Continuous Stirred Tank Reactor (Cstr) (2)

UNIVERSITI TEKNOLOGI MARA

FAKULTI KEJURUTERAAN KIMA CHEMICAL ENGINEERING LABORATORY III

(CHE575)

NAME : RM SYIBLI MILASI B R MUHAMAD FAKIH

STUDENT NO. : 2004624828

EXPERIMENT : CONTINUOUS STIRRED TANK REACTOR (CSTR)

DATE PERFORMED : 17TH JANUARY 2006

SEMESTER :DISEMBER 2005 – APRIL 2006

PROGRAMME / CODE :Bachelor of Engineering (Hons.) in Chemical Engineering/ EH220

No. Title Allocated marks % Marks %

1 Abstract/Summary 5  

2 Introduction 5  

3 Aims/Objectives 5  

4 Theory 5  

5 Procedures 3  

6 Apparatus 5  

7 Results 20  

8 Calculations 10  

9 Discussions 20  

10 Conclusions 10  

11 Recommendations 5  

12 References 5  

13 Appendices 2   TOTAL 100  

Remarks:

Checked by: Rechecked by:DR.RUZITAH

TABLE OF CONTENTS

PK.FKK.PPM.MANUAL MAKMAL CHE565

ABSTRACT/SUMMARY…………………………….….3

INTRODUCTION…………………………………..........4

OBJECTIVES……………………………………………4

THEORY……………………………………………......4-6

PROCEDURES………………………………………...7-8

APPARATUS…………………………………………….9

RESULTS……………………………………………10-15

SAMPLE OF CALCULATIONS………………………16

DISCUSSION……………………………………….17-18

CONCLUSION………………………………………….19

RECOMMENDATION………………………………….19

REFERENCES………………………………………….20

APPENDICES…………………………………………...20

Summary

Our experiment was to observe the order of the saponification reaction and also to

find the rate constant. At first we mix the Ethyl Acetate and Naoh with equal volume.

Then we start the experiment by mixing them using continuous stirred tank reactor. After

5 minutes we will take a sample of solution and mixed with HCL. Then we titrate it with

0.1M NaoH. The amount of Naoh been used in that titration was been taken in the result.

We repeat the same procedure for the next sample that been taken after 10, 15, 20 and 25

minutes.

For the second experiment we do the same procedure as the first but we increase

the temperature. We take 3 different temperatures that was 60°C, 45°C and 30 °C. When

the all the result has been taken, calculation was made and we plot a graph based on that

result. By the graph we can determine the rate of the reaction.

INTRODUCTION

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.

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.

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)

OBJECTIVES

EXPERIMENT A: BATCH STIRRED TANK REACTOR EXPERIMENT

1. To determine the order saponification reaction.2. To determine the reaction rate constant.

EXPERIMENT B: EFFECT TEMPERATURE ON REACTION RATE CONSTANT

1. To determine the effect temperature on reaction rate constant, k for batch reaction.2. To determine the activation energy of saponification.

THEORY

IDEAL STIRRED-TANK REACTOR

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

BATCH STIRRED-TANK REACTOR (BSTR)

In batch reactions, there are no feed or exit streams and therefore equation (1) can be

simplified into:

Rate of A Rate of A

produced = accumulated

within

volume

within

volume

element element

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

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

isothermal operation.

CA

EFFECT OF TEMPERATURE ON RATE OF REACTION

As we increase the temperature the rate of reaction increases. This is because, if

we heat a substance, the particles move faster and so collide more frequently. That will

speed up the rate of reaction. Collisions between molecules will be more violent at higher

temperatures. The higher temperatures mean higher velocities. This means there will be

less time between collisions. The frequency of collisions will increase. The increased

number of collisions and the greater violence of collisions result in more effective

collisions. The rate for the reaction increases. Reaction rates are roughly doubled when

the temperature increases by 10 degrees Kelvin.

In any single homogenous reaction, temperature, composition and reaction rate

are uniquely related. They can be represented graphically in one of three ways as shown

in figure 8 below:

C r3

r2

r1

figure 8

1/-r

A

Area = t

T

PROCEDURES

EXPERIMENT A:

1. The overflow tube in the reactor is being adjusted to give a desired working

volume (2.5liters). The pump P1 was switched on to start on pumping 1.25 liters

of 0.1M ethyl acetate form the feed tank into reactor. The pump P1 stopped.

2. Then the pump P2 was switch on and starts to pump another 1.25 liters of the

0.1M NaOH into the reactor. When the 2.5 liters volume is reached, then the

pump P2 were being stopped. The stirrer then being switches on and the speed

was set in the mid range (180rpm). The time is being observed. The start time are

recorded.

3. 10ml of the 0.25M HCL were quickly measured in a flask.

4. After 1 minute of reaction, sampling valve V7 opened to collect 50ml sample.

10ml of the 0.25M HCL are immediately added into the sample. The HCL quench

the reaction between ethyl acetate and sodium hydroxide.

5. The mixture was titrated with the 0.1M NaOH to evaluate the amount of un-

reacted HCL. This had provided us with the information to determine the amount

NaOH in feed solution which has reacted.

EXPERIMENT B:

1. The overflow tube in the reactor is being adjusted to give a desired working

volume (2.5liters). The pump P1 was switched on to start on pumping 1.25 liters

of 0.05M ethyl acetate form the feed tank into reactor. The pump P1 stopped.

2. Then the pump P2 was switch on and starts to pump another 1.25 liters of the

0.05M NaOH into the reactor. The heater was switched on and the temperature

was set to be 30°c when the heater is fully immersed. The cooling water being

run. The pump P2 was being stopped when the 2.5 liters of volume are reached.

The stirrer then being switches on and the speed was set in the mid range

(180rpm). The time is being observed. The start time are recorded.

3. 10ml of the 0.25M HCL were quickly measured in a flask.

4. After 1 minute of reaction, sampling valve V7 opened to collect 50ml sample.

10ml of the 0.25M HCL are immediately added into the sample. The HCL quench

the reaction between ethyl acetate and sodium hydroxide.

5. The mixture was titrated with the 0.1M NaOH to evaluate the amount of un-

reacted HCL. This had provided us with the information to determine the amount

NaOH in feed solution which has reacted.

6. Steps 4 and 5 were repeated for reaction times of 5, 10, 15, 20 and 25.

7. The experiment was repeated for reaction temperatures 30°C, 35°C and 45°C.

8. The graph ln(CB/CA) vs. t and ln k vs. 1/T were plotted.

9. The activation energy was found from the ln k vs. 1/T graph.

APPARATUS

1. Continuous stirred tank reactor ( Model BP:100)

2. Stopwatch

3. Beaker

4. Pipet

5. Volumetric cylinder

6. Solution : 0.1 NaOH

0.1 Ethyl acetate

0.25 HCl

Sodium hydroxide

RESULTS

EXPERIMENT A

Tim

e(m

in)

Vol

ume

of ti

trat

ing

NaO

H(m

l)

Vol

ume

of q

uenc

hing

H

Cl u

nrea

cted

with

N

aOH

in S

ampl

e(m

l)

Vol

ume

of H

Cl

reac

ted

with

NaO

H in

S

ampl

e(m

l)

Mol

e of

HC

l rea

cted

w

ith N

aOH

in s

ampl

e

Mol

e of

NaO

H

unre

acte

d in

sam

ple

Con

cent

ratio

n of

N

aOH

unr

eact

ed w

ith

Eth

yl A

ceta

te(M

)

Ste

ady

Sta

te fr

actio

n co

nver

sion

of

NaO

H,X

a

Con

cent

ratio

n of

N

aOH

rea

cted

with

E

thyl

Ace

tate

(M)

Mol

e of

NaO

H

reac

ted

with

Eth

hyl

Ace

tate

in

Sam

ple(

ml)

Con

cetr

atio

n of

Eth

yl

Ace

tate

rea

cted

with

N

aOH

(M)

Con

cent

ratio

n of

E

thyl

Ace

tate

U

nrea

cted

(M)

1/C

a

1

14.2

5.68

4.32

1.08

1.08 0.

0216

0.78

4

0.07

84

3.92

0.07

84

0.02

16

46.2

963

5

17.7

4

7.09

6

2.90

4

0.72

6

0.72

6

0.01

452

0.85

48

0.08

548

4.27

4

0.08

548

0.01

452

68.8

7052

10 19.2

7.68

2.32

0.58

0.58 0.

0116

0.88

4

0.08

84

4.42

0.08

84

0.01

16

86.2

069

15 19.2

7.68

2.32

0.58

0.58 0.

0116

0.88

4

0.08

84

4.42

0.08

84

0.01

16

86.2

069

20 19.4

7.76

2.24

0.56

0.56 0.

0112

0.88

8

0.08

88

4.44

0.08

88

0.01

12

89.2

8571

25 19.5

7.8

2.2

0.55

0.55 0.

011

0.89

0.08

9

4.45

0.08

9

0.01

1

90.9

0909

EXPERIMENT B

Temperature = 30°C

Tim

e(m

in)

Vol

ume

of ti

trat

ing

NaO

H(m

l)

Vol

ume

of q

uenc

hing

H

Cl u

nrea

cted

with

N

aOH

in S

ampl

e(m

l)

Vol

ume

of H

Cl

reac

ted

with

NaO

H in

S

ampl

e(m

l)

Mol

e of

HC

l rea

cted

w

ith N

aOH

in s

ampl

e

Mol

e of

NaO

H

unre

acte

d in

sam

ple

Con

cent

ratio

n of

N

aOH

unr

eact

ed w

ith

Eth

yl A

ceta

te(M

)

Ste

ady

Sta

te fr

actio

n co

nver

sion

of

NaO

H,X

a

Con

cent

ratio

n of

N

aOH

rea

cted

with

E

thyl

Ace

tate

(M)

Mol

e of

NaO

H

reac

ted

with

Eth

hyl

Ace

tate

in

Sam

ple(

ml)

Con

cetr

atio

n of

Eth

yl

Ace

tate

rea

cted

with

N

aOH

(M)

Con

cent

ratio

n of

E

thyl

Ace

tate

U

nrea

cted

(M)

1/C

a

1 19 7.6

2.4

0.6

0.6 0.

012

0.88

0.08

8

4.4

0.08

8

0.01

2

83.3

3333

5

19.5

7.8

2.2

0.55

0.55 0.

011

0.89

0.08

9

4.45

0.08

9

0.01

1

90.9

0909

10 19.4

7.76

2.24

0.56

0.58 0.

0112

0.88

8

0.08

88

4.44

0.08

88

0.01

12

89.2

8571

15 19.3

7.72

2.28

0.57

0.57 0.

0114

0.88

6

0.08

86

4.43

0.08

86

0.01

14

87.7

193

20 19.5

7.8

2.2

0.55

0.55 0.

011

0.89

0.08

9

4.45

0.08

9

0.01

1

90.9

0909

25 19.8

7.92

2.08

0.52

0.52 0.

0104

0.89

6

0.08

96

4.48

0.08

96

0.01

04

96.1

5385

Temperature = 45°C

Tim

e(m

in)

Vol

ume

of ti

trat

ing

NaO

H(m

l)

Vol

ume

of q

uenc

hing

H

Cl u

nrea

cted

with

N

aOH

in S

ampl

e(m

l)

Vol

ume

of H

Cl

reac

ted

with

NaO

H in

S

ampl

e(m

l)

Mol

e of

HC

l rea

cted

w

ith N

aOH

in s

ampl

e

Mol

e of

NaO

H

unre

acte

d in

sam

ple

Con

cent

ratio

n of

N

aOH

unr

eact

ed w

ith

Eth

yl A

ceta

te(M

)

Ste

ady

Sta

te fr

actio

n co

nver

sion

of

NaO

H,X

a

Con

cent

ratio

n of

N

aOH

rea

cted

with

E

thyl

Ace

tate

(M)

Mol

e of

NaO

H

reac

ted

with

Eth

hyl

Ace

tate

in

Sam

ple(

ml)

Con

cetr

atio

n of

Eth

yl

Ace

tate

rea

cted

with

N

aOH

(M)

Con

cent

ratio

n of

E

thyl

Ace

tate

U

nrea

cted

(M)

1/C

a

1 19 7.6

2.4

0.6

0.6 0.

012

0.88

0.08

8

4.4

0.08

8

0.01

2

83.3

3333

5 19 7.6

2.4

0.6

0.6 0.

012

0.88

0.08

8

4.4

0.08

8

0.01

2

83.3

3333

10 20 8 2 0.5

0.5

0.01 0.

9

0.09 4.

5

0.09

0.01 10

0

15 20 8 2 0.5

0.5

0.01 0.

9

0.09 4.

5

0.09

0.01 10

0

20 20 8 2 0.5

0.5

0.01 0.

9

0.09 4.

5

0.09

0.01 10

0

25 20 8 2 0.5

0.5

0.01 0.

9

0.09 4.

5

0.09

0.01 10

0

Temperature = 60°C

Tim

e(m

in)

Vol

ume

of ti

trat

ing

NaO

H(m

l)

Vol

ume

of q

uenc

hing

H

Cl u

nrea

cted

with

N

aOH

in S

ampl

e(m

l)

Vol

ume

of H

Cl

reac

ted

with

NaO

H in

S

ampl

e(m

l)

Mol

e of

HC

l rea

cted

w

ith N

aOH

in s

ampl

e

Mol

e of

NaO

H

unre

acte

d in

sam

ple

Con

cent

ratio

n of

N

aOH

unr

eact

ed w

ith

Eth

yl A

ceta

te(M

)

Ste

ady

Sta

te fr

actio

n co

nver

sion

of

NaO

H,X

a

Con

cent

ratio

n of

N

aOH

rea

cted

with

E

thyl

Ace

tate

(M)

Mol

e of

NaO

H

reac

ted

with

Eth

hyl

Ace

tate

in

Sam

ple(

ml)

Con

cetr

atio

n of

Eth

yl

Ace

tate

rea

cted

with

N

aOH

(M)

Con

cent

ratio

n of

E

thyl

Ace

tate

U

nrea

cted

(M)

1/C

a

1 20 8 2 0.5

0.5

0.01 0.

9

0.09 4.

5

0.09

0.01 10

0

5 22 8.8

1.2

0.3

0.3 0.

006

0.94

0.09

4

4.7

0.09

4

0.00

6

166.

6667

10 21 8.4

1.6

0.4

0.4 0.

008

0.92

0.09

2

4.6

0.09

2

0.00

8

125

15 22 8.8

1.2

0.3

0.3 0.

006

0.94

0.09

4

4.7

0.09

4

0.00

6

166.

6667

20 21.4

8.56

1.44

0.36

0.36 0.

0072

0.92

8

0.09

28

4.64

0.09

28

0.00

72

138.

8889

25 20.7

8.28

1.72

0.43

0.43 0.

0086

0.91

4

0.09

14

4.57

0.09

14

0.00

86

116.

2791

GRAPH

EXPERIMENT A

ghraph 1/Ca vs t

0102030405060708090

100110

0 5 10 15 20 25 30

t,min

1/C

a ,

M

EXPERIMENT B

Temperature = 30°C

30C

828486889092949698

0 10 20 30

t

1/C

a

Temperature = 40°C

Chart Title

70

75

80

85

90

95

100

105

0 5 10 15 20 25 30

t

1/C

ae

Temperature = 60°C

Chart Title

0

40

80

120

160

200

0 5 10 15 20 25 30

t

1/C

ae

SAMPLE OF CALCULATION

Volume of quenching HCl = (0.1/0.25) x 20 = 8

Unreacted with Naoh in sample

Volume of HCl reacted with = 10 - 8 = 2

NaoH in sample

Mole of HCl reacted with = 0.25x 2 = 0.5

Naoh in sample

Reaction rate (k) = (82-58)/(15-1) = 1.7

Activation energy from the graph

-Ea = (8.3142)x (-0.39+1.05)/(3.14-3.3)(10^-3)

Ea = 33 kj/mol

Activation energy from equation

ln (k2/k1) = E/R (1/T1-1/T2).

ln (0.65/0.35) /(1.556x106-4) = E/(8.3142)

E = 34.29 kj/mol

Discussion

Batch Stirred Tank Reactor is one of the reactors that widely used in industrial.

Batch stirred Tank reactor is a closed system. For this experiment we used liquid that

have a constant density. For that it is a constant-volume Batch reactor.

For experiment A we want to know the order of the reaction and the value of rate

constant (k) and for experiment B we want to know the effect of the temperature on rate

constant and find the value of the activation energy.

Experiment A: Batch Stirred Tank Reactor

In this experiment, we use room temperature that was 27oC to operate the batch

stirred tank reactor. From the result it seems that the volume of titrating NaOH will

increase when time increasing. After we have plotted the graph, it seems that the reaction

was second order. This was proven by the graph 1/Ca vs t that gives us a straight line that

has a positive slope. We can say that our reaction was elementary.

Based on the equation 1/Ca = kt + 1/Cao we can found the reaction rate from the

slope. After we calculate the value of the slope from the graph the value of k was 1.7.

Experiment B: Effect of temperature on Reaction rate constant, k

From the Arrheniu’s equation k=koe–E/RT it shows that temperature has an effect to

the reaction rate constant. To prove that we made experiments that used 3 different

temperatures 30°C, 45°C and 60°C.

We prove it by finding the value of reaction rate for every temperature and

compare it. For the 30°C we get the value of k was 0.35, for 45°C we get 0.8 and for

60°C we get 0.2.

Based on the equation, we will get an increasing value of rate constant when the

temperature is increase. For our experiment we get the result that satisfied the equation

except for the 60°C this happen because of readings error at time 5 to 15 minutes.

Because of that error we get a zigzag graph that gives us a low rate constant that did not

satisfied the equation. Because of that we neglect the value of k at 60°C.

After we have plotted the graph we can find the value of the activation energy.

Arrheniu’s law says that for a reaction that have same concentration, but at two different

temperatures the value of the activation energy is constant. This can be indicates by the

equation ln (k2/k1) = E/R (1/T1-1/T2).

The activation energy for this experiment can be calculated on two ways. First is

using the equation above, second by finding the value of the slope of the graph ln k vs

1/T. The value of the activation energy is the value of the slope based on the equation

ln k = (Ea/R)(1/t).

Graph to find the activation Energy.

lnk vs 1/T

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

3.14 3.3

1/T

ln k Series1

Using the equation we get the value of the activation energy was 34 kj/mol and

from the graph we get 33 kj/mol. This two value has a very small different. It shows that

we can calculate the activation energy using either ways. Its also show that our graph is

correct.

Conclusions

After all experiment has been done we have find some points that make our

conclusions.

Our 1st conclusions were that this equation is elementary and it is 2nd order. We

conclude this by the graph 1/Ca versus t(time) that has been plotted in experiment A. we

get straight line graph that has a positive slope value. We can write the reaction rate for

this equation that is –ra = kCaCb.

Our second conclusions that the value of k is dependent on temperature and the

rate constant will only constant for a constant temperature. When the temperatures

increase the value of reaction rate also increase. This satisfied the Arrehinu’s equation

k=koe–E/RT

We also conclude that activation energy is constant for reactions that have a same

concentration but different temperatures. This has been proven by the equation ln (k2/k1)

= E/R (1/T1-1/T2) and the graph that we have plotted. We get almost the same value.

Recommendations

After we have finished this experiment, we find that are several factors in this

experiment that can be fixed to make sure that the experiment runs better. This is some of

my recommendation for this experiment:

For experiment B the readings should be taken at least 4 different temperatures.

Not 3 temperatures only. When we take 4 different temperatures we can get a

better graph for findings the activation energy.

The Arrheniu’s equation should be provided in the summary of theory to make

sure the students more understand about the activation energy and not only by

following the instruction only.

Reference

Levenspiel, O, Chemical Reaction Engineering, John Wiley, 1972

Robert H.Perry, Don W.Green, Perry’s Chemical Engineers’ Handbook,

McGraw Hill,1998.

Smith,J.M, Chemical Engineering Kinetics, McGraw Hill, 1981.

Appendics

C r1 r1

r2 r2

r3 r3

r1

r2

r3

T

r

T

r

C