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The emission and flow restriction characteristics of three different ceramic substrates with varying wall thickness and cell density (400 cpsi/6.5 mil, 600/4.3, and 600/3.5) are compared. These 106mm diameter substrates were catalyzed with similar amounts of washcoat and fabricated into catalytic converters having a total volume of 2.0 liters. A Pd/Rh catalyst technology was applied at a concentration of 6.65 g/l and a ratio of 20/1. Three sets of converters (two of each type) were aged for 100 hours on an engine dynamometer stand. After aging, the FTP performance of these converters were evaluated on an auto-driver FTP stand using a 2.4L, four-cylinder prototype engine and on a 2.4L, four-cylinder prototype vehicle. A third set of unaged converters was used for cold flow restriction measurements and vehicle acceleration tests.

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.

A parametric study was performed to investigate the interactions between Pd warm-up and underfloor converters on FTP emissions. Three different Pd warm-up converters were evaluated with six different underfloor converters on two different engines. The Pd warm-up converters primarily differed in the amount of ceria in the catalyst washcoat. These warm-up converters had a catalyst of 0.52 liters and a Pd loading of 100 g/ft3. The underfloor converters had a catalyst volume of 2.67 liters. Two Pt/Rh and one Pd catalyst technology were used in the underfloor converters. Each underfloor catalyst technology was investigated at two different loadings. The Pt/Rh underfloor converters were evaluated at 25 and 50 g/ft3 at a Pt/Rh ratio of 14/1. The Pd containing underfloor converters were evaluated at 50 and 100 g/ft3. All of the converters used in this study were dynamometer aged appropriately with respect to their intended position in the exhaust system.

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.

Close coupled catalysts and new ceramic catalyst substrates have significantly improved the light-off performance of automotive converters required to meet stringent emission requirements. The hotter environment of these catalytic converters and the lower structural strength of the ceramic substrates require the rethinking of converter designs. The development of new package requirements to accommodate the change in environment and new substrates are discussed. A historical perspective on converter durability is presented as reference. Development of durability test protocols is essential to verifying product durability performance to these new environments. Data collection and documentation of testing templates are shown to demonstrate the effectiveness of tests that represent real world environments. Design improvements to address failure modes are discussed along with durability improvement results.

The effects of oil derived poisons and thermal degradation on three-way automotive catalysts is investigated. Dynamometer rapid aging test (RATsm) schedules that incorporate both thermal and oil-derived poison degradation are used to age catalysts for FTP emissions studies. This paper presents three investigations. Vehicle aged converters are analyzed to determine the axial phosphorus distribution through out the catalyst. These phosphorus profiles are compared to dynamometer RATsm aged catalyst. Also, 27 converters were RATsm aged on three different RAT schedules at three different accelerated poison levels. The amount of phosphorus on the catalyst is compared to the amount of equivalent oil consumed by the aging engine. Finally, 24 converters were aged on three different RATsm schedules to determine the effects of catalyst volume, aging temperature and oil derived poisoning on FTP emissions using both Pd and Pt/Rh catalyst technologies.

A theory of diesel exhaust catalysis using an oxidation flow-through type catalyst to reduce particulate emissions is explained. The effects of converter design, catalyst support materials, and the use of noble metals for light and heavy duty applications are discussed. Experiments were performed to determine, 1) the sulfur storage and release characteristics of alumina and silica catalyst support materials and 2) the ability of platinum and palladium to oxidize SO2 to sulfate particulate. Light duty FTP and heavy duty transient results are also presented.

In an effort to reduce hydrocarbon emissions for the upcoming vehicle emission regulations, FTP emissions were measured after the warm-up and underfloor converters using a four cylinder 2.3L 1991 engine on an auto-driver dynamometer stand. The warm-up and underfloor converter were located approximately 13 and 69 cm. respectively from the exhaust manifold. The warm-up and underfloor converter volumes varied from 0 - 2.67 liters. A total catalyst volume of 2.67 liters was distributed in 0.67 liter increments between the warm-up and underfloor converters. All of the converters were dynamometer aged appropriately with respect to their intended position in the exhaust system. Platinum/rhodium catalysts were evaluated in the underfloor location with platinum/rhodium or palladium containing catalysts in the warm-up location.

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.

An investigation into the design, development and evaluation of a “new” washcoat technology family that enables significant reductions in rhodium usage levels has been concluded. These findings were demonstrated on three vehicle applications utilizing different calibration A/F control strategies. Additional testing investigated optimal Rh placement on a two brick catalyst system and the impact on FTP and US-06 test cycles. This study concludes with an evaluation of full useful life aged catalysts tested on 6 and 8 cylinder applications that are shown to have met Bin 4 FFV and ULEVII emission standards.

A 100,000-mile fleet test in nine gasoline-powered passenger cars was carried out. The impact of motor oil phosphorus levels on engine durability, oil degradation, and exhaust emissions has been previously described. The results of additional emissions control systems studies, and measurements of the engine oil additive elements which are present on the catalysts, are now presented. These studies include conversion efficiencies for the aged catalyst at the end of the test by a combination of light-off experiments, air/fuel sweep tests, and an auto-driver FTP. The performance of the lambda sensors is also presented. The relationships between engine oil additive levels and composition and emissions systems durability is presented.

FTP and ECE + EUDC emissions are measured from six converters having similar restriction and platinum group metals on two 1999 prototype engines/calibrations. A 2.2L four cylinder prototype vehicle is used to measure FTP emissions and an auto-driver dynamometer with a prototype 2.4L four cylinder engine is used to determine the ECE + EUDC emissions. The catalytic converters use various combinations of 400/3.5 (400cpsi/3.5mil wall), 400/4.5, 400/6.5, 600/3.5, 600/4.5, and 900/2.5 ceramic substrates in order to meet a restriction target and to maximize converter geometric surface area. Total catalyst volume of the converters varies from 1.9 to 0.82 liters. Catalyst frontal area varies from 68 cm2 to 88 cm2. Five of the six converters use two catalyst bricks. The front catalyst brick uses either a three-way Pd washcoat technology containing ceria or a non-ceria Pd washcoat technology. Pd loadings are 0.1 troy oz. of Pd.