Process for the preparation of 1-alkyl glycerol ethers
A process for the preparation of a 1-alkyl glycerol ether of the formula (I) in which: (a) an alkyl glycidyl ether of the formula (II) in which R is an unbranched or branched C 1 - to C 24 -alkyl group, where the alkyl group may be substituted with one or more hydroxy and/or C 1 - to C 4 -alkoxy group(s) and/or the alkyl chain may be interrupted by up to four oxygen atoms, is added to: (x) a carboxylic acid having 1-10 carbon atoms; (y) an ester of a carboxylic acid having 1-10 carbon atoms; and/or (z) an anhydride of a carboxylic acid having 1-10 carbon atoms. The low-water reaction mixture containing a catalytic amount of a strong acid is reacted at a temperature of more than 40° C. to give an acylated alkyl glycerol ether; and (b) the acylated alkyl glycerol ether is reacted in order to obtain the alkyl glycerol ether of the formula (I).
1. A process for the preparation of a 1-alkyl glycerol ether of the formula (I)
in a high yield with reduced impurities, comprising the stages of:
(a) obtaining an acylated alkyl glycerol ether by reacting, at a temperature of more than 40° C., a reaction mixture comprising:
(i) an alkyl glycidyl ether of the formula (II)
in which R is an unbranched or branched C 1 - to C 24 -alkyl group, where the alkyl group may be substituted with one or more hydroxy and/or C 1 - to C 4 -alkoxy group(s) and/or the alkyl chain may be interrupted by up to four oxygen atoms,
(ii) a carboxylic acid having 1 to 10 carbon atoms,
(iii) a catalytic amount of a strong acid having a pKa value of less than 4, said strong acid not being a carboxylic acid, and
(iv) at most 0.7 mol of water per mole of alkyl glycidyl ether of the formula (II),
said alkyl glycidyl ether of the formula (II) and said a carboxylic acid present in a molar ratio of 1:0.5 to 1:10; and
(b) transesterifying the acylated alkyl glycerol ether obtained from stage (a) by adding an excess molar amount of aliphatic alcohol having 1 to 4 carbon atoms to form a reaction product, distilling off an alkyl ester of the carboxylic acid and of the aliphatic alcohol and excess aliphatic alcohol formed from the transesterifying, neutralizing the strong acid remaining with the reaction product with alkalizing agent, and fractionally distilling in order to obtain the alkyl glycerol ether of the formula (I).
2. The process according to claim 1 , wherein R is a C 3 to C 18 alkyl group.
3. The process according to claim 1 , wherein the carboxylic acid has 1 to 6 carbon atoms.
4. The process according to claim 1 , wherein the carboxylic acid is a monocarboxylic acid, a dicarboxylic acid, or a hydroxycarboxylic acid.
5. The process according to claim 1 , wherein the strong acid is an inorganic acid, an organic acid, or a solid or polymeric acid.
6. The process according to claim 1 , wherein to form the reaction mixture of stage (a), the carboxylic acid is initially introduced, the strong acid is added, the mixture is heated to 50 to 120° C., then the alkyl glycidyl ether of the formula (II) is added in portions, and optionally with stirring, where the temperature of the mixture is at least 45° C.
7. The process according to claim 1 , wherein, the reaction mixture of stage (a) further comprises water-binding agents.
8. The process according to claim 1 , wherein the alkalizing agent in stage (b) is an alkali metal hydroxide, an alkaline earth metal hydroxide, and/or an alkali metal or an alkaline earth metal carbonate or hydrogencarbonate.
9. The process according to claim 1 , wherein, prior to the transesterification in stage (b), the mixture is cooled to a temperature below the boiling temperature of the aliphatic alcohol.
10. The process according to claim 1 , wherein, after the fractional distillation in stage (b), a stabilizer is added to the 1-alkyl glycerol ether of the formula (I).