US3617498A

US3617498A - Catalytic hydrocracking process

Info

Publication number: US3617498A
Application number: US829174A
Authority: US
Inventors: James R Kittrell
Original assignee: Chevron Research and Technology Co
Current assignee: Chevron USA Inc
Priority date: 1969-06-02
Filing date: 1969-06-02
Publication date: 1971-11-02
Anticipated expiration: 1988-11-02

Abstract

In a process wherein jet fuels and gasoline are produced from hydrocarbons boiling in the range 300* to 1,500* F., including substantial quantities of hydrocarbons boiling in the range 300* to 650* F. and substantial quantities of heavier hydrocarbons boiling in the range 550* to 1,100* F., by process steps including catalytic hydrocracking, the improvement which comprises catalytically hydrocracking said hydrocarbons boiling in the range 550* to 1,100* F., and catalytically hydrogenating said hydrocarbons boiling in the range 300* to 650* F. prior to making use of said hydrocarbons boiling in the range 300* F. to 650* F. for jet fuel or for hydrocracking feedstock.

Description

United States Patent Inventor James R. Kittrell [56} References Cited El Cermor Cfllf- UNITED STATES PATENTS g 232 1 3,166,489 1/1965 Mason etal. 208/57 Patented Nov. 2, 1971 3,240,694 3/1966 Mason ct al. 208/59 Assignee Chevron Research Company Primary Examiner- Delbert E. Gantz San Francisco, Calif. Assistant ExaminerG. E. Schmitkons Attorneys-A. L. Snow, F. E. Johnston, C. J. Tonkin and Roy H. Davies ABSTRACT: In aprocess wherein jet fuels and gasoline are produced from hydrocarbons boiling in the range 300 to 1.500" F., including substantial quantities of hydrocarbons fgfifl if PROCESS boiling in the range 300 to 650 F. and substantial quantities Of heavier hydrocarbons boiling in the range 550 to 1.100" F., U.S.Cl 208/80, by process steps including catalytic hydrocracking. the im- 208/57, 208/89, 208/93, 208/108. 208/l l l, provement which comprises catalytically hydrocracking said 260/667 hydrocarbons boiling in the range 550 to l,l00 F., and cata- Int. Cl ClflglJ/Qg, lytically hydrogenating said hydrocarbons boiling in the range Cl0g 23/00, ClOg 37/06 300 to 650 F. prior to making use of said hydrocarbons boil- Field of Search 208/80, 89, ing in the range 300 F. to 650 F.v for jet fuel or for 57 hydrocracking feedstock.

I 1 15 IS IS 300M600 HYDROGENATION 0 o AROMATICS w 20 H2 22 GASOLINE w 1 j 0 Q} HYDROFINING HYDROCRACKING J 2r 300-600F. 1.! 5 6 a 6 2s CATALYTIC HYDROCRACKING PROCESS INTRODUCTION PRIOR ART The production of jet fuel from hydrocarbon feedstocks by various combinations of processing steps, including catalytic hydrocracking, is well known. Certain of these combinations of processing steps are disclosed in U.S. Pats. Nos. 3,172,833, 3,172,839 and 3,240,694. However, there are certain remaining problems in the production of jet fuel by process steps, including catalytic hydrocracking, for which the prior art has not yet provided solutions. The process of the present invention provides a solution to certain of these problems, including the one which now will be discussed.

In a petroleum refinery in which jet fuel is being produced by process steps, including catalytic hydrocracking, there are two primary sources of hydrocarbon feedstock for the catalytic hydrocracking zone: (I) hydrocarbons boiling in the range 550 F. to l,l F., which are to be hydrocracked to produce a jet fuel boiling in the range 300' to 650 F., which jet fuel is termed synthetic" to the extent that it boils below the boiling range of the hydrocarbon feedstock; and (2) hydrocarbons boiling in the range 300 to 650 F., for example cycle oils or coker gas oils. Almost invariably, the more synthetic the jet fuel, the higher its smoke point and the lower its freeze point. However, it is obvious that the 300 to 650 F. boiling range hydrocarbons cannot be converted in large proportion in a hydrocracking zone to synthetic jet fuel.

Nevertheless, efforts have been made to include such 300 to 650 F. boiling range materials in the feed to the hydrocracking zone, in the hope that, while such materials cannot be converted in large proportion to synthetic jet fuel, nevertheless they might be upgraded for jet fuel uses, for example by saturating the aromatics contained therein. Results of these efforts have been extremely poor; not only were these hydrocarbons not convertible in the hydrocracking zone in large proportion to synthetic materials, but in the hydrocracking zone they: (a) were not significantly upgraded for jet fuel uses, that is, the aromatics therein were not substantially saturated, because the presence of heavier hydrocarbons boiling in the 550 to l,l00 F. range suppressed the desired aromatics saturation reaction; and (b) the quality of the total jet fuel being produced in the hydrocracking zone was substantially lower than the quality of the jet fuel that could be produced therein by hydrocracking 550 to l,l00 F. boiling range hydrocarbons in the absence of lighter 300 to 650 F. boiling range hydrocarbons.

OBJECTS In view of the foregoing, it is an object of the present invention to provide a hydrocarbon conversion process, including a catalytic hydrocracking step, capable of producing high yields of valuable fuel products, including jet fuels, from hydrocarbon feedstocks boiling in the range 300 to l,l00 F. and containing substantial quantities of materials boiling in the range 300 to 650 F. and substantial quantities of heavier materials boiling in the range 550 to l,l00 F. It is a more specific object of the present invention to provide a hydrocarbon conversion process. including a catalytic hydrocracking step, which will upgrade the hydrocarbons boiling in the range 300 to 650 F. while at the same time avoiding any adverse effect of such hydrocarbons on the production of jet fuel from heavier 550 to l,l00 F. boiling range hydrocarbons by catalytic hydrocracking.

DRAWlNG The present invention will best be understood, and further objects and advantages thereof will be apparent, from the following description when read in connection with the accompanying drawing.

The drawing is a schematic illustration of apparatus and flow paths suitable for carrying out the process of the present invention.

STATEMENT OF INVENTION In accordance with the present invention, it has been found that: (l) in hydrocarbon materials boiling in the range 300 to l,l00 F. and containing substantial quantities of materials boiling in the range 300 to 650 F. and substantial quantities of heavier materials boiling in the range 550 to 1 F., preponderant quantites of the aromatic compounds are concentrated in the materials boiling in the range 300 to 650 F accordingly, not only is it impossible to convert these materials in large proportion to synthetic jet fuels by catalytic hydrocracking, but jet fuels produced from these materials in a catalytic hydrocracking step have undesirably high aromaticity and low smoke point, unless a substantial amount of aromatics saturation takes place in the hydrocracking reaction zone; and (2) a substantial amount of aromatics in the 300 to 650 F. boiling range hydrocarbons supplied to a hydrocracking reaction zone are not saturated during the hydrocracking reaction when the hydrocarbon feed in the hydrocracking reaction zone includes substantial quantities of heavier hydrocarbons boiling in the range 550 to l,l00 F the presence of the heavier hydrocarbons inhibits saturation of the aromatics contained in the 300 to 650 boiling range materials.

In accordance with the present invention there is provided, in a process wherein at least one hydrocarbon feedstock containing substantial quantities of materials boiling in the range 300 to 650 F. and substantial quantities of heavier materials boiling in the range 550 to l,l00 F. is converted to valuable products including gasoline and jet fuel by process steps including catalytic hydrocracking in a hydrocracking zone, the improvement which comprises catalytically hydrocracking in said zone said materials boiling in the range 550 to l,l00 F., catalytically hydrogenating in a second reaction zone said materials boiling in the range 300 to 650 F and withdrawing valuable fuel products from each of said zones.

Further in accordance with the present invention, said materials boiling in the range 600 to l,l00 F. may be catalytically hydrofined prior to being catalytically hydrocracked.

Further in accordance with the present invention, the liquid effluent from said second reaction zone may be combined with effluent materials from said hydrocracking reaction zone boiling in the range 300 to 650 F. to produce a superior jet fuel.

Still further in accordance with the present invention, at least a portion of the effluent from said second reaction zone may be catalytically hydrocracked in said hydrocracking reaction zone.

HYDROCARBON FEEDSTOC KS Hydrocarbon feedstocks suitable for use in the process of the present invention boil in the range 300 to l,l00 F. and contain substantial quantities of materials boiling in the range 300 to 650 F. and substantial quantities of heavier materials boiling in the range 550 to l,l00 F. The feedstocks preferably boil over a range of at least 50 F. within each of the aforesaid boiling ranges. Suitable feedstocks include those heavy distillates normally defined as heavy straight run gas oils and heavy cracked cycle oils, as well as conventional FCC feeds and portions thereof. Cracked stocks may be obtained from thermal or catalytic cracking of various stocks, including those obtained from petroleum. gilsonite, shale and coal tar. Feedstocks may contain nitrogen and sulfur. in amounts usually associated with the feedstocks previously described.

The materials boiling in the range 300 to 650 F. will contain at least 20 volume percent aromatics.

The materials boiling in the range 300 to 650 F. may have been separate, at all times prior to being processed in accordance with the present invention, from the materials boiling in the range 550 to 1,100 F. Alternatively, the materials boiling in" the range 300 to 650 F. may be separated from a hydrocarbon stock containing both these materials and higher boiling materials. by separation at a cut point in the range 550 to 650 F. It also will be understood that a jet fuel will boil in the range 300 to 650 F., but more preferably in the range 300 to 600 F., and still more preferably in the range 300 to 550 F. In accordance with the foregoing, it further will be understood that: (a) the hydrocarbon feed supplied to the hydrocracking zone in the process of the present invention may have an initial boiling point as low as 550 F. and as high as 650 F.; and (b) to the extent that the jet fuel fraction separated from the hydrocracking zone effluent boils below the initial boiling point of the hydrocracking zone hydro carbon feed, the jet fuel in that fraction will be synthetic.

AROMATICS HYDROGENATION STEP The aromatics hydrogenation step in the process of the present invention is conducted in a hydrogenation zone operated at conventional aromatics hydrogenation conditions, including temperatures in the range 300 to 700 F preferably 400 to 650 F., pressures of at least 300 p.s.i.g., and liquid hourly space velocities of 0.3 to 5.0, effective to saturate a substantial portion, preferably at least 50 volume percent, of the aromatics present in the hydrocarbon feed to the hydrogenation zone. Hydrogen is supplied to the hydrogenation zone at a rate at least sufficient to effect the desired saturation, preferably at the rate of at least 1,000 s.c.f. of hydrogen per barrel of hydrocarbon feed, and more preferably at, least 2,000 s.c.f. of hydrogen per barrel of hydrocarbon feed.

The catalyst used in the hydrogenation zone may be any conventional aromatics hydrogenation catalyst, for example platinum or palladium or compounds thereof on alumina or other carrier having low cracking activity and high surface area. When the hydrocarbon feedstock to the hydrogenation zone contains substantial amounts of sulfur, a platinumor palladium-containing catalyst will be found less desirable than a conventional sulfur resistant hydrogenation catalyst, for example one comprising an alumina support together with molybdenum or tungsten and nickel or cobalt hydrogenation components. The hydrogenation components may be present in the catalyst in the sulfide or oxide form. The Group V] com-. ponent content of the catalyst may be to 25 weight percent expressed as metal, and the Group VIII component content of the catalyst may be 1 to 20 weight percent expressed as metal.

The aromatics hydrogenation step should be so conducted that less than 5 percent cracking of the hydrocarbon feedstock thereto occurs therein, particularly when it is desired to operate the process of the present invention for production of maximum amounts of jet fuel.

H Y DROFIN ING STEP The hydrofining step in the process of the present invention may be conducted in the hydrotiningv zone operated at conventional hydrofining conditions, including temperatures in the range 450 to 850 F preferably 550 to 800 F., pressures of at least 300 p.s.i.g., and liquid hourly space velocities of 0.3 to 5.0. Hydrogen is supplied to the hydrotining zone at the rate of 1,000 to 15,000 s.c.f. of hydrogen per barrel of hydrocarbon feed supplied to that zone. The hydrotining catalyst may be a conventional sulfur-resistant hydrofining catalyst, for example one comprising an alumina support together with molybdenum or tungsten and nickel or cobalt hydrogenation components. The hydrogenation components may be present in the catalystin the sulfide or oxide form. The Group V! component content of the catalyst may be 5 to 25 weight percent expressed as metal, and the Group VIII component content of the catalyst may be 1 to 20 weight percent expressed as metal.

HYDROCRACKING STEP The hydrocracking step in the process of the present invention is conducted in a hydrocracking zone operated at conventional hydrocracking conditions, including temperatures in the range 400 to 900 F preferably 500 to 800 F pressures of at least 300 p.s.i.g., preferably 1,500 to 3,500 p.s.i.g., and liquid hourly space velocities of 0.3 to 5.0. Hydrogen is supplied to the hydrocracking zone at the rate of 1,000 to 20,000 s.c.f. of hydrogen per barrel of hydrocarbon feed supplied to that zone.

The catalyst used in the hydrocracking zone may be any conventional hydrocracking catalyst, for example nickel sulfide on silica-alumina. A hydrocracking catalyst comprising a crystalline zeolitic molecular sieve dispersed in a matrix of other catalyst components, which may include nickel, tungsten and silica alumina, will be especially suitable.

The hydrocracking zone preferably will be operated at a substantially constant conversion of at least 25 volume percent, preferably 35 to volume percent, per pass, of the hydrocarbon feed to products boiling below the initial boiling point of that feed.

DESCRIPTION OF PROCESS OPERATION WITH REFERENCE TO DRAWING Referring now to the drawing, there shown is an exemplary overall process flow diagram suitable for carrying out the process of the present invention. A hydrocarbon feedstock boiling in the range 300 to 600 F., containing at least 20 volume percent aromatics, is passed through line I to hydrogenation zone 2. A hydrocarbon feedstock boiling in the range 600 to 1,100' F. is passed through lines 3 and 4 to hydrofining zone 5 or, alternatively, through lines 3, 6 and 7 to hydrocracking zone 8.

The hydrocarbon feedstocks in lines 1 and 3 may be from separate sources or, as shown in the drawing, may be fractions obtained from a single hydrocarbon feedstock. In the drawing, a hydrocarbon feedstock boiling in the range 300 to l,500 F. is passed through line 10 into distillation column 11 and separated into fractions, including the 300 to 600 F. fraction withdrawn through line 1 and the 600 to l,l00 F. fraction withdrawn through line 3. From distillation column 11 light ends are removed through line 12 and l,lO0 F." materials are removed through line 13.

In hydrogenation zone 2, the hydrocarbon feedstock thereto is hydrogenated at conditions previously described in the presence of hydrogen supplied to zone 2 through line [4. The liquid effluent from zone 2 is recovered as a product through line 15. Alternatively, all or a portion of the liquid effluent from zone 2 may be passed through line 16 to hydrocracking zone 8. All or a portion of the material in line 16 may be passed through lines 17 and 4 to hydrofining zone 5 Any feedstock supplied through line 4 to hydrofining zone 5 is hydrofined in that zone under conditions previously described in the presence of a catalyst as previously described and in the presence of hydrogen supplied to zone 5 through line 18. The liquid effluent from hydrofining zone 5 is passed through line 7 to hydrocracking zone 8.

The hydrocarbon materials supplied through line 7 to hydrocracking zone 8 are hydrocracked in that zone at conditions previously described in the presence of a catalyst as previously described and in the presence of hydrogen supplied to zone 8 through line 20. The effluent from zone 8 is passed through line 21 to distillation column 22, where it is separated into fractions, including a gasoline fraction which is withdrawn through line 23 and a fraction lighter than gasoline which is withdrawn through line 24. From distillation column 22 a fraction boiling in the range 300 to 600 F. is passed through line 25 and blended with the materials in line 15 to form a superior jet fuel product. From distillation column 22, a fraction boiling above 600 F. is recycled through lines 26, 6 and 7 to hydrocracking zone 8.

Although only specific embodiments of the present invention have been described, numerous variations can be made in these embodiments without departing from the spirit of the invention and all such variations which fall within the scope of the appended claims are intended to be embraced thereby.

What is claimed is:

1. In a process wherein an unhydrofined hydrocarbon feedstock containing nitrogen and sulfur in amounts usually associated with said feedstock, said hydrocarbon feedstock containing substantial quantities of materials boiling in the range 300 to 650 F. and substantial quantities of heavier materials boiling in the range 550 to l,l00 F. is converted to valuable products including gasoline and jet fuel by process steps including catalytic hydrocracking in a hydrocracking reaction zone, the improvement which comprises separating said unhydrofined feedstock into a first portion predominantly comprising said materials boiling in the range 550 to l,l00 F. and a second portion predominantly comprising said materials boiling in the range 300 to 650 F., catalytically hydrocracking said first portion in said hydrocracking reaction zone at a temperature in the range 400 to 900 F. a pressure of at least 300 p.s.i.g., and a liquid hourly space velocity in the range 0.3 to 5.0, at a hydrogen supply rate of l,000 to 20,000 s.c.f. of hydrogen per barrel of said materials boiling in the range 550' to 1,100" F., catalytically hydrogenating said second portion in a second reaction zone at a temperature in the range 300 to 700 F., a pressure of at least 300 p.s.i.g., a liquid hourly space velocity of 0.3 to 5.0 and a hydrogen supply rate of at least 1,000 s.c.f. of hydrogen per barrel of said materials boiling in the range 300 to 650 F., to the extent that at least 50 volume percent of the aromatics present in the hydrocarbon feed to said second reaction zone are saturated, separating a fraction boiling in the range 300 to 650 F. from the effluent from said hydrocracking reaction zone, and combining, without further processing, the effluent from said second reaction zone with the said fraction boiling in the range 300" to 650 F. separated from said hydrocracking reaction zone effluent, to produce a jet fuel product.

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