Effect of Gasoline Composition (Olefins, Aromatics and Benzene) on Automotive Exhaust Emissions - A Literature Review

Available information in the literature has been reviewed to understand the effect of gasoline composition (olefins, aromatics and benzene) on the exhaust emissions from two and four wheeled vehicles. Studies show that isolating the effect of an individual compositional characteristics may be difficult. Aromatics in the exhaust could be correlated with the aromatics in the fuel. The benzene and toluene fractions in the exhaust were sometimes more than in the fuel because of dealkylation of higher alkyl aromatics. The olefins fraction in the exhaust were also observed to be more than in the fuel. The olefin fraction was noted to be directly proportional to the sum of olefins and paraffins in the fuel, and, inversely proportional to the aromatics. Exhaust emissions of benzene may be due to benzene content in the fuel or benzene formation during combustion or over the catalytic converter due to dehydroalkylation of the alkyl benzene. Generally, higher olefins in the fuel led to lower HC, lower CO and marginally higher NOx. Higher total aromatics in the fuel led to higher HC, higher CO, and marginally higher NOx.