The synthesis of glycerol from propylene can be classified into two categories: chlorination and oxidation. Propylene chlorination and propylene peracetic acid oxidation are still used in industry.
2.1 Propylene oxidation
This is the most important method to synthesize glycerol, which includes four steps: oxidation of propylene to propylene chloride at high temperature, hypochloritization of propylene chloride to propylene dichloride, saponification of propylene dichloride to epichlorohydrin and hydrolysis of epichlorohydrin to glycerol.
2.2 Propylene Peracetic Acid Oxidation
Propylene reacts with peracetic acid to synthesize propylene oxide, which is isomerized to allyl alcohol, and then oxidized to propylene oxide (glycidyl) by peracetic acid, which is hydrolyzed to glycerol. Or allyl alcohol can be oxidized by hydrogen peroxide to produce glycerol directly.
2.3 Epichlorohydrin process
Glycerol synthesized from epichlorohydrin is a mature process with good product quality. In 1980, China introduced production units. At present, the annual production capacity of synthetic glycerol in China is more than 5 kt. However, due to the high price of epichlorohydrin, the production capacity of synthetic glycerol has been exerted especially. The output of synthetic glycerol abroad is very large. The annual output of glycerol in the United States is 300 kt, of which 150 KT is synthetic glycerol.
In the production of epichlorohydrin, a large number of by-products, propylene trigas, can be comprehensively utilized to produce glycerol by heating and hydrolysis.
Production of Fermented Glycerol
Starch raw materials (grain, corn, sweet potato, etc.) or molasses were produced by microbial fermentation.
The research on fermentation method in China began in the mid-1950s. The research and application of high osmotic yeast strains, which rose in the 1960s, was in its peak period in the 1970s. From 1994 to 1995, it began to enter industrial production, especially in Shandong, Jiangsu, Gansu and other places.