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Emissionsarmer Verkehr - Emissionsminderung durch schadstoffarme Schmierstoffe

: Keller, D.; Boehncke, A.; Mangelsdorf, I.
: Umweltbundesamt -UBA-, Berlin

2001, 83 S.
UBA-FB, 29945143
Fraunhofer ITA ( ITEM) ()
additive; exhaust gas component; NO×-adsorber; sulphated ash; NO2; lubricating oil; fuel additive; sulphur; Catalysts; particle filter; phosphoric acid; combustion

The aim of this study was to collect and evaluate environmentally relevant data on exhaust emissions from the combustion products of engine oils and their effects on the function of (next-generation) emission control systems. Due to the lower EURO 4 emission limits, exhaust aftertreatment systems for heavy- and light-duty vehicles will be necessary which are more efficient than the 3-way- or oxidation-type catalysts common today. Practicable exhaust aftertreatment systems are, for example, particle traps, improved catalysts (including selective catalytic reduction, or fuel-borne catalysts), NO×-adsorbers, and combinations of these systems. Most of these exhaust control devices require fuels with sulphur contents below 10 ppm. In Germany, gasoline that meets this specification has recently been introduced on a small scale. However, the emissions generated by these low sulphur levels are almost in the same order of magnitude as the emissions of sulphur compounds derived from the consumption of lubricants that contain about 0.5 % sulphur. As measurement data in this area is very limited, conclusions have mostly been drawn from experimental results with low sulphur fuels. It cannot be ruled out, expecially for NO×-adsorbers, that sulphur will adversely affect performance all the way down to concentrations of O ppm, thus making a reduction of sulphur levels in engine oils sem necessary. Diesel technologies incorporating precious-metal catalysts (e.g. DOC, CDPF, CR-DPF, UreaSCR) perform better with sulphur levels below 10 ppm because this reduces the mass of sulphate particulate matter formed from fuel or lubricant sulphur. Conventional three-way catalysts are less sensitive, which mainly affects the light-off temperature. In summary, all available studies suggest that the lower the level of sulphur the lower emissions are after passing over the catalyst. Enough evidence is now available to show that phosphorous (associated with the antiwear additive ZDTP) limits catalyst life and, together with thermal degradation, is responsible for reduced catalyst efficiency over time. Lubricants contribute approximately 20 - 26 % to total particulate matter from diesel exhaust (passenger cars) and often more than 50 % to the soluble organic fraction (SOF). Ash deposits derived from additives that contain zinc, calcium, magnesium, or phosphorous are likely to block the newly developed particle filter systems and cannot be removed through thermal regeneration processes. Although there is still a critical lack of available technical information, it can be assumed that engine oil will make a significant contribution to EURO 4 limits of tail-pipe emissions, resulting mainly from secondary poisoning effects on catalyst and filter systems. Further research is thus necessary to make existing engine oil formulations and the important factor vehicle lubricant consumption compatible with the requirements of new exhaust aftertreatment technology.