PROCESS FOR THE MANUFACTURE OF N-PHOSPHONOMETHYLIMINODIACETIC ACID.

摘要

PCT No. PCT/GB94/00018 Sec. 371 Date Jul. 10, 1995 Sec. 102(e) Date Jul. 10, 1995 PCT Filed Jan. 6, 1994 PCT Pub. No. WO94/15939 PCT Pub. Date Jul. 21, 1994.A process for the manufacture of N-phosphonomethyliminodiacetic acid which comprises: 1) reacting iminodiacetic acid with phosphorous acid and a source of formaldehyde in aqueous solution in the presence of concentrated sulphuric acid; 2) filtering and recovering the N-phosphonomethyliminodiacetic acid product precipitated in stage (1); 3) recovering the filtrates from stage (2) and optionally removing a proportion of the water therefrom; 4) transferring the filtrates from stage (3) to a further reaction stage in which further iminodiacetic acid is reacted with phosphorous acid and a source of formaldehyde in the presence of sulphuric acid; and thereafter 5) repeating stages (1), (2), (3) and (4) in a plurality of re-cycles.