Method for producing trans-1,2-difluoroethylene

Abstract

Provided is a method that enables the isomerization of HFO-1132 from a Z-isomer to an E-isomer without using chromium oxide. Specifically provided is a method for producing a composition containing trans-1,2-difluoroethylene (HFO-1132 (E)), said method comprising a step for subjecting a composition containing cis-1,2-difluoroethylene (HFO-1132 (Z)) to an isomerization reaction in the presence of a noble metal catalyst.

Description

Method for producing trans-1,2-difluoroethylene

[0001] The present disclosure relates to a method for producing trans-1,2-difluoroethylene.

[0002] In Patent Document 1, a method is described in which an isomerization reaction between cis-1,2-difluoroethylene (hereinafter, also simply referred to as "HFO-1132(Z)") and trans-1,2-difluoroethylene (hereinafter, also simply referred to as "HFO-1132(E)") is carried out using chromium oxide as a catalyst.

[0003] Japanese Patent Application Laid-Open No. 2019-214535

[0004] In view of the above circumstances, an object of the present disclosure is to provide a method that enables isomerization of the Z-form of HFO-1132 to the E-form without using chromium oxide.

[0005] As a result of intensive studies to solve the above problems, the present inventors have found that by using a noble metal catalyst, an isomerization reaction of the Z-form of HFO-1132 to the E-form can be carried out without using chromium oxide. Based on such findings, the present inventors have further conducted studies and completed the present disclosure.

[0006] That is, the present disclosure provides a method for producing a composition containing the following trans-1,2-difluoroethylene (HFO-1132(E)). Item 1. A method for producing a composition containing trans-1,2-difluoroethylene (HFO-1132(E)), comprising a step of subjecting a composition containing cis-1,2-difluoroethylene (HFO-1132(Z)) to an isomerization reaction in the presence of a noble metal catalyst. Item 2. The method according to Item 1, wherein the noble metal catalyst is at least one selected from the group consisting of palladium, rhodium, ruthenium, silver, platinum, gold, iridium, and osmium. Item 3. The method according to Item 1 or 2, wherein the noble metal catalyst is a supported catalyst supported on a carrier. Item 4. The method according to Item 3, wherein the carrier contains carbon or alumina (Al ２ O ３ ). Item 5. The method according to any one of Items 1 to 4, wherein the isomerization reaction is carried out under temperature conditions of 24 to 400°C.

[0007] According to the method for producing trans-1,2-difluoroethylene according to the present disclosure as described above, the isomerization reaction of HFO-1132 from the Z-isomer to the E-isomer can be carried out without using chromium oxide.

[0008] This graph shows the production ratio of the E-isomer to the Z-isomer of HFO-1132 in Examples 1 and 2. This is a schematic diagram of the automated catalyst reactor used in Examples 3 and 4.

[0009] Conventionally, a method using chromium oxide as a catalyst has been proposed for the isomerization reaction of HFO-1132 from the Z-isomer to the E-isomer. However, using chromium oxide as an isomerization catalyst requires prior treatment with hydrofluoric acid under high temperature conditions, and the cost of this treatment is a problem. Therefore, there is a need to develop a more economical alternative method. The disclosers have found that by employing a noble metal catalyst, the isomerization reaction of HFO-1132 from the Z-isomer to the E-isomer can be efficiently carried out without using chromium.

[0010] In this specification, "contains" is a concept that encompasses all of the following: "contains," "consist essentially of," and "consist of." Furthermore, in this specification, when a numerical range is indicated as "A to B," it means A or greater and B or less.

[0011] (1. Method for producing a composition containing HFO-1132(E)) The method for producing a composition containing HFO-1132(E) according to the present disclosure comprises the step of carrying out an isomerization reaction of a composition containing HFO-1132(Z) in the presence of a noble metal catalyst.

[0012] (1.1. Composition containing HFO-1132(Z)) The composition containing HFO-1132(Z) to be subjected to the isomerization reaction may be a composition that does not contain HFO-1132(E) at all, or it may be a mixture containing both HFO-1132(E) and HFO-1132(Z).

[0013] There are no particular limitations on the method for obtaining a composition containing HFO-1132(Z) for isomerization reactions, and a wide range of known methods can be employed. For example, the method described in International Publication No. 2019 / 194214 can be employed.

[0014] One specific example of such a method is to obtain the product by removing hydrogen fluoride by contacting a predetermined fluorocarbon with a base.

[0015] The fluorocarbons mentioned above are not particularly limited and can be broadly selected. For example, 1,1,2-trifluoroethane (HFC-143), 1,1,1-trifluoroethane (HFC-143a), 1,1,2,2-tetrafluoroethane (HFC-134), and 1,1,1,2-tetrafluoroethane (HFC-134a) can be cited, and are of course not limited to these.

[0016] As another method for obtaining a composition containing HFO-1132(Z), an example can be given of a method in which dehalogenation is performed by contacting a fluorocarbon with a noble metal catalyst.

[0017] The catalyst used in this dehalogenation reaction can be a wide range of known metal catalysts, and there are no particular limitations. For example, chromium-based catalysts such as chromium oxide may be used, and it is also preferable to use noble metal catalysts. As for noble metal catalysts, it is preferable to use palladium catalysts, platinum catalysts, rhodium catalysts, ruthenium catalysts, silver catalysts, gold catalysts, iridium catalysts, or osmium catalysts. Of these, palladium catalysts are more preferable because they are used in a variety of applications and are readily available.

[0018] The temperature conditions for the dehalogenation reaction are preferably, for example, 200°C to 400°C, more preferably 200°C to 350°C, and even more preferably 200°C to 300°C.

[0019] A composition containing HFO-1132(Z) may also contain other substances in addition to HFO-1132(E), provided that these substances do not impede the effects or purposes of the present disclosure. Examples of such substances include 1,1,2,2-tetrafluoroethane (HFC-134), 1-fluoroethylene (HFO-1141), chlorofluoromethane (HCFC-31), 1-chloro-1-fluoroethylene, 3,3,3-trifluoropropene, 2-chloro-1,1-difluoroethylene, 1-chloro-1,2-difluoroethylene, and chloromethane.

[0020] Furthermore, if the above-mentioned other substances are included, the content of these substances is preferably 30 mol% or less, more preferably 20 mol% or less, and even more preferably 10 mol% or less, in 100 mol% of the composition containing HFO-1132(Z).

[0021] (1.2. Isomerization Reaction) The method for producing the composition containing HFO-1132(E) of the present disclosure comprises the step of carrying out an isomerization reaction of the composition containing HFO-1132(Z) in the presence of a noble metal catalyst.

[0022] The above isomerization reaction is based on the following reaction formula 1. The E-isomer of HFO-1132 is thermodynamically less stable than the Z-isomer, and the equilibrium between the E-isomer and the Z-isomer is tilted towards the Z-isomer. The method for producing a composition containing HFO-1132(E) according to this disclosure involves performing an isomerization reaction on a composition containing HFO-1132(Z) to obtain a composition with a higher content of the E-isomer than the original composition containing HFO-1132(Z).

[0023]

[0024] In the method for producing the composition containing HFO-1132(E) of this disclosure, a noble metal catalyst is used in the isomerization reaction. Any known noble metal catalyst can be used as the noble metal catalyst, and there are no particular limitations.

[0025] Examples of such precious metal catalysts include palladium, rhodium, ruthenium, silver, platinum, gold, iridium, and osmium.

[0026] Among the options mentioned above, palladium is preferable because it is used in a variety of applications and is readily available.

[0027] It is preferable to use a supported catalyst that is supported on a carrier as the precious metal catalyst. A wide range of carriers used for metal catalysts can be used, and there are no particular limitations. Specifically, carbon or alumina (Al ２ O ３ A carrier containing ) can be used.

[0028] The support containing carbon or alumina is preferably a high-purity carbon-based support or alumina-based support, respectively. Commercially available products can also be used as such supports.

[0029] The amount of catalyst supported on the support is preferably 10% by mass or less, and more preferably 5% by mass or less, relative to the total mass of the noble metal catalyst and the support. The lower limit of the amount of noble metal catalyst supported is not particularly limited and may be 0%, 0.1%, or 0.5% by mass.

[0030] Commercially available products may be used for such supported precious metal catalysts.

[0031] The reaction temperature in the isomerization reaction is preferably 0°C or higher, more preferably 100°C or higher, and even more preferably 200°C or higher. Furthermore, the reaction temperature is preferably 500°C or lower, more preferably 400°C or lower, and even more preferably 300°C or lower.

[0032] The reaction time for the isomerization reaction is not particularly limited and can be set as appropriate. Increasing the contact time can increase the conversion rate, but this increases the amount of catalyst used, making the equipment larger and less efficient, so an appropriate contact time can be set. Typically, the contact time, expressed as the ratio of the catalyst packing amount W (g) to the flow rate Fo of the raw material gas flowing through the reaction system (flow rate at 0°C and 1 atm: cc / sec): W / F, should be in the range of 10 to 80 g / sec / cc, preferably 20 to 60 g / sec / cc.

[0033] The pressure of the reactor used in the isomerization reaction is not particularly limited and can be set as appropriate. However, since high pressure promotes the formation of polymers such as tar, an appropriate pressure should be set. Usually, a range of 0 to 1 MPa is sufficient.

[0034] The isomerization reaction may be carried out in the presence of a diluent gas. This extends the catalyst lifetime. The mechanism for this is not clearly understood, but it is thought to be because the formation of polymers and / or tar is suppressed. As the diluent gas, gases such as oxygen, nitrogen, helium, HF, and argon can be used, and nitrogen gas is particularly preferred in terms of cost.

[0035] To carry out the isomerization reaction in the presence of a diluent gas, the diluent gas should be supplied to the reactor. The supply amount can be set as appropriate. In particular, it is preferable to supply the gas so that the molar ratio of HFO-1132(E) and HFO-1132(Z) is 0.01 to 3.0, more preferably 0.1 to 2.0, and even more preferably 0.2 to 1.0.

[0036] The reactor outlet gas may also contain unreacted fluoroethane, etc.

[0037] Furthermore, the isomerization reaction may be carried out after obtaining a composition containing HFO-1132(Z) by carrying out the dehydrofluoride reaction or dehydrohalogenate reaction described in 1.1 above, or the isomerization reaction may be carried out simultaneously with obtaining the composition containing HFO-1132(Z).

[0038] While embodiments of this disclosure have been described above, this disclosure is by no means limited to these examples, and can be implemented in various forms without departing from the gist of this disclosure.

[0039] The embodiments of this disclosure will be described in more detail below based on the examples, but this disclosure is not limited to these examples.

[0040] [Production Example (Catalyst Preparation Procedure)] Production Example (1.8 Mass% Ru Alumina) A Ru alumina catalyst was produced by the following method. A test tube containing a magnetic stir bar was placed on a magnetic stirrer (manufactured by Tokyo Rikakikai Co., Ltd.). After adding alumina (1.6 g) (manufactured by Merck) and RuCl3 (97.5 g) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) into the test tube, 10 ml of hydrochloric acid with a concentration of 0.08 mol / L (manufactured by Kanto Chemical Co., Inc.) was added dropwise, and the mixture was stirred for 72 hours. After decanting the stirred solution, the precipitate was washed three times with water (10 ml). 50 ml of methanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to the washed precipitate, and reflux was carried out for 45 minutes using a magnetic stirrer (manufactured by Tokyo Rikakikai Co., Ltd.). Then, the precipitate was recovered and dried in vacuo to obtain the catalyst. The metal loading concentration on the support was analyzed using XPS.

[0041] In addition to the above catalyst, 2 mass% Pd alumina (ENE Chemcat Corporation), 2 mass% Pd carbon (ENE Chemcat Corporation), and 3 mass% Pd spherical carbon (Kawaken Fine Chemicals Co., Ltd.) were used.

[0042] (Example 1) 0.5 g of 2 mass% Pd alumina purchased from ENE Chemcat was placed inside a 100 cc pressure-resistant glass industrial portable reactor equipped with a pressure gauge. After closing the reactor, degassing was performed using a vacuum pump. Then, HFO-1132(Z) gas was filled into the reactor at a pressure of 0.2 MPa. A belt heater was wound around the reactor vessel, and the temperature was set using a digital temperature controller TC-1 (manufactured by AS ONE Corporation). The experiment was started at room temperature, and the temperature was sequentially changed up to a maximum of 250 °C, and the products were analyzed at each temperature. Gas was sampled from the sampling port using a 2 ml glass syringe, and the products were analyzed using Nexis GC-2030 and GCMS-QP2020NX manufactured by Shimadzu Corporation. A PorapLOT Q column (length: 50 m, inner diameter: 0.32 mm, film thickness: 10 μm) manufactured by Agilent Technologies was used for GC-2030. As a result of analyzing the reaction products by GCMS, as shown in Figure 1, the formation of the fluoroolefin R1132E (trans-1,2-difluoroethylene) was observed with an increase in temperature.

[0043] (Example 2) The same operations as in Example 1 were carried out, except that carbon was used instead of alumina as the catalyst support. As a result of analyzing the reaction product by GCMS, the formation of R1132E (trans-1,2-difluoroethylene), which is a fluorolefin, was observed with an increase in temperature (Fig. 1).

[0044] (Examples 3 and 4) Using a catalytic automatic reaction apparatus as shown in Fig. 2, R1132E (trans-1,2-difluoroethylene) was produced. In Fig. 2, F-201CL (Bronkhorst) was used as the flow meter, PGI-50M-MG5.0 (Swagelok) was used as the pressure gauge, ARF3-400-9.52KC (Asahi Rika Seisakusho) was used as the electric furnace, a stainless steel outer diameter 1 / 4-inch pipe was used as the piping, and HFO-1132(Z) was used as the raw material. For the reactor (reaction tube), the material was Hastelloy C276, the inner diameter was 7.53 mm, and the catalyst installed in the reaction tube was heated by covering the outside with an electric furnace. The gas after the reaction was passed through a deacidification tower filled with soda lime (medium granular; Fuji Film Wako Pure Chemical Industries, Ltd.) and a dehydration tower filled with calcium chloride (Fuji Film Wako Pure Chemical Industries, Ltd.).

[0045] As the catalyst, 0.11 g of 1.8 mass% Ru alumina (Example 3) and 0.26 g of 3.0% Pd spherical carbon (Example 4) were used. The raw material HFO-1132(Z) gas was supplied to the reactor at a flow rate of 10 ml / min without applying pressure. After HFO-1132(Z) was circulated for 1 hour at room temperature (21°C) in the reaction tube, the reaction gas was sampled from the exhaust port using a 2-ml glass syringe. Similarly, the same operations were carried out at 50°C, 100°C, 200°C, and 300°C to examine the change in the reaction product. The selectivity and conversion were calculated excluding the compounds considered to be derived from impurities.

[0046] The results of Example 3 are shown in Table 1 below, and the results of Example 4 are shown in Table 2. For any of the examples, no by-products derived from HFO-1132(Z) were observed up to 100°C, and the formation of by-products was observed at 150°C or higher. The conversion increased as the temperature increased.

[0047]

[0048]

Claims

1. A method for producing a composition containing trans-1,2-difluoroethylene (HFO-1132(E)), comprising the step of carrying out an isomerization reaction of a composition containing cis-1,2-difluoroethylene (HFO-1132(E)) in the presence of a noble metal catalyst.

2. The method according to claim 1, wherein the precious metal catalyst is at least one selected from the group consisting of palladium, rhodium, ruthenium, silver, platinum, gold, iridium, and osmium.

3. The method according to claim 1 or 2, wherein the noble metal catalyst is a supported catalyst supported on a carrier.

4. The carrier is carbon or alumina (Al ２ O ３ The method according to claim 3, including ) 5. The method according to claim 1 or 2, wherein the isomerization reaction is carried out under temperature conditions of 24 to 400°C.

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