Acrylonitrile

Acrylonitrile is a colorless liquid with the formula C₃H₃N. Its molecule is a short carbon chain with a double bond at one end and a nitrile group, a carbon triple-bonded to nitrogen, at the other. The double bond lets it link into plastics, and the nitrile group gives those plastics hardness and resistance to oils.

It is made in a single step called ammoxidation, developed at Standard Oil of Ohio (Sohio) in the 1950s. A mix of propylene, ammonia and air, which supplies oxygen, is blown through a hot bed of powdered catalyst at about 400 to 500 °C. The oxygen strips hydrogen from the propylene and ammonia, nitrogen attaches to the end carbon, and water is given off. Hydrogen cyanide and acetonitrile come out as by-products. The product is cooled, washed and distilled to purity.

In ABS plastic it supplies the hardness and chemical resistance. Its other big uses are acrylic fiber for sweaters and blankets, and nitrile rubber for gloves and fuel hoses. It is toxic, flammable and linked to cancer, so it is handled in closed systems.