Process for producing halogenated alkenes

Abstract

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

Description

Technical Field

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

Background Art

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

[0003] For example, Patent Document 1 describes a method for producing a hydrofluoroolefin in which a hydrofluorocarbon is converted into a hydrofluoroolefin in the presence of a fluorine-containing compound having a standard boiling point higher than that of the target hydrofluoroolefin. In the reaction step of this production method, a step of bringing the hydrofluorocarbon into contact with a catalyst is included. Specifically, alumina (Al 2 O 3 ) is used as the catalyst.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when producing a fluoroolefin by a dehydrofluorination reaction of a fluorocarbon using a catalyst as described in Patent Document 1, the catalyst deteriorates over time due to the generated hydrogen fluoride, and the production amount of the fluoroolefin decreases over time.

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

Means for Solving the Problems

[0007] The present disclosure includes the following aspects. <1> A method for producing a halogenated alkene, in which, in the gas phase, in the presence of silicon oxide and an alkali metal element, a halogenated alkane having 2 to 4 carbon atoms and containing fluorine atoms is converted into a halogenated alkene having 2 to 4 carbon atoms and containing fluorine atoms. <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 1 R 2 X 1 -CR 3 R 4 X 2 ···(1) CR 1 R 2 =CR 3 R 4 ···(2) In formula (1) and formula (2), R 1 ~R 4 are each independently a hydrogen atom, a fluorine atom, a methyl group, a fluorinated methyl group, an ethyl group, or a fluorinated ethyl group, and 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>, in which silicon tetrafluoride is produced. <4> In the gas phase, a halogenated alkene and hydrogen fluoride are produced by a dehydrofluorination reaction of the halogenated alkane, and silicon tetrafluoride is produced by a reaction of the produced hydrogen fluoride and silicon oxide. The method for producing a halogenated alkene according to any one of <1> to <3> includes these. <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 butane, 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.

Embodiments 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 step by step in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other step-by-step descriptions. Further, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In the present disclosure, the amount of each component means the total amount of a plurality of substances when there are a plurality of substances corresponding to each component, unless otherwise specified.

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

[0011] According to the method for producing a halogenated alkene of the present disclosure, a decrease in the production amount over time is suppressed as compared with the conventional method. The reason for this is not clear, but it is speculated as follows.

[0012] In the reaction of obtaining a halogenated alkene containing a fluorine atom from a halogenated alkane containing a fluorine atom, hydrogen fluoride is generated. The generated hydrogen fluoride reacts with, for example, alumina (Al 2 O 3 ) to generate AlF 3 when alumina is used as a catalyst, and reacts with calcium carbonate (CaCO 3 ) to generate CaF 2 when calcium carbonate is used as a catalyst. Here, since the boiling point of AlF 3 is 1260 °C and the boiling point of CaF 2 is 2533 °C, these are within the reaction system It is solid. Therefore, the generated AlF 3 and CaF 2 remain in the reaction system and cover the reaction sites existing on the surface of the catalyst. When the reaction sites of the catalyst are covered, the activity of the catalyst decreases rapidly.

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

[0014] Hereinafter, the method for producing a halogenated alkene of the present disclosure will be described in detail.

[0015] (Halogenated alkane) In the method for producing a halogenated alkene of the present disclosure, a specific halogenated alkane is used as a raw material. The carbon number of the specific halogenated alkane is 2 to 4, and it may be 2, 3, or 4. From the viewpoint of the boiling point range of a compound that can be used as a refrigerant, the carbon number of the specific halogenated alkane is preferably 2 or 3. The specific halogenated alkane contains a fluorine atom. The number of fluorine atoms in the specific halogenated alkane is preferably 2 or more. The number of hydrogen atoms in the specific halogenated alkane is preferably 1 or more. The specific halogenated alkane may contain other halogen atoms other than fluorine atoms. Examples of other halogen atoms include a chlorine atom, a bromine atom, and an iodine atom, and a chlorine atom is preferred. The specific halogenated alkane may not contain other halogen atoms.

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

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

[0018] R 1 and R 3 are each preferably independently a hydrogen atom or a fluorine atom, and R 2 and R 4 are preferably a hydrogen atom, a fluorine atom, CH 3 , CH 2 F, CHF 2 or CF 3 .

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

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

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

[0022] Examples of the specific halogenated alkene 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 4is 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.

[0024] R 1 and R 3 are each independently preferably a hydrogen atom or a fluorine atom, and R 2 and R 4 are a hydrogen atom, a fluorine atom, CH 3 , CH 2 F, CHF 2 or CF 3 is preferred.

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

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

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

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

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

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

[0031] The shape of the glass is not particularly limited, and it may be any of irregular shapes such as pulverized materials, callet shapes, flake shapes, spherical shapes, etc. Further, it may be formed into a pellet shape, a hollow shape, a cylindrical shape, etc. These shapes may be appropriately combined.

[0032] Examples of the silicon oxide particles in the composite or the combined use as separate substances include silica sand, quartz, diatomaceous earth, colloidal silica, precipitated silica, silica gel, fumed silica, rice husks, etc., and silica sand is preferable from the viewpoints of purity and price.

[0033] The shape of the silicon oxide particles is not particularly limited, and it may be any of irregular shapes such as natural products and crushed materials, cullet shapes, flake shapes, spherical shapes, etc. Further, it may be formed into pellet shapes, hollow shapes, cylindrical shapes, etc. Further, the silicon oxide particles may have a pore structure (such as porous). These shapes may be appropriately combined, and examples thereof include porous cylindrical molded articles.

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

[0035] From the viewpoint of suppressing clogging in the reactor, the average particle diameter of the glass, composite, and silicon oxide particles is preferably 20 μm or more, more preferably 50 μm or more. From the viewpoint of ensuring the surface area serving as the reaction point, the average particle diameter of the glass, composite, and silicon oxide particles is preferably 10 mm or less, more preferably 5 mm or less, and still more preferably 1 mm or less.

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

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

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

[0039] In the reactant, the content rate (atm%) of silicon is preferably higher than the content rate (atm%) of the alkali metal element, preferably higher than the total content rate of the alkaline earth metal and the Group 13 element of the periodic table, and preferably the element with the highest content rate (atm%) among the elements excluding oxygen is silicon. Also, in the reactant, the content rate (atm%) of the alkali metal element is preferably higher than the respective content rates of the other elements other than silicon, oxygen, and the alkali metal element. In the glass, the content rate (atm%) of the alkali metal element may be higher than, lower than, or the same as the total content rate of the alkaline earth metal and the Group 13 element 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 preferably at least one selected from the group consisting of Na, K, and Cs from the viewpoints of activity, selectivity, or availability. As the alkali metal-containing compound, it is sufficient if it contains an alkali metal element. For example, halides such as fluorides and chlorides of alkali metals, hydroxides, carbonates, etc. may be mentioned. Specifically, NaF, KF, CsF, NaOH, KOH, Na 2 CO 3 、K 2 CO 3 、NaCl, etc. may be mentioned.

[0041] (Reaction scheme) In the method for producing the halogenated alkene of the present disclosure, silicon tetrafluoride (SiF 4) is generated. In the method for producing a halogenated alkene of the present disclosure, in the gas phase, a specific halogenated alkene and hydrogen fluoride are generated by the dehydrofluorination reaction of a specific halogenated alkane (first step), and silicon tetrafluoride is generated by the reaction of the generated hydrogen fluoride with silicon oxide (second step). Such a reaction scheme can be considered. The first step and the second step may proceed continuously without being distinguished. Note that the method for producing a halogenated alkene of the present disclosure may be other than the above reaction scheme. For example, silicon oxide or an alkali metal compound may directly react with the halogenated alkane to generate silicon tetrafluoride. In addition to silicon tetrafluoride, other compounds may be generated.

[0042] Hereinafter, an assumed example of a reaction scheme in which a halogenated alkene represented by the formula (2) is obtained using a halogenated alkane represented by the formula (1) as the specific halogenated alkane will be shown.

[0043]

Chemical formula

[0044] Since the generated silicon tetrafluoride is a gas, it is released from the reaction system. Therefore, the influence of the by-product on silicon oxide is suppressed, and a sharp decrease in the production amount of the halogenated alkene is suppressed.

[0045] Note that in a conventional production method using alumina, calcium carbonate, etc. as a catalyst, the generated hydrogen fluoride reacts with the catalyst as follows.

[0046]

Chemical formula

[0047] The generated aluminum fluoride (AlF 3 ) and calcium fluoride (CaF 2Since is solid, it is not released outside the reaction system but remains inside the reaction system, covering the surfaces of the catalysts, alumina and calcium carbonate. As a result, the active sites on the surface of the catalyst are covered and deactivated. Therefore, in the conventional manufacturing method, there is a need to remove the deteriorated catalyst and replace it with a new one. For this reason, in the conventional manufacturing method using alumina, calcium carbonate, etc. as catalysts, productivity is not stable and it is necessary to stop the reaction each time the catalyst is replaced. In contrast, the method for producing a halogenated alkene of the present disclosure has the advantages of reducing the operation of removing the deteriorated catalyst and maintaining productivity.

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

[0049] Furthermore, when reacting in a fluidized bed, it is desired that the fluidity of the catalyst does not change significantly. However, in the conventional method, since AlF 3 or CaF 2 adheres to the catalyst, the weight and density of the catalyst change and the fluidity fluctuates. Therefore, it is difficult to maintain an appropriate fluid state. In contrast, in the manufacturing method of the present disclosure, since the by-product SiF 4 is a gas and is released outside the reaction system, there is no significant change in the fluidity of silicon oxide, and it is easy to maintain an appropriate fluid state.

[0050] (Reaction conditions) The method for producing a halogenated alkene of the present disclosure is carried out in the gas phase because the specific halogenated alkane is a gas at room temperature. In the method for producing a halogenated alkene of the present disclosure, the raw material gas only needs to contain the specific halogenated alkane, and may also contain components other than the specific halogenated alkane. The raw material gas may consist only of the specific halogenated alkane, or 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 with respect to the total amount of the raw material gas. The content of the halogenated alkane represented by the formula (1) may be 100 mol% with respect to the total amount of the raw material gas.

[0051] The reactor for reacting the halogenated alkane with the reactant may be any reactor that can withstand the temperature and pressure described below, and the shape and structure are not particularly limited. Examples of the reactor include a cylindrical vertical reactor. Examples of the material of the reactor 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, gold, or the like. Further, the reactor may be provided with heating means such as an electric heater for heating the inside of the reactor.

[0052] The reactant may be accommodated in any of a fixed bed type, a fluidized bed type, and a moving bed type. In the case of the fixed bed type, it may be either a horizontal fixed bed type or a vertical fixed bed type. The reactor may rotate as a whole. Also, the reaction mode may be a flow-through type or a batch type.

[0053] In a fixed bed reactor, various molded bodies of a reactant-supporting carrier are filled to reduce the pressure loss of the reaction fluid. Also, a method in which a reactant is filled in the same manner as in a fixed bed reactor, moved by its gravity, and withdrawn from the bottom of the reactor for regeneration is called a moving bed. In a fluidized bed reactor, in order to perform an operation in which the reactant layer exhibits characteristics similar to those of a fluid by the reaction fluid, the reactant is mixed with the reaction fluid and moves inside the reactor. In terms of the wide range of options for the shape of the reactant and the ability to suppress wear of the reactant, a fixed bed reactor is preferred. From the perspective of uniform internal temperature and easy avoidance of local heating, a fluidized bed reactor is preferred.

[0054] Examples of fixed bed reactors include tubular reactors and tank reactors. From the viewpoint of easy control of the reaction temperature, tubular reactors are preferred. Furthermore, a multi-tube heat exchange reaction in which a large number of reaction tubes with a small tube diameter are arranged in parallel and a heat medium is circulated on the outside can be adopted. When a plurality of reactors are provided in series, a plurality of reactant layers will be provided. At least one reactant layer is sufficient, and two or more reactant layers may be provided.

[0055] In the case of a fluidized bed reactor, the raw material gas, and further a dilution gas, may be circulated from the lower side in the vertical direction, and the product gas may be extracted from the upper side in the vertical direction. From the viewpoint of further enhancing fluidity, a stirring blade may be installed in the fluidized bed reactor. Also, from the viewpoint of preventing the gas flow in the fluidized bed reactor from being biased, a gas dispersion plate may be provided in the fluidized bed reactor. The material of the gas dispersion plate is not particularly limited, and it is preferably composed of a material with low reactivity with the raw material gas, product gas, etc. Examples of the material of the gas dispersion plate include sintered metal. The size, arrangement position, and number of the gas dispersion plates may be appropriately adjusted according to the gas flow.

[0056] In the method for producing a halogenated alkene of the present disclosure, it is preferable to convert the halogenated alkane 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 converting at 400 °C or higher, the reaction proceeds appropriately and the conversion rate of the halogenated alkene improves. On the other hand, when converting at 1000 °C or lower, a decrease in selectivity due to cleavage of the carbon-carbon bond of the raw material and disproportionation reaction of the reaction product (unsaturated compound) are suppressed.

[0057] By adjusting to the above temperature range and appropriately maintaining the reaction temperature, it is also possible to suppress a decrease in the conversion rate. To keep the reaction temperature in the reactant layer at a desired temperature, for example, there is a method of heating the reactant layer from the outside with a heat medium, an electric furnace, or the like.

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

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

[0060] In the dehydrofluorination reaction in the present disclosure, since the reaction is a reaction in which the number of molecules increases, increasing the pressure is disadvantageous for the forward reaction. The pressure 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 preferable, -0.01 to 1 MPa is more preferable, and normal pressure to 0.5 MPa is even more preferable. In the present disclosure, the pressure means the 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 residence time (seconds) is calculated using the following formula. Residence time (seconds) = [Length of the reactor filled with the reactant (cm)] / [Linear velocity (cm / second)] The linear velocity means the velocity at which the haloalkane passes through the reactant per unit time.

[0063] Also, the average bulk density of the reactant is preferably 0.05 g / cm 3 or more, more preferably 0.1 g / cm 3 or more, and even more preferably 0.2 g / cm 3 or more. When the average bulk density of the reactant is 0.05 g / cm 3 or more, the conversion rate is improved. The average bulk density of the reactant is the average value of the 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, a reactant is put into a container of known volume until it overflows, and the excess reactant protruding from the edge of the upper surface of the container is removed with a spatula or the like, and the mass of the reactant in the container is measured. The bulk density (g / mL) is calculated from the mass of this reactant and the volume of the container. This measurement is performed three times, and the average value is taken as the average bulk density.

[0064] The conversion of the specific haloalkane 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 the fluorinated methane include monofluoromethane, difluoromethane, trifluoromethane, and tetrafluoromethane. The molar ratio of the specific haloalkane to the diluent gas in the gas phase is preferably 0.1 to 5.0, more preferably 0.5 to 3.0, and even more preferably 0.5 to 2.0.

[0065] Generally, in the method for producing a haloalkene, a diluent gas is used from the viewpoint of suppressing the disproportionation reaction caused by the increase in the concentration of the produced haloalkene and from the viewpoint of the risk of explosion due to the increase in concentration depending on the type of the haloalkene. In the method for producing a halogenated alkene of the present disclosure, since the reactivity can be controlled by the residence time, reaction temperature, etc., the concentration of a specific halogenated alkene in the outlet gas can be controlled by these controls. In the method for producing a halogenated alkene of the present disclosure, since it is possible to suppress the production amount of the halogenated alkene within a certain range while maintaining the production amount of the halogenated alkene by the above controls and the like, a specific halogenated alkane as a raw material can be included in the outlet gas to a certain extent or more. The specific halogenated alkane in the outlet gas also functions as a diluent. Therefore, in the method for producing a halogenated alkene of the present disclosure, it is also possible to suppress the amount of diluent gas used. Note that the method for producing a halogenated alkene of the present disclosure also includes an embodiment in which no diluent gas is used.

[0066] Further, as described in Patent Document 1, in the method for producing a fluoroolefin using an alumina catalyst, when the amount of the diluent is reduced, the conversion rate decreases. Therefore, it is difficult to use the raw material gas as a diluent, and the use of a diluent gas such as nitrogen or carbon dioxide becomes essential. Diluent gases such as nitrogen gas and carbon dioxide have a lower boiling point or a boiling point range close to that of the halogenated alkene which is the reaction product. Therefore, energy is required to separate and purify the diluent gas from the reaction product. In the method for producing a halogenated alkene of the present disclosure, even if the raw material gas is used as part or all of the diluent, a decrease in the production amount of the halogenated alkene over time can be suppressed. Since the boiling point of the raw material halogenated alkane is high and the boiling point range is far from that of the halogenated alkene which is the reaction product, the energy load required for separation and purification can also be reduced in the method for producing a halogenated alkene of the present disclosure. From the viewpoint of controlling the efficiency and selectivity of the reaction, the conversion of the specific halogenated alkane is preferably carried out in the gas phase in the presence of water, and the concentration of water is less than 500 volume ppm with respect to the total amount of the raw material gas containing the specific halogenated alkane.

[0067] From the viewpoint of controlling the efficiency and selectivity of the reaction, the conversion of the specific halogenated alkane is preferably carried out in the gas phase in the presence of water, and the concentration of water is less than 500 volume ppm with respect to the total amount of the raw material gas containing the specific halogenated alkane. In the dehydrofluorination reaction in the present disclosure, water is also generated. Therefore, it can be said that the reaction proceeds without problems even if water is present in the system. Further, when hydrogen fluoride is eliminated from the raw material or when hydrogen fluoride reacts with silicon oxide, the presence of water molecules may cause the reaction to proceed more efficiently via a hydrogen bond network. Therefore, it is possible to add a small amount of water in the dehydrofluorination reaction in the present disclosure, and it is presumed that this may bring about good effects. On the other hand, from the viewpoint of suppressing the blockage of the gas flow path due to the precipitation of hexafluorosilicic acid or the like caused by the reaction of the generated silicon tetrafluoride and water near the outlet, the water concentration is preferably less than the above range.

[0068] As a general method for measuring the water content of a gas, a method of using a commercially available dew point meter can be mentioned. When the water content is less than 500 volume ppm with respect to the total amount of the specific halogenated alkane, the conversion rate becomes high, and the target product can be obtained with high selectivity. From the viewpoint of further improving the conversion rate and obtaining the target compound with even higher selectivity, the water content is preferably 300 volume ppm or less, more preferably 100 volume ppm or less, still more preferably 50 volume ppm or less, and particularly preferably 10 volume ppm or less. Although it is preferable that the water content is low, from the viewpoints of the cost of dehydrating the specific halogenated alkane and the dilution gas and the difficulty of process control, 0.5 volume ppm or more is preferable, and 1 volume ppm or more is more preferable.

[0069] The above water concentration is the water content contained in the raw material gas when the specific halogenated alkane and the reactant are reacted. Note that the water concentration may be replaced with the water content contained in the raw material gas before flowing into the reactor.

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

[0071] The method for drying the reactant is not particularly limited, and it may be dried before filling the reactor with the reactant, or it may be dried after filling the reactor with the reactant. When drying is carried out after filling the reactor with the reactant, the reactor can also be preheated along with the drying of the reactant. Specifically, the reactant may be dried by filling the reactor with the reactant and heating the reactor while flowing a diluent gas.

[0072] In the present disclosure, the conversion rate is the ratio (%) of the molar amount of the specific halogenated alkane consumed in the reaction to the molar amount of the specific halogenated alkane supplied to the reactor. Note that the molar amount of the raw material specific halogenated alkane consumed in the reaction is the difference between the molar amount of the specific halogenated alkane supplied to the reactor and the molar amount of the specific halogenated alkane contained in the off-gas from the reactor outlet. It is the difference between the molar amount of the specific halogenated alkane supplied to the reactor and the molar amount of the specific halogenated alkane contained in the off-gas from the reactor outlet.

[0073] Generally, from the perspective of productivity, a higher conversion rate is preferably. However, in the case of specific halogenated alkenes with a concern of explosion due to high concentration, from the perspective of explosion suppression and suppression of the disproportionation reaction of the specific halogenated alkene, it is preferable to select an operating condition where the conversion rate is 70% or less. The conversion rate is preferably 50% or less, more preferably 30% or less. If the conversion rate is too low, the productivity will decrease and the equipment will become larger, so it is preferable to select an operating condition where the conversion rate is 5% or more. The conversion rate is preferably 10% or more, more preferably 15% or more.

[0074] In the present disclosure, the selectivity means the ratio (mol%) of the molar amount of the target product contained in the reactor outlet gas to the total molar amount of compounds other than the raw material contained in the reactor outlet gas (however, it is a compound derived from the carbon of the specific halogenated alkane as the raw material, excluding compounds such as silicon tetrafluoride that do not have carbon derived from the raw material). The selectivity is preferably 100% because the purification process after the reaction becomes unnecessary, but side reactions may also occur in the reaction temperature range required to obtain the desired conversion rate. A higher selectivity is preferred because it can reduce the amount of waste, lower the energy load of the purification process after the reaction, and extend the lifetime of the reactants. The selectivity is preferably 90% or more, more preferably 93% or more, and even more preferably 95% or more.

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

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

[0077] The production amount is confirmed from the area ratio (GCArea%) corresponding to the specific halogenated alkene by analyzing the reactor outlet gas with a gas chromatograph.

[0078] The silicon tetrafluoride released in the method for producing a halogenated alkene of the present disclosure can be used as a raw material for producing high-performance optical fibers, a gas for semiconductor manufacturing, or the like. In addition, the silicon tetrafluoride released outside the reaction system can be reacted with water or an alkali to be recovered as hydrogen fluoride or a fluoride salt. These recovered compounds can be used as an etching agent or as a raw material for organic fluorine compounds. For example, in a conventional method using calcium carbonate (CaCO 3 ) as a catalyst, to convert calcium fluoride (CaF 2 , fluorite) to hydrogen fluoride, it requires drastic conditions such as reacting with sulfuric acid, and also requires a pretreatment such as crushing the solid CaF 2 .

[0079] (Modified Example) As a modified example, the method for producing a halogenated alkene of the present disclosure may convert a halogenated alkane having 2 to 4 carbon atoms and containing a fluorine atom 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. In this case, the halogenated alkane and the halogenated alkene are the same as those described above. Also, the diluent gas, reactor, etc. that can be used are the same. Boron oxide may be used in combination with other components, and may be in the form of, for example, borosilicate glass.

Examples

[0080] Hereinafter, the present disclosure will be described more specifically by way of examples. However, the present disclosure is not limited to the following examples as long as its gist is not exceeded. Examples 2, 3, 5, 7 to 20 are examples, and Examples 1, 4, 6 are comparative examples.

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

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

[0083] (Rate of Change in Production Amount) The ratio (%) of the production amount of the halogenated alkene at each reaction time based on the production amount of the halogenated alkene at 1 hour from the start of the reaction was determined. In the case where there is no notice, the rate of change in the production amount of the halogenated alkene was determined using the values of the above-described molar composition.

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

[0085]

Table 1

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

[0087]

Table 2

[0088] Comparing Example 1 and Example 2, in Example 1 using α-alumina, the production amount of the halogenated alkene decreased significantly 3 hours after the start of the reaction, and became extremely small after 4 hours. On the other hand, in Example 2 using glass beads 1, it can be seen that the decrease in the production amount was remarkably suppressed. Also, in Example 2, it can be seen that the concentration of HFO-1123 in the outlet gas composition was stably maintained.

[0089] [Example 3] In Example 2, when 5 hours had elapsed from the start of the reaction, the reaction was interrupted, the weight of the glass beads was measured, and 28 g of glass beads 1 corresponding to the weight loss was replenished to resume the reaction. The additional reaction time in Table 3 is the reaction time after resumption. The change rate (%) of the production amount is a value based on the production amount of the halogenated alkene 1 hour after the start of the reaction in Example 2.

[0090]

Table 3

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

[0092] [Example 4] In Example 1, the dehydrofluorination reaction to HFO-1123 was carried out in the same manner except that HFC-134a was changed to HFC-134.

[0093]

Table 4

[0094] [Example 5] In Example 2, the dehydrofluorination reaction to HFO-1123 was carried out in the same manner except that HFC-134a was changed to HFC-134.

[0095]

Table 5

[0096] Comparing Example 4 and Example 5, it can be seen that in Example 4 using α-alumina, the production amount of the halogenated alkene significantly decreased 2.5 hours after the start of the reaction and hardly any was produced after 3.5 hours, while in Example 5 using glass beads 1, the decrease in the production amount was significantly suppressed. Also, in Example 4 using α-alumina, a certain amount or more of the by-product HFC-134a was generated, while in Example 5 using glass beads 1, hardly any HFC-134a was produced. Also, in Example 5, it can be seen that the concentration of HFO-1123 in the outlet gas composition is stably maintained.

[0097] [Example 6] In Example 1, HFC-134a was changed to HFC-125, the diluent gas was changed to difluoromethane (R32), and the dehydrofluorination 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 production amount 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 dehydrofluorination reaction was carried out in the same manner except that α-alumina was changed to the glass beads 1 of Example 2. The change in the production amount 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, it can be seen that in Example 6 using α-alumina, the production amount of the halogenated alkene decreased significantly 2 hours after the start of the reaction, and the production amount became extremely small after 4 hours, while in Example 7 using glass beads 1, the decrease in the production amount was significantly suppressed. In Example 6, the selectivity of the compounds listed in the table was also low at the initial stage of the reaction start. In Example 7, it can be seen that the concentration of FO-1114 was stably maintained in the outlet gas composition.

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

[0103]

Table 8

[0104] [Example 9] In Example 8, the dehydrofluorination reaction was carried out in the same manner except that sodium fluoride was changed to potassium fluoride.

[0105] [Table 9]

[0106] [Example 10] In Example 9, the dehydrofluorination 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 using α-alumina, the production amount of the halogenated alkene decreased significantly 3 hours after the start of the reaction, and was extremely small after 4 hours, while in Examples 8, 9 and 10 using the silicon oxide compound, the decrease in the production amount was significantly suppressed.

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

[0110] [Table 11]

[0111] [Example 12] In Example 5, the dehydrofluorination reaction from HFC-134 to HFO-1123 was carried out in the same manner except that the reaction temperature was changed as shown in Table 12. Table 12 shows the composition of the outlet gas 0.5 hours after the start of the reaction.

[0112]

Table 12

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

[0114] [Example 14] In Example 8, the dehydrofluorination reaction was carried out in the same manner except that sodium fluoride (70 g) was changed to lithium fluoride (35 g) and the mixture was made of silica sand (70 g) and lithium fluoride (35 g). Table 13 shows the composition of the outlet gas at 1.0 hour from the start of the reaction.

[0115]

Table 13

[0116] [Example 15] In Example 8, the dehydrofluorination reaction was carried out in the same manner except that sodium fluoride was changed to cesium fluoride. Table 14 shows the composition of the outlet gas at 0.5 hour from the start of the reaction.

[0117]

Table 14

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

[0119]

Table 15

[0120] [Example 17] In Example 2, the dehydrofluorination reaction to HFO-1141 was carried out in the same manner except that HFC-134a was changed to HFC-152a. Table 16 shows the composition of the outlet gas at 0.5 hours from the start of the reaction.

[0121] [Example 18] In Example 17, the dehydrofluorination reaction to HFO-1141 was carried out in the same manner except that the glass beads were changed to a mixture of silica sand (120 g) and potassium fluoride (20 g). Table 16 shows the composition of the outlet gas at 0.5 hours from the start of the reaction.

[0122] [Table 16]

[0123] [Example 19] In Example 2, the dehydrofluorination reactions to HFO-1132 and 1132a were carried out in the same manner except that HFC-134a was changed to HFC-143. Table 17 shows the composition of the outlet gas at 0.5 hours from the start of the reaction.

[0124] [Example 20] In Example 19, the dehydrofluorination reaction was carried out in the same manner except that the glass beads were changed to a mixture of silica sand (120 g) and potassium fluoride (20 g). Table 17 shows the composition of the outlet gas at 0.5 hours from 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 in this specification are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A method for producing a halogenated alkene, comprising converting a halogenated alkane containing a fluorine atom and having 2 to 4 carbon atoms into a halogenated alkene containing a fluorine atom and having 2 to 4 carbon atoms in a gas phase in the presence of silicon oxide and an alkali metal element, the content of the alkali metal element in the total amount of the silicon oxide and the alkali metal element is 5 atm % or more; The halogenated alkane is converted at a temperature of 450° C. or more; A method for producing halogenated alkenes, in which silicon tetrafluoride is produced.

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

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

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

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

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

7. The method for producing halogenated alkenes according to claim 6, 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.

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

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