JP4088361B2 - Exhaust gas purification method - Google Patents

Description

【０１４４】
次に、実施例１、３、８、１０、１３、１５、１６及び比較例１にて調製した触媒を用いて、反応温度を６００℃とした以外は、上記反応条件で２４時間反応を行なった後、上記反応条件下で排ガスの浄化を行なって、触媒の耐熱性及び耐硫黄酸化物性を評価した。結果を表２に示す。
【０１４５】
【表２】

【０１４６】
【発明の効果】
表１及び表２に示す結果から明らかなように、本発明の方法によれば、排ガスが硫黄酸化物を含んでいても、また、触媒が高温の環境に置かれた場合であっても、安定して窒素酸化物を効率よく除去することができる。
【図面の簡単な説明】
【図１】は、銀アルミネートを担持させたγ−アルミナのＸ線回折図である。
【図２】は、γ−アルミナのＸ線回折図である。[0001]
BACKGROUND OF THE INVENTION
The present invention is a method for treating exhaust gas containing hydrocarbons, carbon monoxide and the like together with nitrogen oxides in an oxygen-excess atmosphere, and removing the hydrocarbons and carbon monoxide and the like together with these nitrogen oxides for purification. About. Specifically, the present invention is a method for removing and purifying nitrogen oxides in exhaust gas discharged from factories, automobiles, etc., and in a nitrogen-excess atmosphere, nitrogen monoxide in exhaust gas is removed on a catalyst. Converted to nitrogen dioxide, then adsorbed on the catalyst together with the nitrogen dioxide present in the exhaust gas from the beginning, where the reducing agent such as fuel intermittently in the exhaust gas for a short time, ie pulsating In addition to the above, the present invention relates to a method for purifying exhaust gas in which the exhaust gas atmosphere is periodically reduced to perform catalytic reduction and to oxidize and remove harmful components such as hydrocarbons and carbon monoxide in an oxidizing atmosphere.
[0002]
[Prior art]
Conventionally, as a method of removing nitrogen oxides in exhaust gas discharged from factories, automobiles, etc., after oxidizing the nitrogen oxides, a method of absorbing them into alkali, ammonia, hydrogen, carbon monoxide, hydrocarbons, etc. A method of converting to nitrogen using a reducing agent is known. However, according to the former method, a measure for treating the generated alkaline waste liquid to prevent the occurrence of pollution is necessary. On the other hand, according to the latter method, when ammonia is used as a reducing agent, it reacts with sulfur oxides in the exhaust gas to generate salts, resulting in a problem that the reduction activity of the catalyst is lowered. In addition, even when hydrogen, carbon monoxide, hydrocarbons, etc. are used as the reducing agent, these react with oxygen present at a higher concentration than nitrogen oxide present at a low concentration, so that nitrogen oxides are reduced. Has the problem of requiring a large amount of reducing agent.
[0003]
For this reason, recently, a method of directly decomposing nitrogen oxides with a catalyst in the absence of a reducing agent has also been proposed. However, conventionally known such catalysts have a nitrogen oxide decomposing activity. Has a problem that it is difficult to put to practical use.
[0004]
In addition, various zeolites and the like have been proposed as new nitrogen oxide catalytic reduction catalysts using hydrocarbons or oxygen-containing compounds as reducing agents, particularly Cu-ZSM-5 and H-type ZSM-5 (SiO 2₂/ Al₂O_ThreeMolar ratio = 30-40) is considered optimal. However, such Cu-ZSM-5 and H-type ZSM-5 are still difficult to say that they still have sufficient reduction activity, and particularly when the exhaust gas contains moisture, the aluminum in the zeolite structure is desorbed. There is a need for a catalyst for catalytic reduction of nitrogen oxides that has a higher reduction activity because it has a sharp decline in performance due to aluminum, and has excellent durability even when the exhaust gas contains moisture. .
[0005]
Therefore, various catalysts such as a catalyst in which silver or silver oxide is supported on an inorganic oxide have been proposed. Among such catalysts, a catalyst having a high reaction rate has high oxidation activity, and nitrogen oxidation. Due to the low selective reactivity to the product, the removal rate of nitrogen oxides is low. On the other hand, a catalyst having high reaction selectivity such as alumina has a slow reaction rate and is difficult to use at a high SV (space velocity). Etc., and has a large problem in practical use. Furthermore, there is a problem that the catalytic activity is significantly deteriorated in the presence of sulfur oxide (Japanese Patent Laid-Open No. 5-317647). Further, conventional nitrogen oxide catalytic reduction catalysts are not sufficiently heat resistant, and there is a strong demand for further heat resistance depending on the application.
[0006]
Therefore, as one method for solving such a problem, nitrogen monoxide (NO) is converted to nitrogen dioxide (NO) on the catalyst under excess oxygen (lean conditions).₂Thus, the generated nitrogen dioxide is adsorbed on the catalyst, and a reducing agent such as a hydrocarbon such as fuel or an oxygen-containing organic compound is intermittently injected for a short time, that is, in a pulsating manner. (Hereinafter referred to as “pulsed” injection), a nitrogen oxide storage catalyst has been proposed in which nitrogen oxides are reduced to nitrogen under a reducing atmosphere (rich condition) (Japanese Patent Laid-Open No. Hei 9-29). 122486). However, since exhaust gas usually contains sulfur oxides, this method adsorbs sulfur oxides at the adsorption points of nitrogen oxides, and therefore, hydrocarbons such as fuel are pulsed. This sulfur oxide does not desorb from the catalyst even when the exhaust gas treatment atmosphere is reduced to a reducing atmosphere by, for example, injecting the fuel into the engine compartment in a pulsating manner, such as by adding hydrocarbons such as fuel to the stoichiometric amount or more. Thus, there is a problem that the amount of nitrogen oxide adsorbed on the catalyst gradually decreases and the nitrogen oxide removal rate rapidly decreases.
[0007]
[Problems to be solved by the invention]
The present invention has been made in order to solve the above-described problems in the exhaust gas purification method using a conventional nitrogen oxide storage exhaust gas purification catalyst. The object of the present invention is to provide a catalyst under excess oxygen. Nitrogen oxide is converted into nitrogen dioxide with high efficiency above, and thus the produced nitrogen dioxide is adsorbed on the catalyst, and a reducing agent is injected in a pulsed manner to make the exhaust gas atmosphere a reducing atmosphere, and nitrogen oxidation. In the exhaust gas purification method using a nitrogen oxide storage catalyst that reduces a product to nitrogen and also oxidizes and removes hydrocarbons and carbon monoxide under excess oxygen, even when the exhaust gas contains sulfur oxide, In a preferred case, the nitrogen oxide storage function of the nitrogen oxide storage catalyst does not deteriorate even at a relatively low temperature, and it also has excellent heat resistance. It, and efficiently reducing nitrogen oxides in the exhaust gas stably, is to provide an exhaust gas purifying catalyst capable of removing.
[0008]
[Means for Solving the Problems]
  The first of the exhaust gas purification methods according to the present invention is that the exhaust gas treatment atmosphere is alternately vibrated between an oxygen-excess atmosphere and a reducing atmosphere, thereby ternary components of nitrogen oxides, hydrocarbons and carbon monoxide in the exhaust gas. Exhaust gas to purifyIn purification methodThe exhaust gas
  (1) (a) at least one platinum group element selected from the group consisting of Pt, Rh, Pd and Ir; and (b)Silver, copper, zinc, gallium, chromium, iron, cobalt and nickel(C) at least one metal selected from the group consisting of:Titanium oxideIn contact with a first catalyst consisting of:
  (2) (a)Nitrogen oxide storageAnd (b) a second catalyst comprising at least one platinum group element selected from the group consisting of Pt, Rh, Pd and Ir.In the exhaust gas purification method, the nitrogen oxide storage material is an oxide of at least one metal selected from alkali metals, alkaline earth metals, and rare earth elements, or selected from alkali metals, alkaline earth metals, and silver. It is a composite oxide of at least one metal and at least one metal selected from aluminum and titaniumIt is characterized by that.
[0009]
Here, the second catalyst is a nitrogen oxide storage catalyst, of which one or two selected from (a) component alkali metal, alkaline earth metal, aluminum, silver, titanium and rare earth elements The above metal oxide or composite oxide is a nitrogen oxide storage material.
[0010]
  The second of the exhaust gas purification method according to the present invention is a ternary component of nitrogen oxides, hydrocarbons and carbon monoxide in the exhaust gas by alternately vibrating the treatment atmosphere of the exhaust gas between the oxygen excess atmosphere and the reducing atmosphere. Exhaust gas to purifyIn purification methodThe exhaust gas
  (1) (a) at least one platinum group element selected from the group consisting of Pt, Rh, Pd and Ir; and (b) silver, copper, zinc, aluminum, gallium, tin, zirconium, chromium, manganese, iron, A first catalyst comprising at least one metal selected from the group consisting of cobalt and nickel, or a compound thereof, or an ion thereof; and (c) at least one oxide selected from the group consisting of titanium oxide, zirconia and tin oxide. And then contact
  (2) (a) at least one platinum group element selected from the group consisting of Pt, Rh, Ir and Pd; and (b) at least one oxide selected from the group consisting of titanium oxide, zirconia and tin oxide. Contact with an intermediate catalyst consisting of
  (3) An exhaust gas purification method comprising contacting a second catalyst comprising (a) a nitrogen oxide storage material and (b) at least one platinum group element selected from the group consisting of Pt, Rh, Pd and Ir. The nitrogen oxide storage material is an oxide of at least one metal selected from alkali metals, alkaline earth metals and rare earth elements, orComplex oxide of at least one metal selected from alkali metals, alkaline earth metals and silver and at least one metal selected from aluminum and titaniumIt is characterized by being.
[0011]
Therefore, the second method is different from the first method only in that the exhaust gas is brought into contact with the intermediate catalyst while the exhaust gas is brought into contact with the first catalyst and the second catalyst, respectively.
[0012]
According to the present invention, in any of the first and second methods, in the first catalyst, the component (b) is silver, copper, zinc, aluminum, gallium, tin, zirconium, chromium, manganese, The compound of at least one metal selected from the group consisting of iron, cobalt and nickel is usually an oxide. However, in the first catalyst, when the component (b) is silver or a compound thereof, such a component is metallic silver or silver aluminate (or silver aluminate, AgAlO₂). On the other hand, in any of the first and second methods, the second catalyst is at least selected from the group consisting of (a) a complex oxide of barium and aluminum and (b) Pt, Rh, Pd and Ir. It is preferably composed of one kind of platinum group element.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
According to the first method of the present invention, a ternary component of nitrogen oxides, hydrocarbons, and carbon monoxide in exhaust gas is obtained by alternately vibrating an exhaust gas treatment atmosphere between an oxygen-excess atmosphere and a reducing atmosphere. In the exhaust gas purification touch method to purify
(1) (a) at least one platinum group element selected from the group consisting of Pt, Rh, Pd and Ir; and (b) silver, copper, zinc, aluminum, gallium, tin, zirconium, chromium, manganese, iron, A first catalyst comprising at least one metal selected from the group consisting of cobalt and nickel, or a compound thereof, or an ion thereof; and (c) at least one oxide selected from the group consisting of titanium oxide, zirconia and tin oxide. And then contact
(2) (a) an oxide or composite oxide of one or more metals selected from alkali metals, alkaline earth metals, aluminum, silver, titanium and rare earth elements, and (b) Pt, Rh, Pd and Contact is made with a second catalyst comprising at least one platinum group element selected from the group consisting of Ir.
[0014]
In the present invention, in the first catalyst, at least one metal selected from the group consisting of copper, zinc, aluminum, gallium, tin, zirconium, chromium, manganese, iron, cobalt, and nickel as component (b) The compound is usually an oxide. However, in the first catalyst, when the component (b) is silver or a compound thereof, preferable specific examples include, for example, metallic silver, silver oxide, or silver aluminate (or silver aluminate, AgAlO₂).
[0015]
The silver aluminate is prepared by, for example, immersing alumina, preferably hydrated alumina, in a mixed aqueous solution of a water-soluble aluminum salt such as aluminum nitrate and a water-soluble silver salt such as silver nitrate. After impregnating the pores of the alumina, it is dried by a suitable means such as a spray dryer, and then this is 600 to 900 ° C., preferably 700 to 800 ° C. in the presence of water vapor in an oxidizing atmosphere. The γ-alumina powder carrying silver aluminate can be obtained by heating and baking at a temperature of about, ie, heating and baking under hydrothermal conditions. The amount of water vapor in the oxidizing atmosphere is usually in the range of 3 to 20% by weight, and preferably in the range of 5 to 15% by weight.
[0016]
In the first method according to the present invention, the first catalyst is preferably (a) at least one platinum group element selected from the group consisting of Pt, Rh, Pd and Ir is 0.1 to 0.1 in terms of metal. In a range of 10% by weight, preferably in a range of 0.5 to 5% by weight, (c) supported on a support made of at least one oxide selected from the group consisting of titanium oxide, zirconia and tin oxide (B) component (however, component (b)ButExcept when contained in the catalyst as metallic silver or silver aluminate. ) Is supported on the carrier (c) in the range of 0.1 to 20% by weight, preferably in the range of 0.5 to 10% by weight in terms of oxide.
[0017]
In the first catalyst, when the component (b) is metallic silver or silver aluminate, the amount supported on the carrier is based on metallic silver. Therefore, according to the present invention, in the first catalyst, Metal silver or silver aluminate is supported on the carrier (c) in the range of 0.1 to 20% by weight in terms of silver, preferably in the range of 0.5 to 10% by weight. (Same below).
[0018]
The second catalyst, which is a nitrogen oxide storage catalyst, comprises (a) at least one metal selected from alkali metals, alkaline earth metals, aluminum, titanium, silver, and rare earth elements as a nitrogen oxide storage material ( Mixed) oxide or 25 to 75% by weight of a composite oxide of at least two metals selected from alkali metals, alkaline earth metals, aluminum, titanium, silver and rare earth elements, and (b) the platinum group element 75 supported by a conventionally known carrier such as alumina, titania, zirconia, silica, silica / alumina, etc. at a ratio of 0.1 to 10% by weight, preferably 0.5 to 5% by weight 75 It consists of ˜25% by weight. In the present invention, the silver composite oxide as component (a) in this second catalyst contains silver aluminate.
[0019]
However, according to the present invention, in this second catalyst, a composite oxide of barium and aluminum is preferably used as the component (a). As already known, this barium-aluminum complex oxide is a complex oxide composed of barium, aluminum and oxygen, and is usually BaO.Al.₂O_Three Or BaO · 6Al₂O_Three (Hirotsu Arai, Masato Machida, “Metal”, June 1989, heat-resistant ceramic fine particles).
[0020]
The first catalyst used in the first method according to the present invention particularly oxidizes sulfur oxide (SOx) by a platinum group element in the catalyst, and at the time of lean, sulfur oxide (SOx) contained in the exhaust gas is oxidized. It is easy to adsorb on the catalyst, and when rich, this sulfur oxide is mainly sulfur dioxide (SO2₂) Or hydrogen sulfide, thus preventing the sulfur oxide from adsorbing to the second catalyst during lean, and the nitrogen dioxide (NO) in the second catalyst.₂) To suppress a reduction in the catalytic reduction ability of the nitrogen oxide of the second catalyst. The second catalyst also converts nitrogen monoxide (NO) to nitrogen dioxide (NO) during lean.₂) And NO₂Is adsorbed on the catalyst, and this adsorbed NO₂It plays the role of reducing to nitrogen with a reducing agent during lean.
[0021]
Therefore, in the first catalyst, the supported amount of (a) the platinum group element carrier, that is, (c) at least one oxide selected from the group consisting of titanium oxide, zirconia and tin oxide is a metal. When the amount is less than 0.1% by weight, the oxidation of sulfur oxides in the exhaust gas is insufficient. However, the loading amount need not exceed 10% by weight.
[0022]
In the first catalyst, the component (b), that is, at least one metal selected from the group consisting of silver, copper, zinc, aluminum, gallium, tin, zirconia, chromium, manganese, iron, cobalt, and nickel Or the amount of the compound or ion thereof supported on the carrier, that is, (c) the amount supported on at least one oxide selected from the group consisting of titanium oxide, zirconia and tin oxide is 0.1 in terms of oxide. When the amount is less than% by weight, the sulfur oxide contained in the exhaust gas cannot be sufficiently adsorbed on the first catalyst at the time of lean, and the sulfur oxide that has not been adsorbed is absorbed by the second catalyst. As a result, when sulfur is rich, sulfur oxide is not desorbed from the second catalyst and gradually accumulates in the catalyst. As a result, the adsorption ability of nitrogen dioxide is lowered, and the ability to reduce nitrogen oxide is lowered. .
[0023]
Here, if titanium oxide is used as the carrier, titanium oxide preferably desorbs sulfur oxide as hydrogen sulfide when rich. Therefore, according to the present invention, titanium oxide is particularly preferably used as the carrier in the first catalyst.
[0024]
However, in the first catalyst, even if the amount of the component (b) supported on the carrier, that is, the amount of the component (c) supported on the component exceeds 20% by weight in terms of oxide, the obtained sulfur oxide of the first catalyst is obtained. This is disadvantageous because the adsorption capacity of the catalyst is not improved correspondingly and the production cost of the catalyst is increased.
[0025]
Next, in the first method according to the present invention, among the second catalysts, in particular, the catalyst component composed of a platinum group element oxidizes nitrogen oxides to nitrogen dioxide during the lean operation, as described above, and alkali metal. The catalyst component comprising an oxide or composite oxide of one or more metals selected from alkaline earth metals, aluminum, silver, titanium and rare earth elements adsorbs the nitrogen dioxide, When rich, it is reduced to nitrogen by a catalyst component comprising a platinum group element in the presence of a reducing agent.
[0026]
In the second catalyst, the alkali metal can be exemplified by lithium, sodium or potassium, the alkaline earth metal can be exemplified by beryllium, magnesium, calcium, strontium or barium, For example, scandium, yttrium, lanthanoid elements, actinoid elements and the like can be exemplified. Among these, yttrium, lanthanum, cerium, thorium and the like are particularly preferable. Among these, as described above, a composite oxide of barium and aluminum is particularly preferably used.
[0027]
According to the present invention, in the second catalyst, when the components (a) and (b) are out of the above ranges, the reduction activity of nitrogen oxides is greatly reduced. In addition, in the component (b), when the supported amount of the platinum group element is smaller than 0.1% by weight, the second catalyst does not have a sufficient nitrogen oxide reduction activity, and on the other hand, 10% by weight. Even if it exceeds, the catalytic reduction ability of the second oxide of the second catalyst is not improved correspondingly, and the production cost of the catalyst is increased, which is disadvantageous.
[0028]
The said 1st and 2nd catalyst used in the method by this invention can be prepared as follows, for example.
[0029]
First, (a) at least one platinum group element selected from the group consisting of Pt, Rh, Pd and Ir and (b) silver, copper, zinc, aluminum, gallium, tin, zirconium, chromium, manganese, iron, cobalt And a first catalyst comprising at least one metal selected from the group consisting of nickel and a compound thereof or ions thereof and (c) at least one oxide selected from the group consisting of titanium oxide, zirconia and tin oxide. It can be prepared as follows.
[0030]
That is, a water-soluble salt such as a nitrate of at least one element selected from the group consisting of silver, copper, zinc, aluminum, gallium, tin, zirconium, chromium, manganese, iron, cobalt, and nickel, and the platinum group element. The oxide carrier, which is the component (c), is immersed in an aqueous solution containing a water-soluble salt, and after removing the excessive aqueous solution adhering to the oxide carrier, the oxide carrier is dried and baked in the air, thereby A catalyst carrying the component (a) and the component (b) can be obtained.
[0031]
Next, one example of the second catalyst is (a) a mixed oxide or composite oxide of an alkali metal or alkaline earth metal and aluminum and (b) a platinum group element. Can be prepared.
[0032]
As a first method, for example, a water-soluble salt of an alkali metal or alkaline earth metal, for example, barium carbonate or barium acetate is dissolved or dispersed in water together with alumina, and sufficiently mixed and pulverized using a ceramic pulverizing medium. Thus, after drying the obtained slurry, it is fired in air at a temperature of 600 to 1500 ° C. to obtain a barium and aluminum composite oxide powder (powder A).
[0033]
On the other hand, a water-soluble salt (for example, nitrate) of a precursor of zirconium oxide, titanium oxide or aluminum oxide is dissolved in ion-exchanged water, and an alkali such as ammonia is gradually added thereto to adjust the pH of the slurry to the above water-soluble property. It is increased until a hydroxide is formed from the salt to form a precipitate, and then the precipitate thus obtained is separated by filtration, washed with water, dried, and then subjected to an oxidizing atmosphere such as air. The powder of zirconium oxide, titanium oxide or aluminum oxide can be obtained by heating and baking at a temperature of about 400 to 800 ° C., preferably about 600 to 800 ° C.
[0034]
Next, the powder of zirconium oxide, titanium oxide or aluminum oxide is dipped in an aqueous solution of a water-soluble salt of a platinum group element separately prepared, dried, and then fired in an oxidizing atmosphere. By baking in an atmosphere, a powder (powder B) is obtained in which a catalyst component composed of a platinum group element is supported on the zirconium oxide, titanium oxide, or aluminum oxide.
[0035]
Therefore, if the powder A and the powder B thus obtained are mixed, a catalyst comprising a mixed oxide or composite oxide of an alkali metal or alkaline earth metal and aluminum such as barium and a platinum group element is prepared. It can be obtained as a powder.
[0036]
As a second method, for example, a water-soluble salt that is a precursor of alumina such as aluminum nitrate, or an aqueous solution of a water-soluble salt that is a precursor of zirconium oxide such as zirconium nitrate, or a homogeneous solution thereof is prepared. A mixed aqueous solution is prepared, and an alkali such as ammonia is gradually added to the aqueous solution to neutralize it to form a precipitate. Then, the precipitate is filtered, washed with water, and repulped. The wet cake is repulped into ion-exchanged water, and further, barium hydroxide is added thereto, and hydrothermal treatment is performed at a temperature of 100 to 300 ° C. in an autoclave. After this hydrothermal treatment, the solid content is washed with filtered water, dried, and then fired in the air at a temperature of 800 to 1500 to obtain alumina and / or zirconia powder supporting barium and aluminum composite oxide. .
[0037]
Next, the powder is immersed in a separately prepared aqueous solution of a water-soluble salt of a platinum group element, dried, and then fired in an oxidizing atmosphere. In some cases, further, by firing in a reducing atmosphere, barium and A catalyst in which a platinum group element is supported on a composite oxide of aluminum and zirconium oxide and / or aluminum oxide can be obtained as a powder.
[0038]
Furthermore, as another method, as described above, after preparing a powder in which silver aluminate is supported on γ-alumina, and immersing this in a separately prepared aqueous solution of a water-soluble salt of a platinum group element, and drying it. By baking in an oxidizing atmosphere and, in some cases, further in a reducing atmosphere, a catalyst in which a platinum group element is supported on γ-alumina together with silver aluminate can be obtained as a powder.
[0039]
According to the second method of the present invention, at least one selected from the group consisting of (a) Pt, Rh, Ir, and Pd during contacting the exhaust gas with the first catalyst and the second catalyst respectively in the first method. The first method is the same as that described above except that it is brought into contact with an intermediate catalyst comprising one platinum group element and (b) at least one oxide selected from the group consisting of titanium oxide, zirconia and tin oxide. .
[0040]
The intermediate catalyst used in the second method is preferably (a) a platinum group element in the range of 0.1 to 10% by weight in terms of metal, preferably in the range of 0.5 to 5% by weight. And (b) supported on the oxide carrier as component. As this oxide, titanium oxide is particularly preferable.
[0041]
According to the second method, the intermediate catalyst serves to prevent the sulfur oxide from being adsorbed by the second catalyst in the subsequent stage by reducing the sulfur compound desorbed from the first catalyst into hydrogen sulfide. Is responsible.
[0042]
Therefore, in the intermediate catalyst, when the amount of platinum group element supported on the oxide carrier is less than 0.1% by weight, the sulfur compound desorbed from the first catalyst can be sufficiently reduced to hydrogen sulfide. Can not. However, the amount of platinum group element supported on the oxide carrier need not exceed 5% by weight.
[0043]
The intermediate catalyst used in the second method can be prepared as follows, for example. That is, titanium oxide, zirconia or tin oxide is immersed in an aqueous solution of a water-soluble salt such as a nitrate of the platinum group element, and after removing the excess aqueous solution, it is dried and fired in air. Thus, a catalyst in which the platinum group element is supported on the oxide carrier can be obtained.
[0044]
Purification of exhaust gas by the method of the present invention is performed by the following mechanism. However, the present invention is not limited by such a mechanism or theory. That is, first, in the first method, an exhaust gas containing hydrocarbons and carbon monoxide together with nitrogen oxides and sulfur oxides is brought into contact with the first catalyst under an oxygen-excess atmosphere (lean conditions), and the platinum group While oxidizing the sulfur oxides in the exhaust gas with the catalyst component consisting of elements, such sulfur oxides are effectively adsorbed on the first catalyst, and then on the second catalyst, nitrogen oxides, in particular , Converting nitrogen monoxide to nitrogen dioxide with high efficiency on a catalyst component comprising a platinum group element, and thus the generated nitrogen dioxide is at least selected from alkali metals, alkaline earth metals, aluminum, titanium, silver and rare earth elements The exhaust gas is placed under a reducing atmosphere (rich condition) by a method such as adsorption onto a catalyst component made of one metal oxide or composite oxide and injection of a reducing agent such as fuel. The sulfur oxide adsorbed on the first catalyst is desorbed as sulfur dioxide or hydrogen sulfide, and is suppressed from adsorbing and accumulating on the catalyst. Catalyst which prevents deterioration of catalyst, and further comprises oxide or composite oxide of at least one metal selected from alkali metal, alkaline earth metal, aluminum, silver, titanium and rare earth element in the second catalyst Nitrogen oxides adsorbed on the components are contact-reduced to nitrogen with the above reducing agent under rich conditions to remove nitrogen oxides from the exhaust gas.
[0045]
In the second method according to the present invention, an exhaust gas containing hydrocarbons and carbon monoxide together with nitrogen oxides and sulfur oxides is brought into contact with the first catalyst under an oxygen-excess atmosphere (lean conditions), and a platinum group element The sulfur oxide in the exhaust gas is oxidized by the catalyst component made of the catalyst, and the sulfur oxide is effectively adsorbed on the first catalyst, and then the exhaust gas is brought into contact with the intermediate catalyst, so that the first catalyst The sulfur compound desorbed from the catalyst is converted into hydrogen sulfide that is not adsorbed by the second catalyst in the subsequent stage, and thereafter, the exhaust gas is brought into contact with the second catalyst, and the nitrogen oxide is converted into nitrogen as in the first method. To reduce the nitrogen oxides from the exhaust gas.
[0046]
In the present invention, the oxygen-excess atmosphere (lean condition) means that the combustible components such as hydrocarbons, carbon monoxide, hydrogen and the like contained in the exhaust gas contain more oxygen than it is sufficient to completely burn with the oxygen contained in the exhaust gas. It means the atmospheric conditions. That is, it refers to an atmospheric condition where the exhaust gas contains more oxygen than the theoretical air fuel ratio condition (stoichiometric condition). On the other hand, the reducing atmosphere (rich condition) is sufficient to completely combust combustible components such as hydrocarbons, carbon monoxide and hydrogen contained in the exhaust gas by oxygen contained in the exhaust gas, contrary to the lean condition. An atmospheric condition that does not contain a quantity of oxygen.
[0047]
According to the first exhaust gas purification method of the present invention, in the process of detoxifying nitrogen oxides in exhaust gas containing nitrogen oxides and sulfur oxides by contact with nitrogen in this way, sulfur in the exhaust gases is removed. The oxide is adsorbed by the component (b) in the first catalyst under the lean conditions while being oxidized by the platinum group element component which is the component (a) in the first catalyst. This catalyst easily desorbs the sulfur oxides partially as hydrogen sulfide in the exhaust gas under rich conditions, and further, the downstream catalyst does not adsorb sulfur oxides under rich conditions. Thus, according to the method of the present invention, the hydrocarbon and carbon monoxide, which are harmful components in the exhaust gas, are rendered harmless, and the exhaust gas purification ability of the catalyst is improved even if the exhaust gas contains sulfur oxide together with nitrogen oxides. Therefore, nitrogen oxides can be catalytically reduced and removed from the exhaust gas stably over a long period of time.
[0048]
Further, according to the second method of the present invention, between the first catalyst and the second catalyst, the exhaust gas is brought into contact with the intermediate catalyst, so that almost all sulfur compounds in the exhaust gas become hydrogen sulfide. Thus, it is possible to completely prevent the deterioration of the nitrogen oxide storage component in the second catalyst in the subsequent stage.
[0049]
Therefore, the exhaust gas purification method according to the present invention can be suitably used, for example, as a catalyst exclusively for lean burn gasoline or GDI (Gasoline Direct Injection) vehicles operated in an oxygen-excess atmosphere. Furthermore, the catalyst used in the process according to the present invention is also excellent in heat resistance.
[0050]
As described above, since the first, second and intermediate catalysts used in the first and second methods of the present invention can be usually obtained as a powder or a granular material, respectively, It can be easily formed into various structures and shapes such as a honeycomb shape, a spherical shape, and an annular shape by a known ordinary forming method. When molding each catalyst into a required structure or shape, various conventionally known molding aids, molded body reinforcing materials, inorganic fibers, organic binders, and the like may be appropriately blended as necessary. .
[0051]
A structure such as a honeycomb or a sphere formed of the catalyst itself as described above can be obtained, for example, as follows. That is, as described above, each catalyst is prepared as a powder, which is kneaded with an organic binder using an appropriate solvent, formed into a honeycomb structure, dried, and then fired.
[0052]
Further, according to the present invention, an inert base material is previously formed into a required shape, and each catalyst in powder form is coated and supported by an appropriate method such as a wash coat method, and thus each catalyst structure. It can also be. Examples of the molded body made of the inactive base material include corrugated honeycombs made of stainless steel foil, and honeycomb bodies made of mineral substances such as cordierite, spherical bodies, and annular bodies. The catalyst can be supported on these to form a three-dimensional catalyst structure.
[0053]
According to the present invention, a catalyst layer is formed on the surface of a structure made of an inert base material such as a honeycomb, a sphere, a ring, or the like by a wash coat method or the like. When supported, the catalyst layer is preferably supported on the surface of the structure so as to have a thickness of 30 μm or more from the surface (hereinafter referred to as catalyst layer thickness for simplicity). Thus, by making the catalyst layer supported by the structure to have a thickness of 30 μm or more from the surface, a catalyst structure having high reactivity to nitrogen oxides, that is, selective reduction of nitrogen oxides, is obtained. be able to. However, according to the present invention, the thickness of the catalyst layer is usually 300 μm or less. Even if the thickness of the catalyst layer is more than 300 μm, it is not preferable from the viewpoint of the cost of the catalyst structure because it is not possible to obtain a selective reduction improvement corresponding to the thickness.
[0054]
In the solid honeycomb catalyst structure itself comprising the catalyst component as described above, the catalyst layer thickness is substantially uniform in the thickness direction of the cell walls of the honeycomb catalyst structure. Therefore, if the cell wall of the honeycomb structure is 60 μm or more, the catalyst is supported over a thickness of 30 μm or more from the surface of the cell wall. This is because the cell wall is in contact with the exhaust gas on the surfaces on both sides thereof.
[0055]
However, when purifying the exhaust gas by the first method of the present invention, the single honeycomb structure is divided into two in the through-hole direction, that is, the exhaust gas flow direction, and sequentially along the exhaust gas flow, The first and second catalysts can be applied and supported by a wash coat method or the like to form catalyst layers made of the first and second catalysts, respectively, adjacent to each other. Further, according to the present invention, for example, the second catalyst layer is formed as a lower layer and the first catalyst layer is formed as an upper layer sequentially by a wash coat method or the like on a single honeycomb structure, Thus, the catalyst layer may be formed in two layers on a single honeycomb structure.
[0056]
Similarly, when purifying exhaust gas by the second method of the present invention, a single honeycomb structure is divided into three in the direction of the through-hole, that is, the flow direction of the exhaust gas, and sequentially along the flow of the exhaust gas. The first, intermediate, and second catalysts can be applied and supported by a wash coat method or the like to form catalyst layers made of the first, intermediate, and second catalysts, respectively, adjacent to each other. In addition, for example, the second catalyst layer is sequentially formed as the lowermost layer on the single honeycomb structure by the wash coat method or the like, the intermediate catalyst layer is formed thereon, and the first catalyst is formed as the uppermost layer. A catalyst layer may be formed, and thus the catalyst layer may be formed in three layers on a single honeycomb structure.
[0057]
In the present invention, hydrogen, hydrocarbons or oxygen-containing organic compounds are preferably used as the reducing agent for placing exhaust gas under rich conditions. Of these, as hydrocarbons, for example, as gaseous, hydrocarbon gases such as methane, ethane, propane, ethylene, propylene, 1-butene, 2-butene, etc., as liquid, pentane, hexane, octane And single component hydrocarbons such as heptane, benzene, toluene and xylene, and mineral oil hydrocarbons such as gasoline, kerosene, light oil and heavy oil. In particular, according to the present invention, among the above, lower alkenes such as ethylene, propylene, isobutylene, 1-butene and 2-butene, lower alkanes such as propane and butane, light oil and the like are preferably used. These hydrocarbons may be used alone or in combination of two or more as required.
[0058]
In particular, according to the present invention, when purifying engine exhaust gas of an automobile, the fuel can be suitably used as a reducing agent. It is also possible to control the combustion of the engine (A / F control) to achieve a rich condition.
[0059]
Examples of the oxygen-containing organic compound include alcohols such as methanol, ethanol, propanol, butanol and octanol, ethers such as dimethyl ether, diethyl ether and dipropyl ether, esters such as methyl acetate, ethyl acetate and fats and oils Examples thereof include ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, and aldehydes such as acetaldehyde and propionaldehyde. These oxygen-containing organic compounds may be used alone or in combination of two or more as required.
[0060]
Furthermore, in the present invention, a mixture of the hydrocarbon and the oxygen-containing organic compound may be used as a reducing agent.
[0061]
In the present invention, the above reducing agent varies depending on the specific hydrocarbon and oxygen-containing organic compound used, but it is usually necessary for oxygen in the exhaust gas to react with the reducing agent and to bring the oxygen concentration to 0%. It is used in a range of about 0.9 to 10 in molar ratio with respect to the minimum amount of reducing agent (ie, stoichiometric amount). When the amount of the reducing agent used is less than 0.9 in terms of the molar ratio relative to the minimum amount (stoichiometric amount), the nitrogen oxides are not sufficiently reduced. On the other hand, when the molar ratio exceeds 10. Since the discharge amount of the unreacted reducing agent is increased, a post-treatment for removing the nitrogen oxide in the exhaust gas is required after the purification treatment of the nitrogen oxide in the exhaust gas.
[0062]
In the present invention, the time for each of the lean condition for oxidizing the nitrogen oxide in the exhaust gas and adsorbing it on the catalyst and the rich condition for reducing and removing the adsorbed nitrogen oxide with a reducing agent is appropriately determined depending on the exhaust gas treatment condition. Usually, the lean condition is 30 seconds to 1 minute, and the rich condition is 1 second to 1 minute.
[0063]
The optimum temperature at which the catalyst according to the present invention exhibits a reducing activity with respect to nitrogen oxides is usually 100 to 800 ° C., although it varies depending on the reducing agent and catalyst type used. In this temperature range, space velocity (SV) 5000-100000 hr.^-1It is preferable to distribute the exhaust gas at a degree. In the present invention, a particularly preferable reaction temperature region is in the range of 200 to 500 ° C.
[0064]
【Example】
EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.
[0065]
(1) Preparation of catalyst
Example 1
(Preparation of the first catalyst for the first method)
2.57 g of dinitrodiammine platinum aqueous solution (15.09 wt% as platinum) and silver nitrate (AgNO_Three) 2.05g and activated titanium oxide (TiO₂, Specific surface area 109m²/ G) 38.74 g was dispersed in 100 mL of ion exchange water. This slurry was dried with a spray dryer and fired at 500 ° C. for 3 hours to obtain a powder in which titanium oxide was supported on 1% by weight of platinum and 2% by weight of silver.
[0066]
60 g of this powder and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) are mixed with an appropriate amount of water, and this is wet pulverized for 5 minutes in a planetary mill using 100 g of zirconia balls as a pulverization medium, and washed. A slurry was prepared. This slurry was applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and platinum-silver / titanium oxide was supported at a rate of about 150 g / L (layer thickness: 77 μm).
[0067]
(Preparation of the second catalyst for the first method)
Barium carbonate (BaCO_Three) 75.00g and hydrated alumina (Al₂O_Three ・ NH₂O, 41.65 g (GB-45 manufactured by Mizusawa Chemical Co., Ltd.) (38.74 g as alumina) was dispersed in 200 mL of ion-exchanged water. To this slurry, 100 mL of zirconia balls was added as a grinding medium, and wet milled with a planetary mill for 30 minutes. The slurry thus obtained was separated by filtration, dried, and then fired in air at 1100 ° C. for 3 hours to produce a composite oxide of barium and aluminum (BaO · Al₂ O_Three )
[0068]
30 g of this complex oxide powder of barium and aluminum, 30 g of γ-alumina powder (AC11K manufactured by Sumitomo Chemical Co., Ltd.) and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) are mixed with an appropriate amount of water. This was wet pulverized for 5 minutes by a planetary mill using 100 g of zirconia balls as a pulverization medium to prepare a slurry for wash coating. This slurry is applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and BaO · AlO is applied._Three / Γ-alumina was supported at a rate of about 150 g / L (layer thickness 79 μm).
[0069]
Next, 6.25 g of a dinitrodiammine platinum aqueous solution (15.09 wt% as platinum) was made up to 30 mL with ion-exchanged water, and the BaO · Al was added to this aqueous solution.₂ O_Three / After immersing the honeycomb substrate carrying γ-alumina, the excess aqueous solution attached is removed, dried at 100 ° C. for 12 hours, and further fired in air at 600 ° C. for 3 hours. BaO · Al loaded with 2% by weight of platinum₂ O_Three / Y-alumina catalyst was obtained. The component ratio (weight ratio) of this catalyst is BaO.Al.₂ O_Three /Pt/γ-alumina=96.2/3.8/96.2.
[0070]
Example 2
(Preparation of the first catalyst for the first method)
2.57 g of dinitrodiammine platinum aqueous solution (15.09 wt% as platinum) and copper nitrate (Cu (NO_Three )₂ ・ 3H₂2.32 g of O) and active titanium oxide (TiO)₂, Specific surface area 109m²/ G) 38.74 g was dispersed in 100 mL of ion exchange water. This slurry was dried with a spray dryer and fired at 500 ° C. for 3 hours to obtain a powder in which titanium oxide was supported by 1% by weight of platinum and 2% by weight of cupric oxide (CuO).
[0071]
60 g of this powder and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) are mixed with an appropriate amount of water, and this is wet pulverized for 5 minutes in a planetary mill using 100 g of zirconia balls as a pulverization medium, and washed. A slurry was prepared. This slurry was applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and platinum-cupric oxide / titanium oxide was supported at a rate of about 150 g / L (layer thickness: 77 μm).
[0072]
(Preparation of second catalyst)
Barium carbonate (BaCO_Three ) 75.00 g and 49.98 g of hydrated alumina (GB-45 manufactured by Mizusawa Chemical Co., Ltd.) (46.48 g as alumina) were dispersed in 200 mL of ion-exchanged water. To this slurry, 100 mL of zirconia balls was added as a grinding medium, and wet milled with a planetary mill for 30 minutes. The slurry thus obtained was separated by filtration, dried, and then fired in air at 1200 ° C. for 3 hours to obtain a composite oxide of barium and aluminum (BaO · Al₂ O_Three And BaO · 6Al₂ O_Three Mixed crystal).
[0073]
30 g of this complex oxide powder of barium and aluminum, 30 g of γ-alumina powder (AC11K manufactured by Sumitomo Chemical Co., Ltd.) and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) are mixed with an appropriate amount of water. This was wet pulverized for 5 minutes by a planetary mill using 100 g of zirconia balls as a pulverization medium to prepare a slurry for wash coating. This slurry was applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and a composite oxide of barium and aluminum / γ-alumina was supported at a rate of about 150 g / L (layer thickness 81 μm).
[0074]
Next, 6.25 g of a dinitrodiammine platinum aqueous solution (15.09% by weight as platinum) was made 30 mL with ion-exchanged water, and the honeycomb base in which the barium / aluminum composite oxide and γ-alumina were supported in this aqueous solution. Barium and aluminum carrying 2% by weight of platinum by immersing the material, removing the excess aqueous solution attached, drying at 100 ° C. for 12 hours, and further firing in air at 600 ° C. for 3 hours A composite oxide / γ-alumina catalyst was obtained. The component ratio (weight ratio) of this catalyst is BaO.Al.₂ O_Three And BaO · 6Al₂ O_Three And mixed crystal / Pt / γ-alumina = 96.2 / 3.8 / 96.2.
[0075]
Example 3
(Preparation of the first catalyst for the second method)
2.80 g of rhodium nitrate aqueous solution (8.45 wt% as Rh) and ferric nitrate (Fe (NO_Three )_Three ・ 9H₂O) 2.70 g and activated titanium oxide (TiO)₂, Specific surface area 109m²/ G) 38.74 g was dispersed in 100 mL of ion exchange water. This slurry was dried with a spray dryer and calcined at 500 ° C. for 3 hours.₂O_Three) 2% by weight of powder was obtained.
[0076]
60 g of this powder and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) are mixed with an appropriate amount of water, and this is wet pulverized for 5 minutes in a planetary mill using 100 g of zirconia balls as a pulverization medium, and washed. A slurry was prepared. This slurry was applied to a honeycomb substrate made of cordierite having 200 cells / square inch,RhodiumFerric oxide / titanium oxide was supported at a rate of about 150 g / L (layer thickness 77 μm).
[0077]
(Preparation of intermediate catalyst)
5.13 g of dinitrodiammine platinum aqueous solution (15.09 wt% as platinum) and activated titanium oxide (TiO₂, Specific surface area 109m²/ G) 38.74 g was added to 100 mL of ion exchange water. This slurry was dried with a spray dryer and calcined at 500 ° C. for 3 hours to obtain a powder in which 2% by weight of platinum was supported on titanium oxide.
[0078]
60 g of this powder and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) are mixed with an appropriate amount of water, and this is wet pulverized for 5 minutes in a planetary mill using 100 g of zirconia balls as a pulverization medium, and washed. A slurry was prepared. This slurry was applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and platinum / titanium oxide was supported at a rate of about 150 g / L (layer thickness: 75 μm).
[0079]
(Preparation of second catalyst)
Barium carbonate (BaCO_Three ) 75.00 g and alumina sol (A-20 manufactured by Nissan Chemical Industries, Ltd., alumina content 20 wt%) 193.70 g (38.74 g as alumina) were dispersed in 200 mL of ion-exchanged water. To this slurry, 100 mL of zirconia balls was added as a grinding medium, and wet milled with a planetary mill for 30 minutes. The slurry thus obtained was evaporated to dryness and then calcined in air at 600 ° C. for 3 hours to obtain a composite oxide of barium and aluminum (BaO · Al₂ O_Three )
[0080]
On the other hand, aluminum nitrate (Al (NO_Three )_Three ・ 9H₂ O) 275.96 g and titanium tetrachloride (TiCl_Four ) 125.01 g of an aqueous solution (containing 10% by weight of titanium as titanium oxide) was dissolved in 2 L of ion-exchanged water. 1 / 10N aqueous ammonia was added dropwise thereto while stirring, while adjusting the pH with a pH controller set to pH 8. After completion of dropping, the mixture was aged for 1 hour to obtain a slurry of a mixture of aluminum hydroxide and titanium hydroxide. The slurry was filtered, washed with water, and then fired in the air at 700 ° C. for 3 hours to obtain a 75/25 weight ratio mixture of alumina and titania.
[0081]
Next, 30 g of the composite oxide powder of barium and aluminum, 30 g of γ-alumina-titania mixture powder and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) were mixed with an appropriate amount of water, and this was mixed with zirconia. A slurry for wash coating was prepared by wet milling with a planetary mill for 5 minutes using 100 g of balls as a grinding medium. This slurry is applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and barium / aluminum composite oxide and γ-alumina-titania are supported at a rate of about 150 g / L (layer thickness 79 μm). It was.
[0082]
Next, 6.25 g of an aqueous solution of dinitrodiammine platinum (15.09 wt% as platinum) was made 30 mL with ion-exchanged water, and the honeycomb base in which the composite oxide of barium and aluminum and γ-alumina-titania were supported in this aqueous solution. After immersing the material, the excess aqueous solution attached was removed, dried at 100 ° C. for 12 hours, further calcined in air at 600 ° C. for 3 hours, and supported with 2% by weight of platinum. A composite oxide of aluminum / γ-alumina-titania catalyst was obtained. The component ratio (weight ratio) of this catalyst is BaO.Al.₂ O_Three /Pt/γ-alumina/titania=96.2/3.8/72.1/24.0.
[0083]
Example 4
(Preparation of the first catalyst for the second method)
2.80 g of rhodium nitrate aqueous solution (8.45 wt% as Rh) and zinc nitrate (Zn (NO_Three )₂・ 6H₂O) 2.83 g and activated titanium oxide (TiO₂, Specific surface area 109m²/ G) 38.74 g was dispersed in 100 mL of ion exchange water. The slurry was dried with a spray dryer and fired at 500 ° C. for 3 hours to obtain a powder in which titanium oxide was supported by 1% by weight of rhodium and 2% by weight of zinc oxide (ZnO).
[0084]
60 g of this powder and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) are mixed with an appropriate amount of water, and this is wet pulverized for 5 minutes in a planetary mill using 100 g of zirconia balls as a pulverization medium, and washed. A slurry was prepared. This slurry was applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and rhodium-zinc oxide / titanium oxide was supported at a rate of about 150 g / L (layer thickness of 77 μm).
[0085]
(Preparation of intermediate catalyst)
5.13 g of dinitrodiammine platinum aqueous solution (15.09 wt% as platinum) and active zirconia (obtained by calcining zirconium hydroxide at 500 ° C. for 3 hours, ZrO₂, Specific surface area 46m²/ G) 38.74 g was added to 100 mL of ion exchange water. The slurry was dried with a spray dryer and fired at 500 ° C. for 3 hours to obtain a powder in which 2% by weight of platinum was supported on zirconia.
[0086]
60 g of this powder and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) are mixed with an appropriate amount of water, and this is wet pulverized for 5 minutes in a planetary mill using 100 g of zirconia balls as a pulverization medium, and washed. A slurry was prepared. This slurry was applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and platinum / zirconia was supported at a rate of about 150 g / L (layer thickness: 75 μm).
[0087]
(Preparation of second catalyst)
Prepared in the same manner as in Example 3.
[0088]
Example 5
(Preparation of the first catalyst for the second method)
  Rhodium nitrate aqueous solution (as Rh 8. 45% by weight) 2. 80g and aluminum nitrate (Al (NO _Three ) _Three ・ 9H ₂ O) 2. 85g and activated titanium oxide (TiO ₂ , Specific surface area 109m ² / G) 3 8. 74 g was dispersed in 100 mL of ion exchange water. This slurry was dried with a spray dryer and calcined at 500 ° C. for 3 hours. The titanium oxide was mixed with 1% rhodium and aluminum oxide (Al ₂ O _Three ) 2% by weight of powder was obtained.
[0089]
  60 g of this powder and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) are mixed with an appropriate amount of water, and this is wet pulverized for 5 minutes in a planetary mill using 100 g of zirconia balls as a pulverization medium, and washed. A slurry was prepared. This slurry was applied to a honeycomb substrate made of cordierite having 200 cells / square inch,RhodiumAluminum oxide / titanium oxide was supported at a rate of about 150 g / L (layer thickness 77 μm).
[0090]
(Preparation of intermediate and second catalysts)
Prepared in the same manner as in Example 3.
[0091]
Example 6
(Preparation of the first catalyst for the second method)
7.75 g of iridium chloride aqueous solution (5.00% by weight as iridium) and manganese nitrate (Mn (NO_Three)₂・ 6H₂O) 2.56 g and tin oxide (obtained by baking tin hydroxide at 500 ° C. for 3 hours, SnO₂Specific surface area 31m²/ G) 38.74 g was dispersed in 100 mL of ion exchange water. This slurry was dried with a spray dryer and calcined at 500 ° C. for 3 hours. The tin oxide was mixed with 1% by weight of iridium and manganese dioxide (MnO₂) 2% by weight of powder was obtained.
[0092]
60 g of this powder and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) are mixed with an appropriate amount of water, and this is wet pulverized for 5 minutes in a planetary mill using 100 g of zirconia balls as a pulverization medium, and washed. A slurry was prepared. This slurry was applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and iridium-manganese dioxide / tin oxide was supported at a rate of about 150 g / L (layer thickness: 77 μm).
[0093]
(Preparation of intermediate catalyst)
Prepared in the same manner as in Example 3.
[0094]
(Preparation of second catalyst)
In the preparation of the second catalyst in Example 3, in place of the dinitrodiammine platinum aqueous solution, chloroplatinic acid aqueous solution (15.09% by weight as platinum) 5.00 g and rhodium nitrate aqueous solution (Rh as 8.45% by weight) 2 A composite of barium and aluminum supporting 1.6% by weight of platinum and 0.4% by weight of rhodium in the same manner as in Example 3 except that an aqueous solution in which .24 g of the mixture was made 30 mL with ion-exchanged water was used. An oxide / γ-alumina catalyst was obtained. The component ratio (weight ratio) of this catalyst is BaO.Al.₂ O_Three /Pt/Rh/γ-alumina=96.1/3.1/0.8/96.2.
[0095]
Example 7
(Preparation of intermediate catalyst for the second method)
In the preparation of the intermediate catalyst in Example 3, titanium oxide was used in the same manner as in Example 3 except that 15.48 g of an iridium chloride aqueous solution (5.00% by weight as iridium) was used instead of the dinitrodiammine platinum aqueous solution. A powder carrying 2% by weight of iridium was obtained.
[0096]
60 g of this powder and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) are mixed with an appropriate amount of water, and this is wet pulverized for 5 minutes in a planetary mill using 100 g of zirconia balls as a pulverization medium, and washed. A slurry was prepared. This slurry was applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and iridium / titanium oxide was supported at a rate of about 150 g / L (layer thickness: 75 μm).
[0097]
(Preparation of first and second catalysts)
Prepared in the same manner as in Example 3.
[0098]
Example 8
(Preparation of second catalyst for second method)
Silver nitrate (AgNO_Three 4.75g and hydrated alumina (Al₂ O_Three ・ NH₂ O, 41.65 g (GB-45 manufactured by Mizusawa Chemical Co., Ltd.) (38.74 g as alumina) was dispersed in 100 mL of ion-exchanged water, this slurry was dried with a spray dryer, and calcined at 500 ° C. for 3 hours. Further, this was baked at 800 ° C. for 18 hours in an air atmosphere containing 10% of water to obtain silver aluminate (AgAlO₂ ) Was supported on γ-alumina in an amount of 2% by weight in terms of silver.
[0099]
FIG. 1 shows an X-ray diffraction diagram of γ-alumina supporting silver aluminate, and FIG. 2 shows an X-ray diffraction diagram of γ-alumina alone. In FIG. 1, ◯ indicates a peak due to silver aluminate, × indicates a peak due to alumina, and Δ indicates a peak due to silver.
[0100]
Next, 30 g of powder obtained by supporting the silver aluminate thus obtained on γ-alumina, 30 g of γ-alumina powder (AC11K manufactured by Sumitomo Chemical Co., Ltd.) and silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) 6 g) was mixed with an appropriate amount of water, and this was wet pulverized with a planetary mill for 5 minutes using 100 g of zirconia balls as a pulverization medium to prepare a slurry for wash coating. This slurry was applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and silver aluminate / γ-alumina was supported at a rate of about 150 g / L (layer thickness: 77 μm).
[0101]
Separately, a mixture of 5.00 g of chloroplatinic acid aqueous solution (15.09 wt% as platinum) and 2.24 g of rhodium nitrate aqueous solution (8.45 wt% as Rh) was made up to 30 mL with ion-exchanged water. The honeycomb substrate carrying aluminate / γ-alumina and γ-alumina is dipped, the excess aqueous solution attached is removed, dried at 100 ° C. for 12 hours, and further in air at 600 ° C. Calcination was performed for 3 hours to obtain a silver aluminate / γ-alumina / γ-alumina catalyst supporting 1.6% by weight of platinum and 0.4% by weight of rhodium. The component ratio (weight ratio) of this catalyst was silver aluminate / γ-alumina / Pt / Rh / γ-alumina = 96.1 / 3.1 / 0.8 / 96.2.
[0102]
(Preparation of first and intermediate catalysts)
Prepared in the same manner as in Example 3.
[0103]
Example 9
(Preparation of the first catalyst for the second method)
2.80 g of rhodium nitrate aqueous solution (8.45 wt% as Rh) and cobalt nitrate (Co (NO_Three )₂・ 6H₂3.01 g of O) and active titanium oxide (TiO)₂, Specific surface area 109m²/ G) 38.74 g was dispersed in 100 mL of ion exchange water. This slurry was dried with a spray dryer and calcined at 500 ° C. for 3 hours._ThreeO_Four) 2% by weight of powder was obtained.
[0104]
60 g of this powder and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) are mixed with an appropriate amount of water, and this is wet pulverized for 5 minutes in a planetary mill using 100 g of zirconia balls as a pulverization medium, and washed. A slurry was prepared. This slurry was applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and rhodium-cobalt oxide / titanium oxide was supported at a rate of about 150 g / L (layer thickness 77 μm).
[0105]
(Preparation of intermediate and second catalysts)
Prepared in the same manner as in Example 3.
[0106]
Example 10
(Preparation of the first catalyst for the second method)
2.57 g of dinitrodiammine platinum aqueous solution (15.09 wt% as platinum) and ferric nitrate (Fe (NO_Three )_Three ・ 9H₂O) 2.70 g and activated titanium oxide (TiO)₂, Specific surface area 109m²/ G) 38.74 g was dispersed in 100 mL of ion exchange water. This slurry was dried with a spray dryer and calcined at 500 ° C. for 3 hours, and 1 wt% platinum and ferric oxide (Fe₂O_Three ) 2% by weight of powder was obtained.
[0107]
60 g of this powder and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) are mixed with an appropriate amount of water, and this is wet pulverized for 5 minutes in a planetary mill using 100 g of zirconia balls as a pulverization medium, and washed. A slurry was prepared. This slurry was applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and platinum-ferric oxide / titanium oxide was supported at a rate of about 150 g / L (layer thickness: 77 μm).
[0108]
(Preparation of intermediate catalyst)
5.13 g of dinitrodiammine platinum aqueous solution (15.09 wt% as platinum) and activated titanium oxide (TiO₂, Specific surface area 109m²/ G) 38.74 g was added to 100 mL of ion exchange water. This slurry was dried with a spray dryer and calcined at 500 ° C. for 3 hours to obtain a powder in which 2% by weight of platinum was supported on titanium oxide.
[0109]
60 g of this powder and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) are mixed with an appropriate amount of water, and this is wet pulverized for 5 minutes in a planetary mill using 100 g of zirconia balls as a pulverization medium, and washed. A slurry was prepared. This slurry was applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and platinum / titanium oxide was supported at a rate of about 150 g / L (layer thickness: 75 μm).
[0110]
(Preparation of second catalyst)
Barium carbonate (BaCO_Three ) 75.00 g and alumina sol (A-20 manufactured by Nissan Chemical Industries, Ltd., alumina content 20 wt%) 193.70 g (38.74 g as alumina) were dispersed in 200 mL of ion-exchanged water. To this slurry, 100 mL of zirconia balls was added as a grinding medium, and wet milled with a planetary mill for 30 minutes. The slurry thus obtained was evaporated to dryness and then calcined in air at 600 ° C. for 3 hours to obtain a composite oxide of barium and aluminum (BaO · Al₂ O_Three )
[0111]
On the other hand, aluminum nitrate (Al (NO_Three )_Three ・ 9H₂ O) 275.96 g and titanium tetrachloride (TiCl_Four ) 125.01 g of an aqueous solution (containing 10% by weight of titanium as titanium oxide) was dissolved in 2 L of ion-exchanged water. 1 / 10N aqueous ammonia was added dropwise thereto while stirring, while adjusting the pH with a pH controller set to pH 8. After completion of dropping, the mixture was aged for 1 hour to obtain a slurry of a mixture of aluminum hydroxide and titanium hydroxide. The slurry was filtered, washed with water, and then fired in the air at 700 ° C. for 3 hours to obtain a 75/25 weight ratio mixture of alumina and titania.
[0112]
Next, 30 g of the composite oxide powder of barium and aluminum, 30 g of γ-alumina-titania mixture powder and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) were mixed with an appropriate amount of water, and this was mixed with zirconia. A slurry for wash coating was prepared by wet milling with a planetary mill for 5 minutes using 100 g of balls as a grinding medium. This slurry is applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and barium / aluminum composite oxide and γ-alumina-titania are supported at a rate of about 150 g / L (layer thickness 79 μm). It was.
[0113]
Next, a mixture of 5.00 g of an aqueous chloroplatinic acid solution (15.09 wt% as platinum) and 2.24 g of an aqueous rhodium nitrate solution (8.45 wt% as Rh) was made up to 30 mL with ion-exchanged water. After immersing the honeycomb substrate carrying the composite oxide of aluminum and aluminum and γ-alumina-titania, the excess aqueous solution adhering to the substrate was removed and dried at 100 ° C. for 12 hours. The mixture was calcined at 3 ° C. for 3 hours to obtain a barium and aluminum composite oxide / γ-alumina-titania catalyst carrying 1.6% by weight of platinum and 0.4% by weight of rhodium. The component ratio (weight ratio) of this catalyst is BaO.Al.₂ O_Three /Pt/Rh/γ-alumina-titania=96.1/3.3/0.8/96.2.
[0114]
Example 11
(Preparation of the first catalyst for the second method)
4.58 g of rhodium nitrate aqueous solution (8.45 wt% as Rh) and gallium nitrate (Ga (NO_Three)_Three・ NH₂O) 7.12 g and activated titanium oxide (TiO₂, Specific surface area 109m²/ G) 38.74 g was dispersed in 100 mL of ion exchange water. This slurry was dried with a spray dryer and calcined at 500 ° C. for 3 hours to obtain a powder in which 1% by weight of rhodium and 2% by weight of gallium were supported on titanium oxide.
[0115]
60 g of this powder and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) are mixed with an appropriate amount of water, and this is wet pulverized for 5 minutes in a planetary mill using 100 g of zirconia balls as a pulverization medium, and washed. A slurry was prepared. This slurry was applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and rhodium-gallium / titanium oxide was supported at a rate of about 150 g / L (layer thickness: 73 μm).
[0116]
(Preparation of intermediate and second catalysts)
Prepared in the same manner as in Example 10.
[0117]
Example 12
(Preparation of the first catalyst for the first method)
2.57 g dinitrodiammine platinum aqueous solution (15.09 wt% as platinum), 8.84 g palladium nitrate aqueous solution (4.37 wt% as Pd) and chromium nitrate (Cr (NO_Three)₂・ 9H₂O) 10.02 g and activated titanium oxide (TiO)₂, Specific surface area 109m²/ G) 38.74 g was dispersed in 100 mL of ion exchange water. This slurry was dried with a spray dryer and calcined at 500 ° C. for 3 hours, and titanium oxide was mixed with 1 wt% platinum, 0.5 wt% palladium and chromium oxide (CrO_Three) 2% by weight of powder was obtained.
[0118]
60 g of this powder and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) are mixed with an appropriate amount of water, and this is wet pulverized for 5 minutes in a planetary mill using 100 g of zirconia balls as a pulverization medium, and washed. A slurry was prepared. This slurry was applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and platinum-palladium / chromium oxide / titanium oxide was supported at a rate of about 150 g / L (layer thickness 73 μm).
[0119]
(Preparation of intermediate and second catalysts)
Prepared in the same manner as in Example 10.
[0120]
Example 13
(Preparation of intermediate catalyst)
2.57 g of dinitrodiammine platinum aqueous solution (15.09 wt% as platinum), 4.58 g of rhodium nitrate aqueous solution (8.45 wt% as Rh) and 8.86 g of palladium nitrate aqueous solution (4.37 wt% as Pd) Titanium oxide (TiO₂, Specific surface area 109m²/ G) 38.74 g was added to 100 mL of ion exchange water. This slurry was dried with a spray dryer and calcined at 500 ° C. for 3 hours to obtain a powder in which titanium oxide was supported by 1% by weight of platinum, 1% by weight of rhodium and 1% by weight of palladium.
[0121]
60 g of this powder and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) are mixed with an appropriate amount of water, and this is wet pulverized for 5 minutes in a planetary mill using 100 g of zirconia balls as a pulverization medium, and washed. A slurry was prepared. This slurry was applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and platinum-rhodium-palladium / titanium oxide was supported at a rate of about 150 g / L (layer thickness: 75 μm).
[0122]
(Preparation of first and second catalysts)
Prepared in the same manner as in Example 10.
[0123]
Example 14
(Preparation of the first catalyst for the first method)
7.75 g of iridium chloride aqueous solution (5.00% by weight as iridium) and ferric nitrate (Fe (NO_Three)₂・ 9H₂O) 9.42g and activated titanium oxide (TiO)₂, Specific surface area 109m²/ G) 38.74 g was dispersed in 100 mL of ion exchange water. This slurry was dried with a spray dryer and calcined at 500 ° C. for 3 hours to obtain a powder in which 1% by weight of iridium and 2% by weight of ferric oxide were supported on titanium oxide.
[0124]
60 g of this powder and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) are mixed with an appropriate amount of water, and this is wet pulverized for 5 minutes in a planetary mill using 100 g of zirconia balls as a pulverization medium, and washed. A slurry was prepared. This slurry was applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and iridium-ferric oxide / titanium oxide was supported at a rate of about 150 g / L (layer thickness: 73 μm).
[0125]
(Preparation of second catalyst)
Barium carbonate (BaCO_Three) 75.00g and hydrated alumina (Al₂O_Three ・ NH₂O, 41.65 g (GB-45 manufactured by Mizusawa Chemical Co., Ltd.) (38.74 g as alumina) was dispersed in 200 mL of ion-exchanged water. To this slurry, 100 mL of zirconia balls was added as a grinding medium, and wet milled with a planetary mill for 30 minutes. The slurry thus obtained was separated by filtration, dried, and then fired in air at 1100 ° C. for 3 hours to produce a composite oxide of barium and aluminum (BaO · Al₂ O_Three )
[0126]
30 g of this complex oxide powder of barium and aluminum, 30 g of γ-alumina powder (AC11K manufactured by Sumitomo Chemical Co., Ltd.) and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries, Ltd.) are mixed with an appropriate amount of water. This was wet pulverized for 5 minutes by a planetary mill using 100 g of zirconia balls as a pulverization medium to prepare a slurry for wash coating. This slurry is applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and BaO · AlO is applied._Three / Γ-alumina was supported at a rate of about 150 g / L (layer thickness 79 μm).
[0127]
Next, 6.25 g of a dinitrodiammine platinum aqueous solution (15.09 wt% as platinum) was made up to 30 mL with ion-exchanged water, and the BaO · Al was added to this aqueous solution.₂ O_Three / After immersing the honeycomb substrate carrying γ-alumina, the excess aqueous solution attached is removed, dried at 100 ° C. for 12 hours, and further fired in air at 600 ° C. for 3 hours. BaO · Al loaded with 2% by weight of platinum₂ O_Three / Y-alumina catalyst was obtained. The component ratio (weight ratio) of this catalyst is BaO.Al.₂ O_Three /Pt/γ-alumina=96.2/3.8/96.2.
[0128]
Example 15
(Preparation of second catalyst for second method)
A solution was prepared by dissolving 9.8 g of potassium acetate, 61.2 g of aluminum triisopropoxide, and 14.2 g of titanium tetraisopropoxide in 345 mL of 2-propanol. This solution was stirred at 80 ° C. for 2 hours, mixed with 18.0 g of 2,4-pentanedione, further stirred for 3 hours, and then mixed with 39.6 mL of ion exchange water and 40 mL of 2-propanol. The solution was added dropwise while maintaining at 80 ° C. and stirred at 80 ° C. for 5 hours. Thereafter, the obtained reaction mixture was dried under reduced pressure, and further calcined at 800 ° C. for 5 hours in an air atmosphere to obtain a composite oxide of potassium, titanium, and aluminum (K₂ O.3Al₂ O_Three ・ TiO₂ ) Was obtained.
[0129]
30 g of this composite oxide powder, 30 g of γ-alumina powder (AC11K manufactured by Sumitomo Chemical Co., Ltd.) and 6 g of silica sol (Snowtex N manufactured by Nissan Chemical Industries Co., Ltd.) are mixed with an appropriate amount of water. A wash coat slurry was prepared by wet milling with a planetary mill using 100 g of zirconia balls as a grinding medium for 5 minutes. This slurry is applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and the above-mentioned composite oxide of potassium, titanium and aluminum / γ-alumina is supported at a rate of about 150 g / L (layer thickness 79 μm). I let you.
[0130]
Next, 6.25 g of an aqueous solution of dinitrodiammine platinum (15.09% by weight as platinum) was made 30 mL with ion-exchanged water, and a honeycomb oxide in which the composite oxide of potassium, titanium, and aluminum / γ-alumina was supported in this aqueous solution. After immersing the substrate, the excess aqueous solution adhering to it was removed, dried at 100 ° C. for 12 hours, and further calcined in air at 600 ° C. for 3 hours to carry 2% by weight of platinum.₂ O.3Al₂ O_Three ・ TiO₂ / Y-alumina catalyst was obtained. The component ratio (weight ratio) of this catalyst is K₂ O.3Al₂ O_Three ・ TiO₂ /Pt/γ-alumina=96.2/3.8/96.2.
[0131]
(Preparation of first and intermediate catalysts)
Prepared in the same manner as in Example 13.
[0132]
Example 16
(Preparation of second catalyst for second method)
Barium carbonate (BaCO_Three) 75.00g and hydrated alumina (Al₂O_Three・ NH₂O, 41.65 g (GB-45 manufactured by Mizusawa Chemical Co., Ltd.) (38.74 g as alumina was dispersed in 200 mL of ion-exchanged water. To this slurry was added 100 mL of zirconia balls as a grinding medium, and a planetary mill for 30 minutes. The slurry thus obtained was filtered and separated, dried and then calcined in air at 1100 ° C. for 3 hours to obtain a composite oxide of barium and aluminum (BaO · Al₂O_Three)
[0133]
25 g of this complex oxide powder of barium and aluminum, 5 g of zirconia stabilized ceria (zirconia content 20%), 30 g of γ-alumina powder (AC11K manufactured by Sumitomo Chemical Co., Ltd.) and silica sol (manufactured by Nissan Chemical Industries, Ltd.) Snowtex N) (6 g) was mixed with an appropriate amount of water, and this was wet pulverized with a planetary mill for 5 minutes using 100 g of zirconia balls as a pulverization medium to prepare a slurry for wash coating. This slurry is applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and BaO · Al₂O_Three-Zirconia stabilized ceria / γ-alumina was supported at a rate of about 150 g / L (layer thickness 79 µm).
[0134]
Next, 6.25 g of a dinitrodiammine platinum aqueous solution (15.09 wt% as platinum) was made up to 30 mL with ion-exchanged water, and the BaO · Al was added to this aqueous solution.₂O_Three/ After immersing the honeycomb substrate carrying γ-alumina, the excess aqueous solution attached is removed, dried at 100 ° C. for 12 hours, and further fired in air at 600 ° C. for 3 hours. BaO · Al loaded with 2% by weight of platinum₂O_Three/ Zirconia stabilized ceria / γ-alumina catalyst was obtained. The component ratio (weight ratio) of this catalyst is BaO.Al.₂O_Three/ Zirconia stabilized ceria / Pt / γ-alumina = 86.6 / 9.6 / 3.8 / 96.2.
[0135]
(Preparation of first and intermediate catalysts)
Prepared in the same manner as in Example 13.
[0136]
Comparative Example 1
Barium carbonate (BaCO_Three) 20 g, 40 g of γ-alumina powder (AC11K manufactured by Sumitomo Chemical Co., Ltd.) and 6 g of silica sol are mixed with an appropriate amount of water. A slurry for wash coat was prepared. This slurry was applied to a honeycomb substrate made of cordierite having 200 cells / square inch, and barium carbonate and γ-alumina were supported at a rate of about 150 g / L (layer thickness 79 μm).
[0137]
6.25 g of dinitrodiammine platinum aqueous solution (15.09 wt% as platinum) is made up to 30 mL with ion-exchanged water, and the honeycomb substrate carrying the barium carbonate and γ-alumina is immersed in this aqueous solution and adhered. Excess aqueous solution was removed, dried at 100 ° C. for 12 hours, and further calcined in air at 600 ° C. for 3 hours to obtain a barium oxide / γ-alumina catalyst supporting 2% by weight of platinum. The component ratio (weight ratio) of this catalyst was BaO / Pt / γ-alumina = 96.2 / 3.8 / 96.2.
[0138]
(2) Evaluation test
Using the catalysts according to the above examples and comparative examples, purification of exhaust gas containing nitrogen oxides (catalytic reduction of nitrogen oxides) was performed under the following test conditions, and the removal rate of nitrogen oxides was determined by chemical luminescence. Obtained by law. At this time, the removal rate of nitrogen oxides was obtained from an integrated value having a function of the time of nitrogen oxide concentration under rich conditions and lean conditions.
[0139]
(Test conditions)
(1) Gas composition
▲ 1 ▼ Rich condition
NO 500ppm
O₂        0% by volume
Propylene 5000ppm
H₂        2% by volume
SO₂      40ppm
6% water
Nitrogen balance
[0140]
(2) Lean conditions
NO 500ppm
O₂        10% by volume
Propylene 500ppm
SO₂      40ppm
6% water
Nitrogen balance
The rich condition and the lean condition were vibrated alternately at 1 minute intervals.
[0141]
(2) Space velocity: 100,000 hrs in each reactor filled with the first and second catalysts or the first, intermediate and second catalysts^-1The exhaust gas was supplied.
[0142]
(3) Reaction temperature 200 ° C, 250 ° C, 300 ° C, 350 ° C, 400 ° C
The results are shown in Table 1.
[0143]
[Table 1]

[0144]
Next, using the catalysts prepared in Examples 1, 3, 8, 10, 13, 15, 16 and Comparative Example 1, the reaction was performed for 24 hours under the above reaction conditions except that the reaction temperature was 600 ° C. Thereafter, the exhaust gas was purified under the above reaction conditions, and the heat resistance and sulfur oxide resistance of the catalyst were evaluated. The results are shown in Table 2.
[0145]
[Table 2]

[0146]
【The invention's effect】
As is apparent from the results shown in Tables 1 and 2, according to the method of the present invention, even if the exhaust gas contains sulfur oxides or the catalyst is placed in a high temperature environment, Nitrogen oxide can be removed efficiently and stably.
[Brief description of the drawings]
FIG. 1 is an X-ray diffraction pattern of γ-alumina supporting silver aluminate.
FIG. 2 is an X-ray diffraction pattern of γ-alumina.

Claims (8)

By vibrating alternate between the processing atmosphere in the exhaust gas and the oxygen-rich atmosphere and a reducing atmosphere, the nitrogen oxides in the exhaust gas, Oite exhaust gas purification method for purifying a ternary component hydrocarbon and carbon monoxide exhaust gas (1) (a) at least one platinum group element selected from the group consisting of Pt, Rh, Pd and Ir, and (b) from the group consisting of silver, copper, zinc, gallium, chromium, iron, cobalt and nickel Contacting with a first catalyst comprising at least one selected metal or compound thereof or ion thereof and (c) titanium oxide;
(2) An exhaust gas purification method comprising contacting a second catalyst comprising (a) a nitrogen oxide storage material and (b) at least one platinum group element selected from the group consisting of Pt, Rh, Pd and Ir. The nitrogen oxide storage material is an oxide of at least one metal selected from alkali metals, alkaline earth metals, and rare earth elements, or at least one metal selected from alkali metals, alkaline earth metals, and silver. An exhaust gas purification method which is a composite oxide of at least one metal selected from aluminum and titanium . By vibrating alternate between the processing atmosphere in the exhaust gas and the oxygen-rich atmosphere and a reducing atmosphere, the nitrogen oxides in the exhaust gas, Oite exhaust gas purification method for purifying a ternary component hydrocarbon and carbon monoxide exhaust gas (1) (a) at least one platinum group element selected from the group consisting of Pt, Rh, Pd and Ir and (b) silver, copper, zinc, aluminum, gallium, tin, zirconium, chromium, manganese, iron First, consisting of at least one metal selected from the group consisting of cobalt and nickel, or a compound thereof, or an ion thereof and (c) at least one oxide selected from the group consisting of titanium oxide, zirconia and tin oxide Contacting the catalyst, then
(2) (a) at least one platinum group element selected from the group consisting of Pt, Rh, Ir and Pd; and (b) at least one oxide selected from the group consisting of titanium oxide, zirconia and tin oxide. Contact with an intermediate catalyst consisting of
(3) An exhaust gas purification method comprising contacting a second catalyst comprising (a) a nitrogen oxide storage material and (b) at least one platinum group element selected from the group consisting of Pt, Rh, Pd and Ir. The nitrogen oxide storage material is an oxide of at least one metal selected from alkali metals, alkaline earth metals, and rare earth elements, or at least one metal selected from alkali metals, alkaline earth metals, and silver. An exhaust gas purification method which is a composite oxide of at least one metal selected from aluminum and titanium .   In the second catalyst, the nitrogen oxide storage material is a composite oxide of an alkaline earth metal and aluminum, a composite oxide of an alkali metal, aluminum and titanium, or a composite oxide of silver and aluminum. 2. The exhaust gas purification method according to 2.   3. The exhaust gas purification method according to claim 1, wherein in the second catalyst, the nitrogen oxide storage material is a composite oxide of barium and aluminum.   The exhaust gas purification method according to claim 1 or 2, wherein in the second catalyst, the nitrogen oxide storage material is a composite oxide of potassium, aluminum, and titanium.   The exhaust gas purification method according to claim 1 or 2, wherein in the second catalyst, the nitrogen oxide storage material is silver aluminate.   The exhaust gas purification method according to claim 1 or 2, wherein a platinum group element is supported on a carrier in the second catalyst. The exhaust gas purification method according to claim 7 , wherein the carrier is alumina or titania.

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