Determination of Rate of Evaporation (Autosaved)

CHE151-1L Chemical Engineering Laboratory 2 1st Quarter SY 2017-2018

Determination of the reaction rate constant and activation energy in a continuous stirred tank reactor

Correia, Feliciana, Maria; Evidente, Ralph Carlo T.; Guillermo, Jollana Dianne A.; Lat, Dheya Kristalyn O. CHE151-1L/A11, School of Chemical Engineering and Chemistry, Mapúa University

INTRODUCTION

the reactor [2,3]. Thus, the temperature and concentration in exit steam are modelled as  being the same as those inside the reactor.

Continuous-flow reactors are widely used in chemical and biological processes for  bulk production. They transfer material as flowing stream whereas reactants are continuously fed to the reactor and exit as continuous stream of product. The three types of continuous-flow reactors are the continuous stirred tank reactor (CSTR), plug-flow reactor (PFR), and the packed bed reactor (PBR) [1]. The most basic and commonly used type of continuous-flow reactor in industrial  processes is the continuous operated stirred tanks. It is generally referred to as continuousstirred tank reactor (CSTR) or back-mix reactor [1] . CSTR is an open system wherein materials are allowed to enter and exit the system. Also, it operates in steady-state basis wherein the conditions are constant throughout the process [2] . CSTR is mainly used for liquid reactions wherein one or more reactants in a solution or slurry are fed into the reactor and the products are continuously removed. The reactor is equipped with a stirrer or an impeller to stir the reactants vigorously for uniform composition as shown in Figure 1. Also, it is assumed to be perfectly mixed; however, inside the CSTR, there is no time dependence,  position dependence in temperature, the concentration or reaction rate which means every variable is the same at every ever y point inside Experiment 07│ September 16 , 2017

Figure 1. Illustration of CSTR [3]

In systems where mixing is highly nonideal, the well-mixed model is inadequate, and one must resort to other modelling techniques, such as residence time distributions, to obtain meaningful results. Moreover, since the composition of the  product stream is identical as those in the tank, the reactant concentrations are usually low. CSTR requires the largest volume of reactor type to acquire the desired conversion of reactant to product as shown in Figure 2. In cases wherein the high conversions are needed, several CSTR in series are used [4].

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CHE151-1L Chemical Engineering Laboratory 2 1st Quarter SY 2017-2018

Figure 2. Levenspiel Plot for CSTR [3]

The objectives of this experiment are to determine the following: (1) reaction rate constant, k (2) relationship between the specific rate constant, k, and the temperature of the reaction, and (3) effect of temperature on the activation energy, EA. METHODOLOGY

 Data Gathering The equipment and materials used in the experiment are the continuous stirred tank reactor (CSTR), reagent vessels, 0.1 M sodium hydroxide, and 0.1 M ethyl acetate. Two reagent vessels are first filled with 2.5 liters each of 0.1M NaOH and 0.1M ethyl acetate. The lid of the vessels was then fitted to the tubing of the CSTR set-up. Below is the set-up for experimental CSTR. It consists of (1) two reagent vessels, (2) CSTR, and (3) conductimeter. 1

1

2

CSTR 

Figure 4. Schematic Diagram of CSTR: (1) vessel for NaOH and (2) vessel for ethyl acetate.

For the first part of the experiment, the software was turned on and the experiment with heater was selected. The set point of PID was adjusted to 30℃ and the mode of operation was changed to automatic. Also, the pump speed was set to 50 ml/min flowrate and the concentrations of the solutions were inputted in the software. The power button was then turned on and the pump started to stir the solution. For the second part, the hot water temperature was maintained at 40℃  with the same concentration of NaOH and ethyl acetate as the previous part, but the volume was not limited to 50 mL. In this part, the experiment ended when the temperature of the reactor reached temperature of 40℃. For both parts, conductivity data was collected until steady state condition was already reached. Treatment of Results

3 2 Figure 3. Experimental CSTR set-up Experiment 07│ September 16 , 2017

The recorded data of conductivity of the solution in the reactor over time was translated into degree of conversion of the constituents. Through Microsoft Excel, required values to compute for concentrations of NaOH and ethyl 2 of 3

CHE151-1L Chemical Engineering Laboratory 2 1st Quarter SY 2017-2018

acetate was determined using the formula shown below.  =

  + 

REFERENCES

[1] Geankoplis, C.J. (2003). Principles of Transport and Separation Processes [2] Gutierrez, C., & Ngo, R. (2005). Chemical Engineering Laboratory Manual Part 2. Mapua Institute of Technology.

Perry, R.H., & Green, D.W. (2008). Perry’s Chemical Engineers’ Handbook. 8th  ed. New [3]

YorkL McGraw Hill. [4] Geankoplis, C. (1993). Transport Processes and Unit Operations 3rd  Ed. New Jersey: PTR Prentice-Hall, Inc. pp. 520-521.

Experiment 07│ September 16 , 2017

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CHE151-1L Chemical Engineering Laboratory 2 1st Quarter SY 2017-2018

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