FIELD: chemistry.
SUBSTANCE: invention relates to a method for producing aqueous solutions of methylglycine-N,N-diacetic acid trialkali metal salts using Strecker synthesis, starting from an aqueous solution of α-alanine by reacting same with formaldehyde and hydrocyanic acid to form α-alanine-N,N-diacetonitrile in a reaction unit and saponifying same with a base to form aqueous solution of corresponding methylglycine-N,N-diacetic acid trialkali metal salt. Method is characterised by that α-alanine is partially neutralised, and addition of formaldehyde and hydrocyanic acid for reacting into α-alanine-N,N-diacetonitrile is controlled such that concentration of free hydrocyanic acid in liquid reaction mixture is limited at all times so that secondary reactions, in particular into formaldehyde cyanohydrin, including subsequent reactions of formaldehyde cyanohydrin, as well as polymerisation of hydrocyanic acid occur only to such an extent that aqueous solution of methylglycine-N,N-diacetic acid trialkali metal salt has content of trialkali metal salt and nitriloacetic acid less than 0.1 wt% with concentration of methylglycine-N,N-diacetic acid trialkali metal salt of 40 wt% per total weight of aqueous solution of methylglycine-N,N-diacetic acid trialkali metal salt. Said addition is performed so that concentration of free hydrogen cyanide in liquid reaction mixture in any moment in time is 10 mol% of added hydrocyanic acid, or so that maximum concentration of free acid in liquid reaction mixture does not exceed 20 mol% of free hydrogen cyanide of amount of added partially neutralised α-alanine.
EFFECT: proposed method allows improves space-time yield and reduces content of toxic secondary components.
11 cl, 10 ex
