US3449096A - Jet fuel compositions containing ammonium oxidates - Google Patents

Description

United States Patent Olhce US. Cl. 44-71 4 Claims ABSTRACT OF THE DISCLOSURE A jet fuel composition containing an ammonium salt of a lubricating oil oxidate which gives high temperature stability of the fuel.

This invention relates to improved jet fuel compositions having excellent high temperature stability.

The composition of the present invention has particular application in the operation of jet aircraft. At supersonic speeds the fuel in a jet aircraft is subjected to high temperatures, largely due to its use as a heat sink for cooling the airframe and the lubrication system and due to exposure to the very high temperatures in the vicinity of the fuel nozzle. Petroleum fuels employed in jet aircraft engines often tend to decompose under the temperatures to which they are subjected with the formation of carbonaceous deposits in the fuel lines, filters and nozzle which can in time prevent operation of the aircraft. The present invention provides a petroleum fuel containing an ashless additive for improved stability at temperatures encountered in the fuel systems of jet aircraft.

The fuels with which this invention is especially concerned are hydrocarbon fractions having an initial boiling point of at least about 250 F. and an end point not higher than about 700 F. Thermal stability is usually imparted to jet fuels in either of two main ways, namely, by refining techniques such as hydrogenation or by the use of additives In accordance with the present invention, an excellent heat stable compositon is formed by the addition of from about two to 200 pounds of an ammonium salt of a refined paraflinic lubricating oil liquid oxidate per thousand barrels of a hydrocarbon jet fuel having a boiling range of between from 250 F. to 700 F. A preferred range of said ammonium oxidate is from five to 50 pounds per thousand barrels of hydrocarbon.

Further, in accordance with the present invention, the heat stability of a hydrocarbon jet fuel containing aforesaid ammonium oxidate is still further improved by the addition of from one-half to five pounds per thousand barrels of N,N'-disalicy1idene-1,2-diaminop-ropane as a carbonaceous deposit inhibitor, hereinafter called C.D.I.

The wax oxidate employed in the preparation of the ammonium salt was derived in accordance with the procedure of US. 2,978,472 issued Apr. 4, 1961 to George B. Kirkwood and John H. Greene. More specifically, a refined paraffinic lubricating oil having a viscosity of between 140 and 180 Saybolt Universal seconds (S.U.S.) at 100 F. by A.S.T.M. Method of Test D88-56, a pour point less than 5 F a Lovibond /2" cell color rating of less than and an aniline point between 215 and 225 is reacted with air in the presence of the potassium per- 3,449,096 Patented June 10, 1969 manganate type oxidation catalyst at a temperature of 330-370 F. and a pressure of 50-90 p.s.i.g. to yield a product having a neutralization number between 55 and 80. This usually requires from 1 to 3 hours. Oxidates produced in this manner generally have a saponification number (Sap. No.) between and 200, an unsaponifiable content less than about 55%, a viscosity less than 200 Saybolt Universal seconds (S.U.S.) at 210 F., a color rating less than 200 in the Lovibond /2 cell, and a pour point less than 30 F.

The wax oxidate was then reacted with ammonia by bubbling anhydrous ammonia into the oxidate for about one hour at room temperature and atmospheric pressure and then heating the reaction mixture to 200 F. of 3 hours under partial vacuum to remove excess ammonia. The resulting ammonium salt was semi-liquid in nature and was soluble in jet fuel. The N,N'-disalicy1idene-1,2- diaminopropane (C.D.I.) used in the examples was purchased as a standard article of commerce.

In order to demonstrate the superior heat stability of jet fuel compositions prepared in accordance with the present invention, the base fuel alone and fuels containing the ammonium oxidate have been tested in the ASTM Test D166061T for Thermal Stability of Aviation Turbine Fuels," described in A.S.T.M. Standards on Petroleum Products and Lubricants, vol. 1, 39th Ed., 1962. This is a test which rates the tendencies of aviation gas-turbine fuels to deposit decomposition products in the fuel system components. The method for measurin'g the high temperature stability of aviation turbine fuels uses the ASTM- CFR Fuel Coker described in detail in Appendix 1 of Method of Test Dl660-61T, referred to above. In this coker, the test fuel is subjected to temperatures and conditions similar to those occurring in some aviation turbine fuel systems. In conducting the test, fuel is pumped at a predetermined rate through a preheater section which simulates the hot fuel line sections of the engine as typified by an engine-fuel-oil cooler and then passes through a heated filter section which represents the nozzle area of small fuel passages in the hot section of the engine where fuel degradation products may become trapped. A precision sintered stainless steel filter in the heated filter section traps fuel degradation products formed during the test. The extent of build-up of deposits on the filter is noted as an increase in the pressure drop across the test filter. Upon completion of the test, the preheater section is disassembled and the preheater tube examined for deposits in comparision with a test rating code. The observed values for the pressure drop AP across the test filter and for the preheater deposits are used as an assessment of the thermal stability of the test fuel.

In the following tests, the thermal stability of each fuel sample was indicated by recording the time required for the filter to partially plug, as indicated by a pressure drop, AP, across the filter, and by observation of the preheater tube in comparison with a test standard. The test is discontinued when either a AP of 25 inches of mercury is reached or until a test duration of 300 minutes is attained. A satisfactory fuel in this test is one for which the pressure drop, AP, across the filter does not exceed 12 inches of mercury after a test duration of 300 minutes and the preheater coderating of less than 3.

The base fuel with which the additives were tested was a fuel of the kerosine type, such as those customarily used by the military and by commercial airlines and which has the following characteristics:

By A.S.T.M. Method of Test D1660-61T with a preheater temperature of 300 F., a filter "temperature of 400 F. and a fuel fiow of six pounds per hour.

A.S.T.M. Thermal Stability Test results obtained with the base fuel and the base fuel plus ammonium oxidate and C.D.I. additives are given in Table II below:

TABLE II.THERMAL STABILITY TEST A.S.T.M. METHOD Dl660-61T Preheater temp, 300 F. Filter temp, 400 F. Fuel flow rate, 6 lb./hr

Filter AP, Time, Preheater Test Composition inches Hg min. code rating A Base fuel 25 42 B Base fuel+2 p.t.b. C.D.I 25 155 0 C Base fuel+20 p.t.b. lube 25 85 4 oil oxidate. D Base luel+20 p.t.b. am- 0. 6 300 4 monimn oxidate. E Base luel+20 p.t.b. am- 0. 1 300 1 monium oxidate+2 p.t.b. F B ase fue1+50 p.t.b. lube 25 111 3 oil oxidate. G Base fuel+50 p.t.b. arn- 0.2 300 monium oxidate. H Base tuel+50 p.t.b. am- 0.08 300 2 monium oxidate+2 p.t.b. C.D.I.

P.t.b.= Pounds per one thousand barrels.

By examination of the results reported in Table II for pressure drops, AP, across the filter at the conclusion of the test, it is evident that either 20 or 50 pound dosages of the lube oil oxidate per thousand barrels of base fuel before reaction with ammonia (Tests C and F) gave no significant improvement over the base fuel itself (Test A). However, the same concentrations of ammonia reacted lube oil oxidate gave marked improvement on the filtering portion of the thermal stability test. Twenty pounds per thousand barrels of ammonium oxidate (Test D) reduced the measured pressure drop across the filter element from 25 inches of mercury in 42 min. to 0.6 inch of mercury of 300 min. A dosage of 50 pounds per barrel (Test G) also reduced the pressure drop across the filter to a low value. The filter pressure drop results are an indication of the amounts of suspended solids formed in the fuel during the test.

Referring again to the same tests (Tests D and G), it is noted that while the lower dosage of 20 pounds of ammonium oxidate per 1,000 barrels gave a satisfactory AP rating, the corresponding preheater code rating of 4 is not acceptable by jet fuel standards. However, it may be noted that increasing the ammonium oxidate dosage to 50 pounds per 1,000 barrels resulted in an extremely satisfactory preheater code rating. Referring to Test E, it is also noted that the addition of 2 pounds per 1,000 barrels of the C.D.I. additive to the fuel containing 20 pounds per 1,000 barrels of ammonium oxidate also resulted in a completely satisfactory fuel from the standpoint of filter pressure drop and preheater code rating. The addition of a like amount of C.D.I. to the base fuel alone gave no significant improvement in stability (Test 4 B). Test H shows that the addition of 2 pounds per 1,000 bbl. of C.D.I. to the fuel containing 50 pounds per 1,000 bbl. of ammonium oxidate also produces a jet fuel which is completely satisfactory in the A.S.T.M. Thermal Stability Test.

Ammonium lube oil oxidates prepared in accordance with this invention are effective in improving the thermal stability of jet fuels, whereas ammonium salts of other oxidized petroleum products either do not act in like manner when added to jet fuels or are not physically suitable. For example, Whereas the ammonium oxidates of this invent-ion are stable ashless liquids, equivalent salts of oxidized petrolatum and oxidized wax tend to be too solid to permit their use in jet fuels without danger of solidifying and depositing in the fuel system of jet aircraft.

The inventors method of preparation of the ammonia salt as described hereinbefore yields a semi-liquid product having a high degree of solubility in jet fuel. Other ammonium salts have been prepared from an oxidized solvent refined neutral oil by conducting the ammonia reaction at elevated temperature rather than at room temperature with the resultant formation of ammonium salts which are relatively insoluble in jet fuel and are not eifective in improving the thermal stability of the fuel. 7

It is also contemplated that other jet fuel additives may be incorporated in the fuel compositions disclosed herein for the purpose of imparting other properties to the fuel, for example, corrosion inhibitors, antioxidants, anti-icing additives, anti-static additives and the like.

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

We claim:

1. A heat stable fuel for operating jet aircraft engines comprising a petroleum distillate boiling within the range of from 250 to 700 F. and from about two to about one hundred pounds per thousand barrels of an ammonium salt of a lubricating oil oxidate prepared by reacting gaseous ammonia at room .temperature with a liquid refined parafiinic lubricating oil oxidate.

2. A heat stable fuel for operating jet aircraft engines comprising a petroleum distillate boiling within the range of from 250 to 700 F. and from about two to about one hundred pounds per thousand barrels of an ammonium salt of a lubricating oil oxidate soluble in said petroleum distillate.

3. A heat stable fuel for operating jet aircraft engines comprising a petroleum distillate boiling within the range of from 250 to 700 F. and from about two to about one hundred pounds per thousand barrels of an ammonium salt of a lubricating oil oxidate and from 0.5 to 5 pounds per thousand barrels of N,N'-disalicylidene-1,2-diaminopropane.

4. The composition of claim 3 wherein said ammonium salt is prepared by reacting gaseous ammonia at room temperature with a liquid refined parafiinic lubricating oil oxidate.

References Cited UNITED STATES PATENTS 2,014,924 9/1935 Benedict 44--66 2,162,454 6/1939 Guthmann 25234 2,228,325 1/1941 Olin et a1. 25234 2,881,140 4/1952 Schrum 44-66 3,036,903 5/1962 Kirkwood et al. 4466 3,227,533 1/1966 Gililland et a1. 44-66 3,265,474 8/1966 Siegel 44- 66 DANIEL E. WYMAN, Primary Examiner.

Y. H. SMITH, Assistant Examiner.

U.S. Cl. X.R. 4458; 252401