US3533938A

US3533938A - Jet fuel from blended conversion products

Info

Publication number: US3533938A
Application number: US665862A
Authority: US
Inventors: Arnold M Leas
Original assignee: Ashland Oil Inc
Current assignee: Ashland LLC
Priority date: 1967-09-06
Filing date: 1967-09-06
Publication date: 1970-10-13
Anticipated expiration: 1987-10-13

Description

Oct. 13, 1970.

Hydrogen Goal Liquids A. M. LEAS Filed Sept. 6, 1967 Destructive Distillation Coke ZIB JET FUEL FROM BLENDED CONVERSION PRODUCTS Desulfurizinq 'r ydrocracking I Reforming Sulfur Olefin Gas 1 IOO V as Ammonia I Polymerization Aromatic Extractor Ol'ef ins Catalytic Thei'mal Crack ng Cracking Alkylation IOG Dehy d rogenati o ,94

Paraffin Gas 74 Hydroq:|enation Slsoparaffin Jet Fuel v /Blending INVENIOR AIkyl Napthene Arno/ d M. Leas ATTORNEY United States Patent US. Cl. 208-80 10 Claims ABSTRACT OF THE DISCLOSURE A high density jet fuel is prepared by hydrocracking a heavy hydrocarbon liquid, preferably coal liquids, separating the hydrocrackate into a light fraction and a heavy fraction, reforming the light fraction and catalytically cracking the heavy fraction, separating the catalytic cracking product into a light and a heavy fraction, thermally cracking the heavy fraction, solvent extracting the light catalytic product and the reformate to recover aromatics therefrom, alkylating the aromatics, and thereafter hydrogenating the aromatics to produce alkyl naphthenes, dehydrogenating paraflin gases, polymerizing the dehydrogenation product, and hydrogenating the polymer to produce isoparaffin. The isoparaffins and alkyl naphthenes are blended in specified proportions to produce the jet fuel.

Field of the invention The present invention relates to a novel high density fuel and a method of preparing the same. In a more specific aspect, the present invention relates to a novel high density fuel or supersonic and faster jet aircraft and a novel method of preparing such fuel from coal liquids.

Description of the prior art Present day specifications for fuels for subsonic aircraft are rather stringent. Among the more important specifications are the volatility characteristics, including flash point, distillation range, and vapor pressure, the low temperature characteristics including viscosity and freeze point, the thermal stability, the burning properties, including smoke point and luminometer number, and the heating value. However, in spite of these specifications and requirements, the needs of subsonic aircraft can be supplied by certain essentially virgin petroleum prod nets and certain specially treated petroleum products. For example, a JP-4 jet fuel consists of a mixture of about 65% gasoline and about 35% light distillate. On the other hand, a ]P5 jet fuel is a specially fractionated kerosene fraction having a higher flash point than most conventional kerosenes. Basically, the primary difference between JP-4 and JP5 fuels are the volatility characteristics thereof, the JP-4 fuel having a higher volatility than JP-5. Special jet fuels, such as JP-6, differ from the previously mentioned fuels primarily in the thermal stability characteristics of the fuel. For example, the volatility characteristics of JP-6 are between those of JP-4 and JP-5, but the thermal stability is substantially higher than either of the previous fuels. In addition, there has also been developed another kerosene-type fuel Whose thermal stability is about equal to that of JP-6 fuel but which has a lower freeze point and a higher smoke point than either JP-5 or JP6 fuels. While these conventional fuels adequately meet the requirements of present-day subsonic and a few supersonic aircraft and they can be produced from unrefined straight run crude oils or special blends of normal parafiins and isoparaffins, these fuels are clearly inadequate for proposed supersonic, hypersonic and faster aircraft.

Specifications for fuels to be used in advanced supersonic and hypersonic jet aircraft, having Mach numbers of 3 or higher are generally dictated by engine and airframe design considerations. For example, airframe structure considerations for high Mach number aircraft in general require that the fuel have a low vapor pressure to thereby alleviate structural design problems for high temperature-high altitude operations and that they have a high B.t.u./gal. for maximum range under the fuel volume limitations imposed. Likewise, optimum engine design requires a high burning quality for cleanliness of the flame in the combuster to thereby reduce the engine linear temperature, a high heat sink capacity so that the fuel can act as the primary heat sink necessary for cooling the aircraft and high thermal stability to withstand the high operating temperatures without premature decomposition. Another requirement of military jet fuels not connected to airframe or engine limitations is a low freeze point to permit in-flight refueling operations. Thus, in order to satisfy all the requirements of an ideal case, such a fuel would have a vapor pressure of less than about 2.6 p.s.i.a. at 300 F., a heat content greater than 135,000 B.t.u. per gal., a luminometer number greater than 100 and a freeze point of less than -60 F. However, such an ideal fuel cannot be produced at any cost since certain of these specifications are contradictory. For example, it is impossible to obtain both low vapor pressure and high B.t.u. per gallon, while at the same time maintaining a high luminometer number. For example, to meet a 135,000 B.t.u. per gallon requirement, the maximum luminometer number possible is 50. Similarly, while normal paraffins and normal paraffins blended with isoparaflins will generally produce high luminometer numbers, such materials are wholly lacking in their heat sink capacity. Further, if the fuel contains in excess of about 40% normal parafiins, which is generally required to obtain a luminometer number above 100, it is practically impossible to obtain a freeze point lower than about -50 F. It has been suggested, however, that the property of lesser criticality appears to be the luminometer number since the luminometer number can be reduced to about to without sacrificing hydrogen content of the fuel, by replacing normal parafiins with isoparafiins. Therefore, the idealized speci fications previously mentioned can be modified to include the following specifications:

Property Maximum requirement Vapor pressure, p.s.i.a. at 300 F. 2-,6 Volumetric heat content, B.t.u./ gal 124,000 Luminometer number 75 to 80 Freeze point, F 56 to 60 Net heat of combustion, B.t.u./lb. 18,750 Flash point, F. (min.) 150 Initial boiling point, F. (min.) 375 10% at 400 F. 50% at 420 F. 90% at 500 F. End point at 550 F. Gravity, degree API 44-50 Viscosity, centistokes at 30 F. 15 Thermal stability 300/ 500/ 600 F? Water separometer index modified, min.

1 Hydrogen content 14%. 2 3 in. pressure drop 3 code preheater deposit.

As a result of the lowered luminometer number, larger volumes of isoparafiins can be substituted for the normal paraflins to produce satisfactory jet fuels. However, highly isoparaflinic jet fuels still lack the high densities required for utilization of the fuel as a heat sink in supersonic and faster aircraft. In addition, the production of isoparaffines from petroleum stocks is a rather expensive operation and cannot be economically justified as a general proposition, except to produce small volumes of specialty fuels. Further, it does not appear that sufficient volumes of normal paraflins and isoparafiins will be available from petroleum sources to meet the predicted volume requirements for supersonic plus jet fuels.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an improved high density fuel and a method of manufacturing the same. Another object of the present invention is to provide an improved high density fuel for use in supersonic and faster aircraft and a method of preparing the same. Still another object of the present invention is to provide an improved high density fuel comprising a major proportion of alkyl naphthenes and a minor proportion of isoparaffins and a method of producing the same. Another and further object of the present invention is to provide an improved high density fuel by hydrogenating polyolefins derived from petroleum and hydrogenating alkyl aromatics derived from coal. Still another object of the present invention is to provide an improved high density fuel by alkylating aromatics derived from coal to produce alkyl aromatics and thereafter hydrogenating the alkyl aromatics. Another and further object of the present invention is to provide an improved high density fuel by hydrocracking coal liquids, alkylating the resultant hydrocrackate to produce substantial volumes of alkyl aromatics and hydrogenating the alkyl aromatics to produce alkyl naphthenes. A further object of the present invention is to provide an improved high density fuel by hydrocracking coal liquids to produce substantial amounts of monocyclic aromatics, alkylating such aromatics with olefins to produce alkyl aromatics and hydrogenating the alkyl aromatics to produce alkyl naphthenes. Another object of the present invention is to provide an improved high density jet fuel by hydrocracking coal liquids to produce substantial volumes of monocyclic aromatics, alkylating the aromatics with olefins to produce alkyl aromatics, hydrogenating the alkyl aromatics to produce alkyl naphthenes, polymerizing olefins to produce polyolefins and hydrogenating the polyolefins to produce isoparaffins. Still another object of the present invention is to provide an improved high density fuel by hydrocracking coal liquids to produce substantial amounts of monocyclic aromatics, alkylating the aromatics with olefins to produce alkyl aromatics, hydrogenating the alkyl aromatics to produce alkyl naphthenes, dehydrogenating parafiins to produce olefins, polymerizing the dehydrogenated olefins, with or without additional olefins, to produce polyolefins, and hydrogenating the polyolefins to produce isoparaffins. Another and further object of the present invention is to provide an improved high density fuel by hydrocracking coal liquids, separating the hydrocrackate into a light liquid product and a heavy product, reforming the light liquid product to produce substantial volumes of monocyclic aromatics, cracking the heavy liquid fraction to produce substantial volumes of monocyclic aromatics, alkylating the aromatics with olefins to produce alkyl aromatics, hydrogenating the alkyl aromatics to produce alkyl naphthenes, dehydrogenating paraffins to produce olefins, polymerizing the dehydrogenated olefins, with or Without additional olefins, to produce polyolefins and hydrogenating the polyolefins to produce isoparaflins. Yet another object of the present invention is to provide an improved high density fuel by hydrocracking coal liquids; separating the hydrocrackate into a light liquid product and a heavy liquid product; reforming the light liquid product to produce substantial volumes of monocyclic aromatics; catalytically cracking the heavy liquid product; separating the catalytically cracked product into a light liquid product and a heavy liquid product, thermally cracking the heavy liquid product; alkylating the liquid reformate, the light liquid product of catalytically cracking and the product of thermal cracking with olefins to produce alkyl aromatics; hydrogenating the alkyl aromatics to produce alkyl naphthenes, dehydrogenating parafiins to produce substantial volumes of olefins, polymerizing the dehydrogenated olefins with or without additional olefins to produce polyolefins, and hydrogenating the polyolefins to produce isoparafiins. A yet further object of the present invention is to provide a high density fuel by hydrotreating coal liquids to remove sulfur therefrom; hydrocracking the desulfurized liquids; separating the hydrocrackate into a light liquid product and a heavy liquid product; reforming the light liquid product to produce substantial volumes of monocyclic aromatics catalytically cracking the heavy liquid product; separating the catalytically cracked product into a light liquid product and a heavy liquid product; thermally cracking the heavy liquid product; alkylating aromatics from the reformate, the light catalytically cracked product, and the thermally cracked product with olefins to produce alkyl aromatics; hydrogenating the alkyl aromatics to produce alkyl naphthenes; dehydrogenating paraffins to produce substantial volumes of olefins; polymerizing the dehydrogenated olefins with or without additional olefins to produce polyolefins, and hydrogenating the polyolefins to produce isoparafiins.

Briefly the present invention comprises a high density fuel containing from 5 to 50% by volume of isoparafiins obtained by hydrogenating polyolefins and from to 50% by volume of alkyl naphthenes obtained by hydrogenating alkyl aromatics.

It has been found, in accordance with the present invention, that by preparing a fuel having substantial volumes of alkyl naphthenes, preferably of monoand dicyclic character, and adding minor proportions of isoparaffins thereto, a high density fuel capable of providing a high heat sink capacity, particularly for use in supersonic and faster aircraft, is obtained, while at the same time providing a high hydrogen content to compensate for a lowered luminometer number and a low vapor pressure. It has also been found in accordance with the present invention that the substantially volumes of alkyl naphthenes required for such high density fuels can be effectively and economically produced from coal liquids. The objects and advantages of the present invention as set forth above, as well as other obvious advantages, will be apparent from the following detailed description when read in conjunction with the single figure of the drawings.

Description of the preferred embodiments Referring, in detail, to the drawing, a wide variety of feed stocks may be utilized in accordance with the present invention. These feed stocks may comprise hydrocarbons boiling all the way from the initial boiling point of gasoline F.) through heavy asphaltic and pitch materials. Preferably, however, feed stocks boiling above F. are used. For example, straight run gasolines and kerosenes of petroleum origin, such as JP-4 jet fuel materials boiling from about 140 to 470 F., JP-S materials boiling between about 360 and 490 F. and kerosenes boiling up to 550 F. may be upgraded in accordance with the present invention. However, for reasons which will become obvious later, these materials are preferably utilized in combination with other feed stocks. In any event, if liquid materials boiling below about 550 F., derived from petroleum stocks, shale oils, tar sands, and the like, are utilized as a part of the feed, these materials should be charged directly to hydrocracking unit 10 through line 12. Normally such petroleum-derived materials contain rather small amounts of sulfur and therefore what sulfur is present will be conveniently removed in the hydrocracking unit or from the gaseous by-products of the hydrocracking unit. Preferably, heavier petroleumderived liquids, including asphaltic materials, are utilized as a feed stock for the hydrocracker. For example, distillate fuel oils derived from petroleum and like sources boiling between about 425 and 1000 F. may be charged directly to hydrocracking unit through line 12. Still heavier fractions boiling above about 1000 F., including liquid, semi-solid and solid residual fuel oils, asphaltic materials, pitches and the like, can be used but these materials should be subjected to a destructive distillation by feeding the same through line 14 to destructive distillation unit 16. Destructive distillation unit 16 may take a variety of well known forms, such as a visbreaking unit, a carbonization unit or a coking unit, preferably a fluidized coking unit. Destructive distillation unit 16 will normally produce coke which is discharged through line 18, a liquid product which is passed through line 20 to hydrocracking unit 10 and a gaseous product which is discharged through line 22.

While limited volumes of alkyl nnaphthenes can be produced from petroleum, shale oil, tar sand, and other like sources, it has been found in accordance with the present invention that high density fuels suitable for use in supersonic and faster aircraft cannot be effectively and economically produced in sufficient quantities from such sources. Accordingly, liquid petroleum and like feed stocks are preferably a supplemental feed stock. In accordance with the preferred embodiment of the present invention, high density fuels containing a major proportion of alkyl naphthenes are produced from coal liquids. The coal liquids may be derived in various manners; for example, they may be liquids produced by the solvent extraction of solid coal, introduced through line 24, and/ or liquids obtained by the low temperature carbonization of solid coal or coal liquids, introduced through line 26. It should be recognized here that heavy petroleum and asphalt fractions can also be processed in a low temperature carbonization unit with the coal, and, therefore, the liquid through line 26 may contain some petroleum derivatives. Such coal liquids ordinarily contain substantial amounts of contaminating sulfur and nitrogen and are predominantly hydrogen-deficient, highly complex, polycyclic compounds and therefore relatively unstable. Therefore, it is preferred that the coal liquids be subjected to a desulfurization treatment in desulfurizer 28. Desulfurizer 28 is preferably a hydrotreating or mild hydrogenation unit and is supplied with hydrogen through line 30. In hydrotreater 28, the bulk of the sulfur is removed from the coal liquids. In addition, a certain degree of stabilization is brought about by partial hydrogenation of the hydrogen-deficient coal liquids. Such stabilization is highly desirable in the subsequent treatment of coal liquids to produce the liquid products of the present invention, since without such stabilization, the hydrogen-deficient coal liquids will be driven toward gasification and coke formation during subsequent treatments. Sulfur will be removed through line 32, While the partially hydrogenated coal liquids will pass through line 34 to hydrocracking unit 10. In hydrocracking unit 10, which is supplied with hydrogen through line 36, the hydrogenation of the hydrogen-deficient coal liquids is completed and the multicyclic complex coal molecules are broken down into hydrocarbons having fewer rings per molecule. In addition, contaminating nitrogen compounds present in the coal liquids are removed by conversion to ammonia, which is discharged through line 38. The hydrocrackate from hydrocracking unit 10 is split into two liquid fractions; a light liquid fraction boiling below the end point of the desired fuel product, preferably about 425 F., and a heavy liquid fraction boiling above about 425 F. The light liquid fraction from hydrocracking unit 10 is passed through line 40 to reforming unit 42. In reforming unit 42, additional cracking occurs as well as some dehydrogenation and isomerization to produce substantial volumes of aromatic hydrocarbons, particularly aromatic hydrocarbons with branched chains and alkyl substituents. The heavy liquid product from hydrocracking unit 10 is passed through line 44 to catalytic cracking unit 46. In catalytic cracking unit 46, the heavy material is further cracked to reduce the number of rings per molecule and reduce the boiling point of the material still further. The catalytic cracking product is also preferably separated into a light liquid fraction and a heavy liquid fraction. The light liquid fraction is discharged through line 48 while the heavy liquid fraction is passed through line 50 to thermal cracking unit 52. In thermal cracking unit 52, additional cracking and reduction of the boiling point of the material is brought about. Ultimately, the light liquid product from catalytic cracking unit 46 (in line 48) is combined with the thermally cracked product in line 54 and the reformate from reforming unit 42 which is discharged through line 56. It should, however, be recognized that these products may be maintained as separate streams and treated separately. In any event, these liquid products generally boil in the kerosene boiling or jet fuel boiling range and contain substantial volumes of aromatic materials, particularly monoand di-cyclic aromatics having alkyl side chains, such as alkyl substituted aromatics and isoalkyl substituted aromatics. Such aromatic materials are removed from the remaining liquids in the mixture by an aromatic selective extraction in aromatic extractor 5'8. Aromatic extractor 58 is preferably a selective solvent extraction unit such as a furfural, ethylene phenolglycol or sulfolane extraction unit. Following removal of the solvent from the aromatic extract, the aromatic material is discharged through line 62. Materials boiling higher than the kerosene or jet fuel range can also be removed at this point and the solvent extraction ratfinate may be further split into two fractionsa light liquid fraction and a heavy liquid fraction. The former is recycled to the thermal cracking unit through line 64, While the heavy material is recycled to the catalytic cracker through line 66. The aromatics from line 62 are fed to alkylation unit 68. In alkylation unit 78, the aromatic material is treated with olefins, such as ethylene, propylene, butylenes, and amylenes, introduced through line 70. Alkylation unit 68 performs the function of further substituting the aromatic materials with alkyl and isoalkyl side chains. Alkyl aromatics from alkylation unit 68 are fed through line 72 to hydrogenation unit 74. Hydrogenation unit 74 is supplied with hydrogen from line 76. In hydrogenation unit 74, the alkyl aromatics are completely saturated to produce substantial volumes of alkyl and isoalkyl substituted naphthenic hydrocarbons. As indicated previously, the ideal alkyl naphthenes are those having a single ring and preferably, not more than 2 rings per molecule. The alkyl naphthenes thus produced in hydrogenation uint 74 may be discharged through line 78 to jet fuel blending unit 80. Depending upon the source of hte feed to hydrocracking unit 10 and the character of the feed, a certain amount of alkyl naphthenes will be produced directly in hydrocracking unit 10. Under these circumstances, this material boiling in the jet fuel range of about 375 F. to about 550 F. may be passed to jet fuel blending unit 80 directly through line 82. Hydrogen from reforming unit 42 is passed to hydrocracking unit 10* through line 84. Normally gaseous hydrocarbons and highly volatile light liquids produced in destructive distillation unit 16-, hydrocracking unit 10, reforming unit 42, catalytic cracking unit 46 and thermal cracking unit 52 and discharged through

lines

22, 86, 88, 90, and 92, respectively, may be separated into paraffiuic and olefinic fractions. The olefinic materials may be utilized in alkylation unit 68 by introduction through line 70. Paraflins, with or without previous separation of olefins, may be introduced to dehydrogenation unit 94 through line 96. In dehydrogenation unit 94, the paraflins are converted to olefins and discharged through line 98. From line 98 the olefins are passed to polymerization unit 100 Where they are converted to polyolefins of higher molecular Weight. Polymerization unit 100 is, of course, operated under conditions such that the primary product is a liquid boiling between about 375 and 550 F. Unreacted paraffins may be separated from the product of polymerization unit 100 and recycled to dehydrogenation unit 94 through line 102. This cyclic passage of olefins through line 98 and paraflins through line 102 is carried out to the substantial extinction of all paraflinic materials in the system. In addition to, or in place of the olefinic materials from dehydrogenation unit 94, olefins materials, particularly normally gaseous olefins, may be fed directly to polymerization unit 100 through line 104. While the olefinic and paraflinic feeds to dehydrogenation unit 94 and polymerization unit 100 may be derived from destructive distillation, hydrocracking, reforming, catalytic cracking and thermal cracking, these sources are generally insutficient to produce enough materials of this character when coal liquids are utilized as feed materials to these units. Accordingly, petroleum is utilized as the primary source of olefins and paratfins for the dehydrogenation and polymerization units. Accordingly, petroleum gases and light ends separated from crude petroleum and/or gases and light ends generally referred to as refinery light ends or gases recovered from various petroleum refining operations are utilized as feeds to the dehydrogenation and polymerization units with supplemental materials of this character being added from the present plant. The refinery light ends referred to are generally recovered for most refinery operations, including reforming, cracking, and the like. The polyolefins from polymerization unit 100 are discharged to line 106 to hydrogenation unit 74. While hydrogenation unit 74 is shown as a single unit, the polyolefins are preferably hydrogenated separately from the alkyl aromatics. The hydrogenated polyolefins will therefore contain substantial volumes of isoparafiins boiling in the range of about 375 to 550 F.; that is, within the jet fuel range. These isoparaflins are discharged through line 108 to jet fuel blending unit 80. As indicated previously, alkyl naphthenes in the amount of about 50 to 95% are blended with isoparaflins in an amount of about to 50% to produce the high density jet fuels of the present invention. Preferably, the amount of alkyl naphthenes will be between 5 and by weight of the total fuel. Ideally, the alkyl naphthenes are triisopropyl cyclo-hexane and like monocyclic materials. With such monocyclic materials predominating, only about 5 to 15% of isoparaffins are necessary to obtain a jet fuel meeting the most stringent specifications and specifically, one having a high density, a low vapor pressure, a high fuel value or hydrogen content, and a reasonably high luminometer number. If, on the other hand, the majority of the alkyl naphthenes are double ring or dicyclic materials, then larger volumes of isoparaffins up to about 50% by volume need to be added.

If a highly aromatic crude feed boiling in the kerosenegasoline range is available, such feed may be fed directly to hydrogenation unit 74, as through line 110, or it may be first resulfurized to produce the naphthenic component of the jet fuel.

The hydrocracking zone may be a conventional unit operated in two stages and containing conventional hydrocracking catalysts, including nickel oxide or nickel sulfide on silica-alumina, cobalt-molybdenum on alumina, a precious metal on silica-alumina, etc. Such a two stage unit should employ a more active catalyst in the second stage. Operation of the hydrocracking units is at a pressure of at least about 500 p.s.i.g. and preferably 1000 to 3500 p.s.i.g., a temperature from about 400 to 1200 F., and preferably 700-850 F., a hydrogen feed rate of about 100 to 20,000 s.c.f. per barrel, and preferably 2000 to 10,000 s.c.f. per

barrel, and a liquid hourly space velocity of about 0.1 to 5.0, and preferably 0.3 to 5.0.

As indicated, where high sulfur contents are encountered in the feed material, a desulfurization step should precede a hydrocracking step. This desulfurization is preferably a conventional hydrofining operation and when such a hydrofining operation is involved, the hydrocracking step may be a single stage hydrocracking step. In the hydrofining operation, sulfur compounds and at least a part of the oxygen and nitrogen compounds are removed by operating with catalysts, such as nickel-molybdate on alumina, etc., at a space velocity of about 1 to 3, a temperature of about 300 to 900 F., a pressure of about 500 to 2000 p.s.i.g., and a hydrogen feed rate of about 1000 to 10,000 s.c.f. per barrel of feed. The hydrofining operation may also serve to partially hydrogenate and stabilize the feed. Preferably, the hydrotreatment is in two stages at 300 to 600 F. and 700 to 900 F respectively.

The coking operation is preferably a fluidized coking operation, as indicated above. In this process, the feed is subjected to a temperature of about 900 to 1050 F., at essentially atmospheric pressure. Coking occurs in a thin liquid film on a circulating, fluidized seed coke agitated by rising gaseous products in the reactor. The fluidized coke is preheated to a temperature of about 1110 to 1200 F., before entering the reactor. The feed enters the reactor at a preheat temperature about 500 to 700 F.

The catalytic cracking is preferably carried out as a fluid catalytic cracking operation. Operating temperature for the fluid catalytic cracking operation should be between a temperature of about 850 to 1100 F., and preferably 880 to 980 F., a pressure of about 0 to 50 p.s.i.g., and preferably 10 to 16 p.s.i.g., a liquid hourly space velocity of about 0.5 to 5, and a catalyst to oil ratio of about 2 to 12/1, and preferably 8 to 12/ 1. Suitable catalysts include silica-alumina, silica-magnesia, etc.

The catalytic reforming is preferably carried out in the presence of a reforming catalyst such as a precious metal on alumina. Conditions of operation include a temperature of about 800 to 1000 F., and preferably 900 to 1000 F., a pressure of about 0 to 1000 p.s.i.g., and preferably 50 to 200 p.s.i.g., a liquid hourly space velocity between about 1 and 20, and preferably 1 and 10, and a hydrogen rate of about to 10,000 s.c.f. per barrel of feed, and preferably 2,000 to 10,000 s.c.f. per barrel.

The thermal cracking operation may be a mixed phase operation operating at a pressure above about 300 p.s.i.g., and at a temperature between about 750 and 900 F., or a vapor phase operation at pressures below 50 p.s.i.g., and a temperature of about 1000 to 1100 F.

As indicated, the solvent extraction is an operation at which the aromatics are removed by aromatic selection solvents and includes conventional extractions with solvents such as phenol, sulfur dioxide, glycol-water, etc.

Aromatic alkylation is preferably carried out in the presence of a solid silica-alumina catalyst with a boron fluoride promoting agent deposited thereon. Suitable operating conditions include a temperature of about 30 to 800 F., and preferably to 450 F., a pressure between about 10 and 2000 p.s.i.g., and preferably 300 to 1000 p.s.i.g., and a liquid hourly space velocity of about 0.1 to 20, and preferably 0.5 to 2.0.

The dehydrogenation operation is carried out in the presence of a catalyst such as chromina on alumina with potassium or sodium promoters, nobel metals, etc. The temperature should be maintained between about 0 and 1200 F., and preferably 800 and 1200 F., the pressure should be between essentially about 0 and 1000 p.s.i.g., and preferably atmospheric pressure, and the liquid hourly space velocity should be about 0.1 to 10, and preferably 0.5 to 2.0.

The polymerization unit preferably employs a boriaalumina or silica-tungstic acid on silica-alumina as a catalyst. Suitable operating conditions include a temperature of about 0 to 500 F., and preferably 75 to 400 F.,

at a pressure of about to 1000 p.s.i.g., and preferably 100 to 1000 p.s.i.g., and a liquid hourly space velocity of about 0.1 to 10, and preferably 0.2 to 5.0.

Hydrogenation of the isoparafiins and alkyl aromatics may be carried out in the prccsence of precious metal such as platinum, on alumina, at a temperature of about 100 to 900 F., and preferably 200 to 600 F., a pressure of about 0 to 10,000 p.s.i.g., and preferably 100 to 1000 p.s.i.g., a liquid hourly space velocity of about 0.1 to 10, and preferably 0.5 to 5.0, and a hydrogen feed rate of about 100 to 3000, and preferably 500 to 3000 s.c.f. per barrel of feed.

The operation of the present invention can be illustrated by a series of runs conducted in a laboratory pilot plant. In this series of runs, aromatic charge stock, comprising primarily benzene, toluenes, xylenes, cumenes and other alkyl aromatic hydrocarbons, boiling generally in the kerosene boiling range and recovered from the refinery operations on crude petroleum oils and equivlent coal liquids, separated from broad boiling range coal liquids, where alkylated with normally gaseous olefins obtained by the thermal and catalytically cracking of crude petroleum oils, including ethylene, propylene, butylcues and amylenes. Alkylation catalysts included phosphoric, sulfuric and hydrofluoric acids, in liquid form and impregnated on inert solids, activated clays, aluminum chloride and molecular seives. The temperatures of alkylation were maintained between about 300 and 800 F., and in most cases between 80 and 650 F., while the pressures were varied between 10 and 2000 p.s.i.g., and in most cases between 100 and 500 p.s.i.g. Liquid hourly space velocities were varied from 0.1 to 20, and in most cases between 0.5 and 2.0, depending upon the type of catalyst employed. When operating at the higher temperatures, small amounts of hydrogen were injected at a very low rate to reduce coking and to maintain the operating pressure of the system. The alkylation product was fractionated to recovery an alkyl aromatic fraction boiling in the kerosene range and to remove unreacted aromatics and olefins therefrom. The aromatics and olefins were recycled essentailly to extinction. Usually a gas oil fraction boiling above the kerosene range was recovered in amounts of about to by volume of the product. This gas oil fraction was dealkylated with a hot clay catalyst to reduce the same to an aromatic kerosene and the aromatic kerosene was then recycled to the alkylation step, essentially to extinction. Accordingly, virtually all of the aromatics and olefins were converted to kero sene boiling range alkylaromatics. The alkyl aromatic products were then hydrogenated under hydrogenation condiitons varying throughout the conventional range and while utilizing a variety of conventional hydrogenation catalysts. Substantial volumes of naphthenic, and particularly high density alkyl naphthenic, materials were produced. These products were also highly stable, and, when treated by the addition of conventional jet fuel additives, met all of the specifications previously mentioned herein. Blending of these materials with from 5 to 50% of isoparaffinic hydrocarbons derived from petroleum crude oils permitted the production of jet fuels meeting specifications for subsonic, supersonic and postulated hypersonic jet fuels.

Having illustrated the present invention by specific examples and a specific drawing, it is to be understood that these are not to be considered limiting, but the present invention is to be limited only by the appended claims.

I claim:

1. A method of producing a high density jet fuel, comprising; subjecting a hydrocarbon liquid boiling between about 425 and 1000 F. to hydrocracking in the presence of a hydrocracking catalyst at a pressure above 500 p.s.i.g., a temperature of about 400 to 1200 F., at a space velocity of about 0.1 to 5.0, and in the presence of hydrogen, at a rate of about 100 to 20,000 s.c.f. per barrel; separating the hydrocracking product into a light product boiling below 425 F and a heavy product boiling above 425 F.; subjecting the light fraction to catalytic reforming in the presence of a reforming catalyst, at a temperature of about 800 to 1000 F., a pressure of about 0 to 1000 p.s.i.g., a liquid hourly space velocity of about 1 to 20, and in the presence of hydrogen at a rate of about 100 to 10,000 s.c.f. per barrel; catalytically cracking the heavy fraction in the presence of a cracking catalyst at a temperature of about 850 to 1100 F., at a pressure of about 0 to 50 p.s.i.g., at a liquid hourly space velocity of about 0.5 to 5, and a catalyst-to-oil ratio of about 2 to 12 to 1; separating the catalytic cracking product into a heavy product fraction and a light fraction, thermally cracking the heavy fraction at a pressure above 300 p.s.i.g. and at a temperature of about 750 to 900 F.; solvent extracting the reformate, the thermal cracking product and the light catalytic cracking product to recover aromatics therefrom; subjecting the aromatic extract to alkylation in the presence of an alkylation catalyst at a temperature of about 30 to 800 F., a pressure of about 10 to'2,000 p.s.i., and a liquid hourly space velocity of about 0.1 to 20; dehydrogenating normally gaseous hydrocarbons in the presence of a dehydrogenation catalyst, at a temperature of about 0 to 1200 F., a pressure of about 0 to 1000 p.s.i.g., and a liquid hourly space velocity of about 0.1 to 10; subjecting the dehydrogenation product to polymerization in the presence of a polymerization catalyst, at a temperature of about 0 to 500 F., at a pressure of about 0 to 1000 p.s.i.g., and at a liquid hourly space velocity of about 0.1 to 10; hydrogenating the alkylation product and the polymerization product in the presence of a hydrogenation catalyst, at a temperature of about 100 to 900 F., a pressure of about 0 ot 10,000 p.s.i.g., a liquid hourly Space velocity. of about 0.1 to 10, and in the preesnce of hydrogen at a rate of 100 to 3,000 s.c.f. per barrel; and blending about 50% to by volume of hydrogenated alkylation product with about 5% to 50% by volume of hydrogenated polymer product.

2. A method in accordance with claim 1 wherein at least a part of the liquid hydrocarbon feed is a liquid separated from a normally solid carbonaceous material.

3. A method in accordance with claim 2 wherein the solid carbonaceous material is coal.

4. A method in accordance with claim 1 wherein the hydrocarbon feed is a liquid separated from a solid carbonaceous material and said liquid is subjected to desulfurization before feeding the same to the hydrocracking step.

5. A method in accordance with claim 1 wherein unconverted parafiins in the polymerization product are recycled to the dehydrogenation step to essential extinction.

6. A method in accordance with claim 1 wherein a nonaromatic fraction is separated from at least the reforming product and at least a part of the separated non-aromatic liquid is recycled to the catalytic cracking step.

7. A method in accordance with claim 1 wherein the reforming product is treated to separate a non-aromatic liquid therefrom prior to its utilization as an liquid aromatic feed, the separated non-aromatic liquid is further separated into a light liquid fraction and a heavy liquid fraction, the light non-aromatic liquid is recycled to the thermal cracking step and the heavy.

8. A method in accordance with claim 1 wherein at least a part of the crude oil to the hydrocracking unit is a crude petroleum oil.

9. A method in accordance with claim 1 wherein a heavy petroleum oil is subjected to a destructive distillation operation under conditions sufficient to reduce the molecular weight thereof and at least a part of the destructive distillation product is utilized as the crude oil feed to the hydrocracking step.

10. A method in accordance with claim 9 wherein the destructive distillation step is a coking step.

(References on following page) References Cited UNITED STATES PATENTS Van Battum 260671 Fox et a1 20815 Gluesenkamp et a1. 20815 Axe et a1. 20815 Leas et a1. 20815 Herder et a1. 20815 Reeg et a1. 20815 12 Barnes et a1 20815- Smith et a1 260666 Edwards 20866 Boodrnan et a1. 20815 HERBERT LEVINE, Primary Examiner U.S. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 533, 938 Dated October 13, 1970 Inventor(s) ARNOLD M. LEAS It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

At Column 10, line 63 (Claim 7) after the word "heavy" delete the period and insert ---non-a.roma.tic liquid is recycled to the catalytic cracking step.

Signed and sealed this 1 at day of June 1971 (SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SGHUYLER, JR. Attesting Officer Commissioner of Patents FORM P0-105O (10-69) USCOMM-DC 0037a P69 0.5 GOVERIIKNT PRINTING OFFICE Ill! 0-361-834