JPH06107650A - Production of hexafluoropropene oxide - Google Patents

Abstract

PURPOSE:To remove the induction period of the initiation and to improve the yield in production of hexafluoropropene oxide by oxidizing hexafluoropropene with oxygen. CONSTITUTION:In the oxidation reaction, a mixture containing one or more kinds of compounds selected from the group of compounds represented by general formulae, F(CF2O)1COF, F(CF2O)mCF2COF or F(CF2O)nOCF2COF is added. This mixture is obtained as a by-product in the production of hexafluoropropene oxide by oxidizing hexafluoropropene with oxygen.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Hexafluoropropene oxide is used as a raw material for synthesizing various fluorine compounds and a raw material for oligomers. Various methods have been developed as a method for producing this hexafluoropropene oxide, and most of them are methods in which hexafluoropropene is used as a raw material and is oxidized to produce it. Although methods using hydrogen peroxide and hypochlorites as oxidants have been known for a long time, the former requires extremely low temperatures, and in both cases, a water-soluble organic solvent or a large amount of water-soluble organic solvent should be considered in consideration of mixing the raw material and the aqueous solution. Since it is necessary to use the above-mentioned surfactant, there are many industrial problems in terms of wastewater treatment. Other known methods include a method of using an organic peroxide as an oxidant, a photo-oxidation method using ultraviolet rays, and a method of anodic oxidation, but they have problems in terms of danger and complexity of equipment. Further, a study of a reaction solvent using oxygen as an oxidizing agent is described in JP-B-45-11683. In this oxidation reaction, inert saturated carbon halide such as 1,1,2-trichloro-1,2,2-trifluoroethane, trichlorofluoromethane, perfluoro (dimethylcyclobutane) and carbon tetrachloride is used as a solvent. ing. However, the yield of this reaction (conversion rate × selectivity) is low, about 50-60%. In addition,
Although not specified in Japanese Patent No. 11683, when this reaction was repeated, it was found that an induction period of 1 to 5 hours was required before the reaction started.

[0003]

The object of the present invention is to oxidize hexafluoropropene with oxygen to produce a hexafluoropropene oxide, eliminate the induction period of the initiation of the reaction, and obtain the yield (conversion rate × selectivity). To improve.

[0004]

The object of the present invention is to provide a compound of the general formula: F (CF ₂ O) ₁ COF [I] F (CF ₂ O) _m CF ₂ COF [II] F (CF ₂ ) in the above oxidation reaction. O) _n OCF ₂ COF [III] (wherein each of l, m and n is an integer of 1 to 50) a mixture containing at least one compound selected from the group consisting of compounds (hereinafter, (Sometimes referred to simply as a "mixture").

In the above formulas [I] [II] [III], l,
When m and n are greater than 1, the bond between the CF ₂ O repeating units is not only a head-to-tail bond, but also a head-to-head bond and / or a tail-to-head bond.
It also includes a tail bond, and forms an ether bond in the case of head-to-tail bond, and forms a peroxide ether bond in the case of head-to-head bond and tail-to-tail bond. The ratio of ether peroxide bonds in the above mixture is such that the active oxygen concentration measured by the iodometric titration method is 0.01 to 25% by weight, that is, 1 to 100 [I], [II] or [III] 1 for the molecule
It is preferred that there be one peroxy ether linkage. As long as the mixture satisfies this condition, [I], [I]
There is no limitation on the ratio of the compounds [I] and [III]. In the present specification, the above “mixture” includes [I],
The case where it consists of any two or only one of [II] and [III] is included.

The above-mentioned compounds [I], [II] and [III] are
It is produced by polymerization of carbonyl fluoride, which is a by-product when hexafluoropropene is oxidized with oxygen to produce hexafluoropropene oxide. Therefore, it is possible to use those synthesized in advance by this method, but after completion of the oxidation reaction during the production of hexafluoropropene oxide, the target hexafluoropropene oxide and the unreacted hexafluoropropene are separated from the reaction mixture. You may use what was done. In this way, one reaction always uses for the next reaction [I], [I
A mixture of I] and [III] can be obtained, and the mixture can be circulated and used.

In the present invention, the solvent is an inert solvent such as perfluorodimethylcyclobutane, fluorotrichloromethane, 1,1,2-trichloro-1,2,2.
-Trifluoroethane, carbon tetrachloride, general formula Cl (CF ₂
Or the like can be used a compound represented by _{CFCl) n Cl (n = 2~30} ). In addition, the above [I], [II], and [III]
It is also possible to use a mixture of the above compounds as a solvent.

The amount of the mixture used in the present invention is preferably such that the active oxygen concentration measured by iodometric titration is 0.01% by weight or more in all the solvents. When an insoluble solvent is used, the mixture contains 2% by weight of the solvent.
It is desirable to have more than one.

The reaction method of this reaction can be carried out either batchwise or continuously in a closed container. A metal autoclave capable of stirring and heating the liquid is suitable. Generally, an autoclave is charged with a solvent containing [I] [II] [III] in an amount of 30 to 50% by volume, and hexafluoropropene in an amount of 1 to 40%, preferably 5 to 35% with respect to the solvent.
Heat to 90-150 ° C. Dispensing pressure of oxygen gas is 0.2 to 5 kg / cm ² · G, preferably 0.5 to 1 kg / cm ² G
The reaction is carried out by dispensing at the partial pressure of. The total amount of oxygen charged can be determined by analyzing the conversion rate of hexafluoropropene as a raw material, but it is approximately the theoretical amount of 1.3 to 1.
7 times the amount. The total reaction pressure at this time varies depending on the solvent species, the hexafluoropropene charging ratio, the temperature conditions, etc., and is not specified, but generally 15-40 kg /
cm ² · G.

After completion of the reaction, the temperature can be returned to room temperature, the crude product can be recovered as a gas, and the by-produced acidic component can be removed by washing with an alkali. Further, in the purification of hexafluoropropene oxide, an inert solvent accompanied by a trace amount can be separated by a rectification method from the difference in boiling points, and unreacted hexafluoropropene can be boiled to have a high boiling point. It can be separated by rectification.

As mentioned above, [I] [II] used in the present invention.
The mixture of the [III] compounds can be used by circulating, but [I] [II] [III] is produced and accumulated as the reaction proceeds. Therefore, when this reaction is carried out in a batch system, each batch reaction is completed. In the continuous method, the solvent component may be analyzed and calibrated at regular intervals, and the treatment operation may be required when the accumulated amount increases. As the analysis / calibration method, a gas chromatographic method, an NMR method or the like can be applied, and the active oxygen concentration can be calibrated by an iodine titration method. As for the treatment operation, when another inert solvent is used, a distillation operation is carried out by [I] [II] [II
For example, a method of separating excess components of [I] and detoxifying by alkali cleaning can be used. When [I] [II] [III] is used as a solvent, a method of extracting an excessive amount as it is and removing it by alkali washing can be used. By this removal operation [I]
[II] and [III] decompose to produce acidic substances,
It is necessary to control the liquidity to be alkaline and be careful not to mix water into the reaction system. If water is mixed in, there is a risk that acidic substances will be generated in the reactor and cause corrosion of the reactor.

[0012]

EXAMPLES [I], [II], and [II] used in the present invention
Specific examples of the method for preparing a mixture of the compounds of [I] and the method for producing hexafluoropropene oxide of the present invention will be described by way of Examples. Of course, the present invention is not limited to these examples.

Example 1 Preparation of [I] [II] [III] Compounds (1) Solvent in a 3 L stainless steel autoclave equipped with a stirring blade, an electric heater, a liquid / gas charging port, and a refined product outlet. 2245 g of Cl (CF ₂ CFCl) ₂ Cl and 1047 g of hexafluoropropene were charged.
Stir this mixture at 400 rpm and heat to 120 ° C.,
Oxygen gas was charged at a dispensing pressure of 1 kg / cm ² · G until the conversion of hexafluoropropene was 94%, and the reaction was allowed to proceed. After the reaction, the mixture is cooled to room temperature and blown with a low boiling point product such as hexafluoropropene oxide,
The Cl (CF ₂ CFCl) ₂ Cl solvent was recovered. At this time, the amount of the solvent increased to 2474 g. This solvent was added to ¹⁹ F NM
When analyzed by R, signals other than Cl (CF ₂ CFCl) ₂ Cl were observed as shown in Table 1.

[0014]

[Table 1]

From this NMR analysis result, Cl (CF ₂ CFC
It was found that the mixture of [I] [II] [III] compounds contained 4.15% in l) ₂ Cl solvent. From the signal intensity ratios in Table 1, the mixing ratio of [I] [II] [III] is 5.4:
At 3.5: 0.7, the average molecular weight was determined to be about 330. Furthermore, when the solvent containing this [I] [II] [III] was analyzed by an iodometric titration method, it was found to be 0.0795% by weight ([I]
[II] It was found to have active oxygen of 1.9168% by weight based on [III].

Example 2 Preparation of [I] [II] [III] Compound (2) 625 g of hexafluoropropene was charged into the 3 L stainless steel autoclave used in Example 1. Then 4
The mixture was stirred at 00 rpm and heated to 110 ° C., and oxygen gas was charged at a dispensing pressure of 1 kg / cm ² · G until the conversion of hexafluoropropene was 98%, and the reaction was carried out. After the reaction, the mixture was cooled to room temperature, low-boiling products such as hexafluoropropene oxide were blown, and high-boiling products were recovered. At this time, the recovered amount was 97.8 g. When this recovered substance was analyzed by ¹⁹ F NMR and ¹³ C NMR, signals as shown in Tables 2 and 3 were observed.

[0017]

[Table 2]

[0018]

[Table 3]

From the results of this NMR analysis, the recovered product was [I] [I
It was found to be a mixture of I] [III] compounds. From the signal intensity ratios in Table 2, it was determined that the mixing ratio of [I] [II] [III] was 5.1: 3.6: 1.5 and the average molecular weight was about 355. Further, the [I] [II] [III] mixture was analyzed by an iodometric titration method and found to have 1.074% by weight of active oxygen.

Examples 3 to 7 The 3L stainless steel autoclave used in Example 1 was charged with the Cl (CF ₂ CFCl) ₂ Cl solvent containing the [I] [II] [III] compound prepared in Example 1. After charging, the reaction was carried out by repeatedly using this solvent for 5 batches. Table 4 shows the composition / recharge amount of the recovered solvent and the charge amount of hexafluoropropene for each batch. All reactions were carried out at a stirring temperature of 400 rpm and temperature of 120 ° C.
/ Cm ² · G was charged separately and the reaction was carried out until the conversion of hexafluoropropene was about 95%. Also, since the weight of the recovered solvent increases due to the production of [I] [II] [III] after each batch reaction is completed, almost the increased amount was extracted and used for the next batch. The reaction results for all batches had no induction period, and the gas chromatographic analysis of the crude gas after the reaction showed that the hexafluoropropene oxide yield was 68.4 to 71.2%. The data for each batch are shown in Table 4. Further, after these crude gases were washed with alkali and trapped in a dry ice-methanol bath, 882.1 to 906.7 g of gas components were recovered. When this was analyzed, it was hexafluoropropene oxide (92.1 to 96.2% pure) and hexafluoropropene as a raw material.

Comparative Example 1 The 3L stainless steel autoclave used in Example 1 contained the pure Cl (C) containing no [I] [II] [III] compounds.
F ₂ CFCl) ₂ Cl solvent was charged and the reaction was carried out. The charging conditions are shown in Table 4. Reaction is stirring 400 rpm, 120
Oxygen was dividedly charged at a dispensing pressure of 1 kg / cm ² · G under a temperature condition of ℃, and the conversion rate of hexafluoropropene was 94.8.
The reaction was carried out until the percentage reached. As a result of the reaction, an induction period of 2.5 hours was required until the start of the reaction, and a gas chromatographic analysis of the crude gas after the completion of the reaction revealed that the hexafluoropropene oxide yield was 51.9%. The details are shown in Table 4. Further, after these crude gases were washed with an alkali and trapped in a dry ice-methanol bath, 640.2 g of gas components were recovered. When this was analyzed, hexafluoropropene oxide (91.7
% Purity) and the starting material was hexafluoropropene.

Examples 8 to 10 The 3L stainless steel autoclave used in Example 1 was charged with the [I] [II] [III] mixture prepared in Example 2, and this was used as a solvent repeatedly for 3 batches, The reaction was carried out. Table 5 shows the recovered [I] [II] [III] mixture amount / recharge amount and hexafluoropropene charge amount for each batch. All reactions are stirring 400 rpm, 1
Under the temperature condition of 10 ° C, oxygen was dividedly charged at a dispensing pressure of 1 kg / cm ² · G, and the conversion rate of hexafluoropropene was 90.
The reaction was carried out until the percentage was exceeded. In addition, since the weight of the recovered mixture increases due to the formation of a new [I] [II] [III] compound after each batch reaction, an amount necessary for the analysis was extracted and used for the next batch. The reaction results of all batches had no induction period, and the gas chromatographic analysis of the crude gas after the completion of the reaction revealed that the hexafluoropropene oxide yield was 61.0 to 66.8%. The details are shown in Table 5.

Comparative Example 2 625 g of hexafluoropropene was charged into the 3 L stainless steel autoclave used in Example 1 and the reaction was carried out. The reaction was carried out at a stirring temperature of 400 rpm and a temperature of 110 ° C., and oxygen was dividedly charged at a dispensing pressure of 1 kg / cm ² · G, and the reaction was carried out until the conversion rate of hexafluoropropene was about 98.2%. The reaction result required an induction period of 2.0 hours before the start of the reaction, and the gas chromatographic analysis of the crude gas after the completion of the reaction revealed that the hexafluoropropene oxide yield was 54.0%. The details are shown in Table 5.

Example 11 A 200 ml stainless steel autoclave equipped with a stirring blade, an electric heater, a liquid / gas / charge port, and a product outlet was prepared in the same manner as in Example 2 [I] [II] [ I
II] using the mixture as a solvent (151 g) and hexafluoropropene (33.2 g), and stirring at 400 rpm for 120
Heated to ° C. Further, oxygen was dividedly charged at a dispensing pressure of 1 kg / cm ² · G, and the conversion rate of hexafluoropropene was about 9
The reaction was carried out until it reached 7.4%. The reaction result had no induction period, and as a result of gas chromatography analysis of the crude gas after the reaction was completed, the hexafluoropropene oxide yield was 64.8%. The details are shown in Table 5.

[0025]

[Table 4]

[0026]

[Table 5]

[0027]

As described above, according to the present invention,
When hexafluoropropene is oxidized with oxygen to produce hexafluoropropene oxide, the induction period of the reaction start is eliminated, the time required for the reaction can be shortened, and hexafluoropropene oxide can be obtained in a high yield. You can

Claims (3)

[Claims] 1. A method for producing hexafluoropropene oxide by oxidizing hexafluoropropene with oxygen, which comprises the general formula: F (CF ₂ O) ₁ COF [I] F (CF ₂ O) _m CF ₂ COF [II _{] F (CF 2 O) n} OCF 2 COF [III] ( wherein l, m, n is an integer of 1~50, l, m,
When n is greater than 1, the bond between the CF ₂ O repeating units includes a head-to-tail bond and also a head-to-head bond and / or a tail-to-tail bond. ) A method for producing hexafluoropropene oxide, characterized in that a mixture containing at least one compound selected from the group consisting of the compounds shown in (4) is added. 2. The method according to claim 1, wherein the mixture has an active oxygen concentration of 0.01 to 25% by weight measured by an iodometric titration method. 3. A method for producing hexafluoropropene oxide, which comprises adding a by-product of the reaction in the case of producing hexafluoropropene oxide by oxidizing hexafluoropropene with oxygen.