Rasto Brezny

Black Carbon Emissions in Gasoline Exhaust and a Reduction Alternative with a Gasoline Particulate Filter

Black carbon (BC) mass and solid particle number emissions were obtained from two pairs of gasoline direct injection (GDI) vehicles and port fuel injection (PFI) vehicles over the U.S. Federal Test Procedure 75 (FTP-75) and US06 Supplemental Federal Test Procedure (US06) drive cycles on gasoline and 10% by volume blended ethanol (E10). BC solid particles were emitted mostly during cold-start from all GDI and PFI vehicles. The reduction in ambient temperature had significant impacts on BC mass and solid particle number emissions, but larger impacts were observed on the PFI vehicles than the GDI vehicles. Over the FTP-75 phase 1 (cold-start) drive cycle, the BC mass emissions from the two GDI vehicles at 0 °F (-18 °C) varied from 57 to 143 mg/mi, which was higher than the emissions at 72 °F (22 °C; 12-29 mg/mi) by a factor of 5. For the two PFI vehicles, the BC mass emissions over the FTP-75 phase 1 drive cycle at 0 °F varied from 111 to 162 mg/mi, higher by a factor of 44-72 when compared to the BC emissions of 2-4 mg/mi at 72 °F. The use of a gasoline particulate filter (GPF) reduced BC emissions from the selected GDI vehicle by 73-88% at various ambient temperatures over the FTP-75 phase 1 drive cycle. The ambient temperature had less of an impact on particle emissions for a warmed-up engine. Over the US06 drive cycle, the GPF reduced BC mass emissions from the GDI vehicle by 59-80% at various temperatures. E10 had limited impact on BC emissions from the selected GDI and PFI vehicles during hot-starts. E10 was found to reduce BC emissions from the GDI vehicle by 15% at standard temperature and by 75% at 19 °F (-7 °C).

Impact of Fuel Metal Impurities on the Durability of a Light-Duty Diesel Aftertreatment System

Alkali and alkaline earth metal impurities found in diesel fuels are potential poisons for diesel exhaust catalysts. A set of diesel engine production exhaust systems was aged to 150,000 miles. These exhaust systems included a diesel oxidation catalyst, selective catalytic reduction (SCR) catalyst, and diesel particulate filter (DPF). Four separate exhaust systems were aged, each with a different fuel: ultralow sulfur diesel containing no measureable metals, B20 (a common biodiesel blend) containing sodium, B20 containing potassium, and B20 containing calcium, which were selected to simulate the maximum allowable levels in B100 according to ASTM D6751. Analysis included Federal Test Procedure emissions testing, bench-flow reactor testing of catalyst cores, electron probe microanalysis (EPMA), and measurement of thermo-mechanical properties of the DPFs. EPMA imaging found that the sodium and potassium penetrated into the washcoat, while calcium remained on the surface. Bench-flow reactor experiments were used to measure the standard nitrogen oxide (NOx) conversion, ammonia storage, and ammonia oxidation for each of the aged SCR catalysts. Vehicle emissions tests were conducted with each of the aged catalyst systems using a chassis dynamometer. The vehicle successfully passed the 0.2 gram/mile NOx emission standard with each of the four aged exhaust systems.

Gasoline Particulate Filters as an Effective Tool to Reduce Particulate and Polycyclic Aromatic Hydrocarbon Emissions from Gasoline Direct Injection (GDI) Vehicles: A Case Study with Two GDI Vehicles

We assessed the gaseous, particulate, and genotoxic pollutants from two current technology gasoline direct injection vehicles when tested in their original configuration and with a catalyzed gasoline particulate filter (GPF). Testing was conducted over the LA92 and US06 Supplemental Federal Test Procedure (US06) driving cycles on typical California E10 fuel. The use of a GPF did not show any fuel economy and carbon dioxide (CO2) emission penalties, while the emissions of total hydrocarbons (THC), carbon monoxide (CO), and nitrogen oxides (NOx) were generally reduced. Our results showed dramatic reductions in particulate matter (PM) mass, black carbon, and total and solid particle number emissions with the use of GPFs for both vehicles over the LA92 and US06 cycles. Particle size distributions were primarily bimodal in nature, with accumulation mode particles dominating the distribution profile and their concentrations being higher during the cold-start period of the cycle. Polycyclic aromatic hydrocarbons (PAHs) and nitrated PAHs were quantified in both the vapor and particle phases of the PM, with the GPF-equipped vehicles practically eliminating most of these species in the exhaust. For the stock vehicles, 2-3 ring compounds and heavier 5-6 ring compounds were observed in the PM, whereas the vapor phase was dominated mostly by 2-3 ring aromatic compounds.

Effect of Accelerated Aging Rate on the Capture of Fuel-Borne Metal Impurities by Emissions Control Devices

Small impurities in the fuel can have a significant impact on the emissions control system performance over the lifetime of the vehicle. Of particular interest in recent studies has been the impact of sodium, potassium, and calcium that can be introduced either through fuel constituents, such as biodiesel, or as lubricant additives. In a collaboration between the National Renewable Energy Laboratory and the Oak Ridge National Laboratory, a series of accelerated aging studies have been performed to understand the potential impact of these metals on the emissions control system. This paper explores the effect of the rate of accelerated aging on the capture of fuel-borne metal impurities in the emission control devices and the subsequent impact on performance. Aging was accelerated by doping the fuel with high levels of the metals of interest. Three separate evaluations were performed, each with a different rate of accelerated aging. The aged emissions control systems were evaluated through vehicle testing and then dissected for a more complete analysis of the devices. Results from these experiments show that increasing the rate of acceleration impacts the amount of fuel-borne metals that are captured by the catalyst, which subsequently impacts the catalyst performance. Beyond a certain threshold, the acceleration rate creates an artificial mechanism for catalyst deactivation. In the range of acceleration rates that were examined in this study, these effects were primarily isolated to the inlet of the catalyst whereas performance further down the length of the catalyst was mostly unaffected.

Emission Performance of California and Federal Aftermarket TWC Converters

Original equipment (OE) catalytic converters are designed to last the life of properly tuned and maintained vehicles. Many high mileage vehicles require a replacement converter because the original catalyst was damaged, destroyed, or removed, and the cost of a new OE converter on an older vehicle is difficult to justify. In the U.S., a federal aftermarket converter program has been in place since 1986 (California in 1988) and it has resulted in the replacement of over 50 million converters. Both Federal and California programs have required aftermarket converters to meet minimum performance and durability standards. Increasingly tighter emission standards and durability requirements for new light-duty vehicles have resulted in significant technology improvements in three-way automotive catalysts, however these advancements have not always made their way into aftermarket converters. California amended their aftermarket converter program in 2009, doubling the durability requirements and tightening the emission standards to match the original certification limits of the vehicles. To evaluate the difference in emissions performance between the state-of-the art California Air Resources Board (ARB) aftermarket converters and those offered in the federal market, a test program was designed to compare the two technologies across five LEV I certified vehicles. Federal and ARB converters were aged over a RAT-A cycle to represent 25,000 and 50,000 equivalent road miles of aging. Fresh and aged converters were tested over the FTP-75 test cycle. The ARB converters reduced criteria pollutants by an average of 77% NOx, 60% HC and 63% CO below today’s Federal aftermarket converters. The data indicates that significant emission benefits could be achieved by revising federal aftermarket regulations to match those required by California. BACKGROUND & INTRODUCTION The catalytic converter is an essential component of a lightduty vehicle’s emission control system. In the U.S., new catalytic converters have been installed on passenger cars and light-duty trucks since 1975 to meet Federal or California light-duty vehicle emission standards. OE catalytic converters are designed to last the life of properly tuned and maintained vehicles. For model year 1998 and newer vehicles, this represents 120,000 miles (for some California-certified Partial Zero Emission Vehicle (PZEV) vehicles, the useful life is 150,000 miles). Due to the high durability requirements necessary to last the full useful life (FUL) of a vehicle, the OE catalysts must use high levels of precious metals and other expensive materials. Over time, however, the emission reduction effectiveness of an OE catalytic converter may be severely degraded or even completely destroyed. Excessive vibration or shock, excessive heat, lack of proper vehicle maintenance, or improper vehicle operation can cause catalyst failures. Contaminants from lubricating oil such as phosphorus, calcium and zinc have been found to poison catalysts over time [1]. In addition, converters can be structurally damaged in accidents or if the vehicle hits an obstruction such as a large rock or debris on the road. If the vehicle is beyond its emissions warranty, the cost of a new original equipment converter can be prohibitive. Many vehicles requiring a replacement converter have considerably less than 100,000 miles of remaining life, making the cost of a new OE converter difficult to justify. Because of this, and the sometimes scarce availability of the original equipment converters for older vehicles, less expensive aftermarket converters give vehicle owners more incentive to replace their ineffective or damaged converters after the original emission warranty has expired. About 10 years after catalytic converters were first introduced in the United States, Environmental Protection Agency (EPA) officials determined that a replacement catalytic converter program offering cost effective replacement for damaged converters on vehicles beyond their full useful life was needed. EPA estimated that the cost of purchasing a new OEM converter could range from

Evaluation of a Gasoline Particulate Filter to Reduce Particle Emissions from a Gasoline Direct Injection Vehicle

300 to

Impact of Ambient Temperature on Gaseous and Particle Emissions from a Direct Injection Gasoline Vehicle and its Implications on Particle Filtration

1,000. An aftermarket converter market began to develop, but some of these converters were inferior products, offering little or no pollution control capability. Without regulatory requirements, there was no way to determine whether these converters were performing properly or if they were installed on the right vehicles. In response, EPA established an aftermarket converter enforcement policy [2]. In the U.S., a Federal aftermarket converter program has been in place since 1986 (California began their program in 1988) and it has resulted in the replacement of over 50 million converters that were damaged, destroyed, or removed. Both the Federal and California programs have required that aftermarket converters meet certain minimum performance standards while also requiring installers to install only converters approved for specific vehicles. The U.S. EPA aftermarket converter program requires that a catalytic converter demonstrate specific conversion efficiencies after 25,000 miles of operation. The metal shell and exhaust pipes must last 5 years or 50,000 miles. The emission reductions at the end of the 25,000 mile durability period must be at least 70% for HCs, 70% for CO, and 30% for NOx below engine-out levels. The EPA program requires that the manufacturer demonstrate, by testing over the EPA Federal Test Procedure (FTP-75) with a chassis dynamometer, that the emission performance requirements can be on a fully aged converter. To demonstrate this level of durability, two catalyst equipped vehicles must be driven over a prescribed route consistent with the driving schedule described in U.S. EPA regulation Title 40 CFR 86 Appendix IV [3] until the accumulated mileage has been achieved. A manufacturer may propose an alternatively accelerated bench aging of the converter that simulates 25,000 miles of service provided a correlation to vehicle road aging was previously demonstrated to EPA. Following the aging protocol, the manufacturer must demonstrate that the converter meets the above tailpipe emission conversion efficiencies. In 1988, the ARB adopted its own regulations that permit the sale and installation of non-OEM replacement catalytic converters on California vehicles [4]. FTP conversion efficiencies of 70% for HC and CO and 60% for NOx after completion of a 25,000 mile converter durability demonstration was chosen primarily to provide some consistency with the EPA program while offering emission reductions beyond the Federal converter replacement policies. In 2001, California amended their aftermarket program to require aftermarket converters installed on vehicles equipped with On-Board Diagnostic (OBD) monitoring to carry a 50,000 mile warranty and be compatible with the OBD system by not illuminating the Malfunction Indicator Lamp (MIL) light over the full warranty period. Furthermore California allowed the use of the dynamometer RAT-A accelerated aging cycle [5] to demonstrate converter full useful life durability. Both programs allowed the sale of used or remanufactured converters which have been removed from salvage vehicles. These converters must pass a simple emissions test to insure a minimum level of performance, however, because the operating history is unknown, the remaining operating life cannot be guaranteed. The most cost-effective replacement converters are newly manufactured aftermarket converters. The catalyzed ceramic honeycombs in these aftermarket converters are manufactured by many of the same companies supplying OEM converters. Due to the lower durability requirements, manufacturers are able to use lower quantities of precious metals and other materials thus offering substantial cost savings to the consumer. Although the function of a three-way catalytic converter (TWC) has remained relatively constant during its nearly forty years of use on light-duty gasoline vehicles, the primary converter components (catalytic coatings, substrates, mounting materials, stainless steels) have gone through a continuous evolution and redesign processes aimed at improving the overall performance of the converter [6]. These catalytic converter advances include improvements in catalytic converter washcoats, precious metal loading, and substrate designs, in combination with better vehicle fuel control systems [7,8,9]. A similar re-engineering effort has occurred with other exhaust system components, such as exhaust manifolds, oxygen sensors and exhaust pipes, that complement improvements in catalytic converter technology. A large driver in the continuous improvement processes for both catalytic converters and exhaust system components has been the adoption of increasingly tighter emission standards and durability requirements for new light-duty vehicles required by the Federal Tier 2 and California’s LEV II regulations. The performance-based catalytic converter re-engineering effort has had three main focuses: wide application of closecoupled converters mounted near the exhaust manifold of engines, the development and use of high cell density, thin wall substrates, and the design of advanced, high performance TWCs for both close-coupled and under-floor converter applications. Manufacturers have gained a greater understanding of the interactions between precious metal catalysts and the oxide support materials used in the washcoat [10,11,12]. The use of more thermally stable support materials and mixed oxides exhibiting important functionalities like oxygen storage have led to a new level of performance from these catalysts [13]. Significant advances have occurred in the coating of the substrate by positioning the precious metals on specific support materials within the washcoat layers to either promote specific reactions or protect the precious metal from poisons in the exhaust. Zone coating is another advance in catalyst coating technology whic