AU660263B2 - Process for producing N-phosphonomethyl glycine - Google Patents

Description

.1 6602 63

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT (Original) APPLICATION NUMBER:

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RELATED ART: rr r NAME OF APPLICANT: ACTUAL INVENTOR(S): ADDRESS FOR SERVICE: INVENTION TITLE: DAVISON INDUSTRIES PTY LTD (ACN 009 159 406) RAVINDRAN VAIKYL and RAE CAMPBELL DAVISON KELVIN LORD AND COMPANY 4 Douro Place West Perth WA 6005 "PROCESS FOR PRODUCING N-PHOSPHONOMETHYL GLYCINE" r r e r ASSOCIATED PROVISIONAL APPLICATION NOS: PL 3385 The following statement is a full description of this invention including the best method of performing it known to me/us:- 1 2 2 The present invention relates to a process for producing 3 N-phosphonomethyl glycine.

4 More particularly, the process of the present invention involves oxidation of N-phosphonomethyl iminodiacetic acid 6 to N-phosphonomethyl glycine.

7 At present, procedures for the preparation of 8 N-phosphonomethyl glycine (glyphosate) include the 9 oxidation of N-phosphonomethyl iminodiacetic acid using a variety of oxidising agents. The oxidising agents used 11 include hydrogen peroxide, nitric acid and peroxyacetic 12 acid. Also known is oxidation in aqueous media. Such 13 reactions have been described previously in US Patent Nos.

14 3950402 and 3969398 as a water solution using a free oxygen 15 containing gas and either a nobel metal or an activated 16 carbon catalyst, respectively.

17 The abovementioned prior art describes the preferred use of 18 approximately saturated solutions of the N-phosphonomethyl 19 iminodiacetic acid in water at the temperature of reaction for ease of reaction and ease of recovery of the product.

21 Such a saturated aqueous solution contains at most about 1% 22 by weight of the acid at 25°C, about 4% by weight at 23 and about 10% by weight at 150°C. This relatively low 24 solubility of the acid in water greatly restricts and limits the amount of N-phosphonomethyl iminodiacetic acid 26 that can be charged and oxidised in a batch reaction system 27 to form the desired N-phosphonomethyl glycine.

28 Consequently, water needs to be distilled off to recover 29 the N-phosphonomethyl glycine from the aqueous solution.

Such distillation requires the expenditure of considerable 3 2 heat energy.

3 The process of the present invention has as one object 4 thereof to minimise the disadvantages of the prior art.

In accordance with one aspect of the present invention 6 there is provided a process for producing N-phosphonomethyl 7 glycine in which an amount of N-phosphonomethyl imino- 8 diacetic acid is mixed with water to form a slarry, the 9 N-phosphonomethyl iminodiacetic acid subsequently being oxidised. by hydrogen peroxide in the presence of sulphuric 11 acid and molecular oxygen.

12 Preferably, concentrated sulphuric acid is employed. Still 13 preferably, oxidation occurs at atmospheric pressure and at 14 an elevated temperature.

15 The present invention will now be described, by way of 16 example only, with reference to the following drawings, in S"17 which:- 18 Figure 1 is a schematic flow diagram of the process of the 19 present invention.

N-phosphonomethyl iminodiacetic acid (PMIDA) having the 21 following formula: 22 0 23 11 24 HO-P---CH 2 -N(CH2--COOH) 2 26 HO 27 28 29 is mixed with water to create a 50 60% slurry by weight.

The concentrated sulphuric acid is then added with stirring 31 at an elevated temperature, 45-50°C over two hours, as can 32 be seen in Figure 1, to promote protonation.

33 The mixture is heated further, to about 90°C and hydrogen J i r i i r itr 1 4 2 peroxide added over several hours under a flow of oxygen to 3 achieve oxidation of the N-phosphonomethyl iminodiacetic 4 acid. The resultant reaction mixture is heated to maintain the 90 0 C temperature for a further 2 hours.

6 It is believed that the reaction takes place in accordance 7 with the following equation: 8 9 0 11 A 12 HO-P-CH 2

-N(CH

2

-COOH)

2 2H202 13 14 HO 16 17 18 0 H 19

HO-P--CH

2

-N-CH

2 COOH HCOOH CO 2 2H 2 0 21 22 HO 23 S 24 25 The reaction mixture is subsequently cooled over a number 26 of hours to a temperature of about 5°C. This cooling 27 promotes the separation of N-phosphonomethyl glycine in 28 crystalline form. The resultant crystals may then be 29 collected, washed in water and air dried.

The conversion of N-phosphonomethyl iminodiacetic acid to 31 N-phosphonomethyl glycine is about 98% by weight and the 32 yield 95 96% by weight. It should be noted that the 33 prior art of US patent No. 3954848 had a yield of only 34 78.43% by weight which is indicative of the broader prior art base.

36 The starting material employed in the process of the 37 invention is N-phosphonomethyl iminodiacetic acid and can 38 be produced by the reaction of iminodiacetic acid with 39 formaldehyde and phosphorous acid in the presence of 1 2 hydrochloric acid.

3 The following example is representative of and illustrates 4 the process of the present invention. All percentages and proportions are by weight unless otherwise indicated.

6 EXAMPLE 7 To a mixture of N-phosphonomethyl iminodiacetic acid 8 (200kg) and water (200kg), 98% sulphuric acid was added, 9 with stirring, at 45-50°C over two hours. The mixture was heated at 90°C and 50% hydrogen peroxide (186kg) was added 11 over six hours with a steady flow of oxygen (500ml/minute) 12 at 90-95 0 C. The reaction mixture was heated at 90-95°C for 13 two additional hours and then cooled to 5-8°C overnight 14 when N-phosphonomethyl glycine separated as white crystals.

15 The product was collected, washed with water and air 16 dried. The yield of essentially pure white crystalline 17 N-phosphonomethyl glycine was 134kg. An additional 8kg of 18 the product was obtained on storage of the filtrate in the 19 refrigerator.

The purity of the product was determined by HPLC analysis 21 which was conducted on a 5p ODS2 column. The mobile phase 22 was 0.2% triethylammonium phosphate in water.

23 It should be noted that the process of the present 24 invention requires no catalyst and no increase in pressure to produce a high yield of N-phosphonomethyl glycine.

26 Prior art processes have required use of expensive 27 catalysts such as platinum on charcoal, palladium on 28 charcoal or pre-treated activated carbon.

29 Modifications and variations such as would be apparent to a skilled addressee are deemed within the scope of the -6- 2 present invention.

3 4 go 0 *go O o* o *o o

Claims (1)

1. 6. A process in accordance with claim 5, in which hydrogen 21 peroxide is added to the N-phosphonomethyl iminodiacetic 22 acid, water and sulphuric acid mix in the presence of 23 molecular oxygen as a second step in the process and 24 whereby the N-phosphonomethyl iminodiacetic acid is oxidised. 26 7. A process in accordance with claim 6, in which the 27 second step takes place at a temperature in the range of 28 90-950C. 29 8. A process in accordance with claim 6 or 7, in which the reaction time of the second step is between 6 and 8 hours. 8 2 9. A process substantially as hereinbefore described with 3 reference to Example 1. 4 10. A process substantially as hereinbefore described with reference to Figure 1. 6 7 8 9 11 DATED JUNE 23 1993 12 DAVISON INDUSTRIES PTY LTD 13 By their Patent Attorneys 14 KELVIN LORD AND COMPANY 15 PERTH, WESTERN AUSTRALIA 16 o& I *t4. l «k 1 9 2 ABSTRACT 3 A process for producing N-phosphonomethyl glycine in which 4 an amount of N-phosphonomethyl iminodiacetic acid is mixed with water to form a slurry, the N-phosphonomethyl 6 iminodiacetic acid subsequently being oxidised by hydrogen 7 peroxide in the presence of sulphuric acid and molecular 8 oxygen, wherein no catalyst or pressure increase is 9 required to achieve oxidation. i. c r r