17CF022387 Usoro Ubong Emmanuel Batch Reactor PDF

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COVENANT UNIVERSITY, OTA. COLLEGE OF ENGINEERING DEPARTMENT OF CHEMICAL ENGINEERING TITLE PAGE

EXPERIMENT 2 BATCH REACTOR BY

USORO UBONG EMMANUEL 17CF022387 SUBMITTED TO THE DEPARTMENT OF CHEMICAL ENGINEERING

IN PARTIAL FULFILMENT OF REQUIREMENTS FOR CHEMICAL ENGINEERING LABORATORY II (CHE 322) AUGUST 18, 2020.

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ABSTRACT A batch reactor is a reactor which the reactant is feed and left in the tank. Reaction kinetics plays a vital role for the development of optimized design of a reactor and is hence of extreme importance for the chemical engineer. This importance can be observed by studying the the liquid phase homogenous saponification reaction kinetics in batch reactor. Hence, this experiment’s main purpose is to study the saponification reaction of ethyl acetate and sodium hydroxide in an isothermal batch reactor. The variables considered for analysis were residence time (seconds), temperature (ºC), conductivity (mS/cm), concentration (M), and conversion (%). The temperature was manipulated and the time taken as well as conductivity values were monitored and recorded. This allowed for the determination of rate constants of the saponification reaction in the temperature range (30–37 ºC). The activation energy ( Ea ) was also determined. Using the raw data from the results table, related trend graphs were generated to portray the relationships. It was observed that the conductivity of a reaction at 30ºC is higher than that of the reaction at 37ºC. Furthermore the rate constant, k value was obtained and used to determine the activation energy to be 93.357kJ/mol. Moreover, The values of rate constants k 1 and k 2 were found to be k 1 = 1.8815 M −1 s−1 at 30ºC; and k 2 = 4.3444 M −1 s−1 at 37ºC. Hence, the rate constant, k value is increased as the temperature is increased. This means the experiment is obeying the Arrhenius theory. This also implies Specific rate constant and conversion increase with temperature within the studied temperature range. The results obtained in this study may be helpful in maximizing the conversion of ethyl acetate saponification reaction at industrial scale in a batch reactor.

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TABLE OF CONTENTS TITLE PAGE..............................................................................................................................................i ABSTRACT.............................................................................................................................................. ii TABLE OF CONTENTS............................................................................................................................. iii CHAPTER ONE: INTRODUCTION.............................................................................................................1 1.1 Definition and Scope....................................................................................................................1 1.2 Objectives....................................................................................................................................1 1.3 Significance..................................................................................................................................1 1.4 Limitations...................................................................................................................................1 CHAPTER TWO: THEORY........................................................................................................................2 2.1 Batch reactor...............................................................................................................................2 2.2 Reaction Kinetics..........................................................................................................................2 2.2.1 Rate Law...............................................................................................................................2 2.2.2 Rate Constant.......................................................................................................................2 2.3 Determination of Conversion based on Conductivity..................................................................3 2.4 Determination of the Activation Energy......................................................................................3 CHAPTER THREE: METHODOLOGY.........................................................................................................4 3.1 Apparatus and Materials Used.....................................................................................................4 3.2 Experimental procedure..............................................................................................................4 3.2.1 Part IA experiment................................................................................................................4 3.2.2 Part IB experiment................................................................................................................4 3.3 Precautions..................................................................................................................................4 CHAPTER FOUR: RESLUTS......................................................................................................................5 CHAPTER FIVE: DISCUSSION OF RESULTS.............................................................................................11 5.1 Effect of Temperature on Conversion.........................................................................................11 5.2 Effect of Temperature on Conductivity......................................................................................11 5.3 Plots of Concentration against Time..........................................................................................11 5.4 Plots of Concentration Ratio against Time.................................................................................12 5.5 Activation Energy....................................................................................................................... 12 5.6 Error analysis............................................................................................................................. 12 CHAPTER SIX: CONCLUSION.................................................................................................................13 RECOMMENDATIONS...........................................................................................................................13 REFERENCES........................................................................................................................................ 14 APPENDIX............................................................................................................................................ 15

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CHAPTER ONE: INTRODUCTION 1.1 Definition and Scope A batch reactor is a constant volume vessel in which the chemicals are placed to react. The feed is charged via two holes in the top of the tank and while the reaction occurs, nothing else can be put in or taken out from the tank until the reaction is completed. This reactor has the advantage of high conversion obtained by leaving the reactant for a long period of time. Batch reactors are used in small- scale laboratory set-ups to study the kinetics of chemical reactions. The variation of a property of the reaction mixture is observed as the reaction progresses in order to determine the order and rate constant of a chemical reaction (Fogler, 2006). The reaction chosen is the saponification of ethyl acetate by sodium hydroxide in an isothermal batch reactor. In this experiment, the change of sodium hydroxide, NaOH concentration is studied in a batch-type reactor by continuously measuring the electric conductivity of reaction solution. The conductometric technique, which depends on the conductivity measurement to determine the composition, was reported by Walker (1906). Also, the experimental activation energy is determined as well by conducting the experiment at different temperatures 30ºC and 37ºC in order to study the effect of temperature on the reaction rate constant

1.2 Objectives The objectives of the experiment include the following: 1. Determination of reaction rate' constant under isothermal conditions of 30°C and 37°C for given reactants. 2. Determination of activation energy for the reactions studied in 1 above using Arrhenius equation

1.3 Significance There are many types of batch reactors in chemical process industries with applications in various large scale operations such as water treatment, chlorinations, and in fermentation processes. Batch reactors are also used in small scale industries to produce materials such as pharmaceuticals, dyes and dye intermediates, which are widely used in daily life.

1.4 Limitations Desorbed species cannot be removed during operation and thus accumulate in the inherently closed system of the batch reactor. This can sometimes result in secondary precipitation 1

reactions, which further complicate data analysis. Also, this experiment uses conductivity data instead of titration which is inexact and error-prone, in determining the conversions.

CHAPTER TWO: THEORY 2.1 Batch reactor A batch reactor is used for small-scale operation, for testing new processes that have not been fully developed, for the manufacture of expensive products, and for processes that are difficult to convert to continuous operations. The reactor can be charged through the holes at the top (Figure 2.1). It contains an agitator arrangement which is a centrally mounted driveshaft with an overhead drive unit. Impeller blades are mounted on the shaft.

Figure 2.1.1: Batch reactor

2.2 Reaction Kinetics Basic hydrolysis of an ester (ethyl acetate) with a caustic soda, also called saponification, is a non-reversible second-order reaction (Ikhazuangbe et al., 2015). The reaction mechanism can be represented by the following reaction equation (Bursali et al., 2006): C H 3 COO C 2 H 5 +NaOH →C H 3 COONa+ C2 H 5 OH It a well known reaction in chemistry which is 2nd order reaction overall, and 1st order with respect to reactants(Mukhtar et al., 2015). This reaction is a homogeneous (liquid-liquid), non-catalytic, and the constant density system. 2.2.1 Rate Law The rate law is determined experimentally and is defined as the expression for the rate of reaction in terms of concentrations of chemical species involved in the reaction; Rate =

k [ A ] [ B] m

n

Where k is the rate constant and the exponents (m) and (n) are determined experimentally. 2.2.2 Rate Constant The rate constant, k, is the proportionality constant that relates the reaction rate to the concentration of the reacting substances, as shown in Equation 4. Batch reactors are used primarily to determine rate law parameters for homogeneous reactions. This determination is usually achieved by measuring concentration as a function of time and then using either the differential, integral method of data analysis to determine the reaction order, α , and specific reaction rate constant, k A . However, this experiment will use the graphical method of data analysis to calculate the specific rate constant k A ii

Figure 2.2.1: Plot of

(a 0−ai ) /( a0 ×a i )

against Time

2.3 Determination of Conversion based on Conductivity During the reaction, sodium hydroxide will dissociate into sodium ion and hydroxide ion while ethyl acetate will also dissociate acetate ion and ethyl ion. Acetate ions will be bound with sodium resulting in sodium acetate. This can be traced by measuring the conductivity of the solution. Thus, conversion of the reaction can be directly related to the conductivity by:

[

[

c1 =

Xa

c∞

=

Xc

]

∧ 0−∧1 (a ∞−a 0 ) ∧ −∧ + a0 0 ∞

a1 =

=

∧0 − ∧1 ∧ 0−∧∞

]

for

(2.3.1)

time

a0

= initial sodium hydroxide concentration

a1

= sodium hydroxide concentration in reactor at time t

a ∞ = sodium hydroxide concentration in reactor after ∞ (2.3.2) c

a0 − a1 a0 c1 c∞

c 0=0

Where

= sodium acetate concentration (same subscripts as above for

a)

(2.3.3) ∧0

for

c 0=0

(2.3.4)

Xa

= initial conductivity (same subscripts as above for a) =conversion of sodium hydroxide

2.4 Determination of the Activation Energy Further experiments were held at the desired reaction temperatures to determine the rate constant of the reaction at different temperatures. The temperature dependence of the reaction rate constant could be correlated by the Arrhenius equation (Ahmad et al., 2013). k

−E

= A e RT (2.4.1)

The Logarimetric expression of the Arrhenius equation can be written as lnk Where

=

ln A−

Ea RT

A = pre-exponential factor or frequency factor (2.4.2) Ea = activation energy, J/mol or cal/mol

R- gas constant = 8.314J/mol K T= absolute temperature K

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Taking two measured values of the rate (at two different temperatures) one can write: k E 1 1 − ln 2 = a k1 R T 1 T 2

(

)

(2.4.3) By plotting the graph between

1 T

from the graph will give the value of

against (- lnk ); the slope of straight-line obtained Ea RT

and A, frequency factor will be obtained from

the intercept, respectively

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CHAPTER THREE: METHODOLOGY 3.1 Apparatus and Materials Used   

Graduated Cylinder Beakers Batch reactor

  

Stirrers Stopwatch Ethyl Acetate

 

Sodium Hydroxide Distilled Water

3.2 Experimental procedure 1 L of Ethyl Acetate was prepared using the procedure below: 900ml of distilled water was added to 9.80 ml of ethyl acetate concentrate. Afterwards, the mixture was vigorously shaken to promote homogeneity. More distilled water was added to top up to 1 L mark. This resulted in 0.1m solution of Ethyl Acetate. 1L NaOH solution was prepared using the following steps: 4g of NaOH was measured and added into 960ml of distilled water. After shaking the mixture, water was added to top up to 1L mark 3.2.1 Part IA experiment 500cm3 of NaOH and Ethyl Acetate solutions were measured out in different containers. Using 30oC, the temperature controller was adjusted to the set point. Following this, the chill/ Heat bath was switched to HEAT on the console and the batch reactor was charged with 0.5 litres of sodium hydroxide solution. The reactor agitator was then switched on and adjusted to 7.0 speed. Conductivity data was collected from the console board at interval of 45 seconds until a stable/ steady condition was reacted in the reactor [usually between 30-60 min]. Afterwards the batch reactor was charged with 0.5 litres of C H 3 COO C 2 H 5 3.2.2 Part IB experiment 500cm3 of NaOH and Ethyl Acetate solutions were measured out in different containers. Using 37oC, the temperature controller was adjusted to the set point. Following this, the chill/ Heat bath was switched to HEAT on the console and the batch reactor was charged with 0.5 litres of sodium hydroxide solution. The reactor agitator was then switched on and adjusted to 7.0 speed. Conductivity data was collected from the console board at interval of 45 seconds until a stable/ steady condition was reacted in the reactor [usually between 30-60 min]. Afterwards the batch reactor was charged with 0.5 litres of C H 3 COO C 2 H 5

3.3 Precautions 1. Pouring and addition of reagents were done slowly to prevent spillage 2. Volumetric measurements of each reagent were taken at eye level to avoid error due to parallax

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CHAPTER FOUR: RESLUTS Table 4.1: Results for Equimolar Reaction of 0.1NaOH and 0.1Ethyl Acetate at 30℃ Time(seconds) Conductivit y (Ms/cm)

ai(M)

Concentratio n ratio

ci (M)

Xa

Xc

0 45 90 135 180 225 270 315 360 405 450 495 540 585 630 675 720 765 810 855 900 945 990 1035 1080 1125

0.1 0.072483 0.057718 0.047987 0.039933 0.033557 0.028523 0.023826 0.02047 0.017114 0.01443 0.012416 0.010403 0.008725 0.007383 0.00604 0.005034 0.004027 0.003356 0.002685 0.001678 0.001342 0.000671 0 0 0

0 3.796296 7.325581 10.83916 15.04202 19.8 25.05882 31.97183 38.85246 48.43137 59.30233 70.54054 86.12903 104.6154 125.4545 155.5556 188.6667 238.3333 288 362.5 586 735 1480

0 0.027517 0.042282 0.052013 0.060067 0.066443 0.071477 0.076174 0.07953 0.082886 0.08557 0.087584 0.089597 0.091275 0.092617 0.09396 0.094966 0.095973 0.096644 0.097315 0.098322 0.098658 0.099329 0.1 0.1 0.1

0 0.275168 0.422819 0.520134 0.600671 0.66443 0.714765 0.761745 0.795302 0.828859 0.855705 0.875839 0.895973 0.912752 0.926174 0.939597 0.949664 0.959732 0.966443 0.973154 0.983221 0.986577 0.993289 1 1 1

0 0.275168 0.422819 0.520134 0.600671 0.66443 0.714765 0.761745 0.795302 0.828859 0.855705 0.875839 0.895973 0.912752 0.926174 0.939597 0.949664 0.959732 0.966443 0.973154 0.983221 0.986577 0.993289 1 1 1

9.98 9.16 8.72 8.43 8.19 8 7.85 7.71 7.61 7.51 7.43 7.37 7.31 7.26 7.22 7.18 7.15 7.12 7.1 7.08 7.05 7.04 7.02 7 7 7

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Table 4.2: Results for Non-Equimolar Reaction of 0.05NaOH and 0.1Ethyl Acetate at 30℃ Time(seconds)

Conductivit y (Ms/cm)

0

10.63

45 90

Concentration ratio

ci (M)

Xa

Xc

0.05

0

0

0

9.54 8.95

0.033022 0.023832

10.28302 21.96078

0.339564 0.523364

0.339564 0.523364

135

8.64

0.019003

32.62295

0.619938

0.619938

180

8.45

0.016044

42.3301

0.679128

0.679128

225

8.31

0.013863

52.13483

0.722741

0.722741

270

8.21

0.012305

61.26582

0.753894

0.753894

315

8.11

0.010748

73.04348

0.785047

0.785047

360

8.03

0.009502

85.2459

0.809969

0.809969

405

7.97

0.008567

96.72727

0.82866

0.82866

450

7.91

0.007632

111.0204

0.847352

0.847352

495

7.86

0.006854

125.9091

0.862928

0.862928

540

7.81

0.006075

144.6154

0.878505

0.878505

585

7.77

0.005452

163.4286

0.890966

0.890966

630

7.73

0.004829

187.0968

0.903427

0.903427

675

7.7

0.004361

209.2857

0.912773

0.912773

720

7.67

0.003894

236.8

0.922118

0.922118

765

7.65

0.003583

259.1304

0.928349

0.928349

810

7.62

0.003115

301

0.937695

0.937695

855

7.6

0.002804