TABLE OF CONTENT No 1 2 3 4 5 6 7 8 9 10 11 12 13
Title Abstract………………………………. Introduction………………………….. Objectives…………………………….. Theory………………………………... Material And Apparatus……………… Methodology…………………………. Data and Results……………………… Calculations…………………………... Discussion……………………………. Conclusion……………………………. Recommendations……………………. Reference……………………………... Appendix……………………………...
EFFECT OF RESIDENCE TIME ON THE REACTION IN TFR
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1.0 ABSTRACT The experiment is carry out with the reaction of Sodium Hydroxide NaOH and Ethyl Acetate, Et(Ac) to determine the effect of residence time to the conversion of the solution. This experiment is conducted to determine the rate law using tubular flow reactor data and to demonstrate the temperature dependence of the reaction and the rate constant. This experiment are conducted in the SOLTEQ® Tubular Flow Reactor (Model: BP 101). The solution were reacted in a PFR and the data was tabulated. The graph of the conversion against residence time were also constructed. The result for this experiment is shown that the residence time are linearly proportional to the conversion. The objective for this experiment was achieved.
EFFECT OF RESIDENCE TIME ON THE REACTION IN TFR
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2.0 INTRODUCTION The chemical reactors are something that is crucial and important in a chemical industries. It is the most important things as it is the place for the reaction to happen. The type of reactor must be suited with the reaction that we seek for. One of the example of the reactors is Plug Flow Reactor (PFR) The Plug Flow Reactor (PFR) can also be named as Turbulent Flow Reactor (TBR) or Piston Flow Reactor. It used for reaction in continuous, flowing systems in a shape of cylinder. The solution that flow in the reactor are describe as Plugs. An ideal plug flow reactor has a fixed residence time: Any fluid (plug) that enters the reactor at time , where
will exit the reactor at time,
is the residence time of the reactor.
Plug Flow Reactor are usually used for a large scale production, slow reactions, and continuous reaction. Besides that, high temperature reaction usually done in the PFR. This is because the PFR can withstand the high temperature of a reaction. PFR have a high volumetric unit conversion and can run for a long periods of time without maintenance. That is why it is widely used in the manufacturing of chemicals.
EFFECT OF RESIDENCE TIME ON THE REACTION IN TFR
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3.0
OBJECTIVE
1) To determine the rate law using tubular flow reactor data. 2) To demonstrate the temperature dependence of the reaction and the rate constant. 3) To understand tubular flow reactor performance and application. 4) To construct the graph of Conversion against Residence Time. 5) To calculate the residence by using the formula.
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4.0 THEORY The chemical reaction is consider as aA + bBcC + dD Residence time, is the average amount of time that a particle spends in a particular system. The residence time, is a representation of how long it takes for the concentration to significantly change in the sediment.
Where VTFR is the reactor volume and v0 is the total feed flow rate. In this experiment, we adjust the pump until the flow rate become constant. The flow rate for each experiment is variable but the reactor volume remain constant for every experiment. Conversion 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 fed to the system. XA
moles of A reacted moles of A fed
A reaction rate constant, k quantifies the rate of a chemical reaction. The reaction rate is often found to have the form rA kC A C B
Where C A and C B are the concentration of the species A and B respectively, each raised to the powers and , while k is the reaction rate constant. The exponents and are the partial reaction orders. In this experiment, we can calculate the reaction rate constant, k by the following formula. (
)
Where, k is the reaction rate constant, the total inlet flow rate of solutions, reactor volume, is the inlet concentration of reactant NaOH in the reactor, and percentage of conversion.
EFFECT OF RESIDENCE TIME ON THE REACTION IN TFR
is the is the
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Rate of reaction is defined as the rate of disappearance of reactants or the rate of formation of products. Rate of reaction can describe about how fast a number of moles of one chemical species reaction to form another species. Rate of reaction of each species corresponds respectively to their stoichiometric coefficient. As such rA rB rC rD a b c d
The negative sign indicates reactants while the positive sign indicates products. A usual equation for rate of reaction is rA k AC ACB
Where C A and C B are the concentration of the species A and B respectively, each raised to the powers and , while kA is the reaction rate constant. The exponents and are the partial reaction orders. The overall order of reaction is given by the following: n
In the experiment that we had done, the and is 1 each. The overall order is 2 and the experiment is second order. So, we had use the following formula to find the rate of reaction. Since CA0 = CB0 , (
( (
)) )
Tubular reactors are one type of flow reactors. It has continuous inflow and outflow of materials. In the tubular reactor, the feed enters at one end of a cylindrical tube and the product stream leaves at the other end. The long tube and the lack stirring prevent complete mixing of the fluid in the tube. In an ideal tubular flow reactor, which is called plug flow reactor, specific assumptions are made regarding the extent of mixing: 1. No mixing in the axial direction. 2. Complete mixing in the radial direction. 3. A uniform velocity profile across the radius.
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5.0 MATERIAL AND APPARATUS 5.1
MATERIAL 1) Ethyl Acetate 2) Sodium Hydroxide 3) Water
5.2
APPARATUS 1) Tubular reactor (R1) i. Stainless steel coil ii. Volume: approx. 0.4-L 2) Water jacket (B4) i. Cylindrical vessel made of borosilicate glass ii. Capacity: approx. 10-L iii. 2x1.0 kW cartridge heater iv. Cooling tubes v. Stirrer:50 – 2000 rpm with LCD display a. max. torque 30 Ncm b. 230VAC / 50-60 Hz / 75 W c. Circulation pump (P3) 3) Feed tanks (B1, B2) i. 20-L cylindrical vessels made of stainless steel ii. Water de-ionizer fitted to tank B1 4) Waste tank (B3) i. 60-L rectangular tank made of stainless steel 5) Pre-heater (B5) i. 3-L cylindrical vessel made of stainless steel ii. Internal coils for each reactants 6) Feed pumps (P1, P2) i. Centrifugal pumps ii. Max delivery rate: 1 usgpm (3.78 LPM) iii. Max delivery height: 25 psi iv. Power: 12V
EFFECT OF RESIDENCE TIME ON THE REACTION IN TFR
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7) Instrumentations Flow measurements (FI-01, FI-02) Temperature measurements (TIC-01, TI-02) Conductivity measurements (QI-01, QI-02) Valves and Instruments List Valves list: Tag V1 V2 V3 V4 V5 V6 V7 V8 V9 V10 V11 V12 V13 V14 V15 V16
Location Drain valve for feed tank B1 Inlet valve for pump P1 De-ionized water supply to feed tank B1 Drain valve for feed tank B2 Inlet valve for pump P2 Valve for feed inlet to reactor from FI 01 Drain valve for FI 01 Valve for feed inlet to reactor from FI 02 Drain valve for FI 02 Drain valve for water jacket B4 Drain valve By-pass valve for pump P3 Inlet flow for pre-heater B5 Sampling valve Sampling valve Drain valve
V17
Cooling water outlet
Initial position Close Close Close Close Close Close Close Close Close Close Close Close Close Open Close Close Close
Instruments list: Tag FI 01 FI 02 QI 01 QI 02 TIC 01 TI 02
Description Liquid flow meter Liquid flow meter Conductivity Conductivity
Units L/min L/min mS/cm mS/cm
Range 0.0 – 3 0.0 – 3 0.0 – 200.0 0.0 – 200.0
Accuracy ± 2% ± 2% ± 1% FS ± 1% FS
Temperature controller
°C
0.0 – 100.0
± 0.5°C
Pre-heater temperature
°C
0.0 – 100.0
± 0.5°C
EFFECT OF RESIDENCE TIME ON THE REACTION IN TFR
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FI 02
FI 01 V8
V3
V9
Sampling
V15
Feed Tank B1
V6
QI 02
V7
QI 01
Vent
LS1
M1
Pre-heater B5 (3-L) Waste Tank B3 (60-L)
V2 TI 02
Tubular Reactor R1 (0.4-L)
Drain V16
V1
Drain
Pump P1
Water Jacket B4 (10-L)
Feed Tank B2
In V17
LS2 Out
V14 Electrical Cart. Heater
W1, W2
(2x1.0 kW)
TIC 01
V10
Drain V11
EFFECT OF RESIDENCE TIME ON THE REACTION IN TFR
V5
V4
Drain
Pump P2
V13 V12 Sampling
Pump P3
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c.w. Water De-ionizer
6.0 METHODOLOGY 6.1
General Start-Up Procedures 1) All valves were initially closed except valves V16. 2) The following solution were prepared:: i) 20 liter of sodium hydroxide, NaOH (0.1 M) ii) 20 liter of ethyl acetate, Et(Ac) (0.1 M) 3) The feed tank B1 was filled with the NaOH solution and feed tank B2 with the Et(Ac) solution. 4) Valve, V17 was opened. V10 and V11 were opened until water jacket, B4 is fill on with 4 L of water. V11 was closed and valve V10, V12 and V13 were opened. 5) Pump, P3 was opened and was allowed clean water to flow through Pre-heater B5 with clean water by opening valve V10, V11, V12 and V13. The vent valve must be open. 6) The power for the control panel was turned on. Valves V2, V5, V6 and V8 were opened. 7) Both pumps P1 and P2 were switched on. P1 and P2 were adjusted to obtain flow of approximately 0.30 L/min at both flow meters FI 01 and FI 02. Both flow rates must be the same. 8) Both solutions were allowed to flow through the reactor R1 and overflow into the waste tank B3. 9) Pump P3 was switched on to circulate the water through pre-heater B5. The stirrer motor was switched on and the speed was set to about 200 rpm to ensure homogeneous water jacket temperature.(Note: Pre-caution, the water level must be higher than the heater.) 10) For experiment, the following additional steps were performed: i) The heater was switched on. ii) Valve V17 was opened to let the cooling water to flow through the cooling tubes. The water supply valve was adjusted to obtain reasonable cooling water flow in order to minimize the temperature overshoot at the TI 01 during heater cut-off. iii) The temperature set point on TI 01 was set to the desired temperature. 11) The unit was ready for experiment.
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6.2
General Shut-Down Procedures 1) Pumps P1, P2 and P3 were switched off. Valves V2 and V5 were closed. 2) The heater was switched off. 3) The cooling water kept circulating through the reactor while the stirrer motor was running to allow the water jacket to cool down to room temperature. 4) The stirrer and the cooling water were off. 5) If the equipment is not going to be used for long period of time, all liquid were drained from the unit by opening valves V1 to V17. The feed tanks were rinsed with clean water. 6) The power for the control panel was turned off.
6.3
Experiment Procedures 1) The general start-up procedures were performed. 2) Valves V6 and V8 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 0.30 L/min at flow meters FI 01 and FI 02. Both flow rates must be the same. The flow rates were recorded. 5) Start monitoring 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 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 were found out from the calibration curve. 7) Optional: Sampling valve V15 was opened and a 50 ml sample was collected. A back titration procedure was carried out to manually determine the concentration of NaOH in the reactor and extent of conversion. 8) The experiment (steps 4 to 7) was repeated for different residence times by reducing the feed flow rates of NaOH and Et(Ac) to about 0.25, 0.20, 0.15, 0.10 and 0.05 l/min. Both flow rates must be the same. 9) The general shutdown procedures were performed.
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7.0 DATA AND RESULTS No
1 2 3 4 5 6
No
1 2 3 4 5 6
Volume, VTFR (L) 4 4 4 4 4 4
Flow rate of NaOH (L/min) 0.30 0.25 0.20 0.15 0.10 0.05
Inlet Outlet Conductivity Conductivity (mS/cm) (mS/cm) 17.00 11.50 16.50 10.70 16.30 10.50 15.60 9.90 13.70 9.60 12.60 8.70
Flow rate of Et(Ac) (L/min) 0.30 0.25 0.20 0.15 0.10 0.05
Total Flow Rate of solutions, (L/min) 0.60 0.50 0.40 0.30 0.20 0.10
Residence Time, (min) 6.6667 8.0000 10.0000 13.3333 20.0000 40.0000
Conversion, X (%)
Reaction Rate Constant, k (L/mol.min) 0.0000 8.8117 x 10-3 1.6260 x 10-2 2.5281 x 10-2 3.4883 x 10-2 4.8701 x 10-2
Rate of Reaction (mol/L.min) 0.0000 8.6888 x 10-5 1.5744 x 10-4 2.3659 x 10-4 3.0481 x 10-4 3.4115 x 10-4
0.0000 0.7000 1.6000 3.2609 6.5217 16.3043
EFFECT OF RESIDENCE TIME ON THE REACTION IN TFR
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Graph of Conversion Against Residence Time Conversion
Linear (Conversion)
18
16
14
Conversion (%)
12
10
8
6
4
2 1.6 0.7
0 0
5 6.66 7
10 8.00
15
20
25
30
35
40
45
Residence Time (min)
EFFECT OF RESIDENCE TIME ON THE REACTION IN TFR
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8.0
CALCULATIONS
Sample Calculation for residence time,
No 1
Calculations
No 4
⁄
⁄
2
Calculations
5 ⁄
3
⁄
6 ⁄
EFFECT OF RESIDENCE TIME ON THE REACTION IN TFR
⁄
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Sample Calculation for Conversion, X Conversion 0% 25% 50% 75% 100% No
Solution Mixtures 0.1 M NaOH 0.1 M Na(Ac) H2 O 100 ml 100 ml 75 ml 25 ml 100 ml 50 ml 50 ml 100 ml 25 ml 75 ml 100 ml 100 ml 100 ml
From the Graph of Conversion Against Residence Time
1
No
Concentration of NaOH (M) 0.0500 0.0375 0.0250 0.0125 0.0000
Conductivity (mS/cm) 10.2 7.9 6.2 5.1 3.9
Calculations
4 ( (
%
) ) %
2
3
5 ( (
) )
( (
) )
6
EFFECT OF RESIDENCE TIME ON THE REACTION IN TFR
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Sample Calculation for The Reaction Rate Constant, k
(
)
Where, k = Reaction rate constant = Total inlet flow rate of solutions (ml/min) = Reactor volume (ml) = Inlet concentration of reactant NaOH in the reactor (mol/L) = Conversion (%) No 1
Calculations
(
)(
)
(
)(
)
(
)(
)
(
)
(
)
(
)
2
3
4 (
)(
)
(
)
5 (
)(
)
(
)(
)
(
)
(
)
6
EFFECT OF RESIDENCE TIME ON THE REACTION IN TFR
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Sample Calculation for Rate of Reaction,
Since CA0 = CB0 , (
( (
No 1
)) )
Calculations (
)(
) (
)
2 (
)(
) (
)
(
)(
) (
)
(
)(
) (
)
(
)(
) (
)
(
)(
) (
)
3
4
5
6
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9.0
DISCUSSION Calibration Curve of Conductivity Vs Conversion 12
Conductivity (mS)
10
9.7
8 6 4
3.7
2 0 0%
20%
40%
60% 80% Conversion, X (%)
100%
120%
The graph shows that the conductivity is inversely proportional with the conversion. Conductivity decreases as the conversion increases. This graph shows the theotherical value and relationship between conversion and conductivity. Based on the graph, we can relate conductivity and conversion into linear equation where, y = mx + c Where, y = The Conductivity (mS) x = The Conversion , X (%) m = The gradient (slope) c = The y-intercept The gradient (slope) of the graph ,
The y-intercept of the graph,
Thus, the linear equation of the graph is
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Graph of Conductivity Vs Conversion 14 12
Conductivity (mS/cm)
10.8
10 8.4
8 6 4 2 0
0
2
4
6
8 10 Conversion, X (%)
12
14
16
18
The graph shows experimental value which the recorded conductivity is inversely proportional with the conversion calculated. The conductivity decreases as the conversion increases. However, when compared to the theotherical graph, we can conclude that the experimental value deviated from the theory. Therefore , the linear equation from the experimental value is also deviated from the theory, where, y = mx + c Where, y = The Conductivity (mS) x = The Conversion , X (%) m = The gradient (slope) c = The y-intercept The gradient (slope) of the graph ,
The y-intercept of the graph,
Thus, the linear equation of the graph is
EFFECT OF RESIDENCE TIME ON THE REACTION IN TFR
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In order to determine the conversion of NaOH, the value of the conductivity is taken as the guidelines. However, since a few data taken for the conductivity falls a bit higher than in the theotherical value, extrapolation of graph is needed to determine the value of conversion at the respected residence time. Thus, the following graph is plotted to determine the conversion and to determine the relationship between conversion and the residence time.
Graph of Conversion Against Residence Time Conversion
Linear (Conversion)
18 16
Conversion (%)
14 12 10 8 6 4 1.6 0.7
2 0 0
5
10
6.66 7
8.00
15
20
25
30
35
40
45
Residence Time (min)
The graph shows that the conversion is directly proportional with the residence time. The conversion increases as the residence time increases. Residence times refer to the time taken needed to process one volume of the reactor fluid at the entrance condition where as the conversion refers to how many moles of products are formed for every mole of NaOH consumed. Three values of conversion which are 0.0% at 6.6667 min, 0.7% at 8 min and 1.6% at 10 min are recorded from the extrapolation of the graph. Conversion data table need to be completed in order to calculate the reaction rate constant which will lead us to the final objective of the experiment which is to determine the rate of reaction of the experiment.
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Plug flow reactor (PFR) or Turbulent flow reactor (TFR) is a reactor for chemical reactions in a continuous, flowing system in a shape of cylindrical. The fluid going through the reactor are refers as a plugs, each with a fix and uniform volume. The fluid or solution in the reactor is well mixed. The residence time of the plug is a position of the fluid in the reactor. The volume of solution that flow into the reactor equal to the volume of the solution out from the solution. In this experiment, we used NaOH and Et(Ac). The Hydrolysis of Ethyl Acetate is one of the most well-known reactions as model example for second order reaction. These solution are mixed together into the Plug Flow Reactor (PFR). Based on the result that we have collected, the residence time can be calculated and be include in the table. The lower the total flow rate of solutions, the higher the residence time for each test. The residence time is the amount of time the particles spends in the particular system. The residence time is affected by the flow rate of the solution in the Tubular Flow Reactor.
Graph of Residence Time vs Flow rates 45 Residence Time (min)
40 35 30 25 20 15 10 5 0 0
0.1
0.2
0.3 0.4 Flow Rates, ( L/min)
0.5
0.6
0.7
The graph shows that the residence time is inversely proportional with the flow rates. As the flow rates increases, the residence time decreases.
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Due to the less concentration that we used, the longer the residence time for the solution in the reactor. The less the concentration, thus less the collision kinetic between the particles to produce the product of the saponification process, Sodium acetate, CH3COONa, and Ethyl Alcohol, C2H5OH. The General Equation for this saponification reaction are CH3COOC2H5 + NaOH → CH3COONa + C2H5OH We also observed that the Inlet conductivity and the outlet conductivity is decreasing going along with the decreasing flow meter. The conductivity or specific conductance is a measure of ability of an electrolyte or a solution to conduct electricity. The conductivity is decreasing due to the less ionic content in the water. This explained the result for decreasing conductivity that we recorded at the reactor. Due to the less concentration of the solutions going down the table that we tabulate, the conductivity can be seem decreasing too. The conversion, x, can be calculated by using the formula X=Moles of Reacted/Moles of Feed. Conversion is the ratio of the feed used or the ratio the product formed. In this case the product formed is Sodium Acetate and the Ethyl Alcohol. After calculated the conversion for all flowrate, the conversion become increase the longer it resides in the reactor. The reaction rate constant, k or also can be called as Kinetic Constant. This constant can be calculated by using a formula. This is a second order reaction, therefore the unit for the constant are Liter Mole-1 Min-1. The rate of reaction, -ra are calculated with the formula also and shown on the sample calculation and the table. The rate of reaction for the second law are or
.
After derive the equation, we can calculate the rate of reaction by using the data that we collected from the reactor, rate constant, k and the conversion, X.
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10.0 CONCLUSION From the experiment, we were able to found out a saponification between Sodium Hydroxide, NaOH and Ethyl Acetate, Et(Ac) in tubular flow reactor, TFR. By using a Plug Flow Reactor, PFR, both Sodium Hydroxide, NaOH and Ethyl Acetate, Et(Ac) were flowed into the reactor, mixed and let to react for a certain period of time. By doing that, saponification process was completed. Next, we were able to determine the reaction rate constant. This was done by calculating the reaction rate as seen in the Sample Calculation section. The value of the reaction rate constant that we get was 0.0000 L/mol.min, 8.8117x10-3 L/mol.min, 1.6260x10-2 L/mol.min, 2.5281x10-2 L/mol.min, 3.4883x10-2 L/mol.min and 4.8701x10-2 L/mol.min respectively. Last but not least, we able to determine the effect of residence time on the conversion in a TFR. Thus, we were able to plot graph of conversion, X against residence time. We can conclude that the experiment was successfully conducted since we were able to fulfill the objective of this experiment.
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11.0 RECOMMENDATION Experimenters need to fully understand the procedure of the experiment in order to avoid making mistakes that should not ever happen during the experiment. This can be done by reading the lab manual over and over again in order to grasp what the experiment is all about and how to make sure that the experiment went well.
In order to make sure that the data collected is accurate, the experiment needs to be done repeatedly for at least three times per experiment. This is to ensure that the data taken is not fall far from the data theory. Then, the average value taken is used for the calculation involved in the experiment. Besides, the values should be taken in approximately 4 decimal places so that the data will be more precise and accurate.
When conducting the experiment there are some errors where the data deviate from the theoretical value. The reason of the errors could be because the time interface for the value of conductivity at inlet and outlet to be stable is too short. Since there are quite few times where the value seems to already stabilize but actually are not and the data might have been taken during that particular time which then lead to the deviation from the theoretical value of the conductivity. Therefore, experimenters should be more aware about the time and be carefull not to misunderstand which value needs to be taken into account. Other than that, student should follow the rules and guidelines before doing the experiment. They need to wear lab coat, gloves and wear shoes for safety purposes. They also need to make sure they alert with the precautions mention in the lab manual and never play around during the experiment being conduct.
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12.0 REFERENCES Books 1) Levenspiel O., “Chemical Reaction Engineering”, John Wiley (USA), 1972. 2) Fogler H.S. , “Elements of Chemical Reaction Engineering, 3rd Ed.”, Prentice Hall (USA) , 1999. 3) Smith J.M., “Chemical Engineering Kinetics”, McGraw Hill (Singapore), 1981. 4) Astarita G., “Mass Transfer With Chemical Reaction”, Elsevier, 1967.
5) Scott Fogler ,“Element of Chemical reaction Engineering”, Fourth Edition H., Pearson International Edition, 2006 Pearson Education, Inc.
Web 1) Batch Reactor Kinetic Analysis. Jan 15, 2005. www.csupomona.edu/~tknguyen/che435/Notes/P5-kinetic.pdf , retrieved in August 2015. 2) Wikipedia , https://en.wikipedia.org/wiki/Plug_flow_reactor_model ,retrieved in August.
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13 APPENDIX
Tubular Flow Reactor (TFR)
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