Organic compounds -- part of the class 532-570 series – Organic compounds – Phosphorus acids or salts thereof
Reexamination Certificate
2000-07-10
2001-08-21
Vollano, Jean F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Phosphorus acids or salts thereof
C562S018000
Reexamination Certificate
active
06278017
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, in general, to a continuous process for the preparation of N-(phosphonomethyl)iminodiacetic acid wherein the process includes an amidocarboxymethylation step.
2. Description of Related Art
N-(phosphonomethyl)glycine, also known by its common name glyphosate, is a highly effective and commercially important herbicide useful for combating the presence of a wide variety of unwanted vegetation, including agricultural weeds. Between 1988 and 1991, approximately 13 to 20 million acres per year worldwide were treated with glyphosate, making it one of the most important herbicides in the world. Convenient and economical methods of preparing glyphosate and other amino carboxylic acids are, therefore, of great importance.
Franz, et al. in
Glyphosate: A Unique Global Herbicide
(ACS Monograph 189, 1997) at p. 233-257 identify a number of routes by which glyphosate can be prepared. According to one of these, iminodiacetic acid disodium salt (DSIDA) is treated with formaldehyde and phosphorous acid or phosphorous trichloride to produce N-(phosphonomethyl)-iminodiacetic acid and sodium chloride. A carboxymethyl group on the N-(phosphonomethyl)iminodiacetic acid is then oxidatively cleaved in the presence of a carbon catalyst to produce glyphosate acid. A significant drawback of this method is that it produces three equivalents of sodium chloride per equivalent of glyphosate as a side product. Sodium chloride streams of this nature are difficult to recycle because typically after precipitation the salt contains significant quantities of entrapped organic matter. Such entrapped organic matter prevents the sodium chloride from being used for many purposes, for example in foods or feed. Further recrystallization of the sodium chloride adds cost which makes recycle economically unfeasible. Alternate methods of disposing of sodium chloride without detriment to the environment are expensive and difficult.
SUMMARY OF THE INVENTION
This invention provides for a well-defined, low-cost process for the production of N-(phosphonomethyl)-iminodiacetic acid in which sodium chloride is not generated as a by-product.
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 a amidocarboxymethylation reactor system, into which a source of each of the following is fed continuously: (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.
Further scope of the applicability of the present invention will become apparent from the detailed description provided below. It should be understood, however, that the following detailed description and examples, while indicating preferred embodiments of the invention, are given by way of illustration only since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
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Franczyk, II Thaddeus S.
Johnson Todd J.
Jorgenson Amy L.
Rogers Michael D.
Stern Michael K.
Monsanto Company
Schaper Joseph A.
Senniger Powers Leavitt & Roedel
Vollano Jean F.
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