UNIVERSITI TEKNOLOGI MARA

FAKULTI KEJURUTERAAN KIMIA

CHEMICAL ENGINEERING LABORATORY III(CHE574)

No.TitleAllocated Marks (%)Marks

1Abstract/Summary5

2Introduction5

3Aims5

4Theory5

5Apparatus5

6Methodology/Procedure10

7Results10

8Calculations10

9Discussion 20

10Conclusion10

11Recommendations5

12Reference / Appendix10

TOTAL MARKS100

Remarks:

Checked by :

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Date :

TABLE OF CONTENTS

1.0 Abstract2

2.0 Introduction3

3.0 Objectives4

4.0 Theory4

5.0 Materials and Apparatus7

6.0 Procedures

6.1 General Start-up Procedure 6.2 Experimental Procedure

6.3 Back Titration Procedure

6.3 General Shut-down Procedure

8

8

9

9

7.0 Results

7.1 Data 7.2 Graph

10

11

8.0 Calculations

12

9.0 Discussions18

10.0 Conclusion20

11.0 Recommendations20

12.0 References21

13.0 Appendices

22

1.0 ABSTRACT

EFFECT OF RESIDENCE TIME ON THE REACTION

This experiment is carried out based on a few objectives. A saponification reaction between sodium hydroxide, NaOH and Ethyl acetate, Et (Ac) by using SOLTEQ Plug Flow Reactor (Model: BP 101) is conducted to determine the effect of residence time on the conversion and to evaluate the reaction rate constant. Two solutions, Sodium Hydroxide, NaOH and Ethyl Acetate, Et(Ac) were reacted in Plug Flow Reactor and then the product was analysed by the method of titration, which is some common laboratory apparatus are used. Titration process is conducted to determine how well did the reaction go. The result shows that the conversion of Sodium Hydroxide, NaOH is slightly changed as residence time increase from 6.667 min until 13.333 min. As it at 20.000 min, the conversion increases from 91.4% to 95.0%. Therefore, one can be postulate that the reason for this phenomenon is that the Plug Flow Reactor have a good mixing process. This experiment also aims to evaluate the rate of reaction and reaction rate constant, hence both these properties have been determined in the calculation section.

2.0 INTRODUCTION

2.1Basic Purpose of Reactors

Reactors are designed due to some purposes, which are for Mixing of substrates by contacting with catalyst, mass and heat transfer, control and containment or protection from/of environment (Heinzle, 2009).

2.2Quantitative Description of Ideal Reactors

There are various criteria in selecting the optimal reactor. The reactors are already installed and process conditions have to be adjusted to fit into the available equipment in fermentation plants and typical fine chemical. However, mainly feeding strategies can be optimized as far as the reactor is concerned (Heinzle, 2009).

In addition, according E. Heinzle, continuous processes are installed for a production of large-scale. Reactor choice is important in order to build a new plant or in certain cases for replacing an existing one. It is useful to study ideal reactors first to improve more understanding. The reactors including the batch reactor (BR), the plug flow reactor (PFR) and the continuous stirred tank reactor (CSTR).

2.3Steady-State Plug Flow Reactor (PFR)

In this experiment, the Plug Flow Reactor (Model: BP 101) is used as it has been properly designed especially for students in conducting an experiment on chemical reaction in liquid phase under isothermal and adiabatic condition. By using this unit, students are capable to conduct the typical saponification reaction between Sodium Hydroxide, NaOH and Ethyl Acetate, Et(Ac) among the others reaction.

The material balance for a component A in a steady-state (dCi/dt=0) plug flow reactor element of volume dV as shown in Figure 1.0 is

Equation 1.0

Figure 1.0: Plug Flow Reactor

3.0 OBJECTIVES

This experiment is conducted to carry out a saponification reaction between sodium hydroxide, NaOH and Ethyl acetate, Et (Ac) by using SOLTEQ Plug Flow Reactor (Model: BP 101) to determine the reaction rate constant. In addition, it is also to determine the effect of residence time on the conversion.

To conducting this experiment, residence times have to be manipulated throughout the experiment and the effects of each one is studied. Residence time is varied by the means of changing the flow rates of the feed solutions. It can be seen that residence time is a function of total flow rates of the feed.

Hence, several residence times can be obtained and the effect of each one is studied by varying the flow rate of the feed solutions.

4.0 THEORY

4.1Rate of reaction and Rate law

The rate of reaction can be defined as the change in the concentration of any one of reactants or product per unit time. Normally, a reactant will diminish while a product will produce when a chemical reaction is occurring.

The rate of reaction changes as the reaction under progress. Initially, the rate of reaction is relatively large. However, the rate of reaction decreases to zero as the time flows. At this point, the reaction is complete (Blauch, 2014).

Guldberg and Waage derived an equilibrium constant by defining equilibrium as the condition when the rates of the forward and reserve reactions are equal. Consider constitutes a chemical reaction as (Christian, 2004):

aA + bB cD + dD

Equation 2.0

From equation above, A and B represent as the reactants, where is being dimished. While C and D represent as the products which are being produced. Rate of reaction of each species corresponds respectively to their stoichiometric coefficient as below:

Equation 3.0

The negative sign indicates the reactants. The products are always positives sign. While a, b, c, and d is the number of moles for each species A, B, C, and D. Usually, equation for rA is defined as:

Equation 4.0

Where,

k: rate constant

CA: concentration of A species

CB: concentration of B species

: stoichiometric coefficient of A

: stoichiometric coefficient of B

The relationship between the concentration of reactant and the rate of reaction is expressed by a rate law. The differential rate law describes how the rate of reaction varies with the concentrations of various species, usually reactants, in the system (Blauch, 2014).

A rate law is a mathematical equation which describes the progress of the reaction that must be determined experimentally. There are two types of a rate law for chemical kinetics, which are differential rate law and the integrated rate law (Blauch, 2014).

Table 1.0 below shows the example of a species in the chemical reaction with the corresponded reaction order, differential rate law and integrated rate law.

Table 1.0: Reaction order with differential and integrated rate law

Reaction OrderDifferential Rate LawIntegrated Rate Law

Zero

First

Second

4.2Conversion

Taking species A as the basis, the reaction expression can be divided through the stoichiometric coefficient of species, hence the reaction expression can arranged as follows:

Equation 5.0Conversion is an improved way of quantifying exactly how far has the reaction moved, or how many moles of products are formed for every mole of A has consumed. Conversion XA is the number of moles of A that have reacted per mole of A to the system as below:

Equation 6.0

4.3Plug Flow Reactors

Reaction rate constant,

Equation 7.0

Where,

Vo: Total inlet flow rateVT: Reactor VolumeCAo: Inlet NaOH concentrationX: Conversion

4.4Residence Time Distribution Function

Plot a graph of conversion versus residence time. The reactors residence time is defined as the reactor volume divided by the total feed flow rates.

Residence time,

Equation 8.0

5.0 MATERIALS/APPARATUS

The unit used for this experiment in SOLTEQ Plug Flow Reactor (Model: BP 101). It is used as it has been properly designed for students experiment on chemical reactions in liquid phase under isothermal and adiabatic conditions.

The chemicals used are 0.1M Sodium Hydroxide, NaOH, 0.1M Ethyl Acetate, Et (Ac), 0.1M Hydrochloric Acid, HCl, and deionized water. Apart from that, there were also some laboratory apparatus involved such as burette, conical flask, measuring cylinder, pH indicator, and beakers.

The unit of jacketed plug reactor is also included, which is the individual reactant feed tanks and pumps, temperature sensors and conductivity measuring sensor. Figure 2.0 shows the unit SOLTEQ Plug Flow Reactor (Model: BP 101).

Figure 2.0: SOLTEQ Plug Flow Reactor (Model: BP 101)

6.0 PROCEDURES

6.1General start-up procedure

1. All valves are ensured that initially closed except valves V4, V8 and V17.

2. The solutions are prepared for each experiment:

Table 2.0: Tanks B1 and B2

TankExperiments 1&2Experiment 3&4

B1Deionized water0.1M NaOH solution

B20.05M NaCl solution0.1M Et(Ac) solution

The water deionized is connected to the laboratory water supply.

3. The power for control panel is turned on.

4. The water jacket B4 and pre heater B5 are filled with clean water. Valves V13 and V18 are opened. Pump P3 is switched on to circulate the water through pre heater B5.

5. The stirrer motor M1 is switched on and the speed is set up to about 200rpm.

6. Valves V2, V4 and V10 are opened. Pump P1 is switched on. P1 is adjusted to flow rate of 150 ml/min at flow meter FI-01. Valves V10 is closed and pump P1 is switched off.

7. Valves V6, V8 and V12 are opened. Pump P2 is switched on. P2 is adjusted to flow rate of 150 ml/min at flow meter FI-02. Valve V12 is closed and pump P2 is switched off.

8. The unit is now ready for the experiment.

6.2Experimental procedure

1. The general start-up procedure was performed.

2. Valves V9 and V11 were opened.

3. Both the NaOH and Et(Ac) solutions were allowed to enter the plug reactor R1 and empty into the waste tank B3.

4. P1 and P2 were adjusted to give a constant flow rate of about 300 ml/min at flow meters F1-01 and F1-02. Both flow rates were make sure to be the same. The flow rates were recorded.

5. The inlet (QI-01) and outlet (QI-02) conductivity values were start monitored until they do not change over time. This is to ensure that the reactor has reached steady state.

6. Both inlet and outlet steady state conductivity values were recorded. The concentration of NaOH exiting the reactor and extent of conversion from the calibration curve were determined.

7. Optional: Sampling valve V15 was opened and 50 ml sample was collected. Titration procedure was carried out to manually determine the concentration NaOH in the reactor and extent of conversion.

8. Steps 4 to 7 were repeated for different residence times by reducing the feed flow rates of NaOH and Et(Ac) to about 250, 200, 150, 100, and 50 ml/min. Both flow rates were make sure to be the same.

6.3Back Titration Procedure

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

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

3. 50mL samples that were collected from the experiment at every controlled flow rate (300, 250, 200, 150, 100 and 50 ml/min) were added into the 10ml HCl to quench the saponification reaction.

4. 3 drops of phenolphthalein were dropped into the mixture of sample and HCl.

5. The mixture then was titrated with NaOH until it turns light pink.

6. The amount of NaOH titrated was recorded.

6.4General shut-down procedure

1. Pumps P1, P2 and P3 are switched off. Valves V2 and V5 are closed.

2. The heaters are switched off.

3. The cooling water is kept circulated through the reactor while the stirrer motor is running to allow the water jacket to cool down to room temperature.

4. If the equipment is not going to be used for long period of time, all the liquid is drained from the unit by opening valves V1 to V19. The feed tanks are rinse with clean water.

5. The power is turned off for the control panel.

7.0RESULTS

Table 7.1: Table for preparation of calibration curve.Conversion (%)Solution mixtures (mL)Concentration of NaOH (M)Conductivity (mS/cm)

0.1 M NaOH0.1 M Na(Ac)

0100-1000.050017.05

2575251000.037514.55

5050501000.025011.45

7525751000.01259.82

100-1001000.00007.96

Graph 7.1: Graph of conductivity versus conversion.Table 7.2: Effect of residence time on the reaction.

Reactor volume

= 4 L

Concentration of NaOH in feed tank= 0.1 M

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

No.Flow rate of NaOH (mL/min)Flow rate of Et(Ac) (mL/min)Total flow rate of solution, (mL/min)Residence time, (min)Outlet conductivity (mS/cm)Conversion X (%)Reaction rate constant (L /mol.min)Rate of reaction (mol/L.min)

13003006006.666711.09.750.61.53640.003749

22502505008.00009.58.450.41.27020.003125

320020040010.00008.47.450.21.00800.002499

415015030013.33337.56.450.20.75600.001875

510010020020.00006.75.550.40.50810.001250

6505010040.00005.74.750.40.25400.000625

Table 7.3Flow rate of NaOH (mL/min)Flow rate of Et(Ac) (mL/min)Residence timeVolume of NaOH, (mL)

30030050.3

25025050.2

20020050.1

15015050.1

10010050.2

505050.2

Graph 7.2: Graph of conversion versus residence time.

8.0CALCULATIONS

Back titration for manual conversion determination:

Unknown quantity:Concentration of NaOH in the reactor= mol/L= 0.1 mol/L

Known quantities:

Volume of sample

=

mL= 50 mL

Concentration of NaOH in the feed vessel= mol/L= 0.1 mol/L

Volume of HCl for quenching

= mL= 10 mL

Concentration of HCl in standard solution= mol/L= 0.25 mol/L

Volume of titrated NaOH

=

mL

Concentration of NaOH used for titration= mol/L= 0.1 M

Sample calculations:

For flow rate = 300 mL/min

Concentration of NaOH entering the reactor,

Volume of unreacted quenching HCl,

Volume of HCl reacted with NaOH in sample,

Moles of HCl reacted with NaOH in sample,

Moles of unreacted NaOH in sample,

Concentration of unreacted NaOH in the reactor,

Conversion of NaOH in the reactor, X

For flow rate = 250 mL/min

Concentration of NaOH entering the reactor,

Volume of unreacted quenching HCl,

Volume of HCl reacted with NaOH in sample,

Moles of HCl reacted with NaOH in sample,

Moles of unreacted NaOH in sample,

Concentration of unreacted NaOH in the reactor,

Conversion of NaOH in the reactor, X

For flow rate = 200 mL/min

Concentration of NaOH entering the reactor,

Volume of unreacted quenching HCl,

Volume of HCl reacted with NaOH in sample,

Moles of HCl reacted with NaOH in sample,

Moles of unreacted NaOH in sample,

Concentration of unreacted NaOH in the reactor,

Conversion of NaOH in the reactor, X

Sample calculations of Residence Time, (min)

where For flow rate = 300 ml/min

=

= = 0.6 L/min

6.6667 minFor flow rate = 250 ml/min

= = 0.5 L/min

8.0000 minOther residence time were calculated by the same way, and varying the flow rates

Sample calculations of Reaction Rate Constant and Rate of Reaction

Flow rate = 300 mL/min

Flow rate = 250 mL/min

9.0DISCUSSION

The experiment was conducted using plug flow reactor by SOLTEQ (model BP 101). Plug flow reactor (PFR) is a type of reactor that consists of a cylindrical pipe and usually operated at steady state. The feed enters at one end of a cylindrical tube and the product leaves at the other end. The reactor has long tube and lack of provision for stirring, thus preventing the fluid from mixing completely. So, the properties of the fluid will vary from one and another. The solution in the tube is treated as a series of layers of volume segments that are unmixed with the segment before and after it like a series of plugs that is stacked together in a pipe. The plug flow reactor experiment was carried out to achieve several objectives that is to carry out a saponification reaction between NaOH and Et(Ac), determine the reaction rate constant and determine the effect of residence time on the conversion.

All the data needed were tabulated as seen in Table 7.1, 7.2 and 7.3. The first table which is the preparation of calibration curve shows the conductivity of solution mixtures for each percent conversion and varies concentration of NaOH. The conductivity values were taken by using conductivity meters device. A graph of conductivity versus conversion is plotted based on the results. From the graph, we can clearly see that as the percent conversion increase from 0% to 100%, the conductivity kept on decreased. At 0% conversion with 0.0500 M of NaOH concentration, the conductivity reading shows value of 17.05 mS/cm. At 25% (0.0375 M NaOH), 50% (0.0250 M NaOH), 75% (0.0125 M NaOH) and 100% (0.0000 M NaOH) conversions, the conductivity values read as 14.55, 11.45, 9.82 and 7.96 mS/cm respectively.

Next, we will discuss on the effect of residence time on the reaction and the results are shown as seen in table 7.2 and 7.3. The volume of reactor used in this experiment is 4 L with the concentration of 0.1 M for both NaOH and Et(Ac) in feed tank. The table 7.2 consist of flow rate for both NaOH and Et(Ac), total flow rate of solutions,, residence time,,outlet conductivity, conversion, X, reaction rate constant,k and rate of reaction,. For table 7.3, it consists of residence time and the volume of NaOH titrated. These tables necessary to fill in the results after the calculations were done.

The residence time was calculated by using the formula where . Total flow rate of solutions, differ for each flow rates starting from 300 mL/min to 50 mL/min. From the calculations, the residence times in minutes calculated to be 6.6667, 8.0000, 10.0000, 13.3333, 20.0000 and 40.0000 for flow rates 300, 250, 200, 150, 100 and 50 mL/min respectively. For the calculation of the conversion,X in percent, there are many steps to be done first before we get to conversion,X and it is all can be seen in calculations sections. The formula to calculate the conversion is . At 300 mL/min flow rate, the conversion is 50.6%, at 250, 100 and 50 mL/min flow rate, the conversion is 50.4%. At flow rates of 200 and 150 mL/min shows the least percent conversion of X with only 50.2%. So, with all these, we were able to plot a graph of conversion versus residence time. Our objective which is to determine the effect of residence time on the conversion is achieved.

Next, we proceed to determine the reaction rate constant as it is one of our main objectives. The reaction rate constant can be determined by the formula;

As soon as we get the reaction rate constant,k ,we were able to calculate the rate of reaction. The formula for rate of reaction is;

From the results, the reaction rate constant,k is the highest at 300 mL/min with 1.5364 and the trend decreases for each flow rates recorded. Flow rate of 50 mL/min has the least value of reaction rate constant with 0.2540 . The same scenario can be seen for rate of reaction where at 300 mL/min, the value recorded is 0.003749 and the lowest is 0.000625 for flow rate 50 mL/min.

In running the experiment, there may be errors occurred. We cannot afford to avoid mistakes but analysis of errors for further improvement prior to the experiment can be done. During taking the conductivity values, make sure the conductivity meter were rinsed with distilled water every time we take the reading for every flow rates. If we do not do these, it may affect the reading of the conductivity hence the overall success of the experiment. 10.0CONCLUSION

This experiment is conducted to with several objectives. The first one is to carry out a saponification process between Sodium Hydroxide, NaOH and Ethyl Acetate, Et(Ac) by using SOLTEQ Plug Flow Reactor (Model: BP 101). These two substances were let to flow into the reactor from feed tank 1 and feed tank 2. Then, it is mixed and let to react for certain period of time. Saponification process then was completed after it had done.

Furthermore, next objective is to study the residence of time with the conversion of the reaction. The relationship was successfully studied and graphed in Figure 3.0. The conversion of the reaction remains fairly constant and the changes are too small at the residence time of 6.667 min until 13.333 min. As it at 20.000 min, the conversion increases from 91.4% to 95.0%. it can be concluded that the Plug Flow Reactor has good mixing process.

Lastly, this experiment is conducted to determine the reaction rate constant and rate of reaction. This has been done by calculating the reaction rate as in calculation section. It shows that those values decreasing as the residence time increasing.11.0RECOMMENDATIONS

There are some recommendations should be considered while conducting the SOLTEQ Plug Flow Reactor (Model: BP 101). Pumps should never be run in dry and titration should be immediately stopped when the indicator turned pink.

In addition, Flow rates should be constantly monitored so that it remains constant throughout the reaction as needed. Next, all valves should be properly placed before the experiment started and it is better to time the sample so well so that the time wasting in taking samples can be reduced or, if possible, avoided.

12.0REFERENCES

Ashe, R. From Batch to Continuous Processing. Chemical Engineering. October 2012, pp. 34-40. Print.

Blauch, D.N., (2014). Chemical Kinetics. Retrieved April 28, 2015 from http://www.chm.david Son.edu/vce/kinetics/differentialratelaws.html

Catalano, S., Wozniak, A., Kaplan, K., Plegue, T. Plug Flow Reactor. Encyclopedia of Chemical Engineering Equipment. Retrieved April 3, 2015 from mich.edu/Pages/Reactors/PFR/PFR.html.

Christian, G.D., (2004). Rate Law. Analytical Chemistry, 6th ed., John wiley & Sons, Inc., 111 River Street, Hoboken, pp.499-505.

Fogler, H.S. Elements of Chemical Reaction Engineering, 4th ed. Levenspeil. Prentice-Hall, 2014. Print.

Heinzle, E., (2009). Introduction to Ideal Reactors. Technische chemie I, WS2009, Chemical Reactors, pp. 1-18.

Siti Wahidah, (n.d.). Design of Ideal Reactor for Single Reaction. Chemical Reaction Engineering, UiTM Shah Alam.

13.0APPENDICES

Figure 6.0: Feed Tank, B1Figure 7.0: Feed Tank, B2

Figure 8.0: Pre-heater, B5Figure 9.0: Plug Reactor, R1

Figure 10.0: Control PanelFigure 11.0: Pumps P1 and P2

Name : Edzharfariz bin tamin 2013594311

: Shahrizat bin smail kassim 2013197421

: Khatijah Binti mokhtar 2013934197

: Nuramanina bt mohd sohadi 2013520381

Group : eh2204

Experiment: 2. plug flow reactor

date performed: 30th october 2015

SEMESTER: 4

programme / code : eh220

submitTED to: madam fazliani binti shoparwe