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The ceramic wall-flow filter has now been globally commercialized for aftertreatment systems in light-duty gasoline engine powered vehicles. This technology, known as the gasoline particulate filter (GPF), represents a durable solution for particulate emissions control. The goal of this study was to track the evolution of tailpipe particulate and gaseous emissions of a 4-cylinder gasoline turbocharged direct injected (GTDI) 2018 North American (NA) mild-hybrid light-duty SUV, from a fresh state to the 4,000-mile, EPA certification mileage level. For this purpose, a production TWC + GPF aftertreatment system designed for a China 6b-compliant variant of this test vehicle was retrofitted in place of the North American Tier 3 Bin 85 TWC-only system. Chassis dyno emissions testing was performed at predetermined mileage points with real-world, on-road driving conducted for the necessary mileage accumulation.

Passive hydrocarbon traps (“HCT”) are limited in performance when installed in an oxygen deprived location, such as an underfloor that is downstream of a CC TWC. An OEM 1.0L close-coupled converter in a 1.4L turbo hybrid PZEV calibrated vehicle was replaced with a 1.24L HC trap. The HC trap consisted of a zeolytic storage layer beneath a Pd/Rh containing three-way catalyst layer. The UF converter was upgraded with a newer TWC technology. The HC trap and UF TWC were engine aged to simulate 150,000 miles, or full useful life conditions. Criteria for accelerated engine aging of the HC trap were selected based on the vehicle application’s peak operating bed temperatures in the field. Vehicle FTP and US-06 tests were conducted on an all-wheel drive dyno which facilitated normal hybrid powertrain operation. A SULEV20 engineering target for FTP nMHC+NOx emissions was met with the full useful life aged CC HC Trap (“HCT”) system, using a PGM amount that was lower than the OEM design.

A 1.0 L underfloor converter of a 1.4 L PZEV calibrated vehicle was replaced with a 1.26 L HC trap and a 1.26 L SCR catalyst. The HC trap consisted of a zeolitic storage layer beneath a three-way catalyst layer. A newly developed catalyzed HC trap technology containing Pd/Rh was used in the current study. Increased trapping efficiency and conversion was assigned to rapid and efficient polymerization of small alkenes and aromatics coupled with more efficient combustion before release. The new trap features include the presence of strong Brønsted acidity, precious metals such as Pd and a base Mn+ redox active metal. The HC trap was followed by an SCR catalyst for NOx clean-up. The production close-coupled catalyst and replacement underfloor catalysts (HC trap and SCR) were aged on a combination of rural and highway roads for 150,000 miles. Peak bed temperatures during road aging of the HC Trap and SCR catalyst were approximately 600 °C.

Federal Test Procedure (FTP) emissions were measured on a 2009 4 cylinder 2.4L Malibu PZEV vehicle with 10 and 30ppm sulfur fuel while varying the PGM (Platinum Group Metals) of the close-coupled and underfloor converters. Base CARB PH-III certification fuel was used. Three consecutive FTPs were used to measure the impact of fuel sulfur and catalyst PGM loading combinations. In general, reducing fuel sulfur and increasing catalyst PGM loadings, decrease FTP emissions. Increasing Pd concentrations can mitigate the impact of higher fuel sulfur concentrations. The results also suggest that a 50% reduction in PGM can be achieved with a reduction in fuel sulfur from 30 to 10 ppm. On average, NMHC, CO and NOx emissions were reduced by 12, 49 and 64%, respectively with the 10 ppm sulfur fuel. In addition, HC and NOx vehicle emission variability were reduced by 74 and 57% with the 10 ppm sulfur fuel.