A method for the preparation of a monopropellant integral catalyst

Abstract

The application discloses a preparation method of a monopropellant monolithic catalyst, selects a honeycomb ceramic carrier which has good heat conductivity and heat shock resistance and can keep stable structure in a high-temperature environment, coats a modified alumina coating on the surface of the ceramic carrier, and then loads noble metal as a catalytic active component through an impregnation method, so that the connectivity between the noble metal active component and the carrier is enhanced, the noble metal loading capacity is increased, the coating firmness is improved, the catalyst breakage rate is significantly reduced, and the catalyst thermal stability is improved. The monolithic catalyst prepared by the application has high catalytic activity, good coating firmness, and the modified alumina coating can also increase the strength of the carrier, can effectively inhibit sintering and phase change of the carrier in a high-temperature environment, improve the thermal stability, and is not easy to break in a high-temperature environment.

Description

Technical Field

[0001] This application relates to the field of catalyst technology for rocket propellants, specifically a method for preparing a monolithic catalyst for a single-component propellant. Background Technology

[0002] Monocomponent liquid propulsion systems are characterized by simple structure, high reliability, high total impulse, and low cost. They are widely used in the propulsion systems of small satellite systems, launch vehicles, emergency power systems for aircraft, and cargo spacecraft. Their main functions include attitude and orbit control, speed regulation, docking and rendezvous of spacecraft, and landing.

[0003] In monocomponent propulsion systems, catalytic ignition offers low energy consumption and a simple propulsion system structure. Shell Industries, Inc. in the United States, has successfully developed the S-405 catalyst to address the catalytic decomposition of hydrazine-based monocomponent propellants. The S-405 catalyst is created by depositing iridium onto alumina particles, with iridium serving as the active material and the alumina particles as the supporting carrier. Hydrazine-based monocomponent propellants are highly toxic, requiring stringent control over operators and storage conditions throughout their use, and also have a low specific impulse. Therefore, the development of green, non-toxic monocomponent propellants has become a research focus. Green, non-toxic monocomponent propellants are less prone to catalytic decomposition than hydrazine-based propellants. Because green, non-toxic liquid monocomponent propellants have high combustion temperatures, the use of particulate catalysts can easily lead to catalyst deactivation and catalyst bed damage, creating cavities between the injector and the catalyst bed, resulting in fluctuations in engine performance.

[0004] To address the problem of easy breakage of catalytic beds in particulate catalysts, there is an urgent need for an integral supported catalyst. Integral supported catalysts have the advantages of high strength, high thermal stability, avoiding the accumulation of local high-temperature gas in micropores that leads to catalyst breakage, extending catalyst service life, and easy loading. Summary of the Invention

[0005] Therefore, the purpose of this application is to provide a method for preparing a monolithic catalyst with a single-component propellant, so as to alleviate the technical problem that particulate catalysts are easily damaged in high-temperature reactions.

[0006] According to some embodiments, this application provides a method for preparing a monolithic catalyst for a single-component propellant. The method includes the following steps: Step S1, preparation of aluminum sol, using boehmite powder as raw material, dissolving it in deionized water, adding nitric acid to adjust the pH value to 3.0-4.0, heating and stirring under reflux for 2-8 hours, aging for 24 hours to obtain an aluminum sol with a solid content of 5%-20%; Step S2, preparation of modified aluminum sol, adding two or three of lanthanum nitrate, cerium nitrate, and zirconium nitrate to the aluminum sol in Step S1 according to a La / Al, Ce / Al, Zr / Al mass ratio of 1wt%-10wt%, stirring and dissolving to obtain modified aluminum sol; Step S3, vacuum impregnation coating of alumina, placing the pretreated honeycomb ceramic carrier into the modified aluminum sol, evacuating the device and impregnating for 10-60 minutes, then removing the honeycomb ceramic. The carrier, after blowing away excess sol in the ceramic channels, is placed in a forced-air drying oven and dried at 60–120℃ for 1–12 h, then calcined at 400–800℃ for 1–5 h, and cooled to room temperature before being removed; Step S4, repeat step S3 until the modified alumina reaches the target coating rate of 10wt%–20wt%; Step S5, load the active metal component, immerse the sample obtained in step S4 in a noble metal precursor solution, vacuum immerse for 10–60 min, remove the sample after immersion, filter to remove excess precursor solution from the sample, place it in a forced-air drying oven and dry at 80–120℃ for 1–4 h, then calcined at 400–800℃ for 1–5 h; Step S6, repeat step S5 until the target loading is reached; Step S7, reduce the product obtained in step S6 at high temperature to obtain the target catalyst.

[0007] Furthermore, the pore shape of the honeycomb ceramic carrier can be triangular, quadrilateral, hexagonal, or circular.

[0008] Furthermore, the pretreatment steps of the honeycomb ceramic carrier include: immersing the honeycomb ceramic carrier in an acid solution, wherein the acid solution is at least one of dilute nitric acid, dilute hydrochloric acid, dilute sulfuric acid, oxalic acid or acetic acid, with a concentration of 5-20 wt%, the immersion temperature is room temperature to 100°C, the immersion time is 1-24 h, and then rinsing with deionized water until neutral and drying.

[0009] Furthermore, the noble metal precursor is one or two of the following: chloroiridic acid, iridium chloride, chloroplatinic acid, chloroauric acid, rhodium chloride, and ruthenium chloride solution, with a concentration of 5–30 wt%.

[0010] Further, the step of reducing the product obtained in step S6 at high temperature includes carrying out a reduction reaction with a reducing gas at a preset temperature for 2 to 10 hours, wherein the preset temperature is 400 to 800°C, and the reducing gas is one of hydrogen, a hydrogen-argon mixture, or a hydrogen-helium mixture.

[0011] Furthermore, the target load is 5–50 wt%.

[0012] The embodiments disclosed herein may have, or at least have, the following advantages:

[0013] 1) The catalyst provided in this application has a honeycomb-like pore structure, which is conducive to the rapid flow and ejection of propellant and high-temperature gas in the pores. It has good thermal shock resistance, reduces thermal shock damage, avoids the accumulation of high-temperature gas in the pores leading to catalyst breakage, and has high mechanical strength, which can withstand greater pressure and impact.

[0014] 2) The lanthanum oxide, cerium oxide, and zirconium oxide modified alumina coating applied in this application can regulate the microstructure of alumina, improve the coating's adhesion, inhibit its sintering and phase transformation at high temperatures, increase the coating's thermal stability at high temperatures, enhance the connection between the noble metal active components and the carrier, and increase the loading of noble metals.

[0015] 3) The bimetallic active component loaded in this application can increase catalytic activity by utilizing the synergistic enhancement effect of bimetals, which is beneficial to the catalytic decomposition of monocomponent propellants.

[0016] 4) The monolithic catalyst provided in this application is easy to fill, and the catalyst bed does not require the installation of a high-temperature resistant mesh plate. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the external structure of an integral catalyst for a single-component propellant according to an embodiment of this application. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of this application. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0019] Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. The application will now be described in more detail with reference to the accompanying drawings. In the various drawings, the same elements are represented by similar reference numerals. For clarity, the various parts in the drawings are not drawn to scale.

[0020] Example 1:

[0021] A method for preparing a monolithic catalyst with a single-component propellant includes the following steps.

[0022] Step S1, Preparation of aluminum sol: Boehmite powder is dissolved in deionized water, nitric acid is added to adjust the pH value to 3.0-4.0, the mixture is heated and stirred under reflux, and aged for 24 hours to obtain aluminum sol with a solid content of 7.5 wt%.

[0023] Step S3, Vacuum impregnation coating of alumina: The honeycomb ceramic carrier is immersed in 12.6 wt% dilute nitric acid, treated at room temperature for 6 hours, removed, washed with deionized water, and dried. The pore shape of the honeycomb ceramic carrier can be triangular, quadrilateral, hexagonal, or circular. For example, refer to... Figure 1 The honeycomb ceramic carrier has quadrilateral pores. The honeycomb ceramic carrier is placed in aluminum sol, the device is vacuumed and immersed for 10 minutes, the honeycomb ceramic carrier is removed, excess sol in the ceramic channels is blown off, and it is placed in a forced-air drying oven and dried at 80℃ for 4 hours. Then it is calcined at 400℃ for 2 hours and cooled to room temperature before being taken out.

[0024] Step S4, repeat step S3 5 times until the alumina reaches the target coating rate of 15wt%.

[0025] Step S5, Loading active metal components: The sample obtained in step S4 is immersed in a 7.5 wt% chloroiridium acid solution under vacuum for 20 min. After immersion, the sample is taken out, filtered to remove excess precursor solution, and placed in a forced-air drying oven to dry at 80°C for 4 h; then calcined at 400°C for 1 h.

[0026] Step S6, repeat step S5 5 times until the loading of the precious metal iridium reaches 15 wt%.

[0027] Step S7: The product obtained in step S6 is reduced at high temperature. Specifically, the product is reduced in hydrogen at 450°C for 2 hours to obtain the catalyst.

[0028] Example 2:

[0029] A method for preparing a monolithic catalyst with a single-component propellant includes the following steps.

[0030] Step S1, Preparation of aluminum sol: Boehmite powder is dissolved in deionized water, nitric acid is added to adjust the pH value to 3.0-4.0, the mixture is heated and stirred under reflux, and aged for 24 hours to obtain aluminum sol with a solid content of 7.5 wt%.

[0031] Step S2, preparation of modified aluminum sol: Lanthanum nitrate and cerium nitrate are added to the aluminum sol in step S1 above according to the mass ratio of La / Al = 3wt% and Ce / Al = 5wt%, and the modified aluminum sol is obtained after stirring and dissolving.

[0032] Step S3, Vacuum impregnation method for coating alumina: The honeycomb ceramic carrier is impregnated in 12.6wt% dilute nitric acid and treated at room temperature for 6 hours. After removal, it is washed with deionized water and dried. The honeycomb ceramic carrier is placed in modified alumina sol, the device is evacuated and impregnated for 10 minutes. The honeycomb ceramic carrier is removed, excess sol in the ceramic channels is blown off, and it is placed in a forced-air drying oven and dried at 80℃ for 4 hours. Then it is calcined at 400℃ for 2 hours and cooled to room temperature before being removed.

[0033] Step S4, repeat step S3 5 times until the modified alumina reaches the target coating rate of 15wt%.

[0034] Step S5, Loading active metal components: The sample obtained in step S4 is immersed in a 7.5 wt% chloroiridium acid solution under vacuum for 30 min. After immersion, the sample is taken out, filtered to remove excess precursor solution, and placed in a forced-air drying oven to dry at 100°C for 2 h; then calcined at 500°C for 1 h.

[0035] Step S6, repeat step S5 5 times until the loading of the precious metal iridium reaches 15 wt%.

[0036] Step S7: The product obtained in step S6 is reduced at high temperature. Specifically, the product is reduced in hydrogen at 500°C for 2 hours to obtain the catalyst.

[0037] Example 3:

[0038] A method for preparing a monolithic catalyst with a single-component propellant includes the following steps.

[0039] Step S1, Preparation of aluminum sol: Boehmite powder is dissolved in deionized water, nitric acid is added to adjust the pH value to 3.0-4.0, the mixture is heated and stirred under reflux, and aged for 24 hours to obtain aluminum sol with a solid content of 7.5 wt%.

[0040] Step S2, preparation of modified aluminum sol: Lanthanum nitrate and cerium nitrate are added to the aluminum sol in step S1 above according to the mass ratio of La / Al = 3wt% and Ce / Al = 5wt%, and the modified aluminum sol is obtained after stirring and dissolving.

[0041] Step S3, Vacuum impregnation method for coating alumina: The honeycomb ceramic carrier is impregnated in 12.6wt% dilute nitric acid and treated at room temperature for 6 hours. After removal, it is washed with deionized water and dried. The honeycomb ceramic carrier is placed in modified alumina sol, the device is evacuated and impregnated for 10 minutes. The honeycomb ceramic carrier is removed, excess sol in the ceramic channels is blown off, and it is placed in a forced-air drying oven and dried at 80℃ for 4 hours. Then it is calcined at 400℃ for 2 hours and cooled to room temperature before being removed.

[0042] Step S4, repeat step S3 5 times until the modified alumina reaches the target coating rate of 15wt%.

[0043] Step S5, Loading active metal components: The sample obtained in step S4 is immersed in a 15wt% chloroiridium acid solution under vacuum for 20 min. After immersion, the sample is taken out, filtered to remove excess precursor solution, and placed in a forced-air drying oven to dry at 80℃ for 4 h; then calcined at 400℃ for 1 h.

[0044] Step S6, repeat step S5 until the loading of the precious metal iridium reaches 25 wt%.

[0045] Step S7: The product obtained in step S6 is reduced at high temperature. Specifically, the product is reduced in hydrogen at 450°C for 2 hours to obtain the catalyst.

[0046] Example 4:

[0047] A method for preparing a monolithic catalyst with a single-component propellant includes the following steps.

[0048] Step S1, Preparation of aluminum sol: Boehmite powder is dissolved in deionized water, nitric acid is added to adjust the pH value to 3.0-4.0, the mixture is heated and stirred under reflux, and aged for 24 hours to obtain aluminum sol with a solid content of 7.5 wt%.

[0049] Step S2, preparation of modified aluminum sol: Lanthanum nitrate, cerium nitrate and zirconium nitrate are added to the aluminum sol in step S1 above according to the mass ratio of La / Al=3wt%, Ce / Al=5wt%, Zr / Al=2wt%, and stirred to dissolve to obtain modified aluminum sol.

[0050] Step S3, Vacuum impregnation method for coating alumina: The honeycomb ceramic carrier is impregnated in 5wt% dilute hydrochloric acid, heated at 60°C for 2 hours, removed, cleaned with deionized water, and dried. The honeycomb ceramic is placed in modified alumina sol, the device is evacuated and impregnated for 20 minutes, the honeycomb ceramic is removed, excess sol in the ceramic channels is blown off, and it is placed in a forced-air drying oven and dried at 80°C for 4 hours, then calcined at 600°C for 1 hour, and removed after cooling to room temperature;

[0051] Step S4, repeat step S3 3 times until the modified alumina reaches the target coating rate of 15wt% or more;

[0052] Step S5, Loading the active metal component: The sample obtained in step S4 is immersed in a 15 wt% chloroiridium acid solution under vacuum for 30 min. After immersion, the sample is removed, filtered to remove excess precursor solution, and placed in a forced-air drying oven at 80°C for 4 h; then calcined at 500°C for 1 h. The sample is then immersed again in a 5 wt% ruthenium chloride solution under vacuum for 30 min. After immersion, the sample is removed, filtered to remove excess precursor solution, and placed in a forced-air drying oven at 80°C for 4 h; then calcined at 500°C for 1 h.

[0053] Step S6, repeat step S5 until the total loading of precious metals iridium and ruthenium reaches more than 25 wt%;

[0054] Step S7: The product obtained in step S6 is reduced at high temperature. Specifically, the product is reduced in hydrogen at 500°C for 2 hours to obtain the catalyst.

[0055] The catalyst prepared in the above embodiments was applied to a 5N engine to investigate its catalytic decomposition ability of HAN-based propellant under steady-state conditions and to evaluate the catalyst's performance. The data are shown in Table 1.

[0056] Table 1 Comparison of Catalyst Performance Data

[0057] Example 1 790 475 Example 2 795 450 Example 3 815 294 Example 4 852 285

[0058] In Table 1, the catalytic chamber pressurization time reflects the catalytic decomposition activity of the catalyst. During engine startup, a shorter catalytic chamber pressurization time indicates higher catalytic decomposition activity. The monolithic catalyst prepared in Example 4 of this invention exhibits even higher startup catalytic decomposition activity.

[0059] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of this application and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of this application should be included within the protection scope of this application. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for preparing a monolithic catalyst with a single-component propellant, characterized in that... The steps of this method include: Step S1, Preparation of aluminum sol: Boehmite powder is dissolved in deionized water, nitric acid is added to adjust the pH value to 3.0-4.0, the mixture is heated and stirred under reflux for 2-8 hours, and aged for 24 hours to obtain aluminum sol with a solid content of 5%-20%. Step S2, preparation of modified aluminum sol: according to the mass ratio of La / Al, Ce / Al, Zr / Al 1wt% to 10wt%, two or three of lanthanum nitrate, cerium nitrate, and zirconium nitrate are added to the aluminum sol in step S1 above, and the mixture is stirred and dissolved to obtain modified aluminum sol. Step S3: Vacuum impregnation method for coating alumina. The pretreated honeycomb ceramic carrier is placed in the modified alumina sol. After the device is evacuated, it is impregnated for 10-60 minutes. The honeycomb ceramic carrier is taken out, and after blowing off the excess sol in the ceramic channels, it is placed in a forced-air drying oven and dried at 60-120℃ for 1-12 hours. Then it is calcined at 400-800℃ for 1-5 hours and taken out after cooling to room temperature. Step S4, repeat step S3, until the modified alumina reaches the target coating rate of 10wt% to 20wt%; Step S5: Loading active metal components. The sample obtained in step S4 is immersed in a noble metal precursor solution under vacuum for 10-60 min. After immersion, the sample is removed, filtered to remove excess precursor solution, and placed in a forced-air drying oven to dry at 80-120℃ for 1-4 h. Then, it is calcined at 400-800℃ for 1-5 h. Step S6: Repeat step S5 until the target load is reached. Step S7: The product obtained in step S6 is reduced at high temperature to obtain the target catalyst.

2. The method according to claim 1, characterized in that, The pores of the cellular ceramic carrier are triangular, quadrilateral, hexagonal, or circular.

3. The method according to claim 1, characterized in that, The pretreatment steps of the honeycomb ceramic carrier include: immersing the honeycomb ceramic carrier in an acid solution, wherein the acid solution is at least one of dilute nitric acid, dilute hydrochloric acid, dilute sulfuric acid, oxalic acid or acetic acid, with a concentration of 5-20 wt%, the immersion temperature is room temperature to 100°C, the immersion time is 1-24 h, and the carrier is rinsed with deionized water until neutral and then dried.

4. The method according to claim 1, characterized in that, The noble metal precursor is one or two of the following: chloroiridium acid, iridium chloride, chloroplatinic acid, chloroauric acid, rhodium chloride, and ruthenium chloride solution, with a concentration of 5-30 wt%.

5. The method according to claim 1, characterized in that, The step of reducing the product obtained in step S6 at high temperature includes carrying out a reduction reaction with a reducing gas at a preset temperature for 2 to 10 hours, wherein the preset temperature is 400 to 800°C, and the reducing gas is one of hydrogen, a hydrogen-argon mixture, or a hydrogen-helium mixture.

6. The method according to claim 1, characterized in that, The target load is 5-50 wt%.

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