JPS6016364B2 - Method for producing sulfur hexafluoride - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing sulfur hexafluoride (SF6), and particularly to a method for easily producing a large amount of SF6 with high purity and at low cost.

SF6 is non-toxic and has high insulation properties, so it can be used at high voltages,
It is widely used as insulating material in cables for large-capacity power supplies, electrical equipment, circuit breakers, lightning rods, and computer circuit wiring.

Several methods have been proposed for producing SF6, including a direct combustion synthesis method and an electrolytic method, but the direct combustion method is industrially adopted due to cost constraints.

According to this method, elemental sulfur and elementary gas must be reacted with each other through direct combustion, and the fluorine gas used is usually obtained by electrolyzing a raw material molten salt such as KF or old F.

For this reason, the electricity cost becomes extremely high, and in order to achieve mass production, there is no other option than simply operating a large number of the same electrolytic cells in proportion to the production volume, or using a large-capacity electrolytic cell. Scaling up using this method is extremely disadvantageous in terms of equipment area and cost. On the other hand, a method using an expensive electrolytic method that does not use emitting gas has also been proposed.

For example, by reacting chlorine gas with NOF and breast presses, once SF
A method has been proposed in which SF5CI is obtained by producing 4, removing by-products produced at the same time, and reacting the purified SF4 with NOF and chlorine. However, the NOF used in this method is extremely corrosive, especially in the presence of even a small amount of moisture, and reaction bags and the like require fairly expensive corrosion-resistant materials, so they are not industrially satisfactory. There were drawbacks that could hardly be described as methods.

In view of this, the present inventor conducted various studies with the aim of finding a means to industrially advantageously produce high-purity SF6 in large quantities at low cost without using generating gas that must be obtained by electrolysis. As a result of our investigation, we found that SF5CI was produced using a new method using sulfur, chlorine, and a specific hydrofluoric acid compound as raw materials.
It has been found that the above object can be achieved by pyrolyzing this to obtain SF6. Thus, the present invention provides a pyridine compound of sulfur or sulfur chloride consisting of sulfur monochloride and/or sulfur dichloride, chlorine and hydrofluoric acid (Py.
SF5CI, which is obtained by reacting with n, n = 1 to 6) in the presence or absence of a solvent, is thermally decomposed to produce SF6, S
Generate F4 and CI2 and yield F4 and CI2,
The gist of this invention is a method for producing sulfur hexafluoride, which is characterized in that it is separated from SF6 by trapping it with a pyridine compound of chlorine and sulfur or sulfur chloride and hydrofluoric acid.

The pyridine compound of hydrofluoric acid used in the present invention is a compound represented by Py(HF)n (Py:pyridine).

Here, the value of n is usually 1 to 6, and when employing 2 to 4 of these, it is particularly preferable because an industrially sufficient reaction rate can be obtained. In addition, during the reaction, the proportions of sulfur, chlorine, and acid-generating pyridine compounds used are 1 sulfur and 1
It is appropriate to employ 4 nl to 15 moles of Py(HF) and 1 to 10 moles of chlorine per mole.

If the amounts used deviate from the above ranges, the utilization of the pyridine compound of hydrofluoric acid and chlorine and the yield of SF5CI will decrease, which is not preferable.

Within these ranges, chlorine per mole of sulfur is 3 to 3.
4 mol, the amount of pyridine hydrofluoric acid compound used is Py(HF)n
Although it varies depending on the n value of
It is particularly preferred because SF5CI can be obtained in high yield and the utilization rate of raw materials is also high.

In the present invention, in order to produce SF5CI using these raw materials, the temperature is usually 0 to 0 in the presence or absence of a solvent.
These are reacted at 60°C, preferably 20 to 40 qo. If the temperature deviates from the above range, the reaction rate will drop significantly and the utilization rate of sulfur chloride and chlorine will decrease, which is not preferable. Examples of the solvent used in the reaction include methylene chloride, chloroform, carbon tetrachloride, fluorotrichloromethane, and trichlorotrifluoro. Halogenated hydrocarbons such as ethane are preferred, and one or more of these may be used in combination as appropriate. In particular, when trichlorotrifluoroethane is used, both liquids, sulfur chloride and a pyridine compound of hydrochloric acid, which are created with the production of SF5CI, are separated into their respective layers in a solvent, and these liquids are recovered. This is particularly preferred since it has the advantage of being reusable as a raw material. Although the reaction can be carried out without using a solvent, using a solvent allows the fluorination reaction to be carried out more uniformly and smoothly, and furthermore, it is easier to separate and reuse the sulfur chloride and pyridine hydrochloride compounds. This is preferable. Further, as for the ratio of the reaction raw materials and the solvent used, it is appropriate to use the solvent in an amount of about 10 to 200% by volume based on the total amount thereof. 0 The reaction is usually carried out at normal pressure, but if desired, it can also be carried out under increased pressure up to about 5 atmospheres of gauge pressure.

As an apparatus for carrying out the reaction, a complete mixing type reaction apparatus having an appropriate outer layer is preferable, for example, and the material thereof is S.
It is preferable to use a corrosion-resistant material that is particularly chlorine-resistant, such as US or base resin for the inner surface. The SF5CI thus obtained is
This is thermally decomposed and converted into SF6. During thermal decomposition, this can be directly converted to SF6 at a temperature of 400°C or higher, but when thermally decomposed in the presence of a catalyst such as copper or mercury, the temperature can be increased to 200-300°C. and relatively low temperature, and SF6
This is preferable because the conversion rate to can be achieved quickly. In order to actually carry out the present invention industrially, pyridine does not directly participate in the reaction and is expensive, and it is preferable to remove by-products, recover, regenerate, and reuse. Although flows can be combined as appropriate, in the present invention,
It is reasonable and preferable to set up a flow as shown in the attached drawings described below.

1 is a reactor, into which a pyridine compound of sulfur or sulfur chloride, chlorine and hydrofluoric acid, and the above-described solvent of trichlorotrifluoroethane are introduced and a reaction is carried out.

SF5CI and some SF4 are created by this reaction, and these are taken out as 2 in gaseous form. These gases are introduced into separator 3, a hydrofluoric acid pyridine compound is introduced through 4, and SF4 is trapped in the hydrofluoric acid pyridine compound and returned to the reactor 1 through the lines from separators 3 to 5. SF5CI is taken out from the upper part of separator 3 through line 6, introduced into pyrolyzer 7, and converted into SF6. Since SF4 and chlorine are created along with SF6 by thermal decomposition, these mixed gases are sent to separator 9 via line 8. Chlorine, sulfur or sulfur chloride, and a pyridine compound of hydrofluoric acid are introduced into the separator 9 from a line 10, and SF4 and chlorine, which are by-products from the thermal decomposition of SF5CI, are trapped in these. Returned to reactor 1. In this way, SF6 as a product is taken out from the separator 9. On the other hand, in the reactor 1, the pyridine compound of hydrochloric acid and sulfur chloride created by the reaction together with the solvent are taken out from the line 12 as a liquid phase and introduced into the regenerator 13, where the pyridine compound of hydrochloric acid is further taken out from the line 14. Sufficient amount of HF is introduced to eliminate the hydrochloric acid therein.

The amount of HF introduced here is set at a molar ratio of 6 or more to the pyridine compound of hydrochloric acid, so that when separating the sulfur chloride and the pyridine compound of the regenerated Aoi acid, which will be described later, the two do not substantially mix. In order to form a separate layer, the molar ratio of hydrochloric acid to the pyridine compound is preferably about 7 to 8.

The pyridine compound of hydrofluoric acid, solvent, and sulfur chloride thus produced by the reaction are sent from line 15 to liquid phase separator 16. In the separator 16, the liquid is allowed to settle, so that the pyridine compound of hydrofluoric acid is separated in the upper layer 17, and the solvent and sulfur chloride are separated in the lower layer. The solvent and sulfur chloride in the lower layer are then returned to the reactor 1 via line 19. On the other hand, the pyridine compound of hydrofluoric acid present in the upper layer is Py(
HF) 6 to 8, and in this state, hydrochloric acid is completely eliminated. This reaction is usually carried out at normal pressure of 0 to 50 psi. The pyridine compound of hydrofluoric acid thus obtained is Py(HF) 8-8 as mentioned above, and since it is inert as it is, it is sent to the distiller 21 via the line 20, and the temperature is 100-30 and the pressure is 0. Distilled under 760-100 skin Hg and regenerated to Py(HF) 2.5-3.5. The regenerated hydrofluoric acid viridine compound is line 4 and line 1.
distributed to 0. In addition, excess HF desorbed by distillation
is sent to line 14 and combined with HF introduced from the outside.

Next, the present invention will be explained by examples.

Chlorine is introduced at a rate of 2.5 mol/hour into a reactor 1 with a crossing vessel made of SUS31$, and Py(HF)3 and sulfur chloride (S2CI2) are introduced from a mixing tank 23 through line 11 and lines 4 and 5. Py(HF)3 introduced through line 1
The reaction was carried out in the presence of trichlorotrifluoroethane (R-113) solvent introduced at a rate of 9 to 2 mol/hour.

Raw material supply molar ratio S:CI2:Py(HF)3=1:3
9, the reaction was carried out under the conditions of a temperature of 350 C and a residence time of 1.0 hour, and the resulting gas was taken out to line 2. This gas is 6
Py(HF)3 is introduced into the separator 3 filled with 0x6 fluororesin tubes, where 2.5 mol/Py(HF)3 is introduced from the line 4.
The mixture was supplied at a temperature of 30 q○ and brought into countercurrent contact. As a result of collecting gas from the upper part of separator 3 and analyzing the 0 reaction product by NMR, SF5CI, SF4, and a trace amount of SOF2 were confirmed, and the composition was 90:9.5:0.5 (molar ratio). Ta.

This gas is taken out from line 6 and introduced into a thermal decomposer 7 consisting of an open column reactor packed with a Cu catalyst.
It was thermally decomposed at 50 oo to produce SF6. The produced gas from the decomposer 7 is sent to the separator 9 via line 8, where -3
Countercurrent contact was made with 0.5 mol/h of sulfur monochloride and 36.5 mol/h of Py(HF) introduced via line 10 at a low temperature of 0.000 m/h. The produced gas from the separator 9 was taken out and liquefied to zero with liquid nitrogen, and its composition was measured by NMR. As a result, SF6 was obtained with a high purity of 99% or more, although it contained SOF2, SF5CI, SF4, and R-11 inferiority. Ta. SF5
SF4 and CI2 produced by thermal decomposition of CI were drawn out from the bottom of the separator 9 and introduced into the reactor 1 again through a line 11, where they were used as raw materials for SF5CI.

On the other hand, in the reactor 1, the pyridine compound of hydrochloric acid and sulfur chloride produced as by-products in the reaction together with the solvent are taken out from the line 12 as a liquid phase, and the regenerator 1 with a sandal scale made of SUS 3.1 billion is taken out.
3, and here, 51 mol/hour of hydrofluoric acid was continuously introduced via line 11, and the reaction was carried out at a temperature of 35° C. and a residence time of 2 hours.

Hydrochloric acid separated from pyridine (Py) in this reaction was taken out to the gas phase via line 24. The acid pyridine compound, solvent, sulfur chloride, etc. generated by the reaction are sent from line 15 to liquid phase separator 17, where they are separated into an R-113 volume soot phase containing sulfur chloride and a hydrofluoric acid pyridine compound phase due to the difference in specific gravity. It was separated into two phases.

The R-113 and sulfur chloride phase in the lower layer is sent to reactor 1 via line 19, and the upper layer *acid pyridine compound phase is sent to reactor 1 through line 2.
0 and sent to a distillation column 21 made of a corrosion-resistant alloy, and in a batch operation, excess HF was produced and regenerated into Py(HF)3. Pyridine hydrofluoride was extracted from line 20 and dissolved sulfur chloride was analyzed by crab light X-ray method, and the result was 400 sulfur chlorides due to S exchange. A pyridine compound of hydrofluoric acid having an average composition of 8 Py(HF) was charged into the distillation column 21, and heated at 150°C x 3
As a result of batch distillation for 3 hours under the condition of 0 shipboard Hg, approximately 1,000 tons of *acid was distilled out from the top of the distillation column, and 1,400 tons of pyridine compound of hydrofluoric acid was recovered from the bottom of the column. The average composition of this compound is Py(HF)3, and the amount of heavy metals mixed in from the analysis using full-spectrum X-rays is Fe30, Ni30, and Cr15.
It was a leg. Thus, this Py(HF)3 is transferred to line 4
It was supplied at a rate of 2.5 mol/hour from line 22 and 6.5 mol/hour from line 22, and used again as a raw material for the next reaction.

Unreacted sulfur chloride, solvent R--113 and regenerated Py(HF
) 3 was circulated to reactor 1 for reaction, and as a result, no significant change was observed in the yield or purity of the final product SF6.

[Brief explanation of drawings]

The accompanying drawing is a flow diagram illustrating one of the preferred reaction systems for carrying out the method of the invention.

Claims (1)

[Scope of Claims] 1. A pyridine compound (Py.(
HF) n, n = 1 to 6) in the presence or absence of a solvent, and thermally decomposes SF_5Cl to obtain S
F_6, SF_4 and Cl_2 are generated, and the SF_
A method for producing sulfur hexafluoride, which comprises trapping 4 and Cl_2 with a pyridine compound of chlorine and sulfur or sulfur chloride and hydrofluoric acid to separate them from SF_6. 2 The pyridine compound of hydrofluoric acid used in the trap is S
The method for producing sulfur hexafluoride according to claim 1, which is obtained by replacing the hydrochloric acid of a pyridine compound of hydrochloric acid by-produced during F_5Cl production with hydrofluoric acid. 3 SF_5Cl
The ratio of sulfur, chlorine, and pyridine compound of hydrofluoric acid used in the reaction to produce is 1 to 15 moles of pyridine compound of hydrofluoric acid and 1 to 10 mole of chlorine per 1 mole of sulfur. Method for producing sulfur hexafluoride. 4. The method for producing sulfur hexafluoride according to claim 1, wherein the reaction to obtain SF_5Cl is carried out at a temperature of 0 to 60°C. 5 The solvent is methylene chloride, chloroform, carbon tetrachloride,
Claim 1: Halogenated hydrocarbons such as fluorotrichloromethane and trichlorotrifluoroethane
2. Method for producing sulfur hexafluoride. 6. The method for producing sulfur hexafluoride according to claim 1, wherein the thermal decomposition for converting SF_5Cl to sulfur hexafluoride is carried out at 200 to 300°C using copper or mercury as a catalyst.