Production of N-phosphonomethyliminodiacetic acid by liberating iminodiacetic acid from sodium salt with strong mineral acid and reaction with formaldehyde and phosphorous acid uses mother liquor from second stage in first stage

摘要

In the production of N-phosphonomethyliminodiacetic acid (PMIDA) by: (a) neutralizing an aqueous solution of the sodium salt of iminodiacetic acid (IDA) with a strong mineral acid (I) at 10-80 deg C; (b) separating IDA; (c) conversion to PMIDA by reaction with formaldehyde and phosphorous acid in aqueous solution in the presence of (I) at 100-150 deg C; and (d) separating PMIDA e.g. by filtration, the mother liquor from (d) is recycled to stage (a). Production of N-phosphonomethyliminodiacetic acid (PMIDA) involves: (a) neutralizing an aqueous solution of the sodium salt (Na2IDA) of iminodiacetic acid (IDA) with a strong mineral acid (I) at 10-80 deg C, (b) separating IDA from the solution, (c) conversion to PMIDA by reacting IDA with formaldehyde and phosphorous acid in aqueous solution in the presence of (I) at 100-150 deg C, optionally under a protective gas atmosphere and (d) separating PMIDA e.g. by filtration. The novelty is that the mother liquor from (d), with small amounts of PMIDA, reactants and by-products from stage (c), is recycled to stage (a).