JP4233031B2 - Ceramic honeycomb filter and manufacturing method thereof - Google Patents

Description

  The present invention relates to a ceramic honeycomb filter for removing fine particles contained in exhaust gas of a diesel engine and a method for manufacturing the same.

  In order to remove particulates discharged from diesel engines, a filter for collecting particulates (diesel particulate filter) that has a porous structure for the partition walls of the ceramic honeycomb structure and allows exhaust gas containing particulates to pass through the partition walls. Consideration is underway. Regarding the characteristics of this filter, three are important: the collection efficiency of fine particles, the pressure loss (pressure loss), and the collection time of fine particles (the time from the start of collection until reaching a certain pressure loss). In particular, the collection efficiency and the pressure loss are in a contradictory relationship. If you try to increase the collection efficiency, the pressure loss increases and the collection time is shortened, and if the pressure loss is low, the collection time can be increased, The efficiency of collection becomes worse. In order to satisfy these contradictory filter characteristics, a technology for controlling the porosity, the average pore diameter, and the size of the pores existing on the partition walls has been conventionally applied to the ceramic honeycomb structure as follows. Has been considered.

In Japanese Examined Patent Publication No. 3-10365, the pores existing on the surface of the filter partition are composed of small pores having a pore diameter of 5 to 40 μm and large pores having a pore diameter of 40 to 100 μm. It is disclosed that, by configuring so as to be 5 to 40 times the number, the collection efficiency can be maintained at a high value from the beginning, and an exhaust gas purification filter with low pressure loss can be obtained. On the other hand, the average pore diameter of the internal pores existing inside the partition walls is larger than 15 μm, and the cumulative pore volume is preferably in the range of 0.3 to 0.7 cm ³ / g. Here, there is no description of the porosity P (volume%) of the partition walls, but when the true specific gravity ρ of the cordierite material described in the examples is 2.5 g / cm ³ , the cumulative pore volume V (cm ³ / G) can be calculated by the following calculation formula. P = 100 × V × ρ / (1 + V × ρ). Therefore, the preferable range of 0.3 to 0.7 cm ³ / g of the cumulative pore volume of the internal pores existing inside the partition walls is 42.8 to 63.6% by volume in terms of porosity. (See Patent Document 1.)
Japanese Patent Publication No. 61-54750 discloses that a filter from a high collection rate type to a low collection rate type can be designed by controlling open porosity (porosity) and average pore diameter. ing. As a preferable specific example in this publication, the open porosity (porosity) and the average pore diameter (average pore diameter) in the zone limited to the boundary connecting the points 1-5-6-4 in FIG. ) Is described. Here, point 1 has an open porosity of 58.5% by volume and an average pore diameter of 1 μm, point 5 has an open porosity of 39.5% by volume and an average pore diameter of 15 μm, and point 6 has an open porosity of 62.0% by volume and an average pore diameter of 15 μm. , Point 4 has an open porosity of 90.0% by volume and an average pore diameter of 1 μm. (See Patent Document 2.)
In JP-A-9-77573, the porosity is 55 to 80%, the average pore diameter is 25 to 40 μm, and the pores on the partition wall surface are 5 to 40 μm small pores and 40 to 100 μm large pores. It is disclosed that a honeycomb structure having a high collection rate, a low pressure loss, and a low thermal expansion coefficient can be obtained by making the number of small holes 5 to 40 times the number of large holes. Has been. (See Patent Document 3)

Japanese Patent Publication No. 3-10365 Japanese Examined Patent Publication No. 61-54750 (FIG. 8) JP-A-9-77573

  However, as shown in the above prior art, the balance between the porosity and the collection efficiency can be achieved to some extent by optimizing the porosity, average pore diameter, and pore size on the partition wall surface, but the partition itself is a porous body. The strength of the porous body is inevitably lowered because the strength of the porous body is in a relationship with the porosity and the average pore diameter. That is, as the porosity and pore size increase, the strength of the ceramic honeycomb structure decreases. In particular, when the porosity is set to 60% or more, or the average pore diameter is set to 15 μm or more in order to obtain a low pressure loss filter, the strength reduction becomes remarkable. For this reason, it is possible to achieve both low pressure loss and high collection efficiency, as well as thermal stress and thermal shock stress generated when used as a diesel particulate filter, stress due to mechanical tightening force and vibration during assembly, etc. Therefore, there is a problem that a ceramic honeycomb filter that is durable for a long period of time cannot be obtained without being damaged, and this has been an obstacle to the practical use of a diesel particulate filter.

  In order to solve the above problems, the present invention was used as a filter for collecting particulates of a diesel engine even when the porosity of the partition wall was 60% or more and the average pore diameter was 15 μm or more so as to obtain a low pressure loss filter. An object of the present invention is to provide a ceramic honeycomb filter having durability over a long period of time without being damaged by thermal stress or thermal shock stress generated in the case, mechanical tightening force during assembly, stress due to vibration, or the like, and a method for manufacturing the same. .

In order to solve the above-mentioned problems, the present inventor has intensively studied and, as a result, devised the manufacturing method to make the distribution of pores formed in the partition walls of the honeycomb structure within a certain range, thereby reducing the pressure. The inventors have found that a ceramic honeycomb filter satisfying three characteristics of loss, high collection efficiency, and high strength can be obtained, and the present invention has been conceived.
That is, in the ceramic honeycomb filter of the present invention, after adding at least a pore former having a particle size distribution with an average particle size of 20 μm or more and a particle size of 20 to 100 μm of 50% or more to the ceramic raw material powder, Etc., the batch ends of the ceramic honeycomb structure obtained by extruding, drying and firing the plugs are plugged, and the end portions of the predetermined flow paths are plugged, and the exhaust gas is supplied to the porous partition walls defining the flow paths. In the ceramic honeycomb filter that removes the fine particles contained in the exhaust gas by allowing it to pass through, the chemical composition of the main component of the porous ceramic constituting the porous partition wall is SiO ₂ : 42 to 56 mass%, Al ₂ O ₃ : 30 to 45 wt%, MgO: at 12-16 wt%, the main component of the crystalline phase is cordierite, wherein when the porous partition measured by mercury porosimetry 6 80% of the porosity has an average pore diameter of 15 ～40Myuemu, following equation for the slope of the cumulative pore volume distribution curve of the porous partition walls (1)
S _n = − (V _n −V _n−1 ) / (log (D _n ) −log (D _n−1 )) (1),
(However, D _n is the pore diameter (μm) at the (n) -th measurement point,
D _n-1 is the pore diameter (μm) at the (n-1) th measurement point,
V _n is the cumulative pore volume (cm ³ / g) at the (n) th measurement point,
V _n−1 is the cumulative pore volume (cm ³ / g) at the (n−1) th measurement point,
_Sn is the slope of the cumulative pore volume distribution curve with respect to the pore diameter at the nth measurement point. The maximum value of _{S n} represented by), characterized in that at least 0.7 at a pore diameter of from 15 to 30 [mu] m.
In this case, the maximum value of _{S n} is not preferable to be 0.9 or more.
In the ceramic honeycomb filter of the present invention, after adding at least a pore former having a particle size distribution with an average particle size of 20 μm or more and a particle size of 20 to 100 μm of 50% or more to the ceramic raw material powder, Etc., the batch ends of the ceramic honeycomb structure obtained by extruding, drying and firing the plugs are plugged, and the end portions of the predetermined flow paths are plugged, and the exhaust gas is supplied to the porous partition walls defining the flow paths. A ceramic honeycomb filter that removes particulates contained in exhaust gas by allowing it to pass through, wherein the porous partition wall is formed in the ceramic honeycomb filter in which a catalyst is supported on the surface of the porous partition wall and inside the porous partition wall. configured to porous main component of the ceramic chemical composition _SiO 2: 42 to 56 _{wt%, Al} 2 O 3: _30~45 wt%, MgO: 12 to 16 mass In the main component of the crystalline phase is cordierite, the porous partition porosity of 60-80% when measured by mercury porosimetry, has an average pore diameter of 15 ～40Myuemu, of the porous partition walls The following formula (1) regarding the slope of the cumulative pore volume distribution curve
S _n = − (V _n −V _n−1 ) / (log (D _n ) −log (D _n−1 )) (1),
(However, D _n is the pore diameter (μm) at the (n) -th measurement point,
D _n-1 is the pore diameter (μm) at the (n-1) th measurement point,
V _n is the cumulative pore volume (cm ³ / g) at the (n) th measurement point,
V _n−1 is the cumulative pore volume (cm ³ / g) at the (n−1) th measurement point,
_Sn is the slope of the cumulative pore volume distribution curve with respect to the pore diameter at the nth measurement point. The maximum value of _{S n} represented by), characterized in that at least 0.7 at a pore diameter of from 15 to 30 [mu] m.

Next, in the method for manufacturing a ceramic honeycomb filter of the present invention, a predetermined flow of a ceramic honeycomb structure obtained by extruding, drying and firing a batch obtained by adding a pore former, water and the like to a ceramic raw material powder is mixed. A method for manufacturing a ceramic honeycomb filter, wherein fine particles contained in exhaust gas are removed by plugging a road end and allowing exhaust gas to pass through a porous partition wall defining the flow path. The pore material is characterized by having an average particle size of 20 μm or more and a particle size distribution in which a particle size of 20 to 100 μm occupies 50% or more and is substantially spherical and hollow .
Furthermore, keep the production method of the present invention, the main component of the chemical composition of the porous ceramics constituting the porous partition walls _SiO 2: 42 to 56 _{wt%, Al} 2 O 3: _30~45 wt%, MgO: 12 ˜16% by mass, the main component of the crystal phase is cordierite, and the porous partition walls of the ceramic honeycomb filter have a porosity of 60 to 80% and an average pore diameter of 15 to 40 μm when measured by a mercury intrusion method. a maximum value of the slope S _n of a cumulative pore volume distribution curve of the barrier to the pore size in the n-th measurement point, is 0.7 or more at a pore diameter of from 15 to 30 [mu] m, the cumulative pore volume slope _{S n} is represented by the following formula of the distribution curve (1)
S _n = − (V _n −V _n−1 ) / (log (D _n ) −log (D _n−1 )) (1),
(However, D _n is the pore diameter (μm) at the (n) -th measurement point,
D _n-1 is the pore diameter (μm) at the (n-1) th measurement point,
V _n is the cumulative pore volume (cm ³ / g) at the (n) th measurement point,
V _n-1 is the cumulative pore volume (cm ³ / g) at the (n−1) -th measurement point. )
Is preferably represented by:

Next, the effect in this invention is demonstrated.
In the ceramic honeycomb filter of the present invention, the porous partition walls of the ceramic honeycomb structure have a porosity of 60 to 80% and an average pore diameter of 15 to 40 μm when measured by a mercury intrusion method. The following formula (1) regarding the slope of the pore volume distribution curve (curve represented by a graph in which the horizontal axis is the pore diameter and the vertical axis is the cumulative pore volume)
S _n = − (V _n −V _n−1 ) / (log (D _n ) −log (D _n−1 )) (1),
(However, D _n is the pore diameter (μm) at the (n) -th measurement point,
D _n-1 is the pore diameter (μm) at the (n-1) th measurement point,
V _n is the cumulative pore volume (cm ³ / g) at the (n) th measurement point,
V _n−1 is the cumulative pore volume (cm ³ / g) at the (n−1) th measurement point,
_Sn is the slope of the cumulative pore volume distribution curve with respect to the pore diameter at the nth measurement point. The maximum value of S _n represented by) is because it is 0.7 or more at a pore diameter of from 15 to 30 [mu] m, the pore distribution becomes sharp, high porosity, with a focus on the average pore diameter was pores Since the proportion occupied is large, the pressure loss can be kept low and the strength can be kept high.
It will now be described in detail the reasons for limiting the inclination S _n of a cumulative pore volume distribution curve.
The strength of the ceramic honeycomb structure is, of course, influenced by the porosity and average pore diameter, but is highly dependent on the pore diameter distribution, and in particular, the pore diameter distribution is sharp, in other words, the pore size is uniform. This is because it has been found that high strength can be obtained even when the porosity is 60 to 80% and the average pore diameter is 15 to 40 μm .
Here the porosity, average pore diameter, the slope S _n of a cumulative pore volume distribution curve, using a Micromeritics Co. Autopore III9410, measured by mercury porosimetry. In this mercury intrusion measurement, a sample for measurement is stored in a measurement cell, the inside of the cell is decompressed, mercury is introduced and pressurized, and the pressure at this time and the pores present in the sample are measured. From the relationship with the volume of mercury pushed in, the relationship between the pore diameter and the cumulative pore volume is obtained. That is, when the applied pressure is large, mercury enters the finer pores, and the volume of the fine pores corresponding to the applied pressure is measured. For this reason, the measurement is sequentially performed from a large pore diameter to a small one. At this time, from the start of measurement, the pore diameter D _n-1 and cumulative pore volume V _n-1 at the (n _-1 ) th measurement point, and the pore diameter D _n and cumulative fineness at the (n) th measurement point. from pore volume _{V n,} as determined by the above equation (1) becomes the slope _{S n} in (n) th measurement point. An example of measurement results of the S _n shown in FIG. FIG point in 3 a the slope _S 1 was determined from the pore diameter _D 1, _{D 2} and a cumulative pore volume _V 1, _{V 2} in the first and second measurement points _{[(V 1 -V 2) /} (logD 1 −logD ₂ )], and the point b is the slope S ₂ [(V ₂ −V ₃₎ obtained from the pore diameters D ₂ and D ₃ and the cumulative pore volumes V ₂ and V _{3 at the} second and third measurement points. ) / (LogD ₂ -logD ₃ )].
Here, the distribution of the slope S _n of the pore size and the cumulative pore volume distribution curve shown in FIG. 3, the pore size distribution and the maximum value of S _n is smaller than 0.7 is broad, the maximum value of S _n It can be seen that the pore size distribution is very sharp when the value is 0.7 or more. If the pore size distribution is broad, the proportion of coarse pores that cause strength reduction and fine pores that cause clogging of fine particles and increase in pressure loss will decrease, making it difficult to achieve both low pressure loss and high strength. It becomes, but when the maximum value of S _n is 0.7 or more, since the pore size distribution becomes sharp, decreases the proportion of coarse pores and fine pores, both low pressure loss and high strength can be achieved. This is also clear from FIG. 4 showing the relationship between the maximum value and the A-axis compressive strength ratio of the slope S _n of a cumulative pore volume distribution curve. Here, the A-axis compressive strength ratio is a relative value of the A-axis compressive strength obtained by setting the conventional product level to 1.0. If the maximum value of S _n is 0.7 or more, A-axis compressive strength is seen that conventional level (maximum value of, for example, S _n is 0.6 or less in the region) becomes 1.5 or more. That is, when the maximum value of S _n is 0.7 or more, the mechanical strength of the ceramic honeycomb structure can be seen that significantly improved. The maximum value of S _n in order to achieve both low pressure loss and high strength is more preferably 0.9 or more.
Here, the porosity of the ceramic honeycomb structure is limited to 60% or more because the pressure loss of the filter increases when the porosity is less than 60%. On the other hand, if the porosity exceeds 80%, the strength of the filter is lowered and the collection efficiency of the fine particles is deteriorated. Therefore, the porosity is preferably 60 to 80%. Furthermore, when the porosity is 65% or more, the effect of reducing the pressure loss is further increased, and when the porosity is 75% or less, the decrease in strength and collection efficiency can be further reduced. Therefore, the porosity is more preferably 65 to 75%. It is.
The reason why the average pore diameter of the pores present in the ceramic honeycomb structure is limited to 15 μm or more is that the pressure loss of the filter increases if the average pore diameter is less than 15 μm. In addition, when the average pore diameter exceeds 40 μm, the strength of the filter is lowered, and small fine particles are not captured but pass through the filter, so that the collection efficiency is deteriorated. Therefore, the average pore diameter of 15 to 40 μm is a preferable range. . Furthermore, since the decrease in strength and collection efficiency can be further reduced when the average pore diameter is 25 μm or less, the average pore diameter of 15 to 25 μm is a more preferable range in which both low pressure loss and high strength conflicting characteristics can be achieved.

In the ceramic honeycomb filter of the present invention, the chemical composition of the main components of the porous ceramics constituting the partition walls of the honeycomb structure is SiO ₂ : 42 to 56 mass%, Al ₂ O ₃ : 30 to 45 mass%, MgO: The reason why the main component of the crystal phase is cordierite is 12 to 16% by mass is to use the low thermal expansion inherent in cordierite, and it is difficult to generate cracks even when a thermal shock is applied. This is because a honeycomb filter is obtained.

Further, in the ceramic honeycomb filter in which the catalyst is supported on the surface of the porous partition wall and inside the porous partition wall, the porous partition wall of the ceramic honeycomb structure has a porosity of 60 to 80% when measured by a mercury intrusion method, and 15 to An average pore diameter of 40 μm , and the following formula (indicated by a graph represented by a graph in which the horizontal axis represents the pore diameter and the vertical axis represents the cumulative pore volume) of the porous partition wall (the curve represented by the horizontal axis) ( 1)
S _n = − (V _n −V _n−1 ) / (log (D _n ) −log (D _n−1 )) (1),
(However, D _n is the pore diameter (μm) at the (n) -th measurement point,
D _n-1 is the pore diameter (μm) at the (n-1) th measurement point,
V _n is the cumulative pore volume (cm ³ / g) at the (n) th measurement point,
V _n−1 is the cumulative pore volume (cm ³ / g) at the (n−1) th measurement point,
_Sn is the slope of the cumulative pore volume distribution curve with respect to the pore diameter at the nth measurement point. The maximum value of S _n represented by) is because it is 0.7 or more at a pore diameter of from 15 to 30 [mu] m, the effect to achieve both low pressure loss as described above, a high collection efficiency, a high strength, This is because it is remarkable in the ceramic honeycomb filter in which the catalyst is supported on the partition wall surface and inside the partition wall.

Next, in the method for manufacturing a ceramic honeycomb filter of the present invention, a predetermined flow of a ceramic honeycomb structure obtained by extruding, drying and firing a batch obtained by adding a pore former, water and the like to a ceramic raw material powder is mixed. A method for manufacturing a ceramic honeycomb filter, wherein fine particles contained in exhaust gas are removed by plugging a road end and allowing exhaust gas to pass through a porous partition wall defining the flow path. The pore material is characterized by having an average particle size of 20 μm or more and a particle size distribution in which a particle size of 20 to 100 μm occupies 50% or more and is substantially spherical and hollow .
First ceramic raw material powder, the average particle diameter of 20μm or more, a porosity of 60-80% obtained after firing the pore former is particularly particle size 20~100μm has substantially spherical and hollow the particle size distribution accounts for 50% or more Add as much as possible. If necessary, a molding aid such as a binder and a lubricant is added to the mixture, and after mixing, water is added to produce a plasticizable batch. After extruding the honeycomb structure with a known extrusion method, the batch is dried, burned and removed from the pore former, and fired to remove the fine pores inherent in the ceramic and the pore former. A honeycomb structure having pores formed by the traces of is obtained. Thus, a pore former having a particle size distribution in which the fine pores originally possessed by ceramics and a uniform particle size have a substantially spherical shape (average particle size of 20 μm or more, particle size of 20 to 100 μm occupies 50% or more) The average pore diameter of the partition walls can be kept in the range of 15 to 25 μm by combining with the pores formed by the above, and the maximum value of Sn indicating the sharpness of the pore distribution should be 0.7 or more Can do. In particular, cordierite ceramics originally have pores with a pore size of about 1 to 20 μm, and therefore have an average particle size of 20 μm or more and a particle size distribution in which the particle size of 20 to 100 μm accounts for 50% or more. A combination with a pore former is effective. In addition, since the pore former is substantially spherical, the pores formed in the partition walls are also substantially spherical, so that the stress concentration on the pores can be reduced, and the ceramic honeycomb having excellent mechanical strength Since a structure is obtained, it becomes possible to manufacture a ceramic honeycomb filter that achieves both low pressure loss and high strength. The substantially spherical pore former is a known graphite, wheat flour, resin powder or the like, and is preferably classified so as to have a particle size distribution in which an average particle size of 20 μm or more and a particle size of 20 to 100 μm occupy 50% or more. Moreover, when using resin powder, it is good also as the particle size distribution which adjusts the manufacturing conditions and occupies 50% or more for the average particle diameter of 20 micrometers or more and 20-100 micrometers of particle diameters.
In the production method of the present invention, the pore former is preferably hollow. When the pore former is hollow, it can be easily removed from the partition wall when the pore former is burned and removed. This is because the problem that the partition wall cracks during combustion removal hardly occurs and the manufacturing yield is improved.
Further, in the manufacturing method of the present invention, the main component of the chemical composition of the porous ceramics constituting the porous partition walls _SiO 2: 42 to 56 _{wt%, Al} 2 O 3: _30~45 wt%, MgO:. 12 to 16 mass%, the main component of the crystal phase is cordierite, and the porous partition walls of the ceramic honeycomb filter have a porosity of 60 to 80% and an average pore diameter of 15 to 40 μm when measured by mercury porosimetry. and, the maximum value of the slope S _n of a cumulative pore volume distribution curve of the barrier to the pore size in the n-th measurement point, is 0.7 or more at a pore diameter of from 15 to 30 [mu] m, the cumulative pore volume distribution The slope S _n of the curve is the following formula (1)
S _n = − (V _n −V _n−1 ) / (log (D _n ) −log (D _n−1 )) (1),
(However, D _n is the pore diameter (μm) at the (n) -th measurement point,
D _n-1 is the pore diameter (μm) at the (n-1) th measurement point,
V _n is the cumulative pore volume (cm ³ / g) at the (n) th measurement point,
V _n-1 is the cumulative pore volume (cm ³ / g) at the (n−1) -th measurement point. )
As described above, it is preferable that both low pressure loss and high strength can be achieved.

According to the ceramic honeycomb filter and production method thereof of the present invention, the maximum value of the inclination S _n in a cumulative pore volume distribution curve of the pores in the partition walls of the ceramic honeycomb structural body constituting the ceramic honeycomb filter of 0.7 or more and Thus, even when the porosity is 60% or more and the average pore diameter is 15 μm or more, when used as a diesel particulate filter, it is a contradictory property, which is low pressure loss and high collection efficiency. It is possible to make both characteristics compatible. Moreover, a ceramic honeycomb filter having excellent durability that is not damaged by thermal stress or thermal shock stress during use, mechanical clamping force during assembly, or stress due to vibration can be obtained.

  Hereinafter, although the actual Example of this invention is described, this invention is not limited to them.

Cordierite such as kaolin, calcined kaolin, alumina, aluminum hydroxide, silica, talc, etc., so that SiO ₂ is 42 to 56 mass%, Al ₂ O ₃ is 30 to 45 mass%, and MgO is 12 to 16 mass%. As a binder, a lubricant, and a pore-forming material in the ceramic raw powder, No. A predetermined amount of each of the three types of spherical resin powders 1 to 3 was mixed. At this time, the particle size distribution of the spherical resin powder used as the pore former is shown in FIG. 5, and the average particle size and the ratio of the particle size of 20 to 100 μm are shown in Table 1. Next, water was added to the mixture to produce a plasticizable batch, and the batch was formed into a cylindrical honeycomb structure by a known extrusion method. Next, the molded body was dried and fired at a temperature range of 1380 to 1420 ° C., and as shown in the front and side views of FIGS. 1 (a) and 1 (b), the porous ceramic partition walls 3 and the through holes 2 and the pore former No. Test Nos. 1 to 3 corresponding to Three to three cordierite ceramic honeycomb structures 1 were obtained. The obtained honeycomb structure had a diameter of 143 mm, a length of 152 mm, a partition wall thickness of 0.3 mm, and 46 channels per 1 cm ² .

Test No. obtained The porosity of the three types of cordierite ceramic honeycomb structural body 1 to 3, the average pore diameter, the slope S _n of a cumulative pore volume distribution curve using a Micromeritics Co. Autopore III9410, measured by mercury porosimetry. The numerical value obtained by the measurement is the pressure of mercury applied to the sample and the volume of mercury injected into the sample, and the pore diameter D _{n at the} (n) th measurement point is expressed as (n ) Cumulative pore volume V _{n at} the first measurement point was calculated from equation (3).
(N) Pore diameter D _n = −4αcos θ / Pn at the second measurement point (2)
Where α is the surface tension of mercury (4.935 × 10 −4 kg / cm)
θ is the contact angle between mercury and solid (130 °)
Pn is the mercury pressure at the (n) th measurement point.
(N) Cumulative pore volume V _n = v _n / w at the third measurement point (3)
Here, v _n is the volume of the sample is pressed into a sample of the (n) th measurement point
w is the weight of the sample.
FIG. 6 shows the relationship between the obtained pore diameter and the cumulative pore volume (cumulative pore volume distribution curve). As apparent from FIG. 6, test Nos. No. 1 honeycomb structure has a very steep slope of the cumulative pore volume distribution curve. No. 2 honeycomb structure has a steep slope of the cumulative pore volume distribution curve. The slope of the cumulative pore volume distribution curve of No. 3 honeycomb structure was relatively gentle.
From the cumulative pore volume distribution curve shown above and FIG. It was determined slope S _n of a cumulative pore volume distribution curve of 1-3 of the honeycomb structure. Slope S _n of a cumulative pore volume distribution curve, determined a smooth approximation curve from a plot of measured data, but on the curve is where should seek a differential value at a minute interval of pore size, as is clear from FIG. 6 Since the cumulative pore distribution curve is sufficiently smooth and the measurement points are substantially equally spaced with respect to the logarithm of the pore diameter (logD _n ), the (n) th measurement point and the (n−1) th measurement point Even if the slope _Sn is obtained from the measured pore diameter at the measurement point and the measured value of the cumulative pore volume, there is almost no error. FIG. 7 shows the relationship between the pore diameter of each honeycomb structure thus obtained and the slope Sn of the cumulative pore volume distribution curve. In the cumulative pore volume distribution curve of FIG. Test No. 1 in which the honeycomb structure No. 1 had the highest Sn and the next steepest was obtained. Then high S _n 2 of the honeycomb structure, the slope was relatively moderate Test No. S _n of the honeycomb structure 3 was the smallest. The maximum values of Sn thus obtained, the measurement results of the porosity and the average pore diameter are shown in Table 2.

The end face of the ceramic honeycomb structure produced as described above is sealed with a sealing material 5 as shown in FIGS. 2 (a) and 2 (b), and a porous ceramic honeycomb filter is obtained. It was.
The filter characteristics of the obtained porous ceramic honeycomb filter were evaluated for pressure loss and breakage resistance. The results are shown in Table 2.
Here, the pressure loss is evaluated by the pressure loss before and after the inflow of the honeycomb filter when a predetermined flow rate of air is flowed in the pressure loss test stand. If the pressure loss exceeds a practically acceptable pressure loss with a pass (◯), it was determined to be a failure and indicated with (×). The breakage resistance is evaluated by the value of the A-axis compression strength ratio, and this is a conventional product level of 1.0, when it is 1.5 or more, it is a pass (◯), and when 2.0 or more is preferable ( In (◎), when it was less than 1.5, it was judged as rejected and indicated by (x). The A-axis compressive strength was measured according to the standard M505-87 “Testing method for ceramic monolithic carrier for automobile exhaust gas purification catalyst” established by the Japan Society for Automotive Engineers.
And as a comprehensive judgment, (○) indicates that both the pressure loss and breakage resistance are acceptable, and (◎) indicates that the judgment is (◎), and if any one fails (×) ).

Among the results shown in Table 2, test No. which is an example of the present invention. The ceramic honeycomb filter and a manufacturing method shown in 1-2, since the maximum value of the inclination _{S n} in a cumulative pore volume distribution curve is 0.7 or more, a porosity of 60-80%, an average pore diameter of 15 ~ Even with a porous material of 40 μm , the pressure loss was low and the breakage resistance was passed, and the overall judgment was (◯) and (◎).
Meanwhile, among the results shown in Table 2, a ceramic honeycomb filter and production method in Test No.3 of the comparative example, the maximum value of the inclination S _n in a cumulative pore volume distribution curve, in the range of pore diameter 15~30μm Although the pressure loss passed because it was below 0.7, the breakage resistance was rejected (x), and the overall judgment was (x).
As can be seen from the results in Table 2, when the overall judgment is made based on the results of pressure loss and breakage resistance, which are important characteristics as a particulate collection filter, the test No. which is an example of the present invention. Both the ceramic honeycomb filters 1 and 2 and the production method were filters satisfying pressure loss characteristics and breakage resistance.

Test No. 1 of Example 1 A plasticizable batch similar to 1 was prepared, and a cylindrical honeycomb structure was formed from this batch by a known extrusion method. At this time, the dimensions of the known mold were adjusted so that various partition wall thicknesses and the number of channels per 1 cm ² were obtained. Next, this formed body was dried and then fired in a temperature range of 1380 to 1420 ° C. to obtain various cordierite ceramic honeycomb structures 1 including the porous ceramic partition walls 3 and the through holes 2. The obtained honeycomb structure had a diameter of 143 mm and a length of 152 mm. As shown in 4 to 8, the wall thickness of the partition walls was 0.15 mm to 0.33 mm, and the number of flow paths per 1 cm ² was 5 to 5 types.
Hereinafter, the end face was sealed by the same method as in Example 1, and then pressure loss and breakage resistance, which are filter characteristics, were measured. The results are shown in Table 3. In addition, Test No. Both 4-8, porosity 65%, mean pore diameter 20.8%, the maximum value of the inclination _{S n} in a cumulative pore volume distribution curve was 1.12.

  As shown in Table 3, test No. which is an example of the present invention. In the ceramic honeycomb filters shown in 4 to 8, regardless of the partition wall structure, the comprehensive judgment of the filter characteristics was (◯) or (◎).

  Test No. used in Example 1 1 to 3 ceramic honeycomb filters were loaded with a catalyst on the surface and inside of the partition walls as follows.

  As a high specific surface area material, activated alumina having a center particle size of 5 μm and alumina sol were mixed with water, and the obtained filter was washed on the stirred activated alumina slurry. Thereafter, the excessively adhered slurry was removed, and coating was repeated to produce a filter with a coating amount of 60 g / L. Further, after being dried at 120 ° C., fired at 800 ° C., immersed in a chloroplatinic acid aqueous solution, dried at 120 ° C., fired at 800 ° C., and supported on the ceramic honeycomb filter. Got. The amount of platinum supported at this time was about 2 g / L.

  The pressure loss of the ceramic honeycomb filter after supporting the catalyst was measured by the same method as in Example 1. Furthermore, when a predetermined amount of carbon is injected at a predetermined flow rate at the pressure loss test stand and the honeycomb filter captures carbon, the pressure loss difference ΔP before and after carbon capture (pressure loss after carbon capture-before carbon capture) Pressure loss), and if the pressure loss difference ΔP is less than or equal to a practically acceptable value, it will be accepted (◯), and if the pressure loss exceeds a practically acceptable value, it will be rejected ( X). The results are shown in Table 4.

Among the results shown in Table 4, test No. which is an example of the present invention. In the ceramic honeycomb filter and the manufacturing method shown in 1-2, almost no increase in pressure loss due to catalyst loading was observed, and all the results of pressure loss passed (◯). On the other hand, test No. which is a comparative example. In the ceramic honeycomb filter and the manufacturing method shown in No. 3, an increase in pressure loss was recognized due to catalyst loading, and the result of pressure loss was rejected (x). In addition, Test No. which is an example of the present invention. In the ceramic honeycomb filter and the manufacturing method shown in FIGS. 1 and 2, the pressure loss difference ΔP before and after the carbon capture was less than a practically acceptable value and passed (◯). In the honeycomb filter and the manufacturing method shown in No. 3, ΔP exceeded the practically allowable value and was rejected (x). As described above, the maximum value of the inclination S _n in a cumulative pore volume distribution curve, ceramic honeycomb filter is 0.7 or more at a pore diameter of from 15~30μm, even after catalyst supporting, Ya increase in pressure loss It is clear that the pressure loss increase due to carbon capture is small and the filter performance is excellent.

(A) And (b) is the front view and side view which respectively show an example of a honeycomb structure. (A) And (b) is the front view and side view which respectively show an example of the filter which uses a honeycomb structure. Is an example graph illustrating the relationship between the pore diameter determined by mercury porosimetry and the slope S _n of a cumulative pore volume distribution curve. Is an example graph illustrating the relationship between the maximum value and the A-axis compressive strength ratio of the slope S _n of a cumulative pore volume distribution curve. 2 is a graph showing the particle size distribution of the pore former used in Example 1. Test No. 1 in Example 1 It is a graph which shows the relationship between the pore diameter of 1-3 test pieces, and a cumulative pore volume. Test No. 1 in Example 1 Is a graph showing pore diameter of 1-3 specimens and the relationship between the slope S _n of a cumulative pore volume distribution curve.

Explanation of symbols

1: Ceramic honeycomb structure, 2: Partition wall, 3: Through hole,
4: Ceramic honeycomb filter, 5: Sealing material,
a: slope S ₁ determined from the first and second measurement results in the cumulative pore volume distribution curve,
b: slope S ₂ determined from the second and third measurement results in the cumulative pore volume distribution curve,

Claims (5)

After adding at least a pore-forming material having a particle size distribution with an average particle size of 20 μm or more and a particle size distribution of 20 to 100 μm of 50% or more to a ceramic raw material powder, a batch in which water or the like is added and mixed is extruded. After that, it is included in the exhaust gas by plugging a predetermined flow path end portion of the ceramic honeycomb structure obtained by drying and firing and allowing the exhaust gas to pass through the porous partition walls that define the flow path. In the ceramic honeycomb filter for removing fine particles, the chemical composition of the main component of the porous ceramic constituting the porous partition wall is SiO ₂ : 42 to 56 mass%, Al ₂ O ₃ : 30 to 45 mass%, MgO: 12 ˜16% by mass, the main component of the crystal phase is cordierite, and the porous partition wall has a porosity of 60 to 80% and an average pore diameter of 15 to 40 μm when measured by mercury porosimetry. A maximum value of the slope S _n of a cumulative pore volume distribution curve of the barrier to the pore size in the n-th measurement point, is 0.7 or more at a pore diameter of from 15 to 30 [mu] m, the cumulative pore volume slope _{S n} is represented by the following formula of the distribution curve (1)
S _n = − (V _n −V _n−1 ) / (log (D _n ) −log (D _n−1 )) (1),
(However, D _n is the pore diameter (μm) at the (n) -th measurement point,
D _n-1 is the pore diameter (μm) at the (n-1) th measurement point,
V _n is the cumulative pore volume (cm ³ / g) at the (n) th measurement point,
V _n-1 is the cumulative pore volume (cm ³ / g) at the (n−1) -th measurement point. )
A ceramic honeycomb filter represented by: Ceramic honeycomb filter according to claim 1, wherein said maximum value of the inclination S _n in a cumulative pore volume of distribution curve of the porous partition walls is 0.9 or more. After adding at least a pore-forming material having a particle size distribution with an average particle size of 20 μm or more and a particle size distribution of 20 to 100 μm of 50% or more to a ceramic raw material powder, a batch in which water or the like is added and mixed is extruded. After that, it is included in the exhaust gas by plugging a predetermined flow path end portion of the ceramic honeycomb structure obtained by drying and firing and allowing the exhaust gas to pass through the porous partition walls that define the flow path. The ceramic honeycomb filter for removing fine particles, wherein the catalyst is supported on the porous partition wall surface and inside the porous partition wall, and the chemical composition of the main component of the porous ceramic constituting the porous partition wall There _SiO 2: 42 to 56 _{wt%, Al} 2 O 3: _30~45 wt%, MgO: at 12-16 wt%, the main component of the crystalline phase is cordierite, before Porous partition 60 to 80% of porosity as measured by mercury porosimetry, has an average pore diameter of 15 ～40Myuemu, the cumulative pore volume distribution curve of the barrier to the pore size in the n-th measurement point maximum value of the slope _{S n} is 0.7 or more at a pore diameter of from 15 to 30 [mu] m, gradient _{S n} of the cumulative pore volume distribution curve the following formula (1)
S _n = − (V _n −V _n−1 ) / (log (D _n ) −log (D _n−1 )) (1),
(However, D _n is the pore diameter (μm) at the (n) -th measurement point,
D _n-1 is the pore diameter (μm) at the (n-1) th measurement point,
V _n is the cumulative pore volume (cm ³ / g) at the (n) th measurement point,
V _n-1 is the cumulative pore volume (cm ³ / g) at the (n−1) -th measurement point. )
A ceramic honeycomb filter represented by: A batch obtained by adding a pore former, water and the like to ceramic raw material powder is extruded and then dried and fired to plug the predetermined flow path end of the ceramic honeycomb structure and partition the flow path. A method for manufacturing a ceramic honeycomb filter that removes fine particles contained in exhaust gas by allowing exhaust gas to pass through a porous partition wall, wherein the pore former has an average particle diameter of 20 μm or more and a particle diameter of 20 to 20 μm. A method for producing a ceramic honeycomb filter, wherein 100 μm has a particle size distribution occupying 50% or more and is substantially spherical and hollow . The chemical composition of the main component of the porous ceramic constituting the porous partition walls is SiO ₂ : 42 to 56 mass%, Al ₂ O ₃ : 30 to 45 mass%, MgO: 12 to 16 mass%, The component is cordierite, and the porous partition walls of the ceramic honeycomb filter have a porosity of 60 to 80% and an average pore diameter of 15 to 40 μm when measured by mercury porosimetry, and are fine at the nth measurement point. maximum value of the slope S _n of a cumulative pore volume distribution curve of the barrier to hole diameter is 0.7 or more at a pore diameter of from 15 to 30 [mu] m, gradient S _n of the cumulative pore volume distribution curve the following formula ( 1)
S _n = − (V _n −V _n−1 ) / (log (D _n ) −log (D _n−1 )) (1),
(However, D _n is the pore diameter (μm) at the (n) -th measurement point,
D _n-1 is the pore diameter (μm) at the (n-1) th measurement point,
V _n is the cumulative pore volume (cm ³ / g) at the (n) th measurement point,
V _n-1 is the cumulative pore volume (cm ³ / g) at the (n−1) -th measurement point. )
The method for manufacturing a ceramic honeycomb filter according to claim 4, wherein:

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