JP5799884B2 - Method for treating fluorine-containing compound-containing liquid - Google Patents

Description

  The present invention relates to a method for treating a fluorine-containing compound-containing liquid, and more particularly to a treatment method for removing a specific compound from a mixture of compounds derived from a carbonyl fluoride oligomer to suppress foaming of the containing liquid.

  Some fluorine-containing compounds act as anionic surfactants. For example, carbonyl fluoride oligomer by-produced in the production of hexafluoropropylene oxide acts as an anionic surfactant in water. An anionic surfactant ionizes in water to become an organic anion and has an action of reducing the surface tension of water.

  Hexafluoropropylene oxide is an important compound in the production of fluorine-containing compounds, for example, used as a raw material for perfluorovinyl ether. Further, the oligomer of hexafluoropropylene oxide is used as a lubricating oil or a heat medium.

  As a method for producing hexafluoropropylene oxide (hereinafter also referred to as HFPO), a method is known in which hexafluoropropylene (hereinafter also referred to as HFP) is oxidized with oxygen to obtain HFPO (see Patent Documents 1 and 2). about).

In such a HFPO production method, carbonyl fluoride (COF ₂ ) is by-produced in addition to the target substance HFPO (see Patent Document 1). Furthermore, in this HFPO production method, carbonyl fluoride (COF ₂ ) is polymerized, and a carbonyl fluoride oligomer is also produced as a by-product (see Patent Document 2). Therefore, a by-product such as a carbonyl fluoride oligomer is separated from the reaction product containing HFPO to obtain a product HFPO.

Japanese Examined Patent Publication No. 45-11683 JP-A-6-107650

  In the method for producing HFPO, in order to separate a by-product such as a carbonyl fluoride oligomer from a reaction product containing HFPO, a composition containing HFPO and carbonyl fluoride oligomer produced by the reaction from HFP is deacidified. It attaches to processing. More specifically, the composition is washed with an alkaline aqueous liquid in a gas phase (gas), and an acid component such as a carbonyl fluoride oligomer is separated into the alkaline aqueous liquid (so that the alkaline aqueous liquid is After deoxidation, an aqueous liquid containing a compound derived from a carbonyl fluoride oligomer or the like in the form of an alkali metal salt (more specifically, an ionized ion) and a gaseous substance containing the target substance HFPO is obtained. (Hereinafter also simply referred to as a HFPO cleaning method).

  In such a HFPO cleaning method, the alkaline aqueous liquid generated by the deoxidation treatment contains a compound derived from a carbonyl fluoride oligomer in the form of an alkali metal salt. Such alkali metal salts act as anionic surfactants. Therefore, if the alkaline aqueous liquid generated by the deoxidation treatment is neutralized, diluted and discharged, the force applied in the dilution process or other discharge processes (for example, impact force applied when mixed with diluted water), etc. In addition, intense bubbling occurs in the aqueous liquid due to contact with the gas generated by the neutralization operation. Such foaming hinders dilution and neutralization operations.

  The objective of this invention is providing the processing method of the fluorine-containing compound containing liquid which suppresses generation | occurrence | production of foaming in the liquid containing the fluorine-containing compound derived from a carbonyl fluoride oligomer.

One gist of the present invention is the following general formula (Y):
_{CF 3 O (CF 2 O)} n -R '(Y)
(In the formula, —R ′ represents —COOH, —OCOOH, or —CF ₂ COOH.)
Or a salt thereof, which is represented by the general formula (Y) and has 4 or more carbon atoms (hereinafter, ≧ C4) from an aqueous liquid containing a plurality of compounds having different n Compound)),
In an aqueous liquid from which ≧ C4 compound is removed, the concentration of ≧ C4 compound is 100 ppm by weight or less, and the n-number average value of the fluorinated carboxylic acid represented by the general formula (Y) or a salt thereof is 0.1 or less. is there,
A method for treating a fluorine-containing compound-containing liquid is provided.

  The method for treating a fluorine-containing compound-containing liquid according to the present invention is to remove a compound derived from an oligomer having a specific polymerization degree from a mixture of compounds derived from a carbonyl fluoride oligomer by-produced in the production of hexafluoropropylene oxide. Including. The fluorine-containing compound-containing liquid treated by the treatment method of the present invention has no or little foaming.

It is the schematic for demonstrating the washing | cleaning method of the hexafluoropropylene oxide which the fluorine-containing compound containing liquid which can apply one Embodiment of this invention generate | occur | produces.

(Background to the present invention)
The target liquid of the treatment method of the present invention is represented by the general formula (Y):
_{CF 3 O (CF 2 O)} n -R '(Y)
(In the formula, —R ′ represents —COOH, —OCOOH, or —CF ₂ COOH.)
Is an aqueous liquid containing a mixture containing a plurality of compounds with different numbers of n. When the fluorine-containing carboxylic acid represented by the general formula (Y) or a mixture thereof includes a compound having 3 or less carbon atoms and a mixture of 4 or more carbon atoms, the number of carbon atoms is 4 It has been found that the above causes foaming and that it is effective to suppress foaming to remove those having 4 or more carbon atoms from an aqueous liquid containing this mixture.

The fluorine-containing carboxylic acid represented by the general formula (Y) or a salt thereof is, for example, a compound obtained by dissolving a mixture of carbonyl fluoride oligomers by-produced in the production of HFPO in an acidic or alkaline aqueous liquid. More specifically, the fluorinated carboxylic acid represented by the general formula (Y) or a salt thereof is present in the liquid in the form of ionized ions. Such a liquid is, for example, an alkaline aqueous solution produced by deoxidation treatment for HFPO separation in the production of HFPO, and the treatment method of the present invention can be used as a defoaming method for alkaline waste liquid produced in the production of HFPO. .
In the following, embodiments of the processing method of the present invention will be described.

[Embodiment 1]
(Fluorine compound-containing liquid to be treated)
In the present embodiment, the fluorine-containing compound-containing liquid to be treated is represented by the general formula (Y):
_{CF 3 O (CF 2 O)} n -R '(Y)
(In the formula, —R ′ represents —COOH, —OCOOH, or —CF ₂ COOH.)
The fluorinated carboxylic acid represented by these or its salt is included. The fluorine-containing carboxylic acid represented by the general formula (Y) is present when the aqueous liquid is acidic, and the salt is present when the aqueous liquid is alkaline. The fluorine-containing carboxylic acid represented by the general formula (Y) or a salt thereof can exist in the form of ions ionized in an aqueous liquid, and among these, an organic anion can act as a surfactant.

  The treatment method of the present embodiment is preferably applied when the liquid to be treated is an alkaline aqueous liquid and contains a salt of a fluorinated carboxylic acid represented by the general formula (Y). Such an alkaline aqueous liquid is, as described above, for example, a waste liquid generated in the production process of HFPO.

  The fluorine-containing carboxylic acid salt represented by formula (Y) may be any salt as long as it can be formed in an alkaline aqueous liquid. For example, the salt of the fluorine-containing carboxylic acid represented by the general formula (Y) in the alkaline aqueous liquid may be a salt obtained by adding the salt itself to the aqueous liquid. In addition, for example, the salt of the fluorine-containing carboxylic acid represented by the general formula (Y) in the alkaline aqueous liquid is obtained by converting a compound represented by the general formula (X) described later into an alkali metal ion, an alkaline earth metal ion, or ammonium. It may be generated by adding and dissolving in an aqueous liquid containing. Therefore, the cation constituting the salt may be originally contained in the compound, or may be a cation contained in the aqueous liquid.

The salt of the fluorinated carboxylic acid represented by the general formula (Y) is preferably an alkali metal salt. Specifically, the alkali metal is Li, K, Na, Rb, Cs and Fr. The alkali metal is preferably potassium or sodium. The alkali metal salt of the fluorinated carboxylic acid represented by the general formula (Y) is represented by the following general formula (Y ′).
_{CF 3 O (CF 2 O)} n -R "(Y ')
(In the formula, —R ″ represents —COOM, —OCOOM or —CF ₂ COOM, and M represents an alkali metal.)

Alternatively, the fluorine-containing carboxylic acid salt represented by the general formula (Y) is preferably an alkaline earth metal salt. Specifically, the alkaline earth metal is Ca, Sr, Ba, and Ra. The alkaline earth metal is particularly preferably calcium. The alkaline earth metal salt of the fluorinated carboxylic acid represented by the general formula (Y) is represented by the following general formula (Y ″).
(CF ₃ O (CF ₂ O) _n —R ′ ″) ₂ M2 (Y ″)
(In the formula, —R ′ ″ represents —COO, —OCOO or —CF ₂ COO, and M2 represents an alkaline earth metal.)

  In the present embodiment, the aqueous liquid is a fluorine-containing carboxylic acid represented by the general formula (Y) or a salt thereof, and includes a mixture of a plurality of compounds having different n. The mixture of a plurality of compounds with different n is, for example, a mixture of a compound where n is 0 and a compound where n ≧ 1. In that case, the compound in which n ≧ 1 may be only the compound in which n = 1, or may be only one kind of compound in which n is 2 or more, or a mixture of two or more compounds in which n is different. It may be. A compound with n ≧ 1 may be one or more compounds where n is greater than 2. Moreover, when a several compound is contained as a compound of n> = 1, n may be continuous or may not be continuous. A mixture comprising a compound with n = 0 and a compound with n ≧ 1 is, for example, a by-product obtained in the production of HFPO. The compound in which n ≧ 1 is preferably a compound in which n is 50 or less, more preferably a compound in which n is 15 or less, or a mixture thereof.

In the general formula (Y), when R ′ is —COOH or —OCOOH, or a salt thereof, a compound in which n is 2 or more is a ≧ C4 compound. In the general formula (Y), when R ′ is —CF ₂ COOH or a salt thereof, a compound in which n ≧ 1 is a ≧ C4 compound.

In the general formula (Y), the bond between _two adjacent CF ₂ O repeating units is
—CF ₂ —O—CF ₂ —O—
—CF ₂ —O—O—CF ₂ —
_{-O-CF 2} -CF ₂ -O-
—O—CF ₂ —O—CF ₂ —
Any of them may be used. In the case of —CF ₂ —O—CF ₂ —O— and —O—CF ₂ —O—CF ₂ —, an ether bond is formed, and in the case of —CF ₂ —O—O—CF ₂ — An ether bond is formed.

  The alkaline aqueous liquid may contain at least one alkaline substance such as an alkali metal hydroxide, an alkaline earth metal hydroxide, and ammonia in an aqueous medium. As the alkali metal hydroxide, for example, potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium hydrogen carbonate, sodium hydrogen carbonate and the like can be used. As the alkaline earth metal hydroxide, calcium hydroxide, barium hydroxide or the like can be used. These may be used in at least one kind, and among these, it is preferable to use either or both of potassium hydroxide and sodium hydroxide. Alkali metal hydroxides and alkaline earth metal hydroxides can be used in the form of aqueous solutions. Ammonia can be used in the form of aqueous ammonia.

  When the aqueous liquid is alkaline, the pH of the fluorine-containing compound-containing liquid is not particularly limited. The pH is preferably 14 or more, for example, in order to prevent the formation of HF in the aqueous liquid.

  The pH is adjusted in advance before the salt of the fluorinated carboxylic acid represented by the general formula (Y) is present in the alkaline aqueous liquid (in other words, the pH is adjusted to a predetermined pH in advance). In the presence of a salt in an alkaline aqueous liquid. Alternatively, the pH of the aqueous phase may be adjusted to a predetermined value by adding an alkaline substance or an alkaline aqueous solution containing an alkaline substance to the aqueous liquid containing the fluorine-containing carboxylic acid salt represented by the general formula (Y). Good.

  The content of the fluorine-containing carboxylic acid represented by the general formula (Y) or the salt thereof in the aqueous liquid is not particularly limited, but is, for example, about 1 ppm by weight or more, specifically about 10 ppm by weight to 10% by weight (all Standard). A liquid containing a fluorine-containing carboxylic acid or a salt thereof in a content within this range is preferably treated by a treatment method (removal by activated carbon, hydrothermal decomposition, or ion exchange resin) described later.

(Processing method)
Next, a method for removing a compound having 4 or more carbon atoms (≧ C4 compound) from an aqueous liquid containing a mixture containing a plurality of compounds having different n will be described. The method for removing the ≧ C4 compound is not particularly limited, and any method can be adopted as long as the ≧ C4 compound can be physically or chemically removed from the liquid.

  For example, ≧ C4 compounds may be removed by adsorption treatment with activated carbon. According to the activated carbon, it is possible to efficiently remove the ≧ C4 compound and effectively reduce the content of the ≧ C4 compound in the liquid. Further, the adsorption of ≧ C4 compound by activated carbon is carried out by bringing the fluorine-containing compound-containing liquid into contact with activated carbon, and can be carried out using a relatively simple apparatus.

  The raw material of activated carbon etc. is not specifically limited. Activated carbon can be produced from a carbonaceous material. Any carbonaceous material may be used as long as it can generate activated carbon by carbonization, activation, etc., such as wood, sawdust, charcoal, palm shell, walnut shell and other fruit shells, fruit seeds and other plant systems, peat, lignite, lignite, Coal such as bituminous coal, anthracite, pitch such as petroleum pitch, coal pitch, coke, coal tar, tar such as petroleum tar, minerals such as petroleum distillation residue, natural materials such as cellulose fibers such as cotton and rayon, phenol resin And synthetic materials such as polyvinyl alcohol and polyacrylonitrile. The shape may be any of powder, granule, and fiber, or may be a molded product thereof.

Activated carbon is manufactured by processing carbonaceous material, such as carbonization and activation. Carbonization is performed, for example, by heating and carbonizing a carbonaceous material at a temperature of about 300 ° C to 700 ° C. In addition, activation methods include chemical activation with zinc chloride, phosphoric acid, sulfuric acid, calcium chloride, sodium hydroxide, potassium hydroxide, etc., and gas activation with water vapor, carbon dioxide, oxygen gas, combustion exhaust gas, and mixed gases thereof. Is done. The size of the activated carbon is generally 0.5 to 5.0 mm. The specific surface area of the activated carbon can be increased by activation. The specific surface area of the activated carbon is 1500 m ² / g or more, for example 1500~2500m ² / g, it is particularly preferably 1800~2500m ² / g. It is particularly preferably 2000 m ² / g or more. The larger the specific surface area of the activated carbon, the more ≧ C4 compounds are adsorbed on the activated carbon.

  The treatment with activated carbon is carried out by bringing the liquid to be treated (including a mixture of a plurality of compounds having different n) into contact with the activated carbon. Specifically, the liquid from which ≧ C4 compound is removed can be obtained by stirring the activated carbon dispersion obtained by adding activated carbon to the liquid and then removing the activated carbon by filtering. Alternatively, a liquid from which ≧ C4 compound has been removed can be obtained by passing the liquid through activated carbon and filtering out the passed liquid as necessary. Alternatively, by filling the packed tower with activated carbon and continuously passing the liquid, a liquid from which ≧ C4 compound has been removed can be obtained from the outlet.

  ≧ C4 compounds can also be removed by hydrothermal decomposition. Hydrothermal decomposition is a method of decomposing ≧ C4 compounds using high-temperature and high-pressure water, subcritical or supercritical water, preferably subcritical water. Since the liquid to be treated is an aqueous liquid and contains water, removal of the ≧ C4 compound by hydrothermal decomposition can be carried out by increasing the temperature and pressure of the liquid to be treated.

  Hydrothermal decomposition is preferably carried out by introducing the liquid to be treated into the reaction vessel and heating and pressurizing the inside of the reaction vessel so that the temperature is 150 ° C. or higher and the pressure (gauge pressure) is 1.5 MPa or higher. . The inside of the reaction vessel more preferably reaches a temperature of 200 ° C. to 400 ° C. and a pressure of 2.0 MPa to 15 MPa, and even more preferably reaches a temperature of 250 ° C. to 350 ° C. and a pressure of 4 MPa to 12 MPa. The reaction time is not particularly limited. For example, the reaction time is preferably 0.01 hours to 2 hours, and more preferably 0.05 hours to 1 hour.

Under this high temperature and high pressure, the water contained in the liquid to be treated decomposes the ≧ C4 compound. The ≧ C4 compound is considered to be decomposed into a compound having a smaller n, CF ₃ COOH, CF ₃ CF ₂ COOH, or a salt thereof, and further decomposed into HF, CO ₂ , a salt thereof, or the like. As a result, the liquid to be processed is less prone to foaming.

  ≧ C4 compounds can also be removed with ion exchange resins. Specifically, the ≧ C4 compound is removed by bringing the liquid to be treated into contact with the anion exchange resin. The removal of the ≧ C4 compound by the anion exchange resin is performed by exchanging an anion previously present in the ion exchange resin with an anion in the liquid to be treated. In general, the ion selectivity is higher for ions having a higher valence and a higher molecular weight. That is, an anion having a higher valence and / or a higher molecular weight has a property of being easily ion-exchanged. Therefore, it is considered that the ≧ C4 compound is favorably removed by anion exchange. In addition, it is estimated that the removal of ≧ C4 compound by the ion exchange resin is performed not only by the mechanism of ion exchange but also by the adsorption mechanism. The molecular chain of the polymer constituting the ion exchange resin has a network structure, and has a large specific surface area like an adsorbent such as activated carbon. For this reason, it is presumed that the ion exchange resin easily permeates water and ions and adsorbs relatively large molecules (or ions). However, the present invention is not limited by these assumptions.

  The contact between the ion exchange resin and the liquid to be processed may be performed by, for example, a method of injecting the liquid into a container filled with the ion exchange resin and taking out the liquid that has passed through the ion exchange resin. Alternatively, the liquid from which the ≧ C4 compound has been removed can also be obtained by a method in which the ion exchange resin is added to the liquid to be treated and stirred, and then the ion exchange resin is removed by filtration. The ion exchange capacity is lost when a certain amount of ion exchange is performed, but is restored by being immersed in an aqueous solution containing the original exchange ions.

Even when ≧ C4 compound is removed by any method, the treatment is performed so that the concentration of ≧ C4 compound in the treated liquid is 100 ppm by weight or less, preferably 50 ppm by weight or less. A liquid containing a ≧ C4 compound at a concentration in such a range is less likely to foam. Therefore, in this embodiment, “to remove ≧ C4 compound” not only eliminates ≧ C4 compound completely, but also causes the concentration of ≧ C4 compound in the liquid after treatment to be within the above range. To reduce. As for the concentration of ≧ C4 compound, the total concentration of the fluorinated carboxylic acid represented by the general formula (Y) or a salt thereof is obtained from the 19F-NMR chart, and the concentration of ≦ C3 compound is subtracted from the obtained total concentration ( Subtract). The total concentration of the carboxylic acid of the general formula (Y) or a salt thereof is obtained by adding a predetermined amount of HCF ₂ CF ₂ CH ₂ OH as an internal standard to the liquid after treatment, and using the addition amount (concentration) of this internal standard as a reference, it can be determined from the integral value of F of -CF ₂ COOH or _-CF 2 COOM. The concentration of ≦ C3 _compounds, CF 3 O-CF ₂ - can be obtained from the integral value of the _CF 3 O-a F.

Moreover, in this Embodiment, the fluorine-containing carboxylic acid represented by general formula (Y) or its salt contained in the liquid after a process has n number average value of 0.1 or less. That is, even when the fluorine-containing carboxylic acid represented by the general formula (Y) or a mixture thereof is included, if the n-number average value is 0.1 or less, bubbling of the liquid is effectively suppressed. The n-number average value is obtained from the ratio of the integral value of F in CF ₃ O (CF ₂ O) _n obtained from the 19 F-NMR chart and the integral value of F in —CF ₂ COOH or —CF ₂ COOM. be able to.

Among the fluorine-containing carboxylic acids represented by the general formula (Y), those in which —R is —COOH or —OCOOH, or a salt thereof, R is unstable (particularly in an alkaline aqueous solution). They decompose and become CF ₃ COOH, CF ₃ OCF ₂ COOH, or a salt thereof and the like, and further easily generate HF, CO ₂ , or a salt thereof. That is, those in which —R is —COOH or —OCOOH, or a salt thereof is often not present in the processed liquid as it is or in a small amount even if it exists. Of the fluorine-containing carboxylic acids represented by the general formula (Y), those in which -R is -COOH, -OCOOH and n = 1 have 3 carbon atoms, They are less likely to cause, and they may not be considered in determining the concentration of ≧ C4 compounds and the n-number average value. Therefore, in the present embodiment, the concentration of ≧ C4 compound and the n-number average value are obtained by the method as described above, thereby confirming that the compound of ≧ C4 has been removed.

(Embodiment 2)
The treatment method of Embodiment 1 is carried out in order to treat the liquid obtained as a liquid phase in the deoxidation treatment after the completion of the deoxidation treatment carried out as the HFPO cleaning treatment in the production of hexafluoropropylene oxide. Good. Hereinafter, as a second embodiment, a method for producing HFPO including a step of producing HFPO (step a) and a step of washing the produced HFPO (step b), wherein the liquid produced in step b) is treated according to the present invention. An embodiment to which is applied will be described.

・ Process a
Hexafluoropropylene oxide can be obtained through a reaction step (step a) in which hexafluoropropylene (HFP) is oxidized with oxygen. Specifically, HFP and oxygen (O ₂ ) are supplied to a reactor (not shown) charged with a solvent in advance, and HFP is oxidized with oxygen (liquid phase reaction) in the reactor to generate HFPO.

  Examples of the solvent include saturated halogen carbon inert to the oxidation reaction, such as 1,1,2-trichloro-1,2,2-trifluoroethane, trichlorofluoromethane, perfluoro (dimethylcyclobutane), carbon tetrachloride and the like. Can be used.

In the oxidation reaction, in addition to HFPO which is a target substance of the production method of the present invention, the following general formula (X):
_{CF 3 O (CF 2 O)} n -R ··· (X)
(Wherein, -R is -COF, indicates -OCOF or _-CF 2 COF, n is an integer of 0 to 50, preferably an integer of 0 to 15.)
(Hereinafter also referred to as oligomer represented by the general formula (X)) is by-produced.

  The oligomer represented by the general formula (X) is usually a mixture in which a plurality of compounds having different terminal groups -R and / or n number are mixed, that is, an oligomer of n = 0 and 1 or 1 of n ≧ 1. It can be a mixture with multiple oligomers. When this oligomer is dissolved in an alkaline aqueous liquid, a fluorine-containing carboxylic acid salt represented by the general formula (Y) (for example, a compound represented by the general formula (Y ′) or (Y ″)) is obtained. It is done.

In the general formula (X), the bond between _two adjacent CF ₂ O repeating units is
—CF ₂ —O—CF ₂ —O—
—CF ₂ —O—O—CF ₂ —
_{-O-CF 2} -CF ₂ -O-
—O—CF ₂ —O—CF ₂ —
Any of them may be used. In the case of —CF ₂ —O—CF ₂ —O— and —O—CF ₂ —O—CF ₂ —, an ether bond is formed, and in the case of —CF ₂ —O—O—CF ₂ — An ether bond is formed.

The ratio of the ether peroxide bond in the oligomer represented by the general formula (X) is preferably such that the active oxygen concentration measured by the iodometric titration method is 0.01 to 25% by weight. As long as the oligomer represented by the general formula (X) satisfies this condition, the general formula (X) end groups in the -R is -COF, there is no limit for the proportion of the compound is -OCOF or _-CF 2 COF.

The produced HFPO and the oligomer represented by the general formula (X) can be extracted from the reactor, for example, in a gas phase. The extracted gas phase is usually HFPO, an oligomer represented by the general formula (X), unreacted HFP, by-produced acetyl fluoride (CF ₃ COF), hexafluoroacetone (CF ₃ COCF _3). ) And carbonyl fluoride (COF ₂ ) and the like.

The reaction conditions can be appropriately set according to the reactor and solvent to be used so that the final HFPO recovery amount becomes large. For example, the reaction conditions may be as follows, but this embodiment is limited to this. is not.
The reactor is charged with 30 to 50% of the solvent, and HFP is charged with 1 to 40%, preferably 5 to 35% of the solvent, and heated to 90 to 150 ° C.
The reaction is carried out by dispensing oxygen gas at a partial pressure of 0.02 to 0.5 MPa (gauge pressure), preferably 0.05 to 0.1 MPa (gauge pressure). The total amount of oxygen charged can be determined by analyzing the conversion rate of HFP as a raw material, but is approximately 1.3 to 1.7 times the theoretical amount.
Further, the total reaction pressure at this time varies depending on the solvent species, the HFP feed ratio, the temperature conditions, and the like, and is not particularly specified, but is generally 1.5 to 4 MPa (gauge pressure).
The reaction time (average residence time) is, for example, 1 to 10 hours.

  Such a reaction operation can be carried out either batchwise or continuously in a closed vessel. The reactor is preferably a metal container capable of stirring and heating the liquid.

In addition to HFPO and the oligomer represented by the general formula (X), the gas phase extracted from the reactor is unreacted HFP, by-produced acetyl fluoride (CF ₃ COF), hexafluoroacetone (CF ₃ COCF ₃ ). And carbonyl fluoride (COF ₂ ) and the like, and may be appropriately subjected to a conventional separation operation (eg, distillation, evaporation, etc.). Of these, at least the oligomer represented by HFPO and general formula (X) may be contained in the composition subjected to step b), and before step b), HFPO and / or general formula ( The oligomer represented by X) may be partially separated.

  By the above, the composition containing the oligomer represented by HFPO and general formula (X) is obtained.

-Process b)
Next, in order to deoxidize the composition obtained above, a washing operation is performed. Specifically, the composition obtained above is washed with an alkaline aqueous liquid, usually an alkaline aqueous solution (hereinafter simply referred to as an alkaline aqueous solution for the sake of simplicity). As a result, acid components (such as oligomers represented by the general formula (X) and hexafluoroacetone) are removed from the composition, and HFPO is washed by paying attention to HFPO which is a target substance of the production method of the present invention. .

  Such a washing operation can be carried out either batchwise or continuously, but can be carried out continuously using, for example, the washing apparatus 11 shown in FIG. The cleaning device 11 includes a deoxidation tower 10 and its attached equipment. The deoxidation tower 10 includes a tower part 10a and a can part 10b connected to the lower part thereof, and the tower part 10a is preferably filled with any appropriate packing. The accessory equipment includes the illustrated composition supply line 1, alkaline aqueous solution supply line 3, gaseous matter discharge line 5, pump 7, alkaline aqueous solution discharge line 9a, waste liquid line 9b, circulation line 9c, and the like.

  Referring to FIG. 1, the composition obtained in step a) is in a gas phase (gas) from composition supply line 1 to tower section 10a of deoxidation tower 10, preferably at the supply port located therebelow. Supply more.

  On the other hand, the alkaline aqueous solution is supplied from the alkaline aqueous solution supply line 3 to the tower portion 10a of the deoxidation tower 10, preferably from the supply port located above.

  As the alkaline aqueous solution, an alkaline aqueous liquid as described in Embodiment 1 can be used. For example, at least one alkaline substance such as an alkali metal hydroxide, an alkaline earth metal hydroxide, or ammonia is contained in the aqueous medium. Can be included.

  The pH of the aqueous alkali solution to be supplied (or the alkali concentration, more specifically, the concentration of the alkaline substance in the aqueous alkali solution) may vary depending on the amount of gas to be treated, etc. The pH of the aqueous alkaline solution in contact with the aqueous solution is selected to be, for example, 14 or higher. When the pH is maintained at 14 or more, foaming during the deoxidation treatment can be suppressed.

  When the cleaning apparatus 11 shown in FIG. 1 is used, specifically, the pH of an alkaline aqueous solution (which is an alkaline aqueous solution after washing and is considered to have the lowest pH) discharged from the can 10b through the alkaline aqueous solution discharge line 9a. The pH of the alkaline aqueous solution can be maintained and managed so that becomes a predetermined value (for example, 14 or more). The pH can be adjusted by adjusting the supply amount of the composition to the cleaning device 11, the supply amount of the alkaline aqueous solution, the pH (or alkali concentration) of the alkaline aqueous solution to be supplied, etc. alone or in combination.

  The composition and the aqueous alkali solution supplied to the deoxidation tower 10 are sufficiently in contact with each other inside, and in the illustrated embodiment, they are in countercurrent contact while flowing through the tower portion 10a. The composition after contact is discharged as a gaseous matter through the gaseous matter discharge line 5 from an outlet located preferably above the tower 10a. On the other hand, the aqueous alkali solution after contact is received by the can 10b connected to the lower portion of the tower 10a, and then discharged by the pump 7 from the can 1b through the alkaline aqueous solution discharge line 9a.

  While the composition and the aqueous alkaline solution are in contact, the acid component in the composition moves into the aqueous alkaline solution. In other words, the aqueous solution of the composition becomes HFPO by focusing on the target substance of the production method of the present invention. Will be washed). During this period, the pH of the alkaline aqueous solution that is the liquid phase is maintained at a predetermined value (for example, 14 or more). The composition after cleaning, that is, the gaseous matter discharged through the gaseous matter discharge line 5 contains HFPO.

  In such a washing operation, when the pH of the alkaline aqueous solution is set to 14 or more, foaming caused by the oligomer represented by the general formula (X) can be effectively suppressed in the tower portion 10a and the can portion 10b of the deoxidation tower 10. it can. Therefore, the aqueous alkaline solution (and consequently the compound derived from the oligomer represented by the general formula (X)) is mixed in the gaseous matter after washing, or the pressure loss of the deoxidation tower 10 increases due to foaming. Can be prevented. As a result, the processing speed of the cleaning operation can be increased, and the process can be carried out stably and continuously efficiently.

  In this washing operation, the maintenance of the pH of the liquid phase may be easily performed by measuring the pH of the aqueous alkaline solution (aqueous phase) using a commercially available pH meter. The actual measured value of the pH measured with the pH meter is generally equal to the theoretical value of pH obtained from the molar concentration of the alkaline substance measured by neutralization titration if the pH is 14 or less. However, some commercially available pH measuring devices can display a value of pH 14 or higher, but it is known that the error increases at pH 14 or higher. Therefore, in order to obtain an accurate pH value at pH 14 or more, it is preferable to obtain a theoretical pH value by neutralization titration.

Further, if the pH of the alkaline aqueous solution is 14 or more, HF and CO ₂ produced by hydrolysis of the oligomer can be further trapped in the alkaline aqueous solution by a neutralization reaction, and F ⁻ and CO ₃ ² respectively. ^- as can be separated in an alkaline aqueous solution (Thus, it is possible to improve the HFPO purity gaseous product is discharged through the gaseous product discharge line 5).

The alkaline aqueous solution is preferably an aqueous solution of potassium hydroxide and / or sodium hydroxide. The compound represented by the general formula (X) can generate HF by hydrolysis, and the fluorine ions can form fluorides with alkali metal ions in the aqueous liquid. Potassium fluoride and sodium fluoride have higher solubility than other fluorides. Therefore, when an aqueous solution of potassium hydroxide and / or sodium hydroxide is used as the alkaline aqueous liquid, HF can be sufficiently trapped in the aqueous liquid as F ⁻ by a neutralization reaction and precipitated as fluoride. Can be effectively avoided. In particular, since potassium fluoride has higher solubility than sodium fluoride, a higher effect can be obtained when a potassium hydroxide aqueous solution is used.

  The upper limit value of the pH of the alkaline aqueous solution may be set as appropriate, and may be, for example, pH 15 or less. By setting the pH to 15 or less, it can be handled in a liquid state. For example, when an alkaline aqueous solution containing potassium hydroxide (potassium hydroxide aqueous solution) is used, an alkali concentration (potassium hydroxide concentration) of 48% by weight can be easily obtained on the market. Is 15 or less.

  The acid component separated in the alkaline aqueous solution includes an oligomer represented by the general formula (X) and hexafluoroacetone when present. The oligomer represented by the general formula (X) is a salt of the fluorinated carboxylic acid represented by the general formula (Y) described in Embodiment 1 (for example, when the alkaline aqueous solution is an aqueous solution of an alkali metal hydroxide). , A fluorine-containing compound represented by the general formula (Y ′), more specifically, an ionized ion. When the alkaline aqueous solution is an alkaline earth metal hydroxide aqueous solution, the general formula (Y ″) The hexafluoroacetone is dissolved in the aqueous alkali solution as a trihydrate.

  Therefore, the alkaline aqueous solution discharged (after washing) through the alkaline aqueous solution discharge line 9a contains a compound derived from the oligomer represented by the general formula (X) and hexafluoroacetone when present.

  Thus, it is preferable to treat the alkaline aqueous solution discharged from the deoxidation tower 10 by the treatment method of the present embodiment. That is, the alkaline aqueous solution discharged from the deoxidation tower 10 through the waste liquid line 9b is treated by the treatment method of the present embodiment (step c). The treated liquid is discarded after being subjected to any post-treatment as necessary. Generally, it is discarded after neutralization. Since hexafluoroacetone trihydrate is stable in a neutral state, neutralize the alkaline aqueous solution after washing, and then separate hexafluoroacetone trihydrate (for example, by extraction, membrane separation, adsorption, etc.). ) It may be taken out stably and used for any purpose.

  In addition, since the alkaline aqueous solution discharged as described above may still have a cleaning effect, a part of the alkaline aqueous solution is returned to the tower portion 10a of the deoxidation tower 10 through the circulation line 9b and passed through the alkaline aqueous solution supply line 3. It may be used together with a newly supplied alkaline aqueous solution. Thereby, the consumption of alkali can be reduced.

In particular, when an aqueous solution of potassium hydroxide and / or sodium hydroxide is used as the alkaline aqueous solution, HF can be sufficiently trapped in the aqueous liquid as F ⁻ by a neutralization reaction as described above. Since precipitation as a chemical compound can be effectively avoided, the alkaline aqueous solution can be circulated at a higher rate. From this viewpoint, it is more preferable to use an aqueous potassium hydroxide solution.

  However, when a sodium hydroxide aqueous solution is used as the alkaline aqueous solution, there is another advantage. Sodium hydroxide is less expensive than potassium hydroxide, and is manufactured by salt electrolysis from seawater. Therefore, sodium hydroxide is hardly affected by market conditions and can be obtained and used stably.

The cleaning conditions can be appropriately set according to the type of the cleaning apparatus used and the alkaline aqueous solution so that the final HFPO recovery amount becomes large. For example, the cleaning conditions may be as follows, but this embodiment is not limited thereto. Is not to be done.
The composition is supplied to the deoxidation tower 10 in a gas phase state, for example, at 0 to 50 ° C. and 0 to 0.6 MPa (gauge pressure).
An aqueous alkali solution is supplied to the deoxidation tower 10 in a liquid state, for example, at 0 to 30 ° C.
The ratio of the aqueous alkali solution circulating in the deoxidation tower 10 is not particularly limited, and may be, for example, 0 to 5000 times the supply flow rate of the aqueous alkali solution newly supplied from the outside.
The supply flow rate of the alkaline aqueous solution may be 2 to 20 L / hr with respect to the supply flow rate of 1 m ³ / hr of the composition.
Although the gaseous matter discharged | emitted from the deoxidation tower 10 depends on each calorie | heat amount of the composition supplied, aqueous alkali solution, the pressure loss of the deoxidation tower 10, etc., for example, 0-50 degreeC and 0-0.6 MPa (Gauge pressure).
The discharged alkaline aqueous solution is, for example, 0 to 50 ° C., although it depends on the amount of heat of the supplied composition and alkaline aqueous solution, the pressure loss of the deoxidation tower 10, and the like.
PH of the alkaline aqueous solution being washed (more specifically, an alkaline aqueous solution comprising an alkaline aqueous solution supplied from the outside and a circulated alkaline aqueous solution in contact with the composition supplied in the gas phase. The pH of the aqueous alkaline solution (or liquid phase), which may be considered to be substantially equal to the pH of the aqueous alkaline solution after washing) is preferably 14 or more, and may be, for example, pH 14 or more and 15 or less.

  In washing (deoxidation treatment), an antifoaming agent may be used to suppress foaming caused by the oligomer represented by the general formula (X). When an antifoaming agent is used, the pH of the aqueous alkali solution is appropriately selected according to the type of antifoaming agent.

  Thus, HFPO, more specifically, a composition containing HFPO and the oligomer represented by the general formula (X) is washed, and HFPO is produced in the form of a gaseous substance after washing. The content of HFPO in the obtained gaseous product is, for example, 80 mol% or more, typically 90 to 100 mol%.

  As described above, as the second embodiment, the embodiment in which the processing method of the present invention is applied to the manufacture of HFPO has been described. In another embodiment, the treatment method of the present invention is a compound obtained when an oligomer represented by the general formula (X) is exposed to acidic conditions, that is, a fluorine-containing compound represented by the general formula (Y). It can be applied to aqueous liquids containing a mixture of carboxylic acids themselves. Thus, for example, in the production of HFPO, the treatment method of the present invention may be carried out in order to treat the obtained acidic aqueous liquid by adding an excess acid to the alkaline waste liquid after the deoxidation treatment to make it acidic. .

(Comparative Example 1)
A potassium hydroxide aqueous solution containing a mixture of a plurality of compounds represented by the general formula (Y) and R ′ being CF ₂ OOH and containing a plurality of compounds having different n was prepared. The concentration of the potassium salt of the fluorine-containing carboxylic acid represented by the general formula (Y) is 0.37% by weight, and KF, CF ₃ COOK, n = 0 compound and ≧ C4 compound (that is, n ≧ 1 compound) ) And the average number of n values are as shown in Table 1.

  30 g of this aqueous solution was placed in a 50 ml sample tube, and the lid was closed and sealed. Then, it was shaken by hand for 20 seconds, left on the experimental table, and the appearance of foaming was observed. As a result, the bubbles did not disappear even after 15 minutes.

(Example 1)
The aqueous potassium hydroxide solution used in Comparative Example 1 was treated with activated carbon. Specifically, 40 g of an aqueous solution and 0.8 g of granular activated carbon (F-400 manufactured by Calgon Carbon Japan Co., Ltd., particle size 10 to 35 Tyler mesh) manufactured using coal as a raw material were placed in a 50 ml sample tube. After the sample tube was closed and sealed, the aqueous solution was stirred with a stirring bar for 17 hours. The activated carbon was removed by filtration, the filtrate was placed in another 50 ml sample tube, the lid was closed and sealed. Then, the sample tube was shaken by hand for 20 seconds and left on the experimental table to observe the disappearance of foaming. As a result, the bubbles disappeared completely in about 12 seconds on average.

(Example 2)
The aqueous potassium hydroxide solution used in Comparative Example 1 was treated with activated carbon. Specifically, 40 g of an aqueous solution and 0.8 g of granular activated carbon (manufactured by Calgon Carbon Japan Co., Ltd.) manufactured using coconut shells as raw materials were placed in a 50 ml sample tube. After the sample tube was closed and sealed, the aqueous solution was stirred with a stirring bar for 17 hours. The activated carbon was removed by filtration, the filtrate was placed in another 50 ml sample tube, the lid was closed and sealed. Then, the sample tube was shaken by hand for 20 seconds and left on the experimental table to observe the disappearance of foaming. As a result, the bubbles disappeared completely in about 3 seconds on average.

(Example 3)
The aqueous potassium hydroxide solution used in Comparative Example 1 was treated with an ion exchange resin. Specifically, 40 g of the solution used in Comparative Example 1 and 0.8 g of an ion exchange resin (acrylic diamond ion WA10 manufactured by Mitsubishi Chemical Corporation) were placed in a 50 ml sample tube. After the sample tube was closed and sealed, the aqueous solution was stirred with a stirring bar for 17 hours. The activated carbon was removed by filtration, the filtrate was placed in another 50 ml sample tube, the lid was closed and sealed. Then, the sample tube was shaken by hand for 20 seconds and left on the experimental table to observe the disappearance of foaming. As a result, foaming could not be confirmed.

(Comparative Example 2)
A potassium hydroxide aqueous solution containing a mixture of potassium salts of fluorine-containing carboxylic acids represented by the general formula (Y) and R ′ being CF ₂ COOH and a plurality of compounds having different n was prepared. The concentration of the potassium salt of the fluorine-containing carboxylic acid represented by the general formula (Y) is 0.34% by weight, the concentration of KF, CF ₃ COOK, the compound of n = 0 and ≧ C4 compound, and the average number of n values Was as shown in Table 1.

  30 g of this aqueous solution was placed in a 50 ml sample tube, and the lid was closed and sealed. Then, it was shaken by hand for 20 seconds, left on the experimental table, and the appearance of foaming was observed. As a result, the bubbles did not disappear even after 15 minutes.

(Comparative Example 3)
The potassium hydroxide aqueous solution used in Comparative Example 2 was subjected to hydrothermal decomposition treatment. Specifically, the decomposition reaction was carried out continuously using a SUS316 tube having an inner volume of 13 ml and an outer diameter of 3/8 inch as a reactor. An ISCO syringe pump was used as the pump, and the flow rate was controlled to be constant at 0.4 ml / min. The pressure was controlled to 2 MPa by installing an automatic back pressure valve (manufactured by JASCO Corporation) at the outlet, and the temperature was controlled so that the temperature at the outlet of the reaction tube was 150 ° C. The hydrothermal decomposition treatment was performed so that the aqueous solution stayed in the reactor for about 0.5 hours.

  The solution was trapped downstream of the back pressure valve. The trapped solution was placed in a 50 ml sample tube. The sample tube lid was closed and sealed. Then, the sample tube was shaken by hand for 20 seconds and left on the experimental table to observe the disappearance of foaming. As a result, it took about 10 minutes for the bubbling to disappear.

Example 4
The potassium hydroxide aqueous solution used in Comparative Example 2 was subjected to hydrothermal decomposition treatment. Specifically, the same reactor as that used in Comparative Example 3 was used, the pressure was controlled to 4 MPa, and the temperature was controlled to be 225 ° C., and the hydrothermal decomposition treatment was performed.

  The solution was trapped downstream of the back pressure valve. The trapped solution was placed in a 50 ml sample tube. The sample tube lid was closed and sealed. Then, the sample tube was shaken by hand for 20 seconds and left on the experimental table to observe the disappearance of foaming. As a result, no bubbling was observed as a result.

(Example 5)
The potassium hydroxide aqueous solution used in Comparative Example 2 was subjected to hydrothermal decomposition treatment. Specifically, the same reactor as that used in Comparative Example 3 was used, the pressure was controlled to 9 MPa, and the temperature was controlled to be 300 ° C., and the hydrothermal decomposition treatment was performed.

  The solution was trapped downstream of the back pressure valve. The trapped solution was placed in a 50 ml sample tube. The sample tube lid was closed and sealed. Then, the sample tube was shaken by hand for 20 seconds and left on the experimental table to observe the disappearance of foaming. As a result, no bubbling was observed as a result.

Table 1 shows the concentration of the fluorine-containing compound, the concentration of KF, CF ₃ COOK, the compound of n = 0 and the compound of ≧ C4, and the average number of n values in the aqueous solutions after the treatment of Examples 1 to 6.

  In each of the aqueous solutions after the treatments of Examples 1 to 5, the reduction degree of the compound of n ≧ 1, that is, the ≧ C4 compound was larger than the reduction degree of the compound of n = 0, compared with the aqueous solution before the treatment. . For example, the concentration of the compound with n = 0 in the aqueous solution after treatment in Example 1 is 0.135% by weight, which is 63% of the concentration of the compound with n = 0 in the aqueous solution before treatment (Comparative Example 1). Degree. In contrast, the treatment of Example 1 decreased the concentration of ≧ C4 compound from 1574 ppm to 80.1 ppm, about 95%. It is considered that this significant decrease in ≧ C4 compound led to suppression of foaming. In all Examples, the concentration of ≧ C4 compound was 100 ppm by weight or less, and the n-number average value was 0.1 or less.

  Hydrothermal decomposition was also confirmed to be effective as a technique for reducing ≧ C4 compounds. In Examples 4 and 5, since all ≧ C4 compounds were decomposed, no foaming occurred in the aqueous solution after treatment. Since the hydrothermal decomposition of Comparative Example 3 was lower in temperature and pressure, the decomposition of ≧ C4 compound was small, the concentration of ≧ C4 compound in the aqueous solution after treatment exceeded 100 ppm by weight, and the n-number average value was 0 .1 exceeded. Therefore, the foaming suppression effect was not sufficiently obtained.

  The method for treating a fluorine-containing compound-containing liquid of the present invention is effective in suppressing foaming of a solution containing a mixture of specific compounds that can function as an anionic surfactant, and cleaning of the production of hexafluoropropylene oxide. When the waste liquid generated in the treatment is further processed, it is effective for suppressing foaming of the waste liquid.

DESCRIPTION OF SYMBOLS 1 Composition supply line 3 Alkaline aqueous solution supply line 5 Gaseous material discharge line 7 Pump 9a Alkaline aqueous solution discharge line 9b Waste liquid line 9c Circulation line 10 Deoxidation tower 10a Tower part 10b Can part 11 Cleaning apparatus

Claims (7)

General formula (Y):
_{CF 3 O (CF 2 O)} n -R '(Y)
(Wherein, -R 'is -COOH, indicates -OCOOH or _-CF 2 COOH, n is shown to an integer of 0-50.)
Or a salt thereof, which is represented by the general formula (Y) and has 4 or more carbon atoms (hereinafter, ≧ C4) from an aqueous liquid containing a plurality of compounds having different n Compound)),
In an aqueous liquid from which ≧ C4 compound is removed, the concentration of ≧ C4 compound is 100 ppm by weight or less, and the n-number average value of the fluorinated carboxylic acid represented by the general formula (Y) or a salt thereof is 0.1 or less. Oh it is,
Removing the ≧ C4 compound comprises hydrothermally decomposing the ≧ C4 compound in a reaction vessel at a temperature of 200 ° C. to 400 ° C. and a gauge pressure of 2.0 MPa to 15 MPa.
A method for treating a fluorine-containing compound-containing liquid.   The method for treating a fluorine-containing compound-containing liquid according to claim 1, wherein the aqueous liquid is alkaline, and the plurality of compounds having different n is an alkali metal salt of a fluorine-containing carboxylic acid combined by the general formula (Y). A plurality of compounds having different n are represented by the general formula (Y), a compound containing fluorinated carboxylic acid or a salt thereof in which —R ′ is —CF ₂ COOH, and n = 0, and a compound represented by the general formula (Y The compound is a fluorine-containing carboxylic acid or a salt thereof in which —R ′ is —CF ₂ COOH, and a compound in which n ≧ 1, and a compound in which n ≧ 1 is removed as a ≧ C4 compound. Or the processing method of the fluorine-containing compound containing liquid of 2 .   The processing method of the fluorine-containing compound containing liquid of Claim 2 whose alkali metal is sodium or potassium. A method for producing hexafluoropropylene oxide, comprising:
a) Oxidation of hexafluoropropylene with oxygen to produce hexafluoropropylene oxide and the following general formula (X):
_{CF 3 O (CF 2 O)} n -R ··· (X)
(Wherein, -R is -COF, indicates -OCOF or _-CF 2 COF, n is an integer of 0 to 50.)
Obtaining a composition comprising a compound represented by:
b) washing the composition with an alkaline aqueous liquid to separate the compound represented by the general formula (X) into the alkaline aqueous liquid to obtain a gaseous substance containing hexafluoropropylene oxide; and c) The manufacturing method including the process of processing the alkaline aqueous liquid used for washing | cleaning by this process b with the processing method of the fluorine-containing compound containing liquid of any one of Claims 1-4 . The method for producing hexafluoropropylene oxide according to claim 5 , wherein the alkaline aqueous liquid contains at least one of potassium hydroxide and sodium hydroxide. The method for producing hexafluoropropylene oxide according to claim 5 or 6, wherein in step b, the pH of the alkaline aqueous liquid is maintained at 14 or more.

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