Influence of gasoline olefin and aromatic content on exhaust emissions of 15% ethanol blends

This research focused on the determination of relationships between aromatic and olefins in fuels with constant concentration of ethanol compared with blends without the oxygenate compound. Nine fuels were used for testing prepared by match blending, four of them were non-oxygenate with high and low levels of aromatics and olefins, another four were fuels with 15% volume of ethanol and similar levels of aromatic and olefins. The ninth fuel was oxygenated with 7% volume ethanol to monitor differences in vehicle performance. This study evaluated the tailpipe emissions of four-model year 2017-2018 light-duty gasoline vehicles subjected to the EPA protocol related to FTP-75. During cold start period CO contribution to emissions increase in the ethanol blends, being greater with the low olefins blends, while, NOx emissions are reduced in the low aromatic fuels without ethanol compared with the high aromatic blends. Principal components analysis was used to investigate the relationship between formulated fuels. Non-oxygenated fuels with high aromatic and olefin content shows higher values of the ozone formation. The aromatic content is positively related with hydrocarbons and CO2 emissions. Additionally the aromatic content is related with 3-methylpentane and the BTEX compounds. NOx emissions are related with ethanol content, but inversely associated with the carbon fraction of fuels.