JP2004016927A

JP2004016927A - Manufacturing method for exhaust gas cleaning catalyst

Info

Publication number: JP2004016927A
Application number: JP2002175583A
Authority: JP
Inventors: Eiji Miyamoto; 宮本　英治; Yasuyoshi Kato; 加藤　泰良
Original assignee: Babcock Hitachi KK
Current assignee: Mitsubishi Power Ltd
Priority date: 2002-06-17
Filing date: 2002-06-17
Publication date: 2004-01-22

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for an exhaust gas cleaning catalyst capable of simplifying a manufacturing process, capable of reducing the thickness of a catalyst substrate and the weight of a catalyst and capable of sharply reducing a production cost. <P>SOLUTION: The manufacturing method (1) for the exhaust gas cleaning catalyst includes a process for preparing a catalyst carrier by coating a catalyst substrate made of a metal with a slurry obtained by mixing titanium oxide, water and colloidal silica and/or an inorganic fiber to prepare a catalyst carrier and a process for infiltrating an aqueous solution of a compound containing vanadium and molybdenum or a mixed solution prepared by mixing colloidal silica with the aqueous solution into the catalyst carrier to support the compound. The catalyst substrate made of the metal (2) is a catalyst substrate structure obtained by integrally laminating the catalyst substrate, which has linear wavy, uneven or tiered projections formed thereto, to the surface of a tabular substrate. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は排ガス浄化用触媒の製造方法に係り、特に製造工程の簡略化および製造コストの低減を図るのに好適な排ガス浄化用触媒の製造法に関する。
【０００２】
【従来の技術】
発電所などから排出される排煙中のＮＯｘは、酸性雨などの原因物質であり、その効果的な除去方法としては、ＮＨ_３を還元剤として選択的接触還元を行う排煙脱硝法が、火力発電所を中心に幅広く採用されている。該排煙脱硝法に用いる触媒としては、バナジウム（Ｖ）、モリブデン（Ｍｏ）、またはタングステン（Ｗ）を活性成分にした酸化チタン（ＴｉＯ_２）系触媒が知られており、通常、ハニカム状、板状に成形されて用いられる。この触媒の調製法としては、酸化チタンとＶ、Ｍｏ、Ｗなどの触媒活性成分の塩類とを水とともに混練し、その後、成形、焼成する方法（混練法）　、酸化チタンの成形焼成体に触媒活性成分の塩類の混合溶液を含浸する方法（含浸法）　、あらかじめ調製した触媒成分粉末をスラリ化し、これを金属製やセラミック製基材にコーティングする方法（特開昭５０−１２８６８１号公報、特公昭５３−３４１９５号公報、特開昭６３−２３４２２４号公報等）などが知られている。
【０００３】
また特開２０００−３０８８３２号公報には、網状物などの基材に酸化チタンをあらかじめ担持させ、乾燥および／または焼成して得られる触媒担体に、酸化モリブデンとメタバナジン酸アンモンを水の共存下に所定時間反応させて得られるＭｏとＶを含む水溶性化合物溶液（以下、単にＭｏ−Ｖ化合物の溶液ということがある）　を含浸させて触媒を調製する方法が提案されている。この方法によれば、触媒担体と触媒活性成分の性状を別々に調整できるため、強度と活性をともに向上させることが可能になる。
【０００４】
図５は、従来技術による触媒の製造工程図である。図５において、まず帯状ＳＵＳ（帯鋼）がメタルラス加工されて金属製触媒基材とされ、次いで、この金属製触媒基材に酸化チタンを含むペースト（担体ペースト）が塗布ローラにより塗布されて触媒担体とされる。さらに該触媒担体に切断、成形、積層などの加工が施され、乾燥、焼成により触媒担体構造体とされた後、該触媒担体構造体にＭｏ−Ｖ化合物の溶液が含浸され、乾燥、焼成により触媒構造体とされる。
しかしながら、上記方法では、触媒担体は、金属製触媒基材の間に担体ペーストを塗布ローラを用いて鋏込むという塗布方法で調製されるため、金属製触媒基材に塗布ローラに挟み込まれても破損しないだけの強度が要求され、該金属製触媒基材の薄板化や、触媒全体の重量を低減させることが困難であり、またＳＯ_２酸化率を同時に低減させるという試みにも限界があった。
【０００５】
【発明が解決しようとする課題】
本発明は、上記従来技術の問題点を解決し、製造工程の簡略化を図ることができ、かつ、触媒基材の薄板化および触媒の軽量化が可能で、製造コストを大幅に低減することができる排ガス浄化用触媒の製造法を提供することにある。
【０００６】
【課題を解決するための手段】
本発明者等は上記課題について鋭意検討した結果、金属製触媒基材に酸化チタンを含む担体スラリをコーティングして触媒担体を調製し、これにＭｏ−Ｖ化合物の溶液を含浸させることにより、上記課題を達成できることを見出し、本発明に到達したものである。
上記課題を達成するために本願で特許請求される発明は以下の通りである。
【０００７】
（１）金属製触媒基材に、酸化チタン、水、コロイダルシリカおよび／または無機繊維を混合して得られるスラリをコーティングして触媒担体を調製する工程と、該触媒担体に、バナジウムとモリブデンを含む化合物の水溶液または該水溶液にコロイダルシリカを混合した混合液を含浸し、前記化合物を担持させる工程とを含むことを特徴とする排ガス浄化用触媒の製造法。
（２）前記金属製触媒基材が、金網、ラス加工された金属板、パンチ穴の多数開いた金属板などの表裏に貫通した孔を多数有する金属板であることを特徴とする（１）に記載の排ガス浄化用触媒の製造法。
（３）前記金属製触媒基材が、平板状の基材表面に線状の波形、凸凹形または階段状の突起が形成された触媒基材を積層し、一体化して得られる触媒基材構造体であることを特徴とする（１）または（２）に記載の排ガス浄化用触媒の製造法。
（４）前記触媒基材構造体が、平板状の触媒基材と前記突起が形成された触媒基材とを交互に積層したものであることを特徴とする（３）に記載の排ガス浄化用触媒の製造法。
（５）前記バナジウムとモリブデンを含む化合物が、バナジウムとモリブデンの原子比Ｖ／Ｍｏが実質的に３／２である示性式（ＮＨ_４）_３Ｍｏ_２Ｖ_３Ｏ_１５で表される化合物であることを特徴とする（１）〜（４）のいずれかに記載の排ガス浄化用触媒の製造法。
【０００８】
【作用】
本発明において、触媒担体は、金属製触媒基材に酸化チタン、水、コロイダルシリカおよび／または無機繊維を混合して得られるスラリをコーティングした後、乾燥および／または焼成することにより得られる。コロイダルシリカまたは無機繊維は、金属製触媒基材に対する触媒の付着性および触媒強度を高めるために添加される。このように触媒担体をコーティング法により調製することにより、従来のように塗布ローラに基材を挟み込んで担体ペーストを塗布する必要がなく、基材に大きな負荷がかかることがないため、基材自体の強度を高く維持する必要がなく、従って、金属製触媒基材の重量低減、触媒全体の軽量化および製造コストの大幅な低減が可能になり、さらにＳＯ_２酸化率の低減を同時に可能にすることができる。また触媒担体と触媒成分の性状を別々に調整できるため、触媒の強度と活性の向上を同時に図ることができる。
【０００９】
【発明の実施の形態】
本発明に用いられる触媒担体は、金属製触媒基材に、酸化チタン、水、コロイダルシリカおよび／または無機繊維を混合して得られるスラリを含浸し、コーテイングすることにより調製される。
該スラリ中の酸化チタンの含有量には特に制限はないが、得られる触媒において、触媒成分である後述するＭｏ−Ｖ化合物と酸化チタンの重量比が０を超えて２０／１００以下となるように含有させるのが好ましく、より好ましくは２／１００〜１０／１００である。
またスラリ中に含有させるコロイダルシリカおよび／または無機繊維の添加量にも特に制限はないが、コロイダルシリカの添加量は酸化チタンに対してＳｉＯ_２量として０を超えて５０重量％以下とするのが好ましく、より好ましくは５〜３０重量％である。また無機繊維の添加量は酸化チタンに対し０〜７０重量％が好ましく、より好ましくは１０〜５０重量％である。無機繊維としてはアルミノシリケート繊維などのセラミック繊維、石英硝子、Ｅ硝子などが好ましく用いられ、該繊維は２００μｍ以下に切断したものが好ましく用いられる。
【００１０】
金属製触媒基材としては、図２に示す金網（ａ）　、ラス加工された金属板（ｂ）　、パンチ穴の多数開いた金属板（ｃ）　などの、表裏に貫通した孔を多数有する金属板が好ましく用いられる。これらはローラ掛け、プレスなどにより圧延されていてもよい。また金属板の多数の貫通孔は上記したスラリのコーティングにより埋められていても、埋められていなくてもよい。なお、図２において、１は金属製触媒基材、２は該触媒基材の開孔部を示す。
また金属製触媒基材は、平板状の基材表面に線状の波形、凸凹形または階段状の突起が形成された触媒基材を積層して一体化した触媒基材構造体であってもよい。図３（ａ）　〜（ｄ）　には該突起が形成された触媒基材の断面形状の一例を示した。また図４（ａ）　〜（ｄ）　にはこれらの触媒基材を複数枚積層して得た触媒基材構造体の概略図を示した。該触媒基材構造体３は、波型、階段型、コの字型などの形状に成形された成形済の触媒基材のみで積層、一体化されていてもよく、平板状の触媒基材と交互に積層、一体化されていてもよい。
【００１１】
本発明に用いられる触媒活性成分は、バナジウム（Ｖ）とモリブデン（Ｍｏ）であるが、ＶとＭｏの原子比Ｖ／Ｍｏ比が実質的に３／２である示性式（ＮＨ_４）_３Ｍｏ_２Ｖ_３Ｏ_１５で表される化合物（Ｍｏ−Ｖ化合物）が好ましい。このような化合物は、例えば、メタバナジン酸アンモニウム（ＮＨ_４Ｖｏ_３）と酸化モリブデン（ＭｏＯ_３）とをＶ／Ｍｏ原子比で３／２（実用的には３／１．７〜３／２．３）で水に添加後、撹拌して得られる。この化合物は赤褐色の物質であり、溶解度が常温で１７０ｇ／Ｌと大きいのが特徴である。この化合物の溶液には、必要に応じて結合剤としてコロイダルシリカを混合させることができる。
【００１２】
得られる触媒の摩耗強度を高める場合には比表面積の低い酸化チタンを用いるのが好ましく、また触媒の活性を向上させる場合には比表面積の高い酸化チタンを用いるのが好ましい。酸化チタンの比表面積は、比表面積の大きく異なる２種の酸化チタンの混合比率を変えることにより任意に制御することができる。また触媒の耐摩耗性を向上させる場合にはＭｏ−Ｖ化合物とコロイダルシリカとの混合液の混合比率（　Ｍｏ−Ｖ／ＳｉＯ_２比）　を減少させるのが効果的である。逆に触媒活性の向上を図る場合はＭｏ−Ｖ／ＳｉＯ_２比を増加させることが効果的である。さらに金属製触媒基材の貫通孔の断面が小さい場合は、スラリに混合する無機繊維の量を低減または０にすることにより、触媒活性を向上させることが可能である。
【００１３】
図１は、本発明の一実施例を示す排ガス浄化用触媒の製造工程図である。
図１において、図５の従来の製造工程と異なる点は、金属製触媒基材をあらかじめ切断、成形した後、該触媒基材に上記した担体スラリをコーティングして触媒担体とした点である。このような方法によれば、触媒基材構造体を形成した後に担体スラリを含浸させることができるため、製造工程の簡略化が図れるだけでなく、従来のように触媒基材に一定以上の強度が要求されないため、金属製触媒基材の薄型化、重量低減が可能となり、ひいては触媒自体の大幅な軽量化を図ることができる。
【００１４】
【実施例】
以下、本発明を実施例により詳細に説明するが、本発明はこれらに限定されるものではない。
実施例１
コロイダルシリカ（　日産化学社製、ＯＳゾル、ＳｉＯ_２分２０％）１０４ｋｇ中にＥ硝子繊維（セントラル硝子社製、ミルドファイバＥＦＨ−１００、平均長さ１００μｍ）１２ｋｇを添加後攪拌して分散させ、さらに比表面積９５ｍ^２／ｇの酸化チタン粉末（石原産業社製、ＭＣ９０）と比表面積２７０ｍ^２／ｇの酸化チタン粉末（ミレニアム社製、Ｇ５）をそれぞれ４５ｋｇ添加後攪拌してスラリを得た。
一方、ＳＵＳ４３０製帯鋼をメタルラス加工して板厚０．６５ｍｍ、送りピッチ０．３５ｍｍ、４９目／１００ｍｍ、目開き幅が約２ｍｍで開孔率７４％、５００ｇ／ｍ^２のメタルラスを得た。これを１００ｍｍ×１００ｍｍに切断して、平板状の金属製触媒基材を得た。
この平板状基材を先に調製したスラリに浸漬し、基材を揺り動かしながら１０分間経過後、スラリから引き上げて液切りした。これを風乾後５００℃で２時間焼成して担持量５００ｇ／ｍ^２の平板状担体を得た。これをＭｏ−Ｖ化合物とコロイダルシリカ（日産化学社製、ＯＳゾル、ＳｉＯ_２分２０％）　をともに１０ｋｇずつ混合して得られた溶液中に１分間浸漬し、引き上げて風乾後５００℃で２時間焼成し、担持量５３０ｇ／ｍ^２の平板状触媒を得た。
【００１５】
実施例２
ＳＵＳ４３０製帯鋼をメタルラス加工して板厚０．１ｍｍ、送りピッチ０．１ｍｍ、６０目／１００ｍｍ、目開き幅が約１．５ｍｍで開孔率６４％、８５ｇ／ｍ^２のメタルラスを得た。これを１００ｍｍ×１００ｍｍに切断して平板状の金属製触媒基材を得た。
この平板状基材を、実施例１で用いた基材の代わりに用い、他は実施例１と同様にして担持量２８０ｇ／ｍ^２の平板状担体を得た。さらに、実施例１と同様にしてＭｏ−Ｖ化合物とコロイダルシリカを等量混合した液に含浸し、担持量３１０ｇ／ｍ^２の平板状触媒を得た。
【００１６】
実施例３
実施例１で用いたメタルラスを金型の間に挟み、図３（ｄ）　の断面の高さ２．０ｍｍの帯状突起部をメタルラスの両端方向と３０°の角度をつけて成形し、幅４９８ｍｍ、長さ５００ｍｍの成形体を得た。これを一枚おきに反転させて図４（ａ）　の構造に積層した後、４００℃で１０分間脱脂処理して金属製基材の構造体を得た。
この構造体を、実施例１で使用したスラリに浸漬し、構造体を揺り動かしながら１０分間経過後、スラリから引き上げて液切りした。これを風乾後５００℃で２時間焼成して担持量４９０ｇ／ｍ^２の触媒担体の構造体を得た。これをＭｏ−Ｖ化合物とコロイダルシリカ（日産化学社製、ＯＳゾル、ＳｉＯ_２分２０％）をともに１０ｋｇずつ混合して得られた溶液中に１分間浸漬し、引き上げて風乾後５００℃で２時間焼成し、担持量５２０ｇ／ｍ^２の触媒構造体を得た。
【００１７】
実施例４
コロイダルシリカ（日産化学社製、ＯＳゾル、ＳｉＯ_２分２０％）１０４ｋｇ中にＥ硝子製繊維（セントラル硝子社製、ミルドファイバＥＦＨ−１００、平均長さ長さ１００μｍ）１２ｋｇを添加後攪拌して分散させ、比表面積２７０ｍ^２／ｇの酸化チタン粉末（ミレニアム社製、Ｇ５）を９０ｋｇ添加後攪拌してスラリを得た。
このスラリを、実施例１で用いたスラリの代わりに用い、他は実施例１と同様にして平板状担体を得た。この担体をＭｏ−Ｖ化合物中に１分間浸漬し、引き上げて風乾後５００℃で２時間焼成し、平板状触媒を得た。
【００１８】
実施例５
コロイダルシリカ（日産化学社製、ＯＳゾル、ＳｉＯ_２分２０％）１０４ｋｇ中にＥ硝子製繊維（セントラル硝子社製、ミルドファイバＥＦＨ−１００、平均長さ長さ１００μｍ）６ｋｇを添加後攪拌して分散させ、比表面積２７０ｍ^２／ｇの酸化チタン粉末（ミレニアム社製、Ｇ５）を９０ｋｇ添加後攪拌してスラリを得た。
このスラリを、実施例２で用いたスラリの代わりに用い、他は実施例２と同様にして平板状担体を得た。この担体をＭｏ−Ｖ化合物中に１分間浸漬し、引き上げて風乾後５００℃で２時間焼成し、平板状触媒を得た。
【００１９】
実施例６
実施例１で用いたメタルラスを金型の間に挟み、図３（ａ）　の断面の高さ２．０ｍｍの帯状突起部をメタルラスの両端方向と平行に成形し、幅４９８ｍｍ、長さ５００ｍｍの成形体を得た。これを、図４（ｂ）　の構造に積層した後４００℃で１０分間脱脂処理して、金属製基材の構造体を得た。
実施例３で用いた構造体の代わりに上記構造体を用い、他は実施例３と同様にして担持量５１０ｇ／ｍ^２の触媒構造体を得た。
【００２０】
実施例７
実施例１で用いたメタルラスを金型の間に挟み、図３（ｄ）　の断面の高さ２．０ｍｍの帯状突起部をメタルラスの両端方向と平行に成形し、幅４９８ｍｍ、長さ５００ｍｍの成形体を得た。
一方、ＳＵＳ４３０製帯鋼をメタルラス加工して板厚０．６７ｍｍ、送りピッチ０．４ｍｍ、２３目／１００ｍｍ、目開き幅が約１０ｍｍで開孔率８４％のメタルラスを得た。このメタルラスを幅４９８ｍｍ、長さ５００ｍｍに切断して、平板状基材を得た。
上記成形体と平板状基材とを、図４（ｅ）　の構造に交互に積層した後４００℃で１０分間脱脂処理して金属製基材の構造体を得た。
この構造体を、実施例５で使用したスラリに浸漬し、構造体を揺り動かしながら１０分間経過後、スラリから引き上げて液切りした。これを風乾後５００℃で２時間焼成して、成形した触媒基材の貫通孔は埋まり、平板状の触媒基材の貫通孔は開いた状態で担持量２７０ｇ／ｍ^２の触媒担体の構造体を得た。これをＭｏ−Ｖ化合物中に１分間浸漬し、引き上げて風乾後５００℃で２時間焼成し、担持量３００ｇ／ｍ^２の触媒構造体を得た。
【００２１】
実施例８
コロイダルシリカ（　日産化学社製、ＯＳゾル、ＳｉＯ_２分２０％）１０４ｋｇ中にＥ硝子製繊維（セントラル硝子社製、ミルドファイバＥＦＨ−１００、平均長さ１００μｍ）１２ｋｇを添加後攪拌して分散させ、さらに比表面積２７０ｍ^２／ｇの酸化チタン粉末（ミレニアム社製、Ｇ５）を９０ｋｇ添加後攪拌してスラリを得た。
このスラリに、実施例２で得られた金属製触媒基材を浸漬し、基材を揺り動かしながら１０分間経過後、スラリから引き上げて液切りした。これを風乾後、５００℃で２時間焼成して担持量２８０ｇ／ｍ^２の平板状担体を得た。
この平板状担体を、実施例１で調製したＭｏ−Ｖ化合物の溶液中に１分間浸漬し、引き上げて風乾後、５００℃で２時間焼成し、担持量３４０ｇ／ｍ^２の平板状触媒を得た。
【００２２】
比較例１
比表面積９５ｍ^２／ｇの酸化チタン粉末（石原産業社製、ＭＣ９０）と比表面積２７０ｍ^２／ｇの酸化チタン粉末（ミレニアム社製、Ｇ５）をそれぞれ４５ｋｇ、カオリン系無機繊維（商品名カオウール）、およびコロイダルシリカ（日産化学社製、ＯＳゾル、ＳｉＯ_２分２０％）を、酸化チタン粉末に対してそれぞれ１５％、５％混ぜ合わせたものが、ペースト状になるように調整しながら水を添加して約３０分間混練し、水分３１．０％の担体ペーストを得た。
一方、ＳＵＳ４３０製帯鋼をメタルラス加工して板厚０．８２ｍｍ、送りピッチ０．５９ｍｍ、４７目／１００ｍｍ、目開き幅が約２ｍｍで開孔率５６％、８５２ｇ／ｍ^２のメタルラスを得た。これを１００ｍｍ×１００ｍｍに切断して、平板状の金属製触媒基材を得た。
このメタルラスに上記ペーストを、一対の圧延ローラで目開き部および基材表面に担持量６５０ｇ／ｍ^２になるよう塗布した。これを１００ｍｍ×１００ｍｍに切り出し、風乾後５００℃で２時間焼成して平板状担体を得た。これをＭｏ−Ｖ化合物とコロイダルシリカ（日産化学社製、ＯＳゾル、ＳｉＯ_２分２０％）をともに１０ｋｇずつ混合して得られた溶液中に１分間浸漬し、引き上げて風乾後５００℃で２時間焼成し、担持量７００ｇ／ｍ^２の平板状触媒を得た。
【００２３】
比較例２
比較例１で用いたメタルラスの代わりに、実施例１で用いたメタルラスを使用して比較例１の担体ペーストを圧延ローラで塗布しようとしたところ、圧延ローラに挟まった部分でメタルラスが切断されたため、うまく塗布できなかった。
【００２４】
＜試験例＞
実施例１、実施例２および比較例１でそれぞれ得られた平板状触媒の板厚および重量を測定後、表１および表２の条件で、それぞれ脱硝率、ＳＯ_２酸化率を測定した。また、実施例１および比較例１で得られた１００ｍｍ×１００ｍｍの平板状触媒を水平面に対し４５°に傾斜させた表面に、粒子径２９７〜１０００μｍの鋼鉄製のグリッド８ｋｇを高さ５０ｃｍから落下させ、触媒の減量を測定した。これらの結果を表３に示す。
【００２５】
【表１】

【００２６】
【表２】

【００２７】
【表３】

【００２８】
表３の結果と上記比較例２の結果から、従来の塗布法で触媒担体を調製し、Ｍｏ−Ｖ液を含浸する製造方法では、基材の板厚が一定以上でないと金属基材が切断され担体の調製ができないが、本発明の製造法によれば、基材の板厚が０．１ｍｍと非常に薄い場合でも触媒担体を調製できることがわかった。また本発明の製造法によれば、触媒の脱硝率を低下させることなく、触媒重量およびＳＯ_２酸化率を大幅に低減できることがわかった。
【００２９】
【発明の効果】
本発明の製造法によれば、金属製触媒基材の薄板化が可能となり、このため、触媒の大幅な軽量化およびＳＯ_２酸化率の低減が可能となる。また触媒基材をあらかじめ積層して一体化した構造体とした後、触媒担体を調製し、さらに触媒成分の含浸工程を行うことができるため、製造工程の簡素化および製造コストの低減が可能となる。
【図面の簡単な説明】
【図１】本発明の一例を示す排ガス浄化用触媒の製造工程図。
【図２】本発明に用いられる金属製触媒基材の加工形状の一例を示す図。
【図３】本発明に用いられる金属製触媒基材の成形形状の一例を示す図。
【図４】本発明に用いられる触媒基材構造体の一例を示す図。
【図５】従来技術の製造方法の製造工程図。
【符号の説明】
１…金属製触媒基材、２…触媒基材の開孔部、３…触媒基材構造体[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing an exhaust gas purifying catalyst, and more particularly to a method for manufacturing an exhaust gas purifying catalyst suitable for simplifying a manufacturing process and reducing manufacturing costs.
[0002]
[Prior art]
NOx in flue gas discharged from power plants and the like is a causative substance such as acid rain. As an effective method for removing NOx, a flue gas denitration method in which selective catalytic reduction is performed using NH ₃ as a reducing agent, Widely used mainly in thermal power plants. As a catalyst used in the flue gas denitration method, a titanium oxide (TiO ₂ ) catalyst containing vanadium (V), molybdenum (Mo), or tungsten (W) as an active component is known. It is used after being formed into a plate shape. As a method for preparing this catalyst, a method of kneading titanium oxide and salts of catalytically active components such as V, Mo, W and the like with water, followed by molding and firing (kneading method); A method of impregnating a mixed solution of salts of active ingredients (impregnation method), a method of slurrying a catalyst component powder prepared in advance, and coating the slurry on a metal or ceramic substrate (Japanese Patent Laid-Open No. 50-128681, JP-A-53-34195, JP-A-63-234224 and the like are known.
[0003]
Japanese Patent Application Laid-Open No. 2000-308832 discloses a method in which titanium oxide is previously supported on a base material such as a mesh, dried and / or calcined, and molybdenum oxide and ammonium metavanadate are added in the presence of water. A method has been proposed in which a catalyst is prepared by impregnating a water-soluble compound solution containing Mo and V obtained by reacting for a predetermined time (hereinafter sometimes simply referred to as a solution of a Mo-V compound). According to this method, the properties of the catalyst carrier and the catalytically active component can be separately adjusted, so that both strength and activity can be improved.
[0004]
FIG. 5 is a manufacturing process diagram of a catalyst according to the related art. In FIG. 5, first, a band-shaped SUS (strip steel) is subjected to metal lath processing to form a metal catalyst base material, and then a paste containing titanium oxide (carrier paste) is applied to the metal catalyst base material by an application roller to form a catalyst. It is a carrier. Further, the catalyst support is subjected to processing such as cutting, molding, lamination and the like, and dried and fired to form a catalyst support structure. Then, the catalyst support structure is impregnated with a solution of a Mo-V compound, and dried and fired. It is a catalyst structure.
However, in the above method, the catalyst carrier is prepared by a coating method of scissoring the carrier paste between the metal catalyst bases using an application roller, so that the catalyst carrier is sandwiched between the metal catalyst bases by the application roller. It is required to have sufficient strength not to be damaged, and it is difficult to reduce the thickness of the metal catalyst base and to reduce the weight of the entire catalyst, and there is a limit to an attempt to simultaneously reduce the SO ₂ oxidation rate. .
[0005]
[Problems to be solved by the invention]
The present invention solves the above-mentioned problems of the prior art, can simplify the manufacturing process, can reduce the thickness of the catalyst substrate and the weight of the catalyst, and significantly reduce the manufacturing cost. It is an object of the present invention to provide a method for producing an exhaust gas purifying catalyst which can be produced.
[0006]
[Means for Solving the Problems]
The present inventors have conducted intensive studies on the above problems, and as a result, prepared a catalyst support by coating a metal catalyst substrate with a carrier slurry containing titanium oxide, and impregnating this with a solution of a Mo-V compound. The inventors have found that the object can be achieved, and have reached the present invention.
The invention claimed in this application to achieve the above object is as follows.
[0007]
(1) A step of coating a metal catalyst substrate with a slurry obtained by mixing titanium oxide, water, colloidal silica and / or inorganic fibers to prepare a catalyst carrier, and adding vanadium and molybdenum to the catalyst carrier. Impregnating an aqueous solution of a compound containing the compound or a mixture of the aqueous solution with colloidal silica, and supporting the compound.
(2) The metal catalyst substrate is a metal plate having a large number of through holes on the front and back, such as a wire mesh, a lathed metal plate, and a metal plate having many punched holes. 3. The method for producing an exhaust gas purifying catalyst according to claim 1.
(3) A catalyst base structure obtained by laminating and integrating a metal catalyst base in which a linear corrugated, uneven or stepped projection is formed on a flat base material surface. The method for producing an exhaust gas purifying catalyst according to (1) or (2), wherein the catalyst is a body.
(4) The exhaust gas purifying apparatus according to (3), wherein the catalyst substrate structure is formed by alternately stacking a plate-shaped catalyst substrate and the catalyst substrate on which the protrusions are formed. Method for producing catalyst.
(5) The compound containing vanadium and molybdenum is a compound represented by the chemical formula (NH ₄ ) ₃ Mo ₂ V ₃ O ₁₅ having an atomic ratio V / Mo of vanadium and molybdenum of substantially 3/2. The method for producing an exhaust gas purifying catalyst according to any one of (1) to (4), wherein:
[0008]
[Action]
In the present invention, the catalyst carrier is obtained by coating a metal catalyst base material with a slurry obtained by mixing titanium oxide, water, colloidal silica and / or inorganic fibers, followed by drying and / or firing. Colloidal silica or inorganic fibers are added to enhance the adhesion of the catalyst to the metal catalyst substrate and the strength of the catalyst. By preparing the catalyst carrier by the coating method in this way, there is no need to apply the carrier paste by sandwiching the substrate between the application rollers as in the related art, and there is no large load on the substrate. It is not necessary to keep the strength of the catalyst high, and therefore, it is possible to reduce the weight of the metal catalyst substrate, reduce the weight of the entire catalyst, and significantly reduce the production cost, and simultaneously reduce the SO ₂ oxidation rate. be able to. In addition, since the properties of the catalyst carrier and the catalyst component can be separately adjusted, the strength and activity of the catalyst can be improved at the same time.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
The catalyst carrier used in the present invention is prepared by impregnating a metal catalyst substrate with a slurry obtained by mixing titanium oxide, water, colloidal silica and / or inorganic fibers, and coating the mixture.
The content of titanium oxide in the slurry is not particularly limited, but the weight ratio of the Mo-V compound, which will be described later, which is a catalyst component, and titanium oxide is more than 0 and not more than 20/100 in the obtained catalyst. Is preferably contained, and more preferably 2/100 to 10/100.
Although no particular limitation on the amount of the colloidal silica and / or inorganic fibers are contained in the slurry, the amount of colloidal silica to less than 50 wt% greater than 0 as the amount of SiO ₂ with respect to titanium oxide Is more preferable, and more preferably 5 to 30% by weight. The amount of the inorganic fiber is preferably from 0 to 70% by weight, more preferably from 10 to 50% by weight, based on titanium oxide. As the inorganic fibers, ceramic fibers such as aluminosilicate fibers, quartz glass, E glass and the like are preferably used, and the fibers cut to 200 μm or less are preferably used.
[0010]
As the metal catalyst base material, a metal having a large number of holes penetrating on both sides, such as a metal mesh (a), a lathed metal plate (b), and a metal plate (c) having a large number of punched holes shown in FIG. A plate is preferably used. These may be rolled by rolling or pressing. Many through holes in the metal plate may or may not be filled with the slurry coating described above. In FIG. 2, reference numeral 1 denotes a metal catalyst substrate, and 2 denotes an opening of the catalyst substrate.
Further, the metal catalyst substrate may be a catalyst substrate structure obtained by laminating and integrating a catalyst substrate in which a linear corrugated, uneven or stepped projection is formed on a flat substrate surface. Good. FIGS. 3A to 3D show examples of the cross-sectional shape of the catalyst base on which the protrusions are formed. FIGS. 4A to 4D are schematic diagrams of a catalyst base structure obtained by laminating a plurality of these catalyst bases. The catalyst base structure 3 may be laminated and integrated only with a formed catalyst base formed into a shape such as a corrugated shape, a stepped shape, or a U-shape, and may be a flat catalyst base material. May be alternately laminated and integrated.
[0011]
The catalytically active components used in the present invention are vanadium (V) and molybdenum (Mo), and the chemical formula (NH ₄ ) _{3 in which} the atomic ratio V / Mo of V and Mo is substantially 3/2. The compound represented by Mo ₂ V ₃ O ₁₅ (Mo-V compound) is preferred. Such compounds include, for example, ammonium metavanadate (NH ₄ Vo ₃ ) and molybdenum oxide (MoO ₃ ) in a V / Mo atomic ratio of 3/2 (practically 3 / 1.7 to 3 / 2.3). It is obtained by adding to water in 3) and stirring. This compound is a reddish-brown substance, and is characterized by a high solubility of 170 g / L at room temperature. Colloidal silica can be mixed with the solution of this compound as a binder, if necessary.
[0012]
In order to increase the wear strength of the obtained catalyst, it is preferable to use titanium oxide having a low specific surface area. To improve the activity of the catalyst, it is preferable to use titanium oxide having a high specific surface area. The specific surface area of titanium oxide can be arbitrarily controlled by changing the mixing ratio of two types of titanium oxides having greatly different specific surface areas. In order to improve the abrasion resistance of the catalyst, it is effective to reduce the mixing ratio (Mo-V / SiO ₂ ratio) of the mixed solution of the Mo-V compound and the colloidal silica. If conversely improve the catalytic activity it is effective to increase the Mo-V / SiO ₂ ratio. Furthermore, when the cross section of the through hole of the metal catalyst base material is small, the catalytic activity can be improved by reducing or reducing the amount of the inorganic fiber mixed with the slurry.
[0013]
FIG. 1 is a manufacturing process diagram of an exhaust gas purifying catalyst showing one embodiment of the present invention.
In FIG. 1, the difference from the conventional manufacturing process of FIG. 5 is that after cutting and molding a metal catalyst base material in advance, the catalyst base material is coated with the above-described carrier slurry to obtain a catalyst support. According to such a method, since the carrier slurry can be impregnated after the catalyst base structure is formed, not only can the manufacturing process be simplified, but also the catalyst base has a certain strength or more as in the conventional case. Is not required, it is possible to reduce the thickness and weight of the metal catalyst base material, and thus to significantly reduce the weight of the catalyst itself.
[0014]
【Example】
Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.
Example 1
In 104 kg of colloidal silica (manufactured by Nissan Chemical Industries, OS sol, SiO ₂ content: 20%), 12 kg of E glass fiber (milled fiber EFH-100, average length 100 μm, manufactured by Central Glass Co., Ltd.) was added, followed by stirring and dispersion. further titanium oxide powder having a specific surface area of ^{95 m} 2 / g (manufactured by Ishihara Sangyo Kaisha, Ltd., MC 90) and a specific surface area of 270 meters ² / g titanium dioxide powder (Millennium Co., G5) of the to give a slurry and stirred after the addition 45kg respectively.
On the other hand, SUS430 strip steel was subjected to metal lath processing to obtain a metal lath having a plate thickness of 0.65 mm, a feed pitch of 0.35 mm, 49 stitches / 100 mm, an opening width of about 2 mm, a porosity of 74% and 500 g / m ² . . This was cut into 100 mm × 100 mm to obtain a flat metal catalyst base material.
This flat substrate was immersed in the previously prepared slurry, and after elapse of 10 minutes while rocking the substrate, the substrate was pulled up from the slurry and drained. This was air-dried and calcined at 500 ° C. for 2 hours to obtain a flat carrier having a loading of 500 g / m ² . This Mo-V compound and colloidal silica (manufactured by Nissan Chemical Industries, Ltd., OS sol, SiO ₂ minutes 20%) were mixed together by 10kg immersed for 1 minute in a solution obtained by, pulled at 500 ° C. After air-drying 2 Calcination was performed for a period of time to obtain a 530 g / m ² supported plate catalyst.
[0015]
Example 2
SUS430 strip steel was subjected to metal lath processing to obtain a metal lath having a plate thickness of 0.1 mm, a feed pitch of 0.1 mm, 60 meshes / 100 mm, an opening width of about 1.5 mm, an opening ratio of 64%, and 85 g / m ² . . This was cut into 100 mm x 100 mm to obtain a flat metal catalyst base material.
This flat substrate was used in place of the substrate used in Example 1, and the other conditions were the same as in Example 1 to obtain a flat carrier having a loading amount of 280 g / m ² . Further, the mixture was impregnated with a liquid obtained by mixing equal amounts of the Mo-V compound and colloidal silica in the same manner as in Example 1 to obtain a plate-like catalyst having a loading amount of 310 g / m ² .
[0016]
Example 3
The metal lath used in Example 1 was sandwiched between metal molds, and a 2.0-mm-high band-shaped projection having a cross section shown in FIG. 3D was formed at an angle of 30 ° with respect to both ends of the metal lath, and the width was 498 mm. To obtain a molded body having a length of 500 mm. This was inverted every other sheet and laminated into the structure shown in FIG. 4A, and then degreased at 400 ° C. for 10 minutes to obtain a metal base material structure.
This structure was immersed in the slurry used in Example 1, and after elapse of 10 minutes while oscillating the structure, the structure was pulled up from the slurry and drained. This was air-dried and then calcined at 500 ° C. for 2 hours to obtain a catalyst support structure having a carrying amount of 490 g / m ² . This was immersed for 1 minute in a solution obtained by mixing 10 kg each of a Mo-V compound and colloidal silica (manufactured by Nissan Chemical Industries, OS sol, 20% of SiO ₂ ) for 1 minute, pulled up, air-dried, and then dried at 500 ° C. for 2 minutes. It was calcined for a time to obtain a catalyst structure having a carrying amount of 520 g / m ² .
[0017]
Example 4
Colloidal silica (manufactured by Nissan Chemical Industries, Ltd., OS sol, SiO ₂ minutes 20%) E glass manufactured fiber in 104 kg (Central Glass Co., milled fiber EFH-100, average length length 100 [mu] m) of 12kg was stirred after the addition 90 kg of titanium oxide powder (G5, manufactured by Millennium) having a specific surface area of 270 m ² / g was dispersed and stirred to obtain a slurry.
This slurry was used in place of the slurry used in Example 1, and the other conditions were the same as in Example 1 to obtain a flat carrier. This support was immersed in the Mo-V compound for 1 minute, pulled up, air-dried, and calcined at 500 ° C. for 2 hours to obtain a plate catalyst.
[0018]
Example 5
Colloidal silica (manufactured by Nissan Chemical Industries, Ltd., OS sol, SiO ₂ minutes 20%) E glass manufactured fiber in 104 kg (Central Glass Co., milled fiber EFH-100, average length length 100 [mu] m) to 6kg and stirred after the addition 90 kg of titanium oxide powder (G5, manufactured by Millennium) having a specific surface area of 270 m ² / g was dispersed and stirred to obtain a slurry.
This slurry was used in place of the slurry used in Example 2, and the other conditions were the same as in Example 2 to obtain a flat carrier. This support was immersed in the Mo-V compound for 1 minute, pulled up, air-dried, and calcined at 500 ° C. for 2 hours to obtain a plate catalyst.
[0019]
Example 6
The metal lath used in Example 1 was sandwiched between molds, and a 2.0-mm-high band-shaped projection having a cross section shown in FIG. 3A was formed in parallel with both ends of the metal lath to have a width of 498 mm and a length of 500 mm. A molded article was obtained. This was laminated on the structure shown in FIG. 4 (b) and then degreased at 400 ° C. for 10 minutes to obtain a metal base structure.
A catalyst structure having a carrying amount of 510 g / m ² was obtained in the same manner as in Example 3 except that the above structure was used instead of the structure used in Example 3.
[0020]
Example 7
The metal lath used in Example 1 was sandwiched between metal molds, and a 2.0-mm-high strip-shaped protrusion having a cross section of FIG. 3D was formed in parallel with both ends of the metal lath. A molded article was obtained.
On the other hand, SUS430 strip steel was subjected to metal lath processing to obtain a metal lath having a plate thickness of 0.67 mm, a feed pitch of 0.4 mm, 23 stitches / 100 mm, an opening width of about 10 mm, and a porosity of 84%. This metal lath was cut into a width of 498 mm and a length of 500 mm to obtain a flat substrate.
The molded body and the flat substrate were alternately laminated in the structure shown in FIG. 4E, and then degreased at 400 ° C. for 10 minutes to obtain a metal substrate structure.
This structure was immersed in the slurry used in Example 5, and after elapse of 10 minutes while rocking the structure, the structure was pulled up from the slurry and drained. This is air-dried and then calcined at 500 ° C. for 2 hours to fill the through-holes of the formed catalyst base, and to form a catalyst support having a loading amount of 270 g / m ² with the through-holes of the flat catalyst base open. Got. This was immersed in a Mo-V compound for 1 minute, pulled up, air-dried, and calcined at 500 ° C. for 2 hours to obtain a catalyst structure having a carrying amount of 300 g / m ² .
[0021]
Example 8
Colloidal silica (manufactured by Nissan Chemical Industries, Ltd., OS sol, SiO ₂ minutes 20%) E glass manufactured fiber in 104 kg (Central Glass Co., milled fiber EFH-100, average length 100 [mu] m) were dispersed with stirring after the addition of 12kg Further, 90 kg of a titanium oxide powder having a specific surface area of 270 m ² / g (manufactured by Millennium Co., Ltd., G5) was added and stirred to obtain a slurry.
The metal catalyst base material obtained in Example 2 was immersed in this slurry, and after elapse of 10 minutes while rocking the base material, the base material was pulled up from the slurry and drained. This was air-dried and calcined at 500 ° C. for 2 hours to obtain a flat carrier having a loading of 280 g / m ² .
The plate-shaped support was immersed in the solution of the Mo-V compound prepared in Example 1 for 1 minute, pulled up, air-dried, and calcined at 500 ° C. for 2 hours to obtain a plate-shaped catalyst having a loading of 340 g / m ^2. Was.
[0022]
Comparative Example 1
A specific surface area of ^{95 m} 2 / g of titanium oxide powder (Ishihara Sangyo Kaisha Ltd., MC 90) with a specific surface area of 270 meters ² / g titanium dioxide powder (Millennium Co., G5) of each 45 kg, kaolin type inorganic fibers (trade name Kaowool), and colloidal silica (manufactured by Nissan chemical Industries, Ltd., OS sol, SiO ₂ min 20%), and 15% respectively of titanium oxide powder, those obtained by mixing 5% addition of water while adjusting to a paste Then, the mixture was kneaded for about 30 minutes to obtain a carrier paste having a water content of 31.0%.
On the other hand, SUS430 strip steel was subjected to metal lath processing to obtain a metal lath having a plate thickness of 0.82 mm, a feed pitch of 0.59 mm, 47 meshes / 100 mm, an opening width of about 2 mm, an aperture ratio of 56%, and 852 g / m ² . . This was cut into 100 mm × 100 mm to obtain a flat metal catalyst base material.
The paste was applied to the metal lath with a pair of rolling rollers so as to have a carrying amount of 650 g / m ² on the openings and the substrate surface. This was cut into 100 mm x 100 mm, air-dried, and fired at 500 ° C for 2 hours to obtain a flat carrier. This was immersed for 1 minute in a solution obtained by mixing 10 kg each of a Mo-V compound and colloidal silica (manufactured by Nissan Chemical Industries, OS sol, 20% of SiO ₂ ) for 1 minute, pulled up, air-dried, and then dried at 500 ° C. for 2 minutes. It was calcined for a time to obtain a plate-like catalyst having a supported amount of 700 g / m ² .
[0023]
Comparative Example 2
When the carrier paste of Comparative Example 1 was applied by a rolling roller using the metal lath used in Example 1 instead of the metal lath used in Comparative Example 1, the metal lath was cut at a portion sandwiched between the rolling rollers. , Could not be applied successfully.
[0024]
<Test example>
Example 1 After measuring the thickness and weight of the resulting tabular catalyst, respectively in Example 2 and Comparative Example 1, under the conditions of Table 1 and Table 2, respectively denitration rate was measured SO ₂ oxidation rate. Further, 8 kg of a steel grid having a particle diameter of 297 to 1000 μm was dropped from a height of 50 cm onto the surface of the 100 mm × 100 mm plate catalyst obtained in Example 1 and Comparative Example 1 inclined at 45 ° with respect to the horizontal plane. Then, the weight loss of the catalyst was measured. Table 3 shows the results.
[0025]
[Table 1]

[0026]
[Table 2]

[0027]
[Table 3]

[0028]
From the results of Table 3 and the results of Comparative Example 2 described above, in the production method in which the catalyst carrier is prepared by the conventional coating method and the Mo-V liquid is impregnated, the metal substrate is cut if the thickness of the substrate is not constant or more. However, according to the production method of the present invention, it was found that a catalyst carrier can be prepared even when the substrate thickness is as thin as 0.1 mm. According to the preparation of the present invention, without lowering the denitration rate of the catalyst, it was found that the catalyst weight and SO ₂ oxidation rate can be significantly reduced.
[0029]
【The invention's effect】
According to the production method of the present invention, it is possible to reduce the thickness of a metal catalyst substrate, and therefore, it is possible to significantly reduce the weight of the catalyst and reduce the SO ₂ oxidation rate. In addition, after the catalyst base material is laminated in advance to form an integrated structure, a catalyst carrier can be prepared and a catalyst component impregnation step can be further performed, so that the manufacturing process can be simplified and the manufacturing cost can be reduced. Become.
[Brief description of the drawings]
FIG. 1 is a production process diagram of an exhaust gas purifying catalyst showing an example of the present invention.
FIG. 2 is a view showing an example of a processed shape of a metal catalyst base used in the present invention.
FIG. 3 is a view showing an example of a molded shape of a metal catalyst base used in the present invention.
FIG. 4 is a view showing an example of a catalyst substrate structure used in the present invention.
FIG. 5 is a manufacturing process diagram of a conventional manufacturing method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Metallic catalyst base material 2 ... Opening part of catalyst base material 3 ... Catalyst base structure

Claims

A step of coating a metal catalyst substrate with a slurry obtained by mixing titanium oxide, water, colloidal silica and / or inorganic fibers to prepare a catalyst carrier, and forming a catalyst carrier containing a compound containing vanadium and molybdenum. Impregnating an aqueous solution or a mixed solution of the aqueous solution and colloidal silica, and supporting the compound.

The metal catalyst substrate according to claim 1, wherein the metal catalyst substrate is a metal plate having a large number of holes penetrating on the front and back sides, such as a metal mesh, a lath-processed metal plate, and a metal plate having a large number of punched holes. Manufacturing method of exhaust gas purifying catalyst.

The metal catalyst substrate is a catalyst substrate structure obtained by laminating a catalyst substrate having a linear corrugated, uneven or stepped projection formed on a flat substrate surface, and integrating the same. The method for producing an exhaust gas purifying catalyst according to claim 1 or 2, wherein:

4. The exhaust gas purifying catalyst according to claim 3, wherein the catalyst substrate structure is formed by alternately stacking a plate-shaped catalyst substrate and the catalyst substrate on which the protrusions are formed. 5. Law.

The compound containing vanadium and molybdenum is a compound represented by the chemical formula (NH ₄ ) ₃ Mo ₂ V ₃ O ₁₅ having an atomic ratio V / Mo of vanadium and molybdenum of substantially 3/2. A method for producing an exhaust gas purifying catalyst according to any one of claims 1 to 4.