The Influence of Synthetic Oxygenates on Euro IV Diesel Passenger Car Exhaust Emissions

In the year 2005, the EURO IV fuel specification came into effect and the requirements for diesel fuel properties have become even more stringent. In this way, the potential of diesel fuel for emissions reduction has already been to a large extent exploited and the most emissions-sensitive fuel parameters can now be changed in a narrow range only. The shortfall in NO_x and PM emissions control in diesel engines is, however, so great that more drastic fuel changes will be needed. One of the most promising fuel modifications for exhaust emissions control seems to be oxygenated additives.

The objective of the study described in this paper was to analyze under transient conditions the influence of synthetic oxygenated fuel additives on exhaust emissions. The tests were conducted on a Euro IV passenger car. Six oxygenated additives were tested over the New European Driving Cycle (NEDC). The main findings followed from research are:

• Synthetic diesel oxygenated additives are effective at a low concentration of 5% v/v.
• Synthetic diesel oxygenated additives reduce significantly CO, HC and PM emissions, however, this effect is connected with slightly increased NO_x emissions.
• PM emissions reduction is generally dependent on the oxygen content in fuel, whereas CO and HC emissions reduction depends also on the molecular structure of the oxygenate.
• Oxygenated diesel fuels produce a favorable shift in PM/NO_x trade-off.