Three-dimensional lead-containing MOFs combustion catalyst, preparation method and application

Abstract

The application provides a three-dimensional lead-containing MOFs combustion catalyst, a preparation method and application, the three-dimensional lead-containing MOFs combustion catalyst is Pb2(H2TCPP)·4(C4H9NO), [PbLi(H2O)](TCPP-Pb) or Pb[(TCPP-Cs)H2O]. The synthesis method of the application successfully prepares lead-containing MOFs crystals by using a solvent thermal method and various novel mineralizers, and the addition of the mineralizers is helpful to the crystallization of the lead-containing MOFs crystals and the more regular crystal morphology. The three compounds prepared by the application are three-dimensional lead-containing MOFs materials, which not only contain lead ions, but also have a large pore structure, so that the three-dimensional lead-containing MOFs materials have better catalytic performance and are helpful to improve the propellant energy. The difference in the lead content in the composition of the MOFs compound of the application can also adjust the combustion performance of the propellant.

Description

Technical Field

[0001] This invention belongs to the field of explosives technology, and relates to combustion catalysts, specifically to a three-dimensional lead-containing MOFs combustion catalyst, its preparation method, and its application. Background Technology

[0002] The regulation of solid propellant combustion performance is a crucial component of propulsion technology research, ensuring the stable operation of rocket engines. Catalysts, as an essential part of solid propellants, not only catalyze combustion and increase the combustion rate but also enable a plateau combustion effect within the engine, reducing the combustion pressure index and ensuring stable engine operation. Generally, lead or copper salts exhibit good catalytic combustion performance when used as catalysts.

[0003] In previous research and applications, to improve the combustion performance of solid propellants, certain amounts of metal oxides (PbO, CuO), organic acid salts (lead phthalate), or complexes composed of lead, copper, and carbon black were added as catalysts. Currently, the most studied organic compounds containing metal ions are metal-organic frameworks (MOFs). These materials have large porous structures and high porosity (specific surface area > 1000 m²). 2 Lead-containing MOFs (Metal-Oxide-Factory Materials) provide a large number of highly dispersed active sites for catalytic reactions. They have been extensively studied in industrial fields such as CO and methane combustion catalysis, H2 storage, ethanol purification, gas adsorption, and seawater purification. However, their application in the combustion catalysis of explosives is relatively limited, and few lead-containing MOF materials have been discovered. Only four lead-containing MOF materials are listed in the Cambridge Crystallography Database (CCDC), which is insufficient to meet the application requirements of solid propellant formulation design. Therefore, there is an urgent need to design and synthesize novel MOF materials to provide guidance for the development of solid propellants used in weapon systems. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a three-dimensional lead-containing MOFs combustion catalyst, its preparation method, and its application, thereby solving the technical problem that existing MOFs combustion catalysts do not contain lead.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A three-dimensional lead-containing MOFs combustion catalyst, wherein the structural formula of the three-dimensional lead-containing MOFs combustion catalyst is as follows:

[0007]

[0008] This invention also protects a method for preparing a three-dimensional lead-containing MOFs combustion catalyst as described above, the method comprising the following steps:

[0009] Step 1: Weigh H2TCPP, NH3-H3BTB and PbCl2 and put them into a 30mL hydrothermal reactor. Add dimethylacetamide solvent, seal the reactor and put it into a programmable temperature-controlled oven.

[0010] Step 2: The reactor is heated from room temperature to 135°C in a temperature-controlled oven for 2 hours, then kept at that temperature for 48 hours. After that, the temperature is lowered to 35°C at a rate of 1.4°C / h, the temperature-controlled oven is turned off, and the reactor is removed.

[0011] Step 3: The reaction product was washed three times with dimethylformamide and then dried at 70°C for 10 hours in a temperature-controlled oven to obtain reddish-brown rhombic Pb2(H2TCPP)·4(C4H9NO) crystals.

[0012] Preferably, in step one, the molar ratio of raw materials H2TCPP, NH3-H3BTB and PbCl2 is 2:1:17; each 50.0 mg of H2TCPP corresponds to 8 mL of dimethylacetamide; and NH3-H3BTB is used as a mineralizing agent.

[0013] This invention also protects a three-dimensional lead-containing MOFs combustion catalyst, the structural formula of which is:

[0014]

[0015] This invention also protects a method for preparing a three-dimensional lead-containing MOFs combustion catalyst as described above, the method comprising the following steps:

[0016] Step 1: Weigh H2TCPP and PbCl2 and place them in a 30mL hydrothermal reactor. Add dimethylacetamide solvent and mix with a magnetic stirrer for 20 minutes.

[0017] Step 2: Add lithium hydroxide solution to the mixture, then add H2O, seal the reactor and place it in a temperature-controlled oven.

[0018] Step 3: The reaction product was washed three times with dimethylformamide and then dried at 70°C for 10 hours in a temperature-controlled oven to obtain reddish-brown rectangular [PbLi(H2O)](TCPP-Pb) crystals.

[0019] Preferably, in step one, the molar ratio of raw material H2TCPP to PbCl2 is 1:45; each 39.4 mg of H2TCPP corresponds to 4 mL of dimethylacetamide; in step two, the concentration of lithium hydroxide solution is 1 mol / L, each 39.4 mg of H2TCPP corresponds to 3 mL of lithium hydroxide solution and 1 mL of H2O, with the lithium hydroxide solution serving as a mineralizing agent.

[0020] This invention also protects a three-dimensional lead-containing MOFs combustion catalyst, the structural formula of which is:

[0021]

[0022] This invention also protects a method for preparing a three-dimensional lead-containing MOFs combustion catalyst as described above, the method comprising the following steps:

[0023] Step 1: Weigh H2TCPP, PbCl2 and La(NO3)3(H2O)6 and place them in a 30mL hydrothermal reactor. Add dimethylacetamide solvent and mix on a magnetic stirrer for 30 minutes.

[0024] Step 2: Add CsOH solution to the mixture, then seal the reactor and place it in a temperature-controlled oven.

[0025] Step 3: The reaction product was washed three times with dimethylformamide and then dried at 70°C for 10 hours in a temperature-controlled oven to obtain reddish-brown rectangular Pb[(TCPP-Cs)H2O] crystals.

[0026] Preferably, in step one, the molar ratio of raw materials H2TCPP, PbCl2 and La(NO3)3(H2O)6 is 1:15:4; each 40.0 mg of H2TCPP corresponds to 6 mL of dimethylacetamide; in step two, the concentration of CsOH solution is 1 mol / L, and each 40.0 mg of H2TCPP corresponds to 2.5 mL of CsOH solution added.

[0027] a(NO3)3(H2O)6 and CsOH solution were used as mineralizing agents.

[0028] The present invention also protects the use of the three-dimensional lead-containing MOFs combustion catalyst described above as a combustion catalyst for solid propellants.

[0029] Compared with the prior art, the present invention has the following technical effects:

[0030] (I) The synthesis method of the present invention successfully prepared lead-containing MOFs crystals by using a variety of novel mineralizing agents through a solvothermal method. The addition of mineralizing agents helps the crystallization of lead-containing MOFs crystals and makes the crystal morphology more regular.

[0031] (II) The Pb2(H2TCPP)·4(C4H9NO), [PbLi(H2O)](TCPP-Pb) and Pb[(TCPP-Cs)H2O] synthesized in this invention are all three-dimensional lead-containing MOFs materials. They not only contain lead ions, but also have large pore structures, which make them have better catalytic performance and help to improve propellant energy.

[0032] (III) The difference in lead content in the MOFs compound composition of the present invention can also regulate the combustion performance of the propellant.

[0033] (IV) The present invention facilitates quality control when preparing MOF crystals in batches, and can provide important technical support for their application in propellants. Attached Figure Description

[0034] Figure 1 The crystal structure diagram of Pb2(H2TCPP)·4(C4H9NO) is shown.

[0035] Figure 2 This is the crystal structure diagram of [PbLi(H2O)](TCPP-Pb).

[0036] Figure 3 This is the crystal structure diagram of Pb[(TCPP-Cs)H2O].

[0037] Figure 4 The powder XRD pattern of Pb2(H2TCPP)·4(C4H9NO).

[0038] Figure 5 SEM image and EDS data for Pb2(H2TCPP)·4(C4H9NO).

[0039] Figure 6 SEM images and EDS data for [PbLi(H2O)](TCPP-Pb).

[0040] Figure 7 SEM image and EDS data for Pb[(TCPP-Cs)H2O].

[0041] Figure 8 The TEM image is of Pb2(H2TCPP)·4(C4H9NO).

[0042] Figure 9 The image shows the FT-IR spectrum of Pb[(TCPP-Cs)H2O].

[0043] Figure 10 The TG curves for HMX and HMX / Pb2(H2TkCPP)·4(C4H9NO) at a heating rate of 10℃ / min are shown.

[0044] Figure 11 The DSC curves for HMX and HMX / Pb2(H2TCPP)·4(C4H9NO) at a heating rate of 10℃ / min are shown.

[0045] Figure 12 The TG-MS curves for HMX at a heating rate of 10 °C / min are shown.

[0046] Figure 13 The TG-MS curves of HMX / Pb2(H2TCPP)·4(C4H9NO) at a heating rate of 10℃ / min are shown.

[0047] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0048] It should be noted that all materials and equipment used in this invention, unless otherwise specified, are those known in the art. For example, H2TCPP and NH3-H3BTB are both commercially available known H2TCPP and NH3-H3BTB. The programmable temperature-controlled oven is a commercially available known programmable temperature-controlled oven.

[0049] H2TCPP refers to 5,10,15,20-tetra(4-carboxyphenyl)porphyrin.

[0050] NH3-H3BTB refers to aniline-2,4,6-tribenzoic acid.

[0051] This invention discloses a three-dimensional lead-containing MOFs combustion catalyst, its preparation method, and its applications. The catalyst comprises three compounds: Pb₂(H₂TCPP)·₄(C₄H₹NO), [PbLi(H₂O)](TCPP-Pb), and Pb[(TCPP-Cs)H₂O]. The preparation method involves mixing tetrakis(4-carboxyphenyl)porphyrin, metallic lead, other alkali metal ions, and a mineralizing agent in a specific ratio in a reaction vessel, adding a solvent, reacting at a certain temperature for a period of time, and then slowly cooling to obtain the lead-containing MOFs material. This invention successfully prepared three lead-containing MOFs crystals using various novel mineralizing agents. The addition of mineralizing agents facilitates the crystallization of lead-containing MOFs crystals, resulting in more regular crystal morphologies, and also improves quality control during batch preparation of MOFs crystals. These three-dimensional lead-containing MOFs combustion catalysts not only possess high porosity, providing a large number of highly dispersed active sites for catalytic reactions, but also contain lead ions, making them suitable as combustion catalysts for propellants.

[0052] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0053] Example 1:

[0054] This embodiment provides a method for preparing a three-dimensional lead-containing MOFs combustion catalyst. Specifically, the three-dimensional lead-containing MOFs combustion catalyst is designated as Pb2(H2TCPP)·4(C4H9NO) and is synthesized using a solvothermal method.

[0055] The structural formula of the three-dimensional lead-containing MOFs combustion catalyst in this embodiment is:

[0056]

[0057] This method is performed according to the following steps:

[0058] 50 mg H2TCPP, 15.0 mg NH3-H3BTB, and 148 mg PbCl2 were weighed and placed in a 30 mL hydrothermal reactor. The molar ratio of H2TCPP, NH3-H3BTB, and PbCl2 was 2:1:17. NH3-H3BTB was used as the mineralizing agent in the synthesis of this crystal. 8 mL of dimethylacetamide was added as a solvent. The reactor was sealed and placed in a temperature-controlled oven. The temperature was raised from room temperature to 135 °C over 2 hours and then maintained at that temperature for 48 hours. Afterward, the temperature was lowered to 35 °C at a rate of 1.4 °C / h. The temperature-controlled oven was then turned off, the reactor was removed, and the mixture was washed three times with dimethylformamide (DMF). Finally, it was dried at 70 °C for 10 hours in a temperature-controlled oven to obtain reddish-brown rhomboid Pb2(H2TCPP)·4(C4H9NO) crystals with a yield of approximately 76%.

[0059] The crystal structure of the reddish-brown rhombic Pb2(H2TCPP)·4(C4H9NO) crystals obtained in this embodiment is as follows: Figure 1 As shown, the powder XRD pattern is as follows: Figure 4 As shown, SEM-EDS Figure 5 As shown, the TEM image is as follows Figure 1 As shown.

[0060] Example 2:

[0061] This embodiment provides a method for preparing a three-dimensional lead-containing MOFs combustion catalyst. Specifically, the three-dimensional lead-containing MOFs combustion catalyst is denoted as [PbLi(H2O)](TCPP-Pb) and is synthesized by a solvothermal method.

[0062] The structural formula of the three-dimensional lead-containing MOFs combustion catalyst in this embodiment is:

[0063]

[0064] This method is performed according to the following steps:

[0065] 39.4 mg H2TCPP and 624 mg PbCl2 were weighed and placed in a 30 mL hydrothermal reactor with a molar ratio of H2TCPP to PbCl2 of 1:45. 4 mL of dimethylacetamide was added as a solvent, and the mixture was stirred with a magnetic stirrer for 20 min. Then, 3 mL of 1 mol / L LiOH solution was added as the mineralizing agent for the crystal synthesis. 1 mL of H2O was added to each reactor. The reactor was sealed and placed in a temperature-controlled oven. The temperature was raised from room temperature to 135 °C over 2 hours and maintained at that temperature for 48 hours. Afterward, the temperature was lowered to 35 °C at a rate of 1.4 °C / h. The temperature-controlled oven was then turned off, the reactor was removed, and the reactor was washed three times with dimethylformamide (DMF). Finally, the reactor was dried at 70 °C for 10 h in a temperature-controlled oven to obtain reddish-brown rectangular [PbLi(H2O)](TCPP-Pb) crystals with a yield of approximately 52.4%.

[0066] The crystal structure of the reddish-brown rectangular [PbLi(H2O)](TCPP-Pb) crystals obtained in this embodiment is as follows: Figure 2 As shown, SEM-EDS Figure 6 As shown.

[0067] Example 3:

[0068] This embodiment provides a method for preparing a three-dimensional lead-containing MOFs combustion catalyst. Specifically, the three-dimensional lead-containing MOFs combustion catalyst is denoted as Pb[(TCPP-Cs)H2O] and is synthesized by a solvothermal method.

[0069] The structural formula of the three-dimensional lead-containing MOFs combustion catalyst in this embodiment is:

[0070]

[0071] This method is performed according to the following steps:

[0072] Weigh 40.0 mg H2TCPP, 208.1 mg PbCl2, and 86.5 mg H2TCPP. La(NO3)3(H2O)6 was placed in a 30 mL hydrothermal reactor with a molar ratio of H2TCPP, PbCl2, and La(NO3)3(H2O)6 of 1:15:4. 6 mL of dimethylacetamide was added as a solvent, and the mixture was stirred with a magnetic stirrer for 30 min. Then, 2.5 mL of 1 mol / L CsOH solution was added. La(NO3)3(H2O)6 and CsOH were used as mineralizing agents for the synthesis of compound (3) crystals. The reactor was sealed and placed in a temperature-controlled oven. The temperature was raised from room temperature to 135 °C in 2 hours and then kept at that temperature for 48 hours. After that, the temperature was lowered to 35 °C at a rate of 1.4 °C / h. The temperature-controlled oven was then turned off, the reactor was removed, and the mixture was washed three times with dimethylformamide (DMF). Then, it was dried at 70 °C for 10 h in a temperature-controlled oven to obtain reddish-brown rectangular Pb[(TCPP-Cs)H2O] crystals with a yield of about 25.8%.

[0073] The crystal structure of the reddish-brown rectangular Pb[(TCPP-Cs)H2O] crystals obtained in this embodiment is as follows: Figure 3 As shown, SEM-EDS Figure 7 As shown, the infrared spectrum is as follows Figure 9 As shown.

[0074] The crystal structure parameters of the three lead-containing MOFs materials prepared in Examples 1 to 3 are shown in Table 1.

[0075] Table 1 Crystallographic data of three lead-containing MOFs

[0076]

[0077] Three lead-containing MOF materials are derived from the organic ligand -tetra(4-carboxyphenyl)porphyrin (C 48 H 30 Pb-MOFs compounds formed by the chelation of N4O8, H2TCPP, metallic lead, and other alkali metal ions.

[0078] The first compound, Pb2(H2TCPP)·4(C4H9NO), has the molecular formula C. 64 H 64 N8O 12 Pb2, crystal structure as follows Figure 1 As shown, it has a three-dimensional microporous structure, belongs to the monoclinic crystal system, has a space group of P21 / c, and a pore size of [missing information]. In this three-dimensional structure, there are no metal ions inside the ligands, and the ligands are connected by Pb ions to form a three-dimensional structure. The channels of the MOF compound contain solvent C4H9NO molecular units.

[0079] The second compound, [PbLi(H2O)](TCPP-Pb), has the molecular formula C. 48 H 29 LiN4O9Pb2, crystal structure as follows Figure 2 As shown, it also has a three-dimensional microporous structure, belongs to the monoclinic crystal system, has a space group of C2 / c, and a pore size of [missing information]. In this three-dimensional structure, some lead ions are located at the center of the TCPP ligand and are connected to nitrogen atoms. The ligands are connected by disordered groups composed of Pb and Li ions to form a three-dimensional structure.

[0080] The third compound, Pb[(TCPP-Cs)H2O], has the molecular formula C. 48 H 26 CsN4O9Pb, crystal structure as follows Figure 3 As shown, it also has a three-dimensional microporous structure, belongs to the monoclinic crystal system, has a space group of C2 / c, and a pore size of [missing information]. In this three-dimensional structure, the cesium ion is located at the center of the TCPP ligand and is connected to the nitrogen atom. The ligands are connected to each other through Pb ions to form a three-dimensional structure.

[0081] The structure and composition of Pb₂(H₂TCPP)·₄(C₄H₉NO) crystals were characterized using X-ray diffraction (XRD). A Cu Kα source was used, with a measurement angle range (2θ) of 5–90° and a scan rate of 8° / min. The XRD results for Pb₂(H₂TCPP)·₄(C₄H₉NO) are shown below. Figure 4 As shown, after refinement, it was found that the experimental diffraction pattern was consistent with the XRD data calculated from the single-crystal CIF file.

[0082] SEM-EDS results of Pb2(H2TCPP)·4(C4H9NO), [PbLi(H2O)](TCPP-Pb) and Pb[(TCPP-Cs)H2O] Figures 5 to 7 It can be seen that the crystal shapes of these three compounds are all irregular polygons, and the presence of metal ions in the three compounds was confirmed by EDS.

[0083] TEM image of b2(H2TCPP)·4(C4H9NO) Figure 8 It can be seen that the atomic arrangement of the compound is consistent with the crystal structure obtained from single-crystal diffraction data.

[0084] The FTIR spectra of Pb[(TCPP-Cs)H2O] are as follows: Figure 9 As shown, in the range of 1540-1630cm -1 The spectral bands correspond to the vibrations of the aromatic ring in the H2TCPP ligand, in the range of 1180-1380 cm⁻¹. -1The spectral bands correspond to the vibrations of the CO bonds on the carboxylic acid groups in the H2TCPP ligands, and the bands are located in the range of 950-1150 cm⁻¹. -1 The corresponding symmetrical vibrations of the Pb-N bond occur in the range of 700-950 cm⁻¹. -1 The vibrations correspond to the Pb-O and Cs-O bonds.

[0085] Example 4:

[0086] This embodiment illustrates the application of three lead-containing MOF materials (Examples 1, 2, and 3) as combustion catalysts for solid propellants. Specifically... Figures 10 to 13 As shown.

[0087] like Figure 10 As shown, the main pyrolysis of the energetic material octogen (HMX) and its Pb2(H2TCPP)·4(C4H9NO) sample occurred in the 180-300℃ range. HMX experienced a 94% mass loss during pyrolysis, while the HMX / Pb2(H2TCPP)·4(C4H9NO) sample suffered a 97.3% mass loss, demonstrating that the addition of the combustion catalyst Pb2(H2TCPP)·4(C4H9NO) resulted in a more complete decomposition of HMX.

[0088] From such Figure 11 The DSC results shown indicate that at 10℃·min -1 Under the heating conditions, HMX has a melting point of 200.1℃ and a thermal decomposition peak temperature of 283.6℃. When mixed with Pb2(H2TCPP)·4(C4H9NO), the melting point of HMX / Pb2(H2TCPP)·4(C4H9NO) is 200.5℃, and the thermal decomposition peak temperature appears at 283.2℃, which is 0.4℃ lower than the thermal decomposition peak temperature of pure HMX. This further confirms that Pb2(H2TCPP)·4(C4H9NO) has a catalytic effect on the decomposition of HMX.

[0089] HMX and HMX / Pb2(H2TCPP)·4(C4H9NO) at 10℃·min -1 TG-MS results under heated conditions are as follows Figure 12 and Figure 13 As shown, the main pyrolysis products of HMX include N (m / z = 14) and NH2. +The following species were detected: / O· (m / z = 16), NH3 / OH (m / z = 17), H2O (m / z = 18), CO / N2 (m / z = 28), ·CHO / ·CH3N (m / z = 29), NO / CH2O (m / z = 30), and CO2 / N2O (m / z = 44). The addition of Pb2(H2TCPP)·4(C4H9NO) significantly reduced the pyrolysis product NH3 / OH (m / z = 17), demonstrating that this lead-containing MOF material catalyzes more complete HMX oxidation.

Claims

1. A method for the preparation of a three-dimensional lead-containing MOFs combustion catalyst, characterized in that, Comprising the following steps: Step one, after weighing H2TCPP, NH3-H3BTB and PbCl2, put them into a 30 mL hydrothermal reactor, add dimethylacetamide solvent, seal the reactor and put it into a programmed temperature oven; Step two, the reactor is heated from room temperature to 135℃ in 2 hours, then keep the temperature for 48 hours, then decrease the temperature to 35℃ at a rate of 1.4℃ / h, turn off the programmed temperature oven and take out the reactor; Step three, the reaction product is washed with dimethylformamide for three times, then dry it in a programmed temperature oven at 70℃ for 10 hours, get the red-brown three-dimensional lead-containing MOFs combustion catalyst crystal with rhombus shape; The structural formula of the three-dimensional lead-containing MOFs combustion catalyst is: 。 2. The method of claim 1, wherein the three-dimensional lead-containing MOFs combustion catalyst is prepared by the steps of: In step one, the molar ratio of raw materials H2TCPP, NH3-H3BTB and PbCl2 is 2:1:17; 8 mL dimethylacetamide corresponds to 50.0 mg H2TCPP; NH3-H3BTB is used as a mineralizer.

3. Application of the three-dimensional lead-containing MOFs combustion catalyst as a combustion catalyst for solid propellant; the three-dimensional lead-containing MOFs combustion catalyst is prepared by the method of claim 1.

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