JPS593926B2 - Method for producing alkali monofluorophosphate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an alkali monofluorophosphate, and more specifically, an alkali metal fluorophosphate salt produced by fluorination of an alkali metal phosphate is used as an intermediate product, and a melt reaction of the product is performed. This is a novel method for producing alkali monofluorophosphate.

Conventionally, alkali monofluorophosphate [general formula M2
PO,F (M=Na% or K), hereinafter referred to as MFP]
As a manufacturing method, a method of neutralizing monofluorophosphoric acid (H2P03F) produced from anhydrous hydrofluoric acid and phosphorus pentoxide with an alkali metal salt (Ind-Eng-Che
m-vol 43. -246-(1951)), by melting metaphosphate and alkali fluoride, or by using MH2PO4 or M2H2P207 instead of metaphosphate to give metaphosphate at the corresponding temperature (U.S. Pat. 2481807).

The present invention provides a new method for producing alkali monofluorophosphate, which is completely different from these conventional methods.
Fluorination is performed by reacting an alkali metal phosphate and hydrogen fluoride gas at room temperature or higher, and the resulting intermediate product is melt-reacted at a temperature of 625°C or higher. The feature of the invention is that after a fluorinated intermediate is produced by a gas-solid reaction, a melting reaction is carried out to complete the reaction.

The alkali metal phosphates used in the present invention include orthophosphates, condensed phosphates such as pyrophosphates, tripolyphosphates, and metaphosphates, and complexes of alkali metal phosphates and alkali fluorides. Any one or more kinds of salts may be used, and the alkali metal is Na.

K is used.

These alkali metal phosphate raw materials can be used in granular or powdered form, and powdered ones are particularly preferred.

In the fluorination reaction, various products are obtained depending on the amount of hydrogen fluoride reacted at each treatment temperature. For example, when sodium pyrophosphate, sodium tripolyphosphate, or sodium metaphosphate is treated with hydrogen fluoride, it is estimated from the X-ray diffraction results of the product. Then, the following reactions proceed.

Na4 P2O7 Room temperature 160°C During fluorination, it is preferable for operation to adjust the alkali metal:P atomic ratio of the alkali metal phosphate in advance to approximately 2:1, and this adjustment is performed using sodium carbonate, caustic soda, potassium carbonate This is done by adding caustic potassium, etc.

In the fluorination reaction, the reaction is insufficient when hydrogen fluoride gas is supplied in a chemical equivalent (F/P = 1.0 mol), so the reaction is usually 1.01 mol.
-1.7 mol, preferably 1.1-1.3 mol.

Sodium pyrophosphate (Na4P207) 0.5 mol (
Figure 1), 0.15 mol of sodium carbonate (Na2CO3) was added to 0.3 mol of sodium tripolyphosphate (Na5p3o10) to form Na:P.
One in which the atomic ratio was adjusted to 2:1 (Figure 2), and one in which 0.5 mole of sodium carbonate was added to 1.0 mole of sodium metaphosphate (NaPO3) to adjust the Na:P atomic ratio to 2:1. (Fig. 3) were placed in a 500m reactor equipped with a stirrer and fluorinated by flowing hydrogen fluoride gas (1.0 mol/hour) at room temperature (○ mark) and 160°C (△ mark). The relationship between the amount and the HF reaction rate is shown in Figures 1 to 3, and as is clear from the figures, it was observed that fluorination under stirring and mixing proceeded sufficiently at room temperature and that the HF reaction rate was high.

That is, in the first stage fluorination reaction, the reactions (1) to (10) are carried out depending on the reaction temperature and the phosphoric acid source, but in any case, the fluorination reaction proceeds sufficiently if the temperature is above room temperature.

However, with this fluorination alone, the target MFP cannot be manufactured.
Since the amount produced is low, it is then subjected to a melting reaction to produce the final product, MFP.

In the melt reaction, the intermediate product is used as is, or an alkali phosphate other than pyrophosphate is used as is.In the case of fluorinated intermediate products, the Na:P atomic ratio is changed by adding a sodium salt such as soda carbonate. Adjust to 2=1 and M
The melting reaction is carried out at a temperature not lower than the melting point of FP (625° C.) and not higher than 900° C. and in an atmosphere substantially free of hydrogen fluoride gas.

If the melting temperature is below 625°C, the reaction will be slow and complete melting will not occur, making it impossible to obtain a product with a uniform composition.
If the temperature exceeds 650°C, no corresponding effect can be expected and phosphoric acid will be released and corrosion of the equipment will rapidly progress, which is undesirable.
A range of 750°C is industrially suitable.

Figure 4 shows sodium pyrophosphate (Na4 P207)
0.5 mol was fluorinated at room temperature (1.3 mol of HF treated), 50 g was taken into a graphite container, and the temperature was raised at a rate of 5 in a nitrogen atmosphere.
This figure shows the relationship between the melting time and the amount of MFP produced when melting is performed in a furnace at 0°C/min and 700°C.

As is clear from this figure, as the content temperature rises, the amount of MFP produced increases linearly, reaching an almost equilibrium state 15 minutes after reaching approximately 700°C, and from then on, it remains unchanged even if the melting time is maintained. No corresponding change in production amount was observed.

It is desirable that the intermediate product after fluorination be in a dry state; the presence of a large amount of water is not preferable because it causes side reactions during the melting reaction and leads to the formation of sodium pyrophosphate and other sodium tripolyphosphates. .

However, even if some moisture is present, MFP can be produced by adding 4 or 5 moles of sodium fluoride and equimole of phosphoric acid to the detected sodium pyrophosphate or sodium tripolyphosphate as shown in the following formula.
It can be converted to .

In the present invention, as mentioned above, it is preferable that the ratio of phosphate and hydrogen fluoride gas that substantially react is a stoichiometric amount of P/)'=1.0, but due to the reactivity, phosphate or It is also possible to use an excess of either hydrogen fluoride; in this case, the atomic ratio of alkali metal/P/F is adjusted to 2:1:i using phosphoric acid, sodium fluoride, etc. during the subsequent molten salt reaction. By properly adjusting the molar ratio, MFP can be finally obtained.

As described above, the present invention relates to a novel method for manufacturing MFP that combines gas-solid reaction and molten salt reaction, and has the advantage that the final product composition can be left to the subsequent molten salt reaction, which has great industrial significance. It has the following.

The method of the present invention will be explained in detail with reference to Examples below.

Example 1 0.5 mol of sodium pyrophosphate was placed in a 500 ml Teflon reactor equipped with a stirrer, and while mixing at room temperature, hydrogen fluoride gas was introduced at a flow rate of 1.0 mol/hour to obtain an amount of approximately 1.3 mol. After being treated with hydrogen fluoride gas, put it in a graphite container and store it for 70 minutes.
It was heated and melted at 0°C.

As a result, the obtained product showed the following analytical values.

Example 2 0.5 mol of sodium pyrophosphate was placed in a similar Teflon reactor and mixed at 190°C, while hydrogen fluoride gas was fed at a flow rate of 1.0 mol/hour to give an amount of about 1.05 mol. After being treated with hydrogen fluoride gas, it was placed in a graphite container and heated and melted at 700°C.

As a result, the obtained product showed the following analytical values.

Example 3 0.5 mol of sodium tripolyphosphate and 0.25 mol of sodium carbonate were placed in a similar Teflon reactor at 180°C.
Hydrogen fluoride gas was fed in at a flow rate of 1.0 mol/hour while mixing at 1.5 mol/hour, and the mixture was treated with hydrogen fluoride gas in an amount of about 1.53 mol, then placed in a graphite container and heated and melted at 700°C.

As a result, the obtained product showed the following analytical values.

Example 4 Sodium fluoride phosphate hydrate (2Na
3PO4・NaF・19H20) 0.5 mol, 0.5 mol of phosphorus pentoxide, and 0.25 mol of sodium carbonate were placed in a similar Teflon reactor and mixed at 200°C while adding 1.0 mol of hydrogen fluoride gas. Injected at a flow rate of approximately 1.5
After being treated with 1 molar amount of hydrogen fluoride gas, it was placed in a graphite container and melted by heating at 700°C.

As a result, the obtained product showed the following analytical values.

Example 5 1.0 mol of Na2HPO was placed in a 500 cc similar Teflon reactor and mixed at room temperature, and then 1.0 mol of HF gas was added.
．． It was treated with hydrogen fluoride gas in an amount of about 1.4 moles by feeding at a flow rate of 0 mole/hour.

This was placed in a 200CC graphite container, heated and melted at 700°C, and then naturally cooled.

As a result, the obtained product showed the following analytical values.

Example 6 Na3PO20.25 mol, Na5P501Q
25 moles of O00 were placed in a similar reactor and mixed at room temperature, and then HF gas was introduced at a flow rate of 1.0 moles/hour to treat the reactor with hydrogen fluoride gas in an amount of about 1.3 moles.

This was placed in a 200CC graphite container, heated and melted at 700°C, and then naturally cooled.

As a result, the obtained product showed the following analytical values.

Example 7 1.0 mol of NaP0 and 0.5 mol of Na2CO3 were placed in a similar reactor and mixed at room temperature, and then 1.0 mol of HF gas was added.
It was treated with hydrogen fluoride gas in an amount of about 1.3 moles, fed at a flow rate of mol/hour.

This was placed in a 200CC graphite container, heated and melted at 700°C, and then naturally cooled.

As a result, the obtained product showed the following analytical values.

In Example 8, 1.0 mol of 2HPO4 was placed in a similar reactor and mixed at room temperature, then HF gas was introduced at a flow rate of 1.0 mol/hour and treated with hydrogen fluoride gas in an amount of about 1.4 mol. did.

This was placed in a 200CC graphite container, heated and melted at 700°C, and then naturally cooled.

As a result, the obtained product showed the following analytical values.

Example 9 1.0 mol of KP03 and 0.5 mol of K2CO3 were placed in a similar reactor and mixed at room temperature, and then HF gas was introduced at a flow rate of 1.0 mol/hour to form an amount of approximately 1.3 mol. Treated with hydrogen fluoride gas.

This was placed in a 200CC graphite container, heated and melted at 700°C, and then naturally cooled.

As a result, the obtained product showed the following analytical values.

In order to clarify the difference in action and effect between fluorination using HF solution or fluoride of NH, F and the use of HF gas as the fluorination agent of the present invention, the following experiment was conducted and the data and X-ray diffraction chart are attached. Use as material for determining significance.

Reference Example 1 (Using HF gas) 0.05 mol of sodium pyrophosphate (Na4P207) was placed in a boat, and 0.12 E/HF gas was supplied at 7 o'clock at 290° C. for 1 hour to carry out a reaction.

The analytical values of the obtained product were 92.8% by weight of Na2P03F and 5% by weight of NaFl.

Incidentally, the X-ray diffraction of the reaction product is shown in FIG.

Reference Example 2 A reaction was carried out in the same manner as in Experiment 1 using 0.05 mole of Na4P20□ and 0.12 mole of 47% hydrofluoric acid.

The analytical values of the obtained product were 78.04% by weight of Na2PO3F and 7.02% by weight of NaF.

The X-ray diffraction of the reaction product is shown in the chart of FIG.

Reference example 3 Na4P2030.05mol and NH4F0.12
The reaction was carried out in the same manner as in Experiment 1 using mol.

The analysis value of the obtained product was Na2P03F 69.70
% by weight, NaF was 9.52% by weight.

The X-ray diffraction of the reaction product is shown in the chart of FIG.

Reference example 4 Na2C030, 1 mol and 87% by weight H3P040
．． After reacting by adding 1 mol, the product was dried, and then 12 mol of NH, FO was added to the dried product, and the mixture was poured into a small platinum plate (
board) and a heating reaction was carried out at 290° C. for 1 hour in a tube furnace.

The chemical analysis value of the obtained product was Na2P03F 61.
44% by weight, and 11.30% by weight of NaF.

The X-ray diffraction of this reaction product is shown in the chart of FIG.

Reference example 5 87% by weight H3PO40.1 to 1 mol of Na2CO30.1
After reacting by adding mole, dry the product, then mix 0.12 mole of 47 wt% HF solution to the dried product, put it in a board, and react in the same manner as in Reference Example 4. Analysis value of the obtained product is Na2P03F 71.60% by weight, NaF8.
It was 95% by weight.

The X-ray diffraction of the reaction product is shown in the chart of FIG.

[Consideration]

As can be seen from the attached chart, when the fluorinating agent according to the cited example was used in NH4F and HF solutions, chart A4 (Figure 8) showed that sodium tripolyphosphate (Na 5 P s 010 ) had a diffraction angle of 2θ of 19.8°. peak and 38
．． A peak of NaF is observed at 8°.

Also, charts A2 (Figure 6), A3 (Figure 7) and /
165 (FIG. 9) also had a peak of NaF at 38.8°, and the presence of NaF was recognized corresponding to the results of chemical analysis.

. On the other hand, it can be seen that the peak of NaF is small in fluorination using HF gas as shown in Chart AI (FIG. 5).

For diffraction of X-ray chart, ASTM (Ameri
can 5ociety for Testing M
at-erial) card Na2PO3F, NaF
, Na5P301 (HN a 4 P207 and Na
Its intensity I/Io at the diffraction angle 2θ of 2H2P2O7
A summary is shown in Table 1.

[Brief explanation of drawings]

Figures 1, 2 and 3 are graphs showing the fluorination reaction rates of various alkali metal phosphates at room temperature and 160°C, and Figure 4 is a graph showing the relationship between melting temperature and the amount of alkali monofluorophosphate produced. It is a graph showing the relationship,
Figures 5 to 9 show reaction products of X in Reference Examples 1 to 5.
This is a line diffraction chart.

Claims (1)

[Claims] 1. After fluorinating an alkali metal phosphate with hydrogen fluoride gas at room temperature or higher, the resulting intermediate product is melt-reacted at a temperature of 625 to 900°C in an atmosphere that does not contain hydrogen fluoride gas. A method for producing an alkali monofluorophosphate, characterized by: