Method for purifying 1,1,1,2-tetrafluoroethane

Abstract

This invention provides a purification method that allows for the simpler and more efficient purification of 1,1,1,2-tetrafluoroethane to a high degree of purity. [Solution] A method for purifying 1,1,1,2-tetrafluoroethane from a mixed gas containing 1,1,1,2-tetrafluoroethane and a fluorocarbon compound having one or more double bonds, the method comprising the step of heating the mixed gas.

Description

[Technical Field]

[0001] This disclosure relates to a method for purifying 1,1,1,2-tetrafluoroethane. [Background technology]

[0002] A known method for purifying 1,1,1,2-tetrafluoroethane involves reducing fluoroalkenes, which are impurities, by reacting them with hydrogen fluoride (Patent Document 1). Another known method for purifying 1,1,1,2-tetrafluoroethane involves removing fluoroalkenes, which are impurities, using an adsorbent (Patent Document 2). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-107572 [Patent Document 2] Japanese Patent Application Publication No. 4-308537 [Overview of the project] [Problems that the invention aims to solve]

[0004] The method described in Patent Document 1 requires the use of hydrogen fluoride, which is economically disadvantageous and can also be complicated to operate.

[0005] Patent Document 2 discloses a purification method using MS-5A (Type A) and MS-13X (Type X) zeolites to remove 1,1,1,2-tetrafluoroethane from a mixture of 1,1,1,2-tetrafluoroethane and reduce the 1,1,2,2-tetrafluoroethane content to 3 ppm by weight. However, depending on the application, particularly in semiconductor manufacturing, higher purity is required.

[0006] The present disclosure aims to provide a purification method capable of purifying 1,1,1,2 - tetrafluoroethane more simply and with higher purity, or with even higher purity.

Means for Solving the Problems

[0007] The present disclosure includes the following aspects. [Item 1] A method for purifying 1,1,1,2 - tetrafluoroethane from a mixed gas containing 1,1,1,2 - tetrafluoroethane and a fluorocarbon - based compound having one or more double bonds, the purification method including a step of heat - treating the mixed gas. [Item 2] The purification method according to Item 1, wherein the fluorocarbon - based compound having a double bond has one double bond. [Item 3] The purification method according to Item 1 or 2, wherein the fluorocarbon - based compound having a double bond has 2 or 3 carbon atoms. [Item 4] The purification method according to any one of Items 1 to 3, wherein the fluorocarbon - based compound having a double bond contains at least one compound selected from the group consisting of 2 - chloro - 1,1 - difluoroethene, 1 - chloro - 1,2 - difluoroethene, and 3,3,3 - trifluoropropene. [Item 5] The purification method according to any one of Items 1 to 4, wherein the step of heat - treating is performed by flowing the mixed gas through a heated reaction tube. [Item 6] The purification method according to Item 5, wherein the flow rate of the mixed gas in the step of heat - treating is 100 ccm or more and 1000 ccm or less. [Item 7] The purification method according to any one of Items 1 to 6, wherein the heating temperature in the step of heat - treating is 100°C or more and 600°C or less. [Item 8] The purification method according to any one of Items 1 to 7, wherein the heating time in the step of heat - treating is 5 seconds or more and 10 minutes or less. [Item 9] The method for purification according to any one of Items 1 to 8, wherein the concentration of the fluorocarbon compound after the step of heat treatment is 1.0 volume ppm or less respectively. [Item 10] The method for purification according to any one of Items 1 to 9, wherein a separation step is further performed after the step of heat treatment. [Item 11] The method for purification according to Item 10, wherein the separation step is a rectification step. [Item 12] The method for purification according to Item 10 or 11, wherein the concentration of 1,1,1,2-tetrafluoroethane after the separation step is 99.9999 volume % or more. [Item 13] A method for purifying 1,1,1,2-tetrafluoroethane from a mixture containing 1,1,1,2-tetrafluoroethane and a fluorocarbon compound having 2 carbon atoms, comprising a step of bringing the mixture into contact with zeolite, wherein the zeolite has an Si / Al ratio of 3 or more. [Item 14] The method for purification according to Item 13, wherein the fluorocarbon compound having 2 carbon atoms contains at least one compound selected from the group consisting of 1,1,2,2-tetrafluoroethane, trifluoroethene, 2-chloro-1,1-difluoroethene, and (E / Z)1-chloro-2-fluoroethene. [Item 15] The method for purification according to Item 13 or 14, wherein the zeolite has one or more selected from the group consisting of sodium, potassium, calcium, and magnesium as cation species. [Item 16] The method for purification according to any one of Items 13 to 15, wherein the zeolite is at least one zeolite selected from the group consisting of chabazite-type zeolite, mordenite-type zeolite, beta-type zeolite, and Y-type zeolite. [Item 17] The method for purification according to any one of Items 13 to 16, wherein the zeolite is chabazite-type zeolite. [Item 18] The purification method according to any one of claims 13 to 17, wherein the temperature in the step of contacting the mixture with the zeolite is 0°C or higher and 60°C or lower. [Section 19] The purification method according to any one of claims 13 to 18, wherein the W / F value in the step of contacting the mixture with the zeolite is less than 10. [Section 20] The purification method according to any one of claims 13 to 19, wherein the pressure in the step of contacting the mixture with the zeolite is 0 kPaG or more and 1000 kPaG or less. [Section 21] The purification method described in any one of items 13 to 20, wherein the concentration of each fluorocarbon compound after purification is 1.0 volume ppm or less. [Section 22] A gas composition containing 1,1,1,2-tetrafluoroethane, wherein the concentration of 1,1,1,2-tetrafluoroethane is 99.9999% by volume or more. [Section 23] The gas composition according to item 22, wherein the concentration of one or more fluorocarbon compounds having double bonds in the gas composition is 1.0 volume ppm or less for each compound. [Section 24] The gas composition according to claim 23, wherein the fluorocarbon compound having a double bond is at least one compound selected from the group consisting of 2-chloro-1,1-difluoroethene, 1-chloro-1,2-difluoroethene, and 3,3,3-trifluoropropene. [Section 25] The gas composition according to item 22, wherein the concentration of each carbon-2 fluorocarbon compound in the gas composition is 1.0 volume ppm or less. [Section 26] The gas composition according to item 25, wherein the carbon-2 fluorocarbon compound is at least one compound selected from the group consisting of 1,1,2,2-tetrafluoroethane, trifluoroethene, 2-chloro-1,1-difluoroethene, and (E / Z)1-chloro-2-fluoroethene. [Effects of the Invention]

[0008] According to the purification method of this disclosure, 1,1,1,2-tetrafluoroethane can be purified more easily and to a higher purity, or to a higher purity. [Modes for carrying out the invention]

[0009] <First Embodiment> The purification method of this embodiment is a method for purifying 1,1,1,2-tetrafluoroethane from a mixed gas containing 1,1,1,2-tetrafluoroethane and a fluorocarbon compound having one or more double bonds, and includes a step of heating the mixed gas.

[0010] (The process of heat treatment) A gas mixture containing 1,1,1,2-tetrafluoroethane may contain fluorocarbon compounds having double bonds and a boiling point similar to that of 1,1,1,2-tetrafluoroethane. Such fluorocarbon compounds are difficult to separate by rectification. According to the purification method of this embodiment, in the purification step of 1,1,1,2-tetrafluoroethane from a gas mixture containing one or more fluorocarbon compounds having double bonds, heating the gas mixture converts the fluorocarbon compounds having double bonds into high-boiling-point compounds. This facilitates the removal of impurities from the gas mixture.

[0011] Here, "fluorocarbon compounds" means hydrocarbon compounds containing a fluorine atom. Fluorocarbon compounds may also contain a chlorine atom. Fluorocarbon compounds include fluorocarbons (FCs), hydrofluorocarbons (HFCs), chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluoroolefins (HFOs).

[0012] The fluorocarbon compounds having the double bond described above are typically hydrofluoroolefins (HFOs).

[0013] Examples of hydrofluoroolefins (HFOs) include 2-chloro-1,1-difluoroethene (HFO-1122), (E / Z)1-chloro-1,2-difluoroethene (HFO-1122a), trifluoroethene (HFO-1123), (E / Z)1-chloro-2-fluoroethene (HFO-1131), 2,3,3,3-tetrafluoropropene (HFO-1234yf), 3,3,3-trifluoropropene (HFO-1243zf), trans-1,3,3,3-tetrafluoropropene (HFO-1234ze), 1,3,3,3-tetrafluoropropene (HFO-1234zd), and 1,2,3,3,3-pentafluoropropene (HFO-1336mzz).

[0014] In one embodiment, the fluorocarbon compound having a double bond has one double bond.

[0015] In one embodiment, the fluorocarbon compound having a double bond has 2 or 3 carbon atoms.

[0016] In a preferred embodiment, the fluorocarbon compound having a double bond includes at least one compound selected from the group consisting of at least one compound selected from the group consisting of 2-chloro-1,1-difluoroethene, 1-chloro-1,2-difluoroethene, and 3,3,3-trifluoropropene.

[0017] The heat treatment process is preferably carried out by circulating the mixed gas through a heated reaction tube. By heating the gas by circulating it through a reaction tube, continuous processing becomes possible, and the processing volume can also be increased.

[0018] The reaction tube described above is preferably made of metal, such as stainless steel (SUS). Using a metal tube as the reaction tube facilitates the heating of the mixed gas.

[0019] The diameter of the reaction tube described above is preferably 0.1 cm or more, more preferably 0.1 cm or more, and even more preferably 0.1 cm or more. Increasing the diameter of the reaction tube makes it easier to increase the flow rate of the mixed gas. The diameter of the reaction tube is preferably 20 cm or less, more preferably 10 cm or less, and even more preferably 5 cm or less, for example, 3 cm or less or 2 cm or less. By decreasing the diameter of the reaction tube, the heating efficiency of the mixed gas is improved, and it becomes possible to heat the mixed gas in a shorter time. The diameter of the reaction tube is preferably 0.1 cm to 20 cm, more preferably 0.5 cm to 10 cm, and even more preferably 1 cm to 5 cm.

[0020] The length of the reaction tube is preferably 10 cm or more, more preferably 20 cm or more, even more preferably 30 cm or more, for example, 1 m or more, 2 m or more, or 3 m or more. Increasing the length of the reaction tube increases the heating time of the mixed gas, allowing for more reliable heating of the mixed gas. Alternatively, the length of the reaction tube may be preferably 10 m or less, more preferably 5 m or less, even more preferably 3 m or less, even more preferably 1 m or less, for example, 80 cm or less or 50 cm or less. Shortening the length of the reaction tube shortens the processing time of the mixed gas. The length of the reaction tube may be preferably 10 cm to 10 m, more preferably 10 cm to 5 m, even more preferably 10 cm to 1 m, for example, 10 cm to 80 cm, or 20 cm to 50 cm.

[0021] In one embodiment, a microreactor may be used as the reaction tube.

[0022] The flow rate of the mixed gas in the heat treatment process is preferably 100 ccm or more, more preferably 200 ccm or more, and even more preferably 300 ccm or more. Increasing the flow rate of the mixed gas increases the amount of mixed gas that can be processed. Alternatively, the flow rate of the mixed gas may be preferably 1000 ccm or less, more preferably 800 ccm or less, and even more preferably 500 ccm or less. By decreasing the flow rate of the mixed gas, it becomes possible to heat the mixed gas more reliably. The flow rate of the mixed gas may be preferably 100 ccm to 1000 ccm, more preferably 200 ccm to 800 ccm, and even more preferably 200 ccm to 500 ccm.

[0023] The heating temperature in the heat treatment step is preferably 100°C or higher, more preferably 200°C or higher, even more preferably 250°C or higher, and even more preferably 300°C or higher. By increasing the heating temperature, the fluorocarbon compound having a double bond can be more reliably converted to other compounds, typically high-boiling point compounds. Alternatively, the heating temperature may be preferably 600°C or lower, more preferably 500°C or lower, for example, 400°C or lower. By setting the heating temperature to 600°C or lower, undesirable reactions, such as the decomposition of 1,1,1,2-tetrafluoroethane, can be suppressed. The heating temperature may be preferably 100°C to 600°C, more preferably 200°C to 500°C, even more preferably 250°C to 500°C, and even more preferably 300°C to 400°C.

[0024] The heating time in the heat treatment step is preferably 5 seconds or more, more preferably 10 seconds or more, even more preferably 30 seconds or more, for example 1 minute or more, or 3 minutes or more. By increasing the heating time, the fluorocarbon compound having a double bond can be more reliably converted to other compounds, typically high-boiling point compounds. Alternatively, the heating time may be preferably 10 minutes or less, more preferably 5 minutes or less, for example 3 minutes or less, or 1 minute or less. By shortening the heating time, undesirable reactions, such as the decomposition of 1,1,1,2-tetrafluoroethane, can be suppressed. The heating time may be preferably 5 seconds to 10 minutes, more preferably 10 seconds to 5 minutes, for example 10 seconds to 3 minutes or 30 seconds to 1 minute.

[0025] The concentration of the fluorocarbon compound having a double bond in the mixed gas after the heat treatment step is preferably 1.0 ppm by volume or less, more preferably 0.5 ppm by volume or less, and even more preferably 0.1 ppm by volume or less.

[0026] (separation process) The purification method of this embodiment may further include a separation step after the heat treatment step.

[0027] The separation process may include rectification, distillation, extraction, and the like.

[0028] The separation step is preferably a rectification step. In the rectification step, 1,1,1,2-tetrafluoroethane is separated from components with different boiling points, such as high-boiling-point compounds produced in the heating step.

[0029] As a result of the heat treatment process described above, fluorocarbon compounds having double bonds with a boiling point similar to that of 1,1,1,2-tetrafluoroethane are converted into high-boiling-point compounds, and these compounds can be easily removed by rectification.

[0030] The theoretical number of stages in a rectification column in the rectification process is preferably 10 or more, more preferably 20 or more. From an economic standpoint, the theoretical number of stages in a rectification column used in the rectification process is preferably 60 or less, more preferably 50 or less.

[0031] In the rectification process, it is preferable to supply the mixed gas obtained in the heat treatment step of this embodiment to the middle section of the rectification column.

[0032] In the rectification process, the pressure used for rectification is preferably 0.05 to 5 MPaG (gauge pressure). The lower limit of this pressure is preferably 0.05 MPaG, more preferably 0.1 MPaG, even more preferably 0.25 MPaG, and particularly preferably 0.5 MPaG. The upper limit of this pressure is preferably 5 MPaG, more preferably 4 MPaG, even more preferably 3 MPaG, and particularly preferably 2 MPaG.

[0033] The reflux ratio of the rectification column in the rectification process is not particularly limited, but is preferably 5 to 30, and more preferably 10 to 20.

[0034] The rectification process can be carried out in discontinuous or continuous operation, but industrially, continuous operation is preferred.

[0035] The concentration of 1,1,1,2-tetrafluoroethane in the gas after the rectification process is preferably 99.9999% by volume or higher. The concentration of fluorocarbon compounds having double bonds is preferably 1.0 ppm by volume or lower, preferably 0.5 ppm by volume or lower, and more preferably 0.1 ppm by volume or lower.

[0036] Accordingly, this embodiment provides a gas composition containing 1,1,1,2-tetrafluoroethane, wherein the concentration of 1,1,1,2-tetrafluoroethane is 99.9999% by volume or higher.

[0037] Furthermore, in other aspects, this embodiment provides a gas composition in which the concentration of one or more fluorocarbon compounds having double bonds in the gas composition is preferably 1.0 ppm by volume or less, more preferably 0.5 ppm by volume or less, and even more preferably 0.1 ppm by volume or less.

[0038] The fluorocarbon compound having the double bond described above is preferably at least one compound selected from the group consisting of 2-chloro-1,1-difluoroethene, 1-chloro-1,2-difluoroethene, and 3,3,3-trifluoropropene.

[0039] (Further purification process) The purification method of this embodiment may include a step of contacting a mixed gas with a zeolite to adsorb impurities. In such an adsorption step, impurity gases, typically fluorocarbon compounds, can be adsorbed onto the zeolite and removed.

[0040] Such a purification process may be carried out before the heat treatment process, between the heat treatment process and the separation process, or after the separation process. Preferably, it is carried out after the heat treatment process.

[0041] Examples of fluorocarbon compounds that can be removed by the adsorption process include, in addition to the fluorocarbon compounds having double bonds mentioned above, fluorocarbons (FCs), hydrofluorocarbons (HFCs), chlorofluorocarbons (CFCs), and hydrochlorofluorocarbons (HCFCs).

[0042] Examples of fluorocarbons (FCs) include hexafluoroethane and tetrafluoroethylene.

[0043] Examples of hydrofluorocarbons (HFCs) include pentafluoroethane (HFC-125), 1,1,2,2-tetrafluoroethane (HFC-134), 1,1,2-trifluoroethane (HFC-143), 1,1,1,2,2-pentafluoroethane (HFC-125), 1,1,1-trifluoroethane (HFC-143a), 1,2-difluoroethane (HFC-152), and 1,1-difluoroethane (HFC-152a).

[0044] Examples of chlorofluorocarbons (CFCs) include 1,1,2-trichloro-1,2,2-trifluoroethane (CFC-113), 1,2-dichlorotetrafluoroethane (CFC-114), and 1-chloro-1,1,2,2,2-pentafluoroethane (CFC-115).

[0045] Examples of hydrochlorofluorocarbons (HCFCs) include 2,2-dichloro-1,1,1-trifluoroethane (HFC-123) and 2-chloro-1,1,1,2-tetrafluoroethane (HFC-124).

[0046] In one embodiment, the fluorocarbon compound to be removed includes at least one compound selected from the group consisting of 1,1,2,2-tetrafluoroethane, trifluoroethene, 2-chloro-1,1-difluoroethene, and (E / Z)1-chloro-2-fluoroethene.

[0047] The above-mentioned zeolite has a Si / Al ratio of preferably 3 or more, more preferably 4 or more. Furthermore, the Si / Al ratio of the zeolite is 15 or less, preferably 10 or less.

[0048] The above Si / Al ratio can be measured by scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDX).

[0049] In one aspect, the zeolite used in the purification method of the present embodiment has sodium, potassium, calcium, or magnesium as cation species.

[0050] The zeolite used in the present embodiment is a kind of clay mineral, and is a hydrated aluminosilicate containing an alkali or alkaline earth metal consisting of a rigid anionic skeleton having regular channels (tubular pores) and cavities (voids).

[0051] In one aspect, the zeolite used in the purification method of the present embodiment generally has the following formula: (MI,MII 1 / 2 ) m (Al m Si n O 2(m+n) )·xH2O,(n≧m) (where MI is Li + , Na + , or K + , and MII is Ca 2+ , Mg 2+ , or Ba 2+ .) It is represented by the composition of, and the cations compensate for the negative charge of the aluminosilicate skeleton.

[0052] The type of cation in the zeolite is not particularly limited, and usually H + , Li + , Na + , K + , Ca 2+ , Mg 2+ , Ba 2+ , etc. are used.

[0053] The basic unit of the structure is a tetrahedral structure of SiO4 or AlO4 (collectively TO4 tetrahedra), and these are continuously connected infinitely in three-dimensional directions to form crystals. The crystals in zeolite are porous, and the diameter of the pores is usually about 0.2 nm to 1.0 nm (2 Å to 10 Å).

[0054] Compositions containing fluorinated hydrocarbon compounds such as 1,1,1,2-tetrafluoroethane (HFC-134a) can be efficiently dehydrated, and even after the dehydration process has elapsed, the release of water from the zeolite is well suppressed. Therefore, the zeolite is preferably at least one selected from the group consisting of chabazite-type zeolite, mordenite-type zeolite, beta-type zeolite, and Y-type zeolite. Only one type of zeolite may be used, or two or more types may be used simultaneously.

[0055] The zeolite mentioned above is preferably a chabazite-type zeolite.

[0056] The above chabazite-type zeolite has a chabazite-type (CHA-type) structure, a three-dimensional pore structure, a pore diameter of approximately 0.38 nm (3.8 Å), and a large cage inside.

[0057] In this embodiment, chabazite-type (CHA-type) zeolite is preferred because it allows for efficient dehydration of compositions containing fluorinated hydrocarbon compounds such as 1,1,1,2-tetrafluoroethane (HFC-134a), and effectively suppresses the release of water from the zeolite even after a period of dehydration. In this embodiment, commercially available chabazite-type zeolite can be used.

[0058] The above mordenite-type zeolite is also called mordenite, and is (Ca,K2,Na2)[AlSi5O 12 It is a silicate mineral represented by 2·7H2O. Mordenite-type mordenite structures generally have a pore structure consisting of 12-membered oxygen rings and 8-membered oxygen rings, in which SiO4 and AlO4 are bonded together with oxygen. The pore size is approximately 0.67 nm × 0.70 nm for the 12-membered oxygen ring and approximately 0.29 nm × 0.57 nm for the 8-membered oxygen ring. In this embodiment, commercially available mordenite-type zeolites can be used.

[0059] The above-mentioned beta-type zeolite is a type of crystalline aluminosilicate containing Si and Al, and has a three-dimensional pore structure including pores of 12-membered oxygen rings. In this embodiment, commercially available beta-type zeolite can be used.

[0060] The above-mentioned Y-type zeolite has pore openings with a diameter of approximately 0.74 nm, making it the zeolite with the largest pores among commercially available zeolites. In this embodiment, commercially available Y-type zeolites can be used.

[0061] The zeolite obtained by the purification method of this embodiment can be recycled after use. In other words, the zeolite obtained by the purification method of this embodiment is reusable.

[0062] The regeneration of zeolite after use can be carried out by circulating an inert gas under heating conditions, although this is not particularly limited.

[0063] The above heating temperature may be, for example, 100°C to 300°C, preferably 150°C to 250°C.

[0064] The above-mentioned inert gas is nitrogen, argon, etc., and is preferably nitrogen.

[0065] The flow time of the inert gas may be, for example, 1 to 24 hours, preferably 3 to 15 hours, and more preferably 5 to 10 hours.

[0066] The temperature in the step of contacting the mixed gas with the zeolite is preferably 0°C or higher, more preferably 20°C or higher, for example 25°C or higher. According to the purification method of this embodiment, impurity gases can be removed even at relatively high temperatures. That is, the purification method of this embodiment is energy efficient because cooling in the above step is unnecessary. Furthermore, the above temperature is preferably 60°C or lower, more preferably 50°C or lower, for example 40°C or lower. Lowering the temperature can further improve the accuracy of purification. The above temperature is preferably 0°C to 60°C, more preferably 20°C to 50°C, for example 25°C to 50°C or 25°C to 40°C.

[0067] In the step of contacting the mixed gas with the zeolite, the W / F value is preferably less than 10, more preferably 8 or less, even more preferably 5 or less, for example 3 or less, 1 or less, or 0.5 or less. The W / F value is not particularly limited, but may be 0.01 or more, 0.1 or more, or 0.5 or more. According to the purification method of this embodiment, impurity gases can be removed even if the W / F value is small, that is, even if the flow rate is large. In other words, according to the purification method of this embodiment, impurity gases can be removed efficiently. The W / F value is preferably 0.01 or more and less than 10, more preferably 0.1 to 8, for example 0.5 to 8, 0.5 to 5, or 1 to 525°C to 40°C.

[0068] Here, the W / F value is an indicator of flow velocity and can be calculated using the following formula. W / F value = Zeolite weight (g) / Gas flow rate (cc / sec.)

[0069] The pressure in the step of contacting the mixed gas with the zeolite is preferably 1000 kPaG or less, more preferably 800 kPaG or less, and even more preferably 650 kPaG or less, for example 450 kPaG or less. According to the purification method of this embodiment, impurity gases can be efficiently removed even at relatively low pressures. That is, the purification method of this embodiment is energy efficient. The above pressure may also preferably be 0 kPaG or more, for example 100 kPaG or more, or 300 kPaG or more. By increasing the pressure, the processing volume can be increased. The pressure may preferably be 0 kPaG to 1000 kPaG, more preferably 0 kPaG to 800 kPaG, for example preferably 0 kPaG to 650 kPaG.

[0070] <Second Embodiment> The purification method of this embodiment is a method for purifying 1,1,1,2-tetrafluoroethane (HFC-134a) from a mixture containing a fluorocarbon compound having 2 carbon atoms, comprising the step of contacting the mixture with a zeolite, wherein the zeolite has a Si / Al ratio of 3 or more.

[0071] By using a zeolite with a Si / Al ratio of 3 or higher, the amount of fluorocarbon compounds with two carbon atoms in 1,1,1,2-tetrafluoroethane can be reduced. Fluorocarbon compounds with two carbon atoms are usually very difficult to separate because they share the same number of carbon atoms as 1,1,1,2-tetrafluoroethane, but they can be efficiently removed using the method of this embodiment.

[0072] The above-mentioned fluorocarbon compounds refer to hydrocarbon compounds containing a fluorine atom. Furthermore, fluorocarbon compounds may also contain a chlorine atom. Fluorocarbon compounds include hydrofluorocarbons (HFCs), chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluoroolefins (HFOs).

[0073] In one embodiment, the carbon-2 fluorocarbon compound to be removed includes at least one compound selected from the group consisting of 1,1,2,2-tetrafluoroethane, trifluoroethene, 2-chloro-1,1-difluoroethene, and (E / Z)1-chloro-2-fluoroethene.

[0074] In one embodiment, the carbon-2 fluorocarbon compound to be removed includes 1,1,2,2-tetrafluoroethane. According to the method of this embodiment, even 1,1,2,2-tetrafluoroethane, which is an isomer of 1,1,1,2-tetrafluoroethane, can be efficiently removed.

[0075] In one embodiment, the fluorocarbon compound to be removed includes at least one compound selected from the group consisting of trifluoroethene, 2-chloro-1,1-difluoroethene, and (E / Z)1-chloro-2-fluoroethene.

[0076] The zeolite used in the purification method of this embodiment has a Si / Al ratio of 3 or more, preferably 4 or more. Furthermore, the Si / Al ratio of the zeolite is 15 or less, preferably 10 or less.

[0077] The above Si / Al ratio can be measured by scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDX).

[0078] The zeolite used in the purification method of this embodiment is a type of clay mineral, and is an aluminosilicate containing alkali or alkaline earth metals, consisting of a rigid anionic skeleton with regular channels (tubular pores) and cavities.

[0079] Zeolites are generally, (MI,MII 1 / 2 ) m (Al m Si n O 2(m+n) )·xH2O,(n≧m) (MI:Li +na + , K + etc., MII:Ca 2+ Mg 2+ Ba 2+ etc.) It is represented by the following composition, where the cations compensate for the negative charge of the aluminosilicate skeleton. There are no particular restrictions on the types of cations in zeolite; typically, H + Li + na + , K + Ca 2+ Mg 2+ Ba 2+ These are used.

[0080] The basic structural unit is a tetrahedral structure of SiO4 or AlO4 (collectively called a TO4 tetrahedron), which is infinitely linked in three dimensions to form a crystal. In zeolites, the crystal is porous, and the diameter of the pores is usually around 0.2 nm to 1.0 nm (2 Å to 10 Å). In addition to the molecular sieving effect due to the pores derived from its skeletal structure, zeolites can possess properties such as solid acidity, ion exchange capacity, catalytic activity, and adsorption capacity.

[0081] In one embodiment, the zeolite used in the purification method of this embodiment has one or more cation species selected from sodium, potassium, calcium, and magnesium.

[0082] In a preferred embodiment, the zeolite is at least one zeolite selected from the group consisting of chabazite-type zeolite, mordenite-type zeolite, beta-type zeolite, and Y-type zeolite. The zeolite may be one type only, or two or more types may be used simultaneously.

[0083] The zeolite mentioned above is preferably a chabazite-type zeolite.

[0084] Chabazite-type zeolite: It has a chabazite-type (CHA-type) structure, a three-dimensional pore structure, a pore diameter of approximately 0.38 nm (3.8 Å), and a large cage inside.

[0085] In this embodiment, it is preferable to use chabazite-type (CHA-type) zeolite because it can efficiently dehydrate a composition containing a fluorinated hydrocarbon compound such as HFC-134a, and the release of water from the zeolite is well suppressed even after the dehydration treatment time has elapsed. In this embodiment, commercially available chabazite-type zeolite can be used.

[0086] Mordenite-type zeolite: Mordenite, also known as mordenite, has the chemical formula (Ca,K2,Na2)[AlSi5O 12 It is 2·7H2O and is a silicate mineral. Mordenite-type mordenite structures are generally zeolites having a pore structure consisting of 12-membered oxygen rings and 8-membered oxygen rings, in which SiO4 and AlO4 are bonded together with oxygen, and the pore size is approximately 0.67 nm × 0.70 nm for the 12-membered oxygen ring and approximately 0.29 nm × 0.57 nm for the 8-membered oxygen ring. In this embodiment, commercially available mordenite-type zeolites can be used.

[0087] Beta-type zeolite: Beta-type zeolite is a type of crystalline aluminosilicate containing Si and Al, and has a three-dimensional pore structure containing 12-membered oxygen ring pores.

[0088] In this embodiment, beta-type zeolite can be used because it can efficiently dehydrate a composition containing a fluorinated hydrocarbon compound such as HFC-134a, and the release of water from the zeolite is well suppressed even after the dehydration treatment time has elapsed. In this embodiment, commercially available beta-type zeolite can be used.

[0089] Y-type zeolite: Y-type zeolite has pores with a diameter of approximately 0.74 nm, making it the zeolite with the largest pores among commercially available zeolites.

[0090] In this embodiment, Y-type zeolite can be used because it can efficiently dehydrate a composition containing a fluorinated hydrocarbon compound such as HFC-134a, and the release of water from the zeolite is well suppressed even after the dehydration treatment time has elapsed. In this embodiment, commercially available Y-type zeolite can be used.

[0091] The zeolite obtained by the purification method of this embodiment can be recycled after use. In other words, the zeolite obtained by the purification method of this embodiment is reusable.

[0092] The regeneration of zeolite after use can be carried out by circulating an inert gas under heating conditions, although this is not particularly limited.

[0093] The above heating temperature may be, for example, 100°C to 300°C, preferably 150°C to 250°C.

[0094] The above-mentioned inert gas is nitrogen, argon, etc., and is preferably nitrogen.

[0095] The flow time of the inert gas may be, for example, 1 to 24 hours, preferably 3 to 15 hours, and more preferably 5 to 10 hours.

[0096] The temperature in the step of contacting the mixture with the zeolite is preferably 0°C or higher, more preferably 20°C or higher, for example 25°C or higher. According to the purification method of this embodiment, impurity gases can be removed even at relatively high temperatures. That is, the purification method of this embodiment is energy efficient because cooling in the above step is unnecessary. Furthermore, the above temperature is preferably 60°C or lower, more preferably 50°C or lower, for example 40°C or lower. Lowering the temperature can further improve the accuracy of purification. The above temperature is preferably 0°C to 60°C, more preferably 20°C to 50°C, for example 25°C to 50°C or 25°C to 40°C.

[0097] In the step of contacting the mixture with the zeolite, the W / F value is preferably less than 10, more preferably 8 or less, even more preferably 5 or less, for example 3 or less, 1 or less, or 0.5 or less. The W / F value is not particularly limited, but may be 0.01 or more, 0.1 or more, or 0.5 or more. According to the purification method of this embodiment, impurity gases can be removed even if the W / F value is small, that is, even if the flow rate is large. In other words, according to the purification method of this embodiment, impurity gases can be removed efficiently. The W / F value is preferably 0.01 or more and less than 10, more preferably 0.1 to 8, for example 0.5 to 8, 0.5 to 5, or 1 to 525°C to 40°C.

[0098] Here, the W / F value is an indicator of flow velocity and can be calculated using the following formula. W / F value = Zeolite weight (g) / Gas flow rate (cc / sec.)

[0099] The pressure in the step of contacting the mixture with the zeolite is preferably 1000 kPaG or less, more preferably 800 kPaG or less, and even more preferably 650 kPaG or less, for example 450 kPaG or less. According to the purification method of this embodiment, impurity gases can be efficiently removed even at relatively low pressure. That is, the purification method of this embodiment is energy efficient. The above pressure may also preferably be 0 kPaG or more, for example 100 kPaG or more, or 300 kPaG or more. The processing volume can be increased by increasing the pressure. The pressure may preferably be 0 kPaG to 1000 kPaG, more preferably 0 kPaG to 800 kPaG, for example preferably 0 kPaG to 650 kPaG.

[0100] The concentration of 1,1,1,2-tetrafluoroethane in the purified mixture is preferably 99.9999% by volume or higher. Furthermore, the concentration of each fluorocarbon compound in the purified mixture is preferably 1.0 ppm by volume or less, more preferably 0.5 ppm by volume or less, and even more preferably 0.1 ppm by volume or less.

[0101] This embodiment provides a gas composition containing 1,1,1,2-tetrafluoroethane in one aspect, wherein the concentration of 1,1,1,2-tetrafluoroethane is 99.9999% by volume or more.

[0102] The concentrations of the carbon-2 fluorocarbon compounds in the gas composition are preferably 1.0 ppm by volume or less, more preferably 0.5 ppm by volume or less, and even more preferably 0.1 ppm by volume or less.

[0103] The above carbon-2 fluorocarbon compound is at least one compound selected from the group consisting of 1,1,2,2-tetrafluoroethane, trifluoroethene, 2-chloro-1,1-difluoroethene, and (E / Z)1-chloro-2-fluoroethene.

[0104] (Further purification process) The purification method of this embodiment may include a step of heating the mixture (mixed gas) and / or a step of separating impurity gases from the mixture.

[0105] (The process of heat treatment) The heating step involves heating a mixture containing 1,1,1,2-tetrafluoroethane and a fluorocarbon compound having one or more double bonds, thereby converting the fluorocarbon compound having double bonds into other compounds, particularly high-boiling point compounds.

[0106] The fluorocarbon compounds having the double bond described above are typically hydrofluoroolefins (HFOs).

[0107] Examples of hydrofluoroolefins (HFOs) include 2-chloro-1,1-difluoroethene (HFO-1122), (E / Z)1-chloro-1,2-difluoroethene (HFO-1122a), trifluoroethene (HFO-1123), (E / Z)1-chloro-2-fluoroethene (HFO-1131), 2,3,3,3-tetrafluoropropene (HFO-1234yf), 3,3,3-trifluoropropene (HFO-1243zf), trans-1,3,3,3-tetrafluoropropene (HFO-1234ze), 1,3,3,3-tetrafluoropropene (HFO-1234zd), and 1,2,3,3,3-pentafluoropropene (HFO-1336mzz).

[0108] In one embodiment, the fluorocarbon compound having a double bond includes at least one compound selected from the group consisting of at least one compound selected from the group consisting of 2-chloro-1,1-difluoroethene, 1-chloro-1,2-difluoroethene, and 3,3,3-trifluoropropene.

[0109] The heat treatment process is preferably carried out by passing the mixture through a heated reaction tube. Heating by passing the mixture through a reaction tube allows for continuous processing and also enables processing of a large volume.

[0110] The reaction tube described above is preferably made of metal, such as stainless steel (SUS). Using a metal tube as the reaction tube facilitates the heating of the mixture.

[0111] The diameter of the reaction tube may preferably be 0.1 cm or more, more preferably 0.1 cm or more, and even more preferably 0.1 cm or more. Increasing the diameter of the reaction tube makes it easier to increase the flow rate of the mixture. Alternatively, the diameter of the reaction tube may preferably be 20 cm or less, more preferably 10 cm or less, and even more preferably 5 cm or less, for example, 3 cm or less or 2 cm or less. Reducing the diameter of the reaction tube improves the heating efficiency of the mixture, making it possible to heat the mixture in a shorter time. The diameter of the reaction tube may preferably be 0.1 cm to 20 cm, more preferably 0.5 cm to 10 cm, and even more preferably 1 cm to 5 cm.

[0112] The length of the reaction tube is preferably 10 cm or more, more preferably 20 cm or more, even more preferably 30 cm or more, for example, 1 m or more, 2 m or more, or 3 m or more. Increasing the length of the reaction tube increases the heating time of the mixture, allowing the mixture to be heated more reliably. Alternatively, the length of the reaction tube may be preferably 10 m or less, more preferably 5 m or less, even more preferably 3 m or less, even more preferably 1 m or less, for example, 80 cm or less or 50 cm or less. Shortening the length of the reaction tube shortens the processing time of the mixture. The length of the reaction tube may be preferably 10 cm to 10 m, more preferably 10 cm to 5 cm, even more preferably 10 cm to 1 m, for example, 10 cm to 80 cm, or 20 cm to 50 cm.

[0113] In one embodiment, a microreactor may be used as the reaction tube.

[0114] The flow rate of the mixture in the heat treatment process is preferably 100 ccm or more, more preferably 200 ccm or more, and even more preferably 300 ccm or more. Increasing the flow rate of the mixture increases the amount of mixture that can be processed. Alternatively, the flow rate of the mixture may be preferably 1000 ccm or less, more preferably 800 ccm or less, and even more preferably 500 ccm or less. By decreasing the flow rate of the mixture, it becomes possible to heat the mixture more reliably. The flow rate of the mixture may be preferably 100 ccm to 1000 ccm, more preferably 200 ccm to 800 ccm, and even more preferably 200 ccm to 500 ccm.

[0115] The heating temperature in the heat treatment step is preferably 100°C or higher, more preferably 200°C or higher, even more preferably 250°C or higher, and even more preferably 300°C or higher. By increasing the heating temperature, the fluorocarbon compound having a double bond can be more reliably converted to other compounds, typically high-boiling point compounds. Alternatively, the heating temperature may be preferably 600°C or lower, more preferably 500°C or lower, for example, 400°C or lower. By setting the heating temperature to 600°C or lower, undesirable reactions, such as the decomposition of 1,1,1,2-tetrafluoroethane, can be suppressed. The heating temperature may be preferably 100°C to 600°C, more preferably 200°C to 500°C, even more preferably 250°C to 500°C, and even more preferably 300°C to 400°C.

[0116] The heating time in the heat treatment step is preferably 5 seconds or more, more preferably 10 seconds or more, even more preferably 30 seconds or more, for example 1 minute or more, or 3 minutes or more. By increasing the heating time, the fluorocarbon compound having a double bond can be more reliably converted to other compounds, typically high-boiling point compounds. Alternatively, the heating time may be preferably 10 minutes or less, more preferably 5 minutes or less, for example 3 minutes or less, or 1 minute or less. By shortening the heating time, undesirable reactions, such as the decomposition of 1,1,1,2-tetrafluoroethane, can be suppressed. The heating time may be preferably 5 seconds to 10 minutes, more preferably 10 seconds to 5 minutes, for example 10 seconds to 3 minutes or 30 seconds to 1 minute.

[0117] The concentration of the fluorocarbon compound having a double bond in the mixture after the heat treatment step is preferably 1.0 ppm by volume or less, more preferably 0.5 ppm by volume or less, and even more preferably 0.1 ppm by volume or less.

[0118] (separation process) The purification method of this embodiment may include a separation step. The separation step is preferably performed after the heat treatment step described above.

[0119] The separation process may include rectification, distillation, extraction, and the like.

[0120] The separation step is preferably a rectification step. In the rectification step, 1,1,1,2-tetrafluoroethane is separated from components with different boiling points, such as high-boiling-point compounds produced in the heating step.

[0121] As a result of the heat treatment process described above, fluorocarbon compounds having double bonds with a boiling point similar to that of 1,1,1,2-tetrafluoroethane are converted into high-boiling-point compounds, and these compounds can be easily removed by rectification.

[0122] The theoretical number of stages in a rectification column in the rectification process is preferably 10 or more, more preferably 20 or more. From an economic standpoint, the theoretical number of stages in a rectification column used in the rectification process is preferably 60 or less, more preferably 50 or less.

[0123] In the rectification process, it is preferable to supply the mixed gas obtained in the heat treatment step of this embodiment to the middle section of the rectification column.

[0124] In the rectification process, the pressure used for rectification is preferably 0.05 to 5 MPaG (gauge pressure). The lower limit of this pressure is preferably 0.05 MPaG, more preferably 0.1 MPaG, even more preferably 0.25 MPaG, and particularly preferably 0.5 MPaG. The upper limit of this pressure is preferably 5 MPaG, more preferably 4 MPaG, even more preferably 3 MPaG, and particularly preferably 2 MPaG.

[0125] The reflux ratio of the rectification column in the rectification process is not particularly limited, but is preferably 5 to 30, and more preferably 10 to 20.

[0126] The rectification process can be carried out in discontinuous or continuous operation, but industrially, continuous operation is preferred. [Examples]

[0127] The purification method of this disclosure will be described in more detail below through the following examples, but this disclosure is not limited to these examples.

[0128] <Examples and comparative examples relating to the first embodiment described above> (Pre-purification mixed gas) A mixed gas containing 1,1,1,2-tetrafluoroethane (HFC-134a) and fluorocarbon compounds with double bonds was prepared. Analysis of the mixed gas by gas chromatography revealed that the fluorocarbon compounds with double bonds were 2-chloro-1,1-difluoroethene (HFO-1122), 1-chloro-1,2-difluoroethene (HFO-1122a), and 3,3,3-trifluoropropene (HFO-1243zf). The content of each fluorocarbon compound is shown in Table 1. The detection limit of the gas chromatography used was 0.1 ppm by volume.

[0129] (Example 1) A mixed gas was passed through a stainless steel (SUS) metal tube (1 / 2 inch in diameter, 30 cm in length) heated to 400°C at a flow rate of 300 ccm. The mixed gas at the outlet was collected and analyzed by gas chromatography. The results are shown in Table 1 below. In addition, the mixed gas was collected at the outlet of the metal tube, and 1 kg of heated mixed gas was obtained. The obtained mixed gas was purified by rectification. The purified gas was analyzed by gas chromatography, and the results are shown in Table 1.

[0130] (Example 2) The purification process was carried out in the same manner as in Example 1, except that the heating temperature was changed to 300°C. The purified gas was analyzed by gas chromatography. The results are shown in Table 1.

[0131] (Example 3) The purification process was carried out in the same manner as in Example 1, except that the heating temperature was changed to 200°C. The purified gas was analyzed by gas chromatography. The results are shown in Table 1.

[0132] (Comparative Example 1) The gas was purified using a rectification column without heat treatment. The purified gas was analyzed by gas chromatography. The results are shown in Table 1.

[0133] The results are summarized in the table below. [Table 1]

[0134] <Examples and comparative examples relating to the second embodiment described above> (Pre-purification mixed gas) A mixed gas containing 1,1,1,2-tetrafluoroethane (HFC-134a) and fluorocarbon compounds was prepared. Analysis of the mixed gas by gas chromatography revealed that the fluorocarbon compounds were 1,1,2,2-tetrafluoroethane (HFC-134), trifluoroethene (HFC-1123), 2-chloro-1,1-difluoroethene (CFC-1122), and (E / Z)1-chloro-2-fluoroethene (HCFC-1131). The content of each fluorocarbon compound is shown in Table 2. The detection limit of the gas chromatography used was 0.1 ppm by volume.

[0135] (Example 1) A 3 / 4-inch diameter cylindrical stainless steel (SUS) tube (100 cm long) was filled with 50 g of chabasite-type zeolite. A mixed gas was supplied to this SUS tube at a flow rate of W / F=5, at 25°C, and at 0 gauge pressure (0 kPaG) to purify HFC-134. The gas at the outlet of the SUS tube was periodically analyzed by gas chromatography. Even after 300 hours, HFC-134, HFC-1123, CFC-1122, and HCFC-1131 were not detected in the purified gas.

[0136] (Example 2) The purification process was carried out in the same manner as in Example 1, except that the pressure was changed to 450 kPaG. The outlet gas was analyzed after 300 hours. HFC-134, HFC-1123, CFC-1122, and HCFC-1131 were not detected in the purified gas.

[0137] (Example 3) Purification was carried out in the same manner as in Example 1, except that the temperature was changed to 40°C and the pressure to 650 kPaG. The outlet gas was analyzed after 300 hours. HFC-134, HFC-1123, CFC-1122, and HCFC-1131 were not detected in the purified gas.

[0138] (Example 4) Under the conditions of Example 3, the mixed gas was circulated until the composition of the outlet gas and the inlet gas were the same. Then, the circulation of the mixed gas was stopped, and the circulation of nitrogen was started. After that, nitrogen was circulated at 200°C for 8 hours to regenerate the adsorbent. Subsequently, purification was performed again in the same manner as in Example 3, and the outlet gas was analyzed after 300 hours. HFC-134, HFC-1123, CFC-1122, and HCFC-1131 were not detected in the purified gas.

[0139] (Example 5) The purification process was carried out in the same manner as in Example 2, except that the W / F ratio was changed to 1, and the outlet gas was analyzed after 300 hours. HFC-134, HFC-1123, CFC-1122, and HCFC-1131 were not detected in the purified gas.

[0140] (Example 6) The purification process was carried out in the same manner as in Example 2, except that the adsorbent was changed to mordenite-type zeolite, and the outlet gas was analyzed after 300 hours. The impurity concentrations of the purified gas were as follows. HFC-134 = 0.03 ppm by volume HFC-1123 = 0.08 ppm by volume CFC-1122 = 0.09 ppm HCFC-1131 = 0.03 ppm by volume

[0141] (Example 7) The purification process was carried out in the same manner as in Example 3, except that the adsorbent was changed to mordenite-type zeolite, and the outlet gas was analyzed after 300 hours. The impurity concentrations of the purified gas were as follows. HFC-134 = 0.04 ppm by volume HFC-1123 = 0.07 ppm by volume CFC-1122 = 0.10 ppm HCFC-1131 = 0.02 ppm by volume

[0142] (Example 8) The purification process was carried out in the same manner as in Example 2, except that the adsorbent was changed to beta-type zeolite, and the outlet gas was analyzed after 300 hours. The impurity concentrations of the purified gas were as follows. HFC-134 = 0.01 ppm by volume HFC-1123 = 0.02 ppm by volume CFC-1122 = Not detected HCFC-1131 = 0.02 ppm by volume

[0143] (Example 9) The purification process was carried out in the same manner as in Example 2, except that the adsorbent was changed to Y-type zeolite, and the outlet gas was analyzed after 300 hours. The impurity concentrations of the purified gas were as follows. HFC-134 = 0.05 ppm by volume HFC-1123 = Not detected CFC-1122 = 0.07 ppm HCFC-1131 = Not detected

[0144] (Comparative Example 1) The purification process was carried out in the same manner as in Example 1, except that the adsorbent was changed to type A zeolite, and the outlet gas was analyzed after 300 hours. The impurity concentrations of the purified gas were as follows. HFC-134 = 32 ppm by volume HFC-1123 = 2.3 ppm by volume CFC-1122 = 10 volumes ppm HCFC-1131 = 3.0 ppm by volume

[0145] The results are summarized in the table below. [Table 2] [Industrial applicability]

[0146] The method for purifying 1,1,1,2-tetrafluoroethane described herein is particularly suitable for use in fields where high-purity 1,1,1,2-tetrafluoroethane is required, such as in the semiconductor industry.

Claims

1. A method for purifying 1,1,1,2-tetrafluoroethane from a mixed gas containing 1,1,1,2-tetrafluoroethane and a fluorocarbon compound having one or more double bonds, the method comprising the step of heating the mixed gas.

2. The purification method according to claim 1, wherein the fluorocarbon compound having a double bond has one double bond.

3. The purification method according to claim 1, wherein the fluorocarbon compound having the double bond has two or three carbon atoms.

4. The purification method according to claim 1, wherein the fluorocarbon compound having a double bond comprises at least one compound selected from the group consisting of 2-chloro-1,1-difluoroethene, 1-chloro-1,2-difluoroethene, and 3,3,3-trifluoropropene.

5. The purification method according to claim 1, wherein the heat treatment step is performed by circulating the mixed gas through a heated reaction tube.

6. The purification method according to claim 5, wherein the flow rate of the mixed gas in the heat treatment step is 100 ccm or more and 1000 ccm or less.

7. The purification method according to claim 1, wherein the heating temperature in the heat treatment step is 100°C or more and 600°C or less.

8. The purification method according to claim 1, wherein the heating time in the heat treatment step is 5 seconds or more and 10 minutes or less.

9. The purification method according to claim 1, wherein the concentration of the fluorocarbon compound after the heat treatment step is 1.0 volume ppm or less.

10. The purification method according to claim 1, further comprising a separation step after the heat treatment step.

11. The purification method according to claim 10, wherein the separation step is a rectification step.

12. The purification method according to claim 10, wherein the concentration of 1,1,1,2-tetrafluoroethane after the separation step is 99.9999% by volume or more.

13. A method for purifying 1,1,1,2-tetrafluoroethane from a mixture containing 1,1,1,2-tetrafluoroethane and a fluorocarbon compound having 2 carbon atoms, The step of bringing the mixture into contact with zeolite is included. The zeolite is purified in a manner in which the Si / Al ratio is 3 or higher.

14. The purification method according to claim 13, wherein the carbon-2 fluorocarbon compound comprises at least one compound selected from the group consisting of 1,1,2,2-tetrafluoroethane, trifluoroethene, 2-chloro-1,1-difluoroethene, and (E / Z)1-chloro-2-fluoroethene.

15. The purification method according to claim 13, wherein the zeolite has one or more cation species selected from sodium, potassium, calcium, and magnesium.

16. The purification method according to claim 13, wherein the zeolite is at least one zeolite selected from the group consisting of chabazite-type zeolite, mordenite-type zeolite, beta-type zeolite, and Y-type zeolite.

17. The purification method according to claim 13, wherein the zeolite is a chabazite-type zeolite.

18. The purification method according to claim 13, wherein the temperature in the step of contacting the zeolite with the mixture is 0°C or more and 60°C or less.

19. The purification method according to claim 13, wherein the W / F value in the step of contacting the mixture with the zeolite is less than 10.

20. The purification method according to claim 13, wherein the pressure in the step of contacting the mixture with the zeolite is 0 kPaG or more and 1000 kPaG or less.

21. The purification method according to claim 13, wherein the concentration of each fluorocarbon compound after purification is 1.0 volume ppm or less.

22. A gas composition containing 1,1,1,2-tetrafluoroethane, wherein the concentration of 1,1,1,2-tetrafluoroethane is 99.9999% by volume or more.

23. The gas composition according to claim 22, wherein the concentration of one or more fluorocarbon compounds having double bonds in the gas composition is 1.0 volume ppm or less for each compound.

24. The gas composition according to claim 23, wherein the fluorocarbon compound having a double bond is at least one compound selected from the group consisting of 2-chloro-1,1-difluoroethene, 1-chloro-1,2-difluoroethene, and 3,3,3-trifluoropropene.

25. The gas composition according to claim 22, wherein the concentration of each carbon-2 fluorocarbon compound in the gas composition is 1.0 volume ppm or less.

26. The gas composition according to claim 25, wherein the carbon-2 fluorocarbon compound is at least one compound selected from the group consisting of 1,1,2,2-tetrafluoroethane, trifluoroethene, 2-chloro-1,1-difluoroethene, and (E / Z)1-chloro-2-fluoroethene.

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