Page 275 - Elements of Chemical Reaction Engineering 3rd Edition

Sec. 5.4 Differential Reactors 247

The exit volumetric flow rate from a differential packed bed containing 10 g of cat-
alyst was maintained at 300 dm3/min for each run. The partial pressures of €€, and
COI were determined at the entrance to the reactor, and the methane concentration
was measured at the reactor exit.

Solution
(a) In this example the product composition, rather than the reactant concentration,
is being monitored. -rA can be written in terms of the flow rate of methane from
the reaction,

Substituting fiar FcH4 in terms of the volumetric flow rate and the concentration of
methane gives

(E5-4.3)

Since uo, CCHb, and AW are known for each run, we can calculate the rate of reaction.
For run 1:
g moudm3 = 7.33 x 10-3 g mol CH,
g cat. X min
The rate for runs 2 through 6 can be calculated in a similar manner (Table E5-4.2).

TABLE E5-4.2. RAW AND CALCULATED DATA
-

~
1 1 .o 1 .o 2.44 x 10-4 7.33 x 10-3
2 1.8 1 .o 4.40 x 10-4 13.2 x 10-3
3 4.08 1 .o 10.0 x 10-4 30.0 x IO-j
4 1.0 0.1 1.65 x 10-4 4.95 x IO-’
5 1 .o 0.5 2.47 x 10-4 7.42 X lo-’
6 1 .o 4.0 1.75 x 10-4 5.25 X IO-j

For constant hydrogen concentration, the rate law

IbH, = kG0 * @H,)
can be written as
-* rkH4 = k‘ Pso (E5-4.4)

Taking the log of Equation (E5-4.4) gives us
In(rkH4) = lnk‘+a InPC,

We now plot In (r&) versus In Pco for runs 1, 2, and 3.