Page 274 - Elements of Chemical Reaction Engineering 3rd Edition

246 Collection and Analysis of Rate Data Chap. 5

cAO + cAe (5-25)
'Ab = 2

However, since very little reaction takes place within the bed, the bed concen-
tration is essentially equal to the inlet concentration,

cAb i=: cAO
so - rA is a function of CAo:

As with the method of initial rates, various numerical and graphical techniques
can be used to determine the appropriate algebraic equation for the rate law.

Example 5-4 Differential Reactor

The formation of methane from carbon monoxide and hydrogen using a nickel cat-
alyst was studied by Pursley.8 The reaction

3Hz + CO -+ CH, + 2HzO
was carried out at 500°F in a differential reactor where the effluent concentration of
methane was measured.
(a) Relate the rate of reaction to the exit methane concentration.
(b) The reaction rate law is assumed to be the product of a function of the partial
pressure of CO, f(CO), and a function of the partial pressure of H,, g( H2):

Determine the reaction order with respect to carbon monoxide, using the data in
Table E5-4.1. Assume that the functional dependence of rbH4 on Pco is of the form

&I4 - Go (E5-4.2)

TABLE E5-4.1 RAW DATA
Run P, (atm) PH2 (atm) CCH4(g mol/dm3)
1 1 1 .o 2.44 x 10-4
PHZ is constant in 2 1.8 1 .0 4.40 x 10-4
Runs 1, 2, 3 3 4.08 1 .0 10.0 x 10-4
Pco is constant in 4 1.0 0.1 1.65 x 10-4
Runs 4, 5, 6 5 I .o 0.5 2.47 x 10-4
6 1 .o 4.0 1.75 x 10-4

J. A. Pursley, An Investigation of the Reaction between Carbon Monoxide and Hydro-
gen on a Nickel Catalyst above One Atmosphere, Ph.D. thesis, University of Michigan.