| 摘要 |
The invention relates to a method for producing aqueous solutions of methylglycine-N,N-diacetic acid trialkali metal salts at a high yield and purity using Strecker synthesis, starting from an aqueous solution of a-alanine, by reacting same with formaldehyde and hydrocyanic acid in an aqueous solution to form a-alanine N,N-diacetonitrile in a reaction unit, and saponifying same with a base to form the corresponding methylglycine-N,N-diacetic acid trialkali metal salt. The method is characterized in that the a-alanine is partially neutralized, and the addition of formaldehyde and hydrocyanic acid for reacting into a-alanine-N,N-diacetonitrile is controlled such that the concentration of free hydrocyanic acid in the liquid reaction mixture is limited at all times so that secondary reactions, in particular into formaldehyde cyanohydrin, including subsequent reactions of the formaldehyde cyanohydrin as well as the polymerization of hydrocyanic acid occur only to such an extent that the specification requirements for the methylglycine-N,N-diacetic acid trialkali metal salt, in particular with respect to the nitrilotriacetic acid content and color, are met. |
