Iron-containing imidazole self-igniting fuel, preparation method and application thereof

Abstract

The application provides an iron-containing imidazole self-ignition fuel, a preparation method and application, and a structural formula is as follows: the preparation method takes FeCl3.6H2O and 1-vinylimidazole (C5H6N2) as raw materials, takes acetonitrile as a solvent, and adopts a liquid phase reaction method to prepare the iron-containing imidazole self-ignition fuel. Fe(VIM)4Cl3 obtained by synthesis is a new type of iron-containing imidazole self-ignition fuel, contains trivalent iron ions, has catalytic performance, promotes full combustion of a fuel and an oxidant, avoids unstable combustion of an engine, and has self-ignition characteristics as the fuel, so that ignition delay time meets the requirement of a rocket engine, so that an igniter is not needed in the engine, and engine parts are simplified.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of explosives, and relates to a self-igniting fuel for a self-igniting hybrid rocket engine, in particular to a self-igniting fuel containing iron imidazole, a preparation method and application. BACKGROUND

[0002] Solid-liquid hybrid rocket engines have the advantages of higher specific impulse, multiple start-ups and adjustable thrust, and have wide application prospects in sounding rockets, small launch vehicles and missiles. As a kind of solid-liquid hybrid propulsion technology, the self-igniting hybrid propulsion can realize multiple start-ups without an external ignition source by using self-igniting fuel, and can also reduce the total mass. In addition, compared with traditional toxic oxidizers such as N2O4, high-concentration hydrogen peroxide (H2O2) is the best choice for oxidizers in self-igniting hybrid propulsion. Therefore, the new strategy of self-igniting fuel particles and high-concentration H2O2 (HTP) is expected to replace the traditional liquid engine toxic hydrazine fuel propellant combination.

[0003] At present, the traditional fuel for self-igniting hybrid rocket engines has the problems of long ignition delay time, low burning surface recession rate and low combustion efficiency, so the development of new green fuels is one of the key research fields for the development of the next generation of HTP self-igniting propulsion systems. More than 10 kinds of solid fuels such as paraffin and ammonia borane for HTP hybrid propulsion have been studied, but only a small number of solid fuel / HTP propellants can achieve the performance of toxic oxidizer / hydrazine fuel propellants. SUMMARY

[0004] In view of the problems in the prior art, the purpose of the present application is to provide a self-igniting fuel containing iron imidazole, a preparation method and application, which solves the technical problem that the combustion stability of the self-igniting fuel in the prior art needs to be further improved.

[0005] In order to solve the above technical problems, the present application adopts the following technical solutions:

[0006] A self-igniting fuel containing iron imidazole has the following structural formula:

[0007]

[0008] The present application also protects a preparation method of the self-igniting fuel containing iron imidazole as described above, which uses FeCl3·6H2O and 1-vinylimidazole (C5H6N2) as raw materials, acetonitrile as a solvent, and adopts a liquid phase reaction method to prepare the self-igniting fuel containing iron imidazole.

[0009] Preferably, the molar ratio of FeCl3·6H2O to 1-vinylimidazole is 1:4.

[0010] Specifically, the preparation method is carried out according to the following steps:

[0011] Step one, acetonitrile solvent is added into a conical flask, then 1-vinylimidazole is added, and mixed for 5 minutes on a magnetic stirrer;

[0012] Step two, then FeCl3·6H2O is added, and the conical flask is sealed;

[0013] Step three, the temperature is raised to 85℃ under magnetic stirring, and the reaction is stirred at this temperature for 2 hours;

[0014] Step four, the magnetic stirrer is turned off, and after the reaction is cooled to room temperature, the acetonitrile solvent is removed under vacuum on a rotary evaporator, and red rectangular crystals, i.e. the iron-containing imidazole-based self-igniting fuel, can be obtained.

[0015] The application also protects the use of the iron-containing imidazole-based self-igniting fuel as described above for the self-igniting fuel of solid-liquid hybrid rocket propulsion.

[0016] Compared with the prior art, the application has the following technical effects:

[0017] (I) The Fe(VIM)4Cl3 synthesized by the application is a new type of iron-containing imidazole-based self-igniting fuel, which not only contains trivalent iron ions and has catalytic properties, but also promotes the full combustion of the fuel and the oxidant, avoids the occurrence of unstable combustion of the engine, and has self-igniting characteristics as a fuel, so that the ignition delay time meets the requirements of the rocket engine, so that no igniter is needed in the engine, and the engine components are simplified.

[0018] (II) The synthesis method of the application is a liquid phase reaction method, which is suitable for batch production of metal-based imidazole-based self-igniting fuels, and the cost of raw materials used is low, which lays a foundation for its wide application in hybrid propulsion in the future. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a crystal structure diagram of Fe(VIM)4Cl3 in the b-axis direction.

[0020] Figure 2 It is a powder XRD diagram of Fe(VIM)4Cl3.

[0021] Figure 3 It is an SEM diagram and EDS data of Fe(VIM)4Cl3.

[0022] Figure 4 It is a TG-DSC curve of Fe(VIM)4Cl3 at different heating rates.

[0023] Figure 5 It is a picture of the self-igniting drop ignition test of Fe(VIM)4Cl3 powder and 95% H2O2.

[0024] Figure 6Picture of self-ignition drop ignition test of solid fuel containing Fe(VIM)4Cl3 and paraffin with 95% H2O2.

[0025] Figure 7 Picture of self-ignition drop ignition test of solid fuel containing Fe(VIM)4Cl3, borane ammonia and paraffin with 95% H2O2.

[0026] Figure 8 Theoretical specific impulse of solid fuel containing Fe(VIM)4Cl3 at different O / F ratios.

[0027] Figure 9 Picture of solid fuel grain containing Fe(VIM)4Cl3.

[0028] Figure 10 Engine pressure curve diagram of solid fuel containing borane ammonia and paraffin.

[0029] Figure 11 Engine pressure curve diagram of solid fuel containing Fe(VIM)4Cl3, borane ammonia and paraffin.

[0030] Figure 12 Engine pressure curve diagram of solid fuel containing Fe(VIM)4Cl3 and paraffin.

[0031] The specific content of the present application is further explained in detail in combination with the following examples. DETAILED DESCRIPTION

[0032] It should be noted that all raw materials and reagents in the present application, unless otherwise specified, are all known raw materials and reagents in the prior art, and can be obtained from commercial channels. All experimental methods in the present application, unless otherwise specified, are conventional methods.

[0033] Self-igniting metal organic framework materials (MOFs) have super-short ignition delay, are not sensitive to explosion, heat or impact, and have high specific energy and adjustable energy density based on nitrogen-containing heterocyclic energetic imidazole metal materials, which are close to or even exceed the energy density of hydrazine fuel. In particular, green energetic non-toxic MOFs materials containing Cu and Fe are expected to replace hydrazine fuel. Therefore, in order to meet the development needs of non-toxic self-igniting propellants, it is urgent to design and synthesize a new type of green self-igniting MOFs material.

[0034] The iron-containing imidazole self-igniting fuel of the present application can be used as a self-igniting fuel and is expected to be applied in a hybrid rocket engine to reduce the ignition delay time of traditional fuel. Meanwhile, the iron containing trivalent metal ions has catalytic properties, which promotes the complete combustion of fuel and avoids the occurrence of unstable engine combustion.

[0035] The following gives specific embodiments of the present application, it is to be noted that the present application is not limited to the following specific embodiments, any equivalent transformation made on the basis of the technical solutions of the present application falls within the protection scope of the present application.

[0036] Embodiment 1:

[0037] This embodiment gives a preparation method of an iron-containing imidazole self-ignition fuel, which is carried out according to the following steps:

[0038] Step one, 1L of acetonitrile solvent is added into a conical flask, then 22.584g of 1-vinylimidazole is added, and mixed on a magnetic stirrer for 5 minutes.

[0039] Step two, then 16.212g of FeCl3·6H2O is added, and the conical flask is sealed.

[0040] Step three, the temperature is raised to 85℃ under magnetic stirring, and the reaction is stirred at this temperature for 2 hours.

[0041] Step four, the magnetic stirrer is turned off, and after the reaction is cooled to room temperature, the acetonitrile solvent is removed on a rotary evaporator under vacuum, and a red rectangular crystal product can be obtained, with a yield of 98wt.%. This is an iron-containing imidazole self-ignition fuel.

[0042] Structure identification:

[0043] The crystal structure of the red rectangular crystal product prepared in this embodiment is shown in Figure 1 , and the crystal structure parameters are shown in Table 1.

[0044] Table 1 Crystal structure parameters of the iron-containing imidazole self-ignition fuel

[0045]

[0046] From Figure 1 and Table 1, it can be seen that the compound is a 0-dimensional structure, belongs to the triclinic system, and the space group is P1. In the structure, the iron ion is connected with the nitrogen atom in 1-vinylimidazole and two chloride ions to form a minimum structural unit, and the remaining space is filled by another chloride ion. The Fe-N bond length is between , and the Fe-Cl bond length is between .

[0047] The structure and composition of the crystal of the red rectangular crystal product prepared in this embodiment are characterized by using powder X-ray diffraction (XRD). A CuKα source is used, the measurement angle range (2θ) is 5-80°, and the scanning rate is 5° / min. The XRD result of Fe(VIM)4Cl3 is as follows: Figure 2As shown, the experimental diffraction pattern is consistent with the XRD data calculated from the single crystal CIF file, which proves that the material has high purity and no other impurities exist.

[0048] The infrared data (KBr, cm -1 ) of the red rectangular crystal product prepared in this example are as follows: 3442 (C-H stretching vibration), 3142 and 3089 (=CH2 antisymmetric stretching vibration), 1730 and 1650 (C=C ring vibration), 1510 (imidazole ring skeleton vibration), 1418 and 1372 (nitro symmetric stretching vibration), 1331 (-CH2 symmetric deformation vibration), 1278, 1237, 1113 and 1094 (C-H and C-N ring vibration), 1008 and 963 (Fe-Cl and Fe-N vibration), 941, 908 and 891 (vinyl C-H deformation stretching vibration), 841 (Fe-Cl and Fe-N vibration), 773, 746, 649 and 597 (imidazole ring out-of-plane vibration), 508 (Fe-Cl vibration).

[0049] The SEM-EDS results of the red rectangular crystal product prepared in this example are shown in Figure 3 From Figure 3 it can be seen that the crystal shape of the compound is square of different sizes, and the existence of metal ion iron of the compound is confirmed by EDS.

[0050] From the above structural identification data, it can be seen that the red rectangular crystal product prepared in this example is the target product iron-containing imidazole self-ignition fuel Fe(VIM)4Cl3, and its structural formula is:

[0051]

[0052] Performance test:

[0053] The DSC curves of Fe(VIM)4Cl3 at different heating rates (5, 10, 15 and 20 ℃ / min) are shown in Figure 4 and Table 2, it can be seen that at a heating rate of 10 ℃ / min, the compound has an endothermic peak at 159.6 ℃, and also has a decomposition peak at 269.1 ℃, which shows that the self-ignition fuel has good chemical stability, in addition, its heat release is 332.4 J / g. With the increase of heating rate, the exothermic peak temperature gradually increases, while the endothermic peak temperature has no obvious change trend; the heat release first increases and then decreases. The thermal decomposition activation energy (E a ) calculated by Kissinger and Ozawa methods is 129.3 KJ / mol and 131.5 KJ / mol, respectively.

[0054] Table 2 DSC parameters of iron-based self-ignition fuel at different heating rates

[0055]

[0056] Note: T o is the initial temperature (°C), T p is the peak temperature (°C), and ΔH is the heat release (J / g).

[0057] The auto-ignition drop test of Fe(VIM)4Cl3 with 95% H2O2 was taken by high speed camera to record the whole ignition process, and the time was counted from the moment when the H2O2 drop contacted the powder sample, as shown in Fig. 1, the ignition delay time (IDT) of this compound was about 2.0 ms, and the ignition delay time was 7.5 ms, which met the requirement of the ignition delay time less than 10 ms for auto-ignition rocket engine. In addition, it could be seen from the flame picture that the flame of this compound presented red light, and the flame was very bright. Figure 5

[0058] Example 2:

[0059] This example shows the application of the iron-containing imidazole auto-ignition fuel in Example 1 to the auto-ignition fuel for solid-liquid mixed rocket propulsion.

[0060] The combustion heat data of Fe(VIM)4(Cl)3 was collected by oxygen bomb calorimeter, and the combustion heat value was -12071 KJ / mol. In order to obtain the formation heat of this compound, the following combustion reaction was used for calculation:

[0061] Fe(VIM)4(Cl)3: Fe(Cl3C 20 H 24 N8) (s) + 26.75O 2(g) = 0.5Fe2O 3(s) + 1.5Cl 2(g) + 20CO 2(g) + 12

[0062] H2O (l) + 4N 2(g) .

[0063] The formation heat of Fe(VIM)4(Cl)3 was 360.29 KJ / mol.

[0064] The compatibility test of Fe(VIM)4(Cl)3 material mixed with several conventional binders showed that the material had good compatibility with hydroxyl-terminated polybutadiene (HTPB), epoxy resin, sylgard 184, high-density polyethylene (HDPE), and paraffin wax (PW), and the samples did not change after long-term storage.

[0065] ​Fe(VIM)4(Cl)3and binder were mixed in a certain mass ratio, and then the fuel was pressed into a round sheet by a tablet press. After two days of storage and drying, ignition test was performed. When high-density polyethylene (HDPE) or paraffin was used as the binder, the solid sheet fuel containing Fe(VIM)4(Cl)3or Fe(VIM)4(Cl)3 / nano-aluminum powder could not be ignited, but the fuel could be ignited after the surface of the solid fuel was roughened. The ignition delay time of the solid fuel containing 80wt.% Fe(VIM)4(Cl)3and 20wt.% paraffin was 7ms, which met the requirements of hybrid power of a rocket engine, as shown in FIG. 1. Figure 6 It was found that Fe(VIM)4(Cl)3had good compatibility with ammonium borohydride (AB), so a solid sheet fuel containing Fe(VIM)4(Cl)3and AB was prepared. In addition, paraffin was used as the binder of the fuel because paraffin had a low melting point (58-60℃) and a low combustion rate. The ignition delay time of the solid fuel containing 10wt.% AB, 40wt.% Fe(VIM)4(Cl)3and 50wt.% paraffin was also 7ms, as shown in FIG. 2. Figure 7

[0066] Example 3

[0067] This example shows the application of the iron-containing imidazole self-igniting fuel in Example 1 to a self-igniting fuel for solid-liquid hybrid rocket propulsion.

[0068] The theoretical specific impulse of the solid fuel containing Fe(VIM)4(Cl)3, AB and paraffin at different O / F ratios was calculated by using CEA software, as shown in FIG. 3. The maximum specific impulse of the fuel (10wt.% AB-90wt.% paraffin) without Fe(VIM)4(Cl)3was 335.8s at a working pressure of 20bar and a nozzle expansion ratio Ae / At of 300 in a near-space orbit environment, and the specific impulse increased first and then decreased with the increase of the O / F ratio. When 40wt.% Fe(VIM)4(Cl)3was used to replace paraffin, the maximum specific impulse was slightly reduced to 331.8s, and the energy reduction was not obvious. Figure 8

[0069] The solid fuel containing Fe(VIM)4Cl3was pressed into a grain by a tablet press, as shown in FIG. 4, to compare the effect of Fe(VIM)4Cl3on the combustion performance of the engine. Figure 9

[0070] Figure 10 ​​​For the solid fuel engine pressure curve graph containing 10 wt.% AB and 90 wt.% paraffin, it can be seen from the graph that the pressure curve has obvious oscillation, which is easy to cause unstable combustion of the engine, and even there is a risk of engine explosion; while the solid fuel engine pressure curve graph containing 5 wt.% AB, 45 wt.% Fe(VIM)4Cl3 and 50 wt.% paraffin is shown in Figure 11 , it can be seen that there is no obvious oscillation, and the engine works stably; the solid fuel engine pressure curve graph containing 80 wt.% Fe(VIM)4Cl3 and 20 wt.% paraffin is shown in Figure 11 , it can be seen that there is no obvious oscillation, and the engine works stably; the solid fuel engine pressure curve graph containing 80 wt.% Fe(VIM)4Cl3 and 20 wt.% paraffin is shown in Figure 12 , it can be seen that there is no obvious oscillation, and the engine works stably; the solid fuel engine pressure curve graph containing 80 wt.% Fe(VIM)4Cl3 and 20 wt.% paraffin is shown in Figure 12 , it can be seen that there is no obvious oscillation, and the engine works stably; the solid fuel engine pressure curve graph containing 80 wt.% Fe(VIM)4Cl3 and 20 wt.% paraffin is shown in

Claims

1. An iron-containing imidazole autoignition fuel, characterized by, The structural formula is: 。 2. A process for the preparation of the iron-containing imidazole-based self-igniting fuel according to claim 1, characterized in that, The preparation method uses FeCl3·6H2O and 1-vinylimidazole as raw materials, acetonitrile as a solvent, and adopts a liquid phase reaction method to prepare the iron-containing imidazole self-ignition fuel.

3. The method for preparing iron-containing imidazole self-igniting fuel as described in claim 2, characterized in that, The molar ratio of FeCl3·6H2O and 1-vinylimidazole is 1:

4.

4. The method for preparing iron-containing imidazole self-igniting fuel as described in claim 3, characterized in that, The preparation method is performed according to the following steps: Step one, acetonitrile solvent is added into a conical beaker, then 1-vinylimidazole is added, and mixing is performed on a magnetic stirrer for 5 minutes; Step two, then FeCl3·6H2O is added, and the conical beaker is sealed; Step three, under magnetic stirring, the temperature is raised to 85 DEG C, and stirring reaction is performed at the temperature for 2 hours; Step four, the magnetic stirrer is turned off, after the reaction is cooled to room temperature, acetonitrile solvent is removed on a rotary evaporator under vacuum, and red rectangular crystals can be obtained, which are the iron-containing imidazole self-ignition fuel.

5. The application of the iron-containing imidazole self-ignition fuel of claim 1 to solid-liquid mixed rocket propulsion self-ignition fuel.

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