HU187438B - Process for preparing n-/phoshono-methyl/-glycine - Google Patents

Abstract

The present invention relates to a novel process for the preparation of N- (phosphonomethyl) glycine. According to the present invention, a reaction mixture of pH 3 or more is added to a pH of 3 or more by adding an acid of up to 2 equivalents of N (phosphonomethyl) iminodiacetic acid, of alkali and water, or of an N- (phosphonomethyl) iminodiacetic acid salt and of the water present. the reaction mixture is treated with a peroxide in the presence of a metal or metal catalyst to promote the radical decomposition of the oxidizing agent and / or by irradiation with ultraviolet light, and, if desired, the N-phosphonomethylglycine formed is isolated in a known manner. -1-

Description

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

N-phosphonomethylglycine can be used in plant cultivation as a plant growth regulator or herbicide. The most widely known known method of preparing N-phosphonomethylglycine is to treat N-phosphonomethyliminodiacetic acid with a liquid, solid or gaseous oxidant (Dutch Patent Publication No. 7,307,449, 3,954). U.S. Patent No. 848, Hungarian Patent No. 167,343). Liquid or solid oxidizing agents include inorganic or organic peroxides such as hydrogen peroxide, peracetic acid, peracetic acid, perbenzoic acid, m-chloroperbenzoic acid, benzoyl peroxide or benzenesulfonic acid, and other commonly known inorganic oxidizing agents, such as sodium hypochlorite, potassium potassium persulphate and similar compounds are used, while the gaseous oxidant is oxygen or oxygen-containing gas mixtures, preferably air.

A common feature of the above-described processes is that the oxidation is carried out at the native pH of the N-phosphonomethyliminodiacetic acid (about pH 2) or in the presence of an acidic additive. The amount of acid added ranges from a relatively insignificant amount of equivalent sulfuric acid as the reaction medium. Experimental experience has shown that oxidation of N-phosphonomethyliminodiacetic acid in the presence of an acid additive is significantly faster than in the absence of an acid.

The disadvantages of using a highly acidic medium are numerous. From an operational point of view, the reaction medium is highly corrosive; therefore, the reaction must either be carried out in a vulnerable, easily damaged glass reactor, or the inside of the metal reactor must have a special corrosion-resistant coating. The highly acidic reaction mixture is difficult to process, the acid cannot be regenerated from the reaction mixture, and the production waste water can only be discharged to the environment after prior neutralization. Further disadvantages result from the fact that the final product, i.e., N-phosphonomethylglycine, is significantly more soluble in the strongly acidic reaction medium than in water. The N-phosphonomethylglycine remaining dissolved in the reaction medium can be separated only with suitable precipitating agents (usually alcohols), which increases the production cost and also removes impurities from the reaction mixture which are not or only very difficult to remove from the final product.

A less common method is the oxidation of N-phosphonomethyliminodiacetic acid by electrochemical methods (British Patent Nos. 1,494,197 and German Patent No. 2,363,634).

A common disadvantage of non-acid additive processes (U.S. Pat. No. 3,696,398 and German Patent No. 2,519,388) is that, apart from the low reaction rate, the starting N- (phosphono- methyl iminodiacetic acid is very poorly soluble in water used as reaction medium (concentration of 95% saturated aqueous solution is only 4% by weight). Therefore, very large volumes of aqueous solutions need to be treated, which significantly reduces the useful capacity of the reactors and increases the energy demand of the process; and a large amount of water must be removed from the reactor leaving solution, which requires additional energy investment.

To overcome the disadvantages of the low solubility of N-phosphonomethyliminodiacetic acid and the use of a highly acidic reaction medium, it has already been proposed to oxidize the salts of N-phosphonomethyliminodiacetic acid, which are N-phosphonomethyl. They are significantly more soluble in water than iminodiacetic acid and form a slightly acidic or near neutral pH aqueous solution. However, according to the literature, salts cannot be oxidized with any of the reagents for oxidizing N-phosphonomethyliminodiacetic acid; only electrochemical oxidation and gaseous oxidation oxidation are known (Belgian Patent Nos. 861,996 and 4,147,719). However, it is clear from the data of both patents that the reaction generates significant amounts of by-products [e.g., N-methylN-phosphonomethylglycine and methylamine methylphosphonic acid when N- (phosphonomethyl) imino] starting from the salt of diacetic acid with isopropylamine], and the use of the appropriate salts in place of the mono-salts of N-phosphonomethyliminodiacetic acid yields a rapid decrease. On the other hand, only the salts possess high solubility solubility.

Earlier Hungarian Patent Application No. 184,168 discloses an acid-free aqueous suspension of N-phosphonomethyliminodiacetic acid for the preparation of N-phosphonomethylglycine. The oxidizing agent used is oxygen gas or oxygen-containing gas mixtures - primarily air. Although this procedure eliminates the difficulties of using a highly corrosive reaction medium and greatly increases the reactor capacity, it has the disadvantage that intensive stirring of the reaction mixture is required and the reaction is relatively slow.

In summary, a process for the preparation of N (phosphonomethyl) glycine in terms of reaction mixture reaction rate, reaction rate, power demand and capacity utilization has not yet been described.

In our studies, it has been found that when a mixture of N-phosphonomethyliminodiacetic acid, water and an organic or inorganic base is prepared, up to two equivalents of acid are added and the pH of the reaction mixture is up to 3 so that solid N- (phosphonomethyl) iminodiacetic acid is not precipitated out of solution, although the amount of solution in the solution is 2-4 times higher than that observed so far. This reaction mixture is oxidized to peroxides by heating to 50-120 ° C in the presence of a metal or metal compound catalyst or irradiating with ultraviolet light. Thus, in a shorter period of time than previously known methods, as described above

187,438 can be used to produce a spectroscopically pure target product with a higher capacity utilization (optionally triple), a favorable energy balance and a good yield.

The observed phenomenon is that outlined above ^! In the case of addition of alkali and acid, the solubility of the resulting product increases, giving two possible explanations. One is that an over saturated solution could be expected. However, this assumption is contradicted by the fact that it is formed from the reaction mixture either ¹¹ vesicle mechanical effect of the product.

Another purely hypothetical explanation could be that the reaction mixture in the form of the N- (phosphonomethyl) iminodiacetic acid is not a free acid, not the salt, but an as yet unexplored structure other ^one derivative (molecular compound, complex adduct). N- (phosphonomethyl) iminodiacetic acid derivative in the reaction mixture "formed of N- (phosphonomethyl) -iminodiecetsav acid and alkali complexes" hereinafter - ^two or briefly "N- (phosphonomethyl) -iminodiecetsav- complex ”. The complex is highly soluble in the reaction medium used and can be formulated into highly concentrated stable aqueous solutions. It is extremely surprising to-PHI ² is our experience that is constructed according to the invention the reaction of N- (phosphonomethyl) iminodiacetic acid is oxidized at a rate substantially higher than the pure aqueous solution anyway, oxidized under the same conditions 3 N- (phosphonomethyl) iminodiacetic acid. All of these experiences suggest that prepared according to the invention the reaction of N- (phosphonomethyl) imino-diacetic acid is a much more susceptible to oxidation resulting complex, and complexes in the oxidation xum ³ - N- (phosphonomethyl) - unlike iminodiacetic acid salts, it proceeds in the desired direction.

The starting reaction mixture used in the process of the present invention can be prepared by dissolving N-4 (phosphonomethyl) iminodiacetic acid in water containing at least 1 molar equivalent of base and adding up to 2 equivalents of acid to the pH of the resulting solution. set to. In the latter case, the order of addition of the components is crucial. In our experience, N- (phosphonomethyl) iminodiacetic acid is not soluble in an aqueous solution (95 'Con) of neutral or acidic solution containing alkaline and acid more than 4% by weight, so that the complex to be oxidized cannot be live.

The process may use any basic chemical, such as inorganic household compounds such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, and organic bases such as primary, secondary and tertiary alkylamines (preferably methylamine, ethylamine, propylamine, isopropylamine, butylamine and dimethylamine), basic cyclic nitro compounds (such as pyridine, 2-methylpyridine, aniline).

At least 1 molar equivalent of base is used per mole of N-phosphonomethyliminodiacetic acid. The upper limit of the amount of base is suitably ca. May be 2 molar equivalents; the use of a larger amount of base _f has no further advantages. Preferably, based on 1 mole of N-phosphonomethyliminodiacetic acid

1.5 to 2 moles of base are used; Thus homogeneous solutions with high concentrations of N-phosphonomethyliminodiacetic acid can be prepared.

The acid used in the process may be any strong acid; For example, sulfuric acid, nitric acid, trifluoroacetic acid and other acids having a pK value of 2 or more can be used. Up to 2 equivalents of acid per mole of base may be added to the reaction mixture. It has been found advantageous to add 0.8 to 1.7 molar equivalents of acid per mole of base. Preferably, about ⁵ moles per ⁵ moles of base. 1 to 1.5 molar equivalents of acid are used; this amount of acid is sufficient to increase the reaction rate but is also optimal from an economic point of view.

In the reaction mixture according to the invention, the acid and base form a buffer system so that the acidity of the mixture is not shifted to the corrosive region even when the maximum amount of acid is added. Most of the basic amines and their acid derivatives have anticorrosive properties, which is a significant advantage for safe operation.

Peroxides used as oxidizing agents in the process of the present invention include, but are not limited to, inorganic peroxides such as hydrogen peroxide, sodium peroxide, percutic acid, potassium peroxydisulfate, permanganic acid, and organic oxidizing agents such as peracetic acid, cumyl hydroperoxide, ethylbenzene hydroperoxide, ditertiary butyl hydroperoxide, di-tertiary butyl peroxide. The amount of oxidizing agent used may be from 1 mol to 5 mol per mole of N-phosphonomethyliminodiacetic acid. One skilled in the art will appreciate that the use of 1 molar equivalent of oxidizing agent is not expected to complete the reaction, whereas at 5 molar equivalents, part of the N-phosphonomethylglycine formed will be further oxidized. Preferably, therefore, 2 to 2.5 moles of oxidant are used per mole of N-phosphonomethyliminodiacetic acid; this ensures that the reaction is complete or nearly complete, but does not further oxidize the resulting product to a significant degree.

The reaction is carried out at an elevated temperature, for example 50-120 ° C, preferably 90-100 ° C.

The manner in which the oxidant is added is not critical, but it is preferable to add the oxidant in portions to the reaction mixture which has already been heated to a sufficient temperature (about 90-100 ° C) in the presence of the catalyst. If the reaction is conducted in such a way that the oxidation is carried out very rapidly (e.g., at a temperature of about 100 ° C and at least an equivalent amount of acid is used in the alkali), then this stepwise addition is of no importance.

In the process of the present invention, any metal of the subgroups of the periodic table may be used as a catalyst, either alone or in the form of a compound which catalyzes the radical decomposition of the oxidizing agent. If the precious metal-31

187,438 catalysts are employed and are conveniently added to the reaction in the form of supported metal. Examples of supported noble metal catalysts include platinum and palladium on activated carbon, alumina, barium sulfate. Other metals are conveniently added in the form of their compounds. The metal compounds are e.g. oxides (such as iron oxide, molybdenum oxide, silver oxide, lead oxide, etc.), salts (such as iron sulfate, tin chloride, manganese chloride, etc.) or compounds containing the metal in the form of anions ( such as ammonium molybdate, etc.). Particularly preferred catalysts have been found to be higher oxidation compounds of molybdenum, vanadium and chromium, especially molybdates.

The reaction may also be catalyzed by irradiation with ultraviolet light. Particularly advantageous is the ultraviolet light in the wavelength range of 250-300 nm. Alternatively, in addition to the catalysts listed above, the reaction mixture is irradiated with ultraviolet light.

Both homogeneous (i.e. soluble in the reaction medium) and heterogeneous (i.e. insoluble in the reaction medium) catalysts can be used in the process of the invention. The lower limit of the amount of catalyst required varies depending on the nature of the metal or metal compound used and its solubility in the reaction medium. Are high-activity catalysts (such as some molybdenum compounds) that are highly soluble in the reaction medium and sometimes contain N- (phosphonomethyl) iminodiacetic acid? 10 to 100 ppm relative to the catalyst also have good catalytic activity, whereas in other cases higher amounts of catalyst have to be used. In general, it is preferred that the amount of N-phosphonomethyliminodiacetic acid is at least about 10% by weight. 0.01-0.1% by weight of catalyst is added to the reaction mixture. The catalyst is usually used in an amount of 0.1 to 10% by weight, based on N-phosphonomethyliminodiacetic acid.

The upper limit of the amount of catalyst is not chemically decisive. Heterogeneous catalysts (such as iron oxide or supported noble metal catalysts) based on the amount of N- (phosphonomethyl) iminodiacetic acid

It can also be used in amounts of 10-30%. Heterogeneous catalysts can be readily separated from the reaction mixture by filtration and reused in the reaction. The economical aspect of increasing the amount of catalyst is limited by the fact that the specific amount of the peroxide compound usually increases with increasing the amount of catalyst.

The final reaction mixture obtained in the process of the invention is worked up in a manner known per se. For example, after neutralization, N- (phosphonomethyl) glycine can be isolated from the reaction mixture by neutralization with known precipitating agents (preferably alcohol). The N-phosphonomethylglycine is then usually precipitated in admixture with inorganic salts. These inorganic salts generally do not interfere with agricultural use, and in some cases, for example when using ammonium hydroxide as the base and nitric acid as the acid, the formed salt (ammonium nitrate) is a valuable agricultural material for use by the crop to be protected. fertilizer). However, if desired, the accompanying salts are simply removed from the product by known means (e.g., washing with water). It is not necessary to isolate N-phosphonomethylglycine from its reaction mixture because, if the composition of the resulting solution is in accordance with the applicable agricultural and environmental standards, the solution can be directly applied to the crop plants or used in agricultural preparations (e.g. for making sprays, etc.).

The main advantages of the process of the invention are summarized below:

(a) the difficulties relating to the corrosivity of the reaction mixture can be eliminated;

b) 5- to 6-fold increase in N- (phosphonomethyl) iminodiacetic acid concentration in the reaction mixture in pure aqueous solution or in the presence of an acid additive, resulting in an equivalent increase in capacity;

c) reduction of reaction time by 5-6 compared to processes using pure aqueous solution or suspension.

The invention is further illustrated by the following non-limiting Examples.

Example 7

A mixture of 20.0 g of N- (phosphonomethyl) iminodiacetic acid (0.09 mol), 70 ml of water and 15.4 ml (0.18 mol) of isopropylamine was stirred until clear, and the mixture was stirred at 100 ° C. and 30 ml of water, 4.7 ml (0.18 mol) of concentrated sulfuric acid and 0.03 g of Na ₂ MoO ₄ · 2H ₂ O (sodium molybdate) were added. The reaction mixture was then stirred at 100 ° C while 18.5 ml of 30% hydrogen peroxide solution was added dropwise over 1 hour. After 1 hour, 0.3 g of the remaining N-phosphonomethylglycine in the reaction mixture was detected by complexometry with 0.3 g of residual N-phosphonomethyliminodiacetic acid.

The reaction mixture was poured into three volumes of 96% ethanol. After cooling, the precipitate was filtered off and dried. 9.22 g of crystalline material were obtained with an N-phosphonomethylglycine content of 86.4% (thus 7.97 g of N-phosphonomethylglycine, corresponding to a yield of 53.5%). The impurity was mainly isopropylamine sulfate.

187,438

Example 2

In the same manner as in Example 1, 247 ml (0.18 mol) of 25% aqueous ammonium hydroxide was used instead of isopropylamine and 12.1 ml (0.18 mol) of 65% nitric acid were used instead of sulfuric acid. up. N- (phosphonomethyl) iminodiacetic acid was not detected in the reaction mixture; 10.5 g (76.6%) of N-phosphonomethylglycine are formed.

Example 3

In the same manner as in Example 1, 14.2 ml (0.18 mol) of pyridine ^{1 were} used instead of isopropylamine. The reaction mixture contained 0.4 g of unreacted N-phosphonomethyliminodiacetic acid and 9.6 g (64.8%) of N-phosphonomethylglycine.

Example 4

A mixture of 2.4 g (0.01 mol) of N-phosphonomethyliminodiacetic acid, 50 ml of water and 2.4 ml (0.028 mol) of isopropylamine was boiled and then 2 ml of 30% hydrogen peroxide solution was added. the reaction mixture in the quartz vessel was placed over a quartz lamp. The warming effect of the quartz lamp kept the reaction mixture boiling. 1 mL of 30% hydrogen peroxide solution was added every hour. After 3 hours, 0.7 g of N- (phosphonomethyl) glycine (41% of theory) was detected in the reaction mixture with 0.6 g of unreacted N- (phosphonomethyl) iminodiacetic acid.

Example 5

A mixture of N-phosphonomethyliminodiacetic acid (2.27 g, 0.01 mol), isopropylamine (1.7 ml, 0.02 mol) and water (10 ml) was heated and 2N aqueous sulfuric acid solution (9 ml) was added. 0.009 moles) was added to the hot mixture and 5 ml of a 30% hydrogen peroxide solution was added and the reaction mixture was irradiated with a medical quartz lamp at a wavelength of 230-300 nm for 20 minutes. The reaction mixture was then sampled and analyzed. The reaction mixture was found to contain 1.4 g (83%) of N-phosphonomethylglycine in 0.1 g of N-phosphonomethyliminodiacetic acid.

The reaction mixture was poured into three volumes of heated 96% ethanol. After cooling, filtration and drying, 0.977 g of crystalline product was obtained with an N-phosphonomethylglycine content of 84.0%. Thus, 6.821 g (48.6% of starting material) of N-phosphonomethylglycine were obtained.

Claims (3)

A process for the preparation of N-phosphonomethylglycine from N-phosphonomethyliminodiacetic acid. oxidation, characterized in that the N-phosphonomethyliminodiacetic acid is dissolved in water containing at least one molar equivalent of an organic or inorganic base and to a pH of 1 to 3 by addition of up to 2, preferably 1 to 1.5 equivalents of acid per alkali present. prepared in the presence of sodium molybdate or by irradiation with 230 to 300 nm ultraviolet light, per mol of N-phosphonomethyl iminodiacetic acid, in the presence of 2 to 2.5 molar equivalents preferably treated with hydrogen peroxide at 50-120 ° C, preferably 90-100 ° C, and optionally isolating the N-phosphonomethylglycine formed in a known manner. 2. A process according to claim 1 wherein the base is ammonium hydroxide, isopropylamine or pyridine. Process according to claim 1 or 2, characterized in that the acid used is an acid of pK 2 or higher, preferably sulfuric acid or nitric acid.