JP2015066469A - Exhaust gas treatment catalyst and exhaust gas treatment apparatus, and exhaust gas treatment catalyst production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an exhaust gas treatment catalyst and an exhaust gas treatment apparatus that may reduce cost while exhibiting sufficient activity for eliminating harmful substances; and an exhaust gas treatment catalyst production method.SOLUTION: An exhaust gas treatment catalyst for eliminating harmful substances included in an exhaust gas contains Ag and a perovskite complex oxide having a perovskite structure represented by general formula ABOwhere the metal elements at A sites are two or more elements including La and Sr and the metal elements at B sites are one or more elements including Mn.

Description

  The present disclosure relates to an exhaust gas treatment catalyst and an exhaust gas treatment device used when purifying exhaust gas discharged from, for example, an engine or a combustor, and a method for manufacturing the exhaust gas treatment catalyst.

In recent years, exhaust gas regulations are becoming stricter from the viewpoint of environmental protection, and it is common for various engines and combustors to be equipped with exhaust gas treatment devices. For example, toxic substances such as carbon monoxide (CO), unburned hydrocarbons (HC), particulate matter (PM), and nitrogen oxides (NO _x ) are contained in combustion exhaust gas discharged from engines and combustors. In general, an exhaust gas treatment apparatus is provided with a catalyst for removing these harmful substances on the exhaust gas path.

The catalyst used in the exhaust gas treatment apparatus, the CO, HC, the ability to purify the harmful substances such as PM or NO _x is required, these have been used often capable of purifying Pt-based catalyst with high efficiency. For example, Patent Documents 1 and 2 disclose a Pt-based catalyst and a filter carrying the catalyst.

  However, a Pt-based catalyst is very expensive because it uses a rare metal, which is a rare metal, and since its reserves are small, it is becoming difficult to obtain it as resources are depleted. Therefore, as a catalyst not using a noble metal catalyst, for example, Patent Document 3 describes a catalyst containing a perovskite composite oxide.

JP 2004-41868 A JP 2004-42021 A Japanese Patent No. 2772130

  As described above, a catalyst using Pt, as represented by a Pt-based catalyst that has been widely used as an exhaust gas treatment catalyst, has high activity as a catalyst, but has a small circulation amount because Pt is a rare metal. It is known to be expensive. For this reason, an exhaust gas treatment apparatus using a Pt-based catalyst has a high catalyst cost component ratio, and therefore a low-cost catalyst is required. On the other hand, although the catalyst using the perovskite complex oxide described in Patent Document 3 can reduce the cost, the activity for purifying the harmful substances contained in the exhaust gas may not be sufficiently obtained.

  An object of at least one embodiment of the present invention is to provide an exhaust gas treatment catalyst, an exhaust gas treatment device, and a method for producing an exhaust gas treatment catalyst that can suppress costs while having sufficient activity for purifying harmful substances. That is.

An exhaust gas treatment catalyst according to at least one embodiment of the present invention comprises:
An exhaust gas treatment catalyst for purifying harmful substances contained in exhaust gas,
In the perovskite structure represented by the general formula ABO ₃ , the perovskite complex oxidation in which the metal element at the A site is two or more elements including La and Sr, and the metal element at the B site is one or more elements including Mn It contains a product and Ag.

As a result of intensive studies, the present inventors have found that a catalyst having high activity without using Pt has a perovskite structure represented by the general formula ABO ₃ , and the A-site metal element contains La and Sr. And a catalyst for exhaust gas treatment containing a perovskite complex oxide in which the metal element at the B site is one or more elements including Mn and Ag. Since this exhaust gas treatment catalyst is excellent in the combustion performance of particulate matter (PM), for example, at the time of forced regeneration of DPF, it is possible to effectively burn and remove PM. In addition to this, the temperature for forcibly regenerating the DPF can be lowered. Moreover, since the temperature at the time of forced regeneration of DPF can be lowered, an expensive heat-resistant material becomes unnecessary, and the risk of excessive temperature rise during PM combustion can be reduced. Furthermore, according to the exhaust gas treatment catalyst, high oxidation performance for NO can be obtained. As a result, the exhaust gas treatment apparatus using the exhaust gas treatment catalyst can extend the DPF forced regeneration interval by continuous regeneration during normal operation, thereby improving fuel efficiency. Furthermore, since the oxidation activity of unburned carbon (HC) and carbon monoxide (CO) can be maintained high, various harmful substances contained in the exhaust gas can be effectively removed.

In some embodiments, in the exhaust gas treatment catalyst, a molar ratio of the Ag to the perovskite composite oxide is 0.05 or more and 0.2 or less.
When the molar ratio of Ag to the perovskite complex oxide is less than 0.05, it cannot be said that sufficient oxidation activity for HC and CO can be obtained. On the other hand, when the molar ratio of Ag is more than 0.2 with respect to the perovskite complex oxide, there are few cost advantages compared to the Pt-based catalyst. Therefore, by setting the content of Ag within the above range, it is possible to provide an exhaust gas treatment catalyst that can obtain a sufficient oxidation activity at low cost.
In one embodiment, in the exhaust gas treatment catalyst, the molar ratio of the Ag to the perovskite composite oxide is 0.1. Thereby, it can be set as the catalyst for waste gas treatment with low cost and high oxidation activity.

In one embodiment, the exhaust gas treatment catalyst has a sum of molar ratios of La, Sr, and Ag of 1 to the perovskite composite oxide.
As described above, by configuring the sum of the molar ratios of La, Sr, and Ag with respect to the perovskite complex oxide to be 1, the oxidation activity of CO, HC, and NO can be further increased, and the catalyst performance Can be improved.
In one embodiment, in the exhaust gas treatment catalyst, La and Sr have the same molar ratio. Thereby, the oxidation activity of the exhaust gas treatment catalyst can be further increased, and the catalyst performance can be improved.

In another embodiment, the exhaust gas treatment catalyst has a structure in which the perovskite composite oxide is used as a carrier and the Ag is supported on the carrier.
As described above, by impregnating the support made of the perovskite complex oxide with the solution containing Ag, Ag can be easily supported on the existing perovskite complex oxide.

An exhaust gas treatment apparatus according to at least one embodiment of the present invention includes:
An exhaust gas treatment device that removes at least nitrogen oxides from exhaust gas discharged from an engine,
An SCR (Selective Catalytic Reduction) catalyst provided in the exhaust gas flow path;
The exhaust gas treatment catalyst provided at substantially the same position as the SCR catalyst or upstream of the SCR catalyst in the exhaust gas flow direction.

According to the exhaust gas treatment apparatus, since the exhaust gas treatment catalyst described above exhibits excellent NO ₂ generation characteristics, the NO ₂ content in the exhaust gas is increased, and the denitration performance in the downstream SCR catalyst can be improved. . Furthermore, since the exhaust gas treatment catalyst described above exhibits excellent C ₃ H ₈ purification performance, it is possible to reduce HC poisoning of the downstream SCR catalyst. That is, by providing the above exhaust gas treatment catalyst at substantially the same position as the SCR catalyst or upstream of the SCR catalyst in the exhaust gas flow direction, the NH ₃ slip amount can be reduced while maintaining high denitration performance of the SCR catalyst. .

The exhaust gas treatment apparatus according to an embodiment further includes an oxidation catalyst (DOC) provided upstream of the SCR catalyst in the exhaust gas flow direction.
Thereby, carbon monoxide (CO) and HC (unburned hydrocarbon) contained in the exhaust gas can be effectively purified.

A method for producing an exhaust gas treatment catalyst according to at least one embodiment of the present invention includes:
A method for producing an exhaust gas treatment catalyst for purifying harmful substances contained in exhaust gas,
Mixing a metal nitrate aqueous solution containing La and Sr, a metal nitrate aqueous solution containing Mn, and a metal nitrate aqueous solution containing Ag to prepare a catalyst solution;
The catalyst solution is dried and then calcined to produce an exhaust gas treatment catalyst containing the perovskite complex oxide containing La, Sr and Mn, and Ag. And

  According to the above method for producing an exhaust gas treatment catalyst, the particulate matter (PM) has excellent combustion performance, high oxidation performance with respect to NO, and high oxidation performance with respect to unburned carbon (HC) and carbon monoxide (CO). An exhaust gas treatment catalyst having the following can be produced. In addition, the exhaust gas treatment catalyst produced by the above exhaust gas treatment catalyst production method is presumed to have a structure in which Ag is incorporated into the lattice of the perovskite structure. Therefore, sintering of Ag having low heat resistance can be suppressed and Ag can be present in high dispersion. Therefore, according to the exhaust gas treatment catalyst produced by the above exhaust gas treatment catalyst production method, high catalyst performance can be obtained.

In some embodiments, in the step of producing the exhaust gas treatment catalyst, the catalyst solution is dried and then calcined at 500 ° C. or more and 900 ° C. or less.
Thus, the catalyst raw material is calcined at a high temperature to produce an exhaust gas treatment catalyst, whereby an exhaust gas treatment catalyst having high heat resistance can be provided. For example, when an exhaust gas treatment catalyst is supported on a DPF, the exhaust gas treatment catalyst can withstand high temperatures during forced regeneration of the DPF.

A method for producing an exhaust gas treatment catalyst according to at least one embodiment of the present invention includes:
A method for producing an exhaust gas treatment catalyst for purifying harmful substances contained in exhaust gas,
Mixing a metal nitrate aqueous solution containing La and Sr and a metal nitrate aqueous solution containing Mn to prepare a carrier solution;
Producing the carrier by drying and then calcining the carrier solution;
Impregnating the carrier with an aqueous metal nitrate solution containing Ag;
A step of producing a catalyst for exhaust gas treatment containing the perovskite composite oxide containing La, Sr and Mn and Ag by drying the support impregnated in the aqueous silver nitrate solution and then firing. It is characterized by providing.

  According to the above method for producing an exhaust gas treatment catalyst, the particulate matter (PM) has excellent combustion performance, high oxidation performance with respect to NO, and high oxidation performance with respect to unburned carbon (HC) and carbon monoxide (CO). An exhaust gas treatment catalyst having the following can be produced. Further, by impregnating a support made of a perovskite composite oxide with a solution containing Ag, Ag can be easily supported on the existing perovskite composite oxide.

In some embodiments, in the step of manufacturing the carrier, the carrier solution is dried and then calcined at 500 ° C. or higher and 900 ° C. or lower.
Thus, by calcining the carrier material at a high temperature, an exhaust gas treatment catalyst having high heat resistance can be provided.

  According to at least one embodiment of the present invention, the particulate matter (PM) has excellent combustion performance, high oxidation performance with respect to NO, and high oxidation performance with respect to unburned carbon (HC) and carbon monoxide (CO). An exhaust gas treatment catalyst can be provided.

NO ₂ generation rate in the catalyst temperature 400 ° C. in an exhaust gas treatment catalyst according to the catalyst and Comparative Examples for exhaust gas treatment according to the present embodiment the (100 × catalyst outlet NO 2 _/ catalyst inlet NO) is a graph showing. C ₃ H ₈ purification rate (100 × (1−catalyst outlet C ₃ H ₈ concentration / catalyst inlet C ₃ H) at a catalyst temperature of 400 ° C. in the exhaust gas treatment catalyst according to the present embodiment and the exhaust gas treatment catalyst according to the comparative example. ₈ concentration)). It is a table | surface which shows the test conditions of FIG.1 and FIG.2. It is a graph which shows the combustion start temperature of C (carbon) in the exhaust gas processing catalyst which concerns on this embodiment, and the exhaust gas processing catalyst which concerns on a comparative example. It is a graph which shows the combustion temperature of C (carbon) in the exhaust gas processing catalyst which concerns on this embodiment, and the exhaust gas processing catalyst which concerns on a comparative example. It is a table | surface which shows the specific surface area of a catalyst powder. It is a flowchart which shows the procedure of the manufacturing method of the catalyst for exhaust gas treatment which concerns on one Embodiment. It is a flowchart which shows a part (procedure of manufacture of a support | carrier) of the procedure of the manufacturing method of the exhaust gas processing catalyst which concerns on other embodiment. It is a flowchart which shows a part of procedure of the manufacturing method of the exhaust gas processing catalyst which concerns on other embodiment (Ag carrying | support to a support | carrier). It is a graph which shows CO purification rate (100x (1-catalyst exit CO density | concentration / catalyst entrance CO density | concentration)) of the exhaust gas processing catalyst which concerns on this embodiment. It is a graph showing the NO ₂ generation rate of the exhaust gas treating catalyst according to the present embodiment. This _{C 3 H 6 (100 × (} 1- catalyst outlet _C 3 _{H 6} concentration / catalyst inlet _C 3 _{H 6} concentration)) of the exhaust gas treating catalyst according to the embodiment is a graph showing a purification rate. It is a figure which shows the structural example of the waste gas processing apparatus which concerns on this embodiment, and its peripheral device. It is a figure which shows the other structural example of the waste gas processing apparatus which concerns on this embodiment. It is a figure which shows the other structural example of the waste gas processing apparatus which concerns on this embodiment. It is a figure which shows the other structural example of the waste gas processing apparatus which concerns on this embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described below as the embodiments or shown in the drawings as the embodiments are not intended to limit the scope of the present invention. It is just an example.

An exhaust gas treatment catalyst according to an embodiment of the present invention is a catalyst for purifying harmful substances including at least one of particulate matter (PM), unburned carbon (HC), and carbon monoxide (CO) contained in exhaust gas. Used for oxidation of nitric oxide (NO).
In some embodiments, the exhaust gas treatment catalyst is a perovskite structure represented by the general formula ABO ₃ , wherein the metal element at the A site is two or more elements including La and Sr, and the metal element at the B site Contains perovskite complex oxide which is one or more elements including Mn, and Ag. In addition, Ag may be included in the metal element at the A site.

In one embodiment, the exhaust gas treatment catalyst has a molar ratio of Ag to the perovskite composite oxide of 0.05 or more and 0.2 or less, and preferably a molar ratio of Ag to the perovskite composite oxide is 0.1.
Here, when the molar ratio of Ag to the perovskite complex oxide is less than 0.05, it cannot be said that sufficient oxidation activity for HC and CO can be obtained. On the other hand, when the molar ratio of Ag is more than 0.2 with respect to the perovskite complex oxide, there are few cost advantages compared to the Pt-based catalyst. Therefore, by setting the content of Ag within the above range, it is possible to provide an exhaust gas treatment catalyst that can obtain a sufficient oxidation activity at low cost. In particular, when the molar ratio of Ag to the perovskite complex oxide is 0.1, an exhaust gas treatment catalyst with even lower cost and higher oxidation activity can be obtained.

In one embodiment, the exhaust gas treatment catalyst has a sum of molar ratios of La, Sr, and Ag to the perovskite composite oxide of 1, and preferably, La and Sr have the same molar ratio.
As described above, the total molar ratio of La, Sr, and Ag to the perovskite complex oxide is set to 1, so that the oxidation activity of CO, HC, and NO can be increased, and the catalyst performance is improved. it can. In particular, when La and Sr have the same molar ratio, the oxidation activity of the exhaust gas treatment catalyst can be further increased, and the catalyst performance can be improved.

As an example, the general formula ABO ₃ may be represented by La _X Sr _1-X MnO ₃ . In that case, x may be 0.5 or more and 0.9 or less (0.5 ≦ x ≦ 0.9).

Hereinafter, the result of performing a test comparing the performance of the exhaust gas treatment catalyst according to the present embodiment and the exhaust gas treatment catalyst according to the comparative example is shown.
As the exhaust gas treatment catalyst according to the present embodiment, in the perovskite structure represented by the general formula ABO ₃ , the metal element at the A site is two kinds of elements including La and Sr, and the metal element at the B site is Mn. and an element of the kind which perovskite complex oxide including (perovskite composite oxide), using a catalyst (Ag0.1 (La0.5Sr0.5) 0.9MnO ₃₎ containing a Ag. The exhaust gas treatment catalyst according to the comparative example, as Pt-based catalyst which has been conventionally used, a catalyst obtained by supporting 2 wt% of Pt on _{Al 2 O 3 (2wt% Pt} / Al 2 O 3), Al 2 O ₃ to 5 wt% of Ag and was supported catalyst and _{(5wt% Ag / Al 2 O} 3), and using a not containing Ag perovskite complex oxide single catalyst (La0.5Sr0.5MnO _3).

FIG. 1 is a graph showing the NO ₂ production rate (100 × catalyst outlet NO ₂ / catalyst inlet NO) at a catalyst temperature of 400 ° C. in the exhaust gas treatment catalyst according to this embodiment and the exhaust gas treatment catalyst according to the comparative example. FIG. 2 shows the C ₃ H ₈ purification rate (100 × (1−catalyst outlet C ₃ H ₈ concentration / catalyst inlet) at a catalyst temperature of 400 ° C. in the exhaust gas treating catalyst according to this embodiment and the exhaust gas treating catalyst according to the comparative example. C ₃ H ₈ concentration)) is a graph showing a. FIG. 3 is a table showing the test conditions of FIGS.
1 and 2 show the results of performance evaluation using a catalyst produced by the production method shown below.
First, a solvent and a binder are added to the calcined catalyst powder, and it is prepared and mixed using a ball mill to make a slurry. And this slurry is apply | coated to the surface of a honeycomb-shaped base material, and a honeycomb type catalyst is manufactured. The graphs shown in FIG. 1 and FIG. 2 are performance evaluation results in a state where the honeycomb catalyst is subjected to heat treatment at 760 ° C. for 100 hours in the air and the catalyst is thermally deteriorated at an accelerated rate.

When the exhaust gas purification test was performed under the test conditions shown in FIG. 3, the results shown in FIGS. 1 and 2 were obtained. As shown in FIG. 1, the exhaust gas treatment catalyst according to this embodiment has a significantly higher NO ₂ production rate than the conventional platinum-based catalyst (2 wt% Pt / Al ₂ O ₃ ) as a comparative example. . Further, a catalyst (5 wt% Ag / Al ₂ O ₃ ) in which 5% by weight of Ag is supported on Al ₂ O ₃ as a comparative example, and a catalyst of a perovskite composite oxide support containing no Ag (La0.5Sr0. Compared with 5MnO ₃ ), the NO ₂ production rate was higher. That shows the purification of the NO _x in the exhaust gas, since NO _x is to be reduced by the reaction of the following equation (1) to (3), the exhaust gas treatment catalyst for excellent NO ₂ generation characteristic of this embodiment From this, it can be seen that a high denitration performance can be obtained by containing the denitration catalyst (for example, SCR catalyst) upstream or in the denitration catalyst.
4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O (1)
2NO + 2NO ₂ + 4NH ₃ → 4N ₂ + 6H ₂ O (2)
6NO ₂ + 8NH ₃ + O ₂ → 7N ₂ + 12H ₂ O (3)

As shown in FIG. 2, the exhaust gas treatment catalyst according to the present embodiment is a conventional platinum-based catalyst (2 wt% Pt / Al ₂ O ₃ ) as a comparative example, 5 wt% Ag in Al ₂ O _3. The C ₃ H ₈ purification rate is significantly higher than the catalyst supporting 5 wt% Ag / Al ₂ O ₃ and the catalyst containing no perovskite complex oxide containing no Ag (La0.5Sr0.5MnO ₃ ). became. That is, it can be seen that the exhaust gas treatment catalyst according to the present embodiment has excellent HC purification performance.

4A and 4B show the results of the C (carbon) combustion performance test. FIG. 4 is a graph showing the combustion start temperature and combustion temperature of C (carbon) in the exhaust gas treatment catalyst according to the present embodiment and the exhaust gas treatment catalyst according to the comparative example, and FIG. FIG. 4B shows the temperature when the weight of the specimen is reduced by 50%. The performance evaluation results shown in FIGS. 4A and 4B are obtained by mixing 10 wt% of C (carbon) with the catalyst powder, and using TG-DTA (Thermogravimetric-Differential Thermal Analysis) to obtain weight change data during the temperature rise. It is the acquired result.
As the exhaust gas treatment catalyst (test body) according to the present embodiment, in the perovskite structure represented by the general formula ABO ₃ , the metal element at the A site is two kinds of elements including La and Sr. and perovskite composite oxide metal element is an element of the kind comprising Mn, using a catalyst (Ag0.1 (La0.5Sr0.5) 0.9MnO ₃₎ containing a Ag. Exhaust gas treatment catalyst according to Comparative Example The (specimen), the Pt-based catalyst which has been conventionally used, catalyst supported with 2 wt% Pt on _{Al 2 O 3 (2wt% Pt} / Al 2 O 3) Was used.

As shown in FIG. 4A and FIG. 4B, the exhaust gas treatment catalyst (Ag0.1 (La0.5Sr0.5) 0.9MnO ₃ ) according to this embodiment has 2% by weight of Pt supported on Al ₂ O _3. The combustion temperature is lower than that of the catalyst (2 wt% Pt / Al ₂ O ₃ ). That is, it can be seen that the PM combustion performance is superior to that of the comparative example.

As described above, according to the exhaust gas treatment catalyst according to this embodiment, the exhaust gas treatment catalyst is excellent in the combustion performance of particulate matter (PM). It can be burned and removed effectively. In addition to this, the temperature for forcibly regenerating the DPF can be lowered. Moreover, since the temperature at the time of forced regeneration of DPF can be lowered, an expensive heat-resistant material becomes unnecessary, and the risk of excessive temperature rise during PM combustion can be reduced. Furthermore, according to the exhaust gas treatment catalyst, high oxidation performance (NO ₂ generation characteristics) for NO can be obtained. In general, it is known that C (carbon) has a lower combustion temperature in combustion with NO ₂ (nitrogen dioxide) than combustion with O ₂ (oxygen). As a result, the exhaust gas treatment apparatus using the exhaust gas treatment catalyst can extend the DPF forced regeneration interval by continuous regeneration during normal operation, thereby improving fuel efficiency. Furthermore, since the oxidation activity of unburned carbon (HC) and carbon monoxide (CO) can be maintained high, various harmful substances contained in the exhaust gas can be effectively removed.

Moreover, according to the exhaust gas treatment catalyst according to the present embodiment, high catalyst performance can be obtained even with a low specific surface area. Here, FIG. 5 shows specific surface area data as basic physical properties of the catalyst. These specific surface areas are data of the catalyst powder before coating the honeycomb of each catalyst. For example, the specific surface area of ₂ wt% Pt / Al ₂ O ₃ (Pt catalyst) as a comparative example is 111 m ² / g. Moreover, the specific surface area of 5 wt% Ag / Al ₂ O ₃ as a comparative example is 110 m ² / g. In contrast, Ag _0.1 (La _0.5 Sr _0.5 ) _0.9 MnO ₃ of the exhaust gas treatment catalyst according to the present embodiment is 19 m ² / g, and 5 wt% Ag / La _0.5 Sr _0.5 ) _0.9 MnO ₃ is 24 m ² / g. As described above, the exhaust gas treatment catalyst according to the present embodiment has a very low specific surface area as compared with the Pt-based catalyst or the like, but exhibits high performance as shown in FIGS. 1, 2, 4A and 4B. . Furthermore, the exhaust gas treatment catalyst according to the present embodiment may be coated on a carrier having a high specific surface area, thereby further improving the performance of the catalyst.

Next, the manufacturing method of the exhaust gas treatment catalyst will be described in this embodiment.
FIG. 6 is a flowchart showing a procedure of a method for manufacturing an exhaust gas treatment catalyst according to an embodiment. In the example shown in FIG. 6, as a method for adding Ag, Ag is also mixed as a solution when preparing a perovskite composite oxide.

  In one embodiment, in step S1 shown in FIG. 6, an A metal nitrate aqueous solution and a B metal nitrate aqueous solution for forming a perovskite complex oxide are mixed with an aqueous silver nitrate solution to prepare a catalyst solution. Here, the A metal nitrate aqueous solution is formed by adding water to a nitrate containing the A site element of the perovskite complex oxide. In the present embodiment, the metal element at the A site contains La and Sr. The B metal nitrate aqueous solution is formed by adding water to a nitrate containing the B site element of the perovskite complex oxide. In this embodiment, the metal element at the B site contains Mn.

  Next, glycine is added to the catalyst solution prepared above and stirred in step S2. The stirring time in step S2 is, for example, 30 minutes. The amount of glycine added is approximately 8 times the total number of metal ion moles. In step S3, the catalyst solution is concentrated using, for example, a magnet stirrer with a heater. In step S4, the catalyst solution concentrated in step S3 is dried. In step S4, for example, drying is performed at 90 ° C. to 265 ° C. for about 3 days. In step S5, the catalyst raw material produced by drying the catalyst solution is mixed in a mortar. And in step S6, a catalyst raw material is baked at the temperature of 500 degreeC or more and 900 degrees C or less. In step S6, the temperature of the catalyst raw material may be raised stepwise, for example, 600 ° C, 700 ° C, 800 ° C. The firing time is approximately 4 hours.

  FIG. 7A is a flowchart showing a part of a procedure (manufacturing of a carrier) of a method for manufacturing an exhaust gas treatment catalyst according to another embodiment, and FIG. 7B is a procedure of a method of manufacturing an exhaust gas treatment catalyst according to another embodiment. It is a flowchart which shows a part of (Ag carrying | support to a support | carrier). In the example shown in FIG. 7, as a method for adding Ag, after the perovskite composite oxide is prepared, Ag is impregnated and supported using the perovskite composite oxide as a support.

  In one embodiment, in step S11 shown in FIG. 7A, an A metal nitrate aqueous solution and a B metal nitrate aqueous solution for forming a perovskite composite oxide are mixed to prepare a carrier solution. Here, the A metal nitrate aqueous solution is formed by adding water to a nitrate containing the A site element of the perovskite complex oxide. In the present embodiment, the metal element at the A site contains La and Sr. The B metal nitrate aqueous solution is formed by adding water to a nitrate containing the B site element of the perovskite complex oxide. In this embodiment, the metal element at the B site contains Mn.

  Next, glycine is added to the prepared carrier solution and stirred in step S12. The stirring time in step S12 is, for example, 30 minutes. The amount of glycine added is approximately 8 times the total number of metal ion moles. In step S13, the carrier solution is concentrated using, for example, a magnet stirrer with a heater. In step S14, the carrier solution concentrated in step S13 is dried. In step S14, for example, the film is dried at 90 ° C. to 265 ° C. for about 3 days. In step S15, the carrier raw material produced by drying the carrier solution is mixed in a mortar. In step S16, the carrier material is fired at a temperature of 500 ° C. or higher and 900 ° C. or lower. In step S16, the temperature of the carrier material may be raised stepwise, for example, 600 ° C., 700 ° C., and 800 ° C. The firing time is approximately 4 hours. In this way, a carrier mainly composed of perovskite complex oxide is produced.

Next, Ag is supported on the carrier manufactured in FIG. 7A.
In step S21 shown in FIG. 7B, the carrier is impregnated with an aqueous silver nitrate solution and mixed. In step S22, the carrier impregnated with the aqueous silver nitrate solution is dried to produce a catalyst raw material. In step S22, for example, a support impregnated with an aqueous silver nitrate solution is dried at a temperature range of 80 ° C. to 100 ° C. for 1 to 2 hours. Then, after mixing a catalyst raw material with a mortar at step S23, a catalyst raw material is baked at step S24. In step S24, baking is performed at 400 ° C. to 600 ° C. for approximately 5 hours.
In addition, the manufacturing method of the exhaust gas treatment catalyst according to the present embodiment is not limited to the above conditions.

FIGS. 8A to 8C show the exhaust gas treatment catalyst (Ag0.1 (La0.5Sr0.5) 0.9MnO ₃ ) produced in FIG. 6 and the exhaust gas treatment catalyst (5 wt% Ag produced in FIGS. 7A and 7B). It is the test result regarding the performance of /La0.5Sr0.5MnO ₃ ). Here, FIG. 8A is a graph showing the CO purification rate (100 × (1−catalyst outlet CO concentration / catalyst inlet CO concentration)) of the exhaust gas treatment catalyst according to the present embodiment, and FIG. 8B is the exhaust gas according to the present embodiment. FIG. 8C is a graph showing the NO ₂ production rate of the catalyst for treatment, and FIG. 8C shows C ₃ H ₆ (100 × (1−catalyst outlet C ₃ H ₆ concentration / catalyst inlet C ₃ H _{6) of the} exhaust gas treatment catalyst according to the present embodiment. Concentration)) is a graph showing the purification rate.
In addition, FIG. 8 has shown the result of having performed performance evaluation using the catalyst manufactured with the manufacturing method shown below.
First, a solvent and a binder are added to all the calcined catalyst powder, and the mixture is prepared and mixed using a ball mill to form a slurry. And this slurry is apply | coated to the surface of a honeycomb-shaped base material, and a honeycomb type catalyst is manufactured. The graph shown in FIG. 8 is a performance evaluation result in a state in which heat treatment at 760 ° C. for 100 hours in air is applied to the honeycomb type catalyst and the catalyst is thermally deteriorated at an accelerated rate.
As shown in FIG. 8A to FIG. 8C, the exhaust gas treatment catalyst (5 wt% Ag / La0.5Sr0.5) produced in FIGS. 7A and 7B was obtained at any purification rate and NO ₂ production rate of CO and C ₃ H ₆ . Compared with 5MnO ₃ ), the exhaust gas treatment catalyst (Ag0.1 (La0.5Sr0.5) 0.9MnO ₃ ) produced in FIG. 6 shows a higher value. That is, it can be seen that the exhaust gas treatment catalyst produced by mixing Ag as a solution when preparing the perovskite complex oxide as in the production method of FIG. 6 has a higher purification rate against various harmful substances. This is presumed that Ag is incorporated into the lattice of the perovskite structure, suppresses sintering of Ag having low heat resistance, and exhibits high performance because Ag exists in high dispersion. Therefore, it can be said that the production method shown in FIG. 6 and the exhaust gas treatment catalyst produced by the production method of FIG. 6 are excellent from the viewpoint of the purification rate for various harmful substances. However, the manufacturing method shown in FIGS. 7A and 7B is still useful because an existing perovskite composite oxide can be used.

Here, the configuration of the exhaust gas treatment apparatus using the exhaust gas treatment catalyst according to the present embodiment will be exemplified.
FIG. 9 is a diagram illustrating a configuration example of the exhaust gas treatment apparatus 20 according to the present embodiment. In addition, although the exhaust gas processing apparatus 20 used for a diesel engine is demonstrated here, this exhaust gas processing apparatus 20 may be used for other apparatuses, such as a gas engine and a combustor. Diesel engine exhaust gas contains, for example, HC, CO, NO _x , and PM.

FIG. 9 is a diagram showing a configuration example of the exhaust gas treatment apparatus and its peripheral devices according to the present embodiment.
First, the configuration of peripheral devices of the exhaust gas treatment apparatus 20 according to the present embodiment will be described.
In some embodiments, the air supply mechanism 1 for the engine 8 shown in FIG. 9 includes an intake pipe 2 for taking in the air supply, an air cooler 4 for cooling the air supply, and an air supply amount. The throttle valve 6 is provided. The intake pipe 2 may be provided with a turbocharger 3 including a compressor 3a and a turbine 3b. The turbocharger 3 may be a variable capacity turbocharger that can vary the supply air flow rate according to operating conditions. Further, the air supply mechanism 1 may have an EGR pipe 10 for returning a part of the exhaust gas of the engine 8 to the air supply inlet side. In this case, the EGR pipe 10 is provided with an exhaust gas recirculation cooler 12 for cooling the EGR and an exhaust gas recirculation valve 14 for controlling the O ₂ concentration of the supply air by adjusting the return amount of the EGR. It has been.
The engine 8 includes an engine main body 81 to which supply air is supplied and a fuel injection device 82 for supplying fuel to the engine main body 81. Part of the exhaust gas discharged from the engine 8 is returned to the supply side via the EGR pipe 10, and the other exhaust gas is sent to the exhaust gas treatment device 20 via the exhaust pipe 21.

In some embodiments, the exhaust gas treatment device 20 illustrated in FIG. 9 includes an SCR (Selective Catalytic Reduction) unit 24 for removing NOx contained in the exhaust gas. The SCR unit 24 includes an SCR catalyst that promotes a reaction between ammonia generated from urea water injected into the exhaust gas and nitrogen oxides (NO _x ), and a support mechanism that supports the SCR catalyst inside the exhaust pipe 21. Including. A urea water supply mechanism 22 for supplying urea water used for denitration is provided upstream of the SCR unit 24 in the exhaust gas flow direction. The urea water supply mechanism 22 includes a urea water tank 22b in which urea water is stored, and a urea water spray nozzle 22a that sprays urea water into the exhaust gas from the urea water tank 22b.

In one embodiment, the exhaust gas treatment catalyst 25 according to this embodiment is provided upstream of the SCR unit 24 or the SCR unit 24 in the exhaust gas flow direction. When the exhaust gas treatment catalyst 25 is provided in the SCR section 24, it is preferably disposed upstream of the SCR catalyst. When the exhaust gas treatment catalyst 25 is provided upstream of the SCR unit 24 in the exhaust gas flow direction, a support mechanism for supporting the exhaust gas treatment catalyst 25 inside the exhaust pipe 21 may be used.
As described above, the exhaust gas treatment catalyst 25 provided in the exhaust gas treatment apparatus 20 has a configuration containing a perovskite complex oxide and Ag. That is, the exhaust gas treatment catalyst 25 is a perovskite structure represented by the general formula ABO ₃ , wherein the metal element at the A site is two or more elements including La and Sr, and the metal element at the B site includes Mn. It contains a perovskite complex oxide, which is one or more elements, and Ag. Further, the exhaust gas treatment catalyst 25 may have a molar ratio of Ag to the perovskite composite oxide of 0.05 to 0.2. Further, the exhaust gas treatment catalyst 25 may have a molar ratio of Ag to the perovskite composite oxide of 0.1. Further, the exhaust gas treatment catalyst 25 may have a sum of molar ratios of La, Sr, and Ag to the perovskite complex oxide. Further, in the exhaust gas treatment catalyst 25, La and Sr may have the same molar ratio. Furthermore, the exhaust gas treatment catalyst 25 may have a structure in which a perovskite composite oxide is used as a carrier and Ag is supported on the carrier.

In the exhaust gas treatment device 20 having such a configuration, the urea water injected into the exhaust pipe 21 by the urea water supply mechanism 22 becomes ammonia (NH ₃ ) by the heat of the exhaust gas, and flows into the SCR unit 24 together with the exhaust gas. In the SCR unit 24, nitrogen oxide (NO _x ) contained in the exhaust gas reacts with ammonia in the presence of the SCR catalyst, whereby the nitrogen oxide is decomposed into nitrogen and water, thereby reducing the nitrogen oxide in the exhaust gas. It is like that. Specifically, nitrogen oxides are reduced by the chemical reactions shown in the above formulas (1) to (3).

Here, as described above, in the present embodiment, the exhaust gas treatment catalyst 25 is provided at substantially the same position as the SCR catalyst or upstream of the SCR catalyst in the exhaust gas flow direction. Since the exhaust gas treatment catalyst 25 exhibits excellent NO ₂ generation characteristics, the NO ₂ content in the exhaust gas becomes high, and the denitration performance in the downstream SCR catalyst can be improved. Further, since the exhaust gas treatment catalyst 25 exhibits excellent C ₃ H ₈ purification performance, it is possible to reduce HC poisoning of the downstream SCR catalyst. That is, by providing the exhaust gas treatment catalyst 25 at substantially the same position as the SCR catalyst or upstream of the SCR catalyst in the exhaust gas flow direction, the NH ₃ slip amount can be reduced while maintaining high denitration performance of the SCR catalyst.

  Hereinafter, with reference to FIG. 10A-FIG. 10C, the other structural example of the exhaust gas processing apparatus using the exhaust gas processing catalyst which concerns on this embodiment is demonstrated. In addition, FIG. 10A-FIG. 10C are figures which show the other structural example of the waste gas processing apparatus which concerns on this embodiment, respectively. In these drawings, the urea water supply mechanism 22 is omitted.

10A, a DOC (Diesel Oxidation Catalyst) unit 26 is provided on the upstream side of the SCR unit 24 in the exhaust gas flow direction. The DOC unit 26 purifies carbon monoxide (CO) and HC (unburned hydrocarbon) in exhaust gas and oxidizes nitric oxide (NO), and this oxidation catalyst is placed inside the exhaust pipe 21. And a supporting mechanism for supporting. In one embodiment, the above-described exhaust gas treatment catalyst 25 may be provided in the DOC unit 26 separately from the oxidation catalyst, or the above-described exhaust gas treatment catalyst 25 may be provided as an oxidation catalyst. Thereby, the high denitration performance of the SCR catalyst can be maintained, and the NH ₃ slip amount can be reduced.
In the exhaust gas treatment apparatus 20 </ b> A, the above-described exhaust gas treatment catalyst 25 may be provided in a part other than the DOC unit 26. For example, the above-described exhaust gas treatment catalyst 25 may be provided in the SCR unit 24, in the exhaust pipe 21 between the DOC unit 26 and the SCR unit 24, in the exhaust pipe 21 upstream of the DOC unit 26, or the like. Good. Further, the above-described exhaust gas treatment catalyst 25 may be provided in two or more parts.

10B, a DPF (Diesel particulate filter) unit 28 is provided on the upstream side of the SCR unit 24 in the exhaust gas flow direction. The DPF unit 28 includes a filter for removing particulate matter (PM) in the exhaust gas. In one embodiment, the exhaust gas treatment catalyst 25 is carried on the filter of the DPF unit 28. Thereby, the high denitration performance of the SCR catalyst can be maintained, and the NH ₃ slip amount can be reduced.
In the exhaust gas treatment apparatus 20B, the exhaust gas treatment catalyst 25 may be provided in a part other than the DPF unit 28. For example, the above-described exhaust gas treatment catalyst 25 may be provided in the SCR unit 24, in the exhaust pipe 21 between the DPF unit 28 and the SCR unit 24, in the exhaust pipe 21 upstream of the DPF unit 28, or the like. Good. Further, the above-described exhaust gas treatment catalyst 25 may be provided in two or more parts.

The exhaust gas treatment apparatus 20C shown in FIG. 10C has a configuration in which a DOC unit 26, a DPF unit 28, and an SCR unit 24 are provided in order from the upstream side in the exhaust gas flow direction. Since the configuration of each of the DOC unit 26, the DPF unit 28, and the SCR unit 24 has been described above, a description thereof will be omitted. FIG. 10C shows a configuration in which the above-described exhaust gas treatment catalyst 25 of the DPF unit 28 is provided as an example. However, the exhaust gas treatment catalyst 25 may be provided either inside the DOC 25, inside the SCR 24, or inside the exhaust pipe 21 connected to these parts.
In the exhaust gas treatment apparatus 20 </ b> C having such a configuration, first, CO, HC, and NO in the exhaust gas are oxidized when passing through the DOC portion 26, and PM in the exhaust gas is removed when passing through the DPF portion 28. At this time, since the exhaust gas treatment catalyst 25 described above is provided in the DPF section 28, CO and HC remaining in the exhaust gas are oxidized here, and NO ₂ is generated from NO in the exhaust gas. Then, in the SCR unit 24, NO ₂ in the exhaust gas is reduced to N ₂ .

  According to the exhaust gas treatment apparatus 20, since the exhaust gas treatment catalyst 25 has high PM combustion performance, it is possible to effectively burn and remove PM during forced regeneration of the DPF unit 28, The temperature for forcibly regenerating the DPF unit 28 can be lowered. Moreover, since the temperature at the time of forced regeneration of the DPF portion 28 can be lowered, an expensive heat-resistant material is not required, and an inexpensive DPF base material such as cordierite can be used, and an excessive temperature rise during PM combustion ( Risk of sudden temperature rise can be reduced. Furthermore, according to the exhaust gas treatment catalyst 25 described above, high oxidation performance with respect to NO can also be obtained. The exhaust gas treatment system 20C using the exhaust gas treatment catalyst 25 can extend the interval of DPF forced regeneration by continuous regeneration during normal operation, thereby improving fuel efficiency. Furthermore, since the oxidation activity of unburned carbon (HC) and carbon monoxide (CO) can be maintained high, various harmful substances contained in the exhaust gas can be effectively removed.

  As described above, according to the above-described embodiment, the particulate matter (PM) has excellent combustion performance, high oxidation performance with respect to NO, and high with respect to unburned carbon (HC) and carbon monoxide (CO). An exhaust gas treatment catalyst having oxidation performance can be provided.

  As mentioned above, although embodiment of this invention was described in detail, it cannot be overemphasized that this invention is not limited to this, In the range which does not deviate from the summary of this invention, various improvement and deformation | transformation may be performed. For example, in FIGS. 10A to 10C, the exhaust gas treatment device for purifying exhaust gas from a diesel engine has been described. However, the application destination of the exhaust gas treatment device may be a gas engine or a combustor. .

1 Exhaust pipe 22 Urea water supply mechanism 24 SCR section 25 Exhaust gas treatment catalyst 26 DOC part 28 DPF part

Claims (11)

An exhaust gas treatment catalyst for purifying harmful substances contained in exhaust gas,
In the perovskite structure represented by the general formula ABO ₃ , the perovskite complex oxidation in which the metal element at the A site is two or more elements including La and Sr, and the metal element at the B site is one or more elements including Mn And a catalyst for exhaust gas treatment, characterized by containing Ag and Ag.   2. The exhaust gas treatment catalyst according to claim 1, wherein a molar ratio of the Ag to the perovskite complex oxide is 0.05 or more and 0.2 or less.   The exhaust gas treatment catalyst according to claim 2, wherein the molar ratio of Ag to the perovskite complex oxide is 0.1.   The exhaust gas treatment catalyst according to any one of claims 1 to 3, wherein a sum of molar ratios of La, Sr, and Ag to the perovskite complex oxide is 1.   The exhaust gas treatment catalyst according to claim 4, wherein La and Sr have the same molar ratio.   The exhaust gas treatment catalyst according to any one of claims 1 to 5, wherein the exhaust gas treatment catalyst has a structure in which the perovskite complex oxide is used as a carrier and the Ag is supported on the carrier. An exhaust gas treatment device that removes at least nitrogen oxides from exhaust gas discharged from an engine,
An SCR (Selective Catalytic Reduction) catalyst provided in the exhaust gas flow path;
An exhaust gas treatment apparatus comprising: the exhaust gas treatment catalyst according to any one of claims 1 to 6 provided at substantially the same position as the SCR catalyst or upstream of the SCR catalyst in the exhaust gas flow direction. A method for producing an exhaust gas treatment catalyst for purifying harmful substances contained in exhaust gas,
Mixing a metal nitrate aqueous solution containing La and Sr, a metal nitrate aqueous solution containing Mn, and a metal nitrate aqueous solution containing Ag to prepare a catalyst solution;
The catalyst solution is dried and then calcined to produce an exhaust gas treatment catalyst containing the perovskite complex oxide containing La, Sr and Mn, and Ag. A method for producing an exhaust gas treatment catalyst.   9. The method for producing an exhaust gas treatment catalyst according to claim 8, wherein in the step of producing the exhaust gas treatment catalyst, the catalyst solution is dried and then calcined at 500 ° C. or higher and 900 ° C. or lower. A method for producing an exhaust gas treatment catalyst for purifying harmful substances contained in exhaust gas,
Mixing a metal nitrate aqueous solution containing La and Sr and a metal nitrate aqueous solution containing Mn to prepare a carrier solution;
Producing the carrier by drying and then calcining the carrier solution;
Impregnating the carrier with an aqueous metal nitrate solution containing Ag;
A step of producing a catalyst for exhaust gas treatment containing the perovskite composite oxide containing La, Sr and Mn and Ag by drying the support impregnated in the aqueous silver nitrate solution and then firing. And a method for producing an exhaust gas treatment catalyst. The method for producing a catalyst for exhaust gas treatment according to claim 10, wherein, in the step of producing the carrier, the carrier solution is dried and then calcined at 500 ° C or higher and 900 ° C or lower.

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