DD300899A7 - PROCESS FOR THE PREPARATION OF PURE ALKALIMONOFLUOROMONOPHOSPHATES - Google Patents

Abstract

The subject of the invention is a preparation process of pure alkali monofluoromonophosphates M 2 PO 3 F, which can be used as fluoridation, corrosion protection and wood preservatives. According to the invention, a phosphorus compound in the form of a P (V) compound (eg alkali phosphates, phosphoric acid, phosphorus (V) oxide) and an alkali or ammonium fluoride or hydrogen fluoride or hydrofluoric acid, and optionally an alkali compound whose anion is volatile on heating ( eg alkali hydroxide, caustic, alkali carbonate) at 180 to 500 degrees C and in an atomic ratio of M: P: F = 2: 1: 1 to 1.1 to M # F2 #? PO # F3 #? F, where M Is K, Rb or Cs, and wherein the starting compounds contain at least 1 mole H ind 2 O per mole of final product M 2 PO ind 3 F or an appropriate amount of water is added.

Description

Field of application of the invention

The invention relates to a preparation process of pure Alkalimonofluoromonophosphaten which are suitable as fluoridation, corrosion protection and wood preservatives.

-2- 300 Known technical solutions

For the preparation of Alkalimonofluorophosphaten a number of methods have already become known. Many patents are based on that described by HILL and AUDRIETH (J.Physic.Colloid Chem., 54, 609 [195O]) Melting process, wherein the anhydrous cyclotriphosphate and / or high molecular weight polyphosphate with fluoride at about 800 ⁰ C.

be implemented. This process necessarily requires expensive anhydrous phosphates as starting materials and, caused by the elimination of Phosphoroxidtrifluorid during the melt reaction, results in impure, varying amounts

Diphosphate containing products. Another disadvantage arises from the occurring corrosive melt, the one

makes appropriate equipment required, including the use of suitable materials for the reactors.

From DD-A-2333808 it is known Huorophosphate containing from ΡΟΗ groups phosphates or their acids or

their ammonium salts in the presence of ureas by reaction with fluorides, hydrogons or

Hydrofluoric acid produce. A disadvantage of this process is the use of ureas.

l ^i; 3 DE-C-3043895 describes a process in which hydrogen fluoride gas is reacted in an amount of 100 to 150% of the theoretical amount required with a / .Ikaliphosphat. Apart from the use of highly corrosive HF gas, which makes special equipment necessary, there is another economic disadvantage. It consists in that only a part of the HF gas used can react in the reaction taking place of solid / gas.

According to DE-AS1724280, the reaction of phosphoric acids, phosphates and / or phosphoric acid adducts takes place with Hydrofluoric acid or fluorides, wherein due to the atomic ratio applied metal: phosphorus: fluorine, in particular the

large Fluorübr.rschusses, and the further reaction conditions always undesirable by-products arise.

SU-A-1018F / 05 describes a process for the preparation of sodium monofluorophosphate from anhydrous Na ₂ HPO ₄ and NH ₄ HF ₂ at 6OJ to 800 ° C, wherein the ratio Na: P: F = 2: 1: 1.5 to 2.5. The high excess of fluoride and the high Temperatures are very unfavorable economic factors in this process. Finally, a process is known from SU-A-512171, in which the starting materials are phosphorus compounds and Alkalimineralsalzverbindungen dried in a first stage at 100 ⁰ C to the alkali metal hydrogen phosphate and in a second Stage be reacted at 250 to 310 ° C after admixing with a fluorine compound. The disadvantages of this method

insist ') that it must be carried out anhydrous and two-stage.

Aim of an invention

It ^! St goal of the invention to improve the process economy over the known methods, especially at low temperature to obtain pure products with high yield.

Essence of the invention The invention is based on the object, a process for the preparation of pure Alkalimonofluoromonophosphaten

provide.

There was a new process for the preparation of pure Alkalimonofluoromonophosphaten M ₂ POaF from phosphorus, alkali and Fluorine compounds found. This method is characterized in that

a) a phosphorus compound in the form of a P (V) compound, including alkali metal phosphates, and

b) an alkali or ammonium fluoride or alkali or Ammoniumhydro.genfluorid or hydrofluoric acid and optionally

c) an alkali compound whose anion is volatile when heated,

at 180 to 500 ^° C and in an atomic ratio of M: P: F = 2: 1: 1 to 1.1 to M ₂ PO ₃ F, where M = K, Rb or Cs, andwherein the starting compounds are at least 1 mole H ₂ O per mole of end product M ₂ PO ₃ F contain or a corresponding

Amount of water is added. Pure Alkalimonofluoromonophosphate be obtained according to the invention, if the starting compounds in a Temperature of 180 to 500 ⁰ C converts. It is essential to the invention that the starting compounds at least 1 mole of H ₂ O per mole of end product M ₂ PO ₃ F, preferably

contain at least 2 moles of H ₂ O, in particular at least 3 moles of H ₂ O per mole of M ₂ PO ₃ F or an appropriate amount of water is added.

The novel process is further characterized in that the starting compounds have at most 100 moles of H ₂ O,

preferably at most 25 moles of H ₂ O, in particular at most 15 moles of H ₂ O per mole of M ₂ PO ₃ F.

The use of a starting compound of group c) is omitted if the Ausgan.gsverbindung (s) of groups a) and b) so

it can be chosen to give an atomic ratio of M: P: F = 2: 1: 1 to 1.1.

It is particularly advantageous if the phosphorus (V) compound is present under one or more compounds of the group

selected from phosphoric acid, phosphorus (V) oxide, alkali metal or Ammoniumaihydrogenphosphat, dialkali or

Diammoniumhydrogenphosphat consists, preferably of phosphoric acid, Alkalidiiiydrogenphosphat, Dinlkalihydrogenphosphat. Furthermore, it is particularly advantageous if the alkali metal compound is one or more compounds of the group

is selected, which consists of alkali metal hydroxide, alkali metal hydroxide, alkali metal carbonate and Afkalihydrogeniarbonat, preferably below

Alkali lye, alkali carbonate. Finally, it is particularly advantageous if the starting compound of group b) under one or more compounds

of the group consisting of hydrofluoric acid, alkali and ammonium hydrogonic fluoride. According to the invention, a potassium monofluoromonophosphate is obtained by reacting

a) a phosphorus (V) compound of the group phosphoric acid, Dikaiiumhydrogenphosphat, potassium hydrogen phosphate and

b) eir e fluorine compound of the group hydrofluoric acid, potassium fluoride, Kaliumhydrogen.'luorid, ammonium hydrogen fluoride and optionally

c) a 3 potassium compound of the group potassium hydroxide, potassium mood, potassium carbonate

at 250 to 35O ⁰ C in an atomic ratio of K: P: F = 2: 1: 1 to 1.1, wherein the starting compounds contain at least 1 mole of H ₂ O per mole of end product K ₂ PO ₃ F or an appropriate amount of water is added. It is particularly advantageous to produce pure rubidium mono-fluoromonomonophosphate or pure cgsium monofluoromonophosphate by:

a) phosphoric acid

b) hydrofluoric acid and

c) rubidium or cesium carbonate

at 250 biu 350 ° C in an atomic ratio of Cs (or Rb): P: F = 2: 1: 1 to 1.1, wherein the alisgangsverbindungen at least 1 mol of H ₂ O per mole of end product Cs ₂ PO ₃ F or Rb ₂ PO ₃ F or an appropriate amount of water is added.

It is essential to the invention that the starting compounds at a temperature of 180 ° to 500 ⁰ C, preferably from 200 to

35O ⁰ C, in particular from 250 to 350 ⁰ C, to be implemented. At temperatures below 18O ⁰ C is hardly a fluorination of the

Starting phosphate to monofluorophosphate, at temperatures above 500 ° C, the Monofluorophospate formed

decomposed by elimination of volatile compounds, in particular Phosphoroxidtrif luorld, in particular

Diphosphates remain as impurities. It is erfindungswerentlich that the starting compounds at least 1 mole of H ₂ O per mole of end product M ₂ PO ₇ F, preferably

contain at least 2 moles of H ₂ O, in particular at least 3 moles of H ₂ O or an appropriate amount of water is added. The origin of the water contained in the starting materials is immaterial, whether it is as water of crystallization,

Constitutional water or solvent water, such as. B. in the presence of phosphoric acid !, lye and / or Hydrofluoric acid, introduced with the starting materials wii d. The role of water in the process of the invention

has not yet been clarified, but it has been found in a V'elzahl of experiments that only in the presence of said minimum amount of water pure monofluorophosphate is obtained. By "pure" it is meant that at least 98 mol% of the phosphorus used has been converted to monofluoromonophosphate and the final product does not contain fluorine in the form of fluoride.

The selection of the minimum amount is easy to recognize for the skilled person by using factors such as ? .. B. used Starting materials, reaction temperature, surface of the starting materials, geometry of the reaction vessel, Heating rate, dwell time, etc. taken into account. According to the invention, the amount of starting material contained in the starting materials is 100 mols H ₂ O, preferably at most 25 mols H ₂ O, in particular at most 15 moles of H ₂ O per mole of M ₂ PO ₃ F. The maximum amount of 100 moles is to be understood as meaning that

According to the invention more than 10OMoI H ₂ O per mole of M ₂ PO ₃ F can be used, but it is then so dilute starting solutions that worked because of the veramptm.den amount of water little energy-economically

For one skilled in the art, the starting atomic ratio of M: P = 2: 1 is plausible, as is one of P: F = 1: 1, although in the

Most known methods with an F: P> 1: 1 is worked. According to the invention in this new method in a

Atomic ratio of P: F = 1: 1 to 1.1 reacted. If a ratio of P: F = 1: 1 is used, then an end product with

already described ohon purity of 98 mol% monofluoromonophosphate, based on the viewed

Phosphorus, obtained. If an initial atomic ratio of P: F = 1: 1.1 is used, ie with 10% fluorine more than the theoretical one

worked the required amount, the end product, based on the phosphorus used, from virtually 100 mol%

Monofluoromonophosphat, and it contains no fluorine in the form of fluoride. The use of a starting compound of group c) is omitted -> .. B. when Dialkalihydrogenphosphat (group a) with Hydrofluoric acid (group b) in the molar ratio of 1: 1 is reacted or if Alkalidihydrogenphosphat, Dialkalihydrogenphosphat (both compounds group a) and alkali hydrogen difluoride (group b) in a molar ratio 1: 1: 1

implements.

The compounds of group c) are not based on the already mentioned alkali compounds -hydroxide, -lauge, -carbonate and

bicarbonate limited. According to the invention, other alkali compounds whose anions are volatile when heated under the conditions of this new process, such as. For example, nitrates or salts of short-chain organic acids,

For example, oxalates and acetates are used as starting materials. '

Among the compounds of group b), anhydrous hydrogen fluoride could also be listed as a suitable starting material

However, the use of this starting material for corrosion reasons is not advantageous.

The compounds of group a) are not on the already mentioned phosphorus (V) compounds phosphoric acid - it is

the same applies to the crystalline acid or the concentrated 85 to 87% ig acid or a dilute acid.

Phosphorus (V) oxide, alkali or ammonium dihydrogen phosphate, dialkali or Diammoniumhydrogenphosphat limited. According to the invention also white phosphorus (V) compounds can be used as starting materials, such as. B. Polyphosphates including hydrogen polyphosphates and polyphosphoric acids represented by the general empirical formula X (n + 2 ^ A _3n + D are characterized in which X is M and / or NH ₄ and / or H and in which η S 2, preferably Diphosphnt (n - 2) and Triphoshpat (n = 3). Exceptions are those high molecular weight polyphosphates, which in a Temperature to 500 ⁰ C under the conditions of this new process can not be reacted, such. B.

high molecular weight KUROL's potassium salt, but in contrast the water-soluble potassium polyphosphate described by KLEMENT and SCHMID (Z. allorg, Chern 290,113 [1957]).

Inventive gels may also be used as phosphorus (V) compounds, e.g. Including cyclophosphates Hydrogencyclcphosphate and cyclophosphoric acids are used, which are represented by the general empirical formula X _n P _n O _3n

in which X is M and / or NH ₄ and / or H and in which η is 3, preferably cyclotriphosphate (n = 3) and cycloietraphosphate (n = 4).

The invention will be further illustrated by the following examples, but is not limited to these. embodiments example 1

In a Platinumwanhe be 112, Og (1 mol) of phosphoric acid (P content = 27.65%, corresponding to an 87.48% acid) submitted first with 407.3g (2 mol) of potassium hydroxide (27.55% pure and then 114.55 g (1.10 mol) of hydrofluoric acid (19.22%) was added. (The starting atomic ratio of this approach is thus K: P, F = 2: 1: 1.10.) The batch is heated at 350 ° C until complete crystallization (duration about 1 hour) and then left for> 1 hour at this temperature ,

Yield: 176.7g. Analysis see Example 4.

Example 2

The procedure is as in Example 1 except that the amount of hydrofluoric acid used is 109.3 g (1.05 mol) and thus the starting atomic ratio K: P: F - 2: 1: 1.05.

Yield: 177.1 g. Analysis see Example 4.

Example 3

The procedure is as in Example 1, but the amount of hydrofluoric acid used is 104.1 g (I, OOmol!) And thus the starting atomic ratio K: P: F = 2: 1: 1.00

 Yield: 176.3g. Analysis see Example 4.

Example 4

The procedure is as in Example 1 except that the amount of hydrofluoric acid used is 93.7 g (0.90 mol) and thus the starting atomic ratio K: P: F = 2: 1: 0.90.

Yield: 175.9g.

Characterization of the products obtained according to Examples 1 to 4

All four products are completely soluble in water. The phosphor used for the reaction is completely contained in the products (potassium also). The distribution of the total phosphorus in the reaction products, determined by quantitative chromatographic analysis by the method of ROESSEL-Z. Analyt Chem. 196, 6 [1963]) results as follows, depending on the amount of fluorine used:

Product n.Bsp.

The phosphorus shift determined by ³¹ P NMR analysis conforms to the results of quantitative paper chromatography. The ^I9 F-NMR spectra of the four reaction products show that no fluoride F "is contained." From the guinea shots of the products prepared according to Examples 1 to 3, it is clear that pure crystalline di-potassium monol fluorophosphorus K ₂ PO ₃ F has been formed. Finally, this is also proved by the wet chemical analysis, the result of which is reproduced below for the product obtained according to Example 3: K ₂ PO ₃ F, Mm = 176.175, K: 44.80 (calculated 44.39), P: 17 , 56 (17.58); F: 10.70 (10.78)% K: P: F = 2.02: 1: 0.99.

Example 5

In a submitted K ₂ HPGvM mother liquor, for example one containing 174.2 g (1 mol) of K ₂ HPOh in 180 g of water, 112.0 g (1 mol) of phosphoric acid (P content = 27.65%), 227 , 2g (2 mol) of potassium hydroxide (49.4%) and 11?, 9g (2.20 mol) of hydrofluoric acid (39.0%). The batch is heated at 320 ° C until complete crystallization and then 1 Rtd. reheated at this temperature. Yield: 351.4 g of pure crystalline KjPO ₃ F, detected by the analytical methods listed above in Examples 1 to 4.

Output atomic ratio Phosphorus distribution (atomic%) as PO ₄ ³ " P: F BIsPO ₃ F ' 0 1: 1.10 100 1 1: 1.05 99 1.5 1: 1.00 98.5 11 1: 0.90 89

Claims (10)

1. A process for the preparation of pure Alkalimonofluoromonophosphaten M ₂ PO ₃ F from phosphorus, alkali and fluorine compounds, characterized in that a) a phosphorus compound in the form of a P (V) compound, including alkali metal phosphates, and b) an alkali or ammonium fluoride or hydrogen fluoride or hydrofluoric acid and optionally c) an alkali compound whose anion is volatile when heated, at 180 to 500 ^° C and in an atomic ratio of M: P: F = 2: 1: 1 to 1.1 to M ₂ PO ₃ F, where M = K, Rb, Cs, and wherein the starting compounds are at least 1 Mol H ₂ O per mole of end product M ₂ PO ₃ F contain or an appropriate amount of water is added. 2. The method according to claim 1, characterized in that at a temperature of 200 to 350 ⁰ C, preferably ^or i0 to 35O ⁰ C is reacted. 3. The method according to claim 1 and 2, characterized in that the starting compounds contain at least 2 moles of H ₂ O, preferably at least 3MoI H ₂ O per mole M ₂ PO ₃ F or an appropriate amount of water is added. 4. The method according to one or more of claims 1 to 3, characterized in that the starting compounds contain at most 100 moles of H ₂ O, preferably at most 25MoI H ₂ O, in particular at most 15MoI H ₂ O per mole of M ₂ PO ₃ F. Process according to claims 1 to 4, characterized in that the starting compound (s) of groups a) and b) are chosen so as to have an atomic ratio of M: P: F = 2: 1: 1 to 1.1. 6. The method according to one or more of claims 1 to 5, characterized in that the phosphorus (V) compound is selected from one or more compounds of the group consisting of phosphoric acid, phosphorus (V) oxide, alkali or ammonium dihydrogen phosphate, Dialkali- or Diammoniumhydrogenphosphat is, preferably phosphoric acid, Alkalidihydroyenphosphat, Dialkalihydrogenphosphat. 7. The method according to one or more of claims 1 to 6, characterized in that the alkali metal compounds is selected from one or more compounds of the group consisting of alkali metal hydroxide, alkali metal hydroxide, alkali metal carbonate and alkali metal bicarbonate, preferably alkali metal hydroxide, alkali metal carbonate. 8. The method according to one or more of claims 1 to 7, characterized in that the starting compound of group b) is selected from one or more compounds of Gruppo, which consists of hydrofluoric acid, alkali metal and ammonium hydrogen fluoride. 9. The method according to claim 1 to 5 for the preparation of pure potassium monofluoromonophosphate, characterized in that a) a ^'5 hosphor (V) compound of the group phosphoric acid, dipotassium hydrogen phosphate, and Kaliumdihydrogenphophat b) a fluorine compound of the group hydrofluoric acid, potassium fluoride, potassium hydrogen fluoride, ammonium hydrogen fluoride and optionally c) a potassium compound of the group potassium hydroxide, potassium hydroxide, potassium carbonate at 250-350 ⁰ C in an atomic ratio of K: P: F = 2: 1: 1 to 1.1, wherein the starting compounds at least 1 mole of H2O per mole of end product K ₂ PO ₃ F or an appropriate amount of water is added. 10. The method according to claim 1 to 5 for the preparation of pure rubidium or cesium monofluoromonophosphate, characterized in that a) phosphoric acid b) hydrofluoric acid and c) rubidium or cesium carbonate reacting 1 to 1.1, wherein the starting compounds is at least 1 mol of H ₂ O per mole of end product Cs ₂ PO: at 250-350 ⁰ C in a Atomverhä.'tnis of Cs (or Rb): P: F = 2: 1 ₃ F or Rb ₂ PO ₃ F contain or an appropriate amount of water is added.