GB1563569A

GB1563569A - Process for the production of salts of ethylene diamine tetra-acetato-iron (iii) acid

Info

Publication number: GB1563569A
Application number: GB33724/77A
Authority: GB
Original assignee: Degussa GmbH; Deutsche Gold und Silber Scheideanstalt
Current assignee: Evonik Operations GmbH
Priority date: 1976-08-26
Filing date: 1977-08-11
Publication date: 1980-03-26
Also published as: DE2638423A1; DE2638423C2

Description

(54) A PROCESS FOR THE PRODUCTION OF SALTS OF ETHYLENE DIAMINE TETRA-ACETATO-lRON (Ill) ACID (71) We, DEUTSCHE GOLD-UND SILBER-SCHEIDEANSTALT VORMALS ROESSLER a body corporate organised under the laws of Germany of 9 Weissfrauenstrasse, 6 Frankfurt Main 1, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a process for the production of salts of ethylene diamine tetraacetato-iron (III) acid. Salts such as these are used for example in photography or as plant nutrients for plant-physiological investigations.

It is known that the ammonium salt of ethylene diamine tetra-acetato-iron (III) acid can be produced by reacting ethylene diamine tetra-acetic acid in aqueous solution with iron (III) hydroxide and neutralising the resulting ethylene diamine tetra-acetato-iron (III) acid with ammonia (CA 69 (1968) 105822x). One disadvantage of this process is that it is difficult to obtain the salt in high yields in the form of a compound having a uniform stoichiometric composition.

It is also known that the sodium salt of ethylene diamine tetra-acetato-iron (III) acid can be produced by reacting iron (III) chloride with the sodium salt of ethylene diamine tetra-acetic acid in aqueous medium (CA 82 (1975), 155367s). The salt is obtained in an unsatisfactory yield. Salts, such as for example the ammonium salt, which are considerably more soluble in water than the sodium salt cannot be obtained by this process or at least not in pure form.

Aqueous solutions of the alkali metal salts and the ammonium salt of ethylene diamine tetra-acetato-iron (III) acid are obtained by reacting aqueous ethylene diamine tetraacetic acid with iron (II) chloride and alkali metal or ammonium salts, followed by oxidation with air (CA 74 (1971), 108338h). This reference only describes the preparation of solutions of these salts and does not mention the preparation of the solid salts. In fact, the salts can only be precipitated from these solutions in poor yields and in moderate purity, since it is not possible to completely separate the ethylene diamine tetra-acetato-iron (III) salts from the other salts present in the solutions.

Finally, it is known that the alkali metal salts, the ammonium salt and the ethylene diamine salt of ethylene diamine tetraacetato-iron (III) acid can be produced by neutralising aqueous ethylene diamine tetraacetic acid with the corresponding base, treating the mixture with iron powder and subjecting it to oxidation with air (CA 82 (1975), 124776v). The disadvantage of this process is that is is expensive and difficult to handle.

The present invention provides a process for the production of a salt of ethylene diamine tetra-acetato-iron (III) acid which comprises neutralising and oxidising ethylene diamine tetra-acetato-iron (II) acid in the presence of water. This process may be generally used for the production of salts of ethylene diamine tetra-acetato-iron (III) acid. The salts are obtained in a solid form high yields and excellent purity.

The ethylene diamine tetra-acetato-iron (11) acid can be obtained by adding equivalent quantities of an iron (II) salt, such as for example iron aI) sulphate, chloride or nitrate, to an aqueous solution of ethylene diamine tetra-acetic acid or of salts of this acid. If an acidic (secondary) salt of the ethylene diamine tetra-acid is present, then it can be reacted directly with the iron (11) salt. If the ethylene diamine tetra-acetic acid is used as such, equivalent quantities of a base (2 mol in the case where a monovalent base is used), pre ferably ammonia or an alkali metal hydroxide, for example sodium hydroxide, should also be added.In cases where a neutral salt of ethylene diamine tetra-acetic acid is used as starting material, however, equivalent quantities of an acid (2 mol in the case of monobasic acid), for example sulphuric acid or hydrochloric acid should also be added. The alkali metal salt, particularly the sodium salts, the disodium salt or the tetrasodium salt, are considered to be particularly suitable salts of ethylene tetra-acetic acid. The reaction of the disodium salt may be carried out, for example, by the process described in DL-PS No. 15205. The ethylene diamine tetra-acetato-iron (II) acid is if necessary purified by recrystallisation from water.

To produce the salts of ethylene diamine tetra-acetato-iron (III) acid, the ethylene diamine tetra-acetato-iron (II) acid is neutralised with the corresponding bases in the presence of water. The salts of the ethylene diamine tetra-acetato-iron (II) acid initially obtained after neutralisation are converted into the salts of ethylene diamine tetraacetato-iron (III) acid by oxidation with oxygen or air, or preferably, with hydrogen peroxide in the presence of water. Although this sequence, i.e. neutralisation followed by oxidation, is preferred, it may also be reversed, i.e. oxidation may be followed by neutralisation, or oxidation and neutralisation may be carried out at the same time.

Both oxidation and neutralisation are best carried out at temperatures of from 5 to 800C and more particularly at temperatures of from 20 to 400C.

In general, it is of advantage to combine substantially equivalent quantities, better still exactly equivalent quantities, of the ethylene diamine tetra-acetato-iron (11) acid and the base for neutralisation. In some cases, however, it can be of advantage where weak bases are employed to use the base in excess. For example when ammonia is used as the base, it is best to use at least about 2 equivalents of ammonia per equivalent of ethylene diamine tetra-acetato-iron (II) acid so that a pH-value of from 7 to 9 and, more particularly, from 7.4 to 8.0 is obtained in the mixture.

For oxidation, oxygen or air is introduced or hydrogen peroxide is added. It is best to use at least substantially equivalent quantities of hydrogen peroxide. Although the hydrogen peroxide may be present in virtually any excess, it is generally advisable to use no more than about 4 equivalents of hydrogen peroxide and, more particularly, about 2 equivalents of hydrogen peroxide. The hydrogen peroxide may be used in the form of aqueous solutions of any concentration. It is preferred to use an at least 30% aqueous solution.

The salt of the ethylene diamine tetraacetato-iron (III) acid is obtained from the reaction mixtures accumulating by the usual methods, for example by cooling the solution, concentration by evaporation, optionally under reduced pressure, or spray drying. Where pure starting substances are used, it is directly obtained in excellent purity. In some cases, it is best to carry out the reaction at the highest possible temperatures and to select the concentration in such a way that a solution saturated at those temperatures is present from which the salt crystallises out on cooling.

The process according to the invention is suitable for the production of any salts of ethylene diamine tetra-acetato-iron (III) acid.

It is used with particular advantage for the production of the salts readily soluble in water, for example the ammonium salt.

EXAMPLES 1. Production of ethylene diamine tetraacetato-iron (II) acid a) 50 ml of concentrated hydrochloric acid (6.5 moles) were added to 192 ml of a 38% aqueous solution (0.25 mole) of the tetrasodium salt of ethylene diamine tetraacetic acid, followed by heating to 40 C. A solution preheated to the same temperature of 42.5 g (0.25 mole) of iron (II) chloride dihydrate in 75 ml of water was then added.

The mixture was kept for 2 hours at 600C and then cooled to 1 50C. The ethylene diamine tetra-acetato-iron (II) acid deposited in the form of the tetrahydrate was filtered off. The yield amounted to 62 g. corresponding to 60% based on the tetrasodium salt of ethylene diamine tetra-acetic acid used.

b) 146 g (0.5 mole) of ethylene diamine tetra-acetic acid were dissolved at 400C in 200 ml of water. 20 g (0.5 mole) of sodium hydroxide and 82 g (0.5 mole) of iron (II) chloride dihydrate were successively added to the solution at 400 C. The mixture was cooled to 150 C. The yield of ethylene diamine tetraacetato-iron (II) acid tetrahydrate amounted to 155 g, corresponding to 74 %, based on the ethylene diamine tetra-acetic acid used.

c) 130 ml of water, 73 g (0.25 mole) of ethylene diamine tetra-acetic acid and, finally, 82 g (0.5 mole) of iron (II) chloride dihydrate were added at 40 C to 230 ml of a 38% solution (0.3 mole) of the tetrasodium salt of ethylene diamine tetra-acetic acid.

The mixture was kept for 5 hours at 400 C and then cooled. The ethylene diamine tetra-acetato-iron (II) acid deposited in the form of its tetrahydrate was filtered off. The yield amounted to 154 g. 36 g of the ethylene diamine tetra-acetic acid used were recovered by acidifying the filtrate to pH 1.3 with 30 ml of concentrated hydrochloric acid. The yield of ethylene diamine tetra-acetato-iron (II) acid, based on the sum of reacted ethylene diamine tetra-acetic acid and its sodium salt, amounted to 86%.

2 Production of the salts of ethylene diamine tetra-acetato-iron (III) acid a) 209 g (0.5 mole of ethylene diamine tetra-acetato-iron (II) acid tetrahydrate were dissolved in a mixture of 94 ml of a 25% ammonia solution (1.4 mole) and 33 ml of water. 50% of a 30% aqueous hydrogen peroxide solution (0.5 mole) were added dropwise to this solution, which had a pH-value of 7.5, while cooling at 200 C. The mixture was concentrated by evaporation under reduced pressure. The yield of the ammonium salt of ethylene diamine tetra-acetato-iron (III) acid amounted to 180 g, corresponding to 99.9%, based on the ethylene diamine tetraacetato-iron (II) acid used.

b) 209 g (0.5 mole) of ethylene diamine tetra-acetato-iron (II) acid tetrahydrate were dissolved in a solution of 28 g (0.5 mole) of potassium hydroxide in 100 ml of water. 50 ml of a 30% aqueous hydrogen peroxide solution (0.5 mole) were then added at 200 C.

191 g of potassium salt of ethylene diamine tetra-acetato-iron (III) acid were obtained from the mixture bv snrav divine. corresponding to a yield of 99.8%, based on the ethylene diamine tetra-acetato-iron (II) acid used.

c) 12 g (0.5 mole) of lithium hydroxide and 209 g (0.5 mole) of ethylene diamine tetraacetato-iron (II) acid tetrahydrate were dissolved in 100 ml of water. 50 ml of a 30% aqueous hydrogen peroxide solution (0.5 mole) were added at 200. 175 g of the lithium salt of ethylene diamine tetra-acetato-iron (III) acid were obtained from the mixture by concentration by evaporation under reduced pressure, corresponding to a yield of 99.7%, based on the ethylene diamine tetra-acetatoiron (II) acid used.

WHAT WE CLAIM IS: 1. A process for the production of a salt of ethylene diamine tetra-acetatoiron (II) acid, which comprises neutralising and oxidising ethylene diamine tetraacetato-iron (II) acid in the presence of water.

2. A process as claimed in Claim 1, wherein oxidation is carried out with hydrogen peroxide.

3. A process for the production of a salt of ethylene diamine tetra-acetato-iron (III) acid substantially as described with particular reference to Example 2.

4. A salt of ethylene diamine tetraacetato-iron (III) acid when produced by a process as claimed in any of Claims 1 to 3.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

2 Production of the salts of ethylene diamine tetra-acetato-iron (III) acid a) 209 g (0.5 mole of ethylene diamine tetra-acetato-iron (II) acid tetrahydrate were dissolved in a mixture of 94 ml of a 25% ammonia solution (1.4 mole) and 33 ml of water. 50% of a 30% aqueous hydrogen peroxide solution (0.5 mole) were added dropwise to this solution, which had a pH-value of 7.5, while cooling at 200 C. The mixture was concentrated by evaporation under reduced pressure. The yield of the ammonium salt of ethylene diamine tetra-acetato-iron (III) acid amounted to 180 g, corresponding to 99.9%, based on the ethylene diamine tetraacetato-iron (II) acid used.

b) 209 g (0.5 mole) of ethylene diamine tetra-acetato-iron (II) acid tetrahydrate were dissolved in a solution of 28 g (0.5 mole) of potassium hydroxide in 100 ml of water. 50 ml of a 30% aqueous hydrogen peroxide solution (0.5 mole) were then added at 200 C.

191 g of potassium salt of ethylene diamine tetra-acetato-iron (III) acid were obtained from the mixture bv snrav divine. corresponding to a yield of 99.8%, based on the ethylene diamine tetra-acetato-iron (II) acid used.

c) 12 g (0.5 mole) of lithium hydroxide and 209 g (0.5 mole) of ethylene diamine tetraacetato-iron (II) acid tetrahydrate were dissolved in 100 ml of water. 50 ml of a 30% aqueous hydrogen peroxide solution (0.5 mole) were added at 200. 175 g of the lithium salt of ethylene diamine tetra-acetato-iron (III) acid were obtained from the mixture by concentration by evaporation under reduced pressure, corresponding to a yield of 99.7%, based on the ethylene diamine tetra-acetatoiron (II) acid used.

WHAT WE CLAIM IS: 1. A process for the production of a salt of ethylene diamine tetra-acetatoiron (II) acid, which comprises neutralising and oxidising ethylene diamine tetraacetato-iron (II) acid in the presence of water.
2. A process as claimed in Claim 1, wherein oxidation is carried out with hydrogen peroxide.
3. A process for the production of a salt of ethylene diamine tetra-acetato-iron (III) acid substantially as described with particular reference to Example 2.
4. A salt of ethylene diamine tetraacetato-iron (III) acid when produced by a process as claimed in any of Claims 1 to 3.