JP2514384B2 - Method for producing hexafluoropropene oxide - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing hexafluoropropene oxide. More specifically, it relates to a method for producing hexafluoropropene oxide by oxidizing hexafluoropropene with oxygen.

[Conventional technology]

Hexafluoropropene oxide is an important compound as a synthetic raw material for various fluorine-containing compounds such as hexafluoroacetone and perfluoroalkyl vinyl ether, and its oligomer derivative is widely used as a lubricating oil, a heat medium, etc. in the high-tech field. ing.

As a method for producing such a useful hexafluoropropene oxide, various methods have been known so far, and the outline thereof is described in JP-B-61-2, which discloses the invention of the applicant's application.
It is described in Japanese Patent No. 1556. Among these methods, the examination of the oxidation reaction of hexafluoropropene with oxygen from the viewpoint of the reaction solvent is described in JP-B-45-11683.

In this oxidation reaction, saturated halocarbons such as 1,1,2-trichloro-1,2,2-trifluoroethane, trichlorofluoromethane, perfluoro (dimethylcyclobutane) and carbon tetrachloride are used as inert reaction solvents. Although it is
The yield of this reaction (conversion rate x selectivity) is low, at most 50-
It remains around 60%.

Further, since it is used as a solvent with a high vapor pressure in this reaction, the solvent is entrained when recovering the crude product in a gaseous state after completion of the reaction, before distilling the desired product,
There is a problem that a distillation step for separating the solvent must be provided. Furthermore, in industrial production, the same solvent is continuously used for a long period of time while being recovered, in which case trichlorotrifluoroethane and the like produces a large amount of hexafluoroacetone, and the use of CFC-based compounds is ozone. Due to the possibility of layer destruction, it is now a global issue.

[Problems to be solved by the invention]

An object of the present invention is to oxidize perfluoropropene with oxygen to produce perfluoropropene oxide,
There is no need for an extra separation operation for the reaction solvent used, and by using the same solvent repeatedly for a long period of time, by-products such as hexafluoroacetone are not by-produced, and the target product can be obtained in good yield. It has been found that the object of the present invention is achieved by using the perfluoropolyether compound represented by the general formula [I] as a reaction solvent.

[Means for solving problems]

Therefore, the present invention relates to a method for producing hexafluoropropene oxide, and the production of hexafluoropropene oxide is carried out by oxidizing the hexafluoropropene with oxygen by reacting a compound of the general formula RfO (XCF ₂ O) n (CF ₂ CF ₂ O) m (CF ₂ O) lRf ′ [I] (wherein Rf and Rf ′ are the same or different perfluoro lower alkyl groups, and X is a —CF (CF ₃ ) — group or —CF ₂ CF ₂ -group, and n
And m are each 0 or an integer of 1 to 100, and l
Is 0 or an integer of 1 to 200, n and m are not 0 at the same time, and each perfluorooxyalkylene group is randomly distributed in the main chain). It is done by

As a typical perfluoropolyether compound,
The following are conventionally known.

C ₃ F ₇ O (CF ₂ CF ₂ CF ₂ O) nC ₂ F ₅ [III] _{CF 3 O (CF 2 CF 2} O) m (CF 2 O) lCF 3 [V] The compound represented by the general formula [II] is obtained by a method of treating the terminal -COF group of a hexafluoropropene oxide oligomer with fluorine gas at a temperature of about 100 to 350 ° C (Japanese Patent Publication No. 62-10490). It is marketed under the trade name of NKL Kluber product Varielta and DuPont product Kleitex. The compound represented by the general formula [III] is obtained by completely fluorinating the compound obtained by ring-opening polymerization of tetrafluorooxetane, and is commercially available under the trade name of Daikin Denmum. Further, the compounds represented by the above general formulas [IV] to [VI] are obtained by removing the peroxide bond from the compound obtained by photopolymerization oxidation of hexafluoropropene, tetrafluoroethylene or both, and further completely fluorinating. Obtained by Montefruos, and is commercially available under the trade names of Fomblin Y, Fomblin Z, and Fomblin K.

Among these perfluoropolyether compounds, (CF ₂ O)
It is preferable to use the compound represented by the general formula [II] or [III] having no group.

In the oxidation reaction, in order to quickly disperse and remove the reaction heat and enable smooth control of the reaction, the boiling point and viscosity of the reaction solvent should be low, but if it is too low, the reaction pressure will increase and Since the solvent is entrained during the recovery of the crude product after the completion, a boiling point of about 140 ° C. or higher, preferably about 250 ° C. or higher is used.

The viscosity is generally about 1 to 1000 Cst (40 ° C), preferably about 10 to 400 Cst (40 ° C). Therefore, from this point of view, those having appropriate numbers of n, m and l in the general formula [I] are used. That is, the following is industrially available.

Compound [II]: Viscosity 2 to 1006Cst (40 ° C) MW660 to 10000 n = 2 to 58 Compound [III]: Viscosity 24 to 200Cst (40 ° C) MW2700 to 8400 n = 14 to 49 Compound [IV]: Viscosity 2 420Cst (40 ° C.) MW660 to 6800 n = 3 to 40, l = 1 or less Compound [V]: Viscosity 7 to 315 Cst (40 ° C.) MW1900 to 16230 n = 3 to 74, l = 21 to 189 Compound [VI]: Viscosity 15 to 105 Cst (40 ° C) For the reaction, a pressure reaction vessel, generally an autoclave is used, charged with a reaction solvent and hexafluoropropene, and heated to about 90 to 140 using an electric furnace or a heating bath.
C., preferably to a temperature of about 110 to 130.degree. C., and oxygen gas is added thereto from a cylinder or the like.

When the reaction scale is about 1 to 10 l, about 0.5 to 10 Nl of oxygen is added per batch in consideration of the controllability of the reaction. The total amount of oxygen charged is more than 1 time and less than about 2 times the theoretical amount.
It is twice. Regarding the reaction pressure, there is no special condition, but it is generally about 10 to 40 Kg / cm ² .

Regarding the amount of the solvent, it is preferable to use a large amount for dispersing and removing the reaction heat, but if it is used in an excessively large amount, the amount of gas volume decreases, which leads to an increase in the reaction pressure. It is used in an amount of about 10 to 60%, and when considering the reaction control and yield points comprehensively,
It is preferably used in an amount occupying 30 to 50%.

After completion of the reaction, the autoclave is returned to room temperature and the crude product is recovered as a gas. At this time, the problem of entrainment at the time of recovery, which occurs when another solvent is used, does not pose a problem when the reaction solvent of the present invention is used because the vapor pressure of the solvent is low.

〔The invention's effect〕

According to the method of the present invention, by using a perfluoropolyether compound as a reaction solvent, an extra separation operation of the solvent used is not required, and even if the same solvent is repeatedly used for a long time, hexafluoroacetone It is possible to obtain the target hexafluoropropene oxide in good yield without producing such by-products.

〔Example〕

 Next, the present invention will be described with reference to examples.

Example 1 After depressurizing the inside of a stainless steel autoclave with an agitator having an internal volume of 1.2 l, the viscosity was 17 Cst (40 ° C.) and the boiling point was 170 ° C./0.6.
Torr, 995 g (550 ml) of perfluoropolyether of the above-mentioned general formula [II] (where n = 10) and 220 g of hexafluoropropene were sequentially charged and heated by an external heater until the internal temperature reached 120 ° C. The internal pressure at this time is 22 kg /
It is cm ^2.

In this state, 0.8 Nl of oxygen gas is added, and after confirming the temperature rise (125 ° C) that shows the start of the reaction, the mixture is naturally cooled. When the internal temperature drops to 120 ° C, 0.8 to 2.0 Nl of oxygen gas is added again. Repeat this operation until the specified oxygen amount (28
Nl) and then aged for 20 minutes for a total reaction time of 3.3
It was time.

After completion of the reaction, the mixture was allowed to cool to room temperature, and the crude gas was collected in an empty cylinder cooled with a dry ice-methanol bath. The recovered amount is 220 g, and its composition, conversion rate, selectivity and yield (conversion rate / selectivity) by gas chromatography are shown in the table below.

Example 2 In Example 1, the viscosity was 389 Cst (40 ° C.) and the vapor pressure was 1 ×.
The above general formula [II] of 10 ⁻⁶ Torr (100 ° C.) (where n = 4
The perfluoropolyether compound of 0) was used.

Example 3 In Example 1, the viscosity was 24 Cst (40 ° C.) and the vapor pressure was 5 × 1.
0 ^-4 Torr (100 ° C) of the above general formula [III] (where n = 1
The perfluoropolyether compound of 6) was used, and the total oxygen charge was set to 25 Nl.

Example 4 In Example 3, the viscosity is 26 Cst (40 ° C.) and the vapor pressure is 1 × 1.
0 ⁻³ Torr (100 ° C.) of the above general formula [IV] (where n = 1
1, 1 = 0.28) perfluoropolyether compound was used.

Comparative Example In Example 3, trichlorotrifluoroethane was used as the reaction solvent.

The results of Examples 2 to 4 and Comparative Example are also shown in the following table.

Claims (2)

(57) [Claims] 1. When oxidizing hexafluoropropene with oxygen, RfO (XCF ₂ O) n (CF ₂ CF ₂ O) m (CF ₂ O) lRf ′ [I] (wherein Rf is used as a reaction solvent) And Rf ′ are the same or different perfluoro lower alkyl groups, X is a —CF (CF ₃ ) — group or a —CF ₂ CF ₂ — group, and n is
And m are each 0 or an integer of 1 to 100, and l
Is 0 or an integer of 1 to 200, n and m are not 0 at the same time, and each perfluorooxyalkylene group is randomly distributed in the main chain). A process for producing hexafluoropropene oxide, which is characterized in that 2. A perfluoropolyether compound having a viscosity of about 1 to 1000 Cst (40 ° C.) is used.
A method for producing hexafluoropropene oxide according to the item 1.