US3441497A - Jet fuels from hydrogenated coal tar derivatives and pinane-containing materials - Google Patents

Description

United States Patent 3,441,497 JET FUELS FROM HYDROGENATED COAL TAR DERIVATIVES AND PINANE-CONTAINING MATERIALS Norman S. Boodman, Penn Hills Township, Allegheny County, George W. Perkins, New Salem, and Jack W. Walter, Penn Hills Township, Allegheny County, Pa., assignors to United States Steel Corporation, a corporation of Delaware No Drawing. Filed Aug. 20, 1965, Ser. No. 481,390 Int. Cl. C101 N04 US. Cl. 208-15 6 Claims ABSTRACT OF THE DISCLOSURE A jet-engine fuel composition comprising by weight between about 10% and 50% of a pinane-containing material, between about 10% and 75% of a hydrogenated naphthalene-containing material, between about 3% and 20% of a hydrogenated coal-tar fraction boiling in a range between about 230 and 270 C. prior to hydrogenation and between about 10% and 40% of a hydrogenated coal-tar fraction boiling in a range between about 270 and 315 C., prior to hydrogenation, said naphthalene-containing and said coal-tar fractions being hydrogenated to substantially complete saturation, said hydrogenated material having an initial boiling point of at least about 350 F.

This invention relates to jet-engine fuel compositions prepared from hydrogenated coal-tar fractions having a nominal boiling range within the limits 210355 C. prior to hydrogenation. More particularly, the invention relates to such compositions comprising at least two hydrogenated coal-tar fractions having boiling ranges within said limits and compositions comprising said two fractions and pinane oil.

The large-scale program for preparation and testing of candidate fuel mate-rials, carried out in this country during the past years, has revealed that no single material or processed fraction can be formulated to have all the desirable physical properties required of an improved jet fuel. The principal difficulty with hydrocarbon fuels is providing both high gravimetric and volumetric heat ing values for the same composition; these are generally mutually exclusive properties. High gravimetric heating values are usually associated with low-boiling and low molecular-weight materials, whereas high volumetric heating values are found in high-boiling, higher molecular-weight materials. Moreover, viscosities generally increase in the direction of the higher-boiling products. As a result of these property variation patterns, fuel developers have resorted to the blending of different fuels, each with its own outstanding property or combination of properties, to obtain products reflecting general overall improvement in the specified properties.

It is an object of the present invention to provide a jet-engine fuel composition especially suitable for use under both high and low extremes of temperature. It is another object of the invention to provide a blended fuel furnishing a high release of energy per unit weight and volume. Other objects will become apparent during the subsequent discussion.

In accordance with this invention, it has been found that a fuel furnishing a high release of energy per unit weight and volume may be prepared from hydrogenated coal tar fractions having a nominal boiling range within the limits 210-355 C. prior to hydrogenation.

It is known to hydrogenate such coal-tar fractions with, for example, molybdenum sulphide catalysts. To mini- 3,441,497 Patented Apr. 29, 1969 mize possible cracking by such methods, the fractions have been prerefined or hydrorefined, to eliminate their hetero-atoms in the form of hydrogen sulphide, ammonia and water. Hydrogenation with, for example, nickel-base catalysts may then be effected under milder conditions.

Our products may be prepared without washing or by first washing the raw oil with, for example, sulfuric acid (20%-50% concentration) to remove basic nitrogen compounds. The oil is then hydrorefined over a nickelmolybdate or cobalt-molybdate catalyst, for example, in the oxide or sulfide form, to destroy the remaining nitrogen compounds as well as sulfurand oxygen-containing materials. In a hydrorefining apparatus, the oil fractions are refined at contact times from 5 to 20 seconds, hydrogen-to-oil mole ratios of from 5- to 1 to 10 to 1, temperatures between about 400 and 450 C. and an operating pressure of between about 225 and 4000 pounds per square inch gage (p.s.i.g.).

In a specific example, hydrorefining was performed at a temperature of 450 C. and a hydrogen pressure of 3500 p.s.i.g. with a catalyst of sulfided nickel molybdateon-alumina. At the end of six hon-rs, the catalyst was removed by filtration. The filtrate was freed of dissolved by-product gases by heating in an open vessel to a temperature of about C.

In a hydrogenation apparatus the hydrorefined fractions may be hydrogenated in the presence of between 10% and 15% by weight of a powdered nickel catalyst at temperatures up to about 330 C. and at hydrogen pressures up to about 3500 p.s.i.g. In a specific example, hydrorefined coal-tar fractions were hydrogenated to saturation with 10% by weight of a nickel catalyst at a hydrogen pressure of about 3000 p.s.i.g. and a temperature of about 250 C. The products were filtered to remove the catalyst and degassed by heating.

Some hydrogenated fractions may contain contaminants responsible for color formation or production of solids at elevated temperatures. Their removal to assure thermal stability and decomposition temperatures in excess of 700 F. may be effected in a number of ways. For example, the hydrogenated fractions may be percolated through a column of silica gel, or treated with activated alumina or washed with sulfuric acid and then fractionated. The latter method is preferred, since it also provides for the separation of a small amount of forerunnings and residue to assure an initial, preferred boiling point of about 350 F. and removal of high-viscosity material, respectively.

In the following examples, coal-tar fractions having wide to relatively narrow, nominal boiling ranges were treated as hereinabove described. The physical properties of the hydrogenated fractions were determined by standard ASTM test methods. All of the fractions met the target specifications for thermal stability, a minimum 700 F. decomposition temperature, a maximum 0.4% sulfur content and a 55 F. maximum freezing point. Additional target specifications were for net heat of combustion, 18,400 minimum B.t.u. per pound (AHg) and 135,- 000 minimum B.t.u. per gallon (Ahv), for kinematic viscosity, 15 maximum centistokes (cs.) at -30 F. and a minimum initial boiling point of 350 F. In Table 1 are listed the boiling ranges of the fractions prior to hydro genation and some physical properties of these fractions when hydrogenated. In Example 2, the hydrogenated prodice ' uct was 78 C. melting point naphthalene, recovered from a fraction similar to Example 1. In Example 5 the 230- 270 C. fraction was washed with 20% sulfuric acid prior to hydrorefining. In Example 6 the fraction was unwashed. The 270-315 C. and 315 355 C. fractions were divided, similarly acid washed in Examples 7 and 9 respectively and unwashed in Examples 8 and 10 respectively.

TABLE 1 Net Eeat of Combustion Specific Kinematic B.t.u./ B.t.u./ Gravity Viscosity, Example Hydrogenated Fraction pound gallon (20 C./4 0.) cs. at 30 F.

1 Naphthalene 210230 18,330 132, 440 0. 8658 9. 3 2... Naphthalene 78 0., M.P 18, 370 135, 170 0. 8818 12. 4 3--- Creosote 230315 C 18, 330 138, 000 0. 903 25 4--- creosote 230355 C 18, 280 137, 760 0. 9030 40 5.-- Acid Washed 230270 0.- 18,400 133,770 0. 8712 12. 6 6- Unwashed 230270 C 18, 360 133, 980 0. 8746 13. 7. Acid Washed 270-3l5 0-- 18, 210 137, 930 0. 9076 30. 7 8- Unwashed 270315 C 18, 330 136, 850 0. 8946 28 9- Acid Washed 3l5355 0.- 18, 320 138, 460 0. 9056 54 Unwashed 315-355 0---- 18, 320 138, 010 0. 9026 48 It may be seen from the above table that the Example 4 (230355 C. fuel has good heat of combustion but, a viscosity which is considerably higher than the target value. Within the broad range 210355 C., the properties of some narrower-range fractions are illustrated in the other examples.

It was found that at least two of the narrower-range fractions should be combined to achieve a jet-engine fuel with enhanced combustion and viscosity properties. More particularly, it was found that a fuel with such enhanced properties resulted from" combining a major portion of a so-called methylnaphthalenes fraction (230-270 C.) and a minor portion of a so-called light creosote fraction (270-315 C.) Most surprisingly, however, it was found that with such binary mixtures, the resulting volumetric combustion values and also the viscosities, varied from what would be expected from calculations based on linear combinations. Both the volumetric combustion values and viscosities were depressed or smaller than expected. This was unfavorable for the combustion value but favorable with respect to viscosity, especially since the percentage depression was much greater than for the volumetric cambustion value.

In Examples 11 and 12. the respective fractions were treated as hereinabove described. In Examples 13 and 14, portions of the same respective fractions were combined and then treated as hereinabove described. The observed physical properties of the fractions and binary blends of fractions and the calculated properties of the blends, assuming linear combinations, are tabulated in Table 2.

pinene and beta-pinene may be converted to pinane on hydrogenation. The isomeric pinenes are the predominant constituents of turpentine derived either from pine oil distillates (gum turpentine) or from the Kraft processing of wood and related cellulosic materials (sulfate turpentine). A pine-oil fraction rich in pinenes is steam-distilled sulfate or wood turpentine, which may contain as high as 80% alpha-pinene together with a mixture of other terpene hydrocarbons, for example, beta-pinene, camphene, dipentene, paramenthane and paracymene. The accompanying terpenes also yield desirable jet-fuel ingredients, on hydrogenation.

As a specific example, a commercial sample of gum turpentine was hydrogenated for 6 hours in a hydrogenation apparatus at a temperature of 130 C. and a hydrogen pressure of 3000 p.s.i.g. with 7% by weight of a nickel catalyst. The hydrogenate, containing about 94 mole percent pinane was used for fuel blending without further refining by distillation. While a hydrogenate may have an initial boiling point of about 315 F., it was found, surprisingly that in ternary blends with binary blends of coal-tar fractions having an initial boiling point of 350 F., the initial boiling point of the ternary blend was about 348 F.

This favorable initial boiling point was higher than would be expected from calculations based on linear combinations. Ternary blends may comprise l0%-50% pinane oil or hydrogenated turpentines; 20%70% hydrogenated methylnaphthalenes (230-270 C.) and 20%40% hydrogenated light creosote (270315 C.).

TABLE 2 Ex. 11 Ex. 12 Ex. 13 Ex. 14

Hydrogenated, Hydrogenated, Blend of Blend of Acid Washed Unwashed 11 and 12 11 and 12 Properties 230-270 O. 270-315 O. (2 to 1) (3 to 1) B.t.u./lb 18, 400 18, 240 18, 345 18, 370 Observed B.t.u./gal1ou.. 133,770 138,350 134,860 134,650 Calculated B.t.u./2allrm 135, 300 134,910 Observed viscosity, cs. at F-.. 12. 6 29. 0 15.9 15.4 Calculated viscosity, cs. at 30 F 18.1 16. 7

It may be seen from the above table that for the blends, the depression between the observed and calculated B.t.u./ gallon values varies between 0.19% and 0.32% and for the kinematic viscosities it varies between 7.8% and 12.1%. The binary blends have enhanced combustion and viscosity properties.

It was found that pinane or a pinane-rich oil when combined with the above binary blends provided ternary blends with even better gravimetric combustion values and viscosities. More particularly, it was found that the precursor of pinane, namely, pinenes occurring as alpha- Present tentative specifications may be met by fuel blends comprising 10%-30% pinane oil, %70% hydrogenated 230270 C. fractions and 20%30% hydrogenated 270-315 C. fractions. Other ternary blends may comprise 15%-25% pinane oil, %65% hydrogenated 230-270 C. fractions and 25%-30% hydrogenated 270315 C. fractions. A ternary blend was also formulated with about 13% hydrogenated turpentine, 58% hydrogenated 230-270 C. fraction and 29% hydrogenated 270-315 C. fraction. The physical properties of the constituents and blends are set forth in Table 3 as Examples 15-19.

TABLE 3 Specific Viscosity B.t.u./ B.t.u.l Gravity at Example Product pound gallon (20 0J4 0.) 30 F. es.

15 Hydrogenated turpentine 18,710 133,500 0.8549 11.5 16- Hydrogenated 230 270 C- 18,400 133, 770 0.8712 12. 6 17. Hydrogenated 270315 C 18, 240 138, 350 0. 9089 29. 0 18. Blend of Ex. 16 and 17 (2:1) 18, 350 134,850 0. 8809 15.9 19 Ternary Blend of 13% Ex. 15 and 87% Ex. 18.- 18, 390 134, 620 0.8771 15. 3

It may be seen from the above table that with respect to the target specifications the binary blend is improved by the addition of pinane oil to produce a ternary blend. With respect to variations in the ternary blend between the observed and calculated figures, the calculated B.t.u./ gallon is 135,090 vs. 134,620 observed and the calculated viscosity is 17.2 centistokes vs. 15.3 observed.

The above-described binary blends are also improved by the addition of hydrogenated naphthalene or a hydrogenated naphthalene-containing fraction boiling in a range between about 210 and 230 C. to provide a ternary blend. From an examination of the properties, these ternary blends, while excellent jet-engine fuels, are somewhat inferior in some target specifications to the above-described ternary blends with hydrogenated turpentine.

When the hydrogenated products of the respective ternary blends are combined in a quaternary blend, however, the fuels are an improvement over either one of the ternary blends. Quaternary blends may comprise 50% pinane oil, 10%-75% hydrogenated naphthalene, 3%20% hydrogenated alkylnaphthalenes and 10% to 40% hydrogenated light creosote. A good commercial blend would comprise %-40% pinane oil, 25 %-60 hydrogenated 210-230 C. fractions, 6%-12% hydrogenated 230-270 C. fractions and 15%-25% hydrogenated 270-315 C. fractions. Other quaternary blends may comprise 25 %35% hydrogenated turpentine, 30%- 40% hydrogenated naphthalene, 8%-11% hydrogenated 230-270 C. fractions and %-25% hydrogenated 270315 C. fractions.

As Example 24 or blend A, a quaternary blend was formulated with about 31% hydrogenated turpentine, 38% hydrogenated naphthalene, 9% hydrogenated 230- 270 C. fraction and 22% hydrogenated 2703l5 C. fraction. As Example or blend B, another quaternary blend was formulated with about 32% hydrogenated turpentine, 33% hydrogenated naphthalene, 11% hydrogenated 230270 C. fraction and 24% hydrogenated 270-315 C. fraction. The physical properties of the constituents and blends are set forth in Table 4 as Examples 20-25.

effect the desired results. While a coal-tar fraction having a nominal boiling range within the limits 210355 C. is a preferred source for the defined narrower boiling range fractions, such fractions may be derived from other sources, for example, naphthalene may be derived from still bottom residues from naphthalene distillations, or coal-tar carbolic oils. Refined alkyl napthalenes, for example, monomethylnaphthalenes or dimethylnaphthalenes may be hydrogenated and used advantageously in the compositions in place of the 230-270 C. boiling fraction. It is obvious the latter compositions are cheaper starting materials containing other valuable constituents that may be hydrogenated. Regardless of the starting materials, the unexpected non-additivity or non-linearity of the viscosity and the boiling-point values will be present in the binary, ternary and quaternary compositions. It is primarily due to the favorable, large variations in these observed properties that the compositions can be formulated in the described proportions to achieve the desirable, attained physical properties. The boiling ranges of all fractions included in the specification and appended claims are nominal boiling ranges.

Although we have disclosed herein the practice of our invention, we intend to cover as well any change or modification therein which may be made without departing from the spirit and scope of the invention.

We claim:

1. A jet-engine fuel composition characterized by a minimum decomposition temperature of 700 F., a maximum sulfur content of 0.4%, a maximum freezing point of 55 F., a minimum heat of combustion of about 18,400 B.t.u. per pound and 135,000 B.t.u. per gallon, a maximum kinematic viscosity of 15 centistokes at 30 F., and a minimum initial boiling point of about 350 F. comprising by weight between about 10% and of a pinane-containing material chosen from the group consisting of pinane, hydrogenated gum turpentine and hydrogenated sul fate turpentine, said turpentines being hydrogenated to substantially complete saturation; between about 10% and 75% of a hydrogenated naphthalene-containing material chosen from the group, prior to hydrogenation, consisting of naphthalene, 78 C. melting point naphthalene and a It may be seen from the above table that with respect to the target specifications the ternary blends are improved by combining the respective constituents thereof as a quaternary blend. With respect to variations between the above observed and calculated figures, for blend A the calculated B.t.u./gallon is 135,070 vs. 135,000 observed and the calculated viscosity is 16.3 cs. vs. 14.0 cs. observed. The initial boiling point of the hydrogenated turpentine was 315 F., the initial boiling points of the other three constituents 350 F. and the initial boiling point of blend A 348 F. Obviously, the initial boiling points of the other three constituents may be increased sufficiently to raise the initial boiling point of a ternary or quaternary blend to 350 F. All of the fractions, binary blends, ternary blends and quaternary blends met the target specifications for thermal stability, at minimum 700 F. decomposition temperature, a minimum 0.4% sulfur content and a F. maximum freezing point.

While the above examples illustrate preferred binary, ternary and quaternary jet-engine fuel compositions, changes therein may be made without departing from the spirit of the invention. It will be apparent that, for commercial preparation of the compositions, the hereinabovedescribed equipment may be of any design known to coal-tar fraction boiling in a range between about 210 and 230 C.; between about 3% and 20% of a hydrogenated coal-tar fraction boiling in a range between about 230 and 270 C. prior to hydrogenation; and between about 10% and 40% of a hydrogenated coal-tar fraction boiling in a range between about 270 and 315 C. prior to hydrogenation; said naphthalene-containing material and said coal-tar fractions being hydrogenated to substantially complete saturation, said hydrogenated naphthalene-containing material and said hydrogenated coal-tar fractions having an initial boiling point of at least about 350 F.

2. A jet-engine fuel composition as defined in claim 1, the four components of said composition comprising by weight, respectively, between about 15% and 40%; 25% and 60%; 6% and 12%; and 15% and 25%.

3. A jet-engine fuel composition as defined in claim 1, the four components of said composition comprising by weight, respectively, between about 25% and 35%; 30% and 40%; 8% and 11%; and 20% and 25%.

4. A jet-engine fuel composition as defined in claim 1, the four components of said composition comprising by weight, respectively, 31%, 38%, 9% and 22%.

5. A jet-engine fuel composition as defined in claim 1,

7 the four components of said composition comprising by weight, respectively, 32%, 33%, 11% and 24%.

6. A jet-engine fuel composition as defined in claim 1, characterized by a hydrogenolysis step to destroy heteroatoms prior to said hydrogenation of said naphthalenecontaining material and said coal-tar fractions comprising contacting said material and fractions in a mole ratio with hydrogen between about 1 to 5 and 1 to 10, at a temperature between about 400 and 450 C. and an operating pressure between about 225 and 4000 pounds per square inch gage (p.s.i.g.) over a catalyst chosen from oxided nickel-molybdate, sulphided nickel-molybdate, oxided cobalt molybdate, and sulphided cobalt molybdate.

References Cited UNITED STATES PATENTS 2,712,497 7/1955 FOX et a1. 20815 2,765,617 10/1956 Gluesenkamp et al. 20815 8 2,913,397 11/1959 Murray et al 208--8 3,012,961 12/1961 Weisz 20815 3,274,224 9/ 1966 Collier et al. 44-69 5 FOREIGN PATENTS 769,293 3/1957 Great Britain. 870,431 6/1961 Great Britain.

OTHER REFERENCES 10 Symposium on Jet Fuels, American Chemical Society,

September 1960, pp. C-19 to C-29.

DANIEL E. WYMAN, Primary Examiner.

15 PAUL E. KONOPKA, Assistant Examiner.

US. Cl. X.R.