JPH0470314B2 - - 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 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 with HFPO in an alkaline hydrogen peroxide medium as described in US Pat. No. 3,358,003, or the presence of an inert solvent as described in Japanese Patent Publication No. 11683/1983 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 control the decomposition of the produced HFPO, or a large amount of by-products are produced, making it impossible to obtain HFPO in a high yield. . Furthermore, in these methods, when increasing the HFP conversion rate, the HFPO selectivity decreases.
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, 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. 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. 3326780 and U.S. Patent No. 4134796 have been proposed, but all of them are complicated separation methods and significantly increase the production cost of HFPO. be.

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. We have discovered a new method for performing reactions in this 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. Furthermore, they discovered that HFPO can be produced continuously at a high yield equivalent to batch reaction by conducting the reaction in a controlled reactor, leading to the completion of the present invention.

That is, the present invention uses hypochlorite as an oxidizing agent, performs a reaction in a two-phase system of hydrogen and an organic phase in the presence of a specific catalyst, and produces hexafluoropropylene oxide from hexafluoropropylene. In the presence of 0.1 gram equivalent or more of an inorganic base per mol of hexafluoropropylene,
The present invention also provides a method for continuously producing hexafluoropropylene oxide, which is characterized by carrying out a flow reaction in a tubular reactor.

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, the amount of hypochlorite used may be small, so it is possible to reduce the cost of hypochlorite, downsize the reaction apparatus, and reduce wastewater treatment cost.

The present invention will be explained in more detail below.

The hypochlorite used in 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 and barium hypochlorite. 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 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, but In the presence of a suitable 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 as long as it mediates the reaction between HFP in the organic phase and hypochlorite in the aqueous phase. Examples include onium salts such as quaternary ammonium salts, quaternary phosphonium salts, and quaternary arsonium salts, or lipophilicity toward alkali metal ions and alkaline earth metal ions in hypochlorite salts. Examples include, but are not limited to, complexing agents.

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 butylammonium chloride, such as tetra-n-butylphosphonium bromide or n-amyltriphenylphosphosulfonium bromide, and examples of the quaternary arsonium salt include tetraphenyl arsonium chloride. Alternatively, triphenylmethylarsonium chloride may be used, but examples of lipophilic complexing agents include macrocyclic polyethers, macrocyclic aminoethers, and polyethylene glycol derivatives.

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. and alkaline earth metal hydroxides such as barium hydroxide. 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 particular upper limit for the amount of inorganic base, which is unexpected for the HFPO reaction, which was previously thought to be easily decomposed in a basic atmosphere.
High HFPO selectivity can be obtained even at extremely high base concentrations. However, the amount of inorganic base added is usually within 100 g equivalent per mole of HFP, which is determined from practical viewpoints such as not making the viscosity too high or making the cost of the base too high. , preferably within 30 gram equivalents,
Particularly preferably, an amount of 15 gram equivalent or less is used.
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 continuously carrying out the two-phase reaction of the present invention, a flow method in a tubular reactor is preferable.

In order to carry out the method of the present invention continuously and industrially advantageously, first, HFP is converted to HFPO by the two-phase reaction method in a tubular reactor of the present invention.
After synthesis, the organic phase and aqueous phase are separated, HFPO is isolated from the phase-separated organic phase, HFP is added to the remaining organic phase containing the catalyst, and the reaction is carried out in a two-phase system in a tubular reactor. The preferred method is to use When conducting a two-phase reaction in a controlled reactor, it is necessary to mix the two phases well in the reactor, and the mixing method that is commonly used for this purpose is to use a stirring blade or a static mixer. used. In other words, in the case of a tubular reaction, the two phases inside the tubular reactor must pass through in a finely dispersed state.
It is necessary to install a two-phase mixer in front of the tubular reactor, or to have a structure in which the two-phase mixer is built inside the control reactor. Furthermore, since a reaction solution in which an organic phase and an aqueous phase are mixed comes out of the tubular reactor, it is necessary to separate the organic phase and the aqueous phase using a decanter or the like. 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
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 a 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.

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 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 passed through the tubular reactor 2 in a finely dispersed state.
During this time, the reaction between the two phases progresses. The reaction liquid that has passed through the tubular reactor 2 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 organic phase from which HFPO and HFP have been distilled is sent to the organic phase storage tank 5, and from there it is circulated again to the static mixer 1.

Comparative Example 1 A reaction with the same reaction solution composition as in the reaction in the tubular reactor of Example 1 was carried out in a batch reaction in a pressure-resistant glass autoclave with an internal volume of 300 ml. In this case, the reactor was cooled by cooling the outside with a -10°C refrigerant, and further cooling the reactor by circulating a -10°C refrigerant from the inside through a stainless steel corrugated tube.

The reaction solution composition consists of the following and.

F-113 solution containing tri-n-octylmethylammonium chloride (0.045 mol/):
72ml Aqueous solution containing sodium hypochlorite (2.0 mol/) and sodium hydroxide (0.78 mol/): 48 ml HFP: 4.20 g (28 mmol) After the reaction solution temperature reaches -10°C, stir the reaction mixture. When the reaction was started, the HFP conversion rate after 2.6 minutes was approximately 99%, and the HFPO selectivity was 49%.

Comparative Example 2 A flow reaction was carried out in a tank reactor with the same reaction solution composition as in the reaction in the tubular reactor of Example 1, except that the catalyst concentration was reduced to 1/3.

As the tank-type reactor, an autoclave made of pressure-resistant glass and having an internal volume of 300 ml, which is the same as that used in Comparative Example 1, was used.

A flow reaction was carried out by continuously supplying the reaction raw material to the tank reactor and continuously drawing out the reaction liquid so that the amount of reaction liquid in the tank reactor was about 120 ml.

Changes in the reaction results were investigated by changing the average residence time in the tank reactor by changing the feed rate of the reaction raw materials.

The reaction results were confirmed by gas chromatography analysis of the effluent.

As a result, the HFP conversion rate at a residence time of 10 minutes was 54
%, but even when the residence time was increased to 30 minutes, the HFP conversion rate was 56%, and the HFP conversion rate hardly increased.

Comparative Example 3 A flow reaction was carried out in the same manner as in Comparative Example 2, except that a multi-stage reactor made of pressure-resistant glass (8 tanks, total volume 240 ml) was used as the reactor.
Even when the residence time was extended to 30 minutes, the HFP conversion rate reached a ceiling and it was not possible to obtain a conversion rate of 85% or higher.

Comparative Example 4 The same operation as in Example 1 was carried out using sodium hypochlorite (2.0 mol/) and sodium hydroxide (0.78 mol/).
Instead of an aqueous solution containing sodium hypochlorite (2.0 mol/) and sodium hydroxide (0.02 mol/), an aqueous solution (PH=12.4) was used. In this case, the molar ratio of sodium hydroxide to HFP in the section of tubular reactor 2 is 0.03, and the molar ratio of sodium hypochlorite to HFP is 3.4.
It is. As a result, the average distillation rate of HFPO from distillation column 4 was 0.96 g/min (5.81 mmol/min), and the average distillation rate of HFP was 0.67 g/min (4.48 mmol/min).
mmol/min).

[Brief explanation of the drawing]

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. 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 catalyst,
In producing hexafluoropropylene oxide from hexafluoropropylene, a flow reaction is carried out in a tubular reactor in the presence of an inorganic base of 0.1 gram equivalent or more per mole of hexafluoropropylene. Continuous production method for fluoropropylene oxide. 2 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 catalyst,
In producing hexafluoropropylene oxide from hexafluoropropylene, a flow reaction is carried out in a tubular reactor in the presence of an inorganic base of 0.1 gram equivalent or more per mole of hexafluoropropylene. After synthesis, the organic phase and the aqueous phase are separated, hexafluoropropylene oxide is isolated from the phase-separated organic phase, hexafluoropropylene is added to the remaining organic phase containing the catalyst, and it is reused in the two-phase reaction. , a method for continuously producing hexafluoropropylene oxide, which comprises continuously producing hexafluoropropylene oxide.