WO1996019485A1

WO1996019485A1 - Process for preparing n-phosphonomethyl glycine

Info

Publication number: WO1996019485A1
Application number: PCT/SI1995/000029
Authority: WO
Inventors: Davorin Bauman; Z^¿eljko KNEZ; Vlasta MARC^¿INKO; Branko PETROVIC^¿; Andreja RIZ^¿NER
Original assignee: Pinus D.D.
Priority date: 1994-12-20
Filing date: 1995-12-18
Publication date: 1996-06-27
Also published as: SI9400449A; AU4127896A

Abstract

Process for preparing N-phosphonomethyl glycine by wet oxidation of N-(phosphonomethyl)iminodiacetic acid with an oxygen enriched air or with hydrogen peroxide at pressures of 100 - 1000 bar, at temperatures of 50 - 500 °C, and reaction times of 0.01 - 10 hours. The process may be performed at subcritical, or preferably supercritical conditions of wet oxidation of N-(phosphonomethyl)iminodiacetic acid. The process is preferably continuous. N-phosphonomethyl glycine, known under the generic name glyphosate, in an active substance indicated for the use in ecologically appropriate herbicides.

Description

PROCESS FOR PREPARING N-PHOSPHONOMETHYL GLYCINE

The present invention relates to a new process for the preparation of N- phosphonomethyl glycine.

N-phosphonomethyl glycine, known under the generic name glyphosate as it will be used in the following text of the description, claims, and abstract for the characterisation of N-phosphonomethyl glycine, is an active substance used in ecologically appropriate herbicides. Such herbicides act on numerous annual or perennial, grass or broad-leafed, woody or other weeds. They are used for the control of weeds in stubble fields, in vineyards, orchards, canals, swamps, grasslands, pasture- lands, drained areas, woods, non-cultivated areas, railway tracks, dams and in other places.

Glyphosate acts on the system and is rapidly transferred into all vital plant organs (roots, rhizome); therefore plants are completely destroyed by herbicides containing it.

From the discovery (US Patent No. 3,950,402) of the outstanding herbicidal activity of glyphosate there were synthesised several derivatives, homologues and analogues thereof. However, glyphosate and its water soluble salts still exhibit the major herbicidal activity.

Glyphosate encompasses many excellent biological properties: a broad activity spectrum, a non-selective and efficient activity on a high number of annual and perennial weeds. One of its most important properties is the rapid transfer from the plant's leaves into its roots, and thus radically destroying the weeds.

The herbicide glyphosate is rapidly adsorbed by the soil where its herbicidal activity is very much diminished. A slight quantity of glyphosate is decomposed via chemical reactions , the majority, however, is decomposed by means of micro-organisms into nutrients for plants, such as: phosphoric acid, ammonia and carbon dioxide. The potential metabolic pathway is described in US Patent No. 3,950,402. Details on the glyphosate metabolism in plants are not well-known.

The current knowledge about the characteristics of glyphosate does not indicate that this herbicide would cause after the application unexpected damage to the soil and the environment. The herbicide itself is also non-polluting for the environment and is practically non-toxic for mammals, birds, fish, insects, and bacieriac.

Toxicity of glyphosate: - acute oral LD50 for rats: 5600 mg/kg,

- acute oral LD50 for rabbits: 3800 mg/kg,

N-phosphonomethyl glycine, generic glyphosate, is a secondary amine of the empirical formula C3H8NO5P and the chemical formula

Glyphosate is a white crystalline solid substance. The solubility of glyphosate in water is low, as evident from the following Table 1.

Temperature Solubility

(°C) (%)

10 1.60

25 4.19

35 5.95

45 7.70

55 9.56

Glyphosate is also practically insoluble in the majority of organic solvents, which is an indication for very strong intermolecular hydrogen bonds in its crystalline structure. It is soluble in acids, bases and amines. Hitherto, several processes for preparing glyphosate have been known.

1. US Patent 3,950,402.

There is described the preparation of glyphosate by means of oxidation of N- (phosphonomethyl)iminodiacetic acid with an oxidising agent, such as hydrogen peroxide or a gas containing free oxygen. In the case of using hydrogen peroxide as an oxidising agent, initially the mixture of N-(phosphonomethyl)iminodiacetic acid, water and cone. H2SO4 is heated and then under stirring 30% H2O2 is added. The stirring is continued till the formation of a colourless solution. The cooling starts the precipitation of glyphosate which is isolated by filtration. When applying a gas containing free oxygen as an oxidising agent the pressure vessel or a glass reaction vessel are filled with a mixture of N-(phosphonomethy])iminodiacetic acid, water and 5% palladium, rhodium, platinum or iridium on carbon.

The mixture is heated to 70 - 120 °C and oxygen or pressurised air are continuously fed in. The mixture is then cooled down to room temperature. The catalyst is separated by filtration, and the filtrate sucked off.

2. YU Patent application No. P-l 175/75 Monsanto Company. In this process a pressure vessel is filled with a mixture of N-(phosphonomethyl)- iminodiacetic acid, water and active carbon. Then pressurised air is fed in. It is important, that the specific surface of the active carbon is sufficient (400 - 1600 m^/g). The reaction temperature is 90 - 150 °C. The pressure range is 0.5 - 203 bar. The most preferred pressures are 1 - 7 bar.

3. YU Patent 35,771 Monsanto Company.

In this process N-(phosphonomethyl)iminodiacetic acid is mixed at increased temperature with a strong acid having a p_K;ι under 2.2. This results in the hydrolysis of N-(phosphonomethyl)iminodiacetic acid into glyphosate and other products. The reaction mixture is then diluted with water and an organic water miscible solvent. Glyphosate precipitates.

4. US patent 5,043,475.

Described is a process for preparing glyphosate by means of oxidation with N- (phosphonomethyl)iminodiacetic acid with peroxide, yielding the intermediate N- (phosphonomethyl)iminodiacetic acid N-oxide. N-(phosphonomethyl)iminodiacetic acid, water and hydrogen peroxide are heated to 20 - 65 °C in the presence of a catalyst, such as a water soluble molybdenum or wolfram (tungsten) salt. After some time the solution is cooled down and then a water soluble salt of vanadium, iron or copper. The temperature should not exceed 65 °C. Glyphosate precipitates and is isolated by filtration.

5. YU Patent 37,363 Monsanto Company.

According to this process N-organo-N-(phosphonomethyl)aminodiacetic acid is dissolved in v HC1. In an electrolytic cell (graphite anode, platinum cathode or a graphite cathode) proceeds the oxidation into N-phosphonomethyl glycine. The reaction may be performed at a temperature of 0 - 110 °C. The reaction time is dependant on the current density, concentration on the electrode surface and the volume of the reaction solution. The glyphosate may be isolated by means of extraction and recrystallisation, centrifugation, concentration and the like.

6. US Patent 4,684,483. Described is a process for the synthesis of N-substituted amino acids. To glyoxal in aqueous medium is added SO2, resulting in the formation of a sulphonated intermediate. Then the nitrogen component (primary or secondary amine, ammonia) is added. The reaction temperature is 80 - 90 °C.

7. WO 90/06929, Monsanto Company.

N-Benzyl-N-phosphonomethyl glycine and its esters in debenzylation with hydrogen halide acids yield benzyl halides and glyphosate or its esters. The reaction temperature is 40 - 100 °C.

8. US Patent 3.927,080.

The process relates to the preparation of glyphosate by means of acid (HC1, HBr, HJ) catalysed hydrolysis of N-t-butyl-N-phosphonomethyl glycine and its esters. The reaction temperature is 110 - 130 °C.

There has now been found a new process, which is the object of the present invention, yielding N-phosphonomethyl glycine denominated glyphosate. Contrary to prior art processes this process proceeds without the use of catalysts in conformance with the following Reaction Scheme.

H₂θ3PCH2N(CH₂COOH)2 + 1/2 0₂ >

H2O3PCH2NHCH2COOH + C0₂ + HCHO In accoi dance with the pi esent inv ention glyphosate is obtained by means of wet oxidation ot N-(phosphonomethyl)ιmιnodιacetιc acid. As oxidising agent air enriched with oxygen or hydi ogen peroxide are used at pressures ot 100 - 1000 bar. The reaction temperature is 50 - 500 °C, the duration ot the reaction is 0.01 - 10 hours. The wet oxidation proceeds in accordance with the present invention, in the following way:

A) At subci itical conditions (T< 374 °C ) and

B) At supercntical conditions (T> 374 °C. P > 220 bar).

A) The wet oxidation at subci itical conditions. It is performed in aqueous phase at temperatures ot 150 - 300 °C and pi essures 100 - 150 bar. This embodiment of the invention is bound by several l estnctions. Upon mixing air and an aqueous solution of the substance the oxygen solubility in watei is significantly lower than the solubility required tor the complete oxidation. A two-phase mixtuie is in the reactor. Since the oxidation is not complete, the gas leaving the process contains significant concentrations ot the volatile oi anic components and has to be usually purified prior to the release into the atmosphere

B) Supercritical wet oxidation in accoi dance with the present invention is an embodiment upgi admg the wet oxidation. The efficiency is much improved, and the investment costs are significantly diminished.

The process comprises a wet oxidation ot oiganic components in an aqueous phase at conditions er the water critical point (Tc = 374 °C, Pc = 220 bar). The basic characteristic is the existence ot oxygen, water and organic substances at supercritical conditions in a single homogeneous thud phase. In the procedure a 30% hydrogen peroxide solution and a 1-50%, pretei abh 1-40%. especially 9-10% aqueous solution of

l)ιmιnodιacetιc acid.

The supercritical water is an excellent medium in which organic substances are oxidised as a result ot high solubility ot organic components and oxygen. The relatively high temperatui e guai antees a l apid oxidation. The process must be performed in a corrosion resistant reactor

The most impoi tant advantages ot the performance of the process in accordance of the present invention at supei critical conditions are:

- the increased solubility ot oxygen in water, thus resulting in a single phase; ft

- the rapid oxidation ot oiganic substances which enables the adiabatic conditions and a high initial temperatui e and a short reaction time;

- a complete oxidation ot the organic substances; tor this reason the purification ot the exhaust gases is not needed;

- the separation ot pi ecipitated inorganic components;

- the heat generated in the decomposition ot the substances is used in the heating ot the supercritical water.

The reaction conditions ai e dependant troπv

- the phase balance ot the system water : oiganic substance,

- the phase balance ot the s\ stem watei ^■ oxygen,

- the ignition temperatui e ot the sy stem w atei : organic substance : oxygen, which is dependant on the pi essui e and composition of the mixture.

The process in accordance with the present invention may be pertormed in one of the apparatus schematically represented on Fig. 1 and Fig. 2.

On Fig. 1 is represented an apparatus foi the charge performance of the process in accordance with the invention

On Fig. 2 is repiesented an appai ius foi the continuous performance of the process in accordance with the invention

The reference numei als stand toi : 1 - high-pressui e pump 2 - valve 3 - one-way vaK e

4 - safety valve

5 - needle valve Pi - manometer.

The process in accoi dance with the pi esent invention is illustrated by the following Examples, however, without limiting its scope Example 1

Into the reactor represented on Fig. ] were charged 170 mis of water and 15 g of N- (phosphono-methyl)iminodiacetic acid. The reaction mixture was heated to 250 °C, and after that air enriched with oxygen (50%) was blown into it. The pressure in the reactor was 200 bar. In the cell a constant pressure was kept up, and the air flow was 0.1 - 10 g/min. The temperature was maintained by means of a heating jacket. The duration of the reaction was 10 minutes.

Glyphosate was isolated by concentrating the filtrate under reduced pressure in a rotary evaporator, or left to cool down and then sucked off. The formed crystals were dried in a drier for 2 hours at 105 °C. The crystals were analysed by HPLC. The synthesis yield was 80%.

Example 2

Into the reactor represented on Fig. 1 were charged 170 is of water and 15 g of N- (phosphono-methyl)iminodiacetic acid. The reaction mixture was heated to 250 °C, and after that air enriched with oxygen (50%) was blown into it. The pressure in the reactor was 500 bar. In the cell a constant pressure was kept up, and the air flow was 0.1 - 10 g/min. The temperature was maintained by means of a heating jacket. The duration of the reaction was 10 minutes.

Glyphosate was isolated by concentrating the filtrate under reduced pressure in a rotary evaporator, or left to cool down and then sucked off. The formed crystals were dried in a drier for 2 hours at 105 °C. The crystals were analysed by HPLC. The synthesis vield was 92%.

Example 3

Into the reactor represented on Fig. 1 were charged 170 mis of water and 15 g of N- (phosphono-methyl)iminodiacetic acid. The reaction mixture was heated to 400 °C, and after that air enriched with oxygen (50%) was blown into it. The pressure in the reactor was 500 bar. In the cell a constant pressure was kept up, and the air flow was 0.1 - 10 g min. The temperature was maintained by means of a heating jacket. The duration of the reaction was 5 minutes. Glyphosate was isolated by concenti ating the filtrate under reduced pressure in a rotary evaporator, or left to cool down and then sucked off. The formed crystals were dried in a drier tor 2 houi s at 105 °C. The crystals were analysed by HPLC. The synthesis yield was 94%.

Example 4

Into the cell were chai ged 50 mis ot water and 15 g of N-(phosphonomethyl)- iminodiacetic acid, whei eυpon the desn ed pressui e was generated by means of water. Then 20 mis ot hydrogen peroxide (30%) wei e added. The reaction mixture was heated to 400 °C, and attei that an enπched with oxygen (50%) was blown into it. The pressure in the reactor was 500 bai . In the cell a constant pressure was kept up, and the air flow was 0.1 - 10 g/min. The tempei ature was maintained by means of a heating _jacket. The duration ot the l euction was 5 minutes.

Glyphosate was isolated by concentrating the filtrate under reduced pressure in a rotary evaporator, or left to cool down and then sucked off. The formed crystals were dried in a drier toi 2 houi s at 105 °C. The HPLC analysis showed that the crystals contained pi acticallv pui e N-(phosphonomethyl)glycιne. The synthesis yield was 93%.

Example 5

Into a continuous reactoi shown on Fig. 2 functioning under a pressure ot 200 bar and at a temperatui e ot 250 °C. was continuously pumped the solution of 9-10% N- (phosphonomethyljimmodiacetic acid in water. By means ot the pump B a 30% solution ot

ogen pel oxide was chai ed into the system.

The duration ot the ieaction was varied in the range of 1 - 100 minutes.

In the reaction product the glyphosate content was analysed. The reactor conversion range grade was 92%

Example 6

Into a continuous reactor shown on Fig. 2 functioning under a pressure of 400 bar and at a temperature ot 400 °C. was continuously pumped the solution of 9-10% N- (phosphonomethyl)ιmιnodιacetιc acid in water. By means of the pump B a 30% solution of hydrogen peroxide was charged into the system. The duration of the reaction was varied in the range of 1 - 100 minutes.

In the ration product the glyphosate content was analysed. The reactor conversion range grade was 94%.

Claims

11)CLAIMS

1. A process tor preparing N-phosphonomethyl glycine by oxidation of N-

(phosphonomethyl)iminodιacetic acid, characterised by the performance of a wet oxidation of N-(phosphonomethyl)iminodιacetic acid with hydrogen peroxide or with an oxygen enriched air at pressures of 100 - 1000 bar, at temperatures of 50 - 500 °C, and reaction times of 0.01 - 10 hours.

2. A process as claimed in claim 1, characterised in that it is performed at wet oxidation subcritical conditions.

3. A process as claimed in claim 1 , characterised in that it is performed at wet oxidation supercritical conditions.

4. A process as claimed in claim 1 and3. characterised in that it is performed in a continuous way.

PINUS d.d.