Plug Flow Reactor

Topics: Rate equation, Time, Reaction rate Pages: 9 (886 words) Published: April 23, 2014
1. Experimental Methods
The aims of this experiment to determine the rate of the reaction by using tubular flow reactor data, to demonstrate the temperature dependence of the reaction and also the rate constant and to observe the effect of different flow rates to the conversion. It is a homogenous reaction with only liquid phase is present. Also the reaction is endothermic. The saponification reaction is as follows; NaOH + EtOAc NaOAc + EtOH

The reactants were taken as 1:1 ratios. 0.1 M NaOH and 0.1 M EtOAc was taken as reactants. The tank volume is 141 mL, the length of the reactor is 20 m and the diameter of the reactor is 1 mm. Reactor is placed in a water bath to keep the temperature constant during the reaction. There is a thermocouple to measure the temperature. To maintain uniform temperature everwhere inside the water bath a stirrer is used.There are two feed tanks which continuously feed reactants to the reactor. The reactants which are NaOH from Tank1 and EtOAc from Tank2 are sent to the reactor with two different pumps. There is a valve that the sample is taken at the bottom of the system. In this report the first week of the experiment was explained. The concentration of NaOH was unknown therefore, it was necessary to determine concentration of it. This was achieved by titrating NaOH with 0.1M HCl. After determining the concentration of NaOH, calibration of rotameters was done. Calibration is important to prevent instrumental errors thus calibration of flowrates of both NaOH and EtOAc. A calibration curve was constructed for both reactants. By using these calibration curves four flow rates for determined for both reactants by keeping 1:1 ratio of the reactants. Space times for these flowrates were determined. Samples were taken at the end of each space time and by using back titration method how much NaOH remained unreacted was determined. This was continued until steady state is reached for each space time. In back titration, 10 mL of HCl is added to the sample which is taken from the reactor to stop the reaction. Phenolphthalein is added as indicator. After that the solution is titrated with NaOH. By that how much HCl is used to neutralize the unreacted NaOH is found. From there conversion can be calculated easily.

2. Results
2.1 Calibration Curve Calculations
Before starting to the experiment, calibration curves for rotameters of NaOH and EtOAc were drawn to find flow rate to be able to determine the actual flow rate. The samples were taken for NaOH and EtOAc for different values of rotameters for 1 minute. The data are presented in the Table 2.1. and Table 2.2 Rotameter

Reading
( mL/min )

First Sample
( mL/min )

Second Sample
( mL/min )

Average
( mL/min )
20
24
24
24
40
51
51
51
60
78
78
78
80
102
102
102
100
132
129
130.5
120
150
150
150

Table 2.1 : Rotameter Readings for Tank 1 (NaOH)
Rotameter
Reading
( mL/min )

First Sample
( mL/min )

Second Sample
( mL/min )

Average
( mL/min )
20
24
24.9
24.45
40
51
51
51
60
84
84
84
80
111
114
112.5
100
138
138
138
120
177
174
175.5

Table 2.2 : . Rotameter Readings for Tank 2 (EtOAc)

By using tables calibration curves are obtained in the Figure 2.1. for NaOH and Figure 2.2. for EtOAc .

Figure 2.1 : Calibration curve of NaOH Rotameter

Figure 2.2 : Calibration curve of EtOAc Rotameter
2.2 Rate Law Determination
For the experiment, 0.1 M NaOH,EtOAc and HCL is used.The experiment is performed four different flow rates which are 30, 60, 90 and 120 ml/min at 25 ˚C.The space time is calculated for these four different flow rates by using this formula;

The space times are calculated for each flow rate. It is shown in Table 2.3. Total Inlet Flow Rate (mL/min)
Space Time (min)
30
4.7
60
2.35
90
1.57
120
1.175

Table 2.3 : Space time values for each flowrate

In the experiment, rotameters were arranged at a specific flow rate for both NaOH...
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