Preparation method and application of high-nitrogen compound HZT and high-energy-density mixed fuel

Abstract

The application provides a preparation method and application of a high-nitrogen compound HZT and a high-energy-density mixed fuel; the application takes sodium azotetrazolate pentahydrate and monohydrochloric hydrazine as raw materials, and through heating reaction, low-temperature crystallization, recrystallization purification and low-temperature vacuum dehydration, anhydrous azotetrazolate dihydrazine salt (HZT) is prepared; the method has the advantages of safe and non-toxic raw materials, simple process, higher yield and purity, and solves the problems of existing synthesis routes, such as danger, toxic raw materials, and difficulty in industrialization. The obtained anhydrous HZT is dissolved in hydrazine, monomethylhydrazine or unsymmetrical dimethylhydrazine to prepare a stable and transparent high-energy-density mixed fuel, which can significantly improve the fuel density and the specific impulse of propellant density, and simultaneously reduce the freezing point of the fuel, and has excellent compatibility with conventional oxidizing agents (nitric acid, N2O4 and liquid oxygen). The HZT and the mixed fuel prepared by the application have outstanding energy performance, good compatibility and green and safe preparation, and are suitable for normal-temperature binary liquid propellants, and effectively break through the problem of improving the energy density of existing propellants.

Description

Technical Field

[0001] This invention belongs to the field of energetic materials; in particular, it relates to a method for preparing and applying a high-nitrogen compound HZT and a high-energy-density mixed fuel. Background Technology

[0002] Currently, the development of room-temperature dual-stage liquid propellants has reached a bottleneck, with significant improvements in energy density proving difficult. If we disregard the oxidizer (i.e., nitric acid, N₂O₄, or liquid oxygen are still used), the ideal approach is to synthesize new fuels. However, such fuels would require significantly higher energy and density than hydrazine (among hydrazine, monomethylhydrazine, and unsymmetrical dimethylhydrazine, hydrazine has the highest energy), a much lower freezing point, and be safe and non-toxic. Progress on this path has been slow because, as a novel fuel, its preparation and application involve numerous factors. Besides developing new fuels, another approach is to prepare blended fuels. Currently, to lower the freezing point of hydrazine and increase its energy, scientists have researched many blended hydrazine fuels, such as blended hydrazine amines and blended hydrazine oils. However, the energy increase has been very limited, and various compatibility issues have arisen.

[0003] Therefore, let's consider a different approach. If we dissolve a large amount of a solid compound—oxygen-free, high-nitrogen, high-enthalpy of formation, high-density, and low-decomposition-temperature—in hydrazine, monomethylhydrazine, or unsymmetrical dimethylhydrazine, we will significantly increase the energy density of the binary liquid propellant. This is because the volume of hydrazine, monomethylhydrazine, or unsymmetrical dimethylhydrazine does not increase significantly after dissolving these solid high-nitrogen compounds. For example, dissolving 200 grams of solid high-nitrogen compound in 1 liter of hydrazine will still maintain a total volume of about 1 liter, while the mass will reach approximately 1.2 kilograms (hydrazine's density is 1.011 g / cm³). 3 In other words, the density of 1 liter of hydrazine containing 200 grams of high-nitrogen compounds would be approximately 1.2 g / cm³. 3 This significantly increases the fuel density, resulting in a marked increase in the density specific impulse of the binary liquid propellant; simultaneously, the freezing point of the resulting mixed fuel is significantly lower than that of pure hydrazine. This is the innovative concept behind this invention.

[0004] Azotetrazole dihydrazine (HZT, C2H) 10 N 14 HZT is a low-cost, high-detonation-velocity, low-burning-temperature, high-enthalpy of formation, and high-nitrogen-content energetic compound. Its energy performance is superior to RDX, its sensitivity is comparable to RDX, its price is comparable to RDX, it is non-hygroscopic, and it does not contain water of crystallization, making it an excellent organic oxygen-free energetic material. Thomas M. Klapoltke first synthesized HZT in 2001, but did not evaluate any of its properties (Anton Hammerl, Thomas M. Klapoltke). , et al. [N2H5] + 2[N4C-N=N-CN4] 2- A new high-nitrogen high-energetic material [J]. Inorganic Chemistry, 2001, 40: 3570-3575.); Furthermore, its synthesis process is complex, with many raw materials being toxic, regulated, difficult to prepare, and having excessively high sensitivity, making industrial production impossible. For example, in Thomas M. Klapoltke's report, he used barium 5,5'-azotetrazolate and hydrazinium hydrate to synthesize dihydrate azotetrazole hydrazine ([N2H5)). + 2[N4C-N=N-CN4] 2- Then, the dihydrate azotetrazole hydrazine is dehydrated under vacuum to obtain HZT. Among these, barium azotetrazole is an extremely sensitive substance, exceptionally dangerous in experiments; its impact sensitivity, friction sensitivity, and detonation sensitivity are far higher than those of sodium pentahydrate azotetrazole (SZT·5H2O, C2N) used in this paper, which has almost zero sensitivity. 10 The original study used sodium azotetrazole pentahydrate and hydrazine hydrochloride (H2·5H2O). Thomas M. Klapoltke used highly toxic, regulated, and expensive high-concentration hydrazine hydrate as a reactant, while this study uses non-toxic, extremely inexpensive, non-decomposing, non-combustible, and unregulated hydrazine hydrochloride (H4N2·HCl) as a reactant. Due to the use of sodium azotetrazole pentahydrate and hydrazine hydrochloride as reactants, the yield of HZT in this invention is significantly higher than that reported by Thomas M. Klapoltke. In particular, this study also includes a purification step, which greatly improves the purity of the obtained HZT. These are the innovations of this invention.

[0005] Since Thomas M. Klapoltke reported HZT in 2001, it has received little attention or been reported beyond this invention. In recent years, with the large-scale, inexpensive industrial production of HZT precursors such as 5-aminotetrazole, the preparation route for HZT has become more environmentally friendly and simpler, significantly reducing preparation costs (currently, apart from this invention, there are no new reports on the preparation of HZT). The chemical formula for HZT is C2H. 10 N 14 Its relative molecular mass is 230.2 g / mol, and its density is 1.510 g / cm³. 3The measured enthalpy of formation is +889.2 kJ / mol, with a nitrogen content as high as 85.2%, a hydrogen content of 4.3%, an oxygen balance of -62.6%, a measured thermal decomposition temperature of approximately 170℃, a theoretical detonation velocity of 8577 m / s (calculated using EXPLO5, RDX is 8838 m / s), an explosion gas production rate of 946.4 L / kg (calculated using EXPLO5, RDX is 726.8 L / kg), and a standard specific impulse of 2376 N·s / kg for the single propellant (calculated using NASA-CEA2). The high nitrogen content and abundant gas production result in a very low combustion temperature for HZT (T0). c =1992℃), and the average molecular weight of the combustion products is also very low (M =1992℃). c =19.235 g / mol). Furthermore, HZT exhibits excellent physical and chemical compatibility with fuel hydrazine, monomethylhydrazine, and unsymmetrical dimethylhydrazine; particularly with hydrazine, the freezing point of hydrazine decreases significantly after dissolving a large amount of HZT. Therefore, HZT shows great promise for use in room-temperature binary liquid propellants to improve their energy density. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing high-nitrogen compound HZT and high-energy-density blended fuels and their applications.

[0007] This invention is achieved through the following technical solution:

[0008] This invention relates to a method for preparing the high-nitrogen compound HZT, comprising the following steps:

[0009] Step 1: Mix sodium azotetrazole pentahydrate (SZT·5H2O) with water, stir, and heat until completely dissolved to obtain solution A;

[0010] Step 2: Add an aqueous solution of hydrazine hydrochloride to solution A, heat to react, and obtain the reaction solution;

[0011] Step 3: Cool the reaction solution, crystallize at low temperature, and filter to obtain crude azotetrazolium dihydrazine monohydrate (HZT·H2O);

[0012] Step 4: The crude azotetrazolium dihydrazine monohydrate is purified by recrystallization.

[0013] Step 5: The purified monohydrate azotetrazolium dihydrazine salt is vacuum dried to obtain anhydrous high-nitrogen compound HZT crystals.

[0014] Preferably, in step 1, the heating temperature is 90-98°C, the solution A is a dark yellow solution, and the mass-to-volume ratio of sodium azotetrazole pentahydrate to water is 1:10.

[0015] Preferably, in step 2, the temperature of the heating reaction is 90-98°C, the reaction time is 15-30 minutes, and the reaction is carried out with stirring.

[0016] Preferably, in step 3, the low-temperature crystallization temperature is -50℃ to -30℃, the crystallization time is 8 to 16 hours, and long needle-shaped pale yellow crystals are precipitated.

[0017] Preferably, in step 4, the recrystallization is carried out using deionized water as a solvent, heated to 90-98°C to dissolve, naturally cooled, and then allowed to stand in an ice-water bath for crystallization. After filtration, the crystals are freeze-dried to obtain refined monohydrate azotetraazole dihydrazine salt.

[0018] Preferably, in step 5, the vacuum drying conditions are: vacuum environment, temperature 85-95℃, and drying time 20-28 hours.

[0019] The present invention also relates to a high-energy-density blended fuel comprising a high-nitrogen compound HZT prepared by the aforementioned method, and at least one liquid fuel selected from hydrazine, monomethylhydrazine, and unsymmetrical dimethylhydrazine; wherein the high-nitrogen compound HZT is dissolved in the liquid fuel to form a homogeneous and transparent system.

[0020] Preferably, the high energy density blended fuel comprises the following components by mass percentage: 40% high-nitrogen compound HZT and 60% liquid fuel; wherein the liquid fuel is at least one of hydrazine, monomethylhydrazine, and unsymmetrical dimethylhydrazine.

[0021] This invention also relates to the application of the aforementioned high-energy-density blended fuel, which is combined with nitric acid, nitrogen tetroxide or liquid oxygen oxidizer for use in dual-stage liquid propellants to improve the propellant density specific impulse and energy density.

[0022] This invention also relates to the application of the high-nitrogen compound HZT, which is dissolved in hydrazine fuel as a high-energy additive to improve propellant density, density specific impulse and lower fuel freezing point.

[0023] The present invention has the following advantages:

[0024] (1) The mixed fuel prepared by the present invention has a higher density than pure hydrazine, monomethylhydrazine or unsymmetrical dimethylhydrazine;

[0025] (2) When the mixed fuel prepared in this invention is used in a binary propellant, the density specific impulse of the propellant is significantly increased compared with that before use;

[0026] (3) The raw materials involved in this invention are cheap and readily available, unregulated, non-toxic, and have extremely low sensitivity. They will not decompose, burn, or detonate, which makes the preparation process very green and safe. Attached Figure Description

[0027] Figure 1 This is the molecular structure diagram of azotetrazole dihydrazine (HZT);

[0028] Figure 2 This is the XRD pattern of azotetrazole dihydrazine (HZT);

[0029] Figure 3 It is the DSC spectrum of monohydrate azotetrazole dihydrazine (HZT·H2O);

[0030] Figure 4 This is the DSC spectrum of azotetrazole dihydrazine (HZT);

[0031] Figure 5 This is a SEM image of azotetrazole dihydrazine (HZT);

[0032] Figure 6 This is a single-crystal diffraction pattern of monohydrate azotetrazolium dihydrazine (HZT·H2O). Detailed Implementation

[0033] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are merely further illustrations of the present invention, but the scope of protection of the present invention is not limited to the following embodiments.

[0034] Example 1

[0035] I. This embodiment relates to a method for preparing HZT crystals, and the specific steps are as follows:

[0036] Step 1, add 30g of sodium azotetrazole pentahydrate (SZT·5H2O, C2N) 10 Place Na2·5H2O and 300mL of water in a 500mL beaker; heat to 95℃ while stirring until completely dissolved, at which point the solution will be dark yellow.

[0037] Step 2: Dissolve 14.2g of hydrazine hydrochloride (H4N2·HCl) in 100ml of water. After complete dissolution, add it to the SZT·5H2O solution that is being stirred and heated. Heat the solution at 95℃ for 20min. At this point, the solution turns into a brown transparent solution, but no precipitate is formed.

[0038] Step 3: Cool the brown solution to room temperature. No crystals form at room temperature. Then, place it in a refrigerator overnight (approximately -40°C). At this point, a large amount of long, needle-like, pale yellow crystals precipitate. After filtration, approximately 17.8 g of pale yellow, needle-like HZT·H2O crude crystals are obtained. (Repeat the preparation 3 times).

[0039] Step 4: Take a 500mL beaker, pour in 400mL of deionized water, and add approximately 40g of coarse HZT·H2O crystals. Heat to 95℃. After maintaining this temperature for 10 minutes, remove the water bath and allow the beaker containing the solution to cool naturally to room temperature. Then, place the beaker in an ice-water bath overnight (use plenty of ice; the beaker should be immersed in the ice-water bath for at least 12 hours). The next day, filter out the long, needle-like, pale yellow crystals that have crystallized in the beaker, freeze-dry, and obtain approximately 22g of refined pale yellow needle-like HZT·H2O crystals.

[0040] Step 5: Place 20 grams of HZT·H2O into a vacuum oven and dry at 90°C for 24 hours under vacuum. After decompression and cooling, light yellow needle-shaped anhydrous HZT crystals are obtained. (See attached image) Figure 1 , 2 3, 4, 5 and Figure 6 As shown.

[0041] The anhydrous HZT crystals obtained in Example 1 were tested, as shown in Tables 1 and 2.

[0042] Table 1

[0043] Table 2

[0044] As can be seen from the test data in Tables 1 and 2, the measured values ​​of C, H, N and O elements are very close to the theoretical values, indicating that the elemental composition of the sample prepared in Example 1 of this invention basically conforms to the elemental composition of the target compound, thus proving that the experiment of this invention is relatively successful.

[0045] II. This embodiment also relates to the preparation of HZT-hydrazine mixed fuel, the specific method of which is as follows:

[0046] 400 grams of HZT prepared in this example were dissolved in 600 grams of hydrazine to obtain a stable and transparent mixed fuel-1.

[0047] Example 2

[0048] I. This embodiment relates to a method for preparing HZT crystals, and the specific steps are as follows:

[0049] Step 1, add 30g of sodium azotetrazole pentahydrate (SZT·5H2O, C2N) 10 Place Na2·5H2O and 300mL of water in a 500mL beaker; heat to 95°C while stirring until completely dissolved, at which point the solution will be dark yellow.

[0050] Step 2: Dissolve 14.2 g of hydrazine hydrochloride (H4N2·HCl) in 100 mL of water. After complete dissolution, add it to the SZT·5H2O solution that is being stirred and heated. React at 95 °C for 20 min. At this point, the solution turns into a brown transparent solution, but no precipitate is formed.

[0051] Step 3: Cool the brown solution to room temperature; no crystals form at room temperature. Then, place it in a refrigerator overnight (approximately -40°C). At this point, a large amount of long, needle-like, pale yellow crystals precipitate. After filtration, approximately 17.8 g of pale yellow, needle-like HZT·H2O crude crystals are obtained. (Repeat the preparation 3 times).

[0052] Step 4: Take a 500mL beaker, pour in 400mL of deionized water, and add approximately 40g of coarse HZT·H2O crystals. Heat to 95℃. After maintaining this temperature for 10 minutes, remove the water bath and allow the beaker containing the solution to cool naturally to room temperature. Then, place the beaker in an ice-water bath overnight (use plenty of ice; the beaker should be immersed in the ice-water bath for at least 12 hours). The next day, filter out the long, needle-like, pale yellow crystals that have crystallized in the beaker, freeze-dry, and obtain approximately 22g of refined pale yellow needle-like HZT·H2O crystals.

[0053] Step 5: Place 20 grams of HZT·H2O into a vacuum oven and dry at 90°C for 24 hours under vacuum. After decompression and cooling, light yellow needle-shaped anhydrous HZT crystals are obtained.

[0054] II. This embodiment also relates to the preparation of HZT-methylhydrazine mixed fuel, the specific method of which is as follows:

[0055] 400 grams of HZT prepared in this example were dissolved in 600 grams of monomethylhydrazine to obtain a stable and transparent mixed fuel-2.

[0056] Example 3

[0057] I. This embodiment relates to a method for preparing HZT crystals, and the specific steps are as follows:

[0058] Step 1, add 30g of sodium azotetrazole pentahydrate (SZT·5H2O, C2N) 10 Place Na2·5H2O and 300mL of water in a 500mL beaker; heat to 95℃ while stirring until completely dissolved, at which point the solution will be dark yellow.

[0059] Step 2: Dissolve 14.2 g of hydrazine hydrochloride (H4N2·HCl) in 100 mL of water. After complete dissolution, add it to the SZT·5H2O solution that is being stirred and heated. React at 95 °C for 20 min. At this point, the solution turns into a brown transparent solution, but no precipitate is formed.

[0060] Step 3: Cool the brown solution to room temperature; no crystals form at room temperature. Then, place it in a refrigerator overnight (approximately -40°C). At this point, a large amount of long, needle-like, pale yellow crystals precipitate. After filtration, approximately 17.8 g of pale yellow, needle-like HZT·H2O crude crystals are obtained. (Repeat the preparation 3 times).

[0061] Step 4: Take a 500mL beaker, pour in 400mL of deionized water, and add approximately 40g of coarse HZT·H2O crystals. Heat to 95℃. After maintaining this temperature for 10 minutes, remove the water bath and allow the beaker containing the solution to cool naturally to room temperature. Then, place the beaker in an ice-water bath overnight (use plenty of ice; the beaker should be immersed in the ice-water bath for at least 12 hours). The next day, filter out the long, needle-like, pale yellow crystals that have crystallized in the beaker, freeze-dry, and obtain approximately 22g of refined pale yellow needle-like HZT·H2O crystals.

[0062] Step 5: Place 20 grams of HZT·H2O into a vacuum oven and dry at 90°C for 24 hours under vacuum. After decompression and cooling, light yellow needle-shaped anhydrous HZT crystals are obtained.

[0063] II. This embodiment also relates to the preparation of HZT-unsymmetrical dimethylhydrazine mixed fuel, the specific method of which is as follows:

[0064] 400 grams of HZT prepared in this example were dissolved in 600 grams of unsymmetrical dimethylhydrazine to obtain a stable and transparent mixed fuel-3.

[0065] Comparative Example 1 is 1000 grams of pure hydrazine (298K).

[0066] Comparative Example 2 is 1000 grams of pure monomethylhydrazine (298K).

[0067] Comparative Example 3 was 1000 grams of pure unsymmetrical dimethylhydrazine (298K).

[0068] Examples 1-3 and Comparative Examples 1-3 were tested, as shown in Table 3.

[0069] Table 3

[0070] Note: HZT in Table 3 is anhydrous azotetrazolium dihydrazine salt, with the molecular formula C2H. 10 N 14 The molecular formula of hydrazine is H4N2; the molecular formula of monomethylhydrazine is C1H6N2; the molecular formula of unsymmetrical dimethylhydrazine is C2H8N2; LO2 is liquid oxygen, with the molecular formula O2; O / F is the optimal oxygen / fuel ratio. The measured density of the mixed fuel (test standard: GJB 772B-2022, density, density bottle method, method 401.1; test location: Laboratory of the Ordnance Industry Explosives Performance Testing Center, North China University of Technology). ρ Density specific impulse is one of the most important parameters in propellant energy performance; T C The combustion chamber temperature; C F This refers to the thrust coefficient. The parameters in Table 1 (I) ρ T C and C F All values ​​are calculated using the well-known American software NASA-CEA2 (using combustion chamber pressure P). c =7.0MPa, nozzle pressure P e =0.1MPa, initial temperature T0=298K (T 0,LO2 =90.17K) and ΔH=0).

[0071] The data in Table 3 show the measured density ρ of the mixed fuel composed of pure hydrazine, monomethylhydrazine, and unsymmetrical dimethylhydrazine after dissolving a certain amount of HZT. EXP The density specific impulse I of the dual-stage liquid propellant increases significantly. ρ Combustion temperature T C and thrust coefficient C F The values ​​all increased significantly, indicating that the energy performance of the propellant was significantly improved after the addition of HZT.

[0072] Figure 2 The XRD pattern of anhydrous HZT after dehydration is shown below. Figure 2 It can be seen that HZT is a crystalline substance.

[0073] Figure 3 This is the DSC spectrum of dihydrazine monohydrate azotetraazole (HZT·H2O). Figure 3 As can be seen, a distinct endothermic peak appears between 75 and 125 °C, corresponding to the removal of water of crystallization from HZT·H2O. A large exothermic peak appears between 170 and 180 °C, corresponding to the thermal decomposition of HZT. Furthermore, the TG spectrum indicates that the final weight loss of HZT·H2O is close to zero, suggesting that the prepared HZT·H2O has high purity and is free of impurities.

[0074] Figure 4 This is the DSC spectrum of the dehydrated azotetrazole dihydrazine salt (HZT). Figure 4 As can be seen, there are no peaks between 50 and 170℃, indicating that the water of crystallization of HZT·H2O has been completely removed during the preparation process, and the dehydration process is perfect. In addition, the TG spectrum shows that the final weight loss of HZT is close to 0, which indicates that the prepared HZT has high purity and no impurities.

[0075] Figure 5 SEM images of azotetrazole dihydrazine (HZT), by Figure 5 It can be seen that the microstructure of the prepared HZT is a needle-like solid structure. This is consistent with the report by Thomas M. Klapoltke.

[0076] Figure 6 These are single-crystal diffraction data for monohydrate azotetrazole dihydrazine (HZT·H₂O), with CCDC number 2522349. Figure 6 It can be seen that the structure of HZT·H2O is completely consistent with the design. Figure 4 , Figure 5 and Figure 6 Based on the combined analysis of the test results in Tables 1 and 2, it can be concluded that the molecular structure of the anhydrous HZT prepared in this invention conforms to... Figure 1 The structure shown indicates that the preparation process was very successful.

[0077] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing the high-nitrogen compound HZT, characterized in that, Includes the following steps: Step 1: Mix sodium azotetrazole pentahydrate with water, stir, and heat until completely dissolved to obtain solution A; Step 2: Add an aqueous solution of hydrazine hydrochloride to solution A, heat to react, and obtain the reaction solution; Step 3: Cool the reaction solution, crystallize at low temperature, and filter to obtain crude azotetrazolium dihydrazine monohydrate. Step 4: The crude azotetrazolium dihydrazine monohydrate is purified by recrystallization. Step 5: The purified monohydrate azotetrazolium dihydrazine salt is vacuum dried to obtain anhydrous high-nitrogen compound HZT crystals.

2. The method for preparing the high-nitrogen compound HZT as described in claim 1, characterized in that, In step 1, the heating temperature is 90-98℃, the solution A is a dark yellow solution, and the mass-to-volume ratio of sodium azotetrazole pentahydrate to water is 1:

10.

3. The method for preparing the high-nitrogen compound HZT as described in claim 1, characterized in that, In step 2, the heating reaction temperature is 90-98°C, the reaction time is 15-30 minutes, and the reaction is carried out with stirring.

4. The method for preparing the high-nitrogen compound HZT as described in claim 1, characterized in that, In step 3, the low-temperature crystallization temperature is -50℃ to -30℃, the crystallization time is 8 to 16 hours, and long needle-shaped light yellow crystals are precipitated.

5. The method for preparing the high-nitrogen compound HZT as described in claim 1, characterized in that, In step 4, the recrystallization is carried out using deionized water as a solvent, heated to 90-98°C to dissolve, naturally cooled, and then crystallized by standing in an ice-water bath. After filtration, the crystals are freeze-dried to obtain refined monohydrate azotetraazole dihydrazine salt.

6. The method for preparing the high-nitrogen compound HZT as described in claim 1, characterized in that, In step 5, the conditions for vacuum drying are: vacuum environment, temperature 85-95℃, and drying time 20-28 hours.

7. A high-energy-density blended fuel, characterized in that, The mixture comprises a high-nitrogen compound HZT prepared by any of the methods described in claims 1 to 6, and at least one liquid fuel selected from hydrazine, monomethylhydrazine, and unsymmetrical dimethylhydrazine; wherein the high-nitrogen compound HZT is dissolved in the liquid fuel to form a homogeneous and transparent system.

8. The high energy density blended fuel as described in claim 7, characterized in that, It includes the following components by mass percentage: 40% high-nitrogen compound HZT and 60% liquid fuel; wherein the liquid fuel is at least one of hydrazine, monomethylhydrazine, and unsymmetrical dimethylhydrazine.

9. An application of a high-energy-density blended fuel, characterized in that, Combining blended fuels with nitric acid, nitrogen tetroxide, or liquid oxygen oxidizers for use in dual-stage liquid propellants can improve the propellant's density specific impulse and energy density.

10. An application of a high-nitrogen compound, HZT, characterized in that, High-nitrogen compound HZT is dissolved in hydrazine fuel as a high-energy additive to improve propellant density, density specific impulse, and lower fuel freezing point.

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