The Disappearance of Ethylene, Propylene, n-Butane, and 1-Butane in Spark-Ignition Engine Exhaust

Ethylene, propylene, n-butane, and 1-butene, which make up a large portion of the photochemically reactive hydrocarbons in automobile exhaust, were reacted individually and as a mixture in a turbulent flow, heated reaction tube made of mild steel.

Methods of predicting the total hydrocarbon disappearance by use of a general empirical equation are presented. Techniques for using hydrocarbon composition and carbon monoxide data to predict exhaust photochemical reactivity and CO concentration from total hydrocarbon disappearance correlations are suggested.

Results show that total hydrocarbon reaction was generally strongly dependent on temperature and on oxygen concentration between 1% and 5%, and was less dependent on initial hydrocarbon concentration. Gas Chromatograph data showed that during certain individual hydrocarbon reactions, the formation of other photochemically reactive hydrocarbons could increase smog-forming potential despite a decreasing total hydrocarbon concentration.