US3540997A - Production of motor and jet fuels - Google Patents

Description

F. K. HAHN ETAL PRODUCTION OF MOTOR AND JET FUELS Nov. 1 7, 1970 United States Patent @ffice 3,540,997 Patented Nov. I7, 1970 U.S. Cl. 208-69 13 Claims ABSTRACT OF THE DISCLOSURE Jet and motor fuels are produced by a process involving hydrocracking and hydrogenation. In a specific embodiment, a crude oil is fractionated to produce naphtha, kerosene and gas oil fractions, the gas oil fraction is catalytically cracked to produce additional naphtha and kerosene fractions and an unconverted gas oil fraction, the unconverted gas oil fraction is hydrocracked and then combined with the various naphtha and kerosene fractions, the resulting mixture is hydrotreated, the product is separated into naphtha and jet fuel, the naphthais catalytically reformed to produce a high octane motor fuel and the reformer by-product hydrogen is recycled to the hydrocracking zone.

This invention relates to the production of motor and jet fuels. More particularly, it is concerned with the production of said fuels by a processing sequence involving hydrocracking and hydrotreating. In a more specific aspect, it is concerned with the production of motor and jet fuels of high quality from crude oil.

It is well known in the art that many current automobile engines require a motor fuel having a research octane number of 95-100 or even higher. Itis equally well known that jet engines of greater thrust are being developed and that these engines require a fuel having a higher luminometer number than can be satisfied by straight run kerosene. Unfortunately the characteristics of a high octane motor fuel are quite different from those of a high luminometer number jet fuel. In high octane motor fuel the most desirable components are isoparafiins and aromatics whereas in high quality jet fuel the desired components are parafiins and naphthenes. It is therefore no longer satisfactory to simply select a hydrocarbon fraction boiling in the motor fuel range for use as a motor fuel or to select a hydrocarbon fraction boiling in the jet fuel range for use as a jet fuel. In order to meet the requirements of conventional and commercial vehicles, it is necessary to process fuels in a particular manner depending on their end use.

It is therefore an object of the present invention to produce a high luminometer number jet fuel. Another object is to provide a combination process for the production of high quality jet and motor fuels. Another object is t hydrocrack a gas oil charge stock and to hydrotreat the product at substantially the same pressure but at a lower temperature to produce a superior jet fuel. Still another object of the invention is to provide a combination hydrocracking-hydrotreating-catalytio reforming process for the production of jet fuel and motor fuel. These and other objects will be obvious to those skilled in the art from the following disclosure.

In its simplest aspect, the present invention provides a process for the production of jet fuel which comprises passing a hydrocarbon charge stock boiling in the gas oil range into contact with a hydrocracking catalyst under hydrocracking conditions, passing the entire effiuent from the hydrocracking zone to a hydrotreating zone where it it contacted with a sulfur resistant hydrogenation catalyst under hydrotreating conditions including a temperature below the hydrocracking temperature and a pressure substantially the same as the hydrocracking pressure. In a more specific aspect, the present invention contemplates catalytically cracking a virgin gas oil, separating the cracked material into a jet fuel fraction and a fraction boiling above the jet fuel range, subjecting the latter fraction to hydrocracking, cooling the hydrocracking zone effluent by direct heat exchange with the cracked jet fuel, passing the combined stream into a hydrotreating zone and recovering high quality jet fuel from the product. In one of its more specic aspects, a crude oil is fractionated into straight nm light and heavy naphthas, a straight run jet fuel fraction, a gas oil fraction and a residual fraction, the gas oil fraction is catalytically cracked and separated into a cracked naphtha, a cracked jet fuel fraction, a gas oil heavier than jet fuel but boiling below about 800 F., and a fraction boiling above 800 F. The gas oil fraction boiling below 800 F. is hydrocracked and the hydrocracking zone effluent cooled by direct heat exchange with the straight run heavy naphtha and jet fuel fractions and the cracked jet fuel fraction, the combined stream hydrotreated, the efiiuent separated into a high quality jet fuel withdrawn as product, a heavier than jet fuel fraction recycled to the catalytic cracking zone or the hydrocracking zone, and a hydrotreated naphtha fraction which is catalytically reformed to produce high quality gasoline and the by-product hydrogen obtained from the catalytic reformer is used to replace a portion of the hydrogen consumed in the hydrocracking and/or hydrotreating reactions.

The hydrogen used in the process of our invention need not necesarily be pure. The hydrogen content of the hydrogenating gas should be at least about and preferably is at least about 75% by volume. Suitable sources of hydrogen are catalytic reformer by-product hydrogen and hydrogen produced either by the partial combustion of hydrocarbonaceous material or steam reforming of light hydrocarbons followed by shift conversion and CO2 removal. Hydrogen rates are expressed in terms of standard cubic feet per barrel of normally liquid charge to the reactor, viz. s.c.f.b.

The catalyst used in the hydrocracking stage of our process contains two components, a hydrogenating component supported on a cracking component. The hydrogenating component comprises a Group VIII metal or compound thereof used alone or in conjunction with a Group VI metal or compound thereof. Particularly suitable hydrogenating components are palladium and nickel and tungsten in the form of the sulfide.

The cracking component of the catalyst comprises a mixture of a modified crystalline zeolite and at least one amorphous inorganic oxide, the modified zeolite being present in an amount between about 15 and 60% by weight. Suitable amorphous inorganic oxides are those displaying cracking activity such as silica, alumina, magnesia, zirconia and beryllia which may have been treated with an acidic agent such as hydrofluoric acid to impart cracking activity thereto. A preferred mixture of amorphous inorganic oxides comprises silica-alumina in a proportion ranging between 60-90% silica and 10-40% alumina.

The modified zeolite portion of the cracking component has uniform pore openings of from 6-15 angstrom units, has a silica-alumina ratio of at least 2.5, eg, 3 10, and has a reduced alkali metal content. The modified zeolite is prepared by subjecting synthetic zeolite Y to ion exchange by contacting the zeolite several times with fresh solution-s of an ammonium compound at temperatures ranging between about and 250 F. until it appears that the ion exchange is substantially complete. The ion exchanged zeolite is then washed to remove solubilized alkali metal and dried at a temperature suiciently high to drive olf ammonia. This converts the zeolite Y to the hydrogen form and reduces the alkali metal content to about 2-4 weight percent. The ion exchanged zeolite is then calcined at a temperature of about 1000 F. for several hours. After cooling, the ion-exchanged calcined zeolite is subjected to additional ion exchange by contact several times with fresh solutions of an ammonium compound and again washed and dried. This treatment results in a further reduction of the alkali metal content of the zeolite to less than 1%, usually to about 0.5% or less. It would appear that after the first calcination, it is possible to engage in further ion exchange with the removal of additional alkali-metal ions not removable in the initial ion exchange. Calcination at e.g. 1000-1500 F. may take place here or it may be postponed until after the incorporation of the inorganic oxide and impregnation with the hydrogenating component, at which time the composite should be calcined. Whether the calcination is postponed or repeated, the nal calcination temperature should not exceed 1200 F.

Hydrocracking catalysts containing a hydrogenating component supported on a cracking component composed of at least one amorphous inorganic oxide and the twice ion exchanged, twice calcined zeolite have superior hydrocracking activity and additionally are more resistant to deactivation when brought into contact with nitrogen compounds and polycyclic aromatics. They also show good stability to steam. The hydrocracking catalyst should also be substantially free from rare earth metals and should have a rare earth metal content below 0.5 weight percent, perferably below 0.2 weight percent. It has been found that although rare earth metals are reputed to enhance the activity and stability characteristics of cracking catalysts, their presence in a hydrocracking catalyst is vundesirable.

When the hydrogenating component of the hydrocracking catalyst is a noble metal, it should be present in an amount between 0.2 and 5.0% by Weight based on the total catalyst composite. Preferably the noble metal is present in an amount between 0.5 and 2%. When the hydrogenating component comprises nickel in conjunction with tugsten, the nickel should be present in an amount between about 2 and 10% and the tungsten present in an amount between about 5 and 30%. Particularly suitable catalysts are those containing between 0.5 and 1.0 weight percent noble metal and those containing between 5 and nickel and between 15 and 30% tungsten. Specific examples of suitable catalysts are those containing 0.75 weight percent palladium or containing about 6% nickel and 20% tungsten on a support made up of about 22% modified zeolite Y, 58% silica and 20% alumina.

The hydrogenating component is deposited on the cracking component by impregnating the latter with a solution of a compound of the hydrogenating component. Such techniques are Well known in the art and require no description here.

When used in the sulfide form the catalyst may be con- `A verted thereto by methods well known in the art such as by subjecting the catalyst at a temperature between about 400 and 600 F. to contact with a sulding agent, for example hydrogen containing 10-20% hydrogen sulfide or a carbon disulfide-oil mixture.

In the hydrocracking reactor, the temperature is generally maintained between about 600 and 850 F., the pressure between 200 and 10,000 p.s.i.g., the liquid hourly space velocity between 0.2 and 10 volumes of oil per volume of catalyst per hour, and the hydrogen rate between 1000 and 50,000 s.c.f.b. A preferred temperature range is 625-750 F. Advantageously, the temperature will to a small degree vary depending on the nitrogen content of the charge, the greater the nitrogen content, the higher the reaction temperature. The preferred pressure range is SOO-3000 p.s.i.g. Other preferred conditions are a space velocity of 0.5-2 v./v./hr. and a hydrogen rate of 30010-- 15,000 s.c.f.b.

The catalyst used in the hydrotreating reactor should have good hydrogenating activity but little if any cracking activity. Suitable catalysts comprise a hydrogenating component as for example the oxide or sulfide of cobalt, nickel, iron, molybdenum, tungsten, chromium, vanadium and mixtures thereof on a support such as silica, alumina, zirconia, magnesia and mixtures thereof used as such or in conjunction with zeolites not necessarily of reduced alkali metal content. Preferred catalysts comprise nickel tungsten on boria-promoted alumina and nickel molybdenum on activated alumina. The hydrogenating component should be present in an amount between about 5% and 40% by weight based on the catalyst composite. Catalysts containing 6% nickel and 20% tungsten or 5% nickel and 15% molybdenum have been found satisfactory.

The temperature Within the hydrotreating zone is maintained between 300 and 800 F., preferably between 400 and 700 F. and below the temperature of the hydrocracking zone. Pressure in the hydrotreating zone is substantially the same as that in the hydrocracking zone, taking into consideration the normal pressure drop required for the flow of materials through the system. Hydrogen should be introduced at a rate of at least 1000 s.c.f. per barrel of feed, a preferred range being from 3000 to 15,000 s.c.f.b. The catalyst bed in the hydrogenating reactor should be of a size sufficient to permit liquid hourly space velocities of 0.2-10 volumes of hydrocarbon liquid per volume of catalyst per hour. Preferably the LHSV is maintained between 0.5 and 5.

Catalytic reforming and uid catalytic cracking are well known in the petroleum refining industry and need no description here.

The following examples of the present invention which are given for illustrative purposes only and are not to be construed as limitations on the invention are described 4in connection with the accompanying ow diagram. In the interest of simplicity, pumps, compressors, flow meters, heat exchangers and the like have'been omitted from the drawing.

EXAMPLE 1 This example is intended to show the present invention operated to produce a substantial quantity of jet fuel and a smaller quantity of motor fuel blending component, both of high quality. The hydrocarbon charge, a South Louisiana Light Regular crude is introduced through line 11 into crude still 12 from which a light naphtha boiling up to about 235 F. is removed through line 13 and sent to stabilization, a heavy naphtha-kerosene fraction boiling from about 23S-525 F. is removed through line 14, a gas oil fraction boiling from about S25-900 F. is removed through line 15 and the residue is withdrawn through line 16. The gas oil fraction is contacted in Huid catalytic cracking unit 21 with a zeolitic cracking catalyst under the following conditions:

Reactor temperature, F. 910 Weight hourly space velocity 2.0 Catalyst/oil weight ratio 7.0 Conversion 525 F. EP, vol. percent 70.0

Regenerator temperature, F. 1150 and the product sent to fractionator 23 through line 22. From fractionator 23, a light naphtha fraction boiling up to about 325 F. is removed through line 24 and sent to stabilization through line 13, a heavy naphtha-kerosene fraction is removed through line 25 and a fraction boiling from about S25-800 F. is removed through line 26. A heavy gas oil boiling above about 800 F. and comprising approximately 5 vol. percent of the charge to the fluid catalytic cracking unit is Withdrawn through line 56. Without any intermediate chemical treatment such as desulfurization or denitrogenation, the cracked S25-800 F. boiling range fraction with hydrogen from line 27 is introduced into hydrocracking unit 28 where it is contacted with a catalyst containing 6% nickel and 18% ion-exchanged twice decationized zeolite Y, 58% silica and 20% alumina. At the start of the on-stream period the reactor temperature is 650 F. and the temperature is gradually increased to obtain and maintain a 60% conversion to 525 F. and lighter material. Other reaction conditions are a pressure of 1800 p.s.i.g., a space velocity of 1.0 and a hydrogen rate of 6000 s.c.f.b. On leaving hydrocracking unit 28 the effluent is combined with naphtha-kerosene streams from lines 14 and 25 introduced into the reactant stream through line 30` at such a temperature that the reactant stream is cooled by direct heat exchange to a temperature of 575 F. The total jet fuel fraction at this point contains approximately 21 volume percent aromatics and has a 38 luminometer number. The mixture is then passed into contact with a catalyst containing 6.0 weight percent Ni and 19% by weight W supported on alumina in hydrotreating unit 32 at a space velocity of 3.0. Effluent from hydrotreating unit 32 passes through line 33 to high pressure separator 34 from which a recycle hydrogen stream passes through lines 35, 40, 27 and 26 to hydrocracking unit 28. Makeup hydrogen is added through line 57 as needed along with the hydrogen from the CRU which is introduced through line 40. The hydrocarbon portion of the hydrotreater eflluent passes through line 39 to fractionator 48 where it is separated into a light naphtha boiling up to about 235 F. removed through line 41, a heavy naphtha fraction boiling from 23S-325 F. removed through line 42, a product jet fuel fraction boiling from 325-525 F. removed through line 43 and a heavier than jet fuel fraction removed through line 44 and recycled to the uid catalytic cracking unit 21 through line 15. The heavy naphtha from line 42 with hydrogen from line 45 is sent to catalytic reforming unit 46 where it is contacted with a catalyst containing 0.375 weight percent platinum on an HF treated alumina base at a temperature of 930 F., a pressure of 500 p.s.i.g., a hydrogen rate of 8000 s.c.f.b. and a space velocity of 3.0. The reformer eflluent is removed through line 50 and separated in separator 51 into a hydrogen stream recycled through lines 52, 4S and 42, and a product motor fuel stream removed through line 53 and sent to stabilization through line 13. The above procedure results in a 47 volume percent yield basis crude charge of a debutanized motor fuel having a research octane number 88 clear and 97 leaded and a 35 volume percent yield of a jet fuel containing 16 volume percent aromatics and having a luminometer number of 53.

Advantageously, depending on the temperature gradient across the hydrocracking catalyst bed, cooling hydrogen may be introduced into hydrocracking unit 28 through line 54. Not only does this serve to maintain good temperature control within the hydrocracking unit, but it also serves to supply the additional hydrogen necessary for hydrotreating the naphtha-kerosene fraction introduced into hydrotreating unit 32 from lines 14 and 25 through line 30. It is also desirable to recycle that portion of the hydrotreating unit effluent boiling above the jet fuel range through line 44 either to hydrocracking unit 28 through lines 18 and 26 or to fluid catalytic cracking unit 21 through line 15.

It may be also desirable to recycle a portion of the gas oil product from fractionator 23 through lines 26, 55, 44 and 15 to fluid catalytic cracking unit 21. Make-up hydrogen, if necessary, is introduced into the system through line 57.

EXAMPLE 2 This example is intended to show the present invention operated to produce a substantial quantity of full boiling range motor fuel (C-425 F.) and a smaller quantity of a jet fuel blending component (425-525 F.).

The process is operated at substantially the same conditions as described in Example 1 with the following exceptions. Fractionater 23 is operated to take a 425 F. end point naphtha stream through line 24 and a 425-525 F. jet fuel fraction through line 25. Fractionator 48 is operated to take a 235 F. end point overhead through line 41, a 23S-425 F. naphtha fraction through line 42 to catalytic reforming unit 46 and a 425-525" F. jet fuel fraction through line 43.

This procedure results in a yield of 69 volume percent debutanized full boiling range (C5-425 F.) motor fuel basis crude charge having a research octane number of clear and 98 leaded and l1 volume percent yield of a jet fuel containing 14 volume percent aromatics and having a luminometer number of 5 6.

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

We claim:

1. A process for the production of jet fuel which comprises passing a hydrocarbon charge stock boiling in the gas oil range into contact with a hydrocracking catalyst comprising a hydrogenating component selected from the group consisting of Group VIII metals and compounds thereof on a support comprising a mixture of a crystalline zeolite and at least one amorphous inorganic oxide under hydrocracking conditions, including a temperature between about 600 F. and 850 F. and a pressure between 200 and 10,000 p.s.i.g., passing the entire effluent from the hydrocracking zone into contact with a hydrotreating catalyst comprising a hydrogenating component selected from the group consisting of cobalt, nickel, iron, molybdenum, tungsten, chromium, vanadium, their compounds and mixtures thereof on a support having substantially no cracking activity under hydrotreating conditions including a temperature below the hydrocracking temperature and a pressure substantially the same as the hydrocracking pressure and recovering a jet fuel fraction from the hydrotreated product.

2. The process of claim 1 in which the charge stock is a gas oil produced in a uidized catalytic cracking zone.

3. The process of claim 1 in which the hydrocracking zone effluent is cooled by direct heat exchange with straight run naphtha.

4. The process of claim 1 in which the hydrocracking zone effluent is cooled by direct heat exchange With a kerosene fraction recovered from the catalytic cracking zone.

5. The process of claim 1 in which the hydrotreating zone effluent is separated into a jet fuel fraction and a heavy naphtha fraction.

`6. Th process of claim 5 in which the heavy naphtha fraction is catalytically reformed.

7. The process of claim 6 in which by-product hydrogen produced in the catalytic reforming is used to replace a portion of hydrogen consumed in the hydrocracking and hydrotreating zones.

8. The process of claim 1 in which the hydrocracking catalyst comprises a hydrogenating component supported on a nitrogen resistant base comprising at least one amorphous` in organic oxide and a crystalline zeolite of reduced alkali metal content.

9. The process of claim 8 in which the crystalline zeolite has been prepared by an alternating sequence of at least two ion exchanges and two calcinations.

10. The process of claim 9 in which the hydrogenating component comprises nickel and tungsten.

11. The process of claim 9 in which the hydrogenating component comprises palladium.

12. A process for the production of jet fuel and motor fuel which comprises fractionating a crude oil into a light naphtha fraction, a heavy naphtha-kerosene fraction, a gas oil fraction and a residual fraction, catalytically crackmg the gas oil fraction and separating the product into a naphtha fraction, a jet fuel fraction and a fraction heavier than jet fuel, passing the fraction heavier than jet fuel into a hydrcracking zone into contact with a hydrocracking catalyst, comprising a hydrogenatng component selected from the group consisting of Group VIII metals and compounds thereof on a support comprising a mixture of a crystalline zeolite and at least one amorphous inorganic oxide under hydrocracking conditions, including a temperature between about 600 F. and 850 F. and a pressure between 200 and 10,000'p.s.i.g., cooling the hydrocracking zone effluent by direct heat exchange with said heavy naphtha-kerosene fraction and said jet fuel fraction, passing the total combined stream into a hydrotreating zone into contact with a hydrotreating catalyst comprising a hydrogenating component selected from the group consisting of cobalt, nickel, iron, molybdenum, tungsten, chromium, vanadium, their compounds and mixtures thereof on a support having substantially no cracking activity, under hydrogenating conditions including a temperature below the hydrocracking temperature and a pressure substantially the same as the hydrocracking pressure, separating the hydrotreating zone efuent into -a naphtha fraction, a jet fuel fraction and a fractionheavier than jet fuel, catalytically reforming said naphtha fraction to produce a motor fuel and replacing a portion of the hydrogen consumed in said hydrocracking zone with by-product hydrogen produced in said catalytic reforming. 13. The process of claim 12 in which hydrogen is introduced into an intermediate section of the hydrocracking zone to cool the reactant stream.

References Cited UNITED STATES PATENTS 2,953,521 46/1969 Bowles 208-108 3,008,895 11/1961 Hansford etal. 208'-68 3,132,087 5/1964 Kelley et al. .208-60 3,236,762 2/1966 Rabo et al. 208-111 DELBERT E. GANTZ, Primary Examiner A. RIMENS, Assistant Examiner U.S. Cl. X.R. 208-97

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