CHEMICAL ENGINEERING DEPARTMENT
INTRODUCTION TO CHEMICAL REACTION ENGINEERING
ONLINE ASSESSMENT
DATE: 08 JULY 2020
QUESTIO N 1
The saponification of ethyl acetate is an irreversible reaction.
In a laboratory experiment, a well-stirred constant volume batch reactor was charged with an
aqueous solution containing NaOH and ethyl acetate (EA), both of initial concentrations equal to
0.1 mol dm-3. Assuming that the reactor was operated at 300 K in 10 dm3 reactor.
a) Perform a mole balance on any chemical species j in a system volume V and derive a
general mole balance equation for the species j that is entering, leaving, reacting, and/or
accumulating with any system volume V, given that all the system variables are spatially uniform
throughout the system volume. State all the relevant assumptions [10]
a) From (A) above, derive a performance equation for a perfectly mixed batch reactor for
species j. state all the relevant assumption(s) [5]
b) If the rate is first order with respect to EA and zero order with respect to NaOH with rate
constant, k = 0.1hr-1. Calculate the time required to achieve 50% conversion of ethyl acetate
(EA)?. [15]
QUESTION 2
Consider isothermal decomposition of phosphine vapour at 650 °C:
If the reaction is first order and the specific rate constant is 9.5 h-1 Determine the size of
PFR operating at 650 °C and total pressure of 12 atm necessary to achieve 80%
conversion of 15 kmol/hr of phosphine. The feed contains 35% inert and 65% phosphine. [15]
Assume a constant volumetric flow
CHEMICAL ENGINEERING DEPARTMENT
INTRODUCTION TO CHEMICAL REACTION ENGINEERING
ONLINE ASSESSMENT
DATE: 08 JULY 2020
QUESTION 3
The reaction was carried out at 10atm and 227 °C and the following data
recorded A + B → C
-rA (mol/dm3.h) 0.2 0.0167 0.0068 0.00286 0.00204
XA 0.0 0.2 0.4 0.8 0.9
Where XA is conversion of A and –rA is the rate of reaction in mol/litre.min. The feed has a total
molar flow rate of 100mol/s, with 41% A, 41% B and the rest are inert.
a) Sketch the plot of 1/-rA versus conversion XA. [5]
b) What are the PFR and CSTR reactor volumes required to achieve 40% conversion? [5]
c) If it is desired to use both CSTR and PFR to achieve 40% conversion in each reactor, what
combination will minimize overall volume? [5]
CHEMICAL ENGINEERING DEPARTMENT
INTRODUCTION TO CHEMICAL REACTION ENGINEERING
ONLINE ASSESSMENT
DATE: 08 JULY 2020
Appendix
1. Equations
2. Integrals
x
dx 1
1 x
0
ln
1 x
x
dx x
1 x
0
2
1 x
x
ln 1 x
dx 1
1 x
0
1 x
x
1 x dx 1 ln 1
x
0
1 x
x
1 x 1 x ln 1
1 x
0
2
dx
1 x 1 x
x
1 x 2 2 1 ln 1 x 2 x
1 2 x
1 x
0
2
dx
1 x
B x
x
dx 1
0
1 x B x
ln
B 1 B 1 x
B 1
2
x
dx 2
ax
0
2
bx c
2ax b b
for b 2 4ac
x
dx 1 q x p
ax
0
2
bx c
ln
a p q p x q
for b 2 4ac
b b 2 4ac
p, q
2a
CHEMICAL ENGINEERING DEPARTMENT
INTRODUCTION TO CHEMICAL REACTION ENGINEERING
ONLINE ASSESSMENT
DATE: 08 JULY 2020
3. Gas constants
J kPa.dm3 dm3.atm m3.atm ft 3.atm cal
R = 8.314 = 8.314 = 0.082 = 0.082 = 0.73 o
= 1.987
mol.K mol.K mol.K kmol.K lbmol. R mol.K
Btu cal ft 3. psia
R = 1.987 = 1.104 = 10.73
lbmol.o R g mol.o R lbmol.o R
