JPH0568882A - Production of honeycomb structural catalyst carrier consisting essentially of titanium oxide composition - Google Patents

Abstract

PURPOSE:To provide a producing method for a titanium oxide system honeycomb structural catalyst carrier consisting of not less than 100 cells having excellent strength properties and a specific surface area. CONSTITUTION:After a metatitanic acid hydrate is molded, calcined and crushed, then, this crushed material is incorporated with barium titanate, molding auxiliary and water and kneaded, moreover, this kneaded material is extrusion molded to a honeycomb type structure and dried, and, thereafter, the honeycomb type structural body is calcined at 500-800 deg.C to produce a honeycomb structural carrier consisting essentially of a titanium oxide composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a honeycomb structure catalyst carrier, which mainly comprises a titanium oxide composition having excellent properties as a catalyst carrier.

[0002]

2. Description of the Related Art Since a catalyst carrier having a honeycomb structure has a large number of parallel flow passages, it has characteristics that a pressure loss is small when flowing a fluid and an apparent surface area per unit volume is large. It is widely used as a catalyst carrier for exhaust gas treatment.

For example, nitrogen oxides in exhaust gas (hereinafter referred to as N
As a catalyst for redox of (O _x ), an active metal such as platinum, palladium, copper, chromium or vanadium is carried on a carrier obtained by coating the surface of a honeycomb structure ceramic substrate such as cordierite or mullite with alumina, silica-alumina or the like. Known catalysts are known.

However, sulfur oxides in these catalysts in the exhaust gas (hereinafter, referred to as SO _x) when coexist SO _x
Due to the poisoning of, it causes a drawback that it cannot withstand long-term use. So far, in order to solve the problem of catalyst performance deterioration for exhaust gas containing SOx, a catalyst in which vanadium, chromium, etc. are supported on a titanium oxide carrier of anatase type structure is excellent without being poisoned by NO _x. It is known that it retains the reducibility of NO _x and has little deterioration.

[0005]

Generally, as a method for obtaining a honeycomb structure catalyst carrier having a practical strength of titanium oxide, titanium oxide is mixed with fibers such as rock wool and alumina, a molding aid and water. In addition, a method of obtaining a honeycomb structure carrier from a kneaded mixture has been proposed, but a preferable honeycomb structure can be obtained if the number of cells of the honeycomb structure (the number of squares per square inch) is 50 cells or less. However, when the number of cells is 100 cells or more, there is a drawback in that the above-mentioned fiber may be clogged in a die for forming a honeycomb structure and a preferable honeycomb structure cannot be obtained.

Generally, the practical breaking strength as a catalyst carrier is 1 cm long, 1 cm wide, and 2 c long for a honeycomb structure carrier.
It is necessary to cut 2 m or more in a size cut into m, but in the case of a titanium oxide type carrier, since the melting point of titanium itself is high, bonding between particles is difficult to occur at low temperature,
To obtain the required strength, firing must be performed at a temperature of 900 ° C or higher. However, on the other hand, when titanium oxide is heated to a high temperature, it transfers heat from the anatase structure to the rutile structure, and the specific surface area is remarkably reduced, which is a minimum value of 10 m ² which is generally considered to be suitable as a catalyst carrier. Since / g is greatly divided, a new problem arises that the catalyst carrier does not function sufficiently.

The present invention solves various problems as described above in the honeycomb structure catalyst carrier of the titanium oxide composition, and has 100 cells having excellent strength characteristics and specific surface area.
It is an object of the present invention to provide a method for efficiently producing the above titanium oxide-based honeycomb structure catalyst carrier.

[0008]

Means for Solving the Problems The present invention for solving the above-mentioned problems and achieving the above-mentioned objects is as follows. After molding metatitanic acid hydrate, drying and firing are carried out, and then, after crushing this, Barium titanate, a molding aid, and water are added to this crushed product, and the mixture is kneaded. The kneaded product is extruded into a honeycomb structure, dried, and fired at a temperature of 500 to 800 ° C. It is a method for manufacturing a honeycomb structure carrier mainly composed of a titanium composition. In the present invention, sulfate SO ₄ contained in the metatitanic acid hydrate used.
Is preferably 5 wt% or less, and the preferable addition amount of barium titanate to be added to the calcined crushed product of metatitanic acid hydrate is preferably in the range of 5 to 25 wt%.

[0009]

The details of the present invention and the operation thereof will be described in more detail below. That is, the metatitanic acid hydrate having an SO ₄ content of 5% by weight or less used in the present invention is metatitanium which is an intermediate when titanium dioxide is obtained by the sulfuric acid method which is widely known as a method for producing titanium oxide. It is obtained by filtering and washing the acid hydrate slurry. Next, the metatitanic acid cake thus obtained is kneaded by heating in a kneader with a heating jacket, and extruded using a molding machine having a die having a desired shape, and then heated to a temperature of about 80 to 120 ° C. The titanium oxide composition is obtained by drying, and further calcination in a temperature range of 400 to 800 ° C., preferably 400 to 700 ° C. for about 2 hours to crush the fired product to an average particle size of 10 to 40 μm. A powder of the product is obtained.

[0010] The sulfate radical contained in metatitanic hydrate in the present invention the reason for limiting to 5% by weight or less SO _4, when used metatitanic hydrate SO ₄ content of more than 5 wt% This is because the specific surface area of the catalyst carrier thus obtained is remarkably reduced, and a catalyst carrier having an appropriate specific surface area cannot be obtained, which is not preferable. In addition, metatitanic acid hydrate is not directly used in the production of the honeycomb structure, and the titanium oxide powder obtained through the steps described above has a honeycomb structure obtained by using metatitanic acid hydrate in which cracks are not generated. This is because a preferable catalyst carrier having a honeycomb structure cannot be obtained.

The calcination temperature of the metatitanic acid hydrate for obtaining the titanium oxide composition powder is set in the range of 400 to 800 ° C. When the calcination temperature is lower than 400 ° C., the oxidation in the composition obtained is performed. This is because titanium does not exhibit an anatase type structure, and when the temperature exceeds 800 ° C., the specific surface area of the catalyst carrier obtained by thermal transfer to the rutile type structure is significantly reduced.

The calcination product is crushed so that the average particle size is in the range of 10 to 40 μm.
This is because if it exceeds 0 μm, the moldability decreases, and it becomes impossible to obtain a preferable honeycomb structure in the subsequent honeycomb structure forming step, and if it is less than 10 μm, the crushing step takes too much time and productivity decreases. Is.

The titanium oxide composition powder thus obtained is added with 5 to 25% by weight of barium titanate, a small amount of a molding aid and water, sufficiently kneaded and plasticized, and then vacuum extrusion molded. A honeycomb structure is obtained by extrusion molding with a honeycomb die of a desired shape using a machine. Then, the honeycomb structure is dried in an atmosphere having a temperature of about 70 to 90 ° C. and a humidity of about 80% or more to obtain a temperature of 500 to 8
The honeycomb structure catalyst carrier is obtained by firing in the temperature range of 00 ° C.

Step of obtaining a honeycomb structure in the present invention
In the above, barium titanate was added to the titanium oxide composition powder.
Adding strengthens the skeleton of the resulting honeycomb structure
This is because barium titanate used for this
Is BaTiO_Three, Ba₆Ti ₁₇O₄₀, Ba_FourTi
_ThirteenO_ThirtyBaO and TiO etc._TwoAnd the compound with
However, BaTiO 3 is the most preferable of these._ThreeIs.
Adjust the addition amount of barium titanate to the range of 5 to 25% by weight.
Is less than 5% by weight, the honeycomb structure catalyst obtained is
If the breaking strength of the body is not sufficient and it exceeds 25% by weight, a comparison table
Because the area decreases and the performance as a catalyst carrier decreases.
is there.

Although the reason why the breaking strength of the honeycomb structure catalyst carrier obtained by adding barium titanate to the titanium oxide composition powder is improved is not clear, the composition in which titanium oxide and barium titanate are bound to each other is not known. If the amount of titanium oxide in the titanium oxide composition is in a large excess, an oxygen deficiency structure is formed, whereby the sintering action of titanium oxide itself is promoted, or 5% by weight or less of SO ₄ contained in the titanium oxide composition is contained. It is presumed that this is because the barium titanate added is partially bonded to barium to form barium sulfate, and strong interparticle bonds can be formed around this barium sulfate.

Further, as a molding aid, a binder, a plasticizer,
A water-soluble cellulose derivative suitable for molding a honeycomb structure such as a lubricant, for example, a carboxylated cellulose derivative, a hydroxyethylated cellulose derivative, a hydroxypropylated cellulose derivative, a carboxymethylhydroxypropylated cellulose derivative, an aminated cellulose derivative. An organic binder blended with etc. is used,
The addition amount is preferably in the range of about 5 to 15% by weight. If the addition amount is less than 5% by weight, a preferable honeycomb structure cannot be obtained, and if the addition amount is more than 15% by weight, it takes time to decompose carbon in the organic matter when the honeycomb structure is dried and fired, so that the production efficiency is improved. It is not good.

The molded honeycomb structure has a humidity of 80%.
The reason for drying in the above atmosphere is that when drying is performed under a low quality condition where the humidity is less than 80%, a crack occurs in a part of the honeycomb structure, and a preferable honeycomb structure cannot be obtained.
Further, the firing temperature of the honeycomb structure is set to a temperature range of 500 to 800 ° C. because firing at a temperature lower than 500 ° C. does not sufficiently decompose organic substances contained in the molding aid and carbon remains. And the firing temperature is 800
This is because if the temperature exceeds ℃, the titanium oxide migrates to the rutile structure, the specific surface area of the obtained honeycomb structure carrier decreases, and the function as the catalyst carrier decreases.

[0018]

EXAMPLES Examples of the present invention will be described below together with comparative examples. The characteristics of the honeycomb structured catalyst carriers obtained in the examples and comparative examples are summarized in Table 1 below. The specific surface area of the honeycomb structure carrier shown in the table was determined by the BET method by nitrogen gas adsorption, and the breaking strength was measured by using a Kiya type hardness tester on a sample obtained by cutting the honeycomb structure carrier into a length of 1 cm, a width of 1 cm and a length of 2 cm. I asked. Example 1 20% by weight of TiO ₂ obtained as an intermediate in the production of titanium dioxide by the sulfuric acid method, and 9 as SO ₄ .
To 10 parts of metatitanic acid slurry containing 8% by weight, 1.
50 parts of 0 wt% ammonium carbonate aqueous solution was added, and after sufficiently stirring, filtered to obtain SO ₄ of 4.5 wt%
A hydrated metatitanic acid cake containing sulfate radicals was obtained. Next, this metatitanic acid hydrate cake was heated and kneaded in a kneader to be molded by an extruder having a die with a diameter of 5.0 mm, and the molded product was dried and calcined in an electric furnace at 500 ° C. for 2 hours. It was then pulverized to obtain a titanium oxide composition powder having an average particle size of 20 μm.

To 1000 g of this titanium oxide composition powder, 185 g (14% by weight) of barium titanate and 130 g (10) of a celander (trade name) manufactured by Yuken Industry Co., Ltd. as a molding aid.
%) And water and kneaded until sufficiently plasticized, and then molded into a honeycomb structure using a honeycomb die having a square cell shape and 100 cells / inch, and a temperature of 8
It was dried under an atmospheric condition of 5 ° C. and 90% humidity for 48 hours, and the dried product was calcined at 700 ° C. for 3 hours to obtain a honeycomb structure carrier A mainly composed of a titanium oxide composition.

The dried honeycomb structure obtained by the same means was fired at a temperature of 500 ° C. and 800 ° C. for 3 hours to obtain honeycomb structure carriers B and C, respectively. Table 1 shows the results of measuring the specific surface area and the breaking strength of these three types of honeycomb structure carriers. From the results of this example, it was found that both the specific surface area and the fracture strength satisfy the values required as the catalyst carrier even if the firing temperature is changed in the range of 500 to 800 ° C., and the catalyst carrier can be sufficiently applied. Karu Comparative Example 1 A honeycomb structure carrier R- was prepared in the same manner as the honeycomb structure carrier A in Example 1 except that barium titanate was not added to the titanium oxide powder obtained by the method substantially similar to the method shown in Example 1. Got 1.

Table 1 shows the specific surface area and breaking strength of the obtained honeycomb structure carrier R-1. It can be seen that the honeycomb structure carrier of this comparative example to which barium titanate is not added has remarkably inferior fracture strength as compared with that of Example 1 and is not suitable for the catalyst carrier. Example 2 Barium titanate to be added to the titanium oxide powder obtained by a method substantially similar to the method shown in Example 1 was added while changing the addition amount to 5% by weight and 25% by weight. Honeycomb structure carriers D and E were obtained in the same manner as in the honeycomb structure carrier A in Example 1 except for the above.

Table 2 shows the results of measuring the specific surface area and the breaking strength of the two types of honeycomb structure carriers in the same manner as in Example 1. From the results of this example, it is considered that the specific surface area of the honeycomb structure carrier falls within the range of 19 to 30 m ² / g when the addition amount of barium titanate added to the titanium oxide powder is in the range of at least 5 to 25% by weight. Therefore, it can be used as a catalyst carrier because it can be sufficiently applied as a catalyst carrier and the breaking strength value is also within a range where it can be sufficiently applied. Comparative Example 2 The amount of barium titanate added to the titanium oxide powder obtained by a method substantially similar to the method shown in Example 1 was changed so as to be 2% by weight and 35% by weight. Except for this, the honeycomb structure carriers R-2 and R-3 were obtained in the same manner as the honeycomb structure carrier A in Example 1.

Two types of the obtained honeycomb structure supports R-
Table 1 shows the results of measuring the specific surface area and the breaking strength of R-3 and R-3. From the results of this comparative example, when the addition amount of barium titanate is 5% by weight or less, the breaking strength is remarkably lowered, and when it is 25% by weight or more, the specific surface area becomes small and the honeycombs obtained in any cases. It has been found that structural supports are not suitable for use as catalyst supports. Comparative Example 3 The dried honeycomb structure obtained by the same method as in Example 1 was fired at a temperature of 900 ° C. for 3 hours to obtain a honeycomb structure carrier R-
Got 4.

Table 1 shows the results of measuring the specific surface area and breaking strength of the obtained honeycomb structure carrier R-4. It can be seen that when the dried honeycomb structure is fired at a temperature of 900 ° C., the specific surface area of the honeycomb structure carrier is extremely reduced because titanium oxide undergoes heat transfer to the rutile structure, which makes it unsuitable for use as a catalyst carrier.

[0025]

[Table 1] ────────────────────────────────── Barium Titanate Firing temperature Specific surface area Fracture strength Addition amount No. (wt%) (℃) (m2 / g) (kg) ────────────────────────────────── Example 1 A 14 700 28 4.0 B 14 500 72 72 C 14 800 15 4.9 ────────────────────────── ──────── Comparative Example 1 R-10 700 35 0.6 ─────────────────────────────── ──── Example 2 D 5 700 31 2.0 E 25 700 18 5.5 ─────────────────────────────── ───── Comparative Example 2 R-2 2 700 34 1.0 R-3 5 700 9 7.1 ────────────────────────────────── Comparative Example 3 R-4 14 900 45 7 ──────────────────────────────────

[0026]

As described above, according to the manufacturing method of the present invention, the skeleton which is preferable as the honeycomb structure is obtained.
It can be said that the invention has a high industrial value because a honeycomb-structured catalyst carrier having a sufficient specific surface area and an excellent fracture strength, which is composed of a titanium oxide-based composition having a honeycomb shape with cells or more finely divided, can be efficiently obtained.

Claims (3)

[Claims] 1. A metatitanic acid hydrate is molded, dried and fired, then crushed, and barium titanate, a molding aid and water are added to this crushed product and kneaded. A method for producing a honeycomb structure catalyst carrier mainly composed of a titanium oxide composition, which comprises extruding a kneaded product into a honeycomb structure, drying and firing it at a temperature of 500 to 800 ° C. 2. The method for producing a honeycomb structure catalyst carrier mainly composed of a titanium oxide composition according to claim 1, wherein the sulfate group contained in the metatitanic acid hydrate is 5% by weight or less as SO ₄ . 3. The method for producing a honeycomb structure catalyst carrier mainly comprising the titanium oxide composition according to claim 1 or 2, wherein the amount of barium titanate added is in the range of 5 to 25% by weight.