Chemical Reactions on Solid Surfaces - Bioprocess Engineering: Kinetics, Biosystems, Sustainability and Reactor Design - page 470

On supported Ni catalyst in the presence of large excess of H 2 (H 2 /CO 25) and

temperature of about 500 K. A correlation proposed that fit their kinetic data is given by

>

aC 0:5

CO C 2

s
ðd þ bC 0:5

r CO ¼ (2)

2

CO Þ

and the catalyst decay follows

(3)
Suggest a mechanism for the methanation that is consistent with this rate expression
and a mechanism for the decay of the catalyst activity.
9.8. (a) For the decomposition of NH 3 (A) on Pt (as catalyst), what is the form of the rate
law, according to the Langmuir e Hinshelwood model, if NH 3 (reactant) is weakly
adsorbed and H 2 (product) strongly adsorbed on Pt? Explain briefly. Assume N 2
does not affect the rate.
(b) Do the following experimental results, obtained by Hinshelwood and Burk (1925)
in a constant-volume batch reactor at 1411 K, support the form used in (a)?

r s ¼ k d C CO C s

t , s 0 10 60 120 240 360 720

P , kPa 26.7 30.4 34.1 36.3 38.5 40.0 42.7

P is total pressure, and only NH3 is present initially. Justify your answer quantitatively,
for example, by using the experimental data in conjunction with the form given in (a).
Use partial pressure as a measure of concentration.

0.8

0.6

0.4

0.2

0

0 50 100 150 200

P A0 , atm

FIGURE P9.9