JPH03254835A - Catalyst for decomposing hydrazine - Google Patents

Abstract

PURPOSE:To smoothly advance hydrazine decomposing reaction and to enhance the decomposition efficiency of hydrazine by supporting irridium on heat- resistant alumina having a high specific surface area prepared by a modified sol-gel method. CONSTITUTION:Aluminum alkoxide is added to hexylene glycol (2-methyl-2,4- pentane diol) to be reacted within the range of 101-200 deg.C under heating and, next, a gel is obtained from a sol by hydrolysis and the formed gel is dried and baked to obtain alumina pref. having a high specific surface area of about 100m<2>/g or more. Next, this alumina is impregnated with an aqueous solution or ethanol solution of irridium chloride and the impregnated one is dried and baked to support irridium on alumina. Since alumina is prepared by a modified sol-gel method as mentioned above and heat-resistance is imparted thereto, hydrazine decomposing reaction is advanced smoothly and decomposition efficiency is enhanced.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a hydrazine decomposition catalyst.

(Prior art) As a conventional catalyst for decomposing hydrazine, 25 to 30 mesh alumina is used as an inorganic carrier by a conventional method (thermal decomposition method, etc.), and iridium (rr) is used as a catalyst.
) is almost uniformly supported at 30 to 40% by weight. When hydrazine (N2H,) is brought into contact with this iridium, the hydrazine decomposes through the reaction N2H4→N2+2H2 or 3N2H4→4N+ (3,000 N2 2NH3→N2+382), generating rocket thrust.

(Problem to be solved by the invention) However, such conventional hydrazine decomposition catalysts have poor heat resistance and have a large amount of iridium supported on alumina, which has a low specific surface area. As the amount of iridium increases, the dispersibility of iridium decreases, resulting in a problem that the activity is not high and the life cannot be further extended.

(Means for Solving the Problems) The present invention was made by focusing on such conventional problems, and instead of the conventional low specific surface area alumina, a high heat resistant high surface area synthesized by an improved sol-gel method was developed. The conventional problems were solved by using alumina.

The present invention will be explained below.

First, to explain the structure, the catalyst of the present invention consists of high specific surface area alumina produced using an improved sol-gel method and a catalyst component of iridium (Ir) supported thereon.

As alumina, aluminum alkoxide is added to hexylene glycol (2-methyl-2,4-pentanediol), heated to react at a temperature in the range of 101°C to 200″C, and then separated from the sol by hydrolysis. A gel is obtained, and the resulting gel is dried and calcined. Preferably, alumina having a specific surface area of 100 m2/g or more is used. It was proposed in No. 221448.

As a method for supporting the catalyst component on the alumina, any solution containing Ir may be used as long as the iridium reagent is soluble in the solvent. , there is a method of firing.

Further, the form of alumina may be powder, granule, or even a three-dimensional honeycomb coating.

Next, the amount of iridium supported is 5 to 30% relative to the weight of the catalyst.
% by weight is preferred. It is believed that iridium is supported from inside the alumina, and if it is less than 5% by weight, iridium is not dispersed on the surface of the alumina and is supported only inside the alumina, resulting in poor performance. Moreover, if it is more than 30% by weight, it will be sufficiently dispersed on the surface of the alumina to be dispersed, so there is no effect even if more than 30% by weight is supported.

The hydrazine decomposition catalyst of the present invention is preferably used in a hydrazine thruster as a thrust device mounted on a satellite tower. FIG. 2 shows an example in which the hydrazine decomposition catalyst of the present invention is used in a hydrazine thruster as a thrust device mounted on a satellite tower. In FIG. 2, propellant valve 1 is a valve that controls the injection amount of liquid hydrazine to be reacted. The liquid hydrazine injected from the propellant valve is thermally protected by a thermal protection standoff 2 before being decomposed, and introduced into a decomposition catalyst 4 using the catalyst of the present invention, which is held by a thrust chamber 3 and a catalyst bed plate. . The hydrazine introduced into the decomposition catalyst undergoes an exothermic decomposition reaction as shown in the above reaction formula. Note that 7 is a temperature sensor. A mixed gas of ammonia, nitrogen and hydrogen generated by the decomposition is injected through a nozzle 6 to generate rocket thrust.

(Example) Next, the present invention will be explained with reference to Examples, Comparative Examples, and Test Examples.

Example 1 599.8 g of aluminum isopropoxide (AI! (OisoPr)s) was placed in a 2000-capacity beaker, and 540.9 g of hexylene glycol was added thereto.
The mixture was heated in a 120°C oil bath and stirred for 4 hours. Next, after cooling the oil bath temperature to 100° C., 449.5 g of water was added to the aluminum alkoxide solution. After being left at the same temperature overnight, the resulting gel was transferred to an eggplant-shaped plasco and dried at 120 to 170° C. under reduced pressure to obtain 195 g of dry gel. This was calcined at 950° C. for 3 hours to obtain 150 g of white alumina powder. After immersing 10 g of this powder in an iridium chloride aqueous solution and drying it, hydrogen reduction was performed at 400° C. for 1 hour to obtain catalyst 1. The Ir content of catalyst 1 was 28.
It was 9%.

Example 2 Except that the impregnating liquid was an iridium chloride ethanol solution,
A catalyst was prepared in the same manner as in Example 1 to obtain Catalyst 2.

The Ir content of catalyst 2 was 29.1%.

Example 3 A catalyst was prepared in the same manner as in Example 1, except that the temperature at which the alumina was fired was changed to 600° C., to obtain catalyst 3. The 1r content of catalyst 3 was 29.096.

Example 4 A catalyst was prepared in the same manner as in Example 2, except that the temperature at which the alumina was fired was changed to 600°C, and Catalyst 4 was obtained. The Ir content of catalyst 4 was 28.8%.

Example 5 A catalyst was prepared in the same manner as in Example 1, except for a catalyst with an Ir content of 5%, and Catalyst 5 was obtained. The Ir content of catalyst 5 was 5.1%.

Comparative Example I Commercially available alumina (5C3-79 manufactured by Lorne Boulin) was calcined at 900°C for 3 hours, 10 g of this powder was immersed in an aqueous iridium chloride solution, dried, and then hydrogen reduced at 400°C for 1 hour to remove the catalyst. I got an A. The Ir content of the catalyst is 29.
It was 0%.

Comparative Example 2 Commercially available alumina (5C3-79 manufactured by Lone Boulan)
A catalyst was prepared in the same manner as in Example 2, except that a product calcined at 900° C. for 3 hours was used to obtain Catalyst B.

The Ir content of catalyst B was 29.1%.

Comparative Example 3 Commercially available alumina (5C5-79 manufactured by Lone Boulan)
A catalyst was prepared in the same manner as in Example 3, except that a product fired at 800° C. for 3 hours was used to obtain Catalyst C.

The Ir content of catalyst C was 28.8%.

Comparative Example 4 Commercially available alumina (5C3-79 manufactured by Lone Boulan)
A catalyst was prepared in the same manner as in Example 4 except that a product calcined at 600° C. for 3 hours was used to obtain a catalyst.

The Ir content of the catalyst was 28.9%.

Comparative Example 5 A catalyst was prepared in the same manner as in Comparative Example 1, except that the Ir content was 5%, and Catalyst E was obtained.

The Ir content of catalyst E was 5.2%.

Test Examples Catalysts 1 to 5 obtained in Examples 1 to 5 and catalysts A to E obtained in Comparative Examples 1 to 5 were subjected to a hydrazine Log open cup test in the following manner. Table 1 shows the results obtained.
and shown in FIG.

Open Cup Test Method A glass container is placed on top of an electronic point large bottle, 10 g of liquid hydrazine is taken into the glass container, a prototype catalyst is added to the glass container, and the weight loss of hydrazine is measured.

(Effects of the Invention) The present invention has the effect that by replacing the alumina in the conventional hydrazine decomposition catalyst with alumina using an improved sol-gel method, the hydrazine decomposition reaction can proceed smoothly and the hydrazine decomposition efficiency can be improved. can get

[Brief explanation of drawings]

Figure 1 is a curve diagram showing the open cup test results of Examples 1 to 5, Comparative Examples 1 to 5, and A-E. FIG. l...Propellant valve 2...Thermal protection standoff 3...Thruster chamber

Claims (1)

[Claims] 1. Aluminum alkoxide is added to hexylene glycol (2-methyl-2,4-pentanediol), heated to react at a temperature in the range of 101°C to 200°C, and then hydrolyzed to form a sol. A catalyst for decomposing hydrazine, characterized in that iridium (Ir) is dispersed and supported on alumina obtained by obtaining a gel from the above, drying and calcining the resulting gel. 2. The catalyst according to claim 1, wherein the amount of iridium supported is 5 to 30% by weight based on the weight of the catalyst.