JPH01193256A - Production of hexafluoropropylene oxide - Google Patents

Abstract

PURPOSE:To easily obtain the above compound useful as a synthetic intermediate for a fluorine-containing compound, in high yield, by reacting hexafluoropropylene in a binary phase system consisting of an aqueous phase and an organic phase, using a hypochlorous acid salt as an oxidizing agent in the presence of a quaternary phosphonium salt. CONSTITUTION:Hexafluoropropylene oxide (abbreviated as HFPO) can be produced by reacting hexafluoropropylene (abbreviated as HFP) in the presence of an organic solvent (e.g., chlorofluorocarbons) and a quaternary phosphonium salt using a hypochlorous acid salt as an oxidizing agent at -25-+100 deg.C. The quaternary phosphonium salt used in the above reaction is those containing at least one alkyl group or its substituted group, e.g., tetra-n-butyl phosphonium bromide. The reaction system is a mixture of an organic phase scarcely miscible with water and an aqueous phase containing the hypochlorous acid salt. HFPO is a synthetic intermediate for a fluorine-containing compound such as hexafluoroacetone, perfluorovinyl ether, etc., and the polymer of HFPO is useful as a thermal medium, lubricant oil, etc.

Description

Detailed Description of the Invention The present invention provides hexafluoropropylene oxide (hereinafter referred to as
The present invention relates to a method for producing HFPO (abbreviated as HFPO). More specifically, the present invention relates to a method for producing HFPO from hexafluoropropylene (hereinafter abbreviated as RFP) using hypochlorite as an oxidizing agent.

HFPO is an intermediate for producing useful fluorine-containing compounds such as hexafluoroacetone and perfluorovinyl ether, and the polymer of HFPO is used as a heating medium, W
It has a wide range of uses such as R lubricant.

HFPO can be produced by the epoxidation reaction of RFP, but because RFP has very different chemical properties from hydrocarbon olefins like propylene and chlorinated hydrocarbon olefins like allyl chloride, liver P 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 RFP using the chlorohydrin method, chlorohydrin is unstable and decomposes into carbonyl compounds, so 1(F
It is not possible to direct them to PO.

Therefore, various methods have been proposed for epoxidizing HFP that are different from those for hydrocarbon olefins and chlorinated hydrocarbon olefins, but all of them are industrially advantageous (IFPO). It cannot be said that it is a manufacturing method.

Previously, HF in a medium of alkaline hydrogen peroxide as described in U.S. Pat.
Method of oxidizing P to HFPO, or Japanese Patent Publication No. 45-1)
The method of oxidizing IFP to oxidized PO with oxygen (in the presence of an inert solvent) described in Japanese Patent No. 683 is known as a typical method for producing oxidized PO. however,
In any of these methods, it is difficult to control the reaction, and the generated HF
HFPO cannot be obtained in high yield because it is difficult to suppress the decomposition of PO or because a large amount of by-products are generated. Furthermore, in these methods, increasing the RFP conversion rate lowers the HFPO selectivity;
In order to use HFPO effectively, it is necessary to stop the reaction at a low RFP conversion rate, separate and recover unreacted RFP from HFPO, and reuse it. However, the boiling point of HFP (-29.4℃
) and HFPO have very close boiling points (-27.4°C), and it is difficult to separate them by distillation, so a special separation operation is required for their separation. Examples include, for example, a method in which phosphorus is reacted with odor to form a high boiling point dibromine and separated from HFPO, or US Pat. No. 3,326,780, US Pat. No. 4,134.
Extractive distillation separation methods, etc., described in the specification of No. 796, etc., have been proposed, but all of them are complicated separation methods, and
This significantly increases the cost of manufacturing POI.

On the other hand, as an oxidation method using hypochlorite, it is known that HFPO is generated from IFP (in a system in which a polar solvent such as acetonitrile or diglyme is added to an aqueous hypochlorite solution) (IZV, ' AKAD, NAUK, 5
SSR, SER, WHIM,, Yu (1)) 2509)
However, when the present inventors investigated this method, the selectivity for PO was around 10%, and a high yield could not be obtained. The reason for this is thought to be that since this reaction system is a homogeneous mixture of a polar solvent and an alkaline hypochlorite aqueous solution, the IFPO (formed) easily reacts with water and decomposes under alkaline conditions. It will be done. Furthermore, this reaction method cannot be used as a practical nppo production technique because it also requires the troublesome step of recovering the polar solvent from the reaction system after the reaction.

The present inventors have overcome the drawbacks of such conventional methods and have
As a result of intensive research to find a method to produce HFPO more easily and with higher yield than FP, we used hypochlorite as an oxidizing agent and separated the aqueous and organic phases in the presence of a quaternary phosphonium salt. The present invention was completed based on the discovery that HFPO can be obtained in a higher yield than IFP when the reaction is carried out in a two-phase system.

That is, the present invention uses hypochlorite as an oxidizing agent,
In the production of hexafluoropropylene oxide from hexafluoropropylene in the presence of an organic solvent and a quaternary phosphonium salt, (al quaternary phosphonium salt contains at least one alkyl group or a substituted form thereof) Provided is a method for producing hexafluoropropylene oxide, which is a quaternary phosphonium salt and is characterized in that (b) a reaction is carried out by mixing an organic phase that is poorly miscible with water and an aqueous phase containing hypochlorite. It is something.

In the two-phase reaction of the present invention, substantially all RFP and IFPO (produced) are contained in the organic phase.
According to the method of the present invention, even if the conversion rate of RFP is increased,
HFPO can be obtained with high selectivity due to the following reasons:
Since the produced HFPO exists in a different phase from the alkaline aqueous solution, H
This seems to be because FPO is less likely to decompose. Therefore,
According to the method of the present invention, by increasing the HFP conversion rate, it is also possible to omit the complicated separation step of RFP and IFPO and the step of recycling I(FP).

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, the remaining organic phase from which HFPO has been removed contains quaternary phosphonium salts, and this remaining organic phase can be recycled and reused in the reaction as is, making recovery of the solvent and catalyst extremely easy. It's easy.

As described above, in the method of the present invention, HFPO can be obtained in high yield, and the manufacturing process is extremely simple.

Therefore, when implementing the method of the present invention, the construction cost and operating cost of the reactor are low, making it a very economical HF solution.
PO manufacturing process becomes 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, sodium hypochlorite and calcium hypochlorite in particular are industrially mass-produced for use as bleaches, disinfectants, etc., and can be obtained at low cost. Passed 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. Also, if the available chlorine concentration is too high, hypochlorite becomes unstable,
It becomes difficult to handle.

The ratio of hypochlorite to RFP can be selected arbitrarily, but in order to obtain a substantial reaction result, the ratio of hypochlorite ion to 1 mole of HFP is usually 0.5 to 30 g equivalent as hypochlorite ion. A range of gram equivalents is desirable, particularly preferably 0
．． It ranges from 8 gram equivalents to 10 gram equivalents.

It is desirable that the quaternary phosphonium used in the method of the present invention has affinity for the organic phase or both the organic phase and the aqueous phase.

As the quaternary phosphonium salt, for example, - formula (I)
Various quaternary phosphonium salts such as those represented by are used.

However, in formula (1), R5, R2, R3 and positions are the same or different from each other and each represents a hydrocarbon group that is substituted with a functional group that is inert under the reaction conditions, or is unsubstituted. The type and length of this hydrocarbon group are appropriately selected depending on the solvent used, the required reaction rate, etc.

Examples of the type of hydrocarbon group include an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, an aralkyl group, an alkenylaryl group, and particularly preferably an alkyl group, an aryl group, an aralkyl group, etc. is used. In addition, the length of the hydrocarbon group is usually selected from the range of 4 to 100 per quaternary phosphonium ion, preferably 8 as the total number of carbon atoms contained in R1, R2, R1 and ~. The number is selected from the range of 70, particularly preferably selected from the range of 10 to 50. The inert functional group that can be used to replace the above hydrocarbon group is limited depending on the reaction conditions, but halogen, acyl group, carboxyl group, ester group, nitrile group, alkoxyl group, etc. are usually used. In addition,
In formula (I), R1, R2 or R51, R2, R2 may be linked to each other to form a heterocycle, and R8,
It may be R□, R3, or a part of a hekapolymer compound.

Examples of quaternary phosphonium ions include tetraethylphosphonium ion, tetra-n-butylphosphonium ion, tri-n-octylethylphosphonium ion, cetyltriethylphosphonium ion, cetyltri-n-butylphosphonium ion, n-butyltriphenylphosphonium ion, n-amyltriphenylphosphonium ion, n-hexyltriphenylphosphonium ion, n-hebutyltriphenylphosphonium ion, methyltriphenylphosphonium ion, benzyltriphenylphosphonium ion, tetraphenylphosphonium ion, and the like.

As described above, various ions can be used as the quaternary phosphonium ion, but the present inventors have found that at least one of - R3, R, 马, and - in formula (1) is an alkyl group. It has been found that 1 or a substitute thereof has particularly excellent activity and 1 (FPO selectivity) and can be used in the method of the present invention.

When the structure of the quaternary phosphonium ion is other than that, for example, R
1) When R2, R1, and all of R7, R2, and R3 are composed of aryl groups, or R7, R2, and R3 are composed of an aryl group and a benzyl group, as in benzyltriphenylphosphonium ion. has a higher reaction activity and HFPO than those containing an alkyl group or a substituent thereof.
Selectivity becomes lower.

Although the reason for this is not clear, it may be because the aromatic rings in the oryl group and benzyl group have an adverse effect on the ionic state of the phosphonium ion.

The anion hook in formula (1) is not particularly limited (various anions can be used, but halogen ions, various mineral acid ions other than halogen ions, organic acid ions, etc. are usually used).

Examples of anion hooks include chloride ion, bromide ion, iodide ion, fluoride ion, hydrogen sulfate ion, sulfate ion, nitrate ion, phosphate ion, perchlorate ion,
Examples include p-nitoluenesulfonic acid ion, and particularly preferred are chlorine ion and bromide ion.

The amount of quaternary phosphonium salt used in the method of the present invention is appropriately selected depending on the type of solvent, the required reaction rate, etc., but is usually based on 1 gram equivalent of hypochlorite ion used. , 0.0001 mol to 1 mol, particularly preferably 0.001 mol to 0.3 mol. If the amount of the quaternary phosphonium 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 as the cost burden 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 is preferably a phase consisting of IFP 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 that is hardly miscible with water, which contains substantially most of HFP, and an aqueous phase that contains hypochlorite. For example, if the organic phase is composed of two types of media with low compatibility, forming two phases, or if the quaternary phosphonium salt is insoluble. The method of the present invention can be carried out even when the material is supported on a carrier and forms a third phase.

When a water-miscible solvent such as acetonitrile or dioxane is used as an organic solvent, not only is the sequential decomposition of the generated HFPO remarkable, but also the recovery and recycling process of the solvent and quaternary ammonium salt becomes complicated. This cannot be a practical method for producing HFPO.

Furthermore, even when using a ta-containing solvent that is poorly miscible with water, as in the reaction under atmospheric pressure, R supplied to the organic solvent
If only a portion of FP is dissolved and most of the I (FP) is present in the gas phase, the conversion rate of HFP is extremely slow (and, although the reason is not clear, the reaction time becomes longer). Moreover, the HFPO selectivity is also low.Furthermore, in this method, it is difficult to carry out continuous reaction, so the productivity is low and it is economically disadvantageous.

In contrast, in the case of a two-phase reaction between an organic phase that is poorly miscible with water, which contains virtually all of the HFP, and an aqueous phase that contains hypochlorite, the reaction proceeds rapidly. ,HFPO
The selection rate is also high.

Also, according to such a reaction, after the reaction, substantially all of the HFPO and quaternary phosphonium salt are present in the organic phase, so isolation of IFPO and recycling of catalyst and solvent (as described above) is It is done extremely easily.

Note that in order to form an organic phase that is poorly miscible with water containing substantially all RFP, it is necessary to carry out the reaction in a pressurized system with an absolute pressure of 1 atm or more; depends on the type and reaction temperature.

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, 1.2
-Chlorinated hydrocarbons such as dichloroethane and chlorobenzene; 1.2-dichloro-1,1,2,2-tetrafluoroethane, ゛fluorotrichloromethane, 1.1.2
-) Lichloro 1.2.2-) Chlorofluorocarbons such as lifluoroethane, 1,1.2.2-tetrachloro-1,2-difluoroethane; perfluorocyclobutane, perfluorodimethylcyclobutane, perfluorohexane, perfluorocyclobutane, Examples include perfluorocarbons such as fluorooctane, perfluorodecane, and hexafluorobenzene; or mixed solvents thereof.

Among the above various solvents, fluorine-containing solvents such as chlorofluorocarbons and perfluorocarbons have high solubility of HFP and HFPO, and are particularly suitable for the method of the present invention.

In fluorine-containing solvents and mixed solvents containing fluorine-containing solvents, H
Due to the high solubility of FP and HFPO, virtually all HFP or HFPO can be easily removed even under low pressure.

It is suitable as a solvent for use in the method of the present invention because it can form an organic phase containing HFPO and, for reasons that are not clear, generally exhibits a high selectivity to HFPO.

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 20 to 20 times the O, OS of the aqueous phase, and particularly preferably 0.2 to 20 times the aqueous phase. 5
This is twice the range.

The reaction temperature when carrying out the present invention is determined depending on the amount of catalyst, the composition of the reaction liquid, the desired reaction rate, etc.
The temperature range is preferably from 5°C to 100°C, 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, not only will the reaction pressure increase, but liver P
The decomposition of O becomes significant, and the IFPO selectivity decreases.

The reaction pressure in carrying out the present invention is not particularly limited as long as it is sufficient to keep substantially all of the IFP-containing organic phase in the liquid phase. Therefore, the reaction pressure is selected depending on the type, composition, temperature, etc. of the organic phase, but a box pressure of 1 atm to 20 atm is usually desirable.

The reaction method for carrying out the present invention includes batch type,
Both semi-flow type and flow type reaction methods are possible. Examples include, for example, a countercurrent reaction or a cocurrent reaction between an organic phase containing RFP and a quaternary phosphonium salt and an aqueous phase containing a secondary chlorate. These methods are easily carried out in commonly used countercurrent or cocurrent reactors. In addition, since virtually all of the oxidized PO produced by the reaction is contained in the organic phase, HFPO can be easily isolated from the organic phase by a separation operation such as distillation to produce Ii. In the remaining organic phase from which HFPO has been removed, quaternary
This organic phase can be recycled directly into the reaction.

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 Content volume 5 containing a stirrer coated with fluororesin
1.1.2-)dichloro-1,2 in a 0+al pressure bottle
, 2-trifluoroethane (hereinafter abbreviated as F-1) 18-1%, 20 ml of an aqueous sodium hypochlorite solution with an effective chlorine concentration of 12%, 1.5 g (10 mmol) of RFP, and tetra-n- as a catalyst. Filled with 0.12g (0.3!5 mmol) of butylphosphonium bromide.Next, after cooling the reaction solution to 0℃, mix the reaction solution by rotating the stirrer inside the reaction vessel using a magnetic cooler. During the reaction, the reaction temperature is set to 0°C.
After 15 minutes, the rotation of the stirrer was stopped, the reaction solution was left standing to separate the aqueous phase and the F-1)3 phase, and the RFP and HFPO contained in the F-1)3 phase were separated by gas chromatography. The conversion rate of OPO was 79% when quantified by graphics.
The selectivity was 64%.

In this reaction, gas chromatography analysis shows that the amount of HFP present in the space of the reaction vessel is less than 1/500 of the amount of HFP present in the organic phase, and that it is almost absent in the aqueous phase. confirmed.

Furthermore, the PO produced by the reaction also shows a similar distribution.

Comparative Example 1 A reaction similar to Example 1 was carried out without using the catalyst tetra-n-butylphosphonium bromide. As a result, only trace amounts of hepatic PO were produced and almost all RFP was recovered.

Example 2 The same reaction as in Example 1 was carried out using 0.04 g of tetra-n-butylphosphonium bromide as a catalyst instead of 0.12 g.
When the reaction temperature was 20° C., the conversion of IFP was 68% and the selectivity of HFPO was 60%.

In this reaction, gas chromatography analysis shows that HFP present in the space of the reaction vessel is less than 1/500 of the HF and P present in the organic phase, and is almost absent in the aqueous phase. confirmed.

Furthermore, HFPO produced by the reaction also shows a similar distribution.

Example 3 When the same reaction as in Example 2 was carried out at a reaction temperature of 40° C., the conversion rate of RFP was 85% and the selectivity of HFPO was 53%.

In this reaction, gas chromatography analysis shows that 1(FP) present in the space of the reaction vessel is less than 1/500 of RFP present in the organic phase, and is almost absent in the aqueous phase. confirmed.

Furthermore, liver po produced by the reaction also shows a similar distribution.

Example 4 The same reaction as in Example 1 was carried out using 0.20 g of tetra-n-butylphosphonium bromide as a catalyst instead of 0.12 g.
g, and the reaction temperature is -10℃ instead of the reaction temperature 0℃.
℃, the conversion rate of IIFP was 71%, HFPO
The selectivity was 68%.

In this reaction, gas chromatography analysis has shown that the amount of phosphorus present in the space of the reaction vessel is less than 1/500 of the amount of HF4' present in the organic phase, and that it is almost absent in the aqueous phase. confirmed.

Furthermore, HFPO produced by the reaction also shows a similar distribution.

Example 5 The same reaction as in Example 1 was carried out using 0.12 g of n-amyltriphenylphosphonium bromide instead of 0.12 g of tetra-n-butylphosphonium bromide as a catalyst (
When the reaction temperature was 3 hours instead of 15 minutes, the liver P conversion rate was 62%.
, HFPO selectivity was 65%.

In addition, in this reaction, it was confirmed by gas chromatography analysis that the RFP present in the space of the reaction vessel was less than 1/500 of the RFP present in the organic phase, and almost completely absent in the aqueous phase. Ta.

Furthermore, HFPO produced by the reaction also shows a similar distribution.

Example 6 A reaction similar to Example 1 was carried out using chloroform instead of F-1)3 and 0.04 g (0.12 mmol) of tetra-n-butylphosphonium bromide instead of 0.12 g. , and instead of RFP 1.5g,
Using 0.6 g (4 mmol) of RFP, the conversion of RFP was 83% and the selectivity of HFPO was 5.
It was 9%.

In this reaction, the RFP present in the space of the reaction vessel is 0.5% of the HFP present in the organic phase,
It was confirmed by gas chromatography analysis that it was hardly present in the aqueous phase. Further, after the reaction, IFPO present in the space of the reaction vessel was 0.9% of the HFPO present in the organic phase, and was hardly present in the aqueous phase.

Example 7 The same operation as in Example 1 was carried out, but instead of 20 ml of sodium hypochlorite aqueous solution with an available chlorine concentration of 12% b, high-grade salashi powder with an available chlorine content of 65% (the main component was hypochlorous acid) was used. When the reaction was carried out for 30 minutes instead of 15 minutes using 20 ml of water-soluble ring containing 4.8 g of carlasim), the conversion rate of RFP was 85%, and the conversion rate of HFPO was 85%.
The selectivity was 58%.

Example 8 The same operation as in Example 1 was carried out, but the reaction was performed using 30 ml of a potassium hypochlorite aqueous solution with an available chlorine content of 7% instead of 20 ml of a sodium hypochlorite aqueous solution with an available chlorine concentration of 12%. The conversion rate of IIFP was 72.
%, the selectivity for HFPO was 63%'.

Example 9 When the same reaction as in Example 1 was carried out using 3.5 g of RFP instead of 1.5 g and using a reaction time of 30 minutes instead of 15 minutes, the conversion rate of RFP was 61. %,
The selectivity for HFPO was 56%.

Examples 10-13 Table 1 shows that the same operations as in Example 1 are performed, except that RFP
The experimental results are shown in which the amount used was 3.0 g, and the quaternary phosphonium salt, solvent, and reaction time were set to the conditions listed in Table 1.

In either case, 1) FP present in the space of the reaction vessel
IIFPO is less than 1/100 of that of IIFPO present in the organic phase, and IIFPO also shows almost the same distribution.

(Margin below) Table 1 *PHF represents perfluorohexane.

Comparative Example 2 A 20% aqueous sodium hydroxide solution (100 ml) was charged into a 200 ml flask equipped with a condenser, a thermocouple, a gas blowing tube, and a stirrer, and while maintaining the temperature at -10°C to -20°C, chlorine gas was added at a pl+ of 10 It was blown until it reached ~1).

After adding 40 ml of chlorobenzene and 0.5 g of benzyl 1-liphenylphosphonium chloride to the flask,
The condenser was cooled with dry ice-methanol until the temperature inside the flask reached 15°C. While stirring the contents in the neutral state, 22 g of HFP was slowly fed over 40 minutes, and then stirring was continued for an additional 2 hours while refluxing IFP and HFPO.

After the reaction, the low-boiling substances inside the flask were collected together with some toluene in a trap cooled with dry ice-methanol.

Analysis of the contents of the trap by gas chromatography showed that the conversion of RFP was 52% and the selectivity of HFPO was 23%.

Patent applicant: Asahi Kasei Industries, Ltd. Representative Patent Attorney Toru Hoshino

Claims (3)

[Claims] (1) In producing hexafluoropropylene oxide from hexafluoropropylene in the presence of an organic solvent and a quaternary phosphonium salt using hypochlorite as an oxidizing agent, (a) the quaternary phosphonium salt is , is a quaternary phosphonium salt containing at least one alkyl group or its substituted product, and (b) the reaction is carried out by mixing an organic phase that is poorly miscible with water and an aqueous phase containing hypochlorite. A method for producing hexafluoropropylene oxide, characterized by: (2) The method according to claim 1, characterized in that the reaction is carried out in a state in which substantially all of the hexafluoropropylene is dissolved in an organic phase that is poorly miscible with water. (3) The method according to claim 1 or 2, wherein the organic phase that is poorly miscible with water is composed of a fluorine-containing organic solvent.