DISCUSSION The aim of this experiment is to t o investigate about saponification reaction by using Continuous Stirred Tank Reactors (CSTR) 40L. This experiment has been conducted to carry out saponification reaction between NaOH and Et(Ac) to determine the effect of residence time onto the reaction extent of conversion and the reacti on rate constant. CSTR is a type of reactor where the contents are uniform throughout the reactor due to its well-stirred nature. The reactor variables can be estimated as the CSTR model itself its elf is used to predict the behaviour of chemical reactors. Meanwhile the saponification process itself, is a process to make so ap and it is one of the continuous reaction. It is a process by which triglycerides are reacted with sodium or potassium hydroxide (NaOH or KOH) KOH) to produce glycerol and fatty acid salt called soap, where where in this experiment, the reaction of saponification is quenching with hydrochloric acid to stop the reaction. The reaction quickly reacts, and back titration is done to investigate the volume reacted. From the data collected and calculated from the experiment, three graphs need to be plotted which are conductivity versus conversion for manually conversion experiment and conversion X versus residence time for reaction in CSTR. In addition, calibration curve, (graph 1) also need to be plotted as the conductivity of the reaction between NaOH and Et (Ac) at certain percentage of conversion need to be determined. determined. The y-intercept from the graph is determined at 106.66% conversion. The reaction of saponification in this experiment is process that based on the principle of quenching the sample with excess acid (hydrochloric acid) to stop further reactions then back titration is used to determine the amount of unreacted acid. From the calculation, it is proven that when the volumetric flow rate decreased, the value of conversion is increased. All the calculated data had proved that the theory form from the calibration curve. From graph 2, we can see that the conversion, X decrease proportionally as the total flow rate increased. The conductivity meanwhile did not show pattern in the data collected as the value of conductivity decreased from total volume flowrate of 100 to 200 mL/min and then start to increase until 600 mL/min. The graph plotted is not as expected from the theory which the conductivity should be decreased as the total volume flowrate increased. This is because when fluid entering the reactor at time t, it will exit at time t + τ, as the residence residence time, τ is time that the fluid elements spend within reactor. The higher the flow rate, the time of reactant spend time in the reactor should be lesser les ser than lower flow rate. The slight error e rror in the experiment lead to the result error. The experiment can be successfully done if some of the error can be avoided. The total volume flow rate need to be accurate ac curate as we need to always keep our eye on the valve V5 and V10 to get the constant and similar flow rates of both NaOH and Et (Ac). The valve, if not controlled can lead to the non-accurate reading r eading of the conductivity. From graph 3, which is conversion versus residence time, we can conclude that the conversion increased as the residence time increased. The highest conversion, 98.2% occur at the highest residence time which is 45 min. From the calculated result, the reaction rate constant is decrease as the volumetric flow rate is increase. And when the reaction rate constant increase, the rate of reaction will decrease. The rate of reaction is highest which is r A= 0.00133 mol/L.min at the lower rate constant which is k = 39.42 L/mol.min. the reaction is second order and the rate law is r A = kCACB. The higher the k value, more volume of NaOH require to convert a mole of NaOH in 1 second.
CONCLUSION As a conclusion, the objectives of this experiment are to determine t he effect of residence time onto the reaction extent of conversion as well as reaction rate constant. The reaction rate constant is well determined and recorded as a data in the result section. As we can see, the highest reaction rate constant is 606.17 L/mol.min when the flowrate is 200 mL/min. The lowest reaction rate constant, which is 39.42 L/mol.min occur when the flowrate is 600 mL/min. We can conclude that the higher the flowrate, the lower the reaction rate constant. From the graph conversion versus residence time, we can conclude that the conversion increased as the residence time increased. Lastly, the rate of reaction will decrease, if reaction rate constant increased.
RECOMMENDATION The percentage of the error will be minimized during this experiment as long as there are some recommendations as to improve the performance and precaution being considered during the experiment. During this experiment, some errors were found out that affect the performance of the reaction process. It is recommended that the sample is supposedly titrated immediately since the conversion is calculated from the titrated sample. Due to late titration of the sample, the samples start to decompose then affect the conversion value. Furthermore, titration should be immediately stopped when the indicator turned light pink because it is the point where it reached equivalent point. In addition, when the sample is being collected, the first millimetres should be thrown away, for it is the remaining of the previous sample trapped in the pipe. The total volume flow rate need to be accurate as we need to always keep our eye on the valve V5 and V10 to get the constant and similar flow rates of both NaOH and Et (Ac). The valve, if not controlled can lead to the non-accurate reading of the conductivity. It is recommended that the time taken for taking sample is increased so that the conversion value will be higher. Follow the concept of CSTR, the longer the time the higher the conversion value. During conducting experiment, the safety precaution especially wearing all PPE should be applied so that any accident during experiment will be prevented.
