Method for producing vinylidene fluoride

Abstract

A method for producing vinylidene fluoride, which comprises a reaction step for obtaining vinylidene fluoride using a starting material composition that contains 1, 1, 2, 2-tetrafluorocyclobutane and water vapor.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a method for producing vinylidene fluoride. BACKGROUND

[0002] Vinylidene fluoride is useful as a monomer of a fluororesin.

[0003] For example, Patent Literature 1 describes a method for obtaining vinylidene fluoride from 1,1,2,2-tetrafluorocyclobutane in the presence of helium gas.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: U.S. Patent No. 3996301 Specification SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] However, in Patent Literature 1, the boiling point of helium gas as a diluent is lower than the boiling point of vinylidene fluoride as a target. Therefore, when helium gas is discharged to the outside of the system in the purification step, it is difficult to avoid the discharge of vinylidene fluoride together with helium gas.

[0009] An object of one embodiment of the present disclosure is to provide a method for producing vinylidene fluoride, which suppresses loss of vinylidene fluoride caused by separation from a diluent.

[0010] MEANS FOR SOLVING THE PROBLEMS

[0011] The present disclosure includes the following modes.

[0012] <1>

[0013] A method for producing vinylidene fluoride includes a reaction step of obtaining vinylidene fluoride using a raw material composition containing 1,1,2,2-tetrafluorocyclobutane and water vapor.

[0014] <2>

[0015] The method for producing vinylidene fluoride according to <1> further includes a separation step of separating at least a part of the water vapor from a post-reaction gas containing vinylidene fluoride and water vapor obtained in the reaction step, to obtain a post-separation composition containing more vinylidene fluoride than the post-reaction gas.

[0016] <3>

[0017] The method for producing vinylidene fluoride according to <2>, in which the separation step is performed at a temperature higher than the boiling point of vinylidene fluoride and lower than the boiling point of water at a pressure in the separation vessel, to separate the water vapor by liquefaction.

[0018] <4>

[0019] The manufacturing method of vinylidene fluoride according to any one of <1> to <3>, wherein the content of water vapor is 95 mol% or less relative to the total content of 1,1,2,2-tetrafluorocyclobutane and water vapor.

[0020] <5>

[0021] The manufacturing method of vinylidene fluoride according to any one of <1> to <4>, wherein the temperature inside the reactor used in the reaction step is 600°C or higher.

[0022] <6>

[0023] The manufacturing method of vinylidene fluoride according to any one of <1> to <5>, wherein the contact time of 1,1,2,2-tetrafluorocyclobutane with water vapor is 1 second or longer.

[0024] <7>

[0025] The manufacturing method of vinylidene fluoride according to any one of <1> to <6>, wherein the pressure inside the reactor used in the reaction step is 0.6 MPaG or lower.

[0026] Effects of the Invention

[0027] According to one embodiment of the present disclosure, there is provided a manufacturing method of vinylidene fluoride that suppresses loss of vinylidene fluoride caused by separation from a diluent. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a schematic configuration view showing one example of a manufacturing apparatus. DETAILED DESCRIPTION

[0029] In the present disclosure, a numerical range indicated using “~” means a range in which the values written before and after “~” are respectively included as the minimum value and the maximum value.

[0030] In the present disclosure, in a numerical range written in stages, the upper limit value or the lower limit value written in a certain numerical range can be replaced with the upper limit value or the lower limit value of another numerical range written in stages. In addition, in the numerical range written in the present disclosure, the upper limit value or the lower limit value written in a certain numerical range can also be replaced with the value shown in the examples.

[0031] In the present disclosure, a combination of two or more preferred modes is a more preferred mode.

[0032] In the present disclosure, the amount of each component, in the case where a plurality of substances conforming to each component exist, means the total amount of the plurality of substances, unless otherwise specified.

[0033] [Method for producing VdF]

[0034] The method for producing vinylidene fluoride (VdF) of the present disclosure includes a reaction step for obtaining VdF using a raw material composition containing 1,1,2,2-tetrafluorocyclobutane (c354) and water vapor.

[0035] According to the method for producing VdF of the present disclosure, loss of VdF caused by separation from the diluent can be suppressed.

[0036] In the method for producing VdF described in Patent Literature 1, helium gas is used as the diluent. The boiling point of helium gas is -269°C. The boiling point of VdF is -83°C, and the boiling point of helium gas is lower than the boiling point of VdF. Therefore, in the purification step, VdF as the target substance also has a tendency to be removed along with helium gas when helium gas is removed. In addition, the boiling point of nitrogen gas is -196°C, and the boiling point of tetrafluoromethane is -184°C, and therefore it is considered that in the case where nitrogen gas or tetrafluoromethane is used as the diluent, VdF as the target substance is also removed in the purification step, similarly to the case where helium gas is used.

[0037] On the contrary, in the method for producing VdF of the present disclosure, water vapor is used together with the raw material composition. The boiling point of water at atmospheric pressure is 100°C. The amount of saturated water vapor at standard state is less than 3%, and therefore by lowering the temperature to room temperature after the reaction, most of the water vapor contained in the gas after the reaction can be removed. Therefore, water vapor and VdF are easily separated, and loss of VdF in the purification step can be suppressed.

[0038] - Reaction step -

[0039] <Raw material composition>

[0040] In the reaction step of the method for producing VdF of the present disclosure, a raw material composition containing c354 and water vapor are used.

[0041] In the present disclosure, the raw material composition refers to a component used in the reaction for generating VdF. Note that the raw material composition can consist only of c354.

[0042] In the present disclosure, water vapor refers to vapor or superheated vapor composed of water (H2O). In addition, a part of the water vapor can be mist, or can be liquid.

[0043] From the viewpoint of reaction efficiency, the content of water vapor is preferably 95 mol% or less, and more preferably 70 mol% or less, relative to the total content of c354 and water vapor. The lower limit of the content of water vapor is not particularly limited, and is, for example, 10 mol%.

[0044] The content of c354 is preferably 30 mol% or more, more preferably 50 mol% or more, relative to the total content of c354 and water vapor. The upper limit of the content of c354 is not particularly limited.

[0045] The raw material composition can include components other than c354. As the other components, for example, components derived from the production of c354 can be given.

[0046] As the components derived from the production of c354, for example, tetrafluoroethylene (TFE), ethylene, chlorodifluoromethane (R22), octafluorocyclobutane (c318), and 3,3-difluoropropene can be given.

[0047] In the raw material composition, the total content of c354 and water vapor is preferably 30 mol% or more, more preferably 50 mol% or more, relative to the total content of the raw material composition. The upper limit of the total content of c354 and water vapor is not particularly limited, and is, for example, 100 mol%.

[0048] <Reaction conditions>

[0049] As the reactor for supplying c354 and water vapor, the shape and structure are not particularly limited as long as the temperature and pressure in the reactor described later can be tolerated, and for example, a cylindrical vertical reactor or the like can be given. As the material of the reactor, stainless steel, glass, an alloy in which iron, nickel, or chromium is a main component, or the like can be given. The reactor can be provided with a heating unit such as an electric heater that heats the inside.

[0050] C354 and water vapor can be directly introduced into the reactor at ordinary temperature, but in order to improve the reactivity in the reactor, it is also possible to be supplied after being heated (preheated) before being introduced into the reactor. In the case of preheating, c354 is preferably heated to a temperature of 50 to 300°C and then supplied to the reactor. Water vapor is preferably supplied to the reactor after being heated to a temperature of 100 to 300°C.

[0051] In addition, each component contained in the raw material composition can be supplied to the reactor after being mixed in advance, or can be supplied to the reactor separately and mixed in the reactor.

[0052] From the viewpoint of improving the yield, the temperature in the reactor in the reaction step is preferably 600°C or higher, more preferably 650°C or higher.

[0053] The reaction step can be performed in a batchwise manner, or can be performed in a continuous manner. From the viewpoint of productivity, the reaction step is preferably performed in a continuous manner, and preferably the contact time is controlled in the continuous manner.

[0054] From the viewpoint of improving the yield, the contact time of c354 with water vapor is preferably 1 second or more, further preferably 5 seconds or more. In addition, the upper limit of the contact time is, for example, 300 seconds.

[0055] The contact time can also be said to be the residence time in the reactor. The contact time (sec) described above is calculated using the following formula.

[0056] Contact time (sec) = [volume of the raw material composition supplied to the reactor per 1 sec at the reaction temperature] / [volume of the reactor]

[0057] From the viewpoint of improving the yield, the pressure in the reactor in the reaction step is preferably 0.6 MPaG or lower, more preferably 0.3 MPaG or lower. The lower limit of the pressure is not particularly limited, and is, for example, 0 MPaG.

[0058] Note that the pressure expressed in MPaG in the present disclosure is gauge pressure.

[0059] - Separation Step -

[0060] The production method of VdF of the present disclosure preferably further includes a separation step in which at least a part of the water vapor is separated from the post-reaction gas containing VdF and water vapor obtained in the reaction step, to obtain a post-separation composition having a higher content of VdF than the post-reaction gas.

[0061] The "post-separation composition has a higher content of VdF than the post-reaction gas" means that the mass ratio of VdF in the total content of VdF and water vapor in the post-separation composition is higher than the mass ratio of VdF in the total content of VdF and water vapor in the post-reaction gas.

[0062] The post-reaction gas is a gas after the end of the reaction step. The post-reaction gas contains VdF and water vapor. In the post-reaction gas, in addition to VdF and water vapor, unreacted raw material composition (containing c354), by-product gas can be contained.

[0063] The method of separating at least a part of the water vapor is not particularly limited, and examples that can be given include liquefaction separation of water vapor, extractive distillation, absorption separation into an absorption liquid, adsorption separation into an adsorbent, and membrane separation. These methods can be performed alone or in combination.

[0064] Among them, the separation step is preferably performed at a temperature of 0 MPaG or higher and lower than the boiling point of water under the pressure in the separation vessel, and the water vapor is liquefied and separated.

[0065] In the separation step, it is preferable that the pressure in the separation vessel is 0 MPaG to 0.6 MPaG and the temperature in the separation vessel is -50°C to 120°C. In addition, it is more preferable that the pressure in the separation vessel is 0 MPaG to 0.5 MPaG and the temperature in the separation vessel is -50°C to 100°C.

[0066] The separation vessel is a vessel that enables a separation process to be performed inside. The shape and material of the separation vessel are not particularly limited. The separation vessel can also be provided with a device that cools the gas after the reaction. The device that cools can be provided immediately in front of the separation vessel, or can be a device that cools the separation vessel itself.

[0067] The water vapor separated in the separation process can also be recovered and supplied to the reactor in the reaction process. The water vapor separated in the separation process can also be recovered and used in other processes other than the reaction process.

[0068] The method of producing VdF of the present disclosure can also include a step of obtaining c354 using a raw material composition A containing at least one selected from the group consisting of TFE, R22, and c318 and containing ethylene.

[0069] In the past, VdF has been synthesized, for example, by a dehydrochlorination reaction of 1-chloro-1,1-difluoroethane (142b). 142b is synthesized in a plurality of stages of chlorination, fluorination, and the like using ethylene or acetylene as a raw material. Chlorine gas and hydrogen fluoride gas used in the reaction are not only difficult to handle, but also the number of processes is large, and thus a production method that is more simple to produce from a readily available raw material is desired.

[0070] In contrast, in the method of producing VdF of the present disclosure, VdF can be produced using a raw material that is easy to handle and has a small number of reaction processes. In addition, c354 has a boiling point of 50°C, and water has a boiling point of 100°C, both of which are liquids at room temperature, and thus can be handled at a high density.

[0071] Examples

[0072] Hereinafter, the present disclosure will be specifically described by examples, but the present disclosure is not limited by these examples.

[0073] [Example 1]

[0074] Use Figure 1 Using the production device 100 shown in the drawing, VdF was obtained using c354 and water vapor by the method shown below.

[0075] c354 was supplied from the c354 tank 1 to the preheater 8 via the c354 supply line 2. The c354 was heated to 80°C with the oven 4.

[0076] The c354 was continuously introduced into the Inconel 600 tube in the preheater 8, which was set to an internal temperature of 350°C ("preheating temperature" in the table), and heated to 350°C.

[0077] In addition, water was supplied from the water tank 5 to the preheater 9 via the water supply line 6. The water was heated to steam (water vapor) using the preheater 9, which was set to an internal temperature of 700°C.

[0078] The thus preheated c354 and steam (water vapor) adjusted to the above temperature were supplied to the reactor 10 managed at an internal pressure (gauge pressure) of 0 MPaG and an internal temperature of 700°C, in a manner that the supply ratio of water vapor to the total of the gas supply amounts was 91% in terms of mol%.

[0079] In the reactor 10, the flow rate (supply amount per unit time) of c354 was controlled in a manner that the contact time of c354 with water vapor was 1.4 seconds.

[0080] The adjustment of the gas supply amounts was performed by the c354 flow rate control device 3 and the water flow rate control device 7.

[0081] In the outlet gas (post-reaction gas) discharged from the reactor 10, in addition to the gases generated or by-produced by the reaction, there were included unreacted raw material compositions.

[0082] The outlet gas was recovered with the gas storage tank 12 via the outlet gas supply / cooling line 11, and after cooling to 100°C or lower to separate water vapor, a crude product was obtained. The crude product was analyzed with the analysis device 13 (gas chromatograph). The analysis results together with the reaction conditions are shown in Table 1.

[0083] In addition, from the analysis results by the gas chromatograph, the molar composition of the crude product was derived. At this time, based on the gas chromatograph relative sensitivities of each component described in Table 1, the total of the components described in Table 1 was calculated to be 100 mol%.

[0084] In Example 4, in the analysis results by the gas chromatograph, c318 was not detected, and thus is described as "n.d.", and in the molar composition of the crude product, is described as "-".

[0085] [Examples 2 to 8]

[0086] In addition to changing the contact time, the temperature in the reactor, the composition of the raw material composition and the diluent shown in Table 1, the reaction was performed in the same manner as Example 1.

[0087] [Table 1]

[0088]

[0089] The obtained crude product was subjected to dew point measurement after being cooled to room temperature (25°C) under atmospheric pressure, and the dew point was 13.8°C, and the amount of water in the crude product was 1.5 mol%. Since the proportion of water vapor used in the reaction was 90 mol% or more, it was found that by cooling to room temperature after the reaction, most of the water vapor contained in the outlet gas could be removed. Note that the dew point measurement used a dew point meter (product name "TK09-501", manufactured by TEKHNE).

[0090] As found from Examples 5 and 6, when the content of water vapor was 95 mol% or less relative to the total content of c354 and water vapor, the content of VdF in the crude product increased.

[0091] As found from Examples 5 and 8, when the temperature in the reactor during the reaction step was 600°C or more, the content of VdF in the crude product increased.

[0092] As found from Examples 1 and 5, when the contact time of c354 with water vapor was 1 second or more, the content of VdF in the crude product increased.

[0093] Note that the disclosure of Japanese Patent Application No. 2023-043647, filed on March 17, 2023, and Japanese Patent Application No. 2023-101231, filed on June 20, 2023, is incorporated herein by reference in its entirety. Also, all documents, patent applications, and technical standards cited in the present specification are incorporated herein by reference to the same extent as if each individual document, patent application, or technical standard were specifically and individually indicated to be incorporated by reference.

Claims

1. A method for producing vinylidene fluoride, comprising a reaction step of obtaining vinylidene fluoride using a raw material composition comprising 1,1,2,2-tetrafluorocyclobutane and water vapor.

2. The method for producing vinylidene fluoride according to claim 1, further comprising a separation step of separating at least a part of the water vapor from a post-reaction gas containing vinylidene fluoride and water vapor obtained in the reaction step to obtain a post-separation composition having a content of vinylidene fluoride more than the post-reaction gas.

3. The method for producing vinylidene fluoride according to claim 2, wherein The separation step is performed at a temperature above the boiling point of vinylidene fluoride and lower than the boiling point of water under a pressure in a separation vessel, and the water vapor is liquefied and separated.

4. The method for producing vinylidene fluoride according to any one of claims 1 to 3, wherein The content of the water vapor is 95 mol% or less relative to the total content of the 1,1,2,2-tetrafluorocyclobutane and the water vapor.

5. The method for producing vinylidene fluoride according to any one of claims 1 to 3, wherein The temperature in the reactor used in the reaction step is 600°C or more.

6. The method for producing vinylidene fluoride according to any one of claims 1 to 3, wherein The contact time of the 1,1,2,2-tetrafluorocyclobutane with the water vapor is 1 second or more.

7. The method of producing vinylidene fluoride according to any one of claims 1 to 3, wherein The pressure in the reactor used in the reaction step is 0.6 MPaG or less.

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