INTRODUCTIONReactor is one of equipment used mostly in the industrials sector. It changes the raw material into the desired product. A good reactor will give a high production and economical. One ofcriteria to choose or to design a good reactor is to know the effectiveness of the reactor itself. There a many types of reactor depending on the nature of the feed materials and products. One of the most important we need to know in the various chemical reaction was the rate of the reaction. The continuous stirred-tank reactor (CSTR) which is also known asvat orback-mix reactor usually is a common ideal reactortype in chemical engineering. A CSTR often refers to a model used to estimate the key unit operation variables when using a continuous agitated-tankreactor to reach a specified output. This reactor works for all fluids, liquids, gases, and slurries. The behavior of a CSTR is always modeled by that of a Continuous Ideally Stirred TankReactor(CISTR). All calculations performed with CISTRs assumed perfect mixing. In a perfect mixed reactor, the output composition is identical to the material inside the reactor, which is a function residence time and rate of reaction. CSTR used in this experiment, (model: BP 143) is designed for students experiments on chemical reaction in liquid phase under adiabatic and isothermal conditions. CSTR consists of two tanks of solutions and one reactor. Thereactorismodeledinorderto perform the saponification reaction between sodium hydroxide and ethyl acetate. Saponification reaction of ethyl acetate and sodium hydroxide produced sodium acetate in batch and the continuous stirred tank reactor evaluate the rate data needed to design a production scale reactor.

OBJECTIVESThe main purposes of conducting this experiment are : to carry outsaponification reaction between Sodium Hydroxide, NaOH and Ethyl Acetate, Et(AC) by usinga ContinuousStirred Tank Reactor, CSTR to determine the effect of residence time to thereaction's extent of conversion to evaluate thereaction rate constant

THEORYRate of equation and rate lawThe rate ofreactions or speed of reaction for areactant and products in particular reactions can be defined as how fast or slow the reaction takes place. For examples is about the oxidation process between iron under the atmospheric is undergoes a slow reaction compare to the combustion of butane in a fire that can becategories as fast reaction. Consider the chemical reaction as below:aA + bB pP+qQThe lowercase letter which are a, b, p, and q refer to the stoichiometric coefficient while the capital letter which are A, B, P and Qrefer to the reactants andproducts.According to the IUPACs Gold Book definition the rate of reaction, rin the chemical reaction is occur in a closed system which is under a constant volume conditions, without build up of reaction intermediates, is defines as:

Where [A], [B], [P] and [Q] arereferred to the morality of thesubstances. Based on IUPAC the times must be in second and therate of reaction is in apositive sign. The mass balance for any system in general is:IN - OUT + GENERATION -CONSUMPTION= ACCUMULATIONMass is a conservative entity, hence given a control volume V the sum of mass flows entering the system will be equal to the sum exiting minus the consumed or accumulated fractions.

Continuous Stirred Tank Reactors (CSTR)

CSTR runs at steady state with continuous flow of reactants and products; the feed assumes a uniform composition throughout the reactor, exitstream has thesame composition as in thetank.General Mole Balance Equation

AssumptionsSteady state, therefore dNA/dt = 0Well-mixed therefore is the same throughout thereactor. Rearranging the generation, V =(FAo - FA)/ -rAIntermsofconversion,X=(FAoFA) / FAoV = (FAoX) / -rAA calibration curve is a method used in analytical chemistry to determine theconcentrationof an unknown sample solution. It isa graph generated by experimental means, with theconcentration of solution plotted on the x-axis and theobservable variable, for example, thesolutions absorbance plotted on the y-axis. The curve is constructed by measuring the concentration and absorbance of several prepared solutions, called calibration standards. Once the curve has been plotted, the concentration of the unknown solution can be determined by placing it on the curve based on its absorbance or other observable variable. Residence TimeThe reactors residence time is defined as the reactorvolume divided by the total feed flow rates.Residence time,

MATERIAL AND APPARATUS

The unit Continuous Stirred Tank Reactor Model BP143 comes complete with a jacketed glass reactor, constant temperature water circulating unit, vapor condenser, individual reactant feed tanks and pumps, temperature and conductivity measuring sensors, and of course, data acquisition system. Apart from that, there were also some laboratory apparatus involved such as: Burette conical flask measuring cylinder ph indicator beakersAmong the chemicals used are: 0.1 MSodiumHydroxide,NaOH 0.1 M EthylAcetate, Et(Ac) 0.1 M Hydrochloric Acid, HCl De-ionized water

PROCEDUREGeneral start-up Procedures:1. The following solution were prepared:i- 40L of sodium hydroxide, NaOH (0.1 M)ii- 40 L of ethyl acetate, Et (Ac) (0.1M)iii- 1 L of hydrochloric acid, HCl (0.25M),for quenching.

2. All valves were initially closed.3. The feed vessels were charged as follows:i- The charge port caps for vessels B1 and B2were opened.ii- The NaOH solution was carefully poured into vessel B1 and Et (Ac) solution was poured into vessel B2.iii- The charge port caps for both vessels wereclosed.

4. The power for control panel was turned on.5. Sufficient water inthermostat T1 was checked.Refill as necessary.6. The overflow tube was adjusted to give aworking volume of 10L in the reactor R1.7. Valves V2, V3, V3, V7, V8 and V11 were opened.8.The unit was readyfor experiment.

Back Titration Procedures for Manual Conversion Determination:1. A burette was filled up with 0.1 MNaOH solution.2. 10 mL of 0.25 MHCl was measured in a flask.3. A 50 mL sample was obtained from the experiment and immediate the sample was added to the HCl in theflask to quench the saponification reaction.4. A few drops of pHindicator were added into the mixture.5. The mixture was titrated with NaOH solution from the burette until the mixture was neutralized. The amount of NaOH titratedwas recorded.

Effect of Residence Time of Reaction in a CSTR:

1. The general start-up procedures were performed.2. Pump 1 and pump 2 were switched on and valves V5 and V10 were opened to obtain the highest possible flow rate into the reactor.3. The reactor was filled up with both ofthe solution until it is just about tooverflow.4. Valves V5 and V10 were readjusted to give a flow rate of about 0.1 L/min. the flow rate for both valves must be same. The flowrates were recorded into a data.5. The stirrer M1 was switched on and thespeed was set about 200 rpm.6. The conductivity value at Q1 was started monitoring until it does not change over time. This is to ensure thatthe reactor has reached steady state.7. The steady state conductivityvalue was recordedand the concentration of NaOHand extent of conversion in the reactor was found out from the calibration curve.8. Sampling valve V12 was opened and 100mL of sample was collected. It directly proceed with the backtitration procedures to manually determine the concentration of NaOH in the reactor and extentof conversion.9. The experiments was repeated (steps 5-9) for different residence times by adjusting the feed flow rate of NaOH and Et(Ac) to about 0.15, 0.20, 0.25, and 0.30 L/min. the flow rate for both must be same.

General shut-down Procedures:1. The cooling water valve V13 was kept open to allow the cooling water to continue flowing.2. Pumps P1 and pumps P2 were switched off. Stirrer M1 wasswitched off.3. The thermostat T1 was switched off. The liquid in the reaction vessel R1 was left to cool down to room temperature.4. Cooling water V13 wasclosed.5. Valves V2, V3, V7, and V8 were closed. Valves V4, V9 and V12 were opened to drain any liquid from the unit.6. The power for control panel was turned off

Preparation of Calibration Curvefor Conversion vs Conductivity:1. The following solution were prepared:i- 1 L of sodium hydroxide, NaOH (0.1M)ii- 1 L of sodium acetate , Et (Ac) (0.1M)iii- 1 L of de-ionized water, H2O.

2. The conductivity and NaoH concentration for each value were determined by mixing the following solution into 100mL of de-ionized water.i- 0%conversion:100mLNaOHii- 25%conversion:75mLNaOH+25mLEt(Ac)iii- 50%conversion:50mLNaOH+50mLEt(Ac)iv- 75%conversion:23mLNaOH+75mLEt(Ac)v- 100%conversion:100mLEt(Ac)

RESULTSTable 1: Preparation of Calibration CurveConversionSolution MixturesConcentration of NaOH (M)Conductivity (mS/cm)

0.1 M NaOH0.1 M Et(Ac)H2O

0 %100 mL-100 mL0.05007.66

25 %75 mL25 mL100 mL0.03755.40

50 %50 mL50 mL100 mL0.02502.90

75 %25 mL75 mL100 mL0.01251.30

100 %-100 mL100 mL0.00000.157

Table 2: Tabulated dataTemperature Flow rate of NaOH (mL/min)Flow rate of Et(Ac) (mL/min)Total flow rate of solutions, F0 (mL/min)Residence time, (min)Conductivity (mS/cm)Exit concentration of NaOH, CNaOH (M)Conversion, X (%)Volume of NaOH (mL)

28.00.10.10.2502.010.0049228.0

28.20.150.150.333.331.910.0049228.0

28.30.200.200.4251.840.003692.828.2

28.40.250.250.5201.750.0049228.0

28.60.300.300.616.661.740.0049228.0

Figure 1: Calibration Curve

Figure 2: The Conversion of NaOH against Residence Time

SAMPLE CALCULATIONVolume of sample, VS = 50 mLConcentration of Initial NaOH, CA0 = 0.1 mol/LVolume of HCL, VHCl = 12 mLConcentration of HCl, CHCl = 0.25 mol/LVolume of NaOH titrated, V1 = 28.0 mLi- Concentration of NaOH entering the reactorCNaOH0 = CA0= (0.1 mol/L)= 0.05 mol/Lii- Volume of unreacted HClV2= (CNaOH/ CHCl) x V1= (0.1 mol/L / 0.25 mol/L) x 28 mL= 11.2 mLiii- Volume of reacted HClV3= VHCl-V2= 12 mL 11.2 mL= 0.08 mLiv- Mole of reacted NaOHn1= (CHCl x V3) / 1000= 0.25 x 0.08 / 1000= 0.00008 molv- Mole of unreacted NaOH n2= n1= 0.00008 molvi- Concentration of unreacted NaOH in ReactorCNaOH= n2/VS x 1000= 0.00008/ 50 x 1000=0.004 mol/Lvii- Conversion of NaOH in reactorX= (1- CNaOH / C NaOH0) x 100%= (1- 0.004 / 0.05) x 100%= 92%viii- Residence time = VCSTR / F0= 10 / 0.2 = 50 minix- Rate reaction constantk = (CA0 CA)/ CA2 = (0.05 -0.004) / 50 (0.004)2DISCUSSIONAccording to the experiment that hadbeen conducted, we need to achieve threeobjectives which are to carry out the saponification process between NaOH and Et (Ac) in a CSTR reactor, to determine the effect of the residence time onto the reaction extent of conversion and lastly to determine the constant rate of reaction. From the data collected, two graph had been plotted which areconductivity versus conversion and residence time versus conversion. From the Figure 1, we can conclude that the conductivity is consistently slows down throughout the overall conversion. The second graph is residence time versusconversion. For this graphit could be seen thatthe residence time is increased proportionally at average 92% conversion. But there are certain fluctuate peak which due to the error that may beaffects the result and graph. Saponification process is the process to make soap. It takes place in acontinuous reaction. Inthis experiment, the reaction of saponification is quenching with hydrochloric acid to stop thereaction. The reaction rapidly reacts in increasing of experiment. Back titration is done to investigate if the reaction is stop .As the result for rates of constant is not correspond to the theory, thus there are some errors occurred during this experimentsuch as while taking the reading of the burette the position of the eyes is not at the same level of the meniscus. So, to improve the reading and get the better results, the positions of the eyes must be parallel to the meniscus. Besides, we have to rinse all the apparatus before we use it. This is to ensure that all the beakers, or burette is clean so that any chemical that we put into these apparatus does not react with any others chemicals. By doing all these precaution, we can get more accurate reading and thus improve the results.CONCLUSION Based on the objectives of this experiment, which is to determine the residence time onto the reaction extent of conversion, the relationship conversion and residence time was directly proportional. But the reaction rates constant were determined for all varies flow rate. From the calculated data, the rate constant of reaction is increasing when the conversion is higher. We can conclude that the experiment was successfully conducted since we getthe right conclusion.

RECOMMENDATION1. Make sure reactor does not have any leaks and valve closed and opened as needed, controlled the valve carefully and slowly when adjusting the flow rate to obtain 0.10 L/min. It is to makesure flow rate will stabilize and the experiment will run smoothly.2. Repeat titrations two or three times because a lot of error comes from titration or use another method other than titration.3. Divide into two teams which is the first team in charge of the CSTR 40 liters machine while the second team would carry out the backtitration procedures.4. Take conductivity reading when the conductivity not changes in time because it can change rapidly in short of time.5. Make sure CSTR 40 liters machine is running appropriately, it to prevent harm to the machine and individual that used the machine.

REFERENCES1. Sulivan, J. A. (1960). Fluid Power Theory and Application., 2nd ed., Reston Publishing Company, Reston, VA.2. Salmi, T. O., et. al. (2011). Chemical Reaction Engineering and Reactor Technology., Taylor & Francis Group, CRC Press, Boca Raton.

APPENDICES

1