Process for producing n-phosphono-methyl-imino-diacetic acid

Abstract

Process for preparing N-phosphono-methyl-iminodiacetic acid by means of phosphonomethylation of iminodiacetic acid performed by reacting an aqueous solution of phosphoric acid and hydrochloric acid, obtained by hydrolysis of phosphorous trichloride, with iminodiacetic acid and formaldehyde, in which phosphorous trichloride is hydrolysed in step (a) with water or an aqueous solution or hydrochloric acid, the reaction temperature and amount of water are regulated such that an aqueous solution of hydrochloric acid and phosphoric acid in a molar ratio of 0.5:1 to 2:1 is formed, and gaseous hydrochloric acid is caused to develop from the reaction medium. The phosphonomethylation reaction is performed in the solution obtained in step (a) in the presence of iminodiacetic acid in a molar ratio of iminodiacetic acid to phosphoric acid between 1:1 and 1:1.2 with the addition of formaldehyde. The N-phosphono-methyl-iminodiacetic acid is then recovered from the reaction medium.

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