Originally, glycerin (propan-1,2,3-triol) was obtained as a by-product in soap production.
The German-Swedish pharmacist and chemist Carl Wilhelm Scheele discovered this compound for the first time in 1779 when saponifying olive oil with lead oxide.
A first process for industrial-scale synthesizing of pure glycerin was developed by the English industrialist, industrial chemist and plant breeder George Fergusson Wilson in 1854.
Today, the trivalent alcohol is obtained, inter alia, from propene that emerges from cracking long-chain alkanes, in a petrochemical process. In this process, the propene is first chlorinated into allyl chloride (3-chlorine propene) and then converted into glycerin in several intermediate steps.
In addition, this alcohol can be produced chemically as a by-product in saponification of natural fats and oils within the soap production process. Previously mainly animal fats were used for this purpose.
Meanwhile, propane-1,2,3-triol is also obtained as a by-product in bio diesel production by transesterification of mainly vegetable oils with methanol. In this process, glycerin and a mixture of fatty acid methyl esters (FAME) are obtained from one fat molecule (triglyceride) and three methane molecules.
Biotechnological production of glycerin through fermentation is also possible. Yeasts convert fermentation under admixture of sulfite to glycerin formation. A suitable substrate is molasses that – besides its high sugar content – contains a great amount of sulfite.
In order to meet the requirements posed by the different application areas of glycerin, this compound is produced in different degrees of purity. As a rule, for industrial purposes crude glycerin is used. In pharmaceutics, however, glycerin with a purity of 99.8, 99.5 or about 86 percent is used. The technical handling of the 86-percent variant is much easier due to its considerably reduced melting point (-10 °C) and its lower viscosity (about 100 mPa·s). To achieve the highest possible purity, the crude glycerin is distilled, deodorized and filtrated in several stages.