MXPA00003776A

MXPA00003776A - Carbon dioxide assisted hydrolysis of aminophosphonates

Info

Publication number: MXPA00003776A
Application number: MXPA/A/2000/003776A
Authority: MX
Inventors: William H Miller; Todd J Johnson
Original assignee: Monsanto Technology Llc
Priority date: 1997-10-15
Filing date: 2000-04-17
Publication date: 2001-12-04

Abstract

The invention provides a process for preparing aminophosphonic acids comprising contacting an aminophosphonate ester with a base in the presence of a hydrolysis facilitator selected from the group consisting of CO2, CS2 and COS. In one embodiment, the aminophosphonate ester is first prepared by contacting an amine, trialkylphosphite, base and formaldehyde.

Description

HYDROPOLISIS OF AMINOPHOSPHONATES ASSISTED BY CARBON DIOXIDE BACKGROUND OF THE INVENTION This invention relates to processes for preparing aminophosphonic acids. This invention relates to a process for preparing aminophosphonic acids, such as N-phosphonomethylglycine, commonly known as glyphosate. Glyphosate is a very effective and widely commercial phytotoxic, useful for the control of a wide variety of harmful herbs and crops. It is applied on the leaves of a very broad spectrum of perennial and annual grasses, as well as plants with broad foliage, to achieve the desired control. Among its industrial uses is the control of noxious weeds and weeds along roads, waterways, transmission lines, storage areas and other non-agricultural areas. Commonly, glyphosate is present in herbicidal compositions in the form of some of its salts, which retain the anionic form of glyphosate in a solution, preferably in water. The phosphonomethylation of amines to produce an aminophosphonic acid using formaldehyde and di- or trialkyl phosphites has been described in certain publications, for example in US Pat. No. 5,041, 628; in Polish patents Nos. 136,276 and 159,424. This phosphonomethylation produces aminophosphonate esters that must be hydrolyzed to obtain the desired aminophosphonic acid. In previous approaches an acid, such as hydrochloric acid, or a base, such as sodium hydroxide, has been used to hydrolyze the esters. A common problem with this type of hydrolysis is that, under certain basic conditions, N-alkylation of the aminophosphonate often occurs. When hydrochloric acid is used for hydrolysis, alkyl chloride is also formed. The formation of these by-products reduces the desired production of aminophosphonic acid and necessitates an additional separation of this aminophosphonic acid from the rest of the reaction mixture. Therefore, a more economical and technically better method for hydrolyzing the aminophosphonate esters is desirable, so that a high conversion and a higher selectivity of the aminophosphonic acid can be achieved, as well as avoiding the formation of side products.

BRIEF DESCRIPTION OF THE INVENTION This invention relates to a process for preparing aminophosphonic acids which comprises contacting, in an aqueous medium, an aminophosphonate ester with a base, in the presence of a hydrolysis facilitator selected from a group consisting of CO2, CS2 and COS . This invention also relates to a process for making aminophosphonic acids which includes contacting an amine, thalkylphosphite, alkali metal hydroxide and formaldehyde to produce a reaction mixture, and hydrolyzing this reaction mixture in the presence of a hydrolysis and conversion facilitator. one base. In one embodiment, alcohol produced during hydrolysis is removed using pressurized carbon dioxide at a convenient flow rate.

DESCRIPTION OF THE PREFERRED MODALITIES This invention relates to a process for preparing aminophosphonic acids, represented by the formula wherein n is from 1 to about 3 and R is hydrogen, an alkyl group containing from 1 to 6 carbon atoms, an aryl group containing from 6 to 12 carbon atoms, salt or carboxylate ester, or hydroxyethyl, which includes contacting in an aqueous medium an aminophosphonate ester with a base, in the presence of a hydrolysis facilitator selected from a group consisting of CO2, CS2 and COS. Commonly, at least 0.5 equivalents of base is added. Alternatively, the aminophosphonate ester can be made first by contacting an amine represented by the formula RNH2, wherein R is the same as in the above formula, trialkylphosphite, wherein the alkyl group contains from 1 to 6 carbon atoms, hydroxide of alkali metal and formaldehyde. Suitable aminophosphonate esters in the processes of the present invention have the following general formula: wherein R is hydrogen, d-6 alkyl, C6-12 aryl. a substituted aryl, aryl (C6-i2) -alkyl (C? -6), - (CH2) n-C02R3 or - (CH2) m-OR3; R1 and R2 are independently hydrogen, C6-6alkyl, C6-12 aryl- (C6-i2) aryl- (C6-6) alkyl, or a salt-forming cation such as Na +, K \ [alkyl ( C? -6)] NH3 +, [(C? -6)] 2NH2 + or [(C1-6) alkyl] 3NH +; R3 is hydrogen, C? -6 alkyl, C? 12 aryl. a substituted aryl, or a salt-forming cation such as Na +, K +, [alk (C? -6)] NH3 +, [(C1-6) alkyl] 2NH2 + or [(C? 6) alkylNH +; n is between 1 and about 6; and m is between 2 and about 6. Preferably, the aminophosphonate ester is the glyphosate monoethyl or diethyl ester, or the glyphosate monomethyl or dimethyl ester. The bases useful in the processes of the present invention are the alkali metal hydroxides, such as sodium hydroxide, potassium hydroxide, lithium hydroxide and cesium hydroxide; alkaline earth metal hydroxides, such as calcium hydroxide; and tertiary amines such as triethylamine. Preferably, the base is sodium hydroxide. Generally, the number of base equivalents added will be within a range of 0.5 to about 3.0 equivalents, preferably 1.5 to 2.0 equivalents. The production of aminophosphonic acids from aminophosphonate esters is carried out in the presence of a hydrolysis facilitator selected from a group consisting of CO2, CS2 and COS. Preferably, C02 is used as hydrolysis facilitator. When CO2 is used as a hydrolysis facilitator, it is desirably pressurized to between 703 kg / cm 2 and about 35.15 kg / cm 2, and most preferably between 10 54 kg / cm 2 and about 28 12 kg / cm 2. The production of aminophosphonic acids from aminophosphonate esters is carried out at a suitable temperature which can vary on a wide scale. The reaction temperature is generally between about 75 ° C and about 120 ° C, preferably about 100 ° C. The hydrolysis reaction is carried out for the suitable time, which can vary on a wide scale depending on a series of parameters, for example, the reaction temperature. Generally, the reaction time will be between the time necessary to hydrolyze the phosphonate esters up to about 6 hours, preferably from about 1 hour to about 4 hours. Also, the production of aminophosphonic acids is carried out at a suitable pH, which is generally between 5 and 14, preferably at a pH of about 7 to about 10. It is possible to carry out the production of aminophosphonic acids from of aminophosphonate esters while eliminating the alcohol produced in the reaction. Preferably, the alcohol is removed by introducing pressurized CO2 at a convenient flow rate. This flow rate is generally from about 0.1 to about 1,000 ml / min, preferably about 100 to about 200 ml / min. The pressure of C02 is preferably around 28.12 kg / cm2. As mentioned above, it is possible to first make the aminophosphonate ester by contacting an amine, trialkylphosphite, a base and formaldehyde. In accordance with the invention, formaldehyde can be used as paraformaldehyde or as an aqueous solution of formaldehyde. It is possible to commercially obtain aqueous formaldehyde in aqueous solutions of 35 to 50% by weight, which may contain methanol, ethanol or n-butanol. The amount of formaldehyde used in the process of the invention can be expressed as a molar ratio of formaldehyde starting material with respect to the phosphite starting material. Commonly, the molar ratio of formaldehyde to phosphite is from about 1: 1 to about 5: 1, preferably from about 1: 1 to about 2: 1, and most preferably from about 1: 1 to 1.5 :1. It is possible to commercially obtain trialkylphosphites, useful in the methods of the invention. The trialkyl phosphites can be represented by the formula P (OR) 3, wherein R is an alkyl group. The alkyl groups of the trialkyl phosphites are linear or branched alkyl groups having from 1 to 6 carbon atoms and are optionally substituted with -OH groups. Preference is given to trialkylphosphites over dialkylphosphites, since unexpectedly high yields can be achieved with the former. The amines useful in the processes of the present invention can be represented by the formula RNH2, wherein R is hydrogen, alkyl, aryl, salt or carboxylate ester, or hydroxyethyl. The preferred amine is glycine. Many of the amines useful in the methods of the present invention are commercially available. The amount of amine used in the processes of the invention can be expressed as a molar ratio of amine starting material with respect to the phosphite starting material. Commonly, the molar ratio of the amine to the phosphite is from about 1: 1 to about 5: 1, and preferably from about 1: 1 to about 2.5: 1. The reaction of the amine, the phosphite and the formaldehyde is carried out at a convenient temperature which can vary on a wide scale. The reaction temperature is generally between about 20 ° C to about 110 ° C, preferably between 40 ° C and 75 ° C. The reaction of the amine, phosphite and formaldehyde is carried out for the appropriate time, which can vary on a wide scale, depending on various parameters, for example, the reaction temperature. It is possible to carry out, optionally, the reaction of the amine, the phosphite and the formaldehyde in the presence of an alcohol solvent, wherein the alcohol is represented by the formula R '(OH) m, where R' is a group alkyl having 1 to 6 carbon atoms and m is 1 to about 3. The alkyl group, R ', may be linear or branched and is preferably the same alkyl group as used in the trialkyl phosphite starting material. Among the suitable alcohols are, but not limited to, methanol, ethanol, isopropanol, n-butanol and mixtures thereof. It is possible to carry out, optionally, the reactions of the present invention in an aqueous or aqueous-alcoholic medium. Preferably, the alcohol used is ethanol or methanol. It is possible to dilute with water, optionally, the reaction mixture produced by contacting the formaldehyde, the amine and the phosphite, before hydrolysis. Once the hydrolysis reaction is complete, the aminophosphonic acid can be recovered using any conventional method known in the art. The following examples are intended to illustrate the preferred embodiments of the invention. It should be noted that the techniques described in the following examples represent techniques whose good functioning was detected by the inventor when putting the invention into practice, and therefore can be considered as preferred embodiments for its application. However, those skilled in the art will appreciate, in light of the present disclosure, that it is possible to make various modifications to the specific embodiments described while still obtaining similar results and without distancing themselves from the intention and scope of the invention.

EXAMPLE 1 This example illustrates the production of glyphosate from glycine and triethylphosphite, after carbon dioxide-assisted hydrolysis of the resulting reaction mixture. Glycine (15.5 g, 200 mmol), 50% sodium hydroxide (12.0 g, 150 mmol) and 6.0 g of water were mixed to form a solution. 37% formaldehyde (8.52 g, 105 mmol) and 10 ml ethanol were added. The temperature was adjusted to 50 ° C, triethylphosphite (16.62 g, 50 mmol) was added over a period of 30 to 45 minutes, keeping the temperature at 50 ° C. After the addition was complete, the reaction was maintained at 50 ° C for an additional 45 minutes to complete the phosphonomethylation reaction. Subsequently, the reaction mixture was saturated with gaseous carbon dioxide which modified the pH of the solution to between 7 and 8, caused the excess of glycine to precipitate, and initiated a significant portion of the hydrolysis. It is possible to eliminate glycine if desired. The reaction mixture was exposed to pressurized carbon dioxide at 14.06 kg / cm2, and heated to between 100 and 120 ° C to complete the hydrolysis, which took between 2 and 4 hours. It is normal for glyphosate isolation to occur once the pH of the reaction mixture is properly adjusted. Glyphosate yields of up to 92% have been obtained based on the phosphite used.

Examples 2 and 3 illustrate the effect of removing alcohol on the selectivity and yield of hydrolysis of glyphosate esters assisted by CO2.

EXAMPLE 2 An autoclave was charged with a solution including glyphosate monoethyl and diethyl ester (0.405 mol), NaOH (0.250 mol), water and ethanol. The pH of this solution was 7.6. subsequently, CO2 (static) was added at 28.12 kg / cm2, and the solution was heated to 100 ° C. after 18 hours, the conversion of the aminophosphonate esters to aminophosphonic acids was 100%. The chemical yield of glyphosate was 74% (0.370 mol). The selectivity for the conversion of aminophosphonate esters to glyphosate and N-ethylglyphosate was 92% and 8%, respectively.

EXAMPLE 3 An autoclave was charged with the same solution as described in example 2. To remove the ethanol from the reagent during hydrolysis, CO2 was incorporated at 28.12 kg / cm2 with a flow rate of 100 ml / min. The solution was heated to 100 ° C. after 5.5 hours, the conversion of the aminophosphonate esters to aminophosphonic acids reached 100%. The chemical yield of glyphosate was 81% (0.405 mol). The selectivity for the conversion of the aminophosphonate esters into glyphosate was 100%. No N-ethylglyphosate was detected.

EXAMPLE 4 This example illustrates the effect of pH on the selectivity and yield of hydrolysis of glyphosate esters assisted by CO2. An autoclave was charged with a solution that includes monoethyl and diethyl esters of glyphosate (0.34 mol), NaOH (0.250 mol), water and ethanol. The pH of this solution was adjusted to 5.6 with trifluoroacetic acid. Subsequently, CO2 (static) was incorporated at 28.12 kg / cm2 and the solution was heated to 100 ° C. after 7.5 hours, the conversion of the aminophosphonate esters to aminophosphonic acids was 41%. The chemical yield of glyphosate was 29% (0.081 mol). The selectivity for the conversion of the aminophosphonate esters into glyphosate and N-ethylglyphosate was 70% and 30%, respectively. Subsequently, the pH of this sample was adjusted from 4.4 to 8.4 with NaOH. Subsequently, CO2 (static) was incorporated at 28.12 kg / cm2 and the solution was heated to 100 ° C. after 5 hours, the conversion of the remaining aminophosphonate esters to aminophosphonic acids was completed. The final chemical yield of glyphosate was 56% (0.28 mol). No production of N-ethyl glyphosate was detected.

EXAMPLE 5 This example illustrates the elimination of the excess glycine before finishing the hydrolysis of glyphosate esters assisted by CO2. This example also illustrates the dilution of the reaction mixture with water to avoid precipitation, without evident effect on the rate or selectivity of the hydrolysis. A mixture comprising monoethyl or diethyl esters of glyphosate (0.45 mol), glycine (0.50 mol), NaOH (0.50 mol), water (60 g) and ethanol (50 ml) was heated at 50 ° C. subsequently, CO2 was bubbled through the mixture for a period of 3 hours. During the addition of CO2 a white precipitate formed, which was recovered by filtration once the reaction mixture was cooled to room temperature. After the test, it was determined that the solid was constituted by 74.4% glycine and 1.3% glyphosate. Likewise, it was determined that the molar percentage of the phosphorus species in the filtrate was 17.1% glyphosate, 69.7% glyphosate monoethyl ester and 13.4% others. A 50 ml microclave was loaded with a 20 g portion of the filtrate and 20 g of water, and heated to 110 ° C. The test of an aliquot taken at this time determined that the solution contained 43.2% glyphosate, 46.3% glyphosate monoethyl ester and 10.4% others. CO2 was added at 28.12 kg / cm2 in the solution. After 5 hours, the solution contained 91.7% glyphosate, 1.4% glyphosate monoethyl ester and 6.9% others, for a conversion of 102% glyphosate based on glyphosate monoethyl and diethyl ester. Based on the original charge of P (OEt) 3, a chemical yield of 93% glyphosate was obtained, after CO2-assisted hydrolysis.

EXAMPLE 6 This example illustrates a procedure in which a base (NaOH) was added before introducing the CO2. A 50 ml autoclave was charged with a 20 g portion of an alkaloidal stream, as defined in U.S. Patent No. 4,486,359 incorporated herein by reference, which had 66% phosphorus in the dimethyl ester form of glyphosate. An additional 20 g of water was added to this stream and its pH adjusted to 10 with NaOH. Subsequently, CO2 was added at 28.12 kg / cm2 and the solution was heated to 100 ° C. After remaining 5 hours at 100 ° C, an aliquot was taken to analyze it. Based on the original amount of glyphosate dimethyl ester, the sample contained 80% glyphosate, and 20% N-methylglifosate. No monomethyl and glyphosate dimethyl ester was detected in the final stream.

EXAMPLE 7 This example illustrates a procedure in which no additional base was added before introducing the CO2. A 50 ml autoclave was charged with a 20 g portion of an alkaloidal stream with 66% phosphorus in the form of glyphosate dimethyl ester. An additional 20 g of water was added to the solution. Subsequently, C02 was added at 28.12 kg / cm2 and the solution was heated to 100 ° C. After remaining at 100 ° C for 5 hours, an aliquot was taken to analyze it. Based on the original amount of glyphosate dimethyl ester, the sample contained 90% glyphosate monomethyl ester, 8% glyphosate and 2% N-methylglifosate. No glyphosate dimethyl ester was detected in the final stream.

COMPARATIVE EXAMPLE 1 This example illustrates a procedure in which NaOH is added, but no CO2 is introduced into the system. A 50 ml autoclave was charged with a 20 g portion of an alkaloidal stream with 66% phosphorus in the form of glyphosate dimethyl ester. An additional 20 g of water was added to this stream and its pH adjusted to 10 with NaOH. Subsequently, the solution was heated to 100 ° C. After remaining 5 hours at 100 ° C, an aliquot was taken to analyze it. Based on the original amount of glyphosate dimethyl ester, the sample contained 100% glyphosate monomethyl ester. All of the compositions and methods described herein may be elaborated and carried out without further experimentation in light of the present disclosure. Although some of the compositions and methods of this invention are described in terms of preferred embodiments, those skilled in the art will appreciate that it is possible to apply variations in the compositions and methods, as well as in the steps or sequences of steps of the methods described in the present, without distancing itself from the concept, intention and scope of the invention. More specifically, it will be appreciated that certain agents that are both chemically and physiologically related can be used to replace the agents described herein, and still achieve results similar to those described herein. All these possible substitutions and modifications appreciated by those skilled in the art are within the spirit, scope and concept of the invention as defined in the appended claims.

Claims

NOVELTY OF THE INVENTION CLAIMS

1. A process for producing an aminophosphonic acid which includes contacting in an aqueous medium an aminophosphonate ester with a base in the presence of a hydrolysis facilitator selected from a group consisting of C02, CS2 and COS.

2. The process according to claim 1, further characterized in that the aminophosphonic acid has the formula: wherein n is 1 to about 3 and R is hydrogen, an alkyl group containing from 1 to 6 carbon atoms, an aryl group containing from 6 to 12 carbon atoms, salt or carboxylate ester, or hydroxyethyl.

3. The process according to claim 1, further characterized in that the molar ratio of the base with respect to the aminophosphonate ester is at least 1: 2.

4. The process according to claim 1, further characterized in that the base is an alkali metal hydroxide.

5. - The process according to claim 4, further characterized in that the alkali metal hydroxide is sodium hydroxide.

6. The process according to claim 1, further characterized in that the base is an alkaline earth metal hydroxide.

7. The process according to claim 1, further characterized in that the base is a tertiary amine.

8. The process according to claim 1, further characterized in that the hydrolysis facilitator is CO2.

9. The method according to claim 8, further characterized in that the CO2 pressure is between .703 kg / cm2 and 35.15 kg / cm2.

10. The method according to claim 8, further characterized in that the CO2 pressure is between 10.54 kg / cm2 and 28.12 kg / cm2.

11. The method according to claim 1, further characterized in that it includes the step of introducing a pressurized C02 flow.

12. The process according to claim 11, further characterized in that the flow rate of the CO2 is between 100 and 200 ml / min.

13. The process according to claim 1, further characterized in that the contact is made at a pH between 7 and 10.

14. - The method according to claim 1, further characterized in that the contact is carried out at a temperature of between 75 ° C and 120 ° C.

15. The process according to claim 1, further characterized in that the aminophosphonate ester is monoethyl ester of glyphosate, glyphosate diethyl ester or a combination thereof.

16. The process according to claim 1, further characterized in that the contact is made in an aqueous-alcoholic medium.

17. A process for producing an aminophosphonic acid including the steps of: contacting an amine, trialkyl phosphite, base and formaldehyde to produce a first reaction mixture, and hydrolyzing this first reaction mixture in the presence of a hydrolysis facilitator selected from a group consisting of CO2, CS2 and COS, to produce a second reaction mixture including aminophosphonic acid and alcohol.

18. The process according to claim 17, further characterized in that the aminophosphonic acid has the following formula: O H HO-P- (CH2) n -N-R HO where n is from 1 to 3 and R is hydrogen, an alkyl group containing from 1 to 6 carbon atoms, an aryl group containing from 6 to 12 carbon atoms, salt or carboxylate ester, or hydroxyethyl.

19. The process according to claim 17, further characterized in that the amine has the formula RNH2, wherein R is hydrogen, an alkyl group containing from 1 to 6 carbon atoms, an aryl group containing from 6 to 12 carbon atoms. carbon, salt or carboxylate ester, or hydroxyethyl.

20. The process according to claim 17, further characterized in that the molar ratio of the base with respect to the aminophosphonate ester is at least 1: 2.

21. The method according to claim 17, further characterized in that the base is an alkali metal hydroxide.

22. The process according to claim 21, further characterized in that the alkali metal hydroxide is sodium hydroxide.

23. The process according to claim 17, further characterized in that the base is an alkaline earth metal hydroxide.

24. The method according to claim 17, further characterized in that the base is a tertiary amine.

25. The method according to claim 17, further characterized in that the hydrolysis facilitator is CO2.

26. The method according to claim 25, further characterized in that the CO2 pressure is between .703 kg / cm2 and 35.15 kg / cm2.

27. - The method according to claim 25, further characterized in that the CO2 pressure is between 10.54 kg / cm2 and 28.12 kg / cm2.

28. The process according to claim 17, further characterized in that it includes the step of removing alcohol during hydrolysis.

29. The method according to claim 28, further characterized in that the elimination includes the step of introducing a pressurized CO2 flow.

30. The method according to claim 25, further characterized in that the flow rate of the CO2 is around 100 to 200 ml / min.

31. The process according to claim 17, further characterized in that the hydrolysis is carried out at a pH of between 7 and 10.

The process according to claim 17, further characterized in that the hydrolysis is carried out at a temperature between 75 ° C and 120 ° C.

33. The method according to claim 17, further characterized in that it includes the step of diluting the first reaction mixture in water, before hydrolysis.

34. The process according to claim 17, further characterized in that the amine is glycine.

35. The process according to claim 17, further characterized in that the trialkylphosphite is triethylphosphite.