Liquid monopropellants

Abstract

A novel formulation of liquid propellants comprising a mixture of high eny ingredients consisting of bis(2-fluoro-2,2-dinitroethyl)amine, bis(2-fluoro-2,2-dinitroethyl)formal and bis(2,2,2-trinitroethyl)formal together with conventional liquid fuels and propellants to create a synergistic formulation having new and unexpected physical and chemical properties.

Description

BACKGROUND OF THE INVENTION

It is well known and conventional to use Otto fuels and other liquid fuels to propel torpedoes and other solid projectiles.

It is likewise common in the liquid propellant art to utilize liquid propellants for guns as well as for rocket fuel.

There are a number of typical problems with these prior art fuels and liquid propellants including low impetus, high flame temperatures and poor gas production per unit mass of fuel.

Other liquid fuels and propellants are very sensitive to shock and present safety problems. Most safety problems with liquid propellants are caused by the sensitivity to temperature and pressure of the material involved.

It is further well known in the art that some liquid propellants are extremely sensitive to shock. In addition many conventional explosives and propellants lack sufficient thermal stability for use in high temperature environments.

Conventional liquid propellants are less stable and more sensitive to shock than the formulations made according to the instant invention.

In the Otto Fuel and Otto Fuel II formulations that are presently used by the navy as torpedo propellants there are drawbacks, primarily because these fuels are extremely corrosive and present health hazards if leakage is allowed to occur. The fumes from Otto Fuel II are extremely toxic to personnel in the area.

Accordingly, it is one object of the invention to formulate liquid propellants, that can be easily formulated and manufactured in commercial quantities.

It is also a primary object to provide Otto Fuel II formulations that combine better performance characteristics with lower toxicity.

It is another object of the present invention to formulate novel mixtures and compositions of liquid propellants that have improved physical and chemical properties.

It is a further object of this invention to incorporate and utilize several high energy ingredients in a number of conventional liquid fuels and propellants, to improve the energetic characteristics of the liquid propellants.

It is another object of this invention to formulate liquid propellants that have superior thermodynamic properties and characteristics that give new and unexpected results.

It is a further object to formulate novel propellants and other similar materials including liquid propellants so as to yield improved safety characteristics.

It is still a further object of this invention to formulate novel mixtures of liquid propellants with better DTA curves, improved test data and oven times and better auto-ignition times when compared with conventional propellant materials.

It is a still further object of this invention to formulate torpedo propellants by increasing energetic properties while decreasing toxicity.

It is another object of this invention to prepare formulations that are less hazardous to personnel who are in close proximity to said Otto Fuel formulations.

It is a still further object of this invention to formulate liquid fuels and propellants that have greatly superior cavity drop test results.

It is another object of this invention to prepare and use formulations of liquid propellants that have greatly lessened sensitivity to shock.

It is another object of this invention to produce formulations of liquid propellants that have greatly increased impetus (foot, pounds per pound) while being combined with a lower flame temperature).

SUMMARY OF THE INVENTION

The invention comprises the product of formulation of a high energy ingredient mixed together with conventional liquid fuels and propellants. The formulated product yields new and unexpected results. The high energy ingredient is a compound usually selected from the group consisting of bis(2-fluoro-2,2-dinitroethyl)amine, bis(2-fluoro-2,2-dinitroethyl)formal, and bis(2,2,2-trinitroethyl)formal. Equivalent compounds selected from Table 1 may be substituted for these components, although the results may not be the same as with each compound but will prove satisfactory.

In most cases the high energy ingredient is present in an amount varying between 5% and 75% of the total mixture.

In general, the use of a compound selected from the group consisting of bis(2-fluoro-2,2-dinitroethyl)amine, bis(2-fluoro-2,2-dinitroethyl)formal, and bis(2,2,2-trinitroethyl)formal, when mixed with well-known liquid fuels and propellants, will yield a formulated product that will have physical and chemical properties that are superior to either the high energy ingredient or the conventional fuels and propellants.

PREFERRED EMBODIMENT

There are several preferred embodiments of the invention. The operative compounds are set forth and disclosed in Table I together with some energy factors.

In one preferred embodiment, Otto Fuel, a well known liquid propellant used by the U. S. Navy for torpedo propulsion can be formulated with one or more compounds selected from the group consisting of bis(2-fluoro-2,2-dinitroethyl)amine, bis(2,-fluoro-2,2-dinitroethyl)formal and bis(2,2,2-trinitroethyl)formal.

TABLE I______________________________________Illustrations of the High Energy Ingredient that may beused in the Preferred Embodiment Formulations H.sub.f.sup.o 298.15.degree. K.Abbrev. Name K cal/mole______________________________________FEFO Bis(2-fluoro-2,2-dinitroethyl)formal -179.8BFDNA Bis(2-fluoro-2,2-dinitroethyl)amine -126.95TEFO Bis(2,2,2-trinitroethyl)formal -96.40______________________________________ The resulting product of the formulation has much higher impetus than Otto Fuel II alone while increasing burning rates and combustion properties. In each instance where the high energy ingredient is used in the range of from 5 to 75% by weight of the mixture, toxicity of Otto Fuel II is decreased significantly.

The experimental data illustrating the results of the combination of bis(2,2,-trinitroethyl)formal, hereinafter referred to as TEFO is set forth in Tables II, III, IV, V, VI, VII and VIII. In another preferred embodiment, diethyl oxalate is formulated with a compound selected from the group consisting of bis(2-fluoro-2,2-dinitroethyl)amine, bis(2-fluoro-2,2-dinitroethyl)formal and bis(2,2,2-trinitroethyl)formal. This experimental data best illustrates the combination of mixing TEFO with diethyl oxalate and is set forth in Tables V, VI, and VII.

In another preferred embodiment a compound selected from the group consisting of bis(2-fluoro-2,2-dinitroethyl)amine, bis(2-fluoro-2,2-dinitroethyl)formal and bis(2,2,2-trinitroethyl)formal is mixed with acetone and methylethyl ketone. The experimental data illustrating the results of the combination of TEFO, acetone and methylethyl ketone is set forth in Table VIII.

High Energy Ingredients Formulated With Otto Fuel II

Otto Fuel II is a liquid fuel that is now used extensively by the U.S. Navy to propel torpedoes.

Surprisingly, it has been found that formulation of one or more of the high energy ingredients selected from Table I when mixed with Otto Fuel II will yield high energy propellants having new and unexpected properties.

Preparation and Testing of Otto Fuel II

Otto Fuel II is comprised of 2-nitrodiphenylamine prepared in accordance with MIL-N-3399; di-n-butyl sebacate; prepared to conform with DOD-B-82669; and propylene glycol dinitrate that is prepared to conform with the requirements of DOD-P-82671.

The chemical composition of Otto Fuel II is: A mixture of propylene glycol dinitrate, 2-nitrodiphenylamine, di-n-butyl sebacate.

______________________________________CHEMICAL COMPOSITION OF OTTO FUEL II Minimum Maximum TestComponent (% by wt) (% by wt) method______________________________________Propylene glycol dinitrate 75.8 76.2 4.5.2.12-Nitrodiphenylamine 1.4 1.6 4.5.2.2Di-n-butyl sebacate 22.2 22.8 4.5.2.3Sodium -- 0.8 4.5.2.5______________________________________

The detailed method of testing the propylene glycol dinitrate for content and quality is set forth in Metail in MIL-O-82652(OS), pages 4 and 5.

The detailed method of testing the #2nitrodiphenylamine for content and quality is set forth in detail in MIL-O-82652(OS), pages 5, 6 and 7.

The detailed method of testing the di-n-butyl sebacate content and quality is set forth in MIL-0-82672(OS), pages 7 and 8.

The detailed method of testing the sodium content and quality set forth in OD 43852 and on page 8 of MIL-O-82672(OS).

EXAMPLE 1

TEFO is prepared by first producing trinitroethanol. In a second step trinitroethanol is reacted with paraformaldehyde and the crude product is purified.

Typical Laboratory Preparation

1. Preparation of trinitroethanol (TNEOH):

The following ingredients were placed in a three-neck 250 ml flask equipped with a stirrer, thermometer, dropping funnel, and a bath for heating or cooling:

______________________________________Aqueous nitroform (33.27% nitroform) = 135.7 grams (0.30 moles)Carbon tetrachloride = 63.4 gramsmethylene chloride = 53.4 gramsparaformaldehyde = 10.4 grams (0.33 moles)______________________________________ Sulfuric acid (51.5 g of 37.5% acid) was slowly added from the dropping funnel into the stirring mixture while maintaining temperature of 35.degree. C. After a one hour reaction time, the mixture was separated into two layers, aqueous and organic, using a separatory funnel. Then the aqueous layer was extracted four times with methylene chloride (40.1 g portions) and discarded. The organic layer, containing most of the TNEO was combined with the extracts and the resulting mixture dried by azeotropic distillation. During this drying, the temperature of the solution was not allowed to exceed 50.degree. C. A small portion of the dried TNEOH solution was used to determine the reaction yield. Vacuum removal of the diluent from the sample (14.6 g) at room temperature left 3.7g of the TNEOH (a white solid with melting point range of 58.degree.-62.degree. C). The TNEOH was formed in a 90% yield.

2. Preparation of TEFO:

Paraformaldehyde (3.9 g) was dissolved in reagent grade concentrated sulfuric acid (110.4 g of 96.5% H.sub.2 SO.sub.4) and then slowly dripped into the well stirred TNEOH solution (44.9 g of TNEOH) prepared in the first step, above. The temperature was maintained at 20.degree. to 25.degree. C. and the stirring continued for one hour. After this time interval, the sulfuric acid layer and the organic layer were separated with the aid of a separatory funnel. The acid layer was extracted once with methylene chloride (66.5 g) and then discarded. Next the extract was combined with the organic layer. This combined solution was washed twice, four times, and three times with 50 ml each of, respectively, water, 3% aqueous sodium bicarbonate and water. After removal of the diluents by using a rotary evaporator and vacuum, an off-white solid remained. This solid, having a melting point range of 59.degree.-61.degree. C., was obtained in a 78% yield.

The crude product was purified by employing a precipitation technique. It was dissolved in ethanol (100 ml) and then precipitated by adding water (100 ml). Filtration and vacuum drying resulted in a 60% total yield of a white solid, which melted at 64.degree. C.

The TEFO produced was mixed with conventional Otto Fuel II at room temperature, in the proportions by weight shown in Table II.

The The results shown in this table indicate the melting points of the TEFO - Otto Fuel II formulations.

The results in Table III indicate the heats of explosion of four (4) different formulations of TEFO and Otto Fuel II.

In the second section of Table III cavity drop tests results are indicated for four (4) different formulations of Otto Fuel II and TEFO.

The results in Table IV indicate the quality of gas (Moles/100 grs), Impetus (ft-lb/lb) and ISp (lb sec/lb) for 16 different formulations of TEFO and Otto Fuel II.

EXAMPLE 2

TEFO as prepared in Example 1 is mixed with conventional diethyl oxalate at room temperature. The results shown in Table V illustrate eight (8) different formulations of diethyl oxalate and TEFO.

The gas generated (moles/100 grams); impetus (ft-lb/lb) and Isp (lb-sec/lb) disclosed in Table V clearly indicate new and unexpected results in chemical and physical properties flowing from the formulation of Otto Fuel II with TEFO.

EXAMPLE 3

TEFO is mixed with a number of conventional solvents including diethyl oxalate, methyethyl ketone and acetone. The results, based upon eight (8) different formulations is set forth in Table VI. The results in Table VII indicate the thermodynamic and test data on TEFO, diethyl oxalate, methyl ethyl ketone and acetone.

EXAMPLE 4

TEFO, acetone, methylethyl ketone were mixed and tested. The experimental data is set forth in Table VIII.

The examples are only intended to be illustrative, since obvious modifications and equivalents in the invention will be evident to those skilled in the chemical arts, and propose to be bound solely by the appended claims.

TABLE II______________________________________Heats of Explosion, cavity drop Test,Density, and Melting Point-Data______________________________________ Density (grs/cc)TEFO 1.70BFDNA 1.72______________________________________IngredientsTEFO Otto-2 Fuel Melting Points (.degree.C.)______________________________________-- 100 -36.510 90 -39.515 85 -40.520 80 -42.025 75 -43.530 70 -45.035 65 -46.540 60 -47.0______________________________________ TABLE III______________________________________Percent Heats of ExplosionOtto-2 Fuel TEFO NOS 365 E.sub.c (cal/gram)______________________________________100 -- -- -732.860 40 -- 942.650 50 -- -1083.540 60 -- -1204.7-- -- 100 893.2______________________________________ Cavity Drop TestPercent cmOtto-II Fuel TEFO NO SET** (2 kilogram weight used)______________________________________100 -- -- 1840 60 -- 10.450 50 -- 3.4-- -- 100 6 to 7______________________________________NO SET (TEGDN = 96, Dibutylsebacate = 3% Ethyl (entralite = 1%) DensityBFDNA 1.72TEFO 1.70DITEFO 1.83 TABLE IV__________________________________________________________________________TEFO, Otto-2 Fuel Formulations__________________________________________________________________________IngredientTEFO -- 5 10 15 20 25 30 35 40Otto-II Fuel 100 95 90 85 80 75 70 65 60Const. Vol. T. (.degree.K.) 2194 2251 2314 2383 2463 2556 2671 2813 2979Const. Press. T. (.degree.K.)* 1390 1434 1503 1615 1753 1901 2052 2234 2363Gas (moles/100 g) 5.417 5.401 5.358 5.387 5.191 5.075 4.946 4.811 4.671(ft-lb/lb) 330755 338408 345008 350703 355732 360995 367656 376618 38740ISP (lb-sec/lb) 205.3 206.9 208.8 211.3 214.5 218.3 222.7 227.6 232.7__________________________________________________________________________TEFO 45 50 55 60 65 70 75Otto-2 Fuel 55 50 45 40 35 30 25Const. Vol. T. (.degree.K.) 3160 3347 3539 -- 3120 3229 3307Const. Press. T. (.degree.K.)* 2522 2681 2838 2987 -- -- --Gas (moles/100 g) 4.533 4.394 4.258 3.994 3.876 3.769(ft-lb/lb) 3989599 409314 419327ISP (lb-sec/lb) 237.7 242.5 247.0 251.2 255 258.4 261.1__________________________________________________________________________ *Constant pressure at 1000 psi TABLE V__________________________________________________________________________Diethyl Oxalate and TEFO Formulations__________________________________________________________________________IngredientDiethyl Oxalate 10 30 50 70 90TEFO 90 70 50 30 10Const. Vol. T. (.degree.K.)* 4394 2866 1994 1664 1314Const. Pre. T. (.degree.K.)** 3326 2291 1283 1161 1010Gas (moles/100 grs) 3.561 4.317 4.746 4.132 3.534IMPETUS (ft-lb/lb) 446467 344124 268111 198720 126135Isp (lb-sec/lb) 259.1 221.3 186.8 167.7 144.6__________________________________________________________________________metyl ethyl Ketare 10 20 30 35 40 50 70 90TEFO 90 80 70 65 60 50 30 10Const. Vol. T. (.degree.K.)* 4154 3032 2335 2166 2057 1867 1527 1145Const. Pre. T. (.degree.K.)** 3249 2407 1527 1380 1334 1258 1119 930Gas (moles/100 grs) 3.829 4.573 5.333 5.300 5.174 4.902 4.326 3.785IMPETUS (ft-lb/lb) 445821 385580 339034 316927 296880 254507 176527 114973Isp (lb-sec/.lb) 258.0 232.2 207.3 202.0 197.5 188.5 168.4 143.3__________________________________________________________________________ *Chamber pressure at 50000 psi **Chamber pressure at 1000 psi TABLE VI__________________________________________________________________________Diethyl Oxalate and TEFO Formulations__________________________________________________________________________IngredientDiethyl Oxalate 32 33 34 35 36 37 38 39 40TEFO 68 67 66 65 64 63 62 61 60Const. Vol. T. (.degree.K.) 2697 2641 2574 2513 2457 2406 2360 2318 2278Const. Press. T. (.degree.K.) 2151 2081 2012 1943 1875 1807 1740 1673 1608Gas (moles/100 g) 4.408 4.454 4.499 4.545 4.591 4.636 4.682 4.726 4.770IMPETUS (ft-lb.lb) 330923 326820 321659 316988 312814 309073 305665 299421Isp (lb-sec/lb) 216.2 213.7 211.2 208.9 206.6 204.4 202.4 200.4 198.6__________________________________________________________________________ TABLE VII__________________________________________________________________________ Thermodynamic and Test Data on Fuels of This Invention__________________________________________________________________________TEFO (% wt) 67 64 70 65 65 65 70 65Diethyl Oxalate (% wt) 33 36 -- -- 17.5 25 -- 20Methyl Ethylketone (% wt) -- -- 30 35 17.5 10 -- 15Acetone (% wt) -- -- -- -- -- -- 30 --Const. Vol. T. (.degree.K.) 2641 2457 2335 2166 -- 2353 2393 2304Const. Press. T. (.degree.K.) 2081 1875 1527 1380 -- 1677 1661 1558Gas (moles/100 g) 4.545 4.591 5.333 5.300 -- 4.850 5.150 4.980Impetus (ft-lb.lb) 326820 312814 339034 316929 -- 318185 338127 319518Isp (lb-sec/lb) 216.2 206.6 207.3 202.0 -- 204.1 208.6 202.7H.O.E. (cal/g) -845 -803 -816 -- -- -- -848 -760Cavity drop test (cm) 10.5 10.5 49 -- -- -- 50 49(2 kg wt.)Density (g/cc) (25.degree. C.) 1.308 1.368 1.247 -- -- -- 1.257 1.301Exotherm T. (.degree. C.) 180 180 203 -- -- -- 209 203TEFO ppt. (.degree.C.) --* -- -30 -25 -45 --* --* --*__________________________________________________________________________ TABLE VIII______________________________________Acetone, Methylethyl ketone and TEFO Formulations______________________________________IngredientAcetone 10 30 50 70 90TEFO 90 70 50 30 10Const. Vol. T. (.degree.K.)* 4215 2393 1882 1543 1161Const. Pre. T. (.degree.K.)** 3275 1661 1258 1122 936Gas (moles/100 g) 3.768 5.150 4.886 4.306 3.762Impetus (ft-lb/lb) 446399 338127 259341 180262 116279Isp (lb-sec/lb) 258.1 208.6 188.1 168.2 143.1______________________________________Diethyl Oxalate 30 25 20TEFO 65 65 65Const. Vol. T. (.degree.K.) 2424 2358 2304Const. Press. T. (.degree.K.) 1807 1677 1558Gas (moles/100 grs) 4.698 4.850 4.980Impetus (ft-lb/lb) 316916 318185 319518Isp (lb-sec/.lb) 206.2 204.1 202.7______________________________________

Claims

1. A liquid fuel formulation comprising a mixture of from about 5 to 40% of a high energy ingredient selected from the group consisting of bis(2-fluoro-2,2-dinitroethyl)amine, bis(2-fluoro-2,2-dinitroethyl)formal and bis(2,2,2-trinitroethyl)formal, and

from 60 to 95% of a mixture of propylene glycol dinitrate, 2-nitrodiphenylamine and di-n-butyl sebacate.

2. A liquid fuel formulation comprising a mixture of a high energy ingredient selected from the group consisting of bis(2-fluoro-2,2-dinitroethyl) amine, bis(2-fluoro-2,2-dinitroethyl) formal and bis(2,2,2-trinitroethyl) formal mixed with diethyl oxalate and methyl ethyl ketone.

3. The formulation of claim 2 wherein the amount of the high energy ingredient is in the range of 50 to 90%.

4. A liquid fuel composition comprising a mixture of propylene glycol dinitrate, 2 nitrodiphenylamine and di-n-butyl sebacate with bis (2,2,2-trinitroethyl) formal.

5. The composition of claim 4 wherein the amount of the bis (2,2,2-trinitroethyl) formal is within the range of 10% to 40% by weight.

6. A liquid fuel composition comprising a mixture of a high energy ingredient selected from the group consisting of bis (2-fluoro-2,2-dinitroethyl) amine, bis(2-fluoro-2,2-dinitroethyl) formal and bis(2,2,2-trinitroethyl) formal mixed with a small quantity of a melting point depressant selected from the group consisting acetone, methyl ethyl ketone and diethyl oxalate.

7. The liquid fuel formulation of claim 6 wherein the amount of the high energy ingredient varies between 30 and 90% of the mixture.

8. The liquid fuel of claim 6 wherein the amount of the melting point depressant varies between 10 and 30% by weight of the total mixture.