PROBLEM SET-2

```Gazi University
Faculty of Engineering and Architecture
Department of Chemical Engineering
ChE 341 Chemical Reaction Engineering
Dr. &Ccedil;iğdem G&Uuml;LD&Uuml;R
Assist. Saliha KILI&Ccedil;ARSLAN
(İ.&Ouml;-02)
PROBLEM SET-2
Batch Reactors
2R takes place at 40oC and 3 atm in batch reactor. Initially, there are
1. The reaction A
85%A and inert.
Time,s
Volume, ml
0
200
30
251
60
276
120
302
240
324
Show that the reaction is second order and find the rate constant.
2. Dimethylether in a gaseous phase decomposes according to the following reaction.
CH3OCH3
(A)
CH4+CO+H2
(B) (C) (D)
Data were obtained from isothermal constant volume batch reactor at 552oC.
Time, sec
Total pressure, mmHg
0
420
57
584
85
662
114
743
182
891
261
1013
299
1054
Show that the reaction is first order according to the reactant and find the rate constant.
3. The reaction A+B
C was studied in a constant volume batch reactor. The reaction is
believed to be first order in each reactant and second order overall. The following data were
reported for their experiments at 20oC. The initial concentration of B was 0.123 kmol/m3.
CA,kmol/m3 0.106
t,sec
0
0.099
150
0.087
480
0.076
870
0.062
1500
0.050
2280
Are these data consistent with the proposed rate expression? If so, determine the reaction rate
constant.
4. Data for the dimerization 2A
solution at 40oC follow:
CA (mmol/dm3)
t (min)
68.0
0
50.2
40
A2 of a certain nitrile oxide(compound A) in ethanol
40.3
80
33.1
120
28.4
160
22.3
240
18.7
300
14.5
420
Find the reaction order using the half- life method.
5. Determine the reaction order for the gas-phase deposition of di-tert-butl peroxide,
(CH3)3COOC(CH3)3
C2H6 + 2CH3CCH3

O
The reaction was carried out in the laboratory in an isotermal batch system in which the total
pressure was recorded at various times during the reaction the data given in table apply to this
reaction. Only pure di-tert-butly peroxide was initially present in the reactin vessel.
Time (min)
0.0
2.5
5.0
10.0
15.0
20.0
Total Pressure (mmHg)
7.5
10.5
12.5
15.8
17.9
19.4
6. Problems 3.15&amp;3.25
The textbook: Levenspiel O., “Chemical Reaction Engineering”,3rd ed.(1999).
7. The rate of decomposition of nitrogen pentaoxide in the inert solvent CCl4 can be followed
by measuring the volume of the O2 evolved at a given temperature and pressure since the
unreacted N2O5 and the other products of the decomposition remain in solution. Some results
at 45oC from batch reactor are as follows:
t(sec)
O2
evolved(cm3)
162
3.41
407
7.78
1721
23
3400
29.33

32.6
Show that the reaction is first order find the first order rate constant.
N2O5
N2O4+1/2O2. Assume reaction goes to completion.
8. Neyens has studied the bromination of metaxylene at 17oC. the reaction is carried out by
introducing small quantities of iodine and bromine into pure liquid xylene and the following
the rate of disappearance of bromine by titrating samples removed from the liquid to
determine their bromine content. The iodine serves as a catalyst for the reaction. Since the
concentration of xylene and catalyst remain essentially unchanged during the course of
reaction, it may be assumed that the rate expression is of the form
r=kCBrm=-dCBr/dt
where k is pseudo rate constant that will depend on the iodine and xylene concentrations.
Determine the order of the reaction and reaction rate constant
t(min)
0.00
4.5
8.0
12.0
17.85 27.0
38.0
45.0
Bromine
0.3335 0.2660 0.2255 0.1910 0.1500 0.1160 0.0830 0.0705
concentration(mol/L)
9.The following gas phase reaction was studied in a constant volume batch reactor at 1030K.
A
B
a)Find the order of the reaction and the reaction rate constant at 1030K. The data as follows:
PAO(mmHg)
t1/2(s)
82.5
860
139
470
296
255
360
212
b)Calculate the activation energy by using the folowing data.
Temperature(K) 1085
1030
967
PA0(mmHg)
345
360
294
t1/2(s)
53
212
1520
10. The reaction 2NO+2H2
N2+2H2O was studied in a constant volume batch reactor
with equimolar quantities of NO and H2 at various initial pressures:
PO(kPa)
t1/2(s)
47.2
81
45.5
102
50.0
95
38.4
140
33.5
180
32.4
176
26.9
224
Calculate the over all order of the reaction.
CSTR&amp;PFR
11. The liquid phase irreversible reaction
A
B+C
İs carried out in a CSTR . the volumetric flow rate 0(hence =V/0) is varried to determine
the rate law and the effluent concentrations of species A recorded as a function of the space
time . Pure A enters the reactor at a concentration of 2 mol/L. Steady state conditions exist
when the measurements are recorded.
Run
(min)
CA (mol/L)
1
15
1.5
2
38
1.25
3
100
1.0
4
300
0.75
5
1200
0.5
Determine the reaction order and specific reaction rate.
12. Balasubramanian, Rihani and Doraiswamy have studied the reaction of ethylene and
chlorine in liquid ethylene dichloride solution in a CSTR. The stoichiometry of the reaction is
C2H4+Cl2
C2H4Cl2
Equimolar flow rates of ethylene and chlorine were used in the following experiment, which
was carried out at 32oC.
0
(sec)
Effulent chlorine
0.0117
concentration(moles/cm3)
300
0.0095
600
0.0082
900
0.0072
1200
0.0065
1500
0.0060
a) Determine the overall order of the reaction and the reaction rate constant.
b) Determine the space time necessary for 75% conversion in CSTR.
c)What would be the conversion in PFR having the space time determined in part b.
1800
0.0057
In part b and c assume that the operating temperature and the initial concentrations are the
same as in part a.
13. A chemical reaction is being studied in a laboratory scale steady-state flow system.the
reactor is a well-stirred 1000cm3 flask containing an aqueous solution. The reactor contents
(1000cm3 of solution) are uniform troughout. The stochiometric equation and data are given
below. What is the expression for the rate of the this reaction?Determine the reaction order
and the activation energy?
Diacetal+H2O
Aldehyde+2Alcohol
Feed Rate(cm3/sec)
Run
1
2
3
0.5
3.0
3.0
Temperature,T(OC)
10
10
25
Concentration of
Aldehyde in
effluent(kmoles/m3)
0.75
0.5
0.75
Feed concentration of diacetal is 1 kmole/m3. (Data are hypothetical. The reaction may be
assumed to be zero-order in aldehyde and alcohol and apparently zero order in water)
14. Decomposition reaction (CH3CHO(g)
CH4(g)+ CO(g)) of acetaldehyde was
investigated at 518 OC and 1 atm. pressure in a plug flow reactor by changing feed rate. The
reactor has 3.3 cm inner diameter and 80 cm length. Data are given below for the reaction:
Feed rate(g/L)
Conversion of
acetaldehyde
130
0.05
50
0.13
21
0.24
10.8
0.35
Show the reaction is second order and find reaction rate constant.(molecular weigh of
acetaldehyde:44 g/mole)
15. Problem 5.19
The textbook: Levenspiel O., “Chemical Reaction Engineering”,3rd ed.(1999).
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