KR102803124B1 - Method of purifying vinylidene fluoride from pyrolysis products of fluorocarbon and Purifying system used therein - Google Patents

Abstract

The present invention discloses a method for purifying ethylene difluoride by removing impurities from a mixture obtained by thermally decomposing carbon fluorocarbon through general distillation and extractive distillation, and discloses a purification system including a _CO2 removal absorption purification tower, a washing tower, a drying tower for removing moisture, a distillation tower for removing compounds having a boiling point higher than ethylene difluoride, an extractive distillation tower for removing compounds having a boiling point lower than or similar to ethylene difluoride, and an extraction solvent inlet used in the method for purifying ethylene difluoride.

Description

{Method of purifying vinylidene fluoride from pyrolysis products of fluorocarbon and purifying system used therein}

The present invention relates to a purification method and a purification system for obtaining difluorinated ethylene from a mixture obtained by thermally decomposing carbon fluorocarbon, and more specifically, to a purification method and a purification system for stably obtaining difluorinated ethylene by sequentially removing various impurities from a thermally decomposed mixture containing difluorinated ethylene obtained by thermally decomposing carbon fluorocarbon at high temperature.

There are two commercially available methods for purifying 1,1-difluoroethylene, better known as VDF (vinylidene fluoride): thermal decomposition of HCFC-142b (ClCF ₂ -CH ₃ ) and co-thermal decomposition of CFC-22 (CF ₂ HCl) and methane chloride (CH ₃ Cl). Both methods produce a large amount of hydrochloric acid, and about 20 types of products are obtained through various series and parallel reactions. In particular, difluorinated ethylene is generated through the above thermal decomposition process, and when looking at the types of gases generated, in addition to the main product, difluorinated ethylene, depending on the reaction conditions, C1 compounds such as CH ₄ , CF ₄ , CO ₂ , CHF ₃ , CH ₂ F ₂ , CH ₃ F, C2 compounds such as TFE (CF ₂ =CF ₂ ), TrFE (CF ₂ =CHF), CTFE (CF ₂ =CFCl) and various C3 to C6 compounds are generated. The generated compounds have various physical properties individually, and various separation processes are used to separate and purify them. Due to the simplicity and economic feasibility of the separation process, a distillation process by the difference in boiling point and vapor pressure can be considered as a priority.

When separating the above mixture through distillation, it is expected that two distillation processes will be necessary to separate the target difluorinated ethylene: ① separation of compounds with lower boiling points than difluorinated ethylene, and ② separation of compounds with higher boiling points than difluorinated ethylene. However, when distilling and purifying difluorinated ethylene, it is very difficult to separate and purify compounds (CO ₂ , CH ₂ F, CHF 3 , CF 2 =CF 2 , CH 2 F ₂ , CH ₂ =CHF, _CHF =CF ₂ , CF ₂ HCl) that have smaller differences in boiling points and vapor pressures _depending on temperature compared to difluorinated ethylene, and even if distillation is performed, it is expected that it will be difficult to utilize commercially because a very high number _of stages is required _. Figure 1 is a simulation of the vapor pressure curves of compounds having similar boiling points to ethylene difluoride among the generated mixtures using the process simulation program Aspen. It can be expected that CHF ₃ is the most difficult to separate, and adjacent CH ₃ F, CF ₂ = CF ₂ , CH ₂ = CHF are also not easy to separate and remove. In addition, if the distillation process using the boiling point is performed at a low temperature, various equipment in the distillation process may be damaged due to CO ₂ , a solid-gas phase change compound, which may cause malfunction of the process equipment. On the other hand, if the operating temperature is increased to separate using vapor pressure rather than boiling point, the pressure of the entire separation process system increases rapidly, which is commercially extremely disadvantageous in terms of manufacturing, licensing, and operating the equipment.

There has been no published case on a separation process for purifying difluoride ethylene with high purity from a mixture containing various impurities and difluoride ethylene obtained by thermal decomposition of 1-chloro-1,1-difluoroethane (HCFC-142b) or co-thermal decomposition of chlorodifluoromethane (CFC-22) and methane chloride (CH ₃ Cl). However, information on the possibility of high-purity distillation of difluoride ethylene model gas containing high-concentration fluoromethane (CHF _3, 10-50%), which is expected to be difficult to separate, by extractive distillation using computer simulation is presented in International Publication No. WO2015/072305. On the other hand, it is difficult to find an example of purifying difluoride ethylene with high purity through a purification process targeting the entire actual pyrolysis mixture gas.

Accordingly, the inventors of the present invention have intensively conducted research for several decades on a separation process for developing a process capable of purifying high-purity difluoroethylene from a mixture containing difluoroethylene obtained by thermal decomposition of 1-chloro-1,1-difluoroethane (HCFC-142b) or co-thermal decomposition of chlorodifluoromethane (CFC-22) and methane chloride (CH ₃ Cl), and have completed the present invention.

An object of one aspect of the present invention is to provide a method and a purification system for purifying difluoride ethylene through a purification process for separating various impurities other than difluoride ethylene from a fluorocarbon pyrolysis mixture containing difluoride ethylene, particularly compounds having a smaller difference in boiling point and vapor pressure according to temperature compared to difluoride ethylene.

In order to solve the above problem, the present invention provides the following solution.

The present invention, in one aspect,

In a method for purifying difluoroethylene from a mixture obtained by thermal decomposition of carbon fluorocarbon,

The above mixture contains difluoroethylene (CH ₂ =CF ₂ ) and trifluoromethane (CHF ₃ ),

The above purification method includes a distillation process using three distillation towers connected in series,

The above distillation process provides a purification method, characterized in that it includes extractive distillation in which an extractant containing a C5-C12 straight-chain alkane that selectively dissolves ethylene difluoride is introduced into the distillation process.

In another aspect, the present invention

In a method for purifying difluoroethylene from a mixture obtained by thermal decomposition of carbon fluorocarbon,

The above mixture contains difluoroethylene (CH ₂ =CF ₂ ) and trifluoromethane (CHF ₃ ),

The above purification method includes a distillation process using three distillation towers connected in series,

The above distillation process is,

A step of introducing the above mixture into distillation tower No. 1 and performing a first distillation to recover a distillation fraction enriched in difluoroethylene and trifluoromethane;

A step of introducing the distillation fraction recovered from the first distillation tower into the second distillation tower and performing a second distillation while introducing an extraction solvent to recover an extraction solvent fraction in which difluoroethylene is dissolved;

A purification method is provided, including the step of introducing the extraction solvent recovered from the second distillation tower into the third distillation tower and performing a third distillation to recover a difluoroethylene fraction.

In another aspect, the present invention

In a method for purifying difluoroethylene from a mixture obtained by thermal decomposition of carbon fluorocarbon,

The above mixture contains difluoroethylene (CH ₂ =CF ₂ ) and trifluoromethane (CHF ₃ ),

The above purification method includes a distillation process using three distillation towers connected in series,

The above distillation process is,

A step of introducing the above mixture into a first distillation tower and performing a first distillation, adding an extraction solvent, and recovering an extraction solvent fraction in which difluoroethylene and high-boiling-point compounds are dissolved;

A step of introducing the extraction solvent fraction recovered from the first distillation tower into the second distillation tower and performing a second distillation to recover the difluoroethylene fraction and the extraction solvent fraction;

A purification method is provided, including a step of introducing an extraction solvent fraction recovered from a second distillation tower into a third distillation tower to remove impurities included in the extraction solvent fraction and recover the extraction solvent.

In another aspect, the present invention

A purification system used in the above purification methods is provided.

Through the high-purity difluorinated ethylene purification method according to the present invention, a fluorocarbon pyrolysis mixture can be subjected to general distillation and extractive distillation to purify difluorinated ethylene, which is a basic raw material with very high industrial utility, such as fluororesin and secondary batteries, to a high purity.

Using the ethylene difluoride purification system according to the present invention, ethylene difluoride, which has a variety of commercial uses, can be easily purified in large quantities with high purity.

Figure 1 shows the results of simulating the vapor pressure change of compounds with similar boiling points to difluoroethylene among pyrolysis products using the process simulation program Aspen.
Figure 2 is a schematic diagram illustrating a purification system for purifying high-purity difluoroethylene from pyrolysis product of fluorocarbon according to the present invention.

The present invention is described in detail below.

Meanwhile, the embodiments of the present invention may be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. In addition, the embodiments of the present invention are provided to more completely explain the present invention to a person having average knowledge in the relevant technical field.

Furthermore, reference throughout the specification to an element “including” means that, unless otherwise specifically stated, it may include other elements, rather than excluding other elements.

In this specification, the term difluoroethylene is used to refer to 1,1-difluoroethylene, i.e., VDF.

The present invention is described in more detail as follows.

In this specification,

The mixture obtained by thermal decomposition of fluorocarbon contains difluoroethylene (CH ₂ = CF ₂ ) and trifluoromethane (CHF ₃ ), and may additionally contain fluorine or chlorine compounds having similar boiling points.

The above mixture may be a mixture obtained through thermal decomposition of 1-chloro-1,1-difluoroethane (HCFC-142b) or co-thermal decomposition of chlorodifluoromethane (CFC-22) and methane chloride (CH ₃ Cl), but the fluorocarbon is not limited thereto.

The above mixture additionally contains carbon dioxide (CO ₂ ), methane (CH ₄ ), fluoromethane (CH ₃ F), tetrafluoroethylene (CF ₂ =CF ₂ ), difluoromethane (CH ₂ F ₂ ), fluoroethene (CH ₂ =CHF), trifluoroethylene (CHF = CF ₂ ), norflurane (CF ₃ CH ₂ F), hexafluoropropylene (CF ₂ =CFCF ₃ ), difluorochloromethane (CF ₂ HCl), chloromethane (CH ₃ Cl), 2,3,3,3-tetrafluoro-1-propene (CF ₃ CF = CH ₂ ), 3,3,3,-trifluoropropene (CF ₃ CH = CH ₂ ), 1-chloro-1-fluoro-ethene (CFCl = CH ₂ ), 2-chloro-1,1-difluoro-ethylene (CF ₂ =CHCl) and It may further include one or more compounds selected from the group consisting of 2-chloro-1,1,1,2-tetrafluoroethane (CF ₃ CFHCl).

The above purification method includes a distillation process using three distillation towers connected in series, wherein each distillation tower can be independently configured with 20 to 60 stages, or 30 to 50 stages.

Meanwhile, the purification method of the present invention is characterized by using an extraction solvent so that trifluoromethane, which is difficult to separate from difluoroethylene, can be efficiently separated through a distillation process. A C5-C12 straight-chain alkane can be used as the extraction solvent, and since the extraction solvent has relatively better solubility in difluoroethylene than in trifluoromethane, it enables separation of trifluoromethane and difluoroethylene, which are difficult to separate through distillation. That is, since difluoroethylene is well soluble in the extraction solvent, it can be separated from trifluoromethane in a form dissolved in the extraction solvent in the fractionation section of the extraction solvent during distillation.

The above extraction solvent can be selected from the group consisting of pentane, hexane, heptane, octane, nonane, decane, undecane and dodecane, and in the present invention, hexane is selected as a specific example.

In the present invention, three distillation towers are connected in series so that the distillation process is performed continuously, and the extraction solvent can be injected into distillation tower 1 or distillation tower 2.

In one aspect of the present invention, the distillation process comprises:

A step of introducing the above mixture into distillation tower No. 1 and performing a first distillation to recover a distillation fraction enriched in difluoroethylene and trifluoromethane;

A step of introducing the distillation fraction recovered from the first distillation tower into the second distillation tower and performing a second distillation while introducing an extraction solvent to recover an extraction solvent fraction in which difluoroethylene is dissolved;

It includes a step of introducing the extraction solvent fraction recovered from the second distillation tower into the third distillation tower and performing a third distillation to recover the difluoroethylene fraction.

In a further example, the distillation process comprises:

A step of introducing the mixture into the central portion of a distillation tower No. 1 consisting of 20 to 60 stages, performing a first distillation, and recovering a distillation fraction enriched in difluoroethylene and trifluoromethane from the bottom;

A step of introducing the distillation fraction recovered from the first distillation tower into the central portion of the second distillation tower consisting of 20 to 60 stages and performing a second distillation, while introducing hexane as an extraction solvent and recovering the extraction solvent fraction in which difluoroethylene is dissolved from the bottom;

It may include a step of introducing the extracted solvent fraction recovered from the second distillation tower into the central portion of the third distillation tower consisting of 10 to 30 stages and performing a third distillation to recover the difluoroethylene fraction from the top.

In another aspect of the present invention, the distillation process comprises:

A step of introducing the above mixture into a first distillation tower and performing a first distillation, adding an extraction solvent, and recovering an extraction solvent fraction in which difluoroethylene and high-boiling-point compounds are dissolved;

A step of introducing the extraction solvent fraction recovered from the first distillation tower into the second distillation tower and performing a second distillation to recover the difluoroethylene fraction and the extraction solvent fraction;

It includes a step of introducing the extraction solvent fraction recovered from the second distillation tower into the third distillation tower to remove impurities included in the extraction solvent fraction and recover the extraction solvent.

In a further example, the distillation process may be:

A step of introducing the mixture into the central portion of a distillation tower No. 1 consisting of 20 to 60 stages, performing a first distillation, and recovering a distillation fraction enriched in difluoroethylene and trifluoromethane from the bottom;

A step of introducing the distillation fraction recovered from the first distillation tower into the central portion of the second distillation tower consisting of 20 to 60 stages and performing a second distillation, while introducing hexane as an extraction solvent and recovering the extraction solvent fraction in which difluoroethylene is dissolved from the bottom;

It may include a step of introducing the extracted solvent fraction recovered from the second distillation tower into the central portion of the third distillation tower consisting of 10 to 30 stages and performing a third distillation to recover the difluoroethylene fraction from the top.

Another aspect of the present invention is:

The method may further include a process of recovering the extraction solvent recovered from the second or third distillation tower and recycling it to the distillation process.

In the above distillation process, the center of the distillation column means a point 1/3 to 2/3 from the bottom of the distillation column, the lower part means a point starting from the bottom of the distillation column to a point 1/3, 2/10, or 1/10 from the bottom of the column, and the upper part means a point starting from the top of the distillation column to a point 1/3, 2/10, or 1/10 from the top of the column.

The above extraction solvent can be fed into the distillation process from the extraction solvent supply section, and can be optionally fed to the top of the second distillation tower or the first distillation tower, and in each case, can be recovered from the bottom of the third distillation tower or the bottom of the second distillation tower.

In this way, the extraction solvent recovered from the bottom of the third or second distillation tower can be recycled to the distillation tower through the extraction solvent supply unit.

In another aspect of the present invention,

The above purification method may optionally further include a pretreatment step.

For pyrolysis mixtures, carbon dioxide (CO ₂ ) may be additionally included.

In this case, the above preprocessing step is,

It may include a step of passing the thermal decomposition mixture through a _CO2 removal absorption reactor containing a basic solution to remove carbon dioxide contained in the mixture;

It may further include a step of passing the thermal decomposition mixture that has passed through the _CO2 removal absorption tower through a cleaning tower to remove the base component contained therein;

The method may additionally include a step of passing the pyrolysis mixture that has passed through the cleaning tower through an adsorption and moisture drying tower to remove moisture.

The present invention additionally provides a purification system in which the above purification method is used.

The above purification system

Distillation tower 1;

2nd distillation tower;

3rd distillation tower; and

Includes an extraction solvent supply unit.

The purification system may optionally further include a fluorocarbon pyrolysis reactor, a _CO2 removal absorption reactor, a scrubbing tower, and an adsorption and moisture drying tower.

The roles performed by each of the above components are as described in the purification method described above.

The purification system is explained with reference to the drawings.

FIG. 2 is a conceptual diagram of an example of a high-purity difluoroethylene purification system according to the present invention, and the present invention is not limited to the scope of FIG. 2. In the conceptual diagram, a fluorocarbon pyrolysis reactor (1) is a reactor that performs co-thermal decomposition, such as pyrolysis of 1-chloro-1,1-difluoroethane (HCFC-142b) or co-thermal decomposition of chlorodifluoromethane (CFC-22) and methane chloride (CH ₃ Cl), using only fluorocarbon or fluorocarbon and high-temperature steam or nitrogen as a heat source. The pyrolysis reaction reactor (1) includes a preheater, a reactor, a rapid cooler, and the reaction temperature may vary depending on the fluorocarbon used, and preferably, the pyrolysis reaction is performed in the range of 500 to 1000°C. The reactor may be either a batch type or a continuous type, and preferably, a continuous plug flow type reactor may be used. The residence time within the reactor at this time can range from 0.05 to 5 seconds.

The mixture obtained from the above thermal decomposition reaction device (1) includes a gas mixture having various types and compositions, representatively listed in Table 1, but is not limited thereto.

The above pyrolysis mixture particularly includes difluoroethylene (CH ₂ = CF ₂ ) and trifluoromethane (CHF ₃ ), and may further include compounds listed in Table 1 excluding these.

number Chemical formula designation Boiling point (℃) 1 CO ₂ Carbon dioxide -78.5 2 CH ₄ methane -182.5 3 CH ₃ F Fluoromethane -78.4 4 CHF ₃ Trifluoromethane (R-23) -82.1 5 CF ₂ =CF ₂ Tetrafluoroethylene -76.3 6 CH ₂ F ₂ Difluoromethane -52 7 CH ₂ =CF ₂ difluoroethylene (VDF) -84 8 CH ₂ =CHF Fluoroethene -72.2 9 CHF=CF ₂ Trifluoroethylene -51 10 CF ₂ =CFCF ₃ Hexafluoropropylene -29.4 11 CF ₃ CH ₂ F Norflurane -26.3 12 CF ₂ HCl Difluorochloromethane -40.7 13 CH ₃ Cl Chloromethane -23.8 14 CF ₃ CF=CH ₂ 2,3,3,3-Tetrafluoro-1-propene -30 15 CF ₃ CH=CH ₂ 3,3,3,-trifluoropropene -18 16 CFCl=CH ₂ 1-chloro-1-fluoro-ethene -24 17 CF ₂ =CHCl 2-chloro-1,1-difluoro-ethylene -17 18 CF ₃ CFHCl 2-Chloro-1,1,1,2-tetrafluoroethane -12

Among the above mixtures, CO ₂ , which is a compound that can cause problems such as equipment malfunction due to phase change from a gaseous phase to a solid phase in the low-temperature distillation process, can be removed in a pretreatment process before the distillation process. To this end, the mixtures can be passed through a CO ₂ removal absorption tower (2) as shown in FIG. 2 to remove CO ₂ in the mixture. A packed tower can be used as the CO ₂ removal absorption tower (2), and in the case of a packed tower, a basic aqueous solution in which a hydroxide such as NaOH is dissolved is used so that the gas and the aqueous solution are crossed in a countercurrent manner to remove most of the CO ₂ in the mixture. When NaOH is used among the hydroxides capable of removing CO ₂ , the concentration of the aqueous solution is not particularly limited, but is preferably 9 to 20 wt%. The mixture obtained by passing through the above _CO2 removal absorption reaction tower (2) is fed to the bottom of a washing tower (3) filled with Raschig rings, and water flowing from the top is passed through to remove basic components such as fine particles of a hydroxide solution, and additional absorption purification of trace amounts of _CO2 and drying of moisture are performed in an absorption and moisture drying tower (4) filled with a molecular sieve, etc., and through this process, _CO2 in the mixture is removed and fed to a distillation process. This process can be modified and designed by a person skilled in the art to which the present invention pertains to suit the purpose of the present invention, and is not limited by the embodiments of the present invention.

The mixture from which the above _CO2 has been removed is purified into high-purity difluorinated ethylene through a distillation process. In the above mixture, there are various compounds having boiling points similar to difluorinated ethylene. Therefore, in order to separate them using a general distillation method, a large facility investment of more than 100 stages is required, and the energy cost is also very high, making it commercially uneconomical. In the present invention, as a result of testing various combinations of distillation processes, it was found that two processes are suitable.

The first process is a method in which the distillation fractions, in which difluoroethylene and trifluoromethane among the low boiling point compounds in Table 1 are concentrated, are purified upwardly in the first distillation tower and high boiling point compounds of CH ₂ = CHF or lower are separated downwardly, and in the second distillation tower, a saturated hydrocarbon that selectively dissolves difluoroethylene is used as an extraction solvent to conduct extractive distillation, thereby discharging compounds that are insoluble in the extraction solvent, such as CH ₄ to CHF ₃ , upwardly and recovering the extraction solvent and difluoroethylene dissolved therein downwardly, and in the third distillation tower, a third distillation is performed to recover high-purity difluoroethylene and the extraction solvent.

The second process is an extractive distillation using a saturated hydrocarbon as an extraction solvent that selectively dissolves ethylene difluoride in the first distillation tower, discharges compounds that are not dissolved in the extraction solvent, such as CH ₄ to CHF ₃ , from the top, recovers high-purity ethylene difluoride from the top through distillation in the second distillation tower, recovers the extraction solvent and compounds dissolved in it from the bottom, and separates high-boiling-point compounds of CH ₂ = CHF or lower dissolved in the extraction solvent in the third distillation tower and recovers the extraction solvent. It was found that this method is suitable.

In the above distillation process, each distillation tower may have a raw material inlet, an extraction solvent supply section, a high boiling point compound recovery section, a low boiling point compound recovery section, or an extraction solvent recovery section. In addition, each distillation tower may have an unlimited number of stages, and in the embodiment of the present invention, 40-stage and 20-stage distillation towers were used, which may be designed and modified to suit the purpose by a person skilled in the art to which the present invention pertains.

The above distillation process may be performed through a plurality of distillation columns, and preferably through three distillation columns. The three distillation columns may be connected in series with each other, and the extraction solvent supply section and the extraction solvent recovery section may be connected to each other.

The above distillation process can be carried out under pressure, and it is preferable that the pressurization be carried out within a commercially usable range. For example, the distillation process can be carried out under a pressure of 15 atm or less.

The above distillation process can be performed by a person skilled in the art to which the present invention pertains selecting the upper and lower temperatures of the distillation column to suit the purpose of the present invention, and preferably, the upper and lower temperatures of the distillation column can be set within a commercially usable range.

In the above extractive distillation process, as an extraction solvent that selectively dissolves ethylene difluoride, a hydrocarbon having 5 to 12 carbon atoms and having a large difference in boiling point from ethylene difluoride and a low polarity (relative polarity) of about 0.01 is suitable. Specific examples thereof include one or more straight-chain alkanes selected from the group consisting of pentane, hexane, heptane, octane, nonane, decane, undecane, and dodecane, and cyclohexane. In the examples of the present invention, hexane was used as an extraction solvent, which can be selected according to the purpose by a person skilled in the art to which the present invention pertains, and is not limited by specific examples.

The above purification method can be carried out using a purification system including the above-mentioned fluorocarbon thermal decomposition reactor (1) and the _CO2 removal absorption reactor (2), the washing tower (3), and the adsorption and moisture drying tower (4) used in the pretreatment process prior to the distillation process, and the high-boiling-point compound removal distillation tower (5), the low-boiling-point and near-boiling-point removal extractive distillation tower (6), and the extraction solvent recovery distillation tower (7) used in the distillation process. This is an example, and the present invention is not limited thereto.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

<Example 1>

Using the pyrolysis reaction system of Fig. 1, the first gas composition as shown in Table 2 was obtained. The obtained gas composition was passed through a CO2 absorption tower, a scrubbing tower, and an adsorption tower to obtain a gas mixture before the distillation process, which was then purified through three distillation towers. Distillation purification separated a low-boiling-point mixed gas including difluorinated ethylene from the top of the first distillation tower, and separated a high-boiling-point compound including monofluorinated ethylene from the bottom. Extractive distillation using hexane was attempted in the second distillation tower, and low-boiling-point substances such as CH ₄ and CHF ₃ that are difficult to separate from difluorinated ethylene were discharged from the top, and difluorinated ethylene and hexane were separated from the bottom. The amount of hexane used at this time was 15 kg/h. In the third distillation tower, difluorinated ethylene and hexane with a large boiling point difference were separated. A trace amount of CH ₃ F and CF ₂ =CF ₂ contained in the hexane solution obtained from the bottom of the third distillation tower were recovered, purified, and released at atmospheric pressure. The three distillation towers had 40, 40, and 20 stages, respectively. The purity of the purified difluoroethylene was 99.95%, and the purification yield was approximately 90.59%. The temperature and pressure at the top and bottom of the three distillation towers were approximately -26℃ and 10~13 atm, which are commercially usable ranges. The refrigeration heat capacity was 3.354 kW, and the heating heat capacity was 5.888 kW.

No Formula pyrolysis
Gas composition
(wt %) Composition after _CO2 absorption tower + cleaning tower + adsorption tower treatment (wt%) Composition after distillation tower 1 (wt%) Composition after distillation tower 2 (wt%) Composition after distillation tower 3 (wt%) Top Bottom Top Bottom Top Bottom 1 CO ₂ 0.0244 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 2 CH ₄ 0.0033 0.0033 0.0062 0.0000 0.0681 0.0000 0.0000 0.0000 3 CH ₃ F 0.0009 0.0010 0.0004 0.0016 0.0000 0.0001 0.0004 0.0000 4 CHF ₃ 0.0179 0.0184 0.0339 0.0003 0.3730 0.0000 0.0000 0.0000 5 CF ₂ =CF ₂ 0.0086 0.0089 0.0001 0.0191 0.0000 0.0000 0.0001 0.0000 6 CH ₂ F ₂ 0.0175 0.0180 0.0000 0.0390 0.0000 0.0000 0.0000 0.0000 7 CH ₂ =CF ₂ 0.5275 0.5407 0.9594 0.0510 0.5589 0.2499 0.9995 0.0000 8 CH ₂ =CHF 0.0056 0.0058 0.0000 0.0125 0.0000 0.0000 0.0000 0.0000 9 CHF=CF ₂ 0.0039 0.0040 0.0000 0.0088 0.0000 0.0000 0.0000 0.0000 10 CF ₂ =CFCF ₃ 0.0165 0.0169 0.0000 0.0366 0.0000 0.0000 0.0000 0.0000 11 CF ₃ CH ₂ F 0.0041 0.0042 0.0000 0.0090 0.0000 0.0000 0.0000 0.0000 12 CF ₂ HCl 0.0088 0.0090 0.0000 0.0195 0.0000 0.0000 0.0000 0.0000 13 CH ₃ Cl 0.0939 0.0963 0.0000 0.2088 0.0000 0.0000 0.0000 0.0000 14 CF ₃ CF=CH ₂ 0.1666 0.1708 0.0000 0.3705 0.0000 0.0000 0.0000 0.0000 15 CF ₃ CH=CH ₂ 0.0057 0.0058 0.0000 0.0126 0.0000 0.0000 0.0000 0.0000 16 CFCl=CH ₂ 0.0083 0.0085 0.0000 0.0184 0.0000 0.0000 0.0000 0.0000 17 CF ₂ =CHCl 0.0081 0.0083 0.0000 0.0180 0.0000 0.0000 0.0000 0.0000 18 CF ₃ CFHCl 0.0784 0.0803 0.0000 0.1743 0.0000 0.0000 0.0000 0.0000 19 n-Hexane - - - - 0.0000 0.7500 0.0000 1.0000 Total 1.00 1.00 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 Total Flow (kg/h) 10.025 10.2041 5.5000 4.7041 0.5000 20.0000 5.0000 15.0000 Driving pressure (atmG) - - 10.0 13.0 10.0 Heat exchanger temperature (℃) - - -26.3 27.9 -26.3 30.1 -25.4 171.9 Heat Duty (kW) - - -2.800 3.128 -0.260 0.791 -0.294 1.969

<Example 2>

In the same system as Example 1, the distillation purification method was changed to input the same amount of 15 kg/h of hexane into the first distillation tower, and after separating the mixture of difluoroethylene and hexane in the second distillation tower, hexane and the remaining compounds were separated in the third distillation tower. The results are shown in Table 3. The purity of the purified difluoroethylene was 99.93%, and the purification yield was approximately 90.57%. The temperatures and pressures at the top and bottom of the three distillation towers were approximately -26 ℃ and 14.0 atm, which are commercially usable ranges. The cooling heat capacity was 3.373 kW, and the heating heat capacity was 4.978 kW.

No Formula pyrolysis
Gas composition
(wt %) Composition after _CO2 absorption tower + cleaning tower + adsorption tower treatment (wt%) Composition after distillation tower 1 (wt%) Composition after distillation tower 2 (wt%) Composition after distillation tower 3 (wt%) Top Bottom Top Bottom Top Bottom 1 CO ₂ 0.0244 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 2 CH ₄ 0.0033 0.0033 0.0851 0.0000 0.0000 0.0000 0.0000 0.0000 3 CH ₃ F 0.0009 0.0010 0.0002 0.0004 0.0005 0.0004 0.0015 0.0000 4 CHF ₃ 0.0179 0.0184 0.4686 0.0000 0.0001 0.0000 0.0000 0.0000 5 CF ₂ =CF ₂ 0.0086 0.0089 0.0001 0.0036 0.0001 0.0045 0.0187 0.0000 6 CH ₂ F ₂ 0.0175 0.0180 0.0000 0.0074 0.0000 0.0093 0.0382 0.0000 7 CH ₂ =CF ₂ 0.5275 0.5407 0.4460 0.2152 0.9993 0.0173 0.0712 0.0000 8 CH ₂ =CHF 0.0056 0.0058 0.0000 0.0024 0.0000 0.0030 0.0122 0.0000 9 CHF=CF ₂ 0.0039 0.0040 0.0000 0.0017 0.0000 0.0021 0.0086 0.0000 10 CF ₂ =CFCF ₃ 0.0165 0.0169 0.0000 0.0069 0.0000 0.0087 0.0358 0.0000 11 CF ₃ CH ₂ F 0.0041 0.0042 0.0000 0.0017 0.0000 0.0021 0.0088 0.0000 12 CF ₂ HCl 0.0088 0.0090 0.0000 0.0037 0.0000 0.0046 0.0191 0.0000 13 CH ₃ Cl 0.0939 0.0963 0.0000 0.0396 0.0000 0.0496 0.2045 0.0000 14 CF ₃ CF=CH ₂ 0.1666 0.1708 0.0000 0.0703 0.0000 0.0880 0.3628 0.0000 15 CF ₃ CH=CH ₂ 0.0057 0.0058 0.0000 0.0024 0.0000 0.0030 0.0123 0.0000 16 CFCl=CH ₂ 0.0083 0.0085 0.0000 0.0035 0.0000 0.0044 0.0180 0.0000 17 CF ₂ =CHCl 0.0081 0.0083 0.0000 0.0034 0.0000 0.0043 0.0176 0.0000 18 CF ₃ CFHCl 0.0784 0.0803 0.0000 0.0331 0.0000 0.0414 0.1707 0.0000 19 n-Hexane - - 0.0000 0.6047 0.0000 0.7574 0.0000 1.0000 Total 1.00 1.00 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 Total Flow (kg/h) 10.025 10.2041 0.4000 24.8041 5.0000 19.8041 4.8041 15.000 Driving pressure (atmG) - - 14.0 10.0 0.5 Heat exchanger temperature (℃) - - -26.1 34.1 -25.5 83.9 -18.6 82.7 Heat Duty (kW) - - -0.209 1.179 -2.525 3.133 -0.639 0.666

<Comparative Example 1>

In the same system as Example 1, the distillation purification method was changed by using only two distillation towers so that compounds having a lower boiling point than difluoride ethylene were normally distilled in distillation tower 1, and compounds having a higher boiling point than difluoride ethylene were distilled and purified in distillation tower 2. The results are shown in Table 4. The purity of the purified difluoride ethylene was 96.93%, and the purification yield was approximately 90.48%. The temperatures and pressures at the top and bottom of the two distillation towers were approximately -22°C and 14 atm, which are commercially usable ranges. The cooling heat amount was 2.834 kW, and the heating heat amount was 3.192 kW. Through this comparative example, it can be seen that high-purity difluoride ethylene cannot be obtained when only two distillation towers are used.

No Formula pyrolysis
Gas composition
(wt %) Composition after _CO2 absorption tower + cleaning tower + adsorption tower treatment (wt%) Composition after distillation tower 1 (wt%) Composition after distillation tower 2 (wt%) Top Bottom Top Bottom 1 CO ₂ 0.0244 0.0000 0.0000 0.0000 0.0000 0.0000 2 CH ₄ 0.0033 0.0033 0.0619 0.0000 0.0000 0.0000 3 CH ₃ F 0.0009 0.0010 0.0003 0.0010 0.0012 0.0008 4 CHF ₃ 0.0179 0.0184 0.0664 0.0157 0.0293 0.0000 5 CF ₂ =CF ₂ 0.0086 0.0089 0.0002 0.0093 0.0002 0.0198 6 CH ₂ F ₂ 0.0175 0.0180 0.0000 0.0190 0.0000 0.0407 7 CH ₂ =CF ₂ 0.5275 0.5407 0.8711 0.5218 0.9693 0.0102 8 CH ₂ =CHF 0.0056 0.0058 0.0000 0.0061 0.0000 0.0130 9 CHF=CF ₂ 0.0039 0.0040 0.0000 0.0043 0.0000 0.0091 10 CF ₂ =CFCF ₃ 0.0165 0.0169 0.0000 0.0178 0.0000 0.0382 11 CF ₃ CH ₂ F 0.0041 0.0042 0.0000 0.0044 0.0000 0.0094 12 CF ₂ HCl 0.0088 0.0090 0.0000 0.0095 0.0000 0.0204 13 CH ₃ Cl 0.0939 0.0963 0.0000 0.1017 0.0000 0.2181 14 CF ₃ CF=CH ₂ 0.1666 0.1708 0.0000 0.1805 0.0000 0.3870 15 CF ₃ CH=CH ₂ 0.0057 0.0058 0.0000 0.0061 0.0000 0.0131 16 CFCl=CH ₂ 0.0083 0.0085 0.0000 0.0090 0.0000 0.0192 17 CF ₂ =CHCl 0.0081 0.0083 0.0000 0.0088 0.0000 0.0188 18 CF ₃ CFHCl 0.0784 0.0803 0.0000 0.0849 0.0000 0.1820 19 n-Hexane - - - - - - Total 1.00 1.00 1.0000 1.0000 1.0000 1.0000 Total Flow (kg/h) 10.025 10.2041 0.5500 9.6541 5.1500 4.5041 Driving pressure (atmG) - - 14.0 11.0 Heat exchanger temperature (℃) - - -22.4 0.5 -22.5 38.4 Heat Duty (kW) - - -0.280 0.374 -2.554 2.818

<Comparative Example 2>

In the system of Example 1, one distillation tower was added and the distillation purification method was changed so that compounds having a boiling point lower than difluorinated ethylene were normally distilled in distillation tower No. 1, 15 kg/h of hexane was fed into distillation tower No. 2 to separate difluorinated ethylene and low-boiling-point substances that were difficult to separate, then difluorinated ethylene was separated from the top in distillation tower No. 3 and a hexane mixture was separated from the bottom, and then hexane and the remaining high-boiling-point substances were separated in distillation tower No. 4. The results are shown in Table 5. The purity of the purified difluorinated ethylene was 99.93%, and the purification yield was approximately 90.57%. The temperatures and pressures at the top and bottom of the four distillation towers were approximately -26℃ and 15 atm, which are commercially usable ranges. The cooling heat capacity was 5.929 kW, and the heating heat capacity was 7.659 kW. When four distillation towers are used, the purity is not significantly higher than when three distillation towers are used, and it is commercially disadvantageous in terms of production equipment cost and operating heat generation.

No Formula pyrolysis
Gas composition
(wt %) Composition after _CO2 absorption tower + cleaning tower + adsorption tower treatment (wt%) Composition after distillation tower 1 (wt%) 2nd distillation tower
After processing
Composition (wt %) 3rd distillation tower
After processing
Composition (wt %) 4th distillation tower
After processing
Composition (wt %) Top Bottom Top Bottom Top Bottom Top Bottom 1 CO ₂ 0.0244 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 2 CH ₄ 0.0033 0.0033 0.1135 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 3 CH ₃ F 0.0009 0.0010 0.0003 0.0010 0.0001 0.0004 0.0003 0.0004 0.0017 0.0000 4 CHF ₃ 0.0179 0.0184 0.0674 0.0169 0.8365 0.0000 0.0000 0.0000 0.0000 0.0000 5 CF ₂ =CF ₂ 0.0086 0.0089 0.0002 0.0091 0.0000 0.0037 0.0003 0.0045 0.0189 0.0000 6 CH ₂ F ₂ 0.0175 0.0180 0.0000 0.0185 0.0000 0.0074 0.0000 0.0093 0.0390 0.0000 7 CH ₂ =CF ₂ 0.5275 0.5407 0.8186 0.5322 0.1634 0.2121 0.9993 0.0123 0.0515 0.0000 8 CH ₂ =CHF 0.0056 0.0058 0.0000 0.0059 0.0000 0.0024 0.0000 0.0030 0.0125 0.0000 9 CHF=CF ₂ 0.0039 0.0040 0.0000 0.0042 0.0000 0.0017 0.0000 0.0021 0.0087 0.0000 10 CF ₂ =CFCF ₃ 0.0165 0.0169 0.0000 0.0174 0.0000 0.0070 0.0000 0.0087 0.0366 0.0000 11 CF ₃ CH ₂ F 0.0041 0.0042 0.0000 0.0043 0.0000 0.0017 0.0000 0.0022 0.0090 0.0000 12 CF ₂ HCl 0.0088 0.0090 0.0000 0.0093 0.0000 0.0037 0.0000 0.0047 0.0195 0.0000 13 CH ₃ Cl 0.0939 0.0963 0.0000 0.0992 0.0000 0.0398 0.0000 0.0499 0.2088 0.0000 14 CF ₃ CF=CH ₂ 0.1666 0.1708 0.0000 0.1760 0.0000 0.0706 0.0000 0.0885 0.3705 0.0000 15 CF ₃ CH=CH ₂ 0.0057 0.0058 0.0000 0.0060 0.0000 0.0024 0.0000 0.0030 0.0126 0.0000 16 CFCl=CH ₂ 0.0083 0.0085 0.0000 0.0087 0.0000 0.0035 0.0000 0.0044 0.0184 0.0000 17 CF ₂ =CHCl 0.0081 0.0083 0.0000 0.0086 0.0000 0.0034 0.0000 0.0043 0.0180 0.0000 18 CF ₃ CFHCl 0.0784 0.0803 0.0000 0.0828 0.0000 0.0332 0.0000 0.0416 0.1743 0.0000 19 n-Hexane - - 0.0000 0.0000 0.0000 0.6072 0.0000 0.7613 0.0000 1.0000 Total 1.00 1.00 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 Total Flow (kg/h) 10.025 10.2041 0.3000 9.9041 0.2000 24.7041 5.0000 19.7041 4.7041 15.0000 Driving pressure (atmG) - - 15.0 11.0 10.0 1.0 Heat exchanger temperature (℃) - - -25.9 2.5 -24.1 24.9 -25.5 87.4 -11.0 92.8 Heat Duty (kW) - - -0.159 0.256 -0.107 0.757 -5.05 5.932 -0.613 0.714

<Comparative Example 3>

In the same manner as in Comparative Example 2, the distillation purification method was changed in a four-column system to normally distill compounds having a boiling point lower than ethylene difluoride in distillation tower 1, normally distill a mixture including ethylene difluoride in distillation tower 2, and then, in distillation tower 3, the same amount of 10 kg/h of hexane was injected to separate ethylene difluoride and low-boiling-point substances that were difficult to separate, and then, in distillation tower 4, ethylene difluoride was separated from the top and hexane was separated from the bottom. The results are shown in Table 6. The purity of the purified ethylene difluoride was 99.91%, and the purification yield was approximately 90.55%. The temperatures and pressures at the top and bottom of the four distillation towers were approximately -26℃ and 14 atm, which are commercially usable ranges. The cooling heat capacity was 3.118 kW, and the heating heat capacity was 5.72 kW. When four distillation towers are used, not only does the manufacturing equipment cost increase compared to when three distillation towers are used, but there is no corresponding increase in purity and yield, which is commercially disadvantageous.

No Formula pyrolysis
Gas composition
(wt %) Composition after _CO2 absorption tower + cleaning tower + adsorption tower treatment (wt%) Composition after distillation tower 1 (wt%) 2nd distillation tower
After processing
Composition (wt %) 3rd distillation tower
After processing
Composition (wt %) 4th distillation tower
After processing
Composition (wt %) Top Bottom Top Bottom Top Bottom Top Bottom 1 CO ₂ 0.0244 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 2 CH ₄ 0.0033 0.0033 0.0973 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 3 CH ₃ F 0.0009 0.0010 0.0003 0.0010 0.0007 0.0013 0.0000 0.0002 0.0007 0.0000 4 CHF ₃ 0.0179 0.0184 0.0648 0.0167 0.0316 0.0001 0.8223 0.0000 0.0000 0.0000 5 CF ₂ =CF ₂ 0.0086 0.0089 0.0002 0.0092 0.0001 0.0192 0.0000 0.0000 0.0001 0.0000 6 CH ₂ F ₂ 0.0175 0.0180 0.0000 0.0186 0.0000 0.0394 0.0000 0.0000 0.0000 0.0000 7 CH ₂ =CF ₂ 0.5275 0.5407 0.8375 0.5301 0.9676 0.0414 0.1777 0.2498 0.9991 0.0000 8 CH ₂ =CHF 0.0056 0.0058 0.0000 0.0060 0.0000 0.0126 0.0000 0.0000 0.0000 0.0000 9 CHF=CF ₂ 0.0039 0.0040 0.0000 0.0042 0.0000 0.0088 0.0000 0.0000 0.0000 0.0000 10 CF ₂ =CFCF ₃ 0.0165 0.0169 0.0000 0.0175 0.0000 0.0370 0.0000 0.0000 0.0000 0.0000 11 CF ₃ CH ₂ F 0.0041 0.0042 0.0000 0.0043 0.0000 0.0091 0.0000 0.0000 0.0000 0.0000 12 CF ₂ HCl 0.0088 0.0090 0.0000 0.0093 0.0000 0.0197 0.0000 0.0000 0.0000 0.0000 13 CH ₃ Cl 0.0939 0.0963 0.0000 0.0997 0.0000 0.2111 0.0000 0.0000 0.0000 0.0000 14 CF ₃ CF=CH ₂ 0.1666 0.1708 0.0000 0.1769 0.0000 0.3745 0.0000 0.0000 0.0000 0.0000 15 CF ₃ CH=CH ₂ 0.0057 0.0058 0.0000 0.0060 0.0000 0.0127 0.0000 0.0000 0.0000 0.0000 16 CFCl=CH ₂ 0.0083 0.0085 0.0000 0.0088 0.0000 0.0186 0.0000 0.0000 0.0000 0.0000 17 CF ₂ =CHCl 0.0081 0.0083 0.0000 0.0086 0.0000 0.0182 0.0000 0.0000 0.0000 0.0000 18 CF ₃ CFHCl 0.0784 0.0803 0.0000 0.0832 0.0000 0.1762 0.0000 0.0000 0.0000 0.0000 19 n-Hexane - - 0.0000 0.0000 0.0000 0.0000 0.0000 0.7500 0.0000 1.0000 Total 1.00 1.00 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 Total Flow (kg/h) 10.025 10.2041 0.3500 9.8541 5.2000 4.6541 0.2000 20.0000 5.0000 15.0000 Driving pressure (atmG) - - 14.0 12.0 11.0 10.0 Heat exchanger temperature (℃) - - -26.4 0.1 -19.8 36.1 -24.2 23.4 -25.4 171.9 Heat Duty (kW) - - -0.185 0.269 -2.529 2.803 -0.100 0.490 -0.304 2.158

1............... Fluorocarbon thermal decomposition reactor
2.............. _CO2 removal absorption reactor
3...............washing tower
4..............Adsorption and moisture drying tower
5..............High boiling point removal distillation tower
6..............Extractive distillation tower for removing low boiling point and similar boiling point substances
7..............Extraction solvent recovery distillation tower

Claims (11)

In a method for purifying difluoroethylene from a mixture obtained by thermal decomposition of carbon fluorocarbon,
The above mixture contains difluoroethylene (CH ₂ =CF ₂ ) and trifluoromethane (CHF ₃ ),
The above purification method includes a distillation process using three distillation towers connected in series,
A purification method, characterized in that the distillation process includes extractive distillation in which an extractant containing a C5-C12 straight-chain alkane that selectively dissolves ethylene difluoride is introduced into the distillation process.
In a method for purifying difluoroethylene from a mixture obtained by thermal decomposition of carbon fluorocarbon,
The above mixture contains difluoroethylene (CH ₂ =CF ₂ ) and trifluoromethane (CHF ₃ ),
The above purification method includes a distillation process using three distillation towers connected in series,
The above distillation process is,
A step of introducing the above mixture into distillation tower No. 1 and performing a first distillation to recover a distillation fraction enriched in difluoroethylene and trifluoromethane;
A step of introducing the distillation fraction recovered from the first distillation tower into the second distillation tower and performing a second distillation while introducing an extraction solvent to recover an extraction solvent fraction in which difluoroethylene is dissolved;
A purification method, comprising the step of introducing the extractant fraction recovered from the second distillation tower into the third distillation tower and performing a third distillation to recover the difluoroethylene fraction.
In a method for purifying difluoroethylene from a mixture obtained by thermal decomposition of carbon fluorocarbon,
The above mixture contains difluoroethylene (CH ₂ =CF ₂ ) and trifluoromethane (CHF ₃ ),
The above purification method includes a distillation process using three distillation towers connected in series,
The above distillation process is,
A step of introducing the above mixture into a first distillation tower and performing a first distillation, adding an extraction solvent, and recovering an extraction solvent fraction in which difluoroethylene and high-boiling-point compounds are dissolved;
A step of introducing the extraction solvent fraction recovered from the first distillation tower into the second distillation tower and performing a second distillation to recover the difluoroethylene fraction and the extraction solvent fraction;
A purification method, comprising the step of introducing the extraction solvent fraction recovered from the second distillation tower into the third distillation tower to remove impurities contained in the extraction solvent fraction and recover the extraction solvent.
In any one of claims 1 to 3,
The above mixture contains carbon dioxide,
The above purification method comprises a step of passing the mixture through a _CO2 removal absorption tower containing a basic solution to remove carbon dioxide contained in the mixture prior to the distillation process;
A step of passing the pyrolysis mixture that has passed through the _CO2 removal absorption tower through a cleaning tower to remove the base component contained therein; and
A purification method comprising a pretreatment process, including a step of passing the pyrolysis mixture that has passed through the cleaning tower through an adsorption and moisture drying tower to remove moisture.
In any one of claims 1 to 3,
A purification method wherein the above mixture is a mixture obtained through thermal decomposition of 1-chloro-1,1-difluoroethane (HCFC-142b) or co-thermal decomposition of chlorodifluoromethane (CFC-22) and methane chloride (CH ₃ Cl).
In paragraph 1,
A purification method wherein the above extraction solvent is selected from the group consisting of pentane, hexane, heptane, octane, nonane, decane, undecane and dodecane.
In any one of claims 1 to 3,
The above mixture is carbon dioxide (CO ₂ ), methane (CH ₄ ), fluoromethane (CH ₃ F), tetrafluoroethylene (CF ₂ =CF ₂ ), difluoromethane (CH2F2), fluoroethene (CH ₂ =CHF), trifluoroethylene (CHF=CF ₂ ), hexafluoropropylene (CF ₂ =CFCF ₃ ), norflurane (CF ₃ CH ₂ F), difluorochloromethane (CF ₂ HCl), chloromethane (CH ₃ Cl), 2,3,3,3-tetrafluoro-1-propene (CF ₃ CF=CH 2 ), 3,3,3,-trifluoropropene (CF ₃ CH=CH ₂ ), _{1-chloro-1-fluoro-ethene (CFCl=CH 2 )} , 2-chloro-1,1-difluoro-ethylene (CF ₂ =CHCl) and A purification method, which may further comprise at least one compound selected from the group consisting of 2-chloro-1,1,1,2-tetrafluoroethane (CF ₃ CFHCl).
In the second paragraph,
The above distillation process is,
A step of introducing the mixture into the central portion of a distillation tower No. 1 consisting of 20 to 60 stages, performing a first distillation, and recovering a distillation fraction enriched in difluoroethylene and trifluoromethane from the bottom;
A step of introducing the distillation fraction recovered from the first distillation tower into the central portion of the second distillation tower consisting of 20 to 60 stages and performing a second distillation, while introducing hexane as an extraction solvent and recovering the extraction solvent fraction in which difluoroethylene is dissolved from the bottom;
A purification method, comprising the step of introducing the extractant fraction recovered from the second distillation tower into the central portion of the third distillation tower consisting of 10 to 30 stages and performing a third distillation to recover the ethylene difluoride fraction from the top.
In the third paragraph,
The above distillation process is,
A step of introducing the above mixture into a distillation tower No. 1 consisting of 20 to 60 stages and performing a first distillation, adding an extraction solvent, and recovering an extraction solvent fraction in which difluoroethylene and high-boiling-point compounds are dissolved;
A step of introducing the extraction solvent fraction recovered from the first distillation tower into the second distillation tower consisting of 20 to 60 stages and performing a second distillation to recover the difluoroethylene fraction and the extraction solvent fraction;
A purification method, comprising the step of introducing the extraction solvent fraction recovered from the second distillation tower into the third distillation tower consisting of 10 to 30 stages to remove impurities contained in the extraction solvent fraction and recover the extraction solvent.
A purification system used in a method for purifying difluoroethylene according to claim 2 or 3,
Distillation tower 1;
2nd distillation tower;
3rd distillation tower; and
A purification system comprising an extraction solvent supply unit.
In Article 10,
The above purification system,
A _CO2 removal absorption reactor comprising a basic solution for removing carbon dioxide contained in a mixture prior to the distillation process;
A cleaning tower for removing basic components contained in a pyrolysis mixture that has passed through a _CO2 removal absorption tower; and
A purification system further comprising an adsorption and moisture drying tower for removing moisture from a pyrolysis mixture passing through a cleaning tower.