Method for producing halogenated alkene

Abstract

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.

Description

Method for producing halogenated alkenes

[0001] The present disclosure relates to a method for producing halogenated alkenes.

[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 into 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. Specific examples of the catalyst include alumina (Al ２ O ３ ) is used.

[0004] International Publication No. 2017 / 104829

[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.

[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. <2> The method for producing a halogenated alkene according to <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 X２ ...(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 ２wherein one of the groups is a hydrogen atom and the other is a fluorine atom. <3> The method for producing a halogenated alkene according to <1> or <2>, in which silicon tetrafluoride is produced. <4> The method for producing a halogenated alkene according to any one of <1> to <3>, comprising: producing the halogenated alkane and hydrogen fluoride in a gas phase by dehydrofluorination of the halogenated alkane; and producing silicon tetrafluoride by reacting the produced hydrogen fluoride with silicon oxide. <5> The method for producing a halogenated alkane according to any one of <1> to <4>, in which 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 any one of <1> to <5>, 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> The method for producing a halogenated alkene according to any one of <1> to <6>, wherein the halogenated alkane is converted in the presence of a diluent gas. <8> The method for producing a halogenated alkene according to <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 any one of <1> to <8>, wherein the halogenated alkane is converted at a temperature of 400 to 1,000°C. <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.

[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.

[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 multiple substances, unless otherwise specified.

[0010] [Method for Producing Halogenated Alkenes] The method for producing halogenated alkenes 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 conventional methods. The reason for this is not clear, but is presumed to be as follows.

[0012] In the reaction of obtaining a halogenated alkene containing a fluorine atom from a halogenated alkane containing a fluorine atom, hydrogen fluoride is generated. The generated hydrogen fluoride is then converted into a halogenated alkene containing a fluorine atom by using, for example, alumina (Al ２ O ３ ) reacts with alumina to form AlF ３ and 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 AlF is 2533°C, they are solid in the reaction system.３ and CaF ２ The catalyst reacts with the catalyst to form a catalyst matrix, which is then reacted with the catalyst to form a catalyst.

[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) is produced regardless of the reaction scheme. ４ ) is generated. Because the boiling point of silicon tetrafluoride is −95° C., it is in the form of a gas within the reaction system and is released outside the reaction system. Therefore, in the method for producing a halogenated alkene according to the present disclosure, it is thought 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 of 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 be used as a refrigerant, the specific halogenated alkane preferably has 2 or 3 carbon atoms. The specific halogenated alkane contains a fluorine atom. The specific halogenated alkane preferably has 2 or more fluorine atoms. The specific halogenated alkane preferably has 1 or more hydrogen atoms. The specific halogenated alkane may contain a halogen atom other than a fluorine atom. Examples of the other halogen atom include a chlorine atom, a bromine atom, and an iodine atom, with a chlorine atom being preferred. The specific halogenated alkane does not necessarily contain any 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 ４X 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 represents 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 CH ２ 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) (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 of 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 specific halogenated alkene has 1 or more fluorine atoms. The specific halogenated alkene may contain a halogen atom other than a fluorine atom. Examples of the halogen atom include a chlorine atom, a bromine atom, and an iodine atom, with a chlorine atom being preferred. The specific halogenated alkene does not necessarily contain any 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 ４ represents 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 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. Furthermore, from the viewpoint of usefulness as a resin, HFO-1141 and FO-1114 are preferred.

[0027] (Silicon Oxide and Alkali Metal Element) In the method for producing a halogenated alkene according to 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 unnecessary by-products when used in a reaction is easily suppressed. Hereinafter, compounds and composites containing both silicon oxide and an alkali metal element, as well as those containing separate substances containing silicon oxide and an alkali metal element, 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 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 a volume-based 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. The silicon content in the reactant may be 90 atm% or less, or 80 atm% or less. The oxygen content in the reactant may be 1 atm% or more, 5 atm% or more, or 10 atm% or more. The oxygen content in the reactant may be 90 atm% or less, or 80 atm% or less. The alkali metal element content in the reactant may be 1 atm% or more, 5 atm% or more, or 8 atm% or more. The alkali metal element content in the reactant may be 90 atm% or less, or 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 greater than the alkali metal content (atm %), and preferably greater than the total content of alkaline earth metals and Group 13 elements of the periodic table. It is preferable that silicon be the element with the highest content (atm %) among elements excluding oxygen. Furthermore, in the reactant, the alkali metal content (atm %) is preferably greater than each of the contents of elements other than silicon, oxygen, and alkali metal elements. In the glass, the alkali metal content (atm %) may be greater than, less than, 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 viewpoint of activity, selectivity, or 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, hydroxides, and carbonates of alkali metals, and specific examples thereof include NaF, KF, CsF, NaOH, KOH, Na ２ CO ３ , K. ２ CO ３ , NaCl, etc.

[0041] (Reaction Scheme) In the method for producing a halogenated alkene of the present disclosure, silicon tetrafluoride (SiF ４ ) 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. Note that the method for producing a halogenated alkene of the present disclosure may employ 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. Furthermore, 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]

[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]

[0047] The resulting aluminum fluoride (AlF ３ ) and calcium fluoride (CaF ２ Since the catalyst is solid, it remains in the reaction system without being released outside, coating the surface of the catalyst, alumina or calcium carbonate. This covers the active sites on the catalyst surface, deactivating it. Therefore, in conventional production methods, the deteriorated catalyst must be removed and replaced with a new one. Therefore, in conventional production methods using alumina, calcium carbonate, or the like as a catalyst, productivity is unstable and the reaction must be stopped each time the catalyst is replaced. In contrast, the method for producing halogenated alkenes of the present disclosure has the advantage of reducing the work of removing the deteriorated catalyst and maintaining productivity.

[0048] In the method for producing a halogenated alkene 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 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 production methods 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. Therefore, it is difficult to properly estimate the amount of catalyst that needs 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. However, in the conventional method, the catalyst is added with AlF ３ or CaF ２ As a result, the weight and density of the catalyst change, causing fluctuations in fluidity. Therefore, it is 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 method for producing halogenated alkenes of 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 only needs to contain the specific halogenated alkane, and may contain components other than the specific halogenated alkane. The raw material gas may consist solely of 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, relative to the total amount of the raw material gas. The content of the halogenated alkane represented by formula (1) may be 100 mol% relative to the total amount of the raw material 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 a fixed bed, fluidized bed, and moving bed type. In the case of a fixed bed type, it may be either a horizontal fixed bed type or a vertical fixed bed type. The reactor may be rotated as a whole. The reaction type may be a flow type or a batch type.

[0053] In fixed-bed reactors, various shaped bodies of reactant-supporting carriers are packed to reduce pressure loss of the reaction fluid. Similarly to fixed-bed reactors, reactants are packed, moved by gravity, and extracted from the bottom of the reactor for regeneration, which is called a moving bed. In fluidized-bed reactors, the reactant layer is operated in such a way that it exhibits fluid-like properties due to the reaction fluid, so the reactants mix with the reaction fluid and move within the reactor. Fixed-bed reactors are preferred in terms of the wide range of reactant shape options and the ability to suppress reactant wear, while fluidized-bed reactors are preferred in terms of uniform internal temperature and the ease of avoiding localized 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 dilution gas may be circulated vertically from below, and the product gas may be withdrawn vertically from above. The fluidized bed reactor may be equipped with a stirring blade to further increase fluidity. Furthermore, the fluidized bed reactor may be equipped with a gas dispersion plate to prevent bias in the gas flow within the fluidized bed reactor. 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, product gas, etc. Examples of materials for 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. When the conversion is carried out at 400°C or higher, the reaction proceeds appropriately and the conversion rate of the halogenated alkene is improved. On the other hand, when the conversion is carried out at 1000°C or lower, the selectivity decreases due to 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 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, and therefore 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 −0.05 to 2 MPa, more preferably −0.01 to 1 MPa, and even more preferably atmospheric pressure to 0.5 MPa. In the present 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 (cm) of the reactor packed with the reactants] / [linear velocity (cm / second)] The linear velocity refers to the speed 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 ３ More preferably, 0.2 g / cm ３ More preferably, the average bulk density of the reactant is 0.05 g / cm or more. ３If this is the case or more, 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 the reactants is measured by the container method. In the container method, the reactants are poured into a container of known capacity until they overflow, and the excess reactants protruding from the edge of the top surface of the container are removed with a spatula or the like, and the mass of the reactants in the container is measured. The bulk density (g / mL) is calculated from the mass of the reactants 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. Examples of fluorinated methane include monofluoromethane, difluoromethane, trifluoromethane, and monofluoromethane. The molar ratio of the specific halogenated alkane to the diluent gas in the vapor phase is preferably 0.1 to 5.0, more preferably 0.5 to 3.0, and even more preferably 0.5 to 2.0.

[0065] Generally, in methods for producing halogenated alkenes, a diluent gas is used to suppress disproportionation reactions caused by high concentrations of the produced halogenated alkenes, and to address concerns about explosions due to high concentrations of certain types of halogenated alkenes. 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, and therefore a certain amount of the specific halogenated alkane as a raw material can be contained in the outlet gas. The specific halogenated alkane in the outlet gas also functions as a diluent. Therefore, the method for producing halogenated alkenes of the present disclosure can also reduce the amount of diluent gas used. The method for producing halogenated alkenes of the present disclosure also includes an embodiment in which a diluent gas is not used.

[0066] Furthermore, as described in Patent Document 1, in the production method of fluoroolefins using an alumina catalyst, reducing the amount of diluent reduces the conversion rate, making it difficult to use the feed gas as a diluent, and the use of a diluent gas such as nitrogen or carbon dioxide is essential. Diluent gases such as nitrogen gas and carbon dioxide have lower boiling points or a similar boiling point range to the halogenated alkene, the reaction product, and therefore require energy to separate and purify the diluent gas from the reaction product. In the method for producing halogenated alkenes disclosed herein, even when the feed gas is used as part or all of the diluent, the decrease in the amount of halogenated alkene produced over time is suppressed. Because the halogenated alkane, the feedstock, has a high boiling point and is in a different boiling point range from the halogenated alkene, the reaction product, the method for producing halogenated alkenes disclosed herein also reduces 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 water concentration is preferably less than 500 ppm by volume relative to the total amount of the feed 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 problems even if water is present in the system. Furthermore, when hydrogen fluoride is desorbed from the feed 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 produce hexafluorosilicic acid, etc., and from the viewpoint of preventing blockage 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. When the moisture content is less than 500 ppm by volume relative to the total amount of the specific halogenated alkane, 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, from the viewpoint of further improving the conversion rate and obtaining the target compound with even 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 control, a moisture content of 0.5 ppm by volume or more is preferable, and a moisture content of 1 ppm by volume or more is more preferable.

[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. Note that the molar amount consumed in the reaction of the specific halogenated alkane as a raw material is the difference between the molar amount of the specific halogenated alkane supplied to the reactor and the molar amount of the specific halogenated alkane contained in the gas effluent from the reactor outlet.

[0073] Generally, 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 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 raw material, excluding compounds such as silicon tetrafluoride that do not have carbon derived from the raw materials). A selectivity of 100% is preferable because it eliminates the need for a post-reaction purification step, but side reactions may occur in the reaction temperature range required to achieve a desired conversion rate. A higher selectivity is preferable because it reduces the amount of waste, reduces the energy load in the post-reaction purification step, and extends the life of the reactants. A selectivity of 90% or more is preferable, 93% or more is more preferable, and 95% or more is even more preferable.

[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, relative to 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 (GCArea%) 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 outside 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 ) can be used as a catalyst. ３ Calcium fluoride (CaF) generated by the conventional method ２ To convert CaF into hydrogen fluoride, the reaction with sulfuric acid is required, which is a drastic condition. ２ Pre-processing such as crushing is required.

[0079] (Modification) As a modification, the method for producing a halogenated alkene of the present disclosure may convert a halogenated alkane containing fluorine atoms and having 2 to 4 carbon atoms in the gas phase in the presence of boron oxide to a halogenated alkene containing fluorine atoms and having 2 to 4 carbon atoms. 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, and may be in the form of, for example, borosilicate glass, etc.

[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 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") 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", 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 (GCArea%) of the reactor outlet gas is shown in the table.

[0082] The area ratio (GCArea%) 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] (Change in Amount of Formation) The ratio (%) of the amount of halogenated alkene formed at each reaction time was determined based on the amount of halogenated alkene formed one hour after the start of the reaction. Unless otherwise specified, the change in the amount of halogenated alkene formed was determined using the molar composition values ​​described above.

[0084] Example 1 A reaction tube made of Inconel 600 and having 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, 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 obtain HFO-1123.

[0085]

[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]

[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 from the start of the reaction, and the amount produced became 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 was stably maintained 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]

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

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

[0093]

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

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

[0096] Comparing Examples 4 and 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 was hardly produced after 3.5 hours, whereas in Example 5, in which glass beads 1 were used, the drop in the amount produced was significantly suppressed. Also, it can be seen that in Example 4, in which α-alumina was used, a certain amount or more of the by-product HFC-134a was produced, whereas in Example 5, in which glass beads 1, almost no HFC-134a was produced. It can also be seen that in Example 5, the concentration of HFO-1123 was stably maintained in the outlet gas composition.

[0097] Example 6 In Example 1, HFC-134a was changed to 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 a HF removal 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]

[0099] [Example 7] A HF dehydrogenation reaction was carried out in the same manner as in Example 6, except that the α-alumina was changed to the glass beads 1 in Example 2. The change in the production amount in Table 7 was calculated from the area ratio of the gas at the reactor outlet (GCArea%).

[0100]

[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 of the start of the reaction, and the amount of production became extremely small after 4 hours, whereas in Example 7, in which glass beads 1 were used, the drop in the amount of production was significantly suppressed. In Example 6, the selectivity of the compounds listed in the table was also low in the early stages of the reaction. It can be seen that in Example 7, the concentration of FO-1114 was stably maintained in the outlet gas composition.

[0102] Example 8 A HF removal reaction was carried out in the same manner as in Example 1, except that α-alumina was replaced with silica sand and sodium fluoride mixed at a mass ratio of 1 / 1 (70 g / 70 g).

[0103]

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

[0105]

[0106] Example 10 A 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]

[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] A fluorine-free 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]

[0111] [Example 12] A dehydrofluorination 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 outlet gas composition 0.5 hours after the start of the reaction.

[0112]

[0113] [Example 13] A HF removal 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] A 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]

[0116] Example 15 A 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]

[0118] [Example 16] The fluorine-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]

[0120] Example 17 A 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 A fluoride removal reaction to obtain 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]

[0123] Example 19 A dehydrofluorination reaction to obtain HFO-1132 and HFO-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] A 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]

[0126] The disclosure of Japanese Patent Application No. 2023-190304 is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated by reference into this specification to the same extent as if each individual document, 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 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 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). １ R ２ X １ -CR ３ R ４ X ２ ... (1) CR １ R ２ =CR ３ R ４ 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. The method for producing a halogenated alkene according to claim 1 or 2, wherein silicon tetrafluoride is produced.

4. A method for producing a halogenated alkene according to claim 1 or 2, comprising: producing, in a gas phase, the halogenated alkane by a dehydrofluorination reaction to produce the halogenated alkene and hydrogen fluoride; and producing silicon tetrafluoride by a reaction between the produced hydrogen fluoride and 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. The method 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 halogenated alkenes according to claim 1 or 2, wherein the halogenated alkane is converted at a temperature of 400 to 1000°C.

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