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JP2004283643A - Catalyst for removing organic chlorine compound and removing method - Google Patents

Catalyst for removing organic chlorine compound and removing method Download PDF

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Publication number
JP2004283643A
JP2004283643A JP2003075596A JP2003075596A JP2004283643A JP 2004283643 A JP2004283643 A JP 2004283643A JP 2003075596 A JP2003075596 A JP 2003075596A JP 2003075596 A JP2003075596 A JP 2003075596A JP 2004283643 A JP2004283643 A JP 2004283643A
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JP
Japan
Prior art keywords
catalyst
palladium
compound
cerium
organic chlorine
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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JP2003075596A
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Japanese (ja)
Inventor
Yasuo Miyoshi
康夫 三好
Tsutomu Shikada
勉 鹿田
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
JFE Engineering Corp
Research Institute of Innovative Technology for the Earth RITE
Original Assignee
JFE Engineering Corp
Research Institute of Innovative Technology for the Earth RITE
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Priority to JP2003075596A priority Critical patent/JP2004283643A/en
Publication of JP2004283643A publication Critical patent/JP2004283643A/en
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  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
  • Catalysts (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To produce a catalyst which can continue to efficiently decompose harmful organic chlorine compounds such as dioxins at low temperatures even when the catalyst carries a small amount of palladium, and to provide a method for decomposing the organic chlorine compounds. <P>SOLUTION: The catalyst for removing the organic chlorine compounds contains chromium, cerium, and palladium and has the peaks of a pore size distribution at a position between 0.1 μm and 0.01μm and at a position exceeding 0.1 μm. The catalyst is used in the method for decomposing the organic chlorine compounds. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【0001】
【発明の属する技術分野】
本発明は、産業廃棄物や都市ごみなどを処理する焼却施設等から排出される排ガス中に含まれるダイオキシン等の有害有機塩素化合物を分解する触媒および方法に関するものである。
【0002】
【従来の技術】
最近、ごみ焼却施設等で発生するダイオキシン等の有害有機化合物が大きな社会問題になっており、その対策が種々講じられている。
【0003】
例えば、触媒の存在下加熱することによって、炭素原子4ないし8個を有するポリハロゲン化シクロアルキル化合物および少なくとも炭素原子5個を有するポリハロゲン化芳香族化合物を分解する方法であって、前記ポリハロゲン化化合物で汚染された固体基質中に存在する揮発性成分、または前記ポリハロゲン化化合物で汚染された液体基質、または前記ポリハロゲン化化合物自体を加熱もしくは焙焼によってガス状態に変換し、そして生成したガスまたは前記ポリハロゲン化化合物で汚染されたガス状物質を、触媒として固定床の形の周期律表Ia,Ib,IIa,IIb,IIIa,IVa,IVb,VIIbもしくはVIIIb族の元素の金属の酸化物、またはそれらの混合物を使用し、前記触媒との緊密な接触下酸素および水の存在下加熱することよりなり、作業温度は200ないし550℃であるポリハロゲン化化合物の分解方法が開示されている(特許文献1参照)。
【0004】
【特許文献1】
特公平6−38863号公報
【0005】
また、廃棄物焼却炉排ガスを冷却後、集塵装置で除塵するとともに、除塵された排ガスを酸化触媒と接触させて排ガス中の有害物質を分解させる排ガス処理方法において、前記集塵装置により除塵された排ガスを、150〜290℃の温度で、酸化チタン担体に五酸化バナジウムと三酸化タングステンを担持させた触媒と接触させて前記排ガス中の少なくともポリ塩素化ジベンゾダイオキシンおよび/またはポリ塩素化ジベンゾフランを分解する方法が開示されている(特許文献2参照)。
【0006】
【特許文献2】
特許第2633316号公報
【0007】
有機塩素化合物を酸素の存在下で炭酸ガス、水および塩化水素に分解する酸化分解触媒成分と、水蒸気の存在下で塩素を除去する脱塩素触媒成分よりなる有機塩素化合物分解触媒とこれを用いた有機塩素化合物の分解方法も知られている(特許文献3参照)。この酸化分解触媒成分はクロム、コバルト、亜鉛、スズ、リン、ビスマス、アンチモン、テルル、ジルコニウム、ニオブ、鉛、ランタン、セリウム、ニッケル、鉄、銅、マンガンまたはビスマスであり、脱塩素触媒成分は白金、イリジウム、ロジウム、パラジウム、ルテニウム、金、レニウム、シリカ・チタニアまたはジルコニア・チタニアである。
【0008】
【特許文献3】
特開2002−1065号公報
【0009】
【発明が解決しようとする課題】
従来技術では低温での有機塩素化合物分解能が不十分であり、排ガス中の有機塩素化合物除去率を向上させるには、触媒量を増加させるかあるいは反応温度を上げる等の方策を実施する必要があった。
【0010】
本発明者らは、このような触媒として、クロム、セリウムおよびパラジウムを含む有機塩素化合物除去用触媒を既に開発した(特許文献4参照)。
【0011】
【特許文献4】
特願2001−354329号明細書
【0012】
この触媒は、低温でも有機塩素化合物の除去が可能な優れた触媒ではあるが、パラジウム担持量が少量の場合は、その除去能が低下する傾向が見られた。
【0013】
本発明の目的は、パラジウムの担持量が少量でもダイオキシン等の有害有機塩素化合物を低温で効率よく分解しつづけうる触媒とこの有機塩素化合物の分解方法を提供することにある。
【0014】
【課題を解決するための手段】
本発明者らは上記課題を解決するべく鋭意検討の結果、クロム、セリウム、およびパラジウムを組み合わせた触媒を調製するに当り、これらの触媒前駆体のうち特にパラジウム触媒前駆体に熱分解性の微粉を混合して焼成の際にこの微粉を熱分解させることによって、パラジウムの担持量が少量でもダイオキシン等の有害有機塩素化合物を低温で効率よく分解しつづけることができることを見出して本発明を完成するに至った。
【0015】
すなわち、本発明は、
クロム、セリウムおよびパラジウムを含み、0.1μmと0.01μmの間と0.1μmを越える位置にそれぞれ孔径分布のピークを有する有機塩素化合物除去用触媒と、
クロム、セリウムおよびパラジウムの各触媒前駆体を焼成してクロム、セリウムおよびパラジウムを含む触媒を製造するに当り、少なくともパラジウム触媒前駆体に平均粒径が0.1〜1,000μmで熱分解温度が100〜600℃の熱分解性化合物を混合して、焼成の際に該熱分解性化合物を熱分解させることを特徴とする、クロム、セリウムおよびパラジウムを含む有機塩素化合物除去用触媒の製造方法と、
排ガス中の有機塩素化合物を120〜350℃の温度範囲で上記の触媒に接触させることを特徴とする有機塩素化合物の除去方法
に関するものである。
【0016】
本発明では、熱分解性化合物を触媒調製時にあらかじめ添加しておき、焼成時に熱分解することにより触媒の細孔径を制御し、パラジウム担持量が少量の場合でも十分な除去性能を有する触媒を得る。
【0017】
【発明の実施の形態】
本発明の触媒は、クロム、セリウム、及びパラジウムよりなるものである。これらの比率は、クロムを酸化クロム(VI)、セリウムを酸化セリウム(IV)、そしてパラジウムを酸化パラジウム(II)にそれぞれ換算した重量比で、クロム1に対して、セリウム0.005〜4程度、好ましくは0.01〜1程度、そしてパラジウムが0.000025〜0.05程度、好ましくは0.0001〜0.01程度が適当である。セリウム対パラジウムの比ではセリウム1に対してパラジウム0.001〜2程度が好ましい。
【0018】
本発明の触媒は、その有する細孔の孔径分布に少なくとも2つのピークを有しているところに特徴がある。1つは孔径が0.01μmと0.1μmの間に、もう1つは0.1μmを越える位置に現われる。前者は本触媒固有のものであって、焼成の際の触媒前駆体の熱分解によって生じたものと思われる。このピークは0.01μmと0.1μmの間であるが、多くは0.01〜0.08μm程度、特に0.015〜0.06μm程度の範囲に現われることが多い。もう1つのピークは焼成の際の熱分解性化合物の熱分解によって生じたものであり、添加する熱分解性化合物の粒径等によって位置を調整することができる。通常は0.1〜100μm程度、好ましくは0.2〜10μm程度、特に好ましくは0.2〜2μm程度である。これらのピークは、触媒固有のピークと熱分解性化合物のいずれも2つ以上であることができる。この細孔の孔径分布の測定方法としては、窒素を用いたガス吸着法を用いることができる。
【0019】
上記の触媒成分を担体に担持させることができる。好ましい担体はチタニア、シリカ、アルミナ、珪藻土等であり、チタニアが特に好ましい。担体の使用量は上記の触媒1重量部に対し2.5〜25重量部程度、通常3.5〜15重量部程度が好ましい。担体がチタニアの場合、上記三成分とチタニアの比率は、チタニアと触媒成分の合計重量に対して、クロムは酸化クロム(VI)換算で2.5〜20重量%程度、セリウムは酸化セリウム(IV)換算で0.1〜10重量%程度、そしてパラジウムは酸化パラジウム(II)換算で0.0005〜0.2重量%程度が好ましい。上記の範囲外であると、クロムを触媒成分とする触媒に対する改善効果が少ない。また、パラジウムは4重量%以上でも効果を発揮するが、触媒が高価なものになってしまい実用的でない。
【0020】
本発明の触媒の製法としては、クロム、セリウムおよびパラジウムの各触媒前駆体を焼成することにより行い、その際、少なくともパラジウム触媒前駆体に熱分解性化合物を混合することに特徴がある。
【0021】
この触媒の製造には、熱分解性化合物の添加を除きこの種の触媒の一般的な調製方法を適用できる。例えば触媒の製造用原料である触媒前駆体には、上記各金属の化合物として、硝酸塩、炭酸塩等の無機酸塩および酢酸塩、シュウ酸塩など有機酸塩が使用される。各触媒前駆体の比率は触媒の設計組成から定まる。
【0022】
熱分解性化合物は、常温で固体であること、微粒子化できること、熱分解生成物が触媒を失活させないこと、熱分散残渣がないかあるいは触媒活性に実質的に影響を与えないことが要求される。また、熱分解温度は100〜600℃程度、好ましくは150〜250℃程度のものが望ましい。このような熱分解性化合物は有機化合物、特に、炭素と水素のみあるいはさらに酸素を含むものが望ましく、また特に塩素、イオウ等を含むものは触媒の性能低下をもたらす可能性があり好ましくない。具体的には熱可塑性、熱硬化性の樹脂やゴム等が挙げられる。より具体的に例示すれば、アセタール樹脂、アクリル樹脂、メタクリル樹脂、フェノール樹脂、不飽和ポリエステル等を挙げることができる。好ましくないものは、ポリ塩化ビニルあるいはポリ塩化ビニリデン等である。
【0023】
熱分解性化合物の粒径(平均粒径)は、触媒の所望の細孔径から定められるが、0.1〜1,000μm程度、好ましくは0.5〜200μm程度、特に好ましくは1〜20μm程度である。
【0024】
熱分解性化合物の添加量は、好ましくは0.1〜30重量%程度(触媒および担体の総重量に対して)より好ましくは1〜10重量%程度、特に好ましくは2〜5重量%程度である。
【0025】
この熱分解性化合物は、通常はクロム、セリウムおよびパラジウムの触媒前駆体の混合物全体に分散状態で配合される。しかしながら、本発明では熱分解性化合物の配合はパラジウム触媒前駆体に対してが特に有効なので、各触媒前駆体を順序を変えて添加する場合、例えば担体にまずクロムとセリウムの触媒前駆体を混練してその後パラジウム触媒前駆体を添加する場合には、熱分解性化合物はパラジウム触媒前駆体に配合することが望ましい。しかしながら、この場合であっても熱分解性化合物は各触媒前駆体のいずれにも配合することもできる。
【0026】
本発明の触媒を担体に担持する操作には、通常の沈殿法、混練法、含浸法およびイオン交換法などの技術が利用できる。このように調製された触媒組成物は、必要があれば常法により焼成する。焼成は、空気中において、300〜600℃の温度で1〜10時間加熱して行うのが好ましい。
【0027】
本発明の触媒は固定床、移動床等のいずれの形態でも使用することができる。そして、触媒の大きさ及び形状は、一般に処理ガス量、ダストの濃度、触媒の設置方法、反応器の大きさ、反応器の設置場所等により決定される。特に、形状に関しては、円柱状、球状、ハニカム状、板状などが考えられるが、ダスト濃度が0.05g/Nm以上と高いガスの場合は、ハニカム状が望ましい。
【0028】
本発明の触媒の分解対象は有機塩素化合物全般であるが、特にポリ塩素化芳香族化合物を対象としており、例えば、2,3,7,8−テトラクロロジベンゾダイオキシンで代表されるようなポリ塩素化ジベンゾダイオキシン類、2,3,4,7,8−ペンタクロロジベンゾフランで代表されるようなポリ塩素化ジベンゾフラン類、3,3’,4,4’,5−ペンタクロロビフェニルで代表されるようなポリ塩素化ビフェニル類、O−クロロフェノールで代表されるような塩素化フェノール類、クロロベンゼンで代表されるような塩素化ベンゼン類等である。
【0029】
本発明の処理対象のガスにおける有機塩素化合物の濃度は特に制限されず、飽和濃度であってもよく、飽和濃度を越えていてミスト等の形態で含むものであってもよい。しかしながら、通常は2,3,7,8−テトラクロロジベンゾダイオキシン換算で0.01〜500ng/Nm程度、特に0.05〜10ng/Nm程度のものである。このガスには、有機塩素化合物に対して、理論量以上の酸素と水蒸気が含まれている必要があるが、一般にごみ焼却炉等からの排ガスには酸素も水蒸気も上記要求量をはるかに超えて含んでいるので、特に酸素や水蒸気を添加あるいは濃度調整する必要はない。
【0030】
分解条件としては、反応温度は120〜350℃程度、好ましくは130〜250℃程度、特に好ましくは140〜190℃程度が適当である。上記温度範囲より低いと排ガス中に含まれる酸性ガスの酸露点の問題から、著しい装置の腐食が短期間で起こる場合がある。また、高い場合は、ダイオキシン(DXN)類が再合成される場合がある。この点で140〜190℃程度が特に好ましい。また、空間速度(触媒1m当りの標準状態におけるガスの供給速度)は1,000〜50,000h−1程度が適当である。
【0031】
【実施例】
実施例1
1.触媒の調製
触媒▲1▼の調製
無水クロム酸(CrO)1.000kg、硝酸セリウム6水和物(Ce(NO・6HO)0.252kg、硝酸パラジウム(Pd(NO)0.188gおよび熱分解温度170〜210℃と、平均粒径4μmのフェノール樹脂0.400kgを硝酸3.5lに溶解し、得られた水溶液を粉末のチタニア8.8999kgに加え、良く混練した。次に、その混練物を120℃,12時間乾燥後、さらに空気中で500℃,3時間焼成し、3〜5mmに分級、触媒▲1▼を得た。
【0032】
上記触媒の成分比(重量比)はCrO:CeO:PdO:TiO=10:1:0.001:88.999であった。
【0033】
触媒の細孔分布をガス吸着法で測定した結果、全細孔容積は0.39cc/gであり、0.01〜0.06μmの範囲と0.2〜0.9μm範囲に細孔分布のピークを有した。ガス吸着法で測定したそれぞれのピークの細孔容積は全細孔容積の54%および34%であり、細孔径分布を図1に示した。また、BET表面積は80m/gであった。
【0034】
比較例
触媒▲1▼の調製の際に、フェノール樹脂を加えなかった以外はその方法に準じて触媒を調製した。上記触媒の成分比(重量比)はCrO:CeO:PdO:TiO=10:1:0.001:88.999であった。
【0035】
触媒の全細孔容積は0.39cc/g、BET表面積は80m/gであり、0.01〜0.08μmの範囲にのみ細孔分布のピークを有し、0.2〜0.9μm範囲ではピークは見られなかった。細孔径分布を図2に示した。
【0036】
2.反応条件および実験結果
内径20cmのステンレス製反応器に上記触媒を1l充填し、常圧固定床流通反応装置で触媒の活性試験を行った。この反応管を電気炉で加熱し反応温度150,165および180℃に設定、ゴミ焼却排ガスをSV4,000h−1になるよう触媒層に流通、DXN類濃度を触媒層入口と出口で測定し、毒性等価換算濃度に換算、それらから除去率を求めた(結果−表1)。
【0037】
なお、ゴミ焼却排ガスの性状はダスト濃度:0.01g/Nm以下、SOx濃度:10ppm以下、NOx濃度:80ppm以下、HCl濃度:50ppm以下であった。また、DXN類分解率は下記の定義に従った。
DXN類分解率(%)=
((入口DXN類濃度−出口DXN類濃度)÷入口DXN類濃度)×100
【0038】
【表1】

Figure 2004283643
【発明の効果】
本発明により、ダイオキシン等の有機塩素化合物を低温でも効率よく分解することができる。
【図面の簡単な説明】
【図1】本発明の実施例で得られた触媒の細孔の孔径分布を示すグラフである。
【図2】本発明の比較例で得られた触媒の細孔の孔径分布を示すグラフである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a catalyst and a method for decomposing harmful organic chlorine compounds such as dioxin contained in exhaust gas discharged from incineration facilities for treating industrial waste and municipal waste.
[0002]
[Prior art]
Recently, harmful organic compounds such as dioxins generated in refuse incineration facilities have become a major social problem, and various countermeasures have been taken.
[0003]
For example, a method for decomposing a polyhalogenated cycloalkyl compound having 4 to 8 carbon atoms and a polyhalogenated aromatic compound having at least 5 carbon atoms by heating in the presence of a catalyst, comprising: Converting volatile components present in the solid substrate contaminated with the halogenated compound, or the liquid substrate contaminated with the polyhalogenated compound, or the polyhalogenated compound itself into a gaseous state by heating or roasting, and producing Gas or a gaseous substance contaminated with said polyhalogenated compound is used as a catalyst in the form of a fixed bed in the form of a metal of an element of the group Ia, Ib, IIa, IIb, IIIa, IVa, IVb, VIIb or VIIIb. The use of oxides or mixtures thereof, under close contact with the catalyst, oxygen and water storage Consists to the lower heating method for decomposing polyhalogenated compounds are disclosed working temperature is to not 200 550 ° C. (see Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Publication No. 6-38863
Further, after cooling the waste incinerator exhaust gas, the dust is removed by a dust collector, and in the exhaust gas treatment method in which the exhausted dust is brought into contact with an oxidation catalyst to decompose harmful substances in the exhaust gas, the dust is removed by the dust collector. The exhaust gas was brought into contact with a catalyst comprising vanadium pentoxide and tungsten trioxide supported on a titanium oxide carrier at a temperature of 150 to 290 ° C. to reduce at least polychlorinated dibenzodioxin and / or polychlorinated dibenzofuran in the exhaust gas. A decomposition method is disclosed (see Patent Document 2).
[0006]
[Patent Document 2]
Japanese Patent No. 2633316 [0007]
An organic chlorine compound decomposition catalyst comprising an oxidative decomposition catalyst component for decomposing an organic chlorine compound into carbon dioxide gas, water and hydrogen chloride in the presence of oxygen, and a dechlorination catalyst component for removing chlorine in the presence of water vapor, and used A method for decomposing an organic chlorine compound is also known (see Patent Document 3). The oxidative decomposition catalyst component is chromium, cobalt, zinc, tin, phosphorus, bismuth, antimony, tellurium, zirconium, niobium, lead, lanthanum, cerium, nickel, iron, copper, manganese or bismuth, and the dechlorination catalyst component is platinum. , Iridium, rhodium, palladium, ruthenium, gold, rhenium, silica titania or zirconia titania.
[0008]
[Patent Document 3]
Japanese Patent Application Laid-Open No. 2002-1065
[Problems to be solved by the invention]
With the conventional technology, the ability to decompose organochlorine compounds at low temperatures is insufficient, and in order to improve the removal rate of organochlorine compounds in exhaust gas, it is necessary to take measures such as increasing the amount of catalyst or increasing the reaction temperature. Was.
[0010]
The present inventors have already developed an organic chlorine compound removal catalyst containing chromium, cerium and palladium as such a catalyst (see Patent Document 4).
[0011]
[Patent Document 4]
Japanese Patent Application No. 2001-354329
This catalyst is an excellent catalyst capable of removing an organic chlorine compound even at a low temperature, but when the amount of supported palladium is small, the removal ability tends to decrease.
[0013]
An object of the present invention is to provide a catalyst capable of continuously decomposing harmful organic chlorine compounds such as dioxin at a low temperature even if the amount of palladium carried is small, and a method for decomposing the organic chlorine compounds.
[0014]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, when preparing a catalyst combining chromium, cerium, and palladium, among these catalyst precursors, in particular, palladium catalyst precursors were finely decomposable powder. And that the fine powder is thermally decomposed at the time of baking to find that the harmful organic chlorine compounds such as dioxin can be efficiently decomposed at a low temperature even with a small amount of palladium carried, thereby completing the present invention. Reached.
[0015]
That is, the present invention
A catalyst for removing an organochlorine compound containing chromium, cerium and palladium, and having pore size distribution peaks at positions between 0.1 μm and 0.01 μm and beyond 0.1 μm, respectively;
In producing a catalyst containing chromium, cerium and palladium by calcining each catalyst precursor of chromium, cerium and palladium, at least the palladium catalyst precursor has an average particle diameter of 0.1 to 1,000 μm and a thermal decomposition temperature of at least 0.1 to 1,000 μm. A method for producing a catalyst for removing an organochlorine compound containing chromium, cerium and palladium, comprising mixing a pyrolyzable compound at 100 to 600 ° C. and pyrolyzing the pyrolyzable compound during firing. ,
The present invention relates to a method for removing an organochlorine compound, which comprises bringing an organochlorine compound in exhaust gas into contact with the catalyst in a temperature range of 120 to 350 ° C.
[0016]
In the present invention, a thermally decomposable compound is added in advance at the time of catalyst preparation, and the pore size of the catalyst is controlled by pyrolysis at the time of calcination to obtain a catalyst having a sufficient removal performance even when the amount of supported palladium is small. .
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
The catalyst of the present invention comprises chromium, cerium, and palladium. These ratios are chromium oxide (VI) for chromium, cerium oxide (IV) for cerium, and palladium oxide (II) for palladium. , Preferably about 0.01 to 1 and palladium is about 0.000025 to 0.05, preferably about 0.0001 to 0.01. The ratio of cerium to palladium is preferably about 0.001-2 palladium to 1 cerium.
[0018]
The catalyst of the present invention is characterized in that it has at least two peaks in the pore size distribution of its pores. One appears at a pore size between 0.01 μm and 0.1 μm, and the other appears at a location over 0.1 μm. The former is specific to the present catalyst and is considered to have been caused by the thermal decomposition of the catalyst precursor during the calcination. This peak is between 0.01 μm and 0.1 μm, but often appears in the range of about 0.01 to 0.08 μm, particularly about 0.015 to 0.06 μm. The other peak is generated by the thermal decomposition of the heat-decomposable compound at the time of firing, and its position can be adjusted by the particle size of the heat-decomposable compound to be added. Usually, it is about 0.1 to 100 μm, preferably about 0.2 to 10 μm, particularly preferably about 0.2 to 2 μm. These peaks can be two or more of both the peak specific to the catalyst and the thermally decomposable compound. As a method for measuring the pore size distribution of the pores, a gas adsorption method using nitrogen can be used.
[0019]
The above catalyst component can be supported on a carrier. Preferred carriers are titania, silica, alumina, diatomaceous earth and the like, with titania being particularly preferred. The amount of the carrier to be used is preferably about 2.5 to 25 parts by weight, usually about 3.5 to 15 parts by weight based on 1 part by weight of the above catalyst. When the carrier is titania, the ratio of the above three components to titania is about 2.5 to 20% by weight in terms of chromium oxide (VI), and cerium is cerium oxide (IV), based on the total weight of titania and the catalyst component. ) And about 0.1 to 10% by weight, and palladium is preferably about 0.0005 to 0.2% by weight in terms of palladium (II) oxide. Outside the above range, the effect of improving the catalyst containing chromium as a catalyst component is small. Although palladium exerts its effect even at 4% by weight or more, the catalyst becomes expensive and is not practical.
[0020]
The method for producing the catalyst of the present invention is carried out by calcining each of the chromium, cerium and palladium catalyst precursors, and at that time, is characterized by mixing at least a thermally decomposable compound with the palladium catalyst precursor.
[0021]
For the preparation of this catalyst, a general method for preparing this type of catalyst can be applied except for the addition of the thermally decomposable compound. For example, in a catalyst precursor which is a raw material for producing a catalyst, inorganic salts such as nitrates and carbonates and organic acid salts such as acetates and oxalates are used as the compounds of the above metals. The ratio of each catalyst precursor is determined from the designed composition of the catalyst.
[0022]
The thermally decomposable compound is required to be solid at room temperature, capable of being finely divided, that the thermal decomposition product does not deactivate the catalyst, that there is no heat dispersion residue or that the catalyst activity is not substantially affected. You. The thermal decomposition temperature is desirably about 100 to 600 ° C, preferably about 150 to 250 ° C. Such a thermally decomposable compound is preferably an organic compound, particularly a compound containing only carbon and hydrogen or further containing oxygen, and a compound containing chlorine, sulfur, or the like is not preferred because it may cause deterioration in the performance of the catalyst. Specific examples include thermoplastic and thermosetting resins and rubbers. More specifically, examples include acetal resins, acrylic resins, methacrylic resins, phenolic resins, unsaturated polyesters, and the like. Less preferred are polyvinyl chloride or polyvinylidene chloride.
[0023]
The particle size (average particle size) of the thermally decomposable compound is determined from the desired pore size of the catalyst, and is about 0.1 to 1,000 μm, preferably about 0.5 to 200 μm, and particularly preferably about 1 to 20 μm. It is.
[0024]
The amount of the thermally decomposable compound is preferably about 0.1 to 30% by weight (based on the total weight of the catalyst and the carrier), more preferably about 1 to 10% by weight, and particularly preferably about 2 to 5% by weight. is there.
[0025]
The thermally decomposable compound is usually incorporated in a dispersed state throughout the mixture of the chromium, cerium and palladium catalyst precursors. However, in the present invention, since the compounding of the thermally decomposable compound is particularly effective for the palladium catalyst precursor, when adding each catalyst precursor in a different order, for example, first kneading the catalyst precursor of chromium and cerium on the carrier. When the palladium catalyst precursor is added after that, the thermally decomposable compound is desirably blended with the palladium catalyst precursor. However, even in this case, the thermally decomposable compound can be blended with any of the catalyst precursors.
[0026]
For the operation of supporting the catalyst of the present invention on a carrier, techniques such as ordinary precipitation, kneading, impregnation, and ion exchange can be used. The catalyst composition thus prepared is calcined by a conventional method if necessary. The firing is preferably performed by heating in air at a temperature of 300 to 600 ° C. for 1 to 10 hours.
[0027]
The catalyst of the present invention can be used in any form such as a fixed bed and a moving bed. The size and shape of the catalyst are generally determined by the amount of processing gas, the concentration of dust, the method of installing the catalyst, the size of the reactor, the location of the reactor, and the like. In particular, regarding the shape, a columnar shape, a spherical shape, a honeycomb shape, a plate shape, and the like can be considered, but in the case of a gas having a high dust concentration of 0.05 g / Nm 3 or more, a honeycomb shape is preferable.
[0028]
The decomposition target of the catalyst of the present invention is organic chlorine compounds in general, and is particularly intended for polychlorinated aromatic compounds, for example, polychlorinated compounds represented by 2,3,7,8-tetrachlorodibenzodioxin. Such as chlorinated dibenzodioxins, polychlorinated dibenzofurans represented by 2,3,4,7,8-pentachlorodibenzofuran, and 3,3 ′, 4,4 ′, 5-pentachlorobiphenyl Polychlorinated biphenyls, chlorinated phenols represented by O-chlorophenol, chlorinated benzenes represented by chlorobenzene, and the like.
[0029]
The concentration of the organochlorine compound in the gas to be treated in the present invention is not particularly limited, and may be a saturated concentration, or may exceed the saturated concentration and be contained in the form of a mist or the like. However, usually about 0.01~500ng / Nm 3 in 2,3,7,8-tetrachloro-dibenzo-dioxin terms, in particular of the order of 0.05~10ng / Nm 3. This gas must contain more than the theoretical amount of oxygen and water vapor with respect to the organochlorine compound, but in general the exhaust gas from refuse incinerators etc. Therefore, there is no need to add oxygen or water vapor or adjust the concentration.
[0030]
Suitable decomposition conditions are a reaction temperature of about 120 to 350 ° C, preferably about 130 to 250 ° C, and particularly preferably about 140 to 190 ° C. If the temperature is lower than the above-mentioned temperature range, significant equipment corrosion may occur in a short period of time due to the problem of the acid dew point of the acidic gas contained in the exhaust gas. When the content is high, dioxins (DXN) may be resynthesized. In this respect, about 140 to 190 ° C. is particularly preferable. The space velocity (supply rate of gas in a standard state per m 3 of catalyst) is preferably about 1,000 to 50,000 h −1 .
[0031]
【Example】
Example 1
1. Catalyst Preparation Catalyst ▲ 1 ▼ prepared chromic anhydride of (CrO 3) 1.000kg, cerium nitrate hexahydrate (Ce (NO 3) 3 · 6H 2 O) 0.252kg, palladium nitrate (Pd (NO 3) 2 ) Dissolve 0.188 g, a pyrolysis temperature of 170 to 210 ° C., and 0.400 kg of a phenol resin having an average particle size of 4 μm in 3.5 l of nitric acid, add the resulting aqueous solution to 8.8999 kg of powdered titania, and knead well. did. Next, the kneaded material was dried at 120 ° C. for 12 hours, and further calcined in air at 500 ° C. for 3 hours, and classified into 3 to 5 mm to obtain a catalyst (1).
[0032]
The component ratio (weight ratio) of the catalyst was CrO 3 : CeO 2 : PdO: TiO 2 = 10: 1: 0.001: 88.999.
[0033]
As a result of measuring the pore distribution of the catalyst by a gas adsorption method, the total pore volume was 0.39 cc / g, and the pore distribution was 0.01 to 0.06 μm and 0.2 to 0.9 μm. It had a peak. The pore volume of each peak measured by the gas adsorption method was 54% and 34% of the total pore volume, and the pore size distribution is shown in FIG. Further, the BET surface area was 80 m 2 / g.
[0034]
Comparative Example A catalyst was prepared according to the same method except that no phenol resin was added during the preparation of the catalyst (1). The component ratio (weight ratio) of the catalyst was CrO 3 : CeO 2 : PdO: TiO 2 = 10: 1: 0.001: 88.999.
[0035]
The catalyst has a total pore volume of 0.39 cc / g, a BET surface area of 80 m 2 / g, a pore distribution peak only in the range of 0.01 to 0.08 μm, and a 0.2 to 0.9 μm No peak was seen in the range. FIG. 2 shows the pore size distribution.
[0036]
2. Reaction Conditions and Experimental Results One liter of the above catalyst was charged into a stainless steel reactor having an inner diameter of 20 cm, and an activity test of the catalyst was carried out using a fixed-bed flow reactor under normal pressure. The reaction tube was heated in an electric furnace to set the reaction temperature to 150, 165 and 180 ° C., and the refuse incineration exhaust gas was circulated through the catalyst layer to SV 4,000 h −1 , and the DXN concentration was measured at the catalyst layer inlet and outlet. The concentration was converted to the equivalent concentration of toxicity, and the removal rate was calculated from them (results-Table 1).
[0037]
In addition, the properties of the refuse incineration exhaust gas were as follows: dust concentration: 0.01 g / Nm 3 or less, SOx concentration: 10 ppm or less, NOx concentration: 80 ppm or less, and HCl concentration: 50 ppm or less. In addition, the DXN decomposition rate was in accordance with the following definition.
DXN decomposition rate (%) =
((Entrance DXNs concentration-exit DXNs concentration) ÷ entrance DXNs concentration) x 100
[0038]
[Table 1]
Figure 2004283643
【The invention's effect】
According to the present invention, an organic chlorine compound such as dioxin can be efficiently decomposed even at a low temperature.
[Brief description of the drawings]
FIG. 1 is a graph showing a pore size distribution of pores of a catalyst obtained in an example of the present invention.
FIG. 2 is a graph showing a pore size distribution of pores of a catalyst obtained in a comparative example of the present invention.

Claims (3)

クロム、セリウムおよびパラジウムを含み、0.1μmと0.01μmの間と0.1μmを越える位置にそれぞれ孔径分布のピークを有する有機塩素化合物除去用触媒Catalyst for removing organochlorine compounds containing chromium, cerium and palladium and having pore size distribution peaks at positions between 0.1 μm and 0.01 μm and over 0.1 μm, respectively クロム、セリウムおよびパラジウムの各触媒前駆体を焼成してクロム、セリウムおよびパラジウムを含む触媒を製造するに当り、少なくともパラジウム触媒前駆体に平均粒径が0.1〜1,000μmで熱分解温度が100〜600℃の熱分解性化合物を混合して、焼成の際に該熱分解性化合物を熱分解させることを特徴とする、クロム、セリウムおよびパラジウムを含む有機塩素化合物除去用触媒の製造方法In producing a catalyst containing chromium, cerium and palladium by calcining each catalyst precursor of chromium, cerium and palladium, at least the palladium catalyst precursor has an average particle size of 0.1 to 1,000 μm and a thermal decomposition temperature of at least 0.1 to 1,000 μm. A method for producing a catalyst for removing an organochlorine compound containing chromium, cerium and palladium, comprising mixing a pyrolyzable compound at 100 to 600 ° C. and pyrolyzing the pyrolyzable compound during firing. 排ガス中の有機塩素化合物を120〜350℃の温度範囲で請求項1に記載の触媒または請求項2に記載の方法で得られた触媒に接触させることを特徴とする有機塩素化合物の除去方法A method for removing an organochlorine compound, comprising bringing an organochlorine compound in an exhaust gas into contact with the catalyst according to claim 1 or the catalyst obtained by the method according to claim 2 in a temperature range of 120 to 350 ° C.
JP2003075596A 2003-03-19 2003-03-19 Catalyst for removing organic chlorine compound and removing method Pending JP2004283643A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2019195795A (en) * 2018-05-11 2019-11-14 株式会社デンソー Catalyzer and fuel reformer
CN112169796A (en) * 2020-10-11 2021-01-05 北京科技大学 Preparation method of bimetal co-doped cerium dioxide catalyst with porous structure

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2019195795A (en) * 2018-05-11 2019-11-14 株式会社デンソー Catalyzer and fuel reformer
CN112169796A (en) * 2020-10-11 2021-01-05 北京科技大学 Preparation method of bimetal co-doped cerium dioxide catalyst with porous structure

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