Particulate matter, diesel exhaust

In addition to their primary fimction of reducing particulate matter, diesel catalysts must convert gas phase CO and HC. Emission limits have come down sharply for U.S. trucks, for example, 2009 standards allow only about 1/10 as much as HC as was permitted in 1994. For CO, 2003/2004 limits for Japanese heavy-duty trucks are about 1/3 of their values in 2000. The much leaner diesel exhaust, compared with gasoline exhaust, helps reduce CO and HC emissions, but diesel exhaust is generally cooler, which suppresses conversion. Low temperature activity is, accordingly, are research priority. Pt, or Pt/Pd, supported on alumina, is standard, but even small changes in thermal stability can confer a competitive advantage. 

Effective with the 1982 model year, particulate matter from diesel vehicles was regulated by the U.S. Environmental Protection Agency for the first time, at a level of 0.37 gm km . Diesel vehicles were allowed to meet an NO level of 0.93 gm km under an Environmental Protection Agency waiver. These standards were met by a combination of control systems, primarily exhaust gas recirculation and improvements in the combustion process. For the 1985 model year, the standards decreased to 0.12 gm of particulate matter per kilometer and 0.62 gm of NO per kilometer. This required the use of much more extensive control systems (1). The Clean Air Act Amendments of 1990 (2) have kept the emission standards at the 1985 model level with one exception diesel-fueled heavy trucks shall be required to meet an NO standard of 4.0 gm per brake horsepower hour. 

Why might you expect exhaust gas recirculation on a diesel engine to increase the particulate matter emissions ... 

The main pollutants in Diesel exhausts are NOx and particulate matter (PM), mostly soot, with lesser amounts of CO and light hydrocarbons (CH). Table 12.1 shows the corresponding emission standards in Europe and in the USA. These standards are becoming progressively stricter and Table 12.2 shows the needed conversion efficiency of the electrochemically promoted unit in order to meet the EUR04 2005 standards. 

Mok, Y.S. and Huh, Y.J. (2005) Simultaneous removal of nitrogen oxides and particulate matters from diesel engine exhaust using dielectric barrier discharge and catalysis hybrid system, Plasma Chem. Plasma Process. 25, 625-39. 

Steerenberg, P., et al., Sensitivity to ozone, diesel exhaust particles, and standardized ambient particulate matter in rats with a listeria monocytogenes-induced respiratory infection, Inhal. Toxicol. 16, 5, 311, 2004. 

Airborne particulate matter may be associated with many carcinogenic and other toxic agents. Hazardous materials include coal dust, fly-ash from power stations, metals and metal oxides from mining, extraction and refining and materials used as catalysts in industrial processes, as well as particulate matter from, for example, diesel exhausts. 

The data in Tables 10.27 and 10.28 also show that the percentage of in-use, gasoline-fueled noncatalyst light-duty automobiles dropped from 44% in 1982 to 8% in 1993 and the percentage of their vehicle miles traveled went from 33% to only 4% during that period. Furthermore, while diesel cars accounted for only 1.9 and 1.5% of the in-use light-duty automobiles in 1982 and 1993, respectively, they were responsible for 45 and 40% of the total auto exhaust particulate matter. Par-... 

FIGURE 10.30 Percent conversion-time profiles for the decay of 5 PAHs in diesel exhaust particulate matter (Dp = 0.5 p.m) collected on glass fiber filters and exposed to 1.5 ppm of ozone in air under Hi-Vol sampling conditions. Half-lives (dotted line) decrease in order of the Nielsen (1984) electrophilic reactivity scale (Table 10.30) BaP, benzo[u]pyrene BghiP, benzo[ghi]pclyIcne BeP, benzolelpyrene IndP, indeno[l,2,3-cd]pyrene BkFI, benzolk]fluoranthene (adapted from Van Vaeck and Van Cauwenberghe, 1984). 

Lofroth, G., Comparison of the Mutagenic Activity in Carbon Particulate Matter and in Diesel and Gasoline Engine Exhaust, in Short-Term Bioassays in the Analysis of Complex Environmental Mixtures, II (M. D. Waters, S. Sandhu, J. Lewtas-Huisingh,... 

Tong, H. Y., and F. W. Karasek, Quantitation of Polycyclic Aromatic Hydrocarbons in Diesel Exhaust Particulate Matter by High-Performance Liquid Chromatography Fractionation and High-Resolution Gas Chromatography, Anal. Chem., 56, 2129-2134(1984). 

Harris SJ, Maricq MM (2001) Signature size distributions for diesel and gasoline engine exhaust particulate matter. J Aerosol Sci 32(6) 749-764... 

Fruin SA, Winer AM, Rodes CE (2004) Black carbon concentrations in California vehicles and estimation of in-vehicle diesel exhaust particulate matter exposures. Atmos Environ 38 4121—4133... 

Braun, A., Mun, B. S., Huggins, F. E., and Huffman, G. P. (2007). Carbon speciation of diesel exhaust and urban particulate matter NIST standard reference materials with C(ls) NEXAFS spectroscopy. Environ. Sci. Technol. 41,173-178. 

Ryno, M., L. Rantanen, E. Papaioannou, A.G. Konstandopoulos, T. Koskentalo, and K. Savela. 2006. Comparison of pressurized fluid extraction, Soxhlet extraction and sonication for the determination of polycyclic aromatic hydrocarbons in urban air and diesel exhaust particulate matter. J. Environ. Monit. 8 488 193. 

One way of improving SFE efficiency is by using a more suitable SF to extract the target analyte. Unfortunately, the choice of fluids other than CO, is restricted by the desire to have reasonable critical parameter values and costs, chemical inertness, low toxicity and little environmental impact. The use of supercritical N2O has proved to increase the extraction efficiency for high-molecular weight PAHs and chlorinated dibenzo-p-dioxins from fly ash and sediment [52]. This extractant, however, does not always improve the extraction efficiency [53] also, it can be explosive in the presence of reactive organics. Other polar fluids such as CHCIF, (Freon-22) have exhibited increased efficiency in the extraction of nitrated and non-nitrated PAHs from particulate matter in diesel exhaust [54]. Freon-22 has also been found to allow significantly fast and effective extraction of... 

Human studies are comprised of both occupational and human experimental exposures consisting of exposure to diesel exhaust in the occupational environment and exposure to diluted diesel exhaust or diesel particulate matter under controlled conditions. 

As a fourth step, discussion continues for the introduction of emission limits for other exhaust gas components, and for particulate matter of diesel powered vehicles. For example, there has been discussion in the USA and some European countries on separate - additional - emission limits for carbon dioxide, benzene and/or aldehydes. In the USA there is a project to consider an additional ozone-formation factor to be allocated to the tailpipe emission of passenger cars. This is because each exhaust gas component has a different potential to contribute to atmospheric ozone formation. This potential is quantified according to the theory of Carter by the maximum incremental reactivity (MIR) factor, expressed as grams of... 

The exhaust gas of diesel engines has a complex composition as gaseous components are present together with liquid and even with solid components (Table 23). The solid exhaust gas components are denoted particulate matter, and defined as any matter that can be collected on a teflon-coated filter paper from diluted exhaust gas at a temperature below 325 K. Scanning and transmission electron microscopic pictures of such particulates are shown in Fig. 95. 

As described in Section 1.2.4.B, several technologies have been considered to reduce the amount of particulate matter in the tailpipe exhaust gas of diesel engines. Of these technologies, only the diesel oxidation catalyst has found widespread application. This technology will be described below. 

Likewise, Fig. 112 shows the conversion efficiency for diesel particulate matter reached in the US transient cycle with a diesel catalyst mounted on a heavy duty engine. Table 29 shows the conversion for CO, HC and particulate matter in the European 13-mode test performed with a heavy duty engine for a fresh and for an engine-aged catalyst. The catalyst performance at operating conditions, reflecting the lowest and the highest exhaust gas temperature in this 13-mode test, is also reported. 

Euro 4 limits on diesel particulate matter necessitated the use of diesel particulate filters on some vehicles, highly efficient exhaust after-treatment filters which remove harmful particulate emissions, even down to ca. 10 nm. One consequence is lhal Ihe engine lubricanl is required lo be compatible with the DPF, ensuring that the device functions correctly and efficiently, not only over the complete service interval but for the lifetime of the system. The DPF compatible lubricant is still required to meet all of the traditional performance targets and remain cost effective. 

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