Page 316 - Elements of Chemical Reaction Engineering 3rd Edition

288 Multiple Reactions Chap. 6

6.1.2 Maximizing the Rate Selectivity Parameter S for Two Reactants
Next consider two simultaneous reactions in which two reactants, A and
B, are being consumed to produce a desired product, D, and an unwanted
product, U, resulting from a side reaction. The rate laws for the reactions
A+B -% D
A+B k2 ,u
are

(4-9)

(6-10)
The rate selectivity parameter

Instantaneous (4- 1 1)
selectivity
is to be maximized. Shown in Figure 4-3 are various reactor schemes and con-
ditions that might be used to maximize SDu.

(a) CSTR (b) Tubular rea&or

0 A

Choose from these
or similar schemes Pure A Pure B
to obtain the intitially intitially
greatest amount of (c) Batch (d) Semibatch (e) Semibatch
desired product and
least amount of
undesired product
7?€3-
A

(9 Tubular reactor (9) Tubular reactor
with side streams with side streams

(h) Tubular reactor
with recycle
(i) Series of small CSTRs
Figure 6-3 Different reactors and schemes for minimking the unwanted ,product.