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INDEX

S.No Contents Page No

1. OBJECTIVE 2. APPARATUS REQUIRED 3. INTRODUCTION 4. THEORY 5. DIAGRAM 6. PROCEDURE 7. OBSERVATION TABLE 8. CALCULATIONS 9. RESULT AND DISCUSSION

10. PRECAUTIONS 11. REFERENCES

OBJECTIVE

To carry out a non-catalytic homogeneous reaction of NaOH and ethyl acetate

in a series of 3 CSTR’s and

i. To study the performance of a cascade of 3 equal volume CSTR in series.

ii. To draw the performance chart for the reactor system and evaluate the

reaction rate constant at ambient condition.

APPARATUS REQUIRED

Apparatus Quantity

i. Measuring cylinder (1000ml) 1

ii. Measuring cylinder (50ml) 1

iii. Pipette (5ml/10ml) 1

iv. Burette (25ml) 1

v. Conical flask (100ml) 4

vi. Beaker (100ml) 3

vii. Volumetric flask 1

viii. Bucket 2

ix. Mug 1

x. Thermometer 1

xi. Conical funnel 1

REAGENTS REQUIRED

Reagents

i. NaOH pellets

ii. HCl

iii. Ethyl acetate

iv. Sodium carbonate

v. Phenolphthalein indicator

INTRODUCTION

Reactor is one of the most important parts in industrial sector. Reactor is

equipment that changes the raw material to the product we want. A good reactor

will give a high production and be economical. One of the criterions to choose a

good reactor is to know the effectiveness of the reactor itself. One of the most

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

reaction. By studying the reaction of ethyl acetate and NaOH to form sodium

acetate in CSTR, we can evaluate the rate data needed to design in production

scale reactor.

The main feature of CSTR reactor is that mixing is complete so that the

properties such as temperature and concentration of reaction were uniform in all

parts of vessel. In experiment, the ethyl and NaOH with equal volume are

mixed. Then the experiment is started by mixing them using CSTR. After 5

mins we will take a solution and mix them with HCl, and then it is titrated with

NaOH. The amount of NaOH used in titration is taken in the result. The

procedure is repeated for the next sample that has been taken after 10,15,20

minutes.

THEORY

Ideal steady-state flow reactor is called the mixed reactor, the back mix reactor,

the ideal stirred tank reactor, the C* (meaning C-star), CSTR, or the CFSTR

(constant flow stirred tank reactor), and, as its names suggest, it is a reactor in

which the contents are well stirred and uniform throughout. Thus, the exit

stream from this reactor has the same composition as the fluid within the

reactor. We refer to this type of flow as mixed flow.

Since the composition is uniform throughout, the accounting may be made

about the reactor as a whole.

If FA0, =ᶹoCAo is the molar feed rate of component A to the reactor, then

considering the reactor as a whole we have

Introducing these three terms into balance equation, we obtain

which on rearrangement becomes

or

where XA and rA are measured at exit stream conditions, which are the same as

the conditions within the reactor.

Graphical representation of these CSTR performance equations-

EQUAL SIZE OF CSTR IN SERIES

Consider a system of N mixed flow reactors connected in series.

Though the concentration is uniform in each reactor, there is, nevertheless, a

change in concentration as fluid moves from reactor to reactor. This stepwise

drop in concentration suggests that the larger the number of units in series, the

closer should the behaviour of the system approach plug flow.

First-Order Reactions. From a material balance for component A about vessel

i gives

Because ᵋ= 0 this may be written in terms of concentrations. Hence

Now the space-time Ʈ (or mean residence time t) is the same in all the equal size

reactors of volume Vi. Therefore

Rearranging, we find for the system as a whole

In the limit, for N →∞, this equation reduces to the plug flow equation

Second-Order Reactions.

DIAGRAM

Schematic Diagram of 3

CSTR in series

PROCEDURE

i. Prepare 10L solution of M/100 NaOH and M/100 ethyl acetate.

ii. Fix the flow rate to CSTR’s using rotameter at equimolar reactant flow rate.

iii. Switch on the stirrer of the 1st CSTR, when the level of the feed reaches at the

stirrer of the impeller level.

iv. Similarly switch on the stirrer of the other reactors when the reaction mixture

reaches the desired level.

v. Once steady state is obtained, take out a10 ml sample of the reaction mixture

using a pipette from the 1st CSTR 5mins after overflow starts and transfer this

reaction mixture immediately into a conical flask containing 20ml of N/40 HCl

to quench the reaction. Titrate 10 ml of aliquot of the resulting solution against

N/100 NaOH.

vi. Repeat the process for CSTR no. 2 and 3 in that order.

vii. To find out initial concentration CAO transfer 5ml NaOH in a conical flask

containing 20ml of N/40 HCl and add 5ml ethyl acetate in it. Titrate 10ml of

aliquot of the resulting solution against N/100 NaOH.

viii. Carry out steps 1to 6 for another flow rate of reactants.

CALCULATIONS & GRAPHS

1. CALCULATION FOR CA0 (INITIAL CONCENTRATION) Volume of aliquot sample = 30ml

Volume of NaOH consumed = 3.7 ml

Volume of HCl consumed in titration = V1 ml

N1VI = N2V2

V1 = ((40/N)*3.7)/ (100) = 1.48ml

Volume of HCl reacted with feed solution

V4 = 20-1.48 = 18.52ml

So, concentration of solution initially

N1V4 = N3V3

N3 = (N/40)*(18.52/10) = 0.0463N

Normality = Molarity = 0.0463mol/lit

2. CALCULATION FOR COCENTRATION AT FLOW RATE = 6LPH

I. For CSTR 1

Volume of aliquot sample = 30ml



N1VI = N2V2

V1 = ((40/N)*5.2)/ (100) = 2.08ml


V4 = 20-2.08 = 17.92ml

So, concentration of solution

N1V4 = N3V3

N3 = (N/40)*(17.92/10) = 0.0448N


II. For CSTR 2




N1VI = N2V2

V1 = ((40/N)*5.4)/ (100) = 2.16ml


V4 = 20-2.16 = 17.84ml


N1V4 = N3V3

N3 = (N/40)*(17.84/10) = 0.0446N


III. For CSTR 3




N1VI = N2V2

V1 = ((40/N)*5.6)/ (100) = 2.24ml


V4 = 20-2.24 = 17.76ml


N1V4 = N3V3

N3 = (N/40)*(17.76/10) = 0.0444N


Thus for flow rate = 6LPH

CA0 = 0.0463 mol/lit




3. CALCULATION FOR COCENTRATION AT FLOW RATE = 9LPH

I. For CSTR 1




N1VI = N2V2

V1 = ((40/N)*4.2)/ (100) = 1.68ml


V4 = 20-1.68 = 18.32ml


N1V4 = N3V3

N3 = (N/40)*(18.32/10) = 0.0458N


II. For CSTR 2




N1VI = N2V2

V1 = ((40/N)*4.6)/ (100) = 1.84ml


V4 = 20-1.84 = 18.16ml


N1V4 = N3V3

N3 = (N/40)*(18.16/10) = 0.0454N


III. For CSTR 3




N1VI = N2V2

V1 = ((40/N)*4.8)/ (100) = 1.92ml


V4 = 20-1.92 = 18.08ml


N1V4 = N3V3

N3 = (N/40)*(18.08/10) = 0.0452N


Thus for flow rate = 9LPH





4. CALCULATION FOR SPACE TIME

Space-time Ʈ = V/ᶹo = Volume of the reactor/Flow rate of fluid (vol.)

Reactor is cylindrical in shape (V) = 𝜋𝐷2ℎ/4 = 1.091*10-3 m3

For flow rate 6LPH

Total flow rate of fluid = 2*6 = (12*10-3)/3600 m3/s

Ʈ = (1.091*10-3*3600)/12*10-3 = 327.31 sec

For flow rate 9LPH

Total flow rate of fluid = 2*9 = (18*10-3)/3600 m3/s

Ʈ = (1.091*10-3*3600)/18*10-3 = 218.06 sec

5. GRAPH BETWEEN (CA)n &(CA)n-1

6. PERFORMANCE CHART CSTR IN SERIES

0.0442

0.0444

0.0446

0.0448

0.045

0.0452

0.0454

0.0456

0.0458

0.046

0.0444 0.0446 0.0448 0.045 0.0452 0.0454 0.0456 0.0458 0.046 0.0462 0.0464

CA

(n)

CA(n-1)

6 LPH 9 LPH

0.0442

0.0444

0.0446

0.0448

0.045

0.0452

0.0454

0.0456

0.0458

0.046

0 200 400 600 800 1000 1200

CO

NC

ENTR

ATI

ON

CA

TIME (IN SEC)

Performance Chart

6 LPH 9 LPH

7. CALCULATION OF RATE CONSTANT

For equal size reactor in series we have,

k = 1

Ʈ [(C0/C1)

1/N – 1]

(According to graph, reaction order is 1st)

For flow rate 6LPH

Ʈ = 327.31 sec



So,

k = 4.2973*10-5 sec

For flow rate 9LPH

Ʈ = 218.06 sec



So,

k = 3.69*10-5 sec

k (average) = (4.2973*10-5 + 3.69*10-5)/2 = 4*10-5 sec

RESULTS

The first order reaction rate is found to have value equal to 4.0*10-5 sec.

The performance chart for three CSTR of equal volume connected in series

is found as attached graph.

CONCLUSIONS

The behaviour of equal volume CSTR connected in series tends to PFR by

increasing the same number of reactors.

For the same interval of time the conversion is lower from any CSTR for

higher feed flow rates.

PRECAUTIONS

i. Wash all the apparatus before and after doing the experiment.

ii. Steady state should be obtained before start of sampling time, t=0 and

should be assumed carefully after steady state.

iii. For NaOH solution after preparing it, it should be titrated with oxalic acid

to determine exact normality. Normality is changed due to hydroscopic

nature of NaOH.

iv. Solution of all components should be prepared accurately.

v. Time measurement and titration should be done accurately.

REFERENCES

i. Octave Levenspiel, Chemical Reaction Engineering., 3rd edition.

ii. Jones, R.W., Chemical Engineering Programme., 47,46.

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