Methods for manufacturing haloolefins

Abstract

A method for producing haloolefins, wherein, in the presence of silicon oxide and alkali metal elements, haloalkanes containing fluorine atoms and having 2 to 4 carbon atoms are converted into haloolefins containing fluorine atoms and having 2 to 4 carbon atoms in the gas phase.

Description

Technical Field

[0001] This disclosure relates to a method for manufacturing haloolefins. Background Technology

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

[0003] For example, Patent Document 1 describes a method for manufacturing hydrofluoroolefins by converting hydrofluorocarbons into hydrofluoroolefins in the presence of a fluorinated compound having a standard boiling point higher than that of the target hydrofluoroolefin. The reaction steps of this manufacturing method include contacting the hydrofluorocarbon with a catalyst. Specifically, alumina (Al₂O₃) is used as the catalyst.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2017 / 104829 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] However, when using a catalyst as described in Patent Document 1 to produce fluoroolefins via the dehydrofluorination reaction of fluorocarbons, the catalyst deteriorates over time due to the generated hydrogen fluoride, and the amount of fluoroolefins produced decreases over time.

[0009] Therefore, one objective of this disclosure is to provide a method for producing a time-dependent reduction in the amount of suppressed haloolefins compared to conventional methods.

[0010] Solution for solving the problem

[0011] This disclosure includes the following methods.

[0012] <1> A method for producing haloolefins, wherein, in the presence of silicon oxide and alkali metal elements, haloalkanes containing fluorine atoms and having 2 to 4 carbon atoms are converted into haloolefins containing fluorine atoms and having 2 to 4 carbon atoms in the gas phase.

[0013] <2> according to <1> The method for manufacturing haloolefins, wherein the haloalkane comprises a haloalkane of formula (1) and the haloolefin comprises a haloolefin of formula (2).

[0014] CR 1 R 2 X 1 -CR 3 R 4 X 2 …(1)

[0015] CR 1 R 2 =CR 3 R 4 …(2)

[0016] In equations (1) and (2), R 1 ~R 4 Each is independently a hydrogen atom, a fluorine atom, a methyl group, a fluoromethyl group, an ethyl group, or a fluoroethyl group, R 1 ~R 4 The total number of fluorine atoms is more than 1, and the number of carbon atoms is 2 to 4.

[0017] In equation (1), X 1 and X 2 One of them is a hydrogen atom, and the other is a fluorine atom.

[0018] <3> according to <1> or <2> The method for manufacturing the haloolefin produces silicon tetrafluoride.

[0019] <4> according to <1> ~ <3> The method for producing any one of the haloolefins comprises:

[0020] In the gas phase, the haloalkane is dehydrofluorinated to produce the haloalkene and hydrogen fluoride; and

[0021] Silicon tetrafluoride is produced by the reaction of the generated hydrogen fluoride with silicon oxide.

[0022] <5> according to <1> ~ <4> The method for producing a haloalkene according to any one of the following, wherein the haloalkane 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.

[0023] <6> according to <1> ~ <5> The method for manufacturing a haloolefin according to any one of the following, wherein the haloolefin is at least one selected from the group consisting of fluoroethylene, 1,1-difluoroethylene, 1,2-difluoroethylene, trifluoroethylene and tetrafluoroethylene.

[0024] <7> according to <1> ~ <6> The method for producing haloalkene according to any one of the following methods involves converting the haloalkane in the presence of a diluent gas.

[0025] <8> according to <7> The method for manufacturing haloolefins, 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 fluoromethane.

[0026] <9> according to <1> ~ <8> The method for producing the haloalkene according to any one of the following methods involves converting the haloalkane at a temperature of 400 to 1000°C.

[0027] <10> A method for producing haloolefins, wherein, in the presence of boron oxide, a haloalkane containing fluorine atoms and having 2 to 4 carbon atoms is converted into a haloolefin containing fluorine atoms and having 2 to 4 carbon atoms in the gas phase.

[0028] The effects of the invention

[0029] According to this disclosure, a method for producing a time-dependent reduction in the amount of inhibited haloolefins is provided compared to conventional methods. Detailed Implementation

[0030] In this disclosure, the numerical range represented by "~" refers to the range in which the values ​​before and after "~" are respectively the minimum and maximum values.

[0031] In the numerical ranges described in this disclosure, the upper or lower limit value recorded in a certain numerical range can be replaced with the upper or lower limit value of other numerical ranges described in different stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value recorded in a certain numerical range can be replaced with the value shown in the embodiments.

[0032] In this disclosure, a combination of two or more preferred methods is a more preferred method.

[0033] In this disclosure, when there are multiple substances that are components, unless otherwise specified, the amount of each component refers to the total amount of the multiple substances.

[0034] [Methods for manufacturing haloolefins]

[0035] The method for producing haloolefins disclosed herein involves converting haloalkanes containing fluorine atoms and having 2 to 4 carbon atoms into haloolefins containing fluorine atoms and having 2 to 4 carbon atoms in the gas phase in the presence of silicon oxide and alkali metal elements.

[0036] Hereinafter, "haloalkanes containing fluorine atoms and having 2 to 4 carbon atoms" will also be referred to as "specific haloalkanes", and "haloalkenes containing fluorine atoms and having 2 to 4 carbon atoms" will also be referred to as "specific haloalkenes".

[0037] According to the method for producing haloolefins disclosed herein, the time-dependent decrease in yield is suppressed compared to conventional methods. The reason for this is not yet clear, but it can be speculated as follows.

[0038] In the reaction from a fluorine-containing alkyl haloalkane to a fluorine-containing alkyl haloalkane, hydrogen fluoride is produced. The produced hydrogen fluoride reacts with alumina (Al₂O₃) as a catalyst to produce AlF₃, and with calcium carbonate (CaCO₃) as a catalyst to produce CaF₂. Here, AlF₃ has a boiling point of 1260°C and CaF₂ has a boiling point of 2533°C, therefore they are solids in the reaction system. Consequently, the produced AlF₃ and CaF₂ remain in the reaction system, covering the reaction sites present on the catalyst surface. Because the reaction sites of the catalyst are covered, the catalyst activity decreases sharply.

[0039] In contrast, the method for producing haloolefins disclosed herein yields specific haloolefins from specific haloalkanes in the presence of silicon oxide and alkali metal elements. In this process, the generated hydrogen fluoride reacts with silicon oxide, or the specific haloalkanes react directly with silicon oxide and alkali metal elements, producing silicon tetrafluoride (SiF4) regardless of the reaction route. Silicon tetrafluoride has a boiling point of -95°C and is therefore a gas within the reaction system, released outside the system. Therefore, it is believed that the method for producing haloolefins disclosed herein can suppress the covering of silicon oxide and prevent a sharp decrease in the amount of haloolefins formed.

[0040] The method for manufacturing the haloolefins disclosed herein will be described in detail below.

[0041] (Halogenated alkanes)

[0042] The method for producing haloalkenes disclosed herein uses specific haloalkanes as raw materials.

[0043] The number of carbon atoms in a particular haloalkane is 2 to 4, and can be 2, 3, or 4. From the viewpoint of the boiling point range of compounds that can be used as refrigerants, the number of carbon atoms in a particular haloalkane is preferably 2 or 3.

[0044] Certain haloalkanes contain fluorine atoms. Preferably, the number of fluorine atoms in a particular haloalkane is 2 or more.

[0045] The number of hydrogen atoms in a particular haloalkane is preferably 1 or more.

[0046] Certain haloalkanes may contain halogen atoms other than fluorine atoms. Examples of other halogen atoms include chlorine, bromine, and iodine atoms, with chlorine atoms being preferred. Certain haloalkanes may also not contain other halogen atoms.

[0047] As a specific haloalkane, haloalkane represented by the following formula (1) can be cited.

[0048] CR 1 R 2 X 1 -CR3 R 4 X 2 ··· (1)

[0049] In equation (1), R 1 ~R 4 Each is independently a hydrogen atom, a fluorine atom, a methyl group, a fluoromethyl group, an ethyl group, or a fluoroethyl group, 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.

[0050] R 1 and R 3 Each atom is preferably a hydrogen atom or a fluorine atom, R 2 and R 4 Preferably, it is a hydrogen atom, a fluorine atom, CH3, CH2F, CHF2, or CF3.

[0051] The following compounds can be cited as haloalkanes represented by formula (1).

[0052] CHF2CH3: 1,1-Difluoroethane (HFC-152a)

[0053] CH2FCH2F: 1,2-Difluoroethane (HFC-152)

[0054] CF3CH3: 1,1,1-Trifluoroethane (HFC-143a)

[0055] CHF2CH2F: 1,1,2-Trifluoroethane (HFC-143)

[0056] CF3CH2F: 1,1,1,2-Tetrafluoroethane (HFC-134a)

[0057] CHF2CHF2: 1,1,2,2-Tetrafluoroethane (HFC-134)

[0058] CF3CHF2: 1,1,1,2,2-Pentafluoroethane (HFC-125)

[0059] The specific haloalkane may include other haloalkane besides the haloalkane shown in formula (1) (wherein, it contains fluorine atoms and has 2 to 4 carbon atoms). The proportion of the haloalkane shown in formula (1) relative to the total amount of the specific haloalkane is preferably 30 mol% or more, more preferably 50 mol% or more.

[0060] (The haloalkene shown in formula (2))

[0061] The method for producing haloolefins disclosed herein can yield specific haloolefins as reaction products.

[0062] Certain haloalkenes have 2 to 4 carbon atoms, which can be 2, 3 or 4.

[0063] Certain haloalkenes contain fluorine atoms. Certain haloalkenes have one or more fluorine atoms.

[0064] Certain haloalkenes may contain halogen atoms other than fluorine atoms. Examples of other halogen atoms include chlorine, bromine, and iodine atoms, with chlorine atoms being preferred. Certain haloalkenes may also not contain other halogen atoms.

[0065] As specific haloolefins, haloolefins represented by the following formula (2) can be cited.

[0066] CR 1 R 2 =CR 3 R 4 …(2)

[0067] In equation (2), R 1 ~R 4 Each is independently a hydrogen atom, a fluorine atom, a methyl group, a fluoromethyl group, an ethyl group, or a fluoroethyl group, R 1 ~R 4 The total number of fluorine atoms is more than 1, and the number of carbon atoms is 2 to 4.

[0068] R 1 and R 3 Each atom is preferably a hydrogen atom or a fluorine atom, R 2 and R 4 Preferably, it is a hydrogen atom, a fluorine atom, CH3, CH2F, CHF2, or CF3.

[0069] Examples of haloalkenes represented by formula (2) include the following compounds.

[0070] CHF=CH2: Vinyl fluoride (HFO-1141)

[0071] CF2=CH2: 1,1-Difluoroethylene (HFO-1132a)

[0072] CHF=CHF: 1,2-Difluoroethylene (HFO-1132(E), HFO-1132(Z))

[0073] CHF=CF2: Trifluoroethylene (HFO-1123)

[0074] CF2=CF2: Tetrafluoroethylene (FO-1114)

[0075] From the viewpoint of its usefulness as a refrigerant composition, the halogenated olefin represented by formula (2) is preferably at least one selected from the group consisting of HFO-1132, HFO-1132a and HFO-1123. Furthermore, from the viewpoint of its usefulness as a resin, HFO-1141 and FO-1114 are preferred.

[0076] (Silicon oxide and alkali metal elements)

[0077] The method for producing haloolefins disclosed herein converts specific haloalkanes into specific haloolefins in the presence of silicon oxide and alkali metal elements.

[0078] Silicon oxide and alkali metal elements can be integrated compounds or complexes containing both, or different substances containing silicon oxide and alkali metal elements can be used, or more than two of them can be used together. Examples include glasses containing silicon oxide and alkali metal oxides, sodium silicate, sodium silicate shards, complexes containing alkali metal compounds supported on silicon oxide particles, and the combined use of silicon oxide particles and alkali metal compounds.

[0079] When silicon dioxide and alkali metal elements are integrated, non-uniform distribution within the reaction system is easily suppressed. When silicon dioxide and alkali metal compounds are used in different forms, it is easy to prepare high-purity substances separately, and it is easy to suppress the generation of unwanted byproducts during the reaction.

[0080] Hereinafter, compounds and complexes containing both silicon oxide and alkali metal elements, as well as different substances containing silicon oxide and alkali metal elements respectively, will be collectively referred to as "reactants".

[0081] The reactants can contain components other than silicon dioxide and alkali metals. Examples of such components include calcium, aluminum, magnesium, iron, boron, lead, and zinc.

[0082] There are no particular restrictions on the shape of the glass; it can be any shape, such as pulverized material, broken glass, flakes, or spheres. Additionally, it can be formed into granules, hollow structures, or cylindrical shapes. These shapes can be combined appropriately.

[0083] Examples of silica particles used in composites or combinations of different substances include silica sand, quartz, diatomaceous earth, colloidal silica, precipitated silica, silica gel, fumed silica, and rice husks. From the perspective of purity and price, silica sand is preferred.

[0084] There are no particular restrictions on the shape of silica particles; they can be any shape, including natural materials, pulverized materials, irregular shapes, glass-like fragments, flakes, spheres, etc. They can also be shaped into granules, hollow structures, cylinders, etc. Furthermore, silica particles can also have a porous structure (porous materials, etc.). These shapes can be appropriately combined; for example, porous cylindrical shapes can be exemplified.

[0085] The silica particles preferably have a low impurity content. From the viewpoint of suppressing the formation of unwanted byproducts, the silica content in the silica 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.

[0086] Regarding the size of the glass, composite, and silica particles, from the viewpoint of suppressing clogging in the reactor, an average particle size of 20 µm or more is preferred, and 50 µm or more is more preferred. Regarding the size of the glass, composite, and silica particles, from the viewpoint of ensuring sufficient surface area for reaction sites, an average particle size of 10 mm or less is preferred, 5 mm or less is more preferred, and 1 mm or less is even more preferred.

[0087] The average particle size of glass, composite, and silica particles is determined as the cumulative 50% particle size (D50) in the weight-cumulative particle size distribution curve obtained by measurement using a Coulter counter. The pore size is appropriately set according to the particle size range of the object being measured.

[0088] The silicon content in the reactant can be above 1 atm%, above 10 atm%, or above 20 atm%. Alternatively, the silicon content in the reactant can be below 90 atm% or below 80 atm%.

[0089] The oxygen content in the reactant can be above 1 atm%, above 5 atm%, or above 10 atm%. The oxygen content in the reactant can be below 90 atm% or below 80 atm%.

[0090] The alkali metal content in the reactant can be above 1 atm%, above 5 atm%, or above 8 atm%. Alternatively, the alkali metal content in the reactant can be below 90 atm% or below 50 atm%.

[0091] The content of each element in the reactant was determined by scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDX analysis).

[0092] In the reactants, the content (atm%) of silicon is preferably greater than that of alkali metals, preferably greater than the total content of alkaline earth metals and Group 13 elements of the periodic table, and preferably silicon is the element with the highest content (atm%) among elements other than oxygen.

[0093] Furthermore, in the reactants, the content (atm%) of alkali metal elements is preferably greater than the individual content of each of the other elements besides silicon, oxygen, and alkali metals. In the glass, the content (atm%) of alkali metal elements can be greater than, less than, or the same as the total content of alkaline earth metals and Group 13 elements of the periodic table.

[0094] The alkali metal element is preferably selected from at least one of the group consisting of Na, K, Rb and Cs, and from the viewpoint of activity, selectivity or availability, it is preferably selected from at least one of the group consisting of Na, K and Cs.

[0095] As a compound containing alkali metals, it is sufficient to contain alkali metal elements. Examples include halides such as fluorides and chlorides, hydroxides, and carbonates of alkali metals. Specifically, examples include NaF, KF, CsF, NaOH, KOH, Na2CO3, K2CO3, and NaCl.

[0096] (Reaction route)

[0097] The method for producing haloolefins disclosed herein generates silicon tetrafluoride (SiF4). The method for producing haloolefins disclosed herein considers the following reaction route: in the gas phase, a specific haloolefin and hydrogen fluoride are generated through a dehydrofluorination reaction of a specific haloalkane (first step); the generated hydrogen fluoride is then reacted with silicon oxide to generate silicon tetrafluoride (second step). The first and second steps can also be carried out continuously without distinction.

[0098] It should be noted that the method for producing haloalkenes disclosed herein can be a reaction route other than the above-mentioned reaction route. For example, silicon oxide and alkali metal compounds can react directly with haloalkanes to generate silicon tetrafluoride.

[0099] In addition to silicon tetrafluoride, other compounds can also be formed.

[0100] The following is a hypothetical example of a reaction route that uses the haloalkane shown in formula (1) as the specific haloalkane to obtain the haloalkene shown in formula (2) as the specific haloalkene.

[0101]

[0102] The generated silicon tetrafluoride is a gas and is therefore released from the reaction system to the outside. Thus, the effect of byproducts on silicon oxide can be suppressed, and the sharp decrease in the formation of haloolefins is inhibited.

[0103] It should be noted that in conventional manufacturing methods that use alumina, calcium carbonate, etc. as catalysts, the generated hydrogen fluoride reacts with the catalyst as follows.

[0104]

[0105] The generated aluminum fluoride (AlF3) and calcium fluoride (CaF2) are solids, and therefore remain within the reaction system, covering the surfaces of the alumina and calcium carbonate catalysts. Consequently, the active sites on the catalyst surface are covered and deactivated, requiring conventional manufacturing methods to remove the degraded catalyst and replace it with a new one. Therefore, conventional manufacturing methods using alumina and calcium carbonate as catalysts have unstable productivity and require stopping the reaction each time the catalyst is replaced.

[0106] In contrast, the method for producing haloolefins disclosed herein reduces the work of removing degraded catalysts and has the advantage of maintaining productivity.

[0107] Furthermore, the method for producing haloolefins disclosed herein allows the reaction to continue by replenishing the consumed silicon dioxide. The amount of silicon dioxide consumed can be calculated from the amount of silicon tetrafluoride released from the reaction system to the outside. Specifically, the released silicon tetrafluoride is reacted with water, an alkaline aqueous solution, etc., to produce hydrogen fluoride, hexafluorosilicic acid, their salts, etc., and the amount of released silicon tetrafluoride can be determined by titrating these solutions.

[0108] On the other hand, in conventional manufacturing methods using alumina or calcium carbonate as catalysts, it is difficult to estimate the amount of degraded catalyst because AlF3 or CaF2 remains in the reaction system. Therefore, conventional manufacturing methods make it difficult to properly estimate the amount of catalyst to be replenished.

[0109] Furthermore, in fluidized bed reactions, it is desirable that the catalyst's flowability does not change significantly. However, in conventional methods, AlF3 or CaF2 adheres to the catalyst, thus altering its weight and density, and consequently, its flowability. Therefore, maintaining a suitable flow state is difficult.

[0110] In contrast, in the manufacturing method disclosed herein, SiF4, as a byproduct, is a gas and is released outside the reaction system. Therefore, the fluidity of silicon oxide does not change significantly and it is easy to maintain an appropriate flow state.

[0111] (Reaction conditions)

[0112] The method for producing haloalkenes disclosed herein is carried out in the gas phase because the specific haloalkanes are gases at room temperature.

[0113] In the method for producing haloalkenes disclosed herein, the feed gas may contain only a specific haloalkane, or it may contain components other than the specific haloalkane. The feed gas may consist only of the specific haloalkane, or it may contain isomers, disproportionation products, impurities, etc., obtained during the production of the specific haloalkane. From the viewpoint of suppressing side reactions, the content of the specific haloalkane 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 feed gas. The content of the haloalkane shown in formula (1) may be 100 mol% relative to the total amount of the feed gas.

[0114] As a reactor for reacting haloalkanes with reactants, its shape and structure are not particularly limited, as long as it can withstand the temperature and pressure described later. For example, a cylindrical vertical reactor can be considered. As for the reactor material, glass, stainless steel, iron, nickel, chromium, and alloys with iron, nickel, or chromium as the main components can be used. The inner surface of the reactor can be coated with platinum, gold, or the like. Furthermore, the reactor can be equipped with a heating device such as an electric heater to heat the interior of the reactor.

[0115] The reactants can be housed in any of the following configurations: fixed bed, fluidized bed, or moving bed. In the case of a fixed bed, it can be either a horizontal or vertical fixed bed. The reactor can be rotated as a whole.

[0116] In addition, the reaction can be either flow-through or batch reaction.

[0117] In fixed-bed reactors, various molded bodies that act as reactant carriers can be used to reduce pressure loss of the reaction fluid. Alternatively, a method similar to a fixed-bed reactor, where reactant is filled and moved by gravity, then removed from the bottom of the reactor for regeneration, is called a moving-bed reactor.

[0118] In a fluidized bed reactor, an operation is performed that causes the reactant layer to exhibit fluid-like properties as it passes through a reaction fluid, thus mixing the reactant with the reaction fluid and moving within the reactor.

[0119] Fixed-bed reactors are preferred in terms of a wide range of reactant shapes and the ability to suppress reactant wear, while fluidized-bed reactors are preferred from the viewpoint of achieving uniform internal temperature and easily avoiding localized heating.

[0120] As fixed-bed reactors, there are tubular reactors and trough reactors. From the perspective of ease of temperature control, tubular reactors are preferred. Furthermore, multi-tube heat exchange reactors can be used, where multiple small-diameter reaction tubes are arranged in parallel and the heat medium circulates on the outside. It should be noted that when multiple reactors are connected in series, multiple reactant layers are set. The reactant layer can be at least one section, or it can be two or more sections.

[0121] In the case of a fluidized bed reactor, the feed gas and subsequently the diluent gas can flow downwards in the vertical direction, while the generated gas is extracted upwards in the vertical direction.

[0122] From the perspective of further improving fluidity, fluidized bed reactors can be equipped with stirring blades. Furthermore, from the perspective of preventing uneven gas flow within the fluidized bed reactor, gas dispersion plates can be installed. The material of the gas dispersion plates is not particularly limited, but it is preferable to be made of a material with low reactivity with the feed gas, product gas, etc. Examples of materials for gas dispersion plates include sintered metals. The size, placement, and number of gas dispersion plates can be appropriately adjusted according to the gas flow.

[0123] The method for producing haloalkane disclosed herein preferably involves converting the haloalkane 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.

[0124] If the conversion is carried out above 400°C, the reaction proceeds appropriately, and the conversion rate of haloolefins increases. On the other hand, if the conversion is carried out below 1000°C, the selectivity caused by the cleavage of carbon-carbon bonds in the starting material decreases, and the disproportionation reaction of the reaction products (unsaturated compounds) is suppressed.

[0125] By adjusting the reaction temperature to the aforementioned temperature range and maintaining it appropriately, the decrease in conversion rate can also be suppressed. To maintain the reaction temperature in the reactant layer at the desired temperature, methods such as heating the reactant layer from the outside using a heat transfer medium or an electric furnace can be employed.

[0126] As described above, the method for producing haloolefins of this disclosure allows the reaction to continue and productivity to be maintained by replenishing the consumed silica. From the viewpoint of continuing the reaction, it is preferable to continuously supply the consumed amount of silica. The location for supplying silica to the reactor is not particularly limited; it can be supplied from the top or bottom of the reactor.

[0127] In the method for producing haloalkanes disclosed herein, the feed gas containing haloalkanes can be supplied directly to the reactor at room temperature, or it can be appropriately heated (preheated) before being supplied to the reactor. When preheating is performed, the feed gas is preferably heated to 80°C or higher and below the reaction temperature inside the reactor before being supplied to the reactor. If the preheating temperature is set to 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, if the preheating temperature is set below the reaction temperature inside the reactor, undesirable reactions are suppressed, and selectivity is improved.

[0128] The defluorination reaction disclosed herein is a molecular increase reaction, therefore the forward reaction becomes unfavorable when the pressure is increased.

[0129] There is no particular limitation on the pressure during the reaction of haloalkanes with the reactants. From the viewpoint of improving the conversion rate, it is preferably -0.05~2MPa, more preferably -0.01~1MPa, and even more preferably atmospheric pressure~0.5MPa.

[0130] In this disclosure, pressure refers to gauge pressure.

[0131] The residence time of the haloalkane 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.

[0132] The above-mentioned dwell time (seconds) is calculated using the following formula.

[0133] Residence time (seconds) = [Length of reactant in the reactor (cm)] / [Linear velocity (cm / second)]

[0134] Linear velocity refers to the rate at which a haloalkane passes through a reactant per unit time.

[0135] Furthermore, the average bulk density of the reactants is preferably 0.05 g / cm³. 3 The above, more preferably 0.1 g / cm 3 The above is further preferred to be 0.2 g / cm³. 3 The average bulk density of the reactants is 0.05 g / cm³. 3 When the above conditions are met, the conversion rate increases.

[0136] The average bulk density of the reactants is the average density of the reactants when no gas is circulated within the reactor.

[0137] The average bulk density of the reactant was determined by the container method. The container method involves adding the reactant to a container of known capacity until it overflows. Then, excess reactant overflowing from the edge of the container's upper surface is removed using a scraper or similar tool, and the mass of the reactant remaining in the container is measured. The bulk density (g / mL) is calculated from the mass of the reactant and the container's capacity (volume). This measurement is performed three times, and the average value is taken as the average bulk density.

[0138] The conversion of specific haloalkanes is preferably carried out in the presence of a diluent gas. The diluent gas is preferably at least one gas selected from the group consisting of nitrogen, hydrogen, carbon dioxide, helium, propane, isobutane, n-butane, ethane, propylene, and fluoromethane. Examples of fluoromethanes include monofluoromethane, difluoromethane, trifluoromethane, and fluoromethane.

[0139] The molar ratio of the specific haloalkane in the gas phase to the dilution gas is preferably 0.1 to 5.0, more preferably 0.5 to 3.0, and even more preferably 0.5 to 2.0.

[0140] Typically, in the manufacturing methods of haloolefins, dilution gases are used from the perspective of suppressing disproportionation reactions caused by high concentrations of the generated haloolefins, and from the perspective of preventing explosions due to high concentrations depending on the type of haloolefin.

[0141] The method for producing haloolefins disclosed herein allows for control of reactivity through residence time, reaction temperature, etc., thereby enabling control over the concentration of specific haloolefins in the outlet gas. In this method, by controlling as described above, the amount of haloolefin produced can be maintained while suppressing it within a certain range, thus ensuring that the outlet gas contains a certain level or higher of the specific haloalkane used as a raw material. The specific haloalkane in the outlet gas also functions as a diluent. Therefore, the method for producing haloolefins disclosed herein can also suppress the amount of dilution gas used. It should be noted that the method for producing haloolefins disclosed herein also includes methods that do not use dilution gas.

[0142] Furthermore, in the method for producing fluoroolefins using an alumina catalyst, as described in Patent Document 1, the conversion rate decreases if the amount of diluent is reduced. Therefore, it is difficult to use the feed gas as a diluent, and diluent gases such as nitrogen and carbon dioxide must be used. The boiling points of diluent gases such as nitrogen and carbon dioxide are lower than or close to those of the halogenated olefins that are reaction products, so energy is required to separate and purify the diluent gases from the reaction products.

[0143] The method for producing haloolefins disclosed herein can suppress the gradual decrease in the amount of haloolefins produced even when the feed gas is used as part or all of the diluent. Since the haloalkane in the feed has a high boiling point, which separates from the boiling point band of the haloolefin as the reaction product, the method for producing haloolefins disclosed herein can also reduce the energy load required for separation and purification.

[0144] From the viewpoint of controlling reaction efficiency and selectivity, the conversion of a specific haloalkane is preferably carried out in the gas phase in the presence of water, with the water concentration being less than 500 ppm by volume relative to the total amount of feed gas containing the specific haloalkane.

[0145] The defluorination reaction of this disclosure also produces water. Therefore, it can be said that the reaction proceeds without problems even in the presence of water in this system. Furthermore, the reaction may proceed more efficiently via hydrogen bonding networks due to the presence of water molecules when hydrogen fluoride is removed from the raw materials or when hydrogen fluoride reacts with silicon oxide. Therefore, it is speculated that adding a small amount of water to the defluorination reaction of this disclosure may also yield beneficial results.

[0146] On the other hand, the silicon tetrafluoride produced reacts with water near the outlet to produce hexafluorosilicic acid, etc. From the viewpoint of suppressing the blockage of the gas flow path caused by this precipitation, the concentration of water is preferably less than the above range.

[0147] A common method for determining the moisture content of a gas is to use a commercially available dew point meter. By ensuring that the water content relative to the total amount of a specific haloalkane is less than 500 ppm by volume, the conversion rate is increased, and the target product can be obtained with high selectivity. From the perspective of further improving the conversion rate and obtaining the target compound with higher selectivity, the water 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. The lower the water content, the more preferred, but from the viewpoint of the cost of dehydration treatment of the specific haloalkane and dilution gas and the increased difficulty of process management, it is preferably 0.5 ppm by volume or more, more preferably 1 ppm by volume or more.

[0148] The water concentration mentioned above refers to the water content in the feed gas during the reaction of a specific haloalkane with the reactant. It should be noted that the water concentration can be replaced by the water content in the feed gas before it flows into the reactor.

[0149] The method for producing haloalkenes disclosed herein may further include a step of drying the reactant before reacting a specific haloalkane with the reactant. By drying the reactant, water contained in the reactant can be removed, and the water concentration can be adjusted to the range described above.

[0150] There are no particular limitations on the method for drying the reactant; it can be dried before or after filling the reactor. When drying the reactant after filling, the reactor can be preheated simultaneously with the drying process. Specifically, the reactant can be filled into the reactor while the reactor is heated, thereby drying the reactant.

[0151] In this disclosure, conversion rate refers to the ratio (%) of the molar amount of a specific haloalkane consumed in the reaction to the molar amount of the specific haloalkane supplied to the reactor. It should be noted that the molar amount consumed in the reaction of the specific haloalkane used as a feedstock is the difference between the molar amount of the specific haloalkane supplied to the reactor and the molar amount of the specific haloalkane contained in the effluent gas from the reactor outlet.

[0152] Generally, from a productivity point of view, a high conversion rate is preferred. However, in the case of specific halogenated olefins that pose an explosion risk due to high concentrations, from the viewpoint of suppressing explosions and the disproportionation reaction of the specific halogenated olefins, operating conditions with a conversion rate of 70% or less are preferred. The conversion rate is preferably 50% or less, more preferably 30% or less. If the conversion rate is too low, productivity decreases and equipment becomes larger; therefore, operating conditions with a conversion rate of 5% or more are preferred. The conversion rate is preferably 10% or more, more preferably 15% or more.

[0153] In this disclosure, selectivity refers to the molar amount of the target product contained in the reactor outlet gas relative to the total molar amount (mole%) of compounds other than the feedstock contained in the reactor outlet gas (wherein, the compounds are carbon compounds derived from specific haloalkanes used as feedstocks. Compounds such as silicon tetrafluoride, which do not have carbon, derived from feedstocks are excluded).

[0154] From the perspective of eliminating the need for post-reaction purification steps, a selectivity of 100% is preferable. However, side reactions may occur within the reaction temperature range required to achieve the desired conversion rate. A high selectivity is preferred to reduce waste, decrease the energy load of post-reaction purification steps, and extend reactant lifetime. A selectivity of 90% or higher is preferred, more preferably 93% or higher, and even more preferably 95% or higher.

[0155] Examples of compounds in the reactor outlet gas other than the feedstock compounds and the target product include carbon monoxide, carbon dioxide, water, and silicon tetrafluoride.

[0156] According to the method for manufacturing haloolefins disclosed herein, it is possible to suppress the decrease in the amount of a specific haloolefin generated during manufacturing over a long period of time (specifically, 5 hours or more). The amount of a specific haloolefin generated 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 a specific haloolefin generated after 1 hour.

[0157] The reactor outlet gas was analyzed by gas chromatography, and the amount produced was determined based on the area ratio (GCArea%) corresponding to a specific halogenated olefin.

[0158] The silicon tetrafluoride released by the method for manufacturing haloolefins disclosed herein can be used as a raw material for manufacturing high-performance optical fibers, a gas for semiconductor manufacturing, etc.

[0159] Furthermore, the silicon tetrafluoride released outside the reaction system can react with water and alkali to be recovered as hydrogen fluoride and fluoride salts. These recovered compounds can be used as etching agents or as raw materials for organofluorine compounds.

[0160] It should be noted that in order to convert calcium fluoride (CaF2, fluorite) produced in conventional methods, such as those using calcium carbonate (CaCO3) as a catalyst, into hydrogen fluoride, it is necessary to use extreme conditions such as reaction with sulfuric acid, or to perform pretreatment such as crushing the solid CaF2.

[0161] (Modified example)

[0162] In the method for producing haloolefins disclosed herein, as a variation, a haloalkane containing fluorine atoms and having 2 to 4 carbon atoms can be converted into a haloolefin containing fluorine atoms and having 2 to 4 carbon atoms in the gas phase in the presence of boron oxide. The haloalkane and haloolefin in this case are the same as described above. Furthermore, the same applies to the dilution gas, reactor, etc., that can be used.

[0163] Boron oxide can be used in combination with other components, for example, in the form of borosilicate glass.

[0164] Example

[0165] The present disclosure is described in more detail below through embodiments, but the present disclosure is not limited to the following embodiments as long as it does not depart from its spirit. Examples 2, 3, 5, 7-20 are embodiments, and Examples 1, 4, and 6 are comparative examples.

[0166] (Composition of the outlet gas)

[0167] At specific time intervals following the start of the reaction, the generated gases exiting the reactor (hereinafter referred to as "reactor outlet gases") are analyzed using a gas chromatograph. Specifically, a chromatographic column (product name "DB-1", Agilent Technologies, 60 m in length, 0.25 mm in inner diameter, 1 µm in film thickness) is mounted on a gas chromatograph (product name "GC6850", Agilent Technologies) and analyzed. The table shows the area ratio (GCArea%) of the reactor outlet gases.

[0168] In addition, based on the relative sensitivity of gas chromatography, the obtained area ratio (GCArea%) is converted so that the total of the components recorded in the table is 100 mol%, and the molar composition is calculated.

[0169] (Rate of change in production)

[0170] Calculate the percentage (%) of haloolefins formed at each reaction time, based on the amount of haloolefins formed 1 hour after the start of the reaction. It should be noted that, unless otherwise specified, the rate of change in the amount of haloolefins formed is calculated using the values ​​of the molar composition described above.

[0171] [Example 1]

[0172] 140g of α-alumina (product name "N612", manufactured by Nichibukai Catalyst Chemical Co., Ltd.) was filled 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 nitrogen / HFC-134a 1 / 1 (mol / mol) mixed gas was passed through at 700°C at the flow rate shown in Table 1, thereby carrying out the HF removal reaction of HFO-1123.

[0173] [Table 1]

[0174]

[0175] [Example 2]

[0176] In Example 1, the α-alumina was replaced with glass beads 1 (UNIBEADS series, manufactured by UNITIKA GLASS BEADS), and the HF removal reaction was carried out in the same manner.

[0177] [Table 2]

[0178]

[0179] Comparing Example 1 and Example 2, it can be seen that in Example 1, which uses α-alumina, the amount of haloalkene produced is significantly reduced after 3 hours from the start of the reaction, and the amount produced becomes very small after 4 hours. In contrast, in Example 2, which uses glass beads 1, the reduction in the amount produced is significantly suppressed.

[0180] Furthermore, it can be seen that in Example 2, the concentration of HFO-1123 was stably maintained in the composition of the outlet gas.

[0181] [Example 3]

[0182] In Example 2, the reaction was interrupted after 5 hours from the start, and the weight of the glass beads was measured. 28g of glass beads (bead 1) were added to compensate for the weight loss, and the reaction was restarted. The reaction time in Table 3 refers to the reaction time after restarting. Furthermore, the rate of change in the amount of product (%) is based on the amount of haloalkene produced 1 hour after the start of the reaction in Example 2.

[0183] [Table 3]

[0184]

[0185] It can be seen that by supplementing glass beads 1, the amount generated is significantly increased and restored.

[0186] [Example 4]

[0187] In Example 1, HFC-134a was changed to HFC-134, and the deHF reaction of HFO-1123 was carried out in the same manner.

[0188] [Table 4]

[0189]

[0190] [Example 5]

[0191] In Example 2, HFC-134a was changed to HFC-134, and the deHF reaction of HFO-1123 was carried out in the same manner.

[0192] [Table 5]

[0193]

[0194] In the table, "-" indicates that the component is below the detection limit.

[0195] Comparing Example 4 and Example 5, it can be seen that in Example 4, which uses α-alumina, the amount of haloalkene formed is significantly reduced after 2.5 hours from the start of the reaction, and almost no alkene is formed after 3.5 hours. In contrast, in Example 5, which uses glass beads 1, the reduction in the amount of alkene formed is significantly suppressed.

[0196] Furthermore, it is known that in Example 4, which uses α-alumina, a certain amount of HFC-134a is generated as a byproduct, while in Example 5, which uses glass beads 1, almost no HFC-134a is generated.

[0197] Furthermore, it can be seen that in Example 5, the concentration of HFO-1123 was stably maintained in the composition of the outlet gas.

[0198] [Example 6]

[0199] In Example 1, HFC-134a was changed to HFC-125, and the diluent gas was changed to difluoromethane (R32). A 1 / 1 (mol / mol) mixture of R32 / HFC-125 was flowed at 400 mL / min to carry out the HF removal reaction of FO-1114. The changes in the amount produced in Table 6 were determined by the area ratio (GCArea%) of the reactor outlet gas.

[0200] [Table 6]

[0201]

[0202] [Example 7]

[0203] In Example 6, the α-alumina was replaced with glass beads 1 as in Example 2; otherwise, the HF removal reaction was carried out using the same method. The changes in the amount produced in Table 7 were determined by the area ratio (GCArea%) of the reactor outlet gas.

[0204] [Table 7]

[0205]

[0206] Comparing Example 6 and Example 7, it can be seen that in Example 6, which uses α-alumina, the amount of haloalkene produced is significantly reduced from 2 hours after the start of the reaction, and the amount produced becomes very small after 4 hours. In contrast, in Example 7, which uses glass beads 1, the reduction in the amount of produced is significantly suppressed.

[0207] In Example 6, the selectivity of the compounds listed in the table was also low at the initial stage of the reaction.

[0208] In Example 7, it can be seen that the concentration of FO-1114 was stably maintained in the composition of the outlet gas.

[0209] [Example 8]

[0210] In Example 1, the α-alumina was replaced with silica sand and sodium fluoride mixed in a mass ratio of 1 / 1 (70g / 70g), and the HF removal reaction was carried out in the same manner.

[0211] [Table 8]

[0212]

[0213] [Example 9]

[0214] In Example 8, sodium fluoride was replaced with potassium fluoride, and otherwise the HF removal reaction was carried out by the same method.

[0215] [Table 9]

[0216]

[0217] [Example 10]

[0218] In Example 9, the mass ratio of silica sand to potassium fluoride was changed to 5 / 2, and the HF removal reaction was carried out in the same manner.

[0219] [Table 10]

[0220]

[0221] Comparing Example 1 with Examples 8, 9 and 10, it can be seen that in Example 1, which uses α-alumina, the amount of haloalkene formed is significantly reduced after 3 hours from the start of the reaction, and the amount formed becomes very small after 4 hours. In contrast, in Examples 8, 9 and 10, which use silicon oxide compounds, the reduction in the amount formed is significantly suppressed.

[0222] [Example 11]

[0223] In Example 2, the reaction temperature was varied as shown in Table 11, and the HF removal reaction from HFC-134a to HFO-1123 was carried out in the same manner. Table 11 shows the composition of the outlet gas 0.5 hours after the start of the reaction.

[0224] [Table 11]

[0225]

[0226] [Example 12]

[0227] In Example 5, the reaction temperature was changed as shown in Table 12, and the deHF reaction from HFC-134 to HFO-1123 was carried out in the same manner.

[0228] Table 12 shows the composition of the outlet gas 0.5 hours after the start of the reaction.

[0229] [Table 12]

[0230]

[0231] [Example 13]

[0232] In Example 8, sodium fluoride was replaced with sodium chloride, and the HF removal reaction was carried out using the same method. Table 13 shows the composition of the outlet gas 1.0 hour after the start of the reaction.

[0233] [Example 14]

[0234] In Example 8, sodium fluoride (70g) was replaced with lithium fluoride (35g), and silica sand (70g) was mixed with lithium fluoride (35g). Otherwise, the HF removal reaction was carried out by the same method. Table 13 shows the composition of the outlet gas 1.0 hour after the start of the reaction.

[0235] [Table 13]

[0236]

[0237] [Example 15]

[0238] In Example 8, sodium fluoride was replaced with cesium fluoride, and the HF removal reaction was carried out using the same method. Table 14 shows the composition of the outlet gas 0.5 hours after the start of the reaction.

[0239] [Table 14]

[0240]

[0241] [Example 16]

[0242] In Example 2, the total flow rate and ratio of the circulating gas were changed as shown in Table 15, except that the HF removal reaction from HFC-134a to HFO-1123 was carried out in the same manner. Table 15 shows the composition of the outlet gas 0.25 hours after the start of the reaction.

[0243] [Table 15]

[0244]

[0245] [Example 17]

[0246] In Example 2, HFC-134a was replaced with HFC-152a; otherwise, the HF removal reaction to HFO-1141 was carried out using the same method. Table 16 shows the composition of the outlet gas 0.5 hours after the start of the reaction.

[0247] [Example 18]

[0248] In Example 17, the glass beads were replaced with a mixture of silica sand (120 g) and potassium fluoride (20 g), and the HF removal reaction to HFO-1141 was carried out using the same method. Table 16 shows the composition of the outlet gas 0.5 hours after the start of the reaction.

[0249] [Table 16]

[0250]

[0251] [Example 19]

[0252] In Example 2, HFC-134a was replaced with HFC-143. Otherwise, the deHF removal reactions to HFO-1132 and 1132a were carried out using the same method. Table 17 shows the composition of the outlet gas 0.5 hours after the start of the reaction.

[0253] [Example 20]

[0254] In Example 19, the glass beads were replaced with a mixture of silica sand (120 g) and potassium fluoride (20 g), and the HF removal reaction was carried out in the same manner. Table 17 shows the composition of the outlet gas 0.5 hours after the start of the reaction.

[0255] [Table 17]

[0256]

[0257] The disclosure of Japanese Patent Application No. 2023-190304 is incorporated herein by reference in its entirety.

[0258] All documents, patent applications and technical standards described in this specification are incorporated herein to the same extent as the specific and separately described documents, patent applications and technical standards.

Claims

1. A method for producing haloolefins, wherein, in the presence of silicon oxide and alkali metal elements, haloalkanes containing fluorine atoms and having 2 to 4 carbon atoms are converted into haloolefins containing fluorine atoms and having 2 to 4 carbon atoms in the gas phase.

2. The method for manufacturing haloolefins according to claim 1, wherein, The haloalkane comprises a haloalkane represented by formula (1) below, and the haloolefin comprises a haloolefin represented by formula (2) below. 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 is independently a hydrogen atom, a fluorine atom, a methyl group, a fluoromethyl group, an ethyl group, or a fluoroethyl group, R 1 ~R 4 The total number of fluorine atoms is more than 1, 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.

3. The method for producing haloolefins according to claim 1 or 2, wherein silicon tetrafluoride is generated.

4. The method for manufacturing haloolefins according to claim 1 or 2, comprising: In the gas phase, the haloalkane is converted into haloolefin and hydrogen fluoride through a dehydrofluorination reaction. as well as Silicon tetrafluoride is produced by the reaction of the generated hydrogen fluoride with silicon oxide.

5. The method for producing haloolefins according to claim 1 or 2, wherein, The haloalkane is selected from at least one of 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 haloolefins according to claim 1 or 2, wherein, The haloolefin is selected from at least one of the groups consisting of fluoroethylene, 1,1-difluoroethylene, 1,2-difluoroethylene, trifluoroethylene and tetrafluoroethylene.

7. The method for producing haloalkenes according to claim 1 or 2, wherein the haloalkane is converted in the presence of a diluent gas.

8. The method for manufacturing haloolefins according to claim 7, wherein, The diluting gas is selected from at least one gas selected from the group consisting of nitrogen, hydrogen, carbon dioxide, helium, ethane, propane, isobutane, n-butane, propylene, and fluoromethane.

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

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