JPS596806B2 - Alkali monofluorophosphate manufacturing method and manufacturing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to alkaline monofluorophosphate [M2P
The present invention relates to a method for producing O3F (M=Na or K) and an apparatus therefor.

Conventionally, as an industrial method for producing alkali monofluorophosphate, (1) a method of neutralizing monofluorophosphoric acid (H2PO3F) produced from anhydrous hydrofluoric acid and phosphorus pentoxide with an alkali metal salt (Ind. Eng.C
hem. vol 43, 246-248 (1951))
or (2) a method of melting a metaphosphate and an alkali fufluoride, or a method of using MH2PO4 or M2H2P20 instead of a metaphosphate to give a metaphosphate at the corresponding temperature (US Pat. No. 24818
No. 07 Specification).

However, since method (1) uses highly toxic and highly corrosive raw materials, it is necessary to handle them with extreme caution, and furthermore, the equipment can be rapidly damaged by corrosion due to these raw materials. Since there is a constant risk of exposure, considerable skill and appropriate equipment are required, 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 makes it difficult to avoid a decrease in purity. was there.

The present inventor had previously proposed a method of directly reacting an alkali metal pyrophosphate or a dialkali metal phosphate with hydrogen fluoride gas as a method to overcome the drawbacks of these conventional methods (Japanese Patent Application No. 150757), the reaction at this time can be expressed by the following formula.

In this method, an alkali metal phosphate is charged into a reactor and the temperature is raised to a reaction temperature of 250 to 400°C, and then hydrogen fluoride gas at room temperature is introduced.
The following reaction proceeds, and alkali fluoride (MF
) was unavoidable and the purity tended to decrease.

As a result of repeated research to avoid the contamination of this alkali fluoride, the inventors of the present invention found that when introducing hydrogen fluoride gas,
If hydrogen fluoride gas preheated to 0°C or higher is introduced, side reactions such as those in equations
It was discovered that an extremely pure alkali metal monofluorophosphate can be obtained by proceeding with the process.

Regarding the preheating temperature of this hydrogen fluoride gas, the above side reaction is unavoidable if it is below 100°C, and the alkali fluoride is likely to be mixed in. If the preheating temperature of the hydrogen fluoride gas is around 450°C, which is the upper limit of the reaction temperature, the reverse happens. In order to reduce the reaction rate and to observe the formation of amorphous fluorophosphate, the temperature is 300'C or less, preferably 250 to 100C.

On the other hand, in conventional molten salt reactions, most corrosion-resistant metal materials could not be used as equipment materials, and only graphite could be used. In the gas-solid reaction, it was possible to use a hydrofluoric anhydride-resistant material if an outlet was provided to discharge the generated moisture.

However, as hydrofluoric anhydride-resistant materials at temperatures of 200 to 450°C, only expensive materials such as nickel, Monel, and Hastelloy are known, and inexpensive iron and the like cannot be used.

The inventors of the present invention repeatedly considered the device material 1, and surprisingly found that the aluminum material system, which is considered to be unusable in a high-temperature hydrogen fluoride gas atmosphere, is optimal for this reaction system. This invention has been achieved.

That is, a reactor with a lid manufactured using an aluminum material is equipped with an aluminum stirrer, and a top plate is equipped with a nozzle for blowing hydrogen fluoride gas, an exhaust port for purging generated steam, and an input port for inputting raw materials. If the reaction between alkali metal phosphate and hydrogen fluoride gas is carried out using a device equipped with a valve for removing the reaction product at the bottom of the reactor and a heating device around the outer circumference of the reactor, no corrosion of the device will occur. Therefore, highly pure alkali metal monofluorophosphate can be obtained.

The heating device for the outer periphery of the reactor includes a combustion furnace, an electric furnace,
Any heating device such as an external heater may be used.

That is, the present invention provides: (1) A method for producing an alkali monofluorophosphate in which an alkali metal pyrophosphate or a di-alkali metal phosphate powder is reacted with hydrogen fluoride gas at 200 to 450°C. Preparation of acid alkali metal salt or phosphoric acid di-alkali metal salt powder 200-45
After raising the temperature to 0℃, add 1 portion of hydrogen fluoride gas while stirring.
A method for producing an alkali monofluorophosphate, characterized by introducing and reacting after preheating to 00°C or above, and (2) a reaction vessel and a stirrer made of aluminum, and a heating device provided around the outer periphery of the reaction vessel. An apparatus for producing an alkali monofluorophosphate by reacting an alkali metal pyrophosphate or a di-alkali metal phosphate powder with hydrogen fluoride gas at 200 to 450°C, characterized in that
It is related to.

The starting material alkali metal phosphate is usually used in the form of powder or granules, preferably 500 to 100 μm or less.

Hereinafter, the present invention will be specifically explained using an example in which a sodium salt is used as the alkali metal salt, but it goes without saying that a potassium salt can also be used.

The reaction vessel is a round-bottom cylindrical reactor made of aluminum with a lid, and the lid has an inlet for hydrogen fluoride gas, an outlet for the generated steam, and an inlet for charging the raw material sodium pyrophosphate or di-sodium phosphate. The reactor is equipped with an outlet for taking out the alkali monofluorophosphate produced at the bottom, and a heating device such as an electric heater, a hot air jacket, etc. is arranged around the reactor.

The amount of alkali metal phosphate powder to be reacted is fed into the reaction vessel from the raw material inlet, and while stirring, the temperature is raised to 200 to 450°C from a heating tube around the outer circumference of the reactor.
Hydrogen fluoride gas is preheated to 100°C or higher and supplied from the introduction nozzle at the top of the reactor.

The reaction uses a flow reaction method in which only preheated hydrogen fluoride gas is continuously supplied, and 1.0 to 1.5 times the theoretical amount of hydrogen fluoride gas is passed through to conduct a gas-solid reaction. Since this is an exothermic reaction, it is difficult to control the temperature of a rapid reaction, so the reaction time is preferably carried out within a range of 0.5 to 3 hours.

After the reaction is complete, introduce dehumidified air or inert gas instead of the fluorinated hydrogen gas from the fluorinated hydrogen gas inlet to replace the residual fluorinated hydrogen gas in the container, and then close the extraction valve while stirring. By opening it, the highly fluid product alkaline monofluorophosphate IJi can be extracted.

On the other hand, the water vapor generated during the reaction is continuously discharged from the exhaust port provided at the top of the reactor.
The inside of the system was kept dry by evacuating the system at a negative pressure of 1,000 yen, and no material erosion occurred.

The inside of the reactor lid is prone to corrosion, so if it is lined with Teflon, corrosion resistance will be further improved.

As for the stirrer used in this reactor 1, it is preferable to use a scoop-type stirrer having a shape that follows the shape of the bottom plate, and can be devised to prevent scaling.

The gas-solid reaction of the present invention is a much milder reaction than the conventional high-temperature melting reaction, and since an aluminum device is used, there is no corrosion of the device material, and for this reason, the preheating of the hydrogen fluoride gas Due to the surprise of side reactions, high purity and high quality alkali monofluorophosphate can be obtained efficiently and at low cost.

Alkali monofluorophosphate is used in toothpastes and the like.

The present invention will be explained below with reference to Examples.

Example 1 Aluminum reactor 1 (800 m
mφ), add 100 kg of sodium pyrophosphate to inlet 5 (
300mmφ) while stirring with stirring blade 2,
The reactor was heated with hot air 9→10 heated in a heating furnace 8 so that the raw material was heated to 300°C.

After raising the temperature by 1 degree, hydrogen fluoride gas preheated to 150°C was introduced into the inlet 3 (25 nmφ) for 12 cycles/Hr.
1.5 hours (1.2 times the theoretical amount) at a speed of 30
The reaction was carried out at 0°C.

After stopping the supply of hydrogen fluoride gas, dehumidified air was introduced from the inlet 3 to replace the residual hydrogen fluoride gas in the reactor.

While continuing to stir, open the valve 7f and the trowel outlet 5 (1).
50-φ) was opened and the reaction product was extracted.

From the exhaust port 4, water vapor generated by the reaction 4.5]y/Hr
and unreacted HF gas2. 0/H r was discharged.

11 is a thermocouple protection tube. The product is 96% sodium monofluorophosphate, 0.5% free sodium monofluorophosphate.
The pH of the 2% solution was 7.0, and the reaction rate of HF gas was 83%.

Comparative Example 1 When hydrogen fluoride gas at 40°C was passed through and reacted in the same manner as in Example 1, the product contained 90% monofluorinated sodium phosphate, 20% free sodium fluoride, and 2
The pH of the % solution was 6.8, and the reaction rate of HF gas was 83%.

Example 2 Using the same apparatus as in Example 1, sodium pyrophosphate 1
．． After raising the temperature of O O k9 to 280°C, 250°C
F{F gas preheated to 1.2 kg/H r.
The product obtained by running the reaction at 280° C. for 7 hours contained 97% monofluorinated sodium phosphate, 0.4% free sodium fufluoride, and had a pH of 6.9 for a 2% solution.

The reaction rate of HF gas was 74%.

Comparative Example 2 Using the same apparatus as in Example 1, sodium pyrophosphate 1
．． After heating O O kg to 280℃, 70℃1
This preheated HF gas was heated at 1.5 kg/H r.
The product obtained by running the reaction at 280'C for an hour was 91% sodium monofluorophosphate, 1.8% free sodium fufluoride, and the pH of the 2% solution was 6.7.

Note that the reaction rate of HF' gas was 83%. Example 3 100 kg of potassium pyrophosphate was prepared using the same equipment as in Example 1.
After raising the temperature to 280°C, HF gas preheated to 150°C was heated at 10 kg/Hr for 1.5 hours (theoretical value 1
．． The product obtained by conducting the reaction at 280°C contained 97% monofluoropotassium phosphate and 0.5% free potassium fluoride, and the pH of the 2% solution was 6.9. Ta.

Note that the reaction rate of HF gas was 81%.

Example 4 Disodium phosphate 100ky using the same equipment as Example 1
After raising the temperature by 300°C, H preheated to 200°C
F gas at 12 kg/Hr for 1.5 hours (theoretical value 1.2
The product obtained by conducting the reaction at 300 °C contains 96% sodium monofluorophosphate, 0.6% free sodium fufluoride, and the pH of the 2% solution is 7.0. there were.

Note that the reaction rate of HF gas was 78%.

[Brief explanation of the drawing]

The accompanying drawing is a longitudinal sectional view showing the structure of an embodiment of the device of the present invention.

Claims (1)

[Scope of Claims] 1. Method for producing alkali monofluorophosphate, in which an alkali metal pyrophosphate or a di-alkali metal phosphate powder is reacted with hydrogen fluoride gas at 200 to 450°C. Preparation of alkali metal pyrophosphate or di-alkali metal phosphate powder 200-450
After raising the temperature to ℃, add 100% hydrogen fluoride gas while stirring.
A method for producing an alkali monofluorophosphate, which is characterized by introducing and reacting with preheating to a temperature above ℃. 2. The reaction container and the stirrer are made of aluminum, and a heating device is provided around the outer periphery of the reaction container. An alkali metal pyrophosphate or a di-alkali metal phosphate powder and hydrogen fluoride gas are heated at 200 to 450°C. Equipment for producing alkali monofluorophosphate by reaction.