Styrene

Styrene, also known as ethenylbenzene, vinylbenzene, and phenylethene, is an organic compound with the chemical formula C₆H₅CH=CH₂. This derivative of benzene is a colorless oily liquid that evaporates easily and has a sweet smell, although high concentrations have a less pleasant odor. Styrene is the precursor to polystyrene and several copolymers. Approximately 25 million tonnes (55 billion pounds) of styrene were produced in 2010.

Occurrence, history, and use

Natural occurrence

Styrene is named for styrax balsam, the resin of Liquidambar trees of the Hamamelidaceae plant family. Styrene occurs naturally in small quantities in some plants and foods (cinnamon, coffee beans, and peanuts), and is also found in coal tar. In the nineteenth century, styrene was isolated by distillation of the natural storax balsam. The yeast-like fungus Exophiala jeanselmei can be used to treat air polluted with styrene.

Industrial production from ethylbenzene

The modern method for production of styrene by dehydrogenation of ethylbenzene was first achieved in the 1930s. The production of styrene increased dramatically during the 1940s, when it was popularized as a feedstock for synthetic rubber. Because it is produced on such a large scale, ethylbenzene in turn prepared on a prodigious scale (by alkylation of benzene with ethylene). Ethylbenzene is mixed in the gas phase with 10–15 times its volume in high-temperature steam, and passed over a solid catalyst bed. Most ethylbenzene dehydrogenation catalysts are based on iron(III) oxide, promoted by several percent potassium oxide or potassium carbonate.