Impact of olefin content on criteria and toxic emissions from modern gasoline vehicles

Olefins are an important component of gasoline and an important property with respect to the development of reformulated gasolines using regulatory models. Currently, the coefficients used in regulatory gasoline development models are primarily based on studies conducted in the early 1990s, as an extensive study of olefin gasoline effects has not been conducted since that time. The goal of this study was to evaluate the impact of gasoline fuel olefin content on modern vehicles compliant with US EPA Tier 2 standards. Vehicles were tested with two fuels with different olefin contents, nominally 3% and 15% by volume, over the LA92 test cycle. The results showed that changing the olefin content with the range in this study had a relatively minor impact on exhaust emissions of these latest technology vehicles, including total hydrocarbons (THCs), nitrogen oxides (NOx), and carbon monoxide (CO) emissions as well as toxic emissions such as formaldehyde, acetaldehyde, and benzene. Only exhaust 1,3-butadiene emissions showed significantly higher emissions at higher olefin levels, consistent with a correlation between olefins in the fuel and in the exhaust. This information from this study will be used to provide updates of fuel properties effects for use in the EPA Complex Model and the CARB Predictive Model. (c) 2012 Elsevier Ltd. All rights reserved.