Fine particles produced from automotive emissions-control catalysts.

High concentrations of metal-containing condensation nuclei have been thermally induced from stabilized catalysts containing chromium, copper, and nickel under conditions closely resembling those found in automobile exhaust. Commercial and developmental catalyst formulations have been found to emit fine particles under a broad range of controlled conditions at temperatures ranging from 185 degrees to 800 degrees C, in filtered air, in a mixture of 3 percent carbon monoxide in molecular nitrogen, and in the product stream of a pulsed flame combustor.