JP2021124070A - Exhaust emission control device - Google Patents

Abstract

To eliminate nitrogen oxide in a wide temperature range.SOLUTION: An exhaust emission control device in one embodiment includes: a first oxidation catalyst; a filter collecting particulate matters included in an exhaust gas, the filter supporting a first selective reduction catalyst including a silver alumina catalyst; a second selective reduction catalyst being provided downstream of the filter in an exhaust passage and including a silver alumina catalyst; a first fuel injector injecting fuel into the exhaust passage between the first oxidation catalyst and the filter; a second fuel injector injecting fuel into the exhaust passage between the filter and the second selective reduction catalyst; and a control device controlling a first injection amount that is an amount of fuel injected from the first fuel injector and a second injection amount that is an amount of fuel injected from the second fuel injector.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to an exhaust gas purification device.

Exhaust gas purification devices that purify the exhaust gas generated by an internal combustion engine are known. For example, Patent Document 1 below describes a first selective reduction catalyst having a platinum catalyst, a second selective reduction catalyst having a silver alumina catalyst or a silver zeolite catalyst, and a third selective reduction catalyst having a copper catalyst. An exhaust purification device including a first addition valve for adding fuel to the exhaust gas on the upstream side of the first selective reduction catalyst and a second addition valve for adding fuel to the exhaust gas on the upstream side of the second selective reduction catalyst. Is described. In this exhaust gas purification device, when the first selective reduction catalyst is activated, fuel is added from the first addition valve, and the second selective reduction catalyst and the third selective reduction catalyst are activated. If so, fuel is added from the second addition valve.

JP-A-2017-40239

In the above-mentioned exhaust gas purification device, the reduction efficiency of nitrogen oxides may be insufficient depending on the temperature of the exhaust gas. For example, in the above-mentioned exhaust gas purification device, a platinum catalyst is used as the first selective reduction catalyst. Since the temperature range in which nitrogen oxides can be reduced by the platinum catalyst is limited to 200 ° C. to 300 ° C., it is difficult for the above-mentioned exhaust purification device to reduce nitrogen oxides in a wide temperature range.

Therefore, there is a demand for an exhaust gas purification device capable of purifying nitrogen oxides in a wide temperature range.

In one aspect, an exhaust purification device is provided that purifies the exhaust gas emitted from the engine. This exhaust purification device is provided on the downstream side of the exhaust passage from the first oxidation catalyst provided in the exhaust passage through which the exhaust gas flows and the first oxidation catalyst, and collects particulate matter contained in the exhaust gas. A filter that carries a first selective reduction catalyst containing a silver alumina catalyst, a second selective reduction catalyst containing a silver alumina catalyst provided on the downstream side of the exhaust passage from the filter, and a second selective reduction catalyst. A first fuel injector that injects fuel into the exhaust passage between the oxidation catalyst 1 and the filter, and a second fuel that injects fuel into the exhaust passage between the filter and the second selective reduction catalyst. It controls the first injection amount, which is the amount of fuel injected from the injector and the first fuel injector, and the second injection amount, which is the amount of fuel injected from the second fuel injector. It includes a control device.

Since the heat of the exhaust gas gradually decreases as it flows to the downstream side of the exhaust passage, a temperature gradient is generated inside the exhaust passage. Therefore, a temperature difference occurs between the first selective reduction catalyst arranged on the upstream side of the exhaust passage and the second selective reduction catalyst arranged on the downstream side of the exhaust passage. Here, since the first selective reduction catalyst and the second selective reduction catalyst both have the silver alumina catalyst, they have the same activation temperature, but the first selective reduction catalyst and the second selective reduction catalyst have the same activation temperature. Since there is a temperature difference between the catalyst and the selective reduction catalyst, there is a difference in activity between the two. In this exhaust gas purification device, even when the exhaust temperature changes, nitrogen oxides can be reduced by using the catalyst having higher activity among the first selective reduction catalyst and the second selective reduction catalyst. , Nitrogen oxides can be reduced over a wide temperature range.

In one embodiment, a first catalyst temperature acquisition unit for acquiring the temperature of the first selective reduction catalyst and a second catalyst temperature acquisition unit for acquiring the temperature of the second selective reduction catalyst are further provided and controlled. The apparatus may control the ratio of the first injection amount to the second injection amount based on the temperatures of the first selective reduction catalyst and the second selective reduction catalyst.

As described above, the reduction efficiency of the first selective reduction catalyst and the second selective reduction catalyst depends on the temperatures of the first selective reduction catalyst and the second selective reduction catalyst. By controlling the ratio of the injection amount of 1 to the second injection amount, the reduction efficiency of nitrogen oxides can be improved.

In one embodiment, when the temperature at which the reduction efficiency of the first selective reduction catalyst and the second selective reduction catalyst is highest is set as the maximum activation temperature, the control device determines that the temperature of the first selective reduction catalyst is set to the maximum activation temperature. When the temperature is closer to the maximum activation temperature than the temperature of the second selective reduction catalyst, the ratio is large, and the temperature of the second selective reduction catalyst is closer to the maximum activation temperature than the temperature of the first selective reduction catalyst. In some cases, the first injection amount and the second injection amount may be controlled so that the ratio becomes small.

In this embodiment, when the temperature of the first selective reduction catalyst is close to the maximum activation temperature, the ratio of the first injection amount to the second injection amount is increased. As a result, the first injection amount is relatively increased, so that the nitrogen oxide can be efficiently reduced by using the first selective reduction catalyst having high reduction efficiency. On the contrary, when the temperature of the second selective reduction catalyst is close to the maximum activation temperature, the ratio of the first injection amount to the second injection amount is reduced. As a result, the second injection amount is relatively increased, so that the nitrogen oxide can be efficiently reduced by using the second selective reduction catalyst having high reduction efficiency.

In one embodiment, an ammonia reducing catalyst which is provided on the downstream side of the exhaust passage with respect to the second selective reduction catalyst and which oxidizes ammonia may be further provided. In the silver-alumina catalyst, ammonia is produced in the process of reducing nitrogen oxides. By providing an ammonia reduction catalyst on the downstream side of the second selective reduction catalyst, ammonia can be oxidized and purified.

In one embodiment, the filter may further carry a platinum-free second oxidation catalyst. In this embodiment, the particulate matter collected in the filter can be oxidized by the second oxidation catalyst. In one embodiment, the second oxidation catalyst may be supported on the inlet side of the filter and the first selective reduction catalyst may be supported on the outlet side of the filter.

According to one aspect of the invention and various embodiments, nitrogen oxides can be purified over a wide temperature range.

It is a figure which shows schematicly the exhaust gas purification apparatus which concerns on one Embodiment. It is sectional drawing which shows a part of the filter schematicly. It is a figure which shows the relationship between the temperature of the 1st selective reduction catalyst and the reduction rate of nitrogen oxides. It is a figure which shows the reduction rate of a nitrogen oxide. It is sectional drawing which shows typically the filter of the modification.

Hereinafter, various embodiments will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals, and duplicate explanations for the same or corresponding parts will be omitted. The terms "upstream" and "downstream" in the present specification are based on the flow direction of the exhaust gas.

FIG. 1 is a schematic configuration diagram of an exhaust gas purification device according to an embodiment. The exhaust gas purification device 20 shown in FIG. 1 is mounted on a vehicle having an engine (internal combustion engine) 1 and purifies the exhaust gas discharged from the engine 1 of the vehicle.

The engine 1 shown in FIG. 1 is, for example, a diesel engine and includes a plurality of cylinders (not shown). Pistons are provided inside the plurality of cylinders, and when fuel is injected into the cylinders, the pistons reciprocate in each cylinder to rotate the crankshaft. An intake manifold 2 for supplying air into the plurality of cylinders and an exhaust manifold 3 for discharging air from the plurality of cylinders are connected to the plurality of cylinders.

An intake passage 4 is connected to the intake manifold 2. The intake passage 4 is provided with a compressor 5 and an intercooler 6 in this order from the upstream side of the intake air. A flow path 7 through which intake air flows is connected to the compressor 5, and an air cleaner 8 is provided in the flow path 7.

An exhaust passage 10 is connected to the exhaust manifold 3 via a turbine 9. The turbine 9 is connected to the compressor 5 via a connecting shaft. The turbine 9 is rotated by the flow of exhaust gas discharged from the exhaust manifold 3 of the engine 1. The compressor 5 rotates with the rotation of the turbine 9, takes in air from the flow path 7, and sends the compressed air to the intake passage 4. The compressor 5 and the turbine 9 form a turbocharger.

The exhaust gas discharged from the exhaust manifold 3 by driving the engine 1 is supplied to the exhaust purification device 20 through the exhaust passage 10. The exhaust gas purification device 20 selectively reduces nitrogen oxides (NOx) contained in the exhaust gas to purify the exhaust gas.

As shown in FIG. 1, the exhaust gas purification device 20 includes a first oxidation catalyst 22, a filter 23, a first selective reduction catalyst 25, a second selective reduction catalyst 26, and an ammonia reduction catalyst 28. The first oxidation catalyst 22, the filter 23, the first selective reduction catalyst 25, the second selective reduction catalyst 26, and the ammonia reduction catalyst 28 are housed in a case forming a part of the exhaust passage 10.

As shown in FIG. 1, the first oxidation catalyst 22 is provided in the exhaust passage 10 on the downstream side of the turbine 9. The first oxidation catalyst 22 is, for example, an alumina carrier on which a noble metal catalyst such as platinum or palladium is supported. The first oxidation catalyst 22 oxidizes and purifies hydrocarbons (HC) and carbon monoxide (CO) contained in the exhaust gas.

The filter 23 is provided in the exhaust passage 10 on the downstream side of the first oxidation catalyst 22. For example, the filter 23 is a DPF (Diesel Particulate Filter) made of cordierite or silicon carbide (SiC), and collects particulate matter in the exhaust gas.

FIG. 2 is a cross-sectional view schematically showing a part of the filter 23. The arrow G shown in FIG. 2 indicates the flow of gas in the filter 23. As shown in FIG. 2, the filter 23 has a partition wall 23w that defines a plurality of passages 23p through which exhaust gas flows, and the partition wall 23w is coated with a first selective reduction catalyst 25. That is, the filter 23 carries the first selective reduction catalyst 25.

The first selective reduction catalyst 25 has a carrier containing alumina and a catalyst component containing silver. That is, the first selective reduction catalyst 25 contains a silver alumina catalyst. The first selective reduction catalyst 25 uses the fuel contained in the exhaust gas as a reducing agent to reduce the nitrogen oxides contained in the exhaust gas to nitrogen (N ₂ ) and water (H ₂ O). The first selective reduction catalyst 25 is activated at a temperature of, for example, 200 ° C. to 650 ° C., and has an ability to reduce nitrogen oxides in a wide temperature range.

The second selective reduction catalyst 26 is provided on the downstream side of the filter 23 in the exhaust passage 10. The second selective reduction catalyst 26 has a carrier containing alumina and a catalyst component containing silver. That is, like the first selective reduction catalyst 25, the second selective reduction catalyst 26 contains a silver alumina catalyst. The second selective reduction catalyst 26 uses the fuel contained in the exhaust gas as a reducing agent to reduce the nitrogen oxides contained in the exhaust gas to nitrogen (N ₂ ) and water (H ₂ O). Like the first selective reduction catalyst 25, the second selective reduction catalyst 26 is activated at temperatures, for example 200 ° C. to 650 ° C., to acquire the ability to reduce nitrogen oxides.

The ammonia reduction catalyst 28 is provided on the downstream side of the second selective reduction catalyst 26 in the exhaust passage 10. The ammonia reduction catalyst 28 contains, for example, a zeolite catalyst, and oxidizes the ammonia generated in the reduction reaction in the second selective reduction catalyst 26. The exhaust gas that has passed through the ammonia reduction catalyst 28 is released into the atmosphere.

The exhaust gas purification device 20 further includes a pump 30, fuel injectors 34, 35, 36, temperature sensors 37, 38, and a control device 40. The pump 30 pumps the fuel stored in the fuel tank 32 to the fuel injectors 34, 35, 36. The fuel sent to the fuel injectors 34, 35, 36 is a liquid fuel such as gasoline or light oil. The fuel injector 34 is provided on the upstream side of the first oxidation catalyst 22, and injects fuel into the exhaust passage 10 on the upstream side of the first oxidation catalyst 22.

The fuel injector (first fuel injector) 35 is provided on the downstream side of the first oxidation catalyst 22 and on the upstream side of the filter 23, and exhausts air between the first oxidation catalyst 22 and the filter 23. Fuel is injected into the passage 10. The fuel injected from the fuel injector 35 into the exhaust passage 10 is added to the exhaust gas and supplied to the first selective reduction catalyst 25. The first selective reduction catalyst 25 uses the fuel supplied from the fuel injector 35 as a reducing agent to reduce nitrogen oxides contained in the exhaust gas.

The fuel injector (second fuel injector) 36 is provided on the downstream side of the filter 23 and on the upstream side of the second selective reduction catalyst 26, and is between the filter 23 and the second selective reduction catalyst 26. Fuel is injected into the exhaust passage 10. The fuel injected from the fuel injector 36 is added to the exhaust gas and supplied to the second selective reduction catalyst 26. The second selective reduction catalyst 26 uses the fuel supplied from the fuel injector 36 as a reducing agent to reduce the nitrogen oxides contained in the exhaust gas.

These fuel injectors 34, 35, and 36 have a valve body whose opening degree can be adjusted, and supply fuel into the exhaust passage 10 with an injection amount corresponding to the opening degree of the valve body. As will be described later, the fuel injection amount from the fuel injectors 34, 35, 36 is controlled by the control device 40.

The temperature sensor (first catalyst temperature acquisition unit) 37 is provided on the upstream side of the first oxidation catalyst 22, and measures the temperature of the exhaust gas flowing in the exhaust passage 10 on the upstream side of the first oxidation catalyst 22. .. The temperature sensor (second catalyst temperature acquisition unit) 38 is provided on the downstream side of the filter 23 and on the upstream side of the second selective reduction catalyst 26, and is between the filter 23 and the second selective reduction catalyst 26. Measures the temperature of the exhaust gas flowing in the exhaust passage 10.

Information indicating the temperature of the exhaust gas measured by the temperature sensors 37 and 38 is output to the control device 40. As will be described later, the control device 40 acquires the temperatures of the first selective reduction catalyst 25 and the second selective reduction catalyst 26, respectively, based on the temperature information of the exhaust gas measured by the temperature sensors 37 and 38. That is, the temperature sensor 37 constitutes a first catalyst temperature acquisition unit that acquires the temperature of the first selective reduction catalyst 25, and the temperature sensor 38 acquires the temperature of the second selective reduction catalyst 26. It constitutes a catalyst temperature acquisition unit. In one embodiment, the temperature sensors 37 and 38 directly measure the temperatures of the first selective reduction catalyst 25 and the second selective reduction catalyst 26, and the measured first selective reduction catalyst 25 and the second selection are selected. The temperature of the reduction catalyst 26 may be transmitted to the control device 40.

In one embodiment, the exhaust purification device 20 may further include a NOx sensor 39. The NOx sensor 39 is provided, for example, on the downstream side of the filter 23 and on the upstream side of the second selective reduction catalyst 26. The NOx sensor 39 detects the concentration of nitrogen oxides (NOx concentration) contained in the exhaust gas flowing in the exhaust passage 10 between the filter 23 and the second selective reduction catalyst 26, and information indicating the detected NOx concentration. Is output to the control device 40.

The control device 40 is an electronic control unit having a CPU [Central Processing Unit], a ROM [Read Only Memory], a RAM [Random Access Memory], a CAN [Controller Area Network] communication circuit, and the like, and operates the entire exhaust purification device 20. To control. The control device 40 realizes various functions described later by, for example, loading the program stored in the ROM into the RAM and executing the program loaded in the RAM in the CPU.

The control device 40 is communicably connected to the fuel injectors 34, 35, 36, the temperature sensors 37, 38, and the NOx sensor 39. For example, the control device 40 acquires the temperatures of the first selective reduction catalyst 25 and the second selective reduction catalyst 26 based on the measured values of the temperature sensors 37 and 38.

Further, the control device 40 individually controls the injection amount of fuel from the fuel injectors 34, 35, 36. For example, when the clogging of the filter 23 is detected, the control device 40 controls the fuel injector 34 so that the fuel is injected from the fuel injector 34 into the exhaust passage 10. When fuel is injected from the fuel injector 34, heat is generated in the first oxidation catalyst 22 due to the oxidation reaction of the fuel, and the heat generates particulate matter collected in the filter 23. At this time, the filter 23 is heated to 500 ° C. to 600 ° C. in order to burn the particulate matter.

Further, the control device 40 determines the amount of fuel injected from the fuel injector 35 into the exhaust passage 10 (hereinafter, referred to as “first injection amount”) based on the temperature of the first selective reduction catalyst 25. In addition to controlling, the amount of fuel injected from the fuel injector 36 into the exhaust passage 10 (hereinafter, referred to as "second injection amount") is controlled based on the temperature of the second selective reduction catalyst 26.

Hereinafter, the control of the first injection amount and the second injection amount executed by the control device 40 will be described in detail.

FIG. 3 is a diagram showing the relationship between the temperature of the first selective reduction catalyst 25 and the NOx reduction rate. As shown in FIG. 3, the NOx reduction rate of the first selective reduction catalyst 25 depends on the temperature of the first selective reduction catalyst 25, and the temperature of the first selective reduction catalyst 25 is the maximum activation temperature. It becomes the highest when it is T, and becomes lower as the temperature of the first selective reduction catalyst 25 moves away from the maximum activation temperature T. That is, the maximum activation temperature T is a temperature at which the reduction efficiency (activity) of the first selective reduction catalyst 25 is highest, for example, 300 ° C. Since the second selective reduction catalyst 26 has a silver alumina catalyst like the first selective reduction catalyst 25, the maximum activation temperature of the second selective reduction catalyst 26 is set to that of the first selective reduction catalyst 25. Equal to the maximum activation temperature T.

Here, since the heat of the exhaust gas gradually decreases as it flows to the downstream side of the exhaust passage 10, a temperature gradient is generated inside the exhaust passage 10. Therefore, a temperature difference may occur between the first selective reduction catalyst 25 arranged on the upstream side of the exhaust passage 10 and the second selective reduction catalyst 26 arranged on the downstream side of the exhaust passage. For example, when the temperature of the exhaust gas is low, the temperature of the first selective reduction catalyst 25 is close to the maximum activation temperature T, and the temperature of the second selective reduction catalyst 26 is that of the first selective reduction catalyst 25. It may be cooler than the temperature. On the other hand, when the temperature of the exhaust gas is high, the temperature of the first selective reduction catalyst 25 is higher than the maximum activation temperature T, and the temperature of the second selective reduction catalyst 26 is the temperature of the first selective reduction catalyst 25. It may be closer to the maximum activation temperature T than the temperature of. The control device 40 has a first injection amount and a second injection amount so that fuel is preferentially supplied to the catalyst having high reduction efficiency among the first selective reduction catalyst 25 and the second selective reduction catalyst 26. Adjust the distribution with the injection amount of.

For example, when the temperature of the first selective reduction catalyst 25 is closer to the maximum activation temperature T than the temperature of the second selective reduction catalyst 26, the control device 40 relatively increases the first injection amount. Then, the fuel injectors 35 and 36 are controlled so that the second injection amount is relatively reduced. That is, the ratio of the first injection amount to the second injection amount is increased. By such control, a large amount of fuel is supplied to the first selective reduction catalyst 25 having a relatively high reduction rate, so that the nitrogen oxides contained in the exhaust gas are reduced with high efficiency.

On the other hand, when the temperature of the second selective reduction catalyst 26 is closer to the maximum activation temperature T than the temperature of the first selective reduction catalyst 25, the control device 40 relatively reduces the first injection amount. Then, the fuel injectors 35 and 36 are controlled so that the second injection amount is relatively increased. That is, the ratio of the first injection amount to the second injection amount is reduced. By such control, a large amount of fuel is supplied to the second selective reduction catalyst 26 having a relatively high reduction rate, so that the nitrogen oxides contained in the exhaust gas are reduced with high efficiency.

The control device 40 determines the total amount of the first injection amount and the second injection amount so that the NOx reduction rate becomes 100%.

As described above, the first selective reduction catalyst 25 and the second selective reduction catalyst 26 have a silver alumina catalyst capable of reducing nitrogen oxides in a wide temperature range. Although the first selective reduction catalyst 25 and the second selective reduction catalyst 26 have the same activation temperature depending on the silver alumina catalyst, the first selective reduction catalyst 25 and the second selective reduction catalyst 26 If there is a temperature difference between the two, there will be a difference in the reduction efficiency between the two. Here, in the exhaust gas purification device 20 described above, the nitrogen oxide can be reduced by using the catalyst having the higher reduction efficiency among the first selective reduction catalyst 25 and the second selective reduction catalyst 26, so that the temperature is wide. Nitrogen oxides can be reduced in the range.

The effect of the exhaust gas purification device 20 will be further described with reference to FIG. The line L1 in FIG. 4 is a graph showing the NOx reduction rate when the exhaust gas is purified by using the exhaust gas purification device 20 described above. On the other hand, line L2 in FIG. 4 is a graph showing a NOx reduction rate when exhaust gas is purified by using an exhaust gas purification device using a filter that does not support a selective reduction catalyst. As shown in line L2 of FIG. 4, when the filter was not subjected to the selective reduction catalyst, the NOx reduction rate decreased as the exhaust temperature deviated from 300 ° C. On the other hand, as shown in line L1 of FIG. 4, it was confirmed that when the exhaust gas purification device 20 was used, a high NOx reduction rate could be realized in a wide temperature range (200 ° C. to 500 ° C.).

Although the exhaust gas purification device according to the various embodiments has been described above, various modifications can be configured without changing the gist of the invention without being limited to the above-described embodiment.

For example, as shown in FIG. 5, the filter 23 may further support a second oxidation catalyst 24 in addition to the first selective reduction catalyst 25. In the modification shown in FIG. 5, the primary side (inlet side) of the filter 23 is coated with the second oxidation catalyst 24, and the secondary side (outlet side) of the filter 23 is coated with the first selective reduction catalyst 25. There is. The second oxidation catalyst 24 is a platinum-free oxidation catalyst and contains, for example, cerium oxide (CeO ₂ ), iron oxide (Fe ₂ O ₃ ) or copper oxide (CuO). The platinum-free second oxidation catalyst 24 can oxidize particulate matter (for example, soot) contained in the exhaust gas while suppressing the combustion of hydrocarbons.

The exhaust gas purification device 20 does not necessarily have to include the second oxidation catalyst 24. Also, the ammonia reduction catalyst 28 is not an essential configuration. Even when the second oxidation catalyst 24 or the ammonia reduction catalyst 28 is not provided, the exhaust gas purification device 20 described above can reduce nitrogen oxides using a catalyst having high reduction efficiency, which is wide. Nitrogen oxides can be reduced in the temperature range.

The exhaust purification device 20 may determine the total amount of the first injection amount and the second injection amount based on the NOx concentration in the exhaust gas flowing through the exhaust passage 10.

1 ... Engine, 10 ... Exhaust passage, 20 ... Exhaust purification device, 22 ... First oxidation catalyst, 23 ... Filter, 24 ... Second oxidation catalyst, 25 ... First selective reduction catalyst, 26 ... Second selection Reduction catalyst, 28 ... Ammonia reduction catalyst, 34 ... Fuel injector, 35 ... Fuel injector (first fuel injector), 36 ... Fuel injector (second fuel injector), 40 ... Control device.

Claims (6)

An exhaust purification device that purifies the exhaust gas emitted from the engine.
A first oxidation catalyst provided in the exhaust passage through which the exhaust gas flows, and
A filter provided on the downstream side of the exhaust passage with respect to the first oxidation catalyst and collecting particulate matter contained in the exhaust gas, and supporting a first selective reduction catalyst containing a silver alumina catalyst. With the filter
A second selective reduction catalyst containing a silver-alumina catalyst provided on the downstream side of the exhaust passage with respect to the filter,
A first fuel injector that injects fuel into the exhaust passage between the first oxidation catalyst and the filter.
A second fuel injector that injects fuel into the exhaust passage between the filter and the second selective reduction catalyst.
A control device that controls a first injection amount, which is the amount of fuel injected from the first fuel injector, and a second injection amount, which is the amount of fuel injected from the second fuel injector. When,
Equipped with an exhaust purification device. A first catalyst temperature acquisition unit that acquires the temperature of the first selective reduction catalyst, and
A second catalyst temperature acquisition unit that acquires the temperature of the second selective reduction catalyst, and a second catalyst temperature acquisition unit.
Further prepare
The first aspect of the present invention, wherein the control device controls the ratio of the first injection amount to the second injection amount based on the temperatures of the first selective reduction catalyst and the second selective reduction catalyst. Exhaust purification device. When the temperature at which the reduction efficiency of the first selective reduction catalyst and the second selective reduction catalyst is highest is set as the maximum activation temperature, the control device determines that the temperature of the first selective reduction catalyst is the temperature of the first selective reduction catalyst. When the temperature is closer to the maximum activation temperature than the temperature of the second selective reduction catalyst, the ratio becomes large, and the temperature of the second selective reduction catalyst is higher than the temperature of the first selective reduction catalyst. The exhaust purification device according to claim 2, wherein the first injection amount and the second injection amount are controlled so that the ratio becomes smaller when the temperature is close to the activation temperature. The exhaust gas purification device according to any one of claims 1 to 3, further comprising an ammonia reducing catalyst that is provided on the downstream side of the exhaust passage with respect to the second selective reduction catalyst and oxidizes ammonia. The exhaust gas purification device according to any one of claims 1 to 4, wherein the filter further supports a second oxidation catalyst containing no platinum. The exhaust gas purification apparatus according to claim 5, wherein the second oxidation catalyst is supported on the inlet side of the filter, and the first selective reduction catalyst is supported on the outlet side of the filter.

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