Robert Henry Hammerle

ORGANIC EMISSIONS PROFILE FOR A LIGHT-DUTY DIESEL VEHICLE

In this report we describe the speciated gas-phase hydrocarbon and carbonyl emissions as collected from a recent model automobile powered by a 2.5l indirect injection diesel engine and outfitted with a production oxidation catalyst for exhaust after-treatment. The vehicle was run on a typical low sulfur (500 ppm S) European diesel fuel and measurements were made over the European MVEG test cycle. The diluted tailpipe emissions were sampled for light hydrocarbons (C1C12) using Tedlar bags and semi-volatile hydrocarbons (C12C20+) using Tenax cartridges. Both the light and semi-volatile hydrocarbon fractions were speciated using capillary gas chromatography. Combining the two sets of speciation data provided a profile of the gas-phase hydrocarbon emissions from a light duty diesel vehicle. Of the total gas phase non-methane hydrocarbons emitted, 80% were accounted for in the light hydrocarbon fraction, and 20% in the semi-volatile fraction. The semi-volatile fraction, which extended only to about C15, was composed almost entirely of unburned fuel molecules, but with enrichment of the aromatic species relative to the fuel itself. n-Alkanes (paraffins) and methylnaphthalenes accounted for approximately 37% of the semi-volatile fraction. Aldehydes and ketones represented 34% of NMOG. Formaldehyde and acetaldehyde, account for 74% of the total carbonyl emissions.

Lean NOx catalysis for diesel passenger cars: Investigating effects of sulfur dioxide and space velocity

Abstract European Stage III emissions requirements will be difficult to meet for diesel passenger cars if lean NOx catalysts are not available. Current prototype lean NOx technology for diesels consists of Pt based and Cu zeolite catalysts. Both types have been examined for this study. The former is most active at low temperatures, approximately 190–250°C. The latter has optimum activity at higher temperatures, usually above 350°C. Maximum flow reactor activity of 40–55% NOx conversion (25 000–50 000/h space velocity) has been measured for Pt catalysts using a synthetic feedgas. During the MVEuro2 driving cycle, 35–40% of mass NOx has been emitted at inlet catalyst temperatures from 120 to 200°C. These temperatures fall below optimum temperatures for current Pt based lean NOx catalysts. For temperatures above 350°C, where Cu zeolite catalysts are active, one vehicle has emitted ca. 30% of mass NOx during MVEuro2. These high temperatures are achieved during high speed, hard acceleration driving; although attained briefly during the MVEuro2 cycle, these high temperature emissions could be a critical contribution under customer driving conditions. Effects of sulfur dioxide (SO2) and space velocity (SV) have been investigated as part of a strategy to optimize NOx removal with lean NOx catalysts. Elimination of feedgas SO2 can lower NOx light off temperature for both Pt and Cu zeolite. Some Pt catalysts do not show this behavior. Additional evaluation of a Cu zeolite catalyst demonstrates that poisoning by feedgas SO2 is reversible during evaluation or aging. This result suggests that if sulfur could be removed from diesel fuel, aged Cu zeolite catalysts could be practical. Decreasing space velocity will help NOx removal over Pt by (i) lowering NOx light off temperature, (ii) lowering the temperature at which peak NOx conversion occurs, (iii) increasing the level of peak NOx conversion, and (iv) widening the temperature window for NOx reduction. For Cu zeolite, decreasing space velocity can help mainly by lowering NOx light off temperature and temperature where maximum NOx conversion starts. Both increased catalyst volume and sulfur removal provide Pt catalysts with a NOx temperature window that coincides better with low temperatures where most NOx mass is emitted. SV effects on lean NOx reduction are explained by discussion of possible mechanistic features.

Technical advantages of urea SCR for light-duty and heavy-duty diesel vehicle applications

The 2007 emission standards for both light-duty and heavy-duty diesel vehicles remain a challenge. A level of about 90% NOx conversion is required to meet the standards. Technologies that have the most potential to achieve very high NOx conversion at low temperatures of diesel exhaust are lean NOx traps (LNTs) and Selective Catalytic Reduction (SCR) of NOx using aqueous urea, typically known as Urea SCR. The LNT has the advantage of requiring no new infrastructure, and does not pose any new customer compliance issues. However, Urea SCR has high and durable NOx conversion in a wider temperature window, a lower equivalent fuel penalty, and lower system cost. On a technical basis, Urea SCR has the best chance of meeting the 2007 NOx targets. This paper reviews the results of some demonstration programs for both light-and heavy-duty applications.

NOx self-inhibition in selective catalytic reduction with urea (ammonia) over a Cu-zeolite catalyst in diesel exhaust

Abstract A NOx self-inhibiting effect was observed in the selective catalytic reduction (SCR) of NOx on a diesel engine over a Cu-zeolite catalyst with NH3 as the reductant (supplied either directly or as urea). The effect was strongest at low-temperatures (

Performance of a Catalyzed Diesel Particulate Filter System During Soot Accumulation and Regeneration

The trapping and regeneration behaviors of a diesel particulate filter (DPF), including particle size, are examined via engine dynamometer testing. The exhaust system consists of two active lean NO x (ALN) catalysts in series followed by a catalyzed DPF. Forced regenerations are accomplished by injecting diesel fuel into the exhaust in front of the ALN catalysts to generate an exotherm sufficient to induce soot oxidation. Results are reported for two diesel fuels, one with 340 ppm sulfur, and the other with 4 ppm sulfur, and as a function of DPF regeneration temperature. The results show the DPF to be very effective at removing particulate matter, >99% efficiency. The <1% of particles that escape trapping exhibit a size distribution very similar to engine out soot. During regeneration, particle emissions remain well below engine out levels for the low sulfur fuel, but exhibit a temporary nucleation mode of about ten times the engine out level for the high sulfur fuel. The regeneration rate increases exponentially with temperature, and the fastest regenerations suffer the lowest fuel economy penalty.

NO reduction by urea under lean conditions over alumina supported catalysts

We prepared Pt on alumina and Au on alumina catalysts using a single step sol–gel process and traditional techniques, such as impregnation and deposition–precipitation. The activity of these catalysts was tested for NO x reduction with aqueous urea solutions under oxidizing conditions. Our results show that when a bubbler was used to feed urea and water, catalysts prepared by the sol–gel process had better performance than the catalysts prepared with impregnation and deposition–precipitation methods. The NOx conversion changed almost linearly over Au on alumina catalysts regardless of preparation techniques but over the single step sol–gel synthesized Pt on alumina catalyst (Pt-SG) a typical dome shape of the conversion versus temperature curve was observed. Oxygen in the feed increased the conversion activity and the presence of SO2 did not have an adverse effect on the activity of Pt-SG and the single step sol–gel Au on alumina (Au-SG) and the impregnation Au on sol–gel alumina (Au-IMP-SG) catalysts.

Urban and regional ozone air quality: Issues relevant to the automobile industry

Abstract Of the six criteria pollutants for which National Ambient Air Quality Standards (NAAQS) have been established in the U.S., ozone has been the most difficult to control. This report assesses the technical issues and control measures relevant to the ozone air quality standard, including health and welfare effects, the effect of past control efforts, the current understanding of ozone‐precursor relationships, Federal and California attainment strategies, and implications of the 1990 Clean Air Act Amendments and California clean air programs. Despite progress in reducing volatile organic compounds (and oxides of nitrogen) emissions over the last 2 decades, improvement in ozone air quality has been slow. It is clear now that in the worst areas even the most costly and stringent of all available control measures will not lower emissions levels sufficiently to meet the ozone air quality standard. A central issue is how rapidly to proceed to reduce ozone levels, i.e., how to balance the urgency of attain...

Hydrocarbon and Aldehyde Emissions From an Engine Fueled With Ethyl-t-Butyl Ether

Organic exhaust emissions (including formaldehyde) from a small-displacement, single-cylinder, spark-ignition engine fueled on either ethyl-t-butyl ether of 2,2,4-trimethylpentane show differences that are less than {plus minus}20 percent from the mean of repeat measurements for all non-fuel species except propylene. Such differences are within the data scatter observed upon repetitive measurements with a single fuel and should not be regarded as significant in these experiments. The factor of 3.5 reduction in propylene when the engine is fueled on ETBE is significant and can be rationalized based on the differences in the molecular structures of the two fuels. These preliminary results suggest that the nonfuel organic exhaust species emissions and total organic mass emissions from ETBE fuel are similar to those from a typical branched alkane to within the {plus minus}20% data uncertainty.

A method for the speciation of diesel fuel and the semi-volatile hydrocarbon fraction of diesel-fueled vehicle exhaust emissions

Although much has been learned in recent years about the atmospheric reactivity of the hydrocarbon (HC) emissions from gasoline-fueled vehicles, there is only a limited database of corresponding information for exhaust emissions from diesel-fueled vehicles. An assessment of exhaust reactivity requires speciation, or measurement of the individual species of the HC fraction. The HC exhaust emissions are a complex mixture of unburned and partially burned fuel components. Because diesel fuel contains a much higher molecular weight range (typically C{sub 9}-C{sub 26}) than gasoline (typically C{sub 5}-C{sub 12}), new methodology was required to accommodate the collection and analysis of the >C{sub 12} fraction of the HC exhaust. As part of a study of the effects of fuel and other factors on the chemical nature of diesel emissions, the authors have developed a method for the collection and analysis of the semi-volatile or heavy HC (>C{sub 12}) fraction of the exhaust. The method has a sensitivity for individual HC species of 0.2 ng/L of dilute exhaust. In this report they describe the method and its application to fuel and exhaust analysis. Speciation results are presented for two fuels and for the heavy hydrocarbon fraction of the exhaust from selected vehicle tests.

Sulfate emissions from vehicles on the road

Experiments have been conducted to measure vehicle sulfate emissions, by vehicle type, at two tunnels on the Pennsylvania Turnpike. A satisfactory balance between estimated fuel sulfur consumption and observed emissions of sulfur compounds corrected for ambient-air contributions was obtained. This work started in 1974 before the introduction of catalyst-equipped automobiles and continued into 1976. The sulfate contributed by vehicles even in the tunnels was found to be generally modest relative to rural ambient sulfate levels. Average sulfate emission rates were found to be approximately 30 mg/km (50 mg/mi) from heavy-duty Diesel trucks, ..SO/sub 4//sup -2/ conversion of the vehicle emissions was 2%.