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    Influence of Vehicle Emission Control Systems on the Relationship Between Gasoline and Vehicle Exhaust Hydrocarbon Composition

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    Relationships have been developed that describe how vehicle exhaust hydrocarbon composition is influenced by hydrocarbon composition of the gasoline and by the use of various emission control systems which give a range of exhaust emission levels. The relationships were obtained by computer regression analysis of the detailed individual hydrocarbon compositions of 15 gasolines of varying aromatic and olefin content and the exhaust emissions from these fuels.

    The gasolines, which consisted of five refinery-component blended fuels and ten matching commercial gasolines, were all leaded premium grade with similar octane quality and volatility characteristics. The aromatic and olefin contents of the blended gasolines were varied according to a statistical design that covered the usual variation found in commercial premium gasolines.

    The vehicles in which these fuels were tested were equipped with several different types of emission control systems. These included no control device, conventional air injection and engine modification systems, and a duPont exhaust manifold reactor system capable of low exhaust emission levels.

    With all four emission control systems, most of the hydrocarbons emitted were formed by degradation of fuel hydrocarbons. Regression analyses results indicate that ethylene was formed from saturates and olefins, propylene and isobutylene/1-butene were formed primarily from saturates, and diolefins were formed primarily from olefins. Toluene was the most important fuel hydrocarbon from the standpoint of contribution to calculated photochemical reactivity, and survived through the vehicle in larger proportion than the other principal fuel hydrocarbons. Along with the toluene that survived, additional amounts were formed from higher aromatics. Similarly, additional benzene and xylenes were formed from higher aromatics. Additional 2-methyl-2-butene was formed from fuel saturates.

    Fuel effects on photochemical reactivity of the hydrocarbon emissions were quite small in relation to the effects of emission control systems. Calculated total photochemical reactivity of the exhaust from the thermal reactor car was only 2 to 3 percent of that of the cars with other control systems.


    automotive fuels, exhaust emissions, air pollution, atmospheric contamination control, fuel additives, exhaust gases, octane number, hydrocarbons, volatility, exhaust systems, combustion control, combustion efficiency, tests

    Author Information:

    Morris, WE
    Supervisor, Fuel Performance Group, and head, Chemical Division, Petroleum Laboratory, E. I. du Pont de Nemours & Co., Inc., Wilmington, Del.

    Dishart, KT
    Supervisor, Fuel Performance Group, and head, Chemical Division, Petroleum Laboratory, E. I. du Pont de Nemours & Co., Inc., Wilmington, Del.

    Committee/Subcommittee: D02.B0

    DOI: 10.1520/STP26894S