UNIVERSITI TEKNOLOGI MARA FAKULTI KEJURUTERAAN KIMIA

PROCESS ENGINEERING LABORATORY II (CPE 554)

No. Title Allocated Marks Marks

1. Abstract/Summary 5

2. Introduction 5

3. Aims 5

4. Theory 5

5. Apparatus 5

6 Methodology/Procedure 10

7. Results 10

8. Calculations 10

9. Discussion 20

10. Conclusion 10

11. Recommendations 5

12. Reference 5

13. Appendices 5

TOTAL 100

Remarks:

Checked by: Rechecked by:

......... ..

Date: Date:

NAME AND MATRIC NO : MUHAMMAD ARSHAD BIN ABDUL RASHID (2014683386)

GROUP : 6 EXPERIMENT : LAB 7 (CONTINUOUS STIRRED TANK REACTOR) DATE PERFORMED : 27 APRIL 2015 SEMESTER : 4 PROGRAMME CODE : EH242 4E SUBMIT TO : MDM UMMI KALTHUM IBRAHIM

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Table of Contents

NO. TITLE PAGES

1 Abstract 3

2 Introduction 4

3 Aims 4

4 Theory 5

5 Apparatus 8

6 Methodology/Procedure 9

7 Results 11

8 Calculations 13

9 Discussion 15

10 Conclusion 16

11 Recommendations 17

12 Reference 17

13 Appendices 18

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1.0 Abstract

Our experiment is carried out using the Continuous Stirrer Tank Reactor (CSTR) 40 L for second experiment which is effect of temperature on the reaction in a CSTR. The objectives in this experiment are to determine the effect of temperature onto the reaction extent of conversion and lastly to determine the reactions activation energy. In this experiment, 0.1 M of acetyl acetate, 0.1 M sodium hydroxide and hydrochloric acid, HCL (0.25M) for quenching were prepared. Then adjust the valves V5 and V10 to give a flow rate of 0.20 L/min. Make sure that both flow rates are the same for the whole experiment. Firstly, the temperature of the water was set at 40C by switch on the thermostat T1. This is to ensure that the reactor has reached steady state. That will be the same as the reactor and reactant temperature. Then, the stirrer was switched on and the stirrer speed was set about 200 rpm. After 5 minutes later, conductivity was observed and valve V12 is open to collect a 150 mL sample. Then we carry out a back titration procedure to manually determine the concentration of NaOH in the reactor for 3 times. The means volume of NaOH collected is then determined. Make sure that the flow rates of both solutions are maintained at 0.20 L/min. The reading was recorded and the steps were repeated for temperature of 50C and 60C. Last but not least, after finishing all the steps in the experiments, mixture inside the reactor was drained off and the reactor was clean properly. All liquid waste (mixture) was dispose immediately after each experiment. In this experiment, we did not manage to get the expected results because we did wrong at temperature 50C. In terms of rate of reaction, as the temperature increasing the rate of reaction will increase due to increasing of its activation energy. There are some recommendation to increase the efficiency of the experiment which are the titrations is repeat for two or three times because a lot of error comes from titration or use another method other than titration.

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2.0 Introduction

The unit used in this experiment, which is Continuous Stirred Tank Reactor. The experiment

was conducted to study the effect of temperature on saponification reaction of ethyl acetate

and sodium hydroxide in batch reactor. A batch reactor was a reactor which characterized by

its operation. Batch reactor is a reactor reached steady state which was a generic term for a

type of vessel widely used in the process industries. Reactor is one of the most important parts

in industrial sector. Reactor is equipment that changes the raw material to the product that we

want. A good reactor will give a high production and economical. One of criteria to choose or

to design a good reactor is to know the effectiveness of the reactor itself. There a many types

of reactor depending on the nature of the feed materials and products. One of the most

important we need to know in the various chemical reaction was the rate of the reaction.

Continuous stirred tank reactor or known as CSTR is a most common ideal reactor type

in chemical engineering .In a continuous stirred tank reactor (CSTR), reactants and products

are continuously added and withdrawn from the reactor. The CSTR is the idealized opposite

of the well-stirred batch and tubular plug flow reactors. Analysis of selected combination of

these reactors types can be useful in quantitatively evaluating more complex solid, gas-, and

liquid- flow behaviors. A stirred tank reactor (STR) may be operated either as a batch reactor

or as a steady state flow reactor (CSTR). The key or main feature of this reactor is that mixing

is complete so that properties such as temperature and concentration of the reaction mixture

are uniform in all parts of the vessel. Material balance of a general chemical reaction described

below. The conservation principle requires that the mass of species A in an element of reactor

volume dV obeys the following statement:

(Rate of A into volume element) - (rate of A out of volume element) + (rate of A produced within

volume element) = (rate of A accumulated within vol. element)

By studying the saponification reaction of ethyl acetate and sodium hydroxide to form

sodium acetate in a batch and in a continuous stirred tank reactor, we can evaluate the rate

data needed to design a production scale reactor.

3.0 Aims

To determine the effect of temperature onto the reaction extent of conversion

To determine the reactions activation energy

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4.0 Theory

A stirred-tank reactor (STR) may be operated either as a batch reactor or as a steady-

state flow reactor (better known as Continuous Stirred-Tank Reactor (CSTR)). The key or main

feature of this reactor is that mixing is complete so that properties such as temperature and

concentration of the reaction mixture are uniform in all parts of the vessel. Material balance of

a general chemical reaction is described below.

The conservation principle required that the mass of species A in an element of reactor volume

V obeys the following statement:

Rate of

A

Rate of

A Rate of A Rate of A

into - out of + produced = Accumulated

volume Volume

within

volume within volume

element Element Element Element

The usual agitator arrangement is a centrally mounted shaft with an overhead drive

unit. Impeller blades are mounted on the shaft. A wide variety of blade designs are used and

typically the blades cover about two thirds of the diameter of the reactor. Where viscous

products are handled, anchor shaped paddles are often used which have a close clearance

between the blade and the vessel walls

Most batch reactors also use baffles. These are stationary blades which break up flow

caused by the rotating agitator. These may be fixed to the vessel cover or mounted on the side

walls. Despite significant improvements in agitator blade and baffle design, mixing in large

batch reactors is ultimately constrained by the amount of energy that can be applied. On large

vessels, mixing energies of more than 5 Watts per liter can put an unacceptable burden on the

cooling system. High agitator loads can also create shaft stability problems. Where mixing is a

critical parameter, the batch reactor is not the ideal solution. Much higher mixing rates can be

achieved by using smaller flowing systems with high speed agitators, ultrasonic mixing or static

mixers (H.S. Fogler, 2005).

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A batch reactor is used for small-scale operation, for testing new processes that have

not been fully develop, for the manufacture of expensive products, and for processes that are

difficult to convert to CSTR. The reactor can be charged through the holes at the top. A batch

reactor has neither inflow nor outflow of reactants or products while the reaction is being carried

out: Fjo = Fj = 0.

In Out + Generation = Accumulation

(H. Scott Fogler, Elements of Chemical Reaction Engineering)

The rate of reaction of component A is defined as:

-rA = 1/V (dNA/dt) by reaction = [moles of A which appear by reaction]

[unit volume] [unit time]

By this definition, if A is a reaction product, the rate is positive; whereas if it is a reactant

which is consumed, the rate is negative.

Rearranging equation (3),

(-rA) V = NAO dXA Dt

Integrating equation (4) gives,

t = NAO dXA__

(-rA)V

dt

dNdVrFF A

V

AA0A

V

AA dVr

dt

dN

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Where t is the time required to achieve a conversion XA for either isothermal or non-

isothermal operation.

There are some advantage and disadvantage for using batch reactor. For advantages it

production of high cell densities due to extension of working time (particularly important in the

production of growth-associated products). Next, it controlled conditions in the provision of

substrates during the fermentation, particularly regarding the concentration of specific

substrates as for example the carbon source. As for disadvantages, it requires previous

analysis of the microorganism, its requirements and the understanding of its physiology with

the productivity. Besides that, it requires a substantial amount of operator skill for the set-up,

definition and development of the process. Lastly in a cyclic fed-batch culture, care should be

taken in the design of the process to ensure that toxins do not accumulate to inhibitory levels

and that nutrients other than those incorporated into the feed medium become limiting, Also, if

many cycles are run, the accumulation of non-producing or low-producing variants may result.

(H.S. Fogler, 2005).

1/-

r A

Area = t

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5.0 Apparatus

1. Continuous Stirred Tank Reactor for 40L

2. Retort Stand

3. 50 mL burette

4. 250 mL conical flasks

5. 100 mL measuring cylinder

6. Beaker

Materials

1. Sodium hydroxide, NaOH (0.1M)

2. Ethyl acetate, Et(Ac) (0.1M)

3. Hydrochloric acid, HCl (0.25M)

4. Deionized Water

5. Phenolphthalein indicator

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6.0 Methodology/Procedure

General start-up Procedures:

1. The following solution were prepared:

i- 40L of sodium hydroxide, NaOH (0.1 M)

ii- 40 L of ethyl acetate, Et (Ac) (0.1M)

iii- 1 L of hydrochloric acid, HCl (0.25M) , for quenching.

2. All valves were initially closed.

3. The feed vessels were charged as follows:

i- The charge port caps for vessels B1 and B2 were opened.

ii- The NaOH solution was carefully poured into vessel B1 and Et (Ac) solution

was poured into vessel B2.

iii- The charge port caps for both vessels were closed.

4. The power for control panel was turned on.

5. Sufficient water in thermostat T1 was checked. Refill as necessary.

6. Cooling water V13 was opened and are let to flow through condenser W1.

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

8. Valves V2, V3, V3, V7, V8 and V11 were opened.

9. The unit was ready for experiment.

General shut-down Procedures:

1. The cooling water valve V13 was kept open to allow the cooling water to continue

flowing.

2. Pumps P1 and pumps P2 were switched off. Stirrer M1 was switched off.

3. The thermostat T1 was switched off. The liquid in the reaction vessel R1 was let to cool

down to room temperature.

4. Cooling water V13 was closed.

5. Valves V2, V3, V7, and V8 were closed. Valves V4, V9 and V12 were opened to drain

any liquid from the unit.

6. The power for control panel was turned off.

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Preparation of Calibration Curve for Conversion vs. Conductivity

1. The following solution were prepared:

i- 1 L of sodium hydroxide, NaOH (0.1M)

ii- 1 L of sodium acetate , Et (Ac) (0.1M)

iii- 1 L of deionized water, H2O.

2. The conductivity and NaoH concentration for each value were determined by mixing

the following solution into 100 mL of deionized water.

i- 0% conversion : 100 mL NaOH

ii- 25% conversion : 75 mL NaOH + 25 mL Et (Ac)

iii- 50% conversion : 50 mL NaOH + 50 mL Et (Ac)

iv- 75% conversion : 23 mL NaOH + 75 mL Et (Ac)

v- 100% conversion : 100 mL Et (Ac)

Back Titration Procedures for Manual Conversion Determination:

1. A burette was filled up with 0.1 M NaOH solution.

2. 10 mL of 0.25 M HCl was measured in a flask.

3. A 50 mL sample was obtained from the experiment and immediate the sample was

added to the HCl in the flask to quench the saponification reaction.

4. A few drops of pH indicator were added into the mixture.

5. The mixture was titrated with NaOH solution from the burette until the mixture was

neutralized. The amount of NaOH titrated was recorded.

EXPERIMENT 2: Effect of temperature on the Reaction in a CSTR

1. The general start-up was performed.

2. Pumps P1 and P2 was switched on simultaneously and valves V5 and V10 was opened

to obtain the highest possible flow rate into the reactor.

3. The reactor are let to fill up with both the solution until it is just overflowed.

4. The valves V5 and V10 are readjusted to give a flow rate of 2.0 L/min. Both flow rates

are ensured recorded at the same time.

5. The stirrer M1 are switched on and the speed are set at about 200 rpm.

6. The thermostat T1 are switched on and the water temperature was set to 40 C.

7. The conductivity value at Q1-401 was started to monitor and the temperature value at

T1-101 until no changed over time. To ensured the reactor had reached to steady state.

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8. The steady state conductivity and the temperature values was recorded and the

concentration of NaOH in the reactor and the extent of reaction of conversion from

calibration curve was found.

9. After 5 minutes, sampling valves V12 was opened and a 50 mL sample was collected.

The titration procedures was carried out back to manually determine the concentration

of NaOH in the reactor and extent of conversion.

10. The experiment was repeated ( steps 7 to 10 ) for different reactor temperatures by

setting the thermostat temperature to 50, and 60 C. The flow rates of both solutions

was ensured maintained at 0.20 L/min.

7.0 Results

Reactor volume = 10 L

Concentration of NaOH in feed vessel = 0.1 M

Concentration of Et(Ac) in feed vessel = 0.1 M

Temperature (oC) 40 50 60

Flow rate of NaOH (mL/min)

200 200 200

Flow rate of Et (Ac) (mL/min)

200 200 200

Total flowrate , Fo (mL/min)

400 400 400

Conductivity 3.27 3.24 3.21

Average Volume of NaOH titrated,

V1(mL)

24.40 23.27 24.53

Residence time, (min)

25 25 25

Volume of unreacted

9.76 9.308 9.812

12

90

92

94

96

98

100

40 50 60

Co

nve

rsio

n, X

(%

)

Temperature (C)

Conversion, X vs Temperature

y = 0.247x + 6.161y = 0.247x + 6.161

0

2

4

6

8

10

0.025 0.02 0.017

ln k

1/t

ln k vs 1/t

quenching HCl, V2 (mL)

Volume of HCl reacted with NaOH

, V3 (mL)

0.24 0.692 0.188

Conversion, X (%) 97.6 93.08 98.12

Rate Constant ,k

(M-1min-1)

1355.56 155.50 2220.91

ln k

7.212

5.047

7.706

1/T 0.025 0.02 0.017

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8.0 Calculations

When the flowrate of both solution is 0.1 L/min (Column 1 of Table 1), the known quantities are :

F0 = 0.2+0.2 = 0.4 mL/min

Volume of sample,Vs 50 mL

Concentration of NaOH in the feed vessel, CNaOH,f

0.1 M

Volume of HCl for quenching, VHCl,s 10 mL

Concentration of HCl in standard solution, CHCl,s

0.25 mol/L

Volume of NaOH titrated, V1 23.1 mol/L

Concentration of NaOH used for titration, CNaOH,s

0.1 mol/L

Example for T = 40C

i- Concentration of NaOH that entering the reactor, CNaOH 0.

CNaOHo = CNaOHs

= (0.1)

= 0.05 mol/L

ii- Volume of unreacted quenching HCl,V2

V2 = (CNaOHs / CHCls) x V1

= (0.1/0.25) x 24.4

= 9.76 mL

iii- Volume of HCl reacted with NaOH in sample, V3

V3 = VHCls V2

= 10 9.76

= 0.24 mL

iv- Moles of HCl reacted with NaOH in sample, n1

n1 = (CHCls x V3) / 1000

= 0.25 x 0.24/1000

= 0.00006 mol

v- Moles of unreacted NaOH in sample, n2

n2 = n1

= 0.00006 mol

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vi- Concentration of unreacted NaOH in the reactor, CNaOH

CNaOH = n2/Vs x 1000

= 0.00006/50 x 1000

= 0.0012 mol/L

vii- Conversion of NaOH in the reactor, X

X = (1- CNaOH / CNaOHo) x 100%

= (1 0.0012/0.05) x 100%

= 97.6 %

viii- Residence time,

= VCSTR / Fo

= 10 / 0.4

= 25 min

ix- Reaction rate constant, k

K = (CAo CA) / CA2

= (0.05 0.0012) / (25 x 0.00122)

= 1355.56 1min -1

Arhenius equation:

() =

ln = ln

(

1

)

= +

From graph equation:

y = 0.247x + 6.161

c = 6.161=ln A

A =6,161=473.9

M=0.247=

15

So for Arhenius equation:

() = (473.9)0.247

= 606.68

Reactions activation energy

1. For 40 ,

0.247=

E = 0.247(8.314)(40+273) = 642.76 J/mol

2. For 50,

0.247=

E = 0.247(8.314)(50+273) = 663.3 J/mol

3. For 60,

0.247=

E = 0.247(8.314)(60+273) = 683.83 J/mol

9.0 Discussion

In this experiment, the two objectives are determine the effect of temperature onto the

reaction extent of conversion and determine the reactions activation energy. From the data

collected from the result, two graph had been plotted which are first one is conversion versus

temperature and the last one is ln versus 1

.

For the purpose of achieving that particular target, the experiment is designed so that two

reactants which are Sodium Hydroxide, NaOH and Ethyl Acetate, Et(Ac) react with each other

in the saponification process. The reactor used is CSTR since the property that is to be varied

is the temperature. As the flow rate of NaOH and Et(Ac) same throughout the experiment, the

residence time is also the same which is 25 min.

, =

0

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Where VCSTR refers to the volume of the reactor (in this case 10 L) and F0 is the total flow rate

of the feed which is 400 mL/min to get same residence time, . And that is exactly what was

done. The temperature in the experiment was varied to be 40, 50 and 60. A graph between

temperature and the conversion of the reactant (in this case NaOH) has to be formed in order

to study the relationship between the conversion of NaOH and temperature. The values of

temperature are known, as explained before, and the values of conversion, X of NaOH can be

determined by

X = (1

,0) x 100%

In this experiment, we did not manage to get the expected results as stated in theory. This is

because our second reading is false. The results should be from the first graph, the conversion

is increase proportionally to the temperature. As we know the hypothesis that conversion is

higher if the temperature is higher. But we get decrease and increase at the third temperature.

The cause of this problem is maybe during the taking of sample for 50, we did not remove

some of the sample first so the sample is not from the reactor, it is from the pipe at V12. Other

reason maybe we lack of skill when titration that may be affects the result and graph

respectively. Thus for the second graph, it will effect too.

From the second graph, the value for Arhennius equation is 606.68 which is calculated from

line equation y = 0.247x + 6.161.

10.0 Conclusion

Based on the objectives of this experiment, which is to determine the effect of temperature

onto the reaction extent of conversion, the relationship conversion and temperature was

directly proportional. From the calculated data, the conversion increasing when the

temperature is higher except for temperature 500C. We can conclude that the experiment was

unsuccessfully conducted since we did not get the right conclusion. By using a Continuous

Stirred Tank Reactor, CSTR, these two substances were flowed into the reactor, mixed and

let to react for a certain by different temperature. By doing that, saponification process was

completed. The experiment also targets to determine the reaction activation energy. From

arhennius equation, the reaction activation energy for 40, 50 and 60 is 642.76 J/mol,

663.3 J/mol and 683.83 J/mol respectively. This show that reaction of rate increasing in high

temperatures.

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11.0 Recommendations

Make sure CSTR 40 liters machine is running appropriately, it to prevent harm to the

machine and individual that used the machine.

Repeat titrations two or three times because a lot of error comes from titration or use

another method other than titration.

Divide into two teams which is the first team in charge of the CSTR 40 liters machine

while the second team would carry out the back titration procedures.

Take conductivity reading when the conductivity not changes in time because it can

change rapidly in short of time.

The indicator should be mixed with the acid first, then the sample.

When the sample is being collected, the first few mililiters should be thrown away, for

it is the remaining of the previous sample trapped in the pipe.

Pumps should never be run dry.

12.0 Reference

Fogler. H.S (2005). Elements of Chemical Reaction Engineering.

Continuous Strir Tank Reactor (CSTR), Retrieve at May 9, 2015 at

http://www.umich.edu/~elements/5e/asyLearn/bits/cstr/index.htm

Lab manual CPE554-CSTR40L

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13.0 Appendices

Samples that were titrated using 0.1 M NaOH which turned into light pink