Topics - Gasoline Components
Gasoline is largely a mixture of hydrocarbons, although some may contain significant quantities of ethanol and some may contain small quantities of additives such as tertiarybutylmethyl ether as ‘anti-knock’ agents to increase the octane rating. The hydrocarbons consist of a mixture of n-paraffins, naphthenes, olefins and aromatics. Naphthenes, olefins and aromatics increase the octane rating of the gasoline whereas the n-paraffins have the opposite effect. The aromatics consist mostly of a mixture of benzene, toluene and the xylenes. The benzene content is kept to a minimum (but is not negligible) due to its perceived toxicity. Originally lead tetraethyl was added as an anti-knock agent but is now rarely used and is prohibited in most countries due to its toxicity. Gasoline is usually analyzed by gas chromatography using a capillary column coated with a suitable dispersive stationary phase and is temperature programmed. The composition of a gasoline can vary significantly depending on the source of the crude oil, the method employed for processing and its intended use.