KINETIC MODELING OF CO OXIDATION ON PT CEO2 IN A GRADIENTLESS REACTOR/

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.