CHE 304 (Spring 2010)
__________________
LAST NAME, FIRST
Problem set #9
(1) Run Heat Effects I (http://www.engin.umich.edu/~cre/icm/cre.html)
Click on the CHE 304 distribution folder, then ICMw, then Menu.exe. Click on the
appropriate program name on the menu. Turn in the last page of the program with
performance number.
(2)1 The endothermic liquid-phase elementary reaction
A + B  2C
proceeds, substantially, to completion in a single steam-jacketed, continuous-stirred reactor
(Table 2-1). From the following data, calculate the steady-state temperature:
Reactor volume: 125 gal.
Steam jacked area: 10 ft2
o
Jacket steam: 150 psig(365.9 F saturation temperature)
Overall heat-transfer coefficient of jacket, U:150 Btu/hrft2oF
Agitator shaft horsepower: 25 hp
o
Heat of reaction,  H Rx
= 20,000 Btu/lbmol of A (independent of temperature)
Table 2-1
Feed (lbmol/hr)
Feed temperature (oF)
Specific heat (Btu/lbmoloF)
Molecular weight
Density (lb/ft3)
A
10.0
80.0
51.0
128
63.0
Component
B
10.0
80.0
44.0
94
67.2
C
0
--47.5
--65.0
Ans: 199.4oF
(3)1 The elementary irreversible organic liquid-phase reaction
A+BC
is carried out adiabatically in a flow reactor. An equal molar feed in A and B enters at 27oC, and
the volumetric flow rate is 2 L/s.
(a) Calculate the PFR and CSTR volumes necessary to achieve 85% conversion.
(b) What is the maximum inlet temperature one could have so that the boiling point of the liquid
(550oK) would not be exceeded even for complete conversion?
(c) Calculate the conversion that can be achieve in one 500-L CSTR and in two 250-L CSTRs in
series.
Additional information:
HoA =  20 kcal/mol, HoB =  15 kcal/mol, HoC =  41 kcal/mol
1
Fogler, H. S., Elements of Chemical Reaction Engineering, Prentice Hall, 1999
CA0 = 0.1 kmol/m3, CpA = CpB = 15 cal/moloK, CpC = 30 cal/moloK
Activation energy E = 10,000 cal/mol, k = 0.01 L/mols at 300oK.
Ans:
(a) VCSTR = 175 L, VPFR = 320 L,
(b) 350oK
(c) 1 500 L CSTR X = 0.921, 2 250 L CSTR X = 0.969
(4)2 Find Q ( t) or Q ( z) necessary to maintain a 5 liter batch reactor or PFR isothermal reactor at
300oK for the reaction A  B. The reaction is first order with k = 2.0 min-1, CA0 = 2 mole/liter,
HRx =  30 kcal/mol. What is the average rate of heat removal for 95% conversion?
Ans: Q (t) = 600exp(2t); Q ave = 190.3 kcal/min
(5)1 The gas phase catalyzed hydrogenation of o-cresol to 2-methylcyclohexanone is given by
o-cresol(A) + 2H2(B)  2-methylcyclohexanone(C)
The reaction rate on a nickel-silica catalyst was found to be
 rA = kPB, where k = 1.74 mol of o-cresol/(kg catminatm) at 170oC
The reaction mixture enters the packed-bed reactor at a total pressure of 5 atm. The molar feed
consists of 67% H2 and 33% o-cresol at a total molar rate of 40 mol/min. Accounting for the
pressure drop in the packed bed using a value of  = 0.34 kg-1, plot the rate of reaction of ocresol and the partial pressure of each species as a function of catalyst weight (to 4.8 kg).
PA =
2
5 1  X 
5
X
, PB = 2PA , PC =
3 1  2 X / 3 
3 1  2 X / 3
Schmidt, L.D., The Engineering of Chemical Reactions, Oxford, 2004, pg. 242
% Problem 5 set 9
%
wspan=0:0.1:4.8;
[w,xy]=ode45('fs9p5',wspan,[0 1]);
plot(w,xy)
grid on
xlabel('w(kg)');ylabel('X, y');
x=xy(:,1);y=xy(:,2);
pa=5*(1-x)./(1-2*x/3)/3;
pb=2*pa;
pc=5*x./(1-2*x/3)/3;
ra=1.74*pb.*y;
pp=[pa pb pc ra];
figure(2);plot(w,pp)
grid on
xlabel('w(kg)');ylabel('p(atm), r(mol/kg.min)');
legend('P_A','P_B','P_C','rate')
% Function for problem 5 set 9
%
function wx=fs9p5(W,xy)
X=xy(1);y=xy(2)
wx(1,1)=0.435*y*(1-X)/(1-2*X/3);
wx(2,1)=-0.34*(1-2*X/3)/(2*y);
(6) Use Comsol Multiphysics to simulate an isothermal reactor (Example 7.6-1 in the notes).
Turn in Figure 2, 3, 4, and 5 of this example.
(7) The hydrogenolysis of thiophene1 (C4H4S) has been studied at 235-265oC over a cobaltmolybdenum catalyst, using a CSTR containing 8.16 g of catalyst. The stoichiometry of the
system can be represented by
C4H4S + 3H2  C4H8 + H2S
C4H8 + H2  C4H10
(Rxn. 1)
(Rxn. 2)
The feed to the CSTR consisted of a mixture of thiophene, hydrogen, and hydrogen
sulfide. The mole fraction of butane (C4H8), butane (C4H10), and hydrogen sulfide in the
reactor effluent were measured. The mole fractions of hydrogen and thiophene were not
measured. The data from one particular experimental run are given below:
Total pressure in reactor = 832 mmHg
Feed rate
Mole fractions in effluent
-4
Thiophene = 0.653×10 mol/min
H2S = 0.0719
Hydrogen = 4.933×10-4 mol/min
Butenes (total) = 0.0178
Hydrogen sulfide = 0
Butane = 0.0541
Calculate:  rT (the rate of disappearance of thiophene) and the partial pressure of
thiophene, hydrogen, hydrogen sulfide, butenes (total), and butane in the effluent. You
may assume that the ideal gas laws are valid.
Mol fraction
Partial pressure, mmHg
1
Thiophene
0.0682
56.7
Hydrogen
0.778
655.8
H2S
0.0719
59.8
Butenes Butane
0.0178 0.0541
14.8
45.0
Roberts, G. W., Chemical Reactions and Chemical Reactors, Wiley, 2006, pg. 59, P. 3-9