JPS6251909B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new and useful aluminum titanate honeycomb.

Exhaust gas from internal combustion engines such as automobiles contains harmful components such as carbon monoxide and hydrocarbons, and together with exhaust gas from general industrial equipment, they cause air pollution. It is necessary to render harmful components harmless, and a catalyst device is considered to be the most effective method.

As a catalyst for purifying exhaust gas from automobiles, etc.,
Currently, catalysts are generally divided into two types: pellet-like catalysts and honeycomb-like monolithic catalysts that are partitioned with thin ceramic walls so that a large number of gas flow passages penetrate in one or two directions. has been adopted as a practical product, and the latter honeycomb-shaped ceramic molded body has advantages such as low exhaust gas pressure drop, high wear resistance under vibration, and light weight and small size. Its use has increased in recent years due to its advantages and increased durability of catalysts.

However, due to their structure, these honeycombs do not have sufficient resistance to thermal shock compared to granular materials, so they must first be made of low-expansion, heat-resistant ceramics with low thermal expansion and contraction. Of course, this is one of the major limitations that prevents ceramic honeycombs from being fully used in this type of application.

So far, materials that are widely known for ceramic honeycomb include alumina-silica (mullite), alumina, zirconia-alumina, zirconia-magnesia, mullite, zirconia-silica (zircon), zircon-mullite, titania, and magnesia. - alumina spinel,
Zirconia and other special materials such as silicon nitride (Si ₃ N ₄ ) made of non-oxide ceramics and carbon (C) have also been proposed, but magnesia, alumina, silica (2MgO,
2Al ₂ O ₃・5SiO ₂ : cordierite), lithium alumina silica (Li ₂ O・Al ₂ O ₃・nSiO ₂ ; n: 2
-8, β-spodiumene, etc.) have rarely been used practically, except in rare cases.

The reason for this is that many materials have too large a coefficient of thermal expansion or are oxidized and consumed at high temperatures.
Improvements to these materials have recently become more important as more severe usage conditions are required, and from this perspective there is little hope for these materials in the future.

On the other hand, the material most widely used at present is the aforementioned cordierite material, which has the characteristics of low expansion as a ceramic (coefficient of thermal expansion of 0.12 to 0.3% at 1000°C) and relatively good high temperature stability. (difficult to decompose).

In addition, the β-spodiumene composition described above has a lower expansion rate than cordierite (− at 1000℃).
0.1 to -0.2%), but the usable temperature is low at 1200℃ or less, and now that higher heat resistance is required, it is almost no longer used, and it is unlikely that it will be used in the future. .

Although cordierite honeycombs are currently useful, they also have some problems.

First of all, there is a demand for higher heat resistance, which is required for engine improvement or for durability that can withstand instantaneous high temperatures (e.g., a blow-off) or longer-term use. One is the requirement for greater thermal shock resistance.

On the other hand, the following physical properties (material properties) as a molded body are required for a ceramic honeycomb serving as a catalyst carrier.

That is, high material strength is required because a high porosity is required to support the catalyst, and the trend is for honeycomb walls to be thinner in order to use expensive catalysts more effectively.

This problem has not been solved in a desirable manner so far, since it is difficult to satisfy both properties since the strength generally decreases when a high porosity is attempted.

From these viewpoints, the present inventors have conducted various studies and researches in order to develop a ceramic honeycomb that can solve or improve all or most of the conventional problems at the same time, and have succeeded in almost satisfactory development. It is.

That is, to put it simply, the present invention successfully combines the properties of high heat resistance, high porosity, high compressive strength, and low coefficient of thermal expansion, all of which are difficult to achieve simultaneously, making it suitable as a ceramic honeycomb used particularly for purifying automobile exhaust gas. We have succeeded in providing a new and useful ceramic honeycomb.

Specifically, the present invention provides a fired honeycomb having a large number of flow passages partitioned by thin walls, in which the material forming the fired honeycomb has a main component in terms of chemical composition. The aluminum titanate composition consists of 80% or more by weight, and 3 to 15% by weight of SiO ₂ , La ₂ O ₃ ,
The gist of the present invention is an aluminum titanate honeycomb characterized in that one or more selected from CeO ₂ and Y ₂ O ₃ is present in an amount of 0.5% to less than 2%.

The present invention will be described in detail below, but first, what is the aluminum titanate (hereinafter abbreviated as ALTITA) honeycomb used in the present invention and its uses will be explained.

First, in this specification, a honeycomb has a fired honeycomb structure having a large number of gas flow passages divided by thin walls, and the cross-sectional shape of the gas flow passages perpendicular to the gas flow direction is 6. It is not limited to a rectangular shape, and various shapes such as an octagonal, quadrangular, triangular, and circular shape are possible, and typical ranges of the opening (size of the flow path, thickness of the thin wall, etc.) will be described later.

In addition, the Altita honeycomb of the present invention was developed as an optimal catalyst carrier for purifying exhaust gas from automobiles due to the above-mentioned circumstances, but it can also be used as a catalyst carrier for purifying exhaust gas from industrial equipment. It can also be used for purposes other than carriers.
Examples include heat exchange carriers, burner tiles, radiant walls, heaters, thermal reactors, supercapacitors, thermal insulation structures, orifices for hot fluids, and the like.

In the honeycomb of the present invention, as described above and below, the main composition of the fired material is chemically composed of altita (Al ₂ O ₃ ·TiO ₂ ), and specific components include SiO ₂ and La ₂ It contains a specific amount of any one of O ₃ , CeO ₂ and Y ₂ O ₃ and has predetermined material properties.

The material properties brought about by the selection and blending of specific compositional components in the present invention are usually incompatible in manufacturing, and Alchita, which was selected as the material of the present invention, was no exception. For example, in Alchita, the coefficient of thermal expansion normally decreases as sintering progresses, but a material with a large porosity that has not been sufficiently sintered has a high coefficient of thermal expansion and a low strength.

The present invention mainly solves these problems by selecting Altita and adding a specific amount of SiO _{2 and}
The problem was solved by specifying the blending of components such as La ₂ O ₃ , Y ₂ O ₃ , CeO ₂ , Fe ₂ O ₃ and, more preferably, the blending ratio of Al ₂ O ₃ and TiO ₂ .

It is known that the Alchita material does not gain strength unless it is sintered, and that the _SiO2 component is one of the effective ingredients for normal sintering, but until now I had never thought about forming honeycombs using Alchita. I'm not sure whether such a product can be obtained practically by adding SiO ₂ , and what's more, in addition to SiO ₂ , there are also La ₂ O ₃ , Y ₂ O ₃ , CeO ₂ , Fe ₂ O ₃ I could never even think of adding something like that. This is due to _{the fact} that Altita has not received much attention as a practical material due to _its poor _stability at high _temperatures .
By specifying the amounts of CeO ₂ and Fe ₂ O ₃ , they were able to successfully provide a molded honeycomb with the desired characteristics described above.

Up to now, the amount of SiO ₂ resulting in the honeycomb of the present invention has been 3 to 15%, particularly 4 to 10% by weight (hereinafter the same unless otherwise specified) as a chemical component in the fired honeycomb. It is.

This is because if the content of SiO ₂ is small, the strength will be low, and if the content is large, the coefficient of thermal expansion will become large, making it impossible to realize the characteristics of an Altitan honeycomb.

Although the physical properties of the altitic honeycomb of the present invention will be described in detail later, we will first discuss the manufacturing method for producing such a honeycomb, which combines SiO ₂ with La ₂ O ₃ , Y ₂ O ₃ , CeO ₂ , and Fe ₂ O ₃ . and
The description will focus on a desirable manufacturing method that takes particular consideration to the Al ₂ O ₃ and TiO ₂ ratios.

A preferred method for obtaining the honeycomb of the present invention is as follows:
By pushing a ceramic plastic composition containing ARCITA as a main component or at least a raw material that can form an ARCITA composition as a main raw material through a die (mold) that can be extruded into a honeycomb shape, a thin wall is formed in the extrusion direction. By molding it into an integrated honeycomb structure with a large number of gas flow passages partitioned by , drying and firing this molded body, the material of the molded body mainly contains Alchita composition,
It contains a specific SiO ₂ component and at least one or more components of La ₂ O ₃ , CeO ₂ and Y ₂ O ₃ , and the material properties of the honeycomb fired from this include the coefficient of thermal expansion as a property in the extrusion direction. This method makes it possible to obtain a ceramic honeycomb with a compressive strength of 350 Kg/cm ² or more when the aperture ratio is converted to 0, and a porosity of 35% or more at 1000°C. A composition is prepared.

Here, the ceramic plastic composition is a refractory raw material mixture whose main raw material is pre-synthesized Alchita or a raw material that can produce Alchita by firing after forming a honeycomb, and to which is added a raw material that produces a component to be blended as a specific component. It is a composition that has fluidity so that it can be pushed through an extrusion molding die. To impart this fluidity or plasticity, an organic polymer such as methyl cellulose or starch may be used as a viscosity regulating substance, or a mixture of clay and water may be used.

In any case, as will be described later, it is desirable to incorporate clay in order to impart plasticity and to provide high strength to the honeycomb of the present invention.

In addition, in order to reduce the coefficient of thermal expansion of the fired honeycomb, sintering with a certain degree of firing shrinkage is unavoidable for the plastic composition, and the porosity is 35 to 45.
%, it is preferable to add a porosity imparting material in order to obtain a sintered body with low expansion and high strength.

As the porosity imparting material, the aforementioned methyl cellulose added as a viscosity regulating substance is also effective, but other materials such as cellulose may also be mixed in.

Incidentally, these sintered materials and porosity imparting bodies may be added in advance when synthesizing ALTITA, which will be described later. It is also advantageous to add it during synthesis.

Each component that brings about the present invention will now be explained.

First, the refractory raw materials that are the main raw materials of the ceramic plastic composition will be explained. These are the alumina (Al ₂ O ₃ ) raw materials that produce Altita and the titania (TiO ₂ ) raw materials. A desirable method in the present invention is to prepare all or most of Altita as a pre-synthesized raw material when blending it into the ceramic plastic composition.

Here, we will discuss the synthesis of Altita. It is synthesized by molding a mixture of an alumina raw material, a titania raw material, a sintering material, a thermal decomposition inhibitor, a binder, etc. into an appropriate shape, and then firing it.

Although alumina (Al ₂ O ₃ ) powder, bauxite powder, and the like can be used as the alumina raw material, it is most desirable to use aluminum hydroxide as the starting raw material, which produces alumina as an oxide upon firing. This is because the use of aluminum hydroxide is advantageous in terms of raw material cost, raw material purity, ease of synthesis, etc., and it is easy to obtain honeycombs with high physical properties.

As a titania raw material, anatase type synthetic TiO ₂ is usually used as a TiO ₂ compound, but rutile sand powder may also be used.

Further, the blending ratio of Al ₂ O ₃ and TiO ₂ is desirably in the range of 1.05:0.95 to 0.80:1.20 in terms of molar ratio with respect to the theoretical composition. This is Al ₂ O ₃ :TiO ₂ =1.05:
As the amount of Al ₂ O ₃ increases from 0.95, the coefficient of thermal expansion increases; on the other hand, from Al ₂ O ₃ :TiO ₂ =0.80: _1.20
This is because as the amount increases, the strength decreases, and the above range is also preferable for high temperature stability in relation to other components.

The sintering of Altita materials made from these raw materials or synthesized requires SiO ₂ as well as La ₂ O ₃ , Y ₂ O ₃ , CeO ₂ ,
Addition of Fe ₂ O ₃ etc. is preferably necessary in advance,
It has been found that the present invention can be achieved by giving sufficient consideration to the amount of the compound as described below.

That is, as mentioned above, the content of the _SiO2 component in the fired honeycomb needs to be 3 to 15%, preferably 4 to 10%.
In particular, it has been found that it is advisable to add a portion of these _SiO2 components, specifically 10 to 60%, in advance during the production of aluminum titanate synthetic raw materials used as refractory raw materials for ceramic plastic compositions. .

That is, the SiO ₂ component is 10 to 60
%, and the remaining 90 to 40% is blended as clay, etc., separately from the synthesized Alchita when preparing a ceramic plastic composition for extrusion.By doing this, it becomes an outstanding material for honeycomb. This makes it possible to advantageously provide a honeycomb that has all the characteristics. Furthermore, it has been found that this distribution of SiO ₂ has the most excellent effect on the strength of the sintered body.

Here, to explain La ₂ O ₃ , CeO ₂ , and Y ₂ O ₃ which are essential components other than SiO ₂ for producing the honeycomb of the present invention, these components are of course used as sintering materials in the present invention. It acts synergistically with SiO ₂ to suppress the decomposition of Alchita at high temperatures, that is, it effectively acts as a high-temperature stabilizer and as a component that provides high-temperature strength.

These components, unlike SiO ₂ , are preferably added in a specific amount in advance when synthesizing the Altita raw material, but in some cases, they may be added to the plastic composition before honeycomb forming. It is also possible to mix it in.

These ingredients are usually combined in the following form:
Although it is added as an oxide, it may of course be added as a compound that becomes an oxide upon firing.

When these components were further explained, La ₂ O ₃ was found to be the most suitable among them.

That is, La ₂ O ₃ has an excellent effect on the strength of the sintered body by acting together with SiO ₂ , but it also acts synergistically with SiO ₂ and has an excellent effect on stability at high temperatures. It was found that it brings about Conventionally, altitic honeycombs had a fatal drawback in terms of stability at high temperatures, and for this reason, they could not be considered for industrial use. i.e. 900
Al ₂ O ₃・TiO ₂ is Al ₂ O ₃ in the range from ℃ to 1400 ℃
It has the disadvantage that it decomposes into TiO ₂ and loses properties such as low expansion and strength. This tendency was particularly noticeable in a reducing atmosphere.

In the present invention, in order to compensate for these drawbacks, as a result of various studies, SiO ₂ and La ₂ O ₃
In combination with this, we succeeded in improving the high-temperature stability of Altita honeycomb without impairing its low expansion properties.

Similar effects have been confirmed by using Y ₂ O ₃ or CeO ₂ instead of La ₂ O ₃ , but there is no problem in adding these at the same time.

The appropriate amount of these components to be added is 0.5% to less than 2% in the fired honeycomb.

This means that 0.5% or less is not sufficient for the effect, while 2% or more is not particularly necessary and will be discussed later.
This is not particularly necessary when the Fe ₂ O ₃ component is further added, because in some cases it may cause problems such as increasing thermal expansion and lowering the melting point.

Here, to explain the addition of Fe ₂ O ₃ component, in addition to the effect as a sintering agent, the addition of Fe ₂ O ₃ has
SiO ₂ , La ₂ O ₃ if the usage condition is an oxidizing atmosphere
It acts synergistically with other substances and exhibits an extremely excellent effect as a high-temperature stabilizer, but in a reducing atmosphere it has the effect of promoting decomposition. Therefore, it is an effective component depending on the purpose of use, and when used, the amount present is preferably 0.5% or more.La ₂ O ₃ , CeO ₂ ,
The preferred range for the total amount with Y ₂ O ₃ is 1.0 to 5%.

Here, if the calcination temperature for synthesizing ALTITA from raw materials to which these necessary components are added, that is, obtaining ARTITA clinker, is too high, it will not have much effect on the coefficient of thermal expansion of the clinker itself, but for some reason It was found that the thermal expansion coefficient of the calcined product honeycomb tends to increase, and that if it is too low, it is not preferable because altitas are not sufficiently generated. Specifically, the temperature is 1450 to 1600°C, preferably 1500 to 1550°C.

It is preferable to use the thus obtained Altita clinker as a refractory raw material by pulverizing it into as fine a powder as possible, and in the present invention, it is preferable to use 80% or more of it as a powder of 300 mesh or less. The reason for this is that keeping the powder to such a fine level is particularly advantageous in stable extrusion molding of honeycombs with a thin wall thickness (for example, 0.15 to 0.2 mm).

The prepared ceramic plastic composition is then fed to a known extrusion molding device and formed into a honeycomb shape.The blending ratio of the refractory raw material in the plastic composition is 80 to 95%.
On the other hand, it is advantageous to prepare the clay in an amount of 20 to 5%, particularly 85 to 95% of the former and 15 to 5% of the latter.

The honeycomb formed through an extrusion device is then fired, and the firing temperature is 1350~1350℃.
The temperature is 1500°C, preferably 1380 to 1450°C. This is because if the temperature is too high, the porosity required of the catalyst-supporting honeycomb will be small, and if the temperature is too low, the coefficient of thermal expansion will not be small.

As described above, according to the present invention, a fired honeycomb having physical properties suitable for a honeycomb, which have not been obtained at all in the past, has been obtained.The physical properties will be explained below.

First, since the honeycomb produced by the present invention has a composition consisting of 80% or more of altita, it is essentially made of a material with a higher melting point than cordierite honeycomb, which is a typical example of conventional honeycomb, and therefore cannot be used normally. However, it can withstand continuous use at high temperatures of 1400°C or higher, even instantaneous temperatures of around 1650°C, and the safe operating temperature of cordierite honeycomb is
It has excellent heat resistance up to 1300℃.

Next, the coefficient of thermal expansion can be obtained as a property along the gas flow path, which is extremely low at 0.15% or less at 1000°C, compared to the lowest coefficient of thermal expansion of cordierite honeycomb, which is 0.12%. However, depending on the purpose, it is possible to obtain a content of less than 0.1% or even less than 0.09%.

This property indicates that it can withstand repeated severe thermal shocks for a sufficiently long period of time as a purifying honeycomb for automobiles.

In addition, the material properties of the fired honeycomb include:
The porosity of the present invention's altita honeycomb is 35%.
Although it has sufficient porosity necessary for catalyst support, it has a compressive strength (converted to 0 open area in the gas flow direction) of 350 kg/cm ² or more, which makes it more heat resistant than cordierite honeycomb. It has characteristics that are usually difficult to achieve, such as superior thermal shock resistance.

Regarding the porosity, it is undeniable that if the porosity becomes too large, the required strength will decrease, so unless there is an improvement in the holding method that allows the porosity to be held in a car so that it can be used even if the strength is low, or the strength It is best to keep it below 45%, as it will be difficult to use it for purposes other than those that do not require much of it.

The structure of the ceramic honeycomb itself, which has a large number of gas flow passages partitioned by thin walls and has such properties, can be easily obtained in the following range.

That is, the thickness of the thin wall is 0.08 to 0.5 mm, the number of holes in the flow passage is 40 to 200 per cm ² , and the cross-sectional aperture ratio perpendicular to the gas flow direction is 50 to 85%.

These are not only comparable in properties to the honeycombs currently in use, but also have the properties of ordinary materials ranging from 800 to
Although the strength of the honeycomb at the operating temperature of 1000°C decreases due to the material, the honeycomb of the present invention has the characteristic that the strength is greater than that at room temperature.
It also has properties that make it more durable during use than cordierite honeycomb.

As described above, the present invention has achieved high heat resistance, high porosity, high compressive strength, and low expansibility, all of which are required for ceramic honeycombs for catalyst carriers, all of which have been difficult to achieve simultaneously. It provides a honeycomb, and its practical value is enormous.

The present invention will be further explained below with reference to Examples.

Example 1 Aluminum hydroxide, synthetic anatase, clay,
Red red iron, lanthanum oxide, Metrose (trade name of methylcellulose manufactured by Shin-Etsu Chemical Co., Ltd.), and water were mixed and kneaded to form a rod-shaped body of 60 mmφ, and dried at 1550℃.
Calcined for 5 hours, SiO ₂ 3%, Fe ₂ O ₃ 2%, La ₂ O ₃ 1%
A synthetic aluminum titanate clinker consisting mostly of Al ₂ O ₃ .TiO ₂ was obtained. This synthetic clinker was pulverized to less than 300 mesh and used as a raw material for synthetic aluminum titanate. (Hereinafter referred to as synthetic Alchita raw material.) Next, 92% of this synthetic Alchita raw material, clay 8
% refractory raw material, 10 parts of cellulose powder and 5 parts of methylcellulose were added and kneaded with water to prepare a ceramic plastic composition, and this composition was passed through a known extrusion die for forming honeycomb. The gas flow passages were formed into a honeycomb shape having a large number of gas flow passages each having a square cross-sectional shape divided by thin walls. This molded product was fired at a maximum temperature of 1400°C to obtain a honeycomb with the following properties.

Composition of Γ honeycomb material Al ₂ O ₃・TiO ₂ 89.0% La ₂ O ₃ 1.0% SiO ₂ 6.5% Others 0.5% Fe ₂ O ₃ 2.0% Γ material characteristics Porosity 38% Coefficient of thermal expansion 0.08% (extrusion direction, 1000℃ ) Compressive strength 445Kg/cm ² (Extrusion direction, opening ratio 73%
120Kg/cm ² ) Heat resistance (Note 1) Thermal shock resistance over 1600℃ (Note 2) Over 900℃ Structural wall of the Γ honeycomb itself Thickness 0.15mm Number of holes in flow passages 95/cm ² Cross-sectional aperture ratio 73% (Note 1) Place a 2cm square honeycomb dice sample into a furnace at a specific temperature for 3 minutes and measure the temperature with no particular change.(Note 2) Raise the furnace temperature in 100℃ increments and maintain it at a specific temperature. A temperature difference durability test was conducted in which one cycle of air cooling in a furnace was repeated three times, and the temperature at which no abnormality occurred was measured. It will be understood from the following representative properties of typical cordierite honeycombs that are currently commercially available and commonly used.

Porosity 32% Thermal expansion coefficient 0.18% (1000℃) Compressive strength 450Kg/cm ² (121Kg/cm2 at 73% aperture ratio)
cm ² ) Heat resistance (Note 1) 1400 or less Thermal shock resistance (Note 2) 600°C or less Example 2 When producing the synthetic Altita raw material in Example 1, a slightly larger amount of clay was blended to create a synthetic Altita with a SiO ₂ content of 6.5%. Raw material Ia was prepared, and a ceramic plastic composition was prepared by adding water to 5 parts of methyl cellulose without adding clay and 10 parts of cellulose powder to 100 parts of this synthetic Altita raw material Ia, and a honeycomb was fired in the same manner as in Example 1. I got it.

Compared to the honeycomb of Example 1, many properties did not change much, but the compressive strength was slightly lower, about 350 kg/cm ² , and it may be subject to limitations depending on the usage conditions for the purpose of the present invention. Although it was unavoidable, it was fully usable depending on the purpose.

Example 3 A fired honeycomb was produced under the same conditions as in Example 1 except that 1.5% Y ₂ O ₃ was added instead of La ₂ O ₃ .

The properties of this honeycomb include a porosity of 37% and a coefficient of thermal expansion.
0.05% (1000℃), compressive strength 460Kg/cm ² (porosity 73
% was 125Kg/cm ² ).

Example 4 A fired honeycomb was produced under the same conditions as in Example 1 except that 1.0% CeO ₂ was added instead of La ₂ O ₃ .

The properties of this honeycomb include a porosity of 41% and a coefficient of thermal expansion.
0.13% (1000℃), compressive strength 370Kg/cm ² (porosity 73
90Kg/cm ² ).

Example 5 In Example 1, red iron was not used, but SiO ₂ 5%,
After creating a synthetic AltiTa raw material' consisting of 1.5% La ₂ O ₃ and the remainder being almost aluminum titanate,
Using the same method as in Example 1, 100 parts of the refractory raw material consisting of 90% synthetic Altita raw material and 10% clay was added.
A fired honeycomb was obtained.

This honeycomb has a higher porosity of 43% than that of Example 1, but a compressive strength of 390 kg/
Other than a slight decrease in ^cm2 , many properties did not change much.

On the other hand, in contrast to Example 1 regarding high-temperature stability, it showed better properties than Example 1 in a reducing atmosphere, but slightly inferior performance in an oxidizing atmosphere. However, none of these problems caused any practical problems.

Claims (1)

[Scope of Claims] 1. In a fired honeycomb having a large number of flow passages partitioned by thin walls, the material forming the fired honeycomb is chemically composed of aluminum titanate as a main component. % or more, and 3 to 15% SiO ₂ by weight,
One or more selected from La ₂ O ₃ , CeO ₂ and Y ₂ O ₃
An aluminum titanate honeycomb with high porosity and high compressive strength, characterized by being present in an amount of 0.5% to less than 2%. 2 Chemical composition: 85% aluminum titanate
The aluminum titanate honeycomb according to claim 1, wherein the SiO ₂ content is 4 to 10%. 3. As a chemical component of aluminum titanate,
The molar ratio of Al ₂ O ₃ and TiO ₂ is 1.05:0.95~0.8:
Claim 1 or 2 that is within the scope of 1.2
Aluminum titanate honeycomb as described in . 4 In terms of chemical composition, Fe ₂ O ₃ is further added to 0.5% by weight.
Contains the above and the total amount of Fe ₂ O ₃ and one or more selected from La ₂ O ₃ , CeO ₂ and Y ₂ O ₃ is 1 to 5% by weight
An aluminum titanate honeycomb according to any one of the existing claims. 5 The wall thickness of the thin wall that partitions the flow path is 0.08 to 0.5
mm, the number of holes in the flow path is 40 to 200 per ^cm2 ,
The aluminum titanate honeycomb according to claim 1, wherein the aluminum titanate honeycomb has a cross-sectional aperture ratio perpendicular to the flow direction of 50 to 85%. 6 The material properties of the fired honeycomb in the direction along the flow path are such that the coefficient of thermal expansion is 1000℃.
0.15% or less, compressive strength is 350Kg/cm2 ^or more when the aperture ratio is converted to 0, and the porosity is 35%.
The aluminum titanate honeycomb according to claim 1 or 5, which is the above. 7. The aluminum titanate honeycomb according to claim 6, which has a coefficient of thermal expansion of 0.1% or less at 1000°C. 8 Claim No. 6 in which the porosity is 45% or less
Aluminum titanate honeycomb as described in .