JPS6127322B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for producing sulfur tetrafluoride, in particular, using a relatively inexpensive fluorine source without using fluorine gas obtained by electrolyzing hydrofluoric acid using expensive electricity. The present invention relates to a method for producing sulfur tetrafluoride with high purity and high yield while regenerating and circulating a fluorine source.

Conventionally, methods for producing sulfur tetrafluoride include a method in which sulfur dichloride and sodium fluoride are reacted in an organic solvent such as acetonitrile (USP 2992073).
(see specification), a method in which sulfur dichloride, chlorine, and hydrogen fluoride are reacted at -50°C, and the reaction product is treated with amines to separate sulfur tetrafluoride (see OLS2363679), NOF sulfur chloride
A method of reacting with 3HF (see US Pat. No. 4,082,839) is known.

Among these methods, the method typified by the above-mentioned USP 2,992,073 is because the sodium fluoride reacted with sulfur dichloride and the by-product common salt are solid.
The reaction has to be carried out in the form of a slurry, making it difficult to carry out the reaction, and the yield of sulfur tetrafluoride varies greatly depending on the particle size of the sodium fluoride, which is not very desirable in terms of reaction operation.

In addition, the method typified by OLS2363679 is
It requires a fairly low temperature of -50°C, requires treatment with amines, is complicated in operation, and has the drawbacks of high cost.

Furthermore, in the method typified by USP 4082839, NOF is corrosive, requires the use of special materials for the equipment, and furthermore, the yield of sulfur tetrafluoride is low, and sulfur is precipitated as a by-product, making operation difficult. It has the disadvantage that it is complicated.

Furthermore, there is a report that sulfur tetrafluoride was obtained in a low yield of _{68% by reacting Py(HF) 9.2 (} Py: pyridine) with sulfur dichloride. (GAOlah et.al.
Inorg.Chem.16, 2637 (′77) short
(See communication) However, according to additional tests by the present inventors, this method not only achieved a yield of 68%, but no production of sulfur tetrafluoride was observed. That is, according to the results of subsequent studies conducted by the present inventors, when various molar ratios of HF/Py were used to react with sulfur dichloride, HF/Py
It has been found that when Py exceeds 5 to 6, the fluorination ability is significantly reduced or completely eliminated. Then, the present inventor produced sulfur tetrafluoride with high purity and a yield of 90% by reacting with sulfur dichloride only when HF/Py = 4 or less.
It was discovered that it could be obtained easily with the above method, and a patent application was already made.
It was proposed as No. 54-130833 (Japanese Unexamined Patent Publication No. 56-54209).

The basic reaction of this method is as follows.

3SCl ₂ +4Py・HF → SF ₄ +S ₂ Cl ₂ +4Py・HCl Among the obtained products, only SF ₄ is gaseous and the others are liquid, so the advantage is that separation of SF ₄ is extremely easy. have.

However, pyridine itself does not take part in the reaction, and as long as this method is used to obtain sulfur tetrafluoride, a large amount of pyridine will be produced in the form of Py-HCl. When producing sulfur fluoride, a one-pass method consumes a huge amount of pyridine.

The present inventors have conducted various research and examinations in order to enable the mass production of sulfur tetrafluoride and to effectively recycle pyridine, while using the necessary minimum amount of pyridine. By reacting a pyridine compound of hydrochloric acid with a sufficient amount of hydrofluoric acid to eliminate the hydrochloric acid, and then eliminating hydrofluoric acid from the resulting reaction product until the required pyridine compound of hydrofluoric acid is obtained. , discovered that the desired pyridine compound of hydrofluoric acid could be regenerated and subjected to the reaction with sulfur dichloride, and proposed it earlier in Japanese Patent Application No. 55-300 (Japanese Unexamined Patent Publication No. 56-100109). .

After further investigation, the inventors found that using sulfur monochloride and chlorine, which do not have the risk of decomposition, is more stable in operation than using sulfur dichloride as a raw material. It was discovered that sulfur can be obtained.

Thus, in the present invention, Py(HF) _{1 to 4} are reacted with sulfur monochloride and chlorine to produce sulfur tetrafluoride, and at the same time, the pyridine compound of hydrochloric acid produced as a by-product has a sufficient amount of water for the hydrochloric acid to be eliminated. amount of hydrofluoric acid is reacted,
Then, hydrofluoric acid is eliminated from the obtained reaction product until it becomes Py(HF) _{1 to 4} , and the obtained pyridine compound of hydrofluoric acid is recycled to the reaction with the sulfur monochloride. The present invention provides a method for producing sulfur fluoride.

In the present invention, as a means for reacting Py(HF) _{1 to 4} with sulfur monochloride and chlorine to produce sulfur tetrafluoride, it is possible to react them immediately, but it is possible to react them immediately, but it is also possible to react them more smoothly. Therefore, it is desirable to use a solvent.

The solvent itself must be inert to the reaction raw materials and reaction products, and halogenated hydrocarbons are generally suitable. Among halogenated hydrocarbons, methylene chloride, chloroform, carbon tetrachloride, fluorotrichloromethane,
Trichlorotrifluoroethane is preferred, and these may be used alone or in appropriate mixtures.

Particularly when trichlorotrifluoroethane solvent is used, only the sulfur tetrafluoride produced during the reaction can be separated in gaseous form, and the unreacted
S ₂ Cl ₂ and the solvent are preferred because they can be substantially completely separated into two layers in the liquid phase from the pyridine compound of hydrochloric acid produced as a by-product, which is extremely convenient for regenerating the pyridine compound as described below.

When the reaction is carried out using a trichlorotrifluoroethane solvent, it is appropriate to use a temperature of 0 to 60°C, preferably 20 to 40°C.

If the temperature is too low than 0°C, the reaction rate will drop significantly, while if it exceeds 60°C, the conversion rate to sulfur tetrafluoride may decrease, which is not preferred.

The reaction is usually carried out at atmospheric pressure, but may be carried out under increased pressure if desired. The ratio of the pyridine compound of hydrofluoric acid, sulfur monochloride, and chlorine used as reaction raw materials strictly depends on the value of n of the pyridine compound of hydrofluoric acid (Py(HF) _o , n=1 to 4) used. For example, when n=3, it is generally preferable to use 3 to 16 moles of the pyridine compound of hydrofluoric acid and 1 to 4.0 moles of chlorine per 1 mole of sulfur monochloride. If the molar ratio deviates from the above range, the conversion rate to sulfur tetrafluoride will decrease sharply, or
This is not preferable because the utilization rate of raw materials becomes poor. or,
The amount of solvent used is based on sulfur monochloride (S ₂ Cl ₂ ).
S ₂ Cl ₂ /solvent=0.2-25 mol/, preferably 1-25 mol/
It is appropriate to adopt 5 mol/. If the amount of solvent used is lower than the above range, the reaction rate will be slow, and chlorine will scatter into the gas phase, reducing the reaction rate; on the other hand, if it exceeds the above range, there will be no further effect and the capacity will simply increase. I don't like it because it's only.

The reaction is thus carried out, and among the products obtained, sulfur tetrafluoride, a pyridine compound of hydrochloric acid, and unreacted sulfur chloride, only sulfur tetrafluoride is gaseous;
Since the others are liquid, only sulfur tetrafluoride can be extracted as a gas, resulting in a highly pure product.

The liquid S ₂ Cl ₂ and the pyridine compound of hydrochloric acid are naturally separated so that the former forms a lower layer together with the solvent, and the latter forms an upper layer.

Thus, hydrofluoric acid is added to the hydrochloric acid pyridine compound present in the upper layer so that the hydrochloric acid is completely eliminated and converted to the hydrofluoric acid pyridine compound.

The amount of hydrofluoric acid added at this time needs to be 6 or more in molar ratio to the pyridine compound of hydrofluoric acid, and is preferably added in order to prevent dissolution of S ₂ Cl ₂ into the upper layer converted to the pyridine salt of hydrofluoric acid. A suitable molar ratio of 7 to 8 is relative to the pyridine compound of hydrochloric acid.

The pyridine compound of hydrofluoric acid thus obtained is Py
(HF) becomes about _{6 to 8} , and in this state, hydrochloric acid is completely eliminated. This reaction is usually carried out at normal pressure and at a temperature in the range of 0 to 50°C.

If the amount of hydrofluoric acid added is less than the above range, the elimination of hydrochloric acid will be incomplete, and an inactive pyridine compound will remain, resulting in a decrease in the utilization efficiency of pyridine.
On the other hand, if it exceeds the above range, not only no further effect can be expected, but also the burden of removing hydrofluoric acid, which will be described later, increases accordingly, which is not preferable.

As a means of converting a pyridine compound of hydrochloric acid to a pyridine compound of hydrofluoric acid, there is also a method of changing temperature and pressure in addition to the method described above.For example, hydrofluoric acid is added at a low temperature and the hydrochloric acid is eliminated at a high temperature and under pressure. In some cases, the amount of hydrofluoric acid used can be reduced.

The pyridine compound of hydrofluoric acid thus obtained is Py(HF) _{6 to 8} as described above, and since it is inactive as it is, hydrofluoric acid is removed from it until it becomes Py(HF) _{1 to 4} .

Such means include, for example, distilling Py(HF) _{6 to 8} under reduced pressure at a temperature of 100 to 300°C and a pressure of 760 to 100 mmHg, and organic solvents such as dimethylformamide, acetonitrile, methylene chloride, dioxane, trichlorotrifluoroethane, etc. 100-200 in the presence of
℃ distillation method, or contact with NaF, KF,
A means for removing hydrofluoric acid as a NaF/HF or KF/HF complex may be used as appropriate.

Among these methods, the method of contacting with NaF or KF can be expected to produce good results when obtaining Py(HF) _1-2 .

Py(HF) _1-4 is thus regenerated and recycled again for reaction with sulfur monochloride and chlorine.
On the other hand, the solvent layer containing unreacted S ₂ Cl ₂ has chlorine and S ₂ Cl ₂ added thereto, and is recycled for the reaction with Py(HF) _o .

Next, the present invention will be explained by examples.

Using a completely mixed reaction tank made of SUS, 26.9 kg of sulfur dichloride, 42.0 kg of Cl ₂ and 333.6 kg of Py(HF) ₃ were dissolved in a solvent 120 consisting of trichlorotrifluoroethane, and the reaction temperature was raised to 40°C. The reaction was carried out to obtain sulfur tetrafluoride as a gas with a yield of 99% (43 kg).
When the reaction was completed and the stirring of the tank was stopped, the liquid separated into two layers. And in the upper layer Py
((HCl + HF) _o , but a solvent phase containing unreacted S ₂ Cl ₂ existed below it. Then, for these,
When 272 kg of hydrofluoric anhydride was introduced and the reaction was carried out at 40°C with stirring, 57.5 kg of HCl was generated (this corresponds to more than 99% of the HCl contained in Py), and Py
(HF) ₈ was generated. When the stirring was stopped, the upper layer
The layer containing Py(HF) ₈ separated into a solvent phase containing S ₂ Cl ₂ in the lower layer, and the upper layer was substantially free of S ₂ Cl ₂ .

The upper layer of Py(HF) ₈ is guided to a SUS distillation column and 150
℃, distillation was carried out for 2 hours under a pressure of 300 mmHg,
Py(HF) ₈ could be converted to Py(HF) ₃ . Solvent and Py containing _{unreacted S2Cl2} in the lower layer
(HF) ₃ is again used as a raw material for the production of sulfur tetrafluoride mentioned above.

Claims (1)

[Claims] 1 Py(HF) _{1 to 4} (Py: pyridine) is reacted with sulfur monochloride and chlorine in the presence or absence of a solvent to produce sulfur tetrafluoride, and at the same time as a by-product. The pyridine compound of hydrochloric acid is reacted with sufficient amount of hydrofluoric acid to eliminate the hydrochloric acid, and then hydrofluoric acid is eliminated from the resulting reaction product until Py(HF) _{1 to 4} is obtained. A method for producing sulfur tetrafluoride, comprising recycling Py(HF) _{1 to 4} in the reaction with the sulfur monochloride. 2. The method of claim 1, wherein the solvent is trichlorotrifuquoroethane. 3. The method according to claim 1, wherein the amount of hydrofluoric acid used to remove hydrochloric acid from the by-produced pyridine compound of hydrochloric acid is in a molar ratio of 6 or more and 7 to 8 with respect to the pyridine compound of hydrochloric acid.