A. Martinez-arias et al., Effect of thermal sintering on light-off performance of Pd/(Ce,Zr)O-x/Al2O3 three-way catalysts: Model gas and engine tests, J CATALYSIS, 204(1), 2001, pp. 238-248
The effect of thermal degradation on the catalytic performance in light-off
tests of Pd three-way catalysts supported on alumina and promoted with Ce-
Zr mixed oxides has been investigated either under synthetic gas mixtures (
for catalysts in powder form) or in engine tests (for catalyst monoliths).
Accelerated aging of the systems by oven heating at 1273 K produces a signi
ficant sintering of both Pd and Ce-Zr mixed oxide active components, indica
ted by X-ray diffraction, transmission electron microscopy, and diffuse ref
lectance Fourier transform infrared (DRIFTS) techniques. In spite of these
effects, the small differences between the light-off performances of fresh
and aged systems show the relatively low relevance (particularly in real co
nditions under engine emissions) of the thermal degradation on the overall
performance of the system. In situ DRIFTS results suggest that this is the
result of the relatively low structural sensitivity of the desorption of hy
drocarbon fragments adsorbed on the active sites, which act mainly as self-
poisons for the catalytic reactions. (C) 2001 Academic Press.