Method for producing hexafluoropropene and composition

Abstract

To provide a method for producing hexafluoropropene in which the formation of octafluorocyclobutane, a by-product, is suppressed, and a composition obtained by the said production method. [Solution] A method for producing hexafluoropropene, comprising preheating trifluoromethane to a first preheating temperature of 450 to 700°C, supplying it to a reactor, and heating the trifluoromethane in the reactor to a reaction temperature of 800°C or higher to obtain a product containing hexafluoropropene.

Description

[Technical Field]

[0001] This disclosure relates to methods and compositions for producing hexafluoropropene. [Background technology]

[0002] Hexafluoropropene is a compound used as a raw material for fluororesins and other materials, and can be obtained, for example, by the thermal decomposition reaction of trifluoromethane. Hereinafter, hexafluoropropene will also be referred to as "HFP," and trifluoromethane as "R23." For example, Patent Document 1 discloses a method for producing a mixture of tetrafluoroethylene and HFP by the thermal decomposition reaction of R23, and then obtaining highly pure tetrafluoroethylene and HFP, respectively, by purification. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Chinese Patent Application Publication No. 107216233 Specification [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] When attempting to obtain HFP through the thermal decomposition reaction of R23, octafluorocyclobutane may also be produced as a by-product. Hereafter, octafluorocyclobutane will also be referred to as "C318". Since C318 has a high global warming potential (GWP), it is desirable to minimize the amount of C318 produced in HFP manufacturing.

[0005] One aspect of this disclosure aims to provide a method for producing hexafluoropropene in which the formation of octafluorocyclobutane, a by-product, is suppressed, and a composition obtained by said production method. [Means for solving the problem]

[0006] This disclosure includes the following aspects: <1> A method for producing hexafluoropropene, comprising preheating trifluoromethane to a first preheating temperature of 450-700°C, supplying it to a reactor, and heating the trifluoromethane in the reactor to a reaction temperature of 800°C or higher to obtain a product containing hexafluoropropene. <2> The trifluoromethane preheated at the first preheating temperature is mixed with a second preheating heat transfer medium heated at a second preheating heat transfer medium heating temperature higher than the first preheating temperature, and this mixture is supplied into the reactor. <1> A method for producing hexafluoropropene as described in [reference]. <3> The heating temperature of the second preheating heat transfer medium is 1100°C or lower. <2> A method for producing hexafluoropropene as described in [reference]. <4> The content of the second preheating heat transfer medium in the mixture is 50 mol% or less relative to the total amount of trifluoromethane preheated at the first preheating temperature and the second preheating heat transfer medium. <2> or <3> A method for producing hexafluoropropene as described in [reference]. <5> The reaction temperature is 1000°C or lower. <1> ~ <4> A method for producing hexafluoropropene as described in any one of the above. <6> The time for heating the trifluoromethane in the reactor at the reaction temperature is 5 seconds or less. <1> ~ <5> A method for producing hexafluoropropene as described in any one of the above. <7> The gauge pressure inside the reactor is 0 kPaG or more and less than 200 kPaG. <1> ~ <6> A method for producing hexafluoropropene as described in any one of the above. <8> The product further comprises octafluorocyclobutane, The ratio of the molar amount of hexafluoropropene contained in the product to the molar amount of octafluorocyclobutane contained in the product is 13.0 or greater. <1> ~ <7> A method for producing hexafluoropropene as described in any one of the above. <9> The product further comprises perfluoroisobutene, The ratio of the molar amount of hexafluoropropene contained in the product to the molar amount of perfluoroisobutene contained in the product is 1.0 or more, and the method for producing hexafluoropropene according to any one of <1> to <8>. <10> A composition containing trifluoromethane, hexafluoropropene, and octafluorocyclobutane, The total content of trifluoromethane, hexafluoropropene, and octafluorocyclobutane is 96.0 mol% or more based on the whole composition, The ratio of the molar amount of hexafluoropropene to the molar amount of octafluorocyclobutane is 13.0 or more, and the composition. <11> Further containing perfluoroisobutene, The ratio of the molar amount of hexafluoropropene to the molar amount of perfluoroisobutene is 1.0 or more, and the composition according to <10>. <12> Further containing at least one selected from the group consisting of tetrafluoroethylene, pentafluoroethane, and hexafluoroethane, and the composition according to <10> or <11>.

Advantages of the Invention

[0007] According to one aspect of the present disclosure, there are provided a method for producing hexafluoropropene in which the generation of octafluorocyclobutane as a by-product is suppressed, and a composition obtained by the production method.

Brief Description of the Drawings

[0008] [Figure 1] It is a schematic diagram showing an example of a production apparatus used in the production method of the present disclosure. [Figure 2] It is a schematic diagram showing another example of a production apparatus used in the production method of the present disclosure.

Modes for Carrying Out the Invention

[0009] The embodiments of this disclosure are described in detail below. However, this disclosure is not limited to the embodiments described below. In the embodiments described below, the components (including elemental steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit this disclosure.

[0010] In this disclosure, the term "process" includes not only processes that are independent of other processes, but also processes that cannot be clearly distinguished from other processes, provided that the purpose of such process is achieved. In this disclosure, the numerical range indicated using "~" includes the numbers before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples. In this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In this disclosure, each component may contain multiple types of the corresponding substance. If multiple types of the substance corresponding to each component are present in the composition, the proportion of each component means the total proportion of the multiple types of substances present in the composition unless otherwise specified. When embodiments are described in this disclosure with reference to the drawings, the configuration of such embodiments is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each figure are conceptual, and the relative relationships between the sizes of the components are not limited thereto.

[0011] In this disclosure, "preheating" means heating R23 before it is supplied to the reactor. The preheating of R23 is carried out in a location separate from the reactor. During the preheating of R23, a small amount of R23 may undergo a thermal decomposition reaction. In this disclosure, “reactor” means a region heated to a reaction temperature of 800°C or higher, where the thermal decomposition reaction of R23 mainly proceeds. In this disclosure, "preheating temperature," "reaction temperature," and "heating temperature" are set temperatures for heating, and at least a portion of the object being heated may be at a temperature different from the set temperature. In this disclosure, “by-product” refers to products other than the target product, HFP.

[0012] [Method for producing hexafluoropropene (HFP)] A method for producing hexafluoropropene (HFP) in one embodiment of the present disclosure includes preheating trifluoromethane (R23) to a first preheating temperature of 450 to 700°C and then supplying it to a reactor, heating the R23 in the reactor to a reaction temperature of 800°C or higher to obtain a product containing HFP. The manufacturing method of this embodiment includes a first preheating step of preheating R23 to a first preheating temperature of 450 to 700°C, a supply step of supplying the R23 preheated to the first preheating temperature into a reactor, and a reaction step of heating the R23 in the reactor to a reaction temperature of 800°C or higher to obtain a product containing HFP.

[0013] The manufacturing method of this embodiment may include other steps besides the first preheating step, the supply step, and the reaction step. Other steps include, for example, a second preheating step in which a mixture is obtained by mixing R23 that has undergone the first preheating step with a second preheating heat medium heated at a heating temperature higher than the first preheating temperature; a discharge step in which the post-reaction composition containing the product obtained in the reaction step is discharged from the reactor; and a washing step in which the post-reaction composition discharged in the discharge step is washed. Hereinafter, "second preheating heat medium" refers to the heat medium used in the second preheating step, and "second preheating heat medium heating temperature" refers to the heating temperature of the second preheating heat medium.Hereafter, the mixture obtained in the second preheating step will also be called the "mixture after second preheating". The manufacturing method of this embodiment preferably further includes the second preheating step described above. That is, in the manufacturing method of this embodiment, it is preferable to supply into the reactor a second preheated mixture obtained by mixing R23 preheated at the first preheating temperature with a second preheating heat medium heated at the second preheating heat medium heating temperature.

[0014] According to the manufacturing method of this embodiment, the amount of octafluorocyclobutane (C318) produced is suppressed. The reason for this is not clear, but it is presumed to be as follows. In this embodiment, in the first preheating step, R23 that has been preheated to a first preheating temperature of 450 to 700°C is supplied to the reactor and heated to a reaction temperature of 800°C or higher. Therefore, compared to cases where there is no preheating step or where the preheating temperature is less than 450°C, the temperature of R23 heated to a reaction temperature of 800°C or higher reaches the reaction temperature in a shorter time. Here, it is thought that when R23 reaches a temperature range of over 700°C but less than 800°C, the selectivity for the reaction that produces C318 increases. And in this embodiment, it is presumed that the production of C318 is suppressed because the time during which the temperature of R23 is in the range of over 700°C but less than 800°C is short.

[0015] Furthermore, the manufacturing method of this embodiment also suppresses the generation of hydrogen fluoride adducts such as pentafluoroethane (hereinafter also referred to as "R125"). Hydrogen fluoride adducts are formed when hydrogen fluoride produced by the thermal decomposition reaction of R23 adds to the reaction intermediate or reaction product. In this embodiment, the temperature of R23, which is heated to the reaction temperature, reaches the reaction temperature in a short time, and the residence time until the desired conversion rate is reached can be shortened. Therefore, the contact time between the reaction intermediate and reaction product and hydrogen fluoride is also shortened, which is thought to suppress the generation of hydrogen fluoride adducts.

[0016] The following describes each step of the manufacturing method of this embodiment.

[0017] <Preheating process> (First preheating process) In the first preheating step, R23 is preheated to a first preheating temperature of 450-700°C. In the first preheating step, R23 may be preheated by supplying R23 to a preheater heated to a first preheating temperature, or by supplying R23 to the preheater and then heating the preheater to the first preheating temperature. Alternatively, the preheating of R23 in the first preheating step may be performed by mixing it with a heat transfer medium, as will be described later. As will be described later, R23 and the diluent may be mixed in advance before the first preheating step, and the mixture of R23 and the diluent (hereinafter also referred to as the "diluted mixture") may be preheated at the first preheating temperature. In other words, the first preheating step may be a step of preheating the R23 contained in the diluted mixture at the first preheating temperature.

[0018] The first preheating temperature is 450 to 700°C. From the viewpoint of suppressing the formation of C318, the first preheating temperature is preferably 480°C or higher, more preferably 500°C or higher, even more preferably 600°C or higher, particularly preferably 650°C or higher, and most preferably 700°C. In the first preheating process, when R23 is preheated by heating a preheater, the first preheating temperature is the set temperature for heating, that is, the heating temperature of the preheater. The preheater is not particularly limited, and one with the same specifications as the reactor described later may be used. Furthermore, the preheater and reactor used in the manufacturing method of this embodiment may have the same specifications or different specifications.

[0019] (Second preheating process) As described above, the manufacturing method of this embodiment preferably further includes a second preheating step. In the second preheating step, a second post-preheated mixture is obtained by mixing R23, which has undergone the first preheating step, with a second preheating heat transfer medium that has been heated at a heating temperature higher than the first preheating temperature. In this disclosure, "thermal fluid" means a fluid that does not substantially decompose on its own at the reaction temperature, and more preferably a fluid that does not substantially decompose on its own at temperatures of 1100°C or below. Examples of the second preheating heat transfer medium include inert gases such as nitrogen gas, helium gas, and argon gas, with nitrogen gas being preferred from the viewpoint of economic efficiency and supply stability.

[0020] The heating temperature of the second preheating heat medium is higher than the first preheating temperature, for example, between 450°C and 1100°C. The heating temperature of the second preheating heat medium is above 450°C, and from the viewpoint of suppressing the formation of C318, it is preferably 480°C or higher, more preferably 500°C or higher, even more preferably 850°C or higher, particularly preferably 900°C or higher, and extremely preferably 1000°C or higher. Also, from the viewpoint of suppressing the formation of C318, the heating temperature of the second preheating heat medium is preferably 1100°C or lower, more preferably 1050°C or lower, and even more preferably 1000°C or lower. In another embodiment, from the viewpoint of suppressing the formation of C318 and from the viewpoint of operability, the heating temperature of the second preheating heat medium is preferably 700 to 1100°C, and more preferably 800 to 1000°C. The heating temperature of the second preheating heat transfer medium is preferably 10°C or more higher than the first preheating temperature, more preferably 50°C or more higher, even more preferably 100°C or more higher, and particularly preferably 300°C or more higher. The second preheating heat transfer medium is heated, for example, by supplying it to a heat transfer medium heater and heating it at the second preheating heat transfer medium heating temperature. The mixing of R23 and the second preheating heat transfer medium may be carried out using a mixer, or by merging the flow path for R23 with the flow path for the second preheating heat transfer medium.

[0021] The amount of the second preheating heat transfer medium added is not particularly limited. For example, the amount of the second preheating heat transfer medium added relative to the total amount of R23 and the second preheating heat transfer medium can be 0 to 50 mol%. The amount of the second preheating heat transfer medium added to the total amount of R23 and the second preheating heat transfer medium is preferably 50 mol% or less, more preferably 40 mol% or less, even more preferably 30 mol% or less, and particularly preferably 20 mol% or less. By keeping the amount of the second preheating heat transfer medium added below the above upper limit, a large amount of HFP is produced in the reaction process, and the separation operation after the reaction becomes easier. Furthermore, the amount of the second preheating heat transfer medium added relative to the total amount of R23 and the second preheating heat transfer medium may be 0 mol% or more, preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 20 mol% or more. By having the amount of the second preheating heat transfer medium added be equal to or greater than the lower limit, the time it takes for R23 to reach the reaction temperature is shortened, and the formation of C318 is suppressed.

[0022] The total content of the first preheating heat transfer medium, diluent medium, and second preheating heat transfer medium relative to the total amount of R23, the first preheating heat transfer medium, the diluent medium, and the second preheating heat transfer medium is not particularly limited, and for example, it can range from 0 to 50 mol%. Hereinafter, the first preheating heat transfer medium, the dilution medium, and the second preheating heat transfer medium will be collectively referred to simply as "the medium." Furthermore, the total amount of the medium relative to the total amount of R23 and the medium will also be called the "total medium content." The total media content is preferably 50 mol% or less, more preferably 40 mol% or less, even more preferably 30 mol% or less, and particularly preferably 20 mol% or less. By keeping the total media content below the above upper limit, a large amount of HFP is produced in the reaction process, and the separation operation after the reaction becomes easier. Furthermore, the total media content may be 0 mol% or more, preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 20 mol% or more. Having the total media content above the lower limit reduces the HFP concentration and the concentration of tetrafluoroethylene (hereinafter also referred to as "TFE"), a reaction intermediate, inside the reactor, which has the advantage of suppressing the generation of sequential reaction by-products such as perfluoroisobutene (hereinafter also referred to as "PFIB").

[0023] (First preheating process using a heat transfer medium) As stated above, the preheating of R23 in the first preheating step may be performed by mixing R23 with a heat transfer medium. Hereinafter, the heat transfer medium used in the first preheating step will also be referred to as the "first preheating heat transfer medium". In the first preheating step using a heat transfer medium, for example, the first preheating heat transfer medium, which has been heated at the first preheating heat transfer medium heating temperature in a heat transfer medium heater, is mixed with R23 to obtain a first post-preheated mixture, thereby preheating the R23 contained in the first post-preheated mixture to the first preheating temperature. The first preheating temperature in the first preheating step using a heat transfer medium, i.e., the set temperature for heating, is the temperature of the mixture after the first preheating, T3(K), which can be theoretically estimated using the following formula, based on the temperature of R23 before mixing T1(K), the heating temperature of the first preheating heat transfer medium T2(K), the flow rate of R23 to be mixed M1(kg / h), the flow rate of the first preheating heat transfer medium M2(kg / h), the average specific heat of R23 C1(kcal / kg·K), and the specific heat of the first preheating heat transfer medium C2(kcal / kg·K). Formula: (T3-T1)×M1×C1=(T2-T3)×M2×C2

[0024] The type of heat transfer medium for the first preheating is the same as that for the second preheating heat transfer medium. When both the first and second preheating heat transfer mediums are used in the preheating process, they may be the same type of medium or different types of medium, but it is preferable that they be the same type of medium from the viewpoint of facilitating separation operations after the reaction. The heating temperature of the first preheating heat medium should be any temperature that can raise the temperature T3 of the mixture after the first preheating to 450-700°C, for example, between 450°C and 1100°C. The heating temperature of the first preheating heat medium is above 450°C, and from the viewpoint of suppressing the formation of C318, it is preferably 480°C or higher, more preferably 500°C or higher, even more preferably 850°C or higher, particularly preferably 900°C or higher, and extremely preferably 1000°C or higher. Also, from the viewpoint of suppressing the formation of C318, the heating temperature of the first preheating heat medium is preferably 1100°C or lower, more preferably 1050°C or lower, and even more preferably 1000°C or lower. In another embodiment, from the viewpoint of suppressing the formation of C318 and from the viewpoint of operability, the heating temperature of the first preheating heat medium is preferably 700-1100°C, and more preferably 800-1000°C.

[0025] The mixing of R23 and the first preheating heat transfer medium may be carried out using a mixer, or by merging the flow path for R23 with the flow path for the first preheating heat transfer medium. The content of the first preheating heat transfer medium in the first preheated mixture before it is supplied to the reactor is not particularly limited as long as it is an amount that brings the temperature T3 of the first preheated mixture to 450-700°C. The content of the first preheating heat transfer medium in the first preheated mixture can be, for example, more than 0 mol% and 50 mol% or less relative to the sum of R23 and the first preheating heat transfer medium. The content of the first preheating heat transfer medium relative to the sum of R23 and the first preheating heat transfer medium is preferably 50 mol% or less, more preferably 40 mol% or less, even more preferably 30 mol% or less, and particularly preferably 20 mol% or less. Furthermore, the content of the first preheating heat transfer medium relative to the sum of R23 and the first preheating heat transfer medium may be greater than 0 mol%, preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 20 mol% or more. If the content of the first preheating heat transfer medium relative to the total of R23 and the first preheating heat transfer medium is below the above upper limit, a large amount of HFP is produced in the reaction process, and the separation operation after the reaction is made easier. On the other hand, if the content of the first preheating heat transfer medium relative to the total of R23 and the first preheating heat transfer medium is above the above lower limit, the time it takes for R23 to reach the first preheating temperature is shortened.

[0026] Furthermore, if a heat transfer medium is used in the first preheating step, in the second preheating step, a second preheating mixture containing R23, the first preheating heat transfer medium, and the second preheating heat transfer medium is obtained by mixing the first preheating mixture, which is a mixture of R23 and the first preheating heat transfer medium, with the second preheating heat transfer medium.

[0027] (Mixing R23 with diluent) As mentioned above, R23 and the diluent may be mixed in advance before the first preheating step. In this disclosure, "dilution medium" means a medium that does not substantially decompose on its own at the temperature at which it is mixed with R23. It is desirable that the dilution medium, like the heat medium, does not substantially decompose on its own at the reaction temperature, and specifically, it is desirable that it does not substantially decompose on its own at temperatures of 1100°C or below. Examples of dilution media include those similar to those used for the second preheating heat medium. When at least one of the first preheating heat medium and the second preheating heat medium is used in the preheating step, the dilution media and at least one of the first preheating heat medium and the second preheating heat medium may be the same type of medium or different types of medium, but it is preferable that they be the same type of medium from the viewpoint of facilitating separation operations after the reaction. The temperature of the diluent when mixing with R23 is not particularly limited, but for example, it may be less than 450°C.

[0028] The mixing of R23 and the diluent may be performed using a mixer, or by merging the channel through which R23 passes with the channel through which the diluent passes. The amount of diluent added relative to the total of R23 and diluent is not particularly limited. For example, the amount of diluent added relative to the total of R23 and diluent is 0 to 50 mol%. Preferably, the amount of diluent added relative to the total of R23 and diluent is 50 mol% or less, more preferably 40 mol% or less, even more preferably 30 mol% or less, and particularly preferably 20 mol% or less. Also, the amount of diluent added relative to the total of R23 and diluent may be 0 mol% or more, preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 20 mol% or more. If the amount of diluent added relative to the total of R23 and diluent is below the above upper limit, the amount of HFP produced in the reaction process is large, and the separation operation after the reaction is easy. On the other hand, if the amount of diluent added relative to the total of R23 and diluent is above the above lower limit, the HFP concentration and TFE concentration inside the reactor are low, which has the advantage of suppressing the generation of sequential reaction by-products such as PFIB.

[0029] Furthermore, if R23 and the diluent are mixed in advance before the first preheating step, and the second preheating step is then performed, the mixture after the second preheating step will include R23, the diluent, and the heat transfer medium for the second preheating step.

[0030] <Supply process> In the supply process, R23, which has been preheated to the first preheating temperature in the first preheating process, is supplied into the reactor. In the supply process, R23 that has undergone the first preheating process may be supplied directly to the reactor, or R23 that has undergone both the first and second preheating processes may be supplied to the reactor. In other words, the R23 supplied to the reactor may be R23 that has been preheated in the first preheating process, or it may be R23 that has undergone further processes (for example, a second preheating process) after being preheated in the first preheating process.

[0031] When supplying R23 that has undergone the first and second preheating steps into the reactor, the supply step involves supplying the aforementioned second preheated mixture into the reactor. Furthermore, when preheating of R23 in the first preheating step is performed by mixing R23 with the first preheating heat transfer medium, and the R23 that has undergone the first preheating step is supplied directly into the reactor, the supply step involves supplying the aforementioned first preheated mixture into the reactor. Additionally, if R23 is mixed with a diluent before the first preheating step, and the resulting diluted mixture is preheated to the first preheating temperature using a preheater, and the second preheating step is not performed, the supply step involves supplying the diluted mixture that has undergone the first preheating step directly into the reactor.

[0032] The reactor only needs to be able to withstand the temperature and pressure described later, and its shape and structure are not particularly limited. Examples of reactors include tubular reactors. Examples of reactor materials include acid-resistant metal materials such as copper, stainless steel, Hastelloy, and Inconel. The reactor may be equipped with heating means such as an electric heater to heat the inside of the reactor. The reactor may be preheated to the reaction temperature before supplying R23. R23 may be supplied into the reactor through a supply channel. The supply channel can be any channel through which R23 and any media used as needed can pass, and its shape and size are not particularly limited. The material of the supply channel can be the same as that of the reactor. Furthermore, when a medium is used in a process prior to the supply process, it is desirable to use a reactor with a mixing mechanism from the viewpoint of suppressing the generation of by-products. Examples of reactors with a mixing mechanism include ejector-type reactors and reactors with mixers. By using a reactor with a mixing mechanism, the mixture containing R23 and the medium becomes nearly homogeneous instantaneously when supplied to the reactor, thereby suppressing the generation of by-products.

[0033] <Reaction Process> In the reaction step, R23 in the reactor is heated to a reaction temperature of 800°C or higher to obtain a product containing HFP. In the reaction step, HFP is produced by the reaction of at least a portion of the R23 supplied to the reactor.

[0034] The reaction temperature is 800°C or higher, preferably 800 to 1000°C. A reaction temperature of 830°C or higher is preferred, and 850°C or higher is more preferred. Furthermore, a reaction temperature of 1000°C or lower is preferred, 950°C or lower is more preferred, 900°C or lower is even more preferred, 870°C or lower is particularly preferred, and 850°C or lower is extremely preferred. A reaction temperature above the lower limit suppresses the formation of C318, improving the production efficiency of HFP. Additionally, a reaction temperature below the upper limit suppresses the formation of PFIB, a by-product other than C318. "Reaction temperature" refers to the set temperature during heating, i.e., the heating temperature of the reactor. In this embodiment, the reaction temperature only needs to be 800°C or higher, and this includes cases where at least a portion of the R23 in the reactor has not reached the reaction temperature. It is presumed that the generation of by-products in the reaction process is more likely to occur near the inner surface of the reactor, which is susceptible to the effects of heating. Therefore, it is considered that the amount of by-products generated is more strongly correlated with the heating temperature of the reactor than with the temperature of R23 in the center of the reactor.

[0035] In the reaction process, the time for heating R23 in the reactor to the reaction temperature is preferably 5 seconds or less. Hereinafter, the time for heating R23 in the reactor to the reaction temperature will also be referred to as the "reaction time". If the reaction method in the reaction process is continuous and the reactor is continuously heated to the reaction temperature, the above reaction time is the residence time from when R23 is supplied to the reactor until the product is discharged. The residence time is calculated, for example, from the reactor volume, supply flow rate, outlet flow rate, average reactor temperature, and reactor pressure. The above reaction time can be, for example, 0.01 to 5 seconds. Preferably, the reaction time is 0.1 seconds or more, more preferably 0.2 seconds or more, even more preferably 0.3 seconds or more, and particularly preferably 0.34 seconds or more. Also, preferably the reaction time is 5 seconds or less, more preferably 3 seconds or less, even more preferably 2 seconds or less, particularly preferably 1 second or less, and extremely preferably 0.5 seconds or less. By keeping the reaction time below the above upper limit, the formation of PFIB, a by-product other than C318, is suppressed. Furthermore, by keeping the reaction time above the above lower limit, energy efficiency is increased, the conversion rate of the raw materials is increased, and the amount of HFP produced is increased.

[0036] In the reaction process, the gauge pressure inside the reactor can be, for example, 0 kPaG or more and less than 200 kPaG. The gauge pressure inside the reactor is preferably 1 kPaG or more, more preferably 3 kPaG or more, and even more preferably 5 kPaG or more. Furthermore, the gauge pressure inside the reactor is preferably 190 kPaG or less, more preferably 150 kPaG or less, even more preferably 100 kPaG or less, particularly preferably 50 kPaG or less, and extremely preferably 10 kPaG or less. In another embodiment, the gauge pressure inside the reactor is preferably 1 to 190 kPaG, more preferably 3 to 150 kPaG, even more preferably 5 to 100 kPaG, and particularly preferably 50 to 100 kPaG. By keeping the gauge pressure inside the reactor below the above upper limits, the formation of PFIB, a by-product other than C318, is suppressed, and pressure adjustment inside the reactor becomes easier. Furthermore, when the gauge pressure inside the reactor is above the lower limit mentioned above, the reaction efficiency per unit volume is high, resulting in a larger amount of HFP being produced.

[0037] The post-reaction composition, after the reaction step, contains at least the product obtained by the reaction of R23, and may further contain unreacted raw material R23. Furthermore, if a medium is used in a step prior to the reaction step, the post-reaction composition may further contain the said medium. Hereinafter, a post-reaction composition obtained without using a medium, or a composition obtained by removing the medium from a post-reaction composition obtained with a medium, will also be referred to as a "specific composition."

[0038] In the reaction process, the product obtained by the reaction of R23 contains at least HFP, and may also contain compounds other than HFP. Examples of compounds other than HFP included in the product include by-products such as C318, PFIB, TFE, R125, and hexafluoroethane (hereinafter also referred to as "C2F6"). In other words, the specific composition may contain at least HFP, and may also contain HFP and the unreacted raw material R23, and may further contain the by-product C318. The specific composition may further contain other by-products PFIB, and may further contain at least one selected from the group consisting of TFE, R125, and C2F6.

[0039] When a specific composition contains R23, HFP, and C318, the total content of R23, HFP, and C318 is preferably 90.0 mol% or more, more preferably 93.0 mol% or more, and even more preferably 95.0 mol% or more, relative to the entire specific composition. The HFP content relative to the entire specific composition is preferably 0.1 mol% or more, more preferably 0.5 mol% or more, even more preferably 1.1 mol% or more, particularly preferably 1.4 mol% or more, and very preferably 2.0 mol% or more.

[0040] If the product contains C318, the molar amount M of C318 contained in the above product is C318 Molar amount M of HFP relative to HFP The ratio (M HFP / M C318) is preferably 13.0 or higher, more preferably 15.0 or higher, even more preferably 21.3 or higher, particularly preferably 25.5 or higher, and extremely preferably 30.0 or higher, in terms of the high production of HFP from by-products. If the product contains PFIB, the molar amount M of PFIB contained in the above product is... PFIB Molar amount M of HFP relative to HFP The ratio (M HFP / M PFIB ) is preferably 1.0 or higher, more preferably 5.0 or higher, even more preferably 11.1 or higher, and particularly preferably 15.0 or higher, in terms of the high production of HFP from by-products.

[0041] <Other processes> In the discharge step, the post-reaction composition, including the product obtained in the reaction step, is discharged from the reactor. As described above, the post-reaction composition may contain unreacted raw material R23. Furthermore, if the second preheated mixture is supplied into the reactor in the supply step, as described above, the medium contained in the second preheated mixture is also contained in the post-reaction composition. In the washing process, the post-reaction composition discharged in the discharge process is washed. Specifically, for example, water is passed through the post-reaction composition to remove the acid generated by the reaction.

[0042] <Manufacturing equipment> Next, an example of a manufacturing apparatus used in the manufacturing method of this embodiment will be described with reference to Figures 1 and 2. The manufacturing apparatus shown in Figure 1 is used in the aforementioned manufacturing method, in which R23 is preheated in the first preheating step by heating a preheater, and R23 is mixed with the second preheating heat transfer medium in the second preheating step. The manufacturing apparatus shown in Figure 1 may also be used in a manufacturing method in which the R23 preheated by heating a preheater in the first preheating step is supplied directly to the reaction apparatus without going through the second preheating step.

[0043] The manufacturing apparatus 100 shown in Figure 1 comprises an R23 container 1 for containing R23 before preheating, an R23 preheater 4 for preheating R23 in the first preheating step, a heat transfer medium container 5 for containing a heat transfer medium for the second preheating step before heating, a heat transfer medium heater 8 for heating the heat transfer medium for the second preheating step, and a reactor 9 for heating R23 at the reaction temperature in the reaction step. Between the R23 container 1 and the R23 preheater 4, there is an R23 supply passage 2 for supplying R23 from the R23 container 1 to the R23 preheater 4. Similarly, between the heat transfer medium container 5 and the heat transfer medium heater 8, there is a heat transfer medium supply passage 6 for supplying a second preheating heat transfer medium from the heat transfer medium container 5 to the heat transfer medium heater 8. The R23 supply passage 2 and the heat transfer medium supply passage 6 are equipped with an R23 flow rate control device 3 for controlling the flow rate of R23 and a heat transfer medium flow rate control device 7 for controlling the flow rate of the second preheating heat transfer medium, respectively.

[0044] On the other hand, R23 supply passages 14 and 23 are provided between the R23 preheater 4 and the reactor 9 to supply R23 from the R23 preheater 4 to the reactor 9. At a confluence point 16 located between the R23 preheater 4 and the reactor 9, the R23 supply passages 14 and 23 merge with a heat transfer medium supply passage 15 that supplies a second preheating heat transfer medium from the heat transfer medium heater 8 to the confluence point 16. Furthermore, in the manufacturing apparatus 100 shown in Figure 1, on the opposite side of the R23 supply passage 23 in the reactor 9, a washing tower 11 for washing the post-reaction composition, a recovery unit 12 for recovering the washed post-reaction composition, and an analytical device 13 for analyzing the components of the post-reaction composition are provided via a discharge passage 10.

[0045] Next, an example of the manufacturing method of this embodiment using the manufacturing apparatus 100 shown in Figure 1 will be described. The R23 contained in the R23 container 1 is supplied via the R23 supply path 2 to the R23 preheater 4, which is heated to the first preheating temperature. Here, the flow rate of R23 is controlled by the R23 flow rate control device 3. Meanwhile, the second preheating heat transfer medium contained in the heat transfer medium container 5 is supplied via the heat transfer medium supply path 6 to the heat transfer medium heater 8, which is heated to the second preheating heat transfer medium heating temperature. The flow rate of the second preheating heat transfer medium is controlled by the heat transfer medium flow rate control device 7, similar to the R23.

[0046] Next, the R23 preheated at the first preheating temperature in the R23 preheater 4 and the second preheating heat medium heated at the second preheating heat medium heating temperature in the heat medium heater 8 are mixed at the confluence point 16 via the R23 supply path 14 and the heat medium supply path 15, respectively, to form the second preheated mixture. The content of the second preheating heat medium in the second preheated mixture is controlled by adjusting the flow rate of R23 and the flow rate of the second preheating heat medium, respectively, using the R23 flow rate control device 3 and the heat medium flow rate control device 7. The second preheated mixture obtained at the confluence point 16 is supplied to the reactor 9, which is heated to the reaction temperature, via the R23 supply channel 23. When the second preheated mixture supplied to the reactor 9 is heated to the reaction temperature within the reactor 9, at least a portion of the R23 contained in the second preheated mixture reacts to form a product containing HFP. In other words, when the second preheated mixture is heated to the reaction temperature within the reactor 9, it becomes a post-reaction composition containing at least the above product and the second preheating heat transfer medium.

[0047] The post-reaction composition is supplied to the washing tower 11 via the discharge channel 10 and washed with water as necessary. Washing in the washing tower 11 removes the acid (e.g., hydrogen fluoride) generated by the R23 reaction from the post-reaction composition. The post-reaction composition, after being washed as necessary, is recovered in the recovery unit 12 via the discharge channel 10. At least a portion of the post-reaction composition recovered in the recovery unit 12 is analyzed by the analyzer 13 as necessary.

[0048] In another example of the manufacturing method of this embodiment using the manufacturing apparatus 100 shown in Figure 1, HFP is manufactured without using a second preheating heat transfer medium. Specifically, for example, the HFP is manufactured in the same manner as the HFP manufacturing method using the second preheating heat transfer medium, except that the flow rate of the second preheating heat transfer medium is set to 0 ml / min by the heat transfer medium flow rate control device 7. In this case, the R23 preheated at the first preheating temperature in the R23 preheater 4 passes directly through the confluence point 16 and is supplied to the reactor 9.

[0049] (Other manufacturing equipment 1) The manufacturing apparatus shown in Figure 2 is used in the aforementioned manufacturing method, in which R23 and the diluent are mixed in advance before the first preheating step, and the resulting diluted mixture is preheated at the first preheating temperature before being supplied to the reactor. Furthermore, the manufacturing apparatus shown in Figure 2 may also be used in a manufacturing method in which R23 is preheated directly at the first preheating temperature without mixing it with a diluent.

[0050] The manufacturing apparatus 101 shown in Figure 2 includes an R23 container 1 for containing R23 before preheating, a dilution medium container 24 for containing a dilution medium, an R23 preheater 4 for preheating R23 in the first preheating step, and a reactor 9 for heating R23 to the reaction temperature in the reaction step. Between the R23 container 1 and the R23 preheater 4, there are R23 supply paths 2 and 27 for supplying R23 from the R23 container 1 to the R23 preheater 4. At a confluence point 28 located between the R23 container 1 and the R23 preheater 4, the R23 supply paths 2 and 27 merge with a dilution medium supply path 25 that supplies dilution medium from a dilution medium container 24 to the confluence point 28. The R23 supply path 2 and the dilution medium supply path 25 are equipped with an R23 flow rate control device 3 for controlling the flow rate of R23 and a dilution medium flow rate control device 26 for controlling the flow rate of the dilution medium, respectively.

[0051] On the other hand, on the opposite side of the R23 supply passage 27 in the R23 preheater 4, a reactor 9 is provided via the R23 supply passage 23. And, similar to the manufacturing apparatus 100 in Figure 1, on the opposite side of the R23 supply passage 23 in the reactor 9, a washing tower 11, a recovery unit 12, and an analysis device 13 are provided via a discharge passage 10.

[0052] In an example of the manufacturing method of this embodiment using the manufacturing apparatus 101 shown in Figure 2, R23 contained in the R23 container 1 and the diluent medium contained in the diluent medium container 24 are mixed at the confluence point 28 via the R23 supply path 2 and the diluent medium supply path 25, respectively, to form a diluted mixture. The content of the diluent medium in the diluted mixture is controlled by adjusting the flow rate of R23 and the flow rate of the diluent medium, respectively, using the R23 flow rate control device 3 and the diluent medium flow rate control device 26. The diluted mixture obtained at the confluence point 28 is supplied via the R23 supply channel 27 to the R23 preheater 4, which is heated to the first preheating temperature. The diluted mixture supplied to the R23 preheater 4 is supplied via the R23 supply channel 23 to the reactor 9, which is heated to the reaction temperature. When the diluted mixture supplied to the reactor 9 is heated to the reaction temperature within the reactor 9, at least a portion of the R23 contained in the diluted mixture reacts to form a product containing HFP. In other words, when the diluted mixture is heated to the reaction temperature within the reactor 9, it becomes a post-reaction composition containing at least the above product and the diluent.

[0053] In another example of the manufacturing method of this embodiment using the manufacturing apparatus 101 shown in Figure 2, HFP is manufactured without using a diluent. Specifically, the HFP is manufactured in the same manner as the HFP manufacturing method using a diluent, except that the flow rate of the diluent is set to 0 ml / min by the diluent flow rate control device 26. In this case, the R23 contained in the R23 container 1 passes directly through the confluence point 28 and is supplied to the R23 preheater 4. [Examples]

[0054] The embodiments of this disclosure will be described in detail below with reference to examples, but the embodiments of this disclosure are not limited to these.

[0055] [Examples 1-13] Using the manufacturing apparatus 100 shown in Figure 1, a product containing hexafluoropropene (HFP) was obtained using trifluoromethane (R23) and nitrogen gas as a second preheating heat transfer medium by the method described below.

[0056] Trifluoromethane (R23) was supplied from R23 container 1 to R23 preheater 4, which was set to the first preheating temperature shown in Tables 1-2, via R23 supply path 2. Meanwhile, nitrogen gas was supplied from heat transfer medium container 5 to heat transfer medium heater 8, which was set to the second preheating heat transfer medium heating temperature shown in Tables 1-2, via heat transfer medium supply path 6. In the R23 preheater 4, the preheated R23 and the nitrogen gas heated in the heat medium heater 8 were mixed at the confluence point 16 of the R23 supply line 14 and the heat medium supply line 15 to obtain a mixture after the second preheating. The obtained mixture after the second preheating was supplied to the reactor 9 controlled at the reaction temperature and gauge pressure values shown in Tables 1 to 2 respectively. The reaction time, that is, the residence time in the reactor 9, is shown in Tables 1 to 2.

[0057] The flow rates of R23 and nitrogen gas were adjusted by the R23 flow rate control device 3 and the heat medium flow rate control device 7 respectively. By adjusting the flow rates of the above R23 and nitrogen gas, the contents of R23 and nitrogen gas in the mixture after the second preheating before being supplied to the reactor 9 were controlled to be the values shown in Tables 1 to 2 respectively.

[0058] The outlet gas (composition after reaction) discharged from the reactor 9 contained, in addition to the product generated by the reaction, unreacted R23 as a raw material. The composition after reaction was supplied to the washing tower 11 via the discharge line 10. In the washing tower 11, the composition after reaction was washed with distilled water to remove the acid components from the composition after reaction. The composition after reaction from which the acid components were removed was recovered by the recovery device 12, and the recovered composition after reaction was analyzed by the analyzer 13. As the analyzer 13, gas chromatography (product name "GC-2014", manufactured by Shimadzu Corporation) and a capillary column (product name "PoraPLOT Q", manufactured by Agilent Technologies) were used. From the results of analyzing the composition of the composition after reaction by the analyzer 13, the contents of R23 as a raw material, HFP as a target product, C318, PFIB, C2F6, TFE, R125, and other products with respect to the total components excluding nitrogen gas as a heat medium in the composition after reaction were calculated. Specifically, based on the relative sensitivity of gas chromatography of each component, it was calculated so that the total of the components described in Tables 1 to 2 became 100 mol%. The results are shown in Tables 1 to 2. Also, the molar amount M of C318 contained in the composition after reaction C318 with respect to the molar amount M of HFP HFP in the composition after reaction, the ratio (M HFP / M C318 ) and the molar amount M of PFIB PFIBMolar amount M of HFP relative to HFP The ratio (M HFP / M PFIB ) are shown together in Tables 1 and 2.

[0059] [Example 14] The post-reaction composition was obtained in the same manner as in Example 1, except that instead of R23, a mixed gas was used as the raw material gas contained in the R23 container 1, consisting of 83 moles of R23, 6 moles of TFE, and 1 mole of R125, and the first preheating temperature, the heating temperature of the second preheating heat transfer medium, the reaction temperature, the gauge pressure in the reactor, the reaction time, and the nitrogen gas content in the mixture after the second preheating before supplying it to the reactor 9 were set to the values ​​shown in Table 3. The composition of the resulting post-reaction composition was analyzed in the same manner as in Example 1, and the content of R23, HFP, C318, PFIB, C2F6, TFE, R125, and other products was calculated relative to the total components of the post-reaction composition excluding the nitrogen gas, which was the heat transfer medium. The results are shown in Table 3. In addition, the molar amount M of C318 contained in the post-reaction composition was calculated. C318 Molar amount M of HFP relative to HFP The ratio (M HFP / M C318 ) and the molar amount M of PFIB PFIB Molar amount M of HFP relative to HFP The ratio (M HFP / M PFIB ) are also shown in Table 3.

[0060] [Examples 15-22] The post-reaction composition was obtained in the same manner as in Example 1, except that nitrogen gas was not used as the second preheating heat transfer medium, and the first preheating temperature, reaction temperature, gauge pressure in the reactor, and reaction time were set to the values ​​shown in Table 4. The composition of the resulting post-reaction composition was analyzed in the same manner as in Example 1, and the content of R23, HFP, C318, PFIB, C2F6, TFE, R125, and other products relative to the total post-reaction composition was calculated. The results are shown in Table 4. In addition, the molar amount M of C318 contained in the post-reaction composition was calculated. C318 Molar amount M of HFP relative to HFP The ratio (M HFP / M C318 ) and the molar amount M of PFIB PFIBMolar amount M of HFP relative to HFP The ratio (M HFP / M PFIB ) are also shown in Table 4.

[0061] [Table 1]

[0062] [Table 2]

[0063] [Table 3]

[0064] [Table 4]

[0065] In the above examples, Examples 1-12, 14, and 15-21 are examples, and Examples 13 and 22 are comparative examples. As shown in Tables 1-3, in Examples 1-12 and 14, the molar amount M of C318 is different compared to Example 13. C318 Molar amount M of HFP relative to HFP The ratio (M HFP / M C318 It can be seen that the ) is high and the formation of C318 is suppressed. Similarly, as shown in Table 4, in Examples 15-21, the molar amount M of C318 is higher compared to Example 22. C318 Molar amount M of HFP relative to HFP The ratio (M HFP / M C318 The high level of C318 indicates that its formation is suppressed. [Explanation of Symbols]

[0066] 1 R23 enclosure 2 R23 supply line 3 R23 Flow Control Device 4 R23 Preheater 5. Heat transfer medium container 6 Heat medium supply path 7. Heat transfer fluid flow control device 8 Heat medium heater 9 Reactor 10 Exhaust channel 11 Washing Tower 12 Recovery unit 13 Analyzer 14, 23, 27 R23 supply route 15 Heat medium supply path 16, 28 confluence 24 Dilution medium container 25 Dilution medium supply channel 26 Dilution medium flow control device 100, 101 Manufacturing equipment

Claims

1. A method for producing hexafluoropropene, comprising preheating trifluoromethane to a first preheating temperature of 450 to 700°C, supplying it to a reactor, and heating the trifluoromethane in the reactor to a reaction temperature of 800°C or higher to obtain a product containing hexafluoropropene.

2. A method for producing hexafluoropropene according to claim 1, comprising supplying into the reactor a mixture obtained by mixing trifluoromethane preheated at the first preheating temperature with a second preheating heat medium heated at a second preheating heat medium heating temperature higher than the first preheating temperature.

3. The method for producing hexafluoropropene according to claim 2, wherein the heating temperature of the second preheating heat transfer medium is 1100°C or lower.

4. The method for producing hexafluoropropene according to claim 2 or 3, wherein the content of the second preheating heat transfer medium in the mixture is 50 mol% or less relative to the total amount of trifluoromethane preheated at the first preheating temperature and the second preheating heat transfer medium.

5. The method for producing hexafluoropropene according to any one of claims 1 to 3, wherein the reaction temperature is 1000°C or less.

6. A method for producing hexafluoropropene according to any one of claims 1 to 3, wherein the time for heating the trifluoromethane in the reactor at the reaction temperature is 5 seconds or less.

7. A method for producing hexafluoropropene according to any one of claims 1 to 3, wherein the gauge pressure in the reactor is 0 kPaG or more and less than 200 kPaG.

8. The product further comprises octafluorocyclobutane, A method for producing hexafluoropropene according to any one of claims 1 to 3, wherein the ratio of the molar amount of hexafluoropropene contained in the product to the molar amount of octafluorocyclobutane contained in the product is 13.0 or more.

9. The product further comprises perfluoroisobutene, A method for producing hexafluoropropene according to any one of claims 1 to 3, wherein the ratio of the molar amount of hexafluoropropene contained in the product to the molar amount of perfluoroisobutene contained in the product is 1.0 or more.

10. A composition comprising trifluoromethane, hexafluoropropene, and octafluorocyclobutane, The total content of trifluoromethane, hexafluoropropene, and octafluorocyclobutane is 96.0 mol% or more of the total composition. A composition in which the ratio of the molar amount of hexafluoropropene to the molar amount of octafluorocyclobutane is 13.0 or greater.

11. Furthermore, it contains perfluoroisobutene, The composition according to claim 10, wherein the ratio of the molar amount of hexafluoropropene to the molar amount of perfluoroisobutene is 1.0 or more.

12. The composition according to claim 10 or 11, further comprising at least one selected from the group consisting of tetrafluoroethylene, pentafluoroethane, and hexafluoroethane.

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