JPH0330593B2 - - 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 propylene 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, various methods have been proposed for epoxidizing HFP that are different from those for hydrocarbon olefins and chlorinated hydrocarbon olefins, but none of them are industrially advantageous.
It cannot be said that it is a manufacturing method for HFPO.

Previously, in an alkaline hydrogen peroxide medium as described in U.S. Pat. No. 3,358,003,
Method of oxidizing HFP to HFPO or Special Publication 1977
A method of oxidizing HFP to HFPO with oxygen in the presence of an inert solvent, which is described in Japanese Patent No. 11683, is known as a typical method for producing HFPO. However, with any of these methods, it is difficult to control the reaction, it is difficult to separate and suppress the produced HFPO, or a large amount of by-products are produced, making it impossible to obtain HFPO in a high yield. do not have. Furthermore, in these methods, increasing the HFP conversion rate lowers the HFPO selectivity, so in order to use HFP effectively, it is necessary to stop the reaction at a low HFP conversion rate and separate and recover unreacted HFP from HFPO. and need to be reused. 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 them by distillation, so special separation operations are required to separate them. Needed. Examples include, e.g. HFP
and bromine to form a high-boiling dibrome compound.
A method for separating HFPO or US Patent No.
Extractive distillation separation methods such as those described in No. 3,326,780 and US Pat. No. 4,134,796 have been proposed, but all of them are complicated separation methods and significantly increase the production cost of HFPO.

On the other hand, as an oxidation method using hypochlorite,
A system in which a polar solvent such as acetonitrile or diglyme is added to an aqueous hypochlorite solution, and it is more effective than HFP.
HFPO is known to be produced [IZV.
AKAD.NAUK.SSSR, SER, KHIM., 79 ,
(11) 2509], but when the present inventors investigated this method, the selectivity of HFPO was around 10%, and it was not possible 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 the troublesome step of recovering the polar solvent from the reaction system after the reaction. From the above points, this reaction method cannot be used as a practical HFPO production technology either.

The inventors of the present invention overcame these drawbacks of conventional methods and conducted extensive research to find a method to produce HFPO more easily and with higher yield than HFP. , and completed the present invention by discovering that HFPO can be obtained in a higher yield than HFP by carrying out the reaction in a two-phase system of an aqueous phase and an organic phase in the presence of a quaternary arsonium salt.

That is, the present invention uses hypochlorite as an oxidizing agent to produce hexafluoropropylene oxide from hexafluoropropylene.
The present invention provides a method for producing hexafluoropropylene oxide, which is characterized in that the reaction is carried out in a two-phase system of an aqueous phase and an organic phase in the presence of a quaternary arsonium salt.

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, HFPO can be obtained with high selectivity even if the conversion rate of HFP is increased. This seems to be because HFPO decomposition is less likely to occur when it comes into contact with an aqueous solution. 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,
Since a quaternary arsonium salt is contained and the remaining organic phase can be recycled and reused in the reaction as it is, recovery of the catalyst from the solvent is very simple.

As described above, the method of the present invention can achieve high yield.
HFPO can be obtained and the manufacturing process becomes very simple. Therefore, when implementing the method of the present invention, the construction cost and operating cost of the reactor are reduced, 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 the hypochlorite 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, sodium hypochlorite and calcium hypochlorite in particular are industrially mass-produced for use as bleaches, disinfectants, etc., and can be obtained at low cost. Suitable as an acid salt.

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 effective chlorine concentration is too low, it is necessary to handle a large amount of aqueous phase, which is 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, it is usually
The amount of hypochlorite ion per mole of HFP is preferably in the range of 0.5 to 30 gram equivalents, particularly preferably in the range of 0.8 to 10 gram equivalents.

The quaternary arsonium salt used in the method of the present invention has an affinity for the organic phase or both the organic phase and the aqueous phase, and can act as a medium for the reaction between the two phases. Any quaternary arsonium ion may be used as long as it can exist stably under the reaction conditions of the present invention. Examples thereof include tetraphenylarsonium chloride, phenylmethylarsonium chloride, tetraphenylarsonium bromide, and polymer derivatives thereof.

The amount of quaternary arsonium salt used in the method of the present invention is appropriately selected depending on the type of solvent, the required reaction rate, etc. , selected from the range of 0.0001 mol to 1 mol, particularly preferably
Selected from the range of 0.001 mol to 0.3 mol. Fourth
If the amount of the class arsonium salt is too small, a substantial reaction rate cannot be obtained, and if it is too large, the reaction rate is too fast and it becomes difficult to control the reaction.
This is economically disadvantageous because the cost burden of the quaternary arsonium salt increases.

The reaction of the present invention is carried out in a two-phase system 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. 4, which is poorly soluble in
The phase may be composed of a class arsonium salt and HFP, or furthermore, it may be a phase 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 that the water containing substantially most of the HFP has a poorly miscible organic phase and an aqueous phase containing hypochlorite. , it does not matter if there are other phases in this system. For example, the organic phase may be composed of two types of media with low compatibility, forming two phases, or a fourth phase may be formed.
The method of the present invention can be carried out even when the class arsonium salt is supported on an insoluble carrier and forms a third phase.

Examples of inert solvents that are substantially immiscible or poorly miscible with the aqueous phase for the organic phase used in the method of the present invention include, for example, n-hexane, n-octane, n-decane, etc. Aliphatic hydrocarbons; alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, and decalin; aromatic hydrocarbons such as benzene, toluene, and xylene; ethers such as diisopropyl ether and di-n-butyl ether;
Methylene chloride, chloroform, carbon tetrachloride, 1,
Chlorinated hydrocarbons such as 2-dichloroethane and chlorobenzene; 1,2-dichloro-1,1,2,2
- Chlorofluorocarbons such as tetrafluoroethane, fluorotrichloromethane, 1,1,2-trichloro-1,2,2-trifluoroethane, 1,1,2,2-tetrachloro-1,2-difluoroethane; Examples include perfluorocarbons such as fluorocyclobutane, perfluorodimethylcyclobutane, perfluorohexane, perfluorooctane, perfluorodecane, and hexafluorobenzene; or mixed solvents thereof. Among the various solvents mentioned above, fluorine-containing solvents such as chlorofluorocarbons and perfluorocarbons have high solubility for HFP and HFPO, and are particularly suitable for the method of the present invention. In addition, chlorinated hydrocarbons generally have high solubility in quaternary arsonium 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,
It is determined depending on the reaction solution composition, the desired reaction rate, etc., but it is usually desirable to range from -25°C to 100°C.
The temperature range is particularly preferably from -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. Furthermore, if the reaction temperature is too high, the decomposition of HFPO will become significant and the HFPO selectivity will decrease.

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 depends on the type of organic phase,
It is selected depending on the composition, but usually from 1 atm to 20
A range of atmospheric pressure is desirable.

As a reaction method when carrying out the present invention, any of batch type, semi-flow type and flow type reaction methods can be used. Examples include, for example, a countercurrent reaction or a cocurrent reaction between an organic phase containing HFP and a quaternary arsonium salt and an aqueous phase containing hypochlorite. These methods are easily carried out in commonly used countercurrent or cocurrent reactors.
Furthermore, since substantially all of the HFPO produced by the reaction is contained in the organic phase, HFPO can be easily isolated and purified from the organic phase by a separation operation such as distillation. The remaining organic phase from which HFPO has been removed contains a quaternary arsonium salt, and this organic phase can be recycled and reused in the reaction as it is.

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 0.02 g (0.04 mmol) of tetraphenylarsonium hydrochloride (Ph ₄ AsCl.HCl) as a catalyst. Next, this reaction solution is cooled to 0° C., and then a stirrer in the reaction vessel is rotated using a magnetic stirrer 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 contained in the chloroform phase was removed.
and HFPO were quantified by gas chromatography, and the conversion rate of HFP was 73%, and the selectivity of HFPO was
It was 72%.

Comparative Example 1 The same reaction as in Example 1 was carried out using the catalyst tetra-n-
This was done without using butylsulfonium bromide. As a result, the production of HFPO is in trace amounts;
Almost all HFP was recovered.

Example 2 The same reaction as in Example 1 was carried out using the catalyst Ph ₄ AsCl.
Reaction temperature using 0.01g instead of 0.02g HCl
When carried out at 20℃, the conversion rate of HFP was 67%,
The selectivity of HFPO was 60%.

Example 3 When the same reaction as in Example 2 was carried out at a reaction temperature of 40°C, the conversion rate of HFP was 80% and the selectivity of HFPO was 52%.

Example 4 The same reaction as in Example 1 was carried out using the catalyst Ph ₄ AsCl.
0.04g was used instead of 0.02g of Hcl, and the reaction temperature was 0.
When the reaction temperature was -10℃ instead of ℃,
The HFP conversion rate was 62% and the HFPO selectivity was 74%.

Example 5 The same reaction as in Example 1 was carried out using Ph ₄ AsCl・HCl
When 0.01 g of triphenylmethylarsonium chloride was used instead of 0.02 g and the reaction temperature was 1 hour instead of 15 minutes, the conversion of HFP was 69%, the selectivity of HFPO was 68%, and Ta.

Example 6 Perform the same operation as Example 1, but with the effective chlorine concentration
Instead of 20ml of a 12% sodium hypochlorite aqueous solution, use 20ml of an aqueous solution containing 4.6g of highly bleached powder (main ingredient is calcium hypochlorite) with an effective chlorine content of 65%, and the reaction time is 15 minutes. When the reaction was carried out for 30 minutes, the conversion rate of HFP was 80%.
The selectivity rate for HFPO was 56%.

Claims (1)

[Claims] 1. When producing hexafluoropropylene oxide from hexafluoropropylene 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 quaternary arsonium salt. A method for producing hexafluoropropylene oxide, characterized by: