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 1 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 1.81 engine on a smaller engine (1.41 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 mu m. The alveolar fraction ( < 3 mu m) was between 11 and 26% (1.81 engine) and between 21 and 36% (1.41 engine). If at all, soluble platinum is emitted in only very small quantities(less than or equal to 1%). (C) 1999 Elsevier Science Ltd. All rights reserved.