JP4938931B2

JP4938931B2 - Method for decomposing a hardly decomposable halogen compound

Info

Publication number: JP4938931B2
Application number: JP2001050948A
Authority: JP
Inventors: 剛西脇; 彰金子
Original assignee: Nippon Soda Co Ltd
Current assignee: Nippon Soda Co Ltd
Priority date: 2001-02-26
Filing date: 2001-02-26
Publication date: 2012-05-23
Anticipated expiration: 2021-02-26
Also published as: JP2002255860A

Description

【０００１】
【本発明の属する技術分野】
本発明は、難分解性ハロゲン化合物、例えば、ポリ塩化ビフェニール（以下、「ＰＣＢ」と略記する）類等を、アルカリにより脱ハロゲン化分解させて処理する難分解性ハロゲン化合物の分解処理方法に関する。
【０００２】
【従来の技術】
ＰＣＢ等に代表される難分解性ハロゲン化合物は環境汚染物質として知られており、このものを無害化する処理方法が幾つか提案されている。中でもアルカリ金属分散体を用いる化学的分解処理方法は、安全でしかも確実に処理できることから最も注目されている。
【０００３】
従来、かかる難分解性ハロゲン化合物の分解処理方法としては、例えば、
▲１▼環境汚染物質であるＰＣＢ類又はＰＣＢ類を含む有機溶媒溶液を分散状態にあるアルカリ金属と共に加熱処理する環境汚染物質の処理方法（特開昭４９−８２５７０号公報参照）、
▲２▼炭化水素ベースの油に溶解している難分解性ハロゲン化合物と溶融ナトリウム粒子群とを１００〜１６０℃の温度範囲で反応させる難分解性ハロゲン化合物の脱ハロゲン化方法（特開昭５９−２０１７９号公報参照）、
▲３▼塩化ビフェニール組成物をアルカリ金属と加熱条件下で反応させる塩化ビフェニール組成物の処理方法（カナダ特許第１１４２５５１号公報参照）、
▲４▼有機溶媒中でハロゲン化合物とアルカリ金属分散体とを、該有機化合物と混じらない活性水素化合物を加えて反応させるハロゲン化合物の分解方法（特開平９−２１６８３８号公報参照）、等が知られている。
【０００４】
【発明が解決しようとする課題】
上記した従来の難分解性ハロゲン化合物の分解処理方法においては、反応をより安全に行なうために、外気と遮断可能な反応容器を用い、該装置の反応容器内に分解処理したい難分解性ハロゲン化合物とアルカリ金属等とを入れ、内部を不活性ガスで置換した後に反応を行うのが通常である。
【０００５】
しかしながら、不活性ガスの置換方法や不活性ガスの純度によって、難分解性ハロゲン化合物の分解処理時間にばらつきが見られたり、難分解性ハロゲン化合物が完全に分解されない場合等があり問題となっていた。
【０００６】
本発明は、かかる実状に鑑みてなされたものであり、難分解性ハロゲン化合物をアルカリにより脱ハロゲン化分解処理する方法において、従来の方法よりも再現性よく安定した難分解性ハロゲン化合物の無害化処理が可能な難分解性ハロゲン化合物の分解処理方法を提供することを課題とする。
【０００７】
【課題を解決するための手段】
本発明者らは、上記課題を解決すべく鋭意検討した結果、難分解性ハロゲン化合物の分解処理時間にばらつきが見られたり、難分解性ハロゲン化合物が完全に分解されない場合には、反応容器の空間部（反応容器内に反応物及び溶媒等を添加した残りの空間部）の酸素濃度が高いことがわかった。そこで、反応容器の空間部の酸素濃度を所定濃度未満として、又は酸素濃度を所定濃度に管理して難分解性ハロゲン化合物の脱ハロゲン化反応を行なうことにより、極めて再現性よく安定した難分解性ハロゲン化合物の無害化処理が実現されることを見出し、本発明を完成するに到った。
【０００８】
即ち、本発明は、難分解性ハロゲン化合物をアルカリを用いて脱ハロゲン化反応させる難分解性ハロゲン化合物の分解処理方法であって、反応系内の酸素濃度を３容量％未満として難分解性ハロゲン化合物の脱ハロゲン化反応を行なうことを特徴とする難分解性ハロゲン化合物の分解処理方法を提供する。
【０００９】
本発明の難分解性ハロゲン化合物の分解処理方法は次の通りである。
（１）外気と遮断可能な反応容器内で、難分解性ハロゲン化合物とアルカリ金属分散体の混合物に活性化剤を添加して脱ハロゲン化反応を行なう難分解性ハロゲン化合物の分解処理方法であって、前記反応容器の空間部内の酸素濃度を３容量％未満に維持しながら、活性化剤を、該活性化剤の添加終了時点における反応混合物中の難分解性ハロゲン化合物の残存量が１ｐｐｍ以下となるように添加する工程を有する難分解性ハロゲン化合物の分解処理方法。
（２）前記反応容器の空間部内の酸素濃度を１容量％以下に維持しながら、活性化剤を添加する工程を有する（１）の難分解性ハロゲン化合物の分解処理方法。
（３）難分解性ハロゲン化合物を脱ハロゲン化反応させる前に、前記反応容器内の気体を不活性ガスで完全に置換する工程を有する（１）又は（２）の難分解性ハロゲン化合物の分解処理方法。
（４）不活性ガスが、酸素含有量が３容量％未満のものである（３）の難分解性ハロゲン化合物の分解処理方法。
【００１０】
（５）反応容器内に不活性ガスの供給を反応終了まで継続する（３）又は（４）の難分解性ハロゲン化合物の分解処理方法。
（６）前記活性化剤が、活性水素化合物であって、その添加量が、アルカリ金属分散体中のアルカリ金属１モルに対して、０．１〜１．５モルの範囲である、（１）〜（５）いずれかの難分解性ハロゲン化合物の分解処理方法。
（７）アルカリ金属分散体を調製する際に用いられる溶媒が、ケロシン、デカリン、電気絶縁油、重油、及びこれらの混合物から選ばれるものである、（１）〜（６）いずれかの難分解性ハロゲン化合物の分解処理方法。
【００１１】
本発明によれば、アルカリ金属分散体により脱ハロゲン化分解処理する方法において、従来の方法よりも再現性よく安定した難分解性ハロゲン化合物の無害化処理が可能となる。また、本発明によれば、反応容器の空間部の酸素濃度を極力低く維持するだけで、従来に比して短時間で完全なハロゲン化合物の脱ハロゲン化分解処理が可能である。
【００１２】
【発明の実施の形態】
以下、本発明を詳細に説明する。
本発明の分解の対象となる難分解性ハロゲン化合物は、一般的に脱ハロゲン化反応が困難な有機ハロゲン化合物である。かかる難分解性ハロゲン化合物としては、例えば、ＰＣＢ、ダイオキシン類、ポリ塩素化ベンゾフラン類、ポリ塩素化ベンゼン、ＤＤＴ等の芳香族ハロゲン化合物；ＢＨＣ等の脂環族ハロゲン化合物；等が挙げられる。本発明は、ＰＣＢ等の廃棄物中に含まれる芳香族ハロゲン化合物を対象とする場合に好適である。
【００１３】
また、本発明は有機溶媒に溶解した難分解性ハロゲン化合物を分解処理する場合にも適用することができる。かかる有機溶媒としては、ケロシン、デカリン、電気絶縁油（ＪＩＳＣ２３２０−１９９３に記載の電気絶縁油）、重油（ＪＩＳＫ２２０５に記載の重油）、潤滑油及びこれらの混合物等が挙げられる。本発明は、電気絶縁油に含まれる難分解性ハロゲン化合物をアルカリ金属分散体と反応させて脱ハロゲン化処理を行う場合に特に好適である。
【００１４】
用いられるアルカリとしては、アルカリ金属、アルカリ金属水酸化物、有機アルカリ金属、アルカリ金属炭酸塩、アルカリ土類金属、アルカリ土類金属水酸化物、有機アルカリ土類金属、アルカリ土類金属炭酸塩等が挙げられる。これらは単独で、あるいは２種以上を組合せて用いることができる。
【００１５】
これらの中でも、本発明においてはアルカリ金属又はアルカリ土類金属を用いるのが好ましい。アルカリ金属としては、例えば、ナトリウム、カリウム、リチウム、セシウム及びこれらの合金等が挙げられる。また、アルカリ土類金属としては、マグネシウム、カルシウム及びこれらの合金等が挙げられる。本発明においては、これらアルカリ金属又はアルカリ土類金属の中でもアルカリ金属分散体を用いるのがより好ましい。アルカリ金属分散体は、アルカリ金属を溶媒に分散させたものを用いることができるが、金属ナトリウム分散体が特に好ましい。
【００１６】
アルカリ金属の分散に用いられる溶媒としては、例えば、ケロシン、デカリン、電気絶縁油（ＪＩＳＣ２３２０−１９９３に記載の電気絶縁油）、重油（ＪＩＳＫ２２０５に記載の重油）、及びこれらの混合物が挙げられるが、ＪＩＳＣ２３２０−１９９３に記載の電気絶縁油であるのが好ましい。
【００１７】
アルカリ金属分散体中のアルカリ金属濃度には特に制限はないが、５〜５０容量％の範囲のものが好ましい。また、保存性、輸送性、再分散性及びハロゲン化合物に対する分解処理能力等の観点から、アルカリ金属の８０％以上が、粒径が３０μｍ以下、好ましくは１５μｍ以下のアルカリ金属微粒子であることが好ましい。
【００１８】
かかるアルカリ金属分散体は、公知の方法、例えば、ＩｎｏｒｇａｎｉｃＳｙｎｔｈｅｓｅｓ．，Ｖｏｌ．５，ｐ６−１０，”ＳｏｄｉｕｍＤｉｓｐｅｒｓｉｏｎｓ”に記載の方法や、特開平１０−１１０２０５号公報に記載されたホモジナイザーを用いた方法等により調製することができる。
【００１９】
難分解性ハロゲン化合物との反応に用いられるアルカリの使用量は、ハロゲン化合物中に含まれるハロゲン原子１モルに対して、含有するアルカリの量に換算して、通常１〜５０モル、好ましくは１．０５〜２０モルの範囲である。
【００２０】
また、難分解性ハロゲン化合物とアルカリ金属分散体とを反応させる場合には、水、低級アルコール等の活性水素化合物を共存させるのが好ましい。用いられる活性水素化合物の量は、アルカリ金属分散体中のアルカリ金属１モルに対して、通常２モル以下、好ましくは０．１〜１．５モルの範囲である。
【００２１】
難分解性ハロゲン化合物をアルカリと反応させて分解する方法は特に制限されない。例えば、アルカリとしてアルカリ金属分散体を用い、活性化剤として水を用いる場合には、▲１▼アルカリ金属分散体と難分解性ハロゲン化合物の混合物中に所定量の水を添加する方法、▲２▼難分解性ハロゲン化合物を含有する有機溶媒と所定量の水とを混合した後、アルカリ金属分散体を添加する方法等を採用することができる。▲１▼の方法の場合には、アルカリ金属と水との反応が激しいので、作業を安全に行うためにアルカリ金属分散体を十分に撹拌しながら水を少量ずつゆっくりと添加する必要がある。また、▲２▼の方法の場合においても安全に分解処理を行うために、難分解性ハロゲン化合物の有機溶媒溶液と所定量の水との混合物を十分に撹拌しながら、アルカリ金属分散体を少量ずつ、あるいは数回に分けて添加するのが好ましい。
【００２２】
難分解性ハロゲン化合物とアルカリとの反応温度は、通常０〜３００℃、好ましくは室温〜２００℃、より好ましくは室温〜１００℃の範囲である。反応時間は、難分解性ハロゲン化合物の種類やその量に依存するが、通常０．５〜３時間である。
【００２３】
本発明は、難分解性ハロゲン化合物をアルカリと反応させる難分解性ハロゲン化合物の分解処理方法において、難分解性ハロゲン化合物をアルカリと反応させる反応系内の酸素濃度を３容量％未満、好ましくは１容量％以下、より好ましくは０．１容量％以下とすることを特徴とする。
【００２４】
反応系内の酸素濃度を３容量％未満とする方法としては、例えば、外気と遮断可能な、若しくは密閉可能な反応容器を用いて、難分解性ハロゲン化合物を脱ハロゲン化反応させる前に該反応容器内の気体を不活性ガスで完全に置換する方法が挙げられる。不活性ガスとしては、酸素含有量が３容量％未満、好ましくは酸素含有量が１容量％以下、より好ましくは酸素含有０．１容量％以下のものを用いる。不活性ガスの具体例としては、窒素、ヘリウム、アルゴン等が挙げられる。
【００２５】
ここで用いられる反応容器としては、難分解性ハロゲン化合物とアルカリとの反応に用いることができるものあれば、その材質や形状、容量（大きさ）等に制限はないが、外気と遮断可能な反応容器が好ましく、不活性ガスを導入し、反応容器内の気体を排気できる構造のものがより好ましい。
【００２６】
反応容器の空間部を不活性ガスで置換する場合には、反応開始前に反応容器の空間部の大きさ、不活性ガスの純度、不活性ガスの流量等に応じて、反応容器の空間部内の気体を不活性ガスと置換して、反応容器の空間部の酸素濃度が所定値未満（又は以下）にする必要がある。
【００２７】
また、本発明は、反応容器内の酸素濃度を所定濃度以下とした後、密閉して脱ハロゲン化反応を行なうことができるが、酸素濃度を所定値未満（又は以下）、具体的には、３容量％未満、好ましくは１容量％以下、より好ましくは０．１容量％以下に維持しながら反応を行なうのが好ましい。酸素濃度を所定値未満に維持する方法としては、例えば、流量計等で流量を適宜調節しながら、反応容器内に不活性ガスの供給を反応終了まで継続する方法が挙げられる。この方法によれば、反応中、反応容器の空間部の酸素濃度を、簡便かつ確実に一定値以下に維持することができる。
【００２８】
本発明の特に好ましい態様としては、外気と遮断可能な反応容器に難分解性ハロゲン化合物を入れ、該容器内の気体を酸素含有量１容量％以下の不活性ガスで完全に置換した後、所定温度に加熱し、不活性ガス雰囲気下に、アルカリ金属分散体を加え、さらに所定量の活性化剤をゆっくりと添加する方法である。この方法によれば、従来の分解処理プロセスに大幅な変更を加えることなく、簡便かつ確実に反応系内の酸素濃度を３容量％未満、好ましくは１容量％以下、より好ましくは０．０１容量％以下に維持することができ、難分解性ハロゲン化合物の安定、かつ速やかな分解処理が実現される。
【００２９】
また、本発明において、活性化剤を添加する場合には、活性化剤の添加工程前、好ましくは添加開始から終了までの間、反応系内の酸素濃度を所定値未満（又は以下）とすることにより、難分解性ハロゲン化合物の脱ハロゲン化反応をより速やかに進行させることができる。活性化剤の添加終了時点における反応混合物中の難分解性ハロゲン化合物の残存量は、通常１ｐｐｍ以下、好ましくは０．８ｐｐｍ以下である。
【００３０】
反応終了後は、通常、大量の水を反応混合物に添加し、未反応のアルカリを分解するのが好ましい。反応溶媒を用いた場合には、反応処理液を分液して回収されるトランスオイル等の有機溶媒は燃料等に再利用することができる。
【００３１】
【実施例】
以下、実施例及び比較例により本発明を更に詳細に説明する。本発明は、下記実施例に限定されることなく、有機溶媒中で、難分解性ハロゲン化合物とアルカリとを反応させて難分解性ハロゲン化合物を分解するあらゆる方法に適用することができる。なお、以下の実施例及び比較例においては、電気絶縁油（出光興産（株）製）に、数ミクロン粒径の金属ナトリウムを分散させて得られる１０容量％金属ナトリウム分散体（以下、「１０％ＳＤ」と略す。）を用いた。
【００３２】
（実施例１）
５００ｍｌの四つ口フラスコにＰＣＢ汚染油２６２．１ｇ（ＰＣＢ濃度３７．１５ｐｐｍ）を入れ、攪拌羽と温度計を取り付け、この四つ口フラスコ内に、純度９９．９９９容量％の窒素ガスを流量計ＫＧ−１（草野科学器械製作所（株）製、以下同じ。）で１００目盛り（０．２６４Ｌ／ｍｉｎ）で流して反応系内を窒素置換しながら、４０分かけて６５℃まで昇温した。その後、窒素ガスの流量を流量計ＫＧ−１で５目盛り（０．０００９Ｌ／ｍｉｎ）とし、１０％ＳＤを３．４８ｇ添加し、６５℃で３０分攪拌した後、更に３．２３ｇの１０％ＳＤを添加した。その後、直ちに活性化剤として水０．２４ｍｌを６０分かけて添加し、更に６５℃で６０分間反応させた。
反応混合物中のＰＣＢ濃度の分析を、２回目の１０％ＳＤ添加終了後、３０分後に行った。その結果、ＰＣＢ濃度は検出限界以下（０．５ｐｐｍ以下、以下にて同じ。）であった。
【００３３】
（実施例２）
５００ｍｌの四つ口フラスコにＰＣＢ汚染油２５４．４ｇ（ＰＣＢ濃度３７．１５ｐｐｍ）を入れ、攪拌羽と温度計を取り付け、純度９９容量％の窒素ガス（酸素含有量１容量％）を流量計ＫＧ−１で１００目盛り（０．２６４Ｌ／ｍｉｎ）で流して窒素置換しながら、４０分かけて６５℃まで昇温した。その後、窒素ガスの流量を流量計ＫＧ−１で５目盛り（０．０００９Ｌ／ｍｉｎ）とし、１０％ＳＤを３．７０ｇ添加し、６５℃で３０分攪拌した後、更に２．７０ｇの１０％ＳＤを添加した。その後、直ちに活性化剤として水０．２４ｍｌを６０分かけて添加し、更に６５℃で６０分間反応させた。
反応混合物中のＰＣＢ濃度の分析を、２回目の１０％ＳＤ添加終了後、３０分経過後に行った。その結果、３０分経過後の残存ＰＣＢ濃度は検出限界以下であった。
【００３４】
（実施例３）
５００ｍｌの四つ口フラスコに、ＰＣＢ汚染油２６２．１ｇ（ＰＣＢ濃度３７．１５ｐｐｍ）を入れ、攪拌羽と温度計を取り付け、純度９９．９９９％窒素ガスを流量計ＫＧ−１で５目盛り（０．００９Ｌ／ｍｉｎ）で流して窒素置換しながら、４０分かけて６５℃まで昇温した。その後、窒素ガスを流量計ＫＧ−１で５目盛り（０．０００９Ｌ／ｍｉｎ）で流しながら、１０％ＳＤを３．５１ｇ添加し、６５℃で３０分攪拌した後、更に２．８４ｇの１０％ＳＤを添加した。その後、直ちに活性化剤として水０．２４ｍｌを６０分かけて添加し、更に６５℃で６０分間反応させた。
反応混合物のＰＣＢ濃度の分析を、２回目の１０％ＳＤ添加終了後、３０分経過時と６０分経過時に行った。
その結果、３０分経過時の残存ＰＣＢ濃度は１６．７４ｐｐｍであり、６０分経過時の残存ＰＣＢ濃度は検出限界以下であった。
【００３５】
（比較例１）
５００ｍｌの四つ口フラスコに、ＰＣＢ汚染油２６３．５ｇ（ＰＣＢ濃度３７．１５ｐｐｍ）を入れ、攪拌羽と温度計とを取り付け、純度９７容量％の窒素ガス（酸素含有量３容量％）を流量計ＫＧ−１で１００目盛り（０．２６４Ｌ／ｍｉｎ）で流して反応系内を窒素置換しながら、４０分かけて６５℃まで昇温した。その後、窒素ガスの流量を流量計ＫＧ−１で５目盛り（０．０００９Ｌ／ｍｉｎ）とし、１０％ＳＤを３．７２ｇ添加し、６５℃で３０分攪拌した後、更に２．７１ｇの１０％ＳＤを添加した。その後、直ぐに活性化剤として水０．２４ｍｌを６０分かけて添加し、更に６５℃で６０分間反応させた。
反応混合物中のＰＣＢ濃度の分析を、２回目の１０％ＳＤ添加終了後、３０分、６０分及び１２０分経過後に行った。
その結果、３０分経過時の残存ＰＣＢ濃度は２１．２４ｐｐｍであり、６０分経過時の残存ＰＣＢ濃度は０．７７ｐｐｍであり、１２０分経過時の残存ＰＣＢ濃度は検出限界以下であった。
【００３６】
（比較例２）
５００ｍｌの四つ口フラスコにＰＣＢ汚染油２６１．１ｇ（ＰＣＢ濃度３７．１５ｐｐｍ）を入れ、攪拌羽と温度計を取り付け、純度９９．９９９容量％の窒素ガスを流して窒素置換しながら１３分かけて６５℃まで昇温した。そのときの四つ口フラスコの空間部の酸素濃度は３．２容量％であった。次いで、１０％ＳＤを２．３４ｇ添加し、６５℃で３０分攪拌した後、更に４．４７ｇの１０％ＳＤを添加した。その後直ぐに活性化剤として水０．２４ｍｌを６０分かけて添加し、更に６５℃で１２０分間反応させた。
反応混合物のＰＣＢ濃度の分析を、２回目の１０％ＳＤ添加終了後、６０分経過後、１２０経過後及び１８０分経過後に行った。
その結果、６０分経過後においては、残存ＰＣＢ濃度は４．０７ｐｐｍ、１２０分経過後においては、残存ＰＣＢ濃度は０．５３ｐｐｍ、１８０分経過後においては、残存ＰＣＢ濃度は検出限界以下であった。
【００３７】
（比較例３）
１Ｌの四つ口フラスコにＰＣＢ汚染油２６１．９ｇ（ＰＣＢ濃度３７．１５ｐｐｍ）をとり、攪拌翼と温度計を取り付け、純度９９．９９９容量％窒素ガスを流して窒素置換した。そのときの空間部内の酸素濃度は４容量％であった。その後、四つ口フラスコ内部を外気と遮断し、６５℃まで昇温して１０％ＳＤを２．９７ｇ添加し、６５℃で３０分攪拌した後、更に３．１４ｇの１０％ＳＤを添加した。その後、直ぐに活性化剤として水０．２４ｍｌを６０分かけて添加し、更に６５℃で１２０分間反応させた。
反応混合物のＰＣＢ濃度の分析を、２回目の１０％ＳＤ添加終了後、６０分経過時及び１８０分経過時に行った。
その結果、６０分経過時の残存ＰＣＢ濃度は１７．９９ｐｐｍであり、１８０分経過時の残存ＰＣＢ濃度は１６．３５ｐｐｍであった。
【００３８】
実施例１は純度９９．９９９容量％の窒素ガスを反応容器内に流しつづけて反応を行なった例であり、実施例２は純度９９容量％の窒素ガスを反応容器内に流して続けて反応を行なった例であり、実施例３は純度９９．９９９容量％の窒素ガスの流量を減らして実施例１と同様に反応を行なった例である。いずれの場合も、６０分以内にＰＣＢの分解が完全に行なわれた。
【００３９】
一方、比較例１は酸素濃度３容量％で反応を行なった例であり、比較例２は酸素濃度３．２％で反応を行なった例であり、比較例３は酸素濃度４容量％で反応を行なった例である。比較例１では、ＰＣＢの分解に１２０分を要している。また、比較例２及び３は、いずれも純度９９．９９９容量％の窒素ガスで置換を行なったが置換が不十分な場合であるが、比較例２ではＰＣＢの分解に１８０分を要し、比較例３ではＰＣＢが完全に分解されなかった。
【００４０】
【発明の効果】
以上説明したように、本発明によれば、アルカリ金属分散体により脱ハロゲン化分解処理する方法において、従来の方法よりも再現性よく安定した難分解性ハロゲン化合物の無害化処理が出来る難分解性ハロゲン化合物の分解処理方法が提供される。また、本発明によれば、反応容器の空間部の酸素濃度を極力低く維持するだけで、従来に比して短時間で完全なハロゲン化合物の脱ハロゲン化分解処理が可能である。[0001]
[Technical field to which the present invention pertains]
The present invention relates to a method for decomposing a hardly decomposable halogen compound such as polychlorinated biphenyl (hereinafter abbreviated as “PCB”) by dehalogenating and decomposing it with an alkali.
[0002]
[Prior art]
Refractory halogen compounds represented by PCB and the like are known as environmental pollutants, and several treatment methods for detoxifying them have been proposed. Among them, the chemical decomposition treatment method using an alkali metal dispersion has received the most attention because it can be treated safely and reliably.
[0003]
Conventionally, as a method for decomposing such a hardly decomposable halogen compound, for example,
(1) A method for treating environmental pollutants, in which PCBs that are environmental pollutants or an organic solvent solution containing PCBs are heat-treated with alkali metals in a dispersed state (see JP-A-49-82570),
(2) A method for dehalogenating a hardly decomposable halogen compound by reacting a hardly decomposable halogen compound dissolved in a hydrocarbon-based oil with molten sodium particles in a temperature range of 100 to 160 ° C. -20179 gazette),
(3) A method for treating a biphenyl chloride composition in which the biphenyl chloride composition is reacted with an alkali metal under heating conditions (see Canadian Patent No. 1142551),
(4) A halogen compound decomposition method in which an active hydrogen compound not mixed with the organic compound is added to react with the halogen compound and the alkali metal dispersion in an organic solvent (see JP-A-9-216838), etc. It has been.
[0004]
[Problems to be solved by the invention]
In the conventional method for decomposing a hardly decomposable halogen compound, in order to perform the reaction more safely, a reaction vessel that can be shut off from the outside air is used, and the hardly decomposable halogen compound that is desired to be decomposed in the reaction vessel of the apparatus. In general, the reaction is carried out after adding alkali metal and the like and substituting the inside with an inert gas.
[0005]
However, depending on the inert gas replacement method and the purity of the inert gas, the decomposition treatment time of the hardly-decomposable halogen compound may vary, or the hardly-decomposable halogen compound may not be completely decomposed. It was.
[0006]
The present invention has been made in view of such a situation, and in the method of dehalogenating and decomposing a hardly decomposable halogen compound with an alkali, the detoxification of the hardly decomposable halogen compound which is more reproducible and stable than the conventional method. It is an object of the present invention to provide a method for decomposing a hardly decomposable halogen compound that can be treated.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have found that when the decomposition treatment time of the hardly decomposable halogen compound is varied or the hardly decomposed halogen compound is not completely decomposed, It was found that the oxygen concentration in the space portion (the remaining space portion in which the reactants and the solvent were added in the reaction vessel) was high. Therefore, the reproducible and stable degradability is achieved by dehalogenating the hardly decomposable halogen compound by setting the oxygen concentration in the space of the reaction vessel to less than the predetermined concentration or by controlling the oxygen concentration to the predetermined concentration. The inventors have found that the detoxification treatment of the halogen compound is realized, and have completed the present invention.
[0008]
That is, the present invention relates to a method for decomposing a hardly decomposable halogen compound by dehalogenating a hardly decomposable halogen compound using an alkali, wherein the oxygen concentration in the reaction system is less than 3% by volume. Provided is a method for decomposing a hardly decomposable halogen compound, which comprises dehalogenating a compound.
[0009]
The method for decomposing a hardly decomposable halogen compound of the present invention is as follows.
(1) A method for decomposing a hardly decomposable halogen compound in which a dehalogenation reaction is performed by adding an activator to a mixture of the hardly decomposable halogen compound and the alkali metal dispersion in a reaction vessel that can be shut off from the outside air. The remaining amount of the hardly decomposable halogen compound in the reaction mixture at the end of the addition of the activator is maintained at 1 ppm or less while maintaining the oxygen concentration in the space of the reaction vessel below 3% by volume. A method for decomposing a hardly decomposable halogen compound, comprising a step of adding so that
(2) The method for decomposing a hardly decomposable halogen compound according to (1), comprising the step of adding an activator while maintaining the oxygen concentration in the space of the reaction vessel at 1% by volume or less .
(3) Decomposing the hardly decomposable halogen compound of (1) or (2) having a step of completely replacing the gas in the reaction vessel with an inert gas before dehalogenating the hardly decomposable halogen compound. Processing method.
(4) The method for decomposing a hardly decomposable halogen compound according to (3), wherein the inert gas has an oxygen content of less than 3% by volume.
[0010]
(5) The method for decomposing a hardly decomposable halogen compound according to (3) or (4), wherein the supply of an inert gas into the reaction vessel is continued until the reaction is completed.
(6) The activator is an active hydrogen compound, and the addition amount thereof is in the range of 0.1 to 1.5 mol with respect to 1 mol of alkali metal in the alkali metal dispersion. ) To (5) A method for decomposing a hardly decomposable halogen compound.
(7) The hard decomposition of any one of (1) to (6), wherein the solvent used in preparing the alkali metal dispersion is selected from kerosene, decalin, electrical insulating oil, heavy oil, and a mixture thereof. Of decomposition of functional halogen compounds.
[0011]
According to the present invention, in a method of dehalogenating and decomposing with an alkali metal dispersion, it is possible to detoxify a hardly decomposable halogen compound that is more reproducible and stable than conventional methods. In addition, according to the present invention, a complete halogenolysis treatment of a halogen compound can be performed in a shorter time than in the prior art only by maintaining the oxygen concentration in the space of the reaction vessel as low as possible.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The hardly decomposable halogen compounds to be decomposed in the present invention are generally organic halogen compounds that are difficult to dehalogenate. Examples of such hardly decomposable halogen compounds include PCB, dioxins, polychlorinated benzofurans, polychlorinated benzene, DDT and other aromatic halogen compounds; BHC and other alicyclic halogen compounds; and the like. The present invention is suitable when an aromatic halogen compound contained in waste such as PCB is used as a target.
[0013]
The present invention can also be applied to the case of decomposing a hardly decomposable halogen compound dissolved in an organic solvent. Examples of the organic solvent include kerosene, decalin, electric insulating oil (electric insulating oil described in JIS C2320-1993), heavy oil (heavy oil described in JIS K2205), lubricating oil, and mixtures thereof. The present invention is particularly suitable when a dehalogenation treatment is performed by reacting a hardly decomposable halogen compound contained in an electrical insulating oil with an alkali metal dispersion.
[0014]
Examples of the alkali used include alkali metal, alkali metal hydroxide, organic alkali metal, alkali metal carbonate, alkaline earth metal, alkaline earth metal hydroxide, organic alkaline earth metal, alkaline earth metal carbonate, etc. Is mentioned. These may be used alone or in combination of two or more.
[0015]
Among these, it is preferable to use an alkali metal or an alkaline earth metal in the present invention. Examples of the alkali metal include sodium, potassium, lithium, cesium, and alloys thereof. Examples of the alkaline earth metal include magnesium, calcium, and alloys thereof. In the present invention, among these alkali metals or alkaline earth metals, it is more preferable to use an alkali metal dispersion. As the alkali metal dispersion, a dispersion in which an alkali metal is dispersed in a solvent can be used, and a metal sodium dispersion is particularly preferable.
[0016]
Examples of the solvent used for dispersing the alkali metal include kerosene, decalin, electric insulating oil (electric insulating oil described in JIS C2320-1993), heavy oil (heavy oil described in JIS K2205), and mixtures thereof. Is preferably an electrical insulating oil described in JIS C2320-1993.
[0017]
Although there is no restriction | limiting in particular in the alkali metal density | concentration in an alkali metal dispersion, The thing of the range of 5-50 volume% is preferable. In addition, from the viewpoints of storage stability, transportability, redispersibility, and ability to decompose halogen compounds, 80% or more of the alkali metal is preferably alkali metal fine particles having a particle size of 30 μm or less, preferably 15 μm or less. .
[0018]
Such an alkali metal dispersion can be obtained by a known method, for example, Inorganic Synthesis. , Vol. 5, p6-10, “Sodium Dispersions”, a method using a homogenizer described in JP-A-10-110205, and the like.
[0019]
The amount of alkali used for the reaction with the hardly decomposable halogen compound is usually 1 to 50 mol, preferably 1 in terms of the amount of alkali to be contained with respect to 1 mol of the halogen atom contained in the halogen compound. The range is from 0.05 to 20 mol.
[0020]
Moreover, when making a hardly decomposable halogen compound and an alkali metal dispersion react, it is preferable to coexist active hydrogen compounds, such as water and a lower alcohol. The amount of the active hydrogen compound used is usually 2 mol or less, preferably 0.1 to 1.5 mol, per 1 mol of the alkali metal in the alkali metal dispersion.
[0021]
There is no particular limitation on the method of decomposing a hardly decomposable halogen compound by reacting with an alkali. For example, when an alkali metal dispersion is used as the alkali and water is used as the activator, (1) a method of adding a predetermined amount of water to the mixture of the alkali metal dispersion and the hardly decomposable halogen compound, (2) (1) A method of adding an alkali metal dispersion after mixing an organic solvent containing a hardly decomposable halogen compound and a predetermined amount of water can be employed. In the case of the method (1), since the reaction between the alkali metal and water is intense, it is necessary to slowly add water little by little while sufficiently stirring the alkali metal dispersion in order to perform the work safely. Further, in the case of the method (2), in order to perform the decomposition process safely, a small amount of the alkali metal dispersion is added while sufficiently stirring the mixture of the organic solvent solution of the hardly-decomposable halogen compound and a predetermined amount of water. It is preferable to add them individually or in several times.
[0022]
The reaction temperature between the hardly decomposable halogen compound and the alkali is usually 0 to 300 ° C, preferably room temperature to 200 ° C, more preferably room temperature to 100 ° C. The reaction time is usually 0.5 to 3 hours although it depends on the kind and amount of the hardly decomposable halogen compound.
[0023]
The present invention relates to a method for decomposing a hardly decomposable halogen compound with an alkali, wherein the oxygen concentration in the reaction system for reacting the hardly decomposable halogen compound with an alkali is less than 3% by volume, preferably 1 It is characterized by being made not more than volume%, more preferably not more than 0.1 volume% .
[0024]
As a method for reducing the oxygen concentration in the reaction system to less than 3% by volume, for example, the reaction is carried out before dehalogenating the hardly decomposable halogen compound using a reaction vessel that can be shut off from the outside air or sealed. A method of completely replacing the gas in the container with an inert gas can be mentioned. As the inert gas, one having an oxygen content of less than 3% by volume, preferably an oxygen content of 1% by volume or less, more preferably 0.1% by volume or less is used. Specific examples of the inert gas include nitrogen, helium, argon and the like.
[0025]
The reaction vessel used here is not limited in its material, shape, capacity (size), etc. as long as it can be used for the reaction between a hardly decomposable halogen compound and an alkali, but can be shut off from the outside air. A reaction vessel is preferable, and a structure capable of introducing an inert gas and exhausting the gas in the reaction vessel is more preferable.
[0026]
When replacing the space of the reaction vessel with an inert gas, the reaction vessel space may be changed according to the size of the space of the reaction vessel, the purity of the inert gas, the flow rate of the inert gas, etc. before starting the reaction. It is necessary to replace the above gas with an inert gas so that the oxygen concentration in the space of the reaction vessel is less than (or less than) a predetermined value.
[0027]
In the present invention, the oxygen concentration in the reaction vessel can be reduced to a predetermined concentration or lower and then sealed to perform the dehalogenation reaction. The oxygen concentration is less than a predetermined value (or lower), specifically, It is preferable to carry out the reaction while maintaining it at less than 3% by volume, preferably 1% by volume or less, more preferably 0.1% by volume or less. As a method for maintaining the oxygen concentration below a predetermined value, for example, there is a method in which the supply of an inert gas in the reaction vessel is continued until the end of the reaction while appropriately adjusting the flow rate with a flow meter or the like. According to this method, the oxygen concentration in the space of the reaction vessel can be easily and reliably maintained at a certain value or less during the reaction.
[0028]
As a particularly preferred embodiment of the present invention, a hardly decomposable halogen compound is placed in a reaction vessel that can be blocked from outside air, and the gas in the vessel is completely replaced with an inert gas having an oxygen content of 1% by volume or less. This is a method of heating to a temperature, adding an alkali metal dispersion under an inert gas atmosphere, and further slowly adding a predetermined amount of an activator. According to this method, the oxygen concentration in the reaction system is less than 3% by volume, preferably 1% by volume or less, more preferably 0.01% by volume, without making a significant change to the conventional decomposition treatment process. % Or less, and stable and prompt decomposition of the hardly decomposable halogen compound is realized.
[0029]
In the present invention, when an activator is added, the oxygen concentration in the reaction system is set to a value less than (or below) a predetermined value before the activator addition step, preferably from the start to the end of the addition. As a result, the dehalogenation reaction of the hardly decomposable halogen compound can proceed more rapidly. The residual amount of the hardly decomposable halogen compound in the reaction mixture at the end of the addition of the activator is usually 1 ppm or less, preferably 0.8 ppm or less.
[0030]
After completion of the reaction, it is usually preferable to add a large amount of water to the reaction mixture to decompose unreacted alkali. When a reaction solvent is used, an organic solvent such as trans oil recovered by separating the reaction treatment liquid can be reused as fuel.
[0031]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to the following examples, and can be applied to any method of decomposing a hardly decomposable halogen compound by reacting a hardly decomposable halogen compound with an alkali in an organic solvent. In the following Examples and Comparative Examples, a 10% by volume metallic sodium dispersion (hereinafter referred to as “10”) obtained by dispersing metallic sodium having a particle size of several microns in electrical insulating oil (manufactured by Idemitsu Kosan Co., Ltd.). % SD ”).
[0032]
Example 1
Put 262.1 g of PCB contaminated oil (PCB concentration 37.15 ppm) into a 500 ml four-necked flask, attach a stirring blade and a thermometer, and flow nitrogen gas with a purity of 99.999% by volume into this four-necked flask. meter KG-1 (Kusano scientific instruments Seisakusho Co., Ltd., hereinafter the same.) with a nitrogen substitution of the reaction system run at 100 scale (0.264L / min), the temperature was raised to 65 ° C. over a period of 40 minutes . Thereafter, the flow rate of nitrogen gas was adjusted to 5 scales (0.0009 L / min) with a flow meter KG-1, 3.48 g of 10% SD was added, and the mixture was stirred at 65 ° C. for 30 minutes, and then 3.23 g of 10% SD was added. Immediately thereafter, 0.24 ml of water was added as an activator over 60 minutes, and the mixture was further reacted at 65 ° C. for 60 minutes.
The PCB concentration in the reaction mixture was analyzed 30 minutes after the completion of the second 10% SD addition. As a result, the PCB concentration was below the detection limit (0.5 ppm or less, the same applies hereinafter).
[0033]
(Example 2)
Put 254.4 g of PCB contaminated oil (PCB concentration 37.15 ppm) into a 500 ml four-necked flask, attach a stirring blade and a thermometer, and supply nitrogen gas with a purity of 99 vol% (oxygen content 1 vol%) to the flow meter KG. The temperature was raised to 65 ° C. over 40 minutes while flowing nitrogen at 100 scale (0.264 L / min) and substituting with nitrogen. Thereafter, the flow rate of nitrogen gas was adjusted to 5 scales (0.0009 L / min) with a flow meter KG-1, 3.70 g of 10% SD was added, and the mixture was stirred at 65 ° C. for 30 minutes, and then 2.70 g of 10% SD was added. Immediately thereafter, 0.24 ml of water was added as an activator over 60 minutes, and the mixture was further reacted at 65 ° C. for 60 minutes.
Analysis of PCB concentration in the reaction mixture was performed 30 minutes after the completion of the second 10% SD addition. As a result, the residual PCB concentration after 30 minutes was below the detection limit.
[0034]
(Example 3)
A 500 ml four-necked flask was charged with 262.1 g of PCB-contaminated oil (PCB concentration 37.15 ppm), a stirring blade and a thermometer were attached, and a purity of 99.999% nitrogen gas was measured on the 5th scale (0 The temperature was raised to 65 ° C. over 40 minutes while purging with nitrogen at 0.009 L / min). Thereafter, 3.51 g of 10% SD was added while flowing nitrogen gas on the flow meter KG-1 at 5 scales (0.0009 L / min), and the mixture was stirred at 65 ° C. for 30 minutes, and then 2.84 g of 10% SD was added. Immediately thereafter, 0.24 ml of water was added as an activator over 60 minutes, and the mixture was further reacted at 65 ° C. for 60 minutes.
The PCB concentration of the reaction mixture was analyzed after 30 minutes and 60 minutes after the completion of the second 10% SD addition.
As a result, the residual PCB concentration after 30 minutes was 16.74 ppm, and the residual PCB concentration after 60 minutes was below the detection limit.
[0035]
(Comparative Example 1)
Into a 500 ml four-necked flask, put 263.5 g of PCB contaminated oil (PCB concentration 37.15 ppm), attach a stirring blade and a thermometer, and flow nitrogen gas with a purity of 97% by volume (oxygen content 3% by volume) The temperature was raised to 65 ° C. over 40 minutes while the reaction system was purged with nitrogen by flowing 100 scales (0.264 L / min) with a total of KG-1. Thereafter, the flow rate of nitrogen gas was adjusted to 5 scales (0.0009 L / min) with a flow meter KG-1, 3.72 g of 10% SD was added, and the mixture was stirred at 65 ° C. for 30 minutes, and then 2.71 g of 10% SD was added. Thereafter, 0.24 ml of water was immediately added as an activator over 60 minutes, and further reacted at 65 ° C. for 60 minutes.
Analysis of PCB concentration in the reaction mixture was performed after 30 minutes, 60 minutes and 120 minutes after the completion of the second 10% SD addition.
As a result, the residual PCB concentration after 30 minutes was 21.24 ppm, the residual PCB concentration after 60 minutes was 0.77 ppm, and the residual PCB concentration after 120 minutes was below the detection limit.
[0036]
(Comparative Example 2)
Place 261.1 g of PCB contaminated oil (PCB concentration 37.15 ppm) into a 500 ml four-necked flask, attach a stirring blade and a thermometer, and flow nitrogen gas with a purity of 99.999% by volume for 13 minutes while replacing the nitrogen. The temperature was raised to 65 ° C. At that time, the oxygen concentration in the space of the four-necked flask was 3.2% by volume. Next, 2.34 g of 10% SD was added and stirred at 65 ° C. for 30 minutes, and then 4.47 g of 10% SD was added. Immediately thereafter, 0.24 ml of water was added as an activator over 60 minutes, and the mixture was further reacted at 65 ° C. for 120 minutes.
The PCB concentration of the reaction mixture was analyzed after 60 minutes, after 120 minutes and after 180 minutes after the second addition of 10% SD.
As a result, the residual PCB concentration was 4.07 ppm after 60 minutes, the residual PCB concentration was 0.53 ppm after 120 minutes, and the residual PCB concentration was below the detection limit after 180 minutes. .
[0037]
(Comparative Example 3)
A 1 L four-necked flask was charged with 261.9 g of PCB-contaminated oil (PCB concentration 37.15 ppm), a stirring blade and a thermometer were attached, and nitrogen was substituted by flowing nitrogen gas with a purity of 99.999% by volume. The oxygen concentration in the space at that time was 4% by volume. Thereafter, the inside of the four-necked flask was shut off from the outside air, heated to 65 ° C., added with 2.97 g of 10% SD, stirred at 65 ° C. for 30 minutes, and then added with 3.14 g of 10% SD. . Thereafter, 0.24 ml of water was immediately added as an activator over 60 minutes, and further reacted at 65 ° C. for 120 minutes.
The PCB concentration of the reaction mixture was analyzed after 60 minutes and 180 minutes after the completion of the second 10% SD addition.
As a result, the residual PCB concentration after 60 minutes was 17.99 ppm, and the residual PCB concentration after 180 minutes was 16.35 ppm.
[0038]
Example 1 is an example in which nitrogen gas having a purity of 99.999% by volume was continuously flowed into the reaction vessel, and Example 2 was continuously reacted by flowing nitrogen gas having a purity of 99% by volume into the reaction vessel. Example 3 is an example in which the reaction was carried out in the same manner as Example 1 while reducing the flow rate of nitrogen gas having a purity of 99.999% by volume. In all cases, the PCB was completely decomposed within 60 minutes.
[0039]
On the other hand, Comparative Example 1 is an example in which the reaction was performed at an oxygen concentration of 3% by volume, Comparative Example 2 was an example in which the reaction was performed at an oxygen concentration of 3.2%, and Comparative Example 3 was reacted at an oxygen concentration of 4% by volume. This is an example of performing. In Comparative Example 1, 120 minutes are required for the PCB decomposition. In Comparative Examples 2 and 3, both were replaced with nitrogen gas having a purity of 99.999% by volume, but the replacement was insufficient. In Comparative Example 2, 180 minutes were required for PCB decomposition, In Comparative Example 3, PCB was not completely decomposed.
[0040]
【Effect of the invention】
As described above, according to the present invention, in the method of dehalogenating and decomposing with an alkali metal dispersion, it is possible to perform detoxification of a hardly decomposable halogen compound that is more reproducible and stable than conventional methods. A method for decomposing a halogen compound is provided. In addition, according to the present invention, a complete halogenolysis treatment of a halogen compound can be performed in a shorter time than in the prior art only by maintaining the oxygen concentration in the space of the reaction vessel as low as possible.

Claims

A method for decomposing a hardly decomposable halogen compound in which a dehalogenation reaction is performed by adding an activator to a mixture of the hardly decomposable halogen compound and the alkali metal dispersion in a reaction vessel that can be shut off from outside air, While maintaining the oxygen concentration in the space of the reaction vessel below 3% by volume, the activator is added so that the residual amount of the hardly decomposable halogen compound in the reaction mixture at the end of the addition of the activator is 1 ppm or less. A method for decomposing a hardly decomposable halogen compound, comprising a step of adding to the process.

While maintaining the oxygen concentration in the space portion of the reaction vessel below 1 volume%, the decomposition processing method according to claim 1 hardly decomposable halogen compounds described comprising the step of adding the active agent.

The method for decomposing a hardly decomposable halogen compound according to claim 1 or 2, further comprising a step of completely replacing the gas in the reaction vessel with an inert gas before dehalogenating the hardly decomposable halogen compound. .

The method for decomposing a hardly decomposable halogen compound according to claim 3, wherein the inert gas has an oxygen content of less than 3% by volume.

The method for decomposing a hardly decomposable halogen compound according to claim 3 or 4, wherein the supply of the inert gas into the reaction vessel is continued until the end of the reaction.

The said activator is an active hydrogen compound, and the addition amount is the range of 0.1-1.5 mol with respect to 1 mol of alkali metals in an alkali metal dispersion. A method for decomposing a hardly decomposable halogen compound according to any one of the above.

The hardly decomposable halogen according to any one of claims 1 to 6, wherein the solvent used in preparing the alkali metal dispersion is selected from kerosene, decalin, electrical insulating oil, heavy oil, and a mixture thereof. Compound decomposition method.