JPH03154683A - Treatment of waste water - Google Patents

Abstract

PURPOSE:To efficiently remove fluorine-containing carboxylate of a waste water phase by bringing the waste water phase containing fluorine-containing carboxylate into contact with an org. phase hardly compatible with water containing a salt of a specific quaternary onium cation. CONSTITUTION:The waste water phase containing fluorine-containing carboxylate formed in a hexafluoroproylene oxide synthetic reaction process as a byproduct is brought into contact with an org. phase hardly compatible with water containing a salt of a quaternary onium cation represented by formula I (wherein A is N or P and R1, R2, R3 and R4 are hydrocarbon). This org. phase is brought into contact with an aqueous phase containing a thiocyanate ion to form quaternary onium thiocyanate in the org. phase and subsequently brought into contact with an aqueous phase containing a water-soluble oxidizing agent to decompose the thiocyanate ion. The obtained org. phase is reutilized as the org. phase brought into contact with the waste water phase.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to hexafluoropropylene oxide (hereinafter referred to as
) Abbreviated as IFPO. ) relates to a method for treating wastewater during the production of More specifically, the present invention uses hypochlorite as an oxidizing agent, conducts the reaction in a two-phase system of an aqueous phase and an organic phase in the presence of a phase transfer catalyst, and processes hexafluoropropylene (hereinafter referred to as "H
This relates to a method for removing fluorine-containing carboxylates from a wastewater phase containing fluorine-containing carboxylates, which are by-products produced in the HFPO synthesis reaction step, in a method for producing HFPO from HFPO. (Prior art) HFPO is an industrially extremely important substance that is a raw material for various highly functional fluorine-based materials such as perfluoro lubricants, perfluoroelastomers, and perfluoro ion exchange resins. Although an economical manufacturing method for
As shown in JP-A No. 105978, JP-A-58-113187, JP-A-58-134086, etc., lipophilic complexing agents for quaternary ammonium salts, quaternary phosphonium salts, or metal cations. When HFP is reacted in a two-phase system consisting of an organic phase that is poorly miscible with water containing various phase transfer catalysts, such as, and an aqueous phase containing hypochlorite as an oxidizing agent, high It has been found by the inventors that HFPO can be obtained in high yield. Next, the present inventors used hypochlorite as an oxidizing agent to achieve an industrially advantageous method for producing HFP from HFP using a phase transfer catalytic reaction method.
In order to establish a process for manufacturing FPO,
A detailed study was conducted on the O synthesis reaction. As a result, when the HFPO synthesis antisynthesis reaction water was analyzed by Gask 9 mudgraphy, F-NMR spectroscopy, etc., the presence of various fluorine-containing carboxylates, which were thought to be by-products during the HFPO synthesis reaction, was confirmed. The fluorine-containing carboxylate anion in the fluorine-containing carboxylate is
Mainly CF2O (hQ and multiple C3 polyfluorocarboxylate anions (19F-NMR spectrum analysis shows that CF3CFXCO□○ (X=F, CE, H
)It is estimated to be. ] It is thought that it is composed of (Hereinafter, the fluorine-containing carboxylate anion in the wastewater will be abbreviated as "Rf, CO□0".) Rf, CO□O
Of these, CFiCFzCO□O is thought to originate from ChCFzCOF produced by isomerization of HFPO. On the other hand, CF, C0tO and other Rf, CO□
Although the detailed production mechanism of O is unknown, it is thought to be produced by decomposition of HFP or HFPO. From the viewpoint of environmental conservation, it is not preferable to discharge the aqueous phase containing Rf+C0ff1(E) to the outside of the HFPO production facility, and it is necessary to remove Rf+C0zO from the aqueous phase by some method. Also, I? Since fluorine-containing carboxylic acids such as f, CO, )l are useful as solvents, catalysts, or raw materials for the synthesis of fluorine-containing compounds, they can be used not only to remove Rf, Co□0 from the aqueous phase, but also to remove Rf, Co□0 from the aqueous phase. Isolating and using it as I has a great economic effect. Conventionally, various methods for separating carboxylic acids from strongly acidic aqueous solutions are known. However, the reaction water for HFPO synthesis and antisynthesis is usually strongly alkaline (for example, pH 10 or higher or pH 11 or higher), so when applying the above carboxylic acid separation method, a large amount of inorganic acid is added to the aqueous phase. It is necessary to add it to make a strongly acidic aqueous solution, which is not economically preferable. (Problem to be solved by the invention) In a method for producing HFPO from HFP by using hypochlorite as an oxidizing agent and carrying out a reaction in a two-phase system of an aqueous phase and an organic phase in the presence of a phase transfer catalyst. , as mentioned above, HF
The presence of various fluorine-containing carboxylates, which are thought to be by-products of the PO synthesis reaction, has been confirmed, and it is necessary to remove these fluorine-containing carboxylates from an environmental conservation perspective and from an economic perspective. However, an appropriate method has not been found. (Means for Solving the Problems) Therefore, the present inventors investigated how to extract Rf, CO from an alkaline aqueous solution containing nr, co, and 0 under alkaline conditions.
□A method for extracting O was intensively studied. As a result, Rf+
CO! The O-containing wastewater phase is expressed by the general formula (1)% formula% (
1) (However, A represents N or P atom, R,, R1゜h
and R4 represents a substituted or unsubstituted hydrocarbon group. The total number of carbons in R, R1, R3 and R4 is at least 8 per onium ion. R,, R2, R3 and R4 may be linked to each other to form a heterocycle, or RI+RI R3 or R4 may contain another onium ion. ) By contacting water containing a salt of a quaternary onium cation (hereinafter abbreviated as Q■) with a poorly miscible organic phase, a quaternary onium salt of a fluorine-containing carboxylic acid is added to the organic phase. It was found that (Rf, CO□OQ■) was formed, and as a result, Rf and CO□O in the aqueous phase were efficiently extracted into the organic phase. Next, the inventors found that Rf, C from Rf, CO□OQ■
We investigated a method of removing O□0 to separate nrIco and O, and at the same time forming a quaternary onium salt that is easy to ion exchange and is effective in extracting and removing Rf and CO□○ from the wastewater phase. For example, the present inventors have developed Rf I by an ion exchange reaction.
C0t OQ ”h) Q■C1 with high ion exchange activity
In order to obtain ○ and Q■OHO, the organic phase containing Rf and Co□OQ■ was brought into contact with a large amount of an aqueous solution containing NaCl and NaOH, but the ion exchange reaction hardly occurred, and R
It was found that f + C (h OQ■ forms a very stable ion pair. Conventionally, Q■C10 and Q oOHO Or, there was no known economically superior method of converting it into a quaternary onium salt such as Q■850.0, which is easy to ion exchange. Examples of salt conversion methods include (CH30) z
Blendst seam CBr saving using sQ,nds t
r'. m) method (C,M,5tarks and C,Li
otta, “Phase Transfer Cat
lysis”, Academic Press,
[Page 74] is known, but it has problems such as complicated operation and the use of toxic (CH30)z SO Therefore, the present inventors conducted further studies to develop an efficient treatment method for Rf, CO□0Q(E), and found that
We have discovered a method that utilizes the properties of thiocyanate ion (SCN O). First, the present inventors found that Rf,C from Rf,CO□OQ3
As a result of intensive study on various ion exchange methods to remove o□O, surprisingly, when the organic phase containing RflCO□OQ■ was brought into contact with the aqueous phase containing thiocyanate ion SCN (F), the results were found to be suitable for use in the present invention. RflCO of Rf+C0tOQ■ to be done! '3 was found to easily undergo ion exchange with SCN O. As a result, a quaternary onium thiocyanate salt is formed in the organic phase, and Rf and CO□O are transferred to the aqueous phase, so Rf and CO□○ can be easily recovered from the aqueous phase. . Note that the quaternary onium thiocyanate salt produced in the organic phase formed a very stable ion pair, and it was difficult to exchange it with various anions in the aqueous phase as it was. Therefore, the present inventors conducted intensive studies to find a method for converting the quaternary onium salt of thiocyanate in the organic phase into an active quaternary onium salt that can be easily exchanged with ions. When the organic phase containing SCN is brought into contact with the aqueous phase containing a water-soluble oxidizing agent, SCN○ is easily decomposed under mild conditions, and as a result, a quaternary onium salt with high ion exchange activity is formed in the organic phase. It was discovered that the organic phase can be used as it is for the extraction of Rf and CO□○ from the wastewater phase, and the present invention was completed. That is, the present invention uses hypochlorite as an oxidizing agent and performs a reaction in a two-phase system of an aqueous phase and an organic phase in the presence of a phase transfer catalyst to produce hexafluoropropylene oxide from hexafluoropropylene. In the method, 1) a wastewater phase containing a fluorine-containing carboxylic acid salt, which is a by-product produced in the hexafluoropropylene oxide synthesis reaction step, is converted into a wastewater phase containing a fluorine-containing carboxylic acid salt, which is a by-product of the hexafluoropropylene oxide synthesis reaction step, using the general formula (1) % formula %) (where A is an N or P atom). represents R,, R2゜R
3 and R4 represent a substituted or unsubstituted hydrocarbon group. The total number of carbons in R+, R2, R3 and R4 is at least 8 per onium ion. R1+ R2, R3 and R4 may be linked together to form a heterocycle, or R, R2, R3 or R4 may contain another onium ion. )
2) A quaternary onium salt of a fluorine-containing carboxylic acid is formed in the organic phase by contacting water containing a salt of a quaternary onium cation represented by the formula with a poorly miscible organic phase. 3) contacting the organic phase containing the thiocyanate quaternary onium salt with an aqueous phase containing thiocyanate ions to form a thiocyanate quaternary onium salt in the organic phase; is brought into contact with an aqueous phase containing a water-soluble oxidizing agent to decompose thiocyanate ions, and 4) the obtained organic phase is returned to the step 1) again. This relates to a removal method. As described above, in order to carry out the present invention, it is only necessary to carry out the two-phase reaction of the organic phase and the aqueous phase three times, and the organic phase containing the active quaternary onium salt produced by the treatment method of the present invention The phase can be used repeatedly as it is for the extraction of Rf and Co□○ from the wastewater phase. Furthermore, according to the method of the present invention, Rf, CO, and O can be easily recovered from the aqueous phase obtained by the treatment in step 2). Therefore, by employing the method of the present invention, it is possible to extract and remove Rr and co20 from the wastewater phase and simultaneously recover Rf and CO□O. The method of the present invention will be explained in more detail below. The organic phase, aqueous phase, and phase transfer catalyst used in the HFPO synthesis step of the present invention are disclosed in JP-A-57-183773, JP-A-58-113187, and JP-A-58-13.
Those disclosed in Japanese Patent Laid-Open No. 4086, Japanese Patent Application Laid-Open No. 58-105978, etc. can be used as they are. For example, phase transfer catalysts include various hydrophobic onium salts such as quaternary ammonium salts and quaternary phosphonium salts, macrocyclic polyethers, macrocyclic aminoethers, amine oxides, polyethylene glycol derivatives, and polyvinylpyrrolidone. Examples include lipophilic complexing agents. The quaternary ammonium salt and quaternary phosphonium salt used as the phase transfer catalyst described above are quaternary ammonium salts and quaternary phosphonium salts represented by the general formula CI) used as extractants for Rf and CO□○ in the method of the present invention. The same salts as onium cations are used. In the method of the present invention, the fourth
Onium cations include R,, l? ,. Hydrophobic quaternary onium cations containing R3 and R4 hydrocarbon groups are used. The type and length of this hydrocarbon group are appropriately selected depending on the solvent used, the purpose of use, etc. Examples of the type of hydrocarbon group include an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, an aralkyl group, an alkenylaryl group, and particularly preferably an alkyl group, an aryl group, an aralkyl group, etc. is used. In addition, the lengths of the hydrocarbon groups are R1, R2, R3 and R
The total number of carbon atoms contained in 4 is at least 8 per onium ion, usually in the range of 8 to 70, preferably in the range of 10 to 50, particularly preferably 12 to 50. The range is 40. The above hydrocarbon group may be substituted with a substituent that is stable under the reaction conditions of the present invention. The inert substituents that can be substituted on the above hydrocarbon groups are limited depending on the reaction conditions, but halogens, acyl groups, ether groups, ester groups, nitrile groups, alkoxyl groups, etc. are usually used. . RI+ R2, R: l and R4 may be linked to each other to form a heterocycle, or R+, R2, R3 or R4 may contain another onium ion. Examples of the hydrophobic quaternary onium cation represented by formula (1) include tetra-n-propylammonium ion, tetra-n-butylammonium ion, tri-n-octylmethylammonium ion, tetra-n-octylammonium ion, tetra-
n-decyl ammonium ion, cetyltrimethylammonium ion, tri-n-decylmethylammonium ion, benzyltrimethylammonium ion, benzyltriethylammonium ion, cetylbenzyldimethylammonium ion, cetylpyridinium ion, n-dodecylpyridinium ion, phenyltrimethylammonium ion, Quaternary ammonium ions such as phenyltriethylammonium ion, N-benzylpicolinium ion, pentamethonium ion, hexamethonium ion; or tetra-n-butylphosphonium ion, tri-lowoctylethylphosphonium ion, tri-n-octylmethylphosphonium ion , cetyltriethylphosphonium ion, cetyltri-n-butylphosphonium ion, n-butyltriphenylphosphonium ion, n-amyltriphenylphosphonium ion, n-hexyltriphenylphosphonium ion, n-hebutyltriphenylphosphonium ion, methyltriphenylphosphonium ion, and quaternary phosphonium ions such as benzyltriphenylphosphonium ion and tetraphenylphosphonium ion. In addition, various types of anions can be used as the anions in the quaternary onium salt used for the initial extraction of Rf and CO□○ in the method of the present invention, but usually chlorine ions and bromide ions are used. Anions that are easily exchangeable such as halogen ions, hydroxide ions, sulfate ions, or hydrogen sulfate ions are used, but the present invention is not limited thereto. The organic phase that is poorly miscible with water used in the wastewater treatment method of the present invention contains a salt of a quaternary onion or rum cation represented by the general formula (1), and forms a phase different from the aqueous phase. It usually consists of a quaternary onium salt and an organic solvent that is poorly miscible with water, but in some cases it may be composed mainly of a liquid quaternary onium salt, The organic phase may consist of two or more types of phases that are poorly miscible with water. Examples of poorly water-miscible organic solvents for the organic phase used in the method of the invention include, for example, aliphatic hydrocarbons such as n-hexane, n-octane, n-decane; cyclohexane, methylcyclohexane, Alicyclic hydrocarbons such as decalin; aromatic hydrocarbons such as benzene, toluene, and xylene; ethers such as diisopropyl ether and di-n-butyl ether; methylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane , chlorinated hydrocarbons such as chlorobenzene: 1,2-dichloro-1,1,2,2
-tetrafluoroethane, fluorotrichloromethane,
1.1.2-) Hydrocarbons substituted with chlorine atoms and fluorine atoms such as dichloro-1,2,2-)realoloethane and 1.1.2.2-tetrachloro-1,2-difluoroethane ; Perfluorocyclobutane, perfluorodimethylcyclobutane, perfluorohexane, perfluorooctane, perfluorodecane, 1,3 di(trifluoromethyl)benzene, hexafluorobenzene, 2
Perfluoro- or polyfluoro-carbons which may contain an oxygen atom such as H-tetradecafluoro-5-(trifluoromethyl)-3,6-sioxanonan, perfluoro-2-butyltetrahydrofuron; or these Examples include, but are not limited to, mixed solvents. When selecting an organic solvent, an appropriate solvent is selected in consideration of the solubility of the quaternary onium salt, phase separation from the aqueous phase, operating temperature at which the method of the present invention is carried out, and the like. Among the above solvents, chlorinated hydrocarbons and hydrocarbons have Rf
, Co□OQ■ is excellent in that it has a high solubility. Further, the fluorine-containing solvent is excellent in that it has good phase separation from the aqueous phase. Incidentally, the above-mentioned organic solvents that are poorly miscible with water can also be used as organic solvents in the HFPO synthesis reaction step of the present invention. The hypochlorite used in the HFPO synthesis reaction step of the present invention may be one that liberates hypochlorite ions in the aqueous phase. Among these, sodium hypochlorite and calcium hypochlorite are particularly suitable because they are industrially mass-produced and can be obtained at low cost. In addition, in the aqueous phase used in the HFPO synthesis reaction step,
In addition to hypochlorite, the presence of an inorganic base such as sodium hydroxide results in a higher IFP conversion even under reaction conditions where only a small amount of hypochlorite is added. This is preferable because a good HFPO selection rate can be obtained even when using the same method. As a method for carrying out the HFPO synthesis reaction step of the present invention, any of the batch method, semi-circulation method and distribution method can be used. The amount of quaternary onium salt used in step 1) of the wastewater treatment method of the present invention mainly depends on the amount of RftCOZO in the wastewater phase, and usually the molar ratio of Q■/RflCOZ○ is 0.
A range of 5 to 20 is used, preferably a range of 1 to 10, more preferably a range of 1 to 5. Mouth○/Rf,
When CO□Q is less than 0.5, the extraction rate of Rf1CO□O is too low to be practical, and also when Q■/Rf,C
If O□○ is 20 or more, it is not preferable because the operating cost of this treatment method becomes high. The method of contacting the organic phase containing the quaternary onium salt with the aqueous phase containing Rf and Co□O in step 1) of the wastewater treatment method of the present invention is normally used as a two-liquid reciprocal stress method. Any of the batch method, semi-circulation method, and distribution method is possible. However, industrially, flow methods such as the countercurrent multistage catalytic reaction system and the continuous stirred tank type reaction system, which can be operated continuously, are advantageous. This is advantageous in that the amount of quaternary onium salt used relative to Rf and CO□O can be small. As the countercurrent multistage reaction apparatus, mixer settlers, rotating disk extractors, perforated plate extraction towers, stirring extraction towers, etc., which are commonly used in extraction operations, etc. can be used as they are. The temperature at which the organic phase containing the quaternary onium salt is reacted with the aqueous phase containing Rr and CO20 may be around room temperature and is not particularly limited; however, if the temperature is too low, the ion exchange rate may become slow. However, if the temperature is too high, problems such as freezing of the aqueous phase and organic phase may occur, and problems such as evaporation of the solvent may occur if the temperature is too high. Therefore, normally -10°C to 10°C
Temperature between 0'C, preferably -5°C to 80°C
A temperature between is chosen. The ion source of thiocyanate ions used in step 2) of the method of the present invention is not particularly limited as long as it forms thiocyanate ions in an aqueous solution.
Various water-soluble thiocyanates are used. Examples of water-soluble thiocyanates include alkali metal salts such as sodium thiocyanate and potassium thiocyanate; alkaline earth metal salts such as calcium thiocyanate and barium thiocyanate; zinc thiocyanate, iron thiocyanate, and thiocyanate. Examples include, but are not limited to, ammonium acid. However, in consideration of price, availability, etc., sodium thiocyanate, potassium thiocyanate, and ammonium thiocyanate, which are used in large quantities industrially, are advantageous as thiocyanate ion sources. Fluorine-containing carboxylic acid quaternary onium salt Rf, CO□○Q■ in the organic phase produced in step 1) of the method of the present invention
There are no particular restrictions on the molar ratio of and SCN (E). However, if the molar ratio of SCN○/Rf, CO□OQO is less than 1, complete exchange of Rr+cO□O is not possible, so when attempting to exchange substantially all Rf and CO□9, , SCN○/Rf, and CO□og o need to be 1 or more in molar ratio. In practice, the molar ratio of SCN O/Rr, co□○gO is usually o, s<SCN<3/R, considering the cost of SCN○, ease of ion exchange reaction, etc.
flCO□Cog■ is in the range of 20, preferably 0.
8< SCN O/Rf ICO
□OQ■ A range of 4 is used. In addition, if an anion other than RflCO□○ exists as a counter ion for Q■ in the quaternary onium salt,
If substantially all RflCO□O is to be exchanged, the molar ratio of SCN○/Q■ must be 1 or more. In addition, the actual molar ratio of SCN○/gO is usually in the range of 0.5 to 20, preferably 0.8 to 1.
A range of 0 is used, particularly preferably a range of 1 to 4. As mentioned above, even if the quaternary onium salt contains anions other than Rf and CO□○, most of them are Rf,
Since CO□O is ion-exchanged with thiocyanate ion, this poses no particular problem. However, significant amounts of hypochlorite ions may be entrained in the organic phase containing RflCO□○Q(E). Since hypochlorite ion has the ability to oxidize thiocyanate ion, when hypochlorite ion is present in the organic phase, thiocyanate ion is Some of the ions are decomposed by reaction with hypochlorite ions. Therefore, if the content of hypochlorite ions in the organic phase is high,
If necessary, the organic phase can be treated with an aqueous solution containing a water-soluble reducing agent such as sodium sulfite or sodium thiosulfate before contacting the thiocyanate ion-containing aqueous solution with the organic phase. It is also possible to suppress the decomposition of acid ions. Further, dissolving a reducing agent in an aqueous solution containing thiocyanate ions is also effective in suppressing decomposition of thiocyanate ions. The method, apparatus, and temperature for contacting the organic phase containing the fluorine-containing carboxylic acid quaternary onium salt and the aqueous phase containing thiocyanate ion in step 2) of the wastewater treatment method of the present invention are as follows:
Exactly the same method as in the case of bringing the organic phase and the aqueous phase into contact in step 1) is employed. Conventionally, as a method for decomposing SCN○, decomposition of SCN○ in an aqueous solution using an oxidizing agent such as sodium hypochlorite is known, but an example of the decomposition of SCN○ in a hydrophobic solvent was reported by the present inventors. As far as I researched, it was unknown. However, the inventors' studies surprisingly revealed that
Although quaternary onium thiocyanate is present in the organic phase, which is poorly miscible with water, various water-soluble oxidizing agents, including sodium hypochlorite, can improve the efficiency of quaternary onium thiocyanate. It was found that it decomposes. The water-soluble oxidizing agent used in step 3) of the present invention includes:
Various oxidizing agents are used that react with the thiocyanate ion to decompose the thiocyanate ion structure. Examples include hypochlorites such as sodium hypochlorite, potassium hypochlorite, and calcium hypochlorite; chlorates such as sodium chlorate; hypochlorous acid, chlorinated water, etc. Chlorine-based oxidizing agents; Peroxide-based oxidizing agents such as hydrogen peroxide and monobutyl hydroperoxide; Nitric acid-based oxidizing agents such as nitric acid, nitrous acid, and sodium nitrate; or Persulfuric acid-based oxidizing agents such as sodium persulfate. etc., but are not limited to these. Among these water-soluble oxidizing agents, inorganic oxidizing agents are superior in that they are easily available and are less likely to remain in the organic phase. Among them, chlorine-based oxidizing agents, especially hypochlorites such as sodium hypochlorite and calcium hypochlorite, are easy to obtain and have excellent safety, operability, and reactivity. and is suitable for the method of the present invention. In the method of the present invention, there is no particular restriction on the molar ratio of the water-soluble oxidizing agent to be reacted with the quaternary onium thiocyanate salt in the organic phase, but in order to sufficiently decompose SCN○, it is necessary to It is preferable to use a molar ratio of oxidizing agent/quaternary onium thiocyanate of 1 or more. In practice, in consideration of economic efficiency, reaction efficiency, etc., the molar ratio of water-soluble oxidizing agent/quaternary onium thiocyanate is usually in the range of 2 to 100, preferably in the range of 2 to 20.
Particularly preferably, a range of 3 to 15 is used. The reaction method for the organic phase containing the quaternary onium thiocyanate salt and the aqueous phase containing the water-soluble oxidizing agent includes the above-mentioned step 2.
) in the organic phase containing Rf + COg OQ O and S
A method quite similar to that of the aqueous phase containing CN 2 O can be used. The temperature at which the organic phase containing the quaternary onium thiocyanate and the aqueous phase containing the water-soluble oxidizing agent are reacted may be around room temperature and is not particularly limited; however, if the temperature is too low, the reaction rate will be slow. If the temperature is too high, problems such as evaporation of the solvent may occur. Therefore, typically -10°C to 10°C
A temperature between 0°C and preferably between -5°C and 60°C is chosen. FIG. 1 shows an example of a block flow sheet for carrying out the method of the present invention. First, in the ion exchange reaction step [Step 1], Rf, CO
□O is extracted from the aqueous phase, and Rr and co20 Q■ are added to the organic phase.
to form. Next, in the ion exchange reaction step [Step 2], Rf and Co□○ are transferred to the aqueous phase by an ion exchange reaction between RflCO□○Q■ and SCN C), and Q is transferred to the organic phase.
■Form SCN O. In the SCN O decomposition step [Step 3], 5CN in Q■SCN○ is removed by a water-soluble oxidizing agent.
A decomposition reaction of O is carried out and active quaternary onium salts with high ion exchange activity are formed in the organic phase. The organic phase containing the active quaternary onium salt thus obtained is returned to the ion exchange reaction step [Step 1] for extracting RflC (hO). ] Extraction of RflCO20 from the wastewater phase in [Step 2]
, CO20 will be recovered at the same time. Note that hypochlorite usually remains in the wastewater phase containing Rf+CO2o after the HFPO synthesis reaction. Therefore, if hypochlorite is present in the wastewater phase,
For example, the molar ratio of [number of moles of hypochlorite ion in the wastewater phase before the treatment]/[number of moles of QθSCN O in the organic phase] is 1 or more, preferably in the range of 2 to 100, and sometimes If it is preferably in the range of 2 to 20, it is also possible to omit the step of treating Q15CN(E) with a water-soluble oxidizing agent in this treatment method. That is, in the above-mentioned "method for removing fluorine-containing carboxylate from a wastewater phase" of the present invention, the organic phase containing the quaternary onium thiocyanate produced in step 2) is directly treated with the fluorine-containing carboxylate of step 1). The fourth step by decomposition of the SCN O by the water-soluble oxidizing agent of step 3) is achieved by contacting the wastewater phase containing the acid salt and unreacted hypochlorite.
It is also possible to simultaneously perform the improvement of the ion exchange ability of the quaternary onium salt and the extraction and removal of the fluorine-containing carboxylic acid salt from the wastewater phase using the resulting active quaternary onium salt in two operations. FIG. 2 shows an example of a block flow sheet for implementing this method. In [Step 4], Rf and CO□9Q(E) are first formed in the organic phase by an ion exchange reaction between the quaternary onium salt and Rf+COz◯ in the wastewater. In the ion exchange reaction step [Step 5], Rf+COz OQ O
Due to the ion exchange reaction between and SCN○, Q■S is present in the organic phase.
CN○ is formed. Next, the organic phase containing Q■SCN O is returned to [Step 4], where Rf, Coz○ and o
By contacting with an aqueous solution containing cio, SCN
Activation of quaternary onium salt by decomposition of ○ and RflC (
Extraction of hO is carried out simultaneously. Thereafter, by repeating [Step 4] and [Step 5] alternately, the fourth
Rf, GO! which repeatedly uses grade onium salts! ○ extraction method becomes possible. When the method shown in FIG. 2 is implemented, the following effects are obtained compared to the method shown in FIG. 1. ■One less process. ■The cost of oxidizing agent for SCN CD decomposition becomes unnecessary. ■ Since hypochlorite in the wastewater phase is consumed by reaction with SCN e, the cost of treating (reducing or decomposing) hypochlorite in wastewater treatment is reduced. In addition, as a method for carrying out the two-component reaction in (Step 3) and [Step 4], the same method as in the case of carrying out the above-mentioned Step 1), Step 2), or Step 3) is adopted. (Effect of the invention) By implementing the method of the invention, under mild conditions,
By simple operations, the by-product fluorine-containing carboxylate can be efficiently removed from the wastewater phase in the HFPO synthesis reaction. (Example) The present invention will be explained below with reference to Examples.
The scope of these examples is not intended to be limiting. Example 1 <HFPO synthesis reaction> Stirring rod coated with fluororesin, thermocouple nozzle, pressure gauge, cooling device, reaction liquid sampling nozzle [A
], Furthermore, a pressure-resistant glass reactor with an internal volume of 300 d and equipped with a nozzle (B) for filling and extracting the reaction solution and product is used for the HFPO synthesis reaction. First, trioctyltrimethylammonium chloride (hereinafter abbreviated as "TOM AC") 0. 160 ml of CF2-1-lichloro1.2.2-trifluoroethane (hereinafter abbreviated as "F-113") solution containing 580 g (1,44 mmol) and 1.5% by weight of sodium hydroxide. Fill with 10 mQ of sodium hypochlorite aqueous solution containing 6% effective chlorine concentration. After cooling the contents to -5°C,
RFP4.20g (28mmol) cooled to -5°C
The reaction is started by charging the solution and stirring the reaction solution vigorously. During the reaction, the temperature of the reaction solution is between 15°C and -
The reactor was cooled to a temperature within the range of 3"C. Stirring was stopped 10 minutes after the start of the reaction, and the reaction product was analyzed by gas chromatography. The reaction rate was 81%. After 10 minutes of reaction, the pressure inside the reactor was reduced and HFPO and about 40 d of F-113 were removed from the nozzle (B). Thereafter, the pressure inside the reactor was reduced to atmospheric pressure. , the wastewater phase was taken out from the reactor.The contents in the wastewater phase were analyzed by F-NMR spectrum, and it was found that CF3CO20 and CF:+
The existence of a fluorine-containing carboxylate anion represented by pFXCOz O (X = F, C1, H) was suggested. In addition, CF3C0ZO/CF:+CFX in the wastewater phase
The COz○ no molar ratio was 88/12. [CF3CO20 and CF:+CFXC02□9
It is abbreviated as flCO□○. ] <Extraction of Rf, CO□○> 50 ml of the wastewater phase containing Rf and CO□O produced in the HFPO synthesis reaction was extracted with fresh TOMAC5 each time.
When extracted three times using 50 ml of F-113 solution containing g, most of Rf and CO□○ in the aqueous phase were extracted into the organic phase. Infrared absorption spectrum and 19F of the organic phase shown below
- According to the results of NMR spectrum analysis, Rf and CO□○ extracted from the aqueous phase to the organic phase are
It was suggested that it exists in the organic phase in some form. (2) A characteristic absorption hand of a fluorine-containing carboxylate anion is observed in the infrared absorption spectrum at 1695 cm-'. ■19F-NMR spectrum The signal shown below was observed, and the 19F-N of the standard substance
Comparison with MR spectrum data suggested the presence of fluorine-containing carboxylate anions of CF3CO20 and CF3CFXCO□O. CF3-CF2-CO20CF3-CFCjl! −
CO□0CF3-CFH-CO2・○ CF3-C
o□O<Ion exchange reaction with 5CNO> Rf, Co□ obtained in the above RflCO20 extraction step
○Quaternary onium salt containing Q9 (about 37.5+n in total)
Approximately 150 ml of F-113 solution containing mo1) was mixed with an aqueous solution containing 5% by weight of Na5CN at 50d and 30°.
Ion exchange treatment was performed by stirring at C for 10 minutes. When this ion exchange treatment was repeated 10 times, it was found by infrared absorption spectral analysis that almost all of the quaternary onium salt in the F-113 solution was converted to QOSCN○. Infrared absorption spectrum data of Q"53CN (E) νSCN e: 2050 cm-'<Decomposition of 5CNO with water-soluble oxidizing agent> , 200% sodium hypochlorite aqueous solution containing 3% NaOH and 12% effective chlorine concentration,
The mixture was vigorously stirred and mixed for 20 minutes at 30°C. As a result, the SCN○ of Q QSCN O in the organic phase is
The fact that all of the components are decomposed is the 2nd part of the infrared absorption spectrum.
This was confirmed because the absorption at 050 cm-' completely disappeared. <Extraction of Rr, co, (E) using regenerated quaternary onium salt> F-113 solution containing the quaternary ammonium salt obtained by the above SCN O decomposition treatment operation
The precept was divided into three equal parts of 50 m each. This solution 50 was added to the F-113 solution 5 containing 5 g of TOMAC in the <Rf+C0zO extraction> step described above.
When a similar Rf+COz○ extraction operation was carried out using 0 m2 instead of 0 m2, most of the Rr, co, and O in the aqueous phase were extracted into the organic phase. This result shows that the quaternary ammonium salt obtained by the above S(, N C) decomposition treatment operation has the same Rf, CO, and O extraction ability as TOMAC. Therefore, the above experimental results confirm that it is possible to implement the method of extracting Rf and CO□O from the wastewater phase by repeatedly using a quaternary onium salt as shown in Figure 1. Ta. Example 2 <Continuous synthesis reaction of HFPO> A tubular reactor with an internal volume of 1.21 mm as shown in Fig. 3 [
6], decanter (7), ) (FPO distillation column [8], and organic phase tank

With a continuous reaction apparatus equipped with [9],
HFPO was synthesized from HFP. First, the tubular reactor [6] was cooled to -5℃, and
9. F-113 solution containing % TOMAC by weight.
Circulate through the reactor at a flow rate of 41/hr. Next, 1.0 mol/f of sodium hypochlorite and 1.
An aqueous solution of sodium hypochlorite containing 5% by weight of sodium hydroxide is poured into a tube-shaped tank [6]. /
hr flow rate, and at the same time the decanter [7]
is discharged from. HFP was installed in a tubular reactor at a flow rate of 0.5 kg/hr.
6] is supplied to the organic phase line before HF
A continuous synthesis reaction of PO is started. The reaction liquid exiting the tubular reactor [6] is transferred to a decanter [7].
] into an organic phase and an aqueous phase, and the aqueous phase is discharged from the reactor. The organic phase containing the produced HFPO is sent to the HFPO distillation column [8], where the produced HFPO and unreacted R
FP is separated from the organic phase by distillation. The remaining organic phase after HFPO and RFP are distilled off is stored in an organic phase tank [
9], from where it is recycled to the tube reactor [6]. According to post-reaction gas chromatography analysis, 15 minutes after the start of the reaction, the HFP conversion rate was 9.
It was 9% or more, and the HFPO selection rate was 81%. In the above continuous reaction, the distribution of Rf and CO□■ in the wastewater phase obtained between 1 hour and 3 hours after the start of the reaction was investigated by F-NMR spectrum, and it was found that CF
The molar ratio of iC(hO/CF3CFXCO□○ is 87/
It was 13. Note that the pH of this aqueous phase was 12°3. [Step A]: 400 g of TOMAC was added to this wastewater phase 52.
Using a jacketed multistage countercurrent extraction column with a column diameter of 40 manφ and having 10 stages of stirring chambers partitioned by perforated plates, a jacket temperature of 20
When subjected to countercurrent contact at °C, Rf, CO□ in the wastewater phase
Almost the entire amount of O is extracted into the organic phase, and Rf, Co, ○Q
It was forming the. [Step B]: Next, in the same multistage countercurrent extraction column as used in [Step A], the organic phase 91 containing Rf and CO□OQ■ is mixed with an aqueous solution 102 containing 300 g of Na5CN. When the mixture was brought into countercurrent contact at a jacket temperature of 20°C, almost all of the quaternary onium salts in the organic phase were 0SCN○. (A part of the 0■SCN○ existed in a suspended state.) [Step C]: Using the multistage countercurrent extraction column used in [Step A], the relevant F containing 0■SCN○ was extracted. -113 solution 81 and sodium hypochlorite aqueous solution 61 with an available chlorine concentration of 12% (approximately 2N) were brought into countercurrent contact at a jacket temperature of 20°C.
Analysis by infrared absorption spectroscopy confirmed that all N 2 O had been decomposed. [Step D]; Using F-113 solution 61 containing the quaternary onium salt obtained in [Step C], [Step A]
When wastewater phase 31 containing CO□○ was treated in the same manner as above, almost all of the RflCO,○ in the wastewater phase was extracted into the organic phase. This result shows that the quaternary onium salt obtained in [Step C] has the same ability to extract Rf + CO□O as TOMAC used in [Step A]. Example 3 The same HFPO synthesis reaction as in Example 2 was carried out by changing the flow rate of the sodium hypochlorite aqueous solution to 8. 'll/hr instead of 9.
8 A/hr, the flow rate of the F-113 solution containing TOMAC was 1.51/hr instead of 9.41/hr, and the RFP supply rate was 0.4 kg/hr instead of 0.5 kg/hr. I went there as an hr. As a result, at the outlet of the back reactor [6], H
30 minutes after the start of FP supply, the HFP conversion rate was approximately 1.
00%, and the HFPO selectivity was 78%. Furthermore, the RFP conversion rate after 5 hours from the start of HFP supply was 96%.
The HFPO selectivity was 81%. In the above HFPO synthesis reaction, after the start of HFP supply, 3
CF in the wastewater phase obtained between approximately 201 and 5 hours.
3CO20/CF3CFXCO! The molar ratio of O is 88/
12, and the pH of this aqueous phase was 12.5. [Step E]: Q 05CN OO, 047 mol prepared from the Q■cp○-containing organic phase and the Na5CN-containing aqueous phase
/l of F-113 solution 121 and the wastewater phase 5.
When 22 was brought into countercurrent contact at a jacket temperature of 20°C using the multistage countercurrent extraction column used in Example 2, SCN O in the organic phase completely disappeared, and Rf in the wastewater phase disappeared. ,
Most of Co□○ is extracted into the organic phase, and Rf, CO□
○Q■ was formed. [Step F); The organic phase 1ON containing Rf, Co□OQO and the aqueous solution 51 containing 200 g of Na5CN were heated at a jacket temperature of 20°C using the multistage countercurrent extraction column used in Example 2. When brought into countercurrent contact with
The quaternary onium salts in the organic phase are almost all Q.
(EI SCN O, and Rf and CO□O had migrated to the aqueous phase. [Step G]: Using the organic phase containing QO5CN O obtained in [Step F], [Step E ], most of the Rf and COz○ in the wastewater phase were extracted into the organic phase. From the above experimental results, the Q
(E) SCN It was confirmed that it is possible to implement the method of repeatedly using (E) to extract Rf, Co, and O from the wastewater phase. Example 4 RflC produced in the same HFPO synthesis reaction as in Example 1
The O□O-containing wastewater phase was treated each time with 6°0 g (12
, 5 mmol) was extracted three times using 50 ml of chloroform solution containing RflCO20 in the aqueous phase.
It was confirmed by 19F-NMR spectrum analysis of the aqueous phase and infrared absorption spectrum analysis of the organic phase that most of it was extracted into the organic phase and formed a salt with trioctylethylphosphonium cation. Ta. A quaternary phosphonium salt containing Rf and COZ9go (in this case, 0■ represents trioctylethylphosphonium cation) obtained as above (approximately 37% in total).
<Ion exchange with SCN○> in Example 1 using a chloroform solution 150 relatives containing 5 mmol),
The same operations as <decomposition of 5cNa with water-soluble oxidizing agent> and extraction of Rf and Co□○ using recycled quaternary onium salt> were performed. As a result of the above experiment, even when Q It was confirmed that the method of extracting Rf and Co□○ as shown in the figure is possible. Example 5 The same HFPO synthesis reaction as in Example 1 was carried out. Rf produced at this time, Wastewater phase containing Co□○ 50
The same operation as <Extraction of RflCO□O> in Example 1 was carried out using d, but instead of using 50 In1 of F-113 solution containing 5 g of TOMAC three times, 50 In of toluene solution containing 5 g of tetrahexylammonium chloride was used.
m1 was used three times, and further, <5CN of Example 1
When the same operation as O ion exchange reaction was carried out,
The same results as in Example 1 were obtained, and finally qoscNo.
(in this case Q(E) represents the tetrahexylammonium cation) 150 ml of toluene solution were obtained. Using 150 d of this toluene solution, the <decomposition of 5CNO with a water-soluble oxidizing agent (sodium hypochlorite)> and <Rf+C (extraction of hO) with regenerated quaternary onium salt> of Example 1 were subsequently carried out. Similar results were obtained, and it was found that the tetrahexylammonium salt/toluene system is useful for extracting Rf and CO□O from the wastewater phase of the HFPO synthesis reaction.Example 6 Example 5 and The same operation was carried out using hydrogen peroxide, nitric acid, chlorine water, and calcium hypochlorite instead of sodium hypochlorite as the water-soluble oxidizing agent in the step of <decomposition of 5CNO with a water-soluble oxidizing agent>. However, the concentration of the aqueous solutions of various water-soluble oxidizing agents was 2N, and the molar ratio of oxidizing agent/SCN○ was 30 (in the case of calcium hypochlorite, aczo
7S (30:NO), stirring was performed at 30'C for 1 hour. As a result, it was confirmed by analysis of the infrared absorption spectrum of the organic phase that most of the SCN O in the organic phase disappeared under the above conditions. In addition, using a toluene solution containing a quaternary ammonium salt obtained by the treatment method using the various oxidizing agents described above,
Rf, CO□ by regenerated quaternary onium salt in Example 1
When the same operation as in [Extraction of O] was carried out, in all cases, most of Rr and coz O in the aqueous phase were extracted into the organic phase. The above results indicate that in the present invention, QO3CN in the organic phase
It has been shown that, in addition to sodium hypochlorite, hydrogen peroxide, nitric acid, chlorine water, calcium hypochlorite, etc. are similarly useful as water-soluble oxidizing agents for decomposing SON○ of ').

[Brief explanation of the drawing]

Figures 1 and 2 are block flow sheets of an example of a wastewater treatment method for removing by-product fluorine-containing carboxylic acid salts from the wastewater phase in the HFPO synthesis reaction. This is an example of a device for manufacturing.

Claims (2)

[Claims] (1) In a method for producing hexafluoropropylene oxide from hexafluoropropylene by using hypochlorite as an oxidizing agent and carrying out a reaction in a two-phase system of an aqueous phase and an organic phase in the presence of a phase transfer catalyst, the method comprises: ) The wastewater phase containing the fluorine-containing carboxylic acid salt, which is a by-product produced in the hexafluoropropylene oxide synthesis reaction step, is expressed by the general formula [
I ] R_1R_2R_3R_4A^■ [ I ] (However, A represents N or P atom, R_1, R_2
, R_3 and R_4 represent a substituted or unsubstituted hydrocarbon group. The total number of carbons in R_1, R_2, R_3 and R_4 is at least 8 per onium ion. R_1, R_2, R_3 and R_4 may be linked to each other to form a heterocycle, or R_1, R_2,
R_3 or R_4 may contain other onium ions. ) to form a quaternary onium salt of a fluorine-containing carboxylic acid in the organic phase by contacting water containing a salt of a quaternary onium cation represented by (2) with a poorly miscible organic phase;
3) contacting the organic phase containing the fluorine-containing carboxylic acid quaternary onium salt with an aqueous phase containing thiocyanate ions to form a thiocyanate quaternary onium salt in the organic phase; 4) decomposing the thiocyanate ions by contacting the organic phase containing the salt with an aqueous phase containing a water-soluble oxidizing agent; and 4) returning the obtained organic phase to the process of 1). Method for removing fluorine-containing carboxylates. (2) In the method according to claim 1, the organic phase containing the quaternary onium thiocyanate produced in step 2) is directly mixed with the fluorine-containing carboxylic acid salt of step 1) and unreacted hypochlorite. By bringing it into contact with the wastewater phase containing an acid salt, the decomposition of thiocyanate ion by the water-soluble oxidizing agent in step 3) and the removal of the fluorine-containing carboxylate from the wastewater phase in step 4) and step 1) can be simultaneously performed. A method characterized by carrying out.