Research Program Area: Emissions Monitoring & Control
Exhaust emissions from five late model vehicles were measured to determine the effect of aromatic fuel components on benzene emissions. The purpose of the work was to determine if there are any fuel components that are major sources of benzene emissions. Reducing the content of such components in gasoline could then be a means of reducing benzene emissions. Analyses of engine-out (before catalyst) and tailpipe-out (after catalyst) exhaust emissions were made to determine catalyst efficiency for reducing benzene emissions.
Benzene (in fuel) effect on benzene exhaust emissions was much greater than that of the other aromatic species. On an equal volume basis, the non-benzene aromatics -- toluene, ethylbenzene, xylenes, and C9+ aromatics -- had an average effect on benzene emissions about 1/12 that of fuel benzene. All of the non-benzene aromatic components tend to increase exhaust benzene levels. However, the ethlybenzene effect was not statistically significantly different from zero.
The benzene reduction efficiency of the exhaust emissions control systems was about the same as total hydrocarbon reduction efficiency. Benzene emissions were reduced by 70 to 95% by the exhaust emission control systems.
Predictive equations were developed using the results of this study. These equations enable estimation of the changes in the benzene emissions as a function of changes in gasoline composition.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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