US2933382A - Jet fuel compositions - Google Patents

Description

JET FUEL COMPOSITIONS Frederick M. Fowkes, Orinda, Calif., and Francis G. 30110, Alton, Ill., assignors to Shell Oil Company, a corporation of Delaware No Drawing. Application May 6, 1957 Serial No. 657,041

6 Claims. Cree-.5

This invention relates to hydrocarbon fuels, particularlyto so-called jet fuels for use in jet aircraft engines.

nited States Patent O. i-

2,933,382 Patented Apr. 19, 1960 carbons, containing only carbon and fluorine and may be obtained by completely fluorinating a light hydrocarbon distillate fraction, such as a fraction in the kerosene and/ or light lubricating oil distillate range. Preferably the hydrocarbon material to be fiuorinated should contain only a minor amount of aromatic and/ or alicyclic hydrocarbons, i.e., it should be composed predominately of aliphatic, open-chain hydrocarbons.

Typical perfluorocarbons which are useful in the practice of the invention are set forth in Table I.

Perfluorocarbons such as composition F (Table I) or fractions thereof, such as fractions F F F F and F (Table I) are suitable foam inhibitors for hydrocarbon jet fuels. They are essentially aliphatic compounds which contain carbon atoms arranged in a normal (straightchain) or branched chain-structure.

TABLE I Properties of various perfluorocarbons Molec- Index of Solubility, wt. Empirical Identiular Density Relrao- Percent at 27 0. Description Formula gcatilgn1 (Weight) Boiling Point, C. C.) tron I Benzene m o a rox. approx. approx. y pp con 1 onion Perfiuorokerosene FCX329) C 21%".-. C 645 20-65 at 10 mm. Hg 1. 922 1. 3082 1 1 Pertiuorokerosene lFCX-IiO) C:4F;n.. D 738 65-130 at 10 mm. Hg. 1. 994 1.3171 3.4 1 1 Perfiuorolube oil (FOX-512) 0201 4;... E 1,038 70240 at 10 mm. Hg 2.059 1.3369 2.7 1 1 Perfluorolube oll (FOX-412) OZ1F4 F 1, 126 130-240 at 10 mm. HQ 1. 3430 1 1 1 This material may be further fractionated into 5 different fractions having the following boiling point ranges at 10 mm. Hg abs. pressure and identified as: j 6 C I i-Fraction No. 1 130-150 lib-Fraction No. 2 150-170 FaFraction No. 3 170-190 F Fraction No. 4 190-210 Fit-Fraction No. 5 210-240 In our copending application, Serial No. 560,867, filed January 23, 1956, now abandoned, of which the present application is a continuation-in-part, it has been shown that conventional foam inhibitors such as silicone polymers are ineffective foam inhibitors for jet fuels, but that certain hydrocarbon-insoluble perfluorocarbons are effective foam inhibitors for jet fuels. However, the perfluorocarbon foam inhibitors tend to separate out of solution' during storage. Therefore, caution must be taken to thoroughly mix stored fuels containing a perfluorocarbon foam inhibitor to redisperse it otherwise the fuel will not be sufficiently foam resistant.

Solubilization of the perfluorocarbon anti-foam agent in the jet fuel can be obtained by the use of solubilizers such as oil-soluble alcohols and oil-soluble amines, but they are unsuitable because they interfere with thefoam inhibiting properties of the perfluorocarbons in the hydrocarbon fuel.

It has now been discovered that storage stable and improved foam resistant hydrocarbon jet fuels are provided by addition to the jet fuels of a minor amount of from about 0.0001% to about 1%, preferably from about 0.01% to about 0.1% by volume, of a hydrocarboninsoluble perfiuorocarbon (containing only carbon and fluorine) having at least 12 carbon atoms and mixtures thereof, and as anti-foam enhancers and emulsifiers for the perfluorocarbons, a minor amount of from about 0.01% to about 10%, preferably from about 0.1% to about 5%, of a polyfiuoroamide containing a hydrocarbon-insoluble perfiuorohydrocarbyl group and an oilsolubilizing aliphatic group in the molecule.

The perfiuorocarbon foam inhibiting agents are prepared by the method described in the articles by Fowler et al. and Burford et al. in the March 1947 issue of Ind. and Eng. Chem. (vol. 39, No. 3, pages 292 and 319). The perfluorocarbons are essentially aliphatic perfluoro- Mixtures of perfluorocarbons boiling above C. at

10 mm. Hg pressure and having more than 12 carbon fying agents for the perfiuorocarbon foam inhibitors in the jet fuel are suitably and readily prepared by reacting perfiuorocarboxylic acid, preferably a perfiuoroaliphatic monocarboxylic acid having from 4 to 22 (better 8 to 18) carbon atoms in the molecule with a hydrocarbon-soluble amine, preferably an aliphatic monoamine or an N-alkyl polymethylene diamine where the aliphatic radical contains from 8 to 22, preferably 12 to 18, carbon atoms. Also the perfluoroamide can be prepared by reacting an organic carboxylic acid preferably a hydrocarbon-soluble aliphatic monocarboxylic acid having from 8 to 18 carbon atoms in the molecule with a perfluoroalkylamine.

The perfiuoro acids include perfiuoro monoand polycarboxylic acids. The C -C perfluoroaliphatic monocarboxylicacids are preferred. Examples of such acids are perfluorobutyric acid, perfluorocaproic acid, perfluoroheptanoie acid, perfluorocaprylic vperfluorocapric acid, perfluorolanric acid, perfluorostearic acid and mixtures thereof. Other suitable perfluoroalkyl substituted carboxylic acids include perfluoroalkyl aryl carboxylic acids such as C C perfluoroalkylbenzoie or salicylic acid; perfiuoroalkyl substituted polycarboxylic acids such as perfluorooctyl, perfluorodecyl or perfluorododecyl succinic, adipic or sebacic acids.

Amines for use in amidizing the above acids include oil-soluble monoor polyamines containing at least one alkyl radical of at least 8 carbon atoms. Monoamines an w of this type include octyl, decyl, dodecyl, tetradecyl, hexadecyl and octadecyl monoarnines. In thesecondary amines the alyl radicals can be the same or different. Aliphatic polyamines include N-alkyl substituted alkylene polyamines wherein the alkyleneradical contains from 2 to 10 carbonatoms, such as N alkyl substituted ethylene diamine, propylene diamine, butylene diamine, diethyl'ene tetramine, tetraethylene pentamine and the alkyl substitu ent group(s) can be attached to the same or different nitrogen atoms in the molecule and should generally have from 8 to 22 carbonatoms. Preferred N-alkyl substituted methylene polyamines include N-C alkyl trimethylene diamine, N-C -alkyl trimethylene diamine, NC -alkyl trimethylene diamine, N-C' trimethylene diamine, and the like.

Also the above corresponding non-fiuorinated acids such as C Ci aliphatic monocarboxylic acids e.g.-, caprylic acid, lau'ric acid or stearicacid can be amidized with peflluoroalkylamines such as perfiuorooctylarnine, perfiuorododdecylamine, perfluorooctadecylamine, N-perfluoro C1248 alkyl trimethylene diamine and the like.

Examples of perfiuoroamides are decyl perfluorocaprylamide, dodecyl perfiuorocaprylamide, octadecyl perfluoro; caprylamide, octyl. perfluorolaurylamide, octalperfiuorostearylarnide, N-C alkyl trimethylene perfiuorocaprylamide, octadecyl perfluorodo'decyladipylamide, perfiuoro-octyl caprylamide, perfluoro-octadecylcaprylamide, perfiuorodod'ecyl stearylamide and mixtures thereof.

The jetfuels for air-crafts" are commonly known bythe JP'-designation such as JP l', JP-3, JP-4roi ZIP- 5 under MIL-F-56 24 B3 specification, the properties of; which are given in TableII.

boil vigorously and to foam as a result thereof. It is considered that foaming is caused by the vigorous boilingof the jet fuel (due to its volatile low boiling constituents) in the presence of and/ or aggravated by the presence of relatively high boiling hydrocarbons, e.g. those hydrocarbons boiling in the range of from about 450 F. to about 600 F. and higher. Accordingly, due to the presence of a greater amount of low boiling hydrocarbons, as evidenced by the higher Reid Vapor Pressure, and also dueto the presence ofa greater proportiotrof high. boiling hydrocarbons, a JP-3 jet fuel boils and foams much more than a JP type of jet fuel. Jetfuels which have Reid- Vapor Pressure between about 0.5 and about 10 lbs. per sq. in at 100" F. and especially between about 2 and 7 lbs. per sq, in. are most susceptible to foam upon boiling and are advantageously improved in this respect,

i.e., foaming is essentially eliminated by addition to such jet fuels (JP-3 fuels), of perfluorocarbons and are rendered storage'stabl'e by addition thereto of polyfluoro amidesi' In order to demonstrate the elfectiveness of compositions of this invention for their stability and resistance to foaming, a number of tests were carried out. The

test apparatusfor measuring foamingconsisted of a long vertical 1 /2 inch diameter glass tube, representinga fuel tank, charged with 100 ml. of a representative type of jet fuel (JP-3). The air space above the test mixture was evacuated at a rate representative of the change in atmospheric'pressure- (ratio-of-climb performance) which wouldbe experienced, by atypical jet aircraft in a rapid. climb. The foaming'tendency'was judgedby the height offoam column producediinthe.tube;ab.ove the fuel liquid.

TABLE III [Basez JP-a'FuelJ- Per- Per- Height Separa- Foam Inhibitor cent Emulslfler cent of tion Vol. wt. Foam, Time in 1. None. N e 2. Dow Corning Silicone No. 200 0:02 do 29 3. Dow Corning Silicone No. 500 R 0.101 -do 34 4. 1,3 bis (trifiuoromethyl) benzene... 0.01v do 30 2 hours 5. Perfluorodimethylcyelohexane.. 051 .do 28 Do. 6. Perflnorocaprylic'aeid; 0:1: do; 30 Do; 7. F 2 Do. 8. 3 Do. 9; i 3" Do. 10. 3. Do. 11.1%-. alkyl" trimethylene 30' 2 days 'fluorocaprylamidei 12. Ft... octadecylperfluorocaprylamide. 0.5 30, D0. 13. F5. 0.02 N Or alkyl trimethylene 0.5 1 5 days fiuorocaprylamide. t 14. 0.02,. ,N-Q trimethylene, 0.5 1. Do.

, fluorocaprylamide. 15. 0.02 octadecylperfluoroeaprylamide. 0. 5' 3 Do.

1 Dow Corning silicones are methyl silicone polymersdescribed-in the Jour. of Ind. Hygiene and Toxicology No, 1948, pp. 332-'352 and in Dow CorningBulletinentitled .New Engineering Materials DC Silicones' b Note Table I for identification of compounds.

ASTM Distillation:

10% Distillation 20% Evaporation at. F 90% Evaporation at F End Point 11... Total Sulfur, Percent wt. Mercaptan sulfur, percent wt. Aromatics, vol. percent; Freezing Point, F Gravity, API

Jet fuels with the above characteristics .upon being sub:

jected to-a rapid decreasein ambientpressure; tend to.

leve1 'I he stability was measured by noting the time ittookfor separation of the perfiuorocarbon from the fuelgcompositions; at room temperature. The results of the. variousjtests are set forth in Table III.-

Erormtheabovedata it can bQItOtedthat conventional foam inhibitors such. as silicone polymers (compositions land 3-); or;certainfluorine containing compounds (com: po iti ns 1- are-imi a ve as oam i i or in j uel'anda e n t bl P fiuo oearbons wh c e f ctive foam inhibitors are unstable; separating out. of the fuel (JP-3) inaboutl hours (compositions 7 -10), The polyfluoroamides. are ineffective. as, .foarn inhibitors, but theafue contain na he n s r e b e p i n 1 1 and.l2.) However, when the twoadditives are used together in the fuel, foaming is inhibited andthe stability asreatln mproved (n ina io s 1. .4 and 5). "th

patent application is a continuation-in-part of copending patent application Serial No. 560,867, filed January 23, 1956, which is, in turn, a continuation-in-part of patent application Serial No. 204,834, filed January 6, 1951, now abandoned.

We claim as our invention:

1. A stable, non-foaming petroleum hydrocarbon jet fuel composition consisting essentially of a major amount of a petroleum hydrocarbon jet fuel having a boiling range from about 240 F. to about 600 F. and containing from about 0.001% to about 1% by volume of a hydrocarbon-insoluble saturated perfiuorocarbon having from 12 to 21 carbon atoms and having a boiling point range of from about 20 C. to about 240 C. at mm. Hg and from about 0.01% to about 10% of a hydrocarbon dispersible polyfiuoroamide of a saturated perfiuoroaliphatic monocarboxylic acid having from 4 to 22 carbon atoms and an alkyl amine having 8 to 22 carbon atoms in the alkyl chain.

2. A stable, non-foaming petroleum hydrocarbon jet fuel composition consisting essentially of a major amount of a petroleum hydrocarbon jet fuel having a boiling range from about 240 F. to about 600 F. and a Reid Vapor Pressure above 0.5 lb. per sq. in. at 100 F. containing from about 0.01% to about 0.1% by volume of a hydrocarbon-insoluble saturated perfiuorocarbon having from 12 to 21 carbon atoms and having a boiling point range of from about 20 C. to about 240 C. at 10 mm. Hg and from about 0.01% to about 10% of a hydrocarbon dispersible polyfiuoroamide of an oil-soluble saturated perfiuoroaliphatic monocarboxylic acid having from 12 to 18 carbon atoms and an oil-soluble amine having an alkyl radical of from 8 to 22 carbon atoms.

3. A stable, non-foaming petroleum hydrocarbon jet fuel composition consisting essentially of a major amount of a petroleum hydrocarbon jet fuel having a boiling range from about 240 F. to about 600 F. and a Reid Vapor Pressure above 0.5 lb. per sq. in. at 100 F. containing from about 0.01% to about 0.1% by volume of a hydrocarbon-insoluble saturated periluorocarbon having from 12 to 21 carbon atoms and having a boiling point range of from about 20 C. to about 240 C. at 10 mm. Hg and from about 0.1% to about 10% of a hydrocarbon dispersible polyfiuoroamide of an oil-soluble saturated aliphatic monocarboxylic acid having from 12 to 18 carbon atoms and an oil-soluble perfluoroalkylamine the perfiuoroalkyl radical having from 8 to 22 carbon atoms.

4. A stable, non-foaming petroleum hydrocarbon jet fuel composition consisting essentially of a major amount of a petroleum hydrocarbon jet fuel having a boiling range from about 240 F. to about 600 F. and a Reid Vapor Pressure of 5-7 lbs. per sq. in at F. containing from about 0.01% to about 0.1% by volume of an aliphatic perfiuorocarbon having at least 21 carbon atoms and a boiling point of at least C. at 10 mm. Hg and from about0.5% to about 5% of N-C alkyl trimethyleue fluoro caprylarnide.

5. A stable, non-foaming petroleum hydrocarbon jet fuel composition consisting essentially of a major amount of a petroleum hydrocarbon jet fuel having a boiling range from about 240 F. to about 600 F. and a Reid Vapor Pressure of 57 lbs. per sq. in. at 100 F. containing from about 0.01% to about 0.1% by volume of a mixture of C F aliphatic perfiuorocarbon having a boiling point of 130-240 C. at 10 mm, Hg and C P- aliphatic perfiuorocarbon having a boiling point of 20-65 C. at 10 mm. Hg in the mole ratio of from 4:1 to 2:1 respectively, and from about 0.5% to about 5% of N-C 1248 trimethylene fiuorocaprylamide.

6. A stable, non-foaming petroleum hydrocarbon jet fuel composition consisting essentially of a major amount of a petroleum hydrocarbon jet fuel having a boiling range from about 240 F. to about 600 F. and a Reid Vapor Pressure of 5-7 lbs. per sq. in. at 100 F. containing from about 0.01% to about 0.1% by volume of a mixture of C 11, aliphatic perfiuorocarbon having a boiling point at 130240 C. at 10 mm. Hg and C F aliphatic perfluorocarbon having a boiling point of 65- 130 C. at 10 mm. Hg in the mole ratio of from 4:1 to 2:1 respectively, and from about 0.5% to about 5% of N-C trirnethylene fiuorocaprylamide.

References Cited in the file of this patent UNITED STATES PATENTS 2,394,596 Davis et a1. Feb. 12, 1946 2,680,717 Little Jan. 8, 1954 FOREIGN PATENTS 202,976 Australia July 19, 1956

Claims (1)

1. A STABLE, NON-FOAMING PETROLEUM HYDROCARBON JET FUEL COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR AMOUNT OF A PETROLEUM HYDROCARBON JET FUEL HAVING A BOILING RANGE FROM ABOUT 40*F. TO ABOUT 600*F. AND CONTAINING FROM ABOUT 0.001% TO ABOUT 1% BY VOLUME OF A HYDROCARBON-INSOLUBLE SATURATED PERFLUORCARBON HAVING FROM 12 TO 21 CARBON ATOMS AND HAVING A BOILING POING RANGE OF FROM ABOUT 20*C. TO ABOUT 240*C. AT 10 MM. HG AND FROM ABOUT 0.01% TO ABOUT 10% OF A HYDROCARBON DISPERSIBLE POLYFLUORAMIDE OF A SATURATED PERFLUOROALIPHATIC MONOCARBOXYLIC ACID HAVING FROM 4 TO II CARBON ATOMS AND AN ALKYL AMINE HAVING 8 TO 22 CARBON ATOMS IN THE ALKYL CHAIN.