Alkylate Gasoline

Alkylate gasoline (petrol) is a fuel that contains significant lower amounts of harmful substances such as aromatic compounds, compared to standard fuel (29,6 %vol vs <0,4 %vol). One of these aromatics is benzene (0,2 %vol vs <0,01 %vol). Many aromatic compounds are poisons, irritants to the skin and eyes and carcinogenic. When used in hand-held machines such as a chainsaw, brushcutter or leaf blower, the use of alkylate petrol is better for your health. German labour law has made it mandatory since 2009 to use alkylate fuel in these machines when they have a two-stroke engine. The cleaner combustion is also better for the machine and the natural environment. The fuel is offered mixed with oil for two-stroke engines but is also available as regular four-stroke petrol.

It is obtained by chemical synthesis instead of distillation and cracking of petroleum which is the production process for regular gasoline. The starting materials for this synthesis are excess gases from petroleum refining. This synthesis is a form of alkylation and is performed in a alkylation unit. Gaseous olefins (substances with a double bond) such as propene and butene and branched saturated hydrocarbons such as isobutane are converted into larger molecules that are liquid. This occurs in the presence of sulfuric acid or hydrogen fluoride to act as a catalyst. Each of these catalysts requires a different proces setup and have different operating conditions. This is because sulfuric acid is a liquid at unit operation conditions, while hydrofluoric acid is a gas at unit operating conditions. Both processes produce almost exclusively alkanes.

Initially, this process was invented during the 1930's and 1940's to obtain high octane aviation fuel. It was used extensively during World War II in aviation fuel for aircraft with a internal combustion engine. Nowadays it is used as a ingredient in most finished fuel blends, to improve both the octane number for a better knock resistance and to meet environmental regulations. The sale of pure alkylate gasoline as a healthier alternative to regular gasoline for usage in gardening and forestry equipment started later. Swedish company Aspen was founded in 1988 with the aim of improving the working conditions of forest workers.

Because alkylate gasoline does not contain aromatics and olefins, it is not only less harmful to health, but also has a shelf life of many years because it does not 'gum'. This gumming is the spontaneous reaction between oxygen and olefins or diolefins known as autoxidation. This makes this gasoline very suitable for use in rarely used devices such as a engine–generator, long-term parked cars such as classic cars and lawn mowers that are not used during the winter months.