Integrated Hydrotreating And Catalytic Cracking System For Refining Sour Crude

Abstract

Desalted crude oil plus a recycle stream from a catalytic cracking unit, e.g., catalytic gas oil (heavy catalytic cycle oil), with or without other cat cracking products, e.g., gasoline and light cycle oil, are mixed and hydrotreated together in a single operation; then fractionated into the desired fractions. Optionally, portions of the products from said hydrotreater can be reformed and/or coked with liquid fractions from said coker optionally being recycled to join the crude oil feed to the hydrotreater.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The following U.S. patent applications relate to the general field of the invention:

Ser. No. 157,529 filed June 28, 1971, Ser. No. 770,724 filed Oct. 24, 1968 now abandoned and Ser No. 771,248 filed Oct. 28, 1968 now U.S. Pat. No. 3,594,309, (both of which are priority documents for published Netherlands patents).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of hydrocarbon conversion processes, and more specifically to hydrotreating and catalytic cracking generally classified in U.S. Patent Office Class 208, subclass 212.

2. Description of the Prior Art

Separate hydrotreating of catalytic cracking recycle streams has been proposed, e.g., in R. A. Flinn and O.A. Larson, "The Effects of Hydrogenation and Catalytic Cracking of Various Molecular Types and Middle Distillates," J. Appl. Chem., 11, July, 1961, pp. 271-6 and M. D. Abbott, R. C. Archibald and R. W. Dorn, "Hydrogen Improves Catalytic Cracker Feed," Petroleum Refiner, 37, 161-6, 1958.

Hydrotreating of petroleum residual is taught by the following: Netherlands Patent NL-6916 218-Q which claims priority of U.S. patent application Ser. No. 771,248 filed Oct. 28, 1968, teaches processes for converting sulfurous, hydrocarbonaceous black oils into lower boiling, normally liquid-hydrocarbon products of reduced sulfur content with an integrated process involving cracking in the presence of hydrocarbon and fixed bed catalytic desulfurization. Netherlands patent NL-6916 017-Q which claims priority of U.S. Patent application Ser. No. 770,724 filed Oct. 25, 1968 teaches hydrodesulfurization of crude oil or reduced crude containing asphaltene fractions at low temperatures in the presence of a Group VI/Group VII metal catalyst on alumina.

Hydrotreating of whole crude oil is described in detail in the recent paper "Isomax Desulfurization of Residum and Whole Crude Oil," by S. G. Paradis, G. D. Gould, D. A. Bea and E. M. Reed as paper 31c presented at the Houston meeting of the American Institute of Chemical Engineers, Feb. 28-Mar. 4, 1971. U.S. Pat. No. 3,562,800 deals with hydrodesulfurization of crude or reduced crude, without recycle of liquid products from other units to mix with incoming crude. U.S. Pat. No. 3,617,501 is also made of reference.

SUMMARY OF THE INVENTION

General Statement of the Invention

According to the present invention, whole crude is hydrotreated, then fractionated and a gas oil fraction is catalytically cracked to produce liquid products, whereupon at least a portion of the liquid products are recycled back to the crude oil feed prior to the hydrotreating step. The advantages of the invention include: capital cost saving by reducing number of fractionating columns and number of hydrotreating units required; reduced quantities of coke (where applicable) and corresponding increases in quantities of more valuable liquid products; lower sulfur content in liquid products, and in any coke produced from the residual fractions; reduced corrosion due to the sulfur removal before contact with crude tower, catalytic cracker, coker and subsequent downstream processing units; high throughput throughout the hydrotreater (the light fractions are hydrotreated in a unit no larger than that required for conventional hydrotreating of the heavier fractions only); and, optionally, lower olefin contents in naptha products, particularly gasoline, in those embodiments where catalytic or coker naptha is recycled.

Utility of the Invention

The present invention produces gasolines and can optionally produce reformed gasoline of improved octane and/or coke. These products have utilities as motor fuels, improved motor fuels, and carbon for the production of electrodes, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of a refinery system hydrotreating whole crude and catalytically cracking according to the present invention.

FIG. 2 shows a refinery which additionally reforms to produce higher octane gasoling (reformate) and hydrogen which can optionally be recycled to the hydrotreater.

FIG. 3 shows a refinery which hydrotreats and catalytically cracks as in FIG. 1, but additionally cokes a residual fraction to produce coker liquids which can optionally be recycled back to mix with the feed of the hydrotreater.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Starting Materials

Hydrocarbons: It is an important aspect of the present invention that whole crude oil is hydrotreated. Previous processes have hydrotreated residuals, e.g., 650.degree.F. plus portions without achieving the advantages of the present invention. Crudes which are particularly useful for the practice of the invention are those which are relatively high in sulfur content but low in asphaltene and heavy metals content. Sour West Texas crude is a good example of this type of crude.

Topped crudes, e.g., those having the portion boiling below about 400.degree.F. fractioned out, can be utilized in place of the whole crude oil.

The preferred gas-oil fraction to be fed to the catalytic cracking unit according to the present invention, is preferably that portion of the mixed overheads from both an atmospheric and a vacuum distillation which remains after the removal of gasoline and light distillates, and will preferably boil within the range of from about 500 to 1,150.degree., more preferably from 550 to 1,100.degree., and most preferably from 600 to about 1,050.degree.F.

Residual fraction: The preferred residual fraction for coking according to the present invention, is the fraction generally boiling above about 900.degree.F, more preferably above about 1,000.degree.F, and most preferably above about 1,050.degree.F.

Catalytic cracking unit liquid products: A catalytic cracking unit produces a liquid output which is conventionally fractionated into a variety of products including catalytic gasoline, catalytic cracker middle distillate, catalytic cracker gas-oil, and a slurry containing entrained catalysts, all or part of which is recovered and recycled to the catalytic cracker unit.

Catalytic cracker gas-oil: In many conventional operations, gasoline is taken as product with middle distillate and/or catalytic cycle gas-oil being recycled to the catalytic cracking unit. The present invention employs the catalytic cracker gas-oil (and, optionally, the middle distillate and/or gasoline) for comingling with the crude oil feed to the hydrotreater. Catalytic cracking unit gas-oil will generally boil in the range of from about 450 to about 950, more preferably from 500 to about 925, and most preferably from 600 to about 900.degree.F.

Coker Liquid products: The coker liquid products selected for recycle will generally consist of the entire liquid product from C.sub.5 or C.sub.6 up through the highest boiling liquid products produced. The lower molecular weight material, particularly the C.sub.3, C.sub.4 and perhaps C.sub.5 portion are advantageously separated for olefin recovery. Any other portions of the coker liquid product may also be separated for separate use, if desired. From about 1 to about 100, more preferably from 50 to about 100, and more preferably from 75 to about 100 volume percent of liquid (C.sub.3 -plus) products from the coker will be mixed with the whole crude entering the hydrotreating process. The remaining coker liquids, if any, can be utilized for conventional purposes, e.g., for gasoline and heavier fuels.

Hydrogen: The hydrogen utilized with the present invention can be of commercial purity such as that derived from the reforming of naphtha as by any of the reforming processes described on pp. 184-193 of the September, 1970 issue of Hydrocarbon Processing or can be manufactured specially for the purpose such as by steam reforming or partial oxidation of hydrocarbons (ibid pp. 269-270). From about 1,000 to about 6,000, more preferably from 2,000 to about 5,000, and most preferably from about 2,500 to about 4,000 standard cubic feet of hydrogen will be contacted with each barrel of oil fed to the hydrotreater.

Hydrotreating Catalyst: A wide variety of hydrogenation catalysts, especially those containing metals selected from the group nickel, molybdenum, cobalt and tungsten, or compounds containing such metals, can be employed including those marketed by the Girdler Division of Chemetron Corp. under the tradename "Girdler G-51," "Girdler G-76"; those marketed by Union Oil Company of California under the tradename "N-21"; those marketed by American Cyanamid Company under the tradename "Cyanamid HDS-2A" and "Cyanamid HDS-1450," "Cyanamid HDS-1441," "Cyanamid HDS-9A," and "Cyanamid HDS-3A"; those marketed by the Davison Chemical Company Division of W. R. Grace & Co. under the tradename "Davison-HDS" and that marketed by Nalco Chemical Company under the tradename "Nalco NM-502" and that marketed by Catalyst and Chemicals, Inc. under the tradename "CCI C-20-07." Of these, nickel-molybdenum catalysts, e.g., American Cyanamid HDS-3A, HDS-9A and Nalco NM-502 are most preferred.

Hydrotreating Catalyst Support: The preferred catalyst supports are alumina, silica, magnesia or combinations thereof. In general, the support should not be sufficiently acidic so as to cause extensive hydrocracking of the oil under the preferred reaction conditions. For use in a fixed-bed hydrotreating unit a catalyst in the form of an extrudate, pellet or sphere of such size as to avoid excessive pressure drop through the catalyst bed but small enough to provide good transport of the oil into the center of the catalyst particle is used. Sizes from about 1/8 to 1/16 inch are generally preferred. In a moving or ebulating bed hydrotreating reactor, 1/32 inch or smaller extrudates or other shaped particles can be used to advantage.

Hydrotreating Temperature: While not narrowly critical, the temperature during the hydrotreating reaction should be from 600 to about 850.degree.F., more preferably from 650 to about 800.degree.F., and most preferably from 675 to about 775.degree.F. The temperature used will depend on the relative hydrosulfurization and hydrocracking activities of the particular catalyst used and will normally be increased during a run to compensate for catalyst deactivation.

Hydrotreating Pressure: While also not narrowly critical, pressure during the hydrotreating reaction should be from about 250 to about 5,000, more preferably from about 600 to about 2,500 and most preferably from 800 to about 2,000 psig.

Hydrotreating Liquid Hourly Space Velocity: The liquid hourly space velocity will generally be in the range of from about 0.5 to about 6, more preferably 0.5 to about 4, and most preferably 1 to about 3 volumes of liquid per volume of hydrotreating catalyst per hour.

Catalytic cracking: The catalytic cracking is carried out under conventional conditions, e.g., those described on pages 174-179 of the September, 1970 issue of Hydrocarbon Processing and in the reference cited therein. The catalytic cracking catalysts will generally be mixtures of silica and alumina or magnesia and preferably will contain crystalline compounds of silica and alumina commonly known as "Zeolites" or "molecular sieves."

Suitable catalytic cracking catalysts are described in Hydrocarbon Processing, Vol. 47, No. 2, pages 125-132 (Feb. 1968).

Coking: The coking is carried out under conventional conditions, e.g., those described on pages 180-181 of the September, 1970 issue of Hydrocarbon Processing and in the references cited therein.

Apparatus: Conventional hydrotreating, distillation, catalytic cracking, reforming, and coking apparatus can be employed. Though not necessary to the invention, with crude having high content of metals and/or particulates, a conventional guard case filled with inexpensive catalyst can be provided upstream of the main hydrotreating reactor to protect the more expensive main catalyst.

Examples: Examples I and III are according to the invention. Examples II and IV are comparative examples to illustrate the loss of advantages when the crude oil and recycle stream are not hydrotreated. Example V demonstrates the use of the naphtha product as reformer feedstock.

EXAMPLE I

(Hydrotreating whole crude and catalytically cracking, according to the invention)

Referring to FIG. 1, whole crude 10 enters the desalter 11 of conventional design which removes inorganic halides. The desalted crude is heated in heat exchanger 12, contacted with make-up hydrogen 14 and recycle hydrogen 33 and further heated in furnace 13. The hot crude plus hydrogen steam is passed over a bed of American Cyanamid HDS-3A nickel-molybdenum catalyst in hydrotreater 15 at 700.degree.F., 1,500 psig, liquid hourly space velocity of 1.64 hr..sup..sup.-1 and hydrogen to oil ratio of 3,350 scf per barrel. The hydrotreated stream is cooled in heat exchanger 16 and fed to separator 17 which separates the gaseous from the liquid products. The gaseous products from separator 17 are scrubbed to remove hydrogen sulfide and ammonia from recycle hydrogen stream 33. A small stream 34 is taken off to prevent build up of C.sub.1 through C.sub.3 hydrocarbons in the recycle stream. The liquid products from separator 17 are fed to the main distillation columns 18 where they are fractionated into product streams; gas, 19 (composed primarily of C.sub.1 through C.sub.4 which is sent to a conventional gas concentration facility); gasoline, 20 (composed primarily of C.sub.5 through C.sub.12 fractions boiling up to about 400.degree.F. is sent to blending and/or catalytic reforming); middle distillate, 21 (which may be more than one fraction and which is composed primarily of kerosine, diesel fuel, and jet fuel); gas oil, 23 (consisting of both atmospheric and vacuum gas oil) which is sent to the catalytic cracker 43 via heater 48; and residuals 22 which are optionally sent to a conventional delayed or fluid coker to produce coke.

Catalytic cracking unit 43 is operated at 900.degree.F. weight hourly space velocity of 2.14 hr..sup..sup.-1 and catalyst to oil ratio (weight) of 5.6 with equilibrium American Cyanamid TS-170 catalyst.

Product from the catalytic cracker 43 is fractioned in fractionating column 27. Overhead 28 from column 27 is partially condensed to separate in separator 40, an overhead 30 composed primarily of C.sub.4 and lighter hydrocarbons which is sent to gas concentration, and a bottoms stream 46 which consists primarily of hydrocarbons from C.sub.5 through 400.degree.F. boiling range which are sent to gasoline blending, or optionally may be comingled with the crude oil stream from desalter 11 for recycle to the hydrotreating unit 15. Fraction 44 from fractionating column 27 consists primarily of hydrocarbons boiling in the range of from about 400 to 600.degree.F. and is used for blending of diesel fuel, heating oil, kerosine and turbine fuel, or optionally may be comingled with the crude oil stream for desalter 11 for recycle to the hydrotreater 15. Fraction 45 from fractionating tower 27 consists primarily of hydrocarbons boiling from about 600 to 850.degree.F. and is recycled back to mix with the effluent from desalter 11. The residual fraction from fractionating tower 27 is cooled in heat exchanger 49 and entrained catalyst is optionally separated in slurry settler 47 for return to the catalytic cracking unit 43 as stream 29.

The crude oil 10 used in Examples I-IV, is a sour West Texas crude containing 1.67 wt. percent sulfur. Sulfur contents of the various distillation fractions of the raw crude oil are shown below.

TABLE 1

Raw Crude Oil

Distillation Fraction Volume Percent Wt. % Sulfur .degree.F. below 400 18.96 0.16 400-600 22.13 0.63 600-1050 38.00 1.65 1050 plus 20.91 2.62

The liquid products obtained after hydrotreating and fractionation have the composition shown below.

TABLE 2

Hydrotreated Products

Distillation Fraction Volume Percent Wt. % Sulfur .degree.F. below 400 18.66 <0.01 400-600 24.38 <0.01 600-1050 41.64 0.12 1050 plus 15.32 0.74

Thus the method of this invention provides a significant reduction in sulfur content of all liquid products including the gas oil 23 subsequently used as catalytic cracking unit feedstock.

In order to demonstrate the improved yeilds resulting from cracking of the gas oil obtained from the hydrotreated blend of catalytic cracking unit gas oil and whole crude oil (compared to the gas oil obtained from the raw crude oil and catalytic cracking unit gas oil described in Example II) blends containing equal (12 vol. %) amounts of catalytic cracking unit gas oil in crude oil are cracked..sup.1 These do not represent the balanced flows of gas oil in each case since less gas oil is produced (under equivalent cracking conditions) from the hydrotreated feed. Yields are shown in the following tables as volume percent of feed unless specified otherwise.

TABLE 3

Example Example Example Example I II III IV Dry Gas (scf/bbl) 111 128 114 129 Propane 2.4 2.5 2.4 2.5 Propylene 7.2 7.0 7.1 7.5 Isobutane 5.6 4.6 5.8 5.2 Normal Butane 1.2 1.2 1.4 1.3 Butylenes 6.4 6.8 6.8 7.9 C.sub.5 --400.degree.F 59.4 50.8 63.1 56.3 400.degree.--600.degree.F 16.1 18.7 14.7 17.2 600.degree.F plus 11.5 17.3 8.5 12.7 Coke (wt.%) 4.75 5.8 4.75 5.57

Example II

This is a comparative example to demonstrate the cracking yields resulting from conventional processing of gas oil obtained from sour crude oil without benefit of the invention. The gas oil described in Table 1 of Example I is cracked under the cracking conditions of Example I. The yields of cracked products are shown in Table 3. The inclusion of 12 volume percent catalytic cracking oil in the crude oil is equivalent to a conventional catalytic cracking operation in which the combined feed ratio (total feed/fresh feed) is about 1.4 to 1. Comparison of the yields from Examples I and II shows the markedly improved conversion and selectively to gasoline as well as reduced coke make resulting from use of this invention.

Example III

This example demonstrates the advantages of hydrotreating coker condensate together with crude oil in the preparation of catalytic cracking charge stock.

Referring to FIG. 3, crude oil 10 is processed as in FIG. 1 to obtain a residual fraction 22 which is used as feedstock to a delayed or fluid coking unit 60. The products from coking unit 60 consist of coke 64 and a hot vapor stream which is cooled and then split in separator 61 into a gaseous stream 62 consisting primarily of hydrogen and C.sub.1 through C.sub.4 hydrocarbons which may be sent to a light ends or gas concentration plant for separation and further processing and a liquid stream 63 which consists principally of C.sub.5 and higher boiling hydrocarbons to an end point of about 950.degree.F. which is comingled with the crude stream from desalter 11. Optionally, the liquid product stream 63 can be fractionated or divided and only a portion of this stream comingled with the effluent from desalter 11, with the remainder being used in product blending and other conventional refinery uses.

The crude oil of Example I, together with 15 volume percent of a coker condensate obtained by delayed coking of a 975.degree.F. plus residual fraction from the crude oil of Example I which has been hydrotreated under the conditions of Example I is hydrotreated and catalytically cracked as in Example I. The coking unit is operated at 925.degree.F. bed temperature with an inlet feed temperature of 1,000.degree.F. The oil to steam feed ratio is 20.5 volume of oil to volume of water. The coking time is 9 hours. Yields.sup.1 obtained by catalytically cracking the 600 to 975.degree.F. gas oil fraction obtained from the hydrotreated mixture of 15 volume percent coker condensate and 85 volume percent crude oil are shown in Table 3.

Example IV

This comparative example shows the lower yield of gasoline which is obtained by conventionally catalytically cracking virgin and coker gas oil which have not been hydrotreated.

A blend of 15 volume percent coker gas oil as described in Example III and 85 volume percent crude oil as described in Example I is distilled to obtain a gas oil cut boiling from about 600 to about 975.degree.F. This gas oil is catalytically cracked as in Example III. Yields.sup.1 are shown in Table 3. The gasoline (C.sub.5 -400.degree.F.) yield is significantly lower than when the process of this invention is used in Example III and the coke make is higher, indicating a greater loss of valuable products to coke and correspondingly greater air requirement to generate the catalyst.

Example V

In this example the naptha product is reformed to produce high octane gasoline and hydrogen which may be used in the hydrotreating operation.

Referring to FIG. 2, crude oil 10 is processed as in Example 1 with the naphtha 20 produced from main column(s) 18 used as feedstock to catalytic reforming unit 50. The reforming unit consists of hydrotreating reactor and several reforming reactors, together with the necessary furnaces and accessory equipment. The product stream is cooled and subsequently separated in a separator 51 into a high octane liquid product 52 and a gas stream 53 consisting predominantly of hydrogen which is partially recycled as stream 54 to the reforming reactor and partially withdrawn as stream 55 for use elsewhere as, for example, in hydrotreating unit 15.

Modifications of the Invention

It should be understood that the invention is capable of a variety of modifications and variations which will be made apparent to those skilled in the art by a reading of the specification and which are to be included within the spirit of the claims appended hereto.

Claims

What is claimed is:

1. In a process for the manufacture of gasoline from gas-oil derived from the fractionation of crude oil, the improvement comprising hydrotreating said crude oil prior to said fractionation which produces said gas-oil, said hydrotreating being accomplished by contacting said crude oil with from about 1,000 to about 6,000 standard cubic feet of hydrogen per barrel of crude oil at a temperature of from about 600 to about 850.degree.F. and at a pressure of from about 250 to about 5,000 psig in the presence of a hydrotreating catalyst, fractionating and catalytically cracking the gas-oil fraction of the resulting hydrotreated crude oil, and recycling at least a portion of the liquid products from said catalytic cracker to mix with said crude oil prior to said hydrotreating.

2. A process according to claim 1 wherein the crude oil is topped to remove its fraction boiling below about 400.degree.F prior to said hydrotreating of said crude oil.

3. A process according to claim 1 wherein the crude oil is contacted with from about 2,000 to about 5,000 standard cubic feet of hydrogen per barrel of crude oil at a temperature of from about 650 to about 800.degree.F. and at a pressure of from about 600 to about 2,500 psig.

4. A process according to claim 1 wherein said catalytic cracker liquid products include gasoline, at least a portion of which is recycled for mixture with said crude oil being fed to said hydrotreater and wherein at least a portion of the effluent from said hydrotreater is reformed to produce a higher octane gasoline.

5. A process according to claim 1 wherein the hydrotreated products from said hydrotreater are fractionated to produce a residual and wherein at least a portion of said residual is coked to produce coke and liquid products.

6. A process according to claim 5 wherein at least a portion of said liquid products from said coker are recycled for admixture with the crude oil being fed to said hydrotreater.

7. A process according to claim 1 wherein said hydrotreating catalyst comprises a metal selected from the group consisting of nickel, molybdenum, cobalt and tungsten or a compound containing one of the foregoing metals.

8. A process according to claim 4 wherein the crude oil is contacted with from about 2,000 to about 5,000 standard cubic feet of hydrogen per barrel of crude oil at a temperature of from about 650 to about 800.degree.F. and at a pressure of from about 600 to about 2,500 psig.

9. A process according to claim 5 wherein the crude oil is topped to remove a fraction boiling below about 400.degree.F. prior to said hydrotreating of said crude oil.

10. A process according to claim 1 wherein said catalytic cracker liquid products include gas-oil, at least a portion of which is recycled for mixture with said crude oil being fed to said hydrotreater.

11. A process according to claim 1 wherein said catalytic cracker liquid products include both a gas-oil and a middle distillate and wherein at least a portion of each of said gas-oil and said middle distillate is recycled for mixture with said crude oil being fed to said hydrotreater.

12. A process for the manufacture of gasoline and refined liquid hydrocarbons by cracking in a catalytic cracker, a gas oil fraction obtained from a whole crude or crude which has been topped to remove a fraction boiling below about 400.degree.F., said process comprising in combination:

a. desalting said crude as necessary to reduce the content of inorganic halides,

b. contacting said crude with at least a portion of the liquid products from said catalytic cracker and with about 2,000 to about 5,000 standard cubic feet of hydrogen per barrel of oil to form a hydrocarbon plus hydrogen stream,

c. passing said hydrocarbon plus hydrogen stream over a hydrotreating catalyst at a temperature of from about 675 to about 755.degree.F. and at a pressure of from about 800 to about 2,000 psig and at a liquid hourly space velocity of from about 0.5 to about 4 volumes of liquid per volume of hydrotreating catalyst per hour to produce a hydrotreated product stream,

d. fractionating said hydrotreated product stream to produce a plurality of refined liquid hydrocarbon products and a residual stream,

e. cracking in a catalytic cracking unit the gas-oil fraction boiling from about 600 to about 1,100.degree.F. from said fractionating step,

f. coking at least a portion of said residual stream in a delayed coker to produce coke and coker overhead,

g. fractionating said coker overhead to produce a lower boiling fraction comprising C.sub.4 and lighter hydrocarbons and at least one high boiling stream comprising C.sub.5 and heavier hydrocarbons.

13. A process according to claim 12 wherein at least a portion of said higher boiling fraction from said fractionation of said coker overhead is recycled for mixing with said crude oil or topped crude being fed to said hydrotreater.

14. A process for the manufacture of gasoline and refined liquid hydrocarbons from whole crude or crude which has been topped to remove a fraction boiling below about 400.degree.F., said process comprising in combination:

a. desalting said crude as necessary to reduce the content of inorganic halides,

b. contacting said crude with at least a portion of the liquid products from said catalytic cracker and with about 2,000 to about 5,000 standard cubic feet of hydrogen per barrel of oil to form a hydrocarbon plus hydrogen stream,

c. passing said hydrocarbon plus hydrogen stream over a hydrotreating catalyst at a temperature of from about 675 to about 775.degree.F. and at a pressure of from about 800 to about 2,000 psig and at a liquid hourly space velocity of from about 0.5 to about 4 volumes of liquid per volume of hydrotreating catalyst per hour to produce a hydrotreated product stream,

d. fractionating said hydrotreated product stream to produce a plurality of refined liquid hydrocarbon products and a residual stream,

e. reforming at least a portion of said refined liquid hydrocarbon products in a reformer to produce gasoline of improved octane and hydrogen,

f. cracking in a catalytic cracking unit the gas-oil fraction boiling from about 600 to about 1,100.degree.F. from said fractionating step.

15. A process according to claim 14 wherein at least a portion of said hydrogen is recycled to said hydrotreater.

16. A process according to claim 14 wherein said hydrotreated product stream is fractionated to produce a plurality of refined liquid hydrocarbon products and a residual stream, and wherein at least a portion of said residual stream is coked in a coker to produce coke and coker overheads, fractionating said coker overhead to produce an overhead comprising C.sub.4 and lighter hydrocarbons and at least one high boiling stream comprising C.sub.5 and heavier hydrocarbons.

17. A process according to claim 16 wherein at least a portion of said higher boiling fraction from said fraction-ation of said coker overhead is recycled for mixing with said crude oil or topped crude being fed to said hydrotreater.

18. A process according to claim 1 wherein said liquid products from said catalytic cracker are fractionated to produce a fraction boiling within the range of from about 600 to about 850.degree.F. and wherein this fraction is recycled back to mix with said crude oil being fed to said hydrotreater; and a substantially residual fraction, at least a portion of which is recycled back to mix with said gas-oil fraction being catalytically cracked.

19. A process according to claim 18 additionally comprising the fractionating from said liquid products of said catalytic cracker of a substantially overhead stream comprised primarily of C.sub.4 and lighter hydrocarbons which stream is not recycled to either said hydrotreating step or said catalytic cracking step.

20. A process according to claim 12 wherein said liquid product from said catalytic cracker are fractionated to produce a fraction boiling within the range of from about 600 to about 850.degree.F. and wherein this fraction is recycled back to mix with said crude oil being fed to said hydrotreater, and a substantially residual fraction, at least a portion of which is recycled back to mix with said gas-oil fraction being catalytically cracked.

21. A process according to claim 20 additionally comprising the fractionating from said liquid products of said catalytic cracker of a substantially overhead stream comprised primarily of C.sub.4 and lighter hydrocarbons which stream is not recycled to either said hydrotreating step or said catalytic cracking step.

22. A process according to claim 14 wherein said liquid products from said catalytic cracker are fractionated to produce a fraction boiling within the range of from about 600 to about 850.degree.F. and wherein this fraction is recycled back to mix with said crude oil being fed to said hydrotreater; and a substantially residual fraction, at least a portion of which is recycled back to mix with said gas-oil fraction being catalytically cracked.

23. A process according to claim 22 additionally comprising the fractionating from said liquid products of said catalytic cracker of a substantially overhead stream comprised primarily of C.sub.4 and lighter hydrocarbons which stream is not recycled to either said hydrotreating step or said catalytic cracking step.