JPH0638914B2 - Method for producing heat-resistant catalyst carrier composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a method for producing a thermally stable heat-resistant catalyst carrier composition.

More specifically, the present invention improves the heat resistance of conventional activated alumina and stabilized alumina and can continue to have a high surface area even when exposed to high temperatures in excess of 1000 ° C. for a long time, specifically 1200 ° C. for 50 hours. The present invention relates to a method for producing a stabilized alumina composition having a specific surface area of at least 10 m ² / g, that is, an alumina-lanthanide-based composite oxide even after the calcination treatment of.

<Prior Art> Activated alumina is a substance having a high surface area and excellent heat resistance, and by utilizing its characteristics, various catalysts such as automobile exhaust gas purification catalyst, industrial exhaust gas treatment catalyst or catalytic combustion catalyst. It is used as a carrier.

However, when activated alumina is exposed to a high temperature of about 1000 ° C. or higher, it has a drawback that the specific surface area is reduced to finally α-alumina due to a change in crystal structure. In the field of use, alkaline earth elements, rare earth elements and the like are usually added to activated alumina as stabilizers in the form of oxides, hydroxides or various compounds.

In this case, the activated alumina and the above-mentioned stabilizer substantially coexist only as a mixture, and are exposed at a temperature of 1000 ° C. or lower, or even at a high temperature of 1100 to 1400 ° C. for a very short time of about several hours. However, when exposed to a high temperature of over 1000 ° C. for a long time of several tens of hours, α-alumina, an oxide of a stabilizer, a spinel or a perovskite structure are eventually formed. It is known that a low surface area composite oxide of alumina and a stabilizer is formed, and the specific surface area thereof is rapidly reduced.

For example, 5-10 wt% as lantana on activated alumina
The mixture obtained by adding and mixing the nitrate solution (1), drying and firing at 1000 ° C. has a specific surface area of about 70 m ² / g and is stabilized, but this is a mixture of activated alumina and lantana.

Also, the product obtained by firing this at 1200 ° C. for 5 hours is partially α-
Although the formation of alumina is recognized, the specific surface area is 18 m ^2.
/ G, which is still fairly stable.

However, when exposed at 1200 ° C. for a further 100 hours, α-alumina and lanthanum aluminate (LaAlO ₃ ) having a perovskite structure are eventually formed, and the specific surface area decreases to 1-2 m ² / g.

On the other hand, the heat resistance temperature required for the catalyst as described above is increasing year by year, and heat resistance of 1000 ° C. or more is being demanded.

Especially in the case of large-capacity boilers and gas turbines for which the application of the catalytic combustion system has been studied in recent years, the catalyst temperature is 10
00 to 1200 ° C, 1300 to 1500 depending on conditions
When stabilized alumina produced by the conventional method is used as a carrier for these catalysts because it reaches a high temperature of ℃, the catalyst undergoes a large thermal history and its specific surface area decreases rapidly with the lapse of time. It has a drawback that the catalytic activity is lowered. In addition, cracks may occur in the catalyst layer and the catalytically active sites may peel off.

<Object of the Invention> The object of the present invention is to overcome the problems in the heat resistance of the above-described activated alumina or alumina stabilized by a conventional method, and to obtain α-alumina even when exposed to a high temperature of more than 1000 ° C for a long time. The present invention provides a method for producing a carrier composition for a catalyst, which has a small change in crystal structure, has a high surface area and has heat resistance capable of continuing, and consequently has a small decrease in catalyst performance.

<Structure of the Invention> In order to achieve the above object, the present invention provides a solution of an alumina hydrate and a solution of a compound of at least one rare earth element selected from the group consisting of lanthanum, cerium, praseodymium, neodymium, samarium and yttrium. And an alkaline earth element consisting of calcium, strontium and barium; a Group 4 element consisting of titanium, zirconium and tin; an eighth group consisting of iron, cobalt and nickel
Alumina-lanthanide-based composite oxidation by mixing with a solution of a compound of at least one element selected from the group consisting of group elements and chromium, gelling the solution of the alumina hydrate, and drying and firing. A method for producing a heat-resistant catalyst carrier composition comprising
It is disclosed that even after calcination at 50 ° C. for 50 hours, a thermally stable catalyst carrier composition having a specific surface area of 10 m ² / g or more is obtained.

Hereinafter, the present invention will be specifically described.

The feature of the present invention is that at least one selected from the group consisting of a solution of alumina hydrate, a solution of a compound of the above rare earth element, the above alkaline earth element, the above Group 4 element, the above Group 8 element and chromium. The method is to mix the solution of the compound (1) with the solution of the compound (1) to gel the alumina hydrate, and to dry and then calcine the gelled product.

Usually, there are a precipitation method, an impregnation method, a mixing method, a coprecipitation method, etc. as a method for producing a complex oxide, and most of the solid industrial catalysts currently used are used by compounding each composition by these methods. ing.

However, in the precipitation method, there is a difference in the solubility product of each composition, in the impregnation method each composition moves when the slurry obtained by impregnation or immersion is dried and baked, and in the mixing method each composition depends on the solid phase reaction. Is difficult to mix uniformly, and it is difficult to uniformly disperse the stabilizer in alumina because the particle size of each composition is non-uniform. Inevitable.

When exposed to a high temperature for a long time, as a result, these become α-alumina and an oxide or aluminate of the stabilizer, which causes a decrease in the specific surface area.

Further, the catalyst carrier composition by the coprecipitation method can be a heat resistant catalyst carrier composition as in the present invention. However, the difference in solubility products of rare earth elements, alkaline earth elements, group 4 elements, group 8 elements or hydroxides of chromium and aluminum as carriers is small, and precipitation occurs almost at the same time. Precipitation due to the adsorption and inclusion of soluble metal ions does not occur completely and is unlikely to cause coprecipitation. Therefore, the operation is greatly affected by conditions such as precipitating agent, temperature, and pH, and strictness is required for the operation.

When it is prepared in a large amount for industrial use, aluminum, rare earth elements, alkaline earth elements, Group 4 elements, Group 8 elements
Preparation with a high-concentration group element element or chromium solution does not result in co-precipitation, and only uniform precipitation occurs.Therefore, it is necessary to prepare a low-concentration solution multiple times, and to control the particle size of the co-precipitation. Is difficult and the operations such as filtration and washing are complicated, and it can be said that it is not practical.

On the other hand, in the catalyst carrier composition of the present invention, a solution of alumina hydrate is gelled by a compound of a rare earth element, an alkaline earth element, a group 4 element, a group 8 element or chromium, and at that time, aluminum is formed. The above elements are uniformly or partially dispersed in a layered form, and by drying and aging this element, it has a high surface area even after being baked for a long time at high temperature.

The reason for this is not well understood, but the stability of the alumina hydrate solution, the addition of a solution of the compound of the above element in the existence region causes a pH change and a cation concentration change, and an electric double layer that causes repulsion between particles is generated. Under the condition that the particles do not sufficiently act, the particles are associated with each other to form a bond with the above element as a crosslinking source, and as a result, aluminum is complexed so as to surround it with the above element as a nucleus or aluminum and the above It is expected that a layered aluminate crystal structure similar to magnetoplumbite is obtained by layering with an element, and a catalyst carrier composition having heat resistance can be obtained.

Further, the catalyst carrier composition according to the present invention is very stable in that the oxides of the above-mentioned various elements that are additives are hardly eluted even by the treatment with an acid, alkali or salt solution, and are chemically stable. It also has advantages.

When the solution of the alumina hydrate is gelled by the compound of the above element, it is suitable to keep it in the temperature range of 40 to 200 ° C, more preferably 60 to 150 ° C.

When the temperature exceeds 200 ° C, the gel formed during gelation is dried at the same time, and since the drying speed is too fast, the above-mentioned elements in the alumina gel move to the surface layer of the solid matter, resulting in uneven distribution. It does not happen.

Further, at a temperature of less than 40 ° C., it is difficult to form a gel in which the compounds of the above elements are uniformly dispersed, and therefore it is necessary to stir and mix for a long time, which is not practical.

Furthermore, at least 30 times during or after gelation
It is suitable to sufficiently knead and stir while maintaining the temperature range of 40 to 200 ° C. for 1 minute or more, preferably 1 hour or more.

As a result, it is possible to disperse the above elements in a uniform or layered manner in such a manner that the above elements are used as nuclei and aluminum is surrounded by the nuclei.

In the case of producing a heat-resistant catalyst carrier composition according to the present invention, a solution of a rare earth element compound, an alkaline earth element, a group 4 element, a group 8 element and chromium are added to a solution of alumina hydrate. The mixed solution with the solution of the compound of at least one element may be added, or vice versa, but in any case, be careful to add gradually over time so as to form a uniform gel. Requires.

Drying of the solid matter after gelation does not require aging after sufficient stirring and kneading, and may be carried out immediately.

In the case of drying, rapid high-temperature drying is not preferable because rare earth elements as additives move to the surface layer of the solid matter, and the temperature is gradually raised by a dryer with a small temperature distribution such as a hot air circulation dryer. Finally, it is preferable to finally dry at 150 to 200 ° C. for 10 hours or more.

The calcination may be carried out after roughly pulverizing the dried solid substance to about 500 μm or, if necessary, after pulverizing it to about 20 to 30 μm.

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

The heat-resistant catalyst carrier composition obtained as described above has an alumina content in the range of 60 to 98% by weight, preferably 70 to
95% by weight, 1-20% by weight as rare earth element oxide, preferably 3-15% by weight, selected from the group consisting of alkaline earth elements, Group 4 elements, Group 8 elements and chromium. It is preferable that the oxide of at least one element has a composition in the range of 1 to 20% by weight, preferably 2 to 15% by weight.

Less than 1% by weight of rare earth element oxides, alkaline earth elements,
When the amount of the oxide of at least one element selected from the group consisting of Group 4 elements, Group 8 elements and chromium is less than 1% by weight, almost no effect as a stabilizer of alumina is recognized, Further, the rare earth element oxide exceeds 20% by weight, and the oxide of at least one element selected from the group consisting of alkaline earth elements, group 4 elements, group 8 elements and chromium exceeds 20% by weight. Also in this case, since uniform dispersion is difficult, it has little effect as a stabilizer, and long-term calcination produces complex oxides with perovskite and alumina having a spinel structure, resulting in a large decrease in specific surface area.

Alumina hydrate having an amorphous or boehmite structure or a cohesive boehmite structure, which is partially soluble in an inorganic acid or an organic acid, is suitable as an alumina raw material for producing the catalyst carrier composition of the present invention. Alternatively, alumina hydrate such as diaspore is not preferred.

As the compound of the rare earth element, lanthanum, cerium, praseodymium, neodymium, samarium and yttrium compounds are preferable, and lanthanum is particularly preferable.
As the alkaline earth element compound, compounds of calcium, strontium, and barium are preferable.

Compounds of titanium, zirconium, and tin are preferable as the compound of the Group 4 element. As the compound of the Group 8 element, compounds of iron, cobalt and nickel are preferable.

As the rare earth element, alkaline earth element, Group 4 element, Group 8 element and chromium compound, any of water-soluble salts such as nitrates, carbonates, acetates, oxalates and ammonium chlorides may be used. Good.

<Effect> The alumina-lanthanide-based catalyst carrier composition prepared by the production method of the present invention has a length of at least 10 m even after being baked at 1200 ° C. for 50 hours at a high temperature as shown in the following examples. Having a specific surface area of ² / g,
The catalyst carrier composition has excellent heat resistance.

Next, the present invention will be specifically described with reference to examples. However,
The composition and manufacturing method are not limited to these.

Example 1 662 g of Condia Boehmite (trade name: Dispural) having a specific surface area of 150 m ² / g was added to 1830 ml of water containing 19.6 ml of 60% nitric acid and stirred for 1 hour with a homomixer to partially dissolve the alumina sol. Obtained.

Next, this sol was transferred to a kneader heated to 80 ° C., and with stirring, 185 g of lanthanum nitrate and 42.6 of barium acetate.
800 ml of water in which g was dissolved was gradually added into the kneader.

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

The dry solid is then crushed with an atomizer for 10-20
Micronized powder is then calcined at 800 ° C for 5 hours and 11.7% by weight as lantana and 4.3 as barium oxide.
A composite oxide containing 40% by weight of alumina and 84% by weight of alumina was obtained.

Example 2 The alumina sol obtained in the same manner as in Example 1 was transferred to a kneader heated to 80 ° C. and stirred with neodymium nitrate 12
800 in which 1.4g and 31g of strontium nitrate were dissolved
ml water was gradually added into the kneader.

Then, as in Example 1, 8.3% by weight as neodymia and 2.7% by weight as strontium oxide.
A composite oxide containing 89% by weight as alumina was obtained.

Example 3 2500 g of alumina sol (manufactured by Nissan Kagaku Co., Ltd.) having a crystalline form of coagulated boehmite structure and having a specific surface area of 245 m ² / g was placed in a kneader heated to 150 ° C., and 71.8 g of lanthanum nitrate and yttrium nitrate were stirred. 1000 ml of water in which 11.2 g and 45.3 g of zirconium nitrate were dissolved were gradually added into the kneader.

After kneading and stirring at the same temperature for 1 hour, the mixture was placed in a dryer kept at 150 ° C. and dried for 15 hours.

The dried solid was then roughly crushed to a powder of 20 to 50 microns and then calcined at 600 ° C for 5 hours to give a lantana of 4.9.
A composite oxide containing wt%, yttria 0.6 wt%, zirconia 3.8 wt%, and alumina 90.7 wt% was obtained.

Example 4 Using the same 2000 g of alumina sol as in Example 3, 10
96.8 g of lanthanum nitrate and 49.9 g of stannous chloride were dissolved with stirring in a kneader heated to 0 ° C. 10
00 ml of water was gradually added into the kneader.

Then, in the same manner as in Example 1, a composite oxide containing 7.8 wt% as lantana, 6.4 wt% as tin oxide, and 85.8 wt% alumina was obtained.

Example 5 To an acetic acid solution prepared by adding 230 ml of acetic acid to 2070 ml of water, 270 g of Boehmite (trade name: SB alumina) manufactured by Conoco Ltd. was added and stirred with a homomixer for 2 hours to obtain an alumina sol.

This sol was transferred to a kneader heated to 60 ° C., and while stirring, 48.4 g of lanthanum acetate and 38.3 g of nickel acetate.
500 ml of water in which was dissolved was gradually added.

Then, in the same manner as in Example 1, a composite oxide containing 9.8 wt% as lantana, 4.9 wt% as nickel oxide, and 85.3 wt% as alumina was obtained.

Example 6 Alumina sol obtained in the same manner as in Example 5, 7.5 g of cerium acetate, 12.8 g of barium acetate, and 13 cobalt acetate.
In the same manner as in Example 1 using g, 3.5% by weight as ceria and 3.5% by weight as barium oxide,
2.5% by weight as cobalt oxide, 9 as alumina
A composite oxide containing 0.5% by weight was obtained.

Example 7 Using the alumina sol obtained in the same manner as in Example 5, 29.5 g of lanthanum acetate, and 36.8 g of ammonium dichromate, 5% by weight as a lantana and 5% by weight as a chromia were prepared in the same manner as in Example 1. A composite oxide containing 90% by weight of alumina was obtained.

Example 8 1000 ml of a solution of 61.9 g of lanthanum nitrate and 10.4 g of zirconium nitrate and 33.3 g of a 30% aqueous solution of oxotitanium monoammonium oxalate in water were transferred to a kneader heated to 60 ° C. and stirred. After adding 1000 g of alumina sol, the kneader was heated to 120 ° C., kneading was continued for 1 hour, and stirring was continued.

Then, in the same manner as in Example 1, a composite oxide containing 9.8 wt% as lantana, 2 wt% as zirconia, 4.2 wt% as titania, and 84 wt% as alumina was obtained.

Comparative Example 1 0.8% by weight of lanthanum and 0.8% by weight of barium oxide were prepared in the same manner as in Example 1 except that 10.9 g of lanthanum nitrate and 800 ml of water in which 6.8 g of barium acetate were dissolved were used. A composite oxide containing 98.4% by weight of alumina was obtained.

Comparative Example 2 22.5% by weight of lanthanum, 4.9% by weight of nickel oxide, and alumina as alumina were used in the same manner as in Example 5 except that 500 ml of water in which 164.8 g of lanthanum acetate and 45 g of nickel acetate were dissolved was used. A composite oxide containing 72.6% by weight was obtained.

Comparative Example 3 500 g of activated alumina having a specific surface area of 120 m ² / g
73.7 g of lanthanum acetate, ammonium dichromate 9
2 g of the product was immersed in 500 ml of dissolved water, mixed and evaporated to dryness.

Then, in the same manner as in Example 1, a composite oxide containing 5% by weight of lantana, 5% by weight of chromia and 90% by weight of alumina was obtained.

Example 9 The composite oxides obtained in Examples 1 to 8 and Comparative Examples 1 to 3 were calcined at 1200 ° C. for 5 hours, 20 hours, and 50 hours in an air atmosphere, respectively, and then the surface area was adsorbed with nitrogen gas. Was measured with a BET-type specific surface meter. Table 1 shows the measurement results of the surface area.

From Table 1, the composite oxides obtained in Examples 1 to 8 are 12
It can be seen that the catalyst carrier composition has a specific surface area of 10 m ² / g or more even after firing at 00 ° C. for 50 hours, and is a thermally stable catalyst carrier composition.

On the other hand, the oxide of the rare earth element (Lantana) in Comparative Example 1 was 1
A composite oxide containing less than 1% by weight of an oxide of an alkaline earth element (barium oxide) below 1% by weight has almost no stabilizing effect on alumina, and becomes α-alumina upon firing at 1200 ° C. for 5 hours, and has a specific surface area of It becomes 10 m ² / g or less.

Further, the oxide of the rare earth element (Lantana) of Comparative Example 2 was 20
The complex oxide added in excess of weight% is complexed with alumina after firing at 1200 ° C. for 5 hours to produce LaAlO ₃ having a perovskite structure, and the specific surface area is also 20.
After the time firing, it becomes 10 m ² / g or less.

Furthermore, the composite oxide prepared by the immersion method of Comparative Example 3 was stabilized by short-time firing for 20 hours, but the stabilizing effect disappeared when the time was further extended.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical indication location B01J 23/26 M 8017-4G ZAB A 8017-4G 23/76 M 8017-4G ZAB A 8017-4G 23/78 M 8017-4G ZAB A 8017-4G 32/00 F23D 14/18 E

Claims (3)

[Claims] 1. A solution of an alumina hydrate, a solution of a compound of at least one rare earth element selected from the group consisting of lanthanum, cerium, praseodymium, neodymium, samarium and yttrium and an alkaline earth consisting of calcium, strontium and barium. A group element; a Group 4 element consisting of titanium, zirconium and tin; a Group 8 element consisting of iron, cobalt and nickel, and a solution of a compound of at least one element selected from the group consisting of chromium; The solution of the alumina hydrate is gelled, dried and calcined, and the obtained composite oxide is in the range of 60 to 98% by weight as alumina, and the rare earth element is in the range of 1 to 20% by weight as oxide. At least one selected from the group consisting of alkaline earth elements, Group 4 elements, Group 8 elements, and chromium. 1 to 20 species of the element as an oxide
A method for producing a heat-resistant catalyst carrier composition, which has a composition in the range of wt%. 2. The method according to claim 1, wherein a part of the heat-resistant catalyst support composition has a layered aluminate crystal structure similar to magnetoplumbite. 3. Gelation of a solution of alumina hydrate is 40 to 2
The method according to claim 1, which is carried out in a temperature range of 00 ° C.