JP3217602B2 - Method for activating catalyst for purifying exhaust gas of internal combustion engine - Google Patents
Method for activating catalyst for purifying exhaust gas of internal combustion engineInfo
- Publication number
- JP3217602B2 JP3217602B2 JP18960794A JP18960794A JP3217602B2 JP 3217602 B2 JP3217602 B2 JP 3217602B2 JP 18960794 A JP18960794 A JP 18960794A JP 18960794 A JP18960794 A JP 18960794A JP 3217602 B2 JP3217602 B2 JP 3217602B2
- Authority
- JP
- Japan
- Prior art keywords
- reducing agent
- exhaust gas
- catalyst
- activating
- supplied
- 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.)
- Expired - Lifetime
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2610/00—Adding substances to exhaust gases
- F01N2610/03—Adding substances to exhaust gases the substance being hydrocarbons, e.g. engine fuel
Description
【０００１】[0001]
【産業上の利用分野】本発明は、内燃機関排気ガス浄化
用触媒の活性化方法に関するものである。詳しくは、内
燃機関排ガス中の有害成分のうち、特に窒素酸化物（Ｎ
Ｏｘ）を低減する触媒の活性を高めることにより、内燃
機関排ガス中のＮＯｘを効率よく除去する方法に関する
ものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for activating an exhaust gas purifying catalyst for an internal combustion engine. Specifically, among the harmful components in the exhaust gas of the internal combustion engine, in particular, nitrogen oxides (N
The present invention relates to a method for efficiently removing NOx in exhaust gas of an internal combustion engine by increasing the activity of a catalyst for reducing Ox).
【０００２】[0002]
【従来の技術】大気中のＮＯｘは、光化学スモッグや酸
性雨の原因となる。ＮＯｘ発生源の一つであるディーゼ
ル車からのＮＯｘの排出が社会的な問題となっており、
今後排出量に関して法規制を行う方向で検討が進められ
ている。そこで排気ガス浄化触媒の開発が進められてい
る。従来、ガソリンエンジンの排気ガスを浄化するため
に三元触媒が用いられている。ガソリンエンジンにおい
ては、排気ガス中に酸素はほとんど残っておらず、未燃
焼の炭化水素や一酸化炭素でＮＯｘを効率よく還元でき
た。しかし、ディーゼルエンジンの排ガスにおいてはそ
のエンジン特性から酸素が大幅に過剰であり、また量論
的にＮＯｘに比較して炭化水素類、一酸化炭素等の還元
剤の排出が少ないため、通常の三元触媒ではＮＯｘはほ
とんど低減できない。2. Description of the Related Art Atmospheric NOx causes photochemical smog and acid rain. The emission of NOx from diesel vehicles, one of the sources of NOx, has become a social problem.
In the future, studies are under way to regulate emissions. Therefore, development of an exhaust gas purifying catalyst is being promoted. Conventionally, a three-way catalyst has been used for purifying exhaust gas of a gasoline engine. In the gasoline engine, almost no oxygen remained in the exhaust gas, and NOx could be efficiently reduced by unburned hydrocarbons and carbon monoxide. However, the exhaust gas of a diesel engine has a large excess of oxygen due to its engine characteristics, and stoichiometrically emits less reducing agents such as hydrocarbons and carbon monoxide than NOx. NOx can hardly be reduced by the original catalyst.
【０００３】ディーゼルエンジン排気ガスやガソリンリ
ーンバーンエンジンの排気ガスのように、酸素を多く含
む排気ガス中のＮＯｘを除去するのにも有効な触媒とし
ては、例えば特開昭６３−１００９１９号に記載されて
いるように、銅−ゼオライト触媒が提案されている。し
かしながら、この触媒は耐熱性に劣り、また硫黄酸化物
により被毒されやすいという問題点がある。As a catalyst effective for removing NOx in exhaust gas containing a large amount of oxygen, such as diesel engine exhaust gas and gasoline lean burn engine exhaust gas, for example, a catalyst described in JP-A-63-100919 is described. As mentioned, copper-zeolite catalysts have been proposed. However, this catalyst has problems in that it has poor heat resistance and is easily poisoned by sulfur oxides.
【０００４】また、例えば、特開平５−１３７９６３号
に記載の方法のように、白金を主触媒として用いる方法
も提案されている。しかしながら、このような白金含有
触媒はＳＯ2 を酸化する活性が強いため、ディーゼルエ
ンジン排気ガスの処理に用いると、ＳＯ2 の酸化によっ
て硫酸塩類を増加させるため排気ガス中の微粒子物質を
増加させてしまうという問題があった。また製造直後に
はＮＯｘ分解能力を有している触媒でも、短時間使用の
うちにその活性が低下するという現象がある。この原因
ははっきりしないが例えば触媒表面が酸化され失活した
り軽油に含まれる硫黄分が触媒を被毒するものと推定さ
れる。Further, a method using platinum as a main catalyst has been proposed, for example, as described in Japanese Patent Application Laid-Open No. 5-137983. However, since such a platinum-containing catalyst has a strong activity of oxidizing SO 2 , when it is used for treating a diesel engine exhaust gas, the sulfates are increased by oxidizing the SO 2 , so that the particulate matter in the exhaust gas is increased. There was a problem that it would. Immediately after production, there is a phenomenon that the activity of a catalyst having NOx decomposing ability is reduced in a short period of use. Although the cause is not clear, it is assumed that, for example, the catalyst surface is oxidized and deactivated, and sulfur contained in light oil poisons the catalyst.
【０００５】このように、現在のところＮＯｘを有効に
除去できる触媒は開発されていないのが現状である。As described above, a catalyst capable of effectively removing NOx has not been developed at present.
【０００６】[0006]
【発明が解決しようとする課題】したがって、本発明の
目的は、内燃機関排ガス浄化用触媒の活性化方法を提供
することにある。SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for activating an exhaust gas purifying catalyst for an internal combustion engine.
【０００７】本発明の他の目的は、内燃機関から排出さ
れる、常に空燃比が酸素過剰である排気ガス中のＮＯｘ
を触媒を用いて浄化する方法において、排気ガス中の空
燃比が常に酸素過剰の状態を保つ範囲で還元剤を排気ガ
ス中に供給することにより触媒を活性化し、排気ガス中
のＮＯｘを効率よく浄化する方法を提供することにあ
る。[0007] Another object of the present invention is to provide a fuel cell system comprising:
In the method of purifying with a catalyst, the catalyst is activated by supplying a reducing agent into the exhaust gas within a range where the air-fuel ratio in the exhaust gas always keeps the state of excess oxygen, and the NOx in the exhaust gas is efficiently removed. It is to provide a method of purifying.
【０００８】ここで酸素過剰の状態とは、排気ガス中の
未燃の炭化水素等や一酸化炭素および供給した還元剤が
排気ガス中の酸素と完全に反応したとしてもなおかつ排
気ガス中に酸素が残存する状態のことをいう。完全に酸
化された場合、メタンであればその２倍量の酸素を消費
し、一酸化炭素であればその０．５倍量の酸素を消費す
るため、例えば、排気ガス中の酸素濃度が８容量％。一
酸化炭素濃度が３００ｐｐｍであれば、一酸化炭素は完
全に酸化された場合１５０ｐｐｍの酸素を消費するた
め、残り７９８５０ｐｐｍの酸素と完全に反応するため
にはメタン換算で３．９９容量％（３９９２５ｐｐｍ）
の還元剤が必要となり、排気ガス中に含まれれている炭
化水素等の還元剤の濃度がメタン換算で３９９２５ｐｐ
ｍ未満の場合は酸素過剰の状態となる。Here, the state of oxygen excess means that unburned hydrocarbons and the like in the exhaust gas, carbon monoxide and the supplied reducing agent completely react with the oxygen in the exhaust gas and still contain oxygen in the exhaust gas. Refers to the state where remains. When completely oxidized, methane consumes twice the amount of oxygen and carbon monoxide consumes 0.5 times the amount of oxygen. capacity%. If the concentration of carbon monoxide is 300 ppm, if carbon monoxide is completely oxidized, it consumes 150 ppm of oxygen. In order to completely react with the remaining 79850 ppm of oxygen, 3.99% by volume in terms of methane (39925 ppm) )
Is required, and the concentration of the reducing agent such as hydrocarbons contained in the exhaust gas is 39925 pp in terms of methane.
If it is less than m, an oxygen excess state results.
【０００９】[0009]
【課題を解決するための手段】これらの諸目的は、内燃
機関から排出されかつ常に空燃比が酸素過剰である排気
ガス中のＮＯｘを触媒を用いて浄化する方法において、
該排気ガス中の空燃比が常に酸素過剰の状態を保つ範囲
で、かつ還元剤を排気ガス中に供給しない時間が還元剤
を排気ガス中に供給する時間の５〜１０，０００倍の割
合で還元剤を定期的に該排気ガスに供給することを特徴
とする白金、ロジウム、パラジウム、銅および鉄よりな
る群から選ばれた少なくとも１種のものを活性成分とし
て含有してなる触媒の活性化方法により達成される。SUMMARY OF THE INVENTION An object of the present invention is to provide a method for purifying NOx in exhaust gas discharged from an internal combustion engine and having an air-fuel ratio that is always in excess of oxygen using a catalyst.
A time period during which the air-fuel ratio in the exhaust gas always keeps the state of excess oxygen, and a period in which the reducing agent is not supplied to the exhaust gas is a reducing agent.
5 to 10,000 times the time for supplying gas into exhaust gas
A catalyst comprising at least one selected from the group consisting of platinum, rhodium, palladium, copper and iron as an active ingredient , wherein the reducing agent is supplied to the exhaust gas periodically. Achieved by the activation method.
【００１０】本発明はまた、該還元剤を排気ガス中に供
給する時に共存する酸素濃度が、該排気ガスの２〜２０
容量％、好ましくは４〜２０容量％である前記触媒の活
性方法である。本発明はまた、該還元剤が炭素を含有す
るものである前記触媒の活性化方法である。本発明はさ
らに、排気ガス中に供給するときの還元剤の濃度が、該
排気ガスに対してメタン換算で５００ｐｐｍ〜１０％、
好ましくは５０００ｐｐｍ〜５％である前記触媒の活性
化方法である。本発明はまた供給される還元剤の量が平
均して燃料消費量の０．０１〜３重量％である前記触媒
の活性化方法である。本発明はまた、該還元剤が水素、
飽和炭化水素類、不飽和炭化水素類、芳香族炭化水素
類、およびアルコール類よりなる群から選ばれた少なく
とも１種のものを含む還元剤である前記触媒の活性化方
法である。本発明はさらに該還元剤が、軽油、灯油、液
化石油ガス、ガソリン、メタノールおよびエタノールよ
りなる群から選ばれた少なくとも１種のものを含む還元
剤である前記触媒の活性化方法である。本発明はまた、
触媒活性成分が、耐火性三次元構造体に担持されてなる
前記触媒の活性化方法である。本発明はさらに、該排気
ガスがディーゼルエンジン由来のものである前記触媒の
活性化方法である。本発明はまた、供給される還元剤の
平均のＴＨＣ／ＮＯｘの比が０．０１〜３である前記触
媒の活性化方法である。The present invention also provides that the concentration of oxygen coexisting when the reducing agent is supplied into the exhaust gas is 2 to 20% of the exhaust gas.
% Of the catalyst, preferably 4 to 20% by volume. The present invention is also the method for activating the catalyst, wherein the reducing agent contains carbon. The present invention further provides the exhaust gas wherein the concentration of the reducing agent is 500 ppm to 10% in terms of methane with respect to the exhaust gas,
The method for activating the catalyst, which is preferably 5000 ppm to 5% . The present invention is also the method for activating the catalyst, wherein the amount of the supplied reducing agent is 0.01 to 3% by weight of the fuel consumption on average. The present invention also provides that the reducing agent is hydrogen,
The method for activating the catalyst, which is a reducing agent including at least one selected from the group consisting of saturated hydrocarbons, unsaturated hydrocarbons, aromatic hydrocarbons, and alcohols. The present invention further provides the method for activating a catalyst, wherein the reducing agent is a reducing agent containing at least one selected from the group consisting of gas oil, kerosene, liquefied petroleum gas, gasoline, methanol and ethanol. The invention also provides
The method for activating a catalyst, wherein the catalytically active component is supported on a refractory three-dimensional structure. The present invention is further the method for activating the catalyst, wherein the exhaust gas is derived from a diesel engine. The present invention is also the method for activating the catalyst, wherein the average THC / NOx ratio of the supplied reducing agent is 0.01 to 3.
【００１１】なお、ここでＴＨＣとは、供給する還元剤
のメタン換算の容量濃度（ｐｐｍ）であり、これと内燃
機関排気ガス中に含まれるＮＯｘの容量濃度（ｐｐｍ）
との比をとったものがＴＨＣ／ＮＯｘの比である。Here, THC is the methane-converted capacity concentration (ppm) of the supplied reducing agent, and this and the NOx capacity concentration (ppm) contained in the exhaust gas of the internal combustion engine.
Is the ratio of THC / NOx.
【００１２】[0012]
【作用】本発明においてＮＯｘ浄化の対象となる排気ガ
スは、内燃機関から排出されるものでかつ常に空燃比が
酸素過剰である排気ガスである。具体的にはディーゼル
エンジンからの排気ガスや常にリーン条件で運転される
ガソリンエンジンからの排気ガスなどである。本発明に
おいては、排気ガス中に還元剤を供給することにより触
媒のＮＯｘ分解能力を高めることができ、しかも触媒が
活性化された状態は還元剤の供給を中止してもしばらく
の間継続する。In the present invention, the exhaust gas to be subjected to NOx purification is exhaust gas which is discharged from the internal combustion engine and whose air-fuel ratio is always excessive in oxygen. Specifically, it is an exhaust gas from a diesel engine or an exhaust gas from a gasoline engine that is always operated under lean conditions. In the present invention, the NOx decomposing ability of the catalyst can be increased by supplying the reducing agent into the exhaust gas, and the activated state of the catalyst continues for a while even after the supply of the reducing agent is stopped. .
【００１３】しかしながら、還元剤供給による触媒の活
性化効果は、数分から数時間の間に失われるため、還元
剤の供給は定期的に行う必要がある。本発明において還
元剤の供給を停止したにもかかわらずＮＯｘを分解でき
る機構については明確ではないが、例えば、比較的高濃
度の炭化水素が触媒に接触することにより、触媒表面が
還元され、一時的にＮＯｘ分解能力が高められるものと
推定できる。しかし、その活性化は一時的なものであ
り、その後酸素過剰の排気ガスにさらされるている間に
触媒表面が徐々に酸化され、やがて触媒が活性化する前
の状態に戻るものと推定される。However, the effect of activating the catalyst due to the supply of the reducing agent is lost within a few minutes to several hours, so that the supply of the reducing agent must be performed periodically. In the present invention, the mechanism by which NOx can be decomposed even though the supply of the reducing agent is stopped is not clear, but, for example, when a relatively high concentration of hydrocarbon comes into contact with the catalyst, the catalyst surface is reduced, and It can be presumed that the NOx decomposing ability can be enhanced. However, the activation is temporary, and it is presumed that the catalyst surface is gradually oxidized during the subsequent exposure to the oxygen-exhausted exhaust gas and eventually returns to the state before the catalyst was activated. .
【００１４】本発明においては、後述する実施例より明
らかなように、定常的に平均して同量の還元剤を供給し
た場合は、ＮＯｘ浄化率が大きく低下するため、単なる
ＮＯｘの還元剤による還元や、触媒に吸着されたＮＯｘ
が還元剤を供給したとき還元剤によって還元されるとい
うような機構では説明がつかない。本発明においては、
還元剤の供給を停止してもＮＯｘを分解できるため、従
来還元剤によりＮＯｘを還元する際には平均還元剤ＴＨ
Ｃ／ＮＯｘ比が３を越える量の還元剤が必要とされてい
たのに対し、本発明では平均還元剤ＴＨＣ／ＮＯｘ比が
０．０１〜３、さらに好ましくは０．０１〜１でも効率
よくＮＯｘを浄化できる。In the present invention, when the same amount of reducing agent is constantly supplied on average, the NOx purification rate is greatly reduced, as is apparent from the examples described later. Reduction or NOx adsorbed on the catalyst
Is not explained by such a mechanism that is reduced by the reducing agent when the reducing agent is supplied. In the present invention,
Since NOx can be decomposed even when the supply of the reducing agent is stopped, when reducing NOx with the conventional reducing agent, the average reducing agent TH is used.
Whereas the C / NOx ratio required a reducing agent in an amount exceeding 3, the present invention efficiently used the average reducing agent THC / NOx ratio of 0.01 to 3 and more preferably 0.01 to 1 even if the ratio was 0.01 to 1. NOx can be purified.
【００１５】本発明方法において供給する還元剤の種類
は特に限定されないが、例えば、水素、飽和炭化水素
類、不飽和炭化水素類、芳香族炭化水素類、アルコール
類等の還元剤が挙げられる。The type of reducing agent supplied in the method of the present invention is not particularly limited, and examples thereof include reducing agents such as hydrogen, saturated hydrocarbons, unsaturated hydrocarbons, aromatic hydrocarbons, alcohols and the like.
【００１６】飽和炭化水素類としては、炭素原子数１〜
３０、好ましくは１〜２０のアルカンが挙げられる。一
例を挙げると、例えばメタン、エタン、プロパン、ブタ
ン、ペンタン、ヘキサン、ヘプタン、オクタン、ノナ
ン、デカン等が挙る。これらの飽和炭化水素類は直鎖状
でも分岐状でもよい。The saturated hydrocarbons include those having 1 to 1 carbon atoms.
30, preferably 1 to 20 alkanes. For example, methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane and the like are mentioned. These saturated hydrocarbons may be linear or branched.
【００１７】またシクロヘキサンのような環状であって
もよい。It may be cyclic, such as cyclohexane.
【００１８】不飽和炭化水素類としては、炭素原子数２
〜３０、好ましくは２〜２０のアルケンが挙げられる。
一例を挙げると、例えばエチレン、プロピレン、ブデ
ン、ブタジエン、ペンテン、ペンタジエン、ヘキセン、
ヘキサジエン、ヘキサトリエン、ヘプテン、ヘプタジエ
ン、ヘプタトリエン、オクテン、オクタジエン、オクタ
トリエン等が挙げられる。これらの不飽和炭化水素類は
直鎖状であっても分岐状であってもよい。The unsaturated hydrocarbons include those having 2 carbon atoms.
To 30, preferably 2 to 20 alkenes.
For example, ethylene, propylene, butene, butadiene, pentene, pentadiene, hexene,
Hexadiene, hexatriene, heptene, heptadiene, heptatriene, octene, octadiene, octatriene and the like can be mentioned. These unsaturated hydrocarbons may be linear or branched.
【００１９】芳香族炭化水素としては、例えばベンゼ
ン、トルエン、キシレン、トリメチルベンゼン等が挙げ
られる。アルコール類としては、炭素数１〜２０、好ま
しくは１〜１０のアルコール類が挙げられる。一例を挙
げると、例えばメタノール、エタノール、プロパノー
ル、ブタノール、ペンタノール、ヘキサノール、ヘプタ
ノール、オクタノール、ノナノール、デカノール等があ
る。これらのアルコール類は直鎖状であっても分岐状で
あってもよい。As the aromatic hydrocarbon, for example, benzene, toluene, xylene, trimethylbenzene and the like can be mentioned. Examples of the alcohols include alcohols having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms. Examples include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol and the like. These alcohols may be linear or branched.
【００２０】供給する還元剤は、常温で気体または液体
のものが取り扱いが容易であり好ましい。さらに好まし
くは軽油、天然ガス、液化石油ガスＬＰＧ、ガソリン、
メタノール、エタノール等、内燃機関の燃料として搭載
している還元剤を用いれば、本発明で供給する還元剤専
用の容器が不要となりメリットは大きい。The reducing agent to be supplied is preferably gaseous or liquid at room temperature because it is easy to handle. More preferably, light oil, natural gas, liquefied petroleum gas LPG, gasoline,
If a reducing agent such as methanol or ethanol, which is mounted as a fuel for an internal combustion engine, is used, a container dedicated to the reducing agent to be supplied in the present invention is not required, and the merit is great.
【００２１】本発明において供給する還元剤の濃度は、
還元剤を排気ガス中に供給しても酸素過剰の状態が維持
される限り特に限定されないが、還元剤の濃度が低すぎ
ると触媒活性化の効果が得られず、還元剤の濃度が高す
ぎてもそれに見合うだけの効果がないことから、好まし
くはＴＨＣ濃度として５００ｐｐｍ〜１０容量％、さら
に好ましくは５０００ｐｐｍから５容量％である。ここ
でＴＨＣ濃度とは、炭化水素等の還元剤をメタンに換算
したときの濃度である。In the present invention, the concentration of the reducing agent supplied is
The supply of the reducing agent into the exhaust gas is not particularly limited as long as the state of excess oxygen is maintained.However, if the concentration of the reducing agent is too low, the effect of activating the catalyst cannot be obtained, and the concentration of the reducing agent is too high. However, since there is no effect corresponding thereto, the THC concentration is preferably 500 ppm to 10% by volume, more preferably 5000 ppm to 5% by volume. Here, the THC concentration is a concentration when a reducing agent such as a hydrocarbon is converted into methane.
【００２２】本発明において、還元剤を定期的に排気ガ
ス中に供給するサイクルが還元剤を排気ガス中に供給す
る時間に対して小さすぎると、還元剤の使用量が増え好
ましくない。また、逆に還元剤を排気ガス中に供給する
サイクルが還元剤を排気ガス中に供給する時間に対して
大きすぎると、活性化した触媒がその効果を失いＮＯｘ
の浄化効率が低下する。したがって、還元剤を排気ガス
中に供給しない時間は、還元剤を排気ガス中に供給する
時間に対して好ましくは５〜１万倍、さらに好ましくは
１００〜１０００倍である。In the present invention, if the cycle in which the reducing agent is periodically supplied to the exhaust gas is too short with respect to the time in which the reducing agent is supplied into the exhaust gas, the amount of the reducing agent used is undesirably increased. On the other hand, if the cycle of supplying the reducing agent into the exhaust gas is too large with respect to the time of supplying the reducing agent into the exhaust gas, the activated catalyst loses its effect and loses NOx.
Purification efficiency decreases. Therefore, the time during which the reducing agent is not supplied into the exhaust gas is preferably 50 to 10,000 times, more preferably 100 to 1000 times the time during which the reducing agent is supplied into the exhaust gas.
【００２３】本発明において供給する平均の還元剤の量
は特に限定されないが、燃料消費量の３重量％を越える
還元剤を供給すると経済的に不利であり、一方、燃料消
費量の０．０１重量％より少ない供給量では触媒活性化
の効果が得られないため、供給する平均の還元剤の量は
好ましくは燃料消費の０．０１〜３重量％である。In the present invention, the average amount of the reducing agent supplied is not particularly limited, but supplying a reducing agent exceeding 3% by weight of the fuel consumption is economically disadvantageous. Since an effect of activating the catalyst cannot be obtained with a supply amount of less than% by weight, the average amount of the reducing agent supplied is preferably 0.01 to 3% by weight of the fuel consumption.
【００２４】本発明において共存する酸素濃度は特に限
定されないが、酸素濃度が高すぎると触媒を活性化させ
る目的で供給した還元剤の一部が酸素により消費されて
しまい好ましくない。また、一方、酸素濃度が低すぎる
と、還元剤の定期的な供給による触媒の活性化効果が少
なくなる。このため、共存する酸素濃度は、好ましくは
２〜２０重量％、さらに好ましくは４〜２０重量であ
る。排気ガス中の酸素濃度は、エンジンでの空気と燃料
との比を変えることにより制御することが可能である
し、また、吸入した空気をバイパス等でエンジンからの
排気ガスに混入することによって排気ガス中の酸素濃度
を制御することも可能である。In the present invention, the coexisting oxygen concentration is not particularly limited. However, if the oxygen concentration is too high, part of the reducing agent supplied for the purpose of activating the catalyst is undesirably consumed by oxygen. On the other hand, if the oxygen concentration is too low, the effect of activating the catalyst by the periodic supply of the reducing agent is reduced. Therefore, the coexisting oxygen concentration is preferably 2 to 20% by weight, and more preferably 4 to 20% by weight. The oxygen concentration in the exhaust gas can be controlled by changing the ratio of air to fuel in the engine, and the exhaust gas can be controlled by mixing the intake air into the exhaust gas from the engine through a bypass or the like. It is also possible to control the oxygen concentration in the gas.
【００２５】本発明において用いる触媒に関しては特に
制限はないが、触媒の例としては、例えば白金、ロジウ
ム、パラジウム、銅、鉄等を活性成分として含むものが
挙げられる。これらの活性成分は単独で用いても良い
し、複数を組合わせて用いても良い。また、これらの活
性成分以外に助触媒としてその他の成分を含有していて
も良い。助触媒の成分に関しては特に制限はないが、一
例を挙げると、例えばナトリウム、カリウム等のアルカ
リ金属、マグネシウム、カルシウム等のアルカリ土類金
属、セリウムやイットリウム、ランタン、プラセオジム
等の希土類等が挙げられる。これらの活性成分や助触媒
は、通常耐火性三次元構造体上に耐火性無機酸化物と共
に担持されて用いられる。The catalyst used in the present invention is not particularly limited, but examples of the catalyst include those containing, for example, platinum, rhodium, palladium, copper, iron and the like as active components. These active ingredients may be used alone or in combination of two or more. In addition to these active components, other components may be contained as co-catalysts. There is no particular limitation on the components of the co-catalyst, but examples include alkali metals such as sodium and potassium, alkaline earth metals such as magnesium and calcium, and rare earths such as cerium, yttrium, lanthanum, and praseodymium. . These active components and cocatalysts are usually used by being supported together with a refractory inorganic oxide on a refractory three-dimensional structure.
【００２６】触媒成分の担持量についても特に制限はな
いが、担持量を多くしすぎると、経済的に不利であり、
また、一方少なすぎると触媒としての効果が低下する。
したがって、触媒成分の担持量としては、白金、ロジウ
ム、パラジウム等の貴金属の場合は、触媒担体１リット
ル当り好ましくは０．１〜１０ｇさらに好ましくは０．
２〜５ｇである。銅や鉄等の卑金属やその他の助触媒に
ついては、触媒担体１リットル当り好ましくは１〜５０
ｇ、さらに好ましくは２〜２５ｇである。There is no particular limitation on the amount of the catalyst component to be carried. However, if the amount is too large, it is economically disadvantageous.
On the other hand, if the amount is too small, the effect as a catalyst is reduced.
Accordingly, the loading amount of the catalyst component is preferably 0.1 to 10 g, more preferably 0.1 to 10 g per liter of the catalyst carrier in the case of a noble metal such as platinum, rhodium, and palladium.
2-5 g. For base metals such as copper and iron and other cocatalysts, preferably 1 to 50 per liter of the catalyst carrier.
g, more preferably 2 to 25 g.
【００２７】耐火性三次元構造体に関しては特に制限は
ないが、例としてはセラミックフォーム、オープンフロ
ーのセラミックハニカム、ウオールフローのハニカムモ
ノリス、オープンフローのメタルハニカム、金属発泡
体、メタルメッシュなどを用いることができる。耐火性
無機材料に関しても特に制限はないが、例として活性ア
ルミナ、シリカ、チタニア、ジルコニア等が挙げられ
る。これらの耐火性無機酸化物は、通常粉末状として使
用され、単独で用いても良いし、混合して用いてもよ
い。またさらに、セリウム、ランタン、プラセオジウ
ム、イットリウム、アルミニウム、ケイ素、チタン、ジ
ルコニウム等の溶液を２種以上混合して共沈法等で得ら
れる複合酸化物およびそれらの混合物を耐火性無機材料
として用いてもよい。The fire-resistant three-dimensional structure is not particularly limited, but examples thereof include ceramic foam, open-flow ceramic honeycomb, wall-flow honeycomb monolith, open-flow metal honeycomb, metal foam, metal mesh, and the like. be able to. There is no particular limitation on the refractory inorganic material, but examples thereof include activated alumina, silica, titania, zirconia and the like. These refractory inorganic oxides are usually used in the form of powder, and may be used alone or as a mixture. Further, a composite oxide obtained by mixing two or more kinds of solutions of cerium, lanthanum, praseodymium, yttrium, aluminum, silicon, titanium, zirconium and the like by a coprecipitation method or the like and using a mixture thereof as a refractory inorganic material. Is also good.
【００２８】本発明に用いる触媒の調製方法に特に制限
はないが、例えば下記（１）または（２）の方法によっ
て調製できる。The method for preparing the catalyst used in the present invention is not particularly limited. For example, the catalyst can be prepared by the following method (1) or (2).
【００２９】（１）耐火性無機酸化物の粉体を湿式粉砕
してスラリー化し、このスラリーに耐火性三次元構造体
を浸漬し、余分なスラリーを取り除いた後、８０〜２５
０℃、好ましくは１００〜１５０℃で乾燥し、ついで３
００〜８５０℃、好ましくは４００〜６００℃で焼成す
る。つぎに上記耐火性三次元構造体を所定量の触媒を含
有する溶液に浸漬して、余分な溶液を取り除いた後８０
〜２５０℃、好ましくは１００〜１５０℃、で乾燥し、
ついで３００〜８５０℃、好ましくは４００〜６００℃
で焼成して目的とする触媒を得る。(1) The powder of the refractory inorganic oxide is wet-pulverized to form a slurry, and the refractory three-dimensional structure is immersed in the slurry to remove excess slurry.
Dry at 0 ° C., preferably 100-150 ° C., then
Baking at 00 to 850 ° C, preferably 400 to 600 ° C. Next, the refractory three-dimensional structure is immersed in a solution containing a predetermined amount of catalyst to remove excess solution, and
Drying at ~ 250C, preferably 100-150C,
Then 300 to 850 ° C, preferably 400 to 600 ° C
To obtain the desired catalyst.
【００３０】（２）所定量の触媒を含有する溶液中に耐
火性無機酸化物粉末を投入してして含浸せしめ、スラリ
ー化し、このスラリーを３００〜８５０℃好ましくは４
００〜６００℃で焼成する。得られた粉体を湿式粉砕し
てスラリー化し、このスラリーに耐火性三次元構造体を
浸漬、余分なスラリーを取り除いた後８０〜２５０℃、
好ましくは１００〜１５０℃で乾燥し、次いで３００〜
８５０℃、好ましくは４００〜６００℃で焼成して目的
とする触媒を得る。(2) A refractory inorganic oxide powder is charged into a solution containing a predetermined amount of a catalyst, impregnated with the powder, and slurried.
Bake at 00-600 ° C. The obtained powder is wet-pulverized to form a slurry, the refractory three-dimensional structure is immersed in the slurry, and after removing excess slurry, the temperature is 80 to 250 ° C.
Preferably dried at 100-150 ° C, then 300-
Calcination at 850 ° C, preferably 400 to 600 ° C, gives the desired catalyst.
【００３１】[0031]
【実施例】以下、実施例を挙げて本発明を具体的に説明
するが、本発明は以下の実施例に限定されるものでない
ことは言うまでもない。EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but it is needless to say that the present invention is not limited to the following Examples.
【００３２】触媒Ａ調製法 比表面積が１０ｍ2 ／ｇであるチタニア粉末（ａ）１０
０ｇ、硝酸ガリウム５４．４ｇおよび硝酸カルシウム４
２．２ｇを白金１０．０ｇを含有する塩化白金酸水溶液
中に投入し、十分混合した後、１５０℃で２時間乾燥
し、さらに５００℃で１時間焼成し、白金、酸化ガリウ
ムおよび酸化カルシウムを分散担持したチタニア粉末を
得た。Method for Preparing Catalyst A Titania powder (a) 10 having a specific surface area of 10 m 2 / g
0 g, gallium nitrate 54.4 g and calcium nitrate 4
2.2 g was put into an aqueous solution of chloroplatinic acid containing 10.0 g of platinum, mixed well, dried at 150 ° C. for 2 hours, and calcined at 500 ° C. for 1 hour to remove platinum, gallium oxide and calcium oxide. A dispersed and supported titania powder was obtained.
【００３３】つぎに、この粉末１１２ｇと前記チタニア
粉末（ａ）と同じチタニア粉末８００ｇおよび比表面積
が１４５ｍ2 ／ｇであるアルミナ３２０ｇを混合し、湿
式粉砕してスラリー化した。このスラリーに横断面積１
平方インチ当り約４００個のオープンフローのガス流通
セルを有する５．６６インチ径×６．００インチ長さの
円筒状のコージライト製ハニカム担体を含浸し、余分な
スラリーを除去した後、１５０℃で２時間乾燥し、つい
で５００℃で１時間焼成した。Next, 112 g of this powder, 800 g of the same titania powder as the above-mentioned titania powder (a) and 320 g of alumina having a specific surface area of 145 m 2 / g were mixed and wet-pulverized to form a slurry. Cross-sectional area 1
After impregnating a 5.66 inch diameter x 6.00 inch length cylindrical cordierite honeycomb carrier having about 400 open flow gas flow cells per square inch, removing excess slurry, For 2 hours, and then fired at 500 ° C. for 1 hour.
【００３４】触媒Ｂ調製法 比表面積が５０ｍ2 ／ｇであるジルコニア粉末１０００
ｇを、硝酸銅３７２ｇを含有する水溶液中に投入し、十
分混合した後、１５０℃で２時間乾燥し、さらに５００
℃で１時間焼成し、銅を分散担持したジルコニア粉末を
得た。Method for Preparing Catalyst B Zirconia powder 1000 having a specific surface area of 50 m 2 / g
g was poured into an aqueous solution containing 372 g of copper nitrate, mixed well, and dried at 150 ° C. for 2 hours.
C. for 1 hour to obtain a zirconia powder carrying copper dispersed therein.
【００３５】つぎに、この粉末を湿式粉砕してスラリー
化した。このスラリーに横断面積１平方インチ当り約４
００個のオープンフローのガス流通セルを有する５．６
６インチ径×６．００インチ長さの円筒状のコージライ
ト製ハニカム担体を含浸し、余分なスラリーを除去した
後、１５０℃で２時間乾燥し、ついで５００℃で１時間
焼成した。Next, this powder was slurried by wet pulverization. Approximately 4 per square inch of cross-sectional area
5.6 with 00 open flow gas flow cells
After impregnating with a cylindrical cordierite honeycomb carrier having a diameter of 6 inches and a length of 6.00 inches, excess slurry was removed, dried at 150 ° C. for 2 hours, and fired at 500 ° C. for 1 hour.
【００３６】ＮＯｘ浄化率の評価方法 過給直噴式ディーゼルエンジン（４気筒、２８００ｃ
ｃ）、燃料として硫黄含有量が０．０５重量％である軽
油を用いた。Evaluation method for NOx purification rate Supercharged direct injection diesel engine (4 cylinders, 2800c
c) Light oil having a sulfur content of 0.05% by weight was used as a fuel.
【００３７】触媒は上記エンジンからの排気ガス管中に
取り付け、エンジン回転数２０００ｒｐｍ、所定の触媒
入口温度となるようにトルクを設定し、触媒入口温度が
十分安定した後、還元剤を定期的に触媒入口に供給しつ
つ、触媒入口および触媒出口の排気ガス中のＮＯｘ濃度
を測定してＮＯｘ浄化率を求めた。The catalyst is installed in the exhaust gas pipe from the engine, and the engine speed is set to 2000 rpm. The torque is set so as to reach a predetermined catalyst inlet temperature. After the catalyst inlet temperature is sufficiently stabilized, the reducing agent is periodically supplied. While supplying the catalyst to the catalyst inlet, the NOx concentration in the exhaust gas at the catalyst inlet and the catalyst outlet was measured to obtain the NOx purification rate.
【００３８】なお、還元剤を供給する前から排気ガス中
に含まれている未燃焼の一酸化炭素および炭化水素類の
濃度（ＴＨＣ）は、３００℃で一酸化炭素３５０ｐｐ
ｍ、ＴＨＣが１５０ｐｐｍ、４００℃では一酸化炭素が
３００ｐｐｍ、ＴＨＣが１３０ｐｐｍであった。The concentration (THC) of unburned carbon monoxide and hydrocarbons contained in the exhaust gas before the supply of the reducing agent was 350 pp at 300 ° C.
m, THC was 150 ppm, and at 400 ° C., carbon monoxide was 300 ppm and THC was 130 ppm.
【００３９】実施例１ 触媒Ａを用い、触媒入口温度３００℃、還元剤としては
軽油を用いた。還元剤を２０分間に１回、排気ガス中の
ＴＨＣ濃度が８０００ｐｐｍとなるようにして１０秒間
触媒入口に供給した。このときの還元剤の平均濃度はメ
タン換算で６３ｐｐｍ（以下、全てメタン換算濃度であ
る）、触媒入口の酸素濃度は１１容量％、触媒入口のＮ
Ｏｘ濃度は４００ｐｐｍ、平均ＴＨＣ／ＮＯｘ比は０．
１６、還元剤供給サイクルと還元剤供給時間との比は１
２０、燃料消費量に対する還元剤供給量は０．１２重量
％、平均ＮＯｘ浄化率は２５％であった。Example 1 Using catalyst A, the catalyst inlet temperature was 300 ° C., and light oil was used as the reducing agent. Once every 20 minutes, the reducing agent was supplied to the catalyst inlet for 10 seconds so that the THC concentration in the exhaust gas became 8000 ppm. At this time, the average concentration of the reducing agent is 63 ppm in terms of methane (hereinafter, all concentrations are methane equivalent), the oxygen concentration at the catalyst inlet is 11% by volume, and the N at the catalyst inlet is
The Ox concentration was 400 ppm and the average THC / NOx ratio was 0.1 ppm.
16. The ratio of the reducing agent supply cycle to the reducing agent supply time is 1
20, the reducing agent supply amount relative to the fuel consumption amount was 0.12% by weight, and the average NOx purification rate was 25%.
【００４０】実施例２ 触媒Ａを用い、触媒入口温度３００℃、還元剤としては
軽油を用いた。還元剤は２００分間に１回、排気ガス中
のＴＨＣ濃度が８０００ｐｐｍとなるようにして１０秒
間触媒入口に供給した。このときの還元剤の平均濃度は
６．３ｐｐｍ、触媒入口の酸素濃度は１１容量％、触媒
入口のＮＯｘ濃度は４００ｐｐｍ、平均ＴＨＣ／ＮＯｘ
比は０．０１、還元剤供給サイクルと還元剤供給時間と
の比は１２００、燃料消費量に対する還元剤供給量は
０．０１重量％、平均ＮＯｘ浄化率は１０％であった。Example 2 Using catalyst A, the catalyst inlet temperature was 300 ° C., and light oil was used as the reducing agent. Once every 200 minutes, the reducing agent was supplied to the catalyst inlet for 10 seconds so that the THC concentration in the exhaust gas became 8000 ppm. At this time, the average concentration of the reducing agent was 6.3 ppm, the oxygen concentration at the catalyst inlet was 11% by volume, the NOx concentration at the catalyst inlet was 400 ppm, and the average THC / NOx.
The ratio was 0.01, the ratio of the reducing agent supply cycle to the reducing agent supply time was 1200, the amount of the reducing agent supplied to the fuel consumption was 0.01% by weight, and the average NOx purification rate was 10%.
【００４１】実施例３ 触媒Ａを用い、触媒入口温度３００℃、還元剤としては
軽油を用いた。還元剤は２０分間に１回、排気ガス中の
ＴＨＣ濃度が８００ｐｐｍとなるようにして１０秒間触
媒入口に供給した。このときの還元剤の平均濃度は６．
３ｐｐｍ、触媒入口の酸素濃度は１１容量％、触媒入口
のＮＯｘ濃度は４００ｐｐｍ、平均ＴＨＣ／ＮＯｘ比は
０．０１、還元剤供給サイクルと還元剤供給時間との比
は１２０、燃料消費量に対する還元剤供給量は０．０１
重量％、平均ＮＯｘ浄化率は９％であった。Example 3 Using catalyst A, the catalyst inlet temperature was 300 ° C., and light oil was used as the reducing agent. Once every 20 minutes, the reducing agent was supplied to the catalyst inlet for 10 seconds so that the THC concentration in the exhaust gas became 800 ppm. At this time, the average concentration of the reducing agent is 6.
3 ppm, oxygen concentration at catalyst inlet 11% by volume, NOx concentration at catalyst inlet 400 ppm, average THC / NOx ratio 0.01, ratio of reducing agent supply cycle to reducing agent supply time 120, reduction to fuel consumption The agent supply amount is 0.01
% By weight, and the average NOx purification rate was 9%.
【００４２】実施例４ 触媒Ａを用い、触媒入口温度３００℃、還元剤としては
軽油を用いた。還元剤は２０分間に１回、排気ガス中の
ＴＨＣ濃度が８０００ｐｐｍとなるようにして３０秒間
触媒入口に供給した。このときの還元剤の平均濃度は１
８９ｐｐｍ、触媒入口の酸素濃度は１１容量％、触媒入
口のＮＯｘ濃度は４００ｐｐｍ、平均ＴＨＣ／ＮＯｘ比
は０．４７、還元剤供給サイクルと還元剤供給時間との
比は４０、燃料消費量に対する還元剤供給量は０．３５
重量％、平均ＮＯｘ浄化率は２５％であった。Example 4 Using catalyst A, the catalyst inlet temperature was 300 ° C., and light oil was used as the reducing agent. The reducing agent was supplied to the catalyst inlet once every 20 minutes so that the THC concentration in the exhaust gas became 8000 ppm for 30 seconds. At this time, the average concentration of the reducing agent is 1
89 ppm, oxygen concentration at catalyst inlet 11% by volume, NOx concentration at catalyst inlet 400 ppm, average THC / NOx ratio 0.47, ratio of reducing agent supply cycle to reducing agent supply time 40, reduction to fuel consumption 0.35 agent supply
% By weight, and the average NOx purification rate was 25%.
【００４３】実施例５ 触媒Ａを用い、触媒入口温度３００℃、還元剤としては
軽油を用いた。還元剤は６分間に１回、排気ガス中のＴ
ＨＣ濃度が８０００ｐｐｍとなるようにして３０秒間触
媒入口に供給した。このときの還元剤の平均濃度は６３
０ｐｐｍ、触媒入口の酸素濃度は１１容量％、触媒入口
のＮＯｘ濃度は４００ｐｐｍ、平均ＴＨＣ／ＮＯｘ比は
１．５８、還元剤供給サイクルと還元剤供給時間との比
は１２、燃料消費量に対する還元剤供給量は１．２重量
％、平均ＮＯｘ浄化率は２６％であった。Example 5 Catalyst A was used, the catalyst inlet temperature was 300 ° C., and light oil was used as the reducing agent. The reducing agent is used once every 6 minutes to reduce T in the exhaust gas.
It was supplied to the catalyst inlet for 30 seconds so that the HC concentration became 8000 ppm. The average concentration of the reducing agent at this time was 63
0 ppm, oxygen concentration at the catalyst inlet is 11% by volume, NOx concentration at the catalyst inlet is 400 ppm, average THC / NOx ratio is 1.58, ratio of reducing agent supply cycle to reducing agent supply time is 12, reduction to fuel consumption The supply amount of the agent was 1.2% by weight, and the average NOx purification rate was 26%.
【００４４】実施例６ 触媒Ｂを用い、触媒入口温度４００℃、還元剤としては
軽油を用いた。還元剤は２０分間に１回、排気ガス中の
ＴＨＣ濃度が８０００ｐｐｍとなるようにして１０秒間
触媒入口に供給した。このときの還元剤の平均濃度は６
３ｐｐｍ、触媒入口の酸素濃度は８容量％、触媒入口の
ＮＯｘ濃度は５００ｐｐｍ、平均ＴＨＣ／ＮＯｘ比は
０．１３、還元剤供給サイクルと還元剤供給時間との比
は１２０、燃料消費量に対する還元剤供給量は０．０９
重量％、平均ＮＯｘ浄化率は１９％であった。Example 6 The catalyst B was used, the catalyst inlet temperature was 400 ° C., and light oil was used as the reducing agent. Once every 20 minutes, the reducing agent was supplied to the catalyst inlet for 10 seconds so that the THC concentration in the exhaust gas became 8000 ppm. The average concentration of the reducing agent at this time was 6
3 ppm, oxygen concentration at catalyst inlet 8% by volume, NOx concentration at catalyst inlet 500 ppm, average THC / NOx ratio 0.13, ratio of reducing agent supply cycle to reducing agent supply time 120, reduction to fuel consumption 0.09
% By weight, and the average NOx purification rate was 19%.
【００４５】実施例７ 触媒Ａを用い、触媒入口温度３００℃、還元剤としては
プロピレンを用いた。還元剤は２０分間に１回、排気ガ
ス中のＴＨＣ濃度が８０００ｐｐｍとなるようにして１
０秒間触媒入口に供給した。このときの還元剤の平均濃
度は６３ｐｐｍ、触媒入口の酸素濃度は１１容量％、触
媒入口のＮＯｘ濃度は４００ｐｐｍ、平均ＴＨＣ／ＮＯ
ｘ比は０．１６、還元剤供給サイクルと還元剤供給時間
との比は１２０、燃料消費量に対する還元剤供給量は
０．１２重量％、平均ＮＯｘ浄化率は３９％であった。Example 7 Catalyst A was used, the catalyst inlet temperature was 300 ° C., and propylene was used as the reducing agent. The reducing agent is added once every 20 minutes so that the THC concentration in the exhaust gas becomes 8000 ppm.
It was fed to the catalyst inlet for 0 seconds. At this time, the average concentration of the reducing agent was 63 ppm, the oxygen concentration at the catalyst inlet was 11% by volume, the NOx concentration at the catalyst inlet was 400 ppm, and the average THC / NO
The x ratio was 0.16, the ratio between the reducing agent supply cycle and the reducing agent supply time was 120, the reducing agent supply amount relative to the fuel consumption was 0.12% by weight, and the average NOx purification rate was 39%.
【００４６】比較例１ 軽油を定常的に６３ｐｐｍの濃度で供給した以外は、実
施例１と同様に行った。その結果、平均ＮＯｘ浄化率は
１％であった。Comparative Example 1 The procedure was as in Example 1, except that light oil was constantly supplied at a concentration of 63 ppm. As a result, the average NOx purification rate was 1%.
【００４７】比較例２ 軽油の供給時間を１秒とした以外は、実施例２と同様に
行った。その結果、平均ＮＯｘ浄化率は０％であった。Comparative Example 2 The same operation as in Example 2 was carried out except that the supply time of light oil was changed to 1 second. As a result, the average NOx purification rate was 0%.
【００４８】比較例３ 軽油を定常的に６３０ｐｐｍの濃度で供給した以外は、
実施例１と同様に行った。その結果、平均ＮＯｘ浄化率
は３％であった。Comparative Example 3 Except that gas oil was constantly supplied at a concentration of 630 ppm,
Performed in the same manner as in Example 1. As a result, the average NOx purification rate was 3%.
【００４９】比較例４ 軽油を定常的に６３ｐｐｍの濃度で供給した以外は、実
施例６と同様に行った。その結果、平均ＮＯｘ浄化率は
１％であった。Comparative Example 4 The same operation as in Example 6 was carried out except that light oil was constantly supplied at a concentration of 63 ppm. As a result, the average NOx purification rate was 1%.
【００５０】比較例５ プロピレンを定常的に６３ｐｐｍの濃度で供給した以外
は、実施例７と同様に行った。その結果、平均ＮＯｘ浄
化率は５％であった。Comparative Example 5 The same procedure as in Example 7 was carried out except that propylene was constantly supplied at a concentration of 63 ppm. As a result, the average NOx purification rate was 5%.
【００５１】以上の実施例１〜７および比較例１〜５で
得られた試験結果を表１および表２に示す。The test results obtained in Examples 1 to 7 and Comparative Examples 1 to 5 are shown in Tables 1 and 2.
【００５２】[0052]
【表１】 [Table 1]
【００５３】[0053]
【表２】 [Table 2]
【００５４】[0054]
【発明の効果】以上述べたように、本発明は、内燃機関
から排出されかつ常に空燃比が酸素過剰である排気ガス
中のＮＯｘを触媒を用いて浄化する方法において、該排
気ガス中の空燃比が常に酸素過剰の状態を保つ範囲で、
かつ還元剤を排気ガス中に供給しない時間が還元剤を排
気ガス中に供給する時間の５〜１０，０００倍の割合で
還元剤を定期的に該排気ガスに供給することを特徴とす
る触媒の活性化方法であるから、触媒は常に活性化さ
れ、排気ガス中の空燃比が常に酸素過剰の状態であって
も排気ガス中のＮＯｘを効率よく浄化できるのである。As described above, the present invention relates to a method for purifying NOx in exhaust gas discharged from an internal combustion engine and always having an excess air-fuel ratio with oxygen using a catalyst. As long as the fuel ratio always keeps excess oxygen,
The time when the reducing agent is not supplied to the exhaust gas
Since the catalyst activation method is characterized in that the reducing agent is periodically supplied to the exhaust gas at a rate of 5 to 10,000 times the supply time to the gas, the catalyst is always used. Thus, even when the air-fuel ratio in the exhaust gas is always in excess of oxygen, NOx in the exhaust gas can be efficiently purified.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平６−285335（ＪＰ，Ａ) 特開 平６−26328（ＪＰ，Ａ) 特開 平４−349939（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) B01D 53/86 F01N 3/08 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-285335 (JP, A) JP-A-6-26328 (JP, A) JP-A-4-349939 (JP, A) (58) Field (Int.Cl. 7 , DB name) B01D 53/86 F01N 3/08
Claims (10)
酸素過剰である排気ガス中のＮＯｘを触媒を用いて浄化
する方法において、該排気ガス中の空燃比が常に酸素過
剰の状態を保つ範囲で、かつ還元剤を排気ガス中に供給
しない時間が還元剤を排気ガス中に供給する時間の５〜
１０，０００倍の割合で還元剤を定期的に該排気ガスに
供給することを特徴とする白金、ロジウム、パラジウ
ム、銅および鉄よりなる群から選ばれた少なくとも１種
のものを活性成分として含有してなる触媒の活性化方
法。1. A method for purifying NOx in exhaust gas discharged from an internal combustion engine and always having an excess air-fuel ratio with oxygen using a catalyst, wherein the air-fuel ratio in the exhaust gas always maintains an excess oxygen state. And supply the reducing agent into the exhaust gas
The time of not supplying the reducing agent to the exhaust gas
Containing at least one selected from the group consisting of platinum, rhodium, palladium, copper and iron as an active ingredient , wherein a reducing agent is periodically supplied to the exhaust gas at a ratio of 10,000 times. A method for activating a catalyst comprising:
共存する酸素濃度が、該外気ガスの２〜２０容量％であ
る請求項１に記載の触媒の活性化方法。2. The catalyst activation method according to claim 1, wherein the concentration of oxygen present when the reducing agent is supplied into the exhaust gas is 2 to 20% by volume of the outside air gas.
求項１に記載の触媒の活性化方法。3. The method according to claim 1, wherein the reducing agent contains carbon.
度が、該排気ガスに対してメタン換算で５００ｐｐｍ〜
１０％である請求項３に記載の触媒の活性化方法。4. The method according to claim 1, wherein the concentration of the reducing agent when supplied into the exhaust gas is 500 ppm or less in terms of methane with respect to the exhaust gas.
The method for activating a catalyst according to claim 3, which is 10%.
費量の０．０１〜３重量％である請求項１〜４のいずれ
か一つに記載の触媒の活性化方法。5. A method for activating a catalyst according to any one of the amount of reducing agent supplied on average fuel consumption of 0.01-3 claims 1-4 by weight.
飽和炭化水素類、芳香族炭化水素類、およびアルコール
類よりなる群れから選ばれた少なくとも１種のものを含
む還元剤である請求項１〜５のいずれか一つに記載の触
媒の活性化方法。6. A reducing agent containing at least one selected from the group consisting of hydrogen, saturated hydrocarbons, unsaturated hydrocarbons, aromatic hydrocarbons, and alcohols. A method for activating a catalyst according to any one of claims 1 to 5 .
ス、ガソリン、メタノールおよびエタノールよりなる群
から選ばれた少なくとも１種のものを含む還元剤である
請求項１〜５のいずれか一つに記載の触媒の活性化方
法。7. A reducing agent is gas oil, kerosene, liquefied petroleum gas, gasoline, any one of claims 1 to 5 which is a reducing agent, including those of at least one selected from the group consisting of methanol and ethanol A method for activating a catalyst according to any one of the first to third aspects.
担持されてなる請求項１〜７のいずれか一つに記載の触
媒の活性化方法。8. catalytic active component, according to claim 1-7 activating a catalyst according to any one of made carried on the refractory three-dimensional structure.
ものである請求項１〜８のいずれか一つに記載の触媒の
活性化方法。9. exhaust gas activation method of the catalyst according to any one of claims 1-8 is derived from the diesel engine.
Ｏｘの比が０．０１〜３である請求項１〜９のいずれか
一つに記載の触媒の活性化方法。10. The average THC / N of the supplied reducing agent.
The method for activating a catalyst according to any one of claims 1 to 9 , wherein the ratio of Ox is from 0.01 to 3.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18960794A JP3217602B2 (en) | 1994-08-11 | 1994-08-11 | Method for activating catalyst for purifying exhaust gas of internal combustion engine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18960794A JP3217602B2 (en) | 1994-08-11 | 1994-08-11 | Method for activating catalyst for purifying exhaust gas of internal combustion engine |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0852358A JPH0852358A (en) | 1996-02-27 |
| JP3217602B2 true JP3217602B2 (en) | 2001-10-09 |
Family
ID=16244143
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP18960794A Expired - Lifetime JP3217602B2 (en) | 1994-08-11 | 1994-08-11 | Method for activating catalyst for purifying exhaust gas of internal combustion engine |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3217602B2 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2778205B1 (en) * | 1998-04-29 | 2000-06-23 | Inst Francais Du Petrole | CONTROLLED HYDROCARBON INJECTION PROCESS INTO AN EXHAUST LINE OF AN INTERNAL COMBUSTION ENGINE |
| JP4548565B2 (en) * | 2001-07-26 | 2010-09-22 | コスモ石油株式会社 | Catalyst for catalytic reduction and removal of nitrogen oxides |
| GB0308944D0 (en) * | 2003-04-17 | 2003-05-28 | Johnson Matthey Plc | Method of decomposing nitrogen dioxide |
| US8418444B2 (en) | 2006-03-30 | 2013-04-16 | Umicore Shokubai Japan Co., Ltd. | Method for purification of exhaust gas from internal combustion engine |
| JP4889585B2 (en) * | 2006-07-13 | 2012-03-07 | 株式会社アイシーティー | Internal combustion engine exhaust gas purification method |
-
1994
- 1994-08-11 JP JP18960794A patent/JP3217602B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0852358A (en) | 1996-02-27 |
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