JP3739032B2 - Catalyst for removing organic halogen compound, method for producing the same, and method for removing organic halogen compound - Google Patents
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【０００１】
【発明の属する技術分野】
本発明は、排ガス中のダイオキシン類等の毒性有機ハロゲン化合物を除去するための排ガス浄化用触媒、その製造方法および有機ハロゲン化合物の除去方法に関する。
【０００２】
【従来の技術】
産業廃棄物や都市廃棄物を処理する焼却施設から発生する排ガス中には、ダイオキシン類、ＰＣＢ、クロロフェノールなどの極微量の毒性有機ハロゲン化合物が含まれている。特にダイオキシン類は微量であってもきわめて有毒であり、人体に重大な影響を及ぼすため、その除去技術が早急に求められている。触媒分解法は最も有効な技術の一つであり、一般的にバナジウム酸化物やタングステン酸化物を酸化チタンに担持した触媒や、白金をはじめとする貴金属触媒が用いられているが、排ガス条件によっては充分な性能を発揮できない場合があり、さらなる触媒性能の向上が求められている。また、排ガス中には、一般に二酸化硫黄などの硫黄酸化物が含まれており、これによって触媒が被毒を受け活性が劣化するという問題があり、触媒性能が高くかつ耐久性に優れた触媒が求められている。
【０００３】
【発明が解決しようとする課題】
したがって、本発明の課題は、排ガス中のダイオキシン類などの有機ハロゲン化合物を効率良く除去することができ、しかも二酸化硫黄を含むガスに対する耐久性に優れた触媒を提供することにある。また、そのような触媒の製造方法およびそのような触媒を用いた有機ハロゲン化合物の除去方法を提供することも課題とする。
【０００４】
【課題を解決するための手段】
上記課題を解決するため、本発明の有機ハロゲン化合物の除去用触媒は、触媒成分として、酸化チタン（ＴｉＯ２）、チタニア−シリカ複合酸化物（ＴｉＯ２−ＳｉＯ２）またはこれらの混合物を含有する有機ハロゲン化合物の除去用触媒であって、さらにバナジウムとモリブデンの複合酸化物を含有し、ＣｕＫα線を用いたＸ線回折プロファイルにおいて、少なくとも２θ＝２１．６゜と２θ＝２４．９゜とに回折ピークを有することを特徴とする。
本発明の有機ハロゲン化合物の除去用触媒の製造方法は、上記の本発明の触媒の製造方法であって、酸化チタン（ＴｉＯ２）、チタニア−シリカ複合酸化物（ＴｉＯ２−ＳｉＯ２）またはこれらの混合物に対し、バナジウムの酸化物または塩類とモリブデンの酸化物または塩類とを含む溶液を添加する工程(a) と、その後、湿度５０％以上、温度６０℃以下で、４８〜１６８時間かけて乾燥を行う工程 (b) とを含むことを特徴とする。
【０００５】
本発明の有機ハロゲン化合物の除去方法は、有機ハロゲン化合物を含む排ガスを、１３０〜３５０℃の温度で上記の本発明の触媒と接触させる。
【０００６】
【発明の実施の形態】
本発明の触媒は、触媒成分として、酸化チタン（ＴｉＯ2）、チタニア−シリカ複合酸化物（ＴｉＯ2−ＳｉＯ2）またはこれらの混合物を含有し、さらにバナジウムとモリブデン（以下、Ｖ−Ｍｏ複合酸化物と表記する）の複合酸化物を含有する。Ｖ−Ｍｏ複合酸化物を含有することにより、比較的低温域で高活性を示し、かつ二酸化硫黄を含むガスに対しても高い耐久性を示すものとなる。その理由は定かではないが、バナジウムとモリブデンとが複合化することにより、バナジウムの原子価あるいは構造が変化し、バナジウムが単独で存在するときよりも二酸化硫黄による被毒が抑制されるためと考えられる。
【０００７】
Ｖ−Ｍｏ複合酸化物は組成式ＭｏＶxＯyで表され、種々の組成物が知られているが、本発明では、ＭｏＶ2Ｏ8、Ｍｏ6Ｖ9Ｏ40およびＭｏＶＯ5の少なくともいずれかに起因するＸ線回折ピークを有することが好ましい。すなわち、Ｘ線回折プロファイルにおいて、少なくとも２θ＝２１．６゜と２θ＝２４．９゜とに回折ピークを有することが好ましく、その他に２θ＝１８．１゜、２７．４゜、３３．２゜、３３．７゜の各回折ピークを有することがより好ましい。ただし、酸化チタン、チタニア−シリカ複合酸化物またはこれらの混合物によってＶ−Ｍｏ複合酸化物は高分散するため、回折ピークは非常に小さく、Ｘ線回折プロファイルにおいては、上記２つのピーク（２θ＝２１．６゜と２θ＝２４．９゜）のみが確認される場合がほとんどである。
【０００８】
本発明の触媒に含まれるチタン成分は、酸化チタン（ＴｉＯ2）、チタニア−シリカ複合酸化物（ＴｉＯ2−ＳｉＯ2、チタンとケイ素の複合酸化物）またはこれらの混合物のいずれでもよく、混合物を用いる場合の両者の混合比も特に限定されない。
本発明の触媒を製造する方法としては、酸化チタン、チタニア−シリカ複合酸化物またはこれらの混合物に対し、バナジウム源とモリブデン源とを含む溶液を添加する工程を含むことが好ましい。酸化チタン、チタニア−シリカ複合酸化物またはこれらの混合物を予め成形した後、その成形体に、バナジウム源とモリブデン源とを含む溶液を含浸してもよいし、あるいは、酸化チタン、チタニア−シリカ複合酸化物またはこれらの混合物と、バナジウム源とモリブデン源とを含む溶液との混合物を混練り成形してもよい。
【０００９】
本発明の触媒の製造方法としては、バナジウムの酸化物等とモリブデンの酸化物等とを混合し、５００〜１０００℃程度で焼成して、Ｖ−Ｍｏ複合酸化物を得た後に、これと酸化チタン、チタニア−シリカ複合酸化物またはこれらの混合物とを混練するという方法も考えられるが、この方法では、酸化チタン、チタニア−シリカ複合酸化物またはこれらの混合物中にＶ−Ｍｏ複合酸化物が高分散することが困難となるため、上記した製法によって製造した触媒と比べて有機ハロゲン化合物の分解活性が著しく低く、また二酸化硫黄含有ガス曝露後の活性も低い。
【００１０】
本発明の触媒の製造の際には、バナジウム源およびモリブデン源を添加後、最終的にＶ−Ｍｏ複合酸化物が生成するように、比較的穏やかな条件で充分時間をかけて乾燥した後、焼成を行うことが望ましい。具体的には湿度５０％以上、温度６０℃以下、好ましくは３０〜４０℃で、１２〜１６８時間、好ましくは４８〜１６８時間かけて乾燥を行った後、３５０〜７５０℃、好ましくは４００〜５５０℃で焼成を行うことが好ましい。高温で急速に乾燥すると、Ｖ−Ｍｏ複合酸化物は生成しにくく、バナジウムとモリブデンのそれぞれの単独酸化物が生成しやすくなる。
【００１１】
上記酸化チタンとしては、酸化チタン粉末の他、焼成して酸化チタンを生成するものであれば、無機および有機のいずれの化合物も使用することができる。例えば、四塩化チタン、硫酸チタンなどの無機チタン化合物、および、蓚酸チタン、テトライソプロピルチタネートなどの有機チタン化合物を用いることができる。
上記チタニア−シリカ複合酸化物の調製に用いるチタン源としては、上記の無機および有機のいずれの化合物も使用することができ、またシリカ源としては、コロイド状シリカ、水ガラス、微粒子ケイ素、四塩化ケイ素などの無機ケイ素化合物、および、テトラエチルシリケートなどの有機ケイ素化合物から適宜選択して使用することができる。
【００１２】
酸化チタンとチタニア−シリカ複合酸化物とを混合するには、従来公知の混合方法にしたがえばよく、例えば、ニーダーなどの混合機に、酸化チタン粉末とチタニア−シリカ複合酸化物粉末とを投入して、撹拌・混合することができる。
上記バナジウム源としては、バナジウムの酸化物または塩類が用いられ、塩類としては、水酸化物、アンモニウム塩、蓚酸塩、ハロゲン化物、硫酸塩などを用いることができる。
上記モリブデン源としては、モリブデンの酸化物または塩類が用いられ、水酸化物、アンモニウム塩、蓚酸塩、ハロゲン化物、硫酸塩などを用いることができる。
【００１３】
本発明の触媒の組成としては、各元素の酸化物重量比で、チタンの酸化物は６０〜９０重量％、ケイ素の酸化物は３〜１５重量％、バナジウムの酸化物は３〜２０重量％、モリブデンの酸化物は３〜２０重量％であることが好ましい。
本発明の触媒の形状は、特に限定されるものではなく、ハニカム状、板状、波板状、網状、円柱状、円筒状など所望の形状に成形して使用することができる。また、アルミナ、シリカ、コージェライト、ムライト、ＳｉＣ、チタニア、ステンレス金属などからなるハニカム状、板状、波板状、網状、円柱状、円筒状などの所望の形状の担体に担持して使用してもよい。
【００１４】
本発明の触媒を用いて処理する排ガスの組成としては、ダイオキシン類、ＰＣＢ、クロロフェノールなどの有機ハロゲン化合物を含有するものであれば特に限定されないが、本発明の触媒は特にダイオキシン類やＰＣＢを含む排ガスの処理に適している。
処理する排ガスの本発明の触媒に対する空間速度は１００〜１０００００Ｈｒ-1が好ましく、２００〜５００００Ｈｒ-1がより好ましい。処理温度は１３０〜３５０℃が好ましく、１５０〜２５０℃がより好ましい。
【００１５】
【実施例】
以下に実施例によりさらに詳細に本発明を説明するが、本発明はこれに限定されるものではない。
［実施例１］
酸化チタン２０ｋｇに、メタバナジン酸アンモニウム２．０ｋｇ、パラモリブデン酸アンモニウム四水和物１．４ｋｇ、シュウ酸２．４ｋｇ、モノエタノールアミン１．０ｋｇを水１２リットルに溶解させた薬液を加え、さらにフェノール樹脂１ｋｇと成形助剤として澱粉を加えて混合しニーダーで混練りした後、押出成形機で外形８０ｍｍ角、目開き４．０ｍｍ、肉厚１．０ｍｍ、長さ５００ｍｍのハニカム状に成形した。次いで、湿度６０〜７０％、温度５０℃で、１００時間かけてゆっくり乾燥した後、４５０℃で５時間空気雰囲気下で焼成し、触媒（Ａ）を得た。こうして得られた触媒（Ａ）の組成は、Ｖ2Ｏ5：ＭｏＯ3：ＴｉＯ2＝７：５：８８（重量比）であった。図１に触媒（Ａ）のＸ線回折プロファイルを示す。２θ＝２１．６゜と２θ＝２４．９゜とに回折ピークが認められ、バナジウムとモリブデンの複合酸化物が生成していることが確認された。
【００１６】
［実施例２］
まず、担体となるチタニア−シリカ複合酸化物粉体を以下に述べる方法で調製した。１０重量％アンモニア水７００リットルにスノーテックス−２０（日産化学社製シリカゾル、約２０重量％のＳｉＯ2含有）２７．３ｋｇを加え、撹拌、混合した後、硫酸チタニルの硫酸溶液（ＴｉＯ2として１２５ｇ／リットル、硫酸濃度５００ｇ／リットル）３４０リットルを撹拌しながら徐々に滴下した。得られたゲルを３時間放置後、濾過、水洗し、続いて１５０℃で１０時間乾燥した。これを５５０℃で焼成した。得られた粉体の組成は、ＴｉＯ2：ＳｉＯ2＝８．５：１．５（モル比）であった。
【００１７】
酸化チタン１０ｋｇと上記で調製したチタニア−シリカ複合酸化物１０ｋｇの混合物に、メタバナジン酸アンモニウム２．０ｋｇ、パラモリブデン酸アンモニウム四水和物１．４ｋｇ、シュウ酸２．４ｋｇ、モノエタノールアミン１．０ｋｇを水１２リットルに溶解させた薬液を加え、さらにフェノール樹脂１ｋｇと成形助剤として澱粉を加えて混合しニーダーで混練りした後、押出成形機で外形８０ｍｍ角、目開き４．０ｍｍ、肉厚１．０ｍｍ、長さ５００ｍｍのハニカム状に成形した。次いで、湿度６０〜７０％、温度５０℃で、１００時間かけてゆっくり乾燥した後、４５０℃で５時間空気雰囲気下で焼成し、触媒（Ｂ）を得た。こうして得られた触媒（Ｂ）のの組成は、Ｖ2Ｏ5：ＭｏＯ3：ＴｉＯ2：ＳｉＯ2＝７：５：８１：７（重量比）であった。触媒（Ｂ）のＸ線回折プロファイルにおいて、２θ＝２１．６゜と２θ＝２４．９゜とに回折ピークが認められ、バナジウムとモリブデンの複合酸化物が生成していることが確認された。
【００１８】
［実施例３］
実施例２で調製したチタニア−シリカ複合酸化物粉体２０ｋｇに、メタバナジン酸アンモニウム２．０ｋｇ、パラモリブデン酸アンモニウム四水和物１．４ｋｇ、シュウ酸２．４ｋｇ、モノエタノールアミン１．０ｋｇを水１２リットルに溶解させた薬液を加え、さらにフェノール樹脂１ｋｇと成形助剤として澱粉を加えて混合しニーダーで混練りした後、押出成形機で外形８０ｍｍ角、目開き４．０ｍｍ、肉厚１．０ｍｍ、長さ５００ｍｍのハニカム状に成形した。次いで、湿度６０〜７０％、温度５０℃で、１００時間かけてゆっくり乾燥した後、４５０℃で５時間空気雰囲気下で焼成し、触媒（Ｃ）を得た。こうして得られた触媒（Ｃ）の組成は、Ｖ2Ｏ5：ＭｏＯ3：ＴｉＯ2：ＳｉＯ2＝７：５：７５：１３（重量比）であった。触媒（Ｃ）のＸ線回折プロファイルにおいて、２θ＝２１．６゜と２θ＝２４．９゜とに回折ピークが認められ、バナジウムとモリブデンの複合酸化物が生成していることが確認された。
【００１９】
［比較例１］
実施例１と同様の方法で得られたハニカム成形体を、２００℃で急速に乾燥した後、４５０℃で５時間空気雰囲気下で焼成し、触媒（Ｄ）を得た。こうして得られた触媒（Ｄ）のＶ2Ｏ5：ＭｏＯ3：ＴｉＯ2＝７：５：８８（重量比）であった。触媒（Ｄ）のＸ線回折プロファイルにおいて、２θ＝２１．６゜と２θ＝２４．９゜とに回折ピークは認められなかった。
［比較例２］
酸化チタン２０ｋｇに、メタバナジン酸アンモニウム１．９ｋｇ、シュウ酸２．４ｋｇ、モノエタノールアミン０．５ｋｇを水１２リットルに溶解させた薬液を加え、さらにフェノール樹脂１ｋｇと成形助剤として澱粉を加えて混合しニーダーで混練りした後、押出成形機で外形８０ｍｍ角、目開き４．０ｍｍ、肉厚１．０ｍｍ、長さ５００ｍｍのハニカム状に成形した。次いで、５０℃でゆっくり乾燥した後、４５０℃で５時間空気雰囲気下で焼成し、触媒（Ｅ）を得た。こうして得られた触媒（Ｅ）のＶ2Ｏ5：ＴｉＯ2＝７：９３（重量比）であった。
【００２０】
［実施例４〜６、比較例３〜４］
実施例１で調製した触媒（Ａ）、実施例２で調製した触媒（Ｂ）、実施例３で調製した触媒（Ｃ）、比較例１で調製した触媒（Ｄ）、比較例２で調製した触媒（Ｅ）の各触媒をそれぞれ用いて、有機塩素化合物分解試験を行った。処理対象となる有機塩素化合物としてクロロトルエン（以下、ＣＴと略す）を用い、以下の試験条件で反応を行い、ＣＴ分解率（初期分解率）を求めた。結果を表１に示す。
（試験条件）
処理ガス組成
ＣＴ：３０ｐｐｍ，Ｏ2：１０％、Ｈ2Ｏ：１５％、Ｎ2：バランス
ガス温度：１７５℃
空間速度（ＳＶ）：４０００Ｈｒ-1
なお、ＣＴ分解率、すなわちＣＴ除去率は下記式により求めた。
【００２１】
（ＣＴ分解率）
ＣＴ分解率（％）＝［（反応器入口ＣＴ濃度）−（反応器出口ＣＴ濃度）］／（反応器入口ＣＴ濃度）×１００
［実施例７〜９、比較例５〜６］
実施例１で調製した触媒（Ａ）、実施例２で調製した触媒（Ｂ）、実施例３で調製した触媒（Ｃ）、比較例１で調製した触媒（Ｄ）、比較例２で調製した触媒（Ｅ）の各触媒を、以下の条件にて二酸化硫黄含有ガスに２０００時間曝露した後、実施例４と同様の有機塩素化合物分解試験を行い、ＣＴ分解率（ＳＯ2曝露後分解率）を求めた。この結果を合わせて表１に示す。
【００２２】
（二酸化硫黄含有ガス曝露条件）
ガス組成
ＳＯ2：１００ｐｐｍ，Ｏ2：１０％、Ｈ2Ｏ：１５％、Ｎ2：バランス
ガス温度：１７５℃
空間速度（ＳＶ）：４０００Ｈｒ-1
【００２３】
【表１】
表１に見るように、実施例１および２の触媒では、初期および二酸化硫黄含有ガス曝露後のいずれにおいても高いＣＴ分解率を示し、二酸化硫黄含有ガス曝露による劣化がほとんど見られず、耐久性が高いことがわかる。一方、比較例１および２の触媒では、初期においては高いＣＴ分解率を示すものの、二酸化硫黄含有ガス曝露後はＣＴ分解率が著しく低下しており、耐久性が低いことがわかる。
［実施例１０］
酸化チタン３０ｇ（ミレニアム社製ＤＴ−５１）に、メタバナジン酸アンモニウム１．５ｇ、パラモリブデン酸アンモニウム四水和物２．６ｇ、シュウ酸３．０ｇ、モノエタノールアミン１．７ｇを水６０ｍｌに溶解させた薬液を加え、充分らいかいした後、湿度６０〜７０％、温度６０℃以下で、２０時間かけてゆっくり乾燥し、打錠成型した。得られた成形品を４５０℃で焼成して触媒（Ｆ）を得た。
【００２５】
［実施例１１］
Ｖ2Ｏ5粉末４ｇとＭｏＯ3粉末７ｇの混合物スラリーを充分らいかいし、窒素雰囲気下７００℃で焼成することによって、Ｖ−Ｍｏ複合酸化物を得た。この複合酸化物３．３ｇにメタチタン酸スラリー（ＴｉＯ2として３０重量％含有）１００ｇを混合して充分らいかいし、１５０℃で乾燥後、打錠成型した。得られた成型品を４５０℃で焼成して触媒（Ｇ）を得た。
［実施例１２〜１３］
実施例１０で調製した触媒（Ｆ）、実施例１１で調製した触媒（Ｇ）の各触媒（打錠成型品）を１０〜２０メッシュに破砕した触媒をそれぞれ用いて、実施例４と同様にして、ＣＴ分解率（初期分解率）を求めた。結果を表２に示す。
【００２６】
［実施例１４〜１５］
実施例１０で調製した触媒（Ｆ）、実施例１１で調製した触媒（Ｇ）の各触媒（打錠成型品）を１０〜２０メッシュに破砕した触媒をそれぞれ用いて、実施例７と同様にして、ＣＴ分解率（ＳＯ2曝露後分解率）を求めた。この結果を合わせて表２に示す。
【００２７】
【表２】
表２に見るように、実施例１０の触媒は、初期および二酸化硫黄含有ガス曝露後のいずれにおいても高いＣＴ分解率を示し、二酸化硫黄含有ガス曝露による劣化がほとんど見られず、耐久性が高いことがわかる。一方、実施例１１の触媒では、初期および二酸化硫黄含有ガス曝露後のいずれにおいてもＣＴ分解率が低い。これは、実施例１０の触媒は、酸化チタンに対し、バナジウムの塩類とモリブデンの塩類とを含む溶液を添加する工程を含む製法により製造されたため、酸化チタン中にＶ−Ｍｏ複合酸化物が高分散しているが、実施例１１の触媒では、異なった製法で製造されたために、酸化チタン中にＶ−Ｍｏ複合酸化物が高分散していないことが原因と推測される。
【００２９】
【発明の効果】
本発明の触媒は、排ガス中のダイオキシン類などの有機ハロゲン化合物を効率良く除去することができ、しかも二酸化硫黄を含むガスに対する耐久性に優れたものである。
【図面の簡単な説明】
【図１】 実施例１で得られた有機ハロゲン化合物の除去用触媒のＸ線回折プロファイルである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas purifying catalyst for removing toxic organic halogen compounds such as dioxins in exhaust gas, a method for producing the same, and a method for removing organic halogen compounds.
[0002]
[Prior art]
Exhaust gas generated from incineration facilities that treat industrial waste and municipal waste contains trace amounts of toxic organic halogen compounds such as dioxins, PCBs, and chlorophenol. In particular, dioxins are extremely toxic even in trace amounts and have a serious effect on the human body, so there is an urgent need for their removal technology. Catalytic decomposition is one of the most effective technologies. Generally, catalysts with vanadium oxide or tungsten oxide supported on titanium oxide or noble metal catalysts such as platinum are used. May not be able to exhibit sufficient performance, and further improvement in catalyst performance is required. In addition, sulfur oxides such as sulfur dioxide are generally contained in exhaust gas, which causes a problem that the catalyst is poisoned and its activity deteriorates, and a catalyst having high catalyst performance and excellent durability is produced. It has been demanded.
[0003]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a catalyst that can efficiently remove organic halogen compounds such as dioxins in exhaust gas and is excellent in durability against a gas containing sulfur dioxide. It is another object of the present invention to provide a method for producing such a catalyst and a method for removing an organic halogen compound using such a catalyst.
[0004]
[Means for Solving the Problems]
In order to solve the above problems, the organic halogen compound removal catalyst of the present invention contains titanium oxide (TiO 2 ), titania-silica composite oxide (TiO 2 —SiO 2 ), or a mixture thereof as a catalyst component. A catalyst for removing organic halogen compounds, which further contains a composite oxide of vanadium and molybdenum, and has an X-ray diffraction profile using CuKα rays of at least 2θ = 21.6 ° and 2θ = 24.9 °. It has a diffraction peak .
The production method of the catalyst for removing an organic halogen compound of the present invention is the production method of the catalyst of the present invention described above, wherein titanium oxide (TiO 2 ), titania-silica composite oxide (TiO 2 —SiO 2 ) or these to a mixture of the step (a) adding a solution containing the oxide or salt of the oxide or salt and molybdenum vanadium, then humidity of 50% or more, at a
[0005]
In the method for removing an organic halogen compound of the present invention, an exhaust gas containing an organic halogen compound is brought into contact with the catalyst of the present invention at a temperature of 130 to 350 ° C.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The catalyst of the present invention contains, as a catalyst component, titanium oxide (TiO 2 ), titania-silica composite oxide (TiO 2 —SiO 2 ) or a mixture thereof, and further vanadium and molybdenum (hereinafter referred to as V-Mo composite oxidation). Compound oxide). By containing the V-Mo composite oxide, it exhibits high activity in a relatively low temperature range and also exhibits high durability against a gas containing sulfur dioxide. The reason for this is not clear, but it is thought that the combination of vanadium and molybdenum changes the valence or structure of vanadium and suppresses sulfur dioxide poisoning more than when vanadium is present alone. It is done.
[0007]
V-Mo composite oxide is represented by the composition formula MoV x O y and various compositions are known. In the present invention, at least one of MoV 2 O 8 , Mo 6 V 9 O 40 and MoVO 5 is used. It is preferable to have an X-ray diffraction peak due to. That is, in the X-ray diffraction profile, it is preferable to have diffraction peaks at least 2θ = 21.6 ° and 2θ = 24.9 °, and 2θ = 18.1 °, 27.4 °, 33.2 °. It is more preferable to have each diffraction peak of 33.7 °. However, since the V-Mo composite oxide is highly dispersed by titanium oxide, titania-silica composite oxide or a mixture thereof, the diffraction peak is very small. In the X-ray diffraction profile, the above two peaks (2θ = 21 .6 ° and 2θ = 24.9 °) are almost always confirmed.
[0008]
The titanium component contained in the catalyst of the present invention may be any of titanium oxide (TiO 2 ), titania-silica composite oxide (TiO 2 —SiO 2 , composite oxide of titanium and silicon), or a mixture thereof. The mixing ratio of both is not particularly limited.
The method for producing the catalyst of the present invention preferably includes a step of adding a solution containing a vanadium source and a molybdenum source to titanium oxide, titania-silica composite oxide or a mixture thereof. After pre-molding titanium oxide, titania-silica composite oxide or a mixture thereof, the compact may be impregnated with a solution containing a vanadium source and a molybdenum source, or titanium oxide, titania-silica composite A mixture of an oxide or a mixture thereof and a solution containing a vanadium source and a molybdenum source may be kneaded and molded.
[0009]
As a method for producing the catalyst of the present invention, a vanadium oxide or the like and a molybdenum oxide or the like are mixed and calcined at about 500 to 1000 ° C. to obtain a V-Mo composite oxide, which is then oxidized. A method of kneading titanium, titania-silica composite oxide or a mixture thereof is also conceivable, but in this method, a high V-Mo composite oxide is contained in titanium oxide, titania-silica composite oxide or a mixture thereof. Since it becomes difficult to disperse, the decomposition activity of the organic halogen compound is remarkably low as compared with the catalyst produced by the above-described production method, and the activity after exposure to the sulfur dioxide-containing gas is also low.
[0010]
In the production of the catalyst of the present invention, after adding the vanadium source and the molybdenum source, after drying for a sufficient time under a relatively mild condition so that a V-Mo composite oxide is finally formed, It is desirable to perform firing. Specifically, after drying at a humidity of 50% or more and a temperature of 60 ° C. or less, preferably 30 to 40 ° C. for 12 to 168 hours, preferably 48 to 168 hours, 350 to 750 ° C., preferably 400 to Baking is preferably performed at 550 ° C. When rapidly dried at a high temperature, V-Mo composite oxides are not easily formed, and single oxides of vanadium and molybdenum are easily formed.
[0011]
As the titanium oxide, in addition to titanium oxide powder, any inorganic and organic compounds can be used as long as they are baked to produce titanium oxide. For example, inorganic titanium compounds such as titanium tetrachloride and titanium sulfate, and organic titanium compounds such as titanium oxalate and tetraisopropyl titanate can be used.
As the titanium source used for the preparation of the titania-silica composite oxide, any of the above inorganic and organic compounds can be used. As the silica source, colloidal silica, water glass, fine particle silicon, tetrachloride are used. It can be appropriately selected from inorganic silicon compounds such as silicon and organic silicon compounds such as tetraethyl silicate.
[0012]
In order to mix titanium oxide and titania-silica composite oxide, conventional mixing methods may be used. For example, titanium oxide powder and titania-silica composite oxide powder are put into a mixer such as a kneader. And can be stirred and mixed.
As the vanadium source, vanadium oxides or salts are used. As the salts, hydroxides, ammonium salts, oxalates, halides, sulfates, and the like can be used.
As the molybdenum source, molybdenum oxides or salts are used, and hydroxides, ammonium salts, oxalates, halides, sulfates, and the like can be used.
[0013]
The composition of the catalyst of the present invention is 60 to 90% by weight of titanium oxide, 3 to 15% by weight of silicon oxide, and 3 to 20% by weight of vanadium oxide by weight ratio of each element. The molybdenum oxide is preferably 3 to 20% by weight.
The shape of the catalyst of the present invention is not particularly limited, and can be used after being formed into a desired shape such as a honeycomb shape, a plate shape, a corrugated plate shape, a net shape, a columnar shape, or a cylindrical shape. In addition, it is used by supporting it on a carrier having a desired shape such as honeycomb, plate, corrugated, net, columnar, cylindrical, etc. made of alumina, silica, cordierite, mullite, SiC, titania, stainless steel, etc. May be.
[0014]
The composition of the exhaust gas treated using the catalyst of the present invention is not particularly limited as long as it contains an organic halogen compound such as dioxins, PCB, chlorophenol, etc., but the catalyst of the present invention particularly contains dioxins and PCBs. Suitable for treatment of exhaust gas containing.
Space velocity relative to the catalyst of the present invention the exhaust gas to be processed is preferably 100~100000Hr -1, 200~50000Hr -1 are more preferred. The treatment temperature is preferably 130 to 350 ° C, more preferably 150 to 250 ° C.
[0015]
【Example】
The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.
[Example 1]
A chemical solution in which 2.0 kg of ammonium metavanadate, 1.4 kg of ammonium paramolybdate tetrahydrate, 2.4 kg of oxalic acid and 1.0 kg of monoethanolamine are dissolved in 12 liters of water is added to 20 kg of titanium oxide, and phenol is further added. After adding 1 kg of resin and starch as a molding aid, mixing and kneading with a kneader, the resultant was molded into a honeycomb shape having an outer diameter of 80 mm square, an opening of 4.0 mm, a thickness of 1.0 mm, and a length of 500 mm by an extruder. Next, after drying slowly over 100 hours at a humidity of 60 to 70% and a temperature of 50 ° C., it was calcined at 450 ° C. for 5 hours in an air atmosphere to obtain a catalyst (A). The composition of the catalyst (A) thus obtained was V 2 O 5 : MoO 3 : TiO 2 = 7: 5: 88 (weight ratio). FIG. 1 shows an X-ray diffraction profile of the catalyst (A). Diffraction peaks were observed at 2θ = 21.6 ° and 2θ = 24.9 °, confirming the formation of a composite oxide of vanadium and molybdenum.
[0016]
[Example 2]
First, a titania-silica composite oxide powder as a support was prepared by the method described below. 27.3 kg of SNOWTEX-20 (silica sol manufactured by Nissan Chemical Co., containing about 20% by weight of SiO 2 ) was added to 700 liters of 10% by weight aqueous ammonia, and after stirring and mixing, a sulfuric acid solution of titanyl sulfate (125 g as TiO 2 ) was added. / Liter, sulfuric acid concentration 500 g / liter) was gradually added dropwise with stirring. The obtained gel was allowed to stand for 3 hours, filtered, washed with water, and then dried at 150 ° C. for 10 hours. This was fired at 550 ° C. The composition of the obtained powder was TiO 2 : SiO 2 = 8.5: 1.5 (molar ratio).
[0017]
To a mixture of 10 kg of titanium oxide and 10 kg of the titania-silica composite oxide prepared above, ammonium metavanadate 2.0 kg, ammonium paramolybdate tetrahydrate 1.4 kg, oxalic acid 2.4 kg, monoethanolamine 1.0 kg After adding a chemical solution dissolved in 12 liters of water, adding 1 kg of phenol resin and starch as a molding aid, mixing and kneading with a kneader, the outer shape is 80 mm square, the opening is 4.0 mm, the wall thickness is It was formed into a honeycomb shape having a length of 1.0 mm and a length of 500 mm. Subsequently, after drying slowly over 100 hours at a humidity of 60 to 70% and a temperature of 50 ° C., it was calcined at 450 ° C. for 5 hours in an air atmosphere to obtain a catalyst (B). The composition of the catalyst (B) thus obtained was V 2 O 5 : MoO 3 : TiO 2 : SiO 2 = 7: 5: 81: 7 (weight ratio). In the X-ray diffraction profile of the catalyst (B), diffraction peaks were observed at 2θ = 21.6 ° and 2θ = 24.9 °, and it was confirmed that a composite oxide of vanadium and molybdenum was formed.
[0018]
[Example 3]
20 kg of the titania-silica composite oxide powder prepared in Example 2 was charged with 2.0 kg of ammonium metavanadate, 1.4 kg of ammonium paramolybdate tetrahydrate, 2.4 kg of oxalic acid, and 1.0 kg of monoethanolamine. A chemical solution dissolved in 12 liters was added, and 1 kg of phenol resin and starch as a molding aid were added and mixed. The mixture was kneaded with a kneader, and then the outer shape was 80 mm square, the aperture was 4.0 mm, and the wall thickness was 1. It was formed into a honeycomb shape having a length of 0 mm and a length of 500 mm. Subsequently, after drying slowly over 100 hours at a humidity of 60 to 70% and a temperature of 50 ° C., it was calcined at 450 ° C. for 5 hours in an air atmosphere to obtain a catalyst (C). The composition of the catalyst (C) thus obtained was V 2 O 5 : MoO 3 : TiO 2 : SiO 2 = 7: 5: 75: 13 (weight ratio). In the X-ray diffraction profile of the catalyst (C), diffraction peaks were observed at 2θ = 21.6 ° and 2θ = 24.9 °, and it was confirmed that a composite oxide of vanadium and molybdenum was formed.
[0019]
[Comparative Example 1]
A honeycomb formed body obtained by the same method as in Example 1 was rapidly dried at 200 ° C. and then fired at 450 ° C. for 5 hours in an air atmosphere to obtain a catalyst (D). The catalyst (D) thus obtained had V 2 O 5 : MoO 3 : TiO 2 = 7: 5: 88 (weight ratio). In the X-ray diffraction profile of the catalyst (D), no diffraction peaks were observed at 2θ = 21.6 ° and 2θ = 24.9 °.
[Comparative Example 2]
Add 20 kg of titanium oxide to 1.9 kg of ammonium metavanadate, 2.4 kg of oxalic acid, 0.5 kg of monoethanolamine dissolved in 12 liters of water, add 1 kg of phenolic resin and starch as a molding aid, and mix. After kneading with a kneader, it was formed into a honeycomb shape having an external shape of 80 mm square, an opening of 4.0 mm, a wall thickness of 1.0 mm, and a length of 500 mm with an extruder. Subsequently, after drying slowly at 50 degreeC, it baked in the air atmosphere at 450 degreeC for 5 hours, and obtained the catalyst (E). The catalyst (E) thus obtained had V 2 O 5 : TiO 2 = 7: 93 (weight ratio).
[0020]
[Examples 4-6, Comparative Examples 3-4]
The catalyst (A) prepared in Example 1, the catalyst (B) prepared in Example 2, the catalyst (C) prepared in Example 3, the catalyst (D) prepared in Comparative Example 1, and the catalyst prepared in Comparative Example 2 were prepared. Using each catalyst of the catalyst (E), an organic chlorine compound decomposition test was conducted. Chlorotoluene (hereinafter abbreviated as CT) was used as the organic chlorine compound to be treated, and the reaction was performed under the following test conditions to obtain the CT decomposition rate (initial decomposition rate). The results are shown in Table 1.
(Test conditions)
Process gas composition CT: 30 ppm, O 2 : 10%, H 2 O: 15%, N 2 : balance gas temperature: 175 ° C
Space velocity (SV): 4000 Hr −1
The CT decomposition rate, that is, the CT removal rate was obtained by the following formula.
[0021]
(CT decomposition rate)
CT decomposition rate (%) = [(reactor inlet CT concentration) − (reactor outlet CT concentration)] / (reactor inlet CT concentration) × 100
[Examples 7 to 9, Comparative Examples 5 to 6]
The catalyst (A) prepared in Example 1, the catalyst (B) prepared in Example 2, the catalyst (C) prepared in Example 3, the catalyst (D) prepared in Comparative Example 1, and the catalyst prepared in Comparative Example 2 were prepared. After each catalyst of catalyst (E) was exposed to sulfur dioxide-containing gas for 2000 hours under the following conditions, the same organic chlorine compound decomposition test as in Example 4 was conducted, and the CT decomposition rate (decomposition rate after SO 2 exposure) Asked. The results are shown in Table 1.
[0022]
(Sulfur dioxide-containing gas exposure conditions)
Gas composition SO 2 : 100 ppm, O 2 : 10%, H 2 O: 15%, N 2 : Balance gas temperature: 175 ° C
Space velocity (SV): 4000 Hr −1
[0023]
[Table 1]
As shown in Table 1, the catalysts of Examples 1 and 2 showed high CT decomposition rates both in the initial stage and after exposure to the sulfur dioxide-containing gas, hardly deteriorated by exposure to the sulfur dioxide-containing gas, and were durable. Is high. On the other hand, the catalysts of Comparative Examples 1 and 2 show a high CT decomposition rate in the initial stage, but the CT decomposition rate is remarkably lowered after exposure to the sulfur dioxide-containing gas, indicating that the durability is low.
[Example 10]
In 30 g of titanium oxide (DT-51 manufactured by Millennium), 1.5 g of ammonium metavanadate, 2.6 g of ammonium paramolybdate tetrahydrate, 3.0 g of oxalic acid, and 1.7 g of monoethanolamine were dissolved in 60 ml of water. After adding a sufficient amount of the chemical solution, it was sufficiently dried and then slowly dried at a humidity of 60 to 70% and a temperature of 60 ° C. or less for 20 hours, and tableted. The obtained molded product was calcined at 450 ° C. to obtain a catalyst (F).
[0025]
[Example 11]
A mixture slurry of 4 g of V 2 O 5 powder and 7 g of MoO 3 powder was sufficiently collected and fired at 700 ° C. in a nitrogen atmosphere to obtain a V-Mo composite oxide. The composite oxide 3.3 g was mixed with 100 g of a metatitanic acid slurry (containing 30 wt% as TiO 2 ), sufficiently dried, dried at 150 ° C., and then subjected to tableting. The obtained molded product was calcined at 450 ° C. to obtain a catalyst (G).
[Examples 12 to 13]
In the same manner as in Example 4, using each catalyst (tablet molded product) of the catalyst (F) prepared in Example 10 and the catalyst (G) prepared in Example 11 to 10 to 20 mesh, respectively. The CT decomposition rate (initial decomposition rate) was obtained. The results are shown in Table 2.
[0026]
[Examples 14 to 15]
In the same manner as in Example 7, using the catalyst (F) prepared in Example 10 and the catalyst (tablet molded product) of the catalyst (G) prepared in Example 11 were crushed into 10 to 20 meshes. The CT decomposition rate (decomposition rate after SO 2 exposure) was determined. The results are shown in Table 2.
[0027]
[Table 2]
As shown in Table 2, the catalyst of Example 10 exhibits a high CT decomposition rate both in the initial stage and after exposure to the sulfur dioxide-containing gas, shows almost no deterioration due to exposure to the sulfur dioxide-containing gas, and has high durability. I understand that. On the other hand, in the catalyst of Example 11, the CT decomposition rate is low both in the initial stage and after exposure to the sulfur dioxide-containing gas. This is because the catalyst of Example 10 was manufactured by a manufacturing method including a step of adding a solution containing vanadium salts and molybdenum salts to titanium oxide, so that the V-Mo composite oxide was high in titanium oxide. Although it was dispersed, the catalyst of Example 11 was produced by a different production method, and therefore it is presumed that the V-Mo composite oxide was not highly dispersed in titanium oxide.
[0029]
【The invention's effect】
The catalyst of the present invention can efficiently remove organic halogen compounds such as dioxins in exhaust gas, and is excellent in durability against a gas containing sulfur dioxide.
[Brief description of the drawings]
1 is an X-ray diffraction profile of an organic halogen compound removal catalyst obtained in Example 1. FIG.
Claims (3)
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