Microstructural evolution of γ-alumina supported rhodium catalysts

In an era of increasing environmental awareness, stricter federal and state regulation of pollutant emissions are emerging. A major source of pollution arises from automobiles which inadvertently form gaseous products such as nitric oxide (NO x ), carbon monoxide (CO), and hydrocarbons (HC). Since the early 1980's, these effluents have been converted to safer forms using a three-way catalytic converter that employs a high dispersion of rhodium and platinum particles supported on a large surface area of transitional γ-phase alumina. Unfortunately such a converter is susceptible to decreased performance over time, and this degradation has been attributed to changes in the catalyst microstructure. The nanoscaled nature of the transition metal catalysts and the submicron-scaled size of the transitional alumina necessitates the use of the high spatial resolution analyses made possible by transmission electron microscopy.