Monostearin CAS 123-94-4

Fatty acids and glycerol can be directly esterified to obtain a mixture of monoglycerides, diglycerides (diglycerides), glycerol and oil esters. The reaction formula is as follows:

The reaction equation of the direct esterification method

Fig. 1 is that R=CnH2n+1 in the reaction equation formula of direct esterification, the same below in order to improve the conversion rate, often add a little excess glycerol in the production process, use acid, alkali or metal oxide as a catalyst, and the reaction temperature is 180~200℃, the reaction time is 2.5~3h. The reaction formula is a reversible reaction, so it is necessary to continuously remove the generated water (using high temperature or introducing CO2) during the reaction process, so that the reaction moves in the direction of ester formation. Changing the ratio of reaction materials, reaction time, reaction temperature, catalyst type and amount will affect the proportion of each component in the esterification product; increasing the amount of glycerol can increase the content of monoglycerides; using dioxane or phenol for the reaction Solvents can also generate higher proportions of monoglycerides.

Alcoholysis reaction method, also known as transesterification method, is actually the redistribution of glycerol and corresponding fatty acid esters under certain conditions to obtain a mixture of monoglycerides and diglycerides. According to the raw materials used, the alcoholysis reaction method can be divided into two types: the alcoholysis method of oil ester glycerol and the alcoholysis method of methyl ester glycerol.

(1) Glycerol hydrolysis method of oil ester Reaction formula:

The reaction equation of the alcoholysis reaction method

Figure 2 shows the reaction equation of the alcoholysis reaction method. This is the most important and common method for producing monoglycerides in industry at present. The usual process is as follows: the oil and glycerol undergo an alcoholysis reaction under the action of an alkaline catalyst (such as sodium hydroxide or potassium hydroxide, etc.), the reaction time is 2~4h, and the reaction temperature is 180~250℃. Inert gas was introduced to prevent the product from being too dark. The product obtained after alcoholysis is a mixture of monoglyceride, diglyceride, unreacted glycerol and oil, and the composition is relatively complex, and purification treatment is required to obtain high-purity monoglyceride.

(2) Glycerol alcoholysis of fatty acid methyl ester Reaction formula:

Reaction equation of fatty acid methyl ester glycerolysis method

Fig. 3 is the reaction equation of fatty acid methyl ester glycerol hydrolysis method. Mix fatty acid methyl ester and glycerin in a certain proportion, add KOH etc. as a catalyst, and react at 215 to 220 ° C under vacuum conditions for 25 to 30 min to obtain monoglyceride. , a mixture of diglycerides and glycerol. Excess glycerol is distilled off under high vacuum, and then purified to obtain high-purity monoglyceride.

Reaction equation of epichlorohydrin method

Fig. 4 is the reaction equation of epichlorohydrin method. This method is divided into esterification and ring-opening two-step reaction, with quaternary ammonium salt cationic surfactant as catalyst, with toluene as solvent, epichlorohydrin and fatty acid soap ratio are 2:1, the reaction temperature is 90~110°C, and the reaction is carried out for 2 hours. After cooling and filtering, the organic phase is washed with water, and after toluene and unreacted epichlorohydrin are evaporated, the intermediate product fatty acid glycidyl ester can be obtained, and then in Ring-opening hydrolysis is carried out under alkaline or acidic conditions, and high-purity monoglyceride products are obtained after cooling, crystallization, filtration and drying.

The reaction equation of the glycidol method

Fig. 5 is the reaction equation of glycidol method. Glycidol is also called 1, 2-glycidol, which has hydroxyl and epoxy groups in the molecule, so its chemical properties are active, and it can be carried out with fatty acid under the catalysis of basic catalyst or cation exchange resin. One-step location-based esterification to produce high-purity monoglycerides. First, a certain proportion of stearic acid, toluene solvent and sodium hydroxide catalyst are heated together and kept at 100°C, and then glycidol is added to fully reflux for esterification. When the acid value of the system drops to a certain value, the reaction is terminated, and the obtained monoglyceride has a purity of more than 93%. (C2H5)4NI can also be used as a catalyst, but the resulting product has a lower purity.

There are three hydroxyl groups in the glycerol molecule. If it is directly esterified, the three hydroxyl groups have the opportunity to form esters, and a mixture of monoglycerides and diglycerides will be formed. Using the action of some compounds and glycerol, after protecting the two hydroxyl groups of glycerol, it is directionally esterified with fatty acid, and finally hydrolyzed to remove the protective group under certain conditions, and high-purity monoglyceride can be obtained. Currently used protective agents are boric acid, ketone and aldehyde.

1. Partial hydrolysis of fats and oils Under the action of enzymes, fats and water undergo directional hydrolysis at positions 1 and 3, and fatty acid esters at positions 2 are retained to generate monoglycerides, but the yield of monoglycerides is low.
2. Esterification method Under the action of enzymes, glycerol is esterified with fatty acids or fatty acid esters to obtain monoglycerides.
3. Glycerol hydrolysis or alcoholysis method Glycerol and oil undergo alcoholysis reaction under the action of lipase to generate monoglyceride.
4. The group protection method will esterify the glycerol derivatives (such as isopropylidene glycerol) with two hydroxyl groups in advance and fatty acids under the action of enzymes to form monoglycerides, and then hydrolyze to remove the protective groups. This method can obtain monoglycerides with high purity.