HU177155B - Process for producing n-phosphonomethyl-imino-diacetic acid - Google Patents

Description

The present invention relates to an improved process for the preparation of N-phosphonomethyliminodiacetic acid from monochloroacetic acid using calcium hydroxide. N-phosphonomethyliminodiacetic acid can be used as an intermediate in the preparation of N-phosphonomethylglycine. N-phosphonomethylglycine is used in agriculture as a starting material for herbicides and growth regulators.

There is a known process for the preparation of N-phosphonoinethyliminodiacetic acid (K. Moedritzer, R. R. Iran:

J. Org. Chem. Initially, the process was of no industrial significance because the iminodiacetic acid required as the starting material was not available on a technical scale.

The iminodiacetic acid can be prepared by reacting monochloroacetic acid with ammonia in an alkaline medium. With a large excess of ammonia, glycine is more likely to be formed, while with a small excess of ammonia it is mainly the nitrilotriacetic acid that is produced, the iminodiacetic acid is formed only to a small extent and its separation is problematic.

Compared to the above, progress has been made in the implementation of Resolution 1,554,236. A process described in French Patent No. 5,198, wherein monochloroacetic acid is reacted with ammonia in the presence of calcium or magnesium hydroxide. According to the method, primer ter177155

-diacetic acid

.

70-75% of iminodiacetic acid hydrochloride is obtained and an additional fraction is obtained by evaporation of the mother liquor.

The major disadvantage of this process in terms of industrial feasibility is that the iminodiacetic acid is isolated in the form of its hydrochloride. The hydrochloride only crystallizes in the presence of a very large excess of hydrochloric acid (6-10 times the equimolar amount). Thus, in the case of any industrial application, very large quantities of concentrated aqueous hydrochloric acid must be used, the hydrochloric acid mother liquors must be filtered, evaporated and the hydrochloride also containing hydrochloric acid dried. Not only is high acid excess not only disadvantageous due to environmental cost of primary material and destruction of hydrochloric acid mother liquors, but also causes severe corrosion problems, the equipment used must be made of expensive, corrosion-resistant structural materials. To illustrate what has been said; yearly

For a plant producing 1001 N-phosphonomethyliminodiacetic acid, about 2 m ^{3 of} concentrated hydrochloric acid per day would be expected to be consumed and destroyed.

Another disadvantage of isolating iminodiacetic acid as the hydrochloride is that the product is not pure enough for Mannich condensation, so that it has to be converted into a pure base in a separate step with a loss of 8-10%, otherwise the yield of the condensation reaction would be at least as much reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the above drawbacks and to provide a process for preparing N-phosphonomethyliminodiacetic acid from inexpensive, readily available starting materials in a simple manner and in high purity.

The present invention is based on the surprising discovery that the water-soluble calcium salt of iminodiacetic acid is converted to a water-insoluble double salt at an acidic pH range consisting of the acidic calcium salt of iminodiacetic acid and calcium chloride. The structure of said double salt is illustrated by formula (I). Because of the water insolubility of the salt, any known separation step (filtration, centrifugation) can be used to separate the reaction mixture.

The present invention relates to a process for the preparation of N-phosphonomethyliminodiacetic acid from chloroacetic acid using calcium hydroxide. The process according to the invention is characterized in that calcium hydroxide is added in small portions to the ammonium salt of monochloroacetic acid in an aqueous medium at a temperature in the range of 40 to 80 ° C, in a small amount of 0.8: 1 to 1.2: 1. beside the ammonia excess is removed and the pH of the solution is adjusted to between 2 and 6 with hydrochloric acid, iminodiacetic acid insoluble, C ₈ H ₁₂ O ₈ N _{2 CaCl2} Calculated internal double salt (formula I) are separated, aqueous is separated salt soluble sulphate, preferably sodium sulphate, used in a medium at a temperature of 50 to 90 ° C, particularly preferably 60 to 80 ° C, in the ratio 1: 1 to 1: 1.5, separating the gypsum precipitated, and mono- to the solution containing the sodium salt, optionally after concentration, paraformaldehyde in a molar ratio of 1: 1.2 to 1: 1.8, followed by phosphorus trichloride in a molar ratio of 0.991 to 1.2: 1

Alkali metal hydroxide, preferably sodium hydroxide, is added until a pH of 1.5-2.0 is obtained, and the precipitated product is isolated.

Preferably, the process comprises the step of forming the ammonium salt of monochloroacetic acid and ammonia and adding small amounts of calcium hydroxide to the solution in small portions. The reaction produces a soluble calcium salt of iminodiacetic acid, removing excess ammonia from the solution by vacuum evaporation and acidifying the solution to a pH of 2 to 6. C ₈ H ₁₂ O ₈ Ca j_CaCl ₂ Calculated (I) as dual in structural precipitated is isolated by filtration or centrifugation, whereby the reaction are removed together with the filtrate. The insoluble double salt is suspended in water and a soluble sulfate, preferably sodium sulfate, is added to the suspension. During the decomposition reaction, calcium is precipitated as gypsum. The gypsum is filtered off. The filtrate contained the iminodiacetic acid monosodium salt, but which was not isolated, but rather as the Mannich condensation ortho foszforossa ^acid is includes in the filtrate, in situ, to a "one pot" reaction, in such a way that paraformaldehyde, and phosphorus trichloride are added. Hydrochloric acid liberated from phosphorus trichloride liberates iminodiacetic acid from its sodium salt and forms it partly with hydrochloride, which

Advantageous for Mannich condensation. The reaction mixture is heated to reflux to complete the reaction. The excess acid is then neutralized with an alkali metal hydroxide, preferably sodium hydroxide, and the N-phosphonomethyliminodiacetic acid is isolated.

The advantages of the process according to the invention can be summarized as follows:

- the target compound can be obtained from simple, readily available starting materials in high purity,

- the ininodiacetic acid hydrochloride as an intermediate is not required, so that the excess hydrochloric acid required for its separation is no longer required,

- according to the invention, the iminodiacetic acid is separated from the by-products in the form of a water-insoluble calcium salt-calcium chloride,

- higher yields of iminodiacetic acid, purity of the product which is important for Mannich condensation, since condensation is more efficient in the case of pure starting material,

- N-phosphonomethyliminodiacetic acid without the preparation of intermediates, except for the insoluble Ca salt, we can produce it in a unique way,

- starting from the sodium salt of iminodiacetic acid, one third of the hydrochloric acid liberated from phosphorous trichloride is sufficient to liberate the acid, the other hydrochloric acids providing optimum conditions for Mannich condensation,

- the sodium chloride formed in the reaction does not disturb the condensation but, on the contrary, increases the boiling point and promotes a faster reaction,

- the particular advantage of in situ production of orthophosphoric acid is that it excludes the possible oxidation, polymerisation of orthophosphoric acid and consequent possible side reactions.

- the process does not require any special equipment, it is feasible on a large scale, it is easy to scale up.

The process of the invention is illustrated by the following embodiment.

Example

To a 500 liter autoclave equipped with a 180 minute ^-1 rotor propeller mixer was added 40 liters of water and 94.5 kg (1 kmole) of monochloroacetic acid was dissolved in it with gentle heating. To the solution was added 81.63 liters of 0.906 g / cm ³ aqueous ammonia (1.1 kmol). Neutralization was carried out under cooling, the temperature of the reaction mixture was then raised to 40 ° C, and a total of 74.84 kg (1.01 km) of solid calcium hydroxide was added in equal portions over two hours. The reaction mixture was stirred at 40 ° C for 8 hours, then warmed to 80 ° C, diluted with 100 L of water at 80 ° C and stirred for an additional 30 minutes. The small amount of insoluble material was separated by filtration in a centrifuge and the resulting filtrate (about 330 liters) was concentrated in vacuo to one third of its volume at a temperature not exceeding 60 ° C. This operation also removes excess ammonia from the system. The still warm solution was made up to 100 liters volume with concentrated hydrochloric acid diluted 1: 1 with water

It is acidified to pH 2.5-3.5 and then cooled to room temperature. The precipitated insoluble calcium salt was isolated by centrifugation. Discard the filtrate containing the by-products.

143.4 kg of a centrifuge wet product having a moisture content of 39% and an active substance content of 95.0% on a dry basis were obtained. The yield of CsHj ₂ O ₈ N ₂ Ca · CaCl _{2 for the} double salt monochloroacetic acid is 80%.

The centrifuged precipitate is suspended in 270 liters of water, heated to 80 ° C and treated with 170 liters of saturated sodium sulfate solution over 5 minutes. This corresponds to 73.9 kg of anhydrous sodium sulfate, i.e. a 30% molar excess. The suspension was stirred at 80 ° C for one hour and then cooled to 60 ° C. The gypsum formed in the decomposition is centrifuged, washed with 60 liters of water and the wash water combined with the filtrate. The volume of the solution is 354 liters.

The iminodiacetic acid mononitrate content of the aqueous solution is determined by potentiometric titration. From this, calculate the iminodiacetic acid content of the solution. One liter of solution contains 135.3 g of iminodiacetic acid, equivalent to 47.9 g (0.36 kmol) of iminodiacetic acid based on the total volume of the solution.

The solution is aspirated into an autoclave equipped with a cool-heat, reflux and descending condenser, a propeller mixer and a liquid dosing tank, where it is concentrated to half its volume. Then 16.21 kg (0.54 km) of paraformaldehyde (50% molar excess) was added. 51.92 kg (0.378 km) of phosphorus trichloride (5% molar excess) are added uniformly from the liquid dosing vessel while the internal temperature is occasionally maintained at 70 ° C to 80 ° C by cooling. The reaction mixture was then heated and refluxed for 3 hours, then cooled to 40 ° C.

A solution of 30.3 kg (0.757 km) of sodium hydroxide in 55 liters of water (pH 1.65) is added. After cooling to 10-20 ° C, the precipitated N-phosphonomethyliminodiacetic acid is isolated by filtration, washed with water and dried.

68.72 kg product is obtained with a potentiometrically determined content of 99.1%. On this basis, the amount of pure (100%) N-phosphonomethyliminododiacetic acid was 68.1 kg. THE

The partial yield of Mannich condensation was 83.3% and the total yield calculated for monochloroacetic acid was 59.97%.

Claims (1)

Claim: A process for the preparation of N-phosphonomethyliminodiacetic acid from chloroacetic acid using calcium hydroxide, characterized in that the ammonium salt of nionochloroacetic acid is in an aqueous medium at a temperature in the range of from 0.8: 1 to 1.2: 1 in an aqueous ratio of 0.8: 1 to 1.2: 1. calcium hydroxide is added, ammonia is removed from the soluble iminodiacetic acid calcium salt formed, the pH of the solution is adjusted to 2 to 6 with hydrochloric acid, and the insoluble inner double salt of iminodiacetic acid of formula (I) is isolated. plkülönített salt in an aqueous medium 50 to 90 ⁵ C, preferably 60-80 ° C, 1: 1 to 1: 1.5 molar ratio of water-soluble sulphate, preferably sodium sulfate is added, the precipitated gypsum is separated, and iminodiacetic acid mono- sodium salt solution, optionally after concentration, in a molar ratio of paraformaldehyde of 1: 1.2 to 1: 1.8 followed by phosphorus trichloride in a molar ratio of 0.8: 1 to 1.2: 1 oride is added and the reaction mixture is refluxed, followed by addition of an alkali metal hydroxide, preferably sodium hydroxide. It is neutralized to pH 1.5-2.0 and the precipitated product is isolated.