JPH0432068B2 - - 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 an improvement in 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 difficult to epoxidize in the same way as propylene and allyl chloride.

To date, several methods have been proposed for producing HFPO from HFP.
None of these methods can be said to be industrially advantageous.
For example, the method of oxidizing HFP to HFPO in an alkaline hydrogen peroxide medium as described in U.S. Pat. The method described below in which HFP is oxidized to HFPO with oxygen 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 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. . Furthermore, in these methods, increasing the HFP conversion rate lowers the HFPO selectivity.
In order to use HFP effectively, it is necessary to stop the reaction at a low HFP conversion rate, separate and recover unreacted HFP from HFPO, and reuse it. However, HFP
The boiling point of (-29.4℃) and the boiling point of HFPO (-27.4℃)
Since they are very close to each other and it is difficult to separate them by distillation, a special separation operation is required to separate them. For example,
A method of reacting HFP and bromine to form a high-boiling dibromine compound and separating it from HFPO, or a method described in the U.S. Patent No.
Extractive distillation separation methods described in specifications such as No. 3,326,780 and US Pat. No. 4,134,796 have been proposed, but all of them are complicated separation methods that significantly increase the production cost of HFPO.

The present inventors have conducted intensive studies to overcome the drawbacks of the conventional methods and to find a method for producing HFPO more easily and with higher yield than HFP. As described in 1981-105978 and 1981-113187, hypochlorite is used as an oxidizing agent, and in the presence of a specific catalyst, a two-phase aqueous phase and an organic phase is formed. The discovery was made using a new method of performing the reaction in a system.

However, when the above reaction method is carried out using various commercially available hypochlorite aqueous solutions and hypochlorite aqueous solutions prepared by the present inventors, even if the available chlorine concentration is the same, the hypochlorite used The reaction results varied greatly depending on the type of acid salt aqueous solution, and it was assumed that there were factors other than the available chlorine concentration that greatly influenced the reaction results. In addition, in the above reaction method, if the HFP conversion rate is increased or the ratio of hypochlorite to HFP is lowered,
It was observed that the HFPO selectivity decreased.

As a result of intensive studies to solve the above problems, the present inventors found that when the reaction is carried out in the presence of a specific amount or more of an inorganic base, stable reaction results can be obtained, and the reaction results can be dramatically improved. The present inventors have discovered that the present invention can be improved.

That is, in the present invention, hypochlorite is used as an oxidizing agent, and a phase transfer catalyst [however, ()-(
CH ₂ CH ₂ O−) Anionic or nonionic surfactant having _{an n} group (where m is 2 or more),
(Excluding nonionic surfactants with amine oxide groups and () amphoteric surfactants)
In order to produce hexafluoropropylene oxide from hexafluoropropylene by carrying out a reaction in a two-phase system of an aqueous phase and an organic phase in the presence of and hexafluoropropylene 1
The present invention provides a method for producing hexafluoropropylene oxide, characterized in that the reaction is carried out in the presence of an inorganic base of 0.1 gram equivalent or more per mole.

The first effect of the inorganic base in the method of the present invention is that a high HFPO selectivity can be obtained even when the conversion of HFP is increased. Therefore,
It is possible to increase the HFP conversion rate and reduce the amount of residual HFP without significantly impairing the HFPO selectivity, making it possible to obtain high-purity HFPO at a high yield without the need for a complicated separation process between HFP and HFPO. . A second effect of the inorganic base in the process of the present invention is that it allows good results to be obtained even at low ratios of hypochlorite to HFP. In the absence of inorganic base or in the presence of very small amounts of inorganic base, lowering the ratio of hypochlorite to HFP
Since the HFPO selectivity decreases and the residual available chlorine concentration decreases during the reaction, the HFP conversion rate may reach a plateau. Therefore, in order to obtain good results, it is necessary to react in the presence of a large excess of hypochlorite. It was necessary to carry out a reaction. However, according to the method of the present invention, only a small amount of hypochlorite is required, making it possible to reduce the cost of hypochlorite, make the reaction equipment more compact, and reduce wastewater treatment costs. .

The present invention will be explained in more detail below.

The hypochlorite used in the method of the present invention includes various hypochlorites, such as alkali metal salts such as sodium hypochlorite and potassium hypochlorite, or hypochlorite. Examples include alkaline earth metal salts such as calcium acid and barium hypochlorite. Among them, sodium hypochlorite and potassium hypochlorite are sometimes industrially produced in large quantities for uses such as bleach and disinfectants.
Since it can be obtained at low cost, it is suitable as the hypochlorite used in the method of the present invention.

In the absence of an inorganic base or in the presence of a very small amount of inorganic base, a large excess of hypochlorite relative to HFP is required to obtain high HFP conversion and high HFPO selectivity. In the presence of a certain amount of inorganic base, good reaction results can be obtained even when the amount of hypochlorite used is about 1.1 to 7 gram equivalents per mole of HFP. However, the amount of hypochlorite used is
It can be arbitrarily selected depending on the purpose and is not limited to the above range.

The catalyst used in the method of the present invention may be any catalyst that mediates the reaction between HFP in the organic phase and hypochlorite in the aqueous phase, that is, a so-called phase transfer catalyst. Examples include onium salts such as quaternary ammonium salts, quaternary phosphonium salts, quaternary arsonium salts, or the general formula [] R ₁ O-(CH ₂ CH ₂ O-) nR ₂ [] [However, n represents a positive integer of 3 or more, R ₁ and
R ₂ represents a substituted or unsubstituted hydrocarbon group having 1 to 30 carbon atoms. ] Lipophilic complexing agents for alkali metal ions, alkaline earth metal ions, etc. in hypochlorites such as polyethylene glycol derivatives or substituted products thereof, macrocyclic polyethers, and macrocyclic aminoethers represented by .

Specific catalysts used in the method of the present invention include JP-A-57-183773 and JP-A-58-105978.
The same catalysts as those exemplified in JP-A-58-113187 and JP-A-58-113187 can be mentioned. For example, examples of quaternary ammonium salts include trioctylmethylammonium chloride or tetra-n
Examples of the quaternary phosphonium salt include tetra-n-butylphosphonium bromide or n-amyltriphenylphosphonium bromide, and examples of the quaternary arsonium salt include tetraphenyl arsonium chloride and -butylammonium chloride. Triphenylmethylarsonium chloride is mentioned.

Examples of compounds represented by the general formula [] are:
Examples include compound [] and compound [].

n-C ₄ H ₉ O- (CH ₂ CH ₂ O-) ₁₀ nC ₄ H ₉ [] Examples of macrocyclic polyethers include dibenzo-18-crown-6 and dicyclohexyl-18-
Crown-6 is mentioned, and examples of macrocyclic aminoethers include compound [ ] and compound [ ].

Examples of inorganic bases used in the method of the present invention include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide, calcium hydroxide, and strontium hydroxide. , alkaline earth metal hydroxides such as barium hydroxide, and the like. These inorganic bases may be completely dissolved in the aqueous phase, or a portion may not be dissolved in the aqueous phase and may exist in the solid phase. Among various inorganic bases, sodium hydroxide is particularly popular due to its price, solubility in water,
It is suitable for the method of the present invention in terms of ease of handling and the like.

Although the amount of inorganic base used in the method of the present invention can be set arbitrarily, in order to obtain a substantial effect,
0.1 gram equivalent or more is used per mole of HFP used in the reaction. There is no upper limit to the amount of inorganic base, and unexpectedly for a reaction with HFPO, which was previously thought to be easily decomposed in a basic atmosphere, a high HFPO selectivity was obtained even at extremely high base concentrations. It will be done. However, the amount of inorganic base added is usually determined from a practical point of view, such as not making the viscosity too high or making the cost of the base too high.
Up to gram equivalents are used, preferably up to 30 gram equivalents, particularly preferably up to 15 gram equivalents. The entire amount of the inorganic base may be present in the reaction system from the beginning of the reaction, or in some cases, it may be added as appropriate during the reaction.

As the organic solvent for the organic phase used in the method of the present invention, an inert solvent that is substantially immiscible or sparingly miscible with the aqueous phase is used. Examples include aliphatic hydrocarbons such as n-hexane, alicyclic hydrocarbons such as cyclohexane, aromatic hydrocarbons such as toluene, ethers such as diisopropyl ether, and chlorinated methylene chloride. Hydrocarbons, 1,1,2-trichloro-1,2,2
Examples include, but are not limited to, chlorofluorocarbons such as -trifluoroethane and perfluorocarbons such as perfluorodimethylcyclobutane. When selecting an organic solvent, consider its solubility for the catalyst used in the reaction,
An appropriate organic solvent is selected in consideration of solubility in HFP and HFPO, reaction conditions such as reaction pressure and reaction temperature, etc.

As a method for carrying out the two-phase reaction of the present invention,
Although any of the batch method, semi-circulation method and distribution method are possible, the distribution method is preferable as an industrial reaction method.

In order to carry out the method of the present invention continuously and industrially advantageously, first, HFPO is synthesized from HFP by the two-phase reaction method of the present invention, and then the organic phase and the aqueous phase are phase-separated. A desirable method is to isolate HFPO from the separated organic phase, add HFP to the remaining organic phase containing the catalyst, and reuse it in the two-phase reaction. The method for carrying out the two-phase reaction at this time is HFP
Both countercurrent and cocurrent reactions of an organic phase containing a catalyst and an aqueous phase containing a hypochlorite and an inorganic base can be used. When carrying out a two-phase reaction, it is necessary to mix the two phases well in the reactor, and the mixing method used for this purpose is a commonly used method using a stirring blade or a static mixer. In the case of a countercurrent reaction, the two-phase system reaction and phase separation occur simultaneously. On the other hand, as a parallel flow reaction method,
Examples include tubular reactions and tank-type flow reactions, but in the case of tubular reactions, the two phases must pass through the tubular reactor in a finely dispersed state, so It is necessary to install a two-phase mixer in the reactor, or to have a structure in which the two-phase mixer is built inside the tubular reactor. In addition, in the co-current reaction, since a reaction solution in which an organic phase and an aqueous phase are mixed comes out of the two-phase reactor, it is necessary to separate the organic phase and the aqueous phase using a decanter. The aqueous phase after the two-phase reaction contains unreacted hypochlorite, chloride produced by the reaction of hypochlorite, an inorganic base, a part of the catalyst, and various reaction by-products. However, this aqueous phase is either disposed of as is, or if a large amount of unreacted hypochlorite or catalyst is present, the hypochlorite or catalyst is recovered from the aqueous phase. It is also possible to reuse it. Furthermore, the organic phase after the two-phase reaction contains generated HFPO, unreacted HFP, catalyst, and the like.
HFPO and HFP are easily isolated from this organic phase by a separation operation such as distillation. HFPO and
Since the organic phase from which HFP has been removed contains a catalyst, HFP can be added to this organic phase and recycled for reuse in the two-phase reaction. However, depending on the catalyst, a part of it will transfer to the aqueous phase during the two-phase reaction, reducing the catalyst content in the organic phase, so in that case, it is necessary to replenish the catalyst into the organic phase as appropriate. There is.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but these explanations are not intended to limit the present invention in any way.

The following types of sodium hypochlorite aqueous solutions were used.

Sodium hypochlorite aqueous solution [A] Effective chlorine concentration 12%, sodium hydroxide concentration
0.025 standard (commercially available sodium hypochlorite aqueous solution) Sodium hypochlorite aqueous solution [B] Effective chlorine concentration 10.2%, sodium hydroxide concentration
0.95 normal (prepared by blowing chlorine gas into a sodium hydroxide aqueous solution cooled to -10°C) Sodium hypochlorite aqueous solution [C] Effective chlorine concentration 3.8%, sodium hydroxide concentration
0.40 normal (Prepared by blowing chlorine gas into an aqueous sodium hydroxide solution cooled to -10°C.) Example 1 Sodium hydroxide was added to a 50 ml pressure bottle containing a stirring bar coated with fluororesin. 20 ml of sodium hypochlorite aqueous solution [A] (contains 40 mmol of sodium hypochlorite and 31 mmol of sodium hydroxide), 1,1,2-trichloro-1,
18 ml of 2,2-trifluoroethane (hereinafter abbreviated as F-113), 1.2 g (8 mmol) of HFP, and 0.12 g (0.3 mmol) of tri-n-octylmethylammonium chloride as a catalyst are charged. In this case, the molar ratio of sodium hydroxide to HFP is 3.8, and the molar ratio of sodium hypochlorite to HFP is 5.0. After cooling the reaction solution to 0° C., 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 60 minutes, the reaction product was analyzed by gas chromatography, and the HFP conversion rate was 99%, and the HFPO selectivity was found to be 99%.
It was 77%.

In this way, in the sodium hydroxide addition system, high
High HFP conversions are achieved, and high HFPO selectivity is maintained even at high HFP conversions.

Comparative Example 1 The same reaction as in Example 1 was carried out using a sodium hypochlorite aqueous solution [A] (without adding sodium hydroxide) instead of the sodium hypochlorite aqueous solution [A] with a sodium hydroxide concentration of 1.53 normal. The test was carried out using a sodium hydroxide concentration of 0.025 (Normal pH = 12.5). At this time, the molar ratio of sodium hydroxide to HFP was 0.06, and the molar ratio of sodium hypochlorite to HFP was 5.0. The reaction results after 60 minutes are HFP
The conversion rate was 87% and the HFPO selectivity was 57%.

In this case, the HFP conversion rate did not improve even if the reaction was continued any further.

Example 2 The same reaction as in Example 1 was carried out using an aqueous sodium hypochlorite solution [A] in which the sodium hydroxide concentration was 0.15N instead of 1.53N. In this case, the molar ratio of sodium hydroxide to HFP is 0.37
and the molar ratio of sodium hypochlorite to HFP is 5.0. The reaction result after 60 minutes is the HFP conversion rate.
The HFPO selectivity was 96% and 65%.

Example 3 The same reaction as in Example 1 was carried out, but instead of the sodium hypochlorite aqueous solution [A] with a sodium hydroxide concentration of 1.53 normal, 20 ml of sodium hypochlorite aqueous solution [B] 34 mmol of sodium and 19 mmol of sodium hydroxide), and 1.5 g (10 mmol) of HFP was used instead of 1.2 g of HFP. In this case, the molar ratio of sodium hydroxide to HFP is 1.9 and the molar ratio of sodium hypochlorite to HFP is 3.4. The reaction results after 15 minutes were HFP conversion of 95% and HFPO selectivity of 78.
%, and the reaction result after 30 minutes is HFP conversion rate of 99
%, and the HFPO selectivity was 76%.

Example 4 In a glass autoclave with an internal volume of 300 m, 150 ml of sodium hypochlorite aqueous solution [A] (300 mmol of sodium hypochlorite,
containing 60 mmol of sodium hydroxide), F-113
100ml, HFP11g (73mmol), tri-n-octylmethylammonium chloride 0.65g
(1.6 mmol) and reaction temperature from -10℃ to -
The reaction was carried out for 25 minutes at 5°C and a stirring speed of 1000 rpm.
The molar ratio of sodium hydroxide and HFP at this time is 0.82
and the molar ratio of sodium hypochlorite to HFP is 4.1. After the reaction was completed, the product was analyzed by gas chromatography and the HFP conversion rate was 96.
%, and the HFPO selectivity was 76%.

Example 5 A reaction similar to Example 4 was carried out using diisopropyl ether as the organic solvent in place of F-113, and the reaction time was 20 minutes. the result,
The HFP conversion rate was 90% and the HFPO selectivity was 70%.

Example 6 The same reaction as in Example 4 was carried out using a mixed solvent of benzene and n-hexane (volume ratio 1:
9) was used as the organic solvent, and 0.33 g (0.8 mmol) of tri-n-octylmethylammonium chloride was used instead of 0.65 g, and the reaction time was 30 minutes. As a result, the HFP conversion rate was 80% and the HFPO selectivity was 78%.

Example 7 The same reaction as in Example 1 was carried out using 5.7 ml of sodium hypochlorite aqueous solution [B] (sodium hypochlorite 9.6 mmol,
containing 5.4 mmol of sodium hydroxide). In this case, sodium hydroxide and HFP
The molar ratio of sodium hypochlorite and
The molar ratio of HFP is 1.2. The reaction results after 15 minutes are
HFP conversion was 50% and HFPO selectivity was 73%.

Example 8 The same reaction as in Example 1 was carried out using 15.2 ml of sodium hypochlorite aqueous solution [C] (sodium hypochlorite) instead of sodium hypochlorite aqueous solution [A] with a sodium hydroxide concentration of 1.53 normal 9.6 mmol, containing 6.1 mmol of sodium hydroxide). In this case, sodium hydroxide and
The molar ratio of HFP is 0.76, and the molar ratio of sodium hypochlorite to HFP is 1.2. The reaction results after 15 minutes were 77% HFP conversion and 74% HFPO selectivity.

Example 9 A static mixer (length 150 mm,
HFPO is synthesized from HFP using a continuous reaction device equipped with 1 (built-in twisted vane type mixing element), 2 tubular reactors (inner volume 160 ml), 3 decanters, HFPO distillation tower 4, and organic phase storage tank (inner volume 1000 ml) 5. did. The static mixer 1, tubular reactor 2 and decanter 3 are cooled to -10°C, and the pressure is maintained at 3 kg/cm ² (gauge) with nitrogen gas. First, a F-113 solution containing tri-n-octylmethylammonium chloride (0.045 mol/) was
Circulate inside the reactor at a flow rate of 36 ml/min, and
An aqueous solution containing sodium hypochlorite (2.0 mol/) and sodium hydroxide (0.78 mol/) was added to the
It is supplied to the static mixer 1 at a flow rate of ml/min, and simultaneously discharged from the decanter 3. Then HFP 2.10
The reaction is started by feeding the organic phase line before the static mixer 1 at a flow rate of g/min (14.0 mmol/min). In this case, the molar ratio of sodium hydroxide to HFP in the part of the tubular reactor 2 is 1.3, and the molar ratio of sodium hypochlorite to HFP is 3.4. The organic phase and the aqueous phase are finely dispersed in the static mixer 1, and pass through the tube mixer 2 in a finely dispersed state.
During this time, the reaction between the two phases progresses. After the reaction passes through the tubular reactor 2, it is separated into an organic phase and an aqueous phase by a decanter 3, the aqueous phase is discharged from the reactor, and the organic phase containing the produced HFPO is sent to the HFPO distillation column 4. The produced HFPO and unreacted HFP are distilled from the HFPO distillation column 4, but the average distillation rate of HFPO from 1 hour to 2 hours after the start of the reaction is
1.59 g/min (9.6 mmol/min), HFP
The average distillation rate is 0.18 g/min (1.2 mmol/
min). The HFPO and HFP distilled organic phases are sent to an organic phase storage tank 3, from where they are circulated again to the static mixer 1.

Example 10 Using the same reaction as in Example 1 as a catalyst, tri-n
-Octylmethylammonium chloride 0.12g
The results obtained by selecting 0.20 g of Compound [V] as a representative example of a lipophilic complexing agent instead of are shown below. In addition, as an aqueous solution, commercially available effective chlorine concentration
10 ml of a 12% sodium hypochlorite solution was used by adding sodium hydroxide to make the sodium hydroxide concentration 2.03N. Also, as an organic solvent, instead of 18ml of F-113, use 10ml of toluene and F-113.
-113 10ml of mixed solvent was used. HFP filling amount is
The test was carried out using 1.0 g (6.7 mmol). In this case, the molar ratio of sodium hydroxide to HFP is 3.0, and the molar ratio of sodium hypochlorite to HFPO is 3.0. As a result of the reaction at 0℃ for 60 minutes, the HFP conversion rate was
The HFPO selectivity was 75% with a rate of over 99%.

Comparative Example 2 The same reaction as in Example 10 was carried out, except that 10 ml of a commercially available sodium hypochlorite aqueous solution with an effective chlorine concentration of 12% (sodium hydroxide concentration: 0.02 normal) was used as the aqueous solution. In this case, the molar ratio of sodium hydroxide to HFP is 0.03, and the molar ratio of sodium hypochlorite to HFP is 3.0. As a result of the reaction at 0°C for 60 minutes, the HFP conversion rate was 78%, and the HFPO
The selection rate was 69%. In addition, even after 120 minutes of reaction at 0°C, the HFP conversion rate was 80%, and HFPO
The selectivity was 63%, and almost no improvement in HFP conversion was observed.

[Brief explanation of drawings]

Figure 1 shows the results obtained from HFP by the method of the present invention.
An example of an implementation apparatus for continuously producing HFPO is shown.

Claims (1)

[Claims] 1. A phase transfer catalyst using hypochlorite as an oxidizing agent [provided that an anionic phase transfer catalyst having ()-(CH ₂ CH ₂ O-) _n group (however, m is 2 or more) or in a two-phase system of an aqueous phase and an organic phase in the presence of a nonionic surfactant (excluding () a nonionic surfactant having an amine oxide group, and () an amphoteric surfactant). When performing the reaction to produce hexafluoropropylene oxide from hexafluoropropylene, use a previously prepared aqueous hypochlorite solution with a pH of 12.5 or higher, and add 0.1 grams per mole of hexafluoropropylene. A method for producing hexafluoropropylene oxide, characterized in that the reaction is carried out in the presence of an equivalent or more amount of inorganic base.