JP2022136804A - Combustion catalyst for liquid propellant, method for producing the same, and use thereof - Google Patents

Abstract

To provide a technique for enhancing ignitability without depending on the composition of a propellant itself.SOLUTION: Provided is an ammonium dinitramide-containing combustion catalyst for liquid propellant that comprises a porous carrier and a catalytic component supported on the carrier, and in which the catalytic component contains a metal element including a noble metal element, an oxide thereof, or an alloy thereof. The combustion catalyst is used by filling in a combustion chamber in a flying object propulsion device.SELECTED DRAWING: Figure 1

Description

The present invention relates to a combustion catalyst for a liquid propellant containing ammonium dinitramide, a method for producing the combustion catalyst, and a flying object propulsion device using the combustion catalyst.

Liquid propellants are generally used as propulsion sources for flying objects such as rockets. In the field of space rockets, it is possible to control the thrust by interrupting combustion and reigniting.

There are generally two types of liquid propellants: a two-liquid mixed system and a one-liquid system. A two-liquid mixture system can obtain a large thrust by burning a liquid oxidizer and a liquid fuel, but the system becomes complicated because two feeders are required. Since the single-liquid system can be burned by contact with the catalyst or external energy, the system can be simplified, and it is used for orbit correction and attitude control thrusters of artificial satellites.

Hydrazine-containing propellants have been used for orbit correction and attitude control thrusters of artificial satellites, but hydrazine is highly toxic and difficult to handle. Therefore, a propellant using ammonium dinitramide (ADN) as an oxidant and alcohol as a fuel has been proposed. In order to improve the combustibility of this propellant, Patent Document 1 discloses a liquid propellant containing ADN, monomethylamine nitrate, urea, and a copper compound-based combustion aid.

Patent Document 2 discloses, as an ammonia decomposition catalyst, a catalyst in which a metal such as iron or copper and a noble metal such as ruthenium palladium are supported on a porous silica alumina carrier.

JP 2019-199395 A International Publication No. WO2006/103754

In order to further improve the convenience of the ADN-containing liquid propellant, it is necessary to increase the degree of freedom in the composition of the propellant itself, in other words, to minimize the requirements for the composition of the propellant itself so that various needs can be met. Therefore, it is preferable to allow the propellant composition to vary. From this point of view, it is desirable to provide a technique for improving ignitability without depending on the composition of the propellant itself, and the object of the present invention is to provide such a technique.

The present inventors completed the present invention shown below as a result of intensive studies.

(1) Combustion catalyst for ammonium dinitramide-containing liquid propellant, comprising a porous carrier and a catalytic component supported on the carrier, wherein the catalytic component comprises a metal element containing a noble metal element, an oxide thereof, or an alloy thereof. .
(2) The combustion catalyst of (1), wherein the noble metal element is one or more selected from the group consisting of Pt, Ir, Pd, Rh and Ru.
(3) The combustion catalyst of (1) or (2), wherein the porous carrier is a sintered body containing one or more selected from the group consisting of alumina, silica, cesium, zeolite and titanium oxide.
(4) The combustion catalyst of (1) to (3) having a specific surface area of 5 to 500 m ² /g.
(5) The combustion catalyst of (1) to (4), wherein the catalyst component is supported on the surface of the porous carrier with a thickness of 1 to 100 μm.
(6) A flying object propulsion device having a combustion chamber for obtaining a propellant gas by combusting the combustible gas after decomposing an ammonium dinitramide-containing liquid propellant into a combustible gas, wherein at least A flying object propulsion device partially filled with the combustion catalysts (1) to (5).
(7) a step of adhering a liquid containing a compound containing a noble metal element to a porous carrier; and, after said step, heating the porous carrier to extract a metal simple substance containing a noble metal element or an oxide thereof from said liquid. or a step of supporting the alloy on the porous carrier by sintering.

According to the present invention, ignitability can be improved by means such as installing the combustion catalyst of the present invention in the combustion chamber without mixing the combustion aid with the ADN-containing liquid propellant itself.

1 is a schematic cross-sectional view of a propulsion device of the present invention; FIG.

The catalyst of the present invention is for ammonium dinitramide-containing liquid propellants. Here, the liquid propellant refers to a propellant that has fluidity when the liquid propellant is supplied and ejected from the engine system of a flying object such as a rocket. The liquid propellant may contain solid substances without impairing its flowability.

Ammonium dinitramide (ADN) is a compound represented by the following chemical formula (1).

ADN is a known compound, and for example, ammonium dinitramide of the above chemical formula (1) can be obtained by preparing the corresponding cation according to the production method described in JP-T-5-500795. .

The liquid propellant may contain various known substances in addition to ADN. For example, the liquid propellant may contain monomethylamine nitrate (MMAN) represented by the general formula (2) below.

Monomethylamine is a known compound, and a commercially available one can be used, or one obtained by a known production method can also be used. Examples of the production method include reacting monomethylamine with nitric acid. When the liquid propellant contains both ADN and MMAN, the ratio of ADN and MMAN in the liquid propellant is not particularly limited, and the ratio of (mass of ADN)/(mass of MMAN) is preferably 0.5. 5 to 2.5, more preferably 0.6 to 2.0. By setting it to this range, it becomes easy to obtain the propellant as a liquid, and an excellent specific impulse can be obtained. Also, ADN and MMAN preferably form a eutectic system.

The liquid propellant may include urea represented by the chemical formula C( _NH2 ) ₂ . Urea is a known compound, and commercially available urea can be used, and urea obtained by a known production method can also be used. When the liquid propellant contains urea, the mass ratio of urea to the liquid propellant is preferably 0.5 to 20 wt %.

Since a combustion catalyst is used in the present invention, the liquid propellant itself need not contain a combustion aid, but the use of a combustion aid is not denied. The liquid propellant may also contain a copper compound-based combustion aid, particularly a copper compound-based combustion aid comprising a divalent copper compound, a specific preferred compound being copper tetraammine nitrate (Cu( _NH3 ) ₄ (NO ₃ ) ₂ ), basic copper nitrate (Cu ₂ (NO ₃ )(OH) ₃ ), and the like. Note that the use of monovalent copper is not denied, and cuprous oxide (Cu ₂ O), for example, can also be used as a copper compound-based combustion aid.

Preferably, the liquid propellant is substantially free of hydrazine. “Substantially free of hydrazine” means, for example, that the content is 1 wt % or less.

Water may or may not be used as a solvent for the liquid propellant, and water may not be used if the propellant is in a liquid state. may be used.

The liquid propellant may further contain alcohols, aminos, ketones, etc. to adjust various properties.
Alcohols include methanol, ethanol, ethanediol, propanol, isopropanol, propanediol, propanetriol, butanol, butanediol and the like.
Aminos include glycine, alanine, valine, leucine, isoleucine and the like.
Ketones include acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, dimethyl ketone, diethyl ketone, methyl amyl ketone, cyclohexanone, isophorone and the like.

The liquid propellant may contain additives other than those described above. As described above, since a combustion catalyst is used in the present invention, the liquid propellant itself does not need to contain a combustion aid. may be

A combustion catalyst is a catalyst that promotes combustion, and more specifically, it increases reaction activity, enables ignition even at low temperatures, and can be used in a wide range. Combustion catalysts include rhodium, ruthenium, platinum, palladium, iridium, and the like.

A combustion aid is an additive that improves the specific impulse of a liquid propellant, and includes powders of aluminum, magnesium, boron, titanium, graphite, and the like.

The combustion catalyst of the present invention comprises a porous carrier carrying catalyst components. The porous carrier is made of a material that does not dissolve in the liquid propellant and has a large number of pores as reaction fields. Suitable materials for the porous carrier include inorganic solid materials, among which ceramic materials are preferred, and sintered bodies containing at least one selected from the group consisting of alumina, silica, cesium, zeolite and titanium oxide are particularly preferred. . From the viewpoint of the balance between the mechanical strength of the porous carrier and the efficiency of catalytic reaction, the specific surface area is preferably 10 to 800 m ² /g. A crushing strength of 50 N or more is suitable for the mechanical strength of the porous carrier. The shape of the porous sintered carrier is preferably in the form of regular or irregular pellets, spheres, rings, or honeycombs. From the viewpoint of ease of handling and ease of filling, the average particle size of each porous carrier is preferably 1 to 5 mm.

The method for producing the porous carrier is not particularly limited, and for example, sintering technology in the production of ceramics, control technology for generated pores, and the like can be appropriately referred to. Alternatively, ceramic materials manufactured with controlled specific surface areas and pores can be obtained from commercial products.

In the combustion catalyst of the present invention, a noble metal is carried on the above porous carrier as at least part of the catalytic component. The eight noble metals are gold, silver, platinum, ruthenium, rhodium, palladium, osmium and iridium. The catalyst component may be a noble metal simple substance, a noble metal oxide, or an alloy containing one or more noble metals. When the catalyst component is an alloy, it may be an alloy of a noble metal and a non-noble metal. All are preferably precious metals.

There are no particular restrictions on the manner in which the catalyst component is supported, as long as the catalyst component is bonded to the extent that the catalyst component does not separate from the porous carrier when the liquid propellant flows. From the viewpoint of catalytic efficiency, the catalytic component is preferably supported on the surface of the porous carrier with a thickness of 1 to 100 μm.

From the viewpoint of catalyst performance, cost, etc., the mass of the noble metal in the total mass of the combustion catalyst of the present invention is preferably 0.5 to 10.0 wt%.

The method for supporting the catalyst component on the porous carrier is not particularly limited, and conventional techniques such as the above-mentioned Patent Document 2 can be referred to as appropriate. Non-limiting examples include a method of attaching catalyst components to a porous carrier by an ion exchange method, an impregnation method, a dipping method, a spray method, or the like, followed by calcination.

As a preferred example, a method using a liquid containing a compound containing a noble metal element will be described.
The liquid may be a solution or a suspension as long as it has fluidity to the extent that it can be applied. Preferably, the noble metal element is dissolved in a cationic state in the liquid, and an acid salt solution of each noble metal is preferred. Examples of the acid salt solution include a hydrochloride solution and a nitrate solution. The liquid medium is not particularly limited, and examples thereof include alcohol.

The resulting liquid material can be adhered to the porous carrier by various means. Means of attachment include application to the porous carrier with a brush, immersion of the porous carrier in a liquid, and attachment to the porous carrier by spraying or spraying. In carrying out each attachment means, the conditions can be determined by appropriately referring to the prior art.

By heating the porous carrier to which the liquid is adhered, the noble metal element in the liquid is sintered on the porous carrier to obtain a metal simple substance or alloy of the noble metal element supported on the porous carrier. be able to. For the firing conditions and the like, reference can be made to the prior art related to noble metal firing technology and metal support as appropriate. In the case of noble metals, heating at about 300 to 700° C. in air can be used.

By the method as exemplified above, the combustion catalyst of the present invention can be obtained in which a catalytic component containing a metal simple substance or an alloy containing a noble metal element is supported on a porous carrier. When the combustion catalyst is obtained by such a method, the specific surface area of the obtained combustion catalyst is about 80 to 98% of the specific surface area of the raw material porous carrier.

The combustion catalyst of the present invention can be used as a combustion catalyst by coexisting with the ADN-containing liquid propellant described above when burning. The form of coexistence is not particularly limited, and for example, it is conceivable to install the combustion catalyst of the present invention at a place where the ADN-containing liquid propellant is to be burned.

As an example of use of the combustion catalyst of the present invention, it is conceivable to fill at least a part of the combustion chamber of a flying object propulsion device with the combustion catalyst of the present invention. Here, flying objects include rockets, artificial satellites, and the like. In such a flying object, the propulsive force is obtained from the gas obtained by burning the ADN-containing liquid propellant. A region in which the ADN-containing liquid propellant is to be burned is called a combustion chamber, and a drive system for flight including the combustion chamber is called a propulsion device.

FIG. 1 is a schematic cross-sectional view of an example of the propulsion device of the present invention.
ADN-containing liquid propellant is injected onto catalyst layer 12 by injector 14 through inlet pipe 13 . At this time, a known technique may be used for the structure of the injector. The ADN-containing liquid propellant is injected onto the catalyst layer 12, decomposed and ignited, and combusted in the combustion chamber 11. Combustion gas is discharged from the nozzle 15, and the flying object obtains propulsion.

The catalyst layer 12 is filled with the combustion catalyst of the present invention. There are no particular limitations on the mode of filling, the amount of filling, and the like, and they can be appropriately set as necessary. When the propulsion device is in use, the catalyst layer 12 is heated to catalyze the combustion catalyst of the present invention to burn the ADN-containing liquid propellant and produce gas to provide propulsion.

EXAMPLES The present invention will be described in detail below based on examples, but the present invention is not limited by these examples.

Each compound used in Examples and Comparative Examples was obtained as follows.

Monomethylamine nitrate (MMAN) was synthesized as follows.
187.6 parts of 70% nitric acid was added dropwise to 146.5 parts of a 40% monomethylamine aqueous solution, and the mixture was stirred at 10° C. or less to react. After the reaction, water was distilled off from the obtained aqueous solution under conditions of 60° C. and 30 mmHg to obtain a saturated aqueous solution of monomethylamine nitrate. A saturated aqueous solution of monomethylamine nitrate was added to 280 parts of isopropyl alcohol and stirred to precipitate crystals of monomethylamine nitrate. The obtained crystals were separated by filtration, washed with isopropyl alcohol and dried to obtain 186.4 parts of monomethylamine nitrate.

Ammonium dinitramide (ADN) and urea were commercially available.

To produce the liquid propellant, ADN, MMAN, and urea were mixed at a mass ratio of 4:4:2 at room temperature and allowed to stand at 60° C. for 1 hour to obtain a eutectic ionic liquid. The resulting eutectic ionic liquid was used as a liquid propellant.

Commercially available alumina balls (manufactured by Seto Chip Industry, diameter 3 mm) were used as the porous carrier. The specific surface area of this alumina ball is 175 m ² /g.

A coating liquid was prepared as follows in order to support the catalyst component on the porous carrier.
・Coating liquid 1
Iridium (IV) chloride hexahydrate was used as the metal raw material for the catalyst, and isopropanol containing 1% by mass of hydrochloric acid was used as the organic solvent. A coating liquid 1 was prepared by blending and stirring for 1 hour in a nitrogen atmosphere.
・Coating liquid 2
A coating solution 2 was prepared in the same manner as the coating solution 1, except that chloroplatinic (IV) acid hexahydrate was used as the metal raw material for the catalyst.
・Coating liquid 3
A coating solution 3 was prepared in the same manner as the coating solution 1, except that palladium (II) chloride was used as the metal raw material for the catalyst.
・Coating liquid 4
A coating solution 4 was prepared in the same manner as the coating solution 1, except that rhodium (III) chloride hydrate was used as the metal raw material for the catalyst.
・Coating liquid 5
Coating Liquid 5 was prepared in the same manner as Coating Liquid 1, except that ruthenium (II) chloride hydrate was used as the metal raw material for the catalyst.
・Coating liquid 6
Coating liquid 1 and coating liquid 2 were mixed so that the molar ratio of Ir and Pt was 1:1, and coating liquid 6 was prepared.
・Coating liquid 7
Coating liquid 1 and coating liquid 3 were mixed so that the molar ratio of Ir and Pd was 1:1, and coating liquid 7 was prepared.
・Coating liquid 8
Coating liquid 1 and coating liquid 4 were mixed so that the molar ratio of Ir and Rh was 1:1, and coating liquid 8 was prepared.
・Coating liquid 9
Coating liquid 1 and coating liquid 5 were mixed so that the molar ratio of Ir and Ru was 1:1, and coating liquid 9 was prepared.

Each of the coating liquids 1 to 9 obtained as described above was applied to the surface of the above porous carrier by a brush coating method, and baked in air at 400° C. for 1 hour. After calcining, the mixture was allowed to stand at room temperature for 3 hours to prepare combustion catalysts 1 to 9.

A combustion catalyst 10 was obtained by baking the above porous carrier under the same conditions as above without applying the coating liquid.

In each of the combustion catalysts 1 to 10, the thickness of the catalyst component and the mass ratio of the catalyst component in the combustion catalyst were as follows.

Combustion catalyst thickness Mass ratio of catalyst components
Combustion catalyst 1 7.5 µm 5.6 wt%
Combustion catalyst 2 7.0 µm 5.0 wt%
Combustion catalyst 3 8.3 µm 3.3 wt%
Combustion catalyst 4 7.1 µm 2.9 wt%
Combustion catalyst 5 7.5 µm 3.1 wt%
Combustion catalyst 6 8.0 μm 5.8 wt%
Combustion catalyst 7 8.1 µm 4.6 wt%
Combustion catalyst 8 7.9 μm 4.6 wt%
Combustion catalyst 9 7.5 µm 4.4 wt%
Combustion catalyst 10 (no catalyst component)

Using the liquid propellant and the combustion catalysts 1 to 10 described above, combustibility evaluations were performed as Experimental Examples 1 to 10, respectively. Experiments were conducted in the following manner.
1) The bottom of the crucible was covered with a combustion catalyst and heated from the outside to a set temperature.
2) After the surface temperature of the combustion catalyst reached the set temperature, one drop of liquid propellant was dropped on the surface of the combustion catalyst.
3) If the flame was visible, it was judged to be burning (o), and if it was not visible, it was judged to be non-burning (x).

The evaluation results are shown below. Experimental examples corresponding to the examples of the present invention are marked with *.

Experimental example Catalyst component 300°C 350°C 400°C 450°C 500°C
Experimental example 1* Ir × × 〇 〇 〇
Experimental example 2* Pt × × × 〇 〇
Experimental example 3* Pd × × × 〇 〇
Experimental example 4* Rh × × × 〇 〇
Experimental example 5* Ru × × × 〇 〇
Experimental example 6* Ir + Pt × 〇 〇 〇 〇
Experimental example 7* Ir + Pd × × 〇 〇 〇
Experimental example 8* Ir + Rh × × × 〇 〇
Experimental example 9* Ir+Ru × × × 〇 〇
Experimental Example 10 No catalyst component × × × × ×

As described above, in the example, a good ignition state could be obtained without adding a combustion aid to the ADN-containing liquid propellant.

11 Combustion Chamber 12 Heater for Heating 13 Catalyst Layer 14 Injector 15 Nozzle

Claims (7)

A combustion catalyst for a liquid propellant containing ammonium dinitramide, comprising a porous carrier and a catalytic component supported on the carrier, wherein the catalytic component comprises a metal element containing a noble metal element, an oxide thereof, or an alloy thereof. 2. The combustion catalyst according to claim 1, wherein said noble metal element is one or more selected from the group consisting of Pt, Ir, Pd, Rh and Ru. 3. The combustion catalyst according to claim 1, wherein said porous carrier is a sintered body containing at least one selected from the group consisting of alumina, silica, cesium, zeolite and titanium oxide. The combustion catalyst according to any one of claims 1 to 3, which has a specific surface area of 5 to 500 m ² /g. The combustion catalyst according to any one of claims 1 to 4, wherein the catalyst component is supported on the surface of the porous carrier with a thickness of 1 to 100 µm. A flying object propulsion device having a combustion chamber for obtaining a propellant gas by burning the combustible gas after decomposing an ammonium dinitramide-containing liquid propellant into a combustible gas, wherein at least a part of the combustion chamber contains or a flying object propulsion device filled with the combustion catalyst according to any one of claims 1 to 5. a step of adhering a liquid containing a compound containing a noble metal element to a porous carrier; and, after the step, heating the porous carrier to remove a simple metal containing a noble metal element or an oxide or alloy thereof from the liquid. A method for producing a combustion catalyst for a liquid propellant containing ammonium dinitramide, comprising the step of supporting the porous carrier by calcination.

Images