JP4415656B2 - Method for purifying carbonyl difluoride - Google Patents

Method for purifying carbonyl difluoride Download PDF

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JP4415656B2
JP4415656B2 JP2003396082A JP2003396082A JP4415656B2 JP 4415656 B2 JP4415656 B2 JP 4415656B2 JP 2003396082 A JP2003396082 A JP 2003396082A JP 2003396082 A JP2003396082 A JP 2003396082A JP 4415656 B2 JP4415656 B2 JP 4415656B2
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carbonyl difluoride
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明典 山本
拓司 久米
征司 田窪
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/151—Reduction of greenhouse gas [GHG] emissions, e.g. CO2

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Description

本発明は、炭酸ガスを含む二フッ化カルボニルから炭酸ガスを分離して、二フッ化カルボニルを精製する方法に関するものである。更に詳しくは、半導体用に用いられる二フッ化カルボニルから炭酸ガスを分離する方法に関するものである。   The present invention relates to a method for purifying carbonyl difluoride by separating carbon dioxide from carbonyl difluoride containing carbon dioxide. More specifically, the present invention relates to a method for separating carbon dioxide from carbonyl difluoride used for semiconductors.

二フッ化カルボニルは、有機フッ素化合物の原料、半導体製造時のクリーニングガスなどの用途があり、有用な物質である。   Carbonyl difluoride is a useful substance because it has uses such as a raw material for organic fluorine compounds and a cleaning gas for manufacturing semiconductors.

二フッ化カルボニルの製造方法としては、炭酸ガスとフッ素ガスとを気相で反応させる方法（特許文献１）、一酸化炭素の電解フッ素化による方法（特許文献２）、溶媒存在化ホスゲンをフッ化水素によりフッ素化する方法或いは溶媒およびトリエチルアミン存在下フッ化水素によりホスゲンをフッ素化する方法（特許文献３）、溶媒中でフッ化ナトリウムによりフッ素化する方法（特許文献４）、ホスゲンを気相で活性炭触媒にてフッ化水素によりフッ素化する方法（特許文献５）がある。これらの方法では、副生成物として或いは未反応の原料として炭酸ガスが二フッ化カルボニル中に少なからず含まれる。また、その他には一酸化炭素をフッ素ガスにより直接フッ素化する方法（非特許文献１）、ホスゲンを気相で無機フッ化物と接触させ、その後気相で活性炭と接触させてホスゲンと塩化フッ化カルボニルを得た後これを気相で活性炭と接触させ、二フッ化カルボニルを得る方法（特許文献６）、テトラフルオロエチレンと酸素とを反応させ二フッ化カルボニルを得る方法（特許文献７）なども報告されている。これらは、炭酸ガスの生成は確認されていないが、二フッ化カルボニルは原料中や触媒中の水分により容易に加水分解して炭酸ガスとフッ化水素を生成するため、反応後に炭酸ガスが生成する可能性も考えられる。特に、副生成物や未反応原料として混入する炭酸ガスは数％から数十％になり、特に半導体製造時のクリーニングガスなどの用途において、その低減若しくは分離が要求される。   As a method for producing carbonyl difluoride, a method of reacting carbon dioxide gas and fluorine gas in a gas phase (Patent Document 1), a method of electrolytic fluorination of carbon monoxide (Patent Document 2), a solvent-exposed phosgene is fluorinated. A method of fluorinating with hydrogen fluoride or a method of fluorinating phosgene with hydrogen fluoride in the presence of a solvent and triethylamine (Patent Document 3), a method of fluorinating with sodium fluoride in a solvent (Patent Document 4), and phosgene in a gas phase There is a method of fluorination with hydrogen fluoride using an activated carbon catalyst (Patent Document 5). In these methods, carbon dioxide gas is contained in the carbonyl difluoride as a by-product or as an unreacted raw material. In addition, a method of directly fluorinating carbon monoxide with fluorine gas (Non-patent Document 1), phosgene is contacted with inorganic fluoride in the gas phase, and then contacted with activated carbon in the gas phase to phosgene and chlorofluorinated. After obtaining carbonyl, this is contacted with activated carbon in a gas phase to obtain carbonyl difluoride (Patent Document 6), a method of reacting tetrafluoroethylene and oxygen to obtain carbonyl difluoride (Patent Document 7), etc. Has also been reported. These have not been confirmed to produce carbon dioxide, but carbonyl difluoride is easily hydrolyzed by water in the raw material or catalyst to produce carbon dioxide and hydrogen fluoride, so carbon dioxide is produced after the reaction. There is a possibility of doing this. In particular, carbon dioxide gas mixed as a by-product or unreacted raw material is several percent to several tens percent, and reduction or separation thereof is required particularly in applications such as cleaning gas during semiconductor manufacturing.

一方、膜分離に関しては多数の報告がある。例えば、特許文献８には希釈剤ガスとフルオロケミカルとを含有しているガス流から膜を利用してフルオロケミカルを分離および回収するための方法が開示されている。ここでいう希釈剤ガスとは窒素やヘリウムなどのガスで炭酸ガスとは記載されていない。また、フルオロケミカルもＣＦ4などのＰＦＣ、ＣＨＦ3などのＨＦＣ、ＮＦ3、ＳＦ6を意味し、ＣＯＦ2を分離するためとの記載はない。また、特許文献９にはフルオロカーボンと炭酸ガスをポリイミド膜で分離する技術が開示されているが、ここでいうフルオロカーボンとはＣＨＦ3、Ｃ2Ｆ6、テトラフルオロエチレン（ＴＦＥ）、ヘキサフルオロプロピレン（ＨＦＰ）、パーフルオロ（アルキルビニルエーテル）（ＰＡＶＥ）、ヘキサフルオロプロピレンオキシド（ＨＦＰＯ）である。これらの化合物と二フッ化カルボニルとを比較すると、特許文献９で分離されるフルオロカーボンは全て化学的に安定な化合物であり、膜分離中における分解を考慮する必要はない。炭素数が近いＣＨＦ3、Ｃ2Ｆ6、ＴＦＥとＣＯＦ2は分子を構成する元素が異なり、膜分離における性質も全く異なることが予想される。特に二フッ化カルボニルは非常に反応性が高く、水酸基、アミド基、イミド基などの反応性基を有する分離膜と反応して分解することが考えられ、また、ＣＯＦ2とＣＯ2とは構造的類似性がより高いため、膜分離において二フッ化カルボニルからのＣＯ2の膜分離性を予測する事は不可能である。
特開平１１−１１６２１６号公報 特公昭４５−２６６１１号公報 特開昭５４−１５８３９６号公報 米国特許３０８８９７５ 米国特許２８３６６２２ ＥＰ０２５３５２７ 米国特許３６３９４２９ 特開平１０−１２８０３４ ＷＯ９８／５０３３１ Ｊ．Ａｍｅｒ．Ｃｈｅｍ．Ｓｏｃ．，９１，４４３２ （１９６９） On the other hand, there are many reports on membrane separation. For example, Patent Document 8 discloses a method for separating and recovering a fluorochemical using a membrane from a gas stream containing a diluent gas and a fluorochemical. The diluent gas here is a gas such as nitrogen or helium and is not described as carbon dioxide. In addition, fluorochemical means PFC such as CF 4 , HFC such as CHF 3 , NF 3 , and SF 6, and there is no description for separating COF 2 . Patent Document 9 discloses a technique for separating a fluorocarbon and carbon dioxide gas with a polyimide membrane. The fluorocarbon here is CHF 3 , C 2 F 6 , tetrafluoroethylene (TFE), hexafluoropropylene ( HFP), perfluoro (alkyl vinyl ether) (PAVE), hexafluoropropylene oxide (HFPO). When these compounds are compared with carbonyl difluoride, all of the fluorocarbons separated in Patent Document 9 are chemically stable compounds, and there is no need to consider decomposition during membrane separation. It is expected that CHF 3 , C 2 F 6 , TFE, and COF 2 having a close carbon number are different in the elements constituting the molecules and have completely different properties in membrane separation. In particular, carbonyl difluoride is very reactive, and is considered to decompose by reacting with a separation membrane having a reactive group such as a hydroxyl group, an amide group, or an imide group, and COF 2 and CO 2 have a structure. It is impossible to predict the membrane separation of CO 2 from carbonyl difluoride in membrane separation because of the higher degree of similarity.
JP-A-11-116216 Japanese Examined Patent Publication No. 45-26611 JP 54-158396 A U.S. Pat. US Pat. No. 2,836,622 EP0253527 US Pat. No. 3,639,429 JP-A-10-128034 WO98 / 50331 J. et al. Amer. Chem. Soc. , 91, 4432 (1969)

二フッ化カルボニルと炭酸ガスとの分離は、蒸留による方法が一般的であるが、二フッ化カルボニルと炭酸ガスは沸点がそれぞれ−８４．６℃と−７８．５℃と近く、二フッ化カルボニルの臨界温度が室温付近であるため、蒸留で分離するためには、高い理論段数の蒸留塔で且つ耐圧も高いものが必要となる。さらに、室温以下好ましくは０℃程度以下に冷却できる設備が必要となり、設備や更にその運転に費用がかかる。一方で、膜分離は経済的な方法として、酸素富化や窒素富化等に用いられているが、使用される膜は用途に適した膜でなければ、その効果は望めない。二フッ化カルボニルと炭酸ガスの分離では、その用途に適した膜の報告はなされていない。そこで経済的に炭酸ガスを二フッ化カルボニルから分離する方法が望まれている。   Separation of carbonyl difluoride and carbon dioxide gas is generally performed by distillation, but carbonyl difluoride and carbon dioxide gas have boiling points close to -84.6 ° C and -78.5 ° C, respectively. Since the critical temperature of carbonyl is around room temperature, in order to separate by distillation, a distillation column having a high theoretical plate number and a high pressure resistance is required. Furthermore, equipment that can be cooled to room temperature or lower, preferably about 0 ° C. or lower is required, and the equipment and its operation are expensive. On the other hand, membrane separation is an economical method used for oxygen enrichment, nitrogen enrichment, etc., but the effect cannot be expected unless the membrane used is a membrane suitable for the application. For separation of carbonyl difluoride and carbon dioxide, no membrane suitable for the application has been reported. Therefore, a method for economically separating carbon dioxide from carbonyl difluoride is desired.

上記課題に対し鋭意検討を行ったところ、ポリイミド膜による炭酸ガスと二フッ化カルボニルの分離、精製方法を見出した。   As a result of intensive studies on the above problems, a method for separating and purifying carbon dioxide gas and carbonyl difluoride using a polyimide membrane was found.

本発明は、以下の二フッ化カルボニルの精製方法に関する。
項１． 炭酸ガス（ＣＯ2）と二フッ化カルボニル（ＣＯＦ2）を含む混合ガスを、ポリイミド分離膜を有する膜分離装置に供給する工程、(2)膜分離装置の透過側ＣＯ2ガスと未透過側ＣＯＦ2ガスに分離する工程を有する二フッ化カルボニルの精製方法。
項２． ＣＯＦ2／ＣＯ2混合ガスが、ＣＯ2を０．１モル％以上含むガスである項１に記載の方法。
項３． 膜分離装置の透過側と未透過側の差圧が、0.01〜1.0 ＭＰａである項１に記載の方法。
項４． 精製された二フッ化カルボニルが半導体製造時のクリーニングガスとして使用されるものである項１に記載の方法。
項５． 膜分離装置の透過側ガスをさらに膜分離装置に供給し、透過側ガス中に含まれる二フッ化カルボニルを未透過側ガスとして回収する工程を繰り返す項１に記載の方法。 The present invention relates to the following method for purifying carbonyl difluoride.
Item 1. Supplying a mixed gas containing carbon dioxide (CO 2 ) and carbonyl difluoride (COF 2 ) to a membrane separation device having a polyimide separation membrane; (2) Permeation side CO 2 gas and non-permeation side of the membrane separation device A method for purifying carbonyl difluoride having a step of separating into COF 2 gas.
Item 2. Item 2. The method according to Item 1, wherein the COF 2 / CO 2 mixed gas is a gas containing 0.1 mol% or more of CO 2 .
Item 3. Item 2. The method according to Item 1, wherein the pressure difference between the permeation side and the non-permeation side of the membrane separator is 0.01 to 1.0 MPa.
Item 4. Item 2. The method according to Item 1, wherein the purified carbonyl difluoride is used as a cleaning gas during semiconductor production.
Item 5. Item 2. The method according to Item 1, wherein the step of further supplying the permeation side gas of the membrane separation device to the membrane separation device and recovering carbonyl difluoride contained in the permeation side gas as the non-permeation side gas is repeated.

以下、本発明をより詳細に説明する。   Hereinafter, the present invention will be described in more detail.

本発明の方法により得られる精製された二フッ化カルボニルは、精製前の混合ガス中の炭酸ガス含量にもよるが、ＣＯＦ2とＣＯ2の混合比率として、ＣＯＦ2が通常８５モル％以上、好ましくは９０モル％以上、より好ましくは９５モル％以上、さらに好ましくは９９モル％以上、特に好ましくは９９．５モル％以上である。 Carbonyl difluoride purified obtained by the method of the present invention will depend on the carbon dioxide content in the mixed gas before purification, as the mixing ratio of COF 2 and CO 2, COF 2 is usually 85 mol% or more, Preferably it is 90 mol% or more, More preferably, it is 95 mol% or more, More preferably, it is 99 mol% or more, Most preferably, it is 99.5 mol% or more.

膜分離装置において、ＣＯ2とともに排出されるＣＯＦ2の損失率は、３０％以下、好ましくは２０％以下、より好ましくは１０％以下、さらに好ましくは５％以下、特に好ましくは３％以下である。膜分離装置を透過した炭酸ガスが濃縮された透過側ガスは、再度膜分離装置に供給することにより、未透過側ガスとして二フッ化カルボニルを濃縮することができる。 In the membrane separator, the loss rate of COF 2 discharged together with CO 2 is 30% or less, preferably 20% or less, more preferably 10% or less, further preferably 5% or less, and particularly preferably 3% or less. . By supplying the permeate side gas enriched with the carbon dioxide gas that has passed through the membrane separator to the membrane separator again, carbonyl difluoride can be concentrated as the non-permeate side gas.

膜分離装置により得られるＣＯＦ2の純度とＣＯＦ2の損失率は、相反する関係にあり、ＣＯＦ2の純度を高くすると損失率も高くなる関係にあるが、特に好ましくはＣＯＦ2９９モル％以上且つＣＯＦ2損失率５％以下である。 Purity and loss rate of COF 2 of COF 2 obtained by the membrane separation device, are inversely related, although the loss rate becomes higher relationship with a higher purity of the COF 2, particularly preferably COF 2 99 mol% or more The COF 2 loss rate is 5% or less.

膜分離装置に供給される混合ガスは、本発明において炭酸ガスを含有する二フッ化カルボニルとは、ＣＯＦ2：ＣＯ2＝99.9〜2モル％：0.1〜98モル％；好ましくはＣＯＦ2：ＣＯ2＝99〜5モル％：1〜95モル％、より好ましくは98〜10モル％：2〜90モル％である。 In the present invention, the mixed gas supplied to the membrane separator is carbonyl difluoride containing carbon dioxide gas, COF 2 : CO 2 = 99.9-2 mol%: 0.1-98 mol%; preferably COF 2 : CO 2 = 99-5 mol%: 1-95 mol%, more preferably 98-10 mol%: 2-90 mol%.

混合ガス中のＣＯＦ2が少なすぎると、半導体製造時のクリーニングガスに使用可能な高純度のＣＯＦ2ガスの分離が困難であり、ＣＯ2が少なすぎると、分離精製する必要性が少なくなるからである。混合ガスには、ＣＯＦ2とＣＯ2以外にＨＦ、Ｆ2、ＨＣｌ、Ｃｌ2、ＣＨＦ3、ＣＦ4、Ｃ2Ｆ6、ＳｉＦ4、ＣＯ、Ｎ2、Ｏ2などのガスを含有していても構わない。これらの含有量は、Ｆ2、Ｃｌ2以外は、炭酸ガスと二フッ化カルボニルの合計に対してモルにして２倍まで含まれていても良い。 If the amount of COF 2 in the mixed gas is too small, it is difficult to separate high-purity COF 2 gas that can be used as a cleaning gas during semiconductor manufacturing. If the amount of CO 2 is too small, the need for separation and purification decreases. It is. In addition to COF 2 and CO 2 , the mixed gas contains gases such as HF, F 2 , HCl, Cl 2 , CHF 3 , CF 4 , C 2 F 6 , SiF 4 , CO, N 2 , and O 2. It doesn't matter. These contents other than F 2 and Cl 2 may be contained up to twice as much as the mole of the total of carbon dioxide gas and carbonyl difluoride.

本発明でポリイミドとは、繰り返し単位の少なくとも一つにイミド結合を有するポリマーでこれらの製造方法としては、例えば最新ポリイミド〜基礎と応用〜（日本ポリイミド研究会編 ２００２年（株）エヌ・ティー・エス）に示されている。これらの製品としては、Ｋａｐｔｏｎ（ＤｕＰｏｎｔ社）、ＭＡＴＲＩＭＩＤ（Ｃｉｂａ Ｇｅｉｇｙ社）、ユーピレックス、ＵＭ、ＤＭシリーズ（宇部興産(株)）などが知られている。   In the present invention, a polyimide is a polymer having an imide bond in at least one of repeating units, and examples of the production method thereof include the latest polyimides: basics and applications (edited by Japan Polyimide Research Association 2002, NTT Corporation). S). As these products, Kapton (DuPont), MATRIMID (Ciba Geigy), Upilex, UM, DM series (Ube Industries) are known.

本発明で用いるガス分離膜は、モジュールの形態で使用される事が望ましく、モジュールの形態としては、中空糸膜、スパイラル膜などが用いられる。モジュールの材質としては、樹脂、金属製の物が通常用いられるが、樹脂はCOF2と反応する材質は用いられない。 The gas separation membrane used in the present invention is preferably used in the form of a module. As the module, a hollow fiber membrane, a spiral membrane, or the like is used. As the material of the module, resin or metal is usually used, but the material that reacts with COF 2 is not used for the resin.

本発明を実施する場合は、分離の効率を良くするため透過側と未透過側とに圧力差（差圧）をつける事も出来、この方法としては透過側を真空ポンプで減圧にする方法、未透過側出口に背圧弁等をとりつけ未透過側を加圧する方法、減圧にする方法と加圧にする方法の両方を組み合わせた方法がある。   When carrying out the present invention, a pressure difference (differential pressure) can be applied between the permeation side and the non-permeation side in order to improve the separation efficiency, and as this method, the permeation side is decompressed with a vacuum pump, There are a method in which a back pressure valve or the like is attached to the non-permeate side outlet to pressurize the non-permeate side, and a method in which both a method of reducing pressure and a method of increasing pressure are combined.

本発明によると、炭酸ガスと二フッ化カルボニルを含むガスをガス分離膜に接触させる事により、透過側に炭酸ガスが濃縮され、未透過側に二フッ化カルボニルが濃縮される。未透過側の圧力を透過側より高くし圧力差をつける事により分離の効率は更に向上する。この時の圧力差としては、通常０．０１ＭＰａ〜１ＭＰａ程度であるが、好ましくは０．０２ＭＰａ〜０．８ＭＰａ、より好ましくは０．０５ＭＰａ〜０．５ＭＰａが選択される。これより少ないと分離効率が悪くなるため流量を下げる必要があり、そのため生産効率が悪くなる。また、これより高いと透過する二フッ化カルボニルの量が増え、回収量が低下してしまう。   According to the present invention, by bringing a gas containing carbon dioxide and carbonyl difluoride into contact with the gas separation membrane, carbon dioxide is concentrated on the permeate side and carbonyl difluoride is concentrated on the non-permeate side. Separation efficiency is further improved by making the pressure on the non-permeate side higher than that on the permeate side and creating a pressure difference. The pressure difference at this time is usually about 0.01 MPa to 1 MPa, preferably 0.02 MPa to 0.8 MPa, more preferably 0.05 MPa to 0.5 MPa. If it is less than this, the separation efficiency will deteriorate, so it will be necessary to reduce the flow rate, and thus the production efficiency will deteriorate. On the other hand, if it is higher than this, the amount of carbonyl difluoride that permeates increases, and the recovered amount decreases.

使用される膜は、予め窒素ガス等不活性なガスを流通させる事により乾燥する事が望ましい。乾燥が不充分だと、膜の表面や内部の水分により二フッ化カルボニルが加水分解を起こし、炭酸ガスとフッ化水素が生成する。これにより炭酸ガスの分離が悪化したり、生成したフッ化水素により膜が劣化したりする原因となる。   It is desirable to dry the membrane to be used in advance by circulating an inert gas such as nitrogen gas. If the drying is insufficient, carbonyl difluoride will be hydrolyzed by moisture on the surface and inside of the membrane, producing carbon dioxide and hydrogen fluoride. As a result, the separation of carbon dioxide gas deteriorates, or the membrane is deteriorated by the generated hydrogen fluoride.

本発明の精製方法を実施するための好ましい膜分離システムを図１に示す。図１に示すように、膜分離システムはポリイミド中空糸膜からなる膜モジュール（Ｍ）、ＣＯＦ2／ＣＯ2混合ガスの膜分離装置への供給速度を調節する調節手段としてのガス供給用流量調節器（Ａ）、透過側へのガス供給用流量調節器（Ｂ）、未透過側圧力調節手段としての圧力調節弁（Ｃ）を備えている。 A preferred membrane separation system for carrying out the purification method of the present invention is shown in FIG. As shown in FIG. 1, the membrane separation system comprises a membrane module (M) made of a polyimide hollow fiber membrane, and a flow rate adjustment for gas supply as an adjustment means for adjusting the supply rate of the COF 2 / CO 2 mixed gas to the membrane separation device. (A), a flow rate regulator (B) for supplying gas to the permeate side, and a pressure control valve (C) as non-permeate side pressure control means.

ＣＯＦ2／ＣＯ2混合ガスは流量調節器（Ａ）を通じて流量を調節した後、膜モジュール（Ｍ）の入り口に導入される。未透過側の圧力は圧力調節弁（Ｃ）により制御される。膜モジュール（Ｍ）の膜を透過したＣＯ2が濃縮されたガスは、流量調節器（Ｂ）を通じて流入したガス（例えばＮ2ガス）といっしょに排出される。膜モジュール（Ｍ）の膜を透過しなかったガスは、クリーニングに必要な純度のＣＯＦ2を含むガス（未透過ガス）として得られる。得られた未透過ガスの純度が不十分である場合には、再度膜モジュール（Ｍ）を通してＣＯ2含量をさらに低下させてもよい。 The COF 2 / CO 2 mixed gas is introduced into the inlet of the membrane module (M) after adjusting the flow rate through the flow rate regulator (A). The pressure on the non-permeate side is controlled by a pressure control valve (C). The gas enriched in CO 2 that has passed through the membrane of the membrane module (M) is discharged together with the gas (for example, N 2 gas) flowing in through the flow rate regulator (B). The gas that has not permeated the membrane of the membrane module (M) is obtained as a gas (non-permeated gas) containing COF 2 having a purity required for cleaning. If the purity of the obtained non-permeate gas is insufficient, the CO 2 content may be further reduced through the membrane module (M) again.

透過側の圧力調節手段としては、圧力調節弁、流量調節器、透過側を減圧にする手段（例えば真空ポンプ）に接続する手段、透過側を加圧にする手段などが例示される。   Examples of the pressure control means on the permeate side include a pressure control valve, a flow rate regulator, a means for connecting to a means for reducing the pressure on the permeate side (for example, a vacuum pump), a means for pressurizing the permeate side, and the like.

未透過側の圧力調節手段としては、圧力調節弁、背圧弁、バッファータンクなどが挙げられる。   Examples of the pressure adjusting means on the non-permeating side include a pressure adjusting valve, a back pressure valve, and a buffer tank.

実質的にクリーニングに必要な純度のＣＯＦ2を含むガスを得るために、分離用の膜モジュールを多段にして用いることも出来る。また、透過側のＣＯ2を多く含むガス中のＣＯＦ2を回収するために膜モジュールを多段にして用いることも可能である。 In order to obtain a gas containing COF 2 having a purity substantially necessary for cleaning, a separation membrane module can be used in multiple stages. It is also possible to use a membrane module in multiple stages in order to recover COF 2 in the gas containing a large amount of CO 2 on the permeate side.

さらに透過側の圧力をコントロールするための圧力調節弁を排出側につけることも可能である。   Furthermore, a pressure control valve for controlling the pressure on the permeate side can be attached to the discharge side.

図１において流量調節器（Ｂ）を通じて供給されるガスとしては、窒素、ヘリウム、アルゴン、ネオンなどの不活性ガスを用いることが可能であるが、経済性の点で窒素が好ましい。空気（特に乾燥した空気）の使用も可能ではあるが、空気中の酸素、水蒸気がＣＯＦ2に悪影響を及ぼす可能性、膜モジュールでの逆透過の可能性などから好ましくない。 In FIG. 1, an inert gas such as nitrogen, helium, argon, or neon can be used as the gas supplied through the flow controller (B), but nitrogen is preferable in terms of economy. Although air (especially dry air) can be used, it is not preferable because oxygen and water vapor in the air may adversely affect COF 2 and the possibility of reverse permeation in the membrane module.

また、ガスを供給する代わりに透過側の一方の口を閉じもう一方の口を通じて真空ポンプ等に接続し減圧とすることも可能である。   Further, instead of supplying gas, it is possible to close the one port on the permeate side and connect it to a vacuum pump or the like through the other port to reduce the pressure.

本発明における膜モジュールのガス分離時の温度としては、−３０〜１５０℃が好ましく、特に０〜５０℃が好ましい。   As temperature at the time of gas separation of the membrane module in this invention, -30-150 degreeC is preferable, and 0-50 degreeC is especially preferable.

本発明により、経済的に炭酸ガスと二フッ化カルボニルとを分離する事が出来る。   According to the present invention, carbon dioxide and carbonyl difluoride can be separated economically.

実施例１
中空糸膜モジュールは市販されているもの（宇部興産株式会社製、製品名：UM-A1、モジュール概寸２８φ×２８６ｍｍ）を用い、ガス供給部に二フッ化カルボニルと炭酸ガスの混合ガスをマスフローコントローラーで流量を調整しながら流した。供給されたガスは中空糸内を流れ、透過しなかったガスが未透過ガス出口から流出し、これをFT IRにて分析した。また、透過側は窒素ガスを約３０ｍｌ／ｍｉｎ流して透過したガスをパージし、透過ガス出口から流出したガスをFT IRで分析した。分離係数を（供給ガスのCO2濃度/供給ガスのCOF2濃度）／（未透過ガスのCO2濃度/未透過ガスのCOF2濃度）として、分離係数を求めた。必要に応じて未透過ガス出口には、背圧弁を取り付け、透過側と未透過側で圧力差をつけた。 Example 1
A commercially available hollow fiber membrane module (product name: UM-A1, manufactured by Ube Industries, Ltd., module approximate size 28φ × 286 mm) is used, and a mixed gas of carbonyl difluoride and carbon dioxide gas is mass-flowed to the gas supply unit. The flow was adjusted with the controller. The supplied gas flowed through the hollow fiber, and the gas that did not permeate outflowed from the non-permeated gas outlet, and this was analyzed by FT IR. On the permeate side, nitrogen gas was allowed to flow at about 30 ml / min to purge the permeated gas, and the gas flowing out from the permeate gas outlet was analyzed by FT IR. The separation factor was determined by setting the separation factor as (CO2 concentration of supply gas / COF2 concentration of supply gas) / (CO2 concentration of non-permeate gas / COF2 concentration of non-permeate gas). If necessary, a back pressure valve was attached to the non-permeate gas outlet to create a pressure difference between the permeate side and the non-permeate side.

FT IRの分析は、MIDAC社製IGA-4000を用いた。   For analysis of FT IR, IGA-4000 manufactured by MIDAC was used.

膜分離には二種類のガスを供給した。   Two kinds of gas were supplied for membrane separation.

Figure 0004415656
Figure 0004415656

実施例１〜５
供給ガスAを用いた。表２に、供給したガスの流量、透過側と未透過側の圧力差（差圧）、透過ガスの組成（ｍｏｌ％）、未透過ガスの組成（ｍｏｌ％）、分離係数を示した。 Examples 1-5
Feed gas A was used. Table 2 shows the flow rate of the supplied gas, the pressure difference between the permeation side and the non-permeation side (differential pressure), the composition of the permeate gas (mol%), the composition of the non-permeate gas (mol%), and the separation factor.

Figure 0004415656
Figure 0004415656

分離係数は、圧力差が大きいほど分離が良くなり、流量も少ない方が分離良く、充分効果がある事がわかる。   It can be seen that the separation factor increases as the pressure difference increases, and the smaller the flow rate, the better the separation.

実施例６〜８
供給ガスBを用いた。表３に、供給したガスの流量、透過側と未透過側の圧力差（差圧）、透過ガスの組成（ｍｏｌ％）、未透過ガスの組成（ｍｏｌ％）、分離係数を示した。 Examples 6-8
Feed gas B was used. Table 3 shows the flow rate of the supplied gas, the pressure difference between the permeate side and the non-permeate side (differential pressure), the composition of the permeate gas (mol%), the composition of the non-permeate gas (mol%), and the separation factor.

Figure 0004415656
Figure 0004415656

本発明の方法に用いる膜分離システムの概略図である。It is the schematic of the membrane separation system used for the method of this invention.

符号の説明Explanation of symbols

Ａ 流量調節器
Ｂ 流量調節器
Ｃ 圧力調節弁
Ｍ 膜モジュール A Flow controller B Flow controller C Pressure control valve M Membrane module

Claims (5)

炭酸ガス（ＣＯ2）と二フッ化カルボニル（ＣＯＦ2）を含む混合ガスを、ポリイミド分離膜を有する膜分離装置に供給する工程、(2)膜分離装置の透過側ＣＯ2ガスと未透過側ＣＯＦ2ガスに分離する工程を有する二フッ化カルボニルの精製方法。 Supplying a mixed gas containing carbon dioxide (CO 2 ) and carbonyl difluoride (COF 2 ) to a membrane separation device having a polyimide separation membrane; (2) Permeation side CO 2 gas and non-permeation side of the membrane separation device A method for purifying carbonyl difluoride having a step of separating into COF 2 gas. ＣＯＦ2／ＣＯ2混合ガスが、ＣＯ2を０．１モル％以上含むガスである請求項１に記載の方法。 The method according to claim 1, wherein the COF 2 / CO 2 mixed gas is a gas containing 0.1 mol% or more of CO 2 . 膜分離装置の透過側と未透過側の差圧が、0.01〜1.0 ＭＰａである請求項１に記載の方法。 The method according to claim 1, wherein the pressure difference between the permeation side and the non-permeation side of the membrane separator is 0.01 to 1.0 MPa. 精製された二フッ化カルボニルが半導体製造時のクリーニングガスとして使用されるものである請求項１に記載の方法。 The method according to claim 1, wherein the purified carbonyl difluoride is used as a cleaning gas in the production of a semiconductor. 膜分離装置の透過側ガスをさらに膜分離装置に供給し、透過側ガス中に含まれる二フッ化カルボニルを未透過側ガスとして回収する工程を繰り返す請求項１に記載の方法。

The method according to claim 1, wherein the process of further supplying the permeation side gas of the membrane separation apparatus to the membrane separation apparatus and recovering carbonyl difluoride contained in the permeation side gas as the non-permeation side gas is repeated.

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