JP2010184183A - Exhaust emission control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control system which can reduce the frequency of a regeneration treatment, and can suppress a rapid temperature rise in an exhaust emission purifying filter without using a complicated system control. <P>SOLUTION: The exhaust emission control system 1 includes an exhaust emission purifying filter 2 provided in an exhaust emission passage 54 of an internal combustion 5 and collecting particulate substances contained in the exhaust emission, and a filter regenerating means 151 for carrying out the regeneration treatment of a collecting ability of the exhaust emission purifying filter 2 by raising the temperature up to a predetermined regeneration temperature to burn and remove the particulate substances deposited in the exhaust emission purifying filter 2. The exhaust emission purifying filter 2 has a substrate comprising a porous body, and an exhaust emission purification catalyst supported by the substrate. The exhaust emission purification catalyst is formed by calcining a mixture of an alkali metal element source and/or an alkaline earth metal element source and zeolite, or sodalite at 600°C or more. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine.

The exhaust gas of an internal combustion engine such as a diesel engine, particulate matter (PM), which contain harmful substances such as NO _x. In addition, direct-injection gasoline engines have an engine (lean burn) that operates with an air-fuel mixture that is thinner than the stoichiometric air-fuel ratio. Even in exhaust gas discharged from such gasoline engines, harmful substances such as PM and NO _x are present. include.
Such harmful substances have been removed by combustion or adsorption by an exhaust gas purification filter provided in the exhaust gas path.

  In general, the exhaust gas purification filter is made of a porous body and can collect particulate matter such as PM. Accumulation of particulate matter increases pressure loss and may adversely affect engine operation. Therefore, a regeneration process has been performed in which particulate matter deposited on the exhaust gas purification filter is intermittently burned and removed. Specifically, the fuel is burned in the internal combustion engine, and the regeneration process is performed using the high-temperature exhaust gas generated thereby.

In order to reliably perform this regeneration process at a relatively low temperature, a noble metal catalyst such as platinum having a combustion promoting action on PM has been carried on an exhaust gas purification filter.
In the exhaust gas purification filter loaded with the noble metal catalyst, the regeneration process is performed at a temperature at which PM burns at 600 ° C. or higher. For more reliable combustion, it was necessary to carry out at 630 ° C. or higher.

  During the regeneration process, for example, when the operating state of the internal combustion engine becomes a deceleration state, the amount of exhaust gas flowing into the exhaust gas purification filter decreases, and PM combustion heat stays in the exhaust gas purification filter. The problem of causing a rapid increase in temperature was caused. This rapid temperature increase may reach a high temperature exceeding 1000 ° C., and as a result, the exhaust gas purification filter may be melted.

In order to suppress a rapid temperature rise, a technique for increasing the idling speed during idling has been developed (see Patent Document 1).
In addition, a technique has been developed that includes an OT determination unit that determines whether or not the temperature of the filter is excessively high (see Patent Document 2).
In addition, a technology has been developed that monitors the temperature of the components of the exhaust pipe and uses the configuration of the multistage means when the temperature is exceeded (see Patent Document 3).

JP 2004-204774 A JP 2005-201210 A JP 2007-170382 A

  However, in the prior art, in order to suppress rapid temperature rise, system control with high robustness is required, and there is a problem that the system becomes complicated. Further, for example, in order to burn PM in a short time of about 15 minutes, combustion at a high temperature of 600 ° C. or more is required, and the fuel consumption may be deteriorated.

  In addition, the rapid temperature increase when the operating state of the internal combustion engine is in a decelerating state is likely to occur as the amount of accumulated PM increases. That is, PM combustion progresses rapidly by combustion propagation once it starts, and combustion propagation is further accelerated, particularly when a precious metal catalyst such as platinum is present in the exhaust gas purification filter. As a result, the rapid temperature rise progresses at an accelerated rate, increasing the possibility that the exhaust gas purification filter will be melted. In order to avoid this, conventionally, it has been necessary to regenerate the exhaust gas purification filter in a state where not much PM is deposited, and to increase the frequency of the regeneration process by making the regeneration timing as early as possible. However, since the regeneration of the exhaust gas purification filter involves fuel consumption, there is a problem that the fuel consumption is further reduced if the regeneration timing is advanced.

  The present invention has been made in view of such conventional problems, and can reduce the frequency of regeneration processing and suppress a rapid temperature increase in the exhaust gas purification filter without using complicated system control. It is intended to provide an exhaust gas purification device that can perform the above.

The present invention provides an exhaust gas purification filter that is provided in an exhaust gas passage of an internal combustion engine and collects particulate matter contained in the exhaust gas, and raises the temperature in the exhaust gas purification filter to a predetermined regeneration temperature, thereby the exhaust gas purification filter. In the exhaust gas purification apparatus comprising filter regeneration means for performing regeneration processing of the collection ability of the exhaust gas purification filter by burning and removing the particulate matter accumulated therein,
The exhaust gas purification filter has a base material made of a porous body and an exhaust gas purification catalyst carried on the base material,
The exhaust gas purifying catalyst is in an exhaust gas purifying apparatus, wherein a mixture of zeolite and an alkali metal element source and / or an alkaline earth metal element source or sodalite is calcined at a temperature of 600 ° C. or more. 1).

In the exhaust gas purification apparatus of the present invention, the exhaust gas purification filter includes the base material and the exhaust gas purification catalyst, and the exhaust gas purification catalyst comprises zeolite, an alkali metal element source and / or an alkaline earth metal element source. A mixture or sodalite is fired at a temperature of 600 ° C. or higher.
The exhaust gas purification catalyst has an excellent combustion promoting action on the particulate matter such as particulate matter (PM). Therefore, in the exhaust gas purification filter, the particulate matter can be burned and removed at a low temperature of, for example, less than 600 ° C. by the action of the exhaust gas purification catalyst. Therefore, the regeneration temperature of the exhaust gas purification filter can be lowered.

Moreover, in the exhaust gas purification filter provided with the exhaust gas purification catalyst, rapid temperature rise is suppressed.
That is, in a conventional exhaust gas purification filter equipped with a noble metal catalyst such as Pt, for example, when the operating state of the internal combustion engine is decelerated, a rapid temperature rise occurs and the temperature in the exhaust gas purification filter is at least partially For example, there is a risk of reaching a high temperature exceeding 1000 ° C., for example. As a result, the base material of the exhaust gas purification filter may be melted.
On the other hand, in the exhaust gas purification filter provided with the exhaust gas purification catalyst obtained by firing the mixture or sodalite at a temperature of 600 ° C. or higher, the temperature rise is slower than that in which a noble metal catalyst such as Pt is supported. Thus, the temperature is not so high as to cause damage such as melting damage to the substrate. Even when the operating state of the internal combustion engine is in a decelerating state during the regeneration process, a rapid temperature rise in the exhaust gas purification filter can be suppressed.
Therefore, according to the present invention, rapid temperature rise can be suppressed without performing complicated system control as in the prior art.

Further, the rapid temperature rise tends to depend on the start temperature of the regeneration process, that is, the regeneration temperature. That is, when the regeneration temperature is set high, the rapid temperature rise during the regeneration process easily reaches a higher temperature.
For example, when a conventional noble metal catalyst is used, it is necessary to set the regeneration temperature to about 630 ° C. in order to surely burn PM. At such a high regeneration temperature, a rapid temperature rise occurs and the exhaust gas purification filter is used. There was a possibility that the temperature of would rise to a high temperature (for example, 900 ° C. or higher) that damages the substrate.
On the other hand, when the exhaust gas purification catalyst is used, even if the regeneration temperature is about 630 ° C., it is possible to prevent the temperature from rapidly rising to a temperature that damages the substrate during the regeneration process. Further, when the exhaust gas purification catalyst is used as described above, the particulate matter such as PM can be combusted even at a low temperature of less than 600 ° C. Therefore, the regeneration temperature can be set to less than 600 ° C., the rapid temperature rise can be suppressed more reliably, and the above-mentioned melting damage can be prevented.

Also, the rapid temperature rise tends to depend on the amount of particulate matter such as PM deposited. That is, as the amount of the particulate matter deposited in the exhaust gas purification filter at the start of the regeneration process increases, a rapid temperature rise is likely to occur even from a lower regeneration temperature, resulting in a higher temperature that damages the substrate. It tends to be easy to reach.
When a conventional noble metal catalyst such as Pt is used, there is a possibility that a rapid temperature rise may occur even if regeneration processing is performed in a state where the amount of PM deposited is about 6 g / L. For this reason, it is necessary to set the PM deposition amount for starting the regeneration process to 5 g / L or less, more preferably 4 g / L or less.
On the other hand, since the exhaust gas purifying catalyst is used in the exhaust gas purifying apparatus of the present invention, the regeneration temperature is less than 600 ° C. By setting to, rapid temperature rise can be suppressed.
Therefore, the frequency of performing the regeneration process can be reduced, and fuel consumption can be reduced.

Further, the exhaust gas purification catalyst has a high holding power for alkali metal elements and / or alkaline earth metal elements.
Therefore, performance degradation of the exhaust gas purification catalyst can be prevented, and the exhaust gas purification filter can stably purify exhaust gas for a long period of time.
Further, the exhaust gas purifying catalyst can also adsorb NO _x. Therefore, the exhaust gas purification filter can also adsorb and remove NO _x from the exhaust gas.

  As described above, according to the present invention, there is provided an exhaust gas purification apparatus that can reduce the frequency of regeneration processing and can suppress a rapid temperature rise in the exhaust gas purification filter without using complicated system control. be able to.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which showed typically the engine system concerning Example 1 incorporating the exhaust gas purification apparatus. BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows the exhaust gas purification filter concerning Example 1. FIG. BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows the cross section of the exhaust gas purification filter concerning Example 1. FIG. BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows the structure by which the expanded cross section of the partition of the exhaust gas purification filter concerning Example 1 is shown, and the exhaust gas purification catalyst was carry | supported by the partition. Explanatory drawing which shows the partial cross section of the exhaust gas purification filter concerning Example 1, and shows a mode that exhaust gas passes the inside of an exhaust gas purification filter. Explanatory drawing which shows the relationship between the differential pressure | voltage in the upstream end side and downstream end side of an exhaust gas purification filter concerning Example 1, and the deposition amount of the particulate matter (soot) deposited in the exhaust gas purification filter. Explanatory drawing which showed typically the engine system concerning Example 2 incorporating the exhaust gas purification apparatus. Explanatory drawing which shows the arrangement | positioning position of the thermocouple in the exhaust gas purification filter concerning Example 2. FIG. According to Example 2. Explanatory drawing which shows the control pattern of the temperature of the exhaust gas purification filter in the position of 10 mm from the timing of the fuel addition and stop in a regeneration process, an engine speed, intake air amount, and an inlet_port | entrance. Detected by the thermocouples A to F provided in the exhaust gas purification filter when the PM deposition mode, the forced regeneration mode, and the deceleration operation mode are performed using the exhaust gas purification device (device E) according to the second embodiment. Explanatory drawing which shows the time-dependent change of the temperature. Detected by the thermocouples A to F provided in the exhaust gas purification filter when the PM accumulation mode, the forced regeneration mode, and the deceleration operation mode are performed using the exhaust gas purification device (device C) according to the second embodiment. Explanatory drawing which shows the time-dependent change of the temperature. Regeneration temperature and exhaust gas purification filter when regeneration processing is performed using the exhaust gas purification apparatus (device E) in which the PM accumulation amount at the start of the regeneration treatment according to Example 2 is set to 6 g / L and 10 g / L (DPF) relationship with the maximum temperature and regeneration temperature and exhaust gas when regeneration processing is performed using an exhaust gas purification device (apparatus C) in which the PM deposition amount when starting regeneration treatment is set to 6 g / L Explanatory drawing which shows the relationship with the highest temperature in a purification filter (DPF). Explanatory drawing which shows DTA exothermic peak temperature when burning carbon black using each catalyst seed | species concerning Example 1 of an experiment, or without using a catalyst. The diagram which shows the relationship between the temperature, TG, and DTA in the case where carbon black according to Experimental Example 1 is burned alone without using a catalyst. The diagram which shows the relationship between the temperature in the case of burning carbon black using a noble metal-type catalyst as a catalyst seed | species concerning Experimental example 1, and TG and DTA. The diagram which shows the relationship between the temperature at the time of burning carbon black using potassium carbonate as a catalyst seed | species concerning Experimental example 1, and TG and DTA. The diagram which shows the relationship between the temperature, TG, and DTA at the time of burning carbon black using the exhaust gas purification catalyst (sample E1) as the catalyst type according to Experimental Example 1. Explanatory drawing which shows the relationship between the calcination temperature concerning Example 1 of an experiment, and the DTA exothermic peak temperature of the exhaust gas purification catalyst before and behind water washing. Explanatory drawing which shows the relationship between the potassium salt seed | species concerning Experiment example 1, and DTA exothermic peak temperature of the exhaust gas purification catalyst before and behind water washing. Explanatory drawing which shows the relationship between the DTA exothermic peak temperature of the exhaust-gas purification catalyst before and after water washing concerning the experiment example 1 and alkali metal element species / alkaline earth metal element species. Explanatory drawing which shows the relationship between the alkali metal element seed | species other than potassium, alkaline-earth metal element seed | species concerning Experimental example 1, and DTA exothermic peak temperature of the exhaust gas purification catalyst before and behind water washing. Explanatory drawing which shows the relationship between the amount of potassium mixed in the mixing process and the DTA exothermic peak temperature of the exhaust gas purification catalyst before and after water washing according to Experimental Example 1. Explanatory drawing which shows the relationship between the amount of barium mixed in the mixing process and the DTA exothermic peak temperature of the exhaust gas purification catalyst before and after water washing according to Experimental Example 1. Explanatory drawing which shows DTA exothermic peak temperature when burning carbon black using each catalyst seed | species concerning Example 2 of an experiment, or without using a catalyst. Explanatory drawing which shows the relationship between the calcination temperature concerning the example 2, and the DTA exothermic peak temperature of the exhaust gas purification catalyst before and behind water washing. Explanatory drawing which shows the relationship between the zeolite seed | species and DTA exothermic peak temperature of a catalyst concerning Experimental example 2. FIG. Explanatory drawing which shows the DTA exothermic peak temperature before and behind water washing when burning carbon black using each catalyst seed | species concerning Example 3 of an experiment, or without using a catalyst. Explanatory drawing which shows the DTA exothermic peak temperature before and behind the water washing of the exhaust gas purification catalyst formed by baking the mixture of various zeolite and potassium carbonate concerning Experimental example 4. FIG. Explanatory drawing which shows the DTA exothermic peak temperature before and behind water washing when the mixture of various zeolite and potassium carbonate concerning Experimental example 4 is used as a catalyst. Explanatory drawing which shows the DTA exothermic peak temperature before and behind the water washing of the exhaust gas purification catalyst produced at the various different calcination temperature concerning Experimental example 5. FIG. Explanatory drawing which shows the DTA exothermic peak temperature before and behind the water washing of the exhaust gas purification catalyst produced by mixing various different amounts of potassium in Experimental Example 6 with zeolite. Explanatory drawing which shows the DTA exothermic peak temperature before and behind the water washing of the exhaust gas purification catalyst produced using the various different alkali metal element seed | species and alkaline earth metal element seed | species concerning Experimental example 7. FIG.

Next, a preferred embodiment of the present invention will be described.
The exhaust gas purification apparatus of the present invention includes the exhaust gas purification catalyst and the filter regeneration means.
The filter regeneration means can be configured as a computer program incorporated in an engine control unit (hereinafter referred to as ECU) that controls, for example, combustion injection in the engine.

The filter regeneration means is preferably configured to start the regeneration process by raising the temperature in the exhaust gas purification filter to the regeneration temperature of 400 ° C. or higher and lower than 600 ° C. (Claim 2).
In this case, the rapid temperature rise can be further suppressed by setting the regeneration temperature to a relatively low temperature of less than 600 ° C. In this case, since the amount of particulate matter such as PM deposited at the start of the regeneration process can be increased, the frequency of the regeneration process can be further reduced. Moreover, the exhaust gas purification catalyst can burn the particulate matter in a short time even at a low regeneration temperature of less than 600 ° C. as described above due to its excellent combustion promoting action.
When the regeneration temperature is lower than 400 ° C., it may be difficult to remove the particulate matter by combustion.

The filter regeneration means starts the regeneration process at the regeneration temperature of less than 600 ° C. when the operation state of the internal combustion engine is in a deceleration state, and when the operation state is in a state other than the deceleration state, The regeneration treatment of the exhaust gas purification filter can be performed at a temperature of 600 ° C. or higher.
In this case, the regeneration process can be performed in a shorter time when the driving state is in a state other than the deceleration state.

Preferably, the filter regeneration means is configured to always perform the regeneration process at the regeneration temperature of less than 600 ° C. regardless of the operating state of the internal combustion engine.
In this case, the rapid temperature rise can be more reliably suppressed regardless of the operating state.
That is, since the driving state depends on the operation of the driver, it is very difficult to predict what the driving state at a certain point will be after that, and there is a limit to the control according to the driving state. is there. As described above, if the regeneration process is always performed at the regeneration temperature of less than 600 ° C. regardless of the operation state, it is not necessary to perform control according to the operation state. And in this invention, since the said exhaust gas purification catalyst is employ | adopted, the combustion removal of the said particulate matter is possible even at the low temperature of less than 600 degreeC, and a rapid temperature rise can be suppressed.
Therefore, the configuration of the exhaust gas purification device having higher robustness can be achieved without using a complicated system.

In the exhaust gas purification apparatus, the filter regeneration means is preferably configured to perform the regeneration process with the temperature at a predetermined position within 10 to 20 mm from the upstream side of the exhaust gas purification filter as the regeneration temperature ( Claim 3).
As described above, the temperature at a predetermined position 10 to 20 mm from the upstream side of the exhaust gas purification filter, that is, the inside of the exhaust gas purification filter 10 to 20 mm from the exhaust gas inlet side in the axial direction of the exhaust gas purification filter By setting the regeneration temperature, it becomes easy to accurately determine the regeneration temperature.
The predetermined position for determining the regeneration temperature is preferably substantially the center in the direction perpendicular to the axial direction of the exhaust gas purification filter.
The temperature at a predetermined position within 10 to 20 mm from the upstream side in the exhaust gas purification filter can be measured by temperature detection means such as a thermistor or a thermocouple.

Next, it is preferable that the filter regeneration means is configured to perform combustion removal of the particulate matter by increasing the temperature of the exhaust gas flowing into the exhaust gas purification filter.
In this case, the temperature in the exhaust gas purification filter can be easily increased.
Specifically, for example, the temperature of the generated exhaust gas can be increased by burning fuel in the internal combustion engine based on the control by the filter regeneration means.
Further, for example, the operation of the heater disposed upstream of the exhaust gas purification filter can be controlled by the filter regeneration means, and the temperature of the exhaust gas flowing into the exhaust gas purification filter can be raised.

Further, it is preferable that an oxidation catalyst is disposed upstream of the exhaust gas purification filter.
In this case, harmful components such as carbon monoxide contained in the exhaust gas can be oxidized and rendered harmless. Further, the temperature of the exhaust gas flowing into the exhaust gas purification filter can be raised by the heat generated by the oxidation.

The filter regeneration means is preferably configured to perform the regeneration process when the amount of the particulate matter deposited in the exhaust gas purification filter reaches 4 g / L to 12 g / L. ).
That is, the exhaust gas purification filter has the exhaust gas purification catalyst, and the regeneration process is started in a state where a large amount of the particulate matter of 4 g / L to 12 g / L is deposited by the excellent catalytic action. However, rapid temperature rise can be suppressed. Therefore, even if the regeneration process is started in a state where a larger amount of particulate matter is accumulated than before, the temperature in the exhaust gas purification filter remains high enough to damage the exhaust gas purification filter (for example, about 900 ° C.). The rise can be prevented. Therefore, the frequency of the regeneration process can be reduced and the fuel consumption can be improved.
When the amount of accumulation during the regeneration process is less than 4 g / L, the frequency of the regeneration process increases, and fuel consumption may be reduced. On the other hand, when it exceeds 12 g / L, the combustion of the particulate matter proceeds by combustion propagation during the regeneration process, and the temperature rise may proceed rapidly. More preferably, 5 g / L to 10 g / L is good. In this case, it is possible to more reliably suppress the rapid temperature rise and prevent the exhaust gas purification filter from being melted.
The accumulation amount of the particulate matter can be calculated from the differential pressure between the axial ends of the exhaust gas purification filter, that is, the upstream end and the downstream end. However, since the value varies depending on the filter shape, it is preferable to grasp the relationship between the accumulation amount and the differential pressure in advance. The differential pressure between the upstream end and the downstream end of the exhaust gas purification filter can be measured with a differential pressure gauge.

Next, the exhaust gas purification filter will be described.
The exhaust gas purification filter includes a base material made of a porous body and an exhaust gas purification catalyst carried on the base material. The gas purification catalyst is obtained by calcining a mixture of zeolite and an alkali metal element source and / or an alkaline earth metal element source or sodalite at a temperature of 600 ° C. or higher.
When the firing temperature of the mixture or sodalite is less than 600 ° C., the durability of the exhaust gas purification catalyst may be deteriorated. As a result, the exhaust gas purification filter may not be used stably for a long period of time. More preferably, the firing temperature is 700 ° C. or higher, more preferably 800 ° C. or higher.
The firing temperature is the temperature of the mixture or sodalite itself, not the ambient temperature. Therefore, at the time of baking, baking is performed so that the temperature of the mixture or sodalite itself is 600 ° C. or higher. In firing, firing at the firing temperature is preferably performed for 1 hour or longer, more preferably 5 hours or longer, and even more preferably 10 hours or longer.

It is preferable that the exhaust gas purification catalyst in the exhaust gas purification filter is supported on the base material after the mixture or sodalite is baked at the temperature of 600 ° C. or higher.
In this case, the exhaust gas purification catalyst obtained after calcination can be pulverized. Since the powdery exhaust gas purification catalyst can be supported on the base material, the surface area of the surface on which the catalyst is supported in the exhaust gas purification filter can be increased. Therefore, the catalytic activity can be improved.
Therefore, it is preferable that the exhaust gas combustion catalyst is pulverized after the mixture or the sodalite is fired and before being supported on the substrate.
At the time of pulverization, it is preferable to adjust the median diameter of the exhaust gas purification catalyst to 50 μm or less. When the median diameter exceeds 50 μm, there is a possibility that clogging may occur or the carrying amount tends to vary when the substrate is coated with the exhaust gas purification catalyst. More preferably, the median diameter is 10 μm or less.
The median diameter of the exhaust gas purification catalyst can be measured by, for example, a laser diffraction / scattering particle size distribution measuring device or a scanning electron microscope.

  Moreover, when pulverizing, it is preferable that the temperature at the time of baking the said mixture or sodalite is 1200 degrees C or less. When the mixture or sodalite is baked at a temperature exceeding 1200 ° C., the exhaust gas-purifying catalyst may be in a lump with high hardness because it is once melted. As a result, in this case, it may be difficult to adjust the exhaust gas purification catalyst to a desired particle size by grinding as described above.

It is preferable that the exhaust gas purification catalyst in the exhaust gas purification filter is baked at a temperature of 600 ° C. or higher after the mixture or sodalite is supported on the base material.
In this case, generation of the exhaust gas purification catalyst obtained by firing the mixture or sodalite at a temperature of 600 ° C. or higher and supporting (baking) on the base material can be performed by one firing. In this case, firing at a high temperature exceeding 1200 ° C. is also possible. As described above, when the firing is performed at a high temperature exceeding 1200 ° C., the exhaust gas purification catalyst is once in a molten state and becomes a lump with high hardness. It shows the effect of promoting combustion against water and has excellent durability.

The exhaust gas purification catalyst can be directly supported on the base material. For example, there are the following methods for carrying directly.
That is, first, the base material is immersed in a slurry containing the exhaust gas purification catalyst and silica sol, and the exhaust gas purification catalyst is allowed to enter the base material. As the substrate, for example, a honeycomb-like or foam-like porous body can be adopted. Next, after excess slurry is blown off by air blow, baking is performed by heating at a temperature of 400 ° C. to 800 ° C., for example. Thereby, the exhaust gas purification catalyst can be directly brought into contact with and supported on the base material.
In this case, the porosity of the exhaust gas purification filter can be increased, and in particular, the combustion efficiency for PM can be improved.

Further, the exhaust gas purification catalyst can be supported on a support layer formed on the surface of the base material.
In this case, the exhaust gas purification catalyst is supported on the base material via the support layer, and the exhaust gas purification catalyst can be easily supported.
Specifically, a washcoat component containing alumina or the like and the exhaust gas purification catalyst are mixed to produce a sol-like or slurry-like composite material, and the composite material is coated on the base material, for example, at a temperature of 400 ° C. Heat at ~ 600 ° C. Thereby, a support layer is formed by the washcoat component, and the exhaust gas purification catalyst can be supported on the support layer.

The support layer is preferably made of one or more oxides selected from Al ₂ O ₃ , ZrO ₂ , TiO ₂ , CeO ₂ , and SiO ₂ .
In this case, the support layer having a large surface area is easily formed, and the surface area of the exhaust gas purification filter can be increased. As a result, the exhaust gas purification catalyst is easily brought into contact with particulate matter such as PM, and the exhaust gas purification filter can perform combustion removal of the particulate matter more efficiently.

As described above, the exhaust gas purification catalyst is obtained by calcining a mixture of zeolite, an alkali metal element source and / or an alkaline earth metal element source, or sodalite at a temperature of 600 ° C. or higher. Here, sodalite can also be used as the zeolite.
That is, the exhaust gas purification catalyst can be obtained by calcining a mixture of zeolite (including sodalite) and an alkali metal element source and / or an alkaline earth metal element source at a temperature of 600 ° C.,
The exhaust gas purification catalyst can also be obtained by burning sodalite at a temperature of 600 ° C. or higher without mixing it alone with other components.

Zeolite except sodalite generally the general formula _{M 2 / n O · Al 2} O 3 · ySiO 2 · zH 2 O ( where, M is at least one element selected Na, K, and from H, y In the present invention, the zeolite represented by the above general formula can also be employed. As the zeolite, for example, zeolite having a structure such as LTA type, FAU (Faujasite) type, MOR type, LTL type, FER type, MFI type, and BEA type can be adopted.
Further, sodalite the general formula _{3 (Na 2 O · Al 2} O 3 · 2SiO 2) represented by · 2NaX. X is an atom or atomic group that becomes a monovalent anion, and is, for example, a halogen such as F, Cl, Br, or I, or OH.

Moreover, it said zeolite is preferably SiO ₂ amount is less than 200 mol with respect to Al ₂ O ₃ 1 mol in the composition (claim 9).
_{That, SiO 2 / Al 2 O 3} ( molar ratio) is less than 200 zeolite in the zeolite composition, in other words further the general formula _{M 2 / n O · Al 2} O 3 · ySiO 2 · zH y in ₂ O It is preferable to employ zeolite whose value is y <200.
Zeolite having an SiO ₂ amount of 200 mol or more relative to 1 mol of Al ₂ O ₃ in the zeolite composition, that is, a zeolite having a y value of y ≧ 200 in the above general formula is called a so-called high silica zeolite. In such a case, the effect of improving the combustion promotion characteristics of the exhaust gas purification catalyst with respect to PM may be reduced.

As the zeolite in the mixture, sodalite is preferably employed (claim 10).
In this case, Na in sodalite and the alkali metal element in the alkali metal element source and / or the alkaline earth metal element in the alkaline earth metal element source are excellent for particulate matter such as PM. Combustion promoting characteristics can be exhibited.

Further, when sodalite is used as the zeolite, in the mixture, the total of the alkali metal element and the alkaline earth metal element contained in the alkali metal element source and / or the alkaline earth metal element source. The amount is preferably 2.25 mol or less with respect to 1 mol of Si element in the sodalite.
When the total amount of the alkali metal element and the alkaline earth metal element exceeds 2.25 mol with respect to 1 mol of Si element in sodalite, the mixture is easily melted during the firing of the mixture. . As a result, the exhaust gas purifying catalyst obtained after calcination may once go through a molten state, so that its hardness may be increased. Therefore, in this case, it may be difficult to adjust the exhaust gas purification catalyst to a desired particle size by pulverizing after firing. In this case, even if the catalytic activity of the exhaust gas purification catalyst itself is excellent, there is a possibility that it may be easily affected by moisture. That is, there is a possibility that the range of decrease in catalytic activity due to moisture becomes large. Therefore, it becomes difficult to maintain a predetermined catalytic activity for a long period of time, which may adversely affect the life of the exhaust gas purification filter.

More preferably, in the mixture, the total amount of the alkali metal element and the alkaline earth metal element contained in the alkali metal element source and / or the alkaline earth metal element source is the Si element 1 in the sodalite. It is good that it is 1 mol or less with respect to mol (Claim 12).
More preferably, in the mixture, the total amount of the alkali metal element and the alkaline earth metal element contained in the alkali metal element source and / or the alkaline earth metal element source is the Si element 1 in the sodalite. It is good that it is 0.5 mol or less with respect to mol.

In the case where a zeolite other than sodalite is used as the zeolite, in the mixture, an alkali metal element and an alkaline earth metal element contained in the alkali metal element source and / or the alkaline earth metal element source Is preferably 0.1 mol or more and 2.0 mol or less with respect to 1 mol of Si element in the zeolite.
When the total amount of the alkali metal element and the alkaline earth metal element with respect to 1 mol of Si element in the zeolite is less than 0.1 mol, the water resistance of the exhaust gas purification catalyst may be deteriorated.
On the other hand, when the amount exceeds 2.0 mol, the combustion promotion characteristics of the exhaust gas purifying catalyst in the presence of moisture are likely to be lowered, and the reduction width may be very large. In this case, the mixture is easily melted during the firing of the mixture. Therefore, since the exhaust gas purification catalyst obtained after the firing may be once in a molten state, its hardness may be increased. As a result, in this case, it may be difficult to adjust the exhaust gas purification catalyst to a desired particle size by pulverizing after firing.

  More preferably, in the mixture, the total amount of the alkali metal element and the alkaline earth metal element contained in the alkali metal element source and / or the alkaline earth metal element source is the Si element in the aluminosilicate. It is good that it is 0.2 mol or more and 1.5 mol or less with respect to 1 mol.

  The total amount of the above-mentioned alkali metal element and alkaline earth metal element is the total amount of the alkali metal element in the alkali metal element source mixed with the zeolite and the alkaline earth metal element in the alkaline earth metal element source. When only one of the alkali metal element source and the alkaline earth metal element source is used, the amount of the other element can be calculated as 0 mol. When a plurality of alkali metal element sources and a plurality of alkaline earth metal element sources are used, the total amount can be calculated.

Examples of the alkali metal element source include an alkali metal compound. Examples of the alkaline earth metal element source include alkaline earth metal compounds.
The mixture preferably contains at least the alkali metal element source (claim 14).
In this case, the combustion promotion characteristics of the exhaust gas purification catalyst with respect to particulate matter such as PM can be further improved.

The alkali metal element source contains one or more selected from Na, K, Rb, and Cs, and the alkaline earth metal element source contains one or more selected from Mg, Ca, Sr, and Ba. (Claim 15).
Also in this case, the combustion promotion characteristics of the exhaust gas purification catalyst with respect to particulate matter such as PM can be further improved.
More preferably, when sodalite is used as the zeolite, a compound containing Ca, Sr or Ba is preferably used as the alkaline earth metal element source, and when a zeolite other than sodalite is used. It is preferable to use a compound containing Ba as the alkaline earth metal element source.

The alkaline earth metal element source preferably contains at least Ba.
In this case, the combustion promotion characteristics of the exhaust gas purifying catalyst can be further improved as compared with the case where the alkaline earth metal element source containing an alkaline earth metal element other than Ba is used.

A mixture of the zeolite and the alkali metal element source and / or the alkaline earth metal element source is prepared by mixing the zeolite and the alkali metal element source and / or the alkaline earth metal element source in a polar solvent, It preferably comprises a solid content obtained by evaporating the polar solvent.
In this case, the zeolite and the alkali metal element source and / or the alkaline earth metal element source can be easily mixed, and the mixture in which these are uniformly mixed can be obtained. Therefore, it is possible to suppress the occurrence of uneven catalytic activity in the exhaust gas purification catalyst obtained after firing.
As said polar solvent, alcohol, such as methanol and ethanol, water, etc. can be used, for example. Moreover, these mixed solvents can be used.
In addition, as the polar solvent, it is preferable to use a solvent that easily volatilizes.
In this case, drying after mixing can be performed easily.

The alkali metal element source and / or the alkaline earth metal element source is preferably a carbonate, sulfate, phosphate, nitrate, organic acid salt, halide, oxide, or hydroxide. Item 16).
In this case, since the alkali metal element source and / or the alkaline earth metal element source can be easily mixed in a polar solvent such as water, the alkali metal element source and / or By mixing the alkaline earth metal element source and zeolite in the polar solvent, the mixture in which these are uniformly dispersed can be easily obtained.

More preferably, an alkali metal salt is used as the alkali metal element source, and an alkaline earth metal element salt is used as the alkaline earth metal element source.
In this case, since the alkali metal element source and the alkaline earth metal element source can be dissolved with excellent solubility in polar solvents such as water, the alkali metal element source and / or the alkaline earth metal When the element source and the zeolite are mixed in a polar solvent such as water, the zeolite and the alkali metal element source and / or the alkaline earth metal element source can be easily and uniformly mixed.

The base material is composed of a porous base material in which porous partition walls are arranged in a polygonal lattice to form a large number of cells extending in the axial direction, and the cells preferably form an exhaust gas flow path. Item 18).
In this case, the exhaust gas purification filter can have an optimum structure for purifying exhaust gas.
In addition, a structure in which all the cells are open on both end faces can be used, but some cells open on both end faces of the substrate (honeycomb structure), and the remaining cells are plug portions formed on both end faces. It is also possible to use a structure closed by.
When a structure in which all the cells are opened at both end faces is used, it becomes suitable for an exhaust gas purification filter for a gasoline engine. On the other hand, when a structure in which some cells are open at both end faces and the remaining cells are closed by plugs is used, it is suitable for an exhaust gas purification filter for a diesel engine.

The substrate is preferably made of cordierite or SiC.
In this case, the exhaust gas purification filter can be optimized for exhaust gas purification.

Example 1
Next, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the exhaust gas purification apparatus 1 of the present example includes an exhaust gas purification filter 2 and a filter regeneration unit 151. The exhaust gas purification filter 2 is provided in the exhaust gas passages 54 and 19 of the internal combustion engine 5 and collects particulate matter contained in the exhaust gas.
As shown in FIGS. 2 to 4, the exhaust gas purification filter 11 includes a base material 20 made of a porous body and an exhaust gas purification catalyst 4 carried thereon. The exhaust gas purification catalyst 4 is formed by calcining a mixture of zeolite and an alkali metal element source and / or an alkaline earth metal element source or sodalite at a temperature of 600 ° C. or higher.
Further, as shown in FIG. 1, the filter regeneration means 151 raises the temperature in the exhaust gas purification filter 2 to a predetermined regeneration temperature and burns and removes the particulate matter deposited in the exhaust gas purification filter 2, thereby purifying the exhaust gas. The collection process of the filter 2 is performed.

Hereinafter, the exhaust gas purifying apparatus of this example will be described in more detail.
As shown in FIGS. 2 and 3, in the exhaust gas purification filter 2, the exhaust gas purification catalyst 4 is supported on a honeycomb-shaped substrate 20. In this example, the base material 20 includes an outer peripheral wall 21, partition walls 25 provided in a honeycomb shape inside the outer peripheral wall 21, and a plurality of cells 3 partitioned by the partition walls 25. The cell 3 is partially open at both end faces 23 and 24 of the base material 20. That is, each cell 3 is opened on one end surface 23 (24) of the base material 20, and is closed by the plug portion 32 formed on the other end surface 24 (23).

As shown in FIGS. 2 and 3, in this example, the openings 31 and the plugs 32 on the both end faces 23 (24) of the cell 3 are alternately arranged to form a so-called checkered pattern.
As shown in FIG. 5, in the exhaust gas purification filter 2 of this example, the end portions of the cells located on the upstream end surface 23 serving as the inlet side of the exhaust gas 10 and the downstream end surface 24 serving as the outlet of the exhaust gas 10 are plugged portions 32. Are alternately arranged and non-arranged portions. A large number of pores are formed in the partition wall 25 of the porous body so that the exhaust gas 10 can pass therethrough.
As shown in FIGS. 2 to 5, the exhaust gas purification catalyst 4 is supported on the partition wall 25 of the base material 20. In this example, as the exhaust gas purification catalyst 4, a catalyst obtained by calcining a mixture of sodalite and K source (potassium carbonate) at a temperature of 800 ° C is employed.

The overall size of the exhaust gas purification filter 2 of this example is a cylindrical shape having a diameter of 129 mm, a length of 150 mm, and a volume of about 2 L, and the cell size is a cell thickness of 3 mm and a cell pitch of 1.47 mm.
The substrate 20 is made of cordierite, and the cell 3 has a quadrangular cross section (see FIG. 2). In addition, the cell 3 can employ various cross-sectional shapes such as a triangle and a hexagon.

The exhaust gas purification filter of this example can be manufactured as follows.
That is, first, powder of sodalite (3 (Na ₂ O · Al ₂ O ₃ · 2SiO ₂ ) · 2NaOH) was prepared. 100 parts by weight of this sodalite and 5 parts by weight of potassium carbonate were put into water and mixed in water.
Subsequently, the liquid mixture was heated at a temperature of 120 ° C. to evaporate water. Thereby, solid content (mixture of sodalite and potassium carbonate) was obtained.
Next, this solid content was baked at a temperature of 700 ° C. Specifically, the solid content was heated at a heating rate of 100 ° C./hour, and when the temperature reached 700 ° C. (calcination temperature), the solid content was held for 10 hours to perform firing.
Next, the obtained fired product was pulverized to a median diameter of 10 μm or less and a maximum particle diameter of 100 μm or less to obtain an exhaust gas purification catalyst.

Next, a substrate having a honeycomb structure was produced as follows.
That is, first, talc, fused silica, and aluminum hydroxide were weighed so as to have a desired cordierite composition, a pore-forming agent, a binder, water, and the like were added and mixed and stirred in a mixer. The obtained clay-like ceramic material was extrusion-molded with a molding machine to obtain a honeycomb-shaped molded body. After drying this, it is cut into a desired length, and has an outer peripheral wall, a partition wall provided in the form of a honeycomb inside, and a plurality of cells partitioned by the partition wall and penetrating through both end faces. A molded body was produced. Next, this formed body was calcined by heating at a temperature of 1400 to 1450 ° C. for 2 to 10 hours to obtain a calcined body (honeycomb structure).

  Next, a masking tape was applied so as to cover the entire both end faces of the honeycomb structure. Then, laser light was sequentially irradiated to the masking tape corresponding to the positions to be plugged on both end faces of the ceramic honeycomb structure, and the masking tape was melted or incinerated to form through holes. Thereby, the through-hole was formed in the part which should be plugged with the plug part in the edge part of a cell. The other part of the end of the cell is covered with masking tape. In this example, the through holes were formed in the masking tape so that the through holes and the portions covered with the masking tape were alternately arranged on both end faces of the cell. In this example, a resin film having a thickness of 0.1 mm was used as the masking tape.

  Next, talc, fused silica, alumina, and aluminum hydroxide, which are the main ingredients of the plug material that is the material of the plug part, are weighed to the desired composition, added with binder, water, etc., and mixed in a mixer The mixture was stirred to prepare a slurry-like plug material. At this time, a pore former may be added as necessary. And after preparing the container which put the slurry-like plug material, the end surface of the honeycomb structure in which the through-hole was partially formed was immersed. Thus, an appropriate amount of plug material was infiltrated into the end portion of the cell from the through hole of the masking tape. The same process was performed on the other end face of the honeycomb structure. In this way, a honeycomb structure in which the plug material was arranged in the opening of the cell to be plugged was obtained.

  Next, the honeycomb structure and the plug material disposed in the portion to be plugged were simultaneously fired at about 1400 to 1450 ° C. As a result, the masking tape is removed by incineration. As shown in FIGS. 2 and 3, a plurality of openings 31 that open the ends of the cells 3 and a plurality of plugs that close the ends of the cells 3 are formed at both ends of the cells 3. Thus, a ceramic honeycomb structure (base material) 20 formed with 32 was prepared.

Next, the exhaust gas purification catalyst was mixed with silica slurry containing 5 wt% silica sol. Further, water was added so that the water content was 400 parts by weight with respect to 100 parts by weight of the solid content to obtain a slurry-like exhaust gas purification catalyst.
Next, the base material 2 was immersed in a slurry-like exhaust gas purification catalyst, and the porous partition walls 25 of the base material 2 were impregnated with the exhaust gas purification catalyst. Next, after excess water was blown off by air blow, baking was performed by heating at a temperature of 500 ° C. In this example, the exhaust gas purification catalyst was coated at 70 g / L (of which the K concentration was about 7 g / L in terms of K ₂ CO ₃ ).
In this way, as shown in FIGS. 2 to 4, an exhaust gas purification filter 2 in which the exhaust gas purification catalyst 4 was carried on the base material 20 was obtained.

In FIG. 1, the schematic diagram of the engine system containing the exhaust gas purification apparatus 1 is shown.
As shown in the figure, the exhaust gas purification filter 2 is used to remove particulates in the exhaust gas discharged from the internal combustion engine 5 (diesel engine).
In a diesel engine vehicle, an intake pipe 52 is connected to an intake port of the engine 5 via an intake manifold 51. In addition, an exhaust pipe 54 is connected to the exhaust port via an exhaust manifold 53, thereby forming an exhaust passage.

The intake pipe 52 is provided with a compressor 521 of a turbocharger 55 provided with a supercharging pressure control means, and an intercooler 522 that cools the intake air compressed by the turbocharger 55.
The exhaust pipe 54 is provided with a turbine 541 of the turbocharger 55.
In the turbocharger 55, the rotor blades (not shown) of the compressor 521 and the rotor blades (not shown) of the turbine 541 are connected by a shaft (not shown), and the turbine 541 is driven by the energy of exhaust gas discharged from the engine. The compressor 521 is configured to rotate and further rotate through a shaft. The intake air in the intake pipe 52 is compressed by the rotation of the compressor 521.

In the middle of the exhaust pipe 54, an oxidation catalyst filter 11 and an exhaust gas purification filter (DPF) 2 are provided in order from the engine side (upstream side of exhaust gas). The oxidation catalyst filter 11 may function not only as an oxidation catalyst but also as a NO _x catalyst. In the oxidation catalyst filter 11, an oxidation catalyst made of a platinum-alumina catalyst or the like is supported on a honeycomb base material made of cordierite.
The oxidation catalyst filter 11 and the exhaust gas purification filter 2 are accommodated in a cylindrical collector 19 in which the diameter of the exhaust pipe 54 is enlarged.
In the collector 19, thermistors 157, 158, 159 as temperature detecting means are arranged upstream of the oxidation catalyst filter, between the oxidation catalyst filter and the exhaust gas purification filter, and downstream of the exhaust gas purification filter, respectively. . Each thermistor 157, 158, 159 can detect the exhaust gas temperature on the inlet side to the oxidation catalyst filter, the exhaust gas temperature on the inlet side of the exhaust gas purification filter, and the exhaust gas temperature on the outlet side of the exhaust gas purification filter, respectively.
The temperature data detected by the thermistors 157, 158, and 159 is sent to an engine control unit (ECU) 15 and used for various controls by the ECU 15.

  Further, the engine 5 is provided with an EGR (Exhaust Gas Recirculation) control valve 56 for recirculating exhaust gas to intake air. Further, an EGR cooler 57 that cools the exhaust gas when the exhaust gas is turned to intake air again is attached.

Air is supplied to the internal combustion engine 5 from the intake pipe 52 through the intake manifold 51. The internal combustion engine 5 is supplied with fuel from a fuel addition valve 50 of a fuel supply system (not shown) including a common rail and a fuel injection device. In the internal combustion engine 5, fuel and air are mixed at a predetermined mixing ratio, and this mixed fuel is combusted by compression ignition.
The exhaust gas after combustion is sent to the exhaust pipe 54 through the exhaust manifold 53. The exhaust gas is oxidized by the oxidation catalyst carried on the oxidation catalyst filter 11 in the collector, and particulate matter such as PM is adsorbed and removed in the exhaust gas purification filter and discharged to the outside.
The ECU 15 collects various operation data such as the output of the over-absorption pressure sensor, the output of the inflow air amount sensor, the engine speed, and the vehicle speed, and controls the fuel addition valve 50, the EGR control valve 56, and the like based on these data. Is configured to do.

When particulate matter accumulates on the exhaust gas purification filter 2, the exhaust resistance increases. In order to avoid this, by controlling the filter regeneration means 151, the temperature in the exhaust gas purification filter 2 is raised to a predetermined regeneration temperature to remove particulate matter such as PM deposited in the exhaust gas purification filter 2 by combustion. Then, the regeneration process of the exhaust gas purification filter 2 is performed.
Specifically, the filter regeneration means 151 increases the temperature of the exhaust gas flowing into the exhaust gas purification filter 2 at a predetermined timing, thereby raising the temperature of the exhaust gas purification filter 2 to the regeneration temperature and performing regeneration processing. In this example, the filter regeneration means 151 is incorporated in the ECU 15 that controls combustion injection control and the like.

  In this example, the filter regeneration means 151 transmits a control signal P for controlling the fuel addition valve 50 and the like at a predetermined timing, and starts combustion of fuel in the internal combustion engine. Thereby, the temperature of the exhaust gas flowing into the exhaust gas purification filter 2 can be raised and the regeneration process can be started. Further, the filter regeneration means 151 is configured to stop the combustion of fuel with a control signal Q for stopping the addition of fuel after reaching a predetermined regeneration temperature. Once the regeneration temperature is reached, the combustion of the particulate matter proceeds in the exhaust gas purification filter because the combustion of the particulate matter proceeds by combustion propagation.

  The exhaust gas purification filter 2 is provided with a differential pressure gauge 155 that measures the differential pressure between its upstream end and downstream end. The filter control means 151 receives the differential pressure measured by the differential pressure gauge 155 as a detection signal R, and deposits particulate matter (soot) such as PM deposited in the exhaust gas purification filter 2 based on the detection signal R. The amount is calculated, and the regeneration process is performed when the deposition amount becomes, for example, 5 to 12 g / L. FIG. 6 shows the relationship between the differential pressure and the deposition amount.

  A thermistor 158 that measures the temperature of the exhaust gas flowing into the exhaust gas purification filter is provided between the oxidation catalyst filter 19 and the exhaust gas purification filter, that is, immediately upstream of the exhaust gas purification filter 2. The filter regeneration means 151 receives the temperature of the exhaust gas measured by the thermistor 158 as a detection signal S, and on the basis of the detection signal S, the inside of the exhaust gas purification filter 2 is 10 to 20 mm (in the direction perpendicular to the axial direction). The temperature at a predetermined position in the center is calculated. The filter regeneration means 151 performs the regeneration process by raising the temperature at the predetermined position to 400 ° C. or more and less than 600 ° C.

Hereinafter, the effect of this example will be described.
In this example, as shown in FIGS. 2 to 5, the exhaust gas purification filter 2 includes a base material 20 and an exhaust gas purification catalyst 4, and the exhaust gas purification catalyst 4 includes zeolite, an alkali metal element source, and / or alkaline earth. A mixture with a metal element source or sodalite is fired at a temperature of 600 ° C. or higher.
The exhaust gas purification catalyst 4 has an excellent combustion accelerating action on particulate matter such as particulate matter (PM) (see experimental examples described later). Therefore, in the exhaust gas purification filter 2, the particulate matter can be burned and removed at a low temperature of, for example, less than 600 ° C. by the action of the exhaust gas purification catalyst 4. Therefore, the regeneration temperature of the exhaust gas purification filter 2 can be set low.

Moreover, in the exhaust gas purification filter 2 provided with the exhaust gas purification catalyst 4, rapid temperature rise is suppressed.
That is, in a conventional exhaust gas purification filter equipped with a noble metal catalyst such as Pt, for example, when the operating state of the internal combustion engine is decelerated, a rapid temperature rise occurs and the temperature in the exhaust gas purification filter is at least partially For example, there is a risk of reaching a high temperature exceeding 1000 ° C. As a result, the base material of the exhaust gas purification filter may be melted.
On the other hand, in the exhaust gas purification filter 2 provided with the exhaust gas purification catalyst 4 obtained by calcining the mixture or sodalite at a temperature of 600 ° C. or higher, the temperature rise is higher than that in which a noble metal catalyst such as Pt is supported. It becomes gentle and does not easily reach a high temperature that causes damage such as melting damage to the base material 20. Even when the operating state of the internal combustion engine is in a decelerating state during the regeneration process, the rapid temperature rise in the exhaust gas purification filter 2 can be suppressed.
Therefore, according to the present invention, rapid temperature rise can be suppressed without performing complicated system control as in the prior art.

Further, the rapid temperature rise tends to depend on the start temperature of the regeneration process, that is, the regeneration temperature. That is, when the regeneration temperature is set high, the rapid temperature rise during the regeneration process easily reaches a higher temperature.
For example, when a conventional noble metal catalyst is used, it is necessary to set the regeneration temperature to about 630 ° C. in order to surely burn PM. At such a high regeneration temperature, a rapid temperature rise occurs and the exhaust gas purification filter is used. There was a possibility that the temperature of would rise to a high temperature (for example, 900 ° C. or higher) that damages the substrate.
On the other hand, when the exhaust gas purification catalyst 4 is used, even if the regeneration temperature is about 630 ° C., it is possible to prevent the temperature from rapidly rising to a temperature that damages the base material 20 during the regeneration process. Further, when the exhaust gas purification catalyst 4 is used as described above, the particulate matter such as PM can be combusted even at a low temperature of less than 600 ° C. Therefore, the regeneration temperature can be set to less than 600 ° C., the rapid temperature rise can be suppressed more reliably, and the above-mentioned melting damage can be prevented.

Also, the rapid temperature rise tends to depend on the amount of particulate matter such as PM deposited. That is, as the amount of the particulate matter deposited in the exhaust gas purification filter 2 at the start of the regeneration process increases, the temperature rises more easily even from a lower regeneration temperature, causing damage to the substrate 20. It tends to reach high temperatures.
When a conventional noble metal catalyst such as Pt is used, there is a possibility that a rapid temperature rise may occur even if regeneration processing is performed in a state where the amount of PM deposited is about 6 g / L. For this reason, it is necessary to set the PM deposition amount for starting the regeneration process to 5 g / L or less, more preferably 4 g / L or less.
On the other hand, in the present example, since the exhaust gas purification catalyst 4 is used, the regeneration temperature is set to, for example, less than 600 ° C. even if the regeneration process is performed in a state where the PM deposition amount is 12 g / L, for example. Thus, rapid temperature rise can be suppressed.
Therefore, the frequency of performing the regeneration process can be reduced, and fuel consumption can be reduced.

Further, the exhaust gas purification catalyst 4 has a high holding power for alkali metal elements and / or alkaline earth metal elements.
Therefore, it is possible to prevent the alkali metal element and / or the alkaline earth metal element from eluting even in the presence of moisture. Therefore, the performance deterioration of the exhaust gas purification catalyst 4 can be prevented, and the exhaust gas purification filter 2 can stably purify the exhaust gas for a long period of time.
Further, the exhaust gas purifying catalyst 4 can also adsorb NO _x. Therefore, the exhaust gas purification filter 2 can also adsorb and remove NO _x from the exhaust gas.

  In this example, the filter regeneration means 151 is configured to start the regeneration process by raising the temperature in the exhaust gas purification filter 2 to a regeneration temperature of 400 ° C. or higher and lower than 600 ° C. Therefore, the rapid temperature rise can be further suppressed. In this case, since the amount of particulate matter such as PM deposited at the start of the regeneration process can be increased, the frequency of the regeneration process can be further reduced. The exhaust gas purification catalyst 4 can burn the particulate matter in a short time even at a low regeneration temperature of less than 600 ° C. as described above due to its excellent combustion promoting action.

Further, the filter regeneration means 151 can be configured to perform the regeneration process at a regeneration temperature of always less than 600 ° C. regardless of the operating state of the internal combustion engine 5.
In this case, the rapid temperature rise can be more reliably suppressed regardless of the operating state. And the structure of the said exhaust gas purification apparatus with higher robustness is attained, without using a complicated system.

  The filter regeneration means 151 is configured to perform combustion removal of the particulate matter by increasing the temperature of the exhaust gas flowing into the exhaust gas purification filter. Therefore, the temperature in the exhaust gas purification filter 2 can be easily raised.

An oxidation catalyst is disposed upstream of the exhaust gas purification filter 2.
In this case, harmful components such as carbon monoxide contained in the exhaust gas can be oxidized and rendered harmless. Further, the temperature of the exhaust gas flowing into the exhaust gas purification filter can be raised by the heat generated by the oxidation.

The filter regeneration means 151 is configured to perform the regeneration process when the amount of the particulate matter accumulated in the exhaust gas purification filter reaches 4 g / L to 12 g / L.
Therefore, the frequency of the reproduction process can be reduced. And even if the regeneration frequency is reduced in this way, it is possible to suppress the exhaust gas purification filter from reaching a high temperature exceeding, for example, 900 ° C. due to the rapid temperature rise due to the action of the exhaust gas purification catalyst. .

  As described above, according to this example, there is provided an exhaust gas purification apparatus that can reduce the frequency of regeneration processing and can suppress a rapid temperature rise in the exhaust gas purification filter without using complicated system control. be able to.

(Example 2)
This example is an example of examining the rapid temperature rise in the exhaust gas purification filter when the operating state of the engine is set to the deceleration state (idle state) during the regeneration process for the exhaust gas purification device having the same configuration as that of the first embodiment. .
As shown in FIG. 7, the exhaust gas purifying apparatus (apparatus E) of this example has the same configuration as that of the first embodiment. Furthermore, in this example, in order to detect temperatures at various positions in the exhaust gas purification filter 2, thermocouples having a sheath diameter of φ0.5 mm are arranged at six positions in the exhaust gas purification filter 2.

FIG. 8 shows the position of the thermocouple. The left side of FIG. 8 is a view of the oxidation catalyst filter 11 and the exhaust gas purification filter 2 disposed in the collector 19 as viewed from the side of the exhaust gas purification filter 2, that is, from the direction perpendicular to the axial direction of the exhaust gas purification filter 2. The positions of the thermocouples arranged in the exhaust gas purification filter 2 are indicated by black circles. Further, the right side of FIG. 8 is a view of the exhaust gas purification filter 2 as viewed from the axial downstream end 24 side, and the position of the thermocouple is indicated by black circles.
As shown in FIG. 8, the first thermocouple A153a is 10 mm from the exhaust gas inlet side of the exhaust gas purification filter 2 (10 mm from the upstream end 23 side of the exhaust gas purification filter 2; a = 10 mm), and has a shaft. It was arranged at the center position in the direction perpendicular to the direction. The second thermocouple B153b was disposed at the center position in the axial direction of the exhaust gas purification filter 2 and at the center position in the direction perpendicular to the axial direction. The third thermocouple C153c is located 10 mm from the exhaust gas outlet side of the exhaust gas purification filter 2 (10 mm from the downstream end 24 side of the exhaust gas purification filter 2; b = 10 mm), and in a direction perpendicular to the axial direction. Arranged in the center position. The fourth thermocouple D153d is 10 mm from the exhaust gas outlet side of the exhaust gas purification filter 2 (10 mm from the downstream end 24 side of the exhaust gas purification filter; b = 10 mm), and is the center in the direction perpendicular to the axial direction. It was arranged 16.25 mm (c = 16.25 mm) outward from the position. The fifth thermocouple E153e is 10 mm from the exhaust gas outlet side of the exhaust gas purification filter 2 (10 mm from the downstream end 24 side of the exhaust gas purification filter; b = 10 mm), and is the center in the direction perpendicular to the axial direction. It was placed 32.5 mm (d = 16.25, c + d = 32.5 mm) outward from the position. The sixth thermocouple F153f is 10 mm from the exhaust gas outlet side of the exhaust gas purification filter 2 (10 mm (b = 10 mm) from the downstream end 24 side of the exhaust gas purification filter 2), and is perpendicular to the axial direction. 48.75 mm (e = 16.25, c + d + e = 48.75 mm).
Each thermocouple A to F is connected to a temperature recording means (data logger) 152 via a conducting wire 150 (see FIG. 7). The temperature recording means 152 can record the temperature at each position in the exhaust gas purification filter 2 over time.

  As shown in FIG. 7, in the same engine (four-cylinder diesel engine) system as in Example 1, PM was deposited up to 8 g / L in the exhaust gas purification filter 2 to perform a regeneration process. The regeneration process is controlled by the filter regeneration means 151. The control pattern of the fuel addition and stop timing in the regeneration process, the engine rotation speed, the intake air amount, and the temperature of the exhaust gas purification filter at 10 mm from the inlet (the temperature detected by the thermocouple A153a (see FIG. 8)). 9 shows.

As shown in the figure, PM was deposited in the exhaust gas purification filter under the conditions of engine speed: 2000 rpm, qfin: 19, and exhaust gas temperature: 300 ° C. (PM deposition mode). When the PM accumulation amount reaches 8 g / L (time t ₀ ), as shown in FIG. 7, the fuel is combusted in the internal combustion engine 5 in the exhaust gas purification filter 2 based on the control of the filter regeneration means 151. By increasing the temperature of the inflowing exhaust gas, a regeneration process for burning the PM accumulated in the exhaust gas purification filter 2 is started, and the temperature at a position 10 mm from the inlet of the exhaust gas purification filter 2 becomes a predetermined temperature (629 ° C.). At the time of arrival (time t ₁ ), fuel combustion was stopped (forced regeneration mode). The forced regeneration mode was performed under the conditions of engine speed: 2000 rpm, qfin: 23, exhaust gas temperature (upper limit): 629 ° C. The time from t ₀ to t ₁ in the forced regeneration mode is about 40 to 50 seconds (see FIG. 9).
Further, in this example, the engine is set in an idling state after time t ₁ and the idling state is continued for 10 minutes (deceleration operation mode).
At this time, the temperature change over time detected by the thermocouples A to F provided at the predetermined positions in the exhaust gas purification filter 2 was measured and recorded by the temperature recording means 152 (FIGS. 7 and 8). reference). The result is shown in FIG.

Moreover, in this example, the rapid temperature rise was examined using the exhaust gas purification apparatus provided with the exhaust gas purification filter which carry | supported the Pt catalyst as a comparison.
That is, first, an exhaust gas purification filter carrying a Pt catalyst was produced. This exhaust gas purification filter can be produced in the same manner as the exhaust gas purification filter of Example 1, except that Pt is supported on a substrate instead of the exhaust gas purification catalyst of Example 1. And the exhaust gas purification apparatus (apparatus C) similar to the above-mentioned apparatus E was comprised using this exhaust gas purification filter for a comparison.

  As for the exhaust gas purifying apparatus (apparatus C) for comparison, as with the apparatus E, thermocouples A to F are arranged at six locations in the exhaust gas purifying filter. The PM deposition mode, forced regeneration mode, and deceleration operation mode were also performed for the device C, and the temperature change over time detected by the thermocouples A to F provided at the predetermined positions in the exhaust gas purification filter was measured. In the apparatus C, the PM deposition amount in the PM deposition mode was 6 g / L, and the start temperature in the forced regeneration mode was 623 ° C. The result is shown in FIG.

  As is known from FIG. 11, in the apparatus C, the regeneration process was started at a PM deposition amount of 6 g / L. However, when the apparatus C was in an idling state, a rapid temperature rise occurred, and the temperature near the outlet side of the exhaust gas purification filter ( The temperature at the position where the thermocouples D to F were provided) was in a high temperature state exceeding 1000 ° C. Since the exhaust gas purification filter may melt in a high temperature region of 900 ° C. or higher, the limit value of the PM deposition amount (SOOT MASS LIMIT; SML) is less than 6 g / L in the apparatus C, and the regeneration process is frequently performed. Is required.

In the exhaust gas purification filter of the apparatus C, the combustion of PM (carbon) proceeds in the following two-stage reaction, and the Pt catalyst promotes these two-stage reactions.
(1) 2C + O ₂ → 2CO 2 × 26.4 kcal (solid-gas reaction)
(2) 2CO + O ₂ → 2CO ₂ 2 × 67.7 kcal (gas phase reaction)
That is, in the apparatus C, since the oxidation exothermic part of CO in the gas phase reaction is added, it is considered that the temperature reaches a high temperature exceeding 1000 ° C.

On the other hand, as is known from FIG. 10, in the apparatus E, the regeneration process was started at the PM accumulation amount of 8 g / L. It was below 750 ° C at the maximum. Therefore, SML exceeds 8 g / L, and the frequency of the reproduction process can be reduced.
In the apparatus E, the exhaust gas purifying catalyst supported on the exhaust gas purifying filter does not promote the gas phase reaction, that is, the oxidation of CO among the above-described two-stage reactions. For this reason, it is possible to prevent an abnormally high temperature exceeding 1000 ° C. and prevent melting.

In addition, for the device E, the condition for performing the forced regeneration mode is the time when the PM accumulation amount reaches 6 g / L or 10 g / L, and the relationship between the regeneration temperature and the maximum temperature in the exhaust gas purification filter (DPF) at this time I investigated. The result is shown in FIG.
FIG. 12 also shows the relationship between the regeneration temperature and the maximum temperature in the DPF for the device C (the forced regeneration mode is performed when the PM deposition amount is 6 g / L).

  As can be seen from FIG. 12, in the apparatus E, when the PM deposition amount is 6 g / L, the maximum temperature in the exhaust gas purification filter does not reach 900 ° C. even if the regeneration temperature is about 635 ° C. In the apparatus E, when the PM deposition amount is 10 g / L, the maximum temperature in the exhaust gas purification filter reaches 900 ° C. when the regeneration temperature reaches 616 ° C. Therefore, it can be seen that by setting the regeneration temperature to less than 616 ° C., the exhaust gas purification filter can be prevented from being melted even if the PM deposition amount during regeneration is 10 g / L. Since the exhaust gas purification catalyst carried on the exhaust gas purification filter of the device E can burn PM even at a temperature of 600 ° C. or less, even if the PM accumulation amount at the time of regeneration is 12 g / L, the exhaust gas purification filter can be prevented from being damaged. It is considered possible. Therefore, the frequency of the reproduction process can be reduced.

  On the other hand, in the apparatus C, when the PM deposition amount is 6 g / L, even if the regeneration temperature is 597 ° C., the maximum temperature in the exhaust gas purification filter reaches 900 ° C., and there is a risk of melting damage. Moreover, if the temperature is less than 600 ° C., the Pt catalyst cannot sufficiently exhibit the combustion promoting effect on PM. Therefore, in the apparatus C, in order to surely burn PM without causing melting damage, it is necessary to reduce the PM deposition amount when performing the regeneration process to 5 g / L or less, more preferably 4 g / L or less. There is. As a result, the frequency of the regeneration process increases, and problems such as a reduction in fuel consumption can occur.

  As described above, the exhaust gas purifying apparatus (apparatus E) according to the embodiment of the present invention can reduce the frequency of regeneration processing and suppress a rapid temperature rise in the exhaust gas purifying filter without using complicated system control. can do.

(Experimental example 1)
In this example, the catalytic action of the exhaust gas purification catalyst used in the exhaust gas purification apparatuses of Examples 1 and 2 is examined.
The exhaust gas purification catalyst is obtained by calcining a mixture of zeolite and an alkali metal element source and / or an alkaline earth metal element source or sodalite at a temperature of 600 ° C. or higher.
In this example, as in Examples 1 and 2, sodalite is used as a zeolite, and an example using a mixture obtained by mixing sodalite with an alkali metal element source and / or an alkaline earth metal element source will be described.

Specifically, first, as the zeolite as a starting material was prepared powder of sodalite _{(3 (Na 2 O · Al} 2 O 3 · 2SiO 2) · 2NaOH). 100 parts by weight of this sodalite and 5 parts by weight of potassium carbonate were put into water and mixed in water.
Subsequently, the liquid mixture was heated at a temperature of 120 ° C. to evaporate water. Thereby, solid content (mixture of sodalite and potassium carbonate) was obtained.
Next, this solid content was baked at a temperature of 800 ° C. Specifically, the solid content was heated at a rate of temperature increase of 100 ° C./hour, and when the temperature reached 800 ° C. (calcination temperature), the solid content was maintained for 10 hours.
Next, the obtained fired product was pulverized to a median diameter of 10 μm or less and a maximum particle diameter of 100 μm or less to obtain an exhaust gas purification catalyst. This is designated as Sample E1.

  Next, the combustion promotion characteristic with respect to PM was investigated about the exhaust gas purification catalyst (sample E1) produced in this example. For comparison, combustion promotion characteristics were also examined for a noble metal catalyst (Pt powder) and potassium carbonate powder.

  Specifically, first, 200 mg of catalyst species (sample E1, noble metal catalyst, or potassium carbonate powder) and 20 mg of carbon black (CB; used as an alternative to PM) were each weighed accurately with an electronic balance. These were mixed for a certain period of time using an agate mortar so that the catalyst species (weight): CB (weight) = 10: 1, and three types of evaluation samples containing each catalyst species and carbon black were obtained. Furthermore, the evaluation sample which consists only of CB was produced for the comparison, without using a catalyst seed | species. Also about the evaluation sample of CB alone, what was mixed for a fixed time using the agate mortar was used similarly to the other samples. That is, four types of samples were prepared as evaluation samples: CB alone, a mixture of a noble metal catalyst and CB, a mixture of samples E1 and CB, and a mixture of potassium carbonate and CB.

Then, using a thermal analysis-differential thermogravimetric (TG-DTA) simultaneous measurement device (TG8120 manufactured by Rigaku Corporation), each evaluation sample 6 mg was heated to a maximum temperature of 900 ° C. at a temperature rising rate of 10 ° C./min, and CB. The DTA exothermic peak temperature at this time and the relationship between the temperature and TG were measured. In addition, about the evaluation sample which consists only of CB, DTA exothermic peak temperature was measured using 0.5 mg. The heating was performed while flowing air through the evaluation sample at a flux of 50 mL // min. The results of the DTA exothermic peak temperature when each catalyst type is used are shown in FIG. As for the measurement results of temperature and TG, the result of using CB alone is shown in FIG. 14, the result of using a noble metal catalyst as the catalyst species is shown in FIG. 15, and the result of using K ₂ CO ₃ is shown in FIG. 16 and the results using the sample E1 are shown in FIG. The vertical axis | shaft of FIGS. 14-17 uses the DTA exothermic peak which shows the maximum burning rate of carbon black.

  Moreover, 1 g of catalyst species (sample E1, noble metal catalyst, or potassium carbonate powder) was put into 500 cc of water and washed by stirring all day and night. Next, the catalyst seed after the water washing treatment was filtered, and further 1500 cc of water was passed through the filtered catalyst seed to sufficiently wash it, followed by drying at a temperature of 120 ° C. 200 mg of the catalyst species (sample E1 and noble metal catalyst) after the water washing treatment and 20 mg of carbon black (CB) were accurately weighed with an electronic balance. These were mixed for a certain period of time using an agate mortar so that the catalyst species (weight): CB (weight) = 10: 1, and two types of evaluation samples containing each catalyst species and carbon black were obtained. In addition, about the evaluation sample which consists of CB independent, it wash | cleaned and dried similarly to the other sample, and used what was mixed with the agate mortar after that. Moreover, since the evaluation sample using potassium carbonate as a catalyst seed was dissolved in water by the washing and washing treatment, the subsequent operation could not be performed. That is, as the evaluation samples after washing with water, three types of samples were prepared: CB alone, a mixture of a noble metal catalyst and CB, and a mixture of samples E1 and CB. About these samples, the DTA exothermic peak temperature was again measured with a thermal analysis-differential thermogravimetric (TG-DTA) simultaneous measurement apparatus. The results of the DTA exothermic peak temperature after the water washing treatment are also shown in FIG.

  As can be seen from FIGS. 1 to 5, the sample using the sample E1 and the sample using potassium carbonate have a low DTA exothermic peak temperature and can burn PM (CB) at a relatively low temperature before washing with water. . As is known from FIGS. 1 and 5, the sample E1 has an exothermic peak in the vicinity of about 400 ° C., but carbon black is actually burned even at a lower temperature (eg, about 350 ° C.). Has been started.

  As can be seen from FIG. 1, the combustion promotion characteristics for CB hardly changed before and after washing with CB alone, the noble metal catalyst, and sample E1. On the other hand, in the sample using potassium carbonate, potassium carbonate was dissolved in water after washing, and measurement was impossible.

  Therefore, the sample E1 has excellent combustion promoting characteristics with respect to PM, and can burn and remove PM at a low temperature. Moreover, since the sample E1 can maintain its excellent characteristics even in the presence of moisture, PM can be stably burned for a long period of time. Therefore, the sample E1 can stably burn PM for a long time even in exhaust gas containing a large amount of water vapor.

The sample E1 is a catalyst prepared by calcining a mixture of 100 parts by weight of sodalite and 5 parts by weight of potassium carbonate at a temperature of 800 ° C. for 10 hours as described above. Next, in this example, in order to investigate the influence of the calcination temperature on the catalyst activity, a mixture of sodalite and potassium carbonate (solid content) was calcined at different temperatures to produce a plurality of catalysts.
Specifically, first, 100 parts by weight of sodalite and 10 parts by weight of potassium carbonate were mixed in water to obtain a mixed solution. Subsequently, the liquid mixture was heated at a temperature of 120 ° C. to evaporate the water, thereby obtaining a solid content (mixture). Next, this mixture was calcined at temperatures of 500 ° C., 600 ° C., 700 ° C., 800 ° C., 900 ° C., 1000 ° C., 1100 ° C., 1200 ° C., and 1300 ° C. to prepare nine types of catalysts. These catalysts were prepared in the same manner except that the calcination temperature was changed, and were the same as the sample E1 except that the mixing ratio of potassium carbonate to sodalite and the calcination temperature were changed. A catalyst prepared as described above. Furthermore, in order to investigate the influence of the calcination time for the calcination at a temperature of 600 ° C., in addition to the catalyst produced by carrying out the calcination for 10 hours in the same manner as the sample E1, a catalyst produced with a calcination time of 5 hours is also prepared. did. Catalysts prepared at other calcination temperatures were prepared by performing calcination for 10 hours in the same manner as the sample E1.

And about these catalysts, the combustion promotion characteristic with respect to PM was investigated similarly to the said sample E1. At this time, the combustion promotion characteristics with respect to PM were also investigated for a mixture of sodalite and potassium carbonate for comparison. As this mixture of sodalite and potassium carbonate, a mixture left at room temperature (about 25 ° C.) for about 10 hours instead of firing was adopted.
The combustion acceleration characteristics were measured by measuring the DTA exothermic peak temperature in the same manner as the sample E1. The result is shown in FIG.

  As can be seen from FIG. 18, the DTA exothermic peak top temperature of the exhaust gas purifying catalyst produced by firing at a temperature of 600 ° C. or higher showed a very low value of about 460 ° C. or lower before and after water washing. Since the DTA exothermic peak temperature of a precious metal (Pt) catalyst generally used as a combustion catalyst for PM is about 520 ° C. (see FIG. 1), these exhaust gas purification catalysts have sufficiently excellent catalytic activity for PM. You can see that it has.

On the other hand, the catalyst calcined at a temperature of less than 600 ° C. had a sufficiently low DTA exothermic peak temperature compared with the noble metal (Pt) catalyst before washing with water, and showed excellent catalytic activity. The DTA exothermic peak temperature was significantly increased, and the catalytic activity was lower than that of the noble metal catalyst. In addition, a mixture of sodalite and potassium carbonate that was not calcined also showed excellent catalytic activity before washing with water, but the catalytic activity was significantly reduced after washing with water.
In the catalyst obtained by calcining at a temperature of less than 600 ° C. and the catalyst prepared without calcining, the reason why the catalytic activity was remarkably lowered after washing with water as described above is considered to be that potassium was eluted after washing with water. It is done.

  Therefore, it can be seen that the firing temperature must be 600 ° C. or higher in order to use as a purification catalyst for exhaust gas containing a large amount of moisture. Further, as can be seen from FIG. 18, it is found that an exhaust gas purification catalyst having a lower DTA exothermic peak temperature, that is, an exhaust gas purification catalyst having excellent catalytic activity, can be obtained by firing at a temperature of 700 ° C. to 1200 ° C. in particular. Furthermore, as is known from the figure, the decrease in the catalytic activity after washing with water was suppressed when the calcination was performed for 10 hours as compared with the case where the calcination was performed for 5 hours.

  In the above example, an exhaust gas purifying catalyst was prepared by mixing sodalite with potassium carbonate as a K source. Next, in this example, a plurality of exhaust gas purification catalysts were produced by changing the kind of potassium salt mixed with sodalite, and the DTA exothermic peak top temperature was examined.

  Specifically, each potassium salt (potassium carbonate, potassium nitrate, potassium chloride, potassium sulfate, potassium acetate, potassium phosphate, or potassium hydroxide) was mixed with sodalite to obtain a mixture. Each potassium salt was mixed so that the amount of potassium element in the potassium salt was 0.225 mol or 0.00225 mol with respect to 1 mol of Si element in sodalite. Moreover, mixing was performed in water similarly to the said sample E1, and the mixture was obtained by drying the water | moisture content of a liquid mixture as mentioned above.

Next, the mixture was heated at a heating rate of 100 ° C./hour, and when the temperature reached 1000 ° C. (baking temperature), the mixture was held for 10 hours to perform baking. Next, the obtained fired product was pulverized to a median diameter of 10 μm or less and a maximum particle diameter of 100 μm or less to obtain an exhaust gas purification catalyst.
For each exhaust gas purification catalyst thus obtained, the DTA exothermic peak temperature before and after washing with water was measured in the same manner as the sample E1. The result is shown in FIG.

  As can be seen from FIG. 7, the exhaust gas purifying catalyst showed excellent catalytic activity before and after washing with water regardless of which potassium salt was used. Further, when the amount of potassium salt was reduced, the catalytic activity was lowered, but even in this case, the DTA peak exothermic top temperature of 450 ° C. or lower was maintained before and after washing with water, and excellent catalytic activity was exhibited.

  In the above-described example, an exhaust gas purification catalyst was produced by mixing potassium salt as an alkali metal element source (alkali metal salt) with sodalite during mixing. Next, in this example, various alkali metal element sources or alkaline earth metal element sources other than potassium salt are mixed with sodalite to produce a plurality of exhaust gas purification catalysts, and the DTA exothermic peak top temperatures are examined. It was.

  Specifically, first, various alkali metal salts (sodium carbonate, potassium carbonate, rubidium carbonate, or cesium carbonate) or alkaline earth metal salts (magnesium hydroxide, calcium carbonate, strontium carbonate, barium carbonate) are added to sodalite. Were mixed to obtain a mixture. Each alkali metal salt or alkaline earth metal salt has an alkali metal element amount in each alkali metal salt or an alkaline earth metal element amount in 0.225 mol per 1 mol of Si element in sodalite. Or it mixed so that it might become 0.00225 mol. Moreover, mixing was performed in water similarly to the said sample E1, and solid content (mixture) was obtained by drying the water | moisture content of a liquid mixture as mentioned above.

Next, the mixture was heated at a heating rate of 100 ° C./hour, and when the temperature reached 1000 ° C. (baking temperature), the mixture was held for 10 hours to perform baking. Next, the obtained fired product was pulverized to a median diameter of 10 μm or less and a maximum particle diameter of 100 μm or less to obtain an exhaust gas purification catalyst.
For each exhaust gas purification catalyst thus obtained, the DTA exothermic peak temperature before and after washing with water was measured in the same manner as the sample E1. The result is shown in FIG. In FIG. 20, the horizontal axis indicates the alkali element species in the alkali metal element source added during mixing and the alkaline earth metal species in the alkaline earth metal element source, and the vertical axis indicates the DTA exothermic peak temperature.

As can be seen from FIG. 20, the exhaust gas purification catalyst prepared by mixing sodalite with various alkali metal elements (Na, K, Rb, Cs) was excellent before and after washing with any alkali metal element. It showed catalytic activity.
On the other hand, in the exhaust gas purification catalyst prepared by mixing various alkaline earth metal elements (Mg, Ca, Sr, Ba) with sodalite, when Mg is selected as the alkaline earth metal element, the catalytic activity is slightly In all cases, the catalyst activity was at a level that was not a problem for practical use.
Thus, it can be seen that an exhaust gas purifying catalyst having excellent catalytic activity can be obtained even when other alkali metals or alkaline earth metals are mixed with sodalite and calcined in addition to K.

Further, the case of using the Mg source as the alkaline earth metal element source will be described in more detail. As can be seen from FIG. 20, 0.00225 mol of Mg is added to 1 mol of Si element in sodalite. The obtained catalyst showed excellent catalytic activity. However, although the catalyst produced by adding 0.225 mol of Mg can be put to practical use, the catalytic activity has been lowered. On the other hand, catalysts obtained using other alkaline earth metal elements (Ca, Sr, Ba) showed excellent catalytic activity in any case.
Therefore, in the case of using sodalite, when selecting an alkaline earth metal element source, it is preferable to employ an alkaline earth metal element source other than Mg. When using the Mg source, the Mg source and sodalite are mixed so that the amount of Mg in the Mg source is less than 0.225 mol with respect to 1 mol of Si element in the sodalite. Is preferred. More preferably, it is 0.00225 mol or less.

  In the above example, an exhaust gas purification catalyst was prepared by mixing sodalite with one kind of alkali metal or alkaline earth metal. Next, in this example, an exhaust gas purification catalyst was prepared by mixing sodalite with a plurality of alkali metal elements and alkaline earth metals during mixing, and the DTA exothermic peak temperature was measured.

Specifically, first, potassium carbonate is added to sodalite, and an alkali metal element source (sodium carbonate, rubidium carbonate, or cesium carbonate) or an alkaline earth metal element source (magnesium hydroxide, calcium carbonate, strontium carbonate, Or barium carbonate) was added and mixed to obtain a mixture. Each mixture thus obtained contains sodalite, potassium carbonate, and an alkali metal element source or alkaline earth metal element source other than potassium carbonate.
In each mixture, potassium carbonate (potassium source) was added to sodalite so that the amount of potassium in potassium carbonate was 0.1125 mol relative to 1 mol of Si element in sodalite, and Si element 1 in sodalite was further added. Various alkali metal element sources or alkaline earths in sodalite so that the alkali metal element amount in each alkali metal element source or the alkaline earth metal element amount in the alkaline earth metal element source is 0.1125 mol per mol. It was prepared by adding a similar metal element source.
Therefore, in each mixture, the total amount of the amount of potassium in potassium carbonate and the amount of other alkali metal elements or alkaline earth metal elements with respect to 1 mol of Si element in sodalite is 0.225 mol. It has become.
Moreover, mixing was performed in water similarly to the said sample E1, and the mixture was obtained by drying the water | moisture content of a liquid mixture as mentioned above.

  Next, the mixture was heated at a temperature rising rate of 100 ° C./hour, and held for 10 hours when the temperature reached 1000 ° C. (calcination temperature). Thereby, the mixture was fired. Next, the obtained fired product was pulverized to a median diameter of 10 μm or less and a maximum particle diameter of 100 μm or less to obtain an exhaust gas purification catalyst.

  For each exhaust gas purification catalyst thus obtained, the DTA exothermic peak temperature before and after washing with water was measured in the same manner as in the sample E1. The result is shown in FIG. In this figure, the vertical axis shows the DTA exothermic peak temperature, and the horizontal axis shows the alkali metal element species in the alkali metal element source added in addition to potassium carbonate or the alkaline earth metal element species in the alkaline earth metal element source. Show. In addition, the figure also shows the DTA exothermic peak temperature before and after washing with respect to an exhaust gas purification catalyst (sample whose horizontal axis is indicated by K in FIG. 21) prepared by mixing and baking potassium carbonate in sodalite. .

As known from FIG. 21, in addition to K (potassium), sodalite is mixed with various alkali metal elements (Na, Rb, Cs) or alkaline earth metal elements (Mg, Ca, Sr, Ba). As in the case of mixing K alone, an exhaust gas purification catalyst having an excellent catalytic activity was obtained.
Thus, it can be seen that an exhaust gas purification catalyst having excellent catalytic activity can be obtained even when a plurality of alkali metal element sources and alkaline earth metal sources are used during mixing.

  Next, in this example, in order to investigate the influence of the addition amount of the alkali metal element source or alkaline earth metal element source on the catalytic activity of the exhaust gas purification catalyst, the alkali metal element source or alkaline earth mixed with sodalite Exhaust gas purification catalysts were prepared by changing the addition ratio of the metal element source, and the DTA exothermic peak temperature was measured.

First, potassium carbonate or barium carbonate was mixed with 100 parts by weight of sodalite in an addition amount of 0 to 100 parts by weight to obtain a mixture.
Specifically, as shown in Table 1 and FIG. 22 described later, 0 parts by weight, 0.1 part by weight, 0.5 part by weight, and 1 part by weight of potassium carbonate with respect to 100 parts by weight of sodalite (SOD), respectively. 3 parts by weight, 3 parts by weight, 5 parts by weight, 10 parts by weight, 15 parts by weight, 20 parts by weight, 40 parts by weight, and 100 parts by weight were mixed to prepare a mixture.
Further, as shown in Table 2 and FIG. 23 described later, 0 parts by weight, 5 parts by weight, 10 parts by weight, 15 parts by weight, 20 parts by weight, 40 parts by weight of barium carbonate with respect to 100 parts by weight of sodalite (SOD). Part by weight, 70 parts by weight, 100 parts by weight, 150 parts by weight, 200 parts by weight, and 300 parts by weight were mixed to prepare a mixture.
These mixings were performed in water in the same manner as the sample E1, and a plurality of mixtures were obtained by drying the water in the mixed solution as described above.

  Next, these mixtures were heated at a temperature rising rate of 100 ° C./hour, and held for 10 hours when the temperature reached 1000 ° C. Thereby, the mixture was baked. Next, the obtained fired product was pulverized to a median diameter of 10 μm or less and a maximum particle diameter of 100 μm or less to obtain an exhaust gas purification catalyst.

For each exhaust gas purification catalyst thus obtained, the DTA exothermic peak temperature before and after washing with water was measured in the same manner as the sample E1.
The results of the DTA exothermic peak temperature before and after water washing of the exhaust gas purification catalyst prepared using potassium carbonate are shown in Table 1 and FIG. 22, and the results of the DTA exothermic peak temperature before and after water washing of the exhaust gas purification catalyst prepared using barium carbonate are shown. It shows in Table 2 and FIG.
Table 1 shows a value obtained by converting a mixed amount (parts by weight) of K with respect to 100 parts by weight of sodalite into a mixed amount (mol) of K with respect to the amount of Si (mol) in sodalite (Table 1). reference). Similarly, Table 2 shows values obtained by converting the amount of Ba mixed (parts by weight) with respect to 100 parts by weight of sodalite into the amount of Ba mixed (moles) with respect to the amount of Si (mol) in sodalite (Table). 2).

As is known from Table 1, Table 2, FIG. 22, and FIG. 23, the exhaust gas purification catalyst obtained showed excellent catalytic activity even when the amount of alkali metal element and alkaline earth metal element during mixing was changed. .
On the other hand, when the amount of alkali metal or alkaline earth metal was increased, the difference in the DTA exothermic peak temperature before and after washing with water increased. As is known from Tables 1 and 2, the amount of alkali metal element (K) contained in the alkali metal element source (K ₂ CO ₃ ) and the alkali contained in the alkaline earth metal element source (BaCO ₃ ) during mixing. If sodalite and an alkali metal element source or an alkaline earth metal element source are mixed so that the amount of the earth metal element (Ba) is 2.25 mol or less with respect to 1 mol of Si element in the sodalite, It can be seen that an exhaust gas purification catalyst having a relatively small difference in DTA exothermic peak temperature before and after washing with water, that is, an exhaust gas purification catalyst having excellent durability against moisture, can be produced. Further, when the amount of the alkali metal element and the amount of the alkaline earth metal element exceeds 2.25 mol, the mixture is easily melted at the time of firing, and it becomes difficult to pulverize the exhaust gas purification catalyst obtained after the firing.
From the same viewpoint, more preferably, the amount of alkali metal element (mole) and the amount of alkaline earth metal element (mole) is 1 mol or less per 1 mol of Si element in sodalite, and still more preferably 0. 5 mol or less is good.

As described above, according to the present example, by firing a mixture of sodalite and an alkali metal element source and / or an alkaline earth metal element source at a temperature of 600 ° C. or higher, PM can be stably stabilized at a low temperature for a long period of time. It can be seen that an exhaust gas purification catalyst that can be removed by combustion is obtained.
As shown in Example 1 and Example 2, such an exhaust gas purification catalyst can be suitably used as an exhaust gas purification filter by being supported on a substrate such as a honeycomb structure. And an exhaust gas purification apparatus can be comprised like Example 1 and Example 2 using this.

(Experimental example 2)
In this example, an exhaust gas purification catalyst is produced by firing sodalite alone, and its characteristics are evaluated.
Specifically, first, it was prepared powder of sodalite _{(3 (Na 2 O · Al} 2 O 3 · 2SiO 2) · 2NaOH).
The sodalite was then fired at a temperature of 1000 ° C. Specifically, baking was performed by heating sodalite at a heating rate of 100 ° C./hour and holding it for 10 hours when the temperature reached 1000 ° C. (baking temperature). Next, the fired product was pulverized to a median diameter of 10 μm or less and a maximum particle size of 100 μm or less to obtain a powdered exhaust gas purification catalyst. This is designated as Sample E2.

  Next, regarding the exhaust gas purification catalyst (sample E2) produced in this example, the combustion promotion characteristics with respect to PM were examined. For comparison, combustion promotion characteristics were also examined for a noble metal catalyst (Pt powder) and potassium carbonate powder.

Specifically, first, in the same manner as in Experimental Example 1, four types of evaluation samples were prepared: CB alone, a mixture of a noble metal catalyst and CB, a mixture of samples E2 and CB, and a mixture of potassium carbonate and CB. did.
Next, as in Experimental Example 1, the DTA exothermic peak temperature was measured. The measurement result of the DTA exothermic peak temperature when using each catalyst type is shown in FIG.

  Also, as in Experimental Example 1, the catalyst species (sample E2, noble metal catalyst or potassium carbonate powder) is washed with water, and the dried catalyst species (sample E2 and noble metal catalyst) and CB are mixed, Two types of evaluation samples containing each catalyst type and carbon black were obtained. Note that the evaluation sample consisting of CB alone was also adjusted in the same manner as in Experimental Example 1. Moreover, since the evaluation sample using potassium carbonate as a catalyst seed was dissolved in water by the washing and washing treatment, the subsequent operation could not be performed. That is, as the evaluation samples after washing with water, three types of samples were prepared: CB alone, a mixture of a noble metal catalyst and CB, and a mixture of samples E2 and CB. About these samples, the DTA exothermic peak temperature was again measured with a thermal analysis-differential thermogravimetric (TG-DTA) simultaneous measurement apparatus. The results of the DTA exothermic peak temperature after the water washing treatment are also shown in FIG.

As can be seen from FIG. 24, the sample using the sample E2 and the sample using potassium carbonate have a low DTA exothermic peak temperature and can burn PM (CB) at a relatively low temperature before washing with water. As is known from FIG. 24, the sample E2 has an exothermic peak near about 450 ° C., but actually, the combustion of carbon black is started even at a lower temperature (for example, about 400 ° C.). Yes.
Further, as can be seen from FIG. 24, the combustion promotion characteristics for CB hardly changed before and after washing with respect to CB alone, noble metal catalyst, and sample E2. On the other hand, in the sample using potassium carbonate, potassium carbonate was dissolved in water after washing, and measurement was impossible.

  Therefore, the sample E2 has excellent combustion promoting characteristics with respect to PM, and can burn and remove PM at a low temperature. Further, since the sample E2 can maintain its excellent characteristics even in the presence of moisture, PM can be stably burned for a long period of time even when used as a purification catalyst for exhaust gas containing a large amount of moisture.

In this example, sodalite was calcined at a calcining temperature different from that of the sample E2, and three types of catalysts were produced.
That is, in sample E2, sodalite was calcined at a calcining temperature of 1000 ° C. (holding time of 10 hours). It was produced by firing at a temperature of 10 ° C. (retention time 10 hours) or a firing temperature of 500 ° C. (retention time 10 hours). And about these 3 types of exhaust gas purification catalysts, the combustion promotion characteristic with respect to PM was investigated similarly to the said sample E2. At this time, the combustion promotion characteristics with respect to PM were also investigated for the sodalite powder used for the preparation of the exhaust gas purification catalyst for comparison. As this sodalite powder, a powder left at room temperature (about 25 ° C.) for about 10 hours instead of firing was adopted. The combustion acceleration characteristics were measured by measuring the DTA exothermic peak temperature in the same manner as the sample E2. The result is shown in FIG. In the figure, the result of the exhaust gas purification catalyst obtained by firing at sample E2, that is, at a firing temperature of 1000 ° C., is also shown.

As is known from FIG. 25, the DTA exothermic peak top temperature of the exhaust gas purification catalyst obtained by calcining sodalite at a temperature of 600 ° C. or higher showed a very low value of 500 ° C. or lower. Since the DTA exothermic peak temperature of a noble metal (Pt) catalyst generally used as a combustion catalyst for PM is about 520 ° C. (see FIG. 24), these exhaust gas purification catalysts have sufficiently excellent catalytic activity for PM. You can see that it has.
In addition, the exhaust gas purification catalyst that is fired at a temperature of 600 ° C. or higher shows the same or lower temperature than the DTA exothermic peak temperature of the noble metal (Pt) catalyst even after washing with water, and is excellent even after washing with water. It can be seen that the catalytic activity can be maintained.

  In contrast, the catalyst obtained by calcining at a temperature of 500 ° C. showed a DTA exothermic peak temperature (about 520 ° C.) similar to that of the noble metal (Pt) catalyst before washing with water, but after washing with water, The DTA exothermic peak temperature rose to about 540 ° C., and the catalytic activity was lower than that of the noble metal catalyst. Moreover, in the sodalite which was not baked, the catalytic activity with respect to combustion of PM was inadequate before and after washing with water.

Further, in this example, as a comparison with the sample E2, various zeolites other than sodalite (SOD) were calcined alone, and this was used as a catalyst to examine the combustion promotion characteristics.
Specifically, first, as a zeolite other than sodalite, a zeolite structure (BEA type, FAU (Faujasite) type, FER type, LTA type, LTL type, MFI type, and MOR type) and / or in the zeolite composition 12 types of zeolites having different SiO ₂ / Al ₂ O ₃ ratios were prepared (see Table 3). These are all zeolites manufactured by Tosoh Corporation. Table 3 shows the product names of these zeolites, the types of zeolite structure types, and the SiO ₂ / Al ₂ O ₃ ratio. The names of the zeolite species in Table 3 and FIG. 26 described later are product names of zeolite manufactured by Tosoh Corporation. Table 3 also shows the sodalite (SOD) used to produce the sample E2.

  Next, various zeolites shown in Table 3 were calcined in the same manner as the sample E2. Specifically, each zeolite was heated at a heating rate of 100 ° C./hour, and when it reached a temperature of 1000 ° C. (calcination temperature), it was calcined by holding for 10 hours. Next, the fired product was pulverized to a median diameter of 10 μm or less and a maximum particle size of 100 μm or less to obtain a powdered catalyst. And about these catalysts, the combustion promotion characteristic with respect to PM was investigated similarly to the said sample E2. In addition, about these catalysts, the combustion promotion characteristic after water washing is not measured. The result is shown in FIG. FIG. 26 also shows “SOD” as the result of the sample E2 obtained by baking sodalite.

  As is known from FIG. 26, when a substance obtained by calcining zeolite other than sodalite was used as a catalyst, the DTA exothermic peak temperature was very high, and PM combustion promotion characteristics were insufficient. On the other hand, the catalyst (sample E2) obtained by calcining SOD exhibits a very low DTA exothermic peak temperature of about 450 ° C., and can burn PM at a low temperature. Therefore, it is understood that it is necessary to employ sodalite among zeolites when firing alone.

As described above, according to this example, it is understood that an exhaust gas purifying catalyst capable of stably removing and burning PM at a low temperature for a long period of time can be obtained by firing sodalite alone at a temperature of 600 ° C. or more. .
As shown in Example 1 and Example 2, such an exhaust gas purification catalyst can be suitably used as an exhaust gas purification filter by being supported on a substrate such as a honeycomb structure. And an exhaust gas purification apparatus can be comprised similarly to Example 1 and Example 2. FIG.

(Experimental example 3)
In this example, an exhaust gas purification catalyst is produced using a zeolite other than sodalite, and its characteristics are evaluated.
Specifically, first, as the zeolite, in LTA type, Al ₂ O ₃ 1 SiO ₂ amount to the molar _{(SiO 2 / Al 2 O 3} ) is 2.0 mol zeolite (manufactured by Tosoh Corporation "A -3 ") was prepared. Moreover, potassium carbonate was prepared as an alkali metal element source.
Next, zeolite and potassium carbonate were added to water in such a ratio that the amount of K in potassium carbonate relative to 1 mol of Si element in the zeolite was 0.225 mol, and both were mixed in water.
Subsequently, the liquid mixture was heated at a temperature of 120 ° C. to evaporate the water, thereby obtaining a solid content (mixture).

Next, the solid content was fired at a temperature of 1000 ° C. Specifically, the solid content was heated at a rate of temperature increase of 100 ° C./hour, and when the temperature reached 1000 ° C. (calcination temperature), the solid content was held for 10 hours to perform firing.
Next, the obtained fired product was pulverized to a median diameter of 10 μm or less and a maximum particle diameter of 100 μm or less to obtain an exhaust gas purification catalyst. This is designated as Sample E3.

  Next, the combustion promotion characteristic with respect to PM was investigated about the exhaust gas purification catalyst (sample E3) produced in this example. For comparison, combustion promotion characteristics were also examined for a noble metal catalyst (Pt powder) and potassium carbonate powder.

Specifically, first, in the same manner as in Experimental Example 1, four types of evaluation samples were prepared: CB alone, a mixture of a noble metal catalyst and CB, a mixture of samples E3 and CB, and a mixture of potassium carbonate and CB. did.
Next, as in Experimental Example 1, the DTA exothermic peak temperature was measured. FIG. 27 shows the measurement results of the DTA exothermic peak temperature when using each catalyst type.

  Also, as in Experimental Example 1, the catalyst species (sample E3, noble metal catalyst, and potassium carbonate powder) are washed with water, and the dried catalyst species (sample E3 and noble metal catalyst) are mixed with CB. Two types of evaluation samples containing each catalyst type and carbon black were obtained. Note that the evaluation sample consisting of CB alone was also adjusted in the same manner as in Experimental Example 1. Moreover, since the evaluation sample using potassium carbonate as a catalyst seed was dissolved in water by washing with water, the subsequent operation could not be performed. That is, as an evaluation sample after washing with water, three types of samples were produced: CB alone, a mixture of a noble metal catalyst and CB, and a mixture of samples E3 and CB. About these samples, the DTA exothermic peak temperature was again measured with a thermal analysis-differential thermogravimetric (TG-DTA) simultaneous measurement apparatus. The result of the DTA exothermic peak temperature after the water washing treatment is also shown in FIG.

  As can be seen from FIG. 27, the sample using the sample E3 and the sample using potassium carbonate have a low DTA exothermic peak temperature and can burn PM (CB) at a relatively low temperature before washing with water. As is known from FIG. 27, the sample E3 has a DTA exothermic peak temperature around 410 ° C. (before washing), but in actuality, even at a lower temperature (for example, about 360 ° C.), the carbon black The combustion of has started.

Further, as is known from FIG. 27, the combustion promotion characteristics for CB hardly changed before and after washing with respect to CB alone, the noble metal catalyst, and sample E3. Among these, sample E3 has the greatest decrease in the combustion acceleration characteristics after washing, but the DTA exothermic peak temperature after washing is about 450 ° C., which is sufficiently lower than CB alone and noble metal catalyst. The value is shown. Therefore, it can be seen that the sample E3 exhibits excellent combustion promoting characteristics with respect to PM even after washing with water.
On the other hand, in the sample using potassium carbonate, potassium carbonate was dissolved in water after washing, and measurement was impossible.

Thus, the exhaust gas purification catalyst (sample E3) produced using zeolite other than sodalite also has excellent combustion promoting characteristics with respect to PM, and can burn and remove PM at a low temperature. In addition, since the sample E3 can maintain its excellent characteristics even in the presence of moisture, PM can be stably burned for a long period of time. In addition, the sample E3 does not require expensive noble metal or the like at the time of manufacture, and thus can be manufactured at a low cost.
As shown in Example 1 and Example 2, the exhaust gas purification catalyst (sample E3) can be suitably used as an exhaust gas purification filter by being supported on a substrate such as a honeycomb structure. And an exhaust gas purification apparatus can be comprised like Example 1 and Example 2 using this.

(Experimental example 4)
In this example, an exhaust gas purification catalyst is prepared using a plurality of zeolites having different compositions, and the combustion promotion characteristics for PM before and after washing with water are examined.
The exhaust gas purification catalyst of this example can be manufactured in the same manner as the sample E3 of Experimental Example 3 except that the zeolite species is changed.

Specifically, first, the SiO ₂ / Al ₂ O ₃ ratio (molar ratio) in the structure and / or composition containing the zeolite (“A-3” manufactured by Tosoh Corporation) used for the preparation of the sample E3. 9 types of zeolites with different values were prepared. These zeolites have an LTA type, BEA type, FAU type, FER type, LTL type, MFI type, or MOR type structure (see Table 3 above), all of which are Tosoh Corporation Made of zeolite. Specifically, “A-3”, “A-4”, “F-9”, “642NAA”, “320NAA”, “500KOA”, “720KOA”, “820NAA” manufactured by Tosoh Corporation, and “940HOA” was used (see Table 3).

  Next, various zeolites and potassium carbonate were mixed. The mixing was performed in water as in Experimental Example 3, and the solid content was obtained by evaporating the water in the mixed solution. Similar to Experimental Example 3, the mixing ratio of various zeolites and potassium carbonate was such that the amount of K in potassium carbonate relative to 1 mol of Si element in various zeolites was 0.225 mol.

Next, each solid content was heated at a temperature rising rate of 100 ° C./hour, and when the temperature reached 1000 ° C. (calcination temperature), the solid content was held for 10 hours to perform firing.
Next, the obtained fired product was pulverized to a median diameter of 10 μm or less and a maximum particle diameter of 100 μm or less to obtain an exhaust gas purification catalyst.

  In this way, nine types of exhaust gas purification catalysts were produced using the various zeolites described above. And about these exhaust gas purification catalysts, the combustion promotion characteristic with respect to PM before and after water washing was investigated similarly to the said sample E1 of Experimental example 1. FIG. The result is shown in FIG.

  Further, in this example, in order to examine the significance of calcination, the solid content before calcination, that is, a mixture of various zeolites and potassium carbonate was used as a catalyst, and PM was washed before and after water washing as in the sample E3 of Experimental Example 3. The combustion promotion characteristics for were investigated. The result is shown in FIG.

  As can be seen from FIG. 28, the exhaust gas purification catalyst showed a low DTA exothermic peak temperature of about 480 ° C. or less before water washing in any case of using any zeolite. This value is sufficiently smaller than a noble metal (Pt) catalyst (DTA exothermic peak temperature: about 520 ° C. (see FIG. 27)) generally used as a PM combustion catalyst. Therefore, it can be seen that the exhaust gas purifying catalyst prepared using various zeolites has excellent combustion promoting characteristics with respect to PM and can burn and remove PM at a low temperature.

  As is known from FIG. 28, the exhaust gas purification catalyst prepared using various zeolites is equivalent to or more than a noble metal (Pt) catalyst (DTA exothermic peak temperature: about 520 ° C. (see FIG. 27)) even after washing with water. Also showed a small DTA exothermic peak temperature. Therefore, it can be seen that these exhaust gas purification catalysts can maintain excellent combustion promotion characteristics with respect to PM even in the presence of moisture.

Further, as is known from FIG. 29, the mixture of various zeolites and potassium carbonate that were not calcined exhibited a very low DTA exothermic peak temperature before washing with water. However, after washing with water, the DTA exothermic peak temperature significantly increased in any mixture.
On the other hand, after firing, as described above, the increase in the DTA exothermic peak temperature was small even after washing with water (see FIG. 28). It can be seen that it can be improved.

  As described above, according to this example, it is understood that an exhaust gas purifying catalyst capable of stably removing PM by burning for a long time even at low temperatures and in the presence of moisture can be obtained even if various zeolites are used. As shown in Example 1 and Example 2, such an exhaust gas purification catalyst can be suitably used as an exhaust gas purification filter by being supported on a filter base material such as a honeycomb structure. And an exhaust gas purification apparatus can be comprised like Example 1 and Example 2 using this.

(Experimental example 5)
In this example, the influence of the calcination temperature on the catalyst activity in the case of using a zeolite other than sodalite is examined.
That is, in this example, a mixture of zeolite and potassium carbonate is calcined at a plurality of different calcining temperatures to produce a plurality of exhaust gas purification catalysts, and the combustion promotion characteristics of these catalysts with respect to PM are examined.
The exhaust gas purifying catalyst of this example is manufactured in the same manner as in Experimental Example 3 except that the firing temperature is changed.

Specifically, first, in the same manner as in Experimental Example 3, in LTA type, SiO ₂ / Al ₂ O ₃ ratio (molar ratio) 2.0 zeolite (manufactured by Tosoh Corporation of "A-3") A mixture of the above and potassium carbonate (the above solid content) was obtained. Also in this example, as in Experimental Example 3, mixing is performed in water, and the mixing ratio of zeolite and potassium carbonate is also the same as in Experimental Example 3, with the amount of K in potassium carbonate relative to 1 mol of Si element in the zeolite. The ratio was 0.225 mol.

Next, the mixture was calcined at different temperatures to produce a plurality of catalysts.
Specifically, the mixture was fired at a firing temperature of 500 ° C, 600 ° C, 800 ° C, 700 ° C, 900 ° C, 1000 ° C, 1100 ° C, 1200 ° C, and 1300 ° C. Firing was performed by setting the firing rate to 100 ° C./h and holding at each firing temperature for 10 hours. Thereafter, the obtained fired product was pulverized to a median diameter of 10 μm or less and a maximum particle size of 100 μm or less, and nine types of catalysts fired at different temperatures were obtained.

And about these 9 types of catalysts, the combustion promotion characteristic before and after the water washing with respect to PM was investigated similarly to the said sample E3 of Experimental example 3. FIG. At this time, as a comparative example, the combustion promoting characteristics with respect to PM were also examined for a mixture of zeolite (A-3) and potassium carbonate that had not been calcined. As a mixture of this zeolite and potassium carbonate, what was left to stand for about 10 hours at room temperature (about 25 degreeC) instead of baking was employ | adopted.
The combustion acceleration characteristics were measured by measuring the DTA exothermic peak temperature in the same manner as in the sample E3 of Experimental Example 3. The result is shown in FIG.

  As can be seen from FIG. 30, the DTA exothermic peak top temperature of the exhaust gas purifying catalyst produced by firing at a temperature of 600 ° C. or higher was below 500 ° C. even before and after water washing. Since the DTA exothermic peak temperature of a noble metal (Pt) catalyst generally used as a combustion catalyst for PM is about 520 ° C. (see FIG. 27), these exhaust gas purification catalysts have sufficiently excellent combustion promotion characteristics for PM. It can be seen that

On the other hand, as is known from FIG. 30, the catalyst calcined at a temperature of less than 600 ° C. had a DTA exothermic peak temperature sufficiently lower than that of the noble metal (Pt) catalyst before washing with water. The DTA exothermic peak temperature significantly increased and was higher than the DTA exothermic peak temperature (about 520 ° C. (see FIG. 27)) of the noble metal catalyst. That is, after water washing, the combustion promotion characteristic for PM was insufficient.
In addition, the mixture of zeolite and potassium carbonate that had not been calcined also showed excellent combustion promoting characteristics with respect to PM before washing with water, but the combustion promoting characteristics were significantly lowered after washing with water.
In the catalyst obtained by calcining at a temperature of less than 600 ° C. and the catalyst prepared without calcining, the reason why the combustion promotion characteristics for PM after the water washing were significantly reduced as described above was because potassium was eluted after the water washing. It is believed that there is.

  Therefore, according to this example, it can be seen that the firing temperature during firing needs to be 600 ° C. or higher. In addition, as is known from FIG. 30, by performing firing at a temperature of preferably 700 ° C. to 1200 ° C., more preferably 800 ° C. to 1100 ° C., exhaust gas purification having better combustion promoting characteristics and water resistance. It can be seen that a catalyst is obtained. As shown in Example 1 and Example 2, such an exhaust gas purification catalyst can be suitably used as an exhaust gas purification filter by being supported on a filter base material such as a honeycomb structure. And an exhaust gas purification apparatus can be comprised like Example 1 and Example 2 using this.

(Experimental example 6)
In this example, the influence of the amount of alkali metal element added to the zeolite during mixing on the catalyst activity is examined.
That is, in this example, potassium carbonate is mixed at a plurality of different mixing ratios with respect to zeolite, a plurality of exhaust gas purification catalysts are produced, and combustion promotion characteristics for these PMs are examined.
The exhaust gas purification catalyst of this example is produced in the same manner as in Experimental Example 3 except that the mixing ratio of zeolite and potassium carbonate is changed.

Specifically, first, in the same manner as in Experimental Example 3, an LTA type zeolite having a SiO ₂ / Al ₂ O ₃ ratio (molar ratio) of 2.0 (“A-3” manufactured by Tosoh Corporation) Prepared.
Next, 0 to 100 parts by weight of potassium carbonate was mixed with 100 parts by weight of the zeolite to obtain a mixture.
Specifically, as shown in Table 4 and FIG. 31 described later, 0 parts by weight, 1 part by weight, 2.5 parts by weight, 5 parts by weight, 10 parts by weight, 20 parts by weight, 40 parts by weight, 60 parts by weight, 80 parts by weight, and 100 parts by weight were mixed to prepare a mixture.
These mixings were performed in water in the same manner as the sample E3 in Experimental Example 3, and the water in the mixed solution was evaporated as described above to obtain a plurality of mixtures (the solid content) having different K blending ratios.

  Next, these mixtures were heated at a temperature rising rate of 100 ° C./hour, and held for 10 hours when the temperature reached 1000 ° C. Thereby, each mixture was baked. Next, the obtained fired product was pulverized to a median diameter of 10 μm or less and a maximum particle diameter of 100 μm or less, thereby obtaining 10 types of exhaust gas purification catalysts having different K compounding ratios.

For each of the exhaust gas purifying catalysts thus obtained, the combustion promotion characteristics before and after washing with respect to PM were examined in the same manner as the sample E3 in Experimental Example 3. The combustion acceleration characteristics were measured by measuring the DTA exothermic peak temperature in the same manner as in the sample E3 of Experimental Example 3. The results are shown in Table 4 and FIG.
Table 4 shows values obtained by converting the amount of K mixed (parts by weight) with respect to 100 parts by weight of zeolite into the amount of K mixed “K / Si” (mol) with respect to the amount of Si (mol) in the zeolite. (See Table 4).

As is known from Table 4 and FIG. 31, at the time of mixing, zeolite and potassium carbonate are mixed so that the amount of K in potassium carbonate is 0.1 mol to 2.0 mol with respect to 1 mol of Si element in the zeolite. When mixed, that is, when 5 to 80 parts by weight of potassium carbonate is mixed with 100 parts by weight of zeolite at the time of mixing in this example, the DTA exothermic peak temperature before and after washing with water is low, and the exhaust gas has excellent combustion promoting characteristics. A purification catalyst was obtained.
On the other hand, when it deviates from the above-mentioned range of 0.1 mol to 2.0 mol, the exothermic peak temperature after washing with water is particularly high, and the obtained catalyst has low water resistance. It was.
In addition, preferably, an exhaust gas purification catalyst with better water resistance can be obtained by setting the amount of K in potassium carbonate to 0.2 mol to 1.5 mol with respect to 1 mol of Si element in the zeolite. You can see (see Table 4, Figure 31).

As described above, according to the present example, during mixing, the amount of K element (alkali metal element) in potassium carbonate with respect to 1 mol of Si element in the zeolite is 0. It turns out that the exhaust gas purification catalyst which is more excellent in water resistance and can stably remove PM by burning for a long period of time can be obtained by mixing so as to be 1 mol to 2.0 mol.
As shown in Example 1 and Example 2, such an exhaust gas purification catalyst can be suitably used as an exhaust gas purification filter by being supported on a substrate such as a honeycomb structure. And an exhaust gas purification apparatus can be comprised like Example 1 and Example 2 using this.

(Experimental example 7)
In this example, during mixing, various alkali metal element sources or alkaline earth metal element sources are added to zeolite to produce an exhaust gas purification catalyst, and its combustion promotion characteristics for PM are examined.
The exhaust gas purification catalyst of this example is produced in the same manner as in Experimental Example 3 except that the alkali metal element source or alkaline earth metal element source mixed in the zeolite is changed.

Specifically, first, in the same manner as in Experimental Example 3, an LTA type zeolite having a SiO ₂ / Al ₂ O ₃ ratio (molar ratio) of 2.0 (“A-3” manufactured by Tosoh Corporation) Prepared.
Then, various alkali metal element sources (sodium carbonate, potassium carbonate, rubidium carbonate, or cesium carbonate) or various alkaline earth metal element sources (magnesium hydroxide, calcium carbonate, strontium carbonate, or barium carbonate) are mixed with this zeolite. did. The mixing ratio of the zeolite and various alkali metal element sources or alkaline earth metal element sources is the same as in Experimental Example 3, with the amount of alkali metal elements or alkaline earth in the alkaline earth metal element source with respect to 1 mol of Si element in the zeolite. The amount of the alkaline earth metal element in the metal source was 0.225 mol.
Also in this example, as in Experimental Example 3, mixing is performed in water, and the water in the mixed solution is evaporated to obtain a mixture of zeolite and various alkali metal element sources or alkaline earth metal element sources (above Solid content).

  Next, these mixtures were heated at a temperature rising rate of 100 ° C./hour, and held for 10 hours when the temperature reached 1000 ° C. Thereby, each mixture was baked. Next, the fired product obtained is pulverized to a median diameter of 10 μm or less and a maximum particle diameter of 100 μm or less, and different alkali metal elements (Na, K, Rb, or Cs) or alkaline earth metal elements (Mg, Ca, Sr) Or 8 types of exhaust gas purification catalysts containing Ba) were obtained.

  For each of the exhaust gas purification catalysts thus obtained, the combustion promotion characteristics before and after washing with respect to PM were examined in the same manner as the sample E3 in Experimental Example 3. The combustion acceleration characteristics were measured by measuring the DTA exothermic peak temperature in the same manner as in the sample E3 of Experimental Example 3. The result is shown in FIG. In FIG. 32, the horizontal axis represents the alkali metal element species in the alkali metal element source added during mixing and the alkaline earth metal element species in the alkaline earth metal element source, and the vertical axis represents the DTA exothermic peak. Indicates temperature.

As is known from FIG. 32, the exhaust gas purification catalyst produced using various alkali metal element sources and alkaline earth metal element sources is almost equal to or lower than the conventional noble metal catalyst before and after washing with water in any case. DTA exothermic peak temperature was shown.
In particular, when an alkali metal element source is used and when a Ba source (barium carbonate) is used as an alkaline earth metal element source, the DTA exothermic peak temperature is below 500 ° C. even after washing with water. It can be seen that an exhaust gas purification catalyst is obtained.

As described above, according to this example, PM can be stably burned and removed for a long period of time even at low temperatures and in the presence of moisture even when using various alkali metal element sources and alkaline earth metal element sources during mixing. It can be seen that an exhaust gas purification catalyst can be obtained.
As shown in Example 1 and Example 2, such an exhaust gas purification catalyst can be suitably used as an exhaust gas purification filter by being supported on a filter base material such as a honeycomb structure. And an exhaust gas purification apparatus can be comprised like Example 1 and Example 2 using this.

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification apparatus 2 Exhaust gas purification filter 151 Filter regeneration means

Claims (19)

An exhaust gas purification filter that is provided in the exhaust gas passage of the internal combustion engine and collects particulate matter contained in the exhaust gas, and the temperature in the exhaust gas purification filter is raised to a predetermined regeneration temperature and deposited in the exhaust gas purification filter. In the exhaust gas purification apparatus comprising filter regeneration means for performing regeneration processing of the collection ability of the exhaust gas purification filter by burning and removing the particulate matter,
The exhaust gas purification filter has a base material made of a porous body and an exhaust gas purification catalyst carried on the base material,
The exhaust gas purifying catalyst is characterized in that a mixture of zeolite and an alkali metal element source and / or an alkaline earth metal element source or sodalite is calcined at a temperature of 600 ° C or higher.   2. The filter regeneration means according to claim 1, wherein the filter regeneration means is configured to increase the temperature in the exhaust gas purification filter to the regeneration temperature of 400 ° C. or more and less than 600 ° C. to start the regeneration process. Exhaust gas purification device.   3. The filter regeneration means according to claim 1, wherein the filter regeneration means is configured to perform the regeneration process using a temperature at a predetermined position within 10 to 20 mm from the upstream side of the exhaust gas purification filter as the regeneration temperature. Exhaust gas purification device.   The filter regeneration means according to any one of claims 1 to 3, wherein the particulate matter is burned and removed by increasing the temperature of the exhaust gas flowing into the exhaust gas purification filter. A featured exhaust gas purification device.   5. The exhaust gas purification apparatus according to claim 1, wherein an oxidation catalyst is disposed upstream of the exhaust gas purification filter.   6. The filter regeneration means according to claim 1, wherein the filter regeneration means performs the regeneration process when the amount of the particulate matter deposited in the exhaust gas purification filter reaches 4 g / L to 12 g / L. An exhaust gas purifying apparatus characterized by comprising:   The exhaust gas purification catalyst in the exhaust gas purification filter according to any one of claims 1 to 6, wherein the mixture or sodalite is baked at the temperature of 600 ° C or higher and then supported on the base material. Exhaust gas purification device.   7. The exhaust gas purification catalyst according to claim 1, wherein the exhaust gas purification catalyst in the exhaust gas purification filter is baked at a temperature of 600 ° C. or higher after the mixture or sodalite is supported on the base material. Exhaust gas purification device. 9. The exhaust gas purifying apparatus according to claim 1, wherein the zeolite has an amount of SiO ₂ of less than 200 mol with respect to 1 mol of Al ₂ O ₃ in the composition.   The exhaust gas purification apparatus according to any one of claims 1 to 9, wherein sodalite is employed as the zeolite in the mixture.   In Claim 10, In the said mixture, the total amount of the alkali metal element and alkaline-earth metal element which are contained in the said alkali-metal element source and / or the said alkaline-earth metal element source is Si element in the said sodalite An exhaust gas purifying apparatus characterized by being 2.25 mol or less per 1 mol.   In Claim 10, In the said mixture, the total amount of the alkali metal element and alkaline-earth metal element which are contained in the said alkali-metal element source and / or the said alkaline-earth metal element source is Si element in the said sodalite An exhaust gas purification apparatus characterized by being 1 mol or less per 1 mol.   In any one of Claims 1-9, zeolite other than sodalite is employ | adopted as the zeolite in the said mixture, In the said mixture, the said alkali metal element source and / or the said alkaline earth metal element source Exhaust gas characterized in that the total amount of alkali metal element and alkaline earth metal element contained therein is 0.1 mol or more and 2.0 mol or less with respect to 1 mol of Si element in the zeolite. Purification equipment.   The exhaust gas purification apparatus according to any one of claims 1 to 13, wherein the mixture contains at least the alkali metal element source.   The alkali metal element source according to any one of claims 1 to 14, wherein the alkali metal element source includes one or more selected from Na, K, Rb, and Cs, and the alkaline earth metal element source is Mg, Ca, Sr. And an exhaust gas purifying apparatus comprising at least one selected from Ba.   16. The alkali metal element source and / or the alkaline earth metal element source according to claim 1, wherein the alkali metal element source and / or the alkaline earth metal element source is carbonate, sulfate, phosphate, nitrate, organic acid salt, halide, oxide. Or an exhaust gas purification apparatus characterized by being a hydroxide.   17. The mixture according to claim 1, wherein the mixture is obtained by mixing the zeolite and the alkali metal element source and / or the alkaline earth metal element source in a polar solvent, and evaporating the polar solvent. An exhaust gas purification apparatus comprising the solid content obtained.   18. The base material according to claim 1, wherein the base material is formed of a porous base material in which a plurality of cells extending in an axial direction are formed by arranging porous partition walls in a polygonal lattice shape, and the cell is an exhaust gas. An exhaust gas purification apparatus characterized by forming a flow path.   The exhaust gas purification device according to any one of claims 1 to 18, wherein the base material is made of cordierite or SiC.

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