MXPA99004118A - Use of monosodium iminodiacetic acid solutions in the preparation of n-phosphonomethyliminodiacetic acid - Google Patents

Abstract

A method is described for making solution stable salts of iminodiacetic acid (IDA), useful as precursors in the manufacture of N-phosphonomethylglycine. Concentrated dialkali salts of IDA which are insoluble at temperatures below about 55°C, such as the disodium salt (DSIDA), are acidified to monoalkali salts, such as monosodium IDA (MSIDA). The resulting salts are stable in solution, and may conveniently be stored or transported in solution without recourse to dilution, heating, or similar measures.

Description

USE OF SOLUTIONS OF ACIDO I INQDIACETICA OF MONOSOPIO IN THE PREPARATION OF N-PHOSPHONOMETHYLAMINODIACETIC ACID BACKGROUND OF THE INVENTION This invention relates to N-phosphonomethylglycan (glyphosate) and, more specifically, to a method for preparing concentrated solutions of monosodium iminodiacetic acid, for the preparation of N-phosphonomethylglycine. N-phosphonomethylglycine (glyphosate) is an important herbicide of broad spectrum. A conventional precursor of glyphosate is N-phosphonomethyliminodiacetic acid (PIDA) having the following formula (I): An early description of the preparation of the compound (I) above appears in US 3, 288,846, from Iranian and co-inventors. In this process iminodiacetic acid (IDA) was used as starting material, prepared by hydrolysis of iminodiacetonitrile. Several process steps are necessary for the recovery and purification of the IDA. Then phosphonomethyla acid with phosphorous acid and formaldehyde, in the presence of a mineral acid- In one embodiment, the addition of phosphorous trichloride to the aqueous reaction mixture provides, by hydrolysis, enough hydrogen chloride to form the salt IDA hydrochloride, while also providing the phosphorous acid for the phosphonomethylation reaction An improvement to the Iranian process and co-inventors is described in US Pat. No. 4,724 103 of Gentlicore. According to this improvement, the metal salt is employed dialcalm of IDA preferably the disodium salt (DSIDA) as the starting material By reaction with a strong mineral acid, typically hydrochloric acid, the DSIDA is converted to the acid salt (IDA HCl) and the alkali metal salt of the acid Then the acid salt is phosphonomethylated by reacting the strong acid salt with phosphorous acid and formaldehyde to give the compound (I) and , io an alkali metal salt Water and caustic are added to the reaction mixture in sufficient quantity to dissolve the alkali metal sai and the compound (I) is separated as a precipitate This procedure eliminates numerous steps for the purification and recovery of IDA to from the IDAN crude hydrolyzate, thereby offering a more economical route for (I) For a description of the numerous steps necessary in the separation and purification of IDA from the IDA hydrolyzate, see British Patent 1 575 469 The elimination of much expensive equipment and many processing steps will be appreciated by a comparison of the Genthcore and The British patent 20 The Gentlicore process requires that the DSIDA starting material be maintained at elevated temperatures during shipment and storage, because this material crystallizes at temperatures around 65 ° C. The crystalline form is highly insoluble and inconvenient. to dissolve in water, with a view to its use in the process to prepare the compound (I). Consequently, DSIDA should be used immediately after its production, or it should be stored in diluted form or heated to maintain solubility. All these alternatives increase costs. An attempt to avoid the problems associated with the use of DSIDA is described in US 5,312,972 to Cullen. Cullen describes an alternative process for preparing compound (I), which comprises reacting solutions of a dialkali metal salt of IDA with formaldehyde, to form the dialkali metal salt of hydroxymethyliminodiacetic acid (H IDA). That precursor has the potential to increase the charges of the N-methyliminodiacetic acid by-product in the final product. The HMIDA may subsequently be reacted with a source of phosphorus, such as phosphorous acid, to produce the compound (I). Although the methods mentioned above obtain the purposes for which they were conceived, they are limited in their use. DSIDA must be diluted or kept warm to preserve the solubility of the concentrate during transport or storage. Dilute solutions contain more liquid and, therefore, are more expensive in shipping. In some cases it is not practical or expensive to store and ship solutions while heating them to a temperature scale sufficient to maintain solubility and prevent crystallization. The use of formaldehyde, as in Cullen, maintaining solubility in concentrated solutions of disodium-imamodiacetic acid is unacceptable, for reasons of toxicity BRIEF DESCRIPTION OF THE INVENTION In accordance with the present invention, a method is provided for preparing concentrated solutions of monosodium iminodiacetic acid, which can be conveniently stored and transported. These storage and transport advantages can impart economic and commercial viability to the solution made from disodium acid. iminodiacetic, as described herein This alternative method of preparing glyphosate precursors should require little dilution or heating to prevent precipitation. In accordance with this invention, a method is provided for preparing a concentrated aqueous solution of monosodium-imamodiacetic acid (AIDS) from Disodium iminodiacetic acid solutions This method comprises adding a strong acid to an aqueous solution consisting essentially of disodium iminodiacetic acid Surprisingly this results in a stable aqueous solution at room temperature, having up to about 29% equivalents of iminodiacetic acid The resulting solution containing MSIDA can then be stored or transported, thereby obtaining additional advantages of the invention, described herein As used herein, the term "stable" means a solution that can be stored and / or shipped without providing a heat source to prevent crystallization. As used herein, the term "concentrate" means a solution having a concentration. greater than approximately 25% IDA equivalents by weight DETAILED DESCRIPTION OF A PREFERRED MODALITY In accordance with the method of this invention, an aqueous solution of concentrated, stable, monosodium-iminodiacetic acid is prepared by adding a strong acid to an aqueous solution of disodium iminodiacetic acid. Typical strong acids include sulfuric acid and acid. hydrochloric acid However, hydrochloric acid is preferred for reasons of economy and compatibility with subsequent processing. Because hydrochloric acid is preferred, the invention will be further described with reference to hydrochloric acid, although any other acid may be used instead. In addition, in another preferred embodiment, one equivalent of phosphorus tpchloride can be added to three equivalents of an aqueous solution of DSl DA to form a solution of three equivalents of monosodium salt of immodiacetic acid and one equivalent of phosphorous acid. use this solution to prepare PIDA, either by adding formalin and more PCl to produce H3PO3 and the HCl necessary to catalyze phosphonomethylation, or by adding appropriate amounts of phosphorous acid, hydrochloric acid and > formaldehyde to obtain the desired phosphonomethylation. In accordance with the principles of this invention, a sufficient amount of strong acid, preferably about 0-8 to 1 -2 molar equivalents of strong acid per mole of disodium iminodiacetic acid, is added to an aqueous solution containing disodium acid -iminodiacetic. Disodium iminodiacetic acid in aqueous solution can be formed according to methods known in the prior art. Those methods include the basic hydrolysis of IDAN or the catalytic dehydrogenation of diethanolamine, as described in US Patents 2,384,817 of US Pat.

Chitwood, 4,782,183 from Goto and co-inventors, 5,292,936 and 5,367,112, both from Francyzk; said patents being incorporated herein by the Reference - Then the resulting aqueous solution is treated with sufficient strong acid to convert the DSIDA to MSIDA- In one example, the strong acid is introduced as gaseous hydrogen chloride, which can be added to the disodium-iminodiacetic acid and heated in a suitable reaction vessel to form a homogenous solution of monosodium-iminodiacetic acid and chloride Í20 sodium. While the strong acid is preferably introduced as a gas (such as HCl gas), it can also be added in other forms, such as aqueous solutions. However, the addition of HCl gas (instead of acid aqueous) gives the additional benefit of reducing the effects of dilution. As noted above, other strong acids can be added in place of hydrochloric acid or sulfuric acid. It should be understood that the term "hydrochloric acid", as used in the claims, also comprises gaseous hydrogen chloride, which forms an acid in aqueous media. Preferably, the gaseous hydrogen chloride is fed below the surface in the reaction vessel, for a period of 45 minutes, at temperatures ranging from 55 ° C to 95 ° C. However, in carrying out the process of this invention, the temperature of the reaction is not critical. Preferably, the boiling of the mixture is prevented, for example, by cooling, and then adding an additional amount of HCl to the mixture, while a thin vacuum is applied. The specific manner in which the disodium acid is reacted Iminodiacetic with strong acid is not critical, and can be achieved in many 5 ways. For example, the strong acid can be introduced into a reaction vessel containing a hot solution of disodium-imamodiacetic acid and then cooled to room temperature. The reaction is carried out in any kind of container that is acid-resistant. strong and having suitable means of heating, or cooling and stirring. The ratio of the reactants, that is, of the solution of disodium-iminodiacetic acid and hydrochloric acid or other strong acid, is not tightly critical. However, for best results, at least 0.8 molar equivalent is introduced, preferably at least 1.0 equivalent molar, of strong acid, for each mole of disodium-iminodiacetic acid In the case of HCl the best results are obtained using 1.0-1.2 moles of hydrochloric acid per mole of disodium-iminodiacetic acid- Thus, it is used about 0-8 a 1 -2 molar equivalents of strong acid per mole of DSIDA in the process of this invention The reaction time and temperature are not tightly critical. In one example, the temperature of the present reaction varies between 57.4 ° C and 93.4 ° C, for a period of at least 45 minutes- The pressure is also not critical- Thus, the solutions of the present invention can be prepared at atmospheric pressure , subatmospheric or superatmospheric - It is preferable to carry out the present invention at atmospheric pressure for ease of reaction and economy. The materials produced by the method of this invention are useful in the manufacture of compounds useful as herbicides and plant growth regulators. As illustrated below, the IDA salts can be subsequently reacted with phosphorous acid, hydrochloric acid and formaldehyde to produce N-phosphonomethyliminodiacetic acid-Because the use of the present invention gives stable solutions of the IDA salt, these materials can be stored conveniently in tanks, before subsequent processing, or they can be transported without providing heating, as a means to maintain solubility. The following examples serve to further illustrate the invention.

EXAMPLE 1 1.400 g (42-38%, 593-3 g, 3-3 mol) of hot solution (57.4 ° C) of disodium iminodiacetic acid (DSIDA) was charged in a reactor equipped with stirrer, heating mantle, water condenser and tube for gas introduction. A strong acid was introduced, adding gaseous hydrogen chloride. The gaseous hydrogen chloride was introduced below the surface, in the reactor, at 57.4 ° C. The gas was fed into the reactor for approximately 45 minutes, at temperatures between 57.4 ° C and 93.4 ° C. The heating mantle of the reactor was replaced by a water bath, and the reaction mixture was cooled to 73 ° C. An additional amount of HCl was fed to the cooled mixture, while a slight vacuum was applied. A total of 139.2 g (3.8 moles) of HCl was added. The solution was cooled to room temperature-It remained homogeneous, with no significantly observable precipitate. The pH was found to be approximately 4- This solution was suitable for storage at the site or for transport to another site for subsequent processing.

EXAMPLE 2 A solution of 43.4 g (30-6% IDA, 13.3 g, 0.1 mol of IDA) of monosodium-iminodiacetic acid was prepared and 26 g of it was placed in a glass reactor, capable of maintaining reactions at low pressure. 18 g was added of hydrochloric acid (37.9% HCl) and 9-46 g of phosphorous acid, and the mixture was heated to 120 ° C. 8.2 g of formalin (48.8% CH2O) and the remainder of the monosodium-IDA solution were added over 30 minutes. The solution to 120 ° C for 90 minutes and cooled. Filtration, cake washing and drying gave 21.4 g of N-phosphonomethyliminodiacetic acid (97%, 91% yield) and 56.5 g of filtrate.

EXAMPLE 3 PREPARATION OF MONOSODIC SALT SOLUTION OF IMINODYACTIC ACID / PHOSPHOROUS ACID A solution at 60 ° C of 921 g (40.35%, 371 -6 g of DSl DA, 2-1 mol) of the disodium iminodiacetic acid was charged in a reactor equipped with stirrer, jacket heating and an auxiliary heater / cooler, as well as with water condenser, and heated to 90 ° C. About 97.6 g (98.5%, 96.1 g of PCI3, 0.7 mole) of phosphorus trichloride, below the surface of the DSIDA solution, was added over a period of about 60 minutes. During the course of this addition, the reaction was heated and the teature was maintained below 105 ° C. The reaction mixture was cooled to 95 ° C and 1.011 g of a solution containing 2.08 moles of AIDS, 2.1 moles of NaCl and 0.7 moles of H3PO3- was obtained. This solution was used to prepare N-phosphonomethyliminodiacetic acid.

Claims (15)

NOVELTY PE THE INVENTION CLAIMS

1 - A method for preparing a concentrated aqueous solution of monosodium iminodiacetic acid, characterized in that it comprises adding to an aqueous solution consisting essentially of disodium iminodiacetic acid, an approximate ratio of 08 to 1 2 molar equivalents of a strong acid, mole of disodium-imipodiacetic acid |

2 - The method according to claim 1, further characterized in that the strong acid is hydrochloric acid or sulfuric acid

3 - The method according to claim 2, further characterized in that the strong acid is acid hydrochloric

4 - The method according to claim 3, characterized in that the "strong acid" is added as gaseous hydrogen chloride

5 - The method according to claim 1, further characterized in that the source of strong acid is provided by the reaction of phosphorus tpchloride and water 6 - A method for preparing a concentrated aqueous solution of

Monosodium-iminodiacetic acid, characterized in that it comprises forming the disodium-immodiacetic acid and adding strong acid to said disodium-mono-diacetic acid, in an amount sufficient to form an aqueous solution consisting essentially of monosodium-iminodiacetic acid

7 -. 7 - The method according to claim 6, further characterized in that the disodium-iminodiacetic acid is formed by hydrolyzing iminodiacetomtplo with an alkali metal base

8 - The method according to claim 6, further characterized by the formation of disodium-iminodiacetic acid by catalytic dehydrogenation of diethanolamm

9 - The method according to claim 6, further characterized in that the strong acid is hydrochloric acid or sulfuric acid

10 - The method according to claim 9, further characterized in that the strong acid is hydrochloric acid

11 - The method according to claim 10, further characterized in that the strong acid is added as gaseous hydrogen chloride

12 - A method for preparing N-phosphonomethyliminodiacetic acid, characterized in that it comprises providing disodium-iminodiacetic acid to add a strong acid to disodium-iminodiacetic acid , for pr Prepare a stable solution, comprising moposodium-immodiacetic acid, and store the stable solution, before subsequent processing, said processing comprising reacting the monosodium-iminodiacetic acid with an additional strong acid, phosphorous acid and formaldehyde.

13 - The method of compliance Claim 12, further characterized in that the additional strong acid and the phosphorous acid are provided by adding phosphorus t-chloride to an aqueous reaction medium.

14 -. 14 - A method for preparing N-phosphonomethyliminodiacetic acid, characterized in that it comprises providing disodium-monolacetic acid, adding a strong acid to the disodium-iminodiacetic acid, to prepare a stable solution comprising monosodium-iminodiacetic acid to transport the stable solution for subsequent processing, which it comprises reacting the monosodium-imipodiacetic acid with additional strong acid, phosphorous acid and formaldehyde. The method according to claim 14, further characterized in that the additional strong acid and the phosphorous acid are provided by adding phosphorus t-chloride to a reaction medium. aqueous