LABORATORY MODULE PTT 255/3 REACTION ENGINEERING SEMESTER 2 (2018/2019)

Transcription

1 LABORATORY MODULE PTT 255/3 REACTION ENGINEERING SEMESTER 2 (2018/2019) Dr. Ng Qi Hwa Dr. Noor Hasyierah Mohd Salleh Dr Azalina Mohamed Nasir Khairunissa Syairah Ahmad Sohaimi Mr. Mohd Qalani Che Kasim Faculty of Engineering Technology University Malaysia Perlis

2 CONTENT CONTENT CLEANLINESS AND SAFETY LABORATORY GUIDELINE ii iii v EXPERIMENT 1 : INTRODUCTION TO THE LABORATORY SAFETY 1 EXPERIMENT 2 : EFFECT OF FLOW RATE ON THE REACTION 4 IN A CONTINUOUS STIRRED TANK REACTOR (CSTR) EXPERIMENT 3 : EFFECTS OF FLOW RATE AND REACTION 11 TEMPERATURE ON CONVERSION IN A TUBULAR REACTOR EXPERIMENT 4 : DETERMINATION OF REACTION RATE 18 CONSTANT AND REACTION ORDER IN BATCH REACTOR EXPERIMENT 5 : EFFECT OF TEMPERATURE ON REACTION 25 AND REACTION S ACTIVATION ENERGY FOR BATCH REACTOR. EXPERIMENT 6 : EFFECT OF RESIDENCE TIME ON 33 THE REACTION IN CATALYTIC TUBULAR REACTOR EXPERIMENT 7 : EFFECT OF PULSE CHANGE IN INPUT 44 CONCENTRATION TO THE CONCENTRATION OF SOLUTE IN STIRRED TANK REACTOR (CSTR) IN SERIES iii

3 CLEANLINESS AND SAFETY CLEANLINESS The Reaction Engineering Laboratory contains equipment that uses water or chemicals as the fluid. In some cases, performing an experiment will unavoidably allow water/chemicals to get on the equipment and/or on the floor. There are housekeeping rules that the user of the laboratory should be aware and abide by. If no one cleaned up their working area after performing an experiment, the lab would not be a comfortable or safe place to work in. Consequently, students are required to clean up their area at the conclusion of the performance of an experiment. Cleanup will include removal of spilled water (or any liquid) or chemicals wiping the table top on which the equipment is mounted The lab should always be as clean as or cleaner than it was when you entered. Cleaning the lab is your responsibility as a user of the equipment. SAFETY This is to serve as a guide and not as a comprehensive manual on safety. Every staff/student has, at all time, a duty to care for Health and Safety of himself/herself and of all people who may be affected by his/her action. PROTECTIVE CLOTHING Lab coat MUST be worn all times. Rubber gloves should be worn when handling corrosive materials, and heat-proof gauntlets when discharging any equipment involving heat. FOOTWARE Wear fully covered shoes with strong grip. EYE PROTECTION Goggles must be used whenever necessary especially when dealing with high pressure equipment. iv

4 ELECTRICITY Sometimes the floor may be wet. Therefore, care is essential. Always switch off power before removing plugs from sockets. CABLES AND HOSES Cables must be suspended and not lying on the floor. All cables and hoses should be routed to avoid walk-ways. BROKEN GLASS This should be disposed off in the glass bin, not in the usual waste bin. Breakage should also be reported to the Instructor in charge. INSTRUCTION SHEETS Any appropriate instruction sheets should be studied before starting the experiment. Particular attention should be given to the recommended precautions, start-up procedure and sequence of operation. There should be NO EATING in the laboratory. Smoking is strictly prohibited in all laboratories. In case of emergency, report to the Instructor in charge or doctor/ambulance/fire fighter from: Hospital Tuanku Fauziah, Kangar Bomba Perlis SAFETY FIRST iv

5 LABORATORY GUIDELINE BRING ALONG: Lab manual Lab coat Shoes (no sandals are allowed) Neat and suitable clothes Necessary stationeries (calculator, pen, marker pen ) Lab Report (Front cover, Objectives, Flowchart, Lab sheet) MUST: Discipline punctual Ready for the experiment read and understand the procedures Be in group and gather at the experiment station as scheduled Participate in the lab activity LABORATORY SAFETY AND CONDUCT EVALUATION Submit the result data (to be stamped by lecturer/teaching engineer) by end of each lab session v

6 EXPERIMENT 1 INTRODUCTION TO THE LABORATORY SAFETY 1.0 OBJECTIVE 1.1 To identify applicable safety measures in performing the reaction engineering laboratory practice. 1.2 To determine the necessary precautions prior to usage of reaction engineering learning apparatus. 2.0 COURSE OUTCOME CO1: Ability to DEMONSTRATE the principles of chemical reaction engineering design for industrial reactors. 3.0 INTRODUCTION TO LABORATORY SAFETY The Engineering Laboratory contains equipment that use chemicals and water as the fluid. In some cases, performing an experiment will inevitably allow water and chemicals to get on the equipment and/or on the floor. Thus, the most basic practice in maintaining safe working environment is to ensure that the workplace is well kept clean and organized at all times. Laboratory users are required to clean up their work area at the end of every experiment performed. Cleanup will include, but not limited to, removal of spilled liquid and wiping the table top on which the equipment is mounted. However, it is imperative that the lab should always be kept clean as practicably possible, even during the experimental run. Beside cleanliness, the use of personal protection equipment (PPE) is also vital to ensure one s safety during the experimental run. PPE is considered as the last resort protection and should be selected appropriately. PPE must be properly fitted, tested, cleansed, maintained and stored. Comfortable PPE will ensure the efficiency of its usage towards protecting the users from specific hazards. 1

7 PROTECTIVE CLOTHING Lab coat MUST be worn all times. Rubber gloves should be worn when handling corrosive materials, and heat-proof gauntlets when discharging any equipment involving heat. FOOTWARE Wear fully covered shoes with strong grip. EYE PROTECTION Goggles must be used whenever necessary especially when dealing with high pressure equipment. ELECTRICITY Sometimes the floor may be wet. Therefore, care is essential. Always switch off power before removing plugs from sockets. CABLES AND HOSES Cables must be suspended and not lying on the floor. All cables and hoses should be routed to avoid walk-ways. BROKEN GLASS This should be disposed off in the glass bin, not in the usual waste bin. Breakage should also be reported to the Instructor in charge. INSTRUCTION SHEETS / LAB PROCEDURES Any appropriate instruction sheets or lab procedures should be studied before starting the experiment. Particular attention should be given to the recommended precautions, start-up procedure and sequence of operation. 3.1 REACTOR ENGINEERING LEARNING APPARATUS The apparatus for the reaction engineering laboratory is listed as follows: i. Continuous-Stirred Tank Reactor ii. Tubular Flow Reactor iii. Batch Reactor iv. Catalytic tubular reactor v. Continuous stirred tank reactor (CSTR) in series. 4.0 EXPERIMENTAL PROCEDURES 1. Based on the physical appearance of the apparatus, assembly of equipment such as pumps and tanks, and connections of piping, fittings and gauges at each apparatus: a) Identify the necessary PPE to be utilized during the experimental run b) Analyze all safety sign in the laboratory 2

8 c) Develop the general start-up and shutdown procedures as well as other necessary precautions for the apparatus. 5.1 RESULTS AND DISCUSSIONS 1. Write the general laboratory Safety and health regulations in Reaction Engineering Laboratory. 2. Present your findings in section 4.0 (No.1) in a tabulated manner. 3. Discuss the first aid measures for each chemical that you will used in the laboratory (Refer to Material Safety Data Sheet, MSDS). 6.0 CONCLUSION Conclude your findings related to importance of laboratory safety. 3

9 EXPERIMENT 2 EFFECT OF FLOW RATE ON THE REACTION IN A CSTR 1.0 OBJECTIVE 1.1 To carry out a saponification reaction between NaOH and Et(Ac) in a CSTR. 1.2 To determine the effect of flow rate on the extent of conversion. 1.3 To determine the reaction rate constant. 2.0 CORRESPONDING COURSE OUTCOME CO 1- Ability to DEMONSTRATE the principles of chemical reaction engineering design for industrial reactors. 3.0 INTRODUCTION The SOLTEQ Reactor Basic Unit (CSTR) (Model: BP 400) has been designed for students experiments on chemical reactions in liquid phase under isothermal condition. The unit comes complete with a glass reactor, individual reactant feed tanks and pumps, temperature sensors and conductivity measuring sensor. The reactor will enable students to conduct the typical saponification reaction between ethyl acetate and sodium hydroxide among other types of reaction. 4.0THEORY 4.1 CONTINUOUS-STIRRED TANK REACTOR As with all continuous flow reactors, CSTRs are almost always operated at steady state. In addition, the contents inside the reactor are assumed to be perfectly mixed. As a result, there is no time or position dependence of the temperature, concentration or reaction rate inside the CSTR. Therefore, all variables are the same at any point within the reaction vessel. From the general mole balance equation, Eq. (1) So, the design equations for the continuous-stirred tank reactor. Eq. (2) 4

10 Figure 1: Mole balance on a CSTR 4.2 CONVERSION IN CONTINUOUS-STIRRED TANK REACTORS In chemical reactions, it is often that one of the reagents deplete before the others. When this occurs, the reaction ceases, and thus this reagent is termed the limiting reagent. In most instances, it is best to choose the limiting reagent as the basis of stoichiometric calculations. Consider a general reaction Eq. (3) where the uppercase letters represent chemical species and the lowercase letters represent stoichiometric coefficients (moles). Suppose that species A were to be the limiting reagent, we then divide the reaction expression by the coefficient of species A, to obtain Eq. (4) Now that the other chemical species are on a per mole of A basis, we would then want to know how far the reaction proceeds to the right, or how many moles of A are consumed to form one mole of C. These can be determined by defining a parameter called conversion. The conversion of chemical species A is simply the number of moles of A that have reacted per mole of A fed into the system. Eq (5) 5

11 4.3 SAPONIFICATION OF ETHERS WITH SODIUM HYDROXIDE Now that we understand the basic chemistry and chemical engineering involved in chemical reactors, consider a chemical reaction between an ether and sodium hydroxide. This process is also known as saponification. The reaction is reversible, and is described by The acetic ether (ethyl acetate) molecules split into acetate ions and ethanol molecules, consuming hydroxide ions provided by the sodium hydroxide in the process. The progress of the reaction can thus be tracked accurately by the change in hydroxide ions. This can be observed by the conductivity change in the reactor vessel, since the presence of hydroxide ions increase the conductivity in a solution. 5.1 MATERIALS AND EQUIPMENT 5.2 Description of Apparatus Figure 2: Unit construction for Single CSTR reactor 5.3 Description and Assembly Before operating the unit and running experiments, students must familiarize themselves with every components of the unit. Please refer to Figure 2 to understand the process. 6

12 1. Reactor (R1) 3.0-L vessel made of borosilicate glass Internal cooling coil 2 Cartridge type heaters (500 W) Stainless steel impeller 2. Stirrer (M1) Medium duty general purpose motor Power: 24V d.c. / 75 W Max. speed: 230 rpm, steplessly adjustable by hand Max torque: 200 mnm 3. Feed tanks (B1, B2) 35-L cylindrical tank made of stainless steel 4. Pumps (P1, P2) Diaphragm pumps Max delivery rate: LPM Max pressure: 25 psi Power: 12V d.c. 5. Instrumentation Temperature measurement (TIC-101) Flow measurement (FI-201, FI-202) Conductivity measurement (QI-301) 5.4 Valves and Instruments List Valves list: Tag V1 V2 V3 Location Drain valve for feed tank B1 Inlet valve for pump P1 By-pass valve from P1 to tank B1 V4 Needle valve for liquid flow regulating at FI 201 V5 V6 V7 Drain valve for feed tank B2 Inlet valve for pump P2 By-pass valve from P2 to tank B2 V8 Needle valve for liquid flow regulating at FI 202 V9 V10 V11 Drain valve for CSTR Reactor R1 Sampling valve Inlet port for cooling water into reactor 7

13 6.1 PROCEDURES 6.2 Preparation of Calibration Curve for Conductivity vs. Conversion Prepare the following solutions: a) 1 liter of sodium hydroxide (0.1 M) b) 1 liter of sodium acetate (0.1 M) c) 1 liter of deionised water, H 2O Determine the conductivity and NaOH concentration for each conversion value by mixing the following solutions into 100 ml of deionised water. 0% conversion : 100 ml NaOH 25% conversion : 75 ml NaOH + 25 ml Na(Ac) 50% conversion : 50 ml NaOH + 50 ml Na(Ac) 75% conversion : 25 ml NaOH + 75 ml Na(Ac) 100% conversion : 100 ml Na(Ac) Tabulate all data in the table of Appendix B Start up Ensure that all valves are initially closed except by-pass valves V3 and V Fill feed tank B1 with the NaOH solution and feed tank B2 with the Et(Ac) solution. Close the feed tanks Turn on the power for the control panel Adjust the overflow tube to give working volume of 1 liter in the reactor R Open valves V2 and V The unit is now ready for experiment. 6.3 Experiment Effect of Flow Rate On The Reaction In A CSTR Switch on both pumps P1 and P2 simultaneously and open valves V4 and V8 to obtain the highest possible flow rate into the reactor Let the reactor fill up with both the solution until it is just about to overflow. Adjust the overflow tube to achieve level of the mixture solution which is 1 liter Set the flow rate of about 200 ml/min at both flow meters. Make sure that both flow rates are the same. Set the temperature controller at 30 o C Switch on the stirrer and set the speed to about 200 rpm. 8

14 Start monitoring the conductivity value until it does not change over time. This is to ensure that the reactor has reached steady state Record the steady state conductivity value Repeat the experiment (steps 3 to 6) for different flow rates by adjusting the feed flow rates of NaOH and Et(Ac) at 100 ml/min. Make sure that both feed flow rates are the same Switch off the main power switch and dosing pump Drain chemicals in the reactor vessels and the waste tank. 7.0 RESULTS 7.1 Record all the results in appropriate tables. 7.2 Plot graph of conductivity vs. conversion, conductivity vs. concentration NaOH. 7.3 Plot a graph of conversion vs. time. 7.4 For different flow rates, calculate the value of the reaction rate constant, k and the rate of reaction, -r A. 8.0 DISCUSSION 8.1 Discuss the effect of flow rate on the conversion. 8.2 Discuss appropriate discussion regarding this experiment. 9.0 CONCLUSION 9.1 Based on the experimental procedure done and the results taken draw some conclusions to this experiment. 9

15 APPENDIX A1: Physical Properties of Et(Ac) and NaOH. Property Ethyl Acetate, Et(Ac) Sodium Hydroxide, NaOH Formula CH3COOCH2CH3 NaOH Appearance clear liquid white solid Molecular weight g/mol g/mol Normal boiling point 77.1 C 1390 C Normal melting point C 323 C Density C 2.1 g/ml Refractive index 20 C APPENDIX B1: Sample Table for Preparation of Calibration Curve Conversion 0.1 M NaOH Solution Mixtures 0.1 M Na(Ac) H 2O Concentration of NaOH (M) Conductivity (ms/cm) 0% 100 ml 25% 100 ml 50% 100 ml 75% 100 ml 100% 100 ml 10

16 EXPERIMENT 3 EFFECTS OF FLOW RATE AND REACTION TEMPERATURE ON CONVERSION IN TUBULAR REACTOR 1.0 OBJECTIVE 1.1 To observe and control the operation of a tubular reactor. 1.2 To determine the effects of flow rate and reaction temperature on conversion rate in a tubular reactor. 2.0 CORRESPONDING COURSE OUTCOME CO 1- Ability to DEMONSTRATE the principles of chemical reaction engineering design for industrial reactors. 3.0 INTRODUCTION The tubular reactor, also known as the plug flow reactor (PFR) is a type of continuous flow reactor commonly used in industrial processing. As with all continuous flow reactors, PFRs are almost always operated at steady state. However, the PFR is often used gas-phase reactions, unlike the batch and continuous-stirred tank reactors. As the reactants flow down the length of the reactor in a PFR, they are continually consumed. When modeling a tubular reactor, it is assumed that the concentration varies continuously in the axial direction through the reactor. Subsequently, the reaction rate also varies axially, since it is a function of concentration (except for zero-order reactions). Now, consider a system which the flow field is modeled by that of a plug flow profile (uniform velocity as in turbulent flow). Thus, there should be no radial variation in reaction rate, as shown in Figure 1. Figure 1: Plug-flow tubular reactor 11

17 4.1 THEORY 4.2 Conversion In Tubular Reactors General mole balance equation: There are two ways we can use to develop a design equation for the PFR; the first involves differentiating the general mole balance equation with respect to volume V, while the second method is by performing a mole balance on species j in a small volume ΔV (as shown in Figure 2). For the second method, the differential volume will be chosen such that there are no spatial variations in reaction rate within this volume. Figure 2: Mole balance on species j in a differential volume ΔV The generation rate, ΔGj would then be 12

18 4.3 Saponification of Ethers with Sodium Hydroxide Now that we understand the basic chemistry and chemical engineering involved in chemical reactors, consider a chemical reaction between an ether and sodium hydroxide. This process is also known as saponification. The acetic ether (ethyl acetate) molecules split into acetate ions and ethanol molecules, consuming hydroxide ions provided by the sodium hydroxide in the process. The progress of the reaction can thus be tracked accurately by the change in hydroxide ions. This can be observed by the conductivity change in the reactor vessel, since the presence of hydroxide ions increase the conductivity in a solution. As the conversion increases, the hydroxide ions depletes to form ethanol, and this should be observed by a decrease in conductivity. 5.1 MATERIALS AND EQUIPMENTS 5.2 Description of Apparatus The Tubular Flow Reactor is used for demonstrating the basics of chemical processing in tubular flow reactors. The apparatus is comprised of a stainless steel top to accommodate 2 glass feed tanks, a workspace to mount the chemical reactor, a hot water reservoir and a process control console. The stainless steel base of the console is fitted with 2 peristaltic pumps with speed controls for feeding the reactants, one heater control and one stirrer control unit. Two reactant tanks are provided with heating coils to bring reactants to reaction temperatures before being dosed into a Y joint into the tubular reactor. 13

19 6.1 PROCEDURES 6.2 Preparation of Calibration Curve for Conductivity vs. Conversion Prepare the following solutions: a) 1 liter of sodium hydroxide (0.1 M) b) 1 liter of sodium acetate (0.1 M) c) 1 liter of deionised water, H 2O Determine the conductivity and NaOH concentration for each conversion value by mixing the following solutions into 100 ml of deionised water. 0% conversion : 100 ml NaOH 25% conversion : 75 ml NaOH + 25 ml Na(Ac) 50% conversion : 50 ml NaOH + 50 ml Na(Ac) 75% conversion : 25 ml NaOH + 75 ml Na(Ac) 100% conversion : 100 ml Na(Ac) Tabulate all data in the table of Appendix A2. 14

20 6.3 General Start-up Procedures Fill the chemical tanks until 80% full Fill the rear left tank with 0.1 M ethyl acetate solution and the rear right tank with 0.1 M sodium hydroxide solution. Safety Caution: ALWAYS use the LEFT tank for the ethyl acetate solution, as the pump for the left tank is specially designed for the chemical. Failure to do so may result in damage to the other pump Connect the reactor tank s water inlet and outlet to a water supply and drain respectively Fill the reactor tank with water until the tubular reactor is completely immersed in water. Safety Caution: Do not overfill the reactor tank, as the high pressure water supply may damage the vessel s seal Plug in the 3-pin plug into a power supply and switch on the power Switch on the mains power on the unit Ensure that the heater is set to 45 C Switch on the agitator/mixer, and set the speed to approximately 100rpm Switch on both pumps for the dosing tanks and set the speed for both to 40% Before conducting experiments, ensure that the hot water valves for all tanks are fully closed If all components are working and in order, the system is ready for use. 6.4 Experiment 1: The Effect of Flow Rate on Conversion Rate Set the speed for both dosing pump to 2 L/h and turn on both dosing pumps Take down the reading of conductivity and temperature at the entry and exit of the reactor for every one minute until no conversion at the exit changes Repeat Step and for the speed of 6 L/h Tabulate all data and calculate the conversion at each time interval in the table of Appendix B Experiment 2: The Effect of Reaction Temperature on Conversion Rate Turn on the heater Make sure hot water temperature reaches 50 o C Open all hot water valves Turn on the hot water pump and wait until temperature of the both chemical tanks and the reactor reached 50 o C Start the both dosing pumps and start timer on the stopwatch. 15

21 6.4.6 Take down the reading of conductivity and temperature at the entry and exit of the reactor for every one minute until no conversion at the exit changes Turn off the both dosing pumps and the hot water pump Tabulate all data and calculate the conversion at each time interval in the table of Appendix B Maintenance and Safety Precautions Read the safety instructions thoroughly before conducting the experiment Wear protective gloves and glasses when conducting the experiment Dispose of all unused chemicals in an appropriate manner after the experiment. Under no circumstances should the chemicals be allowed to flow into the main drains Should any of the chemicals come into contact with the body, rinse off immediately with cold water Be alert and careful at all times when conducting the experiment. 6.6 General Shut Down Procedures Switch off the main power switch Switch off the dosing pump. 7.0 RESULTS 7.1 Record all the results in the table (Appendix B3) for every reading taken by conductivity and temperature meter. 7.2 Plot calibration curve graph. (Conductivity vs. conversion; concentration of NaOH vs. conversion). 7.3 Plot a graph of conversion vs. time for all experiments. 8.0 DISCUSSION 8.1 Discuss the effect of flow rate and temperature on conversion and conversion rate through appropriate graphs. 9.0 CONCLUSION 9.1 Based on the experimental procedure done and the results taken draw some conclusions to this experiment. 16

22 APPENDIX A2: Sample Table for Preparation of Calibration Curve Conversion 0.1 M NaOH Solution Mixtures 0.1 M Na(Ac) H 2O Concentration of NaOH (M) Conductivity (ms/cm) 0% 100 ml 25% 100 ml 50% 100 ml 75% 100 ml 100% 100 ml APPENDIX B2: Sample Table for Experiment 1 & 2 17

23 EXPERIMENT 4 Determination of Reaction Rate Constant and Reaction Order in Batch Reactor 1.0 OBJECTIVES 1.1 To observe and control the operation of a batch reactor for saponification reaction between Sodium Hydroxide and Ethyl Acetate. 1.2 To determine the reaction rate constant and reaction order in batch reactor. 2.0 CORRESPONDING COURSE OUTCOME CO2: Ability to ANALYZE and solve various problem related to reactor design and reaction process. 3.0 INTRODUCTION In the majority of industrial chemical processes, reactor is the key equipment in which raw materials undergo a chemical change to form desired products. The design and operation of chemical reactors is thus crucial to the whole success of an industrial process. Reactors can take a widely varying form, depending on the nature of the feed materials and the products. Understanding the behavior of how reactors function is necessary for the proper design, control and handling of a reaction system. Two main types of reactors are batch reactor and continuous flow reactor. The Reactor Basic Unit (Batch Reactor) has been designed for students experiments on chemical reactions in liquid phase under isothermal and adiabatic conditions. The unit comes complete with a glass reactor, constant temperature water circulating unit, temperature and conductivity measurements. Student shall be able to conduct the typical saponification reaction between ethyl acetate and sodium hydroxide. 18

24 4.1 THEORY 4.2 Rate of Reaction and Rate Law. The rate at which a given chemical reaction proceeds can be expressed in several ways. It can be expressed either as the rate of disappearance of the reactants, or the rate of formation of products. In the following reaction, aa + bb cc + dd [1-1] A and B are the reactants, while C and D are the products. a, b, c, d are the stoichiometric coefficients for the respective species. If species A is considered as the reaction basis, then the rate of reaction can be represented by the rate of disappearance of A. It is denoted by the symbol r A. The numerical value of the rate of reaction, r A is defined as the number of moles of A reacting (disappearing) per unit time per unit volume, and has the typical unit of mol/dm 3.s. Similarly, the rate of reaction can also be represented by the rate of disappearance of another species, such as r B and the rate of formation of a product, such as r C or r D. They can be related in the following equation, r A a r B b r C c r D d [1-2] 4.3 Conversion Using the reaction shown in Equation [1-1], and taking species A as the basis of calculation, the reaction expression can be divided through by the stoichiometric coefficient of species A, in order to arrange the reaction expression in the form, A + b c d B C + D [2-1] a a a The expression has now put every quantity on a per mole of A basis. A convenient way to quantify how far the reaction has progressed, or how many moles of products are formed for every mole of A consumed; is to define a parameter called conversion. The conversion X A is the number of moles of A that have reacted per mole of A fed to the system, X A moles of A reacted moles of A fed [2-2] 19

25 Because the conversion is defined with respect to the basis of calculation (species A), the subscript A can be eliminated for the sake of brevity and let X = X A. 4.4 General Mole Balance Equation To perform a mole balance on any system, the system boundaries must first be specified. The volume enclosed by these boundaries will be referred to as the system volume. In this example, a mole balance will be performed on species j in a system volume, where species j represents the particular chemical species of interest. F j0 F j Figure 2: Balance on the system volume. A mole balance on species j at any instant in time, t, yields the following equation, Rate of j Rate of j Rate of j Rate of j into out of produced accumulated system system within system within system volume volume volume volume in out + generation = accumulation F j0 F j + G j = dn j dt [3-1] where N j represents the number of moles of species j in the system at time t. 20

26 5.0 MATERIALS AND EQUIPMENT Valves list: Figure 6: Unit construction for Batch reactor Tag Location Initial position V1 Drain valve for feed tank B1 Closed V2 Inlet valve for pump P1 Closed V3 By-pass valve from P1 to tank B1 Open V4 Needle valve for liquid feed from pump P1 Closed V5 Drain valve for feed tank B2 Closed V6 Inlet valve for pump P2 Closed V7 By-pass valve from P2 to tank B2 Open V8 Needle valve for liquid feed from pump P2 Closed V9 Drain or sampling valve (batch reaction process) Closed V10 Valve for vacuum pump to jacket vessel Closed V11 Valve for cooling water int reactor R1 Closed V12 Drain valve for water bath tank B3 Closed V13 Inlet valve for pump P3 Closed V14 Hot water inlet valve Closed 6.1 PROCEDURES 6.2 Preparation of Calibration Curve for Conductivity vs. Conversion Prepare the following solutions: a) 1 liter of sodium hydroxide (0.1 M) b) 1 liter of sodium acetate (0.1 M) c) 1 liter of deionised water, H 2O 21

27 6.2.2 Determine the conductivity and NaOH concentration for each conversion value by mixing the following solutions into 100 ml of deionised water. 0% conversion : 100 ml NaOH 25% conversion : 75 ml NaOH + 25 ml Na(Ac) 50% conversion : 50 ml NaOH + 50 ml Na(Ac) 75% conversion : 25 ml NaOH + 75 ml Na(Ac) 100% conversion : 100 ml Na(Ac) Tabulate all data in the table of Appendix B General Start-up Procedures Fill the chemical tanks until full Fill the rear left tank with 0.1 M ethyl acetate solution and the rear right tank with 0.1 M sodium hydroxide solution. Safety Caution: ALWAYS use the LEFT tank for the ethyl acetate solution, as the pump for the left tank is specially designed for the chemical. Failure to do so may result in damage to the other pump Plug in the industrial socket into a power supply and switch on the power Switch on the mains power on the control panel Switch on the agitator/mixer, and set the speed to approximately 200rpm Switch on both pumps for the chemical tanks on the control panel Before conducting experiments, ensure that the hot water valves for all tanks are fully closed If all components are working and in order, the system is ready for use. 6.4 Experiment 1: Batch Saponification Reaction of Et(Ac) and NaOH Ensure that all valves are initially closed except liquid feed needle valve of P1 and P Open inlet valves of P1, P2 and P To begin a batch reaction experiment, turn on pump P1 and fully open liquid feed needle valve of P1 to obtain highest possible flow rate into the reactor. Fill the reactor with the NaOH to 800mL of volume. Stops pump P Turn on pump P2 and fully open liquid feed needle valve of P2 to obtained highest possible flow rate into the reactor. Fill the reactor with the Et(Ac) until solution reaches a total of 1.6L. Stops pump P Switch on the stirrer (record the conductivity reading at time, 0) and start the timer immediately. 22

28 6.4.6 Record the conductivity values at 1 minute interval Stop the experiment when the conductivity values remain constant (i.e. steady state condition) Open drain valve and drain all the solution. 7.0 RESULT 7.1 Record all the results in appropriate tables. 7.2 Plot calibration curve graph. (Conductivity vs. conversion; concentration of NaOH vs. conversion). 7.3 Plot a graph of conversion vs. time. 7.4 For an equimolar reaction with the same initial reactants concentration (C A0 = C B0), the rate law is shown to be: where C A is the concentration of NaOH in the reactor at time t. Plot a graph of ln (-dc A/dt) vs. ln (C A) and evaluate the slope and y-axis intercept. 7.5 Determine the order of the reaction, α and the rate constant, k from the slope and intercept values. 8.0 DISCUSSION 8.1 Discuss the reaction rate constant and reaction order in batch reactor. 9.0 CONCLUSION 9.1 Based on the experimental procedure done and the results taken draw some conclusions to this experiment. 23

29 APPENDIX A3: Physical Properties of Et(Ac) and NaOH. Property Ethyl Acetate, Et(Ac) Sodium Hydroxide, NaOH Formula CH3COOCH2CH3 NaOH Appearance clear liquid white solid Molecular weight g/mol g/mol Normal boiling point 77.1 C 1390 C Normal melting point C 323 C Density C 2.1 g/ml Refractive index 20 C APPENDIX B3: Sample Table for Preparation of Calibration Curve Conversion 0.1 M NaOH Solution Mixtures 0.1 M Na(Ac) H 2O Concentration of NaOH (M) Conductivity (ms/cm) 0% 100 ml 25% 100 ml 50% 100 ml 75% 100 ml 100% 100 ml 24

30 EXPERIMENT 5 Effect of Temperature on Reaction and Reaction s Activation Energy for Batch Reactor 1.0 OBJECTIVES 1.1 To observe and control the operation of a batch reactor for saponification reaction between Sodium Hydroxide and Ethyl Acetate. 1.2 To determine the effect of temperature on the extent of conversion. 1.3 To determine the value of the reaction s activation energy. 2.0 CORRESPONDING COURSE OUTCOME CO2: Ability to ANALYZE and solve various problem related to reactor design and reaction process. 3.0 INTRODUCTION In the majority of industrial chemical processes, reactor is the key equipment in which raw materials undergo a chemical change to form desired products. The design and operation of chemical reactors is thus crucial to the whole success of an industrial process. Reactors can take a widely varying form, depending on the nature of the feed materials and the products. Understanding the behavior of how reactors function is necessary for the proper design, control and handling of a reaction system. Two main types of reactors are batch reactor and continuous flow reactor. The Reactor Basic Unit (Batch Reactor) has been designed for students experiments on chemical reactions in liquid phase under isothermal and adiabatic conditions. The unit comes complete with a glass reactor, constant temperature water circulating unit, temperature and conductivity measurements. Student shall be able to conduct the typical saponification reaction between ethyl acetate and sodium hydroxide. 25

31 4.1 THEORY 4.2 Rate of Reaction and Rate Law. The rate at which a given chemical reaction proceeds can be expressed in several ways. It can be expressed either as the rate of disappearance of the reactants, or the rate of formation of products. In the following reaction, aa + bb cc + dd [1-1] A and B are the reactants, while C and D are the products. a,b,c,d are the stoichiometric coefficients for the respective species.if species A is considered as the reaction basis, then the rate of reaction can be represented by the rate of disappearance of A. It is denoted by the symbol r A. The numerical value of the rate of reaction, r A is defined as the number of moles of A reacting (disappearing) per unit time per unit volume, and has the typical unit of mol/dm 3.s. Similarly, the rate of reaction can also be represented by the rate of disappearance of another species, such as r B and the rate of formation of a product, such as r C or r D. They can be related in the following equation, r A a r B b r C c r D d [1-2] 4.3 Conversion Using the reaction shown in Equation [1-1], and taking species A as the basis of calculation, the reaction expression can be divided through by the stoichiometric coefficient of species A, in order to arrange the reaction expression in the form, A + b c d B C + D [2-1] a a a The expression has now put every quantity on a per mole of A basis. A convenient way to quantify how far the reaction has progressed, or how many moles of products are formed for every mole of A consumed; is to define a parameter called conversion. The conversion X A is the number of moles of A that have reacted per mole of A fed to the system, X A moles of A reacted moles of A fed [2-2] 26

32 Because the conversion is defined with respect to the basis of calculation (species A), the subscript A can be eliminated for the sake of brevity and let X = X A. 4.4 General Mole Balance Equation To perform a mole balance on any system, the system boundaries must first be specified. The volume enclosed by these boundaries will be referred to as the system volume. In this example, a mole balance will be performed on species j in a system volume, where species j represents the particular chemical species of interest. F j0 F j Figure 2: Balance on the system volume. A mole balance on species j at any instant in time, t, yields the following equation, Rate of j Rate of j Rate of j Rate of j into out of produced accumulated system system within system within system volume volume volume volume in out + generation = accumulation F j0 F j + G j = dn j dt [3-1] where N j represents the number of moles of species j in the system at time t. 27

33 5.0 MATERIALS AND EQUIPMENTS 5.1 Unit construction for Batch reactor Figure 6: Unit construction for Batch reactor Valves list: Tag Location Initial position V1 Drain valve for feed tank B1 Closed V2 Inlet valve for pump P1 Closed V3 By-pass valve from P1 to tank B1 Open V4 Needle valve for liquid feed from pump P1 Closed V5 Drain valve for feed tank B2 Closed V6 Inlet valve for pump P2 Closed V7 By-pass valve from P2 to tank B2 Open V8 Needle valve for liquid feed from pump P2 Closed V9 Drain or sampling valve (batch reaction process) Closed V10 Valve for vacuum pump to jacket vessel Closed V11 Valve for cooling water int reactor R1 Closed V12 Drain valve for water bath tank B3 Closed V13 Inlet valve for pump P3 Closed V14 Hot water inlet valve Closed 28

34 6.1 PROCEDURES 6.2 Preparation of Calibration Curve for Conductivity vs. Conversion Prepare the following solutions: a) 1 liter of sodium hydroxide (0.1 M) b) 1 liter of sodium acetate (0.1 M) c) 1 liter of deionised water, H 2O Determine the conductivity and NaOH concentration for each conversion value by mixing the following solutions into 100 ml of deionised water. 0% conversion : 100 ml NaOH 25% conversion : 75 ml NaOH + 25 ml Na(Ac) 50% conversion : 50 ml NaOH + 50 ml Na(Ac) 75% conversion : 25 ml NaOH + 75 ml Na(Ac) 100% conversion : 100 ml Na(Ac) Tabulate all data in the table of Appendix B General Start-up Procedures Fill the chemical tanks until full Fill the rear left tank with 0.1 M ethyl acetate solution and the rear right tank with 0.1 M sodium hydroxide solution. Safety Caution : ALWAYS use the LEFT tank for the ethyl acetate solution, as the pump for the left tank is specially designed for the chemical. Failure to do so may result in damage to the other pump Plug in the industrial socket into a power supply and switch on the power Switch on the mains power on the control panel Ensure that the heater is set to 30 C Switch on the agitator/mixer, and set the speed to approximately 200rpm Switch on both pumps for the chemical tanks on the control panel Before conducting experiments, ensure that the hot water valves for all tanks are fully closed If all components are working and in order, the system is ready for use. 29

35 6.3 Experiment : Effect of Temperature on Batch Saponification Reaction of Et(Ac) and NaOH Turn on the heater Set the setpoint of the temperature controller TIC-101 to 30 C (or other desired reaction temperature) Set the setpoint of the temperature controller TIC-102 to about 5 C more than the desired reaction temperature When the bath temperature is reached, open hot water inlet valve and switch on hot water pump. Close liquid feed needle valve for P1 and P2 valves and run pumps P1 and P2 to stir the feeds. Allow the temperatures in both feed tanks to increase. If necessary, adjust the temperature controller setpoint in step above to achieve feed temperature as near as possible to the desired reaction temperature For different reaction temperature, adjust the setpoint of the temperature controller in step and above accordingly Perform the feed pre-heating procedure above for the desired reaction temperature To begin a batch reaction experiment, turns on pump P1 and open liquid feed needle valve of P1 to obtain highest possible flow rate into the reactor. Fill about 800mL of the 0.1 M NaOH into the reactor. Stops pump P1 and close the liquid feed needle valve of P Turns on pump P2 and open liquid feed needle vale of P2 to obtained highest possible flow rate into the reactor. Fill of the 0.1 M Et(AC) until reaction solution reaches 1.6-L. Stops pump P2 and close the liquid feed needle valve of P Switch on the reactor heater and the stirrer (record the conductivity reading at time, 0). Immediately start the timer Record the conductivity values at 1 minute interval Stop the experiment when the conductivity values remain constant (i.e. steady state condition) Switch off the reactor heater Open drain valve and drain all the solution from the reactor Repeat the experiment (steps to ) for different reaction temperatures of 50 and 60 C After finish the experiment, keep the cooling water to continue flowing Switch off pumps P1, P2 and P3. Switch off the stirrer Switch off both reactor and hot water heaters. Let the liquid in the reaction vessel to cool down to room temperature Turn off the power for the control panel Keep the solutions for subsequent experiment. Otherwise, drain all solutions. 30

36 Dispose all liquids immediately after each experiment. Do not leave any solution or waste in the tanks over a long period of time Wipe off any spillage from the unit immediately. 7.0 RESULT 7.1 Record all the results in appropriate tables. 7.2 For a second order reaction, the rate law is shown to be: dc r A A kc 2 A dt C A dc A t C k dt 2 C A0 0 1 C A A kt 1 C A0 where C A0 is the initial concentration of reactant NaOH in the reactor. For each temperature value, plot the graph of 1/C A vs. time, t and evaluate the slope and y- axis intercept. 7.3 Determine the rate constant, k from the slope value for different temperature values. Examine the change in the rate constant. 7.4 Plot a graph of ln k vs. 1/T and evaluate the slope and y-axis intercept. 7.5 Calculate the saponification reaction s activation energy, E and Arrhenius constant, A from the slope and intercept values using the Arrhenius equation. k(t ) Ae E / RT or ln k ln A E (1/ T ) R where E = activation energy [J/mol] A = Arrhenius constant R = universal gas constant = J/mol.K T = absolute temperature [K] 8.0 DISCUSSION 8.1 Discuss the effect of temperature on reaction and reaction s activation energy for batch reactor. 9.0 CONCLUSION 9.1 Based on the experimental procedure done and the results taken draw some conclusions to this experiment. 31

37 APPENDIX A4: Physical Properties of Et(Ac) and NaOH. Property Ethyl Acetate, Et(Ac) Sodium Hydroxide, NaOH Formula CH3COOCH2CH3 NaOH Appearance clear liquid white solid Molecular weight g/mol g/mol Normal boiling point 77.1 C 1390 C Normal melting point C 323 C Density C 2.1 g/ml Refractive index 20 C APPENDIX B4: Sample Table for Preparation of Calibration Curve Conversion 0.1 M NaOH Solution Mixtures 0.1 M Na(Ac) H 2O Concentration of NaOH (M) Conductivity (ms/cm) 0% 100 ml 25% 100 ml 50% 100 ml 75% 100 ml 100% 100 ml 32

38 EXPERIMENT 6 Effect of Residence Time on the Reaction in Catalytic Tubular Reactor 1.0 OBJECTIVES 1.1 To carry out a hydrolysis reaction of Et(AC) in a catalytic packed bed reactor. 1.2 To determine the effect of residence time on the conversion in catalytic packed bed reactor. 2.0 CORRESPONDING COURSE OUTCOME CO3: Ability to EVALUATE the catalytic reaction mechanism and Residence Time Distribution (RTD) functions in reactors. 3.0 INTRODUCTION In the majority of industrial chemical processes, the reactor is the key equipment in which raw materials undergo a chemical change to form desired products. The design and operation of chemical reactors is thus crucial to the whole success of an industrial process. Reactors can take a widely varying form, depending on the nature of the feed materials and the products. Understanding the behaviour of how reactors function is necessary for the proper control and handling of a reaction system. Basically, there are two main groups of reactors, batch reactors and continuous flow reactors. The SOLTEQ Catalytic Packed Reactor (Model: BP 105) has been designed for students experiments on chemical reactions in liquid phase under isothermal and adiabatic conditions. The unit comes complete with a jacketed tubular reactor, reactant feed tanks and pumps, temperature sensors and conductivity measuring sensors. The reactor will enable students to conduct the acid-catalysed liquid-phase hydrolysis of ethyl acetate (EtAC) to ethanol (EtOH) and acetic acid (HAc), using an immobilized anion ion-exchange resin (Amberlyst 15 (dry)) as catalyst: CH 3COOC 2H 5 + H 2O = CH 3COOH + C 2H 5OH Figure 1 illustrates the process flow diagram for the catalytic packed flow reactor unit. 33

39 Figure 1: Process flow diagram for the catalytic packed bed reactor unit. 4.0 THEORY 4.1 Rate of Reaction and Rate Law The rate at which a given chemical reaction proceeds can be expressed in several ways. It can be expressed either as the rate of disappearance of the reactants, or the rate of formation of products. Let the reaction be: A B + D, rate = kc (1) A = ethyl acetate (EtAC), B = acetic acid (HAc), D = ethanol (EtOH). Let C be the EtAC concentration, V be the running volume (neglect the volume occupied by catalyst) of a plug flow reactor of total volume, V F, and Q be volumetric flow rate. Assuming first order reaction, the steady state reactor equation is: dc/dv = -(1/Q)kC, C(0) = C 0 (2) for 0 <= V <=V F And with k the reaction rate constant, assumed to be a function of temperature only. 34

40 Integrating the above equation: C(V F) = C 0exp(-kV F/Q) (3) From stoichiometry, we have: C F = C(V F) = C 0 - C B (4) Where C B is the effluent concentration of acetic acid (mol/l). and C 0 is the feed concentration. From the integrated equation: kv F = ln(c 0/C F) or k = (Q/V F)ln(C 0/C F) (5) where k(t) = b 1exp(-E/RT) which follows Arrhenius equation where E = activation energy, R = gas constant, b 1 = parameter If a plot of ln(k) vs 1/T is drawn, a straight line with slope E/R will be get. 4.2 Conversion Using the reaction shown in Equation (1), and taking species A as the basis of calculation, the reaction expression can be divided through by the stoichiometric coefficient of species A, in order to arrange the reaction expression in the form, A + a b B + a d D (6) The expression has now put every quantity on a per mole of A basis. A convenient way to quantify how far the reaction has progressed, or how many moles of products are formed for every mole of A consumed; is to define a parameter called conversion. The conversion X A is the number of moles of A that have reacted per mole of A fed to the system, moles of A reacted X A (7) moles of A fed Because the conversion is defined with respect to the basis of calculation (species A), the subscript A can be eliminated for the sake of brevity and let X = X A. 4.3 General Mole Balance Equation To perform a mole balance on any system, the system boundaries must first be specified. The volume enclosed by these boundaries will be referred to as the system volume. In this example, a mole balance will be performed on species j in a system volume, where species j represents the particular chemical species of interest. 35

41 F j0 G j F j Figure 2: Balance on the system volume. A mole balance on species j at any instant in time t, yields the following equation, Rate of flow Rate of flow Rate of generationof j Rate of j of j into of j out of by chemical reaction accumulated system system within system within system volume volume volume volume in out + generation = accumulation F j0 F j + G j = dn j (8) dt where N j represents the number of moles of species j in the system at time t. If all the system variables (e.g. temperature and concentration) are spatially uniform throughout the system volume, the rate of generation of species j, G j, is just the product of the reaction volume, V and the rate of formation of species j, r j, G j r jv (9) Suppose that the rate of formation of species j for the reaction varies with the position in the system volume. Thus, the total rate of generation within the system volume is the integral of all the rates of generation in each of the subvolumes, V G r dv (10) j j Therefore, the general mole balance equation for any chemical species j that is entering, leaving, reacting and/or accumulating within any system volume V, is, V dn j Fj 0 Fj r j dv (11) dt From this general mole balance equation, the design equations for various types of industrial reactors such as batch, semibatch and continuous flow reactors can be developed. Upon evaluation of these design equations, the time (batch) or reactor volume (continuous) necessary to convert a specified amount of reactants to products can then be determined. 4.4 Tubular Flow Reactors The tubular flow reactor (TFR) (sometimes called plug flow reactor (PFR)) is also commonly used in industry in addition to the CSTR and batch reactor. It consists of a cylindrical pipe and is normally operated at steady state. For analysis purposes, the 36

42 flow in the system is considered to be highly turbulent and may be modeled by that of plug flow. Thus, there is no radial variation in concentration along the pipe. In the tubular reactor, the reactants are continually consumed as they flow down the length of the reactor. In modeling the tubular reactor, the concentration is assumed to vary continuously in the axial direction through the reactor. Consequently, the reaction rate, which is a function of concentration for all but zero order reactions, will also vary axially. y Δy F A0 F A F A(y) F A(y + Δy) ΔV Figure 3: Tubular flow reactor (TFR) To develop the TFR design equation, the reactor volume shall be divided into a number of subvolumes so that within each subvolume ΔV, the reaction may be considered spatially uniform. Assuming that the subvolume is located a distance y from the entrance of the reactor, then F A(y) is the molar flow rate of A into volume ΔV and F A(y + Δy) is the molar flow rate of A out of the volume. In a spatially uniform subvolume ΔV, V radv rav (12) For a tubular reactor at steady state, the general mole balance is reduced to, dn A dt 0 FA ( y) FA ( y y ) rav 0 (13) In the above expression, r A is an indirect function of y. That is, r A is a function of reactant concentration, which is a function of the position, y down the reactor. The volume, ΔV is the product of the cross-sectional area, A of the reactor and the reactor length, Δy. V Ay (14) Substituting Equation (13) into Equation (12) yields, FA ( y y ) FA ( y ) Ar y A (15) Taking the limit as Δy approaches zero, F ( y y ) F y ( y ) df dy A A A lim Ar A y 0 (16) 37

43 It is usually most convenient to have the reactor volume, V rather than the reactor length, y as the independent variable. Accordingly, the variables Ady can be changed to dv to obtain this form of the design equation for a TFR, df A r (17) A dv Note that for a reactor in which the cross-sectional area, A varies along the length of the reactor, the design equation remains unchanged. This means that the extent of reaction in a plug flow reactor does not depend on its shape, but only on its total volume. If F A0 is the molar flow rate of species A fed to a system operated at steady state, the molar flow rate at which species A is reacting within the entire system will be [F A0X]. The molar feed rate of A to the system minus the rate of reaction of A within the system equals the molar flow rate of A leaving the system, F A. This is shown in mathematical form to be, F A FA 0 FA 0 X FA 0 (1 X ) (18) The entering molar flow rate F A0 is just the product of the entering concentration C A0 and the entering volumetric flow rate v 0, FA 0 C A0v 0 (19) Combining Equation [4-7] and Equation [4-6] yields the design equation with a conversion term for the TFR, dx FA 0 r A (20) dv Rearranging and integrating Equation 19 with the limit V = 0 when X = 0, we obtain the plug-flow reactor volume necessary to achieve a specified conversion X, X dx V FA 0 (21) 0 r A 5.0 DESCRIPTION OF EQUIPMENTS Before operating the unit and running experiments, students must familiarize themselves with every components of the unit. Please refer to Figure 1 to understand the process. Packed Reactor Material : High quality borosilicate glass Volume : approx. 0.6 L Feed tanks Cylindrical vessels made of stainless steel Water de-ionizer fitted to Feed Tank 1 and Feed tank 2 38

44 Product tank Tank made of stainless steel Pre-heater Cylindrical vessel made of stainless steel Internal coils for reactants Feed pumps Type : Peristaltic Pump Max. Speed : 100 rpm Power : 230V/50Hz/1-phase Instrumentations Flow measurements from the Peristaltic Pump 1 & 2 Temperature measurements (TT1 to TT4) Conductivity measurements (Q1, Q2) 5.1 VALVES AND INSTRUMENTS LIST Valves list: Tag Location V1 Feed Tank 1 drain valve V2 Reactants outlet valve from Feed Tank 1 V3 Feed Tank 2 drain valve V4 Reactants outlet valve from Feed Tank 2 V5 Reactants inlet valve into Reactor V6 Reactants drain valve from Reactor V7 Water circulator inlet valve from Water Circulator V8 Deionized water inlet valve into Feed Tank 2 V9 Deionized water inlet valve into Feed Tank 1 V10 Product drain valve from Product Tank V11 Drain valve for water bath circulator Instruments list: Tag Description Units Range Accuracy Q1 Q2 Conductivity in Conductivity out ms/c m ms/c m TT1 Reactor inlet temparature C TT2 Reactor outlet temparature C TT3 Circulator inlet temperature C TT4 Circulator outlet temperature C ± 1% FS ± 1% FS ± 0.5 C ± 0.5 C ± 0.5 C ± 0.5 C 39

45 6.0 PROCEDURES 6.1 Preparation of Calibration Curve for Conductivity vs. Conversion. The reaction to be studied is the hydrolysis reaction of ethyl acetate Et(AC). EtAC EtOH + HAc Since only acetic acid, HAc will conduct electricity, therefore the conductivity value depends on HAc only Prepare the following solutions: a) 1 liter of HAc b) 2 liter of deionized water Prepare 200 ml HAc solution by adding 5 ml HAc into 195 ml deionized water. Determine the conductivity of HAc solution at this concentration Repeat step by changing the volume of HAc until 100 ml in the increment of 5mL into the deionized water Tabulate all data in the table of Appendix B General Start-Up procedures Ensure that all valves are initially closed Prepare a 10 liter of ethyl acetate solution by adding 400mL of ethyl acetate into 9.6 L of deionized water. And pour the solution into feed tank Fill in 10 L of deionized water into feed tank 2 by opening V Turn on the power for the control panel The unit is now ready for experiment. 6.3 Experiment Procedures Perform the general start-up procedures as in Section Open valves V2, V5, and V Turn on Pump 1 and adjust the flowrate controller to give a constant flow rate of 15 ml/min by adjusting the speed (RPM) of Pump Allow Et(AC) solution to enter the catalytic packed bed reactor Start monitoring the inlet (Q1) and outlet (Q2) conductivity values until they do not change over time. This is to ensure that the reactor has reached steady state. (Note: This may take up to 1 hour to reach steady state.) Record both inlet and outlet steady state conductivity values in table of Appendix C. Find the concentration of HAc exiting the reactor and extent of conversion from the 40

46 calibration curve Before start the new experiment, turn off pump 1. Turn on pump 2 to flow in the deionized water (150 ml/min) into the reactor until obtain a low conductivity value Repeat the experiment (steps to 6.4.7) for different residence times by changing the feed flow rates of EtAC to 20 and 25 ml/min. 6.4 General Shut-Down procedures Switch off the pump Set the water circulator to room temperature Keep the water circulating through the reactor while the circulator motor is running to allow the reactor to cool down to room temperature If the equipment is not going to be used for long period of time, drain all liquid from the unit. Rinse the feed tanks and product tank with clean water Turn off the power for the control panel. 7.0 RESULT 7.1 Record all the results in the table (Appendix C) for every reading taken by conductivity meter. 7.2 Plot a graph of conductivity vs. concentration of HAc. 7.3 Plot a graph of conversion vs. conductivity for calibration curve. 7.4 Plot a graph of conversion vs. residence time. The reactor s residence time is defined as the reactor volume (V TFR=0.387 L) divided by the total feed flow rates. Residence time, V v TFR DISCUSSION 8.1 Discuss the effect of residence time on conversion. 8.2 Discuss appropriate discussion regarding this experiment. 9.1 CONCLUSION 9.1 Based on the experimental procedure done and the results taken draw some conclusions to this experiment. 41

47 APPENDIX A5: Physical Properties of Ethyl Acetate and Acetic Acid. Property Ethyl Acetate Acetic Acid Formula CH 3COOCH 2CH 3 CH 3COOH Appearance Clear liquid Clear liquid Molecular weight g/mol g/mol Normal boiling point 77.1 C C Normal melting point C 16.5 C Density C o C Refractive index 20 C 20 C APPENDIX B5: Sample Table for Preparation of Calibration Curve Volume of HAc (ml) Concentration of HAc (mol/l) Conductivity (ms/cm) 42

48 APPENDIX C: Sample Tables for experiment Time (min) Outlet Conductivity, Q2 (ms/cm) 15 ml/min 20 ml/min 25 ml/min Flow rate of EtAC (ml/min) Residence time, τ (min) Inlet Conductivity, Q1 (ms/cm) Outlet Conductivity, Q2 (ms/cm) Exit concentration of HAc (mol/liter) Conversion, X (%) Concentration of Et(AC) in feed vessel, C AO = mol/l 43

49 EXPERIMENT 7 Effect of Pulse Change in Input Concentration to the Concentration of solute in Continuous Stirred Tank Reactor (CSTR) in Series. 1.0 OBJECTIVES 1.1 To observe and control the operation of a CSTR in series. 1.2 To observe the effect of pulse change in input concentration to the concentration of solute. 1.3 To determine the mean residence time, variance, and skewness for the residence time distribution of CSTR in series. 2.0 CORRESPONDING COURSE OUTCOME CO3: Ability to EVALUATE the catalytic reaction mechanism and Residence Time Distribution (RTD) functions in reactors. 3.0 INTRODUCTION In the majority of industrial chemical processes, a reactor is the equipment in which raw materials undergo a chemical change to form desired products. The design and operation of chemical reactors is thus crucial to the whole success of the industrial operation. Reactors can take a widely varying form, depending on the nature of the feed materials and the products. One particular type of process equipment is the continuous stirred tank reactor. In this reactor, it is important to determine the system response to a change in concentration. This response of concentration versus time is an indication of the ideality of the system. The SOLTEQ CSTR In Series (Model: BP 107A, Figure 1 and 2) has been designed to demonstrate the dynamics of the simplest classic case of a well-mixed, multi-staged process operation. The unit comes with three stirred tank reactors connected in series complete with sump tanks and pumps. Instruments are provided for the measurement of conductivity in each reactor. Students may select either step change input or pulse input to the reactor and will continuously monitor the responses in each reactor at a suitable interval. Based on the experimental data, students will be able to determine the mean residence time (t m), the variance (σ 2 ), and the skewness (s 3 ) of the residence time distribution (RTD) function. 44

50 Figure 1: Unit Assembly of CSTR in Series (Model: BP107A) 1. Stirrers 5. Conductivity Indicator 2. Conductivity Sensor 6. Temperature Indicator 3. Reactors 7. Peristaltic Pump 1 4. Sump Tank 8. Peristaltic Pump 2 45