Preparation and application of hollow fiber-like ammonium perchlorate thermal decomposition catalytic material

Abstract

The application selects biological cotton as a template, and adopts a simple solution combustion method to prepare nano-porous MgCo2O4 material. The method is to use magnesium nitrate and cobalt nitrate as an oxidant, organic fuel citric acid as a reducing agent, dissolve in a certain amount of deionized water to form a mixed solution, soak the biological cotton in the mixed solution for a certain time, and calcine the soaked cotton to obtain nano MgCo2O4 with a porous structure and carbon defects. The MgCo2O4 with porous carbon defects is prepared by one-step solution combustion method, which is fully ground and mixed with AP at a certain mass ratio, and the catalytic material with excellent catalytic performance for thermal decomposition of AP is obtained through differential thermal analysis. Not only the rapid progress of AP thermal decomposition reaction is effectively ensured, but also the apparent decomposition heat of AP thermal decomposition is further improved, which creates conditions for the continuous combustion of composite solid propellant.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of inorganic catalysis, and particularly relates to a one-step method for preparing hollow fiber-like ammonium perchlorate thermal decomposition catalytic material. TECHNICAL BACKGROUND

[0002] China is one of the countries with the richest magnesium resources in the world, including the impressive mineral magnesium and salt lake magnesium. However, the development and utilization of magnesium resources is still mainly in the form of primary products, so it is necessary to improve the added value of products or explore new utilization fields in the utilization of magnesium resources. Binary transition metal oxide MgCo2O4 can be applied to sensors, electrocatalysis, supercapacitors, battery electrode materials, etc. due to its unique crystal structure, excellent physicochemical properties, and easy synthesis. However, there are few reports on its application in catalytic thermal decomposition. Nanostructured MgCo2O4 materials can be obtained by hydrothermal method, solvothermal method, sol-gel method, and precipitation method to obtain the corresponding precursor, and then the precursor is converted to MgCo2O4 by calcination. These methods all need a secondary heat treatment process, and the process is relatively complex and the cycle is relatively long. Solution combustion method as a method for synthesizing nanomaterials usually uses metal nitrate as an oxidant and uniformly disperses organic fuel (glycine, citric acid, etc.) in deionized water, and heats to ignite to quickly synthesize nanometer metal oxide materials in one step. Therefore, it is expected to become a method for synthesizing nano MgCo2O4 with simple operation, short cycle, and high purity. Recent studies have shown that the inherent defects of carbon materials provide abundant activity for catalytic thermal decomposition, and due to the combustibility of carbon materials, synergistic heat can be generated during catalytic thermal decomposition. At present, there is no report on the regulation and optimization of thermal decomposition catalytic activity. Therefore, it is of important scientific value and development prospect to introduce carbon defects into MgCo2O4 materials and apply them to catalytic thermal decomposition.

[0003] As the rocket, missile propulsion energy, the combustion performance of composite solid propellant is an important factor affecting the ballistic performance of rocket, missile and the carrying capacity of spacecraft. Among them, ammonium perchlorate (AP) is the most commonly used energetic oxidizer in solid propellant, accounting for 60-90% of the content of solid propellant, and its thermal decomposition performance is directly related to the combustion performance of solid propellant. Reducing the decomposition temperature of AP and increasing the heat release during the decomposition process will greatly shorten the ignition delay time of solid propellant and increase the burning rate of solid propellant. Considering the risk of refining AP grains, adding a small amount of catalytic material to promote the thermal decomposition of AP to improve the combustion performance of the propellant is the current research focus. Among the many catalytic materials applied to the thermal decomposition of AP, transition metal oxides: Fe2O3, CuO, MnO2, Cr2O3 and ZnO2, etc. Catalytic materials show excellent catalytic performance, however, with the increasing requirements for AP thermal decomposition, single-component metal oxides have certain limitations due to their simple structure and poor electrical conductivity. Therefore, catalytic materials gradually develop towards multi-component composite, among which the nanoscale binary transition metal oxide MgCo2O4 as a P-type semiconductor material can generate electrons and holes under thermal energy excitation, and the metal atoms in the unit cell have unfilled d orbitals and the synergistic effect between the two metals can accelerate the electron transfer in the AP decomposition process, thus showing better catalytic performance than single metal oxide.

[0004] The prior art, such as CN105938761B, discloses a magnesium cobalt oxide / graphene composite material used as a supercapacitor electrode material and a preparation method thereof. The composite material is composed of nanoscale magnesium cobalt oxide and graphene, the nanoscale magnesium cobalt oxide has a petal-like cluster structure, and the graphene is in a sheet layer shape and covers the magnesium cobalt oxide. The preparation steps of the composite material include 1) synthesis of modified graphene oxide; 2) adding magnesium cobalt salt and alkali source into the modified graphene oxide solution, and preparing magnesium cobalt hydroxide / graphene composite material by a hydrothermal reduction method; and 3) calcining the prepared magnesium cobalt hydroxide / graphene composite material at high temperature to obtain MgCo2O4 / graphene composite material. Compared with existing graphene composite electrode materials, the MgCo2O4 / graphene composite material obtained by the present application provides better structural characteristics, larger specific surface area, smaller mass transfer resistance and longer cycle life, and has good application prospect in the field of energy storage.

[0005] In the prior art, for example, CN109529842A discloses a preparation method of ammonium perchlorate thermal decomposition catalyst material. The invention dissolves cobalt nitrate, iron nitrate and urea in water, slowly adds a mixed solution of soft template agent, ethylene glycol and ethanol after complete dissolution, then transfers to a high-pressure reaction kettle, keeps at 180-210 DEG C for 3 hours, then cools to room temperature, centrifuges, washes and dries overnight, finally, the dried sample is annealed at 250-300 DEG C at a heating rate of 3-5 DEG C / min for 3 hours to obtain the ammonium perchlorate thermal decomposition catalyst material, i.e. nano-porous FeCo2O4. The invention provides a simple and practical method for preparing FeCo2O4, which has good catalytic performance for AP. However, the structure of the catalyst material prepared by the invention is single, and the range of catalytic performance regulation is limited, which may be limited in application.

[0006] In view of the problems existing in the prior art, the invention prepares MgCo2O4 with porous carbon defects by one-step solution combustion method, which is fully ground and mixed with AP at a certain mass ratio, and the differential thermal-thermal gravimetric analysis obtains a catalyst material with excellent catalytic performance for AP thermal decomposition. SUMMARY

[0007] To solve the problems existing in the prior art, the invention provides a one-step method for preparing hollow fiber-shaped ammonium perchlorate thermal decomposition catalyst material.

[0008] To achieve the above-mentioned purpose, the invention adopts the following technical solutions:

[0009] S1: clean cotton is activated and pretreated in an ethanol: water: hydrochloric acid mixed solution, ultrasonic for 1 hour, then soaked for 6 hours, finally washed with deionized water for 2-3 times and dried overnight;

[0010] S2: Mg(NO3)2·6H2O, Co(NO3)2·6H2O and C6H8O7·H2O are dissolved in 15ml deionized water and placed in a crucible, and magnetic stirring is performed for 30 minutes to make the raw materials completely dissolved;

[0011] S3: the pretreated cotton is completely immersed in the above solution and soaked for 12 hours;

[0012] S4: the cotton is taken out and calcined with the furnace temperature rising in air atmosphere, and kept for 1 hour to obtain MgCo2O4 with porous carbon defects.

[0013] Preferably, in S1 as described above, the volume ratio of the ethanol: water: 2M hydrochloric acid mixed solution is 1:1:2.

[0014] Preferably, in S2 as described above, the amount of each substance is: 0.8 mmol of Mg (NO3) 2·6H2O, 1.6 mmol of Co (NO3) 2·6H2O and 1.2 mmol of C6H8O7·H2O.

[0015] Preferably, in S4 as described above, the calcination is carried out in an air atmosphere, and the temperature is raised to 400℃ at a rate of 5℃ / min.

[0016] Another object of the present application is to provide a hollow fiber-shaped ammonium perchlorate thermal decomposition catalytic material.

[0017] Preferably, the hollow fiber-shaped ammonium perchlorate thermal decomposition catalytic material as described above is mainly composed of MgCo2O4.

[0018] The present application has the following beneficial effects:

[0019] The nanoscale binary transition metal oxide MgCo2O4 as a P-type semiconductor material can generate electrons and holes under thermal energy excitation, and the metal atoms in the unit cell have unfilled d orbitals and a synergistic effect between the two metals, which can accelerate the electron transfer in the AP decomposition process, thus showing better catalytic performance than single metal oxide. The catalytic performance of the catalytic material for AP thermal decomposition is not only affected by its own composition, but also greatly affected by the morphology structure, catalytic active site and carbon material defects. Therefore, by selecting a biological template-cotton and designing incomplete carbon removal during the solution combustion process, porous defective carbon is introduced while the morphology of the MgCo2O4 nanomaterial is successfully optimized. Not only does it effectively ensure the rapid progress of the AP thermal decomposition reaction, but it also further improves the apparent heat of decomposition of AP thermal decomposition, creating conditions for the sustained combustion of composite solid propellants. BRIEF DESCRIPTION OF DRAWINGS

[0020] The accompanying drawings are used to illustrate the specific embodiments of the present experiment, constitute a part of the application, but do not constitute a limitation on the embodiments of the present application.

[0021] Figure 1 The XRD pattern of the MgCo2O4 sample.

[0022] Figure 2 (a) and (b) are SEM patterns of nanoporous carbon defect MgCo2O4, (c) low magnification and (d) high magnification TEM patterns of MgCo2O4.

[0023] Figure 3 The DSC curve of the AP thermal decomposition with 2% nanoporous carbon defect MgCo2O4 added.

[0024] Figure 4TG curve of AP thermal decomposition with 2% nano-porous carbon-defect MgCo2O4.

[0025] DETAILED DESCRIPTION

[0026] The application will be further described below in connection with specific embodiments and drawings, but the application is not limited to the following embodiments.

[0027] Example 1

[0028] One-step preparation of hollow fiber-like ammonium perchlorate thermal decomposition catalytic material:

[0029] S1: Cleaned cotton was activated and pretreated in a mixed solution of ethanol: water: 2M hydrochloric acid = 1:1:2 by volume ratio, ultrasonic for 1h, then soaked for 6h, finally washed with deionized water for 2-3 times and dried overnight;

[0030] S2: 0.8mmol of Mg(NO3)2·6H2O, 1.36mmol of Co(NO3)2·6H2O and 1.2mmol of C6H8O7·H2O were dissolved in 15ml of deionized water and placed in a crucible, and magnetic stirring was carried out for 30min to make the raw materials completely dissolved;

[0031] S3: The pretreated cotton was completely immersed in the above solution and soaked for 12h;

[0032] S4: The cotton was taken out and calcined in air atmosphere at a heating rate of 5℃ / min to 400℃, and kept for 1h, to obtain multi-cavity carbon-defect MgCo2O4.

[0033] Example 2

[0034] Catalytic performance of nano-porous carbon-defect MgCo2O4 material on ammonium perchlorate thermal decomposition:

[0035] The nano-porous carbon-defect MgCo2O4 prepared by one-step solution combustion method was mixed with AP by 2% mass ratio after sufficient grinding, and differential thermal-thermal gravimetric analysis was carried out at a temperature range of 100-500℃ with a heating rate of 20℃ / min, to study the catalytic performance of MgCo2O4 on AP thermal decomposition and the thermal decomposition behavior of pure AP. The results are shown in Figure 3 Fig. 1. As can be seen from the figure, for pure AP, Figure 3(a)), the curve shows that the thermal decomposition of pure AP consists of three stages, the first stage is the crystal transformation stage, the transformation from orthorhombic phase to cubic phase occurs at 246.53°C, with an endothermic peak; the second stage is that with the temperature rising to about 343.62°C, the low temperature decomposition process (LTD) of AP is entered, and part of the intermediate product is generated; the third stage is that with the temperature rising, the intermediate product will be decomposed into gaseous products, and the high temperature decomposition exothermic process (HTD) is entered, and the temperature of the high temperature decomposition exothermic peak is 473.48°C. From the DSC curve of AP, it can be seen that the thermal decomposition of AP is a two-step process, the first step is the crystal transformation stage, the transformation from orthorhombic phase to cubic phase occurs at 246.53°C, with an endothermic peak; the second step is the low temperature decomposition stage, with the temperature rising to about 343.62°C, the low temperature decomposition process (LTD) of AP is entered, and part of the intermediate product is generated; the third step is the high temperature decomposition stage, with the temperature rising, the intermediate product will be decomposed into gaseous products, and the high temperature decomposition exothermic process (HTD) is entered, and the temperature of the high temperature decomposition exothermic peak is 473.48°C. Figure 3 (b) can be seen that, compared with pure AP, after adding 2% of porous carbon defect structure MgCo2O4 catalyst, the thermal decomposition of AP has changed significantly, the low temperature decomposition peak and the high temperature decomposition peak of AP are combined into one peak, and the peak temperature sharply drops to 258.17°C, which is 215.31°C lower than that of pure AP. At the same time, the heat generated by the decomposition of AP increases from 888.26 J / g to 3669.38 J / g. Adding a small amount of porous carbon defect structure MgCo2O4 not only greatly reduces the temperature of AP decomposition, but also increases the heat release of AP decomposition by an astonishing 4.1 times.

[0036] The TG curve of AP thermal decomposition of nano-porous carbon defect MgCo2O4 prepared by one-step solution combustion method is shown in Figure 4 As can be seen from the figure, in the temperature range of 100-500°C, two obvious weight loss steps can be seen on the TG curve of pure AP, the first weight loss stage is the low temperature decomposition stage at about 340°C, and part of the intermediate product is generated, and the second weight loss stage is the high temperature decomposition stage at about 480°C, and AP is completely decomposed into HCl, H2O, NO, N2O and other gaseous products. The TG curve of AP thermal decomposition of nano-porous carbon defect structure MgCo2O4 catalyst shows only one obvious weight loss process, which is consistent with the DSC analysis result.

[0037] Although the main examples of the factors affecting the experiment have been described and listed, those skilled in the art can understand that various changes, explorations, modifications and combinations can be made to the examples without departing from the principles and purposes of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A method for the preparation of a hollow fibrous ammonium perchlorate thermal decomposition catalytic material, characterized by: Preparation of MgCo2O4 with porous carbon defects by one-step solution combustion method, specifically comprising the following steps: S1: clean cotton is activated and pretreated in an ethanol: water: 2M hydrochloric acid mixed solution, ultrasonic for 1 h, then soaked for 6 h, finally washed with deionized water for 2-3 times and dried overnight; S2: Mg(NO3)2·6H2O, Co(NO3)2·6H2O and C6H8O7·H2O are dissolved in 15 ml deionized water and placed in a crucible, and magnetic stirring is performed for 30 min, so that the raw materials are completely dissolved; S3: the pretreated cotton is completely immersed in the above solution and soaked for 12 h; S4: the cotton is taken out, calcined with the furnace temperature rising in air atmosphere, and kept for 1 h, to obtain MgCo2O4 with porous carbon defects.

2. The method for producing a hollow fiber-shaped ammonium perchlorate thermal decomposition catalytic material according to claim 1, characterized by: In the S1, the volume ratio of the ethanol: water: 2M hydrochloric acid mixed solution is 1:1:

2.

3. The preparation method of the hollow fibrous ammonium perchlorate thermal decomposition catalytic material as described in claim 1, characterized in that: In the S2, the amount of each substance is: 0.8 mmol of Mg(NO3)2·6H2O, 1.6 mmol of Co(NO3)2·6H2O and 1.2 mmol of C6H8O7·H2O.

4. The preparation method of the hollow fibrous ammonium perchlorate thermal decomposition catalytic material as described in claim 1, characterized in that: In the S4, the calcination is performed in air atmosphere, and the temperature is raised to 400℃ at a rate of 5℃ / min.

5. The hollow fibrous ammonium perchlorate thermal decomposition catalyst material prepared by the method according to any one of claims 1 to 4, characterized in that: The porous defective carbon is introduced into the hollow fiber-like material by taking raw cotton as a template.

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