Process for preparing alpha-hydroxycarboxylic acids

Details Process for preparing alpha-hydroxycarboxylic acids Process for preparing alpha-hydroxycarboxylic acids

C - Chemistry, Metallurgy

07

C

C07C 67/20 (2006.01) C07C 67/54 (2006.01) C07C 69/675 (2006.01)

Patent

CA 2658590

A continuous process for preparing alpha-hydroxycarboxylic esters, in which, as reactants, alpha-hydroxycarboxamide is reacted with an alcohol in the presence of a catalyst to obtain a product mixture which comprises alpha-hydroxycarboxylic ester, ammonia, unconverted alpha-hydroxycarboxamide, and also alcohol and catalysts; wherein a') reactant streams comprising, as reactants, an alpha-hydroxycarboxamide, an alcohol and a catalyst are fed into a pressure reactor; b') the reactant streams are reacted with one another in the pressure reactor at a pressure in the range from 1 bar to 100 bar; c') the product mixture which results from step b) and comprises alpha-hydroxycarboxylic ester, unconverted alpha-hydroxycarboxamide and catalysts, and also ammonia and alcohol, is discharged from the pressure reactor; and d') the product mixture is depleted in alcohol and ammonia, ammonia being distilled off at a pressure which is constantly kept greater than 1 bar, without the aid of additional stripping media. The continuous process can be employed on the industrial scale particularly advantageously.

L'invention concerne un procédé continu de fabrication d'esters d'acides alpha-hydroxycarboxyliques, selon lequel un amide d'un acide alpha-hydroxycarboxylique est mis en réaction, en tant qu'adduit, avec un alcool en présence d'un catalyseur pour obtenir un mélange de produits comprenant l'ester de l'acide alpha-hydroxycarboxylique, de l'ammoniac, de l'amide de l'acide alpha-hydroxycarboxylique non réagi, ainsi que l'alcool et le catalyseur. Selon l'invention, a') les courants d'adduit contenant comme adduit un amide de l'acide alpha-hydroxycarboxylique, un alcool et un catalyseur sont introduits dans un réacteur sous pression ; b') les courants d'adduit sont mis en réaction ensemble dans le réacteur sous pression à une pression comprise entre 1 bar et 100 bars ; c') le mélange de produits obtenu à l'étape b) comprenant l'ester de l'acide alpha-hydroxycarboxylique, l'amide de l'acide alpha-hydroxycarboxylique non réagi et le catalyseur, ainsi que l'alcool et l'ammoniac est éliminé du réacteur sous pression ; et d') le mélange de produits est appauvri en alcool et en ammoniac, l'ammoniac étant éliminé par distillation à une pression maintenue constamment au-dessus de 1 bar, sans l'aide d'agents d'élimination additionnels. Le procédé continu est applicable de manière avantageuse à l'échelle industrielle.

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