Method for producing halogenated alkene

Abstract

To provide a method for producing a halogenated alkene which prevents a reduction in yield over time, as compared with traditional methods.SOLUTION: This method for producing a halogenated alkene comprises converting a halogenated alkane which has 2-4 carbon atoms and contains a fluorine atom into a halogenated alkene which has 2-4 carbon atoms and contains a fluorine atom in a gas phase in the presence of silicon oxide and an alkali metal element.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a process for producing halogenated alkenes. [Background technology]

[0002] In recent years, halogenated alkenes (fluoroolefins) have been attracting attention as compounds with low global warming potential.

[0003] For example, Patent Document 1 describes a method for producing hydrofluoroolefins in which hydrofluorocarbons are converted to hydrofluoroolefins in the presence of a fluorine-containing compound having a higher normal boiling point than the normal boiling point of the target hydrofluoroolefin. The reaction step of this production method includes a step of contacting hydrofluorocarbons with a catalyst. Specific examples of the catalyst include alumina (Al 2 O 3 ) is used. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2017 / 104829 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when fluoroolefins are produced by the dehydrofluorination reaction of fluorocarbons using a catalyst such as that described in Patent Document 1, the catalyst deteriorates over time due to the generated hydrogen fluoride, and the amount of fluoroolefin produced decreases over time.

[0006] Therefore, an object of one embodiment of the present disclosure is to provide a method for producing a halogenated alkene in which the decrease in the production amount over time is suppressed as compared to conventional methods. [Means for solving the problem]

[0007] The present disclosure includes the following aspects. <1> A method for producing a halogenated alkene, comprising converting a halogenated alkane containing a fluorine atom and having 2 to 4 carbon atoms in a gas phase in the presence of silicon oxide and an alkali metal element, into a halogenated alkene containing a fluorine atom and having 2 to 4 carbon atoms. <2> The halogenated alkane includes a halogenated alkane represented by the following formula (1), and the halogenated alkene includes a halogenated alkene represented by the following formula (2): <1> 3. The method for producing a halogenated alkene according to claim 1 . CR 1 R 2 X 1 -CR 3 R 4 X 2 (1) CR 1 R 2 =CR 3 R 4 (2) In formula (1) and formula (2), R 1 ~R 4 each independently represents a hydrogen atom, a fluorine atom, a methyl group, a fluorinated methyl group, an ethyl group, or a fluorinated ethyl group; R 1 ~R 4 The total number of fluorine atoms is 1 or more, and the total number of carbon atoms is 2 to 4. 1 and X 2 one of which is a hydrogen atom and the other is a fluorine atom. <3> Silicon tetrafluoride is produced. <1> or <2> 3. The method for producing a halogenated alkene according to claim 1 . <4> a dehydrofluorination reaction of the halogenated alkane to produce the halogenated alkene and hydrogen fluoride in a gas phase; and reacting the produced hydrogen fluoride with silicon oxide to produce silicon tetrafluoride. <1> ~ <3> 13. The method for producing a halogenated alkene according to claim 12. <5> The halogenated alkane is 1,1-difluoroethane, 1,2-difluoroethane, at least one selected from the group consisting of ethane, 1,1,1-trifluoroethane, 1,1,2-trifluoroethane, 1,1,2,2-tetrafluoroethane, 1,1,1,2-tetrafluoroethane, and 1,1,1,2,2-pentafluoroethane; <1> ~ <4> 13. The method for producing a halogenated alkene according to claim 12. <6> The halogenated alkene is at least one selected from the group consisting of fluoroethylene, 1,1-difluoroethylene, 1,2-difluoroethylene, trifluoroethylene, and tetrafluoroethylene. <1> ~ <5> 13. The method for producing a halogenated alkene according to claim 12. <7> The halogenated alkane is converted in the presence of a diluent gas. <1> ~ <6> 13. The method for producing a halogenated alkene according to claim 12. <8> The dilution gas is at least one selected from the group consisting of nitrogen, hydrogen, carbon dioxide, helium, ethane, propane, isobutane, n-butane, propylene, and fluorinated methane; <7> 3. The method for producing a halogenated alkene according to claim 1 . <9> The halogenated alkane is converted at a temperature of 400 to 1000°C. <1> ~ <8> 13. The method for producing a halogenated alkene according to claim 12. <10> A method for producing a halogenated alkene, comprising converting a halogenated alkane containing a fluorine atom and having 2 to 4 carbon atoms in a gas phase in the presence of boron oxide, into a halogenated alkene containing a fluorine atom and having 2 to 4 carbon atoms. Effect of the Invention

[0008] According to the present disclosure, there is provided a method for producing a halogenated alkene in which the decrease in the production amount over time is suppressed compared to conventional methods. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In the present disclosure, a numerical range indicated using "~" means a range that includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in the present disclosure. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples. In the present disclosure, combinations of two or more preferred embodiments are more preferred embodiments. In the present disclosure, when there are multiple substances corresponding to each component, the amount of each component means the total amount of the multiple substances, unless otherwise specified.

[0010] [Method of producing halogenated alkenes] The method for producing a halogenated alkene according to the present disclosure involves converting a halogenated alkane containing a fluorine atom and having 2 to 4 carbon atoms in a gas phase in the presence of silicon oxide and an alkali metal element, into a halogenated alkene containing a fluorine atom and having 2 to 4 carbon atoms. Hereinafter, the "halogenated alkane containing a fluorine atom and having 2 to 4 carbon atoms" will also be referred to as the "specific halogenated alkane", and the "halogenated alkene containing a fluorine atom and having 2 to 4 carbon atoms" will also be referred to as the "specific halogenated alkene".

[0011] According to the method for producing a halogenated alkene of the present disclosure, the decrease in the production amount over time is suppressed compared to the conventional method. Although the reason for this is unclear, it is presumed as follows.

[0012] In the reaction to obtain a halogenated alkene containing a fluorine atom from a halogenated alkane containing a fluorine atom, hydrogen fluoride is generated. The generated hydrogen fluoride is converted into hydrogen fluoride by using, for example, alumina (Al 2 O 3 ) reacts with alumina to form AlF 3 and uses calcium carbonate (CaCO 3 ) is used, CaF 2 where AlF 3 The boiling point of CaF is 1260°C. 2 Since the boiling point of is 2533℃, these are Therefore, the generated AlF 3 and CaF 2 The catalyst reacts with the catalyst surface and the reaction sites on the catalyst surface are covered.

[0013] In contrast, in the method for producing a halogenated alkene according to the present disclosure, a specific halogenated alkene is obtained from a specific halogenated alkane in the presence of silicon oxide and an alkali metal element. In this case, the generated hydrogen fluoride reacts with silicon oxide, or the specific halogenated alkane reacts directly with silicon oxide and an alkali metal element, and silicon tetrafluoride (SiF 4 ) is generated. Since the boiling point of silicon tetrafluoride is −95° C., it is in the form of a gas in the reaction system and is released to the outside of the reaction system. Therefore, in the method for producing a halogenated alkene of the present disclosure, it is considered that the coating of silicon oxide is suppressed and a rapid decrease in the amount of halogenated alkene produced is suppressed.

[0014] The process for producing a halogenated alkene according to the present disclosure will be described in detail below.

[0015] (halogenated alkane) In the method for producing a halogenated alkene according to the present disclosure, a specific halogenated alkane is used as a raw material. The specific halogenated alkane has 2 to 4 carbon atoms, and may have 2, 3, or 4 carbon atoms. From the viewpoint of the boiling point range of the compound that can serve as a refrigerant, the specific halogenated alkane preferably has 2 or 3 carbon atoms. The specific halogenated alkane contains a fluorine atom, and the number of fluorine atoms in the specific halogenated alkane is preferably 2 or more. The specific halogenated alkane preferably has one or more hydrogen atoms. The specific halogenated alkane may contain halogen atoms other than fluorine atoms. Examples of the other halogen atoms include chlorine atoms, bromine atoms, and iodine atoms, and chlorine atoms are preferred. The specific halogenated alkane may not contain other halogen atoms.

[0016] The specific halogenated alkane includes a halogenated alkane represented by the following formula (1). CR 1 R 2 X 1 -CR 3 R 4 X 2 (1)

[0017] In formula (1), R 1 ~R 4 each independently represents a hydrogen atom, a fluorine atom, a methyl group, a fluorinated methyl group, an ethyl group, or a fluorinated ethyl group; R 1 ~R 4 The total number of fluorine atoms is 1 or more, the number of carbon atoms is 2 to 4, and X 1 and X 2 one of which is a hydrogen atom and the other is a fluorine atom.

[0018] R 1 and R 3 are each preferably independently a hydrogen atom or a fluorine atom, and R 2 and R 4 is a hydrogen atom, a fluorine atom, or a CH 3 , C.H. 2 F, CHF 2 or CF 3 It is preferable that:

[0019] Examples of halogenated alkanes represented by formula (1) include the following compounds. CHF 2 CH 3 : 1,1-difluoroethane (HFC-152a) CH 2 FCH 2 F: 1,2-difluoroethane (HFC-152) CF 3 CH 3 : 1,1,1-trifluoroethane (HFC-143a) CHF 2 CH 2 F: 1,1,2-trifluoroethane (HFC-143) CF 3 CH2 F: 1,1,1,2-tetrafluoroethane (HFC-134a) CHF 2 CHF 2 : 1,1,2,2-Tetrafluoroethane (HFC-134) CF 3 CHF 2 : 1,1,1,2,2-Pentafluoroethane (HFC-125)

[0020] The specific halogenated alkane may contain a halogenated alkane other than the halogenated alkane represented by formula (1) (which contains a fluorine atom and has a carbon number of 2 to 4). The proportion of the halogenated alkane represented by formula (1) in the total amount of the specific halogenated alkane is preferably 30 mol % or more, more preferably 50 mol % or more.

[0021] (Halogenated alkene represented by formula (2)) In the method for producing a halogenated alkene according to the present disclosure, a specific halogenated alkene is obtained as a reaction product. The specific halogenated alkene has 2 to 4 carbon atoms, and may have 2, 3, or 4 carbon atoms. The specific halogenated alkene contains a fluorine atom. The number of fluorine atoms in the specific halogenated alkene is 1 or more. The specific halogenated alkene may contain other halogen atoms other than fluorine atoms. Examples of other halogen atoms include chlorine atoms, bromine atoms, and iodine atoms, and chlorine atoms are preferred. The specific halogenated alkene may not contain other halogen atoms.

[0022] The specific halogenated alkene includes a halogenated alkene represented by the following formula (2). CR 1 R 2 =CR 3 R 4 (2)

[0023] In formula (2), R 1 ~R 4each independently represents a hydrogen atom, a fluorine atom, a methyl group, a fluorinated methyl group, an ethyl group, or a fluorinated ethyl group; R 1 ~R 4 The total number of fluorine atoms is 1 or more, and the total number of carbon atoms is 2 to 4.

[0024] R 1 and R 3 are each preferably independently a hydrogen atom or a fluorine atom, and R 2 and R 4 is a hydrogen atom, a fluorine atom, or a CH 3 , C.H. 2 F, CHF 2 or CF 3 It is preferable that:

[0025] Examples of halogenated alkenes represented by formula (2) include the following compounds. CHF=CH 2 : Fluoroethylene (HFO-1141) CF 2 =CH 2 : 1,1-difluoroethylene (HFO-1132a) CHF=CHF: 1,2-difluoroethylene (HFO-1132(E), HFO-1132(Z)) CHF=CF 2 : Trifluoroethylene (HFO-1123) CF 2 =CF 2 : Tetrafluoroethylene (FO-1114)

[0026] Among them, the halogenated alkene represented by formula (2) is preferably at least one selected from the group consisting of HFO-1132, HFO-1132a, and HFO-1123 from the viewpoint of usefulness as a refrigerant composition. Also, from the viewpoint of usefulness as a resin, HFO-1141 and HFO-1114 are preferred.

[0027] (Silicon oxide and alkali metal elements) In the method for producing a halogenated alkene disclosed herein, a specific halogenated alkane is converted to a specific halogenated alkene in the presence of silicon oxide and an alkali metal element.

[0028] Silicon oxide and an alkali metal element may be an integrated compound or composite containing both, or separate substances containing silicon oxide and an alkali metal element may be used, or two or more of these may be used in combination. For example, glass containing silicon oxide and an oxide of an alkali metal, sodium silicate, sodium silicate cullet, etc., a composite in which an alkali metal-containing compound is supported on silicon oxide particles, a combination of silicon oxide particles and an alkali metal-containing compound, etc. may be mentioned.

[0029] When silicon oxide and an alkali metal element are integrated, uneven distribution in the reaction system is easily suppressed. When silicon oxide and an alkali metal-containing compound are used as separate substances, it is easy to prepare high purity substances for each, and the generation of unnecessary by-products when used in the reaction is easily suppressed. Hereinafter, compounds and composites containing both silicon oxide and an alkali metal element, as well as substances containing silicon oxide and an alkali metal element separately, are collectively referred to as "reactants".

[0030] The reactant may contain other components in addition to silicon oxide and alkali metal elements, such as calcium, aluminum, magnesium, iron, boron, lead, and zinc.

[0031] The shape of the glass is not particularly limited, and may be any of an irregular shape such as crushed material, a cullet shape, a scale shape, a sphere shape, etc. Also, the glass may be formed into a pellet shape, a hollow shape, a cylinder shape, etc. These shapes may be appropriately combined.

[0032] Examples of silicon oxide particles used in combination as a composite or separate substance include silica sand, quartz, diatomaceous earth, colloidal silica, precipitated silica, silica gel, fumed silica, rice husk, etc., with silica sand being preferred from the standpoint of purity and cost.

[0033] The shape of the silicon oxide particles is not particularly limited, and may be any of irregular shapes such as natural products and crushed products, cullet-like, scaly, spherical, etc. Also, they may be molded into pellets, hollow, cylindrical, etc. Also, the silicon oxide particles may have a pore structure (porous, etc.). These shapes may be appropriately combined, and examples thereof include porous cylindrical molded products.

[0034] It is preferable that the silicon oxide particles have a low impurity content, and from the viewpoint of suppressing the production of unnecessary by-products, the silicon oxide content in the silicon oxide particles is preferably low, and is preferably 70 mass% or more, more preferably 80 mass% or more, and even more preferably 90 mass% or more.

[0035] The size of the glass, composite, and silicon oxide particles is preferably 20 μm or more, more preferably 50 μm or more, in terms of preventing clogging in the reactor, and is preferably 10 mm or less, more preferably 5 mm or less, and even more preferably 1 mm or less, in terms of ensuring a surface area that serves as a reaction site.

[0036] The average particle size of glass, composite, and silicon oxide particles is determined as the particle size (D50) at which the cumulative weight distribution curve based on the volume is 50% as measured by a Coulter counter. The aperture diameter is appropriately set according to the particle size range to be measured.

[0037] The silicon content in the reactant may be 1 atm% or more, 10 atm% or more, or 20 atm% or more. Also, the silicon content in the reactant may be 90 atm% or less, or 80 atm% or less. The oxygen content in the reactants may be 1 atm% or more, 5 atm% or more, or 10 atm% or more. The oxygen content in the reactants may be 90 atm% or less, or 80 atm% or less. The content of the alkali metal element in the reactant may be 1 atm% or more, 5 atm% or more, or 8 atm% or more. The percentage may be 90 atm% or less, or may be 50 atm% or less.

[0038] The content of each element in the reactant is determined by scanning electron microscope energy dispersive X-ray spectroscopy (SEM-EDX analysis).

[0039] In the reactant, the content of silicon (atm %) is preferably greater than the content (atm %) of alkali metal elements, and is preferably greater than the total content of alkaline earth metals and Group 13 elements of the periodic table, and it is preferable that silicon is the element with the highest content (atm %) among elements excluding oxygen. In addition, the content (atm%) of the alkali metal element in the reactant is preferably higher than the respective contents of elements other than silicon, oxygen, and alkali metal elements. In the glass, the content (atm%) of the alkali metal element may be higher, lower, or the same as the total content of the alkaline earth metals and the elements of Group 13 of the periodic table.

[0040] The alkali metal element is preferably at least one selected from the group consisting of Na, K, Rb, and Cs, and from the viewpoints of activity, selectivity, and availability, it is preferably at least one selected from the group consisting of Na, K, and Cs. The alkali metal-containing compound may contain an alkali metal element, and examples thereof include halides such as fluorides and chlorides of alkali metals, hydroxides, and carbonates. Specific examples thereof include NaF, KF, CsF, NaOH, KOH, Na 2 CO 3 , K 2 CO 3 , NaCl, etc.

[0041] (Reaction scheme) In the disclosed method for producing halogenated alkenes, silicon tetrafluoride (SiF 4In the method for producing a halogenated alkene according to the present disclosure, a reaction scheme is considered in which a specific halogenated alkene and hydrogen fluoride are produced in a gas phase by a dehydrofluorination reaction of a specific halogenated alkane (first step), and silicon tetrafluoride is produced by a reaction between the produced hydrogen fluoride and silicon oxide (second step). The first step and the second step may proceed consecutively without being distinguished from each other. The method for producing a halogenated alkene according to the present disclosure may be a reaction scheme other than the above. For example, silicon oxide or an alkali metal compound may directly react with a halogenated alkane to produce silicon tetrafluoride. In addition to silicon tetrafluoride, other compounds may also be produced.

[0042] Below is a hypothetical example of a reaction scheme in which a halogenated alkane represented by formula (1) is used as the specific halogenated alkane to obtain a halogenated alkene represented by formula (2) as the specific halogenated alkene.

[0043] [ka]

[0044] The silicon tetrafluoride generated is in the form of gas and is released from the reaction system, thereby suppressing the effect of the by-product on silicon oxide and preventing a rapid decrease in the amount of halogenated alkenes produced.

[0045] In the conventional production method using alumina, calcium carbonate, or the like as a catalyst, the generated hydrogen fluoride reacts with the catalyst as follows.

[0046] [ka]

[0047] The resulting aluminum fluoride (AlF 3 ) and calcium fluoride (CaF 2Since ) is a solid, it does not leave the reaction system but remains there, coating the surface of the catalysts, alumina and calcium carbonate. This covers the active points on the catalyst surface and deactivates it, so in conventional manufacturing methods, the deteriorated catalyst must be removed and replaced with a new one. Therefore, in conventional manufacturing methods that use alumina, calcium carbonate, etc. as catalysts, not only is productivity unstable, but the reaction must be stopped every time the catalyst is replaced. In contrast, the method for producing a halogenated alkene according to the present disclosure has the advantage that the work of removing a deteriorated catalyst can be reduced and productivity can be maintained.

[0048] In the method for producing halogenated alkenes of the present disclosure, the reaction can be continued by replenishing the consumed silicon oxide. The amount of consumed silicon oxide can be converted from the amount of silicon tetrafluoride released from the inside to the outside of the reaction system. Specifically, the released silicon tetrafluoride is passed through water, an alkaline aqueous solution, etc. to convert it into hydrogen fluoride, hexafluorosilicic acid, salts thereof, etc., and the amount of released silicon tetrafluoride can be measured by titrating these. On the other hand, in the conventional manufacturing method using alumina or calcium carbonate as a catalyst, AlF 3 or CaF 2 Therefore, it is difficult to estimate the amount of catalyst that has deteriorated due to the fact that the catalyst remains in the catalyst tank. Therefore, it is difficult to appropriately estimate the amount of catalyst to be replenished in the conventional manufacturing method.

[0049] Furthermore, when reacting in a fluidized bed, it is desirable that the fluidity of the catalyst does not change significantly. 3 or CaF 2 As a result, the catalyst's weight and density change, causing fluctuations in fluidity, making it difficult to maintain an appropriate fluid state. In contrast, in the manufacturing method of the present disclosure, the by-product SiF 4 Since is a gas and is released outside the reaction system, there is no significant change in the fluidity of silicon oxide, and it is easy to maintain an appropriate fluid state.

[0050] (Reaction conditions) The process for producing a halogenated alkene according to the present disclosure is carried out in the gas phase because the specific halogenated alkane is a gas at room temperature. In the method for producing halogenated alkenes of the present disclosure, the raw material gas may contain the specific halogenated alkane, and may contain components other than the specific halogenated alkane. The raw material gas may consist of only the specific halogenated alkane, or may contain isomers, disproportionation products, impurities, etc. obtained during the production of the specific halogenated alkane. From the viewpoint of suppressing side reactions, the content of the specific halogenated alkane is preferably 10 mol% or more, more preferably 30 mol% or more, and even more preferably 50 mol% or more, based on the total amount of the raw material gas. The content of the halogenated alkane represented by formula (1) may be 100 mol% based on the total amount of the raw material gas.

[0051] The reactor in which the halogenated alkane and the reactant are reacted may be any reactor capable of withstanding the temperature and pressure described below, and the shape and structure are not particularly limited. The reactor may be, for example, a cylindrical vertical reactor. The reactor may be made of glass, stainless steel, iron, nickel, chromium, or an alloy mainly composed of iron, nickel, or chromium. The inside of the reactor may be coated with platinum, gold, or the like. The reactor may also be equipped with a heating means, such as an electric heater, for heating the inside of the reactor.

[0052] The reactants may be accommodated in any of the following forms: fixed bed, fluidized bed, and moving bed. In the case of a fixed bed, the reactor may be either a horizontal fixed bed or a vertical fixed bed. The reactor may be rotated as a whole. The reaction may be carried out in a flow manner or in a batch manner.

[0053] In a fixed bed reactor, various molded bodies of reactant-supporting carriers are filled to reduce pressure loss of the reaction fluid. A reactor in which reactants are filled in the same way as in a fixed bed reactor, moved by gravity, and withdrawn from the bottom of the reactor for regeneration is called a moving bed. In a fluidized bed reactor, the reactant bed is operated in such a way that it exhibits fluid-like properties due to the reaction fluid, so that the reactants mix with the reaction fluid and move within the reactor. A fixed bed reactor is preferred in that there is a wide range of options for the shape of the reactants and that wear of the reactants can be suppressed, while a fluidized bed reactor is preferred in that the internal temperature becomes uniform and local heating can be easily avoided.

[0054] Fixed bed reactors include tubular reactors and tank reactors, with tubular reactors being preferred due to the ease of controlling the reaction temperature. Furthermore, a multi-tube heat exchange reaction can be used in which a large number of reaction tubes with small diameters are arranged in parallel and a heat transfer medium is circulated on the outside. When multiple reactors are arranged in series, multiple reactant layers are provided. There needs to be at least one reactant layer, but there may be two or more layers.

[0055] In the case of a fluidized bed reactor, the raw material gas and further the dilution gas may be caused to flow vertically from below, and the product gas may be withdrawn vertically from above. The fluidized bed reactor may be provided with stirring blades in order to further increase the fluidity. In addition, in order to prevent the gas flow in the fluidized bed reactor from being biased, the fluidized bed reactor may be provided with a gas dispersion plate. The material of the gas dispersion plate is not particularly limited, and it is preferably made of a material that has low reactivity with the raw material gas, the generated gas, etc. Examples of the material of the gas dispersion plate include sintered metal. The size, arrangement position, and number of the gas dispersion plate may be appropriately adjusted according to the gas flow.

[0056] In the method for producing a halogenated alkene according to the present disclosure, the halogenated alkane is preferably converted at a temperature of 400 to 1000°C, more preferably at a temperature of 450 to 900°C, and even more preferably at a temperature of 500 to 800°C. If the conversion is carried out at 400°C or higher, the reaction proceeds properly and the conversion rate of the halogenated alkene increases. On the other hand, if the conversion is carried out at 1000°C or lower, the selectivity decreases due to the cleavage of the carbon-carbon bonds of the raw material, and the disproportionation reaction of the reaction product (unsaturated compound) is suppressed.

[0057] It is also possible to suppress a decrease in the conversion rate by appropriately maintaining the reaction temperature within the above temperature range. In order to maintain the reaction temperature in the reactant layer at a desired temperature, for example, the reactant layer may be heated from the outside with a heat medium, an electric furnace, or the like.

[0058] As described above, in the method for producing halogenated alkenes of the present disclosure, the reaction can be continued by replenishing consumed silicon oxide, and productivity can be maintained. From the viewpoint of continuing the reaction, it is preferable to continuously supply silicon oxide in an amount equivalent to the consumed amount. The position of silicon oxide supply in the reactor is not particularly limited, and may be from the top or bottom of the reactor.

[0059] In the method for producing halogenated alkenes of the present disclosure, the raw material gas containing the halogenated alkane may be supplied to the reactor as it is at room temperature, or may be appropriately heated (preheated) before being supplied to the reactor. When preheating is performed, it is preferable to heat the raw material gas to 80°C or higher and below the reaction temperature in the reactor before supplying it to the reactor. When the preheating temperature is 80°C or higher, the internal temperature of the reactor is less likely to decrease, and the set conversion rate is easily achieved. In addition, when the preheating temperature is below the reaction temperature in the reactor, undesirable reactions are suppressed, and the selectivity is improved.

[0060] The dehydrofluorination reaction in the present disclosure is a reaction in which the number of molecules increases, so increasing the pressure makes the forward reaction unfavorable. The pressure when reacting the halogenated alkane with the reactant is not particularly limited, but from the viewpoint of improving the conversion rate, it is preferably from −0.05 to 2 MPa, more preferably from −0.01 to 1 MPa, and even more preferably from normal pressure to 0.5 MPa. In this disclosure, pressure means gauge pressure.

[0061] The residence time of the halogenated alkane is preferably from 0.5 to 300.0 seconds, more preferably from 1.0 to 100.0 seconds, and further preferably from 1.5 to 60.0 seconds.

[0062] The residence time (seconds) is calculated using the following formula: Residence time (sec) = [length of reactant packed in reactor (cm)] / [linear velocity (cm / sec)] Linear velocity refers to the rate at which the halogenated alkane passes through the reactants per unit time.

[0063] The average bulk density of the reactant is 0.05 g / cm 3 More than 0.1 g / cm is preferable. 3 More preferably, 0.2 g / cm 3 More preferably, the average bulk density of the reactant is 0.05 g / cm or more. 3 If it is more than this, the conversion rate is improved. The average bulk density of the reactants is the average value of the densities of the reactants when no gas is flowing through the reactor. The average bulk density of a reactant is measured by the container method. In this method, the reactant is poured into a container of known capacity until it overflows, and the excess reactant protruding from the top edge of the container is removed with a spatula or the like, and the mass of the reactant in the container is measured. The bulk density (g / mL) is calculated from the mass of the reactant and the capacity (volume) of the container. This measurement is carried out three times, and the average value is taken as the average bulk density.

[0064] The conversion of the specific halogenated alkane is preferably carried out in the presence of a diluent gas. The diluent gas is preferably at least one selected from the group consisting of nitrogen, hydrogen, carbon dioxide, helium, propane, isobutane, n-butane, ethane, propylene, and fluorinated methane. The fluorinated methane includes monofluoromethane, difluoromethane, trifluoromethane, and monofluoromethane. The molar ratio of the specific halogenated alkane to the diluent gas in the gas phase is preferably from 0.1 to 5.0, more preferably from 0.5 to 3.0, and even more preferably from 0.5 to 2.0.

[0065] In general, in a method for producing a halogenated alkene, a diluent gas is used from the viewpoint of suppressing a disproportionation reaction caused by an increase in the concentration of the produced halogenated alkene and from the viewpoint of a concern of an explosion due to an increase in the concentration of the halogenated alkene depending on the type of the halogenated alkene. In the method for producing halogenated alkenes of the present disclosure, it is possible to control the reactivity by residence time, reaction temperature, etc., and thus the concentration of the specific halogenated alkene in the outlet gas can be controlled by these controls. In the method for producing halogenated alkenes of the present disclosure, it is possible to maintain and suppress the amount of halogenated alkenes produced within a certain range by the above-mentioned controls, and therefore it is possible to contain a certain amount of the specific halogenated alkane as the raw material in the outlet gas. The specific halogenated alkane in the outlet gas also functions as a diluent. Therefore, in the method for producing halogenated alkenes of the present disclosure, it is also possible to suppress the amount of diluent gas used. The method for producing halogenated alkenes of the present disclosure also includes an embodiment in which no diluent gas is used.

[0066] In addition, as described in Patent Document 1, in the method for producing fluoroolefins using an alumina catalyst, the conversion rate decreases when the amount of diluent is reduced, so the raw material gas is used as a diluent. It is difficult to use diluent gases such as nitrogen and carbon dioxide, and it is necessary to use diluent gases such as nitrogen gas and carbon dioxide. Since diluent gases such as nitrogen gas and carbon dioxide have lower boiling points or boiling points close to those of the halogenated alkene, which is the reaction product, energy is required to separate and purify the diluent gas from the reaction product. In the method for producing halogenated alkenes of the present disclosure, even if the feed gas is used as a part or all of the diluent, the decrease in the amount of halogenated alkenes produced over time is suppressed. Since the halogenated alkane as the feedstock has a high boiling point and is in a boiling point zone separate from the halogenated alkene as the reaction product, the method for producing halogenated alkenes of the present disclosure can also reduce the energy load required for separation and purification.

[0067] From the viewpoint of controlling the efficiency and selectivity of the reaction, it is preferable that the conversion of the specific halogenated alkane is carried out in the gas phase in the presence of water, and the concentration of water is less than 500 ppm by volume based on the total amount of the raw material gas containing the specific halogenated alkane. The dehydrofluorination reaction in the present disclosure also produces water. Therefore, it can be said that the reaction proceeds without any problems even if water is present in the present system. In addition, when hydrogen fluoride is desorbed from the raw material or when hydrogen fluoride reacts with silicon oxide, the presence of water molecules may allow the reaction to proceed more efficiently via a hydrogen bond network. Therefore, it is possible to add a small amount of water to the dehydrofluorination reaction in the present disclosure, and it is presumed that this may have a favorable effect. On the other hand, the generated silicon tetrafluoride reacts with water near the outlet to generate hexafluorosilicic acid and the like, and from the viewpoint of preventing clogging of the gas flow path due to the precipitation of this compound, it is preferable that the water concentration be less than the above range.

[0068] A common method for measuring the moisture content of gas is to use a commercially available dew point meter. The moisture content is less than 500 ppm by volume relative to the total amount of the specific halogenated alkane, so that the conversion rate is high and the target product can be obtained with high selectivity. The moisture content is preferably 300 ppm by volume or less, more preferably 100 ppm by volume or less, even more preferably 50 ppm by volume or less, and particularly preferably 10 ppm by volume or less, in order to further improve the conversion rate and obtain the target compound with higher selectivity. A lower moisture content is preferable, but from the viewpoint of the cost of dehydration treatment of the specific halogenated alkane and diluent gas and the difficulty of process management, it is preferably 0.5 ppm by volume or more, and more preferably 1 ppm by volume or more.

[0069] The water concentration is the water content contained in the raw material gas when the specific halogenated alkane is reacted with the reactant. The water concentration may be replaced with the water content contained in the raw material gas before it is introduced into the reactor.

[0070] The method for producing a halogenated alkene according to the present disclosure may further include a step of drying the reactant before reacting the specific halogenated alkane with the reactant. By drying the reactant, water contained in the reactant may be removed, and the water concentration may be adjusted to within the above range.

[0071] The method for drying the reactants is not particularly limited, and the reactants may be dried before being filled into the reactor, or may be dried after being filled into the reactor. When drying the reactants after being filled into the reactor, the reactor can be preheated in addition to drying the reactants. Specifically, the reactants may be dried by filling the reactor with the reactants and heating the reactor while passing a dilution gas through it.

[0072] In the present disclosure, the conversion rate is the ratio (%) of the molar amount of the specific halogenated alkane consumed in the reaction to the molar amount of the specific halogenated alkane supplied to the reactor. The molar amount of the specific halogenated alkane contained in the gas effluent from the reactor outlet is the difference between the molar amount of the specific halogenated alkane and the molar amount of the specific halogenated alkane contained in the gas effluent from the reactor outlet.

[0073] In general, a higher conversion rate is preferable from the viewpoint of productivity. However, in the case of a specific halogenated alkene that is likely to explode due to its high concentration, it is preferable to select operating conditions that result in a conversion rate of 70% or less from the viewpoint of suppressing explosion and suppressing the disproportionation reaction of the specific halogenated alkene. The conversion rate is preferably 50% or less, more preferably 30% or less. If the conversion rate is too low, productivity decreases and the equipment becomes large, so it is preferable to select operating conditions that result in a conversion rate of 5% or more. The conversion rate is preferably 10% or more, more preferably 15% or more.

[0074] In the present disclosure, selectivity means the ratio (mol %) of the molar amount of the target product contained in the reactor outlet gas to the total molar amount of compounds other than the raw materials contained in the reactor outlet gas (however, these are compounds derived from carbon of the specific halogenated alkane that is the raw material, excluding compounds such as silicon tetrafluoride that do not have carbon derived from the raw materials). A selectivity of 100% is preferred since it eliminates the need for post-reaction purification steps, but side reactions may occur in the reaction temperature range required to obtain the desired conversion. A high selectivity is preferred because it reduces the amount of waste, reduces the energy load of post-reaction purification steps, and extends the life of the reactants. A selectivity of 90% or more is preferred, 93% or more is more preferred, and 95% or more is even more preferred.

[0075] Examples of compounds contained in the reactor outlet gas other than the raw material compounds and the target product include carbon monoxide, carbon dioxide, water, silicon tetrafluoride, and the like.

[0076] According to the method for producing halogenated alkenes of the present disclosure, the decrease in the amount of specific halogenated alkenes produced during long-term production (specifically, 5 hours or more) is suppressed. The amount of specific halogenated alkenes produced after 5 hours is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more, relative to the amount of specific halogenated alkenes produced after 1 hour.

[0077] The amount of production is determined by analyzing the reactor outlet gas by gas chromatography and determining the area ratio (GC Area %) corresponding to a specific halogenated alkene.

[0078] The silicon tetrafluoride released in the method for producing halogenated alkenes of the present disclosure can be used as a raw material for producing high-performance optical fibers, a gas for producing semiconductors, and the like. In addition, the silicon tetrafluoride released from the reaction system can be reacted with water or an alkali to recover hydrogen fluoride or a fluoride salt. These recovered compounds can be used as etching agents or as raw materials for organic fluorine compounds. For example, calcium carbonate (CaCO 3 ) generated by the conventional method using calcium fluoride (CaF 2 To convert fluorite (CaF) to hydrogen fluoride, the radical conditions of reacting it with sulfuric acid are required, and the solid CaF 2 Pre-processing such as crushing is required.

[0079] (Modification) In a modified example of the method for producing a halogenated alkene according to the present disclosure, a halogenated alkane containing fluorine atoms and having 2 to 4 carbon atoms may be converted to a halogenated alkene containing fluorine atoms and having 2 to 4 carbon atoms in a gas phase in the presence of boron oxide. The halogenated alkane and halogenated alkene in this case are the same as those described above. The same also applies to the dilution gas, reactor, etc. that can be used. The boron oxide may be used in combination with other components, for example in the form of borosilicate glass. EXAMPLES

[0080] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to the following examples as long as it does not depart from the gist of the disclosure. Examples 2, 3, 5, and 7 to 20 are examples, and Examples 1, 4, and 6 are comparative examples.

[0081] (Outlet gas composition) The generated gas (hereinafter also referred to as "reactor outlet gas") taken out from the outlet of the reactor at specific time intervals from the start of the reaction was analyzed by gas chromatography. Specifically, a column (product name "DB-1", Agilent, length 60 m, inner diameter 0.25 mm, film thickness 1 μm) was attached to a gas chromatograph (product name "GC6850", Agilent) and analyzed. The area ratio (GC Area%) of the reactor outlet gas is shown in the table.

[0082] The area ratio (GC Area %) thus obtained was converted based on the gas chromatography relative sensitivity, and the molar composition was calculated such that the total of the components listed in the table was 100 mol %.

[0083] (Rate of change in production amount) The percentage (%) of the amount of halogenated alkene produced at each reaction time was calculated based on the amount of halogenated alkene produced one hour after the start of the reaction. Unless otherwise specified, the rate of change in the amount of halogenated alkene produced was calculated using the molar composition values ​​described above.

[0084] [Example 1] A reaction tube made of Inconel 600 with an inner diameter of 2.04 cm and a length of 30 cm was filled with 140 g of α-alumina (product name "N612", manufactured by JGC Catalysts and Chemicals Co., Ltd.), and the tube was placed in a tubular electric furnace. A 1 / 1 (mol / mol) mixed gas of nitrogen / HFC-134a was passed through the tube at 700°C at the flow rate shown in Table 1 to carry out a HF decomposition reaction to produce HFO-1123.

[0085] [Table 1]

[0086] [Example 2] The HF desorption reaction was carried out in the same manner as in Example 1, except that α-alumina was changed to glass beads 1 (Unibeads series, manufactured by Unitika Glass Beads Ltd.).

[0087] [Table 2]

[0088] Comparing Example 1 and Example 2, it can be seen that in Example 1, in which α-alumina was used, the amount of halogenated alkene produced dropped significantly in the 3rd hour from the start of the reaction, and the amount produced was extremely small after 4 hours, whereas in Example 2, in which glass beads 1 were used, the drop in the amount produced was significantly suppressed. It can also be seen that in Example 2, the concentration of HFO-1123 in the outlet gas composition is maintained stable.

[0089] [Example 3] In Example 2, the reaction was interrupted 5 hours after the start of the reaction, the weight of the glass beads was measured, and 28 g of glass beads 1 were added to make up for the weight loss, and the reaction was restarted. The additional reaction time in Table 3 is the reaction time after restart. The rate of change in the amount of production (%) is a value based on the amount of halogenated alkene produced in 1 hour from the start of the reaction in Example 2.

[0090] [Table 3]

[0091] It can be seen that the production amount was clearly improved and restored by supplementing with glass beads 1.

[0092] [Example 4] The HF decomposition reaction to obtain HFO-1123 was carried out in the same manner as in Example 1, except that HFC-134a was changed to HFC-134.

[0093] [Table 4]

[0094] [Example 5] The HF decomposition reaction to obtain HFO-1123 was carried out in the same manner as in Example 2, except that HFC-134a was changed to HFC-134.

[0095] [Table 5] In the table, "-" means that the corresponding component was below the detection limit.

[0096] Comparing Example 4 and Example 5, it can be seen that in Example 4, in which α-alumina was used, the amount of halogenated alkene produced dropped significantly 2.5 hours after the start of the reaction, and almost no alkene was produced after 3.5 hours, whereas in Example 5, in which glass beads 1 were used, the drop in the amount of alkene produced was significantly suppressed. Also, in Example 4, in which α-alumina was used, a certain amount of by-product HFC-134a was generated, whereas in Example 5, in which glass beads 1 were used, almost no HFC-134a was generated. It can also be seen that in Example 5, the concentration of HFO-1123 in the outlet gas composition is maintained stable.

[0097] [Example 6] In Example 1, HFC-134a was replaced with HFC-125, the diluent gas was changed to difluoromethane (R32), and a 1 / 1 (mol / mol) mixed gas of R32 / HFC-125 was passed through at 400 mL / min to carry out the HF decomposition reaction to produce FO-1114. The change in the production amount in Table 6 was calculated from the area ratio (GCArea%) of the reactor outlet gas.

[0098] [Table 6]

[0099] [Example 7] In Example 6, the HF decomposition reaction was carried out in the same manner as in Example 2, except that the α-alumina was replaced with the glass beads 1. The change in the production amount in Table 7 was calculated from the area ratio of the reactor outlet gas (GC Area %).

[0100] [Table 7]

[0101] Comparing Example 6 and Example 7, it can be seen that in Example 6, in which α-alumina was used, the amount of halogenated alkene produced dropped significantly in the first 2 hours after the start of the reaction, and the amount produced was extremely small after 4 hours, whereas in Example 7, in which glass beads 1 were used, the drop in the amount produced was significantly suppressed. In Example 6, the selectivity of the compounds listed in the table was also low at the beginning of the reaction. It can be seen that in Example 7, the concentration of FO-1114 is maintained stable in the outlet gas composition.

[0102] [Example 8] The HF decomposition reaction was carried out in the same manner as in Example 1, except that the α-alumina was changed to a mixture of silica sand and sodium fluoride in a mass ratio of 1 / 1 (70 g / 70 g).

[0103] [Table 8]

[0104] [Example 9] The HF decomposition reaction was carried out in the same manner as in Example 8, except that sodium fluoride was changed to potassium fluoride.

[0105] [Table 9]

[0106] [Example 10] The HF decomposition reaction was carried out in the same manner as in Example 9, except that the mass ratio of silica sand to potassium fluoride was changed to 5 / 2.

[0107] [Table 10]

[0108] Comparing Example 1 with Examples 8, 9, and 10, it can be seen that in Example 1, in which α-alumina was used, the amount of halogenated alkene produced dropped significantly within 3 hours of the start of the reaction, and the amount produced was extremely small after 4 hours, whereas in Examples 8, 9, and 10, in which a silicon oxide compound was used, the drop in the amount produced was significantly suppressed.

[0109] [Example 11] The HF desorption reaction from HFC-134a to HFO-1123 was carried out in the same manner as in Example 2, except that the reaction temperature was changed as shown in Table 11. Table 11 shows the outlet gas composition 0.5 hours after the start of the reaction.

[0110] [Table 11]

[0111] [Example 12] In Example 5, the HF decomposition reaction from HFC-134 to HFO-1123 was carried out in the same manner as in Example 5, except that the reaction temperature was changed as shown in Table 12. The outlet gas composition over time is shown.

[0112] [Table 12]

[0113] [Example 13] The HF decomposition reaction was carried out in the same manner as in Example 8, except that sodium chloride was used instead of sodium fluoride. Table 13 shows the outlet gas composition 1.0 hour after the start of the reaction.

[0114] [Example 14] The HF decomposition reaction was carried out in the same manner as in Example 8, except that sodium fluoride (70 g) was replaced with lithium fluoride (35 g) and a mixture of silica sand (70 g) and lithium fluoride (35 g) was used. Table 13 shows the outlet gas composition 1.0 hour after the start of the reaction.

[0115] [Table 13]

[0116] [Example 15] The HF decomposition reaction was carried out in the same manner as in Example 8, except that cesium fluoride was used instead of sodium fluoride. Table 14 shows the outlet gas composition 0.5 hours after the start of the reaction.

[0117] [Table 14]

[0118] [Example 16] The HF desorption reaction from HFC-134a to HFO-1123 was carried out in the same manner as in Example 2, except that the total flow rate and ratio of the flowing gases were changed as shown in Table 15. Table 15 shows the outlet gas composition 0.25 hours after the start of the reaction.

[0119] [Table 15]

[0120] [Example 17] The HF decomposition reaction to obtain HFO-1141 was carried out in the same manner as in Example 2, except that HFC-134a was changed to HFC-152a. Table 16 shows the outlet gas composition 0.5 hours after the start of the reaction.

[0121] [Example 18] The HF decomposition reaction to HFO-1141 was carried out in the same manner as in Example 17, except that the glass beads were replaced with a mixture of silica sand (120 g) and potassium fluoride (20 g). Table 16 shows the outlet gas composition 0.5 hours after the start of the reaction.

[0122] [Table 16]

[0123] [Example 19] The HF decomposition reaction to HFO-1132 and 1132a was carried out in the same manner as in Example 2, except that HFC-134a was changed to HFC-143. Table 17 shows the outlet gas composition 0.5 hours after the start of the reaction.

[0124] [Example 20] The HF decomposition reaction was carried out in the same manner as in Example 19, except that the glass beads were replaced with a mixture of silica sand (120 g) and potassium fluoride (20 g). Table 17 shows the outlet gas composition 0.5 hours after the start of the reaction.

[0125] [Table 17]

[0126] The disclosure of Japanese Patent Application No. 2023-190304 is incorporated herein by reference in its entirety. All publications, patent applications, and technical standards mentioned in this specification are incorporated by reference into this specification to the same extent as if each individual publication, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A method for producing a halogenated alkene, comprising converting a halogenated alkane containing a fluorine atom and having 2 to 4 carbon atoms into a halogenated alkene containing a fluorine atom and having 2 to 4 carbon atoms in a gas phase in the presence of silicon oxide and an alkali metal element.

2. The method for producing a halogenated alkene according to claim 1, wherein the halogenated alkane includes a halogenated alkane represented by the following formula (1), and the halogenated alkene includes a halogenated alkene represented by the following formula (2). CR １ R ２ X １ -CR ３ R ４ X ２ ・・・(1) CR １ R ２ =CR ３ R ４ ・・・(2) In formula (1) and formula (2), R １ ~R ４ each independently represents a hydrogen atom, a fluorine atom, a methyl group, a fluorinated methyl group, an ethyl group, or a fluorinated ethyl group; R １ ~R ４ The total number of fluorine atoms is 1 or more, and the total number of carbon atoms is 2 to 4. １ and X ２ one of which is a hydrogen atom and the other is a fluorine atom.

3. 3. The method for producing a halogenated alkene according to claim 1 or 2, wherein silicon tetrafluoride is produced.

4. a dehydrofluorination reaction of the halogenated alkane to produce the halogenated alkene and hydrogen fluoride in a gas phase; and producing silicon tetrafluoride by reacting the produced hydrogen fluoride with silicon oxide.

5. The method for producing a halogenated alkene according to claim 1 or 2, wherein the halogenated alkane is at least one selected from the group consisting of 1,1-difluoroethane, 1,2-difluoroethane, 1,1,1-trifluoroethane, 1,1,2-trifluoroethane, 1,1,2,2-tetrafluoroethane, 1,1,1,2-tetrafluoroethane, and 1,1,1,2,2-pentafluoroethane.

6. The method for producing a halogenated alkene according to claim 1 or 2, wherein the halogenated alkene is at least one selected from the group consisting of fluoroethylene, 1,1-difluoroethylene, 1,2-difluoroethylene, trifluoroethylene, and tetrafluoroethylene.

7. 3. The process for producing halogenated alkenes according to claim 1 or 2, wherein the halogenated alkane is converted in the presence of a diluent gas.

8. The method for producing halogenated alkenes according to claim 7, wherein the diluent gas is at least one selected from the group consisting of nitrogen, hydrogen, carbon dioxide, helium, ethane, propane, isobutane, n-butane, propylene, and fluorinated methane.

9. The method for producing a halogenated alkene according to claim 1 or 2, wherein the halogenated alkane is converted at a temperature of 400 to 1000° C.

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