ABSTRACT

The objective of this experiment is to carry out the saponification reaction between NaOH and Et(Ac) in CSTR 40L, to determine the effect of temperature on the rate of reaction, rate of reaction constant and the activation energy of the process. To achieve these objectives, an experiment is conducted using a unit called SOLTEQ Continuous Stirrer Tank Reactor (model: BP143), commonly known as CSTR 40L, as well as some common laboratory apparatus for titration process. In this experiment, reaction between two solutions NaOH and Et(Ac) were reacted in the CSTR. Then, the product is then analysed by the method of titration to determine how well did the reaction go. After collecting the data, the value of reaction rate constant and rate of reaction is calculated. We varied the temperature at three different temperatures, which were at 40, 50 and 60 degree C. We kept the flow rate of both reactants at 0.2 L/min. The results show that the relationship between the temperatures with the conversion is the higher temperature the higher the percentage of conversion. This experiment also shows that the reaction rate constant, k is dependent on the temperature. The value of activation energy obtained was 748.91 J. Overall result shows that the objective of the experiment is succeed.

TABLE OF CONTENTPAGEABSTRACT 1TABLE OF CONTENT 2INTRODUCTION 3OBJECTIVE 4THEORY 4APPARATUS 6PROCEDURE 7RESULTS 9SAMPLE OF CALCULATION 11DISCUSSION 14CONCLUSION 15RECOMMENDATION 16REFERENCES 16APPENDIXES 17

INTRODUCTIONBased on all industrial sectors, mostly reactor is the main equipment that is used where it changes from the raw materials into the desire products that are needed. The criteria for the good reactor is it produced a high production and also economical. There are many types of reactor depending on the nature of the feed materials and products. The rate of reaction is the most important thing that we are considered in the reactor because it showed the effectiveness of the processing of the reactor. A most common ideal reactor type in chemical engineering is the continuous stirred tank reactor or known as CSTR. CSTR works for all kinds of phases, fluids, liquids, gases and slurries. The CSTR configuration is widely used in industrial applications and in wastewater treatment units such as activated sludge reactors.In a Continuous stirred-tank reactor (CSTR), two types of liquid reactant are mixed in the reactor which is continuously added and a product also is withdrawn simultaneously. The reactants are mixed using propeller. The propeller is embedded with catalyst. The reactants and products have the same condition such as temperature and pressure as well as concentration. Furthermore, the CSTR which is also known as vat-or back-mix reactor and this kind of model used to estimate the key unit operation variables when using a continuous agitated-tank reactor to reach a specified output. CSTR that are used in the experiment, (model: BP 143) is designed for students experiments on chemical reaction in liquid phase which is under adiabatic and isothermal conditions. CSTR consists of two tanks of solutions and one reactor. The model also consists of jacketed reaction fitted in the agitated and condenser. The unit comes complete with vessels for raw materials and products, feed pumps and thermostat that set at 50C. The reactor is modelled in order to perform the saponification reaction where the reaction is occur between the sodium hydroxide, NaOH and ethylacetate, Et(Ac). The saponification process between this compounds produced sodium acetate in a batch and the continuous stirred tank reactor evaluate the rate data needed to design a production scale reactor.As this experiment involved the saponification process, hence, the term saponification will be defined. The term of saponification was the name given to the chemical reaction that occurs when a vegetable oil or animal fat that was mixed with a strong alkali. The products of the reaction are two which was soap and glycerine. Water was also present, but it does not enter into the chemical reaction. The water was only a vehicle for the alkali, which was otherwise a dry powder.

OBJECTIVESThe main purposes of conducting this experiment are:1) To carry out a saponification reaction between NaOH and Et(Ac) in a CSTR 40L.2) To determine the effect of temperature onto the reaction extent of conversion.3) To determine the reaction`s activation energy.

THEORYContinuous Stirrer Tank ReactorCSTR runs at steady state with continuous flow of reactants and products; the feed assumes a uniform composition throughout the reactor, exit stream has the same composition as in the tank.Figure 1

When the CSTR is operated at steady state, the rate of reaction with respect to species A is:

The familiar form known as the design equation for a CSTR is obtained,

If FAo is the molar flowrate of species A fed to a system operated at steady state, the molar flowrate at which species A is reacting within the entire system will be [FAoX]. The molar flowrate of A to the system minus the reaction of A within the system equals the molar flowrate of A leaving the system, FAo. This is shown, mathematically:

The entering molar flowrate FAo is just the product of entering concentration, CAo and the entering volumetric flowrate vo,

Combining both equation before, yields the design equation with a conversion term for CSTR,

Since the exit composition from the reactor is identical to the composition inside the reactor, the rate of reaction is evaluated at the exit condition.

Effect of temperature on reaction

Figure 1: Effect of temperature on rate of reactionIn theory as the temperature increase, the conversion would increase as we kept the runtime of the reactor as a constant. The conversion increases because when the reactor has a high temperature the heat energy would transfer to the particles with less energy. When the particles have achieved the amount of energy needed and collide with other particles with the right orientation would result in a reaction. With the added heat energy would speed this process. This energy that is needed to be overcome is called activation energy. This can be seen from the figure above.

APPARATUS1. Continuous Stirrer Tank Reactor (CSTR 40L) Model: BP 1432. Conical flask3. 50mL burette4. 200 mL beaker5. Solution: Sodium Hydroxide, NaOH (0.1M) Ethyl Acetate, Et(Ac) (0.1M) Deionized water Phenolphthalein

PROCEDUREGeneral Start-up Procedure1. The following solution were prepared: 40L of sodium hydroxide, NaOH (0.1 M) 40 L of ethyl acetate, Et (Ac) (0.1M) 1 L of hydrochloric acid, HCl (0.25M) , for quenching.2. All valves were initially closed.3. The feed vessels were charged as follows: The charge port caps for vessels B1 and B2 were opened. The NaOH solution was carefully poured into vessel B1 and Et (Ac) solution was poured into vessel B2. The charge port caps for both vessels were closed4. The power for control panel was turned on.5. Sufficient water in thermostat T1 was checked. Refill as necessary.6. Cooling water V13 was opened and is let to flow through condenser W1.7. The overflow tube was adjusted to give a working volume of 10L in the reactor R1.8. Valves V2, V3, V3, V7, V8 and V11 were opened.9. The unit was ready for experiment.Preparation of Calibration Curve for Conversion vs. Conductivity1. The following solution were prepared: 1 L of sodium hydroxide, NaOH (0.1M) 1 L of sodium acetate , Et (Ac) (0.1M) 1 L of deionized water, H2O.2. The conductivity and NaoH concentration for each value were determined by mixing the following solution into 100 mL of deionized water. 0% conversion : 100 mL NaOH 25% conversion : 75 mL NaOH + 25 mL Et (Ac) 50% conversion : 50 mL NaOH + 50 mL Et (Ac) 75% conversion : 23 mL NaOH + 75 mL Et (Ac) 100% conversion : 100 mL Et (Ac)

Back Titration Procedures for Manual Conversion Determination:1. A burette was filled up with 0.1 M NaOH solution.2. 10 mL of 0.25 M HCl 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 the flask to quench the saponification reaction.4. A few drops of pH indicator 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 titrated was recorded.EXPERIMENT 2: Effect of temperature on the Reaction in a CSTR1. The general start-up was performed.2. Pumps P1 and P2 were switched on simultaneously and valves V5 and V10 were opened to obtain the highest possible flow rate into the reactor.3. The reactor is let to fill up with both the solution until it is just overflowed.4. The valves V5 and V10 are readjusted to give a flow rate of 2.0 L/min. Both flow rates are ensured recorded at the same time.5. The stirrer M1 are switched on and the speed are set at about 200 rpm.6. The thermostat T1 is switched on and the water temperature was set to 40 C.7. The conductivity value at Q1-401 was started to monitor and the temperature value at T1-101 until no changed over time. To ensure the reactor had reached to steady state.8. The steady state conductivity and the temperature values were recorded and the concentration of NaOH in the reactor and the extent of reaction of conversion from calibration curve were found.9. Sampling valves V12 was opened and a 50 mL sample was collected. The titration procedures were carried out back to manually determine the concentration of NaOH in the reactor and extent of conversion.10. The experiment was repeated (steps 7 to 10) for different reactor temperatures by setting the thermostat temperature to 50 and 60 C. The flow rate of both solutions was ensured maintained at 0.20 L/min.

General Shut-down Procedure1. 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 was switched off.3. The thermostat T1 was switched off. The liquid in the reaction vessel R1 was let to cool down to room temperature.4. Cooling water V13 was closed.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.

RESULTCalibration table:Conversion (%)VolumeConcentration of NaOH (M)Conductivity (mS/cm)

0.1M NaOH0.1M Et(Ac)H2O

0100 mL-100mL0.05007.66

2575mL25mL100mL0.03755.40

5050mL50mL100mL0.02502.90

7525mL75mL100mL0.01251.30

100-100mL100mL0.00000.16

Reactor Volume : 40LConcentration of NaOH in feed : 0.1MConcentration of Et(Ac) in feed : 0.1MSpeed of blade : 205 rpmTemperature (C)Flow rate of NaOH (mL/min)Flow rate of Et(Ac) (mL/min)Total flowrate of solution,Fo (mL/min)Conductivity (mS/cm)

400.20.20.42.19

500.20.20.41.82

600.20.20.41.69

Back-titration table:Temperature (C)Amount of NaOH reacted (mL)

1st Titration2nd TitrationAverage

4020.820.020.40

5020.920.020.45

6020.621.020.75

Temperature (C)Exit concentration of NaOH,CNaOH (M)Conversion, X (%)k (L/mol-1 min-1)

400.009290.80.9870

500.009190.90.9989

600.008591.51.0765

Graph 2: Conversion, X against reactor temperature, T

Graph 3: ln k against 1/T

SAMPLE OF CALCULATIONConversionFor temperature of 50 C:Moles of reacted NaOH, n1:n1= Concentration NaOH x Volume of NaOH titration = 0.1M x 0.02045 L = 0.002045 moleMoles of unreacted HCl, n2Moles of unreacted HCl = Moles of reacted NaOHn2 = n1n2 = 0.002045 moleVolume of unreacted HCl, V1 = = 0.00818 LVolume of reacted HCl, V2V2 = Total volume of HCl V1 = 0.01 0.00818 = 0.00182 LMoles of reacted HCl, n3n3 = Concentration of HCl x V2 = 0.25 x 0.00182 = 0.000455 moleMoles of unreacted NaOH, n4n4 = n3 = 0.000455 moleConcentration of unreacted NaOH, CACNaOH, unreacted = = = 0.0091 MXunreactedXunreacted = = = 0.091XreactedXreacted = 1 - Xunreacted= 1 0.091= 0.909Conversion for temperature 50C0.909 x 100% = 90.9%Thus, at temperature 50C of NaOH in the reactor, about 90.9% of NaOH is reacted with Et(Ac). Other conversions were calculated by the same way, at varying the temperature.

DISCUSSIONContinuous Stirred Tank Reactor (CSTR) is a type of reactor where the contents are uniform throughout the reactor due to its well-stirred nature. It is a real reactor designed to almost match the performance of an ideal reactor. To do that, it continuously stirs the contents of the reactor, which is the reactants, in a certain amount of time so that the products are form uniformly throughout the system. Thus, when a certain amount of sample is obtained from the reactor, it can be assumed that the composition of products in the sample is similar to the composition of product in the reactor.The objective of this experiment is to determine the effect of temperature on the conversion and to conduct saponification process on CSTR 40L. The experiment conducted also to determine the reaction rate constant and activation energy of the process. To minimize any deviation of the results, the flow rate of feed entering the reactor was set at a constant rate of 0.2 L/min for both reactants. Then the experiment was run at three different temperatures starting at 40, 50 and 60 degree C. The result obtain is tabulated and display as a graph in Result section.From the graph of conductivity vs conversion shows that as the conversion increases the conductivity decreases steadily. This is may be due to the products of the reaction increases in the reactor decreases the capability of the solution to flow electricity. Another reason is that as the reaction precedes the concentration of NaOH decreases, this is because the presence of NaOH helps with the electrical flow.From the graph conversion versus reactor temperature shows that the rate of consumption of reactant is steadily increase as increase in reactor temperature. According to the theory related to the effect of temperature to rate of reaction, as the temperature increase, the conversion would increase as we kept the runtime of the reactor as a constant. The conversion increases because when the reactor has a high temperature the heat energy would transfer to the particles with less energy. When the particles have achieved the amount of energy needed and collide with other particles with the right orientation would result in a reaction. With the added heat energy would speed this process. This energy that is needed to be overcome is called activation energy.In order to determine the value of the activation energy of the process using Arrheniuss Law, the graph ln k versus 1/T were plotted. Based on the graph, the slope was -90.074 and the y-intercept is at 2.1136. By using Arrheniuss Law equation as below:

The activation energy, E is calculated based on the slope from the graph. By using gas constant, R= 8.3144 J/mol.K the activation energy, E is 748.91 J.

CONCLUSIONAs the objectives of this experiment is to determine the effect of temperature on the rate of reaction and to observed the reaction rate constant and activation energy of the process. We can conclude that as the temperature is increased it would increase the conversion. In addition to that, with the higher temperature will also give a higher rate of reaction as this was explained in theory where with the higher temperature means that even more energy to be absorbed by the lesser energized particles which in the end increases the collision in the right orientation of the particles. This is also supported by the graph that was obtained from results. This experiment also shows that the reaction rate constant, k is dependent on the temperature. This is because it can be satisfied by the Arrheniuss Law. From this law we can also determine the activation energy from the slope on the graph that had been obtained and also by doing a simple calculation. Overall result shows that the objective of the experiment is succeed.

RECOMMENDATIONThere are several recommendations that can be taken in order to get more accurate result that are:1) To obtain more accurate results, run several trials on CSTR reactor so we can take the average value from each different molar rate.2) Repeat titrations two or three times because a lot of error comes from titration or use another method other than titration.3) Make sure that the reactor and tubing are cleaned properly after end the experiments.4) During titration, students should be more alert and carefully because the volume of NaOH that will convert the solution to light pink colour are the most important. Thus, the excess of drop of NaOH will give effect on the result in the calculations.5) Titration should be immediately stopped when the indicator turned light pink.

REFERENCESLaboratory Manual Plug Flow Reactor.Fogler, H.S (2006). Elements of Chemical Reaction Engineering (3rd Edition). PrenticeHall.Fundamentals of Chemical Reactor Theory (Retrieved from, http://www.seas.ucla.edu/stenstro/Reactor.pdf on the 20th April 2015).McCabe. (2005). Unit Operations of Chemical Engineering.

APPENDIXES

Continuous Stirrer Tank Reactor (CSTR 40L) Model: BP 1431