JP3893014B2 - Exhaust gas treatment catalyst, its production method and exhaust gas treatment method - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、排ガス処理用触媒、その製造方法および排ガス処理方法に関する。特に、排ガス中のダイオキシン類などの毒性有機ハロゲン化合物を除去する有機ハロゲン化合物除去用触媒、排ガス中の窒素酸化物（ＮＯｘ）を除去するための脱硝触媒として優れた排ガス処理用触媒、その製造方法および排ガス処理方法に関する。
【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おり、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。一般に有機ハロゲン化合物は化学的にきわめて安定であり、特にダイオキシン類においては自然界では半永久的に残存するといわれているほど分解しにくい物質であるのに加え、排ガス中でのその含有量が非常に低いため、これを効率よく除去することは困難である。現在、バナジウム酸化物やタングステン酸化物をチタン酸化物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が得られず、更なる性能の向上が望まれている。
【０００３】
また、現在実用化されている排ガス中の窒素酸化物除去方法としては、アンモニアまたは尿素などの固体還元剤を用いて排ガス中の窒素酸化物を脱硝触媒上で接触還元し、無害な窒素と水とに分解する選択的触媒還元（ＳＣＲ）法が一般的である。これに用いられる脱硝触媒としては、例えば特開平１０−２３５２０６号公報に記載のチタン−バナジウム系触媒などが知られているが、排ガス条件によっては充分な性能とはいえず、さらなる触媒性能の向上が望まれている。
【０００４】
【発明が解決しようとする課題】
本発明の課題は、ダイオキシン類などの有機ハロゲン化合物の除去性能および脱硝性能に優れた排ガス処理用触媒、その製造方法、およびこの触媒を用いた排ガス処理方法を提供することである。
【０００５】
【課題を解決するための手段】
本発明者らは、触媒の化学的組成のみならず、物理特性の改良を行うことによって上記目的を達成できることを見出し、この知見に基づいて本発明を完成するに到った。
具体的には、担体上に担持された微粒子酸化チタンを含有する排ガス処理用触媒であり、前記担体としてＴｉ−Ｓｉ複合酸化物粉体を選び、当該担体上で酸化チタンを微粒子化、高比表面積化、すなわち高分散化することによって、排ガスの触媒に対する接触効率を良くし、排ガス中に含まれる極微量有害物質の分解反応を促進するよう触媒設計したものである。
【０００６】
すなわち、本発明は、Ｔｉ−Ｓｉ複合酸化物粉体を担体として、（１）担体の存在下に、可溶性チタン化合物の中和あるいは熱加水分解、またはチタンアルコキシドの加水分解を行うことにより、チタン水酸化物を担体上に担持させて得られた、担体上に担持された微粒子酸化チタンと、酸化物換算で５重量％以上のバナジウムとを含有する、排ガス処理用触媒；（２）担体上に可溶性チタン化合物またはチタンアルコキシドを担持させたのち、熱分解して得られた、担体上に担持された微粒子酸化チタンと、酸化物換算で５重量％以上のバナジウムとを含有する、排ガス処理用触媒；（３）前記（１）の排ガス処理用触媒を製造する方法であって、担体の存在下に、可溶性チタン化合物の中和あるいは熱加水分解、またはチタンアルコキシドの加水分解を行うことにより、チタン水酸化物を担体上に担持させて、担体上に担持された微粒子酸化チタンを得る工程と、担体上に担持された微粒子酸化チタンにバナジウムを添加する工程とを含む、排ガス処理用触媒の製造方法；（４）前記（２）の排ガス処理用触媒を製造する方法であって、担体上に可溶性チタン化合物またはチタンアルコキシドを担持させたのち、熱分解して、担体上に担持された微粒子酸化チタンを得る工程と、担体上に担持された微粒子酸化チタンにバナジウムを添加する工程とを含む、排ガス処理用触媒の製造方法；（５）排ガスを（１）または（２）に述べた触媒と接触させることを特徴とする排ガス処理方法である。
【０００７】
【発明の実施の形態】
以下、本発明を詳細に説明する。
本発明の触媒は、その構成成分として担体上に担持された微粒子酸化チタンを含有するとともに酸化物換算で５重量％以上のバナジウムを含有することを特徴としたものであるが、これを調製する際に使用する担体としてＴｉ−Ｓｉ複合酸化物を用いることを特徴としている。
【０００８】
また、前記微粒子酸化チタンのチタン源の種類については、酸化チタンの他、焼成してチタン酸化物を生成するものであれば特に制限はなく、四塩化チタン、硫酸チタンなどの無機チタン化合物、及びシュウ酸チタン、テトライソプロピルチタネート等の有機チタン化合物を用いることができる。
本発明の触媒は、バナジウム、モリブデン、タングステン、マンガン、コバルト、ニッケル、亜鉛、ジルコニウム、ニオブ、スズ、タンタル、ランタン、セリウムから選ばれる少なくとも１種類の元素を活性成分として含むことができ、特にバナジウムが好ましく、バナジウムの担持量は酸化物換算で５重量％以上が好ましい。
【０００９】
これらの各元素の出発原料について特に制限はなく、酸化物の他、焼成後にその酸化物を生じる水酸化物、アンモニウム塩、シュウ酸塩、ハロゲン化物、硫酸塩、硝酸塩などのいずれでもよい。ケイ素源につい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、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使用することができる。
本発明の触媒に含まれる、担体上に担持された微粒子酸化チタン（以下、担持微粒子酸化チタンという）は、例えば以下の手順によって調製される。
（１）担体またはその前駆体の存在下に、可溶性チタン化合物の中和あるいは熱加水分解、またはチタンアルコキシドの加水分解を行うことにより、チタン水酸化物を担体上に担持する工程を含む、触媒の製造方法。
（２）担体またはその前駆体上に可溶性チタン化合物またはチタンアルコキシドを担持したのち、熱分解する工程を含む、触媒の製造方法。
【００１０】
（１）の方法として具体的には、次の（Ａ）、（Ｂ）、（Ｃ）が挙げられる。（Ａ）担体またはその前駆体となる粉末をアンモニア水溶液中に分散させ、攪拌しながらこれに可溶性チタン化合物、例えば四塩化チタンを少しずつ滴下する。最終ｐＨが５以上８未満となるように可溶性チタン化合物とアンモニア水の量を設定しておく。本発明における「最終ｐＨ」とは、沈殿操作を終了した時点における沈殿物スラリーもしくはゲルのｐＨを意味する。これにより、チタンの水酸化物ゲルが担体上に高分散に沈着する。上記操作により得られた沈殿物は、スラリーから分離し、よく洗浄し、乾燥した後、焼成することにより担持微粒子酸化チタンを得る。
（Ｂ）担体またはその前駆体となる粉末にテトライソプロピルチタネート等のチタンアルコキシドのアルコール溶液を混練りまたは含浸し、これに少しずつ水を加えることによって加水分解をおこない、担持チタン水酸化物ゲルを得る。これを乾燥した後、焼成することによって担持微粒子酸化チタンを得る。
（Ｃ）担体またはその前駆体となる粉末を可溶性チタン化合物、例えば硫酸チタン水溶液に分散させ、１００〜１２０℃に加熱し、５〜１０時間熱加水分解を行う。得られた沈澱物をスラリーから分離し、よく洗浄し、乾燥した後、焼成することによって担持微粒子酸化チタンを得る。
【００１１】
（２）の方法として具体的には、次の（Ｄ）、（Ｅ）が挙げられる。
（Ｄ）担体またはその前駆体となる粉末に塩化チタン（ＴｉＯＣｌ3）等の可溶性チタン化合物の蒸気を流通して蒸着（担持）し、これを焼成（熱分解）することによって担持微粒子酸化チタンを得る。
（Ｅ）担体またはその前駆体となる粉末にチタンアルコキシド溶液を含浸し、これを熱分解し、焼成することによって担持微粒子酸化チタンを得る。
本発明における担持微粒子酸化チタンとは、担体上に担持され、ＢＥＴ一点法で測定される比表面積が好ましくは２０ｍ2／ｇ以上、より好ましくは１００ｍ2／ｇ〜３００ｍ2／ｇの酸化チタンである。
【００１２】
本発明の触媒が、担持微粒子酸化チタン（以下、「Ａ成分」という）に加えて、バナジウム、モリブデン、タングステン、マンガン、コバルト、ニッケル、亜鉛、ジルコニウム、ニオブ、スズ、タンタル、ランタン、セリウムから選ばれる少なくとも１種類の元素（以下、「Ｂ成分」という）を活性成分として含む場合、その調製方法としては、特に限定されるものではないが、まず担体上に担持された微粒子酸化チタン（Ａ成分）を調製し、その後Ｂ成分を添加することが好ましい。具体的には、例えばＡ成分の粉体又はスラリーとＢ成分の塩類もしくはその溶液の混練りによって担持してもよいし、また、Ａ成分の成型体にＢ成分の塩類の溶液を含浸担持してもよい。すなわち本発明の排ガス処理用触媒の成型体は、上記Ａ成分とＢ成分又はその塩類よりなる粉体やスラリーなどから成型して用いてもよく、また上記Ａ成分よりなる成型体にＢ成分を担持して用いることもできる。
【００１３】
本発明の触媒は、各種排ガスの処理に用いられる。排ガスの組成については特に制限はないが、本発明の触媒は、有機ハロゲン化合物除去用触媒および脱硝触媒として非常に有用である。
本発明の触媒を有機ハロゲン化合物除去用触媒として用いる場合、処理する排ガスの組成については、有機ハロゲン化合物を含むものであれば特に制限はないが、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好適である。本発明の触媒を用いて有機ハロゲン化合物を除去するには、排ガスを１３０〜３５０℃の温度、好ましくは１５０〜２５０℃の温度で、本発明の触媒と接触させることが望ましい。
【００１４】
本発明の触媒を脱硝触媒として用いる場合、本発明の触媒をアンモニアや尿素などの還元剤の存在下、排ガスと接触させ、排ガス中の窒素酸化物を還元除去する。この際の条件については、特に制限がなく、この種の反応に一般的に用いられている条件で実施することができる。具体的には、排ガスの種類、性状、要求される窒素酸化物の分解率などを考慮して適宜決定すればよいが、温度は、１３０〜６５０℃であることが好ましい。排ガス温度が１３０℃より低いと脱硝効率が低下し、６５０℃を超えると活性成分のシンタリングなどの問題が起こる。
処理対象ガスの本発明の触媒に対する空間速度は、１００〜１０００００Ｈｒ-1、好ましくは２００〜５００００Ｈｒ-1の範囲にあるのがよい。１００Ｈｒ-1未満である場合は、処理装置が大きくなりすぎ非効率であり、１０００００Ｈｒ-1を超える場合は、高すぎると分解効率が低下する。
【００１５】
【実施例】
以下に実施例を用いて本発明をさらに詳細に説明するが、本発明はこれら実施例のみに限定されるものではない。
［実施例１］
まず、担体となるＴｉ−Ｓｉ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（日産化学製シリカゾル、約２０重量%−ＳｉＯ2含有）２１．３ｋｇ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５５０ｇ／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。次いで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ＢＥＴ表面積は１９６ｍ2／ｇであった。
【００１６】
次に、担持微粒子酸化チタンを以下に述べる方法で調製した。上記に述べた方法で調製されたＴｉ−Ｓｉ複合酸化物粉体８ｋｇを０．５ｍｏｌ／リットルのアンモニア水溶液１３０リットルに懸濁させ攪拌しながら、これに塩化チタン水溶液（ＴｉＯ2として２００ｇ／リットル）１０リットルを少しずつ滴下した。最終ｐＨは５〜９となった。得られた沈殿物を洗浄し１００℃で１２時間乾燥し、さらに４５０℃で３時間焼成し、Ｔｉ−Ｓｉ複合酸化物担持微粒子酸化チタンを得た。
次に、上記Ｔｉ−Ｓｉ複合酸化物担持微粒子酸化チタン２０ｋｇにメタバナジン酸アンモニウム１．４ｋｇ、シュウ酸１．７ｋｇ、モノエタノールアミン０．４ｋｇを水５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、押し出し成型機で外形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８０℃で乾燥後、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：ＴｉＯ2：Ｔｉ−Ｓｉ複合酸化物＝５：１９：７６（重量比）であった。ＢＥＴ表面積は１０５ｍ2／ｇであった。
【００１７】
［参考例］
ゼオライトＨ−ＺＳＭ−５（Ｓｉ／Ａｌ＝４０、ＺＥＯＬＩＳＴ社製）８ｋｇを０．５ｍｏｌ／リットルのアンモニア水溶液１３０リットルに懸濁させ攪拌しながら、これに塩化チタン水溶液（ＴｉＯ２として２００ｇ／リットル）１０リットルを少しずつ滴下した。最終ｐＨは５〜９となった。得られた沈殿物を洗浄し１００℃で１２時間乾燥し、さらに４５０℃で３時間焼成し、ゼオライト担持微粒子酸化チタンを得た。
次に、上記ゼオライト担持微粒子酸化チタン２０ｋｇにメタバナジン酸アンモニウム１．４ｋｇ、シュウ酸１．７ｋｇ、モノエタノールアミン０．４ｋｇを水５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、押し出し成型機で外形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８０℃で乾燥後、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）の組成は、Ｖ２Ｏ５：ＴｉＯ２：ゼオライト＝５：１９：７６（重量比）であった。ＢＥＴ表面積は２５０ｍ２／ｇであった。
【００１８】
［実施例２］
実施例１で用いたＴｉ−Ｓｉ複合酸化物粉体８ｋｇにテトライソプロピルチタネート７．１ｋｇを含むアルコール溶液を含浸し、混合しながら水を少しずつ滴下した。得られたスラリーを１００℃で１２時間乾燥し、さらに４５０℃で３時間焼成し、Ｔｉ−Ｓｉ複合酸化物担持微粒子酸化チタンを得た。
次に、上記Ｔｉ−Ｓｉ複合酸化物担持微粒子酸化チタン２０ｋｇにメタバナジン酸アンモニウム１．４ｋｇ、シュウ酸１．７ｋｇ、モノエタノールアミン０．４ｋｇを水５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、押し出し成型機で外形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８０℃で乾燥後、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：ＴｉＯ２：Ｔｉ−Ｓｉ複合酸化物＝５：１９：７６（重量比）であった。ＢＥＴ表面積は１２０ｍ２／ｇであった。
【００１９】
［実施例３］
実施例１で用いたＴｉ−Ｓｉ複合酸化物粉体８ｋｇにテトライソプロピルチタネート７．１ｋｇを含むアルコール溶液を含浸し、均一に混合した。１００℃で１２時間乾燥し、さらに４５０℃で３時間焼成し、Ｔｉ−Ｓｉ複合酸化物担持微粒子酸化チタンを得た。
次に、上記Ｔｉ−Ｓｉ複合酸化物担持微粒子酸化チタン２０ｋｇにメタバナジン酸アンモニウム１．４ｋｇ、シュウ酸１．７ｋｇ、モノエタノールアミン０．４ｋｇを水５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、押し出し成型機で外形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８０℃で乾燥後、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）の組成は、Ｖ２Ｏ５：ＴｉＯ２：Ｔｉ−Ｓｉ複合酸化物＝５：１９：７６（重量比）であった。ＢＥＴ表面積は１３３ｍ２／ｇであった。
【００２０】
［比較例１］
０．５ｍｏｌ／リットルのアンモニア水溶液６００リットルを攪拌しながら、これに塩化チタン水溶液（ＴｉＯ2として２００ｇ／リットル）４８リットルを少しずつ滴下した。最終ｐＨは５〜９となった。得られた沈殿物を洗浄し１００℃で１２時間乾燥し、さらに４５０℃で３時間焼成し、酸化チタンを得た。次に、上記酸化チタン２０ｋｇにメタバナジン酸アンモニウム１．４ｋｇ、シュウ酸１．７ｋｇ、モノエタノールアミン０．４ｋｇを水５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、押し出し成型機で外形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８０℃で乾燥後、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）の組成は、Ｖ2Ｏ5：ＴｉＯ2＝５：９５（重量比）であった。ＢＥＴ表面積は６８ｍ2／ｇであった。
【００２１】
［比較例２］
実施例１で用いたＴｉ−Ｓｉ複合酸化物粉体２０ｋｇにメタバナジン酸アンモニウム１．４ｋｇ、シュウ酸１．７ｋｇ、モノエタノールアミン０．４ｋｇを水５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、押し出し成型機で外形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８０℃で乾燥後、４５０℃で５時間空気雰囲気下で焼成し、触媒（Ｆ）を得た。こうして得られた触媒（Ｆ）の組成は、Ｖ2Ｏ5： Ｔｉ−Ｓｉ複合酸化物＝５：９５（重量比）であった。ＢＥＴ表面積は１３０ｍ2／ｇであった。
【００２２】
［比較例３］
実施例１で用いたＴｉ−Ｓｉ複合酸化物粉体１０ｋｇと比較例１で用いた酸化チタン１０ｋｇの混合物にメタバナジン酸アンモニウム１．４ｋｇ、シュウ酸１．７ｋｇ、モノエタノールアミン０．４ｋｇを水５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、押し出し成型機で外形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８０℃で乾燥後、４５０℃で５時間空気雰囲気下で焼成し、触媒（Ｇ）を得た。こうして得られた触媒（Ｇ）の組成は、Ｖ2Ｏ5：ＴｉＯ2：Ｔｉ−Ｓｉ複合酸化物＝５：４７．５：４７．５（重量比）であった。ＢＥＴ表面積は９０ｍ2／ｇであった。
【００２３】
［実施例４］
実施例１で調製した触媒（Ａ）、参考例で調製した触媒（Ｂ）、実施例２で調製した触媒（Ｃ）、実施例３で調製した触媒（Ｄ）、比較例１で調製した触媒（Ｅ）、比較例２で調製した触媒（Ｆ）および比較例３で調製した触媒（Ｇ）を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、以下の条件で反応を行った。結果を表１に示す。ＣＴ分解率すなわちＣＴ除去率は下記式により求めた。
（試験条件）
処理ガス組成 ＣＴ：３０ｐｐｍ，Ｏ２：１０％，Ｈ２Ｏ：１５％，Ｎ２：Balance
ガス温度：１５０〜２００℃
空間速度（ＳＶ）：２０００Ｈｒ−１，４０００Ｈｒ−１
（式）
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
【００２４】
【表１】
［実施例５］
実施例１で調製した触媒（Ａ）および比較例３で調製した触媒（Ｇ）を用いて以下の条件で脱硝反応を行った。脱硝率を下記式により求めたところ、触媒（Ａ）については９５％であり、触媒（Ｇ）については８８％であった。
（試験条件）
処理ガス組成 ＮＯ：１００ｐｐｍ，ＮＨ３：１００ｐｐｍ，Ｏ２：１０％，
Ｈ２Ｏ：１５％，Ｎ２：Balance
ガス温度：２３０℃
空間速度（ＳＶ）：５０００Ｈｒ−１
（式）
脱硝率（％）＝［（反応器入口ＮＯｘ濃度）−（反応器出口ＮＯｘ濃度）］ ／（反応器入口ＮＯｘ濃度）×１００
【００２６】
【発明の効果】
本発明の触媒は、ダイオキシン類などの毒性有機ハロゲン化合物の分解活性やアンモニア分解活性に優れる。また、脱硝性能にも優れ、窒素酸化物とダイオキシン類などの毒性有機ハロゲン化合物の同時除去触媒として有用である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas treatment catalyst, a production method thereof, and an exhaust gas treatment method. In particular, an organic halogen compound removing catalyst for removing toxic organic halogen compounds such as dioxins in exhaust gas, an exhaust gas treating catalyst excellent as a denitration catalyst for removing nitrogen oxide (NOx) in exhaust gas, and a method for producing the same And an exhaust gas treatment method.
[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 chlorophenols. Because it is extremely toxic and has a serious effect on the human body, its removal technology is urgently required. In general, organohalogen compounds are chemically very stable. In particular, dioxins are substances that are said to remain semipermanent in nature and are not easily decomposed, and their content in exhaust gas is very low. Therefore, it is difficult to remove this efficiently. Currently, catalysts with vanadium oxide or tungsten oxide supported on titanium oxide and noble metal catalysts such as platinum are used, but sufficient performance cannot be obtained depending on exhaust gas conditions, and further performance improvement can be achieved. It is desired.
[0003]
In addition, as a method for removing nitrogen oxides in exhaust gas currently in practical use, nitrogen oxides in exhaust gas are contact-reduced on a denitration catalyst using a solid reducing agent such as ammonia or urea, and harmless nitrogen and water are removed. A selective catalytic reduction (SCR) method is generally used which decomposes into As a denitration catalyst used for this, for example, a titanium-vanadium catalyst described in JP-A-10-235206 is known, but depending on the exhaust gas conditions, it cannot be said that the performance is sufficient, and further improvement of the catalyst performance. Is desired.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide an exhaust gas treatment catalyst excellent in removal performance and denitration performance of organic halogen compounds such as dioxins, a production method thereof, and an exhaust gas treatment method using the catalyst.
[0005]
[Means for Solving the Problems]
The present inventors have found that the above object can be achieved by improving not only the chemical composition of the catalyst but also the physical characteristics, and have completed the present invention based on this finding.
Specifically, a exhaust gas treatment catalyst containing fine particles of titanium oxide supported on a carrier, select Ti-Si composite oxide powder as the carrier, the micronized titanium oxide on the carrier, high ratio The catalyst is designed to improve the contact efficiency of the exhaust gas with the catalyst by increasing the surface area, that is, to increase the dispersion, and to promote the decomposition reaction of the trace amount of harmful substances contained in the exhaust gas.
[0006]
That is, the present invention provides a Ti-Si composite oxide powder as a carrier, (1) in the presence of a responsible body, neutralization or thermal hydrolysis of soluble titanium compounds, or by hydrolysis of titanium alkoxide, titanium hydroxide obtained by supporting on the carrier, and the fine particles of titanium oxide supported on a carrier, containing a 5 wt% or more of vanadium in terms of oxide, the catalyst for exhaust gas treatment; (2) responsible After having supported thereon a soluble titanium compound or a titanium alkoxide on the body, obtained by thermal decomposition, and the fine particles of titanium oxide supported on a carrier, containing a 5 wt% or more of vanadium in terms of oxide, the exhaust gas processing catalyst; a method of manufacturing the exhaust gas processing catalyst for (3) above (1), in the presence of a responsible body, neutralization or thermal hydrolysis of soluble titanium compounds or Chitan'arukoki, By performing de hydrolysis, adding a titanium hydroxide be supported on the carrier, a step of obtaining the fine particles of titanium dioxide which is deposited on a support, the vanadium oxide fine particles of titanium supported on a carrier including bets, process for preparing a catalyst for exhaust gas treatment, a method of manufacturing the exhaust gas catalyst for treating (4) the (2), after the soluble titanium compound or a titanium alkoxide was loaded onto responsible body, pyrolysis And a method for producing an exhaust gas treatment catalyst, comprising : a step of obtaining fine particle titanium oxide supported on a carrier; and a step of adding vanadium to the fine particle titanium oxide supported on the carrier; An exhaust gas treatment method comprising contacting with the catalyst described in 1) or (2).
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The catalyst of the present invention is characterized by containing fine titanium oxide supported on a carrier as a constituent and containing 5% by weight or more of vanadium in terms of oxide. In this case, a Ti—Si composite oxide is used as a carrier to be used .
[0008]
In addition to the titanium oxide, the kind of the titanium source of the fine particle titanium oxide is not particularly limited as long as it can be baked to produce a titanium oxide, and an inorganic titanium compound such as titanium tetrachloride and titanium sulfate, and Organic titanium compounds such as titanium oxalate and tetraisopropyl titanate can be used.
The catalyst of the present invention can vanadium, molybdenum, tungsten, manganese, cobalt, nickel, zinc, zirconium, niobium, tin, tantalum, lanthanum, to contain at least one element selected from cerium as an active ingredient, in particular Vanadium is preferred, and the supported amount of vanadium is preferably 5% by weight or more in terms of oxide.
[0009]
There are no particular restrictions on the starting materials for each of these elements, and any of oxides, hydroxides that generate the oxides after firing, ammonium salts, oxalates, halides, sulfates, nitrates, and the like may be used. The silicon source can be appropriately selected from inorganic silicon compounds such as colloidal silica, water glass, fine particle silicon and silicon tetrachloride, and organic silicon compounds such as tetraethyl silicate.
The fine particle titanium oxide supported on the carrier (hereinafter referred to as supported fine particle titanium oxide) contained in the catalyst of the present invention is prepared, for example, by the following procedure.
(1) A catalyst comprising a step of supporting titanium hydroxide on a support by neutralizing or thermally hydrolyzing a soluble titanium compound or hydrolyzing a titanium alkoxide in the presence of the support or a precursor thereof. Manufacturing method.
(2) A method for producing a catalyst, comprising a step of thermally decomposing after supporting a soluble titanium compound or titanium alkoxide on a support or a precursor thereof.
[0010]
Specific examples of the method (1) include the following (A), (B), and (C). (A) A carrier or a precursor powder thereof is dispersed in an aqueous ammonia solution, and a soluble titanium compound, for example, titanium tetrachloride is dropped little by little while stirring. The amounts of soluble titanium compound and aqueous ammonia are set so that the final pH is 5 or more and less than 8. The “final pH” in the present invention means the pH of the precipitate slurry or gel when the precipitation operation is completed. This deposits titanium hydroxide gel on the support in a highly dispersed manner. The precipitate obtained by the above operation is separated from the slurry, washed well, dried, and then fired to obtain the supported fine particle titanium oxide.
(B) The carrier or its precursor powder is kneaded or impregnated with an alcohol solution of titanium alkoxide such as tetraisopropyl titanate, and water is added little by little to hydrolyze to form a supported titanium hydroxide gel. obtain. This is dried and then fired to obtain supported fine particle titanium oxide.
(C) The carrier or its precursor powder is dispersed in a soluble titanium compound, for example, a titanium sulfate aqueous solution, heated to 100 to 120 ° C., and subjected to thermal hydrolysis for 5 to 10 hours. The obtained precipitate is separated from the slurry, washed thoroughly, dried, and fired to obtain supported fine particle titanium oxide.
[0011]
Specific examples of the method (2) include the following (D) and (E).
(D) A vapor of a soluble titanium compound such as titanium chloride (TiOCl 3 ) is circulated and deposited (supported) on a powder serving as a carrier or a precursor thereof, and this is fired (thermally decomposed) to form a supported fine particle titanium oxide. obtain.
(E) A powder serving as a carrier or a precursor thereof is impregnated with a titanium alkoxide solution, thermally decomposed, and fired to obtain supported fine particle titanium oxide.
The carried fine particles of titanium oxide in the present invention, is supported on a support, the specific surface area measured by the BET single point method is preferably 20 m 2 / g or more, more preferably titanium oxide of 100m 2 / g~300m 2 / g is there.
[0012]
The catalyst of the present invention is selected from vanadium, molybdenum, tungsten, manganese, cobalt, nickel, zinc, zirconium, niobium, tin, tantalum, lanthanum, and cerium in addition to supported fine particle titanium oxide (hereinafter referred to as “component A”) In the case of containing at least one kind of element (hereinafter referred to as “component B”) as an active ingredient, the preparation method is not particularly limited, but first, fine particle titanium oxide (A component) supported on a carrier ) Is preferably prepared, and then component B is added. Specifically, it may be supported by, for example, kneading the powder or slurry of component A and the salt of component B or a solution thereof, or impregnating and supporting a solution of salt of component B on the molded component of component A. May be. That is, the molded product of the exhaust gas treatment catalyst of the present invention may be used by molding from the above-mentioned A component and B component or a salt or powder thereof, and the B component may be added to the molded product of the A component. It can also be supported and used.
[0013]
The catalyst of the present invention is used for treating various exhaust gases. The composition of the exhaust gas is not particularly limited, but the catalyst of the present invention is very useful as a catalyst for removing organic halogen compounds and a denitration catalyst.
When the catalyst of the present invention is used as an organic halogen compound removal catalyst, the composition of the exhaust gas to be treated is not particularly limited as long as it contains an organic halogen compound, but the catalyst of the present invention particularly includes dioxins and PCBs. Suitable for exhaust gas treatment. In order to remove the organic halogen compound using the catalyst of the present invention, it is desirable to contact the exhaust gas with the catalyst of the present invention at a temperature of 130 to 350 ° C, preferably 150 to 250 ° C.
[0014]
When the catalyst of the present invention is used as a denitration catalyst, the catalyst of the present invention is brought into contact with exhaust gas in the presence of a reducing agent such as ammonia or urea to reduce and remove nitrogen oxides in the exhaust gas. The conditions at this time are not particularly limited, and can be carried out under conditions generally used for this type of reaction. Specifically, the temperature is preferably 130 to 650 ° C., although it may be determined as appropriate in consideration of the type and properties of exhaust gas, the required decomposition rate of nitrogen oxides, and the like. When the exhaust gas temperature is lower than 130 ° C., the denitration efficiency is lowered, and when it exceeds 650 ° C., problems such as sintering of the active ingredient occur.
Space velocity relative to the catalyst of the present invention to be processed gas, 100~100000Hr -1, preferably, from the 200~50000Hr -1. When it is less than 100 Hr −1 , the processing apparatus becomes too large and inefficient, and when it exceeds 100000 Hr −1 , the decomposition efficiency is lowered when it is too high.
[0015]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.
[Example 1]
First, a Ti—Si composite oxide powder as a support was prepared by the method described below. After adding 21.3 kg of Snowtex-20 (Nissan Chemical silica sol, containing about 20% by weight of SiO 2 ) to 700 liters of 10% by weight aqueous ammonia, stirring and mixing, a sulfuric acid solution of titanyl sulfate (125 g / liter as TiO 2) , 340 liters of sulfuric acid concentration 550 g / liter) was gradually added dropwise with stirring. The obtained gel was allowed to stand for 3 hours, washed with filtered water, and then dried at 150 ° C. for 10 hours. Subsequently, it baked at 550 degreeC. The composition of the obtained powder was TiO 2 : SiO 2 = 8.5: 1.5 (molar ratio), and the BET surface area was 196 m 2 / g.
[0016]
Next, a supported fine particle titanium oxide was prepared by the method described below. 8 kg of the Ti—Si composite oxide powder prepared by the above-described method was suspended in 130 liters of 0.5 mol / liter ammonia aqueous solution and stirred, and this was added with titanium chloride aqueous solution (200 g / liter as TiO 2 ). 10 liters was added dropwise little by little. The final pH was 5-9. The obtained precipitate was washed, dried at 100 ° C. for 12 hours, and further fired at 450 ° C. for 3 hours to obtain Ti—Si composite oxide-supported fine particle titanium oxide.
Next, a chemical solution in which 1.4 kg of ammonium metavanadate, 1.7 kg of oxalic acid, and 0.4 kg of monoethanolamine are dissolved in 5 liters of water is added to 20 kg of the above-mentioned Ti-Si composite oxide-supported fine particle titanium oxide, and further phenol resin 1 kg starch was added as a forming aid, mixed and kneaded with a kneader, and then formed into a honeycomb shape having an outer shape of 80 mm square, an opening of 4.0 mm, a thickness of 1.0 mm, and a length of 500 mm by an extrusion molding machine. Subsequently, after drying at 80 degreeC, it baked in the air atmosphere at 450 degreeC for 5 hours, and obtained the catalyst (A). The composition of the catalyst (A) thus obtained was V 2 O 5 : TiO 2 : Ti—Si composite oxide = 5: 19: 76 (weight ratio). The BET surface area was 105 m 2 / g.
[0017]
[ Reference example ]
While suspending and stirring 8 kg of zeolite H-ZSM-5 (Si / Al = 40, manufactured by ZEOLIST) in 130 liter of 0.5 mol / liter aqueous ammonia solution, titanium chloride aqueous solution (200 g / liter as TiO 2 ) was added thereto. 10 liters was added dropwise little by little. The final pH was 5-9. The obtained precipitate was washed, dried at 100 ° C. for 12 hours, and calcined at 450 ° C. for 3 hours to obtain zeolite-supported fine particle titanium oxide.
Next, a chemical solution in which 1.4 kg of ammonium metavanadate, 1.7 kg of oxalic acid and 0.4 kg of monoethanolamine are dissolved in 5 liters of water is added to 20 kg of the above zeolite-supported fine particle titanium oxide, and further 1 kg of phenol resin and molding aid. After adding starch and mixing and kneading with a kneader, it was formed into a honeycomb shape having an outer shape of 80 mm square, an opening of 4.0 mm, a thickness of 1.0 mm, and a length of 500 mm by an extrusion molding machine. Subsequently, after drying at 80 degreeC, it baked in the air atmosphere at 450 degreeC for 5 hours, and obtained the catalyst (B). The composition of the catalyst (B) thus obtained was V 2 O 5 : TiO 2 : zeolite = 5: 19: 76 (weight ratio). The BET surface area was 250 m 2 / g.
[0018]
[Example 2 ]
8 kg of the Ti—Si composite oxide powder used in Example 1 was impregnated with an alcohol solution containing 7.1 kg of tetraisopropyl titanate, and water was added dropwise little by little while mixing. The obtained slurry was dried at 100 ° C. for 12 hours and further calcined at 450 ° C. for 3 hours to obtain Ti—Si composite oxide-supported fine particle titanium oxide.
Next, a chemical solution in which 1.4 kg of ammonium metavanadate, 1.7 kg of oxalic acid, and 0.4 kg of monoethanolamine are dissolved in 5 liters of water is added to 20 kg of the above-mentioned Ti-Si composite oxide-supported fine particle titanium oxide, and further phenol resin 1 kg starch was added as a forming aid, mixed and kneaded with a kneader, and then formed into a honeycomb shape having an outer shape of 80 mm square, an opening of 4.0 mm, a thickness of 1.0 mm, and a length of 500 mm by an extrusion molding machine. Subsequently, after drying at 80 degreeC, it baked in the air atmosphere at 450 degreeC for 5 hours, and obtained the catalyst (C). The composition of the catalyst (C) thus obtained was V 2 O 5 : TiO 2 : Ti—Si composite oxide = 5: 19: 76 (weight ratio). The BET surface area was 120 m 2 / g.
[0019]
[Example 3 ]
8 kg of the Ti—Si composite oxide powder used in Example 1 was impregnated with an alcohol solution containing 7.1 kg of tetraisopropyl titanate and mixed uniformly. It was dried at 100 ° C. for 12 hours, and further fired at 450 ° C. for 3 hours to obtain Ti—Si composite oxide-supported fine particle titanium oxide.
Next, a chemical solution in which 1.4 kg of ammonium metavanadate, 1.7 kg of oxalic acid, and 0.4 kg of monoethanolamine are dissolved in 5 liters of water is added to 20 kg of the above-mentioned Ti-Si composite oxide-supported fine particle titanium oxide, and further phenol resin 1 kg starch was added as a forming aid, mixed and kneaded with a kneader, and then formed into a honeycomb shape having an outer shape of 80 mm square, an opening of 4.0 mm, a thickness of 1.0 mm, and a length of 500 mm by an extrusion molding machine. Subsequently, after drying at 80 degreeC, it baked in the air atmosphere at 450 degreeC for 5 hours, and obtained the catalyst (D). The composition of the catalyst (D) thus obtained was V 2 O 5 : TiO 2 : Ti—Si composite oxide = 5: 19: 76 (weight ratio). The BET surface area was 133 m 2 / g.
[0020]
[Comparative Example 1]
While stirring 600 liters of an aqueous 0.5 mol / liter ammonia solution, 48 liters of an aqueous titanium chloride solution (200 g / liter as TiO 2 ) was added dropwise thereto. The final pH was 5-9. The obtained precipitate was washed, dried at 100 ° C. for 12 hours, and further calcined at 450 ° C. for 3 hours to obtain titanium oxide. Next, a chemical solution in which 1.4 kg of ammonium metavanadate, 1.7 kg of oxalic acid and 0.4 kg of monoethanolamine are dissolved in 5 liters of water is added to 20 kg of the above titanium oxide, and 1 kg of phenol resin and starch as a molding aid are added. In addition, after mixing and 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 by an extrusion molding machine. Subsequently, after drying at 80 degreeC, it baked in the air atmosphere at 450 degreeC for 5 hours, and obtained the catalyst (E). The composition of the catalyst (E) thus obtained was V 2 O 5 : TiO 2 = 5: 95 (weight ratio). The BET surface area was 68 m 2 / g.
[0021]
[Comparative Example 2]
A chemical solution in which 1.4 kg of ammonium metavanadate, 1.7 kg of oxalic acid, and 0.4 kg of monoethanolamine are dissolved in 5 liters of water is added to 20 kg of the Ti—Si composite oxide powder used in Example 1, and a phenol resin is further added. 1 kg starch was added as a forming aid, mixed and kneaded with a kneader, and then formed into a honeycomb shape having an outer shape of 80 mm square, an opening of 4.0 mm, a thickness of 1.0 mm, and a length of 500 mm by an extrusion molding machine. Subsequently, after drying at 80 degreeC, it baked in the air atmosphere at 450 degreeC for 5 hours, and obtained the catalyst (F). The composition of the catalyst (F) thus obtained was V 2 O 5 : Ti—Si composite oxide = 5: 95 (weight ratio). The BET surface area was 130 m 2 / g.
[0022]
[Comparative Example 3]
A mixture of 10 kg of the Ti—Si composite oxide powder used in Example 1 and 10 kg of titanium oxide used in Comparative Example 1 was charged with 1.4 kg of ammonium metavanadate, 1.7 kg of oxalic acid, and 0.4 kg of monoethanolamine in water 5 Add a chemical solution dissolved in 1 liter, add 1 kg of phenolic resin and starch as a molding aid, mix and knead with a kneader, then use an extrusion molding machine to shape the outer shape 80 mm square, 4.0 mm opening, 1.0 mm wall thickness And formed into a honeycomb having a length of 500 mm. Subsequently, after drying at 80 degreeC, it baked in the air atmosphere at 450 degreeC for 5 hours, and obtained the catalyst (G). The composition of the catalyst (G) thus obtained was V 2 O 5 : TiO 2 : Ti—Si composite oxide = 5: 47.5: 47.5 (weight ratio). The BET surface area was 90 m 2 / g.
[0023]
[Example 4 ]
Catalyst prepared in Example 1 (A), catalyst prepared in Reference Example (B), catalyst prepared in Example 2 (C), catalyst prepared in Example 3 (D), catalyst prepared in Comparative Example 1 Using the catalyst (F) prepared in (E) and Comparative Example 2 and the catalyst (G) prepared in Comparative Example 3, 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 carried out under the following conditions. The results are shown in Table 1. The CT decomposition rate, that is, the CT removal rate was obtained by the following formula.
(Test conditions)
Process gas composition CT: 30 ppm, O 2 : 10%, H 2 O: 15%, N 2 : Balance
Gas temperature: 150-200 ° C
Space velocity (SV): 2000 Hr −1 , 4000 Hr −1
(formula)
CT decomposition rate (%) = [(reactor inlet CT concentration) − (reactor outlet CT concentration)] / (reactor inlet CT concentration) × 100
[0024]
[Table 1]
[Example 5 ]
Using the catalyst (A) prepared in Example 1 and the catalyst (G) prepared in Comparative Example 3, a denitration reaction was performed under the following conditions. When the denitration rate was determined by the following formula, it was 95% for the catalyst (A) and 88% for the catalyst (G).
(Test conditions)
Process gas composition NO: 100 ppm, NH 3 : 100 ppm, O 2 : 10%,
H 2 O: 15%, N 2 : Balance
Gas temperature: 230 ° C
Space velocity (SV): 5000 Hr −1
(formula)
Denitration rate (%) = [(reactor inlet NOx concentration) − (reactor outlet NOx concentration)] / (reactor inlet NOx concentration) × 100
[0026]
【The invention's effect】
The catalyst of the present invention is excellent in decomposition activity and ammonia decomposition activity of toxic organic halogen compounds such as dioxins. In addition, it has excellent denitration performance and is useful as a catalyst for simultaneous removal of toxic organic halogen compounds such as nitrogen oxides and dioxins.
Claims (5)
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| JP2000172261A JP3893014B2 (en) | 1999-08-12 | 2000-06-08 | Exhaust gas treatment catalyst, its production method and exhaust gas treatment method |
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| JP2000172261A JP3893014B2 (en) | 1999-08-12 | 2000-06-08 | Exhaust gas treatment catalyst, its production method and exhaust gas treatment method |
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| BRPI0916868A2 (en) | 2009-10-06 | 2016-02-10 | Mitsubishi Heavy Ind Ltd | nox removal catalyst, and methods for manufacturing a high temperature waste gas nox removal catalyst, and for removing high temperature waste gas nox |
| CN113828349A (en) * | 2021-10-22 | 2021-12-24 | 浙江理工大学 | Catalytic combustion catalyst containing chlorine volatile organic compounds, and preparation method and application thereof |
| CN116251599A (en) * | 2022-09-09 | 2023-06-13 | 南京信息工程大学 | Dioxin removal catalyst and preparation method thereof |
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