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Gasoline Particulate Filters (GPF), are universally acknowledged as a reliable and high cost effective emission control technology for particulate mass (PM) and particulate number (PN). Bare GPFs can be modified by coating with catalytic washcoat to provide emission reduction for THC, CO and NOx while back pressure (BP) and filtration efficiency (FE) might be influenced. In this study, a four cylinder China 6B calibrated 1.6 L TGDI (turbo gasoline direct injection) vehicle was used to evaluate various catalyst combinations in the close-coupled and underfloor locations. In the close-couple 1 position (CC1), PGM loadings were varied on a 1 L TWC. Next in the close-coupled 2 position (CC2), coated and uncoated 1.4 L GPFs were evaluated. PGM loading was varied on the coated GPFs using 300/8 high porosity substrates. The uncoated GPFs used a 200/8 low porosity substrates. In the underfloor location, PGM loadings were varied on two 0.5 L TWC catalysts.

Higher fuel costs and lower greenhouse gas standards, especially CO2, have compelled vehicle manufacturers to downsize engines while simultaneously using turbochargers on more of their applications. The application of turbochargers improves fuel economy as well as torque and power. However, this also results in lower exhaust temperatures which can challenge the ability of three-way catalysts to achieve low emission levels. This work investigates and compares the catalyst heat-up strategies, hardware, and catalyst architecture of four turbocharged 4-cylinder vehicles: a 2010 VW 2.0L DI, a 2013 Chevy Malibu 2.0L DI, a 2013 Ford Fusion 1.6L DI, and a 2013 Dodge Dart 1.4L Multi-Air. In addition, three emission studies are presented. One study will show a strategy to reduce PGM concentrations in a close-coupled (CC) catalyst.

FTP emissions from a 2.2L four cylinder vehicle are measured from six different converters. These converters have been designed to have both similar flow restriction and to have similar platinum group metals. The durability of these six converters is evaluated after dynamometer aging of both 125 and 250 hours of RATsm aging. These catalytic converters use various combinations of 400/3.5 (400 cells/in2/3.5mil 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. To minimize dependence on palladium the rear brick uses a Pt/Rh washcoat at a loading of 0.06 Toz and a ratio of 5/0/1.

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.

An experiment was performed with a 1.3L catalytic converter design containing a front and rear catalyst each having a volume of 0.65 liters. This investigation varied the front catalyst parameters to study the effects of 1) substrate diameter, 2) substrate cell density, 3) Pd loading and 4) Rh loading on the FTP emissions on three different vehicles. Engine displacement varied from 2.4L to 4.7L. Eight different converters were built defined by a Taguchi L-8 array. Cold flow converter restriction results show the tradeoff in converter restriction between substrate cell density and substrate diameter. Vehicle FTP emissions show how the three vehicles are sensitive to the four parameters investigated. Platinum Group Metals (PGM) prices and Federal Test Procedure (FTP) emissions were used to define the emission value between the substrate properties of diameter and cell density to palladium (Pd) and rhodium (Rh) concentrations.

A new family of automotive three-way conversion (TWC) catalyst technologies has been developed using a Precision Metal Addition (PMA) process. Precious metal (PGM) fixation onto the support occurs during the PMA step when the PGM is added to the slurry immediately prior to application to the monolith substrate. PMA slurries can be prepared with high precision and the slurry manufacturing process is greatly simplified. Further, it has been found that with the use of new generation washcoat (WC) materials, the same WC composition can be used for all three PGMs - Pt, Pd & Rh. Negative interactions between Pd and Rh in the same WC layer do not occur, providing advantages over older technologies. Thus, new WC compositions coupled with the PMA process offers precious metal flexibility. This FlexMetal family of catalyst technologies includes single layer Pd-only, Pd/Rh and Pt/Rh and dual layer bi-metal Pd/Rh and Pt/Rh and tri-metal Pt/Pd/Rh.

In-line hydrocarbon (HC) traps are not widely used to reduce HC emissions due to their limited durability, high platinum group metal (PGM) concentrations, complicated processing, and insufficient hydrocarbon (HC) retention temperatures required for efficient conversion by the three-way catalyst component. New trapping materials and system architectures were developed utilizing an engine dynamometer test equipped with dual Fourier Transform Infrared (FTIR) spectrometers for tracking the adsorption and desorption of various HC species during the light-off period. Parallel laboratory reactor studies were conducted which show that the new HC trap formulations extend the traditional adsorption processes (i.e., based on physic-sorption and/or adsorption at acid sites) to chemical reaction mechanisms resulting in oligomerized, dehydro-cyclization, and partial coke formation.

Proposed LEV-III emission level will require improvements in NMOG, CO and NOx emissions as measured over FTP and US06 emission cycles. Incremental improvements in washcoat technologies, cold start calibration and catalyst system design are required to develop a cost effective solution set. New catalyst technologies demonstrated both lower HC and NOx emissions with 25% less platinum group metals (PGM). FTP and US06 emissions were measured on a 4-cylinder 2.4L application which compares a close-coupled converter and close-coupled + underfloor converter systems. A PGM placement study was performed with the close-coupled converter system employing these new catalyst technologies. Emissions results suggest that the placement of PGM is critical in minimizing emissions and PGM costs.

A production calibrated GTDI 1.6L Ford Fusion was used to demonstrate low HC, CO, NOx, PM (particulate mass), and PN (particulate number) emissions using advanced catalyst technologies with newly developed high porosity substrates and coated GPFs (gasoline particulate filters). The exhaust system consisted of 1.2 liters of TWC (three way catalyst) in the close-coupled position, and 1.6L of coated GPF in the underfloor position. The catalysts were engine-aged on a dynamometer to simulate 150K miles of road aging. Results indicate that ULEV70 emissions can be achieved at ∼$40 of PGM, while also demonstrating PM tailpipe performance far below the proposed California Air Resources Board (CARB) LEV III limit of 1 mg/mi. Along with PM and PN analysis, exhaust system backpressure is also presented with various GPF designs.

The Environmental Protection Agency (EPA) and Department of Transportation's National Highway Traffic Safety Administration (NHTSA) have finalized regulation that will reduce greenhouse gases and increase fuel economy for model year (MY) 2012-2016 light-duty vehicles. This ruling not only includes a CO₂ standard that will require vehicles to achieve fleet average 35 mpg by MY 2016, but will apply a cap on nitrous oxide (N₂O) and methane emissions to 10 and 30 mg/mile, respectively, however CO₂ emission reductions can be exchanged for either N₂O or methane credit. The work outlined investigates the N₂O emissions of a variety of low emission vehicles per the Federal Test Procedure (FTP). Fourier Transform Infrared Spectroscopy (FTIR) was used to measure both bag and modal N₂O emissions. N₂O emissions were less than 1 mg/mile for three SULEV vehicles with 6,400 km-aged catalysts.

A Robust Engineering experiment was performed to determine the effects PGM loading and placement on the FTP emissions of a 4 cylinder 2.4L and two 8 cylinder 4.7L vehicles. 1.3L catalytic converters were used containing a front and rear catalyst of equal volume. The experiment is defined by a Taguchi L-8 array. Eight different combinations of catalyst PGM loadings were aged and evaluated. Results show that nmHC and NOx emissions are predominately affected by the PGM loading of the front catalyst. The rear catalyst is insensitive to either Pt or Pd which can be used at low concentrations. Results also compare the benefits of Pd and Rh to reduce emissions. Confirmation runs suggest that significant reductions in PGM cost can be achieved over baseline designs.

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.

Combinations of CC1 TWC and CC2 coated gasoline particulate filters (cGPF) were aged by 4-mode and fuel cut aging to simulate 200K kilometers of in-use aging in China and Europe, respectively. Separate combinations of catalysts were then evaluated on two low emission engines using the WLTC driving cycle. Catalyst volume and PGM mass were varied in the CC1. OSC/washcoat amounts were varied at constant PGM loading in the GPF. For the Chinese application, after the four-mode aging, it was found that the CC1 TWC catalyst volume should be greater than 1.0 L. High levels of OSC were needed in the GPF to meet CO and NOx emission targets. For the European application, after fuel cut aging, Euro 6d emissions were met with any combination of TWC and GPF catalysts. If the gaseous regulations for Euro 7 are similar to China 6b, the CC1 TWC catalyst should also be great than 1.0 L in order to meet CO and NOx emissions.