DEPARTMENT OF CHEMICAL ENGINEERING CHEMICAL REACTION ENGINEERING LAB FALL 2017-18
S. No
LIST OF EXPERIMENTS
I
BATCH REACTOR – I
II
BATCH REACTOR – II
III
SEMI BATCH REACTOR
IV
ADIABATIC BATCH REACTOR
V
TEMPERATURE DEPENDENCY OF REACTION RATE.
VI
CSTR REACTOR
VII
PLUG FLOW REACTOR
VIII
PACKED BED REACTOR
IX
RTD STUDIES IN MIXED FLOW REACTOR (CSTR)
X
RTD STUDIES IN PLUG FLOW REACTOR
XI
RTD STUDIES IN PACKED BED REACTOR
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Expt No:
Date:
BATCH REACTOR – EQUIMOLAR EQUIMOLAR CONSTANT VOLUME SYSTEM AIM:
To verify the order and determine the rate constant for the reaction between equimolar concentration of Sodium Hydroxide and Ethyl acetate in a constant volume batch reactor. APPARATUS:
Conical flasks, Burette, Pipette and Stop Watch CHEMICALS:
Sodium Hydroxide (Na OH) Ethyl Acetate (CH3 COO C2H5) Acetic Acid (CH3 COOH) Phenolphthalein Indicator THEORY:
In the batch reactor the reactants are charged in to a container, well mixed and left to react for a certain period. The resultant mixture is then discharged. This is an unsteady state operation where in the concentration inside the reactor varies with time but uniform at any instant of time. Writing the material balance Input = output + disappearance + accumulation For a batch reactor, first two terms vanish Rate of loss of reactant A within the reactor due to chemical reaction = - rate of accumulation of reactant A within the reactor (-r A)V = -dNA/dt = NA0 dxA/dt xa therefore, t = NA0 dxA/(-r AV) 0 For a constant volume batch reactor, Xa t = CA0 dxA/(-r A) 0
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Determination of order of reaction by the differential method of analysis n
Let the rate equation be represented as -r A = k CA and n is the order of reaction
where k is the reaction rate constant
Taking logarithms on both sides ln(-r A) = ln k + n ln CA Draw tangents at different values of CA to the curve of plot of CA vs t. The slopes of the tangents will be the values of -r A for the corresponding values of CA. The slope of the approximate linear plot of ln (-r A) vs ln CA gives the order of the reaction n, the y-intercept gives ln k from which rate constant k can be calculated. This is only an exercise for verification of order, though it is well known that the order is 2 since this is an elementary reaction Verification of order by integral method of analysis n
-r A = -dCA/dt = k C A n
dCA/CA = -k dt on integration, we get
1-n
1-n
CA – CA0 = (n-1)kt Substituting the value of n as two, k values are calculated for different values of CA. The steady constant value of k proves that the order of reaction is verified and found to be two REACTION : .
In the present experiment the following saponification reaction between Sodium Hydroxide(NaOH) and ethyl Acetate (CH3 COO C2H5 ) is studied. NaOH + CH3 COO C2 H5
CH3 COO Na + C2H5OH
PROCEDURE:
Take 250ml of NaOH and 250ml of CH3 COO C2 H5 of known concentrations CA0 and CBO (CA0 = CBO = 0.05N) in a conical flask and start mixing. The conical flask serves as the batch reactor. Then 10ml of the reaction mixture is taken separately in each of eight different conical flasks labeled 1 to 8. A reaction time of 5, 10, 15, 20, 25, 30, 40 and 50 minutes is given for each sample respectively. After the reaction time, the reaction is arrested by adding excess Acetic acid solution of known concentration and volume (0.05N, 20 ml ).
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The excess Acetic acid is estimated by titration against Sodium Hydroxide solution of known concentration (0.05N) to determine the moles of unconverted Sodium Hydroxide in the reaction mixture at the time of arresting the reaction. From this we can find out the conversion XA at that instant.
OBSERVATION TABLE:
Batch No
Time (min)
1
5
2
10
3
15
4
20
5
25
6
30
7
40
8
50
Initial Volume of Acetic acid Added
Volume of NaOH
Vo ml
V1ml
Run down
CALCULATIONS:
Batch No
Volume of Acetic acid not used V1 ml
Volume of Acetic acid used (Vo - V1)ml
Moles of NaOH unreacted
1 2 3 4 5 6 7 8
4
Con of NaOH CA mol/ lit
XA
XA/(1-XA)
Volume of acetic acid not used (V1 ml)
= Volume of NaOH used in the back Titration
Volume of acetic acid taken (Vo ml) Volume of acetic acid used for arresting Moles of acetic acid used
= 20 ml = (Vo – V1) ml -3 = (Vo – V1) * 0.05 * 10 = Moles of NaOH unused in the reaction mixture at the time of arresting the reaction
Concentration of NaOH in the reaction mixture at the time of arresting the reaction (CA)
= Moles of NaOH unused / Volume of reaction mixture. -3 -3 = [((Vo – V1) * 0.05 * 10 / 10*10 ] mol/lit
Initial concentration of NaOH in the reaction mixture = CAO = 0.05/2 = 0.025 mol/lit Conversion = XA = (CAO – CA)/CAO The rate constant can also be determined from the linear plot of XA/(1-XA) Vs time t the slope of which equal to KCAO from which we can determine the rate constant K by the integral method of analysis with n equal to 2
RESULT:
For the saponification of ethyl acetate by Sodium hydroxide, the order of the reaction is determined by the differential method of analysis and verified by the integral method of analysis and found to be 2 and also the rate constant has been determined .
ANALYSIS REPORT:
Faculty Signature : Date : 5
Expt No:
Date:
BATCH REACTOR - NON-EQUIMOLAR CONSTANT VOLUME SYSTEM
AIM:
To determine the rate constant for the reaction between non-equimolar concentrations of Sodium Hydroxide and Ethyl acetate in a constant volume batch reactor. APPARATUS:
Conical flasks, Burette, Pipette and Stop Watch CHEMICALS:
Sodium Hydroxide (Na OH) Ethyl Acetate (CH3 COO C2H5) Acetic Acid (CH3 COOH) Phenolphthalein Indicator THEORY:
In the batch reactor the reactants are charged in to a container, are well mixed and are left to react for a certain period. The resultant mixture is then discharged. This is an unsteady state operation where in the concentration inside the reactor varies with time but uniform at any instant of time. Writing the material balance Input = output + disappearance + accumulation For a batch reactor, first two terms vanish Rate of loss of reactant A within the reactor due to chemical reaction = - rate of accumulation of reactant A within the reactor (-r A)V = -dNA/dt = NA0 dxA/dt xA therefore, t = NA0 dxA/(-r AV) 0 For a constant volume batch reactor, xA t = CA0 dxA/(-r A) 0 Let the order of the reaction be 2
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We use the integral method of analysis of data of reactants. For the second order reaction of non-equimolar concentrations of A and B, A+B….> products, -r A = -dCA/dt = K CACB
M=CB0 / CA0
We get the expression KCA0(M-1)* t = In [(M-XA)/M(1-XA)] The plot of in [(M-X A)/M(1-XA)] Vs time t gives a straight line of slope equal to KCA0 (M-1) from which we can determine the rate constant K. REACTION : . In the present experiment the following saponification reaction between Sodium Hydroxide(NaOH) and ethyl Acetate (CH3 COO C2 H5 ) is studied.
NaOH+ CH3 COO C2 H5 ……> CH3 COO Na + C2H5OH PROCEDURE: 250ml of NaOH and 500ml of CH3 COO C2 H5 of known concentrations CA0 and CBO (CA0 = CBO = 0.05N) are taken in to a conical flask and start mixing thoroughly. The conical flask serves as the batch reactor. Then 10ml of he reaction mixture are taken separately in each of the eight different conical flasks labeled 1 to 8. A reaction time of 5,10,15,20,25,30, 40 and 50 minutes is given for each sample respectively. After the reaction time, the reaction is arrested by adding excess Acetic acid solution of known concentration and volume (0.05N, 20 ml). The excess Acetic acid is estimated by titration against Sodium Hydroxide solution of known concentration (0.05N) to determine the moles of unconverted Sodium Hydroxide in the reaction mixture at the time of arresting the reaction. From this we can find out the conversion XA at that instant. OBSERVATION TABLE:
Batch No
Time (min)
1
5
2
10
3
15
4
20
5
25
6
30
7
40
8
50
Initial Volume of Acetic acid Added Vo ml
7
Volume of NaOH Run down V1ml
CALCULATIONS:
Batch No
Volume of Acetic acid not used V1 ml
Volume of Acetic acid used (Vo - V1)ml
Moles of NaOH unreacted
Concentratio n NaOH CA Mole/liters
XA
M-XA/M(1XA)
1 2 3 4 5 6 7 8 Volume of acetic acid not used (V1 ml) Volume of acetic acid taken (Vo ml) Volume of acetic acid used for arresting Moles of acetic acid used
= Volume of NaOH used in the back titration = 20 ml = (Vo – V1) ml -3 = (Vo – V1) * 0.05 * 10 = Moles of NaOH unused in the reaction mixture at the time of arresting
Concentration of NaOH in the reaction mixture at the time of arresting the reaction (CA) = Moles of NaOH unused / Volume of reaction mixture. -3 -3 = [((Vo – V1) * 0.05 * 10 / 10*10 ] mol/lit Initial concentration of NaOH in the reaction mixture = CAO = 0.05/3 = Mol/lit Conversion = XA = (CAO – CA)/CAO M= CB0/CA0 =2 GRAPH:
The plot of [(M-XA)/M(1-XA)] Vs time t gives a straight line of slope equal to KC AO (M1) from which we can determine the rate constant K. Related Exercise: (i) Derive rate equation for non Equimolar system for elementary second order reaction, (ii) analysis the result by doing the ex periments with one reactant as excess. RESULT:
For the saponification of ethyl acetate by Sodium hydroxide, the rate constant has been determined and found to be
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Faculty Signature: Date :
Expt No:
Date:
SEMI BATCH REACTOR
AIM:
To study the performance of semi batch reactor for the second order reaction of saponification of ethyl acetate by sodium hydroxide APPARATUS:
Conical flasks Burette Pipette Stop watch CHEMICALS:
Ethyl acetate Sodium hydroxide Acetic acid Phenolphthalein indicator THEORY:
There are two basic types of Semi batch reactors. In the first type, one of the reactants is slowly fed to a rector containing the other reactant, which has already been charged to the reactor. This type of reactor is used when unwanted side reactions occur at high concentrations of A or the reaction is highly exothermic. In the second type, both the reactants are fed to a reactor at constant flow rates. In the present case, we are studying the performance of semi batch reactor of first type. The performance equation of the semi batch reactor is same as that of constant volume batch reactor with time t being replaced by t. K CAo (M-1). t =In [(M-XA )/M(1-XA)] Over the total reaction time of t minutes, the semi batch reactor is treated as a series of N (=t/t) constant volume batch reactors.
PROCEDURE:
Take 50ml of NaOH solution of known concentration (0.05N) in the container (a conical flask of capacity of 250 ml which serves as the reactor) and add ethyl acetate solution 9
of known concentration (0.05N) at a constant known flow rate for a known reaction or operation time of t minutes (say 30 minutes, the total volume of the reaction mixture must increase to about 100ml ). Take a sample of 20ml of reaction mixture into another conical flask and arrest the reaction by adding excess acetic acid of known concentration and volume (0.05N, 20ml). The quantity of acetic acid in excess is determined by titration against standard NaOH solution. This gives the quantity of unreacted NaOH left in the reactor at the time of arresting the reaction (at the reaction time t ) from which we can determine the conversion of NaOH in the semi batch reactor. We can also determine the conversion theoretically from the batch reactor performance equation by approximating the semi batch reactor as a series of N batch reactors. Refer any chemical reaction engineering book for derivation. Xa = OBSERVATIONS:
Volume of NaOH initially taken in the reactor Normality of NaOH Volumetric flow rate of ethyl acetate solution Total reaction or operating time of the semi batch reactor Volume of sample of reaction mixture taken for analysis Volume of acetic acid added to the sample Normality of acetic acid used Volume of NaOH consumed in back titration Normality of NaOH used for back titration
= 50 ml = 0.05 N = QB ml/min = t minutes = 20 ml = 20 ml = 0.05 N = X ml = 0.05 N
MODEL CALCULATIONS:
Moles of acetic acid left in the anal ysis sample after arresting the reaction = Moles of NaOH consumed in the back titration -3 = X * 10 *0.05 Moles of acetic acid used to neutralize NaOH to completely arrest the reaction -3 -3 = 20*10 *0.05 – X* 10 *0.05 Moles of Na OH left at the end of reaction time in 20ml analysis sample -3 = 0.05* (20-X) * 10 Volume of reaction mixture in the reactor = (50 + QB * t) ml Therefore, moles of Na OH left in the reactor at the end of reaction time -3 = [(50 + QB *t) / 20] * 0.05 * (20-X) * 10 -3 Moles of Na OH initially taken in the reactor = 50 * 0.05 * 10 = NAO Experimental value of conversion = XA exp = (NAO-NA)/NAO
THEORETICAL CALCULATIONS:
Total time of semi batch operation = t min
10
For equimolar concentrations, for a second order reaction by the integral method of analysis XA/(1-xA) = kCA0 t k can be calculated by substituting the values of xA, CA0, t(=30min) Time for each interval = t/N = t mins N=1 Volume of ethyl acetate added = t * QB ml Total volume of reaction mixture = V1 = (50 + t * QB)ml -3 Moles of Na OH added = NAO1 = 50 * 10 * 0.05 -3 Moles of ethyl acetate added = NBO1 = t * QB * 10 * 0.05 CB01 = NB01 / V1 CAo1 = NAo1 / V1 M1 = CBo1 / CAo1 k CA o 1 (M1-1) * t = In [(M1 - XA1)/M1 (1-XA1)] the same k value can be substituted from which xA1 can be calculated CA1 =CA01 ( 1-XA1) CBI =CB01 ( 1-XA1/M) NA1 =NA01 ( 1-XA1) NB1 =NB01 (1-XA1/M) N= 2 NB02
= NB1+ Ethyl acetate added in the second interval -3 =(NB1 + t * QB * 10 * 0.05) moles NA02 = NA1 moles Volume of the reaction mixture = V2 =(50+2 * t * QB ) ml = N bo2/V2 CB02 CA02 =NA02/V2 M2 = CB02/ CA02 K CA 02 (M2-1) * t = In [ ( M 2 – XA2 )/M2 (1-XA2)] the same k value can be substituted from which xA2 can be calculated
The calculations are repeated as above up to N =6 The theoretical value of conversion is XA,th = (NA01-NA6)/NA01=
11
i=I
i=6 XAi
Faculty Signature: Date :
Expt No:
Date:
ADIABATIC BATCH REACTOR
AIM:
To study the reaction rate under adiabatic condition for hydrogen peroxide and sodium thiosulfate reaction. APPARATUS:
Thermoflask, thermometer, stop watch and conical flasks. THEORY :
The effect on the temperature of the reaction mixture consisting of H2O2 and Na2S2O3 when the reaction is carried out adiabatically can be observed and correlated with the rate of the reaction. As the reaction is exothermic, temperature increases as the reaction proceeds and becomes constant when reaction is completed. The rate of the reaction and temperature for the reaction is correlated to various parameters as 2 -E / RT 1/(TF – T) dT/dt = K OCAO e / (TF – TO) where, T0 – initial temperature – (K) TF – Final temperature – (K) T - Temperature at any instant of time – (K) K 0 – Frequency factor (lit/mol- min) CA0- Initial concentration of H2O2-(mol/lit) E -Activation energy – (J/k mol) EXPERIMENTAL SETUP :
The apparatus consists of an insulated Dewar vessel (Thermo flask ) fitted with a two 0 holed rubber cork carrying a long mercury thermometer (0-1000 C) through one hole and a glass funnel with a valve in the other. A stopwatch is used to record the time at various intervals and the temperature is noted. PROCEDURE :
Prepare solutions of Na2S2O3 and H2O2 each of 0.10(or) 0.05N concentration. Transfer exactly 200ml of Na2S2O3 solution into the reactor and note its temperature. Transfer exactly 200ml of H2O2 solution. Mix the contents well and after attaining the maximum steady temperature and record the temperature at regular intervals of time until the maximum temperature is reached. 12
OBSERVATIONS and CALCULATIONS
Time
T
DT/dt
1/[TF-T]
Sec 30 60 90 120 150 180 210 240 270 300 330 360 390 420 450 480 510 540 570 600
13
2
ln[(1/(TF-T) )/ (dT/dt)]
1/T
630 660 690 720 750
GRAPH :
A plot of T vs t is made . various dT/dt values are calculated. Then plot a graph between 2 1/T Vs In [1/(TF-T) dT/dt]. From the Slope and intercept, we can calculate the activation energy (E) and frequency factor (K 0)
RESULT :
Activation energy Frequency factor
E Ko
= =
J/k mol. lit/mol- min
Faculty Signature: Date : 14
Expt No:
Date:
TEMPERATURE DEPENDENCY OF REACTION RATE
AIM :
To establish the nature of temperature dependency of the reaction rate constant for the saponification reaction of ethyl acetate with Na O H solution. APPARATUS ;
Conical flask ( one 1000 ml size and 12 of 250 ml ) Burette Pipette Stop Watch CHEMICALS:
Ethyl acetate Sodium hydroxide Acetic acid Phenolphthalein indicator THEORY:
The influence of temperature on the rate constant is expressed in terms of an empirical equation known as Arrhenius equation: K = k o exp (-E/RT) Where k o is called frequency factor and E is called the activation energy of the reaction. This expression fits experiment well over wide temperature ranges and is strongly suggested from various stand points as being a very good approximation to the true temperature dependency. As in batch reactor experiment, we determine the value of the rate constant K at a particular temperature assuming a second order reaction kinetics (i.e. concentration dependent term f 2 (composition) , CA CB . From the values of rate constants at a various temperatures, we can determine the frequency factor and activation energy (i.e. temperature dependency) follows: K 1 = K 0 exp (-E/RT1) at temp T1 K 2 =K 0 exp (-E/RT2) at temp T2 In (K 1 /K 2) =E/R{1/T2 – 1/T1] E = RT1T2 / (T1 – T2) (K 1/K 2) K 0 =K 1 /exp(-E/RT1) 15
REACTION:
The saponification reaction studied is given by NaOH + CH3COOC2H5
CH3cCOONa + C2H5OH
PROCEDURE:
Place 400ml 0.05N NaOH solution in a 1000ml conical flask which as a reactor. Transfer 20ml of Acetic acid solution into each of Eight 250ml conical flasks which are serially labeled. Place the reactor on a hot plate cum magnetic stirrer and start heating by stirring the contents uniformly till the desired temperature is obtained. Carefully transfer 200ml of 0.05N ethyl acetate into the reactor & start the stopwatch simultaneously. At the time intervals of 10 minutes, pepett out 20 ml of the reaction mixture, into each of the conical flask. The Acetic Acid already present in the analysis flask neutralizes the alkali in the sample reaction mixture and arrests the saponification reaction. Back Titrate these reaction sample mixtures with aqueous NaOH solution using phenolphthalein as indicator. Note down the room temperature and conduct the experiment at various temperatures (minimum two temperatures.)
OBSERVATION
S.No
Time Min.
Vol. Of NaOH used in Back titration ml. at temp, T1
1 2 3 4 5 6 7 8 9 10
16
Vol. Of NaOH used in Back titration ml. at temp, T2
Vol. Of NaOH used in Back titration ml. at temp, T3
MODEL CALCULATIONS: ( For temp T1)
CA0 = Initial concentration of Na OH taken in the reactor, mols/litre CB0 = Initial concentration of ethyl acetate, mols/litre M= CB0/ CA0 At the time, t = 1 minute (V1)= ml of HCL excess = (Volume of Na OH used in back titration)*(Normality of Na OH/Normality of HCL = Volume of Na OH used in back titration vol. of HCL added to the sample =20 ml -3 moles of Na OH left in the reaction mixture = (20 – V1 )*(Normality of HCL)* 10 -3
CA = moles of Na OH left in the reaction mixture / (20* 10 XA =(CA0 -CA) / CA Repeat the above calculations for t = 2,…….12mins
The plot of In [(M-XA ) / M(1-X A )] vs t is observed to be a straight line With slope equal to K CA0 (M-1) from which the rate constant k can be calculated Repeat the above procedure at the other two temperatures also and the corresponding k values are noted against the corresponding temperatures. The plot of In k vs T observed to be a straight line with a slop equal to (-E/R), y-intercept equal to In k o from which the activation energy E and the frequency factor k 0 can be calculated TABULATION
t (mins)
XA
T1 In [(M-XA)/M(1XA)]
XA
T2 In [(M-X A)/M(1XA
1 2 3 4 5 6 7 17
XA
T3 In [(M-XA)/M(1XA)]
8 9 10
S.No 1 2 3
T T1 T2 T3
1/T
K K1 K2 K3
In K
GRAPH:
Plot a graph of ln k vs 1/T, rate constant k and frequency factor k 0 can be calculated from slope and y-intercept respectively
RESULT:
1. Activation energy is determined and found to be 2. Temperature effect on Rate constant
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Faculty Signature: Date :
Expt No:
Date:
MIXED FLOW REACTOR ( CSTR)
AIM :
To study the performance of a Mixed Flow Reactor for carrying out a second order reaction of saponification of ethyl acetate by NaOH
CHEMICALS :
Acetic acid , Sodium hydroxide , Ethyl acetate , phenolphthalein indicator. THEORY :
In mixed flow reactor, properties of the reaction mixture are uniform throughout the volume. With equimolar concentration of reactants at inlet for this second order reaction, the outlet concentration of reactants also remain equimolar. i.e., CAO = CBO
i.e., CA = CB
From the design equation of the CSTR,
where – r A = k
2 CA
/CA0 = V/FA0 = XA/ (-r A), 2
A straight line plot is approximated from the plot of x A/(1-xA) vs t , the slope of which gives k CA0 from which the rate constant k can be calculated
REACTION
NaOH + CH3 COO C2H5 A B
CH3 COO Na + C2H5 OH C
D
2
-r A = kCACB = kCA as CA = CB at any time EXPERIMENTAL SETUP
Its consists of a cylindrical container with flow connections for inlet and outlet sections. The constant inflow of reactants can be maintained by rotameters.
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PROCEDURE
Sodium hydroxide and ethyl acetate solutions of known concentrations (CAO = CBO = 0.05 N ) are allowed to enter at constant flow rates in the mixed flow reactor. Sufficient time is given for system to attain steady state conditions.. Now product is collected and the reaction is arrested by adding excess acetic acid(20ml, 0.05N). After mixing thoroughly, ttitration with standard NaOH is done taking 10ml of mixture. OBSERVATIONS:
Volume of reactor Volumetric flow rate Residence time Normality of the acetic acid Volume of acetic acid for arresting the reaction Normality of NaOH Volume of sample Titrate value of NaOH Moles of acetic acid used of arresting Moles of unreacted NaOH CA = Concentration of NaOH at any time
= V = liters = v = lits/min = = V/v = min = 0.05 N = 20 ml = 0.05 N = 10 ml = X ml -3 = (20-X)* 0.05*10 -3 = (20-X)* 0.05*10 -3 = (20-X)* 0.05*10 /
CAO = Initial concentration of NaOH XA = Conversion of NaOH
=0.05 / 2 = 0.025 =(CAO- CA)*100 / CAO
-3
10*10
Flow rate v (ml./min.)
Volume of the reactor V 3 m
(min.)
Reaction mixture volume X ml.
CA
XA
GRAPH :
A plot of 1/ (-r A) vs XA is made and the conversion is calculated by using the area under the curve, which is equal to / CA0 or V/FA0 . 2 Plot a graph of xA/(1-xA) vs t
20
These are compared with those of the experimental values.
RESULT :
For the given reaction, the conversion is calculated experimentally and compared with theoretical values as well as with graphical technique. The rate constant is also determined experimentally.
Faculty Signature: Date :
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