US3476533A - Jet fuel composition - Google Patents

Description

Patented Nov. 4, 1969 3,476,533 JET FUEL COMPOSITION George W. Eckert, Wappingers Falls, N.Y., assignor to Texaco Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed July 15, 1965, Ser. No. 472,354

Int. C1. C] 1/26 US. CI. 4458 9 Claims ABSTRACT OF THE DISCLOSURE A jet fuel composition boiling in the gasoline and/or kerosene ranges containing trimer acid and a monoamine salt of a hydrocarbon substituted hydrogen phosphate, in an amount elfective to provide a fuel having antiwear properties.

This invention relates to a novel jet fuel composition and to a method for operating aturbine engine. The jet fuel of this invention comprises a hydrocarbon or a mixture of hydrocarbons in the gasoline and/ or kerosene boiling ranges containing trimer acid and an amine salt of a hydrocarbon substituted hydrogen phosphate, the additives being present in an amount effective to provide a fuel having a high level of anti-wear properties in addition to the other essential properties for these fuels.

Turbine engines are widely employed both in stationary power generating installations and for powering jet aircraft. These are high-powered engines and consume enormous amounts of the liquid hydrocarbon fuel being used. The fuel requirements of the engine are satisfied with a fuel system having a high capacity fuel pump to deliver the required quantity of fuel.

Distillate petroleum hydrocarbon fractions in the gasoline and kerosene boiling ranges have essentially no lubricity or lubricating value. This is particularly true of light naphtha which is often economically attractive for fueling power turbines. In addition, the high solvent action of the noted fractions makes it extremely difficult if not impossible to maintain any lubricant on the wearing surfaces that are constantly being washed by a large volume of fuel. It is for this reason that fuel pumps on turbine engines are subjected to serious wear which leads to failme of the fuel pump and shut down of the engine.

Turbine fuel compositions having anti-wear properties have been proposed heretofore to solve the problem of fuel pump wear. To date, no turbine fuel composition has been provided which combines outstanding anti-wear properties with an acceptable level of essential fuel properties. In general, it has not been possible as a practical matter to formulate a turbine fuel having a Ryder gear test value of 1000 p.p.i., the minimum set by Pratt and Whitney engine manufacturers without overloading the fuel with additives resulting in an interior fuel having an unacceptable level of deposit and coke formation.

To be acceptable, the fuels of the invention must meet other stringent requirements pertaining to turbine fuels. In particular, the fuels must be thermally stable, have certain anti-oxidant properties and have a satisfactory Water Separometer Index. The latter property is critical in fuels for aircraft service because the entrainment of water in the fuel can lead to engine failure. Also, the fuels must be non-corrosive to steel, copper, and silver, as the fuels contact these metals in service. The fuels should also be free of metallic compounds, sulfur compounds and halogen compounds, because fuels containing these types of additives are either corrosive or form corrosive combustion products.

It is an object of the present invention to provide a method for operating a turbine engine and a unique fuel composition which substantially reduces or overcomes the fuel pump wear problem encountered in the operation of turbine engines.

In accordance with this invention, a turbine engine equipped with a fuel system incorporating a fuel pump is run on a distillate hydrocarbon fraction in the gasoline and/or kerosene boiling ranges containing effective wear inhibiting amounts of trimer acid in combination with an amine salt of a hydrocarbon substituted monohydrogen phosphate. The novel fuel composition comprises a liquid hydrocarbon boiling in the gasoline and/or kerosene boiling ranges containing the aforesaid trimer acid and amine salt of a hydrocarbon substituted hydrogen phosphate.

The method of operating a turbine engine and the fuel composition of the invention are outstanding effective for substantially reducing or eliminating fuel pump wear thereby overcoming what has been a serious limitation in the extended operation of such an engine. This performance is realized with the specified additive combination, the individual additives being ineffective for producing a fuel having an acceptable level of anti-wear properties.

The base fuel of the invention is a hydrocarbon or mixture of hydrocarbons in the gasoline and/or kerosene boiling ranges. Generally, such base fuels will boil in the range from about 90 to 500 F. Typical fuels for turbine engines include J P-3 a mixture of about 70 percent gasoline and 30 percent light distillate having a 90 percent evaporated point of 470 F., LIP-4 a mixture of about 65 percent gasoline and 35 percent light distillate and JP5, an especially fractionated kerosene having a high flash point and a low freezing point. Lead compounds, such as tetraethyl lead, are never employed in jet fuel compositions.

The fuel of the invention consists of a major portion of the base fuel and an effective wear-inhibiting amount of the additive combination consisting of trimer acid and the amine salt of dialkyl hydrogen phosphate. Generally both of these additives are employed in an amount ranging from about 0.001 to 0.05 weight percent with the preferred range being from 0.005 to 0.025 weight percent. It is not necessary that there be present in the fuel equal amounts of the two additives to obtain the advantages of the invention so long as the concentration of each falls within the specified amounts. Indeed, it has been found advantageous at times to employ an excess of the aminephosphate salt amounting to two or more times the amount of the trimer acid. The broad concentration range for each additive corresponds to about 3 to 65 p.t.b. (pounds of additive per thousand barrels of fuel).

Trimer acids used in the turbine fuel of the invention are fatty materials produced by subjecting unsaturated fatty acids having between 12 and 22 carbon atoms per molecule, preferably about 18 carbon atoms, to condensation by moderate steam pressures of from to 300 p.s.i.g. at temperatures from 260 to 360 C. for a period of from about 3 to 8 hours. Processes for forming these acids are set forth in such patents as US. 2,482,761, 2,631,979 and 2,632,695. Another method for preparing the trimer acid materials broadly comprises heating a short chain aliphatic alcohol ester of a diethylenic fatty acid at about 300 C. for several hours in an inert atomsphere. The resulting polymerized esters containing trimer acid material are then separated by distillation and hydrolyzed with hydrochloric acid or its equivalent. Patty oils have also been heat polymerized and thereafter hydrolyzed to produce the polymer acids. The trimer acid is readily separated by distillation or by a solvent extraction process from the monomeric, dimeric and higher polymeric materials usually co-produced in the foregoing methods.

The trimer acids used in the present invention, although preferably conjugation products of three of the same molecules which are dior polyethylenic, are also products of the combination of monoethylenic compounds and polyethylenic compounds, for instance, linoleic acid and oleic acids trimerized to become the trimer of linoleic and oleic acids. It is essential to have at least one polyethylenic compound present in order to form the trimer acid.

Specific fatty acids useful for preparing trimer acid from the class of ethylenic carboxylic acids having from 12 to 22 carbon atoms include 4-dodecanoic, 5,9-dimethyl-2,8-decadienoic, myristoleic, palmitoleic, oleic, linoleic and erucic acid. The preferred acid is linoleic acid on the basis of availability from which is produced the preferred trimer of linoleic acid. This particular trimer acid is produced commercially under the name Empol 1040 by Emery Industries. All of the above acids are generally obtainable by hydrolyzing vegetable oils, such as linseed oil, soybean oil, cottonseed oil, and peanut oil. A surprising feature of the invention is that dimer acid is not effective for imparting anti-wear properties and Water Separometer Index values to the turbine fuel of the invention.

The second essential component of the additive combination is an amine salt of a hydrocarbyl substituted hydrogen phosphate. These salts correspond to the general formulas:

wherein R is a hydrocarbyl radical having from 4 to 24 carbon atoms, R and R" is hydrogen or a hydrocarbyl radical having from 1 to 24 carbon atoms and R is a hydrocarbyl radical having from 1 to 24 carbon atoms. R, R, R" and R may be alkyl, alkaryl or aryl hydrocarbyl radicals. R is preferably a tertiary alkyl radical having from 8 to 22 carbon atoms and R is preferably an alkyl radical having from to 22 carbon atoms. The preferred amines are the t-alkyl primary amines in which the alkyl radical has from 4 to 22 carbon atoms. The salts are generally a 50:50 (mole basis) mixture of A and B above, but also can be predominantly A or B.

The amine salt of a hydrocarbyl substituted monohydrogen phosphate is prepared by reacting a suitable amine and a hydrocarbyl acid phosphate generally in a mole ratio to produce the indicated salt so that the amine is present in an amount theoretically equivalent to the hydroxy groups in the hydrogen phosphate. Examples of suitable amine salts include:

t-butyla'mine mono-di-dodecyl acid phosphate t.-C alkyl primary amine mono-di-octyl hydrogen phosphate t-C alkyl primary amine mono-di-octyl hydrogen phosphate t-C alkyl primary amine mono-di-octyl hydrogen phosphate stearylarnine mono-di-amyl acid phosphate t-octylamine mono-2-ethylhexyl acid phosphate cyclohexylamine di-Z-ethylhexyl acid phosphate Di-n-butylamine mono-di-lauryl acid phosphate trilaurylamine mono-di-stearyl acid phosphate pyridine mono-di-hexyl acid phosphate aniline mono-di-decyl acid phosphate oleylamine mono-di-oleyl acid phosphate amylamine mono-di-cresyl acid phosphate morpholine mono amyl acid phosphate piperidine mono-di-octyl acid phosphate.

Minor amounts of other additives may be employed in the turbine fuel of the invention. It is conventional to employ a hindered phenol in fuel compositions in an amount effective to impart good oxidation inhibiting prop erties to the fuel. Effective phenols include 2,6-di-t-butyl- 4-methyl phenol, 2,6-t-butyl phenol, 4,4'-methylene bis (2,6-di-t-butylphenol), 2,6-di-t-butyl-4-di methylaminomethylphenol, 2,4,6-tri-t-butylphenol, and 2,4-dimethyl-6- t-butyl phenol. Generally, the phenol is employed in a concentration ranging from about 1 to 30 pounds per barrel of fuel.

The anti-wear properties of the fuel composition can be enhanced by adding a small amount of a free acid of the type employed for forming the salt described above. These acids are the hydrocarbyl hydrogen phosphate having the formulas A and B below:

wherein R'" has the values noted above. The commercial alkyl hydrogen phosphates are generally 50:50 (mole basis) ratio mixture of A and B and are designated as mono-dialkyl acid phosphates. The alkyl hydrogen phosphates also can be predominantly A or B. Effective acids include: mono-di-octyl acid phosphate, mono-di-lauryl acid phosphate, mono-di-phenyl acid phosphate, mono-di-cresyl acid phosphate, mono-di-oleyl acid phosphate, mono-distearyl acid phosphate, mono-octyl acid phosphate, dioctyl acid phosphate, and mono-di-cyclohexyl acid phosphate. The acids are generally employed in an amount ranging from about 1 to 20 pounds per thousand barrels of fuel.

The following examples illustrate the practice of this invention. The base fuel employed in the Wear tests was an S0 extracted parafiinic fuel described below:

TABLE I.INSPECTION TESTS ON BASE FUEL The' anti-wear properties of the fuel of the invention was determined in the Ryder Gear Test and in a modified Navy Four-Ball Wear Test using the above noted base fuel. The Ryder Gear Test is described in US. 3,134,737 and Navy Four-Ball Wear Test is described in US. 3,050,- 466 and was modified for testing the fuel of the invention by running the test under a load of 5 kg. at 1800 rpm. for 1 hour and then measuring the Scar Diameter in millimeters.

The Water Separometer Index (W .81.) value of the fuel of the invention was determined according to Federal Test Method 79la-3256 entitled Determination of Water Separation Properties of Aviation Turbine Fuels. According to this test, 2,000 cc. of fuel plus 2 cc. of water are circulated in a closed system by means of a small gear pump having an output rating of 400 cc. per minute. The microammeter in the apparatus is set before water addition so that the Water Separometer Index value of the base fuel without Water is 100. Fuel and water are circulated for five minutes to insure complete mixing of the waterfuel mixture. A portion of this fuel mixture is then circulated through a glass system at a rate of cc./min. This effiuent passes through a glass fiber filter coalescer and then through a glass tube equipped with a light and photoelectric cell for determining'the light transmission upon which the Water Separometer Index is based. The Water Separomete'r Index value of the circulatd fuelwater mixture is taken in the photoelectric measuring device after the mixture has been passed through the glass filter. The higher the Water Separometer Index the better the' fuel is with respect to its water separation properties. A fuel must have a minimum value of 85 to pass the miliary specification MIL-J-5624F for these fuels. Additive concentrations are shown as p.t.b., pounds of additive per 1000 barrels of fuel.

TABLE II.--TESTS RESULTS WITH NAgITI-WEAR ADDITIVE F RMULATIO Base Fuel, Base Fuel plus- No Anti-wear Additive Addi- Additive A tive B Additive Compositions:

(a) Trimer Acid PTB 30 30 (b) Pnmene Bl-R 3 Salt of mono-dioctyl acid phosphate, PTB 60 30 (c) AO-29 PTB 15 10 (d) Mono-di-Octyl acid phosphate, PTB 10 Tests:

Ryder Gear Test, p.p.i 443 1, 070 1, 435 W.S.I. 97-99 95 94 Modified Quickie Corrosion Test (Cold Rolled Steel) Rust, percent (24 hrs.):

Fuel Layer 60-70 0 0 Water Layer 100 25 10 Silver Corrosion 2 (Shell CL-l Test Copper Corrosion Test 122 F 3 hrs., Rating lA 1A 1A Luminometer N 0. 79. 2-86. 0 85. 4 80. 7 CFR Fuel Coker Test 400 F./

Rating 2 1 1 Pressure Increase 0 0 0 l 2,6-di4z-butyl-4-methyl phenol anti-oxidant.

2 90/10 volfiUdex Raffinate/xylene fuel.

8 Primene 81-R is a tertiary alkyl primary amine in which the alkyl chain is a mixture of branched chain isomers having from 11 to 14 carbon atoms.

4 Preparedfrom linoleic acid.

6 No corrosion.

TABLE IIL-FOUR-BALL WEAR TEST Base Blend Blend Fuel A B Trimer Acid, PTB 30 30 Primene 81-R Salt of mono-di-octyl acid phosphate, PTB 60 3O Mono-dl-octyl acid phosphate, PTB.. Scar Diameter, Min. (1,800 r.p.m. 5 kg 1 hr. R.T.) 0. 597 0. 241 0.262

TABLE IV.COMPARISON OF TRIMER ACID AND DIMER ACIDS IN AN ANTI WEAR FORMULATION Blend Blend C D Additive Composition:

Trirner Acid, PIB- 30 Dimer Acid, PTB 30 Primene til-R Salt of mono-di-octyl acid phosphate PTB 30 30 A029, fPTB 10 1o tMono-di-octyl acid phosphate, PTB 10 10 es s:

Ryder Gear Test pp 1 1, 435 760 W.S.I. 87 Fails 1 90/10 vol. Udex Raffinate/xylene fuel. solRfi m in straight run kerosene having an 1131 of 328 and an EP 01 Blend D which contained the dimer acid failed both the Ryder Gear Test and the Water Separometcr Index test and is unacceptable as an anti-wear fuel.

The turbine fuel of the invention possesses outstanding anti-wear properties and a high Water Separometer Index as well as good corrosion inhibiting properties and thermal stability which are essential in a turbine fuel. In particular, this fuel overcomes the problem of fuel pump wear in the fuel system of a turbine engine without the use of additives containing metal compounds, sulfur compounds, or halogen compounds.

Obviously, many modifications and variations of the invention, as hereinabove set forth, may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be made as are indicated in the appended claims.

I claim:

1. A jet fuel composition comprising a mixture of hydrocarbons boiling in the gasoline and/or kerosene boiling ranges containing from about 0.005 to 0.025 weight percent of carboxylic trimer acid and from about 0.005 to 0.025 weight percent of a mono amine salt of a hydrocarbon hydrogen phosphate, said additive combination being efiective to impart anti-wear properties to said fuel composition.

2. A jet fuel according to claim 1 boiling in the range from 500 F.

3. A jet fuel according to claim 1 in which said trimer acid is derived from polymerized linoleic :acid.

4. A jet fuel composition according to claim 1 in which said mono amine-phosphate salt has the formula:

in which R is a hydrocarbyl radical having from 4 to 24 carbon atoms, R and R" are selected from the group c nsisting of hydrogen and a hydrocarbyl. radical having from 1 to 24 carbon atoms and R is a hydrocarbyl radical having from 1 to 24 carbon atoms.

5. A jet fuel composition according to claim 1 in which said salt is the salt of a tertiary C alkyl hydrogen phosphate.

6. A composition according to claim 5 in which said salt is formed from a tertiary C alkyl primary amine and a mono-di-octyl hydrogen phosphate.

7. A jet fuel composition according to claim 1 containing from about 0.0005 to 0.008 weight percent of a hydrocarbyl hydrogen phosphate.

8. A method of operating a turbine engine which comprises supplying to and burning in said engine a jet fuel composition comprising a mixture of hydrocarbons boiling in the gasoline and/or kerosene boiling ranges containing from about 0.005 to 0.025 weight percent of carboxylic trimer acid and about 0.005 to 0.025 weight percent of a mono amine salt of a hydrocarbyl hydrogen phosphate e'ifective to impart anti-wear properties to said fuel composition.

9. A method of operating a turbine engine according to claim 8 in which said trimer acid is derived from polymerized linoleic acid and said mono amine-phosphate salt has the formula:

in which R is a hydrocarbyl radical having from 4 to 14 carbon atoms, R and R" are selected from the group consisting of hydrogen and a hydrocarbyl radical having '7 8 from 1 to 24 carbon atoms and R is a hydrocarbyl 3,251,663 5/1966 Andress et a1. 44-66 radical having from 1 to 24 carbon atoms. 3,273,981 9/ 1966 Furey 4466 3,320,041 5/ 1967 Hemmingway 44--58 References Cited DANIEL E. WYMAN, Primary Examiner UNITED STATES PATENTS 5 Y. H. SMITH, Assistant Examiner 2,631,979 3/1953 McDermott 106-14 2,863,746 12/1953 Cantrell Et al. 44-72 3,043,542 8/1962 Tierney et a1. 25247.5 4463, 72, 76