WO2014193235A1

WO2014193235A1 - Fuel composition for hypergolic bipropellant

Info

Publication number: WO2014193235A1
Application number: PCT/NL2014/050347
Authority: WO
Inventors: Alfons E.H.J. MAYER; Flavia Tata Nardini
Original assignee: Nederlandse Organisatie Voor Toegepast-Natuurwetenschappelijk Onderzoek Tno
Priority date: 2013-05-31
Filing date: 2014-05-30
Publication date: 2014-12-04

Abstract

The invention is directed to a fuel composition comprising an alcohol, a catalytic metal ion, an anion (in particular nitrate) and amide (in particular N,N dimethyl formamide (DMF)), as well as to bipropellants comprising such a fuel composition and hydrogen peroxide.

Description

Title: FUEL COMPOSITION FOR HYPERGOLIC BIPROPELLANT

The invention is directed to a fuel composition, a bipropellant comprising the fuel composition and a method for oxidizing an alcohol.

A hypergolic bipropellant is a combination of two propellant components that spontaneously ignite when they come into contact with each other. Such propellant combinations are for example used in rocket engines. Engines using hypergolic bipropellant are easy to ignite reliably and repeatedly due to the spontaneous ignition of the hypergolic

bipropellant. Such engines do not need an ignition system.

A hypergolic bipropellant consists of a fuel and an oxidizer that are incompatible, i.e. react with each other upon contact. The most common hypergolic bipropellant is the combination of dinitrogen tetroxide as the oxidizer with hydrazine derivates such as monomethylhydrazine (MMH) and unsymmetrical dimethylhydrazine (UDMH), as the fuel. These compounds are all liquids at atmospheric temperature and pressure and stable over long periods of time. This makes them very suitable for spacecraft applications.

A disadvantage of traditional hypergolic bipropellants such as those described above is that they are highly toxic and often carcinogenic. The use of these propellants thus poses a serious threat both to human health and to the environment. For this reason, the use of these

bipropellants is expected to be restricted or forbidden by European legislation in the near future. An alternative is thus needed for the traditional hypergolic bipropellants described above.

An example of such an alternative bipropellant is described in US 5,932,837 describes non-toxic bipropellant containing a non-toxic hypergolic miscible fuel (NHMF) and rocket grade hydrogen peroxide oxidizer. The non-toxic hypergolic miscible fuel contains about 50 to 75 weight % polar organic species miscible with hydrogen peroxide, about 0.1 to 15 weight % propagator, and about 0.1 to 30 weight % inorganic metal salts which react to form a catalyst in solution or as a colloid. The catalyst is in particular formed by adding a soluble inorganic metal salt into the solution consisting of the polar organic species and the propagator. When added to the solution, in situ formation of a microdispersed colloidal metal oxide and acetic acid occurs, which act as the catalyst. The polar organic species can be Ci to C6 alcohols and/or Ci to C₄ ketones, the propagator can be substituted or unsubstituted amides, amines and diamines, and the inorganic metal salts is selected from the group consisting of manganese, copper, cobalt and iron.

Another example of an alternative bipropellant is described in US 6,419,771. Herein, a non-toxic bipropellant is provided containing a nontoxic hypergolic miscible fuel and rocket grade hydrogen peroxide oxidizer. The fuel contains about 60-90 wt.% polar organic species, about 1.0-15 wt.% propagotor, 4.0-23 wt.% inorganic metal salt, which reacts to form a catalyst in solution or as a colloid. Further, 1.0-10 wt.% acetic acid and 1.0-10 wt.% alkali acetate is present in the fuel to buffer the pH.

The inventors found that a disadvantage of the alternative bipropellants such as those described in US 5,932,837 and US 6,419,771 is that the fuel compositions described herein may not be hypergolic (i.e.

capable of spontaneous ignition) when contacted with hydrogen peroxide at relative low temperatures (such as room temperature). If a bipropellant is only hypergolic at high temperatures, this makes the bipropellant less useful in many application, because heating is then required to start the oxidation reaction.

A further disadvantage is that the storability of the fuel mixtures of the prior art may be limited. The solubility of the fuel components in the organic species may be insufficient, such that the resulting fuel may become inhomogeneous which is undesirable with respect to the hypergolic performance of the fuel due to the inhomogeneity of the fuel mixture. Therefore, there is still a need for alternative bipropellants that do not have these disadvantages.

An object of the invention is to provide for a bipropellant that does not suffer from one or more of the disadvantages described above.

In particular, it is an object to provide a non-toxic bipropellant that is hypergolic at relative low temperatures, in particular at

temperatures below 40 °C.

A further object of the invention is to provide a non-toxic bipropellant, which is storable under atmospheric conditions, preferably for at least several years. The term atmospheric conditions as used herein refers to a temperature of about 20 °C (i.e. 15-25 °C) and a pressure of about

100 kPa (i.e. 80-120 kPa).

At least one of these objects was met by providing a specific fuel composition. In a first aspect, the invention provides a fuel composition comprising an alcohol, a catalytic metal ion, an anion (in particular nitrate) and an amide (in particular N,N dimethyl formamide).

The inventors found that the specific combination of certain amides and certain anions may lower the minimum temperature at which the fuel composition is hypergolic. The term "hypergolic" as used herein refers to the ability of a bipropellant to ignite spontaneously when the fuel mixture and the oxidator of the bipropellant are brought into contact with each other. In particular, the term as used herein refers to the ability of the fuel mixture of the invention to spontaneous ignite when brought into contact with hydrogen peroxide. The minimum temperature at which the bipropellant is capable of such spontaneous ignition was found to depend on the type of alcohol, amide and inorganic salt present in the fuel mixture.

Unless indicated otherwise, this temperature is determined or measured at atmospheric pressure (1.0 10⁵ Pa).

Without wishing to be bound by any theory, the inventors believe that DMF is able to interact with certain specific anions, thereby promoting the oxidation of the alcohol. This interaction effectively lowers the

temperature at which the bipropellant is capable of spontaneous ignition. Normally, only the selection of the cation of the inorganic salt is considered important, because it may act as a catalyst in the decomposition of hydrogen peroxide into oxygen and water. However, the inventors realized that anions can also play an important role in the fuel by its interaction with DMF. The inventors found that the particular combination of certain anions with DMF was able to lower the temperature at which the bipropellant is capable of spontaneous ignition to below 30 °C, even as low as 20 °C.

In particular, the inventors believe, again without wishing to be bound by any theory, that the fuel composition of the invention reacts when brought into contact with hydrogen peroxide in the following way. First, upon contact with the fuel composition, the hydrogen peroxide is

catalytically decomposed into oxygen and water, wherein the metal ion acts as a catalyst. This reaction is exothermic and the energy released by this reaction initiates the interaction between DMF and the anion, which interaction promotes the oxidation of alcohol by oxygen and/or hydrogen peroxide. For example, the anions of the inorganic salt may react

exothermically with DMF, thereby locally increasing the temperature of the alcohol and promoting oxidation of the alcohol by the hydrogen peroxide. Alternatively, the anions of the inorganic salt may interact with DMF to decrease the energy need to oxide the alcohol, thereby promoting oxidation of the alcohol by the hydrogen peroxide.

The anion is in particular nitrate. As shown in the Examples, the specific combination of nitrate and DMF is capable of a large decrease in the minimum temperature at which spontaneous ignition may occur, even to temperatures below 25 °C.

The cationic metal ion as used herein refers to a metal cation capable of catalyzing the decomposition reaction of hydrogen peroxide. Such decomposition will result in the formation of oxygen (O2) and water. The skilled person will know which metal cations may act as a catalyst in the decomposition of hydrogen peroxide. Typically, the metal cation is a transition metal, in particular one selected from the group consisting of Fe (e.g. FeQ.1I), Mn (e.g. Mn(II)), Co, V, Ag, Cr, Pt, Ru, Pd, Ni and Cu (e.g.

Cu(n)) cations. Silver cations may for example be used due to their excellent catalytic activity. Preferably, the cation may be selected from the group consisting of iron, cobalt, copper, silver and manganese cations. Good results have been obtained using iron as the cation, in particular Fe(III).

The anion and cation may have been provided in the fuel composition by different salts (e.g. a nitrate salt and a metal ion salt). In this case, additional anions and cations other than nitrate and the catalytic metal cation will be present in the fuel composition. However, the anion and cation preferably have been provided in the fuel composition by the same inorganic salt, i.e. an inorganic salt comprising both the anion and the catalytic metal ion (hereinafter referred to as the "inorganic salt").

Thus, the fuel composition of the invention may comprise DMF, an alcohol and an inorganic salt, wherein the inorganic salt comprises the anion and the catalytic metal ion. The inorganic salt may be hydrated or unhydrated. In case the inorganic salt is unhydrated, this can be desirable because water is considered a contaminant in the fuel composition.

However, surprisingly, it was found that the bests results were obtained using hydrated inorganic salts. For example, particular good results have been obtained using hydrated inorganic salt, e.g. iron(HI)nitrate

nonahydrate.

The inorganic salt may be selected from the group consisting of iron nitrates (e.g. Fe(III)), manganese nitrates, (e.g. Mn(II)) and copper nitrates (e.g. Cu(II)). It was found that these nitrates provide the

composition with good storability. Very good results have been obtained with iron nitrates, in particular Fe(III)(N03)3, as the inorganic salt. Further, silver nitrate may be advantageously used due to the high catalytic activity of silver.

The inventors further found that the selection of the anion and cation of the inorganic salt was critical. The presence or absence of certain anions and cations was found to have a large influence on whether a DMF containing bipropellant would be hypergolic at low temperatures. For example, good results were obtained using manganese acetate as the inorganic salt, whereas manganese nitrate was found to be much less suitable. The inventors found that the cation/anion combinations that were most preferred with respect to providing hypergolicity to the fuel at low temperatures are iron/nitrate palladium/nitrate, manganese/acetate, cobalt/acetate and manganese/acetylacetonate. Accordingly, the inorganic salt is preferably iron nitrate (e.g. iron(Q)nitrate or iron(III)nitrate), manganese acetate (e.g. manganese(II)acetate or manganese(III)acetate), palladium nitrate (e.g. palladium(II)nitrate), cobalt acetate (e.g.

cobalt(II)acetate) and manganese acetylacetonates (e.g.

manganes(II)acetylacetonate). In a preferred embodiment, the inorganic salts are provided in the fuel composition as a hydrate.

It was further found that the presence of anions or cations other than those provided by the inorganic salt had a negative effect on the low temperature hypergolicity of the fuel composition. For example, the presence of cations such as alkali and alkaline earth metals or the presence of anions such as chloride may have a negative effect and are therefore preferably not present in the fuel composition. More preferably, no salt other than the inorganic salt is present in the fuel composition. More in particular, the fuel composition preferably comprises no ions other than those provided by the inorganic salt.

As the presence or absence of certain compounds may influence the low temperature hypergolicity of the fuel composition, the fuel composition preferably consists of the alcohol, the inorganic salt and DMF.The alcohol may be an alcohol having 1-8 carbon atoms. Preferably, the alcohol is selected from the group consisting of methanol, ethanol, propanol, butanol and pentanol. A disadvantage of larger alcohols is that they can result in soot formation when combusted, which may have a negative effect on the performance of the engine wherein the bipropellant is combusted, for example by clogging the injectors of the engine and

promoting combustion instabilities. Most preferably, ethanol is used as the alcohol. Fuel compositions according to the invention comprising ethanol as the alcohol were found to have an excellent combustion performance, as well as a good storability

The specific combination of DMF, certain anions, catalytic metal ions and alcohols has shown to be particularly desirable. In particular, the combination of DMF, nitrate and ethanol showed very good results. This specific combination results in a homogeneous mixture that is hypergolic at temperatures below 25°C and has good storability. In this embodiment, the catalytic metal ion is preferably Fe(III).

The anion may also be an acetate or an acetylacetonate, in which case the alcohol is preferably ethanol.

The fuel composition may comprise 60-99 wt.% alcohol, 1-30 wt.% of the inorganic salt and 0.1-10 wt.% of DMF, based on the total weight of the fuel composition. Preferably, the fuel composition comprises 60-90 wt.% alcohol, 9-30 wt.% of the inorganic salt and 1-8 wt.% of DMF, based on the total weight of the fuel composition.

Nitrate may be present in the fuel composition in an amount of 0.5-15 wt.%, preferably 4-15 wt.%, based on the total weight of the fuel composition.

Furthermore, since nitrate is expected to only initiate (and not to propagate) the combustion reaction of the alcohol, the anion may be present in the fuel composition in relative small amounts. For example, the fuel composition may comprise less than 5 wt.%, less than 3 wt.% or even less than 1 wt.% of the nitrate.

The fuel composition may comprise less than 0.9 wt.% acetic acid, preferably less than 0.5 wt.% acetic acid, more preferably essentially no acetic acid. Alternatively or additionally, the fuel composition may further comprise less than 0.9 wt.% alkali acetate, preferably less than 0.5 wt.% alkali acetate, more preferably essentially no alkali acetate. It was found that the fuel composition of the invention showed excellent solubility and storability in the absence of an acetic acid/acetate buffer, in particular when ethanol is used as the alcohol.

In a further aspect, the invention is directed to a method for preparing a fuel composition, in particular a fuel composition according to the invention, which method includes dissolving an amide (most preferably DMF) and the anion and cation (preferably in the form of an inorganic salt described above) in the alcohol (preferably ethanol).

In the method of the invention, the anion and cation are preferably provided by a single salt, i.e. a single inorganic salt comprising both the anion and the cation. It was found that when providing the anion and cation using separate salts, this may negatively influence the

hypergolicity temperature of the fuel composition. More preferably, the inorganic salt is the only salt that is dissolved in the alcohol and/or present in the resulting fuel composition.

Preferably, the inorganic salt to be dissolved in the alcohol is selected from the group consisting of iron nitrate, manganese acetate, palladium nitrate, cobalt acetate and manganese acetylacetonate. More preferably, a hydrate of these salts is dissolved. Although water is typically considered a contaminant in fuel compositions, it was surprisingly found that by adding the inorganic salt as a hydrate, the resulting fuel

composition may have improved properties, e.g. with respect to the temperature at which the bipropellant is hypergolic In a further aspect, the invention is directed to a bipropellant comprising the fuel composition of the invention and hydrogen peroxide. The hydrogen peroxide may also be referred to as the oxidizer and may be considered the first propellant, while the fuel composition can be considered the second propellant of the bipropellant. The bipropellant may be used in spacecraft applications, in particular in reaction control engines, orbital manoeuvre engines and other in-space propusion systems.

The alcohol used in the method of the invention is as described above for the fuel composition and is most preferably ethanol.

In a further aspect, the invention is also directed to a method for oxidizing an alcohol, which method comprises the step of bringing hydrogen peroxide in contact with the fuel composition according to the invention, wherein the anion of the inorganic salt interacts with the amide to promote oxidation of the alcohol.

Preferably, the fuel composition and hydrogen peroxide both have a temperature below 40 °C, more preferably below 30 °C, even more preferably below 25 °C, even more preferably below 21 °C at the moment they are brought into contact with each other. This can be achieved by carefully selecting the amide and inorganic salt, as explained in more detail above. This has the advantage that no additional heating is required for the spontaneous ignition to occur, even under atmospheric conditions.

The pressure at which the reaction is conducted is typically between 0.1 and 10,000 kPa, preferably about 100 kPa (atmospheric pressure).

The hydrogen peroxide is preferably added as an aqueous solution comprising at least 85 wt.%, more preferably at least 87.5 wt.% hydrogen peroxide. Such high concentrations may also be referred to as rocket grade hydrogen peroxide.

The invention is illustrated by the following examples. Example 1: Effect of Initiator on Spontaneous Ignition

In this Example, ethanol was oxidized with hydrogen peroxide in the presence of iron(III)nitrate and various initiators.

The Example was carried out as follows. First, a fuel mixture was prepared of 2.50 mL ethanol, 1.30 g of iron(III)nitrate nonahydrate (0.18 g of Fe³⁺ , 0.60 g of (NO3)" and 0.52 g of water) and an initiator. Subsequently, 0.10 mL of the fuel mixture was added to rocket grade hydrogen peroxide (88.2 wt.%, remainder water) at atmospheric pressure and temperature. It was analyzed by visual inspection whether decomposition and/or ignition occurred during the reaction.

The following initiators were tested:

1. N,N-dimethylformamide (0.35 mL)

2. formamide (0.35 mL),

3. acetamide (0.35 mL)

4. N,N-dimethylacetamide (0.35 mL)

5. Urea (0.25 g)

6. Ethylenediaminetetraacetic acid (EDTA) (0.25 g)

7. Sodium ethylenediaminetetraacetate (K2EDTA) (0.25 g) Initiators 1-5 all showed good solubility in the fuel mixture, while initiators 6-7 formed a suspension.

After the fuel mixture was added to hydrogen peroxide, decomposition (viz. boiling, steam formation) was observed for all fuel mixtures. However, the fuel mixture with N,N-dimethylformamide also resulted in ignition of the fuel mixture. No ignition was observed for the other fuel mixtures.

It can be concluded that the presence of N,N-dimethylformamide in the fuel mixture causes the fuel mixture to ignite spontaneous with hydrogen peroxide even at a temperature of 20 °C at atmospheric pressure. This desirable result could not be achieved with any of the other initiators that were tested. Example 2: Effect of Temperature on Spontaneous Ignition

In this Example, ethanol was oxidized with hydrogen peroxide in the presence of iron(III)nitrate. First, a fuel mixture of 1.30 g

iron(III)nitrate-nonahydrate (0.18 g of Fe³⁺ , 0.60 g of (N0₃)" and 0.52 g of water) in 2.50 mL was prepared. The temperature of the hydrogen peroxide was then raised to a certain temperature using a heater. Subsequently, 0.10 mL of the fuel mixture was added to rocket grade hydrogen peroxide (88.2 wt.%, remainder water). It was analyzed by visual inspection whether decomposition and/or ignition occurred during the reaction. The results are shown in Table 1.

Table 1:

It can be concluded from this Example that the temperature at which spontaneous ignition of ethanol with hydrogen peroxide in the presence of iron(III)nitrate in the absence of an initiator occurs is a little over 40 °C. When comparing these results to Example 1, it can be concluded that the presence of N,N-dimethylformamide lowers this temperature to a temperature of at least about 20 °C (see Example 1, initiator 1).

Example 3: Effect of Inorganic Salt on Spontaneous

Ignition

In this Example, ethanol was oxidized with hydrogen peroxide in the presence of different types of salts and DMF. The Example was carried out as follows. First, a fuel mixture was prepared of 5 mL ethanol, 0.2 mL DMF and inorganic salt.. Subsequently, 0.10 mL of the fuel mixture was added to rocket grade hydrogen peroxide (88.2 wt.%, remainder water) at atmospheric pressure and temperature. It was analyzed by visual inspection whether decomposition and/or ignition occurred during the reaction.

The following salts were tested:

1. Iron (III) nitrate nonahydrate (1.00 g)

2. Mn(II) Nitrate Hydrate (0.50 g)

3. Mn(II) Nitrate tetra Hydrate (0.60 g)

4. Mn(H) Acetate (0.4 g)

5. Fe(IH) Chloride (0.4 g)

6. Fe(H) Chloride (0.3 g)

7. Fe(H) Acetate (0.20 g)

8. Palladium(II) acetate (0.60 g)

9. Palladium(II) Nitrate Hydrate (0.6 g)

The results are shown in Table 2 below. Table 2:

Exp Ethan Inorganic Salt (g) DMF ignitio decomol n position ml g ml

1 5 Iron (III) nitrate nonahydrate 0.2 Yes Yes

(1.00 g)

2 5 Mn(II) Nitrate Hydrate (0.50 g) 0.2 No No

3 5 Mn(II) Nitrate tetra Hydrate 0.2 No No

(0.60 g)

4 5 Mn(II) Acetate (0.4 g) 0.2 Yes Yes

5 5 Fe(III) Chloride (0.4 g) 0.2 No Slow 6 5 Fe(II) Chloride (0.3 g) 0.2 No No

7 5 Fe(II) Acetate (0.20 g) 0.2 No No

8 5 Palladium(II) acetate (0.60 g) 0.2 No Slow

9 5 Palladium(II) Nitrate Hydrate 0.2 Yes Yes

(0.6 g)

Example 4: Storability

In this Example, the storabihty of possible fuel compositions was determined by measuring the solubility of the different components.

First, catalyst was added to ethanol to determine the solubihty of the components. The results are shown in Table 3 below.

Table 3:

Catalyst Solubility

Cobalt (II) acetate moderate

Cobalt (II) acetylacetonate poor

Cobalt (II) nitrate

hexahydrate poor

Copper (II) acetate hydrate poor

Copper (II) acetylacetonate poor

Copper (II) nitrate trihydrate good

Iron (II) chloride moderate

Iron (III) chloride good

Iron (III) nitrate nonahydrate excellent

Manganese (II) acetate good

Manganese (II) acetate

tetrahydrate moderate

Manganese (II)

acetylacetonate moderate Manganese (II) nitrate

hydrate good

Manganese (II) nitrate

tetrahydrate good

Pyrrole good

Second, various initators were added to ethanol to determine the solubility of the components. The results are shown in Table 4 below. Table 4:

For the catalyst and initiator only good and excellent solubility species remained in solution for one week or more.

Fuel compositions including the catalysts Copper(II)nitrate trihydrate, Iron(III)chloride, Iron (Ill)nitrate nonahydrate,

Manganese(II)acetate, Manganese(II)nitrate hydrate, Manganese(II)nitrate tetrahydrate and Pyrrole showed good storability characteristic during at least one week.

Fuels including the initiators DMF, Formamide, Acetamide, N,N- dimethylacetamide and Urea showed good storabihty characteristic during at least one week. Example 5: Composition Test

In this Example, ethanol was oxidized with hydrogen peroxide in the presence of iron(III)nitrate nonahydrate and DMF. The concentration of iron(III)nitrate nonahydrate and DMF was varied. The temperature of the hydrogen peroxide was ambient. Subsequently, 0.10 mL of the fuel mixture was added to rocket grade hydrogen peroxide (88.2 wt.%, remainder water). It was analyzed by visual inspection whether decomposition and/or ignition occurred during the reaction. The results are shown in Table 5 below. Table 5:

Exp. Ethanol iron(III)nitrate- DMF ignition decomposition nonahydrate

ml g ml

PT6 2.50 1.30 0.35 no yes

PT8 2.50 1.30 0.35 yes yes

PT9 2.50 1.30 0.35 yes yes

PT10 5.00 1.30 0.35 yes yes

PT11 5.00 1.30 0.35 no yes

PT12 5.00 1.30 0.35 yes yes

PT13 5.00 0.65 0.35 no yes

PT14 5.00 1.00 0.35 yes yes

PT15 5.00 1.00 0.35 yes yes

PT16 5.00 1.00 0.20 yes yes

PT17 5.00 1.00 0.20 no yes

PT18 5.00 1.00 0.20 no yes

1 2.5 1.3 0.35 yes yes

2 5.0 1.3 0.35 yes yes

3 5.0 1.0 0.20 yes (50%) yes

4 5.0 1.0 0.35 yes yes 5 5.0 0.5 0.35 yes yes

Within the limitations of the number of tests from this Example, it can be concluded that a reliable fuel mixture to obtain ignition is a mixture of 1.00 g iron(III)nitrate-nonahydrate (0.14 g of Fe3+ , 0.46 g of (N03)- and 0.40 g of water) in 5.00 mL ethanol and 0.20 mL DMF.

Example 6: Effect of using one or multiple salts

In this Example, the fuel composition was prepared using either a single or two different salts to include the required anion and cations.

The Example was carried out as follows. First, a fuel mixture was prepared of 5 mL ethanol, 0.2 mL DMF and one or more inorganic salts. Subsequently, 0.1 mL of the fuel mixture was added to rocket grade hydrogen peroxide (88.2 wt.%, remainder water) at atmospheric pressure and temperature. It was analyzed by visual inspection whether

decomposition and/or ignition occurred during the reaction. The results are shown in Table 6 below.

Table 6:

Exp. Ethano Salt(s) present (g) DMF ignitio decomp 1 n o-sition ml ml

1 5 0.40 gr Fe(III) Chloride 0.2 no yes

0.73 gr Mn(N03)2 . H20

2 5 0.31 gr Fe(II) Chloride 0.2 no yes

0.73 gr Mn(N03)2 . H20

3 5 0.22 gr Fe(II) acetate 0.2 no yes

0.37 gr Mn(N03)2 . H20

4 5 0.43 gr Fe(II) acetate 0.2 no yes 0.73 gr Mn(N03)2 . H20

5 0.43 gr Fe(II) acetate 0.2 no yes

0.93 gr Mn(N03)2 . 4 H20

5 0.43 gr Fe(II) acetate 0.2 no yes

0.93 gr Mn(N03)2 . 4 H20

0.13 gr H20

5 1.00 gr Iron (III) nitrate 0.2 no yes nonahydrate

0.73 gr Mn(N03)2 . H20

5 1.00 gr Iron (III) nitrate 0.2 yes yes nonahydrate

0.40 gr H20

Claims

1. Fuel composition comprising an alcohol, a catalytic metal ion, an anion and N,N dimethyl formamide.

2. Fuel composition according to claim 1, wherein the anion is nitrate and the catalytic metal ion is iron, preferably iron(III).

3. Fuel composition according to claim 1, wherein the anion is nitrate and the catalytic metal ion is palladium.

4. Fuel composition according to claim 1, wherein the anion is acetate and the catalytic metal ion is cobalt.

5. Fuel composition according to claim 1, wherein the anion is acetate and the catalytic metal ion is manganese.

6. Fuel composition according to claim 1, wherein the anion is acetylacetonate and the catalytic metal ion is manganese.

7. Fuel composition according to any of the previous claims, wherein the composition comprises less than 0.9 wt.% acetic acid and/or less than 0.9 wt.% alkali acetate, preferably no acetic acid and/or alkali acetate.

8. Fuel composition according to any of the previous claims, wherein the fuel composition comprises 60-90 wt.% alcohol, 9-30 wt.% metal salt and 1-10 wt.% N,N dimethyl formamide, based on the total weight of the fuel composition, wherein the metal salt consists of the catalytic metal ion and the anion.

9. Fuel composition according to claim 2 or 3, wherein the fuel composition comprises 60-90 wt.% alcohol, 9-30 wt.% metal nitrate and 1-10 wt.% ΔζΝ dimethyl formamide, based on the total weight of the fuel composition.

10. Fuel composition according to any of the previous claims, wherein the alcohol is selected from the group consisting of methanol, ethanol, propanol, butanol, pentanol and hexanol.

11. Fuel composition according to any of the previous claims, wherein the alcohol is ethanol.

12. Fuel composition according to any of the previous claims comprising less than 0.5 wt.% ions selected from the group consisting of alkali ions, alkaline earth metal ions and chloride, preferably no such ions.

13. Method for preparing the fuel composition according to any of the previous claims, comprising dissolving an amide, an anion and catalytic metal ion in an alcohol.

14. Method according to claim 13, wherein the anion and catalytic metal ion are dissolved in the alcohol by dissolving an inorganic salt selected from the group of iron nitrate, manganese acetate, palladium nitrate, cobalt acetate and manganese acetylacetonate in the alcohol.

15. Method according to claim 14, wherein the inorganic salt is a hydrate.

16. Bipropellant comprising hydrogen peroxide as the first propellant and the fuel composition according to any of claims 1-12 as the second propellant.

17. Method for oxidizing an alcohol, comprising the step of bringing hydrogen peroxide in contact with a fuel composition according to any of claims 1-12, wherein the anion interacts with N,N dimethyl formamide to promote oxidation of the alcohol.

18. Method according to claim 17, wherein the fuel composition and hydrogen peroxide both have a temperature below 25 °C, at the moment they are brought into contact with each other.

19. Method according to claim 18, wherein the fuel composition comprises an inorganic salt selected from the group of iron nitrate, manganese acetate, palladium nitrate, cobalt acetate and manganese acetylacetonate in the alcohol.