Glycerol is also produced by various routes from propylene. The epichlorohydrin process is the most important; it involves the chlorination of propylene to give allyl chloride, which is oxidized with hypochlorite to dichlorohydrins, which reacts with a strong base to give epichlorohydrin. Epichlorohydrin is then hydrolyzed to give glycerol.[3]
Because of the emphasis on biodiesel, where glycerol is a waste product, the market for glycerol is depressed, and the old epichlorohydrin process for glycerol synthesis is no longer economical on a large scale. Glycerol can be removed from the process by using a special enzyme that breaks down phytol and starches. This enzyme is biologically produced using a genetically engineered bacterium. Because there is no glycerin produced as a by-product, the biodiesel purity is greatly improved and costs can be reduced.[4]
Only one producer for synthetic glycerol is left, because high-quality glycerol is needed in highly sensitive pharmaceutical, technical and personal care applications. Raw materials used to make glycerol include animal fats, such as beef tallow, and vegetable oils, such as coconut and soybean.