Non-toxic hypergolic bipropellant with a catalytically promoted fuel system and a solution of hydrogen peroxide as oxidising agent, and use of same

Abstract

The present invention relates to non-toxic hypergolic bipropellants with catalytically promoted fuel systems and highly concentrated hydrogen peroxide solution which ignite spontaneously when they come into contact with each other. The non-toxic hypergolic fuel systems of the present invention comprise two propagators based on polyamine and alkanolamine, promoted by reduced amounts of catalyst. The present invention further describes the use of lower alcohol compounds as stability / solubility enhancing agents. A potential bipropellant combination must meet several requirements, such as low ignition delay time (IDT < 20 ms), low viscosity, good storage stability and performance comparable to conventional hydrazine / NTO-based fuels available in the prior art. The novel hypergolic fuel systems with a solution of hydrogen peroxide described in the present application are efficient substitutes for standard methylhydrazine fuel for use in rockets and spacecraft. The present invention further relates to the use of said fuel system in space equipment or operations in pulse and / or multiple restart mode, preferably rockets and spacecraft.

Description

NON-TOXIC HYPERGOLIC BIPROPELLANT WITH CATALYTICALLY PROMOTED FUEL SYSTEM AND A SOLUTION OF HYDROGEN PEROXIDE OXIDIZER, AND USE THEREOF FIELD OF INVENTION

[0001] The present invention relates to the field of propellants for rocket and space vehicle propulsion, particularly non-toxic hypergolic bipropellants. In this context, the present invention relates to novel catalytically promoted non-toxic hypergolic fuels called PAHyp (Polyamine / Alkanolamine-based Hypergolics) using a highly concentrated hydrogen peroxide solution as an oxidizer, as well as a new methodology for developing new formulas and using them in the aerospace sector. BACKGROUND OF THE INVENTION

[0002] For more than six decades, hydrazine and its derivatives have been the standard fuel for aerospace propulsion. In fact, from the Apollo spacecraft that landed the first man on the moon to modern spacecraft like SpaceX's Dragon, hydrazine-based hypergolic propellants remain the most traditional choice.

[0003] However, standard propellants are highly toxic, making testing, handling, and launch preparation more dangerous, complex, and therefore more expensive. Furthermore, in recent decades, environmental concerns have been added to the list of considerations in the fuel development process, thus creating a demand for green (or less toxic) propellants.

[0004] It is worth noting that space launch systems (rockets) already have more environmentally friendly options based on cryogenic or semi-cryogenic combinations (e.g., LOX / LH2 and LOX / kerosene) since the beginning of the space race.

[0005] One of the special characteristics that makes methylated hydrazine fuels, such as monomethylhydrazine (MMH) and unsymmetrical dimethylhydrazine (UDMH), so unique is their ability to ignite spontaneously (or hypergolicly) at room temperature when in contact with a liquid oxidizer, such as nitrogen tetroxide (NTO).

[0006] In other words, the propulsion system does not require an ignition system to start the engine, increasing reliability, which is essential for missions that require pulsed mode operations and / or multiple restarts.

[0007] In an attempt to replace traditional toxic hydrazine-based propellants with more environmentally friendly fuels and oxidizers, significant research has been conducted into using a highly concentrated hydrogen peroxide solution, better known as High-Test Peroxide (HTP) or Rocket-Grade Hydrogen Peroxide (RGHP). Hydrogen peroxide is available in various concentrations with water, but concentrations greater than 70% are required for use as a propellant.

[0008] The HTP began to be used by the Germans during World War II World Cup in the Messerschmitt Me 163 Komet aircraft. At that time, hydrogen peroxide was known as T-Stoff (specified to contain more than 80% hydrogen peroxide in aqueous solution) and reacted with C-Stoff fuel (a mixture of methanol, hydrazine, water and a copper-based catalyst).

[0009] Documents exist in the patent and non-patent literature on non-toxic fuels containing hydrogen peroxide. Document US5932837, for example, reveals a new class of non-toxic fuels called Non-Toxic Homogenous Miscible Fuel (NHMF), which was discovered in the mid-1990s by the U.S. Air Force in conjunction with the U.S. Navy. NHMF (Block 0 being the most famous formulation), like the German C-Stoff, contains methanol and a metal salt in its formulation. Contrary to expectations, Block 0 and its derivatives exhibited poor aging and storage characteristics. Thus, although much knowledge was gained with Block 0 through numerous firing tests, the resulting fuels lacked sufficient stability to meet U.S. Navy requirements.

[0010] Document CN102863994 refers to a four-component hypergolic fuel with 70-98% hydrogen peroxide. The blend also addresses a non-toxic homogeneous miscible fuel and utilizes a catalyzed mixture containing only an ignition propellant composed of catalytically promoted alkyl-substituted amines with 6-10% by weight of a cobalt salt, such as cobalt(II) acetate tetrahydrate, cobalt iso-octoate, or cobalt acetylacetonate. The other two components are optional and include kerosene and an alcohol to increase chemical stability.

[0011] Patent application US2003 / 192633 presents some hypergolic formulations based on some alkanolamines, such as dimethylethanolamine (DMEA), catalytically promoted with 6-10% by weight of cobalt salts using HTP as an oxidant. Furthermore, a boron-based additive (sodium borohydride, NaBH4) was presented, which makes several compounds such as diethylenetriamine (DETA), triethylene glycol dimethyl ether (triglymé), and tetraethylene glycol dimethyl ether (tetraglymé) hypergolic when added in an amount of 6-10% by weight. Specifically, fuels promoted with NaB4 represent a major technological advance, serving as the basis for most hypergolic fuels presented in the prior art. However, this compound reacts with water (which may be dissolved in the fuels or present in the air), releasing hydrogen gas and, consequently, losing reactivity and chemical stability. Furthermore, cobalt salts are known to be extremely toxic.

[0012] Patent application US2003 / 015268 discloses the development of catalysts (metal salts) capable of rendering some polar and nonpolar organic compounds hypergolic with HTP. These catalysts form coordination complexes by the reaction of alkyl-substituted diamines or triamines with metal salts of an aliphatic carboxylic acid or 1,3-dione metal chelates, but they present stability problems and are not a promising alternative.

[0013] Therefore, the need for non-toxic hypergolic fuels that use reduced amounts of catalyst, are low cost and highly safe and stable, remains in the state of the art. SUMMARY OF THE INVENTION

[0014] The present invention provides a new class of non-toxic hypergolic fuels in combination with a concentrated hydrogen peroxide solution. The fuel system, called PAHyp, combines two different classes of propellant, namely polyamine and alkanolamine, with reduced catalyst loadings.

[0015] Furthermore, in addition to the two propagators of different classes and the catalytic agent mentioned above, polar organic compounds comprising a lower alcohol may be added to increase stability or reduce viscosity.

[0016] As a result, it is possible to obtain formulations with low viscosity (less than 20 cP), fast ignition (ignition delays of about 10 ms), high performance (theoretical specific impulse (I sp ) of at least 95% of I spof the conventional toxic systems MMH / NTO and UDMH / NTO) and that present good chemical stability without formation of precipitates during long-term storage.

[0017] Finally, the present invention provides a methodology for producing new formulas derived from said non-toxic hypergolic system PAHyp. BRIEF DESCRIPTION OF THE FIGURES

[0018] Figure 1 shows the screening procedure for selecting possible fuel combinations.

[0019] Figure 2 shows a schematic diagram containing the steps for preparing the TMEDA / DMEA and TMEDA / MDEA systems.

[0020] Figure 3 shows transmittance results from a Fourier transform infrared spectroscopy (FTIR) test for a fresh and aged (10 months) sample of the TMEDA / MDEA fuel system in a (50:50) ratio.

[0021] Figure 4 shows images of ignition tests (drop test, in which a drop of hydrogen peroxide impinges on a small amount of fuel) for fresh and aged samples of TMEDA / MDEA in a ratio (50:50) with 1% catalyst.

[0022] Figure 5 shows an application envelope of the MIm / MDEA system (PAHyp 2). DETAILED DESCRIPTION OF THE INVENTION

[0023] In view of the need to develop low-cost, high-safety, and stable non-toxic hypergolic propellants with suitable potential for use in rockets and space vehicles, the present invention proposes an approach that combines the advantages of a compound from the alkanolamine class and a compound from the polyamine class.

[0024] Alkanolamines are biofunctional molecules containing alcohol and amino functional groups on an alkane backbone. However, since alkanolamines represent a broad class of compounds, the present invention specifically addresses the subclass of ethanolamine derivatives (MEA). MEA is known to be hypergolic with hydrogen peroxide; however, its modest performance prevents it from further development.

[0025] N-methylethanolamine (MMEA) and N,N-dimethylethanolamine (DMEA), which are basically methylated ethanolamines, or N,N-diethylethanolamine, which is basically an ethanolamine with an ethyl radical, were identified as being promising fuel system candidates. Another highly viscous alkanolamine called N-methyldiethanolamine (MDEA) has also been identified as a potential fuel. Although MDEA has not been reported by the hypergolic combustion community, MDEA has received significant attention as a promising sorbent candidate for post-combustion CO2 capture (PCC). In this sense, although non-toxic propellants for space applications are not associated with emissions (unlike non-toxic jet fuels), their technology could contribute to carbon dioxide capture.

[0026] Since polyamines also represent a broad class of compounds, the present invention addresses the subclass of ethylenediamine derivatives (EDA, C2 backbone), which, despite lacking an alcohol function, is very similar to ethanolamine (MEA, C2 backbone) in that both contain two CH2 groups connecting their functional groups. Indeed, an industrial route for the production of EDA involves the reaction of MEA and ammonia.

[0027] In addition to the open carbon chain aliphatic compounds of the family EDA, the present invention also directs to cyclic polyamines derived from piperazine and imidazole that also have a chain with two carbon atoms connecting the nitrogen atoms.

[0028] TMEDA (N,N,N',N'-Tetramethylethylenediamine), which is basically methylated ethylenediamine, was identified as a promising alternative when combined with MMEA, DMEA and MDEA and using a suitable catalyst (preferably copper salt).

[0029] N-methylimidazole (Mim), which is an important precursor for the production of ionic liquids, was identified as a potential candidate when combined with MDEA and using copper chloride dihydrate as a catalyst.

[0030] In certain embodiments, the liquid fuel system may include an amount of a solvent, generally C1-C6 lower alcohols and mixtures thereof, such as methanol (MeOH) or ethanol (EtOH), preferably methanol, for increasing solubility and stability, which are added as stability / solubility enhancing or viscosity reducing agents.

[0031] Catalytic and reactive additives are the two groups of promoters commonly added to a fuel to introduce hypergolic behavior with hydrogen peroxide. The second group is a strong reducing agent that reacts directly in contact with the HTP through a redox reaction. Handling a reducing agent so strong is challenging due to its high sensitivity to water (which may be present in the air or in small amounts in the solvent itself), which neutralizes its reactivity. Furthermore, sodium borohydride also hydrolyzes into alcohol.

[0032] Since methanol is an important solvent in the present invention, catalytic additives have a greater application focus. A catalyst is a substance that increases the speed at which a chemical system approaches equilibrium, promoting a different pathway whose energy profile has a lower activation energy, without being consumed in the process. Preferred catalytic additives comprise transition metal salts of Co, Cu, Fe, Mn, V (among others) that are added to a substance to introduce hypergolic behavior with hydrogen peroxide. These cations promote an exothermic decomposition reaction of the hydrogen peroxide, which releases oxygen and water vapor and heats the entire system. Ignition occurs when the autoignition temperature (AIT) of the fuel is reached.Therefore, the H2O2 concentration should not be less than 70%, otherwise the heat of decomposition will be absorbed by the water, and the adiabatic temperature may not reach the fuel's autoignition temperature. Due to its low toxicity, low cost, and versatility, copper is considered the most prominent and promising transition metal catalyst. MEA, as well as its derivatives such as MMEA, MDEA, and DMEA, form stable complexes with copper salts, as in the following system [Cu(base-MEA). n ] 2+ TMEDA is widely used as a ligand for copper ions and forms stable TMEDA-CUC12 complexes that are soluble in many organic compounds. While the cation (e.g., copper) is the igniter, the anion is very important for the chemical stability of the fuel.

[0033] The hydrogen peroxide oxidizing solution is composed of at least approximately 70% hydrogen peroxide by weight, wherein said hydrogen peroxide solution preferably comprises from about 85% to about 99% by weight hydrogen peroxide with about 1% to about 15% by weight water.

[0034] The non-toxic fuel system contains:

[0035] I) Propagator 1: at least about 10% to about 90% by volume of polyamine compounds based on the total volume of the system, preferably from about 20% to about 70% by volume, comprising an alkyl-substituted diamine or an alkyl-substituted triamine or any mixture thereof. In this regard, said alkyl-substituted diamine may be selected from the group derived from the ethylenediamine (EDA) compound or the imidazole compound, which includes, but is not limited to N,N,N'N'-tetramethylethylenediamine (TMEDA), N,N'-dimethylethylenediamine (DMEDA), N,N-dimethylethylenediamine, N-methylethylenediamine, and N-methylimidazole (Mim). In addition, said alkyl-substituted triamine may be selected from the group derived from the compound diethylenetriamine (DETA), which includes, but is not limited to, N,N,N',N”,N”-pentamethyldiethylenetriamine (PMDTA);

[0036] II) Propagator 2: at least about 10% to about 90% by volume of alkanolamine compounds based on the total volume of the system, preferably from about 30% to about 80% by volume, belonging to the ethanolamine (MEA) family. Said member of the ethanolamine family comprises, but is not limited to, N-methylethanolamine (MMEA), N,N-dimethylethanolamine (DMEA), diethylethanolamine (DEEA), and N-methyldiethanolamine (MDEA), or any mixture thereof;

[0037] III) Promoter: about 0.3% by weight to about 6% by weight of catalytic agent dissolved in the liquid fuel based on the total weight of the system, wherein said catalytic agent is selected from the group consisting of hydrated or non-hydrated metal salts of copper, cobalt, manganese and iron or mixtures thereof, preferably about 0.5% to about 2% by weight of copper (II) salts with chloride, nitrate or acetate anions; and

[0038] IV) Polar organic solvent (optional): about zero to about 60% by volume, based on the total volume of the system, of polar organic compounds comprising at least one lower C1-C6 chain alcohol, such as methanol or ethanol.

[0039] An object of a preferred embodiment of the present invention is to provide a non-toxic homogeneous fuel system with low catalyst concentration (about 1%), low viscosity (less than 20 cP) and stable (preferably for at least 1 year) that combines with a hydrogen peroxide solution to form a hypergolic bipropellant with ignition delay (IDT) less than 20 ms and high performance (I values sp of at least 93%, preferably from about 93% to about 98%, of the I sp of the conventional toxic systems MMH / NTO and UDMH / NTO). EXAMPLES EXAMPLE 1 - TMEDA / DMEA System (PAHyp 0)

[0040] This system has two derivatives depending on the type of catalyst used (Fig. 2). If the catalyst chosen is copper chloride dihydrate, methanol must be added for stability criteria. A stable formulation (at least 1 year in an air-filled vessel) is a TMEDA / DMEA / MeOH mixture with equal volumes of each component catalyzed with 0.5–1% by weight of catalyst. If copper acetate If hydrated copper is chosen as the catalyst, it is not necessary to add methanol or other alcohol. For stability criteria, the TMEDA concentration should be between 20-50% by volume and the catalyst concentration should be between 0.5-1% by weight. In addition to their good hypergolic ignition performance characteristics (IDT values ​​between 10-20 ms), these formulations are resistant to sedimentation, have low viscosity (around 1.5 cP) and theoretical specific impulses (I sp) comparable to conventional hydrazine-based systems. EXAMPLE 2 - TMEDA / MDEA System (PAHyp 1)

[0041] This system is prepared through a three-step process. In the first step, different proportions of TMEDA and MDEA are measured but not yet mixed. Next, 1–3 wt% copper(II) nitrate trihydrate is dissolved in MDEA by stirring under heating for 10–25 min. Copper chloride dihydrate can also be used. Finally, a given amount of TMEDA is mixed with MDEA. Higher proportions of TMEDA result in a less polar and less stable solution. Therefore, for long-term storage, the TMEDA concentration should be kept below 50% in a preferred embodiment. This is a stable formulation (shelf life of at least 1 year in an air-filled container) formed from a 50:50 mixture of TMEDA and MDEA catalyzed with 1–2 wt% copper(II) nitrate trihydrate (Figs. 3 and 4).This synthesized fuel prepared according to the present invention was found to exhibit good ignition performance (RTD values ​​achieved below 10 ms) using reduced catalyst loads. Compared to the TMEDA / DMEA (PAHyp 0) system, the TMEDA / MDEA (PAHyp 1) system exhibits much higher stability, which is an advantage for long-duration missions, but it exhibits higher viscosity (around 10 cP for TMEDA / MDEA (1:1)). EXAMPLE 3 - MIm / MDEA System (PAHyp 2)

[0042] This system is prepared in a manner similar to the TMEDA / MDEA system. It is a stable formulation (shelf life of at least 6 months in an air-filled vessel) formed from a 50:50 mixture of Mim and MDEA catalyzed with 1-3 wt% copper chloride dihydrate (Fig. 5). This synthesized fuel prepared according to the present invention was found to exhibit good ignition performance (RTI around 15 ms) using reduced catalyst loads. Like the TMEDA / MDEA system (PAHyp 1), the present system (PAHyp 2) exhibits good chemical stability when the TMEDA concentration does not exceed 50% of the total volume and the catalyst load is not greater than 3 wt%. This is the system more viscous fuel with a viscosity of about 17 cP for the MIm / MDEA (1:1) formulation with 2% catalyst. EXAMPLE 4 - TMEDA / MMEA System (PAHyp 3)

[0043] For this system, two catalysts were identified: copper chloride dihydrate and copper nitrate trihydrate. For optimal performance and stability, the catalyst concentration should be between 1% and 2%, and the TMEDA ratio should also be less than or equal to 50%. This system has a viscosity of 3 cP for a stable TMEDA / MMEA (50:50) formulation with 2% catalyst.

[0044] Therefore, the present invention has the following main advantages: (1) The use of low-cost, low-toxicity starting materials, equivalent in efficiency to conventional toxic fuels and safer handling. (2) Provide a simplified, robust, reproducible, easily controllable non-toxic hypergolic bipropellant that has a low viscosity (less than 20 cP), a low ignition delay time (IDT) of less than 20 ms, and a specific impulse comparable to that of conventional toxic fuel systems.

[0045] Figure 3 shows a comparative graph of Fourier transform infrared spectroscopy (FTIR) tests for the TMEDA / MDEA (PAHyp 1) fuel system in a 50:50 ratio. It can be seen that the fresh and 10-month-old samples did not show any significant changes in chemical composition. There was also no precipitate formation. Furthermore, the ignition tests showed no change in performance (Fig. 4). These results are quite relevant because virtually all alternative fuels presented in the literature have chemical stability issues, which are overcome by the fuel system of the present invention.

[0046] Furthermore, most studies currently use sodium borohydride as an additive. This additive is unstable because it reacts with water and releases hydrogen, reducing the fuel's ignition performance over time. For this reason, studies generally present sample spectra separated by only one month, ensuring chemical stability for a very limited period. Given the promising results, it is clear that these new hypergolic fuels, developed using a novel preparation route, have the potential to solve this nearly 70-year-old problem and replace the current highly toxic hydrazine derivatives.

[0047] As can be seen from the data and details provided, the present invention advantageously provides a non-toxic hypergolic bipropellant with A catalytically promoted fuel system and an oxidizing hydrogen peroxide solution can be produced and used as propellants for spacecraft propulsion or pulse and / or multiple restart operations, preferably in rockets and spacecraft. This invention minimizes the environmental impacts of conventional toxic hydrazine-based compounds.

[0048] When introducing the elements of this disclosure or the preferred embodiment(s) thereof, the articles "a," "an," and "said" are intended to indicate that there is one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than those listed. While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any invention or what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular inventions. Certain features described in this specification, in the context of separate embodiments, may also be implemented in combination within a single embodiment.Conversely, multiple features described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, while features may be described above as operating in certain combinations, and even initially claimed as such, one or more features of a claimed combination may in some cases be removed from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

[0049] Although the above description contains many specifics, these should not be construed as limiting the scope of the invention, but merely providing an illustration of the currently preferred embodiment of the invention. Accordingly, the scope of this invention should be determined by the appended claims and their legal equivalents.

Claims

CLAIMS 1. Non-toxic hypergolic bipropellant with catalytically promoted fuel system and an oxidizing hydrogen peroxide solution, characterized in that said fuel system comprises: I) Propagator 1: about 10% to about 90% by volume of polyamine compounds based on the total volume of the system, II) Propagator 2: about 10% to about 90% by volume of alkanolamine compounds based on the total volume of the system, III) Promoter: about 0.3% to about 6% by weight of catalytic agent, based on the total weight of the system, which reacts to form complexed amines in solution and stimulates the catalytic decomposition of the hydrogen peroxide oxidizing solution.

2. The hypergolic bipropellant of claim 1, wherein said polyamine species comprises an alkyl-substituted diamine or an alkyl-substituted triamine or any mixture thereof.

3. Hypergolic bipropellant according to claim 2, characterized in that said alkyl-substituted diamine is selected from the group derived from the ethylenediamine compound or the imidazole compound consisting of N,N,N'N'-tetramethylethylenediamine, N,N-dimethylethylenediamine, N,N'-dimethylethylenediamine, N-methylethylenediamine, N,N,N',N”,N”-pentamethyldiethylenetriamine (PMDTA) and N-methylimidazole (Mim).

4. The hypergolic bipropellant of claim 1, wherein said alkanolamine species comprises a member of the ethanolamine family.

5. The hypergolic bipropellant of claim 4, wherein said ethanolamine family member comprises N-methylethanolamine (MMEA), N,N-dimethylethanolamine, N,N-diethylethanolamine, and N-methyldiethanolamine, or any mixture thereof.

6. Hypergolic bipropellant according to claim 1, characterized in that said catalytic agent is selected from the group consisting of hydrated or non-hydrated metallic salts of copper, cobalt, manganese and iron or mixtures thereof.

7. Hypergolic bipropellant according to claim 6, characterized in that said metal salts are selected from chloride, nitrate and acetate anions.

8. The hypergolic bipropellant of any one of claims 1 to 7, wherein said hydrogen peroxide solution comprises an aqueous solution of about 85% to about 99% by weight of hydrogen peroxide.

9. Hypergolic bipropellant according to any one of claims 1 to 8, characterized in that it has an ignition delay time (IDT) of less than 20 ms.

10. Hypergolic bipropellant according to any one of claims 1 to 9, characterized in that it presents specific impulse (I sp ) from about 93 to about 98% of I sp of conventional toxic bipropellant systems.

11. Hypergolic bipropellant according to any one of claims 1 to 10, characterized in that said fuel system additionally comprises: IV) Optional organic solvent: about 0% to about 60% by volume of polar organic compounds based on the total volume of the system.

12. Hypergolic bipropellant according to claim 11, characterized in that said polar organic compounds comprise at least one lower alcohol of C1-C6 chains, preferably methanol, ethanol or any mixture thereof.

13. Hypergolic bipropellant according to any one of claims 1 to 12, characterized in that said fuel system comprises: I) Propagator 1: about 20% to about 70% by volume (based on the total volume of the system) of polyamine compounds, II) Propagator 2: about 30% to about 80% by volume (based on the total volume of the system) of alkanolamine compounds, III) Promoter: about 0.5% to about 2% by weight of catalytic agent, based on the total weight of the system, which reacts to form complexed amines in solution and stimulates the catalytic decomposition of the hydrogen peroxide oxidizing solution, and IV) Optional organic solvent: about 0% to about 60% by volume (based on the total volume of the system) of polar organic compounds (lower alcohols of C1-C6 chains).

14. Use of the hypergolic bipropellant as defined in any one of claims 1 to 13, characterized in that it is in space equipment or operations in pulse and / or multiple restart mode, preferably rockets and space vehicles.

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