JPH09313892A - Cleaning method of exhaust gas - Google Patents
Cleaning method of exhaust gasInfo
- Publication number
- JPH09313892A JPH09313892A JP9039866A JP3986697A JPH09313892A JP H09313892 A JPH09313892 A JP H09313892A JP 9039866 A JP9039866 A JP 9039866A JP 3986697 A JP3986697 A JP 3986697A JP H09313892 A JPH09313892 A JP H09313892A
- Authority
- JP
- Japan
- Prior art keywords
- exhaust gas
- silver
- oxide
- purifying material
- oxygen
- 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.)
- Pending
Links
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- Catalysts (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は窒素酸化物と過剰の
酸素を含む燃焼排ガスから、窒素酸化物を効果的に還元
除去することのできる排ガス浄化方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification method capable of effectively reducing and removing nitrogen oxides from a combustion exhaust gas containing nitrogen oxides and excess oxygen.
【０００２】[0002]
【従来の技術及び発明が解決しようとする課題】自動車
用エンジン等の内燃機関や、工場等に設置された燃焼機
器、家庭用ファンヒーター等から排出される各種の燃焼
排ガス中には、過剰の酸素とともに一酸化窒素、二酸化
窒素等の窒素酸化物が含まれている。ここで、「過剰の
酸素を含む」とは、その排ガス中に含まれる一酸化炭
素、水素、炭化水素等の未燃焼成分を燃焼するのに必要
な理論酸素量より多い酸素を含むことを意味する。ま
た、以下における窒素酸化物とは一酸化窒素及び／又は
二酸化窒素を指す。2. Description of the Related Art Excessive combustion exhaust gas emitted from internal combustion engines such as automobile engines, combustion equipment installed in factories, household fan heaters, and the like is excessive. It contains nitrogen oxides such as nitric oxide and nitrogen dioxide together with oxygen. Here, "containing excess oxygen" means that the exhaust gas contains more oxygen than the theoretical amount of oxygen necessary to burn unburned components such as carbon monoxide, hydrogen, and hydrocarbons. I do. In the following, nitrogen oxide refers to nitric oxide and / or nitrogen dioxide.
【０００３】この窒素酸化物は酸性雨の原因の一つとさ
れ、環境上の大きな問題となっている。そのため、各種
燃焼機器が排出する排ガス中の窒素酸化物を除去するさ
まざまな方法が検討されている。[0003] This nitrogen oxide is one of the causes of acid rain and is a major environmental problem. Therefore, various methods for removing nitrogen oxides in exhaust gas discharged from various combustion equipments are being studied.
【０００４】過剰の酸素を含む燃焼排ガスから窒素酸化
物を除去する方法として、特に大規模な固定燃焼装置
（工場等の大型燃焼機等）に対しては、アンモニアを用
いる選択的接触還元法が実用化されている。[0004] As a method for removing nitrogen oxides from a combustion exhaust gas containing excess oxygen, a selective catalytic reduction method using ammonia is used particularly for a large-scale fixed combustion device (a large-scale combustor in a factory or the like). Has been put to practical use.
【０００５】しかしながら、この方法においては、窒素
酸化物の還元剤として用いるアンモニアが高価であるこ
と、またアンモニアは毒性を有すること、そのために未
反応のアンモニアが排出しないように排ガス中の窒素酸
化物濃度を計測しながらアンモニア注入量を制御しなけ
ればならないこと、一般に装置が大型となること等の問
題点がある。However, in this method, ammonia used as a reducing agent for nitrogen oxides is expensive, and ammonia is toxic. Therefore, the nitrogen oxides in the exhaust gas must be removed so that unreacted ammonia is not discharged. There are problems that the amount of injected ammonia must be controlled while measuring the concentration, and that the apparatus generally becomes large.
【０００６】また、別な方法として、水素、一酸化炭
素、炭化水素等のガスを還元剤として用い、窒素酸化物
を還元する非選択的接触還元法があるが、この方法で
は、効果的な窒素酸化物の低減除去を実行するためには
排ガス中の酸素との理論反応量以上の還元剤を添加しな
ければならず、還元剤を多量に消費する欠点がある。こ
のため非選択的接触還元法は、実際上は、理論空燃比付
近で燃焼した残存酸素濃度の低い排ガスに対してのみ有
効となり、汎用性に乏しく実際的でない。As another method, there is a non-selective catalytic reduction method in which a nitrogen oxide is reduced by using a gas such as hydrogen, carbon monoxide, or a hydrocarbon as a reducing agent. In order to reduce and remove nitrogen oxides, it is necessary to add a reducing agent in an amount equal to or more than a theoretical reaction amount with oxygen in exhaust gas, and there is a disadvantage that a large amount of the reducing agent is consumed. For this reason, the non-selective catalytic reduction method is practically effective only for exhaust gas having a low residual oxygen concentration burned near the stoichiometric air-fuel ratio, and is not practical because of poor versatility.
【０００７】そこで、チタニア、アルミナなどの金属酸
化物と希土類酸化物とＲｕ、Ｒｈ、Ｐｄ、銀、Ｐｔの内
の少なくとも一種とからなる炭化水素による窒素酸化物
接触還元用触媒が提案された（特開平4-27431 号) 。し
かしながら、本発明者等の実験結果によると、この触媒
では高い空間速度における窒素酸化物除去率が低く、特
に排ガス温度の低い領域では窒素酸化物の除去が低い。
また、水分を含むような排ガスでは、窒素酸化物の除去
率が著しく低下する。Therefore, a catalyst for catalytic reduction of nitrogen oxides by a hydrocarbon comprising a metal oxide such as titania or alumina, a rare earth oxide and at least one of Ru, Rh, Pd, silver and Pt has been proposed ( JP-A-4-27431). However, according to the experimental results of the present inventors, this catalyst has a low nitrogen oxide removal rate at a high space velocity, and particularly in a region where the exhaust gas temperature is low, the nitrogen oxide removal is low.
Further, in an exhaust gas containing water, the removal rate of nitrogen oxides is significantly reduced.
【０００８】また、多孔質担体に貴金属元素及びモリブ
デンを担持し、排ガス中の水素による窒素酸化物浄化方
法が提案された（特開平8-10574 号) 。しかしながら、
この方法では排ガス温度の低い領域での窒素酸化物除去
率が高いものの、３００℃以上の温度領域での窒素酸化
物除去率が極めて低く、また一酸化炭素、不飽和炭化水
素等を含む排ガスでは窒素酸化物の除去率が著しく低下
する。Further, a method of purifying nitrogen oxides by using hydrogen in exhaust gas by supporting a noble metal element and molybdenum on a porous carrier has been proposed (JP-A-8-10574). However,
In this method, although the nitrogen oxide removal rate is high in a region where the exhaust gas temperature is low, the nitrogen oxide removal ratio in a temperature region of 300 ° C. or more is extremely low. In the case of exhaust gas containing carbon monoxide, unsaturated hydrocarbon, etc. The nitrogen oxide removal rate is significantly reduced.
【０００９】したがって、本発明の目的は、固定燃焼装
置及び酸素過剰条件で燃焼するガソリンエンジン、ディ
ーゼルエンジン等からの燃焼排ガスのように、窒素酸化
物や、一酸化炭素、水素、炭化水素等の未燃焼分に対す
る理論反応量以上の酸素を含有し、水分、硫黄酸化物な
どを含有する燃焼排ガスから、効率良く窒素酸化物を還
元除去することができる排ガス浄化方法を提供すること
である。Accordingly, it is an object of the present invention to provide a method for producing nitrogen oxides, carbon monoxide, hydrogen, hydrocarbons, and the like, such as combustion exhaust gas from a fixed combustion device and a gasoline engine, a diesel engine, or the like, which burns under oxygen excess conditions. An object of the present invention is to provide an exhaust gas purification method capable of efficiently reducing and removing nitrogen oxides from a combustion exhaust gas containing oxygen in an amount equal to or more than a theoretical reaction amount with respect to unburned components and containing moisture, sulfur oxides, and the like.
【００１０】[0010]
【課題を解決するための手段】上記課題に鑑み鋭意研究
の結果、本発明者は、多孔質無機酸化物に銀成分を担持
してなる排ガス浄化材を用い、排ガス中に還元剤として
炭化水素と水素、又は含酸素有機化合物と水素との混合
物を添加することにより、二酸化炭素、酸化硫黄、水分
の存在下でも広い温度領域で窒素酸化物を効果的に除去
することができることを発見し、本発明を完成した。Means for Solving the Problems In view of the above problems, as a result of intensive studies, the present inventor has used an exhaust gas purifying material in which a silver component is supported on a porous inorganic oxide, and used a hydrocarbon as a reducing agent in the exhaust gas. By adding hydrogen and a mixture of hydrogen or an oxygen-containing organic compound and hydrogen, it has been discovered that nitrogen oxides can be effectively removed in a wide temperature range even in the presence of carbon dioxide, sulfur oxide, and moisture, The present invention has been completed.
【００１１】すなわち、本発明の排ガス浄化方法は、多
孔質の無機酸化物に銀及び銀化合物からなる群より選ば
れる一種以上の元素及び／又は化合物０．２〜１５重量
％（金属元素換算値）を担持してなる排ガス浄化材を用
い、窒素酸化物と、共存する未燃焼成分に対する理論反
応量より多い酸素とを含む燃焼排ガスから窒素酸化物を
還元除去する方法であり、前記排ガス浄化材を排ガス導
管の途中に設置し、前記浄化材の上流側で炭化水素及び
含酸素有機化合物からなる群より選ばれた一種以上と水
素とを添加した排ガスを、２００〜５５０℃において前
記浄化材に接触させ、前記窒素酸化物を除去することを
特徴とする。That is, in the exhaust gas purifying method of the present invention, the porous inorganic oxide comprises at least one element and / or compound selected from the group consisting of silver and silver compound in an amount of 0.2 to 15% by weight (in terms of metal element). A) reducing and removing nitrogen oxides from combustion exhaust gas containing nitrogen oxides and oxygen in excess of the theoretical reaction amount for coexisting unburned components using an exhaust gas purifying material carrying the exhaust gas purifying material; Is installed in the middle of an exhaust gas conduit, and an exhaust gas obtained by adding hydrogen and one or more selected from the group consisting of hydrocarbons and oxygen-containing organic compounds on the upstream side of the purification material is added to the purification material at 200 to 550 ° C. Contacting and removing the nitrogen oxides.
【００１２】[0012]
【発明の実施の形態】以下、本発明を詳細に説明する。 ［１］排ガス浄化材 本発明で用いる排ガス浄化材は、多孔質無機酸化物に銀
及び銀化合物からなる群より選ばれる一種以上の元素及
び／又は化合物を担持してなり、広い温度領域での窒素
酸化物除去に作用する。BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. [1] Exhaust gas purifying material The exhaust gas purifying material used in the present invention comprises a porous inorganic oxide carrying one or more elements and / or compounds selected from the group consisting of silver and a silver compound. Acts on nitrogen oxide removal.
【００１３】多孔質の無機酸化物としては、アルミナ単
独、又はチタニア、シリカ、ジルコニア、酸化亜鉛、酸
化錫、酸化マグネシウム、ゼオライトのいずれかとアル
ミナとの複合又は混合酸化物を用いることができる。ア
ルミナ含有複合又は混合酸化物を用いる場合、アルミナ
の含有率を５０重量％以上とするのが好ましい。アルミ
ナ又はアルミナの複合又は混合酸化物を用いることによ
り、触媒の耐熱性及び耐久性が向上する。なお、本発明
でいう酸化錫は各種酸化状態の錫の酸化物を含み、例え
ば酸化第一錫、酸化第二錫等が挙げられる。As the porous inorganic oxide, alumina alone, or a composite or mixed oxide of alumina with any one of titania, silica, zirconia, zinc oxide, tin oxide, magnesium oxide and zeolite can be used. When an alumina-containing composite or mixed oxide is used, the alumina content is preferably 50% by weight or more. The use of alumina or a composite or mixed oxide of alumina improves the heat resistance and durability of the catalyst. The tin oxide referred to in the present invention includes tin oxide in various oxidation states, such as stannous oxide and stannic oxide.
【００１４】アルミナ等の多孔質の無機酸化物の比表面
積は１０ｍ2 ／ｇ以上であるのが好ましい。比表面積が
１０ｍ2 ／ｇ未満であると、銀成分の分散が低下し、良
好な窒素酸化物の除去が行えない。より好ましい多孔質
無機酸化物の比表面積は３０ｍ2 ／ｇ以上である。The specific surface area of a porous inorganic oxide such as alumina is preferably at least 10 m 2 / g. If the specific surface area is less than 10 m 2 / g, the dispersion of the silver component is reduced, and good removal of nitrogen oxides cannot be performed. More preferred specific surface area of the porous inorganic oxide is 30 m 2 / g or more.
【００１５】銀化合物は銀の酸化物、ハロゲン化銀、硫
酸銀及び燐酸銀等からなる群より選ばれた少なくとも一
種であり、好ましくは銀の酸化物、塩化銀及び硫酸銀の
いずれか一種以上であり、更に好ましくは銀の酸化物及
び／又は塩化銀である。銀成分の担持量は、多孔質無機
酸化物１００重量％に対して０．２〜１５重量％（銀元
素換算値）とする。０．２重量％未満では窒素酸化物の
除去率が低下する。また、１５重量％を超す量の銀成分
を担持すると還元剤自身の酸化が起きやすく、窒素酸化
物の除去率はかえって低下する。好ましい銀成分の担持
量は０．５〜１２重量％である。The silver compound is at least one selected from the group consisting of silver oxide, silver halide, silver sulfate, silver phosphate and the like, and preferably at least one of silver oxide, silver chloride and silver sulfate. And more preferably silver oxide and / or silver chloride. The supported amount of the silver component is 0.2 to 15% by weight (in terms of silver element) based on 100% by weight of the porous inorganic oxide. If the amount is less than 0.2% by weight, the removal rate of nitrogen oxides decreases. If the silver component exceeds 15% by weight, oxidation of the reducing agent itself is likely to occur, and the nitrogen oxide removal rate is rather lowered. The preferred loading of the silver component is 0.5 to 12% by weight.
【００１６】アルミナ等の無機酸化物に銀を担持する方
法としては、公知の含浸法、沈澱法等を用いることがで
きる。含浸法を用いる際、銀の硝酸塩、塩化物、硫酸
塩、炭酸塩等の水溶液又はアンモニア性水溶液に多孔質
無機酸化物を浸漬する。又は硝酸銀水溶液に多孔質無機
酸化物を浸漬し、乾燥後、塩化アンモニウム又は硫酸ア
ンモニウムの水溶液に再び浸漬する。沈澱法でハロゲン
化銀を調製するには硝酸銀とハロゲン化アンモニウムと
を反応させて、ハロゲン化銀として多孔質無機酸化物上
に沈澱させる。これを５０〜１５０℃、特に７０℃程度
で乾燥後、１００〜６００℃で段階的に昇温して焼成す
るのが好ましい。焼成は、空気中、酸素を含む窒素気流
下や水素ガス気流下で行うのが好ましい。水素ガス気流
下で行う場合には、最後に３００〜６５０℃で酸化処理
するのが好ましい。アルミナ、アルミナ系混合又は複合
酸化物への銀の担持では、ベーマイト等のアルミナ水和
物を出発物質として利用すると効果的である。As a method of supporting silver on an inorganic oxide such as alumina, a known impregnation method, precipitation method, or the like can be used. When using the impregnation method, the porous inorganic oxide is immersed in an aqueous solution of silver nitrate, chloride, sulfate, carbonate, or the like, or an aqueous ammonia solution. Alternatively, the porous inorganic oxide is immersed in an aqueous solution of silver nitrate, dried, and then immersed again in an aqueous solution of ammonium chloride or ammonium sulfate. To prepare silver halide by the precipitation method, silver nitrate and ammonium halide are reacted to precipitate silver halide on the porous inorganic oxide. After drying at 50 to 150 ° C., particularly at about 70 ° C., it is preferable to raise the temperature stepwise at 100 to 600 ° C. for firing. The calcination is preferably performed in air, under a stream of nitrogen containing oxygen or under a stream of hydrogen gas. When the treatment is performed under a hydrogen gas stream, it is preferable to perform the oxidation treatment at 300 to 650 ° C. at last. In carrying silver on alumina, an alumina-based mixed or composite oxide, it is effective to use alumina hydrate such as boehmite as a starting material.
【００１７】本発明で用いる浄化材の第一の好ましい形
態は、上記銀系触媒を浄化材基体にコートしてなる浄化
材である。浄化材の基体を形成するセラミックス材料と
しては、アルミナ、ジルコニア、チタニア−ジルコニア
等の多孔質で表面積の大きい耐熱性のものが挙げられ
る。高耐熱性が要求される場合、コージェライト、ムラ
イト、アルミナ及びその複合物等を用いるのが好まし
い。また、排ガス浄化材の基体に公知の金属材料を用い
ることもできる。A first preferred embodiment of the purifying material used in the present invention is a purifying material obtained by coating the above-mentioned silver-based catalyst on a purifying material base. Examples of the ceramic material forming the base of the purifying material include heat-resistant ceramics having a large surface area such as alumina, zirconia, and titania-zirconia. When high heat resistance is required, it is preferable to use cordierite, mullite, alumina and a composite thereof. In addition, a known metal material can be used for the base of the exhaust gas purifying material.
【００１８】排ガス浄化材の基体の形状及び大きさは、
目的に応じて種々変更できる。またその構造としては、
ハニカム構造型、フォーム型、繊維状耐火物からなる三
次元網目構造型、あるいは顆粒状、ペレット状等が挙げ
られる。ウォッシュコート法、ゾル−ゲル法、粉末法等
を用いて上記基体に銀系触媒をコートした後、焼結する
ことにより排ガス浄化材を製造することができる。The shape and size of the substrate of the exhaust gas purifying material
Various changes can be made according to the purpose. Also, as its structure,
Examples include a honeycomb structure type, a foam type, a three-dimensional network structure type made of a fibrous refractory, a granular form, a pellet form, and the like. An exhaust gas purifying material can be manufactured by coating the above-mentioned substrate with a silver-based catalyst using a wash coat method, a sol-gel method, a powder method or the like, and then sintering.
【００１９】本発明で用いる浄化材の第二の好ましい形
態は、上記銀系触媒をハニカム構造型、フォーム型、板
状、ペレット状又は顆粒状に成形したものを焼結した
後、所望形状のケーシングに充填してなる浄化材であ
る。In a second preferred embodiment of the purifying material used in the present invention, the above silver-based catalyst is formed into a honeycomb structure, foam, plate, pellet or granule, and then sintered into a desired shape. Purifying material filled in the casing.
【００２０】なお、浄化材の形態を上述した第一の好ま
しい形態とする場合、浄化材基体上に設ける銀系触媒の
厚さは、一般に、基体材と、この触媒との熱膨張特性の
違いから制限される場合が多い。浄化材基体上に設ける
触媒の厚さを３００μｍ以下とするのがよい。このよう
な厚さとすれば、使用中に熱衝撃等で浄化材が破損する
ことを防ぐことができる。浄化材基体の表面に銀系触媒
を形成する方法は公知のウォッシュコート法等によって
行われる。When the purifying material is in the above-described first preferred embodiment, the thickness of the silver-based catalyst provided on the purifying material substrate generally depends on the difference in thermal expansion characteristics between the substrate material and this catalyst. Is often restricted from. The thickness of the catalyst provided on the purifying material base is preferably 300 μm or less. With such a thickness, it is possible to prevent the purifying material from being damaged by thermal shock or the like during use. The method of forming the silver-based catalyst on the surface of the purifying material base is performed by a known wash coat method or the like.
【００２１】また、浄化材基体の表面上に設ける銀系触
媒の量は、浄化材基体の２０〜３００ｇ／リットルとす
るのが好ましい。触媒の量が２０ｇ／リットル未満では
良好なNOx の除去が行えない。一方、触媒の量が３００
ｇ／リットルを超えると除去特性はそれほど上がらず、
圧力損失が大きくなる。より好ましくは、浄化材基体の
表面上に設ける銀系触媒を浄化材基体の５０〜２００ｇ
／リットルとする。The amount of the silver-based catalyst provided on the surface of the purifying material base is preferably 20 to 300 g / liter of the purifying material base. If the amount of the catalyst is less than 20 g / liter, good NOx removal cannot be performed. On the other hand, when the amount of the catalyst is 300
When the amount exceeds g / liter, the removal characteristics do not increase so much.
Pressure loss increases. More preferably, the silver-based catalyst provided on the surface of the purifying material base is 50 to 200 g of the purifying material base.
/ Liter.
【００２２】上述した構成の浄化材を用いれば、２００
〜５５０℃の広い温度領域において、水分１０％程度を
含む排ガスでも、良好な窒素酸化物の除去を行うことが
できる。If the purifying material having the above configuration is used, 200
In a wide temperature range of up to 550 ° C., good removal of nitrogen oxides can be performed even with exhaust gas containing about 10% of water.
【００２３】［２］排ガス浄化方法 次に、本発明の方法について説明する。まず、上記排ガ
ス浄化材を排ガス導管の途中に設置する。[2] Exhaust gas purification method Next, the method of the present invention will be described. First, the exhaust gas purifying material is installed in the middle of the exhaust gas conduit.
【００２４】排ガス中には、残留炭化水素としてエチレ
ン、プロピレン等がある程度は含まれるが、一般に排ガ
ス中のNOx を還元するのに十分な量ではないので、外部
から還元剤として排ガス中に導入する。還元剤の導入位
置は、浄化材を設置した位置より上流側である。Although the exhaust gas contains ethylene, propylene and the like to some extent as residual hydrocarbons, it is generally not enough to reduce NOx in the exhaust gas, so it is introduced into the exhaust gas as a reducing agent from outside. . The position where the reducing agent is introduced is upstream of the position where the purifying material is installed.
【００２５】本発明では、還元剤として炭化水素及び含
酸素有機化合物からなる群より選ばれた一種以上と水素
とを混合して用いる。炭化水素及び／又は含酸素有機化
合物だけでは、窒素酸化物の除去率が十分ではないだけ
でなく、硫黄酸化物、水分などを含有する排ガスでは窒
素酸化物の除去率の低下が著しい。一方、水素だけで
は、窒素酸化物除去効果がほとんどない。In the present invention, one or more selected from the group consisting of hydrocarbons and oxygen-containing organic compounds are mixed with hydrogen as the reducing agent. Not only hydrocarbons and / or oxygen-containing organic compounds are not sufficient in the removal rate of nitrogen oxides, but also in exhaust gas containing sulfur oxides and water, the reduction rate of nitrogen oxides is remarkably reduced. On the other hand, hydrogen alone has almost no nitrogen oxide removing effect.
【００２６】炭化水素としては、標準状態でガス状又は
液体状のアルカン、アルケン及び／又はアルキンを用い
ることができる。特にアルカン又はアルケンの場合では
炭素数２以上が好ましい。標準状態で液体状の炭化水素
としては、具体的に、軽油、セタン、ヘプタン、灯油、
ガソリン等の炭化水素が挙げられる。その中でも、沸点
５０〜３５０℃の炭化水素が特に好ましい。含酸素有機
化合物として、アルコール、アルデヒド、ケトン等が挙
げられ、好ましくはエタノール、イソプロピルアルコー
ル等の炭素数２以上のアルコール類である。As the hydrocarbon, alkanes, alkenes and / or alkynes in a gaseous or liquid state under standard conditions can be used. In particular, in the case of an alkane or alkene, it preferably has 2 or more carbon atoms. Specific examples of hydrocarbons that are liquid in the standard state include light oil, cetane, heptane, kerosene,
And hydrocarbons such as gasoline. Among them, hydrocarbons having a boiling point of 50 to 350 ° C are particularly preferable. Examples of the oxygen-containing organic compound include alcohols, aldehydes, and ketones, and are preferably alcohols having 2 or more carbon atoms such as ethanol and isopropyl alcohol.
【００２７】外部から導入する還元剤の量は、重量比
（添加する還元剤の重量／排ガス中の窒素酸化物の重
量）が０．１〜５となるようにするのが好ましい。この
重量比が０．１未満であると、窒素酸化物の除去率が大
きくならない。一方、５を超えると、燃費悪化につなが
る。また、炭化水素及び含酸素有機化合物からなる群よ
り選ばれた一種以上の有機化合物と水素との重量比は
１：１〜２００：１とする。有機化合物と水素との重量
比が１：１未満で、水素過剰な場合では、高温側での窒
素酸化物除去率が低下し、逆に重量比が２００：１を超
えて、有機化合物過剰な場合では、低温側での窒素酸化
物除去率が低下する。好ましい有機化合物と水素との重
量比は２：１〜１００：１である。The amount of the reducing agent introduced from the outside is preferably such that the weight ratio (the weight of the reducing agent to be added / the weight of the nitrogen oxides in the exhaust gas) is 0.1 to 5. If the weight ratio is less than 0.1, the removal rate of nitrogen oxides does not increase. On the other hand, if it exceeds 5, fuel efficiency will be degraded. The weight ratio of one or more organic compounds selected from the group consisting of hydrocarbons and oxygen-containing organic compounds to hydrogen is from 1: 1 to 200: 1. If the weight ratio of the organic compound to hydrogen is less than 1: 1 and the amount of hydrogen is excessive, the removal rate of nitrogen oxides on the high temperature side decreases, and if the weight ratio exceeds 200: 1, the excess In some cases, the nitrogen oxide removal rate on the low temperature side decreases. The preferred weight ratio of organic compound to hydrogen is 2: 1 to 100: 1.
【００２８】本発明では、還元剤による窒素酸化物の還
元除去を効率的に進行させるために、浄化材の空間速度
は 150,000ｈ-1以下、好ましくは 100,000ｈ-1以下とす
る。[0028] In the present invention, in order to advance the reduction removal of nitrogen oxides with a reducing agent efficiently, the space velocity of the cleaning member is 150,000H -1 or less, preferably 100,000 h -1 or less.
【００２９】また、本発明では、還元剤と窒素酸化物と
が反応する部位である浄化材設置部位における排ガスの
温度を２００〜５５０℃に保つ。排ガスの温度が２００
℃未満であると還元剤と窒素酸化物との反応が進行せ
ず、良好な窒素酸化物の除去を行うことができない。一
方、５５０℃を超す温度とすると還元剤自身の燃焼が始
まり、窒素酸化物の還元除去が行えない。好ましい排ガ
ス温度は２５０〜５００℃である。Also, in the present invention, the temperature of the exhaust gas at the purifying material installation site where the reducing agent reacts with the nitrogen oxide is kept at 200 to 550 ° C. Exhaust gas temperature is 200
If the temperature is lower than 0 ° C., the reaction between the reducing agent and the nitrogen oxide does not proceed, and good removal of the nitrogen oxide cannot be performed. On the other hand, if the temperature exceeds 550 ° C., combustion of the reducing agent itself starts, and reduction and removal of nitrogen oxides cannot be performed. The preferred exhaust gas temperature is 250-500 ° C.
【００３０】[0030]
【実施例】本発明を以下の具体的実施例によりさらに詳
細に説明する。実施例１ 市販のγ−アルミナ粉末（比表面積２００ｍ2 ／ｇ）に
硝酸銀水溶液を用いて２重量％（金属元素換算値）の銀
を担持し、乾燥後、空気中で段階的に６００℃まで焼成
して、銀触媒を調製した。銀触媒にバインダー（アルミ
ナゾルバインダー）を加えて混練し、乾燥させた後空気
中で６００℃まで段階的に焼成した後、粉砕し、平均粒
径３ｍｍのペレットに成形し、排ガス浄化材を調製し
た。The present invention will be described in more detail with reference to the following specific examples. Example 1 A commercially available γ-alumina powder (specific surface area: 200 m 2 / g) was loaded with 2% by weight (in terms of metal element) of silver using an aqueous silver nitrate solution, dried, and gradually heated to 600 ° C. in air. By calcining, a silver catalyst was prepared. A binder (alumina sol binder) was added to the silver catalyst, kneaded, dried, and fired stepwise in the air to 600 ° C., pulverized and formed into pellets having an average particle diameter of 3 mm to prepare an exhaust gas purifying material. .
【００３１】反応管内に上記排ガス浄化材５ｇをセット
し、表１に示す組成のガス（一酸化窒素、酸素、二酸化
炭素、水素、プロピレン、窒素及び水分）を毎分２リッ
トル（標準状態）の流量で流して（浄化材の見かけ空間
速度は約１２，８００ｈ-1である。）、反応管内の排ガ
ス温度を２００〜５５０℃の範囲に保ち、窒素酸化物の
還元除去を行った。5 g of the above exhaust gas purifying material was set in a reaction tube, and a gas (nitrogen monoxide, oxygen, carbon dioxide, hydrogen, propylene, nitrogen and water) having a composition shown in Table 1 was supplied at a rate of 2 liters per minute (standard state). By flowing at a flow rate (the apparent space velocity of the purifying material was about 12,800 h -1 ), the temperature of the exhaust gas in the reaction tube was kept in the range of 200 to 550 ° C., and nitrogen oxides were reduced and removed.
【００３２】反応管通過後のガスの窒素酸化物の濃度を
化学発光式窒素酸化物分析計により測定し、窒素酸化物
除去率を求めた。結果を表４に示す。The concentration of nitrogen oxides in the gas after passing through the reaction tube was measured with a chemiluminescent nitrogen oxide analyzer to determine the nitrogen oxide removal rate. Table 4 shows the results.
【００３３】 表１ 成分 濃度 一酸化窒素 500 ppm 酸素 10 容量％ 二酸化炭素 10 容量％ 水素 1000 ppm プロピレン 500 ppm 窒素 残部 水分 10 容量％（上記成分の総体積に対して）Table 1 Component concentration Nitric oxide 500 ppm Oxygen 10% by volume Carbon dioxide 10% by volume Hydrogen 1000 ppm Propylene 500 ppm Nitrogen Residual moisture 10% by volume (based on the total volume of the above components)
【００３４】実施例２ 実施例１と同じ方法で、硝酸銀水溶液を用いて粉末状シ
リカ・アルミナ（シリカ含有率５重量％、比表面積３５
０ｍ2 ／ｇ）に４重量％（金属元素換算値）の銀を担持
し、実施例１と同じ方法で焼成して、銀触媒を作製し
た。銀触媒にバインダー（アルミナゾルバインダー）を
加えて混練し、乾燥させた後空気中で６００℃まで段階
的に焼成した後、粉砕し、平均粒径３ｍｍのペレットに
成形し、排ガス浄化材を調製した。 Example 2 In the same manner as in Example 1, powdery silica-alumina (silica content 5% by weight, specific surface area 35
0 m 2 / g), 4% by weight (in terms of metal element) of silver was supported and calcined in the same manner as in Example 1 to produce a silver catalyst. A binder (alumina sol binder) was added to the silver catalyst, kneaded, dried, and fired stepwise in the air to 600 ° C., pulverized and formed into pellets having an average particle diameter of 3 mm to prepare an exhaust gas purifying material. .
【００３５】反応管内に上記排ガス浄化材５ｇをセット
した。実施例１と同様の反応条件（流速２リットル／
分、浄化材の見かけ空間速度は約１２，８００ｈ-1であ
る）で、表２に示す組成のガスを用いて評価を行った。
結果を表４に示す。5 g of the above exhaust gas purifying material was set in the reaction tube. The same reaction conditions as in Example 1 (flow rate 2 liters /
And the apparent space velocity of the purifying material was about 12,800 h -1 ), and the evaluation was performed using a gas having a composition shown in Table 2.
Table 4 shows the results.
【００３６】 表２ 成分 濃度 一酸化窒素 500 ppm 酸素 10 容量％ 二酸化炭素 10 容量％ 水素 1000 ppm プロピレン 500 ppm 二酸化硫黄 100 ppm 窒素 残部 水分 10 容量％（上記成分の総体積に対して）Table 2 Component concentration Nitric oxide 500 ppm Oxygen 10% by volume Carbon dioxide 10% by volume Hydrogen 1000 ppm Propylene 500 ppm Sulfur dioxide 100 ppm Nitrogen Residual moisture 10% by volume (based on the total volume of the above components)
【００３７】実施例３ 実施例１の排ガス浄化材１．７ｇを反応管内にセット
し、流速２リットル／分、浄化材の見かけ空間速度約３
８，４００ｈ-1の反応条件で、実施例1 と同じ方法で表
３に示す組成のガスを用いて評価を行った。結果を表４
に示す。 Example 3 1.7 g of the exhaust gas purifying material of Example 1 was set in a reaction tube, and the flow rate was 2 liter / min and the apparent space velocity of the purifying material was about 3
Evaluation was performed using the gas having the composition shown in Table 3 in the same manner as in Example 1 under the reaction conditions of 8,400 h -1 . Table 4 shows the results
Shown in
【００３８】 表３ 成分 濃度 一酸化窒素 1000 ppm 酸素 10 容量％ 二酸化炭素 10 容量％ 水素 500 ppm エタノール 1250 ppm 窒素 残部 水分 10 容量％（上記成分の総体積に対して）Table 3 Component Concentration Nitric Oxide 1000 ppm Oxygen 10% by volume Carbon dioxide 10% by volume Hydrogen 500 ppm Ethanol 1250 ppm Nitrogen Residual moisture 10% by volume (based on the total volume of the above components)
【００３９】実施例４ 実施例１と同じ方法で、硝酸銀水溶液と塩化アンモニウ
ム水溶液を用いて粉末状γ−アルミナ（比表面積２００
ｍ2 ／ｇ）に３重量％（金属元素換算値）の塩化銀を担
持し、実施例１と同じ方法で焼成して、塩化銀触媒を作
製した。塩化銀触媒にバインダー（アルミナゾルバイン
ダー）を加えて混練し、乾燥させた後空気中で６００℃
まで段階的に焼成した後、粉砕し、平均粒径３ｍｍのペ
レットに成形し、排ガス浄化材を調製した。 Example 4 In the same manner as in Example 1, a powdery γ-alumina (specific surface area: 200
(m 2 / g), 3% by weight (converted to metal element) of silver chloride was supported, and calcined in the same manner as in Example 1 to prepare a silver chloride catalyst. A binder (alumina sol binder) is added to the silver chloride catalyst, kneaded and dried, and then 600 ° C. in air.
After baking stepwise, the mixture was pulverized and formed into pellets having an average particle diameter of 3 mm to prepare an exhaust gas purifying material.
【００４０】反応管内に排ガス浄化材１．７ｇをセット
した。実施例３と同様の反応条件（流速２リットル／
分、浄化材の見かけ空間速度は約３８，４００ｈ-1であ
る）で、表３に示す組成のガスを用いて評価を行った。
結果を表４に示す。1.7 g of an exhaust gas purifying material was set in the reaction tube. The same reaction conditions as in Example 3 (flow rate 2 liters /
And the apparent space velocity of the purifying material was about 38,400 h -1 ), and the evaluation was performed using a gas having a composition shown in Table 3.
Table 4 shows the results.
【００４１】実施例５ 実施例１と同じ方法で、硝酸銀水溶液を用いて粉末状酸
化第二錫（比表面積７１ｍ2 ／ｇ）に２重量％（金属元
素換算値）の銀を担持し、実施例１と同じ方法で焼成し
て、銀触媒を作製した。銀触媒にバインダー（アルミナ
ゾルバインダー）を加えて混練し、乾燥させた後空気中
で６００℃まで段階的に焼成した後、粉砕し、平均粒径
３ｍｍのペレットに成形し、排ガス浄化材を調製した。 Example 5 In the same manner as in Example 1, 2% by weight (in terms of metal element) of silver was supported on powdered stannic oxide (specific surface area: 71 m 2 / g) using an aqueous silver nitrate solution. By calcination in the same manner as in Example 1, a silver catalyst was produced. A binder (alumina sol binder) was added to the silver catalyst, kneaded, dried, and fired stepwise in the air to 600 ° C., pulverized and formed into pellets having an average particle diameter of 3 mm to prepare an exhaust gas purifying material. .
【００４２】反応管内に上記排ガス浄化材５ｇをセット
した。実施例１と同様の反応条件（流速２リットル／
分、浄化材の見かけ空間速度は約１２，８００ｈ-1であ
る）で、表１に示す組成のガスを用いて評価を行った。
結果を表４に示す。5 g of the above exhaust gas purifying material was set in the reaction tube. The same reaction conditions as in Example 1 (flow rate 2 liters /
And the apparent space velocity of the purifying material was about 12,800 h -1 ), and the evaluation was performed using a gas having a composition shown in Table 1.
Table 4 shows the results.
【００４３】比較例１ 実施例１の排ガス浄化材５ｇを排ガスの導管にセット
し、実施例１と同様の反応条件（見かけ空間速度は約１
２，８００ｈ-1である）で、表１に示す組成のうち水素
ガス成分を除いた組成のガスを用いて評価を行った。結
果を表４に示す。 Comparative Example 1 5 g of the exhaust gas purifying material of Example 1 was set in an exhaust gas conduit, and the same reaction conditions as in Example 1 (the apparent space velocity was about 1
At 2,800 h −1 ), evaluation was performed using a gas having a composition shown in Table 1 except for a hydrogen gas component. Table 4 shows the results.
【００４４】比較例２ 実施例２の排ガス浄化材５ｇを排ガスの導管にセット
し、実施例２と同様の反応条件（見かけ空間速度は約１
２，８００ｈ-1である）で、表２に示す組成のうち水素
ガス成分を除いた組成のガスを用いて評価を行った。結
果を表４に示す。 Comparative Example 2 5 g of the exhaust gas purifying material of Example 2 was set in an exhaust gas conduit, and the same reaction conditions as in Example 2 (apparent space velocity was about 1
At 2,800 h −1 ), the evaluation was performed using a gas having a composition shown in Table 2 excluding the hydrogen gas component. Table 4 shows the results.
【００４５】比較例３ 実施例４の排ガス浄化材１．７ｇを排ガスの導管にセッ
トし、実施例４と同様の反応条件（見かけ空間速度は約
３８，４００ｈ-1である）で、表３に示す組成のうち水
素ガス成分を除いた組成のガスを用いて評価を行った。
結果を表４に示す。 Comparative Example 3 1.7 g of the exhaust gas purifying material of Example 4 was set in an exhaust gas conduit, and under the same reaction conditions as in Example 4 (apparent space velocity was about 38,400 h -1 ), Table 3 The evaluation was performed using a gas having a composition excluding the hydrogen gas component among the compositions shown in FIG.
Table 4 shows the results.
【００４６】 表４ 排ガス温度（℃） 例No. 200 250 300 350 400 450 500 550 実施例１ 15.3 21.6 29.4 37.5 49.6 64.6 59.4 23.2 実施例２ 25.6 30.4 43.4 54.5 57.0 56.1 49.1 21.5 実施例３ 38.9 45.6 89.8 95.2 98.2 94.9 67.6 50.4 実施例４ 37.8 43.8 86.5 92.7 96.8 97.9 69.8 55.5 実施例５ 18.4 23.8 38.4 42.3 52.4 64.0 55.0 22.5 比較例１ 0.2 1.0 1.4 3.5 20.4 56.9 59.4 25.9 比較例２ 1.4 2.4 7.9 21.3 43.5 50.4 45.7 25.9 比較例３ 16.6 20.4 36.8 89.8 97.5 95.2 73.0 53.2 Table 4 Exhaust gas temperature (° C) Example No. 200 250 300 350 400 450 500 550 Example 1 15.3 21.6 29.4 37.5 49.6 64.6 59.4 23.2 Example 2 25.6 30.4 43.4 54.5 57.0 56.1 49.1 21.5 Example 3 38.9 45.6 89.8 95.2 98.2 94.9 67.6 50.4 Example 4 37.8 43.8 86.5 92.7 96.8 97.9 69.8 55.5 Example 5 18.4 23.8 38.4 42.3 52.4 64.0 55.0 22.5 Comparative Example 1 0.2 1.0 1.4 3.5 20.4 56.9 59.4 25.9 Comparative Example 2 1.4 2.4 7.9 21.3 43.5 50.4 45.7 25.9 Comparative Example 3 16.6 20.4 36.8 89.8 97.5 95.2 73.0 53.2
【００４７】表４からわかるように、水素を添加しなか
った比較例１〜３に比べて、炭化水素、含酸素有機化合
物と水素とを同時に用いた実施例１〜５では広い排ガス
温度領域で、特に低い温度領域で窒素酸化物の良好な除
去がみられた。As can be seen from Table 4, as compared with Comparative Examples 1 to 3 in which no hydrogen was added, Examples 1 to 5 in which a hydrocarbon, an oxygen-containing organic compound and hydrogen were used simultaneously had a wider exhaust gas temperature range. In particular, good removal of nitrogen oxides was observed in a low temperature range.
【００４８】[0048]
【発明の効果】以上詳述したように、本発明の排ガス浄
化方法を用いれば、広い温度領域において過剰の酸素を
含む排ガス中の窒素酸化物を効率良く除去することがで
きる。本発明の排ガス浄化方法は、各種燃焼機、自動車
等の排ガス中の窒素酸化物除去に広く利用することがで
きる。As described in detail above, the use of the exhaust gas purifying method of the present invention makes it possible to efficiently remove nitrogen oxides in exhaust gas containing excess oxygen in a wide temperature range. INDUSTRIAL APPLICABILITY The exhaust gas purifying method of the present invention can be widely used for removing nitrogen oxides from exhaust gas of various combustors, automobiles, and the like.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 浮須 祐二 茨城県つくば市小野川16番３ 工業技術院 資源環境技術総合研究所内 (72)発明者 吉田 清英 埼玉県熊谷市末広四丁目14番１号 株式会 社リケン熊谷事業所内 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yuji Ukisu 16-3 Onogawa, Tsukuba, Ibaraki Pref. National Institute of Advanced Industrial Science and Technology (72) Inventor Kiyohide Yoshida 4-1-1, Suehiro, Kumagaya, Saitama Rikken Kumagaya Office
Claims (6)
らなる群より選ばれる一種以上の元素及び／又は化合物
０．２〜１５重量％（金属元素換算値）を担持してなる
排ガス浄化材を用い、窒素酸化物と、共存する未燃焼成
分に対する理論反応量より多い酸素とを含む燃焼排ガス
から窒素酸化物を還元除去する排ガス浄化方法におい
て、前記排ガス浄化材を排ガス導管の途中に設置し、前
記浄化材の上流側で炭化水素及び含酸素有機化合物から
なる群より選ばれた一種以上と水素とを添加した排ガス
を、２００〜５５０℃において前記浄化材に接触させ、
前記窒素酸化物を除去することを特徴とする排ガス浄化
方法。An exhaust gas purification comprising a porous inorganic oxide carrying 0.2 to 15% by weight (in terms of a metal element) of one or more elements and / or compounds selected from the group consisting of silver and silver compounds. In the exhaust gas purification method for reducing and removing nitrogen oxides from a combustion exhaust gas containing a nitrogen oxide and a larger amount of oxygen than a theoretical reaction amount of a coexisting unburned component using the material, the exhaust gas purification material is installed in the middle of an exhaust gas conduit. An exhaust gas containing at least one selected from the group consisting of hydrocarbons and oxygen-containing organic compounds and hydrogen on the upstream side of the purifying material is contacted with the purifying material at 200 to 550 ° C.
An exhaust gas purification method comprising removing the nitrogen oxides.
て、前記銀化合物は銀の酸化物、ハロゲン化銀、硫酸銀
及び燐酸銀からなる群より選ばれた少なくとも一種であ
ることを特徴とする排ガス浄化方法。2. The exhaust gas purifying method according to claim 1, wherein the silver compound is at least one selected from the group consisting of silver oxide, silver halide, silver sulfate and silver phosphate. Exhaust gas purification method.
において、前記多孔質無機酸化物は、アルミナ単独、又
はチタニア、シリカ、ジルコニア、酸化亜鉛、酸化錫、
酸化マグネシウム、ゼオライトのいずれかとアルミナと
の複合又は混合酸化物であることを特徴とする排ガス浄
化方法。3. The exhaust gas purifying method according to claim 1, wherein the porous inorganic oxide is alumina alone, or titania, silica, zirconia, zinc oxide, tin oxide,
An exhaust gas purification method comprising a composite or mixed oxide of either magnesium oxide or zeolite and alumina.
浄化方法において、前記排ガス浄化材がセラミックス製
又は金属製の基体の表面にコートされていることを特徴
とする排ガス浄化方法。4. The exhaust gas purifying method according to claim 1, wherein the exhaust gas purifying material is coated on a surface of a ceramic or metal substrate.
浄化方法において、前記排ガス浄化材がハニカム型、フ
ォーム型、板状、ペレット状、顆粒状のいずれかに成形
されていることを特徴とする排ガス浄化方法。5. The exhaust gas purifying method according to claim 1, wherein the exhaust gas purifying material is formed into any one of a honeycomb type, a foam type, a plate shape, a pellet shape, and a granular shape. Characteristic exhaust gas purification method.
浄化方法において、前記炭化水素及び含酸素有機化合物
からなる群より選ばれた一種以上と水素との重量比は２
００：１〜１：１であることを特徴とする排ガス浄化方
法。6. The exhaust gas purification method according to claim 1, wherein the weight ratio of hydrogen to one or more selected from the group consisting of hydrocarbons and oxygen-containing organic compounds is 2 or more.
A method for purifying exhaust gas, wherein the ratio is from 00: 1 to 1: 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9039866A JPH09313892A (en) | 1996-02-23 | 1997-02-07 | Cleaning method of exhaust gas |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6170496 | 1996-02-23 | ||
| JP8-61704 | 1996-02-23 | ||
| JP9039866A JPH09313892A (en) | 1996-02-23 | 1997-02-07 | Cleaning method of exhaust gas |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH09313892A true JPH09313892A (en) | 1997-12-09 |
Family
ID=26379277
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP9039866A Pending JPH09313892A (en) | 1996-02-23 | 1997-02-07 | Cleaning method of exhaust gas |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH09313892A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009112948A (en) * | 2007-11-06 | 2009-05-28 | Honda Motor Co Ltd | Adsorption removing agent of nitrogen oxide, and this adsorption removing method using the same |
| JP2010000440A (en) * | 2008-06-19 | 2010-01-07 | Honda Motor Co Ltd | Exhaust gas treatment catalyst and exhaust gas treatment apparatus using the same |
-
1997
- 1997-02-07 JP JP9039866A patent/JPH09313892A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009112948A (en) * | 2007-11-06 | 2009-05-28 | Honda Motor Co Ltd | Adsorption removing agent of nitrogen oxide, and this adsorption removing method using the same |
| JP2010000440A (en) * | 2008-06-19 | 2010-01-07 | Honda Motor Co Ltd | Exhaust gas treatment catalyst and exhaust gas treatment apparatus using the same |
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