the

“attach note” button on the view diagram page as you did with the batch reactor. This

will insert your temperature measurement in the “notes” column on the spreadsheet at

the appropriate time. Add the temperature each time it changes when you are close to

steady state. You will then have a detailed log at the end of the experiment.

14.) Hold in the temperature button (with the picture of the thermometer on it) and adjust the

set point level up or down with the black buttons on the right. You will be increasing the

reactor temperature in ~1-2°C intervals and recording the steady state parameters for

each set point. Monitor the conductivity graphically on the computer to watch the

conductivity level out, and record the conductivity and reactor temperature at each

steady state. (Note: The temperature controller often overshoots the set point, so adjust

the set point to 1°C above the current reactor temperature for each new steady state; e.g.,

if the reactor is at 25°C, set the controller to 26°C.)

Note: Adjust your setpoint temperature increase as you see fit in order to obtain

approximately 2 oC temperature intervals.

15.) Repeat step 14.) until you collect a total of 7 ~ 10 data points. You may need to refill

the feed vessels during this time. Keep an eye on the level and make sure you have

enough volume left to refill the feed tanks without disrupting the flow rates into the

reactor. If you can avoid refilling, do so. Even a very small difference in feed

concentration can throw off steady state.

16.) Save your conductivity and temperature data.

24

Shutdown

1.) Set the pumps to “remote” to temporarily turn them off.

2.) Return the temperature set point back to 20 oC.

3.) Flip the silver toggle switch back to 0 on the temperature panel to turn off the hot water

circulator.

4.) Open the black plastic drain valves to drain the reactor and both feed vessels. Close the

valves after draining.

5.) Add about 1 L of distilled water to each feed vessel and to the reactor.

6.) Pump some distilled water from the feed tanks into the reactor to flush the feed lines by

setting the pump switches back to “manual”.

7.) Dial the pumps and agitator back to 0.

8.) Open the black plastic drain valves to drain the rinse water from the reactor and both feed

vessels.

9.) Turn off the main power to the unit with the white switch. The temperature and

conductivity displays should go out.

10.) Empty the waste solution bucket down the drain in the sink.

11.) Turn the digital thermometer off.