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Understanding the Role of a nano Ce Additive in the Size Distribution and Organic Composition of Diesel Emissions
Citation:
Nash, D. Understanding the Role of a nano Ce Additive in the Size Distribution and Organic Composition of Diesel Emissions. 31st Annual Meeting of the American Association for Aerosol Research, Minneapolis, MN, October 09 - 12, 2012.
Impact/Purpose:
Iron, cerium, and platinum fuel additives have demonstrated abilities to reduce carbon monoxide and visible emissions of soot from diesel engines, so that there are now commercial products containing these elements being offered for this application. While the use of these fuel additives may be effective in reducing particle mass emissions, and are reported to improve engine performance, their use without the accompanying use of diesel particle traps may result in increases in particle number emissions. Further, in addition to the emissions of the metals themselves, these catalysts may affect the composition and emissions of organic species. This study examines the use of nano cerium as a diesel fuel additive. Particle mass emissions, size distributions, morphology, and chemical composition are being characterized and compared to previous results using ferrocene.
Description:
A number of alkali, alkaline earth, transition, and metalloid elements are known to act as fuel catalysts to limit the formation of soot precursors or promote its oxidation. These have been used with varying success on a variety of stationary and mobile combustion sources. Iron, cerium, and platinum additives have demonstrated abilities to reduce carbon monoxide and visible emissions of soot from diesel engines, so that there are now commercial products containing these elements being offered for this application. While the use of these additives may be effective in reducing particle mass emissions, and are reported to improve engine performance, their use without the accompanying use of diesel particle traps may result in increases in particle number emissions. Further, in addition to the emissions of the metals themselves, these catalysts may affect the composition and emissions of organic species. This study examines the use of nano cerium as a diesel fuel additive. Particle mass emissions, size distributions, morphology, and chemical composition are being characterized and compared to previous results using ferrocene. Dependent variables include fuel metal concentration and engine load. A Yanmar Powersystem YDG-5500E diesel generator is being used to produce representative diesel emissions. Particle mass measurements indicate that cerium is a more effective oxidation catalyst than iron. Particle size distributions indicate a decreasing accumulation mode and a growing ultrafine mode with increasing fuel cerium content. GC/MS analysis of filter samples show a significant increase in particle phase polycyclic aromatic hydrocarbons (PAHs), nitro PAHs (nPAHs), organic acids (OAs) and alkanes (ALs) per volume of exhaust, when cerium is added. Our current efforts employ electron microscopy to indicate where on or within particulate emissions cerium resides and how that might correlate to the relative abundance of each class of organics. Aerosol time-of-flight mass spectrometry (ATOF-MS) methods are being developed and compared with particle size classified inductively coupled plasma – atomic emission spectroscopy (ICP-AES) results to determine cerium’s relative abundance as a function of additive concentration and engine load, yielding information about particle formation mechanisms.