JPS61204037A - Production of thermally stable catalyst carrier composition - Google Patents

Abstract

PURPOSE:To obtain the catalyst carrier having a wide surface area and heat resistance by mixing the solution of an alumina hydrate and the solution of a lanthanum compound, both solution of which act as the catalyst carrier, then by gelatinizing said mixture, drying, thereafter sintering it. CONSTITUTION:The solution of alumina hydrate and the solution of a lathanum compound, both solution of which act as the catalyst for purifying an automobile exhaust gas, industrial exhaust gas, etc. are mixed. The solution of an alumina hydrate is gelatinized with the lanthanum compound, at that time lanthanum is dispersed on aluminium uniformly, dried and aged. The resultant catalyst carrier, even if exposed to a >1,000 deg.C high temperature, can prossess a small change of the crystalline structure to alpha-alumina and a heat resistance which can hold a wide surface area, consequently, deterioration of its catalytic performance is small.

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 10 hours. The present invention relates to a method for producing a stabilized alumina composition, that is, an alumina-lanthana composite oxide, which has a specific surface area of at least 101 rt/q 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 exhaust gas treatment, and catalysts for catalytic combustion. It's being used.

However, activated alumina has the disadvantage that when exposed to high temperatures of about 1000°C or higher, the crystal structure changes and the specific surface area decreases, resulting in a decrease in the specific surface area. In the field of application, 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, activated alumina and the above-mentioned stabilizer essentially coexist as a mixture, and can be exposed to temperatures below 1000°C or even at high temperatures of 1100 to 1400°C for a very short period of several hours. In some cases, the stabilizing effect is recognized, but if exposed to high temperatures exceeding 1000°C for a long period of time, for several tens of hours or more, the oxides of α-alumina and the stabilizer, and even the spinel or perovskite structure It is known that a low surface area composite oxide of alumina and a stabilizer is produced, and its specific surface area is rapidly reduced.

For example, activated alumina contains 5 to 10% by weight of lantana.
The product obtained by adding and mixing a nitrate solution, drying and calcining at i ooo°C has a specific surface area of about 70 TIt,/Q and is stabilized, but this is a mixture of activated alumina and lantana. .

Also, some of the products baked at 1200℃ for 5 hours have α-
Although the formation of alumina is observed, the specific surface area is 18TI
t/q, and it is still quite stable.

However, when exposed for another 100 hours at 1200°C, it becomes lanthanum aluminate (LaAIo3) with α-alumina and perovskite structure, with a specific surface area of 1 to 2.
Tlt/q.

On the other hand, the heat resistance temperature required of the above-mentioned catalysts is increasing year by year, and heat resistance of 1000° C. or more is being required.

Particularly in boilers and gas turbines, where the application of catalytic combustion methods has been considered in recent years, the catalyst temperature is 10
00~1200℃, 1300~1500 depending on conditions
When conventionally produced stabilized alumina is used as a support for these catalysts, the catalysts undergo a large thermal history and their specific surface area rapidly decreases over time, resulting in It has the disadvantage that the catalyst activity decreases.

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 in heat resistance of activated alumina or alumina stabilized by conventional methods, and to prevent the crystal structure from changing to α-alumina even when exposed to high temperatures exceeding 1000°C for a long time. It is an object of the present invention to provide a method for producing a carrier composition for a catalyst, which has a heat resistance that allows it to maintain a high surface area, and which results in less deterioration in catalytic performance.

[Structure of the invention]

In order to achieve this object, the present invention mixes a solution of alumina hydrate and a solution of a lanthanum compound, gels the solution of alumina hydrate, and then calcinates the solution after drying. Provided is the production of a thermally stable catalyst carrier composition made of a composite oxide, which
10TI1.7 even after 100 hours baking at 0℃
It is disclosed that a catalyst carrier composition having a specific surface area of 9 or more has unprecedented heat resistance.

The present invention will be specifically explained below.

The feature of the present invention is that a solution of alumina hydrate and a solution of a lanthanum compound are mixed, the alumina hydrate is gelled, and the gelled product is dried and then fired.

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, each composition is caused by an in-phase reaction. It is difficult to mix uniformly, and it is difficult to uniformly disperse the stabilizer into alumina due to the uneven particle size of each composition, avoiding the presence of free alumina and stabilizer. I can't do it.

When exposed to high temperatures for a long time, these eventually become oxides or aluminates of α-alumina and the stabilizer, causing a decrease in the specific surface area.

In addition, in the coprecipitation method, the difference in the solubility product of the hydroxide of lanthanum or aluminum as a carrier is small, and precipitation occurs almost simultaneously. Since this does not occur completely and it is difficult to cause co-precipitation, it is greatly affected by conditions such as precipitating agent, temperature, and pH, and strict operation is required.

When manufacturing the product for industrial use, preparation with a high concentration solution of aluminum and lanthanum is unlikely to result in co-precipitation and only produces a homogeneous precipitate, so it must be prepared multiple times with a low concentration solution. Furthermore, 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, in the catalyst carrier composition of the present invention, a solution of alumina hydrate is gelled by a lanthanum compound, and at that time, lanthanum is uniformly dispersed in aluminum.
By dry-ripening this material, it has a high surface area even after long-term high-temperature firing.

The reason for this is not well understood, but when a lanthanum compound solution is added to the stable and existing region of the alumina hydrate solution, P
H changes and cation concentration changes occur, and under conditions where the electric double layer that causes repulsion between particles does not function sufficiently, the particles come together and bonds with lanthanum as the crosslinking source occur, and with lanthanum as the core, It is expected that the composite will be surrounded by aluminum, resulting in a thermally stable catalyst carrier composition.

As a result of the above, the catalyst carrier composition of the present invention has the advantage that lanthana, which is a stabilizer, is hardly eluted even when treated with various acid, alkali, or salt solutions, and is chemically stable. It also has

When gelling a solution of alumina hydrate with a lanthanum compound, it is appropriate to maintain the temperature in the range of 40 to 200°C, more preferably in the range of 60 to 150°C.

At temperatures exceeding 200°C, the gel produced during gelation simultaneously dries, and because the drying rate is too fast, the lanthanum in the alumina gel moves to the surface layer of the solid material, resulting in uneven distribution of lanthanum. This is not a good thing to happen.

Moreover, at temperatures below 40° C., it is difficult to form a gel in which the lanthanum compound is uniformly dispersed, and therefore it is necessary to stir and mix for a long time, which is not practical.

Furthermore, during or after gelation, at least 30%
It is appropriate to sufficiently knead and stir the mixture while maintaining the temperature in the range of 40 to 200°C for a minute, preferably for at least one hour.

As a result, it is possible to uniformly disperse the lanthanum in a form in which the aluminum is almost completely surrounded by the core.

Suitable alumina raw materials for producing the catalyst carrier composition of the present invention are amorphous alumina hydrates having a boehmite structure or a precipitated boehmite structure that are partially soluble in inorganic or organic acids. Alternatively, hydrated alumina such as Diasbore is not preferred.

In addition, lanthanum compounds include nitrates, carbonates, and vinegar i! Any water-soluble salt, oxalate, chloride, etc. may be used.

When producing a thermally stable catalyst carrier composition according to the present invention, a lanthanum compound solution may be added to a solution of alumina hydrate, or vice versa, but in either case, the composition is uniformly gelled. Care must be taken to add it gradually over time.

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 lanthanum moves to the surface layer of the solid material, so the temperature should be gradually raised in a dryer with a narrow temperature distribution, such as a hot air circulation dryer.
It is preferable to finally 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.

Then, the dried powder is calcined in the presence of air at a temperature range of 500 to 1100° C., preferably 600 to 100° C., for at least 3 hours to obtain a finished catalyst carrier composition.

[effect]

The alumina-lanthana catalyst support composition prepared by the manufacturing method of the present invention has a ratio of at least 1.7 g of 10TI even after high temperature and long-term calcination at 1200° C. for 100 hours, as demonstrated in the following examples. It is a highly thermally stable catalyst support composition with a high surface area.

In other words, when prepared by the coprecipitation method, a considerably thermally stable composition can be obtained compared to the impregnation method or the mixing method, and after firing at 1200°C for 5 hours, 32-Irt/C1,2
Although it had a specific surface area of 2411 L/q after 0 hours of firing, it rapidly gelatinized after 50 hours of firing and had a specific surface area of 7 r/q.
It is clear that the thermal stability is extremely inferior to that of the gelling method of the present invention.

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

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

Example 1 662 g of Condeia's boehmite (trade name: Disboular) having a specific surface area of 150 Td/g was added to 1830 d of water containing 60% nitric acid, and stirred for 1 hour with a homomixer to partially dissolve it to form an alumina sol. I got it.

Next, this sol was transferred to a kneader heated to 80°C, and while stirring, 500% of lanthanum nitrate hexahydrate 176Q was dissolved.
1 dl of water was gradually added into the kneader at regular intervals for 10 minutes.

After the addition, kneading and stirring with a kneader was continued for 2 hours, and then the gelled solid was placed in a hot air circulation dryer, heated to 150°C at a rate of 30°C/hour, and dried at the same temperature for 12 hours.

Next, the dry solid is pulverized with an atomizer to 10 to 20
The mixture was poured into micron powder and calcined at 800° C. for 5 hours to obtain a composite oxide containing 11.7% by weight of lanthana and 88.3% by weight of alumina.

Example 2 2500 g of alumina sol (manufactured by Nissan Chemical ■) having a crystalline form with a precipitated boehmite structure and a specific surface area of 245 TIt/(J)
was placed in a kneader heated to 150°C, and while stirring, 600 d of water in which lanthanum nitrate hexahydrate 97Q was dissolved was gradually added into the kneader at regular intervals for 10 minutes. 1 at the same temperature
After kneading and stirring for an hour, put it in a dryer kept at 150℃.
It was dried for 5 hours.

Next, the dry solid was coarsely pulverized and calcined at 800°C for 5 hours to yield 6.8% by weight as lantana and 9% as alumina.
A composite oxide containing 3.2% by weight was obtained.

Example 3 270 g of Conoco's boehmite (trade name: SB Alumina) was added to an acetic acid solution prepared by adding 230 d of acetic acid to 2070 g of water, and the mixture was stirred for 2 hours using a homomixer to obtain an alumina sol.

This sol was transferred to a kneader heated to 60° C., and while stirring, 500 d of water in which 30 q of lanthanum acetate had been dissolved was gradually added at regular intervals for 10 minutes. The subsequent operation was as in Example 1, followed by drying and firing to obtain 17
．． A composite oxide containing 6=ffl amount % and 82.4 weight ω% as alumina was obtained.

Comparative Example 1 As a solution of lanthanum compound, lanthanum nitrate hexahydrate 38
100 (Example 1 except that water of 7 was used)
A composite oxide containing 22.5% by weight of lanthana and 77.5% by weight of alumina was obtained by gelation, drying and firing in the same manner as in .

Comparative Example 2 500 g of activated alumina (γ-aluminum t) having a specific surface area of 80 TIt/g was immersed in 500 d of water in which 176 q of lanthanum nitrate hexahydrate was dissolved, and evaporated to dryness while mixing.

Then, C was crushed in the same manner as in Example 1.

1 q of composite oxide containing 11.7% by weight of lanthana and 88.3% by weight of alumina after firing.

Comparative Example 3 1000ml of aluminum nitrate 9 water 1u203Q was dissolved in 100d of water containing 9.7g of lanthanum nitrate hexahydrate dissolved.
- water was added and kept at 80°C.

Next, 1N aqueous ammonia was gradually added dropwise while sufficiently stirring with a stirrer to adjust the final P1-1 to 8.

Decantation was repeated three times, followed by further washing with water and filtration, followed by drying at 150° C. for 16 hours.

The dry solid was then ground and calcined as in Example 1 to produce 11.7 i! of lantana. A composite oxide containing ω% and 88.3% by weight of alumina was obtained.

Example 4 Example 1.2, 3. The composite oxides obtained in Comparative Examples 1 and σ2 were heated at 1200°C for 5 hours and 20 hours, respectively.
BET baked in an air atmosphere for 50 hours, 100 hours, and 200 hours, and its surface area was filled with nitrogen gas as an adsorbent gas.
Measured using a formula specific surface meter. Table 1 shows the surface area measurement results.

From Table 1, the composite oxides obtained in Examples 1, 2, and 3 have a specific surface area of 10 TIt/g or more even after calcination at 1200°C for 100 hours, and are thermally stable catalyst carrier compositions. I understand.

On the other hand, the composite oxide produced by the gelling method with the composition ratio of β-alumina in Comparative Example 1 has a specific surface area of 10 TIt/9 or more after 50 hours of firing, but after 100 hours, it has halved to 1
0m/(below 7.

Furthermore, although the composite oxide obtained by the dipping method of Comparative Example 2 was stabilized by short-time firing of 5 hours, the stabilizing effect disappeared over a long time.

Furthermore, although the composite oxide produced by the coprecipitation method of Comparative Example 3 was fairly stabilized until 20 hours of calcination, the surface area changed over time after 50 hours of sintering, and the stabilizing effect disappeared.

Claims (4)

[Claims] (1) A heat treatment consisting of a composite oxide of alumina and lanthana characterized by mixing a solution of alumina hydrate and a solution of a lanthanum compound, gelling the solution of alumina hydrate, drying and then firing. A method for producing a catalyst carrier composition that is stable in terms of stability. (2) The method according to claim (1), wherein the composite oxide has a composition of 80 to 95% by weight of alumina and 20 to 5% by weight of lanthana. (3) Gelation of alumina hydrate solution at 40-200℃
The method according to claim (1), which is carried out in a temperature range of . (4) The method according to claim (1), wherein the alumina hydrate is amorphous, has a boehmite structure, or a solidified boehmite structure, and is partially soluble in acids.