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Synthesis of Glycerol Monostearate with High Purity

2003; Wiley; Volume: 24; Issue: 8 Linguagem: Inglês

10.5012/bkcs.2003.24.8.1229

1229-5949

Che Chul Yu, Youn-Sik Lee, Byung Soo Cheon, Sang‐Hee Lee,

biodegradable polymer synthesis and properties

Glycerol monoesters synthesized from glycerol have many applications, such as emulsifying agents in food, phar maceuticals, cosmetics, or in detergents.1 Monoglycerides are generally obtained from the (i) glycerolysis or (ii) hydrolysis of triglycerides, or (iii) the direct esterification of glycerol with fatty acids.2The industrial processes involved generally use homogeneous acid or basic catalysts, which lead to a mixture of mono-, di-, and triglycerides in general (40 : 50 : 10) after direct esterification (Scheme 1).Many different ways to improve the selectivity of the mono-esterification of glycerol have been attempted, includ ing enzymatic methods,3 guanidine,4 solid acid catalysts, such as zeolites,5 and basic catalysts, such as ZnO.6 Since glycerol and fatty acids react spontaneously at 110 °C and the reaction is significant at higher temperatures, it is difficult to prevent the formation of the diglyceride (2, 3) and triglyceride (4) completely during direct esterification at higher temperatures.7To overcome the subsequent acylation problem, several research groups employed protected glycerols.For example, using 1,2-O-isopropylidene glycerol (5)8-12 instead of glycerol, highly pure GMS was synthesized, as shown in Scheme 2. Scheme 2 shows two different approaches using 5; enzymatic and acid-catalyzed procedures.However, we found that the esterification of 5 with stearic acid in the presence of ptoluenesulfonic acid followed by acidic hydrolysis yielded less than 70% GMS (1) along with 2-4, and several unidenti fied side products.The side products are thought to result