JPH06373A - Catalyst carrier, its production and catalyst for decomposition of hydrazine - Google Patents

Abstract

PURPOSE:To increase the catalytic active point and to obtain a catalyst having low temp. activity by increasing the specific surface area of catalyst carrier to a specified value. CONSTITUTION:An alumina carrier source material 2 is dipped in a soln. containing an Al compd. (e.g. aluminum. chrolide), while maintaining the liquid temp. to 50-100 deg.C and an alkali soln. is added to control the pH of the liquid to 7-10. After precipitating alumina hydrate 4 on the surface of the carrier source material 2, the carrier source material 2 is taken from the liquid and heated at 150-400 deg.C. This process is performed once or repeated several times to obtain an alumina carrier (A) having 330-500m<2>/g specific surface area. By depositing platinum elements such as Ir on the surface of this carrier, a catalyst having extremely high catalytic activity can be obtd. When this decomposition catalyst is used for a propelling device or the like, high decomposition efficiency can be obtd. even the hydrazine supplied is at low temp., and decrease in propelling force due to low temp. of the hydrazine supplied can be prevented. Thus, preheating of hydrazine to be supplied to the decomposition catalyst can be omitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst carrier made of alumina having an extremely large specific surface area, a method for producing the same, and a hydrazine-decomposing catalyst using the carrier.

[0002]

2. Description of the Related Art Hydrazine and lower alkyl-substituted hydrazine (hereinafter abbreviated as hydrazines) are useful as a single propellant for thrusters such as rockets. Since hydrazines are decomposed by a decomposition catalyst and generate high-temperature decomposed gas when decomposed, they can be used not only for the operation of rocket or space satellite attitude control jets, but also for generating gas for turbine operation. .

Conventionally, as a decomposition catalyst for hydrazines,
Mainly platinum group metal catalysts were used. When this decomposition catalyst is used in a thruster or a gas generator, a catalyst having a very high activity and a long period of validity as a catalyst is required. That is, since hydrazine is a relatively stable substance that can be stored in a storage tank for a long period of time, a very active catalyst is required for spontaneous ignition at the high flow rate adopted in rocket engines. . In addition, when hydrazine decomposes, it reaches temperatures as high as 1000 ° C or higher, so it must be extremely stable if it is to be reignited many times.

A catalyst for decomposing hydrazine described in Japanese Patent Publication No. 1-13900 is known as a catalyst having extremely high activity and excellent stability. The catalyst for decomposing hydrazines has a carrier of about 0.3 to 0.5 cm ^3.
/ G and a pore volume and alumina with a specific surface area of about 100 to 300 m ² / g, 20 weight of the catalyst on the carrier
-40% of iridium or a mixture of iridium and ruthenium is supported.

[0005]

However, in the catalyst for decomposing hydrazines described in this Japanese Patent Publication No. 1-13900, decomposition does not occur sufficiently when the liquid temperature of hydrazines is low, and the thrust is There was a problem that it decreased. The inventors of the present invention have investigated the cause of the decrease in the decomposition activity at low temperature in this conventional hydrazine decomposition catalyst, and as a result, it has been found that the decomposition activity at low temperature deteriorates when the specific surface area of the carrier used for the catalyst is small. I found it. As disclosed in the above publication, the carrier for this hydrazine decomposition catalyst has a pore volume of 0.3 to 0.5 cm ³ / g and a pore volume of 100 to 100 cm ^3.
Alumina-based carriers and the like are known as materials having a specific surface area of 300 m ² / g. Among them, as a carrier material having a particularly large specific surface area, there is an alumina carrier using gibbsite as a raw material. Also has a specific surface area of 300 m ² / g or less (usually 120 to 150 m ² /
g), and no carrier having a specific surface area higher than that was provided.

The present invention has been made in view of the above circumstances, and a catalyst carrier capable of increasing the specific surface area of the catalyst carrier to increase the catalytic activity points and constituting a catalyst having high low-temperature activity. It is intended to provide a hydrazine decomposition catalyst using the production method and the carrier.

[0007]

The invention according to claim 1 is
A catalyst carrier made of alumina having a specific surface area of 330 to 500 m ² / g.

According to a second aspect of the invention, a carrier raw material made of alumina is dipped in a solution containing an aluminum compound,
While maintaining the liquid temperature at 50 to 100 ° C., an alkaline solution was added to adjust the pH of the liquid to 7 to 10 to precipitate hydrous alumina on the surface of the carrier raw material, and then the carrier raw material was taken out from the liquid to obtain 150 The specific surface area of 330 to 500 m ^{2 is} performed by repeating the step of heating to 400 ° C. once or plural times.
A method for producing a carrier for a catalyst, which comprises producing an alumina carrier having an amount of / g.

According to a third aspect of the present invention, a carrier raw material made of alumina is dipped in an acid or alkali solution to roughen the surface of the carrier raw material to have a specific surface area of 330 to 500 m ² / g.
A method for producing a carrier for a catalyst, which comprises producing an alumina carrier having

According to a fourth aspect of the present invention, the specific surface area is from 330 to
A catalyst for decomposing hydrazines, characterized in that a platinum group element such as iridium is supported on a catalyst carrier made of alumina having 500 m ² / g.

[0011]

The catalyst carrier of the present invention has a specific surface area of 330 to 50.
Since it is composed of alumina having 0 m ² / g, a catalyst having an extremely high catalytic activity can be obtained by supporting platinum group elements such as iridium and other catalysts on the surface thereof. This carrier is prepared by immersing a carrier raw material made of alumina in a solution containing an aluminum compound and adjusting the liquid temperature to 50
While maintaining at -100 ° C, an alkaline solution is added to adjust the pH of the solution to 7 to 10 to precipitate hydrous alumina (gibbsite) on the surface of the carrier raw material, and then the carrier raw material is added to 150
The step of heating to 400 ° C. is repeated once or plural times to form innumerable fine crystals of alumina on the surface of the carrier raw material, or the carrier raw material made of alumina is immersed in an acid or alkaline solution to form a carrier raw material. It is obtained by roughening the surface of. Alumina carrier raw materials made from gibbsite have a specific surface area of 300 m ² / g or less (usually 120
˜150 m ² / g), but by depositing fine crystals of hydrous alumina on the surface of this carrier material and heating,
Alternatively, by roughening the surface of the carrier raw material, one having a specific surface area of 330 to 500 m ² / g can be obtained. The specific surface area thus obtained is 330 to 500 m ²
A catalyst for decomposing hydrazines in which a platinum group element such as iridium is supported on a carrier having an amount of / g has an increased number of catalytic active points and improved catalytic activity at low temperatures, as compared with conventional products.

[0012]

EXAMPLE A catalyst carrier according to the present invention has a specific surface area of 330.
It is composed of alumina having ˜500 m ² / g. Alumina that constitutes the carrier is obtained by firing gibbsite under an appropriate temperature condition. The raw material, gibbsite (Al ₂ O ₃ .3H ₂ O), is known as an intermediate product in the production of alumina that precipitates in the hydrolysis step in the Bayer method and is obtained by hydrolysis of aluminum hydroxide. This gibbsite is relatively cold (30
Alumina obtained by heating at 0 to 400 ° C.) has numerous fine pores 1 formed on the surface as shown in FIG. 1 (a), and has a specific surface area of about 100 to 300 m ² / g, usually It is about 120 to 150 m ² / g and is used as a catalyst carrier.

The catalyst carrier according to the present invention is made of alumina having such a large specific surface area as a raw material, and further, as shown in FIG.
As shown in FIG. 3, the specific surface area is set to 330 to 500 m ² / g by forming fine alumina fine crystals 3 on the surface of the carrier raw material 2 or by roughening the surface of the carrier raw material 2. . When the specific surface area is less than 330 m ² / g, the catalyst activity improving effect when forming and using the catalyst, particularly the catalyst activity improving effect at low temperature, cannot be obtained, and the difference from the conventional product is eliminated. Further, even if the specific surface area is higher than 500 m ² / g, the production is difficult and the supportability of the catalyst metal is deteriorated, which adversely affects the stability. The carrier A has a platinum group element such as iridium or other catalyst supported on the surface thereof, whereby a catalyst having an extremely high catalytic activity can be obtained.

FIGS. 1 (a) to 1 (c) are for explaining an example of the method for producing a catalyst carrier according to the present invention.
FIG. 1A shows a carrier raw material made of alumina used as a catalyst carrier raw material. As described above, the carrier raw material 2 has numerous holes 1 formed on its surface. The internal pore diameter of the pores is on the order of tens to hundreds of angstroms, and the specific surface area is usually about 120 to 150 m ² / g. The surface of the carrier raw material 2 including the surface of the hole 1 is relatively smooth. The carrier raw material 2 may be a commercially available product and may be used.
It is also possible to manufacture it by firing at low temperature at 00 ° C., and it is possible to manufacture carrier raw materials of various shapes and sizes.

In this production example, first, the above-mentioned carrier raw material 2 is prepared, and also a dilute aqueous solution of a soluble salt of aluminum is prepared. As the soluble salt of aluminum used here, aluminum chloride, aluminum sulfate, aluminum nitrate and the like can be used, and usually aluminum chloride is preferably used. The salt concentration of the aqueous solution used here is preferably about 10 ⁻³ to 10 ⁻⁶ mol / liter. If the salt concentration is higher than this range, excessive hydrated alumina may be precipitated when the hydrated alumina made of gibbsite (hereinafter referred to as hydrated alumina) is generated, and the pores 1 may be blocked. If the salt concentration is lower than the above range, the amount of hydrous alumina deposited will be too small and the efficiency will be poor.

Next, the dilute aqueous solution of the aluminum-soluble salt is heated to a liquid temperature of 50 to 100 ° C., preferably 60.
The carrier raw material 2 was dipped in the solution while maintaining the temperature at around 0 ° C, and an aqueous alkaline solution such as aqueous ammonia or aqueous sodium hydroxide was added dropwise to the aqueous solution to adjust the pH of the solution to 7 to 1
It is set to 0, preferably 8 to 9 (FIG. 1 (b)). If the liquid temperature is out of the above range, hydrous alumina will not be uniformly deposited on the surface of the carrier raw material 2.

A hydrated alumina layer 4 is formed on the surface of the carrier raw material 2 including the inner surface of the hole 1. Next, the carrier raw material 2 is taken out from this solution and dried to obtain 150 to 400
C., preferably about 350.degree. C., and put in a baking furnace to bake in dry air. By this low temperature firing, the hydrous alumina layer 4 formed on the surface of the carrier raw material 2 is changed to alumina,
As shown in FIG. 1C, innumerable fine crystals 3 of alumina are formed on the surface of the carrier raw material 2, and the specific surface area 330 to 5
Carrier A with 00 m ² / g is obtained. The operation including the formation of the hydrous alumina layer 4 and the subsequent firing step may be repeated a plurality of times as necessary.

The method for producing the carrier A having a specific surface area of 330 to 500 m ² / g is not limited to the above example, and various applications are possible. For example, a method is also used in which the surface of the carrier raw material 2 is roughened to make the specific surface area 330 to 500 m ² / g. In this method, the carrier raw material 2 is immersed in a strong acid solution such as hydrochloric acid or a strong alkaline solution to be appropriately corroded (etched) to roughen the surface. Even by such an operation, the surface area of the carrier raw material 2 can be increased, and the specific surface area of 330 to 50
0 m ² / g of carrier can be produced.

FIG. 2 shows an example of the hydrazine decomposition catalyst according to the present invention. The hydrazine decomposition catalyst B (hereinafter referred to as a decomposition catalyst) has a specific surface area of 33
The catalyst layer 5 made of a platinum group element such as iridium is formed on the surface of the carrier A having a thickness of 0 to 500 m ² / g. Of the platinum group elements, iridium, ruthenium and a mixture thereof are particularly preferable as the material of the catalyst layer 5.

The method of forming the catalyst layer 5 on the surface of the carrier A is, as disclosed in Japanese Patent Publication No. 1-13900, immersing the carrier in an aqueous solution of a soluble salt of a catalyst element such as iridium, After impregnating the carrier with the aqueous solution, it is dried,
Next, a method in which the carrier is heated in a hydrogen stream to decompose the salt adhering to the surface to deposit the catalyst metal is repeated a plurality of times, which is preferably used. As a soluble salt of a catalyst element such as iridium, iridium trichloride, ruthenium trichloride, etc. are preferably used. Further, it is desirable that the supported amount of these catalytic metals is about 20 to 40% by weight of the catalyst weight.

The thus-obtained decomposition catalyst B has an increased number of catalytic active points and an improved catalytic activity at low temperatures as compared with the conventional product. Therefore, when this decomposition catalyst B is used in a propulsion device or the like, a high decomposition rate of hydrazines to be supplied can be obtained even at a low temperature, and it is possible to prevent a decrease in thrust that occurs due to a low supply temperature of hydrazines. Preheating of hydrazines supplied to the catalyst can be omitted.

(Experimental Example) Two commercially available alumina carriers (Comparative Examples 1 and 2) and a carrier according to the present invention (invention product) prepared by using one of the alumina carriers as a raw material were prepared, Iridium was carried on a carrier to form decomposition catalysts, and the activity of each decomposition catalyst at low temperature was compared.

Comparative Example 1 An alumina carrier commercially available from A company. Specific surface area 150 m ² / g. Comparative Example 2 An alumina carrier commercially available from Company B. Specific surface area 120 m ² / g. The alumina support of the present invention product Comparative Example 1 as a raw material, which 10 ^-4 mo
1 / liter aluminum chloride aqueous solution (liquid temperature 60 ° C)
1N ammonia water is added dropwise with stirring, and p
H was adjusted to 8-9. After being left for 30 minutes, the carrier raw material was taken out, dried, put in a baking furnace at 350 ° C., and baked for 1 hour. This operation was repeated twice to prepare a carrier. The specific surface area of the obtained carrier was about 350 m ² / g. The specific surface area of these carriers was measured by a known gas diffusion method.

Each of the carriers of Comparative Examples 1 and 2 and the product of the present invention was 0.2%.
After immersing in 1% iridium trichloride solution and drying,
Step 5 of heating in a hydrogen stream to deposit iridium
The decomposition catalyst was produced by repeating the process repeatedly. The amount of iridium supported on each decomposition catalyst was about 28% by weight of the amount of catalyst.

Using each decomposition catalyst thus obtained, the relationship between the liquid temperature of liquid hydrazine and the decomposition activity was measured, and the results are shown in FIG. FIG. 3 is a graph showing, as an Arrhenius plot, the relationship between the liquid temperature and the generated energy when liquid hydrazine acts on the decomposition catalyst. As is clear from FIG. 5, the catalyst using the carrier of the present invention shows less decrease in decomposition activity at low temperatures than conventional decomposition catalysts.

[0026]

As described above, the present invention has the following effects. Since the catalyst carrier according to the present invention is made of alumina having a specific surface area of 330 to 500 m ² / g, it has an extremely high catalytic activity by supporting a platinum group element such as iridium or another catalyst on the surface thereof. A catalyst is obtained. Further, in the method for producing a carrier for a catalyst according to the present invention, on the surface of a conventional carrier raw material, fine crystals of hydrous alumina are deposited and heated, or the surface of the carrier raw material is roughened to give a specific surface area. Is 33
Since a catalyst carrier of 0 to 500 m ² / g is produced, a high-performance catalyst carrier having an extremely large specific surface area can be easily produced at low cost. Further, the hydrazine-decomposing catalyst according to the present invention comprises a platinum group element such as iridium supported on a carrier having a specific surface area of 330 to 500 m ² / g. The catalytic activity at low temperature is improved. Therefore, when this decomposition catalyst is used in a propulsion device or the like, a high decomposition rate can be obtained even when the supplied hydrazines have a low temperature, and it is possible to prevent the thrust from decreasing due to the low supply temperature of the hydrazines. It is possible to omit the preheating of the hydrazines supplied to.

[Brief description of drawings]

FIG. 1 shows a method for producing a catalyst carrier according to the present invention, in which (a) is a carrier raw material, (b) is a hydrous alumina layer forming step, and (c) is an enlarged view of an essential part of the carrier. Is.

FIG. 2 is an enlarged view of a main part showing an example of a hydrazine-decomposing catalyst according to the present invention.

FIG. 3 is a graph showing measurement results of hydrazine decomposition activity of decomposition catalysts produced in Experimental Examples.

[Explanation of symbols]

1 ... Pores, 2 ... Carrier raw material, 3 ... Alumina crystallites,
4 ... Hydrous alumina layer, 5 ... Catalyst layer, A ... Carrier, B
…… Hydrazine decomposition catalyst.

Claims (4)

[Claims] 1. A catalyst carrier comprising alumina having a specific surface area of 330 to 500 m ² / g. 2. A carrier raw material made of alumina is immersed in a solution containing an aluminum compound and the liquid temperature is adjusted to 50 to 100.
While keeping the temperature at 0 ° C., an alkaline solution was added to adjust the pH of the liquid to 7 to 10 to precipitate hydrous alumina on the surface of the carrier raw material, and then the carrier raw material was taken out of the liquid to 150 to 40 ° C.
A process for producing a catalyst carrier, which comprises performing the step of heating to 0 ° C. once or a plurality of times to produce an alumina carrier having a specific surface area of 330 to 500 m ² / g. 3. A carrier raw material made of alumina is immersed in an acid or alkaline solution to roughen the surface of the carrier raw material,
A method for producing a carrier for a catalyst, comprising producing an alumina carrier having a specific surface area of 330 to 500 m ² / g. 4. A catalyst for decomposing hydrazines, characterized in that a platinum group element such as iridium is supported on a catalyst carrier made of alumina having a specific surface area of 330 to 500 m ² / g.