JP2016137452A - Han-based propellant decomposition catalyst and manufacturing method thereof and one liquid thruster using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a HAN-based propellant decomposition catalyst having sufficient heat resistance to use a HAN-based propellant having low toxicity as a thruster and efficient decomposition activity of the HAN-based propellant and a manufacturing method therefore and a one liquid thruster having the HAN-based propellant decomposition catalyst.SOLUTION: A HAN-based propellant decomposition catalyst containing La, θ type alumina carrying a platinum group metal and having BET specific surface area of 40 m/g or more, a manufacturing method therefor and a one liquid thruster having the HAN-based propellant decomposition catalyst are used.SELECTED DRAWING: Figure 1

Description

The present invention relates to a HAN-based propellant decomposition catalyst for decomposing a hydroxyammonium nitrate (NH ₂ OH · HNO ₃ , hereinafter referred to as “HAN”)-based propellant having a large specific surface area and excellent heat resistance, and a method for producing the same. The present invention relates to a one-component thruster equipped with this HAN-based propellant decomposition catalyst.

  A small propulsion unit (hereinafter referred to as “thruster”) for satellite attitude / propulsion control decomposes hydrazine, which has been used as a propellant, by a catalyst filled in the thruster to generate high-temperature gas. It is a device that generates propulsive force by doing.

The thruster includes a propellant valve that supplies a propellant, a gas generator, a heat control device (a heater, a temperature sensor, etc.), and a hydrazine decomposition catalyst.
Here, hydrazine is useful as a single propellant for use in thrust devices such as rockets. Hydrazine is decomposed by a decomposition catalyst and generates high-temperature decomposition gas during the decomposition, so it has been used to generate gas for turbine operation in addition to the operation of attitude control jets for rockets and space satellites. .

  Further, as a hydrazine decomposition catalyst, a platinum group element catalyst has been mainly used. When this decomposition catalyst is used in a propulsion generator or a gas generator, a catalyst having a high activity and a long effective period as a catalyst is required. In particular, a catalyst having a very high activity is required to ignite spontaneously at a high flow rate employed in a rocket engine.

  In addition, since hydrazine decomposes and reaches a high temperature of 800 ° C. or higher, the catalyst must be very stable if it is to have the ability to re-ignite many times.

For this reason, a hydrazine decomposition catalyst in which a noble metal such as Ir (iridium) is supported on alumina (Al ₂ O ₃ ) having a large specific surface area is known as an extremely active and excellent catalyst (for example, , See Patent Document 1).

Thus, as a hydrazine decomposition catalyst, Ir is generally used because of its high activity, and specifically, a catalyst in which Ir is supported on alumina is used.
The decomposition reaction of hydrazine is represented by the following formulas (1) and (2).
2N ₂ H ₄ → 2NH ₃ + N ₂ + H ₂ (1)
2NH ₃ → N ₂ + 3H ₂ (2)

  However, since hydrazine, a propellant, has high toxicity, development of a propellant that is less toxic, can reduce environmental burden, and is easy to manufacture and handle has been promoted. Since HAN propellants have low toxicity, they are currently being studied in Japan and overseas as potential alternatives to hydrazine.

When HAN is supplied to the catalyst, the reactions represented by the following formulas (3) to (6) proceed. This reaction is an exothermic reaction and is a volume increasing type reaction.
NH ₃ OHNO ₃ (aq) → 2H ₂ O (l) + N ₂ (g) + O ₂ (g) (3)
NH ₃ OHNO ₃ (aq) → 2H ₂ O (l) + 1 / 2N ₂ (g) + NO ₂ (g or l) (4)
NH ₃ OHNO ₃ (aq) → 2H ₂ O (l) + 2NO (g) (5)
NH ₃ OHNO ₃ (aq) → 2H ₂ O (l) + N ₂ O (g) + 1 / 2O ₂ (g) (6)
(In the formulas (3) to (6), aq represents an aqueous solution, g represents a gas, and l represents a liquid.)

  HAN propellants have low toxicity but generally have low reactivity. For this reason, in order to decompose a liquid HAN propellant with a catalyst, it is necessary to heat the catalyst in the catalyst layer in advance to increase the activity of the catalyst at a high temperature. In addition, the HAN propellant has a problem that the temperature of the catalyst is greatly increased due to generation of combustion gas, and the deterioration and wear of the catalyst are increased.

Therefore, a catalyst having higher heat resistance than the conventional alumina catalyst supporting Ir for hydrazine propellant is required.
On the other hand, when alumina used as a catalyst support is heat-treated, its specific surface area generally decreases significantly at 1000 ° C. or higher, so that the catalyst performance tends to decrease (see, for example, Non-Patent Document 1).

  Therefore, in order to use a HAN propellant, which is less reactive than a hydrazine propellant, as a propellant for a thruster for the attitude and propulsion control of a satellite, sufficient activity is maintained even if the catalyst in the catalyst layer is preheated. There has been a demand for a catalyst having high heat resistance.

Japanese Patent Publication No. 1-013900

H. Arai et al, Applied Catalysis A: General, 138, pp 161-176, 1996.

  The present invention has been made in view of the above circumstances, and has sufficient heat resistance and has sufficient decomposition activity of the HAN propellant so that a HAN propellant having low toxicity can be used for the thruster. It is to provide a system propellant decomposition catalyst and a production method thereof.

  Still another object of the present invention is to provide a one-part thruster provided with a HAN-based propellant decomposition catalyst.

  As a result of diligent investigations to solve the conventional problems, the present inventors have found that alumina, which is a carrier for supporting a catalyst, has a high specific surface area among various structures such as γ-type, θ-type, α-type, etc. It has been found that it can solve the problem by adding La (lanthanum) to alumina and forming it with platinum group elements such as Ir supported on alumina. The present invention has been completed.

Hereinafter, the present invention will be described in detail.
The present invention relates to a decomposition catalyst for a HAN (hydroxyammonium nitrate) propellant containing θ-type alumina containing La and carrying a platinum group element such as Ir and having a BET specific surface area of 40 m ² / g or more. It is invention concerning. Furthermore, in order to further improve the heat resistance, it is preferable to contain 1 to 20% by weight of La. Further, regarding the heat resistance, the BET specific surface area after heating at 1000 ° C. for 5 hours is preferably 40 m ² / g or more.

  The present invention also includes a step of immersing a θ-type alumina molded body containing La in a solution containing an Ir compound, and taking out the immersed θ-type alumina molded body from the solution and heating to 150 to 400 ° C. This invention relates to a method for producing a decomposition catalyst for a HAN-based propellant obtained by repeating once or a plurality of times.

  The present invention also relates to a one-component thruster equipped with the above-described HAN propellant decomposition catalyst.

Further, the present invention is an invention related to a carrier containing La and comprising a θ-type alumina having a BET specific surface area of 40 m ² / g or more, which is used for the above-mentioned HAN-based propellant decomposition catalyst. Alumina powder can be molded and fired to produce a carrier having a BET specific surface area of 40 m ² / g or more.

The present invention has the following effects.
(I) Since the carrier used for the HAN-based propellant decomposition catalyst according to the present invention is composed of θ-type alumina having a specific surface area of 40 m ² / g or more, a platinum group element such as Ir is supported on the surface thereof. As a result, a catalyst having high catalytic activity can be obtained.
(Ii) The catalyst according to the present invention is excellent in heat resistance because it contains La, and can maintain its activity sufficiently even if the catalyst in the thruster is preheated. Attitude / propulsion control becomes possible.

It is a section explanatory view showing one embodiment of the one liquid thruster concerning the present invention. It is a figure which shows the relationship between a calcination temperature, a specific surface area, and a pore volume in manufacture of the La addition theta type | mold alumina molded object which concerns on Example 1,2. It is a figure which shows the measurement result of pore diameter distribution in manufacture of the La addition theta type | mold alumina molded object which concerns on Example 1,2. 6 is a diagram showing diffraction peaks in X-ray diffraction measurement of raw material powder and a molded body in the production of a La-added θ-type alumina molded body according to Example 3. FIG. 6 is a graph showing the relationship between the heat treatment temperature and the BET specific surface area of a synthesized Ir / La-added θ-type alumina catalyst and Shell (registered trademark) 405 catalyst, which is a typical hydrazine propellant decomposition catalyst, according to Example 4. It is a figure which shows the measurement result of a differential thermogravimetric analysis (TG-DTA analysis) as a result of the catalytic reaction test which concerns on Example 5. FIG. In Example 8, it is a figure which shows the relationship between the BET specific surface area and the heat processing time of the synthetic | combination Ir / La addition theta type | mold alumina catalyst, the Ir / gamma type alumina catalyst used as a comparison, and Shell (trademark) 405 catalyst. . In Example 9, it is a figure which shows the relationship between the crystallite diameter of the synthetic | combination Ir / La addition theta type | mold alumina catalyst and the Ir / gamma type | mold alumina catalyst used as a comparison reference, and heat processing time. In Example 10, it is a figure which shows the outline | summary of the batch type small reactor for a propellant decomposition test using various catalysts. In Example 10, the temperature of the thermostatic chamber and the catalyst in the propellant decomposition test performed using the synthesized Ir / La-added θ-type alumina catalyst, the Ir / γ-type alumina catalyst as a comparative control, and the Shell (registered trademark) 405 catalyst It is a figure which shows the time-dependent change of temperature and pressure. In Example 10, it is a figure which shows a time-dependent change of a thermostat temperature, a catalyst temperature, and a pressure in the propellant decomposition | disassembly test performed using Shell (trademark) 405 catalyst, Shell (trademark) 405 catalyst is 1000 degreeC. And after heat treatment for 0 hour (fresh), 1 hour, 20 hours, and 40 hours. In Example 10, it is a figure which shows the relationship between the reaction start temperature and heat processing time of the synthesized Ir / La addition theta type | mold alumina catalyst, the Ir / gamma type alumina catalyst used as a comparison reference, and Shell (trademark) 405 catalyst.

Hereinafter, the present invention will be described as a one-component thruster equipped with a HAN-based propellant decomposition catalyst, a method for producing the same, and the HAN-based propellant decomposition catalyst.
<HAN-based propellant decomposition catalyst>
In the method for producing a HAN-based propellant decomposition catalyst according to the present invention, a material in which La is added to θ-type alumina is used as a raw material, which is molded and fired to produce a carrier to carry a platinum group element on the carrier. Obtain the carrier before Next, the step of immersing this carrier in a solution containing a platinum group element compound such as Ir, taking it out of the solution and heating it to 150 to 400 ° C. is repeated once or a plurality of times, so that A platinum group element is supported on a carrier, and the HAN propellant decomposition catalyst of the present invention can be obtained.

The HAN-based propellant decomposition catalyst obtained as described above has a BET specific surface area of 40 m ² / g or more, and because of this high specific surface area, the decomposition activity of the HAN-based propellant is also increased.

  The HAN-based propellant decomposition catalyst of the present invention retains the crystal structure of θ-type alumina as a raw material powder after molding and firing, and has high heat resistance as well as a high specific surface area. The HAN-based propellant decomposition catalyst of the present invention stays in space for a long time as a thruster, and in order to properly perform orbit control, the reactivity of the HAN-based propellant decomposition catalyst is weak compared to the hydrazine decomposition reaction. Therefore, it is preferable to heat the catalyst layer in the thruster in advance in order to allow sufficient reaction. Thereby, in order to maintain sufficient catalytic activity while maintaining the preheating temperature, it is necessary to maintain the structure of θ-type alumina having a high specific surface area for a long period of time, and the heat resistance can be reinforced by adding La.

  The example demonstrates that the addition of La has the heat resistance of the θ-type alumina, but the addition amount of La is preferably in the range of 1 to 20% by weight with respect to the catalyst weight.

  Since the HAN propellant decomposition catalyst of the present invention is filled in the catalyst packed bed of the thruster device, it is preferably a molded body having a certain particle size.

  The method for forming the catalyst carrier before supporting the platinum group element such as Ir is not particularly limited as long as it is a method usually used in this field. For example, rolling granulation, extrusion granulation, spray granulation A method such as fluid granulation or compression granulation is used. In the granulation, if necessary, a binder and a granulation aid are added, water is further added, these are sufficiently kneaded, and then molded using a granulator or the like.

  The particle size of the molded body is not limited as long as it is a shape and particle size that can be filled in the thruster device. From the efficiency of work and the size of the voids or mesh of the mesh (mesh-shaped partition wall) provided in the thruster The particle diameter of 0.1 to 5 mm is preferable, the particle diameter of 0.5 to 2 mm is more preferable, and the particle diameter is usually about 1 mm.

  The method of supporting a platinum group element such as Ir on the molded catalyst carrier is not particularly limited as long as it is a method usually used in this field. For example, a molded body of a platinum group element compound solution is used. For example, the catalyst carrier is immersed and impregnated with a platinum group element. What is necessary is just to select the immersion time to the solution of the compound of a platinum group element suitably, for example, what is necessary is just to immerse for several minutes or more. In particular, by immersing under reduced pressure, Ir can be uniformly supported up to the inside of the carrier.

  The impregnation step is not particularly limited as long as it is a method or number of times usually used in this field, and immersion, drying, and firing (including provisional firing, and “firing” and “temporary firing” are to heat an object. And the like may be repeated once or a plurality of times.

Furthermore, since chlorine or the like derived from the raw material may remain, it may be washed with hot water of 50 to 60 ° C. and dried.
When a catalyst carrying a platinum group element such as Ir is used, it is aerated for 1 minute to several hours at a temperature of, for example, about 500 ° C. in a reducing gas stream such as hydrogen (H ₂ ) gas. You can also.

<Thruster>
As shown in FIG. 1, the one-component thruster 1 includes a tank 2 containing a HAN propellant and an injector (HAN propellant introduction unit) 3 and is supplied from the tank 2 through the injector 3. The chamber 5 is mainly composed of a chamber 5 filled with a catalyst layer 4 for decomposing a system propellant to generate decomposition gas, and a nozzle 6 for obtaining thrust by jetting the decomposition gas generated in the chamber 5. An electromagnetic valve 7 is disposed between the tank 2 and the feed tube 3 b that constitutes the injector 3 together with the support rod 3 a located on the second side.

  In the chamber 5, the space between the upstream mesh (mesh-like partition wall portion) 8 for dispersing the HAN-based propellant disposed adjacent to the injector 3 and the downstream mesh 9 disposed near the nozzle 6 is catalyzed. It is set as the layer accommodating part 5A. On the other hand, the space between the downstream mesh 9 and the nozzle 6 is a cracked gas chamber 5B.

  In the catalyst layer 4, about 30% by weight of Ir is supported on alumina particles to which 1 to 20% by weight of La is added, and is usually a packed layer of catalyst particles having a particle diameter of about 1 mm.

In the one-component thruster 1, when the HAN propellant supplied from the tank 2 is introduced into the chamber 5 through the injector 3 and the upstream mesh 8 by the valve opening operation of the electromagnetic valve 7, When the decomposition reaction occurs in contact with the catalyst layer 4 and the inside of the chamber 5 becomes a steady state, the decomposition reaction of the above reaction formulas (3) to (6) occurs, and high-temperature nitrogen, oxygen, nitrogen oxide (N ₂ O, NO, NO ₂ ) gas and water vapor are decomposed, and propelling force is obtained by injecting these decomposition gases held at a high pressure in the decomposition gas chamber 5B from the nozzle 6.

  The one-component thruster of the present invention uses a HAN propellant and is less toxic than the conventional hydrazine propellant, so it is easy to handle and can maintain the same propulsive force as the conventional propellant. Excellent performance.

  In the one-component thruster 1 according to this embodiment, the HAN propellant is diffusely supplied from the tip of one feed tube 3b constituting the injector 3, but the present invention is not limited to this. A shower head may be attached to the tip of 3b to supply the HAN propellant separately from a plurality of locations. Moreover, it is good also as a structure provided with two or more feed tubes.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is limited and interpreted by this Example. First, a measurement method in this example will be described.

(1) Measurement of BET specific surface area The BET specific surface area was measured using an autosorb iQ station 1 manufactured by Quantachrome Instruments Co., Ltd. as a pretreatment at a degassing temperature of 200 ° C. and then at 77 K (absolute temperature) with nitrogen (absolute temperature). N ₂ ) Adsorption method.
(2) Pore volume measurement The pore volume measurement was performed by mercury porosimetry using a mercury porosimeter manufactured by Quantachrome Instruments.
(3) X-ray diffraction measurement The X-ray diffraction measurement was performed using an X'Pert PRO MPD type fully automatic multipurpose X-ray diffractometer manufactured by Panalical.
The crystal state of the compact was measured at a voltage of 45 kV and a current of 40 mA.
The crystallite size of the catalyst was determined by the Scherrer equation shown below using the XRD peak of the Ir (111) plane.
D = K × λ / (β × cos θ)
(Where D is the diameter of the crystallite (angstrom), K is the Scherrer constant (1.15), λ is the wavelength of the X-ray tube used (1.54056 angstrom), β is the spread of the diffraction line depending on the diameter of the crystallite, θ Indicates a diffraction angle.)
(4) Differential thermogravimetric analysis Differential thermogravimetric analysis was performed using a TG-DTA2000S apparatus manufactured by Netch Japan.
Both the sample container and the reference container were made of alumina, the temperature increase rate was 10 ° C./min, and the atmosphere was analyzed with a nitrogen gas (N ₂ ) stream of 100 ml / min.
(5) Determination of Ir The amount of Ir supported after catalyst preparation was analyzed by ICP (inductively coupled plasma method).

Example 1 Production of La-added θ-type Alumina Molded Body As a carrier of an Ir-supported catalyst, θ-type alumina powder added with 3.5% by weight of La based on the weight was used as raw material alumina. That is, the weight ratios of Al, La, and O in the La-added θ-type alumina powder are 48.4 wt%, 3.5 wt%, and 48.1 wt%, respectively.

  The raw material alumina was pulverized and classified after pressure forming so that the average particle diameter was about 1 mm. The molded raw material was heated in a firing furnace at a predetermined temperature for a predetermined time as shown in Example 2 to obtain a La-added θ-type alumina molded body.

Example 2 Production of La-added θ-type Alumina Molded Body and Evaluation of Heat Resistance Regarding the production of La-added θ-type alumina molded body produced in Example 1, firing temperature and firing time, BET specific surface area, pores The relationship between the volume and the pore size distribution was examined and shown in Table 1, FIG. 2 and FIG.
In FIG. 2, the horizontal axis (X axis) is the firing temperature (“° C.”), the left side of the vertical axis (Y axis) is the BET specific surface area (“m ² / g”) and is shown by a black rhombus (♦) broken line, The right side of the vertical axis (Y axis) is the pore volume (“ml / g”) indicated by a black square (■) broken line.
In FIG. 3, the pore size distribution was measured under the condition of containing 18% by weight of PP (polypropylene). In the figure, the horizontal axis (X-axis) is the pore diameter (“nm (nanometer)”), the vertical axis (Y-axis) is the pore volume differential value (dV / d (log D), and V is the pore size. Volume (“cc / g”), D indicates pore diameter). The firing conditions are as shown in FIG. 3 (a) at 1100 ° C. for 5 hours, FIG. 3 (b) at 1200 ° C. for 5 hours, and FIG. 3 (c) at 1300 ° C. for 5 hours.

As can be seen from Table 1 and FIG. 2, the BET specific surface area and pore volume of the La-added θ-type alumina molded body increase both as the BET specific surface area and pore volume decrease as the heat treatment temperature increases. Under the baking conditions of 5 hours, the BET specific surface area decreased to 5 m ² / g.

As can be seen from FIG. 2 and FIG. 3, micro pores having an average pore diameter of about 20 nm (in each of FIGS. 3 (a), 3 (b) and 3 (c), the pore diameter on the left side is small). In the region, the pore diameter was almost constant up to 1200 ° C. for 5 hours, but it was confirmed that the pore diameter increased to about 150 nm under 1300 ° C. for 5 hours. It was done. On the other hand, macroscopic pores having a pore diameter of several μm (shown in a region with a large pore diameter on the right side in each of FIGS. 3A, 3B, and 3C) are fired. Even when the temperature was increased to 1300 ° C. for 5 hours, the pore size distribution was maintained. Thus, it was shown that the pore volume gradually decreases as the pore diameter of the micropores increases.

[Example 3] Evaluation of heat resistance of La-added θ-type alumina molded body (X-ray diffraction measurement)
The La-added θ-type alumina molded bodies produced in Example 1 and Example 2 were measured by powder X-ray diffraction, and the results are shown in FIG.
In FIG. 4, the XRD diffraction measurement was performed under the condition containing 18% by weight of PP (polypropylene). The horizontal axis (X-axis) is the diffraction angle (“°”) 2θ, the vertical axis (Y-axis) indicates arbitrary intensity, and in the figure, the white circle (◯) indicates the peak attributed to θ-type alumina, and the black circle (● ) Shows a peak attributed to α-type alumina, and the firing conditions are as follows. FIG. 4 (a) is the raw material powder, FIG. 4 (b) is 1000 ° C. for 1 hour, and FIG. 4 (c) is 1100 ° C. for 5 hours. 4 (d) is fired at 1200 ° C. for 5 hours, and FIG. 4 (e) is fired at 1300 ° C. for 5 hours.

  As shown in FIGS. 4B and 4C, the crystal structure under each firing condition is the raw material powder (La-added θ-type) shown in FIG. 4A until firing at 1100 ° C. for 5 hours. It is the same θ type as alumina), but when it is fired at 1200 ° C. for 5 hours as shown in FIG. 4 (d), it becomes a mixed phase of θ phase and α phase, and when it is fired at 1300 ° C. for 5 hours as shown in FIG. It was confirmed that it was rearranged into the α phase. The decrease in the specific surface area and pore volume of the alumina molded body due to the increase in the firing temperature was thought to be due to the phase transition from the θ type to the α type of alumina.

Based on the above results, a carrier having several μm macropores and 20 nm micropores and a surface area of about 100 m ² / g is prepared by molding and firing as La-added θ-type alumina raw material powder. I was able to confirm that it was possible. It was also found that this support can maintain a BET specific surface area of about 40 m ² / g after firing, that is, after heat treatment, even at a high temperature of firing at 1200 ° C. for 5 hours. Therefore, a catalyst in which Ir is supported using this support has high heat resistance and is suitable as a thruster catalyst for a HAN propellant.

[Example 4] Evaluation of heat resistance of Ir / La-added θ-type alumina molded body (BET specific surface area measurement)
Next, in order to evaluate the heat resistance of a catalyst (Ir / La-added θ-type alumina) supporting Ir as an active metal, the catalyst was heat-treated at a high temperature, and the change in the BET specific surface area was measured.

  Ir was supported on the La-added θ-type alumina molded body as a support as follows. First, a chlorinated Ir acid aqueous solution (Ir concentration: 0.064 g-Ir / ml) was prepared. The classified carrier was immersed in this aqueous solution of chlorinated Ir acid and impregnated for 3 minutes while reducing the pressure with an evaporator. After impregnation, a sample of the La-added θ-type alumina molded body impregnated with Ir was taken out and filtered under reduced pressure to remove excess Ir chloride aqueous solution. Thereafter, the sample was dried by a dryer (100 ° C., 30 minutes). Next, the catalyst was calcined (380 ° C., 30 minutes) in an electric furnace. The impregnation, drying, and calcination processes of the catalyst were repeated 10 times, and the sample was finally fired at 400 ° C. (1 hour).

Since chlorine derived from the raw material remains in the sample after firing, the sample was washed with warm water (50 to 60 ° C.) in order to remove this chlorine. The washing amount was approximately 0.5 L of warm water with respect to 1 g of the catalyst. The sample after washing was dried, and then the catalyst was reduced in a hydrogen (H ₂ ) stream at 500 ° C./1 hour.

After the catalyst was prepared, the supported amount of Ir analyzed by ICP (Inductively coupled plasma method) was about 40% by weight.
FIG. 5 shows the relationship between the specific surface area of the synthesized Ir / La-added θ-type alumina catalyst and the Shell (registered trademark) 405 catalyst, which is a typical hydrazine propellant decomposition catalyst, and the heat treatment temperature. The BET specific surface area of Shell (registered trademark) 405 catalyst decreased to 14 m ² / g by heat treatment at 1000 ° C., and further decreased to 10 m ² / g or less by increasing the heat treatment temperature to 1100 ° C. or higher.
In FIG. 5, the horizontal axis (X axis) is the heat treatment temperature (“° C.”), the vertical axis (Y axis) is the BET specific surface area (“m ² / g”), and the black square (■) polygonal line is Shell ( (Registered trademark) 405 catalyst, the black triangle (▲) polygonal line shows the data for the synthesized Ir / La-added θ-type alumina catalyst.

On the other hand, it was confirmed that the synthesized catalyst (indicated as “catalyst B” in FIG. 5) had a relatively high specific surface area of 48 m ² / g at a heat treatment temperature of 1000 ° C. and 41 m ² / g even at 1100 ° C. . Furthermore, when it heat-processed to 1200 degreeC or more, it fell to 10 m < ² > / g or less.
From the above results, it is considered that the Ir / La-added θ-type alumina catalyst according to the present invention has a higher BET specific surface area at a higher temperature than the Shell (registered trademark) 405 catalyst, so that the catalytic activity can be maintained up to a higher temperature. That is, it was confirmed that it was suitable as a thruster catalyst for HAN propellants.

[Example 5] Catalytic reaction test (differential thermogravimetric analysis (TG-DTA analysis))
Carriers A, B, and C described below were fired at 1000 ° C. Catalysts A, B, and C produced from the carriers A, B, and C were produced in the same manner as in Example 4 by impregnating the carriers A, B, and C with Ir, respectively.
The compositions of the HAN propellants used in Examples 5 and 6 were HAN (hydroxyammonium nitrate): HN (hydrazine nitrate): TEAN (triethanolammonium nitrate): water = 46: 23: 6: 25 (weight) %).
FIG. 6 shows the catalytic reaction test.
In FIG. 6, the horizontal axis (X axis) is time (“minute”), the vertical axis (Y axis) is shown on the left side with temperature (“° C.”) and DTA (“μV (microvolt)”), and the vertical axis ( (Y axis) The right side is indicated by TG (“mg”), FIG. 6 (a) is a HAN propellant, FIG. 6 (b) is Shell (registered trademark) 405 (fresh), and FIG. 6 (c) is the present invention. It is the result of the TG-DTA analysis of the catalyst A (support A, fresh) according to the present invention.
FIG. 6 (a) shows the results of a TG / DTA test conducted with a HAN propellant alone. As shown in the figure, the weight gradually decreased between about 50 ° C. and 100 ° C., then started to decrease rapidly from around 180 ° C. and finally ended at around 280 ° C. From this result, it was found that the temperature at which decomposition of the HAN propellant alone ended was approximately 280 ° C.

  FIG. 6B shows a TG / DTA measurement result of Shell (registered trademark) 405 catalyst (fresh), which is a typical commercial catalyst for hydrazine decomposition. The reaction proceeded in two stages. The first stage was about 79 ° C., the second stage was about 117 ° C., and the weight decreased rapidly with an exothermic peak. This result showed that in the presence of Shell® 405 catalyst, the HAN propellant decomposes at a lower temperature than when it was alone.

  FIG. 6C shows a TG / DTA measurement result of an Ir catalyst (catalyst A) manufactured using the carrier A. The exothermic peak was about 109 ° C., and the reaction proceeded with rapid weight loss. Unlike Shell (registered trademark) 405, decomposition was completed in one stage.

  From the above results, it was confirmed that the HAN propellant can be decomposed at a low temperature by using the prototype Ir catalyst.

[Example 6] Simple reaction test In addition to the TG / DTA measurement, a small amount of a HAN propellant was dropped onto the catalyst surface heated to a constant temperature, and the decomposition behavior was observed. The catalyst (about 10 mg) was placed in an alumina container and heated to 150 ° C. on a hot stirrer. While maintaining the temperature of the catalyst at 150 ° C., a HAN propellant was dropped using a microsyringe, and the decomposition behavior was observed. When the HAN propellant did not decompose at 150 ° C., the temperature of the stirrer was raised to heat the catalyst, and the behavior of the HAN propellant being decomposed was observed. The temperature was measured using a sheathed thermocouple (K type) installed in the vicinity of the alumina container.

(Decomposition behavior of HAN propellant alone)
HAN propellant alone was tested. The HAN propellant foamed slightly after dropping at 150 ° C., but did not decompose. When the temperature was further increased, the foaming started from about 230 ° C. while foaming, and finally the decomposition was completed at around 280 ° C. while changing the color to brown. Also from the TG / DTA result of Example 5, it is known that the decomposition end temperature of the HAN propellant is about 280 ° C., which shows good consistency with this result.

(Decomposition test of HAN propellant with Shell (registered trademark) 405 catalyst (fresh))
In the case of Shell (registered trademark) 405 catalyst (fresh), it was confirmed that the HAN propellant reacted vigorously immediately after dropping at 150 ° C. and decomposed with ignition.

(Decomposition test of HAN propellants with Catalysts B and C (both fresh and reduced))
The HAN-based propellant decomposition test was also carried out on the catalysts B and C on which Ir was made on trial using the carriers B and C, respectively. For both the catalysts, those previously reduced at 500 ° C. in a hydrogen (H ₂ ) gas stream were used for the test.

In catalyst B (fresh), foaming and decomposition began vigorously immediately after the HAN propellant was dropped, and the decomposition was completed with ignition in a very short time.
Similarly, in the catalyst C (fresh, hydrogen (H ₂ ) reduced), immediately after the HAN propellant was dropped, the foaming and reaction started vigorously, and the decomposition was completed with ignition in a very short time.

  From the above results, it was confirmed that the prototyped Ir-supported catalyst can efficiently decompose the HAN propellant at a low temperature.

[Example 7] Manufacture of Ir / La-added θ-type alumina molded body In order to evaluate the heat resistance of a catalyst carrying Ir, an active metal (Ir / La-added θ-type alumina), the catalyst was heat-treated at a high temperature. Changes in BET specific surface area and crystallite diameter were measured.

  Ir was supported on the La-added θ-type alumina molded body obtained in Example 1 as follows. First, a chlorinated Ir acid aqueous solution (Ir concentration: 0.064 g-Ir / ml) was prepared. The classified carrier was immersed in this aqueous solution of Ir chloride chloride and impregnated for 10 minutes while reducing the pressure with an evaporator. After impregnation, a sample of the La-added θ-type alumina molded body impregnated with Ir was taken out and filtered under reduced pressure to remove excess Ir chloride aqueous solution. Thereafter, the sample was dried by a dryer (100 ° C., 30 minutes). Next, the catalyst was calcined (380 ° C., 30 minutes) in an electric furnace. The impregnation, drying, and calcination treatments of the catalyst are repeated about 20 to 40 times until the Ir impregnation amount is 20% by weight (analyzed by ICP (inductively coupled plasma method)) per catalyst weight, and finally 400 ° C. (1 hour) The sample was baked.

Since chlorine derived from the raw material remains in the sample after firing, the sample was washed with warm water (50 to 60 ° C.) in order to remove this chlorine. The washing amount was approximately 0.5 L of warm water with respect to 1 g of the catalyst. The sample after washing was dried, and then the catalyst was reduced in a hydrogen (H ₂ ) stream at 500 ° C./1 hour.

  A catalyst supporting Ir (Ir / γ-type alumina) was produced in the same manner as described in Example 1, except that γ-type alumina powder was used as raw material alumina instead of La-added θ-type alumina powder.

  As the Shell (registered trademark) 405 catalyst used in the test, a commercially available product was used as it was.

[Example 8] Evaluation of heat resistance of Ir / La-added θ-type alumina catalyst and Ir / γ-type alumina catalyst (BET specific surface area)
Regarding the Ir / La-added θ-type alumina catalyst and Ir / γ-type alumina catalyst produced in Example 7, the relationship between the heat treatment time at 1000 ° C. and the BET specific surface area was examined and shown in FIG.

In FIG. 7, the horizontal axis (X axis) represents the heat treatment time (“time”), and the vertical axis (Y axis) represents the BET specific surface area (“m ² / g”). The results of the Ir / La-added θ-type alumina catalyst (shown as “Ir / θ-Al ₂ O ₃ ”) are indicated by the white triangle (Δ) broken line, and the Ir / γ-type alumina catalyst (“Ir / γ-Al ₂ O”) is displayed. The result of “ ₃ ” is indicated by a polygonal black diamond (♦). Note that the Shell (registered trademark) 405 catalyst had a fresh BET specific surface area of about 110 m ² / g when not heat-treated, and is indicated by a cross (×) in FIG.

As can be seen from FIG. 7, the BET specific surface areas of the Ir / La-added θ-type alumina catalyst and the Ir / γ-type alumina catalyst are reduced by the heat treatment as compared with the case of fresh (treatment is 0 hour). However, the Ir / La-added θ-type alumina catalyst according to the present invention maintains a BET specific surface area of 80 m ² / g or more even when the heat treatment time is increased. In contrast, the Ir / γ-type alumina catalyst decreased as the heat treatment time increased, and the heat treatment for 100 hours slightly exceeded 20 m ² / g. This is because the Ir / La-added θ-type alumina catalyst according to the present invention has higher heat resistance than the Ir / γ-type alumina catalyst, which is due to the adoption of La-added θ-type alumina.

[Example 9] Evaluation of heat resistance of Ir / La-added θ-type alumina catalyst and Ir / γ-type alumina catalyst (crystallite diameter)
Regarding the Ir / La-added θ-type alumina catalyst and Ir / γ-type alumina catalyst produced in Example 7, the relationship between the heat treatment time at 1000 ° C. and the crystallite diameter was examined and is shown in FIG.

In FIG. 8, the horizontal axis (X axis) indicates the heat treatment time (“time”), and the vertical axis (Y axis) indicates the crystallite diameter (“angstrom”). The results of the Ir / La-added θ-type alumina catalyst (shown as “Ir / θ-Al ₂ O ₃ ”) are indicated by the white triangle (Δ) broken line, and the Ir / γ-type alumina catalyst (“Ir / γ-Al ₂ O”) is displayed. The result of “ ₃ ” is indicated by a polygonal black diamond (♦).

  As can be seen from FIG. 8, the crystallite diameters of the Ir / La-added θ-type alumina catalyst and the Ir / γ-type alumina catalyst are increased by the heat treatment as compared with the case of fresh (treatment is 0 hour). However, the Ir / La-added θ-type alumina catalyst according to the present invention maintained a crystallite diameter of about 500 Å even when the heat treatment time was long. In contrast, the Ir / γ type alumina catalyst gradually increased as the heat treatment time increased, and reached about 700 angstroms in the heat treatment for 100 hours. This is because the Ir / La-added θ-type alumina catalyst according to the present invention is more heat-resistant than the Ir / γ-type alumina catalyst from the viewpoint of the crystal structure of crystallite diameter, and this employs La-added θ-type alumina. It is because.

[Example 10] Propellant decomposition test using various catalysts The Ir / La-added θ-type alumina catalyst, Ir / γ-type alumina catalyst and Shell (registered trademark) 405 catalyst produced in Example 7 are shown in FIG. Using a batch type small reactor 11 for the propellant decomposition test, evaluation was made based on the reaction start temperature by various catalysts.

  The test by the batch type small reactor shown in FIG. 9 was performed as follows. That is, the thermostatic chamber 15 is provided with a metal sealed container 16, and various catalysts and propellants are held in the metal sealed container 16. The thermocouple 19 is provided for the inside of the metal sealed container 16, and the other thermocouple 18 is provided for the thermostatic chamber 15. These thermocouple 18 and thermocouple 19 are controlled by a control means (computer) via a cable 21. 12 is connected.

  The metal hermetic container 16 is connected to the valve 14 via a pipe 22 on the metal hermetic container side, and is connected to the pressure gauge 13 via a pipe 23 on the pressure gauge side from the valve 14. The pressure gauge 13 is connected to a control means (computer) 12 via a cable 20. The valve 14 exhausts gas or the like to the outside through a pipe 24 on the exhaust side.

  In the propellant decomposition test, the temperature of the thermostatic chamber 15 is gradually increased, and at the same time, the temperature of the metal sealed container 16 inside the thermostatic chamber 15 and the temperature of the catalyst and propellant in the metal sealed container 16 are also increased. The temperatures inside the thermostatic chamber 15 and the metal sealed container 16 are detected by the thermocouple 18 for the thermostatic chamber 15 and the thermocouple 19 for the metal sealed container 16, and via the cable (thermocouple side) 21. It is sent to the control means 12 and recorded. Further, the temperature of the catalyst and propellant held inside the metal sealed container 16 rises, the propellant is decomposed at a certain temperature, and the pressure rises due to the gas generated by the decomposition. This pressure is detected over time by the pressure gauge 13, sent to the control means 12 via the cable (pressure gauge side) 20, and recorded.

  Through the above operation, FIG. 10 shows the time-dependent changes in the thermostat temperature, the catalyst temperature, and the pressure.

  FIG. 10 shows the results of a propellant decomposition test using various fresh catalysts that were not heat-treated at 1000 ° C. FIG. 10A shows a propellant decomposition test using an Ir / La-added θ-type alumina catalyst, FIG. 10B using an Ir / γ-type alumina catalyst, and FIG. 10C using a Shell® 405 catalyst. Results are shown. Further, as FIG. 11, Shell (registered trademark) 405 catalyst heat-treated at 1000 ° C. for 1 hour, 20 hours, and 40 hours in the atmosphere is shown in FIGS. 11 (d), 11 (e), and 11, respectively. Shown as (f).

  In FIG. 10, the horizontal axis (X axis) is the elapsed time (“second”), the vertical axis (Y axis) is the temperature (“° C.”), and the dotted line is the thermocouple held in the thermostat 15 (the thermostat side). The temperature indicated by 18 and the solid line indicate the temperature indicated by the thermocouple 19 held inside the metal sealed container 16 (indicated as “temperature (catalyst)”), and the broken line indicates the pressure indicated by the pressure gauge 13.

  As can be seen from FIG. 10, in the fresh catalyst not subjected to the heat treatment at 1000 ° C. (FIG. 10 (a) to FIG. 10 (c)), in any catalyst, as indicated by the pressure by the pressure gauge 13, When the propellant decomposes, gas is generated and the pressure rises rapidly at about 120 ° C. Hereinafter, the temperature at which this reaction starts and the pressure starts to increase rapidly is called the reaction start temperature. Further, in the vicinity of the reaction start temperature, a maximum point is observed in the temperature indicated by the thermocouple 19 held inside the metal sealed container 16. On the other hand, in the result of the propellant decomposition test using the Shell (registered trademark) 405 catalyst shown in FIG. 11 which was heat-treated at 1000 ° C. for 1, 20, and 40 hours, the reaction start temperature was as shown in FIG. ) Is about 130 ° C., FIG. 11 (e) is about 160 ° C., and FIG. 11 (f) is about 170 ° C. The Shell® 405 catalyst is heated at 1000 ° C., and the reaction start temperature rises. In addition, it can be seen that the increase width also increases with the heat treatment time. This is understood that the structure of the Shell (registered trademark) 405 catalyst was changed by the heat treatment at 1000 ° C., so that the start of the propellant decomposition reaction became higher.

FIG. 12 shows the results of the propellant decomposition test using various catalysts described above, and the Ir / La-added θ-type alumina catalyst (indicated as “Ir / θ-Al ₂ O ₃ ”) and the Ir / γ-type alumina catalyst (“ “Ir / γ-Al ₂ O ₃ ”) is a summary of results (not shown individually) showing the effect of heat treatment time at 1000 ° C.

  As can be seen from FIG. 12, in the Ir / La-added θ-type alumina catalyst, although the heat treatment time at 1000 ° C. was 0 hours (fresh) to 100 hours, the reaction start temperature slightly increased from about 120 ° C., but 100 hours Also in the heat treatment, it is about 150 ° C. and does not rise so much. On the other hand, in the Ir / γ type alumina catalyst, the reaction start temperature increased from about 120 ° C. over time, and reached about 170 ° C. in the heat treatment for 100 hours. Furthermore, with Shell (registered trademark) 405 catalyst, the temperature increased from about 120 ° C. over time, and reached nearly 180 ° C. after 100 hours of heat treatment.

  This is because the Ir / La-added θ-type alumina catalyst has heat resistance and can sufficiently maintain the catalytic activity of the HAN decomposition reaction, whereas the Ir / γ-type alumina catalyst and Shell (registered trademark) 405 catalyst This shows that the heat resistance is not as high as that of an Ir / La-added θ-type alumina catalyst. In particular, the result that the Ir / La-added θ-type alumina catalyst produced based on La-added θ-type alumina instead of γ-type alumina has the heat resistance as described above is surprising.

  From the above results, the Ir / La-added θ-type alumina catalyst according to the present invention has a structural stability such as a BET specific surface area and a crystallite diameter at a higher temperature than the Ir / γ-type alumina catalyst and Shell (registered trademark) 405 catalyst. The catalyst activity can be maintained up to a high temperature. That is, it was confirmed that it was suitable as a thruster catalyst for HAN propellants.

1 One-component thruster 2 Tank 3 Injector (hydrazine introduction part)
3a Support rod 3b Feed tube (injector)
4 catalyst layer 5 chamber 5A catalyst layer housing part 5B decomposition gas chamber 6 nozzle 7 solenoid valve 8 upstream mesh (mesh-shaped partition wall part)
9 Downstream mesh (mesh partition)
11 Batch type small reactor 12 Control means 13 Pressure gauge 14 Valve 15 Thermostatic bath 16 Metal enclosure 17 Catalyst and propellant 18 Thermocouple 19 Thermocouple 20 Cable 21 Cable 22 Tube 23 Tube 24 Tube

Claims (7)

A HAN-based propellant decomposition catalyst comprising La-containing, θ-type alumina supporting a platinum group element and having a BET specific surface area of 40 m ² / g or more.   The HAN-based propellant decomposition catalyst according to claim 1, comprising 1 to 20% by weight of La. The HAN-based propellant decomposition catalyst according to claim 1 or 2, wherein the BET specific surface area after heating at 1000 ° C for 5 hours is 40 m ² / g or more.   The HAN-based propellant decomposition catalyst according to any one of claims 1 to 3, wherein the platinum group element is Ir.   A step of immersing a θ-type alumina molded body containing La in a solution containing an Ir compound, taking out the θ-type alumina molded body from the solution and heating to 150 to 400 ° C. is repeated once or a plurality of times. A method for producing a HAN-based propellant decomposition catalyst.   A one-component thruster comprising the HAN-based propellant decomposition catalyst according to any one of claims 1 to 4. The support | carrier used for the HAN type propellant decomposition catalyst as described in any one of Claims 1-4 which consists of (theta) type | mold alumina which contains La and has a BET specific surface area of 40 m < ² > / g or more.

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