TABLE OF CONTENT NUMCONTENTSPAGE

1.0Abstract1

2.0 Introduction2

3.0 Theory/Literature Review4

4.0Methodology6

5.0 Results And Discussion7

6.0 Conclusion17

7.0 References17

8.0 Appendices17

1.0 ABSTRACTThe experiment aims to study the saponification reaction of sodium hydroxide an ethyl acetate in a ContinuousStirred Tank Reactor (CSTR). In this experiment, the aims also include investigating the operational behaviour of a reaction in the CSTR system, techniques when using CSTR for a reaction process and effect of flow changes on the reaction. Before all apparatus is set-up, the conductivity calibration curve with different molar concentration were prepared to determine the conversion of the reactants to products in the reactor since we cannot distinguish the mixture of reactants and products easily from the mixture. Then, both sodium hydroxide and ethyl acetate were prepared according to the given volume and concentration before transferred to the tanks. When the process starts, the conductivity and temperature of the reaction were recorded in every two minutes for 30 minutes. When the liquid level in the CSTR reached 2L, the space time as well as conductivity and temperature was recorded. After flow the reaction medium into the buffer tank, the readings are recorded for another 10 minutes. Then, all valves and pumps were closed, and all liquid will be discarded through valve V4. The process is repeated several times using different feeds of flow rates. Theoretically, as the time goes once the experiment starts, the conductivity values should gradually close up its value to the conductivity value of pure product that is determined before the reaction starts. The conversion should gradually increase as the time goes by. From the result obtained, it shows that on the graph concentration versus time, we get the value of rate constant which is in this experiment we get k = 0.6342 L/mol. min and little bit differ by using by formula which is k = 1.317 L/mol .min. Other than that, the reaction order is successfully to approve which is second order of reaction based on linear graph of concentration versus time. The errors and recommendations also were discussed in the discussion section. The conclusion section concludes all the objectives and calculations on this experiment.

2.0 INTRODUCTIONThe Continuous- Stirred Tank Reactor (CSTR) is common type of reactor used in industrial processing which is primarily used for liquid phase reaction. The reactor was operate in steady state condition with continuous flow of reactants and products and assumed as perfectly mixed. The feed assumes a uniform composition throughout the reactor; exit stream has the same composition as in the tank. There is no time dependence or position dependence of the temperature, the concentration and the reaction rate in the tank. The usage of the CSTR is when agitation is required and series configurations for different concentration streams. Besides that, the advantages using this reactor compare to the other are it has good temperature control, easily adapt to two phases, low operating cost and easy to clean. But, the CSTR has lowest conversion per unit volume and requires large volume to obtain the desired conversions. When high conversions of reactants are needed, several CSTRs in series can be used. Equally good results can be obtained by dividing a single vessel into compartments while minimizing back-mixing and short-circuiting. The larger the number of CSTR stages, the closer the performance approaches that of a tubular plug-flow reactor.This experiment was carried out to study the saponification reaction between sodium hydroxide and ethyl acetate in a continuous stirred tank reactor (CSTR). This process was conducted to produce soap, usually from fat and lye. Technically, the saponification process involves base (caustic soda NaOH) hydrolysis of triglycerides, which are ester of fatty acids, to form sodium salt of carboxylate. Beside saponification reaction, the other scopes of this experiment are to investigate the operational behavior of a reaction in CSTR, to calculate the reactant conversion based on the conductivity calibration curve. Also, the significant of doing this experiment was to verify the reaction order obtained from the hypothesis of the experiment and to determine the rate constant of saponification reaction between sodium hydroxide and ethyl acetate using graphical and analytical technique. The result of CSTR of the reaction kinetics, rate law and conversion is compared with a batch reactor for the same reaction as stated in scope of experiment.The reaction kinetics and rate law of saponification reaction in a CSTR can be determined using conductivity calibration curve. Conductivity is a measure of how well a solution can conducts electricity. A solution must contain charged particles, or ions to carry a current. Most conductivity measurements are made in aqueous solutions, and the ions responsible for the conductivity come from electrolytes dissolved in the water. There are two ways to calibrate conductivity sensors. The sensor can be calibrated against a solution of known conductivity or it can be calibrated against a previously calibrated sensor and analyzer. Normally, the sensor should be calibrated at a point near the midpoint of the operating range calibration changes the cell constant. For this experiment, the calibration curve is prepared using different molar concentration of sodium hydroxide and sodium acetate.3.0 LITERATURE REVIEW

In this experiment we are going to use continuous stirred tank reactor (CSTR) to react sodium hydroxide and ethyl acetate to produce sodium acetate. Based on H. Scott Fogler, Elements of Chemical Reaction CSTR normally operated at steady state and is assumed to be perfectly mixed. Based on this statement, the temperature of the reactor and reaction mixture should not have any major change throughout the experiment. Concentration and volume of the reactants should be the same as another reactant since it is a one-to-one ratio for the reaction. The reactants are well mixed and so the reaction must be efficient. However, reactants and products are always mixed well together in the reactor making it difficult to determine the product conversion. That is why a standard conductivity calibration curve has to be prepared before the experiment. Conductivity of the mixture will indicate the percent products present which is determine using conductivity meter.

TheorySaponification between sodium hydroxide (NaOH, denotes as A ) and ethyl acetate (EA, denotes as B) is basically second order elementary reaction. For steady state constant volume isothermal CSTR, the design equation is :

Where V is the reactor volume, X is the reactant and is the total volumetric flow rate feeds into the reactor.For elementary-bimolecular second order reaction, the rate equation is :

Basically, reactant conversion, X, can be calculated using the following equation :

The design equation of CSTR also can be written in terms of initial concentrations, reactant conversion, reactor volume and feed flow rate. Thus, we need to use the relations :

when Therefore,

If we combine the above equation, we see that

And further simplified to

4.0 METHODOLOGY

A. Calibration graph plot1. Conductivity calibration curve is prepared using three points:i. X = 0.0, use 10mL 0.1M NaOHii. X = 0.5, use a mixture of 5 mL NaOH and 5 mL sodium acetateiii. X = 1.0, use 10 mL 0.1M sodium acetate

B. Operating procedure1. 9L solution of 0.1M NaOH (8g per 2L H2O) and 9L solution of 0.1M EA (19.6mL per 2L H2O) are prepared and these solutions were poured into tanks T1 and T2 respectively.2. Next, pumps P1 and P2, and stirrer S1 are switched on. The feed flow rates into the CSTR are adjusted to be at 40 cm3/min using valves F1 and F2. The stopwatch was started immediately as the pumps and stirrer were switched on. The conductivity and temperature of the reaction medium in the CSTR were measured for every 2 minutes for over 30 minutes.3. When liquid level inside the CSTR reached 2000 cm3(2L), the space time, conductivity and temperature of the reaction medium were recorded.4. Then, the reaction is flowed into the buffer tank by opening valve V3. Measurements were continued taken for 10 minutes.5. After 30 minutes, valves F1 and F2 were closed, and pumps P1 and P2 were stopped. All liquids were discharged through valve V4.6. The experiment was repeated for different feed flow rates at 60 cm3, 100 cm3 and 120 cm3.7. All residual NaOH and Ethyl Acetate were discharged once the experiments were done.8. The pilot plant was cleaned up.

5.0 RESULTS AND DISCUSSION

RESULTCallibration Data0.1M NaOH0.05M NaOH + 0.05M Sodium Acetate0.1M Sodium Acetate

Conversion0.00.51.0

Conductivity (S)12.178.695.17

Table 1: Calibration Data

Figure 1: Graph of Conversion against Conductivity of three different concentrations of reactants.

Table 2: Experimental Data for Flow Rate = 40 cm3/min

Time, t (min)Conductivity (S)Temperature (C)ConversionCA (mol/L)CB (mol/L)CC (mol/L)CD (mol/L)1/CA (L/mol)

010.7528.50.20330.079670.079670.020330.0203312.55

218.2730.2-0.87130.187130.18713-0.08713-0.087135.34

44.9630.01.0307-0.00307-0.003070.103070.10307-325.56

67.3830.00.68490.031510.031510.068490.0684931.74

89.3030.00.41050.058950.058950.041050.0410516.96

109.1430.00.43340.056660.056660.043340.0433417.65

129.0630.10.44480.055520.055520.044480.0444818.01

148.9530.10.46050.053950.053950.046050.0460518.54

168.8930.10.46910.053090.053090.046910.0469118.84

188.7930.20.48340.051660.051660.048340.0483419.36

208.7330.20.49200.050800.050800.049200.0492019.68

228.6630.20.50200.049800.049800.050200.0502020.08

248.5830.30.51340.048660.048660.051340.0513420.55

268.5630.30.51630.048370.048370.051630.0516320.67

288.5030.30.52490.047520.047520.052490.0524921.05

308.4630.30.53060.046940.046940.053060.0530621.30

328.4430.30.53340.046660.046660.053340.0533421.43

CA: Concentration of NaOHCB: Concentration of Ethyl AcetateCC: Concentration if Sodium AcetateCD: Concentration of Ethyl Alcohol

Table 3: Experimental Data for Flow Rate = 60 cm3/minTime, t (min)Conductivity (S)Temperature (C)ConversionCA (mol/L)CB (mol/L)CC (mol/L)CD (mol/L)1/CA (L/mol)

03.4630.61.2451-0.02451-0.024510.124510.12451-40.81

29.7930.80.34050.065950.065950.034050.0340515.16

49.5630.70.37340.062660.062660.037340.0373415.96

69.0930.70.44050.055950.055950.044050.0440517.87

89.0230.70.45050.054950.054950.045050.0450518.20

108.8130.70.48060.051940.051940.048060.0480619.25

128.6030.70.51060.048940.048940.051060.0510620.43

148.3830.80.54200.045800.045800.054200.0542021.83

168.2630.80.55910.044090.044090.055910.0559122.68

188.1830.80.57060.042940.042940.057060.0570623.29

208.0430.80.59060.040940.040940.059060.0590624.43

228.0030.80.59630.040370.040370.059630.0596324.77

247.9630.90.60200.039800.039800.060200.0602025.13

Table 4: Experimental Data for Flow Rate = 100 cm3/minTime, t (min)Conductivity (S)Temperature (C)ConversionCA (mol/L)CB (mol/L)CC (mol/L)CD (mol/L)1/CA (L/mol)

04.3031.11.1250-0.01250-0.012500.112500.11250-79.98

210.1031.00.29620.070380.070380.029620.0296214.21

49.0331.00.44910.055090.055090.044910.0449118.15

69.4231.00.39340.060660.060660.039340.0393416.48

89.0531.00.44630.055370.055370.044630.0446318.06

108.7731.00.48630.051370.051370.048630.0486319.47

128.6031.00.51060.048940.048940.051060.0510620.43

148.5231.00.52200.047800.047800.052200.0522020.92

168.4731.00.52910.047090.047090.052910.0529121.24

188.4331.00.53490.046510.046510.053490.0534921.50

Table 5: Experimental Data for Flow Rate = 120 cm3/min

Time, t (min)Conductivity (S)Temperature (C)ConversionCA (mol/L)CB (mol/L)CC (mol/L)CD (mol/L)1/CA (L/mol)

02.9631.01.3165-0.03165-0.031650.131650.13165-31.59

29.3131.00.40910.059090.059090.040910.0409116.92

48.6830.90.49910.050090.050090.049910.0499119.97

68.3630.90.54490.045510.045510.054490.0544921.97

88.0430.90.59060.040940.040940.059060.0590624.43

107.9030.90.61060.038940.038940.061060.0610625.68

127.8830.90.61340.038660.038660.061340.0613425.87

147.7930.90.62630.037370.037370.062630.0626326.76

167.7030.90.63920.036080.036080.063920.0639227.71

187.6630.90.64490.035510.035510.064490.0644928.16

Figure 2: Graph of 1/CA against Timefor v0 = 40cm3/min

Figure 3: Graph of 1/CA against Time for v0 = 60cm3/min

Figure 4: Graph of 1/CA against Timefor v0 = 100cm3/min

Figure 5: Graph of 1/CA against Time for v0 = 120cm3/min

Table 6: Experimental Data for Space Time

Flow Rate, v0 (cm3/min)Space time, (min)Conductivity (S)Temperature, T (C)Conversionk(L/mol.min)Theoretical space time, th(min)

4022.408.6430.20.50480.411725.00

6014.008.3830.80.54200.516816.67

1008.518.9131.00.46630.327410.00

1206.478.2830.90.55630.56518.33

CALCULATION

Based on Graph 1 the conductivity calibration curve, we get the linear equation of the curve as y = -0.1429x + 1.7395, where

y represents conversion value, Xx represents conductivity (S).

When flow rate is 40 cm3/min, the conductivity at time, t=10 min is 9.14 S,the conversion value isy = -0.1429(9.14) + 1.7395= 0.4334

For the concentration of NaOH after the reaction, CACA = CA0 (1 - X)= 0.1 M (1 0.4334)= 0.05666 M= 0.05666 mol/L

For the concentration of Ethyl Acetate, CBCB = CA= 0.05666 mol/L

For the concentration of Sodium Acetate, CCCC = CAO.X= 0.1M (0.4334)= 0.04334 M= 0.04334 mol/LFor the concentration of Ethyl Alcohol, CDCD = CC= 0.04334 mol/L

Four linear graphs of 1/CA vs. time are plotted, which indicates the second order reaction of the saponification process.

1/CA =1/CA0 + kt

By using graphical method, we know that the slope of the graph indicates the value of k.

Average value of k based on the four graphs (of different flow rates)kav= (2.7364+1.3881+2.9988+2.0007)/4= 9.124/4= 2.281 L/mol.min

Whereas by using analytical method, from the equation simplifiedV=

k =

At v0 = 40 cm3/min, V= 2000cm3, X = 0.5048, CA0 = 0.1mol/L

k =

= 0.4117 L/mol.min

So the value of k average using analytical method,kav= (0.4117+0.5168+0.3274+0.5651)/4= 1.8210/4= 0.4553 L/mol.min

Theoretical Space time, th can be calculated through the equation below:

= V/v0

whereV is volume of reactor and v0 is the volumetric flow rate entering the reactor.

For flow rate v0 = 40 cm3/min, because there are two reactants flowing in the reactor with the same flow rate, thus we use v0 = 2(40) = 80 cm3/min.

th =

= 25 min

DiscussionAt the end of our experiment and after done the calculation, we can calculate the reactant conversion, verify the reaction order and determine the rate constant.

Based on the graph 1 which is graph of conversion against conductivity of three different concentrations of reactants or known as conductivity calibration curve, we get the linear equation of the curve as y = -0.0621x +1.1918, where x represents as conductivity and y represents as reactant conversion. The conductivity calibration curve represents the conversion-conductivity relationship of the reaction mixture and provides a mean to get concentration versus time data. Hence we can calculate the value of the conversion at every minute and followed the calculation to find concentration sodium hydroxide (CA), ethyl acetate (CB), sodium acetate (CC) and ethyl alcohol (CD).

1/CA =1/CA0 + kt

By using graphical method which is concentration versus time graph, we know that the slope of the graph indicates the value of rate constant of saponification reaction between sodium hydroxide and ethyl acetate. Hence the average value of rate constant based on the four different flow rate is 0.6342 L/mol.min. Whereas by using analytical method based on the equation, the average value of rate constant is 1.317 L/mol.min. From these two different values we found that the value of rate constant k by using graphical method is lower than by using the design equation of CSTR due to several factors.

Overall, the theoretical space time is higher than experimental due to some error during taken the space time. Unfortunately, we are late recorded the space time because we are not clearly see either the liquid reach the valve V3 or not.

Saponification between sodium hydroxide and ethyl acetate is basically second order elementary reaction..It is proved by our graph respect to reaction between sodium hydroxide and ethyl acetate since graph 1/CA versus time is a linear graph which is corresponding to the second order and the slope of the graph referring to the positive rate of constant.

Comparison between batch reactor and CSTR in term of reaction kinetics, rate law and conversion for the same reaction:

Batch ReactorCSTR

Reaction kineticsBoth reactors will process the reaction at the same speed

Rate LawBoth reactors have the same rate law which is second order. Rate law is independent of type of reactors used.

ConversionConversion increases with the time spent in the reactor. The longer reactant stays in the reactor, the more the reactant is converted to product until reach equilibrium.Time usually increases with the increasing reactor volume. The bigger/longer the reactor, the more time it will take the reactants to flow completely through the reactor and more time to react

Some errors in the process of experiment include errors during preparation of the solutions, side reaction occurs during the experiment and inconsistency of flow rates from tanks to CSTR reactor. The flow rate went up and down due to possibly faulty valve since another valve from another tank was working fine.

Some recommendations to improve the result include study the experiment before entering the lab to conduct the experiment and always check for errors before starting the experiment including preparation of reactants material (weighing and dissolving in solution) and systematic errors like zero errors.

6.0 CONCLUSION

A common type of reactor used in industrial processing is the continuous-stirred tank reactor (CSTR) which is used primarily for liquid phase reaction. It is normally operated at steady state and assumed to be perfectly mixed. The conductivity calibration curve is prepared using different molar concentration of sodium hydroxide and ethyl acetate. This calibration curve can be used to determine the reaction kinetics and the rate law of the process. Based on the graph concentration versus time, we get the value of rate constant which is in this experiment we get k = 0.6342 L/mol.min and little bit differ by using by formula which is k = 1.317 L/mol.min. Other than that, the reaction order is successfully to approve which is second order of reaction based on linear graph of concentration versus time.

7.0 REFERENCES

H. Scott Fogler, Elements of Chemical Reaction Engineering, 4rd edition, Pearson Education Limited, 2014.Schmidt, Lanny D. (1998). The Engineering of Chemical Reactions. New York: Oxford University Press

8.0 APPENDICES

Figure shows Continuous stirred tank reactors, (a) With agitator and internal heattransfer surface, (b) With pump around mixing and external heat transfer surface.

(a) (b)(c)

The figure show the (a) zero order reaction (b) first order reaction (c) second order reaction