US3148136A - Treatment of hydrocarbons to produce a jet fuel and high octane gasoline - Google Patents

Description

Sept. 8, 1964 R. A. WOODLE 3,148,136

TREATMENT OF HYDROCARBONS TO PRODUCE A JET v FUEL AND HIGH OCTANE GASOLINE Filed Sept. 14, 1959 United States Patent 3,148,136 TREATMENT (3F EDRUtZARBQNS T0 PRGDUCE A JET FUEL AND HEGH UQTANE GAStELiNE Robert A. Woodie, Nederianrl, Tex assignor to Texaco Inc, New York, FLY a corporation of Delaware Filed Sept. 14, 1959, Ser. No. 339,646 5 Claims. (Cl. Z08-69) This invention relates to the treatment of hydrocarbons. More particularly it is concerned with the production of improved fuels for gas turbine engines especially those used in the propulsion of aircraft.

Two of the problems currently encountered in the operation of jet aircraft, as gas turbine propelled aircraft are commonly called, are that the fuels currently employed produce excessive smoke during takeoff and the highly luminous flame produced by the burning of the fuel makes frequent engine overhauls necessary. To prevent or reduce the production of smoke during take-ofl it is customary to inject a water-alcohol mixture into the engine with the fuel during take-off. This procedure requires a dual tankage system in the aircraft and is an expensive solution to the problem of reducing or eliminating smoke. Furthermore, it is an added complication at a critical moment in the operation of the aircraft. Also, because the fuels currently used burn with highly luminous flames which radiate large amounts of heat, it is necessary to inspect and overhaul the gas turbine engine after from about 500-600 hours of operation. Those parts in close proximity to the flame, particularly the flame tube which surrounds the combustion zone having a temperature of 3000 F. and higher, are subjected to extreme thermal stress which results in creeping, warping and buckling of the flame tube and other par-ts. In some instances the high radiation from the flame also causes buckling of the turbine rotor to such an extent that malfunctioning and sometimes complete failure of the engine results.

It has been found that fuels having a high luminosity number have a reduced tendency to produce smoke during take-off and also tend to burn with a flame of low radiation. Hence, when high luminosity number fuels are used, the engine parts are subjected to less thermal stress than in the case of fuels currently in use such as JP-4, J P-5 and kerosene which have luminosity numbers of about 54, 37 and 36 respectively. The present invention contemplates the production of fuels having luminosity numbers ranging from 85100 and higher.

It is therefore an object of the present invention to provide a high luminosity number fuel for gas turbine or jet engines.

Another object of the invention is to provide a jet fuel which subjects the jet engine parts to reduced thermal stress.

Another object of the invention is to provide an improved process for the production of jet fuels which produce reduced amounts of smoke during take-off. These and other objects will be obvious from the following disclosure.

' The luminosity number which is used to rate gas turbine engine fuels is defined by the following equation:

A T (test fuel) A T (tetralin) A T (isooctane) A T (tetralin) LuminOsity NO. X 100 AS'lM Standards on Petroleum Products and Lubricants, published 1956 by the American Society for Testing Materials.

temperature of the incoming air, the other shielded from the flame and inserted in the chimney to measure the temperature of the combustion gases. A radiometer is also adjustably positioned 'to measure the amount of radiation emanating from the flame.

To determine the luminosity number, several determinations are made burning tetralin in the lamp, each run being made at a different Wick height, the radiometer being positioned at the zone of maximum radiation and the amount of radiation for each determination and the temperature differential between the incoming air and the combustion gases being recorded. After several determinations have been made on tetralin a curve is drawn plotting AT against the amount of radiation. Similar curves are then made for isooctane and the test fuel. The AT for each material at a selected amount of radiation, e.g., 0.3 mv. is read from the curves and is inserted in the appropriate place in the above formula. The luminosity number of the test fuel is then easily calculated.

Accordingly, the present invention contemplates a process for the production of a jet fuel of improved properties which comprises passing the feed hydrocarbon in the liquid phase serially through a plurality of reaction zones maintained at elevated temperatures and pressures, the pressure in each zone being at least 25 p.s.i.g. and preferably at least 50 p.s.i.g. lower than the pressure of the preceding zone and recovering the fraction boiling from about 250600 F. or any selected portion thereof such as the BOO-480 P. fraction from the reaction product. The present invention also contemplates an after-treatment for the production of superior fuels.

The process of the invention is carried out in the absence of a catalyst. In other words, the reaction zones are void and contain neither catalyst nor packing. The reaction conditions such as temperature and pressure are maintained high enough to keep substantially all of the reactants in the liquid phase. Thus, at least and preferably at least of each reaction zone will contain reactants in the liquid phase. Temperatures will range from 770 to 930 F., preferably 790 to 870 F. Pressures will range from 50 to 1000 p.s.i.g. or higher, the pressure in each reactor being lower than the pressure in the preceding reactor. Normally, all of the reactors will be maintained at substantially the same temperature. Reaction times of 60 to 300 minutes may be employed for the liquid material, preferably reaction times of 90 (to 180 minutes 'are used. The ratio of liquid to vapor in the system should be maintained between about 18:1 and 180: 1.

Any suitable hydrocarbon material may be treated by the process of the present invention. Preferably, the feed stock has an initial boiling point above the desired end point of the product jet fuel. The charge stock may be a virgin distillate, a deasphalted reduced crude, a deasphalted furfural refined reduced crude or distillate, a furfural refined propane distillate prepared from a deasphalted reduced crude, paraflin wax or a mixture thereof. A particularly desirable jet fuel is produced by topping crude, deasphalting the reduced crude, subjecting the DA oil to a mild low conversion catalytic denaphthenization treatment, extracting the product with furfural, and subjecting the r aflinate to the liquid phase thermal treatment described above.

The invention may be better understood from the following example described in connection with the accompanying drawing which shows diagrammatically a flow scheme for the practice of the present invention.

The feed, which in this case is a rafiinate fraction obtained by subjecting a deasphalted oil to a mild catalytic denaphthenization at a temperature of 750 F., atmospheric pressure, a space velocity of 1.0 volume of feed per volume of catalyst per hour using a silica-alumina Patented Sept. 8, 1964 spanner;

bead catalyst and extracting the product with furfural, and which has an initial boiling point of 550 F., is introduced through line 21, passes through heat exchanger 22, line 23, heat exchanger and line 26 to heater 27 where it is heated to a reaction temperature of 850 F. The feed then passes through transfer line 28 to reactor 29 which is maintained at a pressure of 400 p.s.i.g. The feed is then removed from the bottom of reactor 29 and sent through lines 38 and 30 to reactor 31, which is maintained at a temperature of 860 F. and a pressure of 300 p.s.i.g. In the upper portion of reactor 31 where a vapor space is maintained and into which the feed from line 30 is introduced, the vapors are disengaged from the incoming liquid and removed through line 33. The liquid passes downwardly through reactor 31 and by means of lines 32 and 35 is introduced into the upper portion of reactor 36 which is maintained at a temperature of 870 F. and a pressure of 150 p.s.i.g. Vaporous material disengaged from the liquid is removed from the upper portion of reactor 36 by means of line 37 and the liquid material is withdrawn through lines 39 and 40 and introduced into the upper portion of reactor 42 which is maintained at a temperature of 880 F. and a pressure of p.s.i.g. Vaporous material is removed from reactor 42 through line 43 and the liquid material is removed from the lower portion of reactor 42 and is sent by means of line 44, heat exchanger 25 and line 46 to flash tower 47. In flash tower 47 material boiling through the gas oil range or up to about 800 F. is removed as overhead through line 43 and residual material is Withdrawn through line 50. This latter material is removed from the system through line 51. The overhead withdrawn from flash tower 47' through line 48 is combined with the vapors and gaseous material in line 34 and is introduced into the lower portion of fractionating tower 52. The fractionating tower 52 is operated at essentially atmospheric pressure and the overhead withdrawn through line 53 has the end point of the desired jet fuel, which, in this example, is 480 F. The overhead passes through condenser 54 and line 55 to separator 56 in which the non-condensibles are separated from the liquid and withdrawn through line 63. The liquid prodnot is removed from separator 56 through line 57 and sent through line 58 to a fractionator (not shown) from which the desired jet fuel fraction is withdrawn as bottoms. The product has a boiling range of 300480 F. and a luminosity number of 102.

To improve the separation of the desired product a portion of the material withdrawn from separator 56 through line 57 may be recycled to fractionating tower 52 through line 60.

The residue from fractionator 52 withdrawn through line 62 is passed through heat exchanger 22, line 64- and a portion may be withdrawn from the system through line 65. Another portion thereof after passing through heat exchanger 22. is recycled as reflux to flash tower 47 through lines 64 and 66. Another portion of this residue may be diverted through line 7 0 and split into separate streams which are fed through lines 71, '70 and 72, through heaters 80, 81 and 82 and then through lines 84, 85 and 86 respectively to supply the heat necessary to maintain the reactant stream at the desired reaction temperature and also to subject this residual material to additional thermal treatment. When this last portion is recycled to extinction, no material will be Withdrawn through line 65. If desired, hydrogen and/or inert gas such as nitrogen, methane, natural gas may be introduced into the system through line 89 and separated into streams which pass through lines 91, 89, 92, lines 71, 70, 72, heaters 80, 81, 82, lines 84, 85, 86, lines 30, 35, 40 into reactors 31, 36 and 42 respectively. The gas so introduced into the system serves to maintain the reactant liquid at reaction temperature and also serves to assist in disengaging vaporous material contained in the liquid reactant. Hydrogen, in addition, serves to suppress the 4: formation of olefins and reduce their tendency to form high polymers.

It will be obvious to those skilled in the art that various devices such as pumps, compressors, liquid level controls, pressure letdown valves and the like have been omitted from the drawing for the sake of simplicity. For example, the operation of reactors 31, 36 and 42 is such that each reactor contains at least liquid and preferably liquid reactant. The vapor space is maintained by a liquid level control which operates valves (not shown) in lines 32, 39 and 46 in conjunction with pressure control valves (not shown) located in lines 33, 37 and 43.

For the production of superior fuels, i.e. fuels having luminosity numbers approaching or exceeding the product of the desired boiling range may be further treated for the elimination of aromatic hydrocarbons, particularly bicyclic aromatics.

One method for reducing the aromatic hydrocarbon content is to contact the fuel with a hydrogenation catalyst such as nickel-kieselguhr at a temperature between about 500 and 675 F., a pressure between about 250 and 750 p.s.i.g., a space velocity between about 0.2 and 10 v./v./ hr. and a hydrogen ratio of between about 5000 and 15,000 s.c.f./bbl. of feed. This treatment generally results in an increase of about 20 to 40 in the luminosity number of the fuel. Advantageously, the product frac tion boiling below the desired fraction, that is, the BP- 300 P. fraction, is subjected to catalytic reforming for conversion to a motor fuel of high octane number and the hydrogen produced by this treatment is used for the hydrogenation of the desired fraction. In cases where the fuel has an undesirably high sulfur content a sulfactive catalyst such as a nickel-tungstensulfide or cobaltmolybdenum oxide or sulfide catalyst may be used.

Another suitable method for the elimination of aromatic compounds is to treat the fuel with a selective adsorbent such as silica gel or a molecular sieve. When the fuel is treated with silica gel, the aromatic hydrocarbons are adsorbed and the resulting product is essentially paraffinic and isoparaffinic and free from aromatics. When the fuel is treated with a molecular sieve having a pore size of 5 A. the straight chain parafiins are adsorbed and the unadsorbed material is composed essentially of nonstraight chain hydrocarbons. Desorption of the molecular sieve using a desorbing agent such as hydrogen or light hydrocarbons, for example, propane or butane, produces a fuel essentially paraffinic in nature and having a luminosity number of about 150.

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.

I claim:

1. A process for the production of a jet fuel of high luminosity number and a motor fuel of high octane number which comprises contacting a hydrocarbon oil with a denaphthenization catalyst under denaphthenization conditions, extracting the product with furfural to produce an extract phase and a raflinate phase, passing the rafiinate phase serially through a plurality of reaction zones at a temperature between 770 and 930 F. and an,

elevated pressure not greater than about 1000 p.s.i.g., the pressure in each reaction zone being at least 25 p.s.i. lower than the pressure in the preceding reaction zone, removing vaporous material formed in each reaction zone from the reactant stream prior to passing the reactant stream into the next down stream reaction zone whereby the hydrocarbon reactant introduced into each reaction zone is substantially completely in the liquid phase, subjecting the liquid product stream to flash distillation to remove material boiling through the gas oil range as overhead from a residual fraction, combining said mate rial boiling through the gas oil range with said vaporous material said vaporous material having been maintained apart from the liquid reactant stream after separation therefrom, subjecting the combined stream to fractional distillation, removing as liquid bottoms from said fractional distillation material boiling above about 500 F., separating the overhead from said fractional distillation into a light liquid fraction boiling up to about 300 F. and a heavy fraction boiling from about 300-500 F., contacting the light fraction with a reforming catalyst under reforming conditions with the concomitant production of hydrogen to produce a motor fuel of high octane number, contacting the heavy fraction with a hydrogenation catalyst under hydrogenation conditions to reduce the aromatic content thereof in the presence of hydrogen produced by the reforming reaction to produce a jet fuel of high luminosity number.

2. The process of claim 1 in which a heated gas is introduced into the reactant stream with said heated stream.

3. The process of claim 2 in which the gas is hydrogen.

4. The process of claim 1 in which a portion of the bottoms removed from the fractional distillation zone is recycled to the flash distillation zone.

5. A process for the production of a jet fuel of high luminosity number and a motor fuel of high octane number which comprises contacting a hydrocarbon oil with a denaphthenization catalyst at a temperature of about 750 F. atmospheric pressure, a space velocity of about volume of feed per volurne of catalyst per hour, extracting the product with furfural to produce an extract phase and a raffinate phase, passing the rafiinate phase in the liquid phase into a first reaction zone maintained at a temperature of about 850 F. and a pressure of about 400 p.s.i.g., removing the reactant stream from said first reaction zone, reducing the pressure on said reactant stream to about 300 psig. to disengage vaporous material from the liquid material, separating the vaporous material from the liquid material, passing the liquid material to a second reaction zone maintained at a temperature of about 860 F. and a pressure of about 300 p.s.i.g., withdrawing the reactant stream from said second reaction zone, reducing the pressure on the reactant stream to about 150 p.s.i.g. to disengage vaporous material from liquid material, separating the vaporous material from the liquid material and passing the liquid to a third reaction zone maintained at a temperature of about 870 F. and a pressure of about 150 p.s.i.g., withdrawing reactant stream from the said third reaction zone, reducing the pressure on the reactant stream to about 50 p.s.i.g. to disengage vaporous material from the liquid material,

separating the vaporous material from the liquid, passing the liquid through a fourth reaction zone maintained at a temperature of about 880 F. and a pressure of about p.s.i.g., the contents of each reaction zone being substantially completely in the liquid phase, withdrawing the liquid material from said fourth reaction zone, subjecting the withdrawn liquid to flash distillation, removing as overhead from said flash distillation material having a distillation end point of about 800 F., combining the overhead from said flash distillation with the streams of vaporous material removed from the reaction zones as aforesaid, said vaporous material having been maintained apart from the liquid reactant stream after separation therefrom, subjecting the combined stream to a fractional distillation, removing as liquid bottoms from said fractional distillation material boiling above about 500 F., heating a portion of the bottoms removed from said fractional distillation zone, separating the heated portions into a plurality of streams and introducing each of said streams into the reactant stream as the reactant passes from one reaction zone to the next, separating the overhead from said fractional distillation zone into a light liquid fraction boiling up to 300 F. and a heavy fraction boiling from about 300500 F., contacting the light fraction with a reforming catalyst under reforming conditions with the concomitant production of hydrogen to produce a motor fuel of high octane number, contacting the heavy fraction with a hydrogenation catalyst under hydrogenation conditions to reduce the aromatic content thereof in the presence of hydrogen produced by the reforming reaction to produce a jet fuel of high luminosity number.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Conversion of Petroleum, Sachanen, Reinhold Co., New York, 1940, pages 122 and 123.

Chemical Technology of Petroleum, by Gruse et al., page 402, McGraW-Hill Book Co., New York, 1942.

Jet Fuels, Gas & Oil Journal, October 6, 1952, pages 96 to 98.

Pub.

Claims (1)

1. A PROCESS FOR THE PRODUCTION OF A JET FUEL OF HIGH LUMINOSITY NUMBER AND A MOTOR FUEL OF HIGH OCTANE NUMBER WHICH COMPRISES CONTACTING A HYDROCARBON OIL WITH A DENAPHTHENIZATION CATALYST UNDER DENAPHTHENIZATION CONDITIONS, EXTRACTING THE PRODUCT WITH FURFURAL TO PRODUCE AN EXTRACT PHASE AND A RAFFINATE PHASE, PASSING THE RAFFINATE PHASE SERIALLY THROUGH A PLURALITY OF REACTION ZONES AT A TEMPERATURE BETWEEN 770 AND 930*F. AND AN ELEVATED PRESSURE NOT GREATER THAN ABOUT 1000 P.S.I.G., THE LOWER THAN THE PRESSURE IN THE PRECEDING REACTION ZONE, REMOVING VAPOROUS MATERIAL FORMED IN EACH REACTION ZONE FROM THE REACTANT STREAM PRIOR TO PASSING THE REACTANT STREAM INTO THE NEXT DOWN STREAM REACTION ZONE WHEREBY THE HYDROCARBON REACTANT INTRODUCED INTO EACH REACTION ZONE IS SUBSTANTIALLY COMPLETELY IN THE LIQUID PHASE, SUBJECTING THE LIQUID PRODUCT STREAM TO FLASH DISTILLATION TO REMOVE MATERIAL BOILING THROUGH THE GAS OIL RANGE AS OVERHEAD FROM A RESIDUAL FRACTION, COMBINING SAID MATERIAL BOILING THROUGH THE GAS OIL RANGE WITH SAID VAPOROUS MATERIAL SAID VAPOROUS MATERIAL HAVING BEEN MAINTAINED APART FROM THE LIQUID REACTANT STREAM AFTER SEPARATION THEREFROM, SUBJECTING THE COMBINED STREAM TO FRACTIONAL DISTILLATION, REMOVING AS LIQUID BOTTOMS FROM SAID FRACTIONAL DISTILLATION MATERIAL BOILING ABOVE ABOUT 500*F., SEPARATING THE OVERHEAD FROM SAID FRACTIONAL DISTILLATION INTO A LIGHT LIQUID FRACTION BOILING UP TO ABOUT 300*F., CONTACTING THE LIGHT FRACTION WITH A REFORMING CATALYST UNDER REFORMING CONDITIONS WTH THE CONCOMITANT PRODUCTION OF HYDROGEN TO PRODUCE A MOTOR FUEL OF HIGH OCTANE NUMBER, CONTACTING THE HEAVY FRACTION WITH A HYDROGENATION CATALYST UNDER HYDROGENATION CONDITIONS TO REDUCE THE AROMATIC CONTENT THEREOF IN THE PRESENCE OF HYDROGEN PRODUCED BY THE REFORMING REACTION TO PRODUCE A JET FUEL OF HIGH LUMINOSITY NUMBER.

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