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Automotive catalysts deactivate by thermal and poison mechanisms. Thermal degradation reduces catalyst efficiency by both agglomeration of precious metals and by reduction in surface area of the washcoat. Engine oil derived poisons degrade catalyst performance by coating the outer surface of the washcoat. Numerous catalyst technologies are aged using accelerated dynamometer aging schedules that simulate the thermal and poison degradation of field aged catalysts. Pd, Pd/Rh, Pt/Pd/Rh, and Pt/Rh catalyst technologies are aged and evaluated on various rapid aging test (RATsm) schedules in an effort to ascertain what catalyst technologies may be best for low temperature and high temperature applications. The performance of these catalyst technologies are evaluated on an air/fuel sweep test and a 3.8L auto-driver FTP stand. Results show that the RATsm schedule applies a phosphorus poison distribution (due to engine oil consumption) similar to vehicle aged catalysts.

The relationship between engine oil formulations and catalyst performance was investigated by comparatively testing five engine oils. In addition to one baseline production oil with a calcium plus magnesium detergent system, the remaining four oils were specifically formulated with different additive combinations including: one worst case with no detergent and production level zinc dialkyldithiophosphate (ZDTP), one with calcium-only detergent and two best cases with zero phosphorus. Emissions performance, phosphorus loss from the engine oil, phosphorus-capture on the catalyst and engine wear were evaluated after accumulating 100,000 miles of taxi service in twenty vehicles. The intent of this comparative study was to identify relative trends.

Parametric studies were performed to determine the effects and interactions between aged warm-up and underfloor converters with respect to 1) catalyst volume, 2) precious metal loading and 3) catalyst technology. All the converters were dynamometer aged appropriately with respect to their intended position in the exhaust system prior to emission testing. FTP emissions were measured using a 2.3L engine on an auto-driver dynamometer stand. Catalyst volumes of the warm-up and underfloor converters varied from 0.00 to 1.03 and 1.34 to 2.67 liters, respectively. Precious metal loading of the warm-up converters varied from 50 to 300 g/ft3 of palladium (Pd). The underfloor converters used both platinum/rhodium (Pt/Rh) and Pd precious metal combinations. Pt/Rh loadings varied from 25 to 50 g/ft3 at a 14/1 ratio. Pd loadings varied from 50 to 100 g/ft3. The underfloor catalyst technologies varied in base metal content and/or high temperature stabilizers.