JP2021014802A - Exhaust emission control system - Google Patents

Abstract

To provide an exhaust emission control system including an adsorptive layer which can control the desorption of adsorbed NOx, independently of a catalyst temperature or an air-fuel ratio.SOLUTION: An exhaust emission control system 10 for eliminating predetermined components from exhaust gas from an internal combustion engine 20, includes an adsorptive layer 35 including adsorbent installed in an exhaust pipe 12 of the internal combustion engine 20 for adsorbing nitrogen oxide from the exhaust gas and for supplying predetermined additive to release the adsorbed nitrogen oxide, an emission control catalyst layer 41 including an emission control catalyst installed in the exhaust pipe 12 for eliminating the nitrogen oxide from the exhaust gas with reductive reaction, and an additive supply device 60 for supplying the additive to the adsorptive layer 35.SELECTED DRAWING: Figure 1

Description

The present invention relates to an exhaust gas purification system that purifies the exhaust gas of an internal combustion engine.

As typical catalysts used for purifying nitrogen oxides (NOx) contained in the exhaust of internal combustion engines, NOx storage reduction catalysts such as LNT (Lean NOx Trap) catalysts and NSR (NOx Strage Reduction) catalysts, selective reduction (Selective Catalytic Reduction: SCR) Catalysts and the like are known.

As described in Patent Document 1, the NOx storage reduction catalyst adsorbs NOx in the exhaust when the air-fuel ratio in the exhaust is lean, and when the air-fuel ratio in the exhaust is stoichiometric or rich, it adsorbs NOx in the exhaust. Releases the adsorbed NOx. In addition, the adsorbed NOx is released by raising the temperature of the NOx storage-reduction catalyst.

Japanese Unexamined Patent Publication No. 2009-85178

As described in Patent Document 1, as a method for desorbing NOx adsorbed on a NOx storage reduction catalyst, it is known to raise the catalyst temperature and control the air-fuel ratio to the rich side. It takes a certain amount of time to change the catalyst temperature and air-fuel ratio, and the change may affect the characteristics of the internal combustion engine and the exhaust gas purification system, so it is difficult to change it arbitrarily. For example, if the catalyst temperature and the air-fuel ratio are controlled in order to desorb NOx, there are concerns about catalyst deterioration and deterioration of fuel consumption in an internal combustion engine.

In view of the above, it is an object of the present invention to provide an exhaust gas purification system provided with an adsorption layer capable of controlling the desorption of adsorbed NOx regardless of the catalyst temperature and the air-fuel ratio.

The present invention is an exhaust purification system that purifies a predetermined component in an exhaust gas from an internal combustion engine, and adsorbs the nitrogen oxides in the exhaust gas and supplies a predetermined additive to adsorb the nitrogen oxides. Provided is an exhaust gas purification system including an adsorption layer containing an adsorbent for releasing an substance and a purification catalyst layer containing a purification catalyst for purifying nitrogen oxides in the exhaust gas by a reduction reaction.

According to the present invention, the adsorption layer contains an adsorbent that adsorbs nitrogen oxides in the exhaust gas and releases the adsorbed nitrogen oxides by supplying a predetermined additive. Since the desorption of adsorbed NOx can be controlled by controlling the supply of additives, in order to desorb NOx, the temperature of the adsorption layer and the purification catalyst layer is raised, and the air-fuel ratio of the internal combustion engine is controlled to the rich side. There is no need to do it. Therefore, it is possible to control the desorption of adsorbed NOx while avoiding adverse effects such as deterioration of the purification catalyst and deterioration of fuel consumption in the internal combustion engine as a result of controlling the catalyst temperature and the air-fuel ratio.

The schematic diagram of the exhaust gas purification system which concerns on 1st Embodiment. The schematic diagram of the crystal structure of the composite oxide which concerns on embodiment. The figure which shows the adsorption characteristic of the adsorbent. The figure explaining the adsorption / reduction / temperature rise desorption test of an adsorbent. The figure which shows the balance of the nitrogen-containing component in an adsorbent. The figure which shows the relationship between a catalyst activity and a catalyst temperature. FIG. 7A is a schematic view showing the configuration inside the exhaust pipe according to the first embodiment. FIG. 7B is a schematic view showing the configuration inside the exhaust pipe according to the modified example of the first embodiment. The schematic diagram which shows the structure in the exhaust pipe which concerns on other embodiment. The schematic diagram which shows the structure in the exhaust pipe which concerns on other embodiment. The figure which shows the mixer arranged in the exhaust pipe. The schematic diagram which shows the structure in the exhaust pipe which concerns on other embodiment. The conceptual diagram which shows the structure of the adsorption layer shown in FIG. FIG. 12 is a sectional view taken along line XIII-XIII of FIG. The schematic diagram which shows the structure in the exhaust pipe which concerns on other embodiment. 15 (a) and 15 (b) are schematic views showing the configuration in the exhaust pipe according to another embodiment. 16 (a) and 16 (b) are schematic views showing the configuration in the exhaust pipe according to another embodiment. The schematic diagram which shows the structure in the exhaust pipe which concerns on other embodiment. The schematic diagram which shows the structure in the exhaust pipe which concerns on other embodiment. The schematic diagram which shows the structure in the exhaust pipe which concerns on other embodiment.

(First Embodiment)
As shown in FIG. 1, the vehicle exhaust purification system 10 is mounted on the vehicle and includes a first catalyst layer 30, an adsorption layer 35, a second catalyst layer 40, an ECU 50, and a reducing agent supply device 60. ing. The exhaust gas purification system 10 is a system capable of purifying a predetermined component contained in the exhaust gas by circulating the exhaust gas discharged from the internal combustion engine 20 to the first catalyst layer 30, the adsorption layer 35, and the second catalyst layer 40. It is configured as.

The internal combustion engine 20 is a diesel engine, and the air sucked from the intake pipe 11 is compressed by the supercharging device 13 and sucked into the combustion chamber of the internal combustion engine 20, and the fuel injected from the fuel injection valve in this combustion chamber. It is used for combustion together.

The supercharging device 13 includes an intake compressor 14 arranged in the intake pipe 11, an exhaust turbine 15 arranged in the exhaust pipe 12, and a rotating shaft 16 connecting the intake compressor 14 and the exhaust turbine 15. When the exhaust turbine 15 is rotated by the exhaust from the internal combustion engine 20, the intake compressor 14 is rotated along with the rotation, and the intake air is supercharged.

In the exhaust pipe 12, the first catalyst layer 30, the adsorption layer 35, and the second catalyst layer 40 are arranged in this order from the upstream side to the downstream side. The exhaust gas from the internal combustion engine 20 is purified by passing through the first catalyst layer 30, the adsorption layer 35, and the second catalyst layer 40 arranged in the exhaust pipe 12. Mixing members 37 and 38 are installed on the inlet side of the adsorption layer 35 and the inlet side of the second catalyst layer 40, respectively.

The reducing agent supply device 60 includes injectors 61 and 62, reducing agent supply pipes 63 and 64, a pump 65, and a tank 66. The injector 61 is connected to the exhaust pipe 12 at a position on the upstream side of the mixing member 37. The injector 62 is connected to the exhaust pipe 12 at a position on the downstream side of the inlet NOx sensor 23 and on the upstream side of the mixing member 38. A liquid containing a reducing agent is stored in the tank 66. The reducing agent supply pipe 63 connects the injector 61 and the tank 66, and the reducing agent supply pipe 64 connects the injector 62 and the tank 66. The pump 65 is installed between the tank 66 and the reducing agent supply pipes 63 and 64, and distributes and supplies the reducing agent stored in the tank 66 to the reducing agent supply pipes 63 and 64.

By driving the pump 65, the liquid containing the reducing agent stored in the tank 66 is supplied to the injectors 61 and 62 through the reducing agent supply pipes 63 and 64, and is supplied from the injectors 61 and 62 into the exhaust pipe 12. Be jetted. The liquid supplied into the exhaust pipe 12 is agitated by the mixing members 37 and 38, and is supplied as a reducing agent to the adsorption layer 35 and the second catalyst layer 40 located downstream thereof. The injector 61, the reducing agent supply pipe 63, the pump 65, and the tank 66 have a function as an additive supply mechanism for supplying the reducing agent as an additive to the inlet side of the adsorption layer 35. The injector 62, the reducing agent supply pipe 64, the pump 65, and the tank 66 are a reducing agent supply mechanism that supplies the reducing agent to the inlet side of the second catalyst layer 40 (more specifically, the inlet side of the NOx purification catalyst layer 41). It has the function as.

The exhaust pipe 12 is further provided with an inlet NOx sensor 23 and an outlet NOx sensor 24 near the inlet and outlet of the second catalyst layer 40. The inlet NOx sensor 23 detects the amount of NOx in the exhaust gas flowing into the second catalyst layer 40 as a concentration. Further, the outlet NOx sensor 24 detects the amount of NOx in the exhaust gas after being purified by the second catalyst layer 40 as a concentration.

The first catalyst layer 30 is a non-NOx purification catalyst layer provided with a purification catalyst having a function of mainly purifying components other than nitrogen oxides (NOx) in the exhaust gas. For example, a catalyst having a function of purifying unreacted fuel and particle components in the exhaust gas can be used for the first catalyst layer 30. Specific examples of the catalyst used in the first catalyst layer 30 include an oxidation catalyst layer (DOC layer) containing a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and the like. Can be mentioned.

DOC is a catalyst that oxidizes soluble organic components (SOF) in particulate matter (PM) contained in exhaust gas, and CO and HC in exhaust gas. As the DOC, for example, a catalyst containing a carrier such as a metal oxide and an active species of a noble metal or a base metal is used. As a typical example of DOC, a catalyst in which a noble metal catalyst such as Pt or Pd is supported on alumina or zeolite can be exemplified. When arranged in the exhaust pipe 12, it is often used in the form of supporting Pt and Pd on an alumina carrier having a honeycomb structure.

The DPF is a particulate filter equipped with a catalyst for purifying particulate components in exhaust gas. As the DPF, for example, a catalyst containing a carrier such as a metal oxide and an active species of a noble metal or a base metal is used. As a typical example of the DPF, a catalyst in which a noble metal catalyst such as Pt or Pd is supported on alumina having a honeycomb structure can be exemplified. The DPF filters and collects particulate matter (PM) in the exhaust.

As another name for DPF, DPR (Diesel Particulate Assistation System), DPD (Diesel Particulate Defecter), CRT (Continuary Particulate Defuser), CRT (Continuously Regenerating Trap, etc.), and Control In the present specification, the term DPF is used in the sense of including each catalyst referred to by the above alternative names.

According to DOC, hydrocarbons (HC), CO, and NO in the exhaust gas are oxidized by the catalytic reactions represented by the following formulas (1) to (3).

HC + O ₂ → H ₂ O + CO ₂ … (1)
2CO + O ₂ → 2CO ₂ … (2)
2NO + O ₂ → 2NO ₂ ... (3)

According to the DPF, the carbon (C) in the exhaust gas is oxidized by the catalytic reaction represented by the following formula (4). Further, as the DPF, a catalyst having activity in the catalytic reaction represented by the above formula (3) may be used. By promoting the reaction of the above formula (3) to generate NO ₂ , the catalytic reaction represented by the following formula (4) can be promoted.

C + 2NO ₂ → CO ₂ + 2NO… (4)

Instead of DOC or DPF, a NOx adsorption (Passive NOx Addition: PNA) catalyst may be placed. As the PNA catalyst, for example, a catalyst containing a carrier such as a metal oxide and a NOx-adsorbed species is used. As a specific example of the PNA catalyst, a catalyst having a structure that does not contain Rh, which is a reducing agent, can be exemplified with respect to the LNT catalyst.

The first catalyst layer 30 may contain one or more non-NOx purification catalysts having a function of purifying components other than NOx mainly in the exhaust such as DOC and DPF. For example, only the DOC layer and only the DPF layer may be installed as the first catalyst layer 30. Further, for example, as shown in FIG. 1, the first catalyst layer 30 may be composed of the DOC layer 31 arranged on the upstream side and the DPF layer 32 arranged on the downstream side. The DOC layer 31 corresponds to an oxidation catalyst layer provided with an oxidation catalyst that oxidizes unburned components in the exhaust, and the DPF layer 32 corresponds to a particulate filter that purifies the particulate components in the exhaust.

The adsorption layer 35 contains an adsorbent that adsorbs NOx in the exhaust gas and releases the adsorbed NOx by supplying a predetermined additive. As a specific example of the adsorbent having such a function, the adsorbent Q containing the first composite oxide described in JP-A-2019-34299 can be exemplified. JP-A-2019-34299 is cited by reference and the entire description thereof is incorporated herein by reference. In addition, in this specification, the term "adsorption" includes both physical adsorption and chemical adsorption, and further includes the concept of "occlusal" which means a phenomenon in which a gas or liquid is taken into a solid. Used.

This first composite oxide is represented by the general formula I: A _a B _b C _c O _8.5-δ . In the general formula I, A is at least one selected from the group consisting of rare earth elements, Ca, and In. A is preferably at least one selected from the group consisting of Y, Pr, Dy, Ho, Er, Tm, Yb, Lu, Ca, and In, and more preferably at least one of Y and Ca (that is,). , Y and / or Ca), and particularly preferably at least Y. In this case, the adsorption performance of the adsorbent Q with respect to NOx can be further improved.

For the first composite oxide, for example, the A element source, the B element source, and the C element source constituting this compound are mixed at a desired compounding ratio so that a compound represented by the general formula I can be obtained. Obtained by heating. In the general formula I, a is 0 <a ≦ 1. When a = 0, elements B and C are surplus with respect to the compound represented by the general formula I, and an oxide phase other than the compound represented by the general formula I may be formed. The oxide phase may degrade the adsorption performance for NOx. On the other hand, when a> 1, the surplus element A may form an oxide phase other than the compound represented by the general formula I, and this oxide phase may deteriorate the adsorption performance for NOx. is there. From the viewpoint of forming the compound phase represented by the general formula I as a single phase, 0.5 ≦ a ≦ 1 is more preferable, and 0.9 ≦ a ≦ 1 is further preferable.

B is at least one selected from the group consisting of alkaline earth metal elements. B is preferably at least one of Ba and Sr (that is, Ba and / or Sr). In this case, the adsorption performance of the adsorbent Q with respect to NOx can be further improved. Further, it is particularly preferable that B contains at least Ba from the viewpoint that the crystal structure of the compound represented by the general formula I can be stabilized.

In the general formula I, b is 0 <b ≦ 1. When b = 0, elements A and C are surplus with respect to the compound represented by the general formula I, and an oxide phase other than the compound represented by the general formula I may be formed. The oxide phase may degrade the adsorption performance for NOx. On the other hand, when b> 1, the surplus element B may form an oxide phase other than the compound represented by the general formula I, and this oxide phase may deteriorate the adsorption performance for NOx. is there. From the viewpoint of forming the compound phase represented by the general formula I as a single phase, 0.5 ≦ b ≦ 1 is more preferable, and 0.9 ≦ b ≦ 1 is even more preferable.

In the general formula I, C is an element consisting of at least one selected from the group consisting of transition metals, Al, Zn, and Ga, and having four coordinations of oxygen. C is preferably at least one selected from the group consisting of Fe, Co, Mn, Ni, Al, and Ga, and more preferably at least selected from the group consisting of Fe, Co, and Ga. It is good to be one kind. C may more preferably contain at least Co, and particularly preferably contain Co and Ga and / or Fe (that is, at least one of Ga and Fe). By selecting C in this way, the adsorption performance of the adsorbent Q with respect to NOx can be further improved.

In the general formula I, c is 0 <c ≦ 4. When c = 0, elements A and B are surplus with respect to the compound represented by the general formula I, and an oxide phase other than the compound represented by the general formula I may be formed. The oxide phase may degrade the adsorption performance for NOx. On the other hand, when c> 4, the surplus C element may form an oxide phase other than the compound represented by the general formula I, and this oxide phase may deteriorate the adsorption performance for NOx. is there. From the viewpoint of forming the compound phase represented by the general formula I as a single phase, 3.5 ≦ c ≦ 4 is more preferable, and 3.9 ≦ c ≦ 4 is further preferable.

The first composite oxide has an oxygen-deficient structure as represented by the oxygen-deficient amount δ in the general formula I. δ satisfies 0 <δ ≦ 1.5. When δ> 1.5, the crystal structure may change and the adsorption performance for NOx may decrease.

FIG. 2 shows the crystal structure of the first composite oxide 2 when A is Y, B is Ba, and C is Co in the general formula I. As illustrated in FIG. 2, the first composite oxide 2 has a crystal structure represented by the general formula I, and the crystal structure is formed from Y, Ba, Co and O. Oxygen deficiency 3 is present in the crystal structure.

In FIG. 2, the oxygen deficiency 3 is indicated by a small circle with a broken line. The broken line circle bonded to the oxygen atom O indicates a C element such as Co. Since element C exists inside the bond surface between oxygen atoms, it is shown by a broken line in FIG. As illustrated in FIG. 2, in the crystal structure of the first composite oxide, C in the general formula I has four coordinations of oxygen. In the first composite oxide 2, the oxygen atom exists as an anion.

In the first composite oxide 2, for example, it is considered that the oxygen deficiency 3 is the starting point to generate an adsorption site for NOx in the crystal structure, or the oxygen deficiency 3 itself becomes an adsorption site. When the oxygen deficiency 3 is the starting point, it is considered that the crystal structure is changed by, for example, the oxygen deficiency 3, and as a result, an adsorption site is generated in the crystal structure. That is, the oxygen deficiency 3 is the starting point for the generation of the adsorption site. Then, it is considered that NOx is adsorbed on the adsorption site in the form of nitrate ion, nitric oxide, and nitrogen dioxide.

The first complex oxide having an adsorption site can be represented by the general formula II: A _a B _b C _c O _8.5-δ (NO _x ) _θ . A, B, C, a, b, c, and δ in the general formula II are the same as those in the general formula I. NO _x is a nitrogen oxide. The general formula II indicates that the first composite oxide 2 represented by the general formula I has an adsorption site for NOx, indicating that the first composite oxide 2 can adsorb NOx. ..

In the general formula II, 0 ≦ θ ≦ 1.5. When θ = 0, NOx is not adsorbed, which is the same as the general formula I. When θ> 0, it indicates a state in which NOx is adsorbed on the adsorption site. Θ ≦ 1.5 because NOx is adsorbed on the adsorption site.

The oxygen deficiency 3 can be identified by measuring the thermogravimetric analysis of the adsorbent Q. That is, δ in the general formulas I and II can be determined by thermogravimetric analysis. Specifically, it is as follows. Using a thermogravimetric analyzer STA449 F3 manufactured by NETZSCH, powdered adsorbent Q; 100 mg is first heated in a reducing atmosphere. As a result, the adsorbent Q having an oxygen deficiency amount δ = 0 is produced. For heating in a reducing atmosphere, a reducing atmosphere gas consisting of hydrogen: 5% by volume and nitrogen: the balance is circulated through the adsorbent Q at a flow rate of 100 mL / min, and heated to 500 ° C. at a heating rate of 10 ° C./min. Do it by. Next, the adsorbent Q with δ = 0 is heated in an oxygen atmosphere. The oxygen deficiency amount δ can be obtained as the weight increase at this time. The heating in an oxygen atmosphere is performed by heating the adsorbent Q to 500 ° C. at a heating rate of 2 ° C./min while circulating 100% by volume of oxygen gas through the adsorbent Q at a flow rate of 100 mL / min.

The adsorbent Q can contain a second compound different from the first composite oxide. The second compound is preferably a compound containing at least one selected from the group consisting of transition metal elements, alkaline earth metal elements, aluminum (Al), and zinc (Zn). In this case, the thermal durability of the adsorbent Q is improved. The second compound may be one kind, but may be two or more kinds of compounds.

The second compound is preferably a compound containing at least one element selected from the elements A, B, and C in the general formula I. In this case, the adsorbent Q containing the first composite oxide and the second compound can be obtained by adjusting the blending ratio of the raw materials without increasing the raw material species at the time of producing the first composite oxide. Can be manufactured.

The second compound preferably contains at least one of an oxide and a salt, and more preferably contains at least a carbonate of an alkaline earth metal element. In this case, the thermal durability of the adsorbent Q can be further improved.

The adsorbent Q preferably contains a main phase composed of the first composite oxide and a subphase composed of the second compound. The main phase is the main component phase, and the sub-phase is the sub-component phase. In this case, the thermal durability of the adsorbent Q can be further improved. The main phase and the sub-phase are confirmed by, for example, X-ray diffraction (XRD).

As illustrated in FIGS. 1 and 2, the adsorbent Q contains the specific first composite oxide 2. The first composite oxide 2 has an oxygen-deficient structure as represented by the general formula I: A _a B _b C _c O _8.5-δ . This oxygen-deficient structure can be the starting point for the formation of adsorption sites for NOx or the adsorption sites. That is, the first composite oxide 2 has an adsorption site. Therefore, the adsorbent Q can adsorb NOx even at a high temperature, but can sufficiently adsorb NOx even at a low temperature of, for example, 250 ° C. or lower. This is because NOx can be adsorbed on the adsorption site.

The method for producing the adsorbent Q is not particularly limited, and the adsorbent Q can be produced by a solid phase reaction method, a complex polymerization method, or the like. For example, in the solid-phase reaction method, first, the A source, the B source, and the C source are mixed in a solid state by the stoichiometric ratio produced by the compound represented by the above general formula. Mixing can be performed in a ball mill, a mortar or the like. The mixture is then fired. As a result, the adsorbent Q can be obtained. As the A source, B source, and C source in the solid phase reaction method, oxides, salts, and other compounds containing elements A, B, and C, respectively, can be used.

Further, in the complex polymerization method, a salt containing element A (that is, salt A), a salt containing element B (that is, salt B), and a salt containing element C (that is, salt C) are used. These salts are used to form metal complexes of element A, element B, and element C in water, and then the aqueous solution is gelled with a gelling agent. Next, the gelled metal complex is calcined and fired to obtain the adsorbent Q as an oxide. As the gelling agent, a polyhydric alcohol such as ethylene glycol or propylene glycol can be used.

Further, although the adsorbent Q can be used in combination with the noble metal, NOx can be adsorbed even if the adsorbent Q is prepared by reducing the noble metal content and further setting the noble metal content to 0. .. It is considered that this is because the first composite oxide 2 has the above-mentioned adsorption site, so that the adsorbent Q can adsorb NOx in any form of NO, NO ₂ , or nitric acid. That is, the adsorbent Q can adsorb NO as it is, can be adsorbed as NO ₂ obtained by oxidizing NO with a noble metal, or can adsorb NO ₂ as nitrate ion. The adsorbent Q and the noble metal may be combined. In this case, for example, Pt, Pd, Rh and the like can be used as the precious metal.

Further, conventionally, as a NOx adsorbing material, for example, an alkaline earth metal such as barium (Ba), calcium (Ca), magnesium (Mg), strontium (Sr), or an alkali such as barium oxide (BaO). Earth metal oxides were used. These adsorbents are used by supporting them on a porous carrier, but alkaline earth metals are chemically unstable because they easily react with other members such as carriers when heated. As a result, the adsorption performance for NOx may deteriorate. On the other hand, the first composite oxide 2 contains an alkaline earth metal element B inside the crystal structure as represented by the general formula I. Therefore, the adsorbent Q of this embodiment is chemically stable. That is, even if the adsorbent Q is heated, it is possible to prevent the alkaline earth metal B from reacting with other members such as a carrier. Therefore, the adsorbent Q can suppress the deterioration of the adsorption performance due to heating.

Further, the adsorbent Q preferably contains a compound containing at least one of Mg and Sr. In this case, sulfur poisoning of the adsorbent Q can be suppressed. Examples of the compound containing at least one of Mg and Sr include MgAl ₂ O ₄ and SrCO ₃ .

As described above, according to the present embodiment, it is possible to provide the adsorbent Q having excellent adsorption performance for NOx at low temperature. The adsorbent Q exhibits excellent adsorption performance for NOx even at a low temperature of 250 ° C. or lower. Further, the adsorbent Q can also be used at a high temperature exceeding 250 ° C. Even in this case, it exhibits excellent adsorption performance for NOx.

When the exhaust gas discharged from the internal combustion engine 20 is passed through the adsorbent Q, NOx in the exhaust gas is adsorbed by the adsorbent Q and captured in a lean atmosphere or the like. On the other hand, in a rich atmosphere or the like, the adsorbed NOx is released.

Furthermore, as a result of diligent research, the present inventor has found that the adsorbed NOx can be released by supplying a predetermined additive to the above-mentioned adsorbent Q. It is presumed that the adsorption of NOx on the adsorbent Q is due to an acid-base bond using the adsorption site of the adsorbent Q as a base and NOx as an acid. Therefore, as the additive, a material capable of promoting the cleavage of the acid-base bond of the adsorbent Q can be preferably used.

FIGS. 3 and 5 show an adsorbent Q1 (hereinafter abbreviated as adsorbent Q1) containing YBaCo4O7, which is an example of the composite oxide represented by the above general formula I, and its adsorption performance and desorption performance. Is shown by an experimental evaluation.

FIG. 3 is a diagram showing the adsorption characteristics of the adsorbent Q1 obtained by the NOx adsorption / temperature desorption (TPD) test. The vertical axis of FIG. 3 shows the adsorption rate (%) of NOx supplied to the adsorbent Q1, and the horizontal axis shows the adsorption amount of NOx accumulated in the adsorbent Q1. The NOx adsorption rate Yr can be calculated by the following formula (5), where Xin is the amount of NOx in the exhaust gas flowing into the adsorption layer 35 and Xout is the amount of NOx in the exhaust gas flowing out of the adsorption layer 35.

Yr (%) = 100 × (Xin-Xout) / Xin… (5)

When NOx is adsorbed, the sample temperature is set to a predetermined adsorption temperature, and an N ₂ balanced supply gas containing NO; 100 ppm, H ₂ O; 3 vol%, O ₂ ; 10 vol%, CO ₂ ; 3 vol% as components is used as a space. Feed at a rate SV; 47,000 (1 / h) for 20 minutes. At the time of desorption by raising the temperature of NOx, an N ₂ balanced supply gas containing 10 vol% of O ₂ as a component was supplied with a space velocity SV; 47,000 (1 / h), and the temperature was raised from 100 ° C. to 550 ° C. in 20 minutes. Reference numbers 4 to 7 shown in FIG. 3 show different data in the adsorption temperature at the time of adsorption of NOx. Reference numbers 4, 5, 6 and 7 indicate the cases where the adsorption temperatures are 100 ° C., 150 ° C., 200 ° C. and 250 ° C., respectively.

As shown in FIG. 3, in the adsorbent Q1, when the amount of NOx adsorbed is small, NOx in the supplied exhaust can be adsorbed with a high probability of about 100%, but when the amount of NOx adsorbed is larger than a certain level, The NOx adsorption rate began to decline. That is, it was found that the NOx adsorption rate decreases as the NOx adsorption amount increases. Further, it was clarified that the higher the temperature of the adsorbent Q1, the larger the NOx adsorption amount at which the NOx adsorption rate begins to decrease.

FIG. 4 shows the sample temperature in the NOx adsorption / reduction / thermal desorption (TPD) test, the NOx concentration of the inlet gas (reference number 8), the NOx concentration of the outlet gas (reference number 9), and the NH _{3 of the} inlet gas. It is the figure which showed each time change about the concentration on the same time axis. Specifically, this test was carried out by supplying a predetermined inlet gas to the sample chamber in which the adsorbent Q1 was installed as a sample, and detecting the components in the outlet gas after passing through the sample chamber. 4, during the time 0~t1 the NOx adsorption stroke, heating process during the t1 to t2, during t2~t3 is NH ₃ addition step, during the t3~t4 shows a purge step.

First, in the NOx adsorption process, as shown in FIG. 4 (a), the sample temperature is maintained at a predetermined adsorption temperature Tm1 (150 ° C. in this test), and as shown in Reference No. 8 of FIG. 4 (b), It was supplied as an inlet gas containing NOx having a predetermined concentration. As the inlet gas, an N ₂ balanced adsorption stroke gas containing NO; 100 ppm, H ₂ O; 3 vol%, O ₂ ; 10 vol%, CO ₂ ; 3 vol% was used, and the space velocity was SV; 47,000 (1 / h). Supplied for 20 minutes. As shown in reference number 9 in FIG. 4 (b), NOx was detected in the outlet gas. Reference number 101 indicates an area obtained by integrating the difference between the NOx concentration of the inlet gas (reference number 8) and the NOx concentration in the outlet gas (reference number 9) between 0 and t1. By calculating the area of the reference number 101, the amount of NOx adsorbed on the adsorbent Q1 in the NOx adsorption process can be obtained.

Next, in the heating step, as shown in FIG. 4 (a), the inlet gas switched to N ₂ purge gas from the adsorption process gas, the sample temperature, at a predetermined reduction temperature Tm2 (this test from the adsorption temperature Tm1 is The temperature was raised to 400 ° C.). As the N ₂ purge gas, an N ₂ balanced gas containing 10 vol% of O ₂ as a component was used and supplied at a space velocity SV; 47,000 (1 / h). As the sample temperature rises, a part of NOx adsorbed on the adsorbent Q1 is released in the adsorption process, and NOx is detected in the outlet gas as shown in Reference No. 9 of FIG. 4 (b). Reference numeral 102 indicates the area obtained by integrating the NOx concentration in the outlet gas between t1 and t2 in time. By calculating the area of the reference number 102, the amount of NOx thermally desorbed from the adsorbent Q1 in the heating process can be obtained.

Then, the NH ₃ addition step, as shown in FIG. 4 (a), the temperature of the adsorbent Q1 maintains the reduction temperature Tm2, as shown in FIG. 4 (c), an inlet including additives having a predetermined concentration Supplyed gas. As the inlet gas, an N ₂ balanced addition stroke gas containing NH ₃ ; 50 ppm, H ₂ O; 3 vol%, O ₂ ; 10 vol%, CO ₂ ; 3 vol% was used, and the space velocity SV; 47000 (1 / h). Was supplied for 100 seconds. As shown in FIG. 4B, NOx was detected in the outlet gas by supplying NH ₃ as an additive to the adsorbent Q1 even when the reduction temperature was kept at a constant Tm2.

Moreover, the purging process, as shown in FIG. 4 (a), while maintaining the temperature of the adsorbent Q1 to reduction temperature Tm2, the inlet gas was switched to N ₂ purge gas from the adsorption process gas. The purging process continued until NOx was no longer detected in the outlet gas. Reference numeral 103 indicates the area obtained by integrating the NOx concentration in the outlet gas between t2 and t4 in time. By calculating the area of the reference number 103, the NH ₃ addition step and purge step, additives can be determined amount of NOx desorbed from the adsorbent Q1 resulted from the supply.

Further, the later time t4, and continues the supply of the N ₂ purge gas as an inlet gas, until NOx is not detected in the outlet gas was heated to sample temperature. Reference numeral 104 indicates the area where the NOx concentration in the outlet gas is integrated after the time t4. By calculating the area of the reference number 104, it is possible to obtain the amount of NOx remaining adsorbed on the adsorbent Q1 at the end of the purging process.

FIG. 5 is a diagram showing the balance (in / out) of the nitrogen-containing component in the adsorbent Q1. The "NOx-derived" component, the "thermal desorption" component, the "additive desorption" component, and the "residual" component shown in FIG. 5 are obtained from the areas of reference numbers 101 to 104 in FIG. 4, respectively. As shown in FIG. 5, the breakdown of the nitrogen-containing component (in component) adsorbed on the adsorbent Q1 at the time of NOx adsorption is the "NOx-derived" component derived from the NOx component contained in the adsorption stroke gas and the addition stroke gas. It was an "additive-derived" component derived from NH ₃ contained in. Further, the breakdown of the nitrogen-containing component (out component) released after being adsorbed on the adsorbent Q1 is the "residual" component remaining adsorbed on the adsorbent Q at the end of the purging process and the adsorption temperature Tm1 (adsorption temperature Tm1). The "heat desorption" component that was thermally desorbed from the adsorbent Q when the temperature was raised from 150 ° C.) to the reduction temperature Tm2 (400 ° C.), and the "additive desorption" that was desorbed from the adsorbent Q by supplying the additive. It was an ingredient.

As shown in FIG. 5, the nitrogen-containing component supplied to and adsorbed on the adsorbent Q1 is also released from the adsorbent Q1 by raising the temperature of the adsorbent Q1, but ammonia (NH ₃ ) is added as an additive. It was revealed that the adsorbent Q1 was released from the adsorbent Q1. One of the factors that cause the phenomenon that NOx adsorbed by the adsorbent Q1 is released by supplying the additive is that NO ₂ and nitric acid adsorbed on the adsorbent Q1 supply NH ₃ as an additive. Therefore, it can be presumed that this is because it was reduced to NO, which is less likely to be adsorbed. Based on this estimation, it can be inferred that a material that promotes the reduction of NOx adsorbed on the adsorbent Q can be suitably used as an additive. For example, ammonia (NH ₃ ), hydrocarbon (HC), hydrogen (H ₂ ), aldehydes (RCHO), nitrogen monoxide (CO), etc., which are used as reducing agents for SCR catalysts and LNT catalysts, are additives. Can be suitably used as.

The adsorption layer 35 is an adsorption layer in which the above-mentioned adsorption material Q is supported on the honeycomb structure. The adsorption layer 35 is provided with an adsorption layer temperature sensor 25 that detects the temperature of the adsorption layer 35.

In addition to the honeycomb structure, the adsorbent Q may be supported on a general structure that can be used as a catalyst carrier such as a porous body. Further, it may be supported on a structure installed in the exhaust pipe 12 for a main purpose other than supporting the catalyst, such as the mixing member 37 shown in FIG.

Furthermore, the above-mentioned adsorbent Q may be supported on a carrier together with a noble metal. When a noble metal is supported on the carrier together with the above-mentioned adsorbent Q, the adsorption performance for NOx is improved. It is considered that this is because the noble metal can oxidize NO to NO ₂ and nitric acid, and the above-mentioned adsorbent Q is more likely to adsorb NO ₂ and nitric acid than NO.

Further, the adsorbent Q may be supported on the carrier together with an inorganic binder consisting of at least one selected from the group consisting of alumina, silica, and titania.

Further, the adsorbent Q may be supported on the carrier together with a co-catalyst consisting of at least one selected from the group consisting of ceria, zirconia, and ceria-zirconia solid solution.

When a co-catalyst is further supported on the carrier, the oxidation performance of the noble metal with respect to nitric oxide is improved. As a result, the adsorption performance of nitrogen oxides on the adsorbent Q is improved.

The method for supporting the adsorbent Q on the carrier is not particularly limited. For example, it can be supported by an impregnation method or an ion exchange method. Examples of the impregnation method include an evaporative drying method, a parallel adsorption method, and a pore filling method. The evaporation dry method is preferable from the viewpoint that the catalyst can be adjusted relatively easily.

When a noble metal is used, for example, by supporting the adsorbent Q on which the noble metal is supported on the carrier, the adsorbent Q can be supported on the carrier together with the noble metal.

The co-catalyst and the inorganic binder can be supported on the carrier together with the adsorbent Q. For example, in the evaporation-drying method, the carrier can be supported together by impregnating the carrier with a slurry containing the adsorbent Q, the co-catalyst, and the inorganic binder.

The material of the carrier is not particularly limited, but a material having excellent heat resistance is preferable, and more specifically, a metal oxide material or a ceramic material having excellent heat resistance as exemplified by cordierite, SiC, etc. Is preferable.

Since the above-mentioned adsorbent Q has high adsorption performance for NOx at low temperature and does not easily react chemically with the carrier even when heated, it can stably exhibit high adsorption performance.

The second catalyst layer 40 includes a NOx purification catalyst layer 41 containing a NOx purification catalyst that purifies NOx in exhaust gas by a reduction reaction. The second catalyst layer 40 can be configured to include a reducing agent removing layer 42 on the downstream side of the NOx purification catalyst layer 41, if necessary. A second catalyst temperature sensor 21 for detecting the temperature of the NOx purification catalyst layer 41 is installed in the NOx purification catalyst layer 41.

The NOx purification catalyst layer 41 includes at least a catalyst layer containing a NOx purification catalyst that purifies NOx. Examples of the NOx purification catalyst include a selective reduction catalyst (SCR catalyst), an LNT catalyst, and a three-way catalyst (TWC). The SCR catalyst and the three-way catalyst are NOx purification catalysts that are not NOx storage reduction type, and are generally not prepared so as to have high NOx adsorption. Therefore, the amount of NOx adsorbed is generally lower than that of a NOx storage reduction type catalyst called an LNT catalyst or the like.

The SCR catalyst is a catalyst that selectively reduces NOx by a reducing agent supplied to the exhaust pipe 12. Representative examples of substances used as reducing agents in SCR catalysts include NH ₃ , hydrocarbons (HC), H ₂ , and aldehydes (RCHO). In the SCR catalyst, NOx (NO, NO ₂ ) is reduced to N ₂ by a reducing agent. The reducing agent is oxidized to produce water (H ₂ O), carbon dioxide (CO ₂ ), N _{2 and the} like depending on the type of reducing agent. When NH ₃ is used as a reducing agent, it is supplied to the exhaust pipe 12 as urea water or the like, and NH ₃ is generated in the exhaust pipe 12.

As the SCR catalyst, for example, a catalyst containing a carrier such as a metal oxide or a ceramic and an active species of a noble metal or a base metal is known. More specifically, as a specific example of an SCR catalyst using NH ₃ as a reducing agent, a zeolite catalyst such as ZSM5 containing copper (Cu), iron (Fe) or the like as a cation species can be exemplified. Further, as a specific example of the SCR catalyst using HC, H ₂ , and RCHO as a reducing agent, a catalyst in which silver (Ag) or platinum (Pt) is supported on alumina (Al ₂ O ₃ ) can be exemplified.

The LNT catalyst adsorbs NOx on the catalyst during normal operation of the internal combustion engine 20, and occasionally reduces oxygen (O ₂ ) in the exhaust gas by rich spikes (injecting a large amount of fuel), and also Increases carbon monoxide (CO), hydrocarbons (HC), etc. Then, it reacts with the adsorbed NOx and is reduced to nitrogen. As the LNT catalyst, for example, a catalyst containing a carrier such as a metal oxide or a ceramic, an active species of a noble metal or a base metal, and a NOx-adsorbed species is used. More specifically, as a specific example of the LNT catalyst, a catalyst containing noble metal species such as Pt, Pd, Rh and barium (Ba) and cerium (Ce) as NOx adsorbing species can be exemplified.

Examples of the LNT catalyst include NSR (NOx Strage Reduction) catalyst, NAC (NOx Absorption Catalyst), DPNR (Diesel Particulate-NOx Reduction) catalyst and the like. In the present specification, the term LNT catalyst is used to include each catalyst referred to by the above alternative names.

The three-way catalyst is a catalyst that reduces NOx using CO or hydrocarbon (HC) in the exhaust as a reducing agent. According to the three-way catalyst, for example, by the catalytic reaction represented by the following formulas (6) to (8), CO is oxidized to CO ₂ , hydrocarbon (HC) is oxidized to H ₂ O or CO ₂ , and NOx is converted to CO ₂ . It is reduced to N ₂ .

2CO + 2NO → 2CO ₂ + N ₂ ... (6)
2H ₂ + 2NO → 2H ₂ O + N ₂ ... (7)
[HC] + NO → N ₂ + CO ₂ + H ₂ O ... (8)

As the three-way catalyst, for example, a catalyst containing a carrier such as a metal oxide or a ceramic and an active species of a noble metal is known. More specifically, as shown in FIG. 2, as a specific example of the three-way catalyst, a noble metal catalyst such as platinum (Pt), palladium (Pd), rhodium (Rh) is used as alumina, ceria / zirconia (CeO ₂ / ZrO). _The catalyst carried in ₂ ) and the like can be exemplified. The three-way catalyst may further contain, as a co-catalyst, ceria (CeO ₂ ), zirconia (ZrO ₂ ), lanthania (La ₂ O ₃ ), etc., which have an oxygen storage capacity.

As the reducing agent removing layer 42, a catalyst layer provided with a catalyst for removing components not purified by the NOx purification catalyst layer 41 is arranged. For example, when an SCR catalyst using NH ₃ as a reducing agent is used as the NOx purification catalyst layer 41, it is preferable to use an ammonia slip catalyst (ASC) or the like as a catalyst for the reducing agent removing layer 42. ASC is an oxidation catalyst, mainly for the purpose of suppressing NH ₃ from slipping (passing through) the SCR catalyst and being released into the outside air when the exhaust gas temperature is low (for example, less than 200 ° C.). Will be installed. In ASC, NH ₃ is converted to N ₂ , H ₂ O, and NOx.

In the present embodiment, the DOC layer 31 and the DPF layer 32 are used as the first catalyst layer 30, and the adsorption layer 35 in which the adsorbent Q is supported on the honeycomb is used as the adsorption layer 35, and the NOx of the second catalyst layer 40 is used. A case where an SCR catalyst using NH ₃ as a reducing agent is used as the purification catalyst layer 41 and ASC is used as the reducing agent removing layer 42 will be described as an example. When the SCR catalyst is used as the NOx purification catalyst layer 41, the reducing agent for supplying the NOx purification catalyst layer 41 can be used as an additive for supplying the adsorption layer 35. Therefore, the reducing agent supply device 60 can be configured to also serve as the additive supply device, and the adsorption layer 35 can be mounted without complicating the exhaust gas purification system using the conventional SCR catalyst.

Urea water (urea aqueous solution) is stored in the tank 66 of the reducing agent supply device 60 as a liquid containing the reducing agent. By driving the pump 65, the urea water stored in the tank 66 passes through the reducing agent supply pipes 63 and 64 and is supplied to the injectors 61 and 62, and the urea water is injected from the injectors 61 and 62 into the exhaust pipe 12. can do.

The urea water droplets ejected from the injectors 61 and 62 collide with the mixing members 37 and 38 and the inner wall surface of the exhaust pipe 12 to become finer, or adhere to the wall surface and evaporate, and then the following formula (9) ), And the hydrolysis represented by the following formula (10), changes from urea (CO (NH ₂ ) ₂ ) to NH ₃ , and is supplied to the adsorption layer 35 and the second catalyst layer 40, respectively. To.

CO (NH ₂ ) ₂ → NH ₃ + HNCO… (9)
HNCO + H ₂ O → NH ₃ + CO ₂ … (10)

In the second catalyst layer 40, the catalytic reaction represented by the following formulas (11) to (13) occurs due to the SCR catalyst. As a result, NOx is reduced using NH ₃ as a reducing agent and changed to N ₂ and H ₂ O. The following formula (11) is called a Fast reaction, the formula (12) is called a Standard reaction, and the formula (13) is called a Slow reaction.

NO + NO ₂ + 2NH ₃ → 2N ₂ + 3H ₂ O… (11)
4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O… (12)
6NO ₂ + 8NH ₃ → 7N ₂ + 12H ₂ O… (13)

The detected values of the second catalyst temperature sensor 21, the inlet NOx sensor 23, the outlet NOx sensor 24, and the adsorption layer temperature sensor 25 are output to the ECU 50. The ECU 50 is an electronic control unit mainly composed of a microcomputer including a CPU, ROM, RAM, etc., and by executing various control programs stored in the ROM, based on the detection signals of the various sensors described above. , Performs various controls of the internal combustion engine 20 and the exhaust purification system 10. The ECU 50 has a function of executing combustion control of the internal combustion engine 20, and also has a function of a control device for executing control of the amount of reducing agent supplied from the reducing agent supply device 60.

The ECU 50 includes a temperature information acquisition unit 51, a component amount acquisition unit 52, an adsorbent state acquisition unit 53, a catalyst state acquisition unit 54, a reducing agent control unit 55, and a combustion control unit 56.

The temperature information acquisition unit 51 acquires temperature information of each catalyst layer constituting the first catalyst layer 30, the adsorption layer 35, and the second catalyst layer 40, respectively. The temperature information acquired by the temperature information acquisition unit 51 may be stored in the ECU 50. The temperature information of each catalyst layer may be a detected value of the temperature detected by a temperature sensor (for example, the second catalyst temperature sensor 21) installed in each catalyst layer, or may be an estimated value.

The temperature information acquisition unit 51 may acquire other parameters related to the temperature of the NOx purification catalyst layer 41 as temperature information. The temperature information of each catalyst layer means the temperature of each catalyst layer and other parameters related to the temperature. For example, the elapsed time from the start of temperature rise of each catalyst layer and the warm-up of the internal combustion engine 20. The completion of the above, the temperature of the cooling return water of the internal combustion engine 20, the fuel consumption amount from the start of the internal combustion engine 20, the elapsed time, the mileage, and the like can be mentioned.

In addition to the temperature information of the NOx purification catalyst layer 41, the temperature information acquisition unit 51 further provides temperature information of the adsorption layer 35, temperature information of the DOC layer 31 and the DPF layer 32 constituting the first catalyst layer 30, and a reducing agent. It may be configured so that the temperature information of the removal layer 42 can be acquired.

The component amount acquisition unit 52 acquires a detected value or an estimated value of the component amount of each component contained in the exhaust gas. The component amount of each component may be a detected value detected by various sensors, or may be an estimated value estimated based on other parameters related to the component amount or the like. For example, the component amount acquisition unit 52 acquires an estimated value of the NOx amount discharged from the internal combustion engine 20 as the NOx component amount, and the NOx component amount in the exhaust detected by the inlet NOx sensor 23 and the outlet NOx sensor 24. To get. The amount of NOx discharged from the internal combustion engine 20 can be estimated based on, for example, the combustion state of the internal combustion engine 20. The data acquired by the component amount acquisition unit 52 may be stored in the ECU 50.

The adsorbent state acquisition unit 53 acquires information indicating the state of the adsorbent layer 35. As the information indicating the state of the adsorption layer 35, for example, the temperature information of the adsorption layer 35 and the information on the amount of NOx adsorbed on the adsorption layer 35 and the amount of the additive can be exemplified. The temperature information of the adsorption layer 35 means the temperature of the adsorption layer 35 and other parameters related to the temperature. Similarly, the information regarding the amount of NOx and the amount of the additive adsorbed on the adsorption layer 35 means the amount of NOx and the amount of the additive, and other parameters related thereto.

The higher the temperature of the adsorption layer 35, the easier it is for NOx adsorbed on the adsorption layer 35 to be released. Further, the larger the amount of NOx adsorbed on the adsorption layer 35 and the amount of additives, the easier it is for the NOx adsorbed on the adsorption layer 35 to be released. Therefore, the adsorption performance of the adsorption layer 35 can be obtained based on the temperature information of the adsorption layer 35 and the information on the amount of NOx adsorbed on the adsorption layer 35 and the amount of the additive.

The catalyst state acquisition unit 54 detects the activated state of the catalyst in the first catalyst layer 30 and the second catalyst layer 40. The activated state of the catalyst is the degree of activity of the catalytic reaction, and can be obtained based on the temperature information of the catalyst, the adsorbed substance information on the substance adsorbed on the catalyst, and the like.

For example, the activated state of the NOx purification catalyst layer 41 can be determined based on the temperature information of the NOx purification catalyst layer 41 and the amount of the reducing agent adsorbed on the NOx purification catalyst layer 41. As the temperature information of the NOx purification catalyst layer 41, the detected value of the second catalyst temperature sensor 21 can be used. As the adsorbed substance information of the NOx purification catalyst layer 41, for example, the adsorbed amount of the reducing agent can be used.

The reducing agent control unit 55 controls the supply amount, supply timing, and the like of the reducing agent supplied from the reducing agent supply device 60 to the exhaust pipe 12. For example, the supply amount and supply timing of the reducing agent supplied from the injector 61 to the inlet side of the adsorption layer 35 based on the amount of NOx contained in the exhaust on the inlet side and the outlet side of the adsorption layer 35 acquired by the component amount acquisition unit 52. Etc. are controlled. The reducing agent control unit 55 has a function as an additive control unit that controls the reducing agent supply device 60 as an additive supply device based on the amount of NOx acquired by the component amount acquisition unit 52. The reducing agent control unit 55 uses information indicating the state of the adsorbent layer 35 acquired by the adsorbent state acquisition unit 53 when controlling the reducing agent supplied as an additive from the injector 61. For example, the supply amount and supply timing of the reducing agent are controlled according to the adsorption performance of the adsorption layer 35. Further, the reducing agent control unit 55 controls the reducing agent supplied as an additive from the injector 61 with reference to the information indicating the state of the second catalyst layer 40 acquired by the catalyst state acquisition unit 54. Thereby, the NOx released from the adsorption layer 35 by the additive can be controlled so as to be sufficiently purified by the NOx purification catalyst layer 41 of the second catalyst layer 40.

Further, the reducing agent control unit 55 supplies the NOx purification catalyst layer 41 from the reducing agent supply device 60 to the exhaust pipe 12 in response to the NOx purification request when the NOx reduction reaction activity is sufficiently obtained. For example, the amount of reducing agent supplied from the injector 62, which is a reducing agent supply mechanism, to the exhaust pipe 12 is controlled based on the temperature information of the NOx purification catalyst layer 41 and the amount of NOx to be reduced. The reducing agent control unit 55 uses information indicating the state of the second catalyst layer 40 acquired by the catalyst state acquisition unit 54 when controlling the reducing agent supplied from the injector 62. For example, the supply amount and supply timing of the reducing agent are controlled according to the activated state of the NOx purification catalyst layer 41.

More specifically, it is determined that the NOx reduction reaction activity is sufficiently obtained in the NOx purification catalyst layer 41 when the temperature information of the NOx purification catalyst layer 41 is in a state indicating that it is equal to or higher than a predetermined temperature threshold. Therefore, the reducing agent may be controlled to be supplied from the injector 62 to the NOx purification catalyst layer 41. The temperature threshold can be set, for example, to the active temperature TA of a predetermined catalyst contained in the second catalyst layer 40. More specifically, the activity temperature TA of the LNT catalyst, the SCR catalyst, or the three-way catalyst arranged in the NOx purification catalyst layer 41 may be set.

The active temperature TA is a temperature at which the NOx purification capacity of the catalyst (an index in which the maximum purification capacity of the catalyst is 100%) has a high probability (for example, about 90%). As shown in FIG. 6, in NOx purification catalysts such as SCR catalysts, LNT catalysts, and three-way catalysts, when the catalyst temperature rises from a low temperature range where the catalyst temperature is up to about T2 and there is almost no catalytic activity, the catalyst temperature T1 to 1 In the medium temperature range shown in T2, the catalytic activity increases remarkably and reaches a high probability. Then, in the high temperature region after the catalyst temperature reaches T2, the catalytic activity becomes substantially constant. For example, the catalyst temperature T2 at which the significant increase in catalytic activity is completed can be used as the active temperature TA.

The supply amount of the reducing agent can be set based on the amount of NOx in the exhaust gas supplied to the NOx purification catalyst layer 41. More specifically, the injection rate and the injection time in the injector 62, which is the reducing agent supply mechanism, can be set according to the supply amount of the reducing agent.

The combustion control unit 56 controls the combustion state of the internal combustion engine 20. The combustion control unit 56 may be configured to be able to control the amount of each component in the exhaust gas by controlling the amount or timing of the fuel and air supplied to the internal combustion engine 20.

(Modification example)
7 (a) shows the first catalyst layer 30, the adsorption layer 35, the second catalyst layer 40, the mixing members 37 and 38, the injectors 61 and 62, and the inlet NOx sensor 23, which are installed in the exhaust pipe 12 shown in FIG. It is a figure which shows typically the outlet NOx sensor 24. As shown in FIG. 7A, the exhaust purification system 10 may further include an adsorption layer inlet NOx sensor 22 that detects the amount of NOx in the exhaust upstream of the injector 61.

Further, when the NOx purification catalyst layer 41 is an SCR catalyst layer provided with an SCR catalyst as a NOx purification catalyst and a reducing agent supplied to the SCR catalyst layer is used as an additive, the exhaust purification system 10 is shown in FIG. 7 (b). ), The injector 62 may not be provided. In this case, the injector 61 functions as a common reducing agent supply mechanism that supplies the total amount of the reducing agent supplied to the adsorption layer 35 and the reducing agent supplied to the NOx purification catalyst layer 41 to the inlet of the adsorption layer 35. By adopting the common reducing agent supply mechanism, the exhaust gas purification system 10 can be simplified.

Further, as shown in FIG. 8, the adsorption layer 35 may be replaced with an adsorption layer 35a having a filter structure in which the adsorbent Q is supported on the DPF. In this case, the first catalyst layer 30 may be replaced with the first catalyst layer 30a containing the DOC catalyst layer but not the DPF layer. Since the adsorption layer 35a has a DPF function, the DPF layer 32 can be omitted, and the configuration inside the exhaust pipe 12 can be simplified.

Further, as shown in FIG. 9, the adsorption layer 35 may be an adsorption layer 35b in which the adsorption material Q is supported on the mixing member. As the mixing member, for example, as shown in FIG. 10, a disk-shaped mixing member 70 provided with a plurality of holes 71 can be exemplified. The mixing member 70 is fitted and fixed, for example, so that its circular outer edge is in contact with the inner wall surface of the exhaust pipe 12. A plurality of mixing members 70 may be installed at intervals in the exhaust flow direction. In this case, it is preferable to stagger the positions of the holes 71 in the mixing member 70 adjacent to the exhaust flow direction so that the exhaust does not flow linearly. In addition to the shape shown in FIG. 10, it may have various shapes such as a propeller blade shape and a spiral blade shape that can agitate the flow of exhaust gas.

Further, as shown in FIG. 11, the adsorption layer 35 may be replaced with the adsorption layer 35c connected to the upstream side of the SCR catalyst layer. The adsorption layer 35c is an adsorption layer in which the adsorbent Q is supported on a filter-like carrier having a function of diffusing exhaust gas. Specific examples of such a filter include a PE (Performed foil) carrier manufactured by Emitech, an LS (Longitudinal Structured file) carrier, and a carrier having a structure in which these are combined.

As shown in FIGS. 12 and 13, the PE carrier is a columnar filter in which the perforated foil 80 and the wavy foils 81 and 82 are wound in a spiral shape in a stacked state. By being wound in a spiral shape, the perforated foil 80 and the wavy foils 81 and 82 have a structure in which they are alternately layered in the R direction, which is the radial direction of the cylinder. The hole 83 is formed in the perforated foil 80, and the wavy foil 82 is provided with the hole 84 at the same position as the hole 83 in the circumferential direction of the exhaust pipe 12. The wavy foil 81 is not provided with a hole. The gas passing through the PE carrier can be diffused in the R direction through the pores 83 and 84, and the wavy foils 81 and 82 disturb the gas flow and turbulently flow. By improving the diffusion state of the gas and turbulent flow, the catalytic reaction carried on the PE carrier can be brought close to the reaction rate-determining state, which can contribute to the improvement of the catalytic activity.

As shown in FIGS. 9 and 11, when the adsorption layers 35b and 35c having a function of stirring the exhaust flow are used, the mixing members 37 and 38 shown in FIG. 1 need not be installed in the exhaust pipe 12. May be good. Therefore, the configuration inside the exhaust pipe 12 can be simplified. Adsorption layer Further, in FIG. 11, the adsorption layer 35c and the second catalyst layer 40 are those in which the adsorbent Q, the SCR catalyst, and the ASC catalyst are supported in this order on one filter-like carrier from the upstream side. It may be.

As shown in FIG. 14, a second catalyst layer 40a provided with an LNT catalyst as a NOx purification catalyst may be provided instead of the SCR catalyst. Since the second catalyst layer 40a includes an LNT catalyst, it is not necessary to include a reducing agent removing layer 42. In this case, an injector 91 that supplies hydrocarbons can be installed on the inlet side of the second catalyst layer 40a. Further, as the hydrocarbon source supplied from the injector 91, the fuel supplied to the internal combustion engine 20 can be used. By making the fuel available as an additive, the tank 66 for the reducing agent becomes unnecessary, so that the exhaust gas purification system equipped with the LNT catalyst which does not require the reducing agent as the NOx purification catalyst can be easily adsorbed. The layer 35 can be mounted.

As shown in FIGS. 15A and 15B, the adsorbent Q is supported on the upstream side of one filter-shaped carrier, and the NOx purification catalyst is supported on the downstream side, whereby the adsorption layer 35b and the second The catalyst layer 40b may be formed in a series. In this case, the injector 61 has a function as a common reducing agent supply mechanism that injects both the additive and the reducing agent from one place.

As shown in FIGS. 16A and 16B, the adsorption layer and the NOx purification catalyst layer are integrated by supporting the adsorbent Q and the NOx purification catalyst in a mixed manner on one filter-like carrier. The adsorption / NOx purification catalyst layer 39 may be provided. In this case, the injector 61 has a function as a common reducing agent supply mechanism that injects both the additive and the reducing agent from one place. In the second catalyst layer 40b and the adsorption / NOx purification catalyst layer 39, the NOx purification catalyst is not particularly limited, and an SCR catalyst, an LNT catalyst, and a three-way catalyst can be used.

The second catalyst layer may be divided into a plurality of second catalyst layers, and may be further arranged apart from each other in the exhaust pipe 12. Specifically, for example, as shown in FIG. 17, the second catalyst layer may be divided into a plurality of second catalyst layers 40c and 40d. The upstream side second catalyst layer 40c arranged on the upstream side need only include the NOx purification catalyst layer, and does not need to include the ASC catalyst layer. Further, the downstream second catalyst layer 40d preferably includes both a NOx purification catalyst layer and an ASC layer. When the NOx purification catalyst layer is divided into a plurality of parts, as shown in FIG. 17, injectors 62a and 62b for injecting a reducing agent upstream of the second catalyst layers 40a and 40b, and injectors 62a, respectively. , 62b and the mixing members 38a and 38b arranged between the second catalyst layers 40c and 40d, and the outlet NOx sensors 24a and 24b for detecting the amount of NOx in the exhaust on the outlet side of the second catalyst layers 40c and 40d. It may be configured to be provided.

When the second catalyst layer is divided into a plurality of second catalyst layers, the second catalyst layer on the upstream side may be arranged upstream of the first catalyst layer. Specifically, for example, as shown in FIG. 18, even if the second catalyst layer 40e on the upstream side, the first catalyst layer 30, the adsorption layer 35, and the second catalyst layer 40f on the downstream side are arranged in this order from the upstream side. Good. Further, the mixing members 38e arranged between the injectors 62e and 62f for injecting a reducing agent into the second catalyst layers 40e and 40f on the upstream side and the injectors 62e and 62f and the second catalyst layers 40e and 40f, respectively. , 38f and the like. The second catalyst layer 40e is installed mainly for the purpose of improving the NOx purification performance at the time of cold start when the internal combustion engine or the exhaust gas purification system is started at a temperature equal to or lower than the outside air temperature. However, according to the configuration shown in FIG. 18, even when the purification performance of the second catalyst layers 40e and 40f at the time of cold start is not sufficient, the purification performance can be improved by the adsorption layer 35.

The adsorption layer may be divided into a plurality of adsorption layers, and may be further installed separately in the exhaust pipe 12. Specifically, for example, as shown in FIG. 19, in order from the internal combustion engine 20 side, the upstream side adsorption layer 35 g, the upstream side second catalyst layer 40e, the first catalyst layer 30, the downstream side adsorption layer 35h, and the downstream side first. The two catalyst layers 40f may be arranged in this order. Further, each of the adsorption layers 35g and 35h is provided with injectors 61g and 61h for injecting a reducing agent on the upstream side thereof, and mixing members 37g and 37h arranged between the injectors 61g and 61h and the adsorption layers 35g and 35h. It may be configured to be provided. According to the configuration of FIG. 19, even when the purification performance of the second catalyst layers 40e and 40f at the time of cold start is not sufficient, the purification performance is improved by the upstream side adsorption layer 35h and the downstream side adsorption layer 35g. be able to. In addition to the configuration shown in FIG. 18, the upstream adsorption layer 35 g is also installed upstream of the second catalyst layer 40e, which is installed mainly for the purpose of improving the purification performance at the time of cold start. , The purification performance can be further improved as compared with the configuration of FIG.

In the above-described embodiment and its modifications, the case where the SCR catalyst and the LNT catalyst are used as alternatives as the NOx purification catalyst has been described as an example, but the SCR catalyst, the LNT catalyst, and the three-way catalyst are included. A plurality of types of NOx purification catalysts may be used in combination. For example, in the configuration shown in FIG. 17, the second catalyst layer 40a on the upstream side may be configured to have an LNT catalyst as a NOx purification catalyst, and the second catalyst layer 40b on the downstream side may be configured to have an SCR catalyst as a NOx purification catalyst. Good. Further, for example, the second catalyst layer may be divided into three, and the catalyst layer divided into three may be configured to include an SCR catalyst, an LNT catalyst, and a three-way catalyst, respectively.

According to each of the above embodiments, the following effects can be obtained.

The exhaust purification system 10 that purifies a predetermined component in the exhaust gas from the internal combustion engine 20 includes an adsorption layer 35 and a NOx purification catalyst layer 41 installed in the exhaust pipe of the internal combustion engine 20, and a reducing agent supply device that supplies a reducing agent. 60 and. The adsorption layer 35 contains an adsorbent that adsorbs NOx in the exhaust gas and releases the adsorbed NOx by supplying a predetermined additive. The NOx purification catalyst layer 41 contains a NOx purification catalyst that purifies nitrogen oxides in the exhaust gas by a reduction reaction. The reducing agent supply device 60 has a function as an additive supply device for supplying the additive to the adsorption layer 35.

According to the exhaust gas purification system 10, by supplying the additive to the adsorption layer 35 by the reducing agent supply device 60, NOx adsorbed on the adsorbent can be released, so that the temperature of the adsorption layer and the NOx purification catalyst layer can be released. NOx can be arbitrarily released without increasing the air-fuel ratio or controlling the air-fuel ratio of the internal combustion engine to the rich side.

The adsorbent that adsorbs NOx in the exhaust and releases the adsorbed NOx by supplying a predetermined additive is not limited, but is not limited to the general formula I: A _a B _b C _c O _8.5-δ. An adsorbent Q containing a composite oxide (first composite oxide) represented by and having an adsorption site for NOx can be exemplified. In the general formula I, A is composed of at least one selected from the group consisting of rare earth elements, Ca, and In, B is composed of at least one selected from the group consisting of alkaline earth metal elements, and C is a transition. It consists of at least one selected from the group consisting of metal elements, Al, Zn, and Ga, and a, b, c, and δ are 0 <a≤1, 0 <b≤1, 0 <c≤4, respectively. Satisfy 0 <δ ≦ 1.5.

The first composite oxide is represented by the general formula II: A _a B _b CcO _8.5-δ (NOx) _θ , and in the above general formula II, A is a group consisting of rare earth elements, Ca, and In. It consists of at least one selected, B consists of at least one selected from the group consisting of alkaline earth metal elements, and C consists of at least one selected from the group consisting of transition metal elements, Al, Zn, and Ga. , A, b, c, δ, θ satisfy 0 <a ≦ 1, 0 <b ≦ 1, 0 <c ≦ 4, 0 <δ ≦ 1.5, 0 ≦ θ ≦ 1.5, respectively. , May be a composite oxide.

Further, the adsorbent Q may contain a second compound different from the first composite oxide. Further, the adsorbent Q may have a main phase composed of the first composite oxide and a subphase composed of the second compound. Further, the above-mentioned second compound may contain at least one selected from the group consisting of transition metal elements, alkaline earth metal elements, Al, and Zn. In addition, the above-mentioned second compound may contain at least one of an oxide and a salt. In addition, the above-mentioned second compound may contain at least a carbonate of an alkaline earth metal element.

The above-mentioned adsorbent Q may be supported on a carrier. The carrier may be, for example, a structure used as a catalyst carrier such as a honeycomb structure or a porous body, or is exhausted mainly for purposes other than supporting the catalyst, such as the mixing member shown in FIG. It may be a structure installed in the pipe 12. Furthermore, the above-mentioned adsorbent Q may be supported on a carrier together with a noble metal. When a noble metal is supported on the carrier together with the above-mentioned adsorbent Q, the adsorption performance for NOx is improved.

Further, the adsorbent Q may be supported on the carrier together with an inorganic binder consisting of at least one selected from the group consisting of alumina, silica, and titania. Further, the adsorbent Q may be supported on the carrier together with a co-catalyst consisting of at least one selected from the group consisting of ceria, zirconia, and ceria-zirconia solid solution. When a co-catalyst is supported, the oxidation performance of the noble metal with respect to nitric oxide is improved. As a result, the adsorption performance of nitrogen oxides on the adsorbent Q is improved.

As the NOx purification catalyst provided in the NOx purification catalyst layer 41, a conventionally known NOx reduction catalyst that reduces and purifies NOx can be used. Specifically, NOx reduction catalysts called LNT catalysts, SCR catalysts, three-way catalysts and the like can be used.

When an SCR catalyst that selectively reduces and purifies NOx by supplying a reducing agent is used as the NOx purification catalyst, the additive may be a substance common to the reducing agent or another substance. It may be. When the additive and the reducing agent are common substances, a reduction having both a function as a reducing agent supply device for supplying the reducing agent to the SCR catalyst and a function as an additive supply device like the exhaust purification system 10. It may be configured to include the agent supply device 60. When the additive and the reducing agent are different, the additive supply device and the reducing agent supply device are configured as separate devices, but even if they are common substances, they are configured as separate devices. You may.

Like the exhaust purification system 10, the exhaust pipe 12 further has at least one of a DOC layer 31 provided with an oxidation catalyst that oxidizes unburned components in the exhaust and a DPF layer 32 that purifies the particulate components in the exhaust. It is preferable to have it inside.

Like the exhaust gas purification system 10, the injector 61 as an additive supply mechanism for supplying an additive to the inlet side of the adsorption layer 35 and the reducing agent supply mechanism for supplying a reducing agent to the inlet side of the NOx purification catalyst layer 41. It may be configured so that the injector 62 and the injector 62 are separately provided. When the additive and the reducing agent are common substances, the amount of the reducing agent (reducing agent as an additive) supplied to the adsorption layer 35 and the NOx purification catalyst layer 41 arranged on the downstream side of the adsorption layer 35. The sum of the amount of the reducing agent to be supplied to the adsorbent may be supplied from the position of the injector 61 to the inlet of the adsorption layer. In this case, the injector 61 has a function as a common reducing agent supply mechanism that injects both the additive and the reducing agent from one place.

Examples of the reducing agent supplied to the SCR catalyst include, but are not limited to, ammonia, hydrocarbons, and carbon monoxide. These reducing agents can also be used as additives to be supplied to the adsorbent to release NOx.

The adsorbent may be configured as an adsorption layer for the purpose of NOx adsorption, such as the adsorption layer 35 according to the exhaust purification system 10, or may be arranged in the exhaust pipe 12 for a purpose other than NOx adsorption. The adsorbent may be supported on another structure. For example, a mixing member that mixes exhaust gas or a particle collecting filter that purifies particulate components in exhaust gas may be used as an adsorbent layer on which an adsorbent is adsorbed.

In the exhaust gas purification system 10, one DOC layer 31, one DPF layer 32, one adsorption layer 35, and one NOx purification catalyst layer 41 are provided, and they are arranged from the internal combustion engine 20 side in this order. Not limited to this. The number of each layer may be singular or plural, and the arrangement of each layer may be appropriately changed.

For example, when one layer each of the DOC layer, the DPF layer, and the adsorption layer is provided, and two NOx purification catalyst layers are provided, the upstream NOx purification catalyst arranged on the upstream side in order from the internal combustion engine 20 side. The layer, the DOC layer, the DPF layer, the adsorption layer, and the downstream NOx purification catalyst layer arranged on the downstream side may be arranged in the exhaust pipe 12 in this order.

Further, when the DOC layer and the DPF layer are provided one by one, and the adsorption layer and the NOx purification catalyst layer are provided by two layers each, the upstream side arranged on the upstream side in order from the internal combustion engine 20 side. The adsorption layer, the upstream NOx purification catalyst layer, the DOC layer, the DPF layer, the downstream adsorption layer arranged on the downstream side, and the downstream NOx purification catalyst layer may be arranged in the exhaust pipe 12 in this order.

Further, the exhaust gas purification system 10 includes an ECU 50 having a function as a control device for controlling the reducing agent supply device 60. The ECU 50 has a component amount acquisition unit 52 that detects or estimates the amount of NOx in the exhaust gas discharged from the internal combustion engine 20 and the amount of NOx in the exhaust gas on the inlet side and the outlet side of the NOx purification catalyst layer 41, and a component. It is provided with a reducing agent control unit 55 that controls the reducing agent supply device 60 based on the amount of NOx acquired by the amount acquisition unit 52. Therefore, based on the obtained amount of NOx, the amount of the reducing agent supplied to the adsorption layer 35 as an additive or the amount of the reducing agent supplied to the NOx purification catalyst layer 41 can be appropriately controlled.

In each of the above embodiments, an adsorbent that releases adsorbed NOx by supplying a reducing agent such as ammonia, hydrocarbon, and carbon monoxide, which is supplied to the SCR catalyst, as an additive is exemplified. However, it is not limited to this. Since the adsorbent Q tends to adsorb NO ₂ and nitric acid more easily than NO, a material that reduces NO ₂ and nitric acid adsorbed on the adsorbent to NO, which is less likely to be adsorbed, is preferably used as an additive. Can be done.

The controls and methods thereof described in the present disclosure are realized by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. May be done. Alternatively, the controls and methods thereof described in the present disclosure may be implemented by a dedicated computer provided by configuring the processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and method thereof described in the present disclosure may be a combination of a processor and memory programmed to perform one or more functions and a processor composed of one or more hardware logic circuits. It may be realized by one or more dedicated computers configured. Further, the computer program may be stored in a computer-readable non-transitional tangible recording medium as an instruction executed by the computer.

10 ... Exhaust purification system, 12 ... Exhaust pipe, 20 ... Internal combustion engine, 35 ... Adsorption layer, 41 ... NOx purification catalyst layer, 60 ... Reducing agent supply device

Claims (14)

An exhaust gas purification system (10) that purifies a predetermined component in exhaust gas from an internal combustion engine (20).
An adsorption layer (35) that is installed in the exhaust pipe of the internal combustion engine and contains an adsorbent that adsorbs the nitrogen oxides in the exhaust gas and releases the adsorbed nitrogen oxides by supplying a predetermined additive. When,
A purification catalyst layer (41) installed in the exhaust pipe and containing a purification catalyst that purifies nitrogen oxides in the exhaust gas by a reduction reaction.
An exhaust gas purification system including an additive supply device (60) for supplying the additive to the adsorption layer. The adsorbent contains a composite oxide (2) represented by the general formula I: A _a B _b C _c O _8.5-δ .
The composite oxide has an adsorption site for the nitrogen oxide and
In the general formula I, A is composed of at least one selected from the group consisting of rare earth elements, Ca, and In, B is composed of at least one selected from the group consisting of alkaline earth metal elements, and C is a transition metal. It consists of at least one selected from the group consisting of elements, Al, Zn, and Ga, and a, b, c, and δ are 0 <a≤1, 0 <b≤1, 0 <c≤4,0, respectively. The exhaust purification system according to claim 1, which satisfies <δ ≦ 1.5. The purification catalyst is a selective reduction catalyst that selectively reduces and purifies the nitrogen oxides by supplying a reducing agent.
The exhaust gas purification system according to claim 1 or 2, wherein the exhaust gas purification system includes a reducing agent supply device (60) for supplying the reducing agent. The additive supply device (60) includes an additive supply mechanism (61) that supplies the additive to the inlet side of the adsorption layer (35).
The exhaust gas purification system according to claim 3, wherein the reducing agent supply device (60) includes a reducing agent supply mechanism (62) that supplies the reducing agent to the inlet side of the purification catalyst layer (41). The additive is a substance common to the reducing agent, and is
The exhaust gas purification system according to claim 3 or 4, wherein the reducing agent supply device (60) further includes a function as the additive supply device. The reducing agent supply device supplies a total amount of the reducing agent supplied to the adsorption layer and the reducing agent supplied to the purification catalyst layer arranged on the downstream side of the adsorption layer to the inlet of the adsorption layer. The exhaust purification system according to claim 5, further comprising a supply mechanism (61a). The exhaust purification system according to claim 5 or 6, wherein the additive and the reducing agent are ammonia. The exhaust gas purification system according to claim 5 or 6, wherein the additive and the reducing agent are hydrocarbons or carbon monoxide. The adsorption layer (35a) includes a mixing member that mixes the exhaust gas.
The exhaust gas purification system according to any one of claims 1 to 8, wherein the adsorbent is supported on the mixing member. At least one of the oxidation catalyst layer (31) provided with an oxidation catalyst for oxidizing the unburned components in the exhaust and the particle collection filter (32) for purifying the particulate components in the exhaust is provided in the exhaust pipe ( The exhaust gas purification system according to any one of claims 1 to 9, further provided in 12). The exhaust gas purification system according to claim 10, wherein the adsorption layer (35c) has a filter structure in which the adsorbent is supported on the particle collection filter. In order from the internal combustion engine (20) side
Upstream purification catalyst layers (41a, 40e) including a selective reduction catalyst that selectively reduces and purifies the nitrogen oxides by supplying a reducing agent as the purification catalyst.
An oxidation catalyst layer (31) including an oxidation catalyst that oxidizes the unburned components in the exhaust gas.
A particle collecting filter (32) that purifies the particulate component in the exhaust gas, and
With the adsorption layer (35)
The exhaust purification system according to any one of claims 1 to 11, wherein a downstream purification catalyst layer (40b, 40f) including a selective reduction catalyst as the purification catalyst is provided in the exhaust pipe (12). The adsorption layer is a downstream adsorption layer (35h).
The exhaust purification system according to claim 12, further comprising an upstream adsorption layer (35 g) in the exhaust pipe (12) on the internal combustion engine (20) side upstream of the upstream purification catalyst layer (41a). A component amount acquisition unit (52) that detects or estimates the amount of nitrogen oxides in the exhaust gas discharged from the internal combustion engine and the amount of nitrogen oxides in the exhaust gas on the inlet side and the outlet side of the purification catalyst layer.
An additive control unit (55) that controls the additive supply device (60) based on the amount of nitrogen oxides acquired by the component amount acquisition unit.
The exhaust gas purification system according to any one of claims 1 to 13, further comprising a control device (50) including.

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