Engine dynamometer experiments: platinum emissions from differently aged three-way catalytic converters

Depending on the operating conditions and the age of the converter, mean platinum emissions ranged from 7 to 123 ng m-3 corresponding to emission factors between 9 and 124 ng km-1. There were no statistically significant differences between the four converter brands tested. The data from new (12–90 ng km-1) and old catalytic converters (9–26 ng km-1) installed on a medium-powered gasoline engine (1.8 l 66 kW) showed a tendency towards decreasing platinum emission with increasing use. The platinum emissions increased with rising simulated speed and exhaust temperature. The lowest mean emission from new converters (12 ng km-1) was found at a constant speed of 80 km h-1, the highest (90 ng km-1) at 130 km h-1. Using the US72 or the US72-EUDC test cycles the emission factors were higher (37 or 19 ng km-1) than at 80 km h-1 indicating that additional mechanical or thermal impacts enhance the platinum abrasion at cycle conditions. After installing catalytic converters tested with the 1.8 l engine on a smaller engine (1.4 l 44 kW), the platinum emissions measured at the US72 cycle and a high-speed condition (140 km h-1) were only 9 and 22 ng km-1, respectively. Platinum is almost exclusively emitted bound to aluminum oxide particles where (depending on the driving conditions) 43–74% of these emitted particles had aerodynamic diameters >10 μm. The alveolar fraction (<3 μm) was between 11 and 26% (1.8 l engine) and between 21 and 36% (1.4 l engine). If at all, soluble platinum is emitted in only very small quantities ( 1%).