(1) Run Heat Effects I (

CHE 304 (Spring 2010) ______

LAST NAME, FIRST

Problem set #9

(1) Run Heat Effects I (

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

Jacket steam: 150 psig(365.9oFsaturation temperature)

Overall heat-transfer coefficient of jacket, U:150 Btu/hrft2oF

Agitator shaft horsepower: 25 hp

Heat of reaction, = 20,000 Btu/lbmol of A (independent of temperature)

Table 2-1

Component
A / B / C
Feed (lbmol/hr)
Feed temperature (oF)
Specific heat (Btu/lbmoloF)
Molecular weight
Density (lb/ft3) / 10.0
80.0
51.0
128
63.0 / 10.0
80.0
44.0
94
67.2 / 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?

Additional information:

HoA =  20 kcal/mol, HoB =  15 kcal/mol, HoC =  41 kcal/mol

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 t) or 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: (t) = 600exp(2t); 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 o-cresol and the partial pressure of each species as a function of catalyst weight (to 4.8 kg).

PA = , PB = 2PA , PC =

% 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 thiophene[2] (C4H4S) has been studied at 235-265oC over a cobalt-molybdenum catalyst, using a CSTR containing 8.16 g of catalyst. The stoichiometry of the system can be represented by

C4H4S + 3H2 C4H8 + H2S(Rxn. 1)

C4H8 + H2 C4H10(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
Thiophene = 0.653×10-4 mol/min
Hydrogen = 4.933×10-4 mol/min
Hydrogen sulfide = 0 / H2S = 0.0719
Butenes (total) = 0.0178
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.

Thiophene / Hydrogen / H2S / Butenes / Butane
Mol fraction / 0.0682 / 0.778 / 0.0719 / 0.0178 / 0.0541
Partial pressure, mmHg / 56.7 / 655.8 / 59.8 / 14.8 / 45.0

[1] Fogler, H. S., Elements of Chemical Reaction Engineering, Prentice Hall, 1999

[2] Schmidt, L.D., The Engineering of Chemical Reactions, Oxford, 2004, pg. 242

[2] Roberts, G. W., Chemical Reactions and Chemical Reactors, Wiley, 2006, pg. 59, P. 3-9