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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.

A new adsorber system for reducing cold start HC emissions has been developed that offers a passive and simplified alternative to previous HC adsorber technologies. The series flow in-line adsorber concept combines existing catalyst technology with a zeolite based HC adsorber by simply incorporating one additional adsorber catalyst substrate into conventional catalytic converters without any valving, purging lines or special substrates. The HC adsorber catalyst consist of a durable zeolite, a washcoat binder, precious group metals and rare earth promoters on standard monolithic substrates. For selected vehicle applications, a single converter containing a light off catalyst, a catalyzed HC adsorber and a standard three-way catalyst can be used in the underfloor position. Even after severe engine aging, the vehicle FTP results show that this new technology remains effective in reducing the cold start HC emissions while providing good CO and NOx conversions.

An adsorber system for reducing cold start hydrocarbon (HC) emissions has been developed combining existing catalyst technologies with a zeolite-based HC adsorber. The series flow in-line concept offers a passive and simplified alternative to other technologies by incorporating one additional adsorber substrate into existing converters without any additional valving, purging lines, or special substrates. This contribution describes the current development status of hydrocarbon adsorber aftertreatment technologies. We report results obtained with a variety of adsorber, start-up, and underfloor catalyst system combinations. In each case, it was possible to achieve HC emission levels in compliance with the ULEV standards, and in the best cases, demonstrating HC emissions substantially below the legislated standard.

The project objective was to generate experimental data to evaluate the impact of metals doped B20 on DPF ash loading and performance compared to that of conventional petrodiesel. Accelerated ash loading was conducted on two DPFs – one exposed to regular diesel fuel and the other to B20 containing metal dopants equivalent to 4 ppm B100 total metals (currently total metals are limited to 10 ppm in ASTM D6751, the standard for B100). Periodic performance evaluations were conducted on the DPFs at 10 g/L ash loading intervals. After the evaluations at 30 g/L, the DPF was cleaned with a commercial DPF cleaning machine and another round of DPF evaluations were conducted. A comparison of the effect of ash loading with the two fuels and DPF cleaning is presented. The metals doped B20 fuel resulted in ash that was similar to that deposited when exposed to ULSD (lube oil ash) and exhibited similar ash cleaning removal efficiency.

This project’s objective was to generate experimental data to evaluate the impact of metals doped B20 on diesel particle filter (DPF) ash loading and performance compared to that of conventional petrodiesel. The effect of metals doped B20 vs. conventional diesel on a DPF was quantified in a laboratory controlled accelerated ash loading study. The ash loading was conducted on two DPFs – one using ULSD fuel and the other on B20 containing metals dopants equivalent to 4 ppm B100 total metals. Engine oil consumption and B20 metals levels were accelerated by a factor of 5, with DPFs loaded to 30 g/L of ash. Details of the ash loading experiment and on-engine DPF performance evaluations are presented in the companion paper (Part I). The DPFs were cleaned, and ash samples were taken from the cleaned material. X-ray Fluorescence (XRF), X-Ray Photoelectron Spectroscopy (XPS) and X-Ray Diffraction (XRD) were conducted on the ash samples.

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.

Advances in extrusion die technology allow ceramic substrate suppliers to provide new monolithic automotive substrates with considerably higher cell densities and thinner wall thicknesses. These new substrates offer both faster light off and better steady state efficiencies providing new flexibility in the design of automotive catalytic converters. The effectiveness-NTU methodology is used to evaluate various design parameters of the HCD substrates. Various theoretical derivations are supported with experimental results on substrates with cell densities ranging from 400 to 1200 cells per square inch with varying wall thicknesses. Performance effects such as steady state conversion, transient response both thermal and emission, flow restriction and FTP emissions results are evaluated. Poison deposition is studied and the effects on emissions performance evaluated.

Although improvements in NOx adsorber formulations are increasing the sulfur resistance of these materials, and legislation continues to further restrict sulfur levels in fuels, sulfur poisoning remains as one of the key issues associated with successful commercialization of NOx adsorber technology throughout the world. Because of the stability of the sulfate poisons, high temperatures which stress the thermal stability of some of the most efficient NOx adsorbents are required for desulfation. Additionally, the rich condition which favors sulfur release simultaneously increases the H2S content of the emission. Sulfur traps offer the potential for reducing the formation of poisoning sulfates on downstream NOx adsorbents. Results characterizing the sulfur scavenging efficiency of these materials, as well as the conditions required for their regeneration will be presented. Strategies for their successful application on motor vehicles will be discussed.

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.