The effect of total olefin content on ozone forming potential has been widely studied. As a result a stringent limit for olefins is already given in California Specification for “Phase 2” gasoline and the 18 vol% limitation of olefins is expected to tighten also in Europe. However, it is not clear how determining the light olefins are and what is the role of heavy olefins regarding ozone forming potential.
Ethanol is widely used as gasoline component in many countries, but not extensively in Europe. The biofuels have the potential to provide a renewable source of energy and contribute to lower global CO2 emissions. The unregulated emissions, especially particulates and their quality have not been studied extensively with ethanol containing gasoline using European test fleet.
The objective was to study the applicability of heavy olefins in non-oxygenated and ethanol oxygenated gasolines. Alkylates in gasoline were replaced by isooctene. Exhaust emission were measured and ozone forming potential was estimated.
Adding heavy olefins in the form of isooctene showed no major changes in the tailpipe exhaust emissions: regulated emissions, particulate matter, carbon dioxide emission, fuel consumption or unregulated emissions. However some changes for individual hydrocarbons were seen. The preliminary work and estimations indicated that adding isooctene would not increase the ozone forming potential. Thus no real environmental benefit is expected, if the total content of olefins is limited. The limitation should cover only the amount of light olefins (C5 and lighter).
According to our measurements it is also possible to replace ethers to ethanol with same volumetric content without degrading exhaust emissions.