Propene, also known as propylene, is an unsaturated organic compound having the chemical formula C₃H₆. It has one double bond, and is the second simplest member of the alkene class of hydrocarbons, and it is also second in natural abundance.

Properties

At room temperature, propene is a colourless, odourless gas, though when used as a fuel, it is mixed with minute quantities of foul-smelling sulfurous compounds (mercaptans) so that gas leaks can be readily detected.

Propene has a higher density and boiling point than ethylene due its greater size. It has a slightly lower boiling point than propane and is thus more volatile. It lacks strongly polar bonds, yet the molecule has a small dipole moment due to its reduced symmetry (its point group is C_s).

Propene has the same formula as cyclopropane but a different connectivity of atoms, making these molecules structural isomers.

Synthesis

All propene is obtained from non-renewable sources; petroleum or natural gas deposits (and coal to a lesser extent). It is a fossil fuel. Propene is extracted from these by fractional distillation during oil refining, but demand exceeds supply so most is manufactured by cracking. The products from this process contain a mixture of products and the propene is separated from the other products by fractional distillation.

Production and Uses

Propene is the raw material for the production of polypropylene, a versatile polymer widely used in several different grades for packaging. Most propene is polymerized using Ziegler-Natta catalysis, which produces isotactic polypropylene. Along with benzene, propene is a key feedstock in the cumene process, a reaction carried out on industrial scales to produce acetone and phenol. Propene is also used during the production of many other chemical products such as isopropanol (propan-2-ol), acrylonitrile, and propylene oxide (epoxypropane).

The production of propene has remained static at around 35 million tonnes (Europe and North America only) from 2000 – 2008 but has been increasing in East Asia, most notably Singapore and China.Total world production of propene is currently about half that of ethylene.

References