Method for producing halogenated alkenes

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 method for producing halogenated alkenes. [Background technology]

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

[0003] For example, Patent Document 1 describes a method for producing hydrofluoroolefins in which a hydrofluorocarbon is converted to a hydrofluoroolefin in the presence of a fluorine-containing compound having a normal boiling point higher than that of the target hydrofluoroolefin. The reaction step of this production method includes a step of contacting the hydrofluorocarbon with a catalyst. Specifically, alumina (Al2O3) is used as the catalyst. [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 a fluoroolefin is produced by a dehydrofluorination reaction of a fluorocarbon 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 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 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 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> 1. 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 are each independently a hydrogen atom, a fluorine atom, a methyl group, a fluorinated methyl group, an ethyl group, or a fluorinated ethyl group, and 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 is a hydrogen atom on one side and a fluorine atom on the other side. <3> Silicon tetrafluoride is produced, <1> or <2> 1. 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> 10. The method for producing a halogenated alkene according to claim 9, wherein the halogenated alkene is a halogenated alkene. <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> 10. The method for producing a halogenated alkene according to claim 9, wherein the halogenated alkene is a halogenated alkene. <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> 10. The method for producing a halogenated alkene according to claim 9, wherein the halogenated alkene is a halogenated alkene. <7> converting the halogenated alkane in the presence of a diluent gas; <1> ~ <6> 10. The method for producing a halogenated alkene according to claim 9, wherein the halogenated alkene is a halogenated alkene. <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> 1. 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> 10. The method for producing a halogenated alkene according to claim 9, wherein the halogenated alkene is a halogenated alkene. <10> 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 boron oxide. [Effects 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 INVENTION

[0009] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages 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 stages. Furthermore, 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, a combination of two or more preferred embodiments is a more preferred embodiment. 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 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. 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 conventional methods. The reason for this is not clear, but is presumed to be 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. For example, when alumina (Al2O3) is used as a catalyst, the generated hydrogen fluoride reacts with the alumina to generate AlF3, and when calcium carbonate (CaCO3) is used as a catalyst, it generates CaF2. Here, the boiling points of AlF3 and CaF2 are 1260°C and 2533°C, respectively, so they are in the reaction system. Therefore, the generated AlF3 and CaF2 remain in the reaction system and cover the reaction points on the surface of the catalyst. Covering the reaction points of the catalyst causes a rapid decrease in the activity of the catalyst.

[0013] In contrast, in the method for producing halogenated alkenes of the present disclosure, specific halogenated alkenes are obtained from specific halogenated alkanes in the presence of silicon oxide and an alkali metal element. During this process, 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 (SiF4) is generated regardless of the reaction scheme. Since the boiling point of silicon tetrafluoride is −95°C, it is a gas in the reaction system and is released outside the reaction system. Therefore, in the method for producing halogenated alkenes of the present disclosure, it is believed that coating with silicon oxide is suppressed, and a rapid decrease in the amount of halogenated alkene produced is suppressed.

[0014] The method 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 fluorine atoms, and the number of fluorine atoms in the specific halogenated alkane is preferably 2 or more. The number of hydrogen atoms in the specific halogenated alkane is preferably 1 or more. The specific halogenated alkane may contain halogen atoms other than fluorine atoms. Examples of other halogen atoms include chlorine atoms, bromine atoms, and iodine atoms, with chlorine atoms being preferred. The specific halogenated alkane may not necessarily 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 are each independently a hydrogen atom, a fluorine atom, a methyl group, a fluorinated methyl group, an ethyl group, or a fluorinated ethyl group, and R 1 ~R 4 The total number of fluorine atoms is 1 or more, the total number of carbon atoms is 2 to 4, and X 1 and X 2 is a hydrogen atom on one side and a fluorine atom on the other side.

[0018] R 1 and R 3 are preferably each independently a hydrogen atom or a fluorine atom, and R 2 and R 4 is preferably a hydrogen atom, a fluorine atom, CH3, CH2F, CHF2 or CF3.

[0019] Examples of halogenated alkanes represented by formula (1) include the following compounds: CHF2CH3: 1,1-difluoroethane (HFC-152a) CH2FCH2F: 1,2-difluoroethane (HFC-152) CF3CH3: 1,1,1-trifluoroethane (HFC-143a) CHF2CH2F: 1,1,2-trifluoroethane (HFC-143) CF3CH2F: 1,1,1,2-tetrafluoroethane (HFC-134a) CHF2CHF2: 1,1,2,2-tetrafluoroethane (HFC-134) CF3CHF2: 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) (provided that the halogenated alkane contains a fluorine atom and has 2 to 4 carbon atoms). The proportion of the halogenated alkane represented by formula (1) relative to the total amount of the specific halogenated alkanes 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, and the number of fluorine atoms in the specific halogenated alkene is 1 or more. The specific halogenated alkene may contain halogen atoms other than fluorine atoms. Examples of other halogen atoms include chlorine atoms, bromine atoms, and iodine atoms, with chlorine atoms being preferred. The specific halogenated alkene may not necessarily 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 4 are each independently a hydrogen atom, a fluorine atom, a methyl group, a fluorinated methyl group, an ethyl group, or a fluorinated ethyl group, and 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 preferably each independently a hydrogen atom or a fluorine atom, and R 2 and R 4is preferably a hydrogen atom, a fluorine atom, CH3, CH2F, CHF2 or CF3.

[0025] Examples of the halogenated alkene represented by formula (2) include the following compounds: CHF=CH2: Fluoroethylene (HFO-1141) CF2=CH2: 1,1-difluoroethylene (HFO-1132a) CHF = CHF: 1,2-difluoroethylene (HFO-1132(E), HFO-1132(Z)) CHF=CF2: Trifluoroethylene (HFO-1123) CF2=CF2: Tetrafluoroethylene (FO-1114)

[0026] Among these, 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, and HFO-1141 and HFO-1114 from the viewpoint of usefulness as a resin.

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

[0028] The silicon oxide and the 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. Examples include 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, and a combination of silicon oxide particles and an alkali metal-containing compound.

[0029] When silicon oxide and an alkali metal element are integrated, uneven distribution within 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 unwanted 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, will be 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 irregular shapes such as crushed material, cullet-like, scaly, spherical, etc. It may also be formed into pellets, hollow, cylindrical, etc. These shapes may be combined as appropriate.

[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 husks, 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 pulverized products, cullet-like, scaly, spherical, etc. Also, they may be molded into pellets, hollow, cylindrical, etc. Furthermore, 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] The silicon oxide particles preferably have a low impurity content, and the silicon oxide content in the silicon oxide particles is preferably low from the viewpoint of suppressing the generation of unnecessary by-products, and is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by 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 the size of the glass, composite, and silicon oxide particles 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% in the cumulative particle size distribution curve obtained by measurement using a Coulter counter. The aperture diameter is appropriately set depending on 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, and 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 silicon content (atm %) is preferably higher than the alkali metal element content (atm %), and is preferably higher than the total content of alkaline earth metals and Group 13 elements of the periodic table, and silicon is preferably the element with the highest content (atm %) among elements excluding oxygen. In addition, the content (atm %) of alkali metal elements in the reactants is preferably higher than the content of each of elements other than silicon, oxygen, and alkali metal elements. In the glass, the content (atm %) of alkali metal elements may be higher, lower, or the same as the total content of alkaline earth metals and Group 13 elements 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 alkali metal halides such as fluorides and chlorides, hydroxides, and carbonates. Specific examples include NaF, KF, CsF, NaOH, KOH, Na2CO3, K2CO3, and NaCl.

[0041] (Reaction scheme) In the method for producing a halogenated alkene of the present disclosure, silicon tetrafluoride (SiF4) is produced. In the method for producing a halogenated alkene of the present disclosure, a reaction scheme is considered in which a specific halogenated alkane and hydrogen fluoride are produced in a gas phase by a dehydrofluorination reaction (first step), and the produced hydrogen fluoride is then reacted with silicon oxide to produce silicon tetrafluoride (second step). The first step and the second step may proceed consecutively without being separated. The method for producing a halogenated alkene according to the present disclosure may be one other than the above reaction scheme. For example, silicon oxide or an alkali metal compound may be reacted directly with a halogenated alkane to produce silicon tetrafluoride. Also, other compounds may be produced in addition to silicon tetrafluoride.

[0042] Below is shown 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 produced is in the form of a gas and is released from the reaction system, thereby minimizing the impact of by-products 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] Because the produced aluminum fluoride (AlF3) and calcium fluoride (CaF2) are solids, they are not released outside the reaction system but remain within the system, coating the surface of the catalysts, alumina and calcium carbonate. This covers the active points on the catalyst surface, deactivating 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, productivity is unstable and 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 a halogenated alkene according to the present disclosure, the reaction can be continued by replenishing the consumed silicon oxide. The amount of consumed silicon oxide can be calculated from the amount of silicon tetrafluoride released from the reaction system to the outside. Specifically, the released silicon tetrafluoride is passed through water, an alkaline aqueous solution, or the like to convert it into hydrogen fluoride, hexafluorosilicic acid, or a salt thereof, and the amount of released silicon tetrafluoride can be measured by titrating these. On the other hand, in conventional manufacturing methods using alumina or calcium carbonate as a catalyst, AlF or CaF remains in the reaction system, making it difficult to estimate the amount of degraded catalyst. Therefore, in conventional manufacturing methods, it is difficult to appropriately estimate the amount of catalyst to be replenished.

[0049] Furthermore, when reacting in a fluidized bed, it is desirable that the fluidity of the catalyst does not change significantly. However, in conventional methods, AlF or CaF adheres to the catalyst, causing changes in the weight and density of the catalyst and resulting in fluctuations in fluidity. Therefore, it is difficult to maintain an appropriate fluidized state. In contrast, in the manufacturing method of the present disclosure, the by-product SiF4 is in the form of gas and is released outside the reaction system, so there is no significant change in the fluidity of the silicon oxide, making it easy to maintain an appropriate fluid state.

[0050] (Reaction conditions) The method 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 a halogenated alkene according to the present disclosure, the feed gas may contain the specific halogenated alkane, but may also contain components other than the specific halogenated alkane. The feed gas may consist solely of the specific halogenated alkane, or may contain isomers, disproportionation products, impurities, and the like 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 feed gas. The content of the halogenated alkane represented by formula (1) may be 100 mol% based on the total amount of the feed gas.

[0051] The reactor for reacting the halogenated alkane with the reactant is not particularly limited in shape or structure as long as it can withstand the temperatures and pressures described below. Examples of the reactor include a cylindrical vertical reactor. Examples of materials for the reactor include glass, stainless steel, iron, nickel, chromium, and alloys containing iron, nickel, or chromium as a main component. 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 forms of a fixed bed, a fluidized bed, or a 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 rotate as a whole. The reaction may be carried out in a flow manner or a batch manner.

[0053] In a fixed-bed reactor, various molded bodies of reactant-supporting carriers are packed to reduce pressure loss of the reaction fluid. Similarly to a fixed-bed reactor, a reactor is packed with reactants, which are moved by gravity and then extracted from the bottom of the reactor for regeneration, and this 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 it has a wide range of options for the shape of the reactants and can suppress wear of the reactants, while a fluidized-bed reactor is preferred in that it makes the internal temperature uniform and makes it easy to avoid local heating.

[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 exchanger 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. At least one reactant layer is sufficient, but two or more layers are also acceptable.

[0055] In the case of a fluidized bed reactor, the raw material gas and further the diluent gas may be passed through from below in the vertical direction, and the product gas may be withdrawn from above in the vertical direction. The fluidized bed reactor may be provided with a stirring blade to further enhance fluidity. Furthermore, the fluidized bed reactor may be provided with a gas dispersion plate to prevent the gas flow in the fluidized bed reactor from becoming uneven. 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 gas dispersion plates may be adjusted appropriately depending on 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. Conversion at 400°C or higher allows the reaction to proceed properly, improving the conversion rate of halogenated alkenes. On the other hand, conversion at 1000°C or lower reduces selectivity due to cleavage of carbon-carbon bonds in the raw material, and inhibits disproportionation of the reaction products (unsaturated compounds).

[0057] It is also possible to suppress a decrease in conversion 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 externally 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, thereby maintaining productivity. From the viewpoint of continuing the reaction, it is preferable to continuously supply silicon oxide in an amount equivalent to the amount consumed. The position at which silicon oxide is supplied to the reactor is not particularly limited, and it 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 at room temperature, or may be appropriately heated (preheated) before being supplied to the reactor. When preheating is performed, the raw material gas is preferably heated to a temperature of 80°C or higher but lower than the reaction temperature in the reactor before being supplied to the reactor. When the preheating temperature is 80°C or higher, the internal temperature of the reactor is less likely to decrease, making it easier to achieve the set conversion rate. Furthermore, when the preheating temperature is lower than the reaction temperature in the reactor, undesired 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 less favorable. 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 0.5 to 300.0 seconds, more preferably 1.0 to 100.0 seconds, and even more preferably 1.5 to 60.0 seconds.

[0062] The residence time (seconds) is calculated using the following formula: Residence time (seconds) = [length of the reactor packed with reactants (cm)] / [linear velocity (cm / second)] Linear velocity refers to the rate at which the halogenated alkane passes through the reactant 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 3 If the temperature 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 volume until it overflows, and the excess reactant that protrudes from the top edge of the container is removed with a spatula or similar, and the mass of the reactant in the container is measured. The bulk density (g / mL) is calculated from this mass of the reactant and the capacity (volume) of the container. This measurement is performed 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. Fluorinated methanes include 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 methods for producing halogenated alkenes, a diluent gas is used from the viewpoint of suppressing a disproportionation reaction caused by an increase in the concentration of the halogenated alkene produced, and from the viewpoint of concerns about explosion due to an increase in the concentration of some types of halogenated alkene. In the method for producing halogenated alkenes of the present disclosure, reactivity can be controlled by residence time, reaction temperature, etc., and 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, the amount of halogenated alkene produced can be maintained and kept within a certain range by the above-mentioned controls, etc., and therefore, the outlet gas can contain a certain amount of the specific halogenated alkane as the raw material. 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 reduce the amount of diluent gas used. Note that the method for producing halogenated alkenes of the present disclosure also includes an embodiment in which no diluent gas is used.

[0066] Furthermore, in the method for producing fluoroolefins using an alumina catalyst, as described in Patent Document 1, 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 the use of diluent gases such as nitrogen gas and carbon dioxide is essential. Diluent gases such as nitrogen gas and carbon dioxide have boiling points lower than or close to those of the halogenated alkene, which is the reaction product, and therefore energy is required to separate and purify the diluent gas from the reaction product. In the method for producing a halogenated alkene according to the present disclosure, even when a feed gas is used as a part or all of a diluent, the decrease in the amount of halogenated alkene produced over time is suppressed. Since the halogenated alkane as a feedstock has a high boiling point and is in a boiling point range separate from that of the halogenated alkene as a reaction product, the method for producing a halogenated alkene according to the present disclosure can also reduce the energy load required for separation and purification.

[0067] From the viewpoint of controlling the reaction efficiency and selectivity, the conversion of the specific halogenated alkane is preferably carried out in the gas phase in the presence of water, and the concentration of water is preferably less than 500 ppm by volume relative to 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 system. Furthermore, 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 silicon tetrafluoride produced reacts with water near the outlet to produce hexafluorosilicic acid and the like, and from the viewpoint of preventing clogging of the gas flow path due to this precipitation, it is preferable that the water concentration be less than the above range.

[0068] A common method for measuring the moisture content of a gas is to use a commercially available dew point meter. A moisture content of less than 500 ppm by volume relative to the total amount of the specific halogenated alkane results in a high conversion rate and enables the target product to 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 even higher selectivity. A lower moisture content is preferable, but from the viewpoints of the cost of dehydration treatment of the specific halogenated alkane and diluent gas and the difficulty of process control, a moisture content of 0.5 ppm by volume or more is preferred, and more preferably 1 ppm by volume or more is preferred.

[0069] The water concentration is the amount of water contained in the raw material gas when the specific halogenated alkane is reacted with the reactant. Note that the water concentration may be replaced with the amount of water 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 fall 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 also be preheated in addition to drying the reactants. Specifically, the reactants may be filled into the reactor and then heated while flowing a diluent gas through the reactor, thereby drying the reactants.

[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 halogenated alkane is the difference between the molar amount of the halogenated alkane and the molar amount of the specific halogenated alkane contained in the effluent gas from the reactor outlet.

[0073] Generally, a higher conversion rate is preferable from the viewpoint of productivity. However, in the case of specific halogenated alkenes that are prone to explosion due to their high concentration, it is preferable to select operating conditions that result in a conversion rate of 70% or less from the viewpoint of suppressing explosions and suppressing disproportionation reactions of the specific halogenated alkenes. 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 refers to 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 in 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 because it eliminates the need for post-reaction purification steps, but side reactions may occur within the reaction temperature range required to achieve the desired conversion. A higher 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 higher is preferred, 93% or higher is more preferred, and 95% or higher 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 a halogenated alkene of the present disclosure, a decrease in the amount of the specific halogenated alkene produced is suppressed during long-term production (specifically, 5 hours or more). The amount of the specific halogenated alkene produced after 5 hours is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more, of the amount of the specific halogenated alkene produced after 1 hour.

[0077] The amount of the product is determined by analyzing the gas at the outlet of the reactor 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, etc. Furthermore, the silicon tetrafluoride released from the reaction system can be recovered as hydrogen fluoride or fluoride salts by reacting it with water or alkali. These recovered compounds can be used as etching agents or as raw materials for organic fluorine compounds. Furthermore, converting calcium fluoride (CaF2, fluorite), which is generated using conventional methods that use calcium carbonate (CaCO3) as a catalyst, into hydrogen fluoride requires extreme conditions, such as reacting it with sulfuric acid, and also requires pretreatment such as crushing the solid CaF2.

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

[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 spirit of the present disclosure. Examples 2, 3, 5, and 7 to 20 are working examples, and Examples 1, 4, and 6 are comparative examples.

[0081] (Outlet gas composition) The product gas (hereinafter also referred to as "reactor outlet gas") extracted from the reactor outlet at specific time intervals from the start of the reaction was analyzed by gas chromatography. Specifically, a column (product name "DB-1", manufactured by Agilent, length 60 m, inner diameter 0.25 mm, film thickness 1 μm) was attached to a gas chromatograph (product name "GC6850", manufactured by Agilent) and the analysis was performed. 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 relative sensitivity of gas chromatography, and the molar composition was determined 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] An Inconel 600 reaction tube 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 removal reaction to produce HFO-1123.

[0085] [Table 1]

[0086] [Example 2] The HF removal reaction was carried out in the same manner as in Example 1, except that α-alumina was replaced with 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 within 3 hours of the start of the reaction, and the amount produced was extremely low after 4 hours, whereas in Example 2, in which glass beads 1 were used, the drop in the amount produced was significantly suppressed. In addition, it can be seen that in Example 2, the concentration of HFO-1123 is maintained stably in the outlet gas composition.

[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 from the restart. The rate of change (%) in the amount of produced halogenated alkene 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 removal 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 removal 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 halogenated alkene was produced after 3.5 hours, whereas in Example 5, in which glass beads 1 were used, the drop in the amount of halogenated alkene produced was significantly suppressed. Furthermore, in Example 4, in which α-alumina was used, a certain amount or more of the by-product HFC-134a was generated, whereas in Example 5, in which glass beads 1 were used, almost no HFC-134a was generated. Furthermore, it can be seen that in Example 5, the concentration of HFO-1123 is stably maintained in the outlet gas composition.

[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 (GC Area %) 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 within 2 hours from the start of the reaction, and the amount produced was extremely low 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. In Example 7, it can be seen that 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 α-alumina was changed to silica sand and sodium fluoride mixed at a mass ratio of 1 / 1 (70 g / 70 g).

[0103] [Table 8]

[0104] [Example 9] The HF removal 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 removal 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 decreased significantly within 3 hours from the start of the reaction, and the amount produced became extremely small after 4 hours, whereas in Examples 8, 9, and 10, in which a silicon oxide compound was used, the decrease in the amount produced was significantly suppressed.

[0109] [Example 11] The HF decomposition 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] The HF removal 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. Table 12 shows the reaction time from the start of the reaction to 0.5 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 fluoride was changed to sodium chloride. Table 13 shows the outlet gas composition 1.0 hour after the start of the reaction.

[0114] [Example 14] The HF removal 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 removal 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 removal 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 gases being passed 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 removal 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 removal reaction to produce 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 obtain 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 removal 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, or technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. at least one halogenated alkene selected from the group consisting of fluoroethylene, 1,1-difluoroethylene, 1,2-difluoroethylene, trifluoroethylene, and tetrafluoroethylene; and silicon tetrafluoride; The composition further comprises at least one halogenated alkane selected from the group consisting of 1,1-difluoroethane, 1,2-difluoroethane, 1,1,2-trifluoroethane, 1,1,2,2-tetrafluoroethane, 1,1,1,2-tetrafluoroethane, and 1,1,1,2,2-pentafluoroethane.

2. the halogenated alkene comprises trifluoroethylene; The composition of claim 1 , wherein the halogenated alkane comprises 1,1,1,2-tetrafluoroethane.

3. the halogenated alkene comprises trifluoroethylene; The composition of claim 1 , wherein the halogenated alkane comprises 1,1,2,2-tetrafluoroethane.

4. the halogenated alkene comprises trifluoroethylene; The composition of claim 1, wherein the halogenated alkane comprises both 1,1,2,2-tetrafluoroethane and 1,1,1,2-tetrafluoroethane.

5. the halogenated alkene comprises tetrafluoroethylene; The composition of claim 1 , wherein the halogenated alkane comprises 1,1,1,2,2-pentafluoroethane.

6. the halogenated alkene comprises tetrafluoroethylene; the halogenated alkane includes 1,1,1,2,2-pentafluoroethane; The composition of claim 1 further comprising difluoromethane.

7. The halogenated alkene comprises fluoroethylene; The composition of claim 1 , wherein the halogenated alkane comprises 1,1-difluoroethane.

8. The halogenated alkenes include both 1,2-difluoroethylene and 1,1-difluoroethylene; The composition of claim 1 , wherein the halogenated alkane comprises 1,1,2-trifluoroethane.

9. The composition according to any one of claims 1 to 8, further comprising hydrogen fluoride.

10. The composition according to any one of claims 1 to 9, further comprising water.

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