Acrolein

Acrolein (systematic name: propenal) is the simplest unsaturated aldehyde. It is a colourless liquid with a piercing, disagreeable, acrid smell. The smell of burnt fat (as when cooking oil is heated to its smoke point) is caused by glycerol in the burning fat breaking down into acrolein. It is produced industrially from propylene and mainly used as a biocide and a building block to other chemical compounds, such as the amino acid methionine.

Production

Acrolein is prepared industrially by oxidation of propene. The process uses air as the source of oxygen and requires metal oxides as heterogeneous catalysts:

About 500,000 tons of acrolein are produced in this way annually in North America, Europe, and Japan. Additionally, all acrylic acid is produced via the transient formation of acrolein. The main challenge is in fact the competing over oxidation to this acid. Propane represents a promising but challenging feedstock for the synthesis of acrolein (and acrylic acid).

When glycerol (also called glycerin) is heated to 280 °C, it decomposes into acrolein: