JPS6222925B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to the production of alkali monofluorophosphate [M ₂ PO ₃ F (M = Na or K), hereinafter referred to as MFP], and more specifically, the present invention relates to the production of alkali monofluorophosphate [M 2 PO 3 F (M = Na or K), hereinafter referred to as MFP], and more specifically, the present invention relates to the production of alkali monofluorophosphate [M 2 PO 3 F (M = Na or K), hereinafter referred to as MFP]. Consists of reacting a salt with an alkali metal compound and anhydrous hydrogen fluoride at 200-450℃
This is an MFP manufacturing method. Conventionally, methods for manufacturing MFP include (1) a method in which monofluorophosphoric acid (H ₂ PO ₃ F) produced from anhydrous hydrogen fluoride and phosphorus pentoxide is neutralized with an alkali metal salt [Ind.Eng. Chem.vol43.246−248
(1951)], or (2) melting and granulating metaphosphate and alkali fluoride, or providing metaphosphate at the corresponding temperature instead of metaphosphate.
There is a method using MH ₂ PO ₄ or M ₂ H ₂ P ₂ O ₇ (US Pat. No. 2,481,807). However, method (1) uses highly toxic and highly corrosive raw materials, which must be handled with great care, and there is always a 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. In addition, 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 solve the drawbacks of these conventional methods, the present inventors discovered that alkali metal pyrophosphate (M ₄ P ₂ O ₇ ) or dialkali metal phosphate (M ₂ HPO ₄ ) and fluoride It was discovered that MFP can be easily produced by reaction with hydrogen, and an application has already been filed (Japanese Unexamined Patent Publication No.
56-73610) However, as a result of further investigation of the starting material for the phosphate used here, it was found that phosphates other than alkali metal pyrophosphate or dialkali metal phosphate could be used. ,
Efficiently achieves high purity without going through the molten state
We discovered that it is possible to manufacture MFPs and completed the present invention. That is, the present invention provides a phosphate other than an alkali metal pyrophosphate or a di-alkali metal phosphate with a molar ratio (M/P) of alkali metal and phosphoric acid.
Add an alkali metal compound to the range of 1.8 to 2.2, and add anhydrous hydrogen fluoride gas to the mixture at 200%
It is characterized by a gas-solid reaction at ~450°C. The content of the present invention will be specifically explained below. Invention filed by the present inventors (Japanese Unexamined Patent Publication No. 56-73610
In No. 1), di-alkali metal phosphate was used, but the reaction with hydrogen fluoride gas in this case proceeds according to the following formula. M ₄ P ₂ O ₇ +2HF→2M ₂ PO ₃ F+H ₂ O M ₂ HPO ₄ +HF→M ₂ PO ₃ F+H ₂ O Therefore, in this case, if the amount of hydrogen fluoride gas is adjusted, the reaction will proceed smoothly. Only MFP is produced with high purity through a gas-solid reaction at 200-450°C. However, if phosphates other than these are used, MFP alone will not be produced because the reaction with anhydrous hydrogen fluoride gas will cause an excess or deficiency of alkali metal.
Difluorophosphates, alkali metal fluorides, etc. are produced as by-products, and unreacted phosphates remain, resulting in a decrease in purity. By combining it with salt and reacting with fluorine gas, it is possible to generate highly pure MFP with few by-products and unreacted substances. The phosphates used in the present invention include alkali metal phosphates other than alkali metal pyrophosphates or dialkali metal phosphates, such as tripolysalt (M ₅ P ₃ O ₁₀ ), primary alkali metal salt ( MH ₂ PO ₄ ), tertiary alkali metal salts (M ₃ PO ₄ ), metaphosphates (MPO ₃ ), alkaline ammonium phosphates (MNH ₄ HPO ₄ ) and ammonium phosphate salts, such as monoammonium phosphate (NH ₄ H ₂ PO ₄ ), diammonium phosphate ((NH ₄ ) ₂ HPO ₄ ), etc., and these may be used alone or in mixtures. On the other hand, as the alkali metal compound, hydroxide (MOH), carbonate (M ₂ CO ₃ ), bicarbonate (MHCO ₃ ), fluoride (MF), etc. may be used alone or in mixtures. Note that anhydrous hydrogen fluoride or diluted fluorine gas is used as the hydrogen fluoride gas, and hydrofluoric acid containing water is not preferable because it causes severe corrosion and also increases the amount of impurities mixed in. The amount of reaction raw materials to be charged is a mixture of phosphate, an alkali metal compound, and anhydrous hydrogen fluoride gas, with a molar ratio of alkali metal to phosphorus (M/P) of 1.8 to 1.
A value in the range of 2.2 is preferable, and if it is less than 1.8, the amount of difluorophosphate etc. increases, which is not preferable. Moreover, if it is 2.2 or more, unreacted substances increase, which is not preferable. In addition, the molar ratio of fluorine to phosphorus (F/P) is preferably in the range of 1.0 to 1.5. If hydrogen fluoride of 1.5 or more is supplied, the generated MFP will be decomposed according to the following formula, so excessive anhydrous fluoride will be used. Hydrogen supply should be avoided as much as possible. Na ₂ PO ₃ F + 2HF → NaPO ₂ F ₂ + NaF + H ₂ O The reaction temperature is preferably 200°C or higher and 450°C or lower. If it is lower than 200°C, NaF will be produced along with MFP, and in some cases, NaF may be stronger than MFP. produce more than that. On the other hand, a reaction at a temperature exceeding 450°C is unfavorable because it is difficult to avoid the presence of difluorophosphate and these by-products increase. Note that the starting materials, phosphate and alkali metal compound, are usually used in the form of powder or granules, and Na and K are mainly used as the alkali metals. These raw material powders improve reactivity,
It is desirable to use as fine a material as possible, preferably several tens to several hundred microns or less. The reaction apparatus can be either a batch type or a continuous type, and any method can be used, such as a method in which raw material powder is placed in a reactor and reacted with anhydrous hydrogen fluoride gas while stirring. In this way, fluorination in the present invention ranges from 200 to
A theoretical amount of phosphate and alkali metal compound is charged at 450℃ and normal pressure, and fluorination is performed using anhydrous hydrogen fluoride in an amount of 1 to 1.5 times the theoretical amount. MFP can be made using any phosphate salt. The present invention will be described in detail below with reference to Examples. Examples 1 to 9 A mixture of an alkali metal phosphate or an alkali metal phosphate with a particle size of 100 μ shown in Table 1 and an alkali metal compound was placed in a reactor made of Nickel with a single stirrer, and a predetermined reaction was carried out. A predetermined amount of anhydrous hydrogen fluoride gas was passed through the reactor at a certain temperature to carry out the fluorination reaction.
The results are shown in Table 1.

[Table] Comparative Examples 1 to 11 Using the same alkali metal phosphates and alkali metal compounds as in Examples, the reaction temperature was 160°C.
Fluorination was carried out at 500℃. The results are shown in Table 2.

【table】

【table】

Claims (1)

[Claims] 1 Add an alkali metal compound to a phosphate other than an alkali metal pyrophosphate or a di-alkali metal phosphate so that the molar ratio of alkali metal to phosphorus (M/P) is in the range of 1.8 to 2.2. A method for producing an alkali monofluorophosphate, which comprises reacting the mixture with anhydrous hydrogen fluoride gas at 200 to 450°C.