JPS593927B2 - Method for producing alkali monofluorophosphate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing alkali metal hydrogen monofluorophosphate (7), more specifically, an alkali metal hydrogen monofluorophosphate obtained by reacting an alkali metal metaphosphate with hydrogen fluoride gas. The present invention relates to a method for producing alkali monofluorophosphate through alkali neutralization treatment.

Conventionally, alkali monofluorophosphate [general formula M2
POa F (M = N a , or K), hereinafter MF
(1) monofluorophosphoric acid (H) produced from anhydrous hydrofluoric acid and phosphorus pentoxide;
2P03F) with an alkali metal salt (Ind
-Eng -Chem-vol 43.246-2
48 (1951)), or (2) a method of manufacturing by melting a metaphosphate and an alkali fluoride, or MH which provides a metaphosphate at the corresponding temperature instead of a metaphosphate.
There is a method using 2PO or M2H2P20□ (US Pat. No. 2,481,807).

However, method (1) uses highly toxic and highly corrosive raw materials, which must be handled with extreme caution, and there is also a constant risk that the equipment will be rapidly damaged by corrosion due to these raw materials. This requires considerable skill and appropriate equipment, resulting in high costs.

Method (2) requires heating at 650 to 700°C, and furthermore, the resulting molten material is corrosive and corrodes the reaction vessel, which inevitably impures the product and inevitably reduces purity. There was a problem.

As a result of various studies in order to eliminate the drawbacks of these conventional methods, the present inventors have developed an alkali metal salt solution using an alkali metal hydromonofluorophosphate (MHP03F) obtained by treating an alkali metal metaphosphate (MP03) with hydrogen fluoride. The present invention was achieved by discovering that MFP (M2P03F) can be easily produced by neutralizing with .

That is, the basic reaction in the present invention is as shown in the following formula.

The first stage fluorination treatment is performed at a temperature range of room temperature to 150°C.
This is carried out by adding and mixing an equivalent molar amount or more of hydrogen fluoride gas to an alkali metal metaphosphate, and the alkali metal metaphosphate used is in the form of powder, particles, or the like.

As an example of this fluorination, fluorination is performed when 0.5 mol of sodium metaphosphate with a particle size of 100 μ is mixed at room temperature (○) and 150°C (Δ) and treated at a hydrogen fluoride gas flow rate of 0.02 mol/min. The relationship between time and the amount of reaction product (alkali metal hydrogen monofluorophosphate) was clarified by the peak height in the specific diffraction line by X-ray analysis, and the results are shown in the attached drawings.

As is clear from this figure, in the fluorination reaction, even if hydrogen fluoride gas is supplied in excess, it does not have much effect on the product, and it is within the range of 1 to 1.2 times the stoichiometric amount (25 to 30 minutes). is preferred.

Furthermore, the amount of alkali metal hydrogen monofluorophosphate produced does not change whether the temperature is room temperature or 150°C, so room temperature is sufficient. On the other hand, when fluorinated at 300°C, the product remains as N a Po 3 and is not fluorinated. It was acknowledged that it was difficult.

The alkali metal hydrogen monofluorophosphate obtained in this way is converted into the formula 0 to form alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkali metal carbonates such as sodium carbonate and potassium carbonate, and hydrogen carbonate. Neutralize with alkali metal salts such as alkali metal bicarbonates such as sodium and potassium bicarbonate.

In the neutralization treatment, the alkali metal salt solution is placed in a Teflon externally cooled reaction tank, an equivalent amount of MHP03F is added while stirring, and the reaction is carried out for 30 minutes.

At this time, the temperature rises due to the heat of neutralization and the fluorophosphate becomes easily decomposed, so it is preferable to cool it and maintain the temperature at 0 to 20°C, and the reaction proceeds easily like a normal neutralization reaction.

After the reaction, it is separated by suction filtration and then dried, but the drying temperature at this time becomes high enough that a part of the alkali monofluorophosphate decomposes (2M2 P03F + H2
02M4P207 12HF), its temperature is 1
00°C or less is desirable.

As described above, the fluorination and neutralization in the present invention proceed sufficiently at room temperature and normal pressure, and the present invention allows for the easy production of alkali monofluorophosphate under mild conditions using a simple device and method. It can be said that the effect is greater than that of the

The present invention will be described in detail below with reference to Examples.

Example 1 1.0 mol of powdered sodium metaphosphate was placed in a 500 cc Teflon stirred tank reactor, and hydrogen fluoride gas was fed at a flow rate of 0.02 mol/min for 1 hour while mixing at room temperature. Then, 1.0 mol of the obtained sodium hydrogen monofluorophosphate was neutralized with 1 mol of 30% sodium hydroxide solution while maintaining the temperature at 0 to 20°C, and after separation by filtration, it was dried at 100°C.

As a result, the yield of the obtained product was approximately 95 g, and the following analytical values were shown.

The pH value was measured after dissolving 2 g of the sample in 100 g of pure water.

Na2P03F 84.05wt%N
aF 5.0 Weight % Heavy metals 5 ppm or less Other phosphates Balance pH 6.5 Example 2 1.6 mol of powdered sodium metaphosphate was placed in a 500 CC Teflon stirred tank reactor and mixed at 150°C. 1.5 hydrogen fluoride gas at a flow rate of 0.02 mol/min
After feeding for an hour, 1.6 mol of the obtained sodium hydrogen monofluorophosphate was neutralized with 1.6 mol of 30% by weight sodium hydroxide solution while keeping the temperature between O and 20°C, and after filtration and separation, it was heated at 100°C. Dry.

As a result, the yield of the obtained product was approximately 96 g, and the following analytical values were shown.

Na2P03F 83.21% by weight
Heavy metals 4.5 Weight% heavy metals
5 ppm or less Other phosphates Balance pH 6,7 Example 3 Powdered KPo, 1.0 mol was placed in a 5 oocc Teflon stirred tank reactor, mixed at room temperature, and then HF gas was added at approximately 0.02 mol. Fluorination was carried out by feeding for 1 hour at a flow rate of mol/min.

Thereafter, 1.0 mol of the obtained KHPO3F was added to 35% by weight.
The mixture was neutralized with a 1.0 mol KOH solution while maintaining the temperature at 0 to 20°C, and after separation, it was dried at 100°C.

As a result, the yield of the product was approximately 80 g, and the following analytical values were shown.

K2P03F 85.14% by weight KF
4.8 Weight% heavy metals
Other phosphates below sppm
Remaining pH 7.1 1 Implementation 4 1.0 mol of powdered KPO was placed in a 500ee Teflon stirred tank reactor and mixed at 150°C, then HF gas was fed at a flow rate of about 0.02 mol/min for 1 hour. and fluorinated it.

Thereafter, 1.0 mol of the obtained KHPO3F was added to 35% by weight.
The mixture was neutralized with a 1.0 mol KOH solution while maintaining the temperature at 0 to 20°C, and after separation, it was dried at 100°C.

As a result, the yield of the product was approximately 829, and the following analytical values were shown.

K2P03F 82.37%K by weight
F 4.5 Weight% Heavy metals 5 ppm or less Other phosphoric acid Part balance pH 7.1

[Brief explanation of the drawing]

The attached drawings show the amount of HF in the present invention. It is a graph showing the relationship with the amount of NaHPO3F produced.

Claims (1)

[Claims] 1. Treating an alkali metal metaphosphate with hydrogen fluoride gas to produce an alkali metal hydrogen monofluorophosphate, which is then neutralized with an alkali metal hydroxide or an alkali metal salt solution,
Method for producing alkali metal monofluorophosphate.