Composition of Vapor Emitted From a Vehicle Gasoline Tank During Refueling

An experimental test program was conducted to determine the detailed hydrocarbon composition of the vapor emitted from a vehicle fuel tank during refueling with gasoline. The composition of the equilibrium vapor in the tank was strongly dependent on the composition of the liquid gasoline, but, as expected, the vapor was composed primarily of the more volatile components of the gasoline. The composition of the vapor could be calculated satisfactorily from the liquid composition, using ideal solution theory.

In the refueling tests in which the tank fuel and dispensed fuel were the same, there was little difference in the composition of the equilibrium vapor in the tank before refueling and the vapor expelled during refueling. When the tank fuel and dispensed fuel had different compositions, the vapor expelled during refueling was composed of about two-thirds dispensed fuel vapor and about one-third tank fuel vapor.