JP4985351B2 - Exhaust gas treatment catalyst and exhaust gas purification device - Google Patents

Description

  The present invention relates to an exhaust gas treatment catalyst and an exhaust gas purification device, and is particularly effective when used for removing nitrogen oxides, hydrocarbons, and carbon monoxide in exhaust gas discharged from a diesel engine or the like.

  As an exhaust gas treatment catalyst for removing nitrogen oxides in exhaust gas discharged from a diesel engine or the like, for example, a honeycomb substrate is coated with a carrier on which a noble metal and a storage material that stores NOx are supported Is mentioned. Examples of the carrier include alumina, ceria, zirconia, and titania. Moreover, platinum, rhodium, and palladium are mentioned as said noble metal. Examples of the occlusion material include alkali metals such as potassium and alkaline earth metals such as barium.

  By installing such an exhaust gas treatment catalyst in an exhaust pipe of a diesel engine or the like, nitrogen oxides in the exhaust gas are removed. That is, when the exhaust gas is in a lean state (oxygen concentration is high (3% or more)), NO and oxygen react on the noble metal to generate NOx, and this NOx is occluded in the occlusion material.

  Also, create a reducing atmosphere in which exhaust gas is rich (oxygen concentration is low) by spraying organic compounds and fuels that serve as reducing agents on the exhaust gas treatment catalyst, or by increasing the amount of fuel injected by the engine. Thus, the NOx stored in the storage material moves onto the noble metal, and this NOx reacts with hydrocarbons and CO to produce water, nitrogen and carbon dioxide, which are discharged. Therefore, in the exhaust gas treatment catalyst, occlusion of nitrogen oxides and discharge of the occluded nitrogen oxides as nitrogen (catalyst regeneration treatment) are repeatedly performed.

  However, the basic metal (alkali metal, alkaline earth metal) of the above-described occlusion material is poisoned by sulfur contained in the fuel, and the occlusion performance of the nitrogen oxide is lowered. Sulfur is desorbed and removed by exposing the sulfur-poisoned occlusion material to a reducing atmosphere at a high temperature. The reducing atmosphere can be created by, for example, fuel injection or exhaust gas temperature increase, but the fuel consumption is deteriorated by such operation. Moreover, since the catalyst is exposed to a high temperature, thermal degradation occurs. Furthermore, the active metal is sintered and the performance of the exhaust gas treatment catalyst is degraded. Furthermore, when a diesel particulate filter (DPF) that removes particulate matter (PM) contained in the exhaust gas is installed in the exhaust pipe, the PM collected by the DPF is removed by combustion, and the exhaust gas treatment catalyst is hot. The chance of being exposed to increases.

  Various types of exhaust gas treatment catalysts containing perovskite catalysts, so-called complex oxides, have been developed as catalysts having high sulfur resistance and heat resistance in NOx storage catalysts such as NOx storage catalysts (see, for example, Patent Document 1).

JP 2006-346602 A

  Although nitrogen oxides contained in exhaust gas can be removed with the above-described exhaust gas treatment catalyst containing the composite oxide, further improvement in denitration performance is desired with such an exhaust gas treatment catalyst.

  Therefore, the present invention has been proposed in view of the above-described problems, and an object of the present invention is to provide an exhaust gas treatment catalyst and an exhaust gas purification device with further improved denitration performance.

The exhaust gas treatment catalyst according to the first invention for solving the above-mentioned problem is La _x Ba _(1-x) (Co _y Nb _1-y ) _(1-z) Pd _z O ₃ (where 0.5 ≦ x ≦ 0.9, 0.60 ≦ y ≦ 0.90, 0.01 ≦ z ≦ 0.15, and the molar amount of Nb is in the range of 0.15 to 0.25. comprising composite oxides have a, characterized in that it comprises a binder consisting mainly of cerium oxide.

The exhaust gas treatment catalyst according to the second invention for solving the above-mentioned problem is La _x Ba _1-x Nb _1-z Pd _z O ₃ (where 0.5 ≦ x ≦ 0.9, 0.01 ≦ a z ≦ 0.15 is.) the composite oxide possess consisting, characterized in that it contains a binder consisting mainly of cerium oxide.

  An exhaust gas treatment catalyst according to a third invention that solves the above-described problem is an exhaust gas treatment catalyst according to the first or second invention, and includes at least one kind of noble metal of Pt, Rh, Ir, and Ru. It is characterized by.

  An exhaust gas treatment catalyst according to a fourth invention that solves the above-described problem is an exhaust gas treatment catalyst according to the third invention, wherein the noble metal is contained in an amount of 0.01 to 5 wt% with respect to the composite oxide. It is characterized by being.

An exhaust gas purifying apparatus according to a fifth aspect of the present invention that solves the above-described problem is an exhaust gas purifying apparatus that reduces and purifies nitrogen oxides in exhaust gas, and is a collecting means that collects particulate matter in the exhaust gas. And an exhaust gas treatment catalyst according to any one of the first to fourth inventions, which is disposed downstream of the collecting means in the flow direction of the exhaust gas.

An exhaust gas purifying apparatus according to a sixth invention for solving the above-mentioned problem is an exhaust gas purifying apparatus according to the fifth invention, and is disposed upstream of the collecting means in the flow direction of the exhaust gas, It further has an oxidation catalyst for oxidizing unburned hydrocarbons, carbon monoxide, nitrogen oxides and graphite carbon components.

According to the exhaust gas treatment catalyst of the first invention, La _x Ba _(1-x) (Co _y Nb _1-y ) _(1-z) Pd _z O ₃ (where 0.5 ≦ x ≦ 0.9 And 0.60 ≦ y ≦ 0.90, 0.01 ≦ z ≦ 0.15, and the molar amount of Nb is in the range of 0.15 to 0.25. A conventional nitrogen oxide storage catalyst in which a noble metal containing at least one of barium carbonate and platinum, palladium, and rhodium is applied to or supported on a base material made of ceria, zirconia, or alumina. In comparison, the denitration rate is improved when the exhaust gas temperature is as high as 350 ° C. or 400 ° C. By including a binder containing cerium oxide as a main component, it is possible to suppress a decrease in the denitration rate as compared with the case where a conventional binder including aluminum oxide, silicon oxide, or zirconia oxide is included.

According to the exhaust gas treatment catalyst of the second invention, La _x Ba _1-x Nb _1-z Pd _z O ₃ (where 0.5 ≦ x ≦ 0.9 and 0.01 ≦ z ≦ 0. 15)), it adheres to a base material made of ceria, zirconia or alumina by applying or carrying a noble metal containing at least one of barium carbonate and platinum, palladium and rhodium. Compared with the conventional nitrogen oxide storage catalyst, the NOx removal rate is improved in a high temperature range where the exhaust gas temperature is about 310 ° C. or higher. In addition, by including a binder mainly composed of cerium oxide, it is possible to suppress a decrease in the denitration rate as compared with the case of including a conventional binder including aluminum oxide, silicon oxide, and zirconia oxide. .

  According to the exhaust gas treatment catalyst according to the third and fourth inventions, the same effect as the exhaust gas treatment catalyst according to the first and second inventions can be obtained, and the denitration performance when the exhaust gas temperature is high is maintained. However, the denitration performance on the low temperature side is improved.

According to the exhaust gas purification apparatus of the fifth aspect of the present invention, there is provided an exhaust gas purification apparatus that reduces and purifies nitrogen oxides in the exhaust gas, the collecting means for collecting the particulate matter in the exhaust gas, and the capture unit The exhaust gas treatment catalyst according to any one of the first to fourth inventions is disposed on the downstream side in the exhaust gas flow direction of the exhaust gas treatment catalyst. The collecting means collects and removes the particulate matter in the exhaust gas, can suppress the aged deterioration of the exhaust gas treatment catalyst due to the adhesion of the particulate matter, and can suppress an increase in operation cost.

According to the exhaust gas purification apparatus of the sixth aspect of the present invention, the exhaust gas purification device is disposed upstream of the collection means in the flow direction of the exhaust gas, and unburned hydrocarbons, carbon monoxide, nitrogen oxide, and graphite carbon in the exhaust gas. By having an oxidation catalyst that oxidizes the components, the same effect as the exhaust gas purifying apparatus according to the fifth aspect of the invention can be obtained, and unburned carbonization in the exhaust gas can be performed upstream of the exhaust gas treatment catalyst in the exhaust gas flow direction by the oxidation catalyst. Hydrogen, carbon monoxide, nitrogen oxides and graphite carbon components are oxidized, and nitrogen oxides can be efficiently purified by the exhaust gas treatment catalyst.

  Hereinafter, embodiments of an exhaust gas treatment catalyst and an exhaust gas purification apparatus according to the present invention will be specifically described with reference to the drawings.

[First embodiment]
The first embodiment of the exhaust gas treatment catalyst according to the present invention contains a composite oxide composed of a perovskite catalyst that purifies the exhaust gas by reducing nitrogen oxide in the exhaust gas to nitrogen. Specifically, it is represented by the following general formula (1).

A _x A ′ _(1-x) (B _y B ′ _(1-y) ) _(1-z) (PM) _z O ₃ (1)
However, the A component is lanthanum (La), the A ′ component is barium (Ba), the B component is cobalt (Co), the B ′ component is niobium (Nb), and PM (noble metal) is palladium (Pd). To do.

  In the above general formula (1), the range of x is 0.5 or more and 0.9 or less, the range of y is 0.60 or more and 0.90 or less, or 0, and the range of z is 0.01 or more and 0.00. 15 or less. Preferably, in the general formula (1), the range of x is 0.7 or more and 0.9 or less, the range of y is 0.70 or more and 0.90 or less or 0, and the range of z is 0.01 or more. 0.10 or less.

[Method for preparing exhaust gas treatment catalyst]
Here, examples of the method for preparing the exhaust gas treatment catalyst described above include the following two types (liquid phase method and solid phase method), but are not particularly limited thereto.

<Liquid phase method>
In this method, as a starting material, a metal salt solution containing La, Ba, Co, and Pd and an organic acid aqueous solution (acetic acid, oxalic acid, amino acid, niobium dioxide aqueous hydrogen peroxide solution or oxalic acid containing the above-described Nb component) Aqueous solutions such as aqueous niobium hydrogen starting sources). However, the above-mentioned starting materials are prepared in an aqueous solution having an arbitrary concentration before the following preparation process.

<Preparation procedure>
(1) First, each metal salt solution and an organic compound such as an organic acid aqueous solution are weighed so as to have a predetermined element ratio.
(2) Subsequently, each weighed aqueous metal salt solution is added to the reactor and mixed. This liquid is hereinafter referred to as a mixed liquid.
(3) Subsequently, the organic acid aqueous solution described above is gradually added while stirring the mixed solution, and stirred until the entire amount is dissolved.
(4) Subsequently, the water is evaporated and concentrated by an evaporator.
(5) Subsequently, it is put in a dryer, and the atmosphere in the vessel is dried at 250 ° C. to make a powder.
(6) Subsequently, the powder is pulverized in a mortar and then calcined at 600 to 1200 ° C. for 5 hours to obtain an exhaust gas treatment catalyst.
(7) If necessary, a noble metal is included in the exhaust gas treatment catalyst obtained in (6) above. For example, an exhaust gas treatment catalyst containing a noble metal can be obtained by impregnating the exhaust gas treatment catalyst in an organic acid aqueous solution in which the noble metal is dissolved and supporting the noble metal on the catalyst.

<Solid phase method>
In this method, starting materials such as oxides or carbonates containing La, Ba, Co, Nb, and Pd, a dispersant, and various solvents (H ₂ O, ethanol, methanol, etc.) are used. However, the above-described starting materials are sufficiently dried by placing them in a dryer having an internal atmosphere of 120 ° C. before the following preparation steps.

<Preparation procedure>
(1) First, various starting materials (dried at 120 ° C.), a dispersant and a solvent are weighed (the amount of the dispersant is 5 wt% of the powder weight, and the solvent is the same amount as the raw material powder).
(2) Subsequently, each weighed starting material, dispersant, solvent and grinding ball are placed in a container.
(3) Subsequently, pulverization, stirring, and mixing are performed in a ball mill.
(4) Subsequently, the water is evaporated and concentrated by an evaporator.
(5) Subsequently, it is put in a dryer, and the atmosphere in the vessel is dried at 120 ° C. to make a powder.
(6) Subsequently, the powder is pulverized in a mortar and then calcined at 800 to 1200 ° C. for 5 hours to obtain an exhaust gas treatment catalyst.
(7) If necessary, a noble metal is included in the exhaust gas treatment catalyst obtained in (6) above. For example, an exhaust gas treatment catalyst containing a noble metal can be obtained by impregnating the exhaust gas treatment catalyst in an organic acid aqueous solution in which the noble metal is dissolved and supporting the noble metal on the catalyst.

[Preparation of aqueous solution of niobium dioxide in hydrogen peroxide]
The above-described aqueous solution of niobium dioxide in hydrogen peroxide is prepared, for example, as follows.
Dissolve ₅ g of niobium chloride (NbCl ₅ ) in dilute aqueous ammonia (50 mL water + 4 mL aqueous ammonia (28%)), stir at room temperature for 30 minutes, collect the precipitated white precipitate by filtration and wash with water. Immediately after washing with water, the filtered product washed with water is added to a mixed solution of hydrogen peroxide (35% aqueous solution 25 mL + water 25 mL) and aqueous ammonia (28%, 6 mL) to obtain a colorless solution. This colorless solution is added (added) to 100 mL of acetone, and the resulting white precipitate is collected by filtration. The white precipitate collected by filtration was dissolved in 3.5% aqueous hydrogen peroxide to obtain a 3.5% aqueous hydrogen peroxide solution of niobium dioxide.

  As the noble metal used in the above-described method for preparing an exhaust gas treatment catalyst, a noble metal containing at least one of platinum (Pt), rhodium (Rh), iridium (Ir), and ruthenium (Ru) is particularly effective. The precious metal content is preferably 0.01 to 5 wt% with respect to the composite oxide. This is because if the content of the noble metal is less than 0.01 wt%, only the denitration performance similar to the case where the exhaust gas treatment catalyst does not contain the noble metal appears, and even if it exceeds 5 wt%, the denitration performance is constant and cannot be improved. .

  As the binder used in the above-described method for preparing an exhaust gas treatment catalyst, a binder containing cerium oxide as a main component is particularly effective.

[Catalyst Preparation Method 1]
1 mol of lanthanum nitrate hexahydrate, barium nitrate, cobalt nitrate hexahydrate, 3.5% hydrogen peroxide aqueous solution of niobium dioxide and palladium nitrate solution (Pd = 50 g / L) were each added with water. Solutions with concentrations of / L, 0.2 mol / L, 1 mol / L, 0.08 mol / L and 0.05 mol / L are prepared.

  Subsequently, a predetermined amount of the solution prepared to a predetermined concentration is taken and mixed. Specifically, the amount of lanthanum nitrate aqueous solution is 180 ml, the amount of barium nitrate aqueous solution is 100 ml, the amount of cobalt nitrate aqueous solution is 155 ml, the amount of niobium hydroxide aqueous solution is 242 ml, the amount of palladium nitrate aqueous solution is 120 ml, the amount of each metal ion Were mixed so that the molar ratio (La: Ba: Co: Nb: Pd) was 0.90: 0.10: 0.776: 0.194: 0.03 to obtain a mixed solution.

Further, 240 g of glycine was added to the above mixed solution and stirred for 30 minutes. Subsequently, the mixed solution to which glycine was added was concentrated by a rotary evaporator to be gelled. The gelled sample is put in a dryer, dried at 250 ° C., and the dried sample is calcined at 700 ° C. for 5 hours to have a composite oxide (La _0.9 Ba _0.1 Co _0.776 Nb _0.194 Pd _0.03 O ₃ ). 50 g of an exhaust gas treatment catalyst was obtained. The obtained exhaust gas treatment catalyst was used as a test catalyst (No. 1).

[Catalyst preparation method 2]
A predetermined amount of the solution prepared to a predetermined concentration by the catalyst preparation method 1 described above is taken and mixed. Specifically, the amount of lanthanum nitrate aqueous solution is 180 ml, the amount of barium nitrate aqueous solution is 100 ml, the amount of niobium hydroxide aqueous solution is 1212 ml, the amount of palladium nitrate aqueous solution is 120 ml, and the molar ratio of each metal ion (La: Ba: Nb: Pd) was mixed so as to be 0.90: 0.10: 0.97 : 0.03 to obtain a mixed solution.

Thereafter, the same operation as in the above-described catalyst preparation method 1 was performed to obtain 50 g of an exhaust gas treatment catalyst having a composite oxide (La _0.9 Ba _0.1 Nb _0.97 Pd _0.03 O ₃ ). The obtained exhaust gas treatment catalyst was used as a test catalyst (No. 2).

[Catalyst Preparation Method 3]
The test catalyst (No. 2) obtained by the catalyst preparation method 2 described above was blended with the catalyst 100 so that the binder containing cerium oxide as the main component was 5 to 20 wt% with respect to the catalyst 100 (No. 2). 3) was obtained.

[Catalyst preparation method 4]
The test catalyst (No. 4) was obtained by impregnating and supporting Pt and Rh on the test catalyst (No. 1) obtained by the catalyst preparation method 1 described above. However, the amount of Pt and the amount of Rh were 0.4 wt% and 0.04 wt% in weight ratio with respect to the test catalyst (No. 1).

(Comparative Example 1)
[Comparative Catalyst Preparation Method 1]
A nitrogen oxide storage catalyst (comparative catalyst (No. 1)) is prepared by applying or supporting a noble metal containing at least one of barium carbonate and platinum, palladium and rhodium to a base material made of ceria, zirconia or alumina. )

(Comparative Example 2)
[Comparative Catalyst Preparation Method 2]
The test catalyst (No. 2) obtained by the catalyst preparation method 2 described above was blended with the catalyst 100 so that the binder mainly composed of silicon oxide was 5 to 20 wt%, and the comparative catalyst (No. 2) was obtained.

(Comparative Example 3)
[Comparative Catalyst Preparation Method 3]
The test catalyst (No. 2) obtained by the catalyst preparation method 2 described above was blended with the catalyst 100 so that the binder mainly composed of zirconium oxide was 5 to 20 wt%, and the comparative catalyst (No. 2). 3) was obtained.

(Comparative Example 4)
[Comparative Catalyst Preparation Method 4]
The test catalyst (No. 2) obtained by the catalyst preparation method 2 described above was blended with the catalyst 100 so that the binder mainly composed of aluminum oxide was 5 to 20 wt% with respect to the catalyst 100 as a comparative catalyst (No. 4) was obtained.

(Comparative Example 5)
[Comparative Catalyst Preparation Method 5]
Platinum and barium carbonate were attached to an oxide containing cerium to obtain a nitrogen oxide storage catalyst (comparative catalyst (No. 5)).

[First denitration performance evaluation test]
With respect to the test catalyst (No. 1) and the comparative catalyst (No. 1), exhaust gas was circulated under the conditions shown in Table 1 below, and the denitration performance was measured. In Table 1, SV indicates space velocity (fluid flow rate / catalyst volume), and Lean / Rich indicates the ratio of lean / rich processing time.

The measurement results are shown in FIG.
In FIG. 1, the denitration rate is the average of the denitration rate when the processing gas is in a lean state and the denitration rate when the processing gas is in a rich state.

  When the exhaust gas temperature is 350 ° C., as shown in FIG. 1A, the test catalyst (No. 1) described above has a niobium content of about 0.05 mol around 0.2 mol. The denitration rate was higher than about 42%, and it was found that the denitration rate was higher than that of the comparative catalyst (No. 1).

  On the other hand, when the exhaust gas temperature is 400 ° C., as shown in FIG. 1 (b), the test catalyst (No. 1) described above has a niobium content of about 0.08 mol around 0.2 mol. Thus, the denitration rate was higher than about 32%, and it was found that the denitration rate was higher than that of the comparative catalyst (No. 1).

Therefore, according to the exhaust gas treatment catalyst of the first embodiment of the present invention, La _x Ba _(1-x) (Co _y Nb _{1 -y} ) _(1-z) Pd _z O ₃ (however, 0.5 ≦ x ≦ 0.9, 0.60 ≦ y ≦ 0.90, and 0.01 ≦ z ≦ 0.15.) By having a composite oxide consisting of ceria, zirconia, or alumina The exhaust gas temperature is 350 ° C. or 400 ° C. compared to a conventional nitrogen oxide storage catalyst in which a noble metal containing at least one of barium carbonate and platinum, palladium, and rhodium is applied or supported on the base material. The denitration rate is improved at such high temperatures. Furthermore, as a result, even when the exhaust gas temperature is high, such as when the engine is operating at high speed and high load, it can have a higher NOx removal rate compared to conventional catalysts, and the exhaust pressure increases and the exhaust gas temperature increases. As a result, the catalyst substrate having a high specific surface area that increases the temperature can be used, and the denitration apparatus can be made compact. Furthermore, since palladium is used as a noble metal element, it can be produced at a significantly lower cost than a catalyst containing platinum and is excellent in heat resistance at high temperatures. Therefore, when performing the sulfur removal process (regeneration process) required at the time of catalyst performance deterioration, there is little catalyst deterioration.

  In the above description, the exhaust gas treatment catalyst prepared by the liquid phase method in each example has been described. However, an exhaust gas treatment catalyst prepared by the solid phase method may be used. Even the exhaust gas treatment catalyst prepared by such a technique has the same effects as the above-described exhaust gas treatment catalyst.

[Second denitration performance evaluation test]
With respect to the test catalyst (No. 2) and the comparative catalyst (No. 1), exhaust gas was circulated under the conditions shown in Table 2 below, and the denitration performance was measured. In Table 2, SV indicates space velocity (fluid flow rate / catalyst volume), and Lean / Rich indicates the ratio of lean / rich processing time.

The measurement results are shown in FIG.
In FIG. 2, the denitration rate is an average of the denitration rate when the processing gas is in a lean state and the denitration rate when the processing gas is in a rich state.

  As shown in FIG. 2, the test catalyst (No. 2) described above was found to have a higher denitration rate than the comparative catalyst (No. 1) when the exhaust gas temperature was about 310 ° C. or higher.

Therefore, according to the exhaust gas treatment catalyst of the second embodiment of the present invention, La _x Ba _1-x Nb _1-z Pd _0.03 O ₃ (where 0.5 ≦ x ≦ 0.9; 01 ≦ z ≦ 0.15), by applying a noble metal containing at least one of barium carbonate, platinum, palladium, and rhodium to a substrate made of ceria, zirconia, or alumina. Alternatively, the denitration rate is improved in a high temperature range where the exhaust gas temperature is about 310 ° C. or higher as compared with a conventional nitrogen oxide storage catalyst deposited and supported. Furthermore, as a result, even when the exhaust gas temperature is high, such as when the engine is operating at high speed and high load, it can have a higher NOx removal rate compared to conventional catalysts, and the exhaust pressure increases and the exhaust gas temperature increases. As a result, the catalyst substrate having a high specific surface area that increases the temperature can be used, and the denitration apparatus can be made compact. Furthermore, since palladium is used as a noble metal element, it can be manufactured at a significantly lower cost than a catalyst containing platinum and is excellent in heat resistance at high temperatures. Therefore, when performing the sulfur removal process (regeneration process) required at the time of catalyst performance deterioration, there is little catalyst deterioration.

[Denitration performance of exhaust gas treatment catalyst by binder type]
With respect to the test catalyst (No. 3) and the comparative catalysts (No. 2 to No. 5), exhaust gas was circulated under the conditions shown in Table 2 above, and the denitration performance was measured.

The measurement results are shown in FIG.
In FIG. 3, the horizontal axis represents the exhaust gas temperature, and the vertical axis represents the denitration rate. This denitration rate is an average of the denitration rate when the processing gas is in a lean state and the denitration rate when the processing gas is in a rich state.

  The denitration rate of the test catalyst (No. 3) was about 32% when the exhaust gas temperature was 250 ° C. as shown in FIG. On the other hand, the comparison catalyst (No. 2) is about 28%, the comparison catalyst (No. 3) is about 15%, the comparison catalyst (No. 4) is about 18%, and the comparison catalyst (No. 5). ) Was about 23%. When the exhaust gas temperature was 300 ° C., the denitration rate of the test catalyst (No. 3) was about 41%. On the other hand, the comparative catalyst (No. 2) is about 32%, the comparative catalyst (No. 3) is about 28%, the comparative catalyst (No. 4) is about 27%, and the comparative catalyst (No. 5). ) About 33%. When the exhaust gas temperature was 350 ° C., the denitration rate of the test catalyst (No. 3) was about 43%. On the other hand, the comparative catalyst (No. 2) is about 33%, the comparative catalyst (No. 3) is about 29%, the comparative catalyst (No. 4) is about 31%, and the comparative catalyst (No. 5). ) About 34%. When the exhaust gas temperature was 400 ° C., the denitration rate of the test catalyst (No. 3) was about 48%. On the other hand, the comparative catalyst (No. 2) is about 28%, the comparative catalyst (No. 3) is about 24%, the comparative catalyst (No. 4) is about 29%, and the comparative catalyst (No. 5). ) Was about 32%. Therefore, it was found that the denitration rate of the test catalyst (No. 3) is higher than that of the comparative catalyst (No. 2 to No. 5) in the exhaust gas temperature range of 250 ° C. or higher and 400 ° C. or lower.

  Therefore, according to the exhaust gas treatment catalyst according to the third embodiment of the present invention, the conventional binder of aluminum oxide, silicon oxide, or zirconium oxide is obtained by including a binder mainly composed of cerium oxide. Compared with the case where it contains, the fall of a denitration rate can be suppressed. Furthermore, a high-density cell structure such as a honeycomb structure can be obtained, and the catalyst can be made compact.

[Third denitration performance evaluation test]
With respect to the test catalyst (No. 1) and the test catalyst (No. 4), exhaust gas was circulated under the conditions shown in Table 3 below, and the denitration performance was measured. In Table 3, Lean / Rich indicates the ratio of lean / rich processing time.

The measurement results are shown in FIG.
In FIG. 4, the horizontal axis indicates the exhaust gas temperature, and the vertical axis indicates the denitration rate. This denitration rate is an average of the denitration rate when the processing gas is in a lean state and the denitration rate when the processing gas is in a rich state.

  As shown in FIG. 4, the NOx removal rate of the test catalyst (No. 1) is about 9%, about 23%, and about 42% at exhaust gas temperatures of 270 ° C., 320 ° C., 370 ° C., 420 ° C., and 470 ° C., respectively. About 42% and about 36%. On the other hand, the denitration rate of the test catalyst (No. 4) is about 22%, about 64%, about 62%, about 270 ° C, 320 ° C, 370 ° C, 420 ° C, 470 ° C, respectively. 50%, about 35%. That is, it was found that the denitration rate of the test catalyst (No. 4) was higher than that of the test catalyst (No. 1) in the exhaust gas temperature range of 250 to 450 ° C.

  Therefore, according to the exhaust gas treatment catalyst according to the fourth embodiment of the present invention, the Pt and Rh noble metals are contained in the composite oxide described above, so that the exhaust gas temperature is increased to 350 ° C or 400 ° C, for example. Thus, the NOx removal performance comparable to that of the exhaust gas treatment catalyst according to the first and second embodiments described above is maintained (without degrading the performance), and the exhaust gas temperature is, for example, 250 ° C. The reduction reaction to nitrogen is promoted, and the denitration performance is greatly improved as compared with these exhaust gas treatment catalysts.

[Exhaust gas purifying apparatus according to the first embodiment]
Below, 1st Embodiment of the exhaust gas purification apparatus using the exhaust gas treatment catalyst mentioned above is described.
FIG. 5 is a schematic view of the exhaust gas purification apparatus.

  As shown in FIG. 5, the exhaust gas purification apparatus 10 according to the first embodiment of the present invention includes a diesel particulate filter (DPF) 11 that is a collecting means for collecting particulate matter, an exhaust gas treatment catalyst 12, have. In the exhaust gas purification device 10, the exhaust gas 21 is introduced into the DPF 11, and particulate matter (PM) in the exhaust gas 21 is collected by the DPF 11 and PM is removed from the exhaust gas 21. The exhaust gas from which PM has been removed is introduced into the exhaust gas treatment catalyst 12, and the exhaust gas treatment catalyst 12 can purify nitrogen oxides in the exhaust gas. That is, in the exhaust gas purification apparatus 10, the DPF 11 and the exhaust gas treatment catalyst 12 are arranged in this order from the upstream side in the exhaust gas distribution direction.

As the exhaust gas treatment catalyst 12, it is possible to use a catalyst represented by the general formula: La _x Ba _(1-x) (Co _y Nb _{1 -y} ) _(1-z) Pd _z O ₃ . . However, the range of x is 0.5 or more and 0.9 or less, the range of z is 0.01 or more and 0.15 or less, and the range of y is 0 or 0.60 or more and 0.90 or less. is there.

  In the exhaust gas purification apparatus 10 described above, a fuel injection nozzle (fuel injection means) (not shown) is disposed upstream of the DPF 11 in the exhaust gas flow direction. By supplying the fuel as a reducing agent from the fuel injection nozzle periodically, for example, only for 4 seconds in 1 minute and supplying the exhaust gas to the exhaust gas treatment catalyst 12, the oxygen concentration in the exhaust gas 21 is lowered and stored in the exhaust gas treatment catalyst 12. Nitrogen oxide can be reduced and discharged as nitrogen. When the DPF 11 collects PM in the exhaust gas and collects a predetermined amount, the fuel injection nozzle performs post-injection that performs sub-injection after injection or in-cylinder main injection in the internal combustion engine, and raises the exhaust gas temperature. Thus, the PM collected in the DPF 11 is burned and removed.

  Therefore, according to the exhaust gas purification apparatus 10 according to the first embodiment of the present invention, the exhaust gas purification apparatus that reduces and purifies nitrogen oxides in the exhaust gas, the DPF 11 that collects PM in the exhaust gas, By having the exhaust gas treatment catalyst 12 disposed downstream of the DPF 11 in the exhaust gas distribution direction, the DPF 11 collects and removes PM in the exhaust gas. In addition to suppressing deterioration, nitrogen oxides in the exhaust gas from which PM has been removed by the exhaust gas treatment catalyst 12 can be removed. As a result, the life of the exhaust gas treatment catalyst 12 itself is extended, and an increase in operation cost due to maintenance such as periodic replacement of the catalyst 12 can be suppressed.

[Exhaust gas purification apparatus according to the second embodiment]
Below, 2nd Embodiment of the exhaust gas purification apparatus using the exhaust gas treatment catalyst mentioned above is described.
FIG. 6 is a schematic view of the exhaust gas purifying apparatus.

The exhaust gas purifying apparatus according to the present embodiment is the exhaust gas purifying apparatus 10 according to the first embodiment described above, in which an oxidation catalyst is arranged on the upstream side of the DPF 11 in the exhaust gas distribution direction, and the other configurations are the same. is doing.
In the exhaust gas purifying apparatus according to the present embodiment, the same components as those in the exhaust gas purifying apparatus according to the first embodiment described above are denoted by the same reference numerals, and description thereof is omitted.

  In the exhaust gas purification apparatus 30 according to the second embodiment of the present invention, as shown in FIG. 6, the oxidation catalyst 31, the DPF 11, and the exhaust gas treatment catalyst 12 are arranged in this order from the upstream side in the flow direction of the exhaust gas 40. The oxidation catalyst 31 oxidizes unburned hydrocarbons, carbon monoxide, nitrogen oxides, graphite carbon components and the like in the exhaust gas 40.

  Therefore, according to the exhaust gas purifying apparatus 30 according to the present embodiment, the unburned hydrocarbons, carbon monoxide, nitrogen oxide, and graphite carbon in the exhaust gas are upstream of the exhaust gas treatment catalyst 12 in the exhaust gas flow direction by the oxidation catalyst 31. Components and the like are oxidized, and nitrogen oxides can be efficiently purified by the exhaust gas treatment catalyst 12.

It is a graph which shows the relationship between the addition amount of niobium in an exhaust gas treatment catalyst, and a denitration rate. It is a graph which shows the relationship between the denitration rate of an exhaust gas treatment catalyst, and exhaust gas temperature. It is a graph which shows the relationship between the denitration rate by a binder seed | species, and exhaust gas temperature. It is a graph which shows the relationship between the denitration rate of an exhaust gas treatment catalyst, and exhaust gas temperature. 1 is a schematic configuration diagram of an exhaust gas purification apparatus according to a first embodiment of the present invention. It is a schematic block diagram of the exhaust gas purification apparatus which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

10, 30 Exhaust gas purification device 11 DPF
12 Exhaust gas treatment catalyst 31 Oxidation catalyst 20, 21, 40, 41 Exhaust gas

Claims (6)

La _x Ba _(1-x) (Co _y Nb _1-y ) _(1-z) Pd _z O ₃ (where 0.5 ≦ x ≦ 0.9 and 0.60 ≦ y ≦ 0.90 There are 0.01 ≦ z ≦ 0.15, binders molar amount of Nb is in the range of 0.15 to 0.25.) the composite oxide possess consisting mainly of cerium oxide exhaust gas treatment catalyst according to claim <br/> contain. It has a composite oxide composed of La _x Ba _1-x Nb _1-z Pd _z O ₃ (where 0.5 ≦ x ≦ 0.9 and 0.01 ≦ z ≦ 0.15). An exhaust gas treatment catalyst comprising a binder mainly composed of cerium oxide. An exhaust gas treatment catalyst according to claim 1 or claim 2,
An exhaust gas treatment catalyst comprising at least one precious metal of Pt, Rh, Ir and Ru. An exhaust gas treatment catalyst according to claim 3,
The exhaust gas treatment catalyst, wherein the precious metal is contained in an amount of 0.01 to 5 wt% with respect to the composite oxide. An exhaust gas purification device that reduces and purifies nitrogen oxides in exhaust gas,
A collecting means for collecting particulate matter in the exhaust gas;
An exhaust gas purification apparatus comprising the exhaust gas treatment catalyst according to any one of claims 1 to 4 , wherein the exhaust gas treatment catalyst is disposed downstream of the collection means in the flow direction of the exhaust gas. An exhaust gas purification device according to claim 5 ,
It further comprises an oxidation catalyst that is disposed upstream of the collecting means in the flow direction of the exhaust gas and oxidizes unburned hydrocarbons, carbon monoxide, nitrogen oxides, and graphite carbon components in the exhaust gas. Exhaust gas purification device.

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