JPH0113709B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing hexafluoropropylene oxide (hereinafter abbreviated as HFPO). More specifically, the present invention relates to a method for producing HFPO from hexafluoropropylene (hereinafter abbreviated as HFP) using hypochlorite as an oxidizing agent.

HFPO is an intermediate for producing useful fluorine-containing compounds such as hexafluoroacetone and perfluorovinyl ether, and HFPO polymers have a wide range of uses such as heat transfer agents and lubricating oils.

HFPO can be produced by the epoxidation reaction of HFP, but HFP has very different chemical properties from hydrocarbon olefins such as propyrene and chlorinated hydrocarbon olefins such as allyl chloride. It is often difficult to epoxidize it in the same way as propylene or allyl chloride.

For example, both propylene and allyl chloride are epoxidized by the chlorohydrin method, in which the ring is closed with an alkali via chlorohydrin. On the other hand, when trying to epoxidize HFP using the chlorohydrin method, chlorohydrin is unstable and decomposes into carbonyl compounds, so it cannot be converted to HFPO.

Therefore, as a method for epoxidizing HFP,
Until now, various methods different from the epoxidation methods for hydrocarbon olefins and chlorinated hydrocarbon olefins have been proposed, but none of them can be said to be an industrially advantageous method for producing HFPO.

Previously described in US Pat. No. 3,358,003. A method of oxidizing HFP to HFPO in a medium of alkaline hydrogen peroxide, or
It is described in Special Publication No. 11683/1973. A method of oxidizing HFP to HFPO with oxygen in the presence of an inert solvent is known as a typical method for producing HFPO. However, in any of these methods, it is difficult to control the reaction, it is difficult to suppress the decomposition of the produced HFPO, or a large amount of by-products are produced, making it impossible to obtain HFPO in high yield. do not have. Furthermore, these methods
Increasing the conversion rate lowers the HFPO selectivity, so in order to use HFP effectively, a low HFP
It is necessary to stop the reaction at the conversion rate and separate and recover unreacted HFP from HFPO for reuse. However, the boiling point of HFP (-29.4℃) and the boiling point of HFPO (-
27.4℃) are very close to each other and it is difficult to separate the two by distillation, so a special separation operation is required to separate them. For example,
For example, a method has been proposed in which HFP and bromine are reacted to form a high-boiling dibromine compound and separated from EFPO, or an extractive distillation separation method described in U.S. Pat. No. 3,326,780, U.S. Pat. No. 4,134,796, etc. However, both methods are complicated separation methods and significantly increase the production cost of HFPO.

On the other hand, as an oxidation method using hypochlorite,
In a system in which a polar solvent such as acetonitrile or diglyme is added to an aqueous hypochlorite solution, HFPO is more effective than HFP.
is known to be generated [IZV.AKAD.
NAUK.SSSR, SER.KHIM., 79, (11) 2509]
However, when the inventors examined this method, they found that
The selectivity of HFPO was around 10%, making it impossible to obtain a high yield. The reason for this is thought to be that the reaction system is a homogeneous mixture of a polar solvent and an alkaline hypochlorite aqueous solution, so the generated HFPO easily reacts with water and decomposes under alkaline conditions. . Furthermore, this method requires a troublesome step of recovering the polar solvent from the reaction system after the reaction. From the above points, this reaction method is also practical.
It cannot be used as HFPO manufacturing technology.

The present inventors have conducted intensive studies to overcome the drawbacks of conventional methods and to find a method for producing HFPO more easily and with higher yield than HFP.
It was discovered that HFPO can be obtained in a higher yield than HFP by using hypochlorite as an oxidizing agent and carrying out the reaction in a two-phase system of an aqueous phase and an organic phase in the presence of a sulfonium salt, and has developed the present invention. completed.

That is, the present invention is characterized in that when producing HFPO from HFP using hypochlorite as an oxidizing agent, the reaction is carried out in a two-phase system of an aqueous phase and an organic phase in the presence of a sulfonium salt. new to
It provides a method for producing HFPO.

In the two-phase reaction of the present invention, substantially all of the HFP and produced HFPO are contained in the organic phase. According to the method of the present invention, HFP
HFPO can be obtained with high selectivity even if the conversion rate of This is probably because it is less likely to occur. Therefore, according to the method of the present invention, by increasing the HFP conversion rate, it is also possible to omit the complicated process of separating HFP and HFPO and the process of recycling HFP.

After the reaction, the organic phase and the aqueous phase are separated, and HFPO is easily isolated from the organic phase by a separation operation such as distillation. In addition, in the remaining organic phase from which HFPO has been removed,
It contains a sulfonium salt, and the remaining organic phase can be recycled and reused in the reaction as it is, making it very easy to recover the solvent and catalyst.

As described above, the method of the present invention can achieve high yield.
HFPO can be obtained and the manufacturing process is very simple. Therefore, when carrying out the method of the present invention, the construction cost and operating cost of the reactor are low, and a very economical HFPO production process is possible.

The present invention will be explained in more detail below.

The hypochlorite used in the present invention may be one that releases hypochlorite ions under the reaction conditions. Examples of hypochlorites used in the present invention include alkali metal salts such as sodium hypochlorite and potassium hypochlorite, and alkaline earth salts such as calcium hypochlorite and barium hypochlorite. Examples include similar metal salts. Among them, especially sodium hypochlorite and calcium hypochlorite,
It is industrially mass-produced for uses such as bleach and disinfectant, and is available at low cost, making it suitable as the hypochlorite used in the method of the present invention.

In the present invention, hypochlorite is mainly used dissolved in the aqueous phase, but there are no particular restrictions on its concentration. Usually, the effective chlorine concentration is preferably in the range of 1% to 25%, particularly preferably in the range of 3% to 20%. If the available chlorine concentration is too low, it is necessary to handle a large amount of aqueous phase;
Economically disadvantageous. Furthermore, if the available chlorine concentration is too high, hypochlorite becomes unstable and difficult to handle.

The ratio of hypochlorite to HFP can be selected arbitrarily, but in order to obtain substantial reaction results, the ratio of hypochlorite ion to HFPI mole is usually
A range of 0.5 gram equivalent to 30 gram equivalent is preferred, and a range of 0.8 gram equivalent to 1 gram equivalent is particularly preferred.

The sulfonium salt used in the method of the present invention is preferably one that exists stably under the reaction conditions and has an affinity for the organic phase or both the organic phase and the aqueous phase. ) Sulfonium salts such as those represented by:

R ₁ , R ₂ , R ₃ , S X () In the general formula (), R ₁ , R ₂ and R ₃ are the same or different and represent a hydrocarbon group or a secondary amino group. The type and length of the hydrocarbon group contained in the hydrocarbon group or secondary amino group are appropriately selected depending on the solvent used, the required reaction rate, etc. Types of hydrocarbon groups include, for example, alkyl groups, alkenyl groups,
A cycloalkyl group, a cycloalkenyl group, an aryl group, an aralkyl group, an alkenylaryl group, etc. are used, and an alkyl group, an aryl group, an aralkyl group, etc. are particularly preferably used. In addition, the length of the hydrocarbon group is usually 1 sulfonium ion in terms of the total number of carbon atoms contained in R ₁ , R ₂ and R ₃ .
Each number is selected from a range of 6 to 100, preferably 8 to 90, particularly preferably 10 to 80. The above hydrocarbon group can also be used after being substituted with an inert functional group. The inert functional group is limited depending on the reaction conditions, but usually halogen, acyl group, carboxyl group, ester group, nitrile group, alkoxyl group, etc. are used. In the R ₁ , R ₂ , R ₃ , and S ions, a heterocycle may be formed within the ions, or R ₁ , R ₂ , or R ₃ may be part of a polymer compound. do not have.

As the anion X in the general formula (),
Various anions can be used, but usually halogen ions, various mineral acid ions other than halogen ions,
Organic acid ions etc. are used.

Examples of the anion Examples include porate ion, difluorotrimethylsilicate ion, and the like.

Examples of the sulfonium salt represented by the general formula () include dibutylmethylsulfonium iodide, tri-n-butylsulfonium tetrafluoroporate, dihexylmethylsulfonium iodide, dicyclohexylmethylsulfonium iodide, dodecylethylmethylsulfonium chloride, Methyldioctadecylsulfonium iodide, dodecylbenzylmethylsulfonium methylsulfate, 1,6-
Hexamethylenebis(dimethylsulfonium bromide), tris(dimethylamino)sulfonium difluorotrimethylsilicate, tris,
Examples include (diethylamino)sulfonium difluorotrimethylsilicate, tris(N-methyl-N-octadecylamino)sulfonium difluorotrimethylsilicate, tris(dimethylamino)sulfonium chloride, and the like.

The amount of sulfonium salt used in the method of the present invention is appropriately selected depending on the type of solvent, required reaction rate, etc., but is usually from 0.0001 mol to 1 gram equivalent of hypochlorite ion used. It is selected from a range of 1 mol, particularly preferably from a range of 0.001 mol to 0.3 mol. If the amount of sulfonium salt is too small, a substantial reaction rate cannot be obtained, and if it is too large, the reaction rate will be too fast and it will be difficult to control the reaction, or the cost burden of the sulfonium salt will increase. This is economically disadvantageous.

The reaction of the present invention is carried out in a two-phase system consisting of an aqueous phase and an organic phase. In this case, the organic phase only needs to contain HFP and form a phase different from the aqueous phase, and there is no particular restriction beyond that. It can also be a phase consisting of a sulfonium salt and HFP, which is poorly soluble in
Furthermore, the phase may be composed of HFP and an inert solvent that is substantially immiscible or hardly miscible with the aqueous phase.

Furthermore, when carrying out the method of the present invention, it is sufficient to have an organic phase containing substantially most of HFP and an aqueous phase containing hypochlorite; It doesn't matter if there are other aspects of . For example, even when the organic phase is composed of two types of media with low compatibility to form two phases, or when the sulfonium salt is supported on an insoluble carrier and forms a third phase, the present invention can be applied. You can do the method.

Examples of inert solvents that are substantially immiscible or sparingly miscible with the aqueous phase for the organic phase used in the method of the invention include, for example, n-hexane, n-hexane,
-Aliphatic hydrocarbons such as octane and n-decane;
Number of alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, decalin; benzene, toluene,
Aromatic hydrocarbons such as xylene; ethers such as diisopropyl ether and di-n-butyl ether; methylene chloride, chloroform, carbon tetrachloride,
Chlorinated hydrocarbons such as 1,2-dichloroethane and chlorobenzene; 1,2-dichloro-1,1,
2,2-tetrafluoroethane, fluorotrichloromethane, 1,1,2-trichloro-1,2,
Chlorofluorocarbons such as 2-trifluoroethane, 1,1,2,2-tetrachloro-1,2-difluoroethane; perfluorocyclobutane, perfluorodimethylcyclobutane, perfluorohexane, perfluorooctane, perfluorodecane, hexa Examples include perfluorocarbons such as fluorobenzene; or mixed solvents thereof. Among the various solvents mentioned above, fluorinated compounds such as chlorofluorocarbons and perfluorocarbons have high solubility for HFP and HFPO, and are particularly suitable for the method of the present invention. or,
Chlorinated hydrocarbons generally have high solubility in sulfonium salts and are suitable for the method of the present invention.

The volume ratio of the organic phase to the aqueous phase can be arbitrarily selected depending on the reaction method, reaction conditions, etc., but the organic phase is usually preferably 0.05 to 20 times the aqueous phase, and particularly preferably.
It ranges from 0.2 times to 5 times.

The reaction temperature when carrying out the present invention is determined by the amount of catalyst,
The temperature is determined depending on the reaction solution composition, the desired reaction rate, etc., but it is usually preferably in the range of -25°C to 100°C, and particularly preferably in the range of -17°C to 50°C. If the reaction temperature is too low, a substantial reaction rate may not be obtained or, in some cases, the aqueous phase may freeze, making it impossible to carry out the reaction. Also, if the reaction temperature is too high
HFPO decomposition becomes significant and HFPO selectivity decreases.

The reaction pressure when carrying out the present invention is not particularly limited as long as it is a pressure sufficient to keep the organic phase in a liquid phase. Therefore, the reaction pressure is selected depending on the type and composition of the organic phase, but is usually preferably in the range of 1 atm to 20 atm.

As a reaction method when carrying out the present invention, any of batch, semi-flow, and flow reaction methods are possible. Examples include, for example, a countercurrent reaction or a cocurrent reaction between an organic phase containing HFP and a sulfonium salt and an aqueous phase containing hypochlorite. These methods are easily carried out in commonly used countercurrent or cocurrent reactors.
In addition, since virtually all of the HFPO produced by the reaction is contained in the organic phase, HFPO can be easily isolated from the organic phase by separation operations such as distillation.
It can be refined. The remaining organic phase from which HFPO has been removed contains sulfonium salts,
This organic phase can be recycled and reused in the reaction as it is.

EXAMPLES The present invention will be explained in more detail below using Examples and Comparative Examples, but these explanations are not intended to limit the present invention in any way.

Example 1 18 ml of chloroform and 20 ml of sodium hypochlorite aqueous solution with an effective chlorine concentration of 12% in a 50 ml pressure bottle containing a stirring bar coated with fluororesin.
ml, 0.6 g (4 mmol) of HFP and di-n-butylmethylsulfonium iodide as catalyst.
Fill 0.12 g (0.42 mmol). Next, this reaction solution is cooled to 0° C., and then a magnetic stirrer is used to rotate a stirrer in the reaction container to mix the reaction solution and start the reaction. The reaction temperature is maintained at 0°C during the reaction. After 30 minutes, the rotation of the stirrer was stopped and the reaction solution was allowed to stand still to separate the aqueous phase and chloroform phase, and the HFP and HFPO contained in the chloroform phase were quantified by gas chromatography.
The HFP conversion rate was 89% and the HFPO selectivity was 68%.

Comparative Example 1 A reaction similar to Example 1 was carried out without using di-n-butylmethylsulfonium iodide as a catalyst. As a result, only trace amounts of HFPO were produced, and almost all HFP was recovered.

Example 2 The same reaction as in Example 1 was carried out at a reaction temperature of 30°C using 0.04 g of di-n-butylmethylsulfonium iodide instead of 0.12 g as a catalyst, and the conversion rate of HFP was 73%. The selectivity rate for HFPO was 61%.

Example 3 The same reaction as in Example 1 was carried out using 0.20 g of di-n-butylmethylsulfonium iodide as a catalyst instead of 0.12 g, and at a reaction temperature of -10°C instead of 0°C. The HFP conversion rate was 88% and the HFPO selectivity was 71°C.

Example 4 The same reaction as in Example 1 was carried out, but instead of 0.12 g of di-n-butylmethylsulfonium iodide,
When carried out using 0.12 g of tri-n-butylsulfonium tetrafluoroborate, the conversion of HFP was 71% and the selectivity of HFPO was 67%.

Example 5 The same reaction as in Example 1 was carried out, but instead of 0.12 g of di-n-butylmethylsulfonium iodide,
Methyldioctadecylsulfonium iodide
When 0.30 g was used, the conversion of HFP was 89% and the selectivity of HFPO was 72% in a reaction time of 20 minutes.

Example 6 The same reaction as in Example 1 was carried out, but instead of 0.12 g of di-n-butylmethylsulfonium iodide,
When carried out using 0.20 g of tris(diethylamino)sulfonium difluorotrimethylsilicate, the conversion rate of HFP was 64% in 1 hour of reaction time.
The selectivity rate for HFPO was 63%.

Example 7 The same operation as in Example 1 is carried out, but instead of 20 ml of a sodium hypochlorite aqueous solution with an available chlorine concentration of 12%, highly refined white powder with an available chlorine content of 65% (the main component is hypochlorous acid) is used. Calcium) 4.6g in 20ml aqueous solution
When the reaction was carried out using , the conversion rate of HFP was 71% and the selectivity of HFPO was 46%.

Example 8 The same reaction as in Example 1 was carried out, but instead of 0.12 g of di-n-butylmethylsulfonium iodide,
Tris (N-methyl-N-octadecylamino)
Sulfonium difluorotrimethyl silicate
When 0.30 g was used, the conversion of HFP was 65% and the selectivity of HFPO was 69% in a reaction time of 1 hour.

Claims (1)

[Claims] 1. In producing hexafluoropropylene oxide from hexafluoropropylene using hypochlorite as an oxidizing agent, the reaction takes place in a two-phase system of an aqueous phase and an organic phase in the presence of a sulfonium salt. A method for producing hexafluoropropylene oxide, characterized by carrying out the following steps. 2. The method for producing hexafluoropropylene oxide according to claim 1, characterized in that a sulfonium salt represented by the general formula () is used as the sulfonium salt. _{R 1 , R 2 ,} R ₃ S R ₁ , R ₂ , and R ₃ S ions may form a heterocycle within the ion. _R1 ,
The size of R ₂ and R ₃ is calculated as the total number of carbon atoms contained in R ₁ , R ₂ and R ₃ , and the size of sulfonium ion 1
The number ranges from 6 to 100 pieces per piece. X represents an organic or inorganic anion. 3. The method for producing hexafluoropropylene oxide according to claim 1 or 2, characterized in that sodium hypochlorite or calcium hypochlorite is used as the hypochlorite.