US3089762A - Jet fuel compositions - Google Patents

Description

m sank 3,089,762 BET FUEL COMPOSETKGNS Harold D. Orloif, Oak Park, and John P. Napolitano, Royal Oak, Mich, assignors to Ethyl Corporation, New York, N.Y., a corporation of Virginia No Drawing. Filed July 28, 1969, Ser. No. E5396 (Ilaims. (Cl. 44-78) This invention relates to thermally stable jet aircraft fuels, and more particularly to such fuels containing methylenebis phenols which are halogen substituted and which compounds have outstanding properties as thermal stability additives to jet aircraft fuel.

Fuel temperatures in modern jet aircraft power plants are becoming so high that harmful deposits are formed in the precombustion phase of the fuel system. Contribu ting to this has been the practice of using the fuel as a heat sink in connection with cooling the lubricating oil which ha increased fuel temperatures to the point where deposits are so severe that they interfere with normal fuel combustion as well as lubricating oil temperature control. The jet fuel thermal stability problem is so serious in some fuels that their use can eventually lead to engine failure of the turbine section due to uneven temperature patterns.

Prior investigators have found that conventional gasoline antioxidants are incapable of overcoming this problem. For example, it has been stated that neither 4- methyl-Z,6-di-tert-butylphenol nor N,N'-di-sec-butyl-pphenylenediamine, both well-known antioxidants, improves the high temperature stability of jet fuels. Indeed, some gasoline antioxidants have been shown to increase the severity of the problem. Consequently, other types of additives have been investigated. One approach has been the use of dispersants in an attempt to keep the deposits suspended in the fuel and thereby prevent them from adhering to critical engine surfaces. However, this approach has not proved satisfactory because the deterioration of the fuel does occur under jet engine operating conditions and little, if any, improvements in engine performance have been attained. Another approach has been tlie hse of various jet fuel treating procedures. These are not always satisfactory because they are expensive and complicated, and in many cases, little improvement is achieved. Also, many of these additives cause intolerable difficulties in removal of moisture from jet fuel, and cause serious foamy problems.

It is an object of this invention to provide phenolic compounds having an extremely high degree of efiectiveness as jet fuel thermal stabilizers. Another object of this invention is to alleviate the thermal stability problems in jet fuels. A further object is to provide new jet fuel compositions which are characterized by a high degree of thermal stability. A still further object is to provide processes of inhibiting deterioration in jet fuel normally tending to occur at elevated temperatures below the cracking temperature of the fuel during operation of the aircraft. A specific object of this invention is the provision of jet fuel compositions containing the compound 2,2- methylenebis-'(4-chloro-6-tert-butylphenol). Other objects will be apparent from the following description.

3,989,762 Patented May 14, 1963 The objects of this invention are accomplished by a liquid hydrocarbon jet aircraft fuel, heavier than gasoline, containing from about 0.001 to about 0.2 percent by weight of a compound having the formula:

Where R is an alkyl group substituted on the alpha carbon atom and which has from 4-8 carbon atoms, and X is a halogen selected from the class consisting of chlorine, bromine and iodine. Thus, the alkyl groups desig nated by R in the above formula are secondary and tertiary alkyl groups illustrated by the sec-butyl group, the various secondary hexyl groups, the tertiary butyl, amyl, hexyl, heptyl and octyl groups.

A preferred group of compounds falling within the above class are those in which the halogen atom designated by X in the above formula is chlorine. These compounds are preferred as they have properties which render them outstandingly suited as additives to jet fuel and because they are more readily prepared in commercial operations.

Compounds of the above formula in which the alkyl group is a tertiary butyl group are especially preferred because of their compatibility with various organic media, by their ease of preparation and their outstanding antioxidant and stabilizing properties. Thus, the most particularly preferred compound of this invention is 2,2-

methylenebis-(4-chloro-6-tert-butylphenol) which is both readily prepared and will be further illustrated below and is an outstanding additive to jet fuel compositions for increasing the thermal stability thereof.

A particularly preferred embodiment of this invention is jet fuel containing 2,2'-methylenebis-(4-chloro-6-tertbutylphenol) The thermal stabilizers of this invention exhibit the unique property of greatly improving the thermal stability of jet fuels and this effectiveness is independent of the hydrocarbon types from which the jet fuel has been prepared. Thus, the present invention affords eXtreme protection against thermal instability of all present day jet fuels.

The jet fuels of this invention overcome the jet fuel thermal instability problem by conferring greatly improved thermal stability characteristics upon the fuels. Thus, a direct benefit accruing from the practice of this invention is the considerable reduction in the amount of insoluble products formed when the jet fuels of this invention are subjected to elevated temperatures. Hence, markedly reduced is the amount of insoluble thermal decomposition products which heretofore deposited in the fuel system. The additives of this invention do not introduce secondary problems in use, such as forming of the fuel at high altitudes, emulsification dimculties, interference with low temperature flow and the like. At the 3 same time, all of these advantages are achieved in a simple manner and at very low cost.

It is known that jet fuels tend to deteriorate when subjected to the condition of elevated temperatures below the cracking of the fuel, i.e., temperatures in the range with JP-3. The gravity requirements are from 45.0 to 570 API.

JP-S is a high flashpoint type fuel which is an essen-' tially fractionated kerosene having a 10 percent evapo- 5 rated minimum temperature of 400 F. and a maximum f a ut 300 t about 0 Thus, another P of end point of 550 F. It is heavier than the other fuels, this invention is a process of inhibiting such deterioration the gravity requirements ranging from 3648 API. which comprises subjecting a jet fuel containing from JP-6 is also a distillate fuel having a minimum initial about (1001 to about Percent y Weight of a boiling point of 250 F. and a 90 percent evaporation methylenebis(4-halo-6-alkylphenol) to said condition. 10 point maximum of 500 F. The gravity of this fuel may Thus, enhanced thermal stability of a jet fuel is achieved va y f 37,0 t 50 APL y blending With the fuel froIn about (1001 to about Other requirements of these fuels are as described in Percent y Weight of a y y the military specifications referred to above.

P U- A Preferred range of additive concentration is Recently, however, increased civilian use of jet planes fr m 0. 05 t about (3-05 Weight Percent of Such a has increased the consumption of civilian types of jet y y P 1). This conce fuels. These fuels usually conform to ASTM standards range is preferred as it has been found adequate to very f j f types A A 1 d ]3 T A i a id t effectively Stabilize a Vast j y of the fuels gasoline-kerosene blend used for short to medium range The j fuels Whose thermal Stability is greatly operations, while type A-l is a blend similar to type A Proved Pursuant to this invention are Principally Y P' but having a lower freezing point and employed more for carbon fuels which are heavier than gasoline, i.e., d1slong range flighw Type B is also a gasoline-kemsene tilled liquid hydrocarbon fuels having a higher end Peint blend. It is similar to JP-4. While most commercial than gasoline- In general, the j fuels can he eompl'ieed fuels conform to these ASTM specifications, some equipof distillate fuels and haphthas and blends of the above, ment operations require fuels to have special properties including blends with lighter hydrocarbon fractions. not i d b h ASTM ifi ti n The end Point of the filial j fuel is above A very recent development in fuels for jet aircraft inusually is at least and Preferably greater than volves the use of certain pure hydrocarbon, or blends 480 F. It Will be und however, that the l of hydrocarbons as fuels. Among these are parafiins, fuels which are employed according to this invention can monocyclic hydrocarbons, polycyclic isolated ring and contain certain other ingredients such as alcohols or the onde d ring compounds d t i d t t d h d like, provided the resulting fuel blend meets the specicarbons, These include bis(methy1cy1ohexy1) ethane fic i p p l fueis- Volatile and y isopropylbicyclohexane, dimethanedecahydronaphthalene, carbon composition requirements of a jet fuel are prin na nd th lik mafily p d y the nature of l engine operation- Whereas the concentrations of additives of this inven- Thus, it is impossible without catastrophic effects to 5 tion have been described above in terms of weight peremploy an ordinary gasoline as a jet fuel due to the cent of the fuel and this terminology is used in the subordinarily high volatility of gasoline. sequent examples in the specification, it is common prac- Until recently, the major use of jet fuels has been in flee to express additive concentrations in pounds per military aircraft. The military establishment has im- 1,000 barrels of fuel treated. Since the gravity of these posed rigorous standards of hydrocarbon content and 4.0 fuels varies from about 36 API to 60 API, this exother properties on the fuels according to various classipression is only approximately precise in terms of weight fio i All of the i fy j fuels are eheol'hpassed percent. For a 36 API gravity fuel, 0.001 percent by Wlthul the Scope of thlS invention e y include weight corresponds roughly to 3.0 pounds per 1,000 bar- JP-3, -h and The requirements for three rels, whereas for a 60 API gravity fuel 0.001 percent of i fuelsi namely IF-4 and are 4r by weight of additive amounts to about 2.6 pounds per bod1ed 1n specification MIL-J-5624-D, dated December 0 1000 barrels Thus for a fuel 0 001 Wei ht 24, 1957. JP-6 requirements are outlined in specificais from 'about t ab t275 d g 6 tion MIL-F-25656 (USAF), dated September 10, 1955. b I d 02 3 Per In general, JP-3 is referred to as a high vapor pressure arm S an Welght percent is eqmvalent to 516450 type fuel which may be a mixture containing up to about Pounds: per 1000 barrels In a fuel 0'001 Percent 70 percent gasoline and about 30 percent light distillate. by welght amounts, to about per 1,000 one of the requirements Set forth in the military speci barrels and 0.2 we1ght percent 1s equ1valent to 520-560 fication is that JP-3 must have a 90 percent evaporation Pounds Per 1,000 barrels- For fuel o-ool Pement point minimum at 4 and a ifi gravity rangby weight amounts to from 2.753.0 pounds per 1,000 ing f om 50 to 0,0 barrels and 0.2 weight percent is equivalent to 550-600 JP-4 is a low vapor pressure type fuel which may be pounds per 1,000 barrels, etc. Even though the gravity a mixture of up to about percent gasoline and 35 of the fuels vary, an excellent approximation to the percent distillate. It is a fuel especially designed for weight percent can be obtained by converting from high altitude performance and also must have a perpounds per 1,000 barrels. cent evaporation minimum temperature at 470 F. How- Table I shows the specification of a number of typical ever, in distinction to JP-3 the 20 percent evaporation 60 hydrocarbon jet fuels which are benefited by the practice minimum temperature is 290 F. instead of 240 F. as of this invention.

TABLE I Fuel A Fuel 13 Fuel C Fuel D Fuel E Fuel F Fuel G Fuel H uel (Oom- (JP-4) (.TP5) (JP-4) (JP-4 Re-(Kerosene (Oorn- (JP-5) (JP-5) mercial) ference) Type) mercial) 10 Percent Evaporated, F 380 220 395 2 380 376 382 400 90 Percent Evaporated, F- 457 470 480 379 460 480 477 403 480 Endpoint, F 490 550 550 480 6 519 496 524 Gravity, API 43. 9 45 35 47. 3 4s. 5 43 42. 0 4a. a 41. 2 Existent Gurn,mg./1(l0 n11., max... 0. 7 7 7 1. 0 1. 4 1. 7 0. 2 1. 0 0. 6 Potential Gum, mg./10O 1111., max 14 14 1.0 9 6 Reid Vapor Pressure, psi 3. 0 0 5 0.5 Aromatics, vol. Percent 14.1 25.0 25.0 12.5 14 6 14.3 13 4 13.5 10.7 Olefins, vol. Percent 5.0 5.0 0.3 1 2 3 0 0. 53 1.0

s eaves Example 1 To 100,000 parts of Fuel A is added with stirring one part (0.001 percent) of 2,2-methylenebis-(4-chloro-6- tert-butylphenol) dissolved in 20 parts of ethanol. The resulting fuel is found to possess improved thermal stability characteristics.

Example 2 To 100,000 parts of Fuel B is added 200 parts (0.2 percent of 2,2'-methylenebis-(4-bromo 6-isopropylphenol) dissolved in 1,000 parts of methanol. The resulting fuel possesses improved thermal stability properties.

Example 3 With 100,000 parts of Fuel C is blended 5 parts (0.005 percent) of 2,2-methylenebis-(4-iodo-6-sec-dodecylphe- 1101). The resulting fuel blend possesses improved thermal stability characteristics.

Example 4 To 100,000 parts of Fuel D is added 50 parts (0.05 percent) of 2,2-methylenebis-(4-chloro-6-tert-butylphe- I101). The resulting fuel blend is found to possess vastly superior thermal stability characteristics.

Example 5 With 100,000 parts of Fuel E is blended 80 parts (008 percent) of 2,2-methylenebis-(4-chloro-6-tert-amyiphenol). The resulting fuel blend possesses enhanced thermal stability properties.

Example 6 To 100,000 parts of Fuel F is added 200 parts (0.2 percent) of 2,'2-methylenebis-(4-bromo-6-sec-octylphenol) dissolved in 1,500 parts of isopropanol. After mixing, the resulting fuel blend is found to possess enhanced thermal stability properties.

Example 7 Example 8 To 100,000 parts of Fuel H is added 150 parts (0.15 percent) of 2,Z'-methy1enebis-[4-iodo-6-(1,1,3,3-te amethylbutyl)phenol] dissolved in 1,500 parts of mixed Xylenes. The resulting jet fuel possesses superior thermal stability properties.

Example 9 With 100,000 parts of Fuel B is blended 60 parts (0.06 percent) of 2,2'-methylenebis-(4-chloro-6-sec-butylphe- 1101). This fuel after mixing possesses improved thermal stability characteristics.

Example 10 170 parts of 2,2-methylenebis-(4-chloro-6-tert-butylphenol) is blended with 100,000 parts of Fuel 1. The resulting jet fuel containing 0.17 percent of the phenol possesses improved thermal stability characteristics.

Example 11 With 100,000 parts of Fuel C is blended 70 parts (0.07 percent) of 2,2-me-thylenebis-(4-chloro-5-tert-butylphen01). The resulting jet fuel blend possesses superior thermal stability characteristics.

Example 12 To 10,000 parts of Fuel H is added with agitation 160 parts (0.16 percent) of 2,2-methylenebis-(4-bromo-6- sec-octylphenol). The resulting fuel is found to have greatly improved thermal stability characteristics.

Example 13 To show the great improvements in thermal stability resulting from the practice of this invention, tests were conducted in an apparatus known as the Coordinating Fuel Research (CFR) Jet Fuel Coker, commonly called the Erdco Rig. The test procedure and equipment are described in Petroleum Processing, December 1955, pages 1909-1911, and in Coordinating Research Council Manual No. 3. In this equipment a jet fuel under 150 pounds pressure is forced through a pre-heater tube having a centrally located heating element to raise the temperature of the fuel to a predetermined point. The heated fuel is then forced through a hot filter of sintered steel into a second tube. When thermal decomposition of the fuel occurs at the elevated temperature, the filter becomes plugged and a pressure drop occurs across the filter. This pressure drop is measured by a manometer placed across the filter. The following tests were conducted until a pressure drop across the fuel filter of 25" of mercury caused by decomposition of the fuel and filter plugging occurred, or if a pressure drop of 25" of mercury did not occur across the filter within 300 minutes, the tests were discontinued. In all tests the fuel flow rate was maintained at 6 pounds per hour.

let fuels of this invention were prepared by blending 2,2'-methylenebis-(4-chloro6-tert-butylphenol), the most particularly preferred compound of this invention, with samples of three different commercially available JP-S fuels which meet all of the requirements of the above mentioned military specification except for the thermal stability properties. In these tests on JP-S, a sample of each of the fuels without a thermal stability additive of this invention was also tested. The test conditions were adjusted so that the pre-heater temperature was 400 F. and the filter temperature was 500 F. The results of these tests are shown in Table 11.

TABLE Il.lP-5 FUELS WITH AND WITHOUT 2,2'- THIOBIS- 6-TERT-BUTYL-4-CHLOROPHENOL) 2.2-Methylenebls (G-tert- Pressure Time of Fuel butyl--chlorm Across Fi1- Test, min.

phenol) Cone, tcr, inches lbs/1,000 bbl.

The data in Table II indicate that outstanding improvements in thermal stability were achieved in both of the above fuels by the addition respectively of 100 and 50 pounds per 1,000 barrels of the fuels tested. However, in addition to the great improvement in the alleviation of filter plugging, other benefits accrue from the practice of this invention. Fuel J containing no additive, deteriorated to such an extent during the 91 minute test that the pro-heater tube was coated with black, dark brown and tan decomposition products to the extent of 20 percent of the surfaces thereof. However, with the addition of pounds per 1,000 barrels of 2,2-methylenebis-(4-chloro-6-tert-butylphenol), the deposits were reduced to a very light tan color indicating the amazing improvement in the condition of deposit on the preheater tubes. Similarly, in Fuel K during the 39 minutes of the test on the fuel which contained no additive, a total of 70 percent of the pro-heater surfaces were coated "with deposits ranging in character from dark brown to light tan. However, with the addition of 50 pounds per 1,000 barrels of the preferred additive of this invention, the total deposit area was reduced to 10 percent after a 300 minute period and the deposit ranged in character from light tan to brown. In both of these instances, great improvement in the fuel was achieved by the use of the especially preferred additive of this invention, 2,2'-methylenebis-( l-chloro 6 tert-butylphe- 1101).

Example 14 To further demonstrate the effects of the additives of this invention on the thermal stability properties of jet fuels, a test was run in a commercially available ZIP-4 fuel. In this test the pro-heater temperature was adjusted to 300 F. and the filter was maintained at 400 F. Other test conditions were as described above. The fuel with no additive developed 25" of mercury pressure drop across the filter in 109 minutes and during this time 40 percent of the pro-heater surfaces were covered with deposits ranging from brown to tan. However, when 25 pounds per 1,000 barrels of 2,2'-methylenebis-(4-chloro- 6-tert-butylphenol) was added to this fuel, a total pressure drop of only 0.1" of mercury accrued over a 300 minute period. Furthermore, the pro-heater surfaces were completely clean under these conditions. This test further demonstrates the outstanding ability of the compounds of this invention to alleviate jet fuel thermal stability problems even at low concentrations of additive. With other compounds of this invention similar results are obtained.

As noted above the amount of the additive of this invention used in jet aircraft fuels can range from about 0.001 to about 0.2 percent by weight. Ordinary concentrations varying from 0.005 to about 0.05 weight percent of additive are found to be satisfactory for most present day fuels. Variations from these concentration ranges are permissible and sometimes desirable. For example, in jet fuels initially possessing a fair degree of thermal stability, very small amounts of additive are sulficient to improve the characteristics in order to meet the military specifications, and in some cases, provide improved storage stability properties. On the other hand, where the jet fuel initially has a very poor thermal stability, larger amounts-up to 0.2 percent by weight or more-can be effectively employed.

Typical jet fuel thermal stability additives of this invention include 2,2-methylenebis-(4-chloro-6isopropylphenol), 2,2-methylenebis- (4-bromo=6-sec-butylphenol) 2,2'-methylenebis-(4 chloro-6 tert-butylphenol), 2,2- methylenebis-(4-iodo-6-sec-amylphenol), 2,2'-rnethylenebis-(4-chloro-6-tert-hexylphenol), 2,2 methylenebis-( lbromo-6-tert-butylphenol), 2,2-methylenebis-(4-iodo-6- sec-heptylphenol), and the like. As noted above the chloro compounds are preferred and the preferred alkyl group is the tertiary butyl group.

In preparing the improved fuels of this invention, the use of solvents for the 2,2-methylenebis-(4-ha1o-6-alkyl phenol) compounds is sometimes advantageous. While the solubility of these compounds in jet fuel is sufficiently high to provide the desired concentrations blending procedures may be simplified by pre-dissolving the additives in a suitable solvent. The resulting concentrates can then be conveniently and readily blended with the jet fuels while all the components are in the liquid phase. Suitable solvents for this purpose include both aromatic and aliphatic hydrocarbons, alcohols and ketones. In general, ketones and alcohols containing up to 6 carbon atoms and liquid aromatic hydrocarbons containing 6 to 18 carbon atoms are suitable solvents. They include, for example, benzene, toluene, xylenol, acetone, methyl ethyl ketone, methanol, diethyl ketone, ethanol, isopropanol, methyl isobutyl carbonyl and the like.

In addition to the 2,2-methylenebis-(4-halo-6-alkylphenol) thermal stabilizer of this invention, jet fuels may have added to them such other materials as anti-rust additives, dispersants, dyes, and in general other additives which do not adversely effect the thermal stability of the fuel.

The 2,2'-methylcnebis-(4-halo 6 alkylphenol) compounds used in this invention are prepared for example by a process which comprises reacting a 4-halo-6-alkylphenol having the formula:

where X is a halogen such as chlorine, bromine and iodine and R is an alkyl group which is branched on the alpha carbon atom which contains from 48 carbon atoms, formaldehyde in the presence of an alkali metal hydroxide and a non-aqueous solvent. This reaction is illustrated by the following example for the preferred compound of this invention.

Example 15 In a reaction vessel equipped with reflux condenser, heating means, means for agitating reactants and means for charging liquid reactants was placed 3142 parts of isopropanol and 66 parts of potassium hydroxide. The mixture was agitated until the potassium hydroxide was completely dissolved at which point 1846 parts of 4-chloro-6-tert-butylphenol was added and the mixture was heated to 45 C. While maintaining the temperature 420 parts of a 36.3 percent formalin solution was added incrementally. The reaction temperature was thereafter maintained with agitation for 6 hours, cooled to room temperature and acidified with about 200 parts of dilute hydrochloric acid. The acidified mixture was added to about 5500 parts of petroleum ether, the isopropanol was extracted with Water and the water phase discarded. The organic phase was then distilled through a helix packed column and 665 parts of 2,2'-methylenebis-(4- chloro-6-tert-butylphenol) were recovered at 209-2l3 C. at 0.3 ml. pressure. A portion of this material was recrystallized from petroleum ether to yield white crystals of pure 2,2'-methylenebis(4-chloro-6-tert-butylphenol) having a melting point of 114-1145 C. Upon analysis these crystals were found to contain 64 percent carbon, 6.6 percent hydrogen and 19.6 percent chlorine. The calculated content for the compound is 66.1 percent carbon, 6.8 percent hydrogen and 18.6 percent chlorine. An infrared spectrum of the compound showed bands of a partially hindered hydroxyl of a bisphenol compound. The ring substitution as determined from the infrared spectrum showed the compound to contain a 1,2,4,6-substituted benzene ring.

We claim:

1. A thermally stabilized distilled hydrocarbon jet fuel having an end point, higher than gasoline, of at least 480 F. and an API gravity, higher than hydrocarbon mineral lubricating oil, of from 35-50", containing from about 0.01 to about 5 percent by weight of a compound having the formula:

OH OH i R- (|J-- R H l I X X where R is an alpha-branched alkyl group which has 20 10 from 4-8 carbon atoms, and X is a halogen selected from the class consisting of chlorine, bromine and iodine.

5. A process for cooling the lubricating oil in a jet engine comprising using as a coolant for heat transfer With the lubricating oil a thermally stabilized jet fuel consisting essentially of a distilled hydrocarbon fuel having an end point of at least about 480 F. and containing from about 0.01 to about 0.1 percent by weight of 2.2- methylenebis-(4-chloro-6-tert-butylphenol) References Cited in the file of this patent UNITED STATES PATENTS 2,542,972 Thompson Feb. 27, 1951 2,734,088 Knowles et a1. Feb. 7, 1956 2,829,175 Bowman et a1. Apr. 1, 1958 2,841,627 Beaver et a1. July 1, 1958 2,932,942 Ecke et a1. Apr. 19, 1960 2,959,915 Dille et a1 Nov. 15, 1960 3,012,049 Bill Dec. 5, 1961

Claims (1)

1. A THERMALLY STABILIZED DISTILLED HYDROCARBON JET FUEL HAVING AN END POINT, HIGHER THAN GASOLINE, OF AT LEAST 480* F. AND AN API GRAVITY, HIGHER THAN HYDROCARBON MINERAL LUBRICATING OIL, OF FROM 35-50* , CONTAINING FROM ABOUT 0.01 TO ABOUT 5 PERCENT BY WEIGHT OF A COMPOUND HAVING THE FORMULA: