JPS61287447A - Production of heat resistant catalytic carrier composition - Google Patents

Abstract

PURPOSE:To obtain the titled composition which continues to hold a high surface area even if exposed at high temp. for a long period and has the heat resistance by adding a specified elemental compd. to a mixed aq. soln. of Al2O3 hydrate and colloidal SiO2, thickening and gelatinizing the mixture, drying and calcining the obtained gelatinized material. CONSTITUTION:Nitrate of one kind selected from among Mg, Sr and Ti is added to a mixed aq. soln. of both Al2O3 hydrate which is amorphous and has the partial solubility for an acid and colloidal SiO2 and the mixture is thickened and gelatinized by performing the kneading and the stirring at 10-150 deg.C temp. region. Then gel wherein SiO2 is uniformly dispersed to Al2O3 is dried, crushed and thereafter calcined. Since the aimed composition consisting of a composite oxide of Al2O3 and SiO2 obtained by such a way is thermally stable even if exposed at >=1,000 deg.C for a long period, it is available as a carrier of a catalyst for the catalytic combustion and the purification of exhaust gas of an automobile.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a thermally stable catalyst carrier composition.

Specifically, the present invention improves the heat resistance of conventional activated alumina and stabilized alumina, so that they can continue to have a high surface area even when exposed to high temperatures exceeding 1000°C for a long time, particularly at 1200°C for 20 hours. The present invention relates to a method for producing a stabilized alumina composition, that is, an alumina-silica composite oxide, which has a converted surface area of at least 20 Td/g even after the calcination treatment.

[Prior art]

Activated alumina is a material with a high surface area and excellent heat resistance, and by taking advantage of its properties, it can be used as a support for various catalysts, including catalysts for automobile exhaust gas purification, catalysts for industrial υ1 gas treatment, and catalysts for catalytic combustion. It is used for such things.

However, activated alumina has the disadvantage that when exposed to high temperatures of around 1000°C or higher, its crystal structure changes and the specific surface area decreases, resulting in a change in the crystal structure and a decrease in the specific surface area. In the above-mentioned fields of application, silica, alkaline earth elements, rare earth elements, etc. are usually added as stabilizers to activated alumina in the form of oxides, hydroxides, or various compounds.

In this case, the activated alumina and the above-mentioned stabilizer essentially coexist as a mixture, but at temperatures below 100'C or even at high temperatures of 1,100 to 1,400 degrees Celsius, the activated alumina and the above-mentioned stabilizer coexist for a short period of time at the top of several hours. When exposed, the stabilizing effect is recognized, but when exposed to high temperatures exceeding 1000°C for a long period of time, for several tens of hours or more, α-alumina, stabilizer oxides, and even spinel or perovskite Low surface f of structured alumina and stabilizer! It is known that complex oxides are formed and the specific surface area thereof is rapidly reduced.

For example, activated alumina is dipped in silica sol containing 5 to 10% by weight of silicon dioxide (SiO2), and after drying,
The one fired at 00°C has a specific surface area of about 90 m/Q and is stabilized, but it is a mixture of activated alumina and amorphous silica.

Also, some α-
Although the formation of alumina is observed, the specific surface area is 28 m/
g, and is still fairly stable.

However, when exposed for a further 1001Rj at 1200℃, α-alumina and S having the structure
iO2, and the specific surface area decreases to 3=5ffl/Q.

On the other hand, the heat and humidity resistance i required for the above-mentioned catalysts is increasing year by year, and heat resistance of 1000° C. or higher is becoming required.

Particularly in large-capacity boilers and gas turbines, where the application of catalytic combustion methods has been examined in recent years, the catalyst temperature in J3 (1) is 1000-1200℃,
When conventionally produced stabilized alumina is used as a support for these catalysts, the catalysts undergo a large thermal history (their specific surface area decreases rapidly over time), since temperatures reach temperatures as high as 500°C. This has the disadvantage that the catalytic activity decreases as a result.

Furthermore, there is a risk that cracks may occur in the catalyst layer and the catalyst active sites may peel off.

[Purpose of the invention]

The purpose of the present invention is to overcome the above-mentioned problems with the heat resistance of activated alumina or alumina stabilized by conventional methods, and to improve the heat resistance of α-alumina even when exposed to high temperatures exceeding 1000°C for long periods of time. It is an object of the present invention to provide a method for producing a carrier composition for a catalyst that exhibits little change in crystal structure, has a high surface area, has long-lasting heat resistance, and, as a result, has little deterioration in catalytic performance.

[Structure of the invention]

That is, the present invention adds magnesium (Mq), strontium (Sr), yttrium (Y), and lanthanum (Ia) to a mixed aqueous solution of alumina hydrate and colloidal silica.
), cerium (Ce), neodymium (Nd), titanium (T
+> A compound of at least one element selected from the group consisting of zircon (Zr), chromium (Cr) and tin (Sn) is added to thicken and gel the mixed aqueous solution, and the resulting gel is This is a method for producing a heat-resistant catalyst carrier composition, which is characterized by drying and firing.

The catalyst carrier composition obtained by the present invention has 1
20TIi even after baking at 200℃ for 200 hours
It exhibits unprecedented heat resistance with a specific surface area of /g or more.

Normally, methods for producing composite oxides include precipitation methods, impregnation methods, mixing methods, coprecipitation methods, etc., and most of the solid industrial catalysts currently used are composites of each composition using these methods. ing.

However, in the precipitation method, due to the difference in the solubility product of each composition, in the impregnation method, due to the movement of each composition when the slurry obtained by impregnation or immersion is dried and fired, and in the mixing method, due to the solid phase reaction, each composition Solid phase 1 consists of uniformly mixing the stabilizers, and because the particle sizes of each composition are uneven, it is difficult to uniformly disperse the stabilizer in the alumina, and the alumina and stabilizer exist in a free state. I can't avoid it.

And when exposed to high temperatures for long periods of time, these eventually lead to the formation of alpha-alumina and stabilizer oxides or alumina.
1, which causes a decrease in the specific surface area.

In addition, in the coprecipitation method, alkaline earth elements as carriers,
The difference in the solubility product of the hydroxides of rare earth elements and aluminum is small, and precipitation occurs almost simultaneously. Since coprecipitation is difficult to occur, precipitants,
It is greatly influenced by conditions such as temperature and Pl-1, and requires strict operation.

When preparing a large amount for industrial use, preparation with a high concentration solution is unlikely to cause co-precipitation and only produces a homogeneous precipitate, so it is necessary to prepare it multiple times with a low concentration solution, or However, it is difficult to control the particle size of the coprecipitate, and operations such as filtration and washing are complicated, making it impractical.

On the other hand, the catalyst carrier composition of the present invention is thickened and gelled by adding a compound of the element specified by the present invention to a homogeneous mixed aqueous solution of alumina hydrate and colloidal silica. The silica is uniformly dispersed in the material, and by drying and aging it, a high surface area can be achieved even after long-term high-temperature firing.

The reason for this is not well understood, but when a compound of the element specified by the present invention is added to the stable existence region of alumina hydrate and colloidal silica, a PH change occurs, causing an electric double layer that causes repulsion between particles. Under conditions in which the particles do not work sufficiently, the particles come together, and bonds based on silica crosslinking occur, and aluminum surrounds the highly dispersed silica as a core. It is expected that gelatinization of alumina will be prevented, and as a result, a thermally stable catalyst carrier composition will be obtained.

Compounds of elements specified by the present invention, namely Ma, Sr
, Y, La, Ce, Nd, Ti, Zr.

Mg, S r SY −, l a 1Ce −N d
-T i.

At least one selected from the group of 7r, Cr, J: and Sn
When a mixed aqueous solution of alumina hydrate and colloidal silica is thickened and gelled by a compound of a seed element, 10 to 15
It is appropriate to maintain the temperature in the 0° C. range, more preferably in the 20-80° C. range, and gradually add the compound of the above elements while sufficiently stirring the mixed aqueous solution.

If the temperature during thickening gelation exceeds 150°C, the gel produced during gelation will dry at the same time, and the drying rate will be too fast, causing the solids in the alumina gel to move to the surface layer and cause silica formation. Or MO, Sr, Y, La, Ce
XNd.

The uneven distribution of Ti, Zr, Cr, and Sn is not favorable.

Further, at temperatures below 10°C, it is difficult to form a gel in which these solids are uniformly dispersed, and therefore it is necessary to stir and mix for a long time, which is not practical.

In addition, when thickening and gelling a homogeneous mixed aqueous solution of alumina hydrate and colloidal silica, ammonia, ammonia carbonate, aliphatic amines such as 1-helimedylamine, etc. It is also possible to use a base f#1 compound in combination.

Furthermore, during or after gelation, there is also a small amount (7 at least 2
It is appropriate to sufficiently knead, stir, and cover the mixture for 0 minutes, preferably for 30 minutes or longer while keeping the mixture at a temperature in the range of 10 to 150°C.

As a result, aluminum can be uniformly dispersed almost completely with silica as a core surrounded by aluminum.

In drying the solid material after gelation, aging is not necessary and may be carried out immediately after sufficient stirring and kneading.

When drying, rapid high-temperature drying is undesirable because the stabilizer such as silica moves to the surface layer, and the temperature is gradually raised in a dryer with a small temperature distribution, such as a hot air circulation dryer, until the final It is preferable to dry at 150 to 200°C for 10 hours or more.

The calcination may be carried out after the dry solid is roughly pulverized to about 500 microns or, if necessary, after pulverized to about 20 to 30 microns.

The dried powder is then calcined in the presence of air at a temperature range of 500 to 1100°C, preferably 600 to 1000°C for at least 3 hours to obtain a finished catalyst carrier composition.

The heat-resistant catalyst carrier composition obtained as described above contains alumina in a range of 70 to 99.4% by weight, silica in a range of 0.5 to 20% by weight, preferably 0.8 to 12% by weight.
Weight % range and MO.

The oxide of at least one element selected from the group consisting of Sr, Y, La, Ce, Nd, Ti, Zr, Cr and Sn is in the range of 0.1 to 10% by weight, preferably 1 to 6% by weight. % is preferred.

Suitable raw materials for alumina are amorphous alumina hydrates that are partially soluble in inorganic or organic acids, and have a Boehmite 1 structure or a coagulated Boehmite 1 structure.Alumina hydrates such as gibbsite or diaspore are suitable. Undesirable.

When the amount of silica is less than 0.5% by weight, the effect of silica as a stabilizer is hardly recognized, and when the amount exceeds 20% by weight, the effect as a stabilizer is recognized. However, if fired for a long time, Murai 1~, which is a composite oxide with alumina, will begin to form, and its effect will decrease.

Colloidal silica can be used regardless of its hydrogen ion S degree, such as acidic, neutral, 1n-based, etc.
Acidic ones are particularly preferred, and particle diameters of J50 millimicrons or less are particularly preferred, with those having a particle size of 10 to 20 millimicrons being particularly preferred.

If thorium is present as a silica sol stabilizer, it will weaken the effect of silica as an alumina stabilizer.
-Rium is preferably 0.05% or less.

Next, the present invention will be specifically explained using examples.

However, the composition, manufacturing method, etc. are not limited to these.

Example 1 Boehmai 1~ (Kono Hansei, trade name: SB Alumina) 270 was added to an acid-resistant solution prepared by adding 230 d of acetic acid to 2070 ml of water.
g was added and stirred for 2 hours using a homomixture to obtain an alumina sol.

This sol was placed in a kneader heated to 60°C, and 13.9G of colloidal silica (manufactured by Kuchikagaku Kogyo Co., Ltd., trade name: Nisnortex) was added, and while stirring, 56.3G of chromium nitrate was added.
200mf of an aqueous solution containing 0! was added and further kneaded and stirred for 1 hour.

The PH of the kneaded product at this time was 7.5.

After that, the gelled solid was placed in a hot air circulation dryer for 150 minutes.
Dry at °C for 12 hours. Next, the dry solid is pulverized with an eye mizer to form a powder of 10 to 20 microns.
Calcined at 00℃ for 5 hours, 1.3% by weight of silica,
A composite oxide containing 5% by weight of chromia and 93.7% by weight of alumina was obtained.

Example 2 Boehmei 1 to 662Q (manufactured by Condeia, trade name: Dispural) to determine the specific surface area of 150TIL10
The mixture was added to 1830 mQ of water containing 219.6 mQ of 0% nitric acid W' and stirred for 1 hour using a Bomomiki 1J"- to obtain partially dissolved zealumina sol.

Next, this sol was transferred to a kneader heated to 80°C, and colloidal silica (manufactured by Yosan Kagaku Kogyo Co., Ltd., trade name: Snowtex) 1269 was added while stirring to obtain a uniform mixed solution. While stirring the solution, add lanthanum nitrate 81.
200 d of an aqueous solution in which 20 was dissolved was gradually added to obtain a mixed material.The pH of the mixed material at this time was 8.4.

Next, it was dried and calcined in the same manner as in Example 1, and 1 watt of a composite oxide containing 4.5% by weight of silica, 5.5% by weight of lanthana, and 90% by weight of alumina was added.

Comparative Example 1 Colloidal silica 126q (manufactured by Kuchikagaku Kogyo Kyoku, trade name Nisnortex) and lanthanum nitrate 81.2 to Boehmy 1 to 662q (manufactured by Condeia, trade name: Dispural) with a specific surface area of 150 rIl/q. The mixture was immersed in a mixed solution of 470 g of water in which 1 g was dissolved, and evaporated to dryness while thoroughly mixing and stirring.

Next, the mixture was crushed and calcined in the same manner as in Example 1 to obtain a composite oxide containing 4.5% by weight of silica, 5.5% by weight of lanthana, and 90% by weight of alumina.

Example 3 The composite oxides obtained in Examples 1 and 2 and Comparative Example 1 were heated at 1200°C for 20 hours, 50 hours, and 10 hours, respectively.
After baking in an air atmosphere for 0 hours, 200 hours, and 300 hours, the surface area was measured using a BET specific surface meter using nitrogen gas as an adsorption gas. Table 1 shows the surface area measurement results.

= 16- Table 1, Example 1, 2, J: The composite oxide thus obtained had a specific surface area of 20/Q or more even after sintering at 1200°C for 200 hours, and was thermally stable. It can be seen that the catalyst carrier composition is stable.

On the other hand, the composite oxide obtained by the immersion method in Comparative Example 1 was stabilized up to 20 hours of calcination, but after 50 hours of sintering, the surface area changed over time so much that the stabilizing effect disappeared.

Table 1 Specific surface area after firing at 1200℃ (TIiha
) Procedural amendment (voluntary) 1985? 30th of the month

Claims (4)

[Claims] (1) Magnesium, strontium, yttrium,
A compound of at least one element selected from the group consisting of lanthanum, cerium, neodymium, titanium, zircon, chromium, and tin is added to thicken the mixed aqueous solution into a gel, and the resulting gel is dried and fired. A method for producing a heat-resistant catalyst carrier composition. (2) The heat-resistant catalyst carrier composition is 70 to 70% as alumina.
99.4% by weight, 0.5 to 20% by weight as silica, and at least one member selected from the group consisting of magnesium, strontium, yttrium, lanthanum, cerium, neodymium, titanium, zircon, chromium, and tin. Claim (1) characterized in that it has a composition in which the oxides of the elements range from 0.1 to 10% by weight.
Method described. (3) Claims (1) characterized in that the alumina hydrate is amorphous, has a boehmite structure, or a solidified boehmite structure, and has partial solubility in acids.
) or the method described in (2). (4) Claims (1), (2), or (3) characterized in that the thickening and gelation of the mixed aqueous solution of alumina hydrate and colloidal silica is carried out at a temperature range of 10 to 150°C. ) method described.