Method for producing hexafluoropropylene oxide

Abstract

To provide a method for producing hexafluoropropylene oxide that enables shortening of the induction period.SOLUTION: A method for producing hexafluoropropylene oxide includes contacting hexafluoropropylene with oxygen in the presence of hexafluoropropylene oxide to produce hexafluoropropylene oxide.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a method for producing hexafluoropropylene oxide.

Background Art

[0002] Hexafluoropropylene oxide (hereinafter also referred to as "HFPO") is an important compound as a raw material for hexafluoroacetone, perfluoroalkyl vinyl ether, etc., which are intermediates such as fluororesins. Further, oligomers of HFPO are widely used in lubricating oils, heat transfer oils, etc.

[0003] As a method for producing HFPO, a method of partially oxidizing hexafluoropropene (hereinafter also referred to as "HFP") can be mentioned. As methods of partial oxidation, methods using oxidizing agents such as alkaline hydrogen peroxide, molecular oxygen, hypochlorite, organic peroxides, etc., electrolytic oxidation methods, etc. are known. For example, in Patent Documents 1 and 2, among these partial oxidation methods, a method using molecular oxygen as an oxidizing agent is disclosed. The method using molecular oxygen as an oxidizing agent is advantageous in that inexpensive oxygen is used.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the method of producing HFPO by partially oxidizing HFP with oxygen, the time from when HFP and oxygen come into contact until the reaction starts, that is, the "induction period", may become long. Therefore, from the viewpoint of improving the industrial production efficiency of HFPO, it is required to shorten the induction period.

[0006] An object in one embodiment of the present invention is to provide a method for producing hexafluoropropylene oxide capable of shortening the induction period.

Means for Solving the Problems

[0007] This disclosure includes the following aspects. <1> A method for producing hexafluoropropylene oxide, comprising contacting hexafluoropropene and oxygen in the presence of hexafluoropropylene oxide to produce hexafluoropropylene oxide. <2> The method for producing hexafluoropropylene oxide according to <1>, wherein the contacting is performed by contacting a liquid composition containing hexafluoropropylene oxide, hexafluoropropene, and a solvent with oxygen in a liquid phase. <3> The method for producing hexafluoropropylene oxide according to <2>, wherein the content of hexafluoropropylene oxide in the liquid composition before the contacting is 0.02% by mass or more based on the whole liquid composition. <4> The method for producing hexafluoropropylene oxide according to <2> or <3>, wherein the solvent contains at least one selected from the group consisting of F3C(OCF2)4COF and 1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorohexane. <5> The method for producing hexafluoropropylene oxide according to any one of <2> to <4>, wherein the contacting is performed at a pressure of 3.5 MPaG or less. <6> The method for producing hexafluoropropylene oxide according to any one of <2> to <5>, wherein the contacting is performed at a temperature of 110°C or higher. <7> The production method of hexafluoropropylene oxide according to <1>, wherein the contact is carried out by bringing a gaseous composition containing hexafluoropropylene oxide and hexafluoropropene into contact with oxygen in the gas phase. <8> The production method of hexafluoropropylene oxide according to <7>, wherein the content of hexafluoropropylene oxide in the gaseous composition before the contact is 0.5% by volume or more based on the total of hexafluoropropylene oxide and hexafluoropropene. <9> The production method of hexafluoropropylene oxide according to <7> or <8>, wherein the contact is carried out at a pressure of 1.0 MPaG or less. <10> The production method of hexafluoropropylene oxide according to any one of <7> to <9>, wherein the contact is carried out at a temperature of 140°C or higher. <11> Further comprising supplying hexafluoropropylene oxide, hexafluoropropene, and oxygen to a reactor, The production method of hexafluoropropylene oxide according to any one of <1> to <10>, wherein the contact is carried out in the reactor in the presence of the hexafluoropropylene oxide supplied to the reactor. <12> The production method of hexafluoropropylene oxide according to any one of <1> to <11>, wherein the ratio of the molar amount of oxygen to the molar amount of hexafluoropropene is 0.6 or less. <13> The hexafluoropropylene oxide present before the contact is the hexafluoropropylene oxide remaining after passing through a step of generating hexafluoropropylene oxide by bringing hexafluoropropene into contact with oxygen to obtain a composition containing hexafluoropropene and hexafluoropropylene oxide, and a step of removing a part of hexafluoropropylene oxide from the composition, according to any one of <1> to <12>. <14> The generation occurs by oxidizing hexafluoropropene with oxygen, and is a method for producing hexafluoropropylene oxide according to any one of <1> to <13>.

Advantages of the Invention

[0008] According to the present disclosure, there is provided a method for producing hexafluoropropylene oxide that can shorten the induction period.

Modes for Carrying Out the Invention

[0009] In the present disclosure, the numerical range indicated using "~" means a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other stepwise descriptions. Also, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In the present disclosure, the amount of each component means the total amount of a plurality of substances corresponding to each component, unless otherwise specified, when there are a plurality of substances corresponding to each component.

[0010] [Method for Producing Hexafluoropropylene Oxide] The method for producing hexafluoropropylene oxide (HFPO) of the present disclosure includes bringing hexafluoropropene (HFP) and oxygen into contact with each other in the presence of HFPO to generate HFPO. According to the method for producing HFPO of the present disclosure, the induction period can be shortened. Although the reason for this is not clear, it is presumed that when HFPO is present during the contact of HFP and oxygen, the carbene generated by the thermal decomposition of HFPO promotes the reaction between HFP and oxygen, thereby shortening the induction period.

[0011] In addition, since HFPO is the target compound, compared with the case where a third component is present during the contact of HFP and oxygen instead of HFPO to shorten the induction period, in the purification process of HFPO, an operation of separating the third component from HFPO to remove the third component added for the purpose of shortening the induction period becomes unnecessary, and the purification process is omitted.

[0012] The method for producing HFPO of the present disclosure further includes supplying HFPO, HFP, and oxygen to a reactor, and in the reactor, it is preferable to generate HFPO by bringing HFP and oxygen into contact with each other in the presence of HFPO supplied to the reactor. The supply of HFPO, HFP, and oxygen to the reactor may be performed simultaneously or separately. For example, the step of supplying HFPO, HFP, and oxygen to the reactor may include a step of supplying a composition containing HFPO and HFP to the reactor and a step of supplying oxygen to the reactor.

[0013] Examples of the reaction mode of the method for producing HFPO include liquid-phase batch reaction, liquid-phase continuous reaction, gas-phase continuous reaction, and the like. In the liquid-phase batch reaction, when the reaction between HFP and oxygen starts in the reactor, heat is generated and the temperature in the reactor rises. The time change of the temperature in the reactor is confirmed, for example, by measuring the time change of the temperature of the liquid composition using a thermometer. Specifically, a thermocouple is used as the thermometer, and the temperature near the center of the reactor avoiding the stirrer is measured from the start of the reaction (that is, the point when the temperature starts to rise due to the reaction) for 10 hours at a data acquisition interval of 1 second. In the liquid-phase batch reaction according to the present disclosure, the period from the start of the contact between HFP and oxygen until the temperature in the reactor reaches +2°C with respect to the temperature at the start of the reaction (that is, the temperature before it starts to rise) is defined as the "induction period".

[0014] In a liquid-phase continuous reaction, when HFP and oxygen are supplied into the reactor, a so-called hunting state may occur. The hunting state is a state in which the temperature rises and falls repeatedly. Specifically, in the region where HFP and oxygen come into contact, the reaction proceeds locally and generates heat, causing the temperature at a specific position in the reactor to rise rapidly. Then, as the oxygen is consumed and the oxygen concentration decreases locally, the progress of the reaction is suppressed, and the temperature at the specific position repeatedly decreases. The time change of the temperature at a specific position in the reactor can be confirmed, for example, by installing a thermometer at a specific position in the reactor and measuring the time change of the temperature of the liquid composition introduced at that position. Specifically, a thermocouple is used as the thermometer, and the temperature near the center of the reactor avoiding the stirrer is measured from the start of supply for 1 hour at a data acquisition interval of 1 second. In the liquid-phase continuous reaction according to the present disclosure, the case where the temperature in the reactor passes through a hunting state in which the temperature rises to a temperature of +3°C or more above the temperature at the start of supply and then falls to a temperature of -3°C or less below the temperature at the start of supply is referred to as "having an induction period", and other cases are referred to as "having no induction period".

[0015] In a gas-phase continuous reaction, the conversion rate of HFP increases while HFP and oxygen are supplied and retained in the reactor. The change in the HFP conversion rate with the residence time in the gas-phase continuous reaction is measured as follows. Specifically, by adjusting the flow rate when continuously adding a gas composition containing HFP and a gas containing oxygen gas into the reactor, the residence time is changed in 5-minute increments from 5 minutes to 60 minutes, and the HFP conversion rate at each residence time is determined respectively. The HFP conversion rate is determined by analyzing the composition discharged from the outlet of the reactor by gas chromatography. Also, the HFP conversion rate between measurement points is determined by linear interpolation. In the gas-phase continuous reaction according to the present disclosure, the period from when HFP and oxygen are supplied into the reactor until the conversion rate of HFP exceeds 2% is defined as the "induction period".

[0016] Hereinafter, embodiments of the method for producing HFPO according to the present disclosure will be described in detail.

[0017] <Liquid-phase reaction> In the method for producing HFPO using a liquid-phase reaction, a liquid composition containing HFPO, HFP, and a solvent is brought into contact with oxygen in the liquid phase. Here, the contact in the liquid phase only requires the liquid composition to be in a liquid state, and the oxygen during contact may be in a gaseous state. In the liquid-phase reaction, an oxidation reaction occurs in which HFP in the liquid composition is oxidized by oxygen to produce HFPO, and a composition containing HFPO as the reaction product is obtained. The liquid-phase reaction may be a liquid-phase batch reaction or a liquid-phase continuous reaction. From the perspective of industrial production efficiency, the liquid-phase reaction is preferably a liquid-phase continuous reaction.

[0018] Examples of the reaction apparatus used for the liquid-phase batch reaction include a reaction apparatus equipped with a reactor and a gas introduction section for introducing a gas containing oxygen gas into the reactor. In the liquid-phase batch reaction, for example, the above liquid composition is charged into the reactor, and under the condition that the liquid composition is in a liquid state, a gas containing oxygen gas is introduced from the gas introduction section and bubbled in the liquid composition to bring HFP and oxygen in the liquid composition into contact and allow the reaction to proceed. Then, after stopping the reaction by stopping the bubbling or the like, the composition containing the reaction product is taken out from the reactor. In the liquid-phase batch reaction, stirring of the liquid composition during the reaction may or may not be performed. The introduction amount of the gas containing oxygen gas into the reactor is controlled by, for example, a mass flow controller or the like, the pressure in the reactor is controlled by, for example, a valve at the reactor outlet or the like, and the temperature in the reactor is controlled by, for example, a heating bath or the like.

[0019] Examples of the reaction apparatus used for the liquid-phase continuous reaction include a reaction apparatus equipped with a reactor, a liquid composition introduction section for introducing the above liquid composition into the reactor, a gas introduction section for introducing a gas containing oxygen gas into the reactor, a composition discharge section for discharging the composition containing the reaction product from the reactor, and a gas discharge section for discharging the gas containing oxygen gas from the reactor. Here, the composition discharge section and the gas discharge section may be the same discharge section, and the gas and the liquid may be discharged simultaneously from the same location. In the liquid-phase continuous reaction, for example, the above liquid composition and a gas containing oxygen gas are continuously introduced into the reactor, respectively, and the gas containing oxygen gas is bubbled into the liquid composition in the reactor to bring HFP into contact with oxygen to advance the reaction. Then, the composition containing the obtained reaction product is continuously discharged from the composition discharge section. In the liquid-phase continuous reaction, the liquid composition may or may not be stirred during the reaction. The introduction amount of the liquid composition into the reactor is controlled by, for example, a pump or the like. Examples of the control of the introduction amount of the gas containing oxygen gas into the reactor, the control of the pressure in the reactor, and the control of the temperature in the reactor include the same methods as those in the liquid-phase batch reaction.

[0020] The reactor used for the liquid-phase reaction may be any reactor that can withstand the temperature and pressure described later, and the shape and structure are not particularly limited. Examples of the reactor used for the liquid-phase reaction include a pressure reaction vessel capable of internal stirring, and an autoclave made of an acid-resistant metal material such as stainless steel or Hastelloy is particularly preferable.

[0021] (Liquid composition) The liquid composition is a liquid and contains HFPO, HFP, and a solvent, and may contain other components as necessary. Examples of the other components include benzene. The liquid composition preferably contains benzene as the other component. The total content of HFPO, HFP, and the solvent in the entire liquid composition is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 98% by mass or more.

[0022] As the solvent, 1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorohexane (hereinafter also referred to as "C6H"), F3C(OCF2)4COF (hereinafter also referred to as "C5PECOF"), 3,3-dichloro-1,1,1,2,2-pentafluoropropane, 1,3-dichloro-1,1,2,2,3-pentafluoropropane, 1,1,2,2,-tetrafluoroethyl-2,2,2-trifluoroethyl ether, CF3CF2CF2-O-CF(CF3)C(=O)F, CF3CF2CF2OCF(CF3)CF2OCF(CF3)C(=O)F, CF2Cl-CFCl2, CF3(CF2)2O[CF(CF3)CF2O] n CF(CF3)COF (n = 0 to 4), etc. may be mentioned. The solvent may be used alone or in combination of two or more kinds. From the viewpoint of shortening the induction period, the solvent preferably contains at least one selected from the group consisting of C6H and C5PECOF, and more preferably contains C5PECOF.

[0023] From the viewpoint of shortening the induction period, the content of HFPO in the liquid composition before HFP and oxygen come into contact is preferably 0.02% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more, particularly preferably 0.3% by mass or more, and extremely preferably 0.8% by mass or more, based on the whole liquid composition. Particularly in the liquid-phase batch reaction, from the viewpoint of shortening the induction period, the content of HFPO in the liquid composition before HFP and oxygen come into contact is preferably 0.5% by mass or more, more preferably 0.8% by mass or more, still more preferably 1% by mass or more, and particularly preferably 2% by mass or more, based on the whole liquid composition.

[0024] The content rate of HFPO in the liquid composition before HFP comes into contact with oxygen is preferably 7% by mass or less, more preferably 5% by mass or less, still more preferably 4% by mass or less, particularly preferably 3% by mass or less, extremely preferably 2% by mass or less, and most preferably 1% by mass or less, based on the entire liquid composition, from the viewpoints of improving the selectivity of the generated HFPO and improving the production efficiency such that only a small amount of the target product is required. Particularly in the liquid-phase continuous reaction, the content rate of HFPO in the liquid composition before HFP comes into contact with oxygen is preferably 1% by mass or less, more preferably 0.8% by mass or less, still more preferably 0.5% by mass or less, and particularly preferably 0.3% by mass or less, based on the entire liquid composition, from the viewpoints of improving the selectivity of HFPO and improving the production efficiency.

[0025] The content rate of HFPO in the liquid composition before HFP comes into contact with oxygen is preferably 0.02 to 7% by mass, more preferably 0.05 to 5% by mass, still more preferably 0.1 to 4% by mass, and particularly preferably 0.15 to 3.4% by mass, based on the entire liquid composition. Particularly in the liquid-phase batch reaction, the content rate of HFPO in the liquid composition before HFP comes into contact with oxygen is preferably 0.5 to 7% by mass, more preferably 0.8 to 5% by mass, still more preferably 1 to 4% by mass, and particularly preferably 2 to 3.4% by mass, based on the entire liquid composition. Also in the liquid-phase continuous reaction, the content rate of HFPO in the liquid composition before HFP comes into contact with oxygen is preferably 0.02 to 1% by mass, more preferably 0.05 to 0.8% by mass, still more preferably 0.1 to 0.5% by mass, and particularly preferably 0.15 to 0.3% by mass, based on the entire liquid composition.

[0026] From the viewpoint of shortening the induction period, the content of HFPO in the liquid composition before HFP comes into contact with oxygen is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, still more preferably 0.6% by mass or more, and particularly preferably 1% by mass or more, based on the total of HFP and HFPO. Particularly in the liquid-phase batch reaction, from the viewpoint of shortening the induction period, the content of HFPO in the liquid composition before HFP comes into contact with oxygen is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 10% by mass or more, and particularly preferably 15% by mass or more, based on the total of HFP and HFPO.

[0027] From the viewpoints of improving the selectivity of the produced HFPO and improving the production efficiency such that a small amount of the target product suffices, the content of HFPO in the liquid composition before HFP comes into contact with oxygen is preferably 35% by mass or less, more preferably 20% by mass or less, still more preferably 5% by mass or less, and particularly preferably 2% by mass or less, based on the total of HFP and HFPO. Particularly in the liquid-phase continuous reaction, from the viewpoints of improving the selectivity of HFPO and improving the production efficiency, the content of HFPO in the liquid composition before HFP comes into contact with oxygen is preferably 2% by mass or less, more preferably 1% by mass or less, still more preferably 0.8% by mass or less, and particularly preferably 0.7% by mass or less, based on the total of HFP and HFPO.

[0028] The content of HFPO in the liquid composition before HFP comes into contact with oxygen is preferably 0.3 to 35% by mass, more preferably 0.3 to 20% by mass, still more preferably 0.5 to 5.0% by mass, and particularly preferably 0.5 to 2.0% by mass, based on the total of HFP and HFPO. Particularly in the liquid-phase batch reaction, the content of HFPO in the liquid composition before HFP comes into contact with oxygen is preferably 3 to 35% by mass, more preferably 5 to 20% by mass, still more preferably 10 to 20% by mass, and particularly preferably 15 to 20% by mass, based on the total of HFP and HFPO. In the liquid-phase continuous reaction, the content of HFPO in the liquid composition before HFP and oxygen come into contact is preferably 0.3 to 2% by mass, more preferably 0.5 to 1% by mass, still more preferably 0.5 to 0.8% by mass, and particularly preferably 0.6 to 0.7% by mass, based on the total of HFP and HFPO.

[0029] From the viewpoint of improving the yield, the total content of HFP and HFPO in the liquid composition before HFP and oxygen come into contact is preferably 10 to 50% by mass, more preferably 16 to 26% by mass, and still more preferably 20 to 25% by mass, based on the whole liquid composition.

[0030] The HFPO contained in the liquid composition may be the second HFPO which is the HFPO remaining after passing through a pre-reaction step of bringing the first HFP into contact with oxygen to produce HFPO and obtaining a composition containing the second HFP which is the HFP remaining without reacting and the first HFPO produced, and a pre-removal step of removing a part of the first HFPO from the composition. That is, the HFPO contained in the liquid composition may be recycled HFPO obtained by reusing the HFPO remaining without being removed in the pre-removal step. Note that the HFPO contained in the liquid composition may be the above-mentioned recycled HFPO or newly added HFPO.

[0031] The HFP contained in the liquid composition may be obtained by passing through a pre-reaction step of bringing the first HFP into contact with oxygen to produce HFPO and obtaining a composition containing the second HFP which is the HFP remaining without reacting and the produced HFPO, and a pre-removal step of removing at least a part of HFPO from the composition. That is, the HFP contained in the liquid composition may be recycled HFP obtained by reusing the second HFP remaining without reacting in the pre-reaction step. Note that the HFP contained in the liquid composition may be the above-mentioned recycled HFP or newly added HFP.

[0032] When removing HFPO from a composition containing HFP and HFPO, generally, from the viewpoint of improving the isolation yield of HFPO, it is preferable to remove as much HFPO as possible from the composition to obtain HFP free of HFPO. On the other hand, the liquid composition containing recycled HFP and HFPO may be a composition obtained by mixing HFP free of HFPO and separately prepared HFPO, or may be a composition in which only a part of HFPO has been removed in the pre-removal step. When using, as the liquid composition containing recycled HFP and HFPO, a composition in which only a part of HFPO has been removed in the pre-removal step, the content of HFPO in the composition is, for example, 0.001% by mass or more based on the total of HFP and HFPO.

[0033] Also, the solvent contained in the liquid composition may be a recycled solvent obtained by recycling the solvent contained in the composition that has undergone the pre-reaction step. The liquid composition containing recycled HFP, HFPO, and the solvent may be a mixture of HFP free of HFPO and the solvent, and separately prepared HFPO, or may be a composition in which only a part of HFPO has been removed without removing the solvent in the pre-removal step.

[0034] (Gas containing oxygen gas) The gas containing oxygen gas may be oxygen gas alone or a mixture in which oxygen gas is diluted with an inert gas. Examples of the mixture in which oxygen gas is diluted with an inert gas include a mixture in which oxygen gas is diluted with nitrogen gas, air, and the like. The concentration of oxygen gas contained in the above gas is, for example, 50% by volume or more, preferably 80% by volume or more, and more preferably 90% by volume or more from the viewpoint of improving the conversion rate of HFP. The concentration of oxygen gas contained in the above gas may be 100% by volume or may be 99% by volume or less.

[0035] From the perspective of improving the selectivity of HFPO, the ratio of the molar amount of oxygen gas introduced into the reactor to the molar amount of HFP contained in the liquid composition (O2 / HFP) is preferably 0.6 or less, more preferably 0.5 or less. From the perspective of improving the conversion rate of HFP, the ratio (O2 / HFP) is preferably 0.01 or more, more preferably 0.05 or more, further preferably 0.2 or more, and particularly preferably 0.3 or more.

[0036] (Reaction conditions) From the perspective of reducing the production cost of HFPO, the pressure in the reactor where HFP and oxygen are brought into contact is preferably 3.5 MPaG or less, more preferably 3.2 MPaG or less. From the perspective of suppressing behaviors such as bumping and improving the stability of the reaction, the pressure in the reactor is preferably 1.5 MPaG or more, more preferably 2.5 MPaG or more. Note that "G" after the pressure unit MPa indicates gauge pressure. From the perspective of improving the productivity per reactor due to an increase in the conversion rate, etc., the temperature in the reactor where HFP and oxygen are brought into contact is preferably 110 °C or more, more preferably 140 °C or more, and further preferably 150 °C or more. From the perspective of improving the yield, the temperature in the reactor is preferably 180 °C or less, more preferably 165 °C or less, and further preferably 160 °C or less.

[0037] In the liquid-phase batch reaction, the time for bringing HFP and oxygen in the liquid composition into contact by bubbling a gas containing oxygen gas (hereinafter also referred to as "bubbling time") is preferably 0.5 to 240 minutes, more preferably 1 to 180 minutes, from the perspective of achieving both an increase in the conversion rate of HFP and an increase in the selectivity of HFPO. In the liquid-phase continuous reaction, the time for bringing HFP and oxygen in the liquid composition into contact by the residence of the liquid composition and the gas containing oxygen gas in the reactor, that is, the reaction time, is preferably 5 to 360 minutes, more preferably 15 to 120 minutes, from the perspective of achieving both an increase in the conversion rate of HFP and an increase in the selectivity of HFPO. In the liquid-phase continuous reaction, the flow rate of introducing HFP into the reactor is, for example, in the range of 0.5 to 3 mol / hour. Also, in the liquid-phase continuous reaction, the flow rate of introducing oxygen into the reactor is, for example, in the range of 0.1 to 1.5 mol / hour.

[0038] <Gas-phase reaction> In the method for producing HFPO using a gas-phase reaction, a gaseous composition containing HFPO and HFP is brought into contact with oxygen in the gas phase. In the gas-phase reaction, an oxidation reaction occurs in which HFP in the gaseous composition is oxidized by oxygen to produce HFPO, and a composition containing HFPO as the reaction product is obtained. From the viewpoint of industrial production efficiency, the gas-phase reaction is preferably a gas-phase continuous reaction.

[0039] Examples of the reactor used for the gas-phase continuous reaction include a reactor, a gaseous composition introduction section for introducing the gaseous composition into the reactor, a gas introduction section for introducing a gas containing oxygen gas into the reactor, a composition discharge section for discharging the composition containing the reaction product from the reactor, and a gas discharge section for discharging the gas containing oxygen gas from the reactor. In the gas-phase continuous reaction, for example, the gaseous composition and the gas containing oxygen gas are continuously introduced into the reactor, HFP and oxygen are brought into contact in the reactor to allow the reaction to proceed, and the composition containing the obtained reaction product is continuously discharged from the composition discharge section. In the gas-phase continuous reaction, the introduction amounts of the gaseous composition and the gas containing oxygen gas into the reactor are controlled by, for example, a mass flow controller or the like. Also, the pressure in the reactor is controlled by, for example, a pressure regulating valve or the like, and the temperature in the reactor is controlled by, for example, an electric heater provided in the reactor or the like.

[0040] The reactor used for the gas-phase reaction may be any reactor that can withstand the temperature and pressure described later, and the shape and structure are not particularly limited. Examples of the reactor used for the gas-phase reaction include a tubular reactor. Examples of the material of the reactor include acid-resistant metal materials such as stainless steel and Hastelloy in addition to copper. The reactor may be provided with heating means such as an electric heater for heating the inside of the reactor.

[0041] (Gaseous composition) The gaseous composition is a gas, contains HFPO and HFP, and may contain other components as necessary. Examples of the other components include inert gases such as nitrogen gas, helium gas, and argon gas. When the gaseous composition contains an inert gas, nitrogen gas is preferred as the inert gas. The total content ratio of HFPO and HFP in the gaseous composition is 5 to 95% by volume, preferably 10 to 60% by volume, and more preferably 18 to 40% by volume from the viewpoint of safety.

[0042] From the viewpoint of shortening the induction period, the content ratio of HFPO in the gaseous composition before HFP comes into contact with oxygen is preferably 0.5% by volume or more, more preferably 1.0% by volume or more, further preferably 3.0% by volume or more, and particularly preferably 5.0% by volume or more based on the total of HFP and HFPO. From the viewpoint of improving the selectivity of the generated HFPO, the content ratio of HFPO in the gaseous composition before HFP comes into contact with oxygen is preferably 10% by volume or less, more preferably 9.0% by volume or less based on the total of HFP and HFPO. The content ratio of HFPO in the gaseous composition before HFP comes into contact with oxygen is preferably 0.5 to 10% by volume, more preferably 1.0 to 10% by volume, further preferably 3.0 to 10% by volume, and particularly preferably 5.0 to 9.0% by volume based on the total of HFP and HFPO.

[0043] The HFPO contained in the gaseous composition may be the second HFPO which is the HFPO remaining after passing through a pre-reaction step of bringing the first HFP into contact with oxygen to generate HFPO and obtaining a composition containing the second HFP which is the HFP remaining without reacting and the generated first HFPO, and a pre-removal step of removing a part of the first HFPO from the composition. That is, the HFPO contained in the gaseous composition may be recycled HFPO obtained by recycling the HFPO remaining without being removed in the pre-removal step. Note that the HFPO contained in the gaseous composition may be the recycled HFPO or the newly added HFPO.

[0044] The HFP contained in the gaseous composition may be obtained through a pre-reaction step of bringing the first HFP into contact with oxygen to produce HFPO, and obtaining a composition containing the second HFP that is the HFP remaining without reacting and the produced HFPO, and a pre-removal step of removing at least a part of HFPO from the composition. That is, the HFP contained in the gaseous composition may be recycled HFP that reuses the second HFP remaining without reacting in the pre-reaction step. Note that the HFP contained in the gaseous composition may be the recycled HFP or may be newly added HFP.

[0045] The gaseous composition containing recycled HFP and HFPO may be a composition obtained by mixing HFP not containing HFPO and separately prepared HFPO, or may be a composition in which only a part of HFPO is removed in the pre-removal step. When using, as the gaseous composition containing recycled HFP and HFPO, a composition in which only a part of HFPO is removed in the pre-removal step, the content rate of HFPO in the composition is, for example, 0.001% by volume or more with respect to the total of HFP and HFPO.

[0046] (Gas containing oxygen gas) Examples of the gas containing oxygen gas used in the gas-phase reaction include the same as those of the gas containing oxygen gas used in the liquid-phase reaction, and a mixture in which oxygen gas is diluted with nitrogen gas is preferable. Examples of the concentration of oxygen gas contained in the gas include 1 to 50% by volume, preferably 5 to 40% by volume, and more preferably 10 to 30% by volume from the viewpoint of achieving both an improvement in the conversion rate of HFP and an improvement in the selectivity of HFPO.

[0047] From the viewpoint of improving the selectivity of HFPO, the ratio (O2 / HFP) of the molar amount of oxygen gas introduced into the reactor to the molar amount of HFP contained in the gaseous composition is preferably 0.6 or less, and more preferably 0.56 or less. From the viewpoint of improving the conversion rate of HFP, the ratio (O2 / HFP) is preferably 0.1 or more.

[0048] (Reaction conditions) From the perspective of reducing the production cost of HFPO, the pressure in the reactor where HFP and oxygen are brought into contact is preferably 1.0 MPaG or less, more preferably 0.4 MPaG or less. From the perspective of volumetric efficiency, the pressure in the reactor is preferably 0.1 MPaG or more, more preferably 0.3 MPaG or more. From the perspective of the stability of the reaction, the temperature in the reactor where HFP and oxygen are brought into contact is preferably 140°C or higher, more preferably 150°C or higher, and even more preferably 160°C or higher. From the perspective of improving the yield of HFPO, the temperature in the reactor is preferably 180°C or lower.

[0049] In the gas-phase continuous reaction, the time for contacting HFP and oxygen in the gas-phase composition by the retention of the gas-phase composition and the gas containing oxygen gas in the reactor, that is, the reaction time, is preferably 1 to 40 minutes, more preferably 10 to 30 minutes, from the perspective of achieving both an improvement in the conversion rate of HFP and an improvement in the selectivity of HFPO. In the gas-phase continuous reaction, the flow rate of introducing HFP into the reactor is, for example, in the range of 0.05 to 100 NL / h. Also, in the gas-phase continuous reaction, the flow rate of introducing oxygen into the reactor is, for example, in the range of 0.05 to 100 NL / h.

Examples

[0050] Hereinafter, the present disclosure will be described more specifically by way of examples. However, the present disclosure is not limited to the following examples as long as its gist is not exceeded.

[0051] [Examples A1 to A7 (liquid-phase batch reaction)] HFP, HFPO, and the solvents of the types shown in Table 1 were mixed to prepare liquid compositions A1 to A7, respectively. The content of HFPO in the total obtained liquid composition ("HFPO / composition" in the table), the content of HFPO in the total of HFP and HFPO in the obtained liquid composition ("HFPO / HFP + HFPO" in the table), and the total content of HFP and HFPO in the total obtained liquid composition ("HFP + HFPO / composition" in the table) are shown in Table 1.

[0052] Into an autoclave (reactor) made of Hastelloy with a volume of 2.5 liters, 1.0 liter of each of the obtained liquid compositions was charged. The temperature at the start of the reaction in the reactor was controlled at 160 °C, and the pressure in the reactor was controlled at 3 MPaG. While stirring the liquid composition, pure oxygen gas was introduced into the reactor and bubbled in the liquid composition for 1 minute (i.e., the bubbling time was 1 minute). Table 1 shows the ratio (O2 / HFP) of the molar amount of oxygen gas introduced into the reactor to the molar amount of HFP contained in the liquid composition charged into the reactor in each example. By the above-mentioned method, the induction period time in each example was determined from the time change of the temperature in the reactor. The results are shown in Table 1.

[0053] The bubbling of oxygen gas was stopped, and the temperature was maintained at 160 °C and the pressure at 3 MPaG, and it was left standing for 60 minutes. Then, the composition remaining in the reactor was taken out and measured using gas chromatography (GC-2030, manufactured by Shimadzu Corporation) to confirm the ratio of each component contained in the composition. In the above measurement, DB-1301 (manufactured by Agilent Technologies, length 60 m × inner diameter 250 μm × thickness 1 μm) was used as the column, and a flame ionization detector (FID) was used as the detector. For each example, the conversion rate of HFP and the selectivity of HFPO were determined from the composition of the liquid composition charged into the reactor and the composition of the composition after the bubbling was stopped. The results are shown in Table 1. In the following table, in the HFPO selectivity, A indicates that the selectivity is 75% or more, B indicates that the selectivity is 70% or more and less than 75%, and C indicates that the selectivity is less than 70%.

[0054]

Table 1

[0055] Examples A2 to A5 and A7 are examples, and Examples A1 and A6 are comparative examples. As shown in Table 1, in Examples A2 to A5 where the liquid composition contains HFPO, it was found that the induction period was shortened compared to Example A1 using the same solvent and without HFPO in the liquid composition. Similarly, in Example A7 where the liquid composition contains HFPO, it was found that the induction period was shortened compared to Example A6 using the same solvent and without HFPO in the liquid composition. In Examples A2 to A5 and A7, since no third component other than the raw material HFP and the target compound HFPO was added, there is no need to separate the third component from HFPO in the HFPO purification process, and both shortening of the induction period and simplification of the purification process are achieved. Also, in Example A2, after stopping the bubbling of oxygen gas, the composition remaining in the reactor was taken out, and after a step of removing a part of HFPO contained in the composition, a liquid composition containing recycled HFPO, recycled HFP, and recycled solvent and having the same composition as the liquid composition of Example A2 was obtained. Then, when the obtained liquid composition was used to carry out the reaction under the same conditions as in Example A2, the same results as in Example A2 were obtained.

[0056] [Examples B1 to B5 (liquid-phase continuous reaction)] HFP, HFPO, and the solvents of the types shown in Table 2 were mixed to prepare liquid compositions B1 to B5, respectively. Table 2 shows the content rate of HFPO with respect to the entire obtained liquid composition ("HFPO / composition" in the table), the content rate of HFPO with respect to the total of HFP and HFPO in the obtained liquid composition ("HFPO / HFP+HFPO" in the table), and the total content rate of HFP and HFPO with respect to the entire obtained liquid composition ("HFP+HFPO / composition" in the table).

[0057] Into a Hastelloy autoclave (reactor) with a volume of 0.49 liters, the obtained liquid composition and oxygen gas alone were continuously introduced respectively to bubble oxygen gas in the liquid composition in the reactor. After the start of bubbling, the temperature at the start of the reaction in the reactor was controlled at 150°C and the pressure in the reactor was controlled at 3 MPaG. The flow rate of introducing HFP into the reactor was 0.7 mol / hour, the flow rate of introducing oxygen into the reactor was 0.35 mol / hour, and the reaction time was 60 minutes. The ratio of the mass of oxygen gas introduced into the reactor to the mass of HFP contained in the liquid composition introduced into the reactor (O2 / HFP) in each example is shown in Table 2. By the above method, the presence or absence of an induction period in each example was confirmed from the time change of the temperature in the reactor. The results are shown in Table 2.

[0058] The composition containing the reaction product was withdrawn from the reactor and measured using gas chromatography (GC-2030, manufactured by Shimadzu Corporation) to confirm the ratio of each component contained in the composition. In the above measurement, DB-1301 (manufactured by Agilent Technologies, length 60 m × inner diameter 250 μm × thickness 1 μm) was used as the column, and a flame ionization detector (FID) was used as the detector. For each example, the conversion rate of HFP and the selectivity of HFPO were determined from the composition of the liquid composition introduced into the reactor and the composition of the withdrawn composition. The results are shown in Table 2. In the following table, in the HFPO selectivity, A indicates that the selectivity is 70% or more, B indicates that the selectivity exceeds 58% and is less than 70%, and C indicates that the selectivity is 58% or less.

[0059]

Table 2

[0060] Examples B1 and B3 to B5 are examples, and Example B2 is a comparative example. As shown in Table 2, an induction period was confirmed in Example B2 in which the liquid composition did not contain HFPO, whereas it was found that there was no induction period in Examples B1 and B3 to B5 in which the liquid composition contained HFPO. In Examples B1 and B3 to B5, since no third component other than the raw material HFP and the target compound HFPO was added, an operation for separating the third component from HFPO in the HFPO purification step is unnecessary, and both shortening of the induction period and omission of the purification step are achieved. Also, in Example B1, through the step of removing a part of the HFPO contained in the composition withdrawn from the reactor, a liquid composition containing recycled HFPO, recycled HFP, and recycled solvent and having the same composition as the liquid composition of Example B1 was obtained. Then, when the reaction was carried out under the same conditions as in Example B1 using the obtained liquid composition, the same results as in Example B1 were obtained.

[0061] [Examples C1 - C7 (Gas-Phase Continuous Reaction)] HFP, HFPO, and nitrogen gas were mixed to prepare gaseous compositions C1 - C7, respectively. Table 3 shows the content ratio of HFPO to the total of HFP and HFPO in the obtained gaseous composition ("HFPO / HFP + HFPO" in the table) and the total content ratio of HFP and HFPO to the entire obtained gaseous composition ("HFP + HFPO / composition" in the table).

[0062] While continuously introducing the obtained gaseous composition and a mixed gas of oxygen gas and nitrogen gas into a reactor in which four copper reaction tubes with an inner diameter of 1 / 4 inch and a length of 4 m were connected in series, the temperature at the start of the reaction in the reactor was controlled to the reaction temperature shown in Table 3, and the pressure in the reactor was controlled to 0.4 MPaG. The concentration of oxygen gas in the entire mixed gas was 10% by volume. Note that the flow rate of HFP introduced into the reactor was 0.33 NL / h for Example C1, 0.68 NL / h for Example C2, 1.28 NL / h for Example C3, 1.31 NL / h for Example C4, 0.33 NL / h for Example C5, 0.33 NL / h for Example C6, and 0.33 NL / h for Example C7. Also, the flow rate of oxygen introduced into the reactor was 0.18 NL / h for Example C1, 0.38 NL / h for Example C2, 0.71 NL / h for Example C3, 0.70 NL / h for Example C4, 0.18 NL / h for Example C5, 0.18 NL / h for Example C6, and 0.18 NL / h for Example C7. Table 3 shows the ratio of the mass of oxygen gas contained in the mixed gas introduced into the reactor to the mass of HFP contained in the gaseous composition introduced into the reactor in each example (O2 / HFP). From the time change of the HFP conversion rate after HFP and oxygen were supplied into the reactor by the above method, the induction period time in each example was determined. The results are shown in Table 3.

[0063]

Table 3

[0064] Examples C2 to C7 are examples, and Example C1 is a comparative example. As shown in Table 3, it was found that in Examples C2 to C7 where the gaseous composition contains HFPO, the induction period was shortened compared to Example C1 where the gaseous composition does not contain HFPO. In Examples C2 to C7, since no third component other than the raw material HFP and the target compound HFPO was added, an operation to separate the third component from HFPO in the HFPO purification step is unnecessary, and both shortening of the induction period and omission of the purification step are achieved. Also, in Example C2, through a step of removing a part of the HFPO contained in the composition taken out from the reactor, a gaseous composition containing recycled HFPO and recycled HFP and having the same composition as the gaseous composition of Example C2 was obtained. Then, when the obtained gaseous composition was used to carry out the reaction under the same conditions as in Example C2, the same results as in Example C2 were obtained.

Claims

1. A method for producing hexafluoropropylene oxide, comprising contacting hexafluoropropene and oxygen in the presence of hexafluoropropylene oxide to produce hexafluoropropylene oxide.

2. The method for producing hexafluoropropylene oxide according to claim 1, wherein the contacting is performed by contacting a liquid composition containing hexafluoropropylene oxide, hexafluoropropene, and a solvent with oxygen in a liquid phase.

3. The method for producing hexafluoropropylene oxide according to claim 2, wherein the content of hexafluoropropylene oxide in the liquid composition before the contacting is 0.02% by mass or more based on the whole liquid composition.

4. The solvent is F ３ C(OCF ２ ) ４ The method for producing hexafluoropropylene oxide according to claim 2 or 3, comprising at least one selected from the group consisting of COF and 1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorohexane.

5. The method for producing hexafluoropropylene oxide according to claim 2 or 3, wherein the contacting is performed at a pressure of 3.5 MPaG or less.

6. The method for producing hexafluoropropylene oxide according to claim 2 or 3, wherein the contacting is performed at a temperature of 110°C or higher.

7. The method for producing hexafluoropropylene oxide according to claim 1, wherein the contacting is performed by contacting a gaseous composition containing hexafluoropropylene oxide and hexafluoropropene with oxygen in a gas phase.

8. The method for producing hexafluoropropylene oxide according to claim 7, wherein the content of hexafluoropropylene oxide in the gaseous composition before the contacting is 0.5% by volume or more based on the total of hexafluoropropylene oxide and hexafluoropropene.

9. The method for producing hexafluoropropylene oxide according to claim 7 or 8, wherein the contacting is performed at a pressure of 1.0 MPaG or less.

10. The method for producing hexafluoropropylene oxide according to claim 7 or 8, wherein the contacting is performed at a temperature of 140°C or higher.

11. Further comprising supplying hexafluoropropylene oxide, hexafluoropropene, and oxygen to a reactor, The method for producing hexafluoropropylene oxide according to any one of claims 1 to 3 and 7 to 8, wherein the contacting is performed in the reactor in the presence of the hexafluoropropylene oxide supplied to the reactor.

12. The ratio of the molar amount of oxygen to the molar amount of the hexafluoropropene is 0.6 or less. The method for producing hexafluoropropylene oxide according to any one of claims 1 to 3 and 7 to 8.

13. The hexafluoropropylene oxide present before the contact is obtained by a step of contacting hexafluoropropene and oxygen to produce hexafluoropropylene oxide and obtaining a composition containing hexafluoropropene and hexafluoropropylene oxide, and a step of removing a part of the hexafluoropropylene oxide from the composition. The method for producing hexafluoropropylene oxide according to any one of claims 1 to 3 and 7 to 8, which is the remaining hexafluoropropylene oxide after the above steps.

14. The production occurs by oxidizing hexafluoropropene with oxygen. The method for producing hexafluoropropylene oxide according to any one of claims 1 to 3 and 7 to 8.

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