Page 352 - Elements of Chemical Reaction Engineering Ebook

Chap. 6 Questions and Problems 323

The feed, which is equimolar in A and C, enters at a flow rate of 10 Ib
mol/s. What reactor volume is required for a 50% conversion of A to B?
(Am: V = 105 ft3.)
P6-5, A mixture of 50% A, SO% B is charged to a constant-volume batch reactor in
which equilibrium is rapidly achieved. The initial total concentration is 3.0
mol/dm3.
(a) Calculate the equilibrium concentrations and conversion of A at 330 K
for the reaction sequence

Reaction 1: A + B e C 4 D K,, (330 K) = 4.0, K,, (350 K) = 2,.63.
+
X
Y
Reaction 2: C + B e K,,(330 K) = 1.0, KC2 (350 K) = 1.51
(b) Suppose now the temperature is increased to 350 K. As a result, a third
reaction must now be considered in addition to the reactions above:
Reaction 3: A + X e Z K,, (350 K) = 5.0 dm3/mol
Calculate the_ equilibrium concentrations, conversion of A and overall
selectivities SCX , SDZ , and SYZ .
(c) Vary the temperature-over the-range 300 to 500 K to learn the effect
of selectivities SCX , SDZ, and Syz on temperature.
Additional information:
AH,, = -20,000 Jlmoi A AHRz = +20,000 Jlmol B
AH,, = -40,000 J/mol A
P6-6* Consider the following system of gas-phase reactions:
A __j X rx = k, k, = 0.002 rnoYdm3.min
B
A + rB = kzCA k, = 0.06 min-1
A ---+ I' ry = k3Ci k, = 0.3 dm3/mol * min
B is the desired product, and X and Y are foul pollutants that are expensive: to
get rid of. The specific reaction rates are at 27°C. The reaction system is to be
operated at 27°C and 4 atm. Pure A enters the system at a volumetric flow rate
of 10 dm3/min.
(a) Sketch the instantaneous selectivities (S,,, SB,,and S,,, = rB/(rx + rll))
as a function of the concentration of CA.
(b) Consider a series of reactors. What should be the volume of the first reactor?
(c) What are the effluent concentrations of A, B, X, and Y from the first reactor.
(d) What is the conversion of A in the first reactor?
(e) If 90'% conversion of A is desired, what reaction scheme and reactor
sizes should you use?
(f) Suppose that El = 10,000 cal/mol, E2 = 20,000 cal/mol, and E, = 30,000
cal/mol. What temperature would you recommend for a single CSTR with
a space-time of 10 min and an entering concentration of A of 0.1 mol/dn13?
P6-78 Pharmacokinetics concerns the ingestion, distribution, reaction, and elimina-
tion reaction of drugs in the body. Consider the application of pharmacokinet-
ics to one of the major problems we have in the United States, drinking and
driving. Here we shall model how long one must wait to drive after having a
tall martini. In most states the legal intoxication limit is 1.0 g of ethanol per
liter of body fluid. (In Sweden it is 0.5 g/L, and in Eastern Europe and Russia
it is any value above 0.0 g/L.) The ingestion of ethanol into the bloodstream