UNIVERSITI TEKNOLOGI MARAFAKULTI KEJURUTERAAN KIMIACHEMICAL ENGINEERING LABORATORY 3CHE (574)

NAME : NIK NUR SHAHIRA BINTI IBRAHIM (2012209148)GROUP : EH220(4A)EXPERIMENT : EXPERIMENT OF TUBULAR FLOW REACTOR BP 101DATE PERFORMED : 18 MARCH 2014SEMESTER : 4PROGRAMME / CODE : CHE 574SUBMIT TO : DR JEFRI JAAPAR

No.TitleAllocated Marks (%)Marks

1Abstract/ Summary5

2Introduction5

3Aims5

4Theory5

5Apparatus5

6Methodology/ Procedure10

7Result10

8Calculations20

9Discussion20

10Conclusion10

11Recommendations5

12Reference5

13Appendix5

TOTAL MARKS100

Remarks:Checked by:_________________Date:

Contents

Abstract3Introduction3Aims3Theory4Apparatus5Procedure5Result7Discussion8Conclusion10Recommendations11Reference11Appendix12

Abstract

This experiment was performed to carry out saponification reaction between Sodium Hydroxide, NaOH and Ethyl Acetate, Et(AC), to determine the effect of residence time on the conversion in a Tubular Flow Reactor (TFR) and to determine the reaction rate constant. A unit called SOLTEQ Plug Flow Reactor (Model:BP 101) is used in this experiment, commonly known as PFR. The two solutions Sodium Hydroxide, NaOH and Ethyl Acetate, Et(Ac) were reacted in the PFR and the product is then analyzed by the method of titration to determine how did the reaction go. Thus, the experiment was carried out and the resultsshow that as the residence time increases, the amount of conversion of Sodium Hydroxide, NaOH is almost unchanged.

Introduction

Chemical reactor is a place where chemicalreactions take place and it is one of the important part of any chemical process design. A reactors design must finely create to suit the mechanism of the process to be carried out. The reactor depends on the nature of the materials in both the feedand theproducts. In this experiment, the Plug Flow Reactor (Model: BP101) is used as ithas been properly designed for students' experiment on chemical reactions in liquid phase under isothermal and adiabatic conditions. The unit also includes a jacketed plug flow reactor; individual reactant feed tanks and pumps, temperature sensors and conductivity measuring sensor. Thisspecific unit enable students to conduct the typical saponification reaction between ethyl acetate and sodium hydroxide among the others reaction.

Aims

To carry out a saponification reaction between NaOH and Et(Ac) in a TFR. To determine the reaction rate constant. To determine the effect of residence time on the conversion in a TFR.

Theory

Tubular flow reactor consists of a cylindrical pipe and operated at steady state condition. For analytical purposes, the flow in the system is considered to be highly turbulent and may be modeled by that of a plug flow. Therefore, there is no radialvariation in concentration along the pipe. Tubular reactors are one type of flow reactors. It has continuous input and output ofmaterials. The feed enters at one end of a cylindrical tube and the product stream leaves at the other end. The long tube and the lackof provision for stirring prevent complete mixing of the fluid in the tube. Hence the properties of the flowing stream will vary from onepoint to another. In an ideal tubular flow reactor, specificassumptions are made regarding the extent of mixing:1. No mixing in the axial direction2. Complete mixing in the radial direction3. A uniform velocity profile across the radius. Rate of reaction is defined as the rate of disappearance of reactantsorthe rate of formation of products. Rate of reaction shows how fast the reactants diminish or how fast the product is formed. A reactant disappeared and a product produced when a chemical reaction occurred. For example:aA + bB cC + dD

In the chemical equation above, A and B represent reactants whileC and D represent products. A and B is being disappeared and C and D is being produced. Rate of reaction of each species corresponds respectively to their stoichiometric coefficient. The negative sign indicates reactants and the positive sign indicates products.

= = =

Rate of equation for reactant A is: = krateconstant concentrationofAspeciesconcentrationofBspeciesstoichiometriccoefficientofAstoichiometriccoefficientofB

While conversion shows how many moles of products are formed for every mole of A has consumed. Residence time is a characteristic of the mixing that occurs in the chemical reactor. There is no axial mixing in a plug flow reactor, PFR and this omission can be seen in the residence time. The continuous stirred tank reactor CSTR is thoroughly mixed and its residence time is hugely different as compared to the residence time of PFR.

Apparatus

Plug Flow Reactor Model Bp101 Burette Measuring cylinder Beakers pH indicator Conical flask 0.1M Sodium Hydroxide, NaOH 0.1M Ethyl Acetate, Et(Ac) 0.1M Hydrochloric Acid, HCl De-ionized water

Procedure

General Start-up Procedures1. All the valves are ensured closed except V4, V8 and V17.2. The following solutions are prepared: 20 liter of NaOH (0.1M) 20 liter of Et(Ac) (0.1M)1 liter of HCL (0.25M) for quenching3. Feed tank B1 was filled with NaOH while feed tank B2 was filled with the Et(Ac).4. The water jacket B4 was filled with water and pre-heater B5 was filled with clean water.5. The power for the control panel was turned on.6. Valves V2, V4, V6, V8,V9 and V11 were opened.7. Both pumps P1 and P2 were switched on. P1 and P2 were adjusted to obtain flow rate approximately 300mL/min at both flow meters Fl-01 and Fl-02. Both flow rates were made sure to be equal.8. Both solutions then were allowed to flow through the reactor R1 and overflow into waste tank B3.9. Valves V13 and V18 was opened. Pump P3 then was switched on in order to circulate the water through pre-heater B5. The stirrer motor M1 was switched on and set up to speed about200 rpm to ensure homogeneous water jacket temperature.Experiment Procedures1. The general starts up procedures were performed.2. Valves V9 and V11 wereopened.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 ofabout 300 ml/min at flow metersFI-01 and FI-02. Both flow rates were ensured same. The flow rates were recorded.5. The inlet (QI-01) and outlet (QI-02) were started to monitor the conductivity values until they do not change over time. This is to ensure that thereactor has reached steady state.6. Both inlet and outlet steady state conductivity values were recorded. The concentration ofNaOH exiting the reactor and extent of conversion from the calibration curve.7. Optional: Sampling was opened from valve V15 and 50ml of sample was collected. A backtitration procedure was carried out manually to determine the concentration of NaOH in the reactor and extent of conversion.8. The experiment was repeated from step 4 to7 for different residence timesby reducing the feed flow ratesof NaOH and Et(Ac)to about 250,200,150,100 and 50 ml/min. Both flow rates were made sure to be equal.Titration Procedures1. The burette was filled up with 0.1 M NaOH solution.2. 10 mL of 0.25 M HCl was poured in a flask.3. 50 mL samples that were collected from theexperiment at every controlled flow rate(300,250, 200, 150, 100 and 50 mL/min) were added intothe 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.

Result

ConversionSolution MixturesConcentration of NaOH (M)Conductivity (mS/cm)

0.1M NaOH0.1M Na(Ac)Water

0%100mL-100mL0.050010.7

25%75mL25mL100mL0.03759.7

50%50mL50mL100mL0.02507.5

75%25mL75mL100mL0.01255.6

100%-100mL100mL0.00004.0

Table 1: Preparation of Calibration Curve

Reactor volume: 4LConcentration of NaOH in feed tank: 0.1MConcentration of Et(Ac) in feed tank: 0.1MNoFlow rate of NaOH (mL/min)Flow rate of Et(Ac) (mL/min)Total flow rate of solutions, (mL/min)Residence time, (min)Outlet conductivity (mS/cm)Volume of NaOHConversion, X (%)Reaction Rate Constant (L/mol.min)Rate of Reaction (mol/L.min)

Q1Q2

13003006006.6711.17.30.350.61.543.76

22502505008.0012.07.00.250.41.273.12

320020040010.0011.56.80.150.21.012.50

415015030013.3310.96.20.150.20.761.88

510010020020.0010.25.40.250.40.511.25

6505010040.008.64.80.250.40.256.15

Table 2: Experiment 3

Calculation

Residence timeFor flow rates of 300 ml/min,

Total flow rate, = Flow rate of NaOH + Flow rate of Et(Ac) = 300 mL/min NaOH + 300 mL/min Et(Ac) = 600 mL/min = 0.6 L/min.Hence, Residence time, = 4L/0.6L/min = 6.67 min

ConversionFor flow rates of 300mL/min:Moles of reacted NaOH,

= 0.1 M 0.0003L = 0.00003 moleMoles of unreacted HCl, Moles of unreacted HCl = Moles of reacted NaOHVolume of unreacted HCl, = 0.00003 / 0.25 = 0.00012LVolume of HCl reacted, = 0.01 0.00012 = 0.00988LMoles of reacted HCl, = Concentration HCl = 0.25 0.00988= 0.00247 moleMoles of unreacted NaOH, = = 0.00247 moleConcentration of unreacted NaOH

= 0.0494/0.1 = 0.494 = 0.506Conversion for flow rate 300mL/min0.506 100% = 50.6%

Reaction rate constant, k For flow of 300mL/min

Rate of reaction, = k (For flow rates of 300 mL/min = 1.54 ( = 3.76 mol.L/min

Discussion

Plug Flow Reactor (PFR) is a reactor thatcomprises of a cylindrical pipe and isperformed at steady state in which the feed enters at one end of a cylindrical tube and the product stream leaves at the otherend. The properties of the flowing stream will vary from one point to another point. The fluid is thin and unmixed layer. In this experiment, the solutions used NaOH and Et(Ac) reacts together in the reactor to complete saponification reaction. The main objective of thisparticular experiment is to study the effect of residence time on the performance of this reactor.Residence times are manipulated variable in the experiment. Residence times were manipulated by the means of changing the flow rates of the feed solutions. The total flow rates and outlet conductivity value are tabulated in Table 2. A series ofcalculations were made and the values of residence times, conversion of the reactions, reaction rate constants and rate of reactions were determined and tabulated in Table 2 and a graph is plotted to study the conversion against time residence. Conversion is a property that shows how much ofthe reaction has taken place. Hence, by comparing this property with the residence timeparameter, one can analyse the effects of increasing residence time to the reaction itself. It shows that the conversion of the reaction remains fairly constant with the increasing residence time. Therefore, residence time is not a factor of reaction conversion. This is because PFR lacks a good mixing process. Since the PFR is designed not to stir the solution vigorously to maximise mixing process, the conversion of the reaction by using PFR is fairly low. The experiment also aims to evaluate the reaction rate constants and rate ofreaction values ofthe reaction..

Conclusion

The experiment was conducted to carry out a saponification process between Sodium Hydroxide, NaOH and Ethyl Acetate, Et(Ac). By using a Plug Flow Reactor, PFR, these two substances were flowed into the reactor, mixed and react for acertain period of time to completing the saponification process. The experiment also performs to determine the reaction rate of this particularreaction. Thirdly, this experiment conducted to study the relationship between the residence time and the conversion of the reactants. This relationship was successfully studied.Recommendations

There are several recommendations during conduct this experiment: Wear protective clothing, shoes, helmet and goggles throughout the laboratory session to prevent injured. It is better to time the sample well so that time-wasting in taking samples can be reduced or, if possible, avoided. All valves should be properly placed before the experiment started. Flow rates should be constantly monitored so that it remains constant throughout the reaction, as needed. Titration should be immediately stopped when the indicator turned pink. Pumps should never be run dry.

Reference

1. Fogler, H.S (2006). Elements of Chemical Reaction Engineering (3rd Edition). PrenticeHall.2. Levenspiel, O. (1999). Chemical Reaction Engineering (3rd Edition). John Wiley.3. Laboratory Manual Tubular Flow Reactor.

Appendix