CONTINUOUS PROCESS FOR THE PREPARATION OF N-(PHOSPHONOMETHYL) IMINODIACETIC ACID

摘要

In the process of the present invention, N-acetyliminodiacetic acid is formed via a continuous amidocarboxymethylation reaction. In this reaction, N-(acetyl)iminodiacetic acid is formed in an amidocarboxymethylation reactor system, into which a source of each of the following is continuously fed: (1) acetamide or an acetamide derivative (2) formaldehyde or a formaldehyde generator or derivative (3) a carbonylation catalyst (4) carbon monoxide and optionally (5) hydrogen. In turn, an amidocarboxymethylation reaction product stream, which contains N-(acetyl)iminodiacetic acid and the carbonylation catalyst, is withdrawn from the amidocarboxymethylation reactor system. The carbonylation catalyst is separated from the amidocarboxymethylation reaction product stream to recover the carbonylation catalyst and form a catalyst depleted product stream which contains N-(acetyl)iminodiacetic acid. The separated carbonylation catalyst is returned to the amidocarboxymethylation reactor system, and the N-(acetyl)iminodiacetic acid in the catalyst depleted product stream is either: (1) reacted with a source of phosphorous and a source of formaldehyde in the presence of an acid to form a phosphonomethylation reaction product stream containing N-(phosphonomethyl)iminodiacetic acid and acetic acid; or (2) deacylated and cyclized to form a 2,5-diketopiperazine, and then reacted with a source of phosphorous and a source of formaldehyde in the presence of an acid to form a phosphonomethylation reaction product stream containing N-(phosphonomethyl)iminodiacetic acid and acetic acid. Either way, the N-(phosphonomethyl)iminodiacetic acid is precipitated from the phosphonomethylation reaction product stream in the presence of acetic acid, and the precipitate is recovered to form a filtrate stream. The filtrate stream is separated into an acetic acid enriched stream and an acetic acid depleted stream. At least a portion of the acetic acid enriched stream is fed to an acetamide synthesis reactor into which ammonia is simultaneously fed to form an acetamide product stream, which is fed (directly or indirectly) back to the amidocarboxymethylation reactor system.