JPS6125647B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for producing sulfur tetrafluoride, in particular a method for producing sulfur tetrafluoride, which uses a relatively inexpensive fluorine source without using fluorine gas obtained by electrolyzing hydrofluoric acid using expensive electric power. This 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 OLS No. 2363679), 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 OLS No. 2363679); sulfur dichloride
A method of reacting with NOF/3HF (see USP 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, which makes the reaction operation difficult, and it has undesirable disadvantages in terms of reaction operation, such as the yield of sulfur tetrafluoride varying greatly depending on the particle size of the sodium fluoride.

Further, the method typified by OLS 2363679 requires a considerably low temperature of -50°C and requires treatment with amines, which has the drawbacks of complicated operations and 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. It has the disadvantage that the operation 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. (GAOlahet.al,
Inorg.Chem.16, 2637 ('77)
(See Short Communication) However, according to additional tests conducted 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 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. In addition, the present invention produces 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 Patent Application 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 we have the advantage that separation of SF ₄ is extremely easy. have.

However, pyridine itself does not participate 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 mass production of sulfur tetrafluoride and to effectively recycle pyridine while using such pyridine to the minimum necessary level. By reacting the pyridine compound with a sufficient amount of hydrofluoric acid to eliminate the hydrofluoric acid, and then eliminating the hydrofluoric acid from the resulting reaction product until the required pyridine compound of hydrofluoric acid is obtained, It has been found that the desired pyridine compound of hydrofluoric acid can be regenerated and used again for reaction with sulfur dichloride.

Thus, the present invention produces sulfur tetrafluoride by reacting Py(HF) 1 to 4 with sulfur dichloride,
At the same time, the pyridine compound of hydrochloric acid produced as a by-product is reacted with a sufficient amount of hydrofluoric acid to eliminate the hydrochloric acid, and then the hydrofluoric acid is eliminated from the resulting reaction product until Py(HF) 1 to 4. Another object of the present invention is to provide a method for producing sulfur tetrafluoride, which comprises recycling the obtained pyridine compound of hydrofluoric acid in the reaction with the sulfur dichloride.

In the present invention, as a means for reacting Py(HF) 1 to 4 with sulfur dichloride to generate sulfur tetrafluoride, it is possible to react them immediately, but in order to carry out the reaction more smoothly, Preferably, a solvent is used.

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.

In particular, when using a mixed solvent of methylene chloride and trichlorotrifluoroethane, only the sulfur tetrafluoride produced by the reaction can be separated in gaseous form, and the by-product S ₂ Ci ₂ and the solvent can also be separated. This is preferable because it has the advantage that it 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 later.

In order to obtain this advantage, the mixing ratio of methylene chloride and trichlorotrifluoroethane should be 30%.
It is appropriate to employ at least 50% by weight, preferably 50 to 70% by weight.

When carrying out the reaction using these solvents, it is appropriate to employ a temperature of 0 to 60°C, preferably 20 to 40°C.

If the temperature is too low below 0°C, the reaction rate will drop significantly, and if it exceeds 60°C, part of the raw material sulfur dichloride will begin to decompose, leading to a decrease in the conversion rate to sulfur tetrafluoride. Therefore, I don't like either of them.

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 and sulfur dichloride used as reaction raw materials is determined by the pyridine compound of hydrofluoric acid (Py
Although it is strictly determined by the value of n in (HF) _o , n = 1 to 4), in general, per mole of sulfur dichloride,
It is preferable to use the pyridine compound of hydrofluoric acid in a proportion of 1 to 6 moles. When the molar ratio deviates from the above range, it is preferable because the conversion ratio to sulfur tetrafluoride decreases rapidly. In addition, the amount of solvent used is SCl ₂ /solvent = 0.1 to 50 mol / sulfur dichloride (SCi ₂ ).
1, preferably 2 to 10 mol/l. If the amount of solvent used is lower than the above range, the reaction rate will be slow and the decomposition of SCl ₂ will occur, resulting in a decrease in 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. So I don't like it.

The reaction is thus carried out, and among the products obtained, sulfur tetrafluoride and the pyridine compound of S ₂ Cl ₂ hydrochloric acid, only sulfur tetrafluoride is gaseous and the others are liquid, so sulfur tetrafluoride Since it can only be extracted as a gas, a highly pure product can be obtained.

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.

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

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 the above range is exceeded, not only no further effect can be expected, but also the burden of removing hydrofluoric acid, which will be described later, increases accordingly.
I don't like either of them.

In addition to the methods described above, there is also a method of changing temperature and pressure to convert a pyridine compound of hydrochloric acid into a pyridine compound of hydrofluoric acid.For example, hydrofluoric acid is added at a low temperature, and the hydrochloric acid is removed under heating and pressure. In some cases, it is possible to reduce the amount of hydrofluoric acid used.

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, Py(HF)6-8
is distilled under reduced pressure at a temperature of 100 to 300 °C and a pressure of 760 to 100 mmHg, but in the presence of an organic solvent such as dimethylformamide, acetonitrile, methylene chloride, dioxane, trichlorotrifluoroethane, etc.
A method of distilling at ~200° C., or a method of contacting with NaF.KF to remove hydrofluoric acid as NaF.HF or a KF/HF complex, etc. may be used as appropriate.

Among these means, the means of contacting with NaF or KF can be expected to give favorable results when obtaining Py(HF) 1-2.

Py(HF) 1-4 is thus regenerated and recycled to the reaction with sulfur dichloride. on the other hand
The layer containing S ₂ Cl ₂ can be reacted with chlorine to regenerate sulfur dichloride. That is, the mixture of S ₂ Cl ₂ and solvent present in the lower layer is taken out and reacted with a reaction equivalent amount of chlorine gas. The reaction is
It is appropriate to adopt a temperature of -20 to 60°C, preferably -10 to 30°C. If the temperature is lower than the above range
SCl ₄ is produced, making it impossible to obtain a uniform composition, and conversely, if the above range is exceeded, some of the sulfur dichloride decomposes, which is not preferable. Such a reaction is usually carried out at normal pressure, but may be carried out under increased pressure if desired.

Next, the present invention will be explained by implementation.

Using a completely mixed reaction tank made of SUS, 26.9 kg of sulfur dichloride and 104 kg of Py(HF) ₃ were dissolved in 120 liters of a mixed solvent consisting of 50 mol% methylene chloride and 50 mol% trichlorotrifluoroethane, and then reacted. The reaction was carried out at a temperature of 40°C, and sulfur tetrafluoride was obtained as a gas in a yield of 92%. When the reaction was completed and the stirring of the tank was stopped, the liquid separated into two layers. There was a solvent bath containing Py(HCl+HF) _o in the upper layer and S ₂ Cl ₂ in the lower layer. Then for these,
When 81.2 kg of hydrofluoric anhydride was introduced and the reaction was carried out at 40℃ with stirring, 1.16 kg of HCl (this corresponds to ~99% or more of the HCl contained in Py) was generated.
(HF) ₈ was generated. When the stirring was stopped, the upper layer
The layer containing Py(HF) ₈ separated into a solvent bath containing S ₂ Cl ₂ in the lower layer, and the upper layer was substantially free of S ₂ Cl ₂ .

Next, the lower layer portion was extracted, and 5.68 kg of chlorine gas was blown into it at 10° C. to convert S ₂ Cl ₂ to SCl ₂ . On the other hand, Py(HF) ₈ in the upper layer was introduced into a SUS distillation column and distilled for 2 hours at 150°C and under a pressure of 300 mmHg, whereupon Py(HF) ₈ was converted to Py(HF) ₃ . did it. These SCl ₂ and Py(HF) ₃
is used again as a raw material for producing the aforementioned sulfur tetrafluoride.

Claims (1)

[Claims] 1 Py(HF) 1 to 4 (Py: pyridine) and sulfur dichloride are reacted in the presence or absence of a solvent to produce sulfur tetrafluoride, and at the same time, the by-produced hydrochloric acid is The pyridine compound is reacted with a 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, characterized in that HF) 1 to 4 are recycled in the reaction with the sulfur dichloride. 2. The method of claim 1, wherein the solvent is a mixture of methylene chloride and trichlorotrifluoroethane. 3. The method according to claim 2, wherein the mixing ratio of methylene chloride and trichlorotrifluoroethane is 70% by weight or less, preferably 50 to 30% by weight. 4 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, preferably 7 to 8, relative to the pyridine compound of hydrochloric acid. Method 1.