Method for producing alkenes fluoride

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 invention Hmph This relates to a method for producing alkenes. [Background technology]

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

[0003] For example, Patent Document 1 describes a method for producing hydrofluoroolefins in which hydrofluorocarbons are converted to hydrofluoroolefins in the presence of a fluorine-containing compound having a standard 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 [Overview of the project] [Problems that the invention aims to solve]

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

[0006] Therefore, the objective of one embodiment of this disclosure is to provide a method for producing alkenes with halogenated compounds in which the decrease in the amount produced 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 having 2 to 4 carbon atoms and containing fluorine atoms into a halogenated alkene having 2 to 4 carbon atoms and containing fluorine atoms in the 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 (2). CR 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 the total number of fluorine atoms of R 1 ~R 4 is 1 or more, and the number of carbon atoms is 2 to 4. In formula (1), X 1 and X 2 are such that one is a hydrogen atom and the other is a fluorine atom. <3> The method for producing a halogenated alkene according to <1> or <2>, wherein silicon tetrafluoride is generated. <4> In the gas phase, the halogenated alkene and hydrogen fluoride are generated by the dehydrofluorination reaction of the halogenated alkane, and silicon tetrafluoride is generated by the reaction of the generated hydrogen fluoride and silicon oxide. The method for producing a halogenated alkene according to any one of <1> to <3>. <5> The halogenated alkane is 1,1-difluoroethane, 1,2-difluoroeth The method for producing a halogenated alkene according to any one of <1> to <4>, which is at least one selected from the group consisting of tan, 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 1000 °C. <10> A method for producing a halogenated alkene, in which a halogenated alkane having 2 to 4 carbon atoms and containing a fluorine atom is converted into a halogenated alkene having 2 to 4 carbon atoms and containing a fluorine atom in the gas phase in the presence of boron oxide.

Advantages of the Invention

[0008] According to the present disclosure, there is provided a method for producing a halogenated alkene in which a decrease in the production amount over time is suppressed as compared with the conventional method.

Modes for Carrying Out the Invention

[0009] In the present disclosure, the numerical range indicated using "~" means a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples. In this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In this disclosure, unless otherwise specified, the amount of each component refers to the total amount of multiple substances if there are multiple substances corresponding to each component.

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

[0011] The method for producing halogenated alkenes described herein suppresses the decrease in the amount produced over time compared to conventional methods. The reason for this is not clear, but it is presumed to be as follows.

[0012] In the reaction to obtain a fluorine-containing alkene halogen from a fluorine-containing alkane halogen, hydrogen fluoride is produced. The produced hydrogen fluoride reacts with alumina (Al2O3) to produce AlF3 when alumina is used as a catalyst, and with calcium carbonate (CaCO3) to produce CaF2 when calcium carbonate is used as a catalyst. Here, the boiling point of AlF3 is 1260°C and the boiling point of CaF2 is 2533°C, so these are within the reaction system. Therefore, it is a solid. Consequently, the generated AlF3 and CaF2 remain in the reaction system and coat the reaction sites on the surface of the catalyst. This coating of the catalyst's reaction sites causes a rapid decrease in the catalyst's activity.

[0013] In contrast, the method for producing halogenated alkenes according to this disclosure yields a specific halogenated alkene from a specific halogenated alkane in the presence of silicon oxide and an alkali metal element. In this process, the generated hydrogen fluoride reacts with silicon oxide, or the specific halogenated alkane directly reacts with silicon oxide and the alkali metal element, generating silicon tetrafluoride (SiF4) regardless of the reaction scheme. Since the boiling point of silicon tetrafluoride is -95°C, it is a gas within the reaction system and is released outside the system. Therefore, in the method for producing halogenated alkenes according to this disclosure, the coating of silicon oxide is suppressed, and the rapid decrease in the amount of halogenated alkene produced is suppressed.

[0014] The method for producing the halogenated alkenes described herein will be explained in detail below.

[0015] (Alkanes halide) In the method for producing halogenated alkenes described herein, 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 compounds that can act as refrigerants, the specific halogenated alkane has 2 or 3 carbon atoms. The specific halogenated alkane contains fluorine atoms. Preferably, the number of fluorine atoms in the specific halogenated alkane is two or more. The number of hydrogen atoms in the specific halide alkane is preferably 1 or more. The specified halide alkane may contain halogen atoms other than fluorine. Examples of other halogen atoms include chlorine, bromine, and iodine atoms, with chlorine being preferred. The specified halide alkane does not need to contain other halogen atoms.

[0016] Examples of specific halogenated alkanes include those represented by the following formula (1). CR 1 R 2 X 1 -CR 3 R 4 X 2 ...(1)

[0017] In formula (1), R 1 ~R 4 Each of these is 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 number of carbon atoms is 2 to 4, X 1 and X 2 One of them is a hydrogen atom, and the other is a fluorine atom.

[0018] R 1 and R 3 Each of these is preferably a hydrogen atom or a fluorine atom, R 2 and R 4 Preferably, the element is a hydrogen atom, a fluorine atom, CH3, CH2F, CHF2, or CF3.

[0019] Examples of 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 specified halide alkane may include other halide alkanes other than the halide alkane represented by formula (1) (provided that it contains a fluorine atom and has 2 to 4 carbon atoms). The proportion of the halide alkane represented by formula (1) to the total amount of the specified halide alkane is preferably 30 mol% or more, and more preferably 50 mol% or more.

[0021] (Alkene halide represented by formula (2)) In the method for producing halogenated alkenes according to this disclosure, a specific halogenated alkene is obtained as a reaction product. The specific halogenated alkene has 2 to 4 carbon atoms; it can be 2, 3, or 4 carbon atoms. Certain halide alkenes contain fluorine atoms. The number of fluorine atoms in a specific halide alkene is one or more. The specified halide alkene may contain halogen atoms other than fluorine. Examples of other halogen atoms include chlorine, bromine, and iodine atoms, with chlorine being preferred. The specified halide alkene does not need to contain other halogen atoms.

[0022] Examples of specific halogenated alkenes include halogenated alkenes represented by the following formula (2). CR 1 R 2 =CR 3 R 4 ...(2)

[0023] In formula (2), R 1 ~R 4 Each of these is 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 number of carbon atoms is between 2 and 4.

[0024] R 1 and R 3 Each of these is preferably a hydrogen atom or a fluorine atom, R 2 and R 4Preferably, the element is a hydrogen atom, a fluorine atom, CH3, CH2F, CHF2, or CF3.

[0025] Examples of alkene halides 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] In particular, 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 its usefulness as a refrigerant composition. Furthermore, from the viewpoint of its usefulness as a resin, HFO-1141 and FO-1114 are preferred.

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

[0028] Silicon oxide and alkali metal elements may be integrated compounds or composites containing both, or separate substances containing silicon oxide and alkali metal elements may be used, or two or more of these may be used in combination. Examples include glass containing silicon oxide and alkali metal oxides, sodium silicate, sodium silicate cullet, composites in which alkali metal-containing compounds are supported on silicon oxide particles, and combinations of silicon oxide particles and alkali metal-containing compounds.

[0029] When silicon dioxide and alkali metal elements are integrated, their uneven distribution within the reaction system is easily suppressed. When silicon dioxide and alkali metal-containing compounds are used as separate substances, it is easier to prepare highly pure versions of each, and the generation of unwanted by-products in the reaction is easily suppressed. Hereinafter, compounds and complexes containing both silicon dioxide and alkali metal elements, as well as substances containing silicon dioxide and alkali metal elements separately, will be collectively referred to as "reactants."

[0030] The reactant may contain components other than silicon dioxide and alkali metal elements. Examples of other components include calcium, aluminum, magnesium, iron, boron, lead, and zinc.

[0031] The shape of the glass is not particularly limited and may be irregular in shape, such as crushed material, cullet, flakes, or spheres. It may also be molded into pellets, hollow shapes, cylindrical shapes, etc. These shapes may be combined as appropriate.

[0032] Examples of silicon dioxide particles used in composite materials or as separate substances include silica sand, quartz, diatomaceous earth, colloidal silica, precipitated silica, silica gel, fumed silica, and rice husks, with silica sand being preferred from the viewpoint of purity and cost.

[0033] The shape of silicon dioxide particles is not particularly limited and may be irregular in shape, such as natural products or pulverized materials, or may be cullet-like, flaky, or spherical. They may also be molded into pellets, hollow shapes, cylindrical shapes, etc. Furthermore, silicon dioxide particles may have a porous structure (e.g., porous). These shapes may be combined as appropriate, for example, a porous cylindrical molded product.

[0034] The silicon dioxide particles preferably have a low impurity content. From the viewpoint of suppressing the generation of unwanted by-products, the silicon dioxide content in the silicon dioxide particles is preferably low, preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0035] From the viewpoint of suppressing clogging in the reactor, the average particle size of the glass, composite, and silicon dioxide particles is preferably 20 μm or more, and more preferably 50 μm or more. From the viewpoint of ensuring a sufficient surface area for reaction sites, the average particle size of the glass, composite, and silicon dioxide particles is preferably 10 mm or less, more preferably 5 mm or less, and even more preferably 1 mm or less.

[0036] The average particle size of glass, composites, and silicon dioxide particles is determined as the particle size (D50) at which the cumulative weight distribution curve obtained by measurement using a Coulter counter reaches 50%. The aperture diameter is set appropriately according to the particle size range of the object being measured.

[0037] The silicon content in the reactant may be 1 atm% or more, 10 atm% or more, or 20 atm% or more. Furthermore, 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 humidity level 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 microscopy 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 is preferably greater than the total content of alkaline earth metals and Group 13 elements of the periodic table. Furthermore, silicon is preferably the element with the highest content (atm%) among the elements excluding oxygen. Furthermore, it is preferable that the content (atm%) of alkali metal elements in the reactant is greater than the content of silicon, oxygen, and other elements other than alkali metal elements. In the glass, the content (atm%) of alkali metal elements may be greater than, less than, or equal to 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 is preferably at least one selected from the group consisting of Na, K, and Cs from the viewpoint of activity, selectivity, or availability. Alkali metal-containing compounds can be any compound that contains an alkali metal element, such as alkali metal fluorides, halides such as chlorides, hydroxides, and carbonates. Specifically, examples include NaF, KF, CsF, NaOH, KOH, Na2CO3, K2CO3, and NaCl.

[0041] (Reaction scheme) In the method for producing a halogenated alkene according to this disclosure, silicon tetrafluoride (SiF4) is produced. In the method for producing a halogenated alkene according to this disclosure, a reaction scheme is conceivable in which, in the gas phase, a specific halogenated alkane and hydrogen fluoride are produced by a dehydrofluorination reaction of a specific halogenated alkane (first step), and silicon tetrafluoride is produced by a reaction of the produced hydrogen fluoride with silicon oxide (second step). The first and second steps may proceed continuously without distinction. Furthermore, the method for producing the halide alkene described herein may be other than the reaction scheme described above. For example, silicon dioxide or an alkali metal compound may react directly with the halide alkane to produce silicon tetrafluoride. In addition to silicon tetrafluoride, other compounds may also be produced.

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

[0043] [ka]

[0044] Since the generated silicon tetrafluoride is a gas, it is released from the reaction system. Therefore, the influence of by-products on silicon oxide is suppressed, and the rapid decrease in the amount of alkene halogens produced is prevented.

[0045] In conventional manufacturing methods using alumina, calcium carbonate, etc. as catalysts, the generated hydrogen fluoride reacts with the catalyst as follows.

[0046] [ka]

[0047] Since the generated aluminum fluoride (AlF3) and calcium fluoride (CaF2) are solids, they are not released outside the reaction system but remain within it, coating the surfaces of the alumina and calcium carbonate catalysts. As a result, the catalysts become inactive as their active sites are covered. Therefore, in conventional manufacturing methods, it is necessary to remove the degraded catalyst and replace it with a new one. Consequently, conventional manufacturing methods using alumina, calcium carbonate, etc., as catalysts have unstable productivity and require stopping the reaction each time the catalyst is replaced. In contrast, the method for producing alkene halogens according to this disclosure has the advantage of reducing the work required to remove degraded catalysts while maintaining productivity.

[0048] Furthermore, in the method for producing alkene halides according to this disclosure, the reaction can be continued by replenishing the consumed silicon dioxide. The amount of consumed silicon dioxide can be calculated from the amount of silicon tetrafluoride released from the reaction system. Specifically, the amount of released silicon tetrafluoride can be measured by passing the released silicon tetrafluoride through water, an alkaline aqueous solution, etc., to obtain hydrogen fluoride, hexafluorosilicic acid, or salts thereof, and then titrating these. On the other hand, in conventional manufacturing methods using alumina or calcium carbonate as a catalyst, AlF3 or CaF2 remains in the reaction system, making it difficult to estimate the amount of degraded catalyst. Therefore, it is difficult to accurately estimate the amount of catalyst to be replenished in conventional manufacturing methods.

[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, AlF3 or CaF2 adheres to the catalyst, causing changes in the catalyst's weight and density, which in turn causes fluctuations in fluidity. Therefore, it is difficult to maintain an appropriate fluid state. In contrast, in the manufacturing method of this disclosure, the by-product SiF4 is a gas and is released outside the reaction system, so there is no significant change in the fluidity of silicon dioxide, and it is easy to maintain an appropriate fluid state.

[0050] (Reaction conditions) The method for producing the halogenated alkene described herein 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 according to this disclosure, the raw material gas may contain a specific halogenated alkane, or it may contain components other than the specific halogenated alkane. The raw material gas may consist only of the specific halogenated alkane, or it may contain isomers, disproportionation products, impurities, etc., obtained when producing the specific halogenated alkane. From the viewpoint of suppressing side reactions, the content of the specific halogenated alkane is preferably 10 mol% or more, more preferably 30 mol% or more, and even more preferably 50 mol% or more, based on the total amount of the raw material gas. The content of the halogenated alkane represented by formula (1) may be 100 mol% of the total amount of the raw material gas.

[0051] The reactor used to react the halogenated alkane with the reagent can be any reactor capable of withstanding the temperature and pressure described later, and its shape and structure are not particularly limited. Examples of reactors include cylindrical vertical reactors. Examples of reactor materials include glass, stainless steel, iron, nickel, chromium, and alloys mainly composed of iron, nickel, or chromium. The inside of the reactor may be coated with platinum or gold. The reactor may also be equipped with heating means such as an electric heater to heat the inside of the reactor.

[0052] The reaction agent may be contained in a fixed-bed, fluidized-bed, or mobile-bed reactor. If it is a fixed-bed reactor, it may be either a horizontal or vertical fixed-bed reactor. The reactor may rotate as a whole. Furthermore, the reaction method may be a flow-through system or a batch system.

[0053] In fixed-bed reactors, various molded bodies of reactant-supporting carriers are packed into the reactor to reduce pressure loss of the reaction fluid. A moving-bed reactor is another type of reactor where the reactant is packed in a similar manner to a fixed-bed reactor, moved by gravity, and then extracted from the bottom of the reactor for regeneration. In a fluidized bed reactor, the reaction fluid is used to make the reactant layer behave like a fluid, so the reactant mixes with the reaction fluid and moves within the reactor. Fixed-bed reactors are preferred because they offer a wide range of reagent shapes and suppress reagent wear, while fluidized-bed reactors are preferred because they ensure a uniform internal temperature and make it easier to avoid localized heating.

[0054] Fixed-bed reactors include tubular reactors and tank reactors, with tubular reactors being preferred due to their ease of controlling the reaction temperature. Furthermore, multi-tube heat exchange reactions, in which many small-diameter reaction tubes are arranged in parallel and a heat transfer medium is circulated around the outside, can be employed. When multiple reactors are arranged in series, multiple reactant layers will be 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 even the diluent gas may be circulated from the bottom in a vertical direction, and the product gas may be withdrawn from the top in a vertical direction. A fluidized bed reactor may be equipped with stirring blades to further enhance fluidity. Furthermore, a gas dispersion plate may be provided in the fluidized bed reactor to prevent uneven gas flow. The material of the gas dispersion plate is not particularly limited, but it is preferably made of a material with low reactivity with the raw material gas, product gas, etc. Examples of gas dispersion plate materials include sintered metal. The size, placement, and number of gas dispersion plates may be adjusted as appropriate according to the gas flow.

[0056] In the method for producing halogenated alkenes 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 reaction is carried out at temperatures above 400°C, the reaction proceeds appropriately and the conversion rate of the halide alkene improves. On the other hand, when the reaction is carried out at temperatures below 1000°C, the selectivity decreases due to carbon-carbon bond cleavage of the starting materials, and the disproportionation reaction of the reaction product (unsaturated compound) is suppressed.

[0057] By adjusting the temperature within the above temperature range and maintaining the reaction temperature appropriately, it is possible to suppress the decrease in the conversion rate. To maintain the reaction temperature in the reactant layer at the desired temperature, for example, the reactant layer can be heated externally using a heat transfer medium, an electric furnace, or the like.

[0058] As described above, in the method for producing alkene halogens according to this disclosure, the reaction can be continued by replenishing the consumed silicon dioxide, thereby maintaining productivity. From the viewpoint of continuing the reaction, it is preferable to continuously supply the consumed silicon dioxide. The supply location of silicon dioxide in the reactor is not particularly limited and may be from the top or bottom of the reactor.

[0059] In the method for producing halogenated alkenes according to this disclosure, the raw material gas containing the halogenated alkane may be supplied to the reactor at room temperature, or it may be appropriately heated (preheated) before being supplied to the reactor. When preheating is performed, it is preferable to heat the raw material gas to 80°C or higher and below the reaction temperature inside the reactor before supplying it to the reactor. Setting the preheating temperature to 80°C or higher makes it less likely for the internal temperature of the reactor to drop, and makes it easier to achieve the set conversion rate. Furthermore, setting the preheating temperature below the reaction temperature inside the reactor suppresses undesirable reactions and improves the selectivity.

[0060] In the dehydrofluoride reaction described herein, since the reaction involves an increase in molecules, increasing the pressure makes the forward reaction unfavorable. The pressure used when reacting the halogenated alkane with the reactant is not particularly limited, but from the viewpoint of improving the conversion rate, -0.05 to 2 MPa is preferred, -0.01 to 1 MPa is more preferred, and atmospheric pressure to 0.5 MPa is even more preferred. 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 above dwell time (in seconds) is calculated using the following formula. Residence time (seconds) = [Length of reactor filled with reagent (cm)] / [Linear velocity (cm / second)] Linear velocity refers to the rate at which an alkane halide passes through the reactant per unit time.

[0063] Furthermore, the average bulk density of the reactant is 0.05 g / cm³. 3 The above is preferable, 0.1 g / cm³ 3 The above is more preferable, 0.2 g / cm³ 3 The above is even more preferable. The average bulk density of the reactant is 0.05 g / cm³. 3 The conversion rate improves when the above conditions are met. The average bulk density of the reactant is the average density of the reactant when no gas is flowing through the reactor. The average bulk density of the reactant is measured by the container method. In the container method, the reactant is poured into a container of known capacity until it overflows, and any excess reactant overflowing from the rim of the container is removed with a spatula or similar tool. The mass of the reactant in the container is then measured. The bulk density (g / mL) is calculated from this mass of 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 specific halogenated alkanes 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. In the gas phase, the molar ratio of the specific halogenated alkane to the diluent gas is preferably 0.1 to 5.0, more preferably 0.5 to 3.0, and even more preferably 0.5 to 2.0.

[0065] In general, in methods for producing alkene halides, diluent gases are used to suppress disproportionation reactions caused by high concentrations of the resulting alkene halides, and also to address concerns about explosions due to high concentrations, depending on the type of alkene halides. In the method for producing halogenated alkenes according to this 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 according to this disclosure, the amount of halogenated alkene produced can be kept within a certain range while maintaining the amount of production by the above controls, so that the outlet gas can contain a certain amount or more of the specific halogenated alkane, which is the raw material. The specific halogenated alkane in the outlet gas also functions as a diluent. Therefore, in the method for producing halogenated alkenes according to this disclosure, it is also possible to reduce the amount of diluent gas used. The method for producing halogenated alkenes according to this 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, therefore, the raw material gas is used as the diluent. Using these gases directly is difficult, and the use of diluent gases such as nitrogen and carbon dioxide is essential. Since the boiling points of these diluent gases, such as nitrogen and carbon dioxide, are lower than or close to those of the reaction products (halogenated alkenes), energy is required to separate and purify the diluent gases from the reaction products. In the method for producing halogenated alkenes according to this disclosure, even when the raw material gas is used as part or all of the diluent, the decrease in the amount of halogenated alkene produced over time can be suppressed. Since the raw material halogenated alkane has a high boiling point and its boiling point range is far removed from that of the reaction product halogenated alkene, the energy load required for separation and purification can also be reduced in the method for producing halogenated alkenes according to this disclosure.

[0067] From the viewpoint of controlling the efficiency and selectivity of the reaction, it is preferable that the conversion of the specific halogenated alkane be carried out in the gas phase in the presence of water, and that the concentration of water be less than 500 volume ppm relative to the total amount of the raw material gas containing the specific halogenated alkane. The dehydrofluoride reaction in this disclosure also produces water. Therefore, the reaction can proceed without problems even if water is present in the system. Furthermore, the presence of water molecules during the elimination of hydrogen fluoride from the starting material, or during the reaction of hydrogen fluoride with silicon dioxide, may allow the reaction to proceed more efficiently via a hydrogen bonding network. Therefore, it is possible to add a small amount of water to the dehydrofluoride reaction in this disclosure, and it is speculated that this may yield favorable results. On the other hand, the silicon tetrafluoride produced reacts with water near the outlet to form hexafluorosilicic acid, etc., and from the viewpoint of suppressing blockage of the gas flow path by the precipitation of this product, it is preferable to keep the water concentration below 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 volume ppm relative to the total amount of the specific halogenated alkane results in a high conversion rate and allows for the acquisition of the target product with high selectivity. From the viewpoint of further improving the conversion rate and obtaining the target compound with even higher selectivity, a moisture content of 300 volume ppm or less is preferable, more preferably 100 volume ppm or less, even more preferably 50 volume ppm or less, and particularly preferable 10 volume ppm or less. While a lower moisture content is preferable, 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 volume ppm or more is preferable, and more preferably 1 volume ppm or more.

[0069] The water concentration mentioned above refers to the water content in the raw material gas when reacting a specific halogenated alkane with a reagent. Alternatively, the water concentration may be replaced with the water content in the raw material gas before it enters the reactor.

[0070] The method for producing halogenated alkenes according to this 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 adjusted to the above range.

[0071] The method for drying the reactant is not particularly limited; it may be dried before filling the reactor, or after filling the reactor. If the reactant is dried after filling the reactor, the reactor can be preheated at the same time as drying the reactant. Specifically, the reactant may be dried by filling the reactor with the reactant and heating the reactor while circulating a diluent gas.

[0072] In this disclosure, the conversion rate is the ratio (%) of the molar amount of specific halogenated alkane consumed in the reaction to the molar amount of specific halogenated alkane supplied to the reactor. The molar amount of the specific halogenated alkane used as a raw material consumed in the reaction is the molar amount of the specific halogenated alkane supplied to the reactor. This is the difference between the molar amount of alkane genation and the molar amount of 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 pose an explosion risk due to 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 the disproportionation reaction of specific halogenated alkenes. A conversion rate of 50% or less is preferable, and 30% or less is more preferable. If the conversion rate is too low, productivity will decrease and the equipment will become larger, so it is preferable to select operating conditions that result in a conversion rate of 5% or more. A conversion rate of 10% or more is preferable, and 15% or more is more preferable.

[0074] In this 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, compounds derived from the carbon of the specific halogenated alkane that is the raw material, excluding compounds such as silicon tetrafluoride that do not have carbon derived from the raw material). A selectivity of 100% is preferable because it eliminates the need for a post-reaction purification step; however, side reactions may occur in the reaction temperature range required to obtain the desired conversion rate. A higher selectivity is preferable because it reduces the amount of waste, lowers the energy load of the post-reaction purification step, and extends the life of the reagent. A selectivity of 90% or higher is preferable, 93% or higher is more preferable, and 95% or higher is even preferable.

[0075] Compounds other than the raw material compounds and target products contained in the reactor outlet gas include, for example, carbon monoxide, carbon dioxide, water, silicon tetrafluoride, and the like.

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

[0077] The amount produced is determined by analyzing the reactor outlet gas using gas chromatography and calculating the area ratio (GCArea%) corresponding to the specific halogenated alkene.

[0078] The silicon tetrafluoride released in the method for producing alkene halides according to this disclosure can be used as a raw material for manufacturing high-performance optical fibers, a gas for semiconductor manufacturing, and the like. Furthermore, silicon tetrafluoride released outside the reaction system can be recovered as hydrogen fluoride or fluoride salts by reacting with water or alkali. These recovered compounds can be used as etching agents or as raw materials for organofluorine compounds. Furthermore, converting calcium fluoride (CaF2, fluorite), generated by conventional methods using calcium carbonate (CaCO3) as a catalyst, into hydrogen fluoride requires harsh conditions such as reaction with sulfuric acid, and also necessitates pretreatment such as crushing the solid CaF2.

[0079] (modified version) As a modification of the method for producing halogenated alkenes described herein, a halogenated alkane containing a fluorine atom and having 2 to 4 carbon atoms may be converted to a halogenated alkene containing a fluorine atom and having 2 to 4 carbon atoms in the 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 applies to the diluent 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. [Examples]

[0080] The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to the following examples unless it exceeds the spirit of the disclosure. Examples 2, 3, 5, and 7-20 are examples, and Examples 1, 4, and 6 are comparative examples.

[0081] (Outlet gas composition) At specific time intervals from the start of the reaction, the product gas (hereinafter also referred to as "reactor outlet gas") extracted from the reactor outlet was analyzed using a gas chromatograph. Specifically, the analysis was performed using a gas chromatograph (product name "GC6850", manufactured by Agilent) with a column (product name "DB-1", manufactured by Agilent, length 60m, inner diameter 0.25mm, film thickness 1μm). The table shows the area ratio (GCArea%) of the reactor outlet gas.

[0082] Furthermore, the obtained area ratio (GCArea%) was converted based on the relative sensitivity of gas chromatography, and the molar composition was determined so that the sum of the components listed in the table equaled 100 mol%.

[0083] (Rate of change in production amount) The percentage (%) of the amount of halide alkene produced at each reaction time was determined, relative to the amount of halide alkene produced at 1 hour from the start of the reaction. Unless otherwise specified, the rate of change in the amount of halide alkene produced was calculated using the molar composition values ​​mentioned above.

[0084] [Example 1] 140g of α-alumina (product name "N612", manufactured by JGC Catalysts & Chemicals Co., Ltd.) was packed into an Inconel 600 reaction tube with an inner diameter of 2.04cm and a length of 30cm, and placed in a tubular electric furnace. The de-HF reaction to HFO-1123 was carried out at 700°C by flowing a 1 / 1 (mol / mol) mixture of nitrogen / HFC-134a gas at the flow rates shown in Table 1.

[0085] [Table 1]

[0086] [Example 2] In Example 1, the HF removal reaction was carried out using the same method except that α-alumina was replaced with glass bead 1 (Unibeads series, manufactured by Unitika Glass Beads Co., Ltd.).

[0087] [Table 2]

[0088] Comparing Example 1 and Example 2, in Example 1, which uses α-alumina, the amount of alkene halide produced decreases significantly after 3 hours from the start of the reaction, and after 4 hours the amount produced becomes extremely small, whereas in Example 2, which uses glass beads 1, the decrease in the amount produced is significantly suppressed. Furthermore, in Example 2, it can be seen that the concentration of HFO-1123 is 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 28g of glass beads 1 were added to compensate for the weight loss, and the reaction was restarted. The additional reaction time in Table 3 is the reaction time from the restart. The percentage change in the amount of product is a value based on the amount of alkene halide produced 1 hour after the start of the reaction in Example 2.

[0090] [Table 3]

[0091] It is clear that the production rate has improved and recovered after replenishing glass beads 1.

[0092] [Example 4] In Example 1, the HF removal reaction to HFO-1123 was carried out using the same method except that HFC-134a was replaced with HFC-134.

[0093] [Table 4]

[0094] [Example 5] In Example 2, the HF removal reaction to HFO-1123 was carried out using the same method, except that HFC-134a was replaced with HFC-134.

[0095] [Table 5] In the table, "-" indicates that the component in question was below the detection limit.

[0096] Comparing Example 4 and Example 5, it can be seen that in Example 4, which uses α-alumina, the amount of alkene halide produced decreases significantly after 2.5 hours from the start of the reaction, and hardly any is produced after 3.5 hours, whereas in Example 5, which uses glass beads 1, the decrease in the amount produced is significantly suppressed. Furthermore, in Example 4, which uses α-alumina, a certain amount or more of the by-product HFC-134a is generated, whereas in Example 5, which uses glass beads 1, almost no HFC-134a is generated. Furthermore, in Example 5, it can be seen that 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 the HF removal reaction to FO-1114 was carried out by flowing a 1 / 1 (mol / mol) mixed gas of R32 / HFC-125 at 400 mL / min. The change in the amount of product in Table 6 was determined from the area ratio (GCArea%) of the reactor outlet gas.

[0098] [Table 6]

[0099] [Example 7] In Example 6, the HF removal reaction was carried out in the same manner as in Example 2, except that α-alumina was replaced with glass bead 1. The change in the amount of product in Table 7 was determined from the area ratio (GCArea%) of the reactor outlet gas.

[0100] [Table 7]

[0101] Comparing Example 6 and Example 7, in Example 6, which uses α-alumina, the amount of alkene halide produced decreases significantly after 2 hours from the start of the reaction, and after 4 hours the amount produced becomes extremely small, whereas in Example 7, which uses glass beads 1, the decrease in the amount produced is significantly suppressed. In Example 6, the selectivity of the compounds listed in the table was also low in the initial stages of the reaction. In Example 7, it can be seen that the concentration of FO-1114 is stably maintained in the outlet gas composition.

[0102] [Example 8] In Example 1, the 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 in a mass ratio of 1 / 1 (70g / 70g).

[0103] [Table 8]

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

[0105] [Table 9]

[0106] [Example 10] In Example 9, the HF removal reaction was carried out in the same manner 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, which uses α-alumina, the amount of halide alkenes produced decreases significantly after 3 hours from the start of the reaction, and after 4 hours the amount produced becomes extremely small, whereas in Examples 8, 9, and 10, which use silicon dioxide compounds, the decrease in the amount produced is significantly suppressed.

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

[0110] [Table 11]

[0111] [Example 12] In Example 5, the de-HF 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 at 0.5 hours from the start of the reaction.

[0112] [Table 12]

[0113] [Example 13] In Example 8, the de-HF reaction was carried out in the same manner except that sodium fluoride was replaced with sodium chloride. Table 13 shows the outlet gas composition at 1.0 hour from the start of the reaction.

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

[0115] [Table 13]

[0116] [Example 15] In Example 8, the de-HF reaction was carried out in the same manner except that sodium fluoride was replaced with cesium fluoride. Table 14 shows the outlet gas composition 0.5 hours after the start of the reaction.

[0117] [Table 14]

[0118] [Example 16] In Example 2, the de-HF reaction from HFC-134a to HFO-1123 was carried out using the same method, except that the total flow rate and ratio of the circulating gas were changed as shown in Table 15. Table 15 shows the outlet gas composition at 0.25 hours from the start of the reaction.

[0119] [Table 15]

[0120] [Example 17] In Example 2, the HF removal reaction to HFO-1141 was carried out using the same method, except that HFC-134a was replaced with HFC-152a. Table 16 shows the outlet gas composition 0.5 hours after the start of the reaction.

[0121] [Example 18] In Example 17, the de-HF reaction to HFO-1141 was carried out in the same manner, 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] In Example 2, the HF removal reaction to HFO-1132 and 1132a was carried out using the same method, except that HFC-134a was replaced with HFC-143. Table 17 shows the outlet gas composition 0.5 hours after the start of the reaction.

[0124] [Example 20] In Example 19, the de-HF reaction was carried out in the same manner, 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 documents, patent applications, and technical standards described herein are incorporated by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted as being incorporated by reference.

Claims

1. In the presence of silicon dioxide and alkali metal elements, in the gas phase, fluorinated alkanes having 2 to 4 carbon atoms are converted to fluorinated alkenes having 2 to 4 carbon atoms at a temperature of 450°C or higher. Silicon oxide is consumed and silicon tetrafluoride is produced. A method for producing alkenes fluoride, comprising replenishing silicon dioxide to continue the reaction.

2. A method for producing alkene fluorides according to claim 1, comprising replenishing silicon dioxide without stopping the reaction to continue the reaction.

3. A method for producing alkene fluorides according to claim 1 or 2, comprising continuously replenishing silicon dioxide to continue the reaction.

4. A method for producing alkene fluorides according to claim 1 or 2, comprising determining the amount of silicon dioxide to replenish based on the amount of silicon dioxide consumed.

5. A method for producing a fluoride alkene according to claim 1 or 2, wherein the fluoride alkane includes a fluoride alkane represented by the following formula (1), and the fluoride alkene includes a fluoride alkene represented by the following formula (2). CR １ R ２ X １ -CR ３ R ４ X ２ ・・・(1) CR １ R ２ =CR ３ R ４ ・・・(2) In equations (1) and (2), R １ ~R ４ Each of these is 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 number of carbon atoms is 2 to 4. In equation (1), X １ and X ２ One of them is a hydrogen atom, and the other is a fluorine atom.

6. In the gas phase, the fluoride alkene and hydrogen fluoride are produced by the dehydrofluoridation reaction of the fluoride alkane, A method for producing alkene fluorides according to claim 1 or 2, comprising the reaction of generated hydrogen fluoride with silicon oxide to produce silicon tetrafluoride.

7. The method for producing a fluorinated alkene according to claim 1 or 2, wherein the fluorinated 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.

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

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

10. A method for producing an alkene fluoride according to claim 1 or 2, wherein the alkane fluoride is converted in the presence of a diluent gas.

11. The method for producing alkene fluorides according to claim 10, wherein 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.

12. A method for producing an alkene fluoride according to claim 1 or 2, wherein the alkane fluoride is converted at a temperature of 450 to 1000°C.

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