Ma. Shalabi et al., KINETIC MODELING OF CO OXIDATION ON PT CEO2 IN A GRADIENTLESS REACTOR/, Journal of chemical technology and biotechnology, 65(4), 1996, pp. 317-324
Cerium oxide is a major additive in three-way catalysts used in emissi
on control of automobile exhaust. Pt/CeO2 was studied in order to bett
er understand the role of ceria in promoting CO oxidation reaction. Th
e kinetics of carbon monoxide oxidation on Pt/cerium oxide catalyst, w
as studied over the temperature range 100-170 degrees C. Steady state
kinetic measurements of CO oxidation were obtained in a computer contr
olled micro-CSTR reactor. Activation energies were reported to vary be
tween 39.5 and 512 kJ mol(-1). At low concentrations of either reactan
t (CO, O-2) and total conversion, the catalyst exhibited multiple stea
dy states, similar to the multiplicity behavior of Pt/Al2O3. The total
conversion was reached at 120 degrees C. In comparison, the total con
version at low reactant concentrations was reached at a temperature of
148 degrees C for the alumina-supported catalyst. Langmuir-Hinshelwoo
d mechanisms gave a good fit to the data. However, no single rate expr
ession could effectively describe the CO oxidation data over the whole
concentration in the product of the CSTR reactor. The facts gathered
indicate that oxygen adsorbed on interfacial Pt/Ce sites and ceria lat
tice oxygen provides oxygen for CO oxidation. Cerium oxide has been fo
und to lower CO oxidation activation energy, enhance reaction activity
and tends to suppress the usual CO inhibition effect.