Combined fluid catalytic cracking and hydrocracking process

An integrated combination of fluid catalytic cracking and hydrocracking select fractions of crude oil and FCC cycle oils to conserve hydrogen process requirements in the production of gasoline is discussed. Liquid products of hydrocracking are separated into low boiling components and a high boiling fraction is recycled to the FCC operation. Select fractions obtained from hydrocracking, FCC and crude oil distillation are upgraded by reforming and alkylation.

BACKGROUND OF THE INVENTION 
The present invention relates to a combination process for upgrading high 
boiling portions of crude oil by catalytic cracking and hydrocracking. 
Some prior art patents having a bearing on the subject are identified 
below: 
U.S. Pat. No. 2,911,352 is directed to a process for producing high octane 
naphtha by the combination of catalytic cracking, desulfurization, and 
hydrocracking. 
U.S. Pat. No. 2,939,836 is directed to the destruction of heavy crude oils 
obtained from catalytic cracking by hydrocracking a product fraction 
boiling above 260.degree. C. (500.degree. F.). 
U.S. Pat. No. 3,072,560 is directed to a combination process for conversion 
of residual oils to gasoline by coking, hydrocracking, catalytic cracking, 
hydrocracking and reforming. 
U.S. Pat. No. 3,193,488 is directed to a combination catalytic cracking and 
hydrocracking process involving two separate stages of catalytic cracking 
and hydrocracking a solvent oil extract of a high boiling product of 
catalytic cracking. 
U.S. Pat. No. 3,349,023 is directed to a combined cracking process for 
maximizing middle distillate production by thermal cracking and 
hydrocracking. 
U.S. Pat. No. 3,983,029 is directed to a combination process comprising 
hydrotreating a hydrocarbon feed boiling above 200.degree. F. before 
hydrocracking thereof. The hydrocracked product is fractionated to produce 
a 180.degree.-400.degree. F. fraction passed to catalytic reforming and a 
550.degree. F. plus fraction either charged to catalytic cracking or 
recycled to either the hydrocracking zone or the hydrotreating zone. 
U.S. Pat. No. 3,185,639 relates to a combination process for upgrading 
crude oil which comprises deasphalting atmospheric tower bottoms before 
catalytic cracking, separating the product of catalytic cracking to obtain 
a fraction product, and of hydrofining light and heavy atmospheric gas 
oils in combination with light and heavy cycle oils of catalytic cracking 
before hydrocracking thereof. 
SUMMARY OF THE INVENTION 
The present invention is directed to an integrated combination process for 
upgrading crude oil to produce lower boiling materials comprising gasoline 
boiling range products. More particularly, the combination process of the 
present invention generally relies upon the sequence of fluid catalytic 
cracking followed by hydrocracking of selected feed materials higher 
boiling than gasoline range products. The liquid products of hydrocracking 
are separated at a boiling point in the range of 400.degree. to 
600.degree. F. to recover a low boiling product fraction recycled to a 
crude atmospheric distillation tower with a higher boiling fraction with 
an initial boiling point in the range of 400.degree. to 600.degree. F. 
being recycled to the fluid catalytic cracking unit. Cycle oils of fluid 
catalytic cracking with or without a straight run middle distillate 
fraction of the crude oil are desulfurized and hydrocracked. 
In the processing sequence above briefly defined, the fluid catalytic 
cracking unit is relied upon to accomplish a selective cracking operation 
including substantial desulfurization, denitrogenation and dematalization 
of higher boiling portions of the crude oil charge to be subsequentially 
hydrocracked. In a more particular embodiment, partially desulfurized 
light and heavy cycle oils of fluid catalytic cracking are further 
desulfurized and denitrogenated to form hydrogen sulfide and ammonia 
before affecting hydrocracking thereof in the presence of a zeolite 
containing hydrocracking catalyst to hydrogenate and crack polycyclic 
compounds in the hydrocracking and the fluid catalytic cracking steps of 
the combination operation to produce gasoline boiling range product 
material. 
The synergistic contributions of the combination process comprising a 
zeolite fluid catalytic cracking operation in combination with a 
downstream hydrocracking operation, hydrocracking a 
desulfurized-denitrogenated cycle oil product of fluid catalytic cracking 
boiling above gasoline boiling range material and subjecting a product of 
hydrocracking boiling above about 400.degree. to 600.degree. F. to the 
fluid catalytic cracking operation of the combination which hydrogenated 
fraction contributes significantly and measurably to the production of 
gasoline of acceptable octane rating as well as gaseous components 
convertible to gasoline boiling components. Furthermore, the cyclic flow 
of the combination operation contributes significantly to the production 
of dicylic components recoverable in LCO from higher boiling polycyclic 
compounds as well as gasoline boiling range components of acceptable 
octane rating. 
In a particular aspect the integrated combination operation of this 
invention is concerned with utilizing demetalization desulfurization and 
denitrogenization aspects of a fluid catalytic cracking operation to 
provide a relatively clean feed material boiling above about 400.degree. 
F. of substantially reduced sulfur and nitrogen content as well as reduced 
metallo-organic compounds as an oil change or feed to a downstream 
hydrocracking operation comprising catalytic desulfurization and 
denitrogenation operations for cycle oils which further reduces residual 
sulfur and particularly nitrogen in the feed to a level of about 10 ppm. 
The 400.degree. F. plus clean feed material thus desulfurized and 
denitrogenated is thereafter subjected to a selective hydrocracking 
operation employing preferably a zeolite containing hydrocracking catalyst 
or other suitable catalyst maintained under operation conditions of 
temperature and pressure which will particularly reduce multicyclic 
compounds to lower orders of cyclic compounds comprising gasoline boiling 
range components and provide hydrogenated higher boiling polycyclic 
compounds in the range of 2 to 5 ring components ultimately converted by 
the combination cracking operations to mono and dicyclic aromatics. A 
hydrocracked product boiling above a selected boiling range herein defined 
is recycled as a hydrogenated product to the fluid cracking operation for 
catalytic conversion thereof in the presence of a reduced crude oil charge 
boiling above a middle distillate fraction of the crude oil as herein 
defined to produce gasoline and lower boiling range product components and 
cycle oils. The selected recycled product of hydrocracking, herein defined 
as having an IBP in the range of about 400.degree. F. up to about 
600.degree. F., is mixed with atmospheric bottoms from crude oil 
distillation generally boiling above about 600.degree. F. to provides a 
source of labile hydrogen from hydrocracking suitable for effecting 
hydrogen transfer reactions during the fluid catalytic cracking of the 
high boiling fresh feed residual oil portion of crude oil charged feed. In 
this combination the fresh residual oil feed is demetallized while also 
effecting desulfurization and denitrogenation of the charged residual oil. 
Thus the hydrocracking operation is a hydrogen contributor to residual oil 
conversion processed in a special reduced crude cracking operation herein 
below more particularly discussed. 
In view of the synergistic contributions between the special combination of 
cracking operations and desulfurizing operations herein defined and the 
conditions of operation of the individual steps, it is evident that they 
may be considerably varied to particularly emphasize the production of 
gasoline boiling range material and/or middle distillates in response to 
seasonal changes particularly requiring more or less of the products of 
the combination operation. 
The combination process of this invention is considered economically 
advantageous and synergistically efficiently cooperative in hydrogen 
utilization in the following manner: 1. A feed charged to hydrotreating 
will normally further hydrogen enrich the front end of the feed which is 
already rich in hydrogen, whereas in the particular fluid 
cracking/hydrotreating/hydrocracking steps of the combination process of 
this invention, cycle oil products of hydrocracking will artificially 
hydrogen enrich particularly the heavier portions of the crude residual 
oil feed charged to fluid catalytic cracking operation. This process 
combination therefore provides for a more efficient use of within process 
generated hydrogen as discussed herein. 
2. Hydrotreating/hydrocracking the cycle oils of FCC requires considerably 
less hydrogen than hydrotreating the total crude oil feed portion thus 
making for greater use optimization of available hydrogen. 
3. In the combination of this invention the FCC unit is regarded as a 
pivotal unit in the overall refinery operation. That is, compared to 
hydrotreating the total feed, the FCC operation is more efficient, as well 
as an economically more attractive process for use as a residual oil 
"cleaning up" process unit. That is, metals, solids, and Conradson carbon 
components are removed continuously as well as more efficiently and 
economically from a crude residual oil portion comprising vacuum tower 
bottoms charged to a fluid catalytic cracking operation. 
4. Recycling of a select hydrogenated product fraction from a hydrocracking 
operation to the FCC operation improves substantially the equilibrium 
flash characteristics of the higher boiling portion of a reduced crude, 
thus allowing for a better catalytic conversion thereof by effectively 
lowering the required feed pseudo-critical operating temperature. 
5. Using the Fluid Catalytic Cracking Unit (FCCU) as a pivotal process in 
the overall cracking combination as herein provided requires at least 60 
percent less hydrogen to produce desired upgraded products when compared 
to an operation employing total feed hydrotreating. The combination 
operation of this invention allows the refiner to stay in more complete 
hydrogen balance with the hydrogen produced from the selective cracking 
operations of the invention in combination with that obtained from naphtha 
reforming. 
6. The efficient and economic upgrading of a crude oil into gasoline 
producing components is directly related to the optimized utilization of 
hydrogen transfer reactions. The combination operation of the invention 
particularly identifies a most efficient utilization of available hydrogen 
by the combination of; 
(1) hydrogen production through naphtha reforming, 
(2) hydrogen transfer redistribution through fluid catalytic cracking in 
the presence of a hydrogen donor material, 
(3) hydrogen absorption through cycle oils of hydrocracking transferred to 
catalytic cracking, and 
(4) hydrogen transfer from isobutane to olefins through alkylation. 
Thus a combination operation of selective distillations, naphtha reforming, 
light product olefin alkylation, the combination of selective catalytic 
cracking of a residual oil or a reduced crude in the presence of cycle oil 
of hydrocracking in cooperation with FCC cycle oil hydrocracking with or 
without the presence of a crude oil middle distillate provides for a 
highly efficient and integrated hydrogen redistribution combination 
operation for upgrading residual or reduced crude oils into high yields of 
gasoline boiling range materials. 
The processing combination of the diagrammatic drawing of FIG. 1, may be 
modified to eliminate one or both of separation zones 14 and 20 discussed 
below so that a desalted crude oil or one of low salt content can be 
charged to an atmospheric distillation tower. On the other hand, all or 
only a portion thereof comprising n-C.sub.6 plus hydrocarbons and 
comprising higher boiling crude oil component materials may be charged as 
a feed to the fluid catalytic cracking operation in the manner herein 
identified. Other modifications and variations in the combination process 
are more specifically discussed below. 
In any of the operation combinations herein particularly identified, it is 
intended that sodium and other water-soluble alkaline metals of the crude 
oil be reduced to a level of about 2 ppm commensurate with maintaining 
acceptable economic processing conditions before charging the fresh 
reduced crude feed to the process combination and particularly the (FCC) 
fluid catalytic cracking operation. The FCC operation of this invention is 
a special FCC operation identified below for processing residual oils and 
reduced crudes comprising metals and/or Conradson carbon producing 
components. In a particular embodiment, the FCC unit is more particularly 
identifiable with that disclosed in copending application Ser. No. 169,086 
filed July 15, 1980, now U.S. Pat. No. 4,332,674 and that of application 
Ser. No. 324,450 filed on Nov. 24, 1981 the subject matter of which is 
incorporated herein by reference thereto. The FCC fluid cracking operation 
of this invention is therefore a particularly selective crystalline 
zeolite catalyst cracking operation concerned with cracking high boiling 
portions of a crude oil charge comprising a reduced crude, a residual oil 
portion of the crude boiling above about 600.degree. F., or a portion of a 
reduced crude oil comprising material boiling above vacuum gas oils such 
as a vacuum resid containing metallo-organic compounds of multicyclic 
compositions of 3 to 6 adjoined ring configuration and boiling above about 
1025.degree. F. and more usually boiling above 1050.degree. to 
1100.degree. F. 
A further desulfurization and denitrogenation of a product of the fluid 
cracking operation boiling above about 400.degree. F. with or without the 
presence of a separated crude oil middle distillate fraction such as a 
straight run or atmospheric fraction of the crude oil charge is 
accomplished under elevated exothermic temperature conditions generally 
restricted in the range of about 600.degree. F. up to about 800.degree. F. 
and a pressure above about 1000 psig, it being preferred to restrict the 
pressure thereof below about 3000 psig. The further desulfurization and 
denitrogenation of the identified high boiling oil charge is accomplished 
with a catalyst suitable for the purpose and known in the prior art such 
as a catalyst comprising cobalt-molybdenum, nickel tungsten or a 
nickel-molybdenum. Since a substantial portion of sulfur and nitrogen in 
the charge is effectively removed from the 600.degree. F. plus material in 
the hydrogen transfer FCC operation of this invention, the severity of the 
further downstream desulfurization-denitrogenation operation may be more 
critically optimized to recover a product therefore comprising no more 
than about 10 ppm total nitrogen and 10 ppm combined sulfur. 
In addition, to the above, the sequence of FCC and desulfurizing steps 
herein identified increase the API gravity of the cycle oil product of FCC 
from 5 to 10 numbers by the subsequent desulfurizing step to provide a 
demetallized feed more suitable for charging to a hydrocracking operation 
and comprising FCC cycle oil with or without crude oil middle ditillate 
material boiling from about 400.degree. F. up to about 600.degree. F. The 
desulfurized cycle oil products of fluid catalytic cracking boiling above 
about 400.degree. F. of reduced metals, residual sulfur and nitrogen 
components with or without admixture with a middle distillate of the crude 
oil feed as herein provided is thereafter hydrocracked at a temperature 
restricted to within the range of about 650.degree. to about 800.degree. 
F., and a pressure in the range of about 1000 psig up to about 3500 psig, 
but preferably in the range of about 1500 psig up to about 2500 psig. 
Hydrocracking is generally regarded as a severe hydrogenation operation 
since it occurs at temperatures high enough to affect some catalytic 
cracking of charged hydrocarbons and is promoted by a catalyst composition 
comprising active crystalline zeolite catalytic component material. The 
course of the reaction and products obtained depend upon the composition 
of the feed charged as well as catalyst composition and on the relative 
rates of the hydrogenation and cracking reactions promoted therein. When 
charging a paraffinic feed, the hydrogen functions to saturate a primary 
olefinic product of the cracking reaction and thus prevents significant 
condensation reactions from occurring to the refractory polycyclic 
molecules. Furthermore, at the relatively low temperatures of 
hydrocracking, the hydrogenation of multi-ring aromatics is favored at the 
expense of producing a low octane gasoline. However, at more severe 
hydrocracking conditions, the rates of cracking increase faster than the 
rates of hydrogenation and materials such as tetralin crack to form lower 
forms of cyclic hydrocarbons. Thus, when hydrogenation of polycyclics is 
desired, the pressure of the operation must be high enough for the 
equilibriums to be favorable. In the particular synergistically integrated 
fluid catalytic cracking-hydrocracking combination operation of this 
invention and the composition of feeds charged thereto, cracking and 
hydrogenation operations of the separate cracking operations are 
selectively maintained and optimized to promote the hydrogenation and 
cracking of at least dicyclic and particularly multi-ring compounds to 
dicyclic ring compounds and particularly monocyclic compounds useful in 
producing high yields high octane of gasoline boiling range product. The 
catalyst employed in a sequence of catalyst beds in the hydrocracking zone 
is preferably a zeolite containing hydrocracking catalyst and is selected 
from one commercially available in the industry. That is, the catalyst 
employed in the hydrocracking zones is providing 
hydrogenation-dehydrogenation activity deposited upon an otherwise 
inactive support or on an active working or cracking support material and 
preferably is one comprising a crystalline zeolite cracking component. The 
cracking component may also comprise a second acidic material such as 
silica-alumina, silica-magnesia, silica-alumina-zirconia, alumina-boria, 
various acid treated clays and halogenated composites. The 
hydrogenation-dehydrogenation components may be selected from one or more 
metals of Groups VI, VII and VIII. Metals of particular importance for 
this purpose include the oxides and sulfides of molybdenum, tungsten, 
vanadium, chromium, iron, nickel, cobalt, palladium, and platinum type 
transition metals or combinations thereof. The feed hydrotreating or 
desulfurizing step above discussed and coupled with the downstream 
hydrocracking step is a high pressure operation which permits the cascade 
of pressured feed and desulfurized product directly from one step to the 
other at a suitable elevated temperature and pressure and through the 
sequence of exothermic catalyst bed steps in the combination of reaction 
zones without requiring intermediate pressurization between catalyst beds 
or steps. Thus, a pressure drop is enountered between the inlet to the 
desulfurizing zone and the high pressure separation of hydrocracked 
product downstream of the hydrocracking zone.

The combination operation of this invention is more specifically discussed 
below. 
FIG. 1 is a diagrammatic block flow arrangement of primary components of 
the combination process of the invention comprising fluid catalytic 
cracking, hydrocracking, product and feed separation devices 
interconnected by transfer conduits for passing select fractions to and 
from the FCC and hydrocracking operations. The combination process also 
contemplates the inclusion of catalytic reforming, alkylation and product 
gas separation and recovery of components thereof having use in the 
combination operation as more fully discussed below. 
In the integrated process arrangement of FIG. 1, a crude oil charged to the 
process by conduit 2 is desalted by one or more methods and means known in 
the art and comprising in one embodiment two stages of desalting, 4 and 6 
with or without sodium hydroxide addition between stages by conduit 8 to 
the crude oil charge passed from stage 4 to 6 by conduit 10. In some 
cases, when the chloride level in the crude unit overhead tail water is 
found below about 20 ppm, there is no need to add any caustic between 
desalting stages. A desalted crude oil is recovered and passed by conduit 
12 to a preatmospheric fractionation or flash separation zone 14. In zone 
14, a rough separation is made to particularly recover C.sub.6 minus 
hydrocarbons overhead by conduit 16 from a higher boiling crude oil 
portion charged thereto and comprising C.sub.6 plus hydrocarbons of the 
charged high boiling crude oil comprising a vacuum bottoms portion. The 
C.sub.6 plus portion of the crude oil comprising components boiling above 
about 1025.degree. F. is then passed by conduit 18 to a separate 
atmospheric distillation zone or tower 20. In atmospheric distillation 
zone 20, a separation is made to recover gasoline boiling range material 
by conduit 22 boiling in the range of 150.degree. F. up to about 
400.degree. F. The end point of this gasoline fraction may be varied 
considerably within the range of about 320.degree. F. up to about 
420.degree. F., it being preferred to limit the end boiling point within 
the range of 380.degree. F. to about 400.degree. F. A middle distillate 
fraction boiling above gasoline and generally boiling initially in the 
range of about 320.degree. F. to 400.degree. F. up to about 600.degree. F. 
to 700.degree. F. is recovered from tower 20 by conduit 24 for use as 
desired or catalytic processing as more fully discussed below. It is to be 
understood that the boiling range of this middle distillate fraction may 
be varied with respect to its (IBP) initial boiling point depending upon 
the (EP) end boiling point of the gasoline fraction and its EP may be 
varied within the range of about 600.degree. F. up to about 700.degree. 
F., depending upon crude source and composition thereof. In a particular 
embodiment, the selected IBP of the middle distillate is about 400.degree. 
F. so that material boiling above about 600.degree. F. in the crude oil 
charged may be recovered from the bottom portion of tower 20 by conduit 26 
for further catalytic processing as discussed below. A high boiling 
product fraction of about 400.degree. to 600.degree. F. IBP obtained as a 
product of hydrocracking as hereinafter provided is added by conduit 28 to 
the recovered 600.degree. F. plus bottom fraction of the crude oil in 
conduit 26 for passage directly to an FCC or to a hot feed accumulator or 
feed mixing drum 30. The initial boiling point (IBP) of the recycled 
material in conduit 28 may range of about 400.degree. F. up to about 
600.degree. F., depending upon the separation selected to be accomplished 
in a hydrocracked product splitter operation discussed below. In one 
particular operation, the splitter bottom temperature is about 550.degree. 
F. and the top temperature is about 200.degree. F. Other splitter 
temperature combinations may be employed depending on crude oil source and 
boiling range processed by the technique herein discussed. 
The combined high boiling oil feed materials collected in drum 30 
comprising fresh high boiling crude oil material comprising sulfur and 
nitrogen components as well as materials boiling above 1025.degree. F. 
recovered by atmospheric distillation in combination with a high boiling 
product of hydrocracking is charged by conduit 32 to a fluid catalytic 
cracking (FCC) unit 34 for processing as herein discussed. In the 
combination operation of this invention, the fluid cracking performs a 
dual cracking function directed to catalytic conversion of the high 
boiling portion of crude oil passed thereto comprising material boiling 
above about 1025.degree. F. at an elevated temperature approaching or at 
least equal to the pseudocritical temperature of the charged oil feed in 
combination with the high boiling 400.degree. F. to 600.degree. F. IBP 
product fraction of hydrocracking obtained as hereinafter discussed to 
obtain desulfurization-denitrogenation-demetallization of crude oil 
charged, effect hydrogen transfer reactions and product gasoline material 
of acceptable octane rating. The effective demetallization, 
desulfurization and denitrogenation of charged reduced crude in the 
presence of a hydrogenated product of hydrocracking contributes measurably 
to the economic efficiency of the operation. A cracked oil product 
fraction of (FCC) fluid catalytic cracking and boiling between a selected 
gasoline end boiling point of about 400.degree. F. and up to a product end 
point of about 1000.degree. F. is recovered as a particularly suitable 
hydrocracking feed charge material. The operating latitude within which 
the fluid cracking unit may be adjusted and operated in the presence of a 
hydrogenated product of hydrocracking varies considerably as a function of 
the source of the crude oil feed processed and the operating severity 
which the FCC unit is pushed or maintained to produce gasoline boiling 
range products and particularly a demetallized-desulfurized-denitrogenated 
light and heavy cycle oils particularly suitable as a hydrocracking feed 
as herein discussed. In a particular embodiment, it is intended to employ 
the fluid cracking unit at least as a gasoline producing operation as well 
as a feed preparation unit for a downstream hydrocracking operation. That 
is, high boiling cycle oil products of the fluid catalytic cracking 
operation obtained by converting a residual oil or reduced crude portion 
of a crude oil in the presence of a hydrogen donor material of 
hydrocracking to produce light and heavy cycle oils substantially reduced 
in metals, sulfur and nitrogen compounds are recovered for use as a feed 
charge material to a hydrocracking operation. A further significant 
advantage in this hydrocracker feed preparation operation of the FCC unit 
is in the production of a high quality gasoline product of crystalline 
zeolite catalytic cracking as well as feed material suitable for the 
hydrocracking operation over and beyond that initially separated from the 
crude oil feed by atmospheric distillation as discussed above. The fluid 
catalytic cracking operation may employ the same apparatus arrangements as 
that identified in copending application Ser. No. 169,086 filed July 15, 
1980, the subject matter of which is incorporated by reference thereto or 
the cracking operation may be modified with respect to catalyst utilized 
as filed in copending application identified as Ser. No. 324,450, filed 
Nov. 24, 1981 which subject matter is also incorporated herein by 
reference thereto. 
It is important to recognize that the combination of fluid catalytic 
cracking and hydrocracking as related to one another in the processing 
arrangement of this invention contribute in a novel manner to the 
conversion of polycyclic compounds to mono and dicyclic compounds, 
produces a hydrogenated product of hydrocracking with an IBP of 
400.degree. F. to 600.degree. F. which provides a hydrogen donor 
contributing material for use in the FCC operation thereby further 
contributing to ultimate improvements in product selectivity of the 
combination operation. 
The products of the fluid cracking operation obtained as herein provided 
are passed by conduit 36 to a product recovery zone 38. In product 
recovery zone 38, a separation is made to recover C.sub.4 minus product 
material by conduit 40, a C.sub.4 plus gasoline product fraction by 
conduit 42, a light cycle oil product stream by conduit 44, a heavy cycle 
oil product stream by conduit 46 and a fuel oil fraction by conduit 48. 
The fuel oil product fraction may be recycled to the FCC unit as desired 
or used as fuel in the combination process. The C.sub.4 minus fraction is 
preferably further separated in an unsaturate gas plant and/or a cryogenic 
gas plant not shown to recover valuable components such as hydrogen and 
methane separately from higher boiling normally gaseous materials such as 
C.sub.2, C.sub.3, C.sub.4 hydrocarbons. The higher boiling olefinic 
hydrocarbons may be alkylated as by sulfuric acid or HF alkylation 
techniques known in the art. 
The light and heavy cycle oil products (LCO & HCO) of the fluid catalytic 
cracking operation are passed by conduit 50 as a combined product stream 
in one embodiment to a feed accumulator drum 52 wherein they may be mixed 
with the middle distillate fraction recovered by conduit 24 from the 
atmospheric main fractionator 20. Of course, the LCO and HCO recovered 
from column 38 may be passed alone or with middle distillate in conduit 24 
directly to the hydrocracking operation. On the other hand, in yet another 
embodiment, a selected light cycle oil of desired boiling range may be 
recovered as a product of the process and only the heavier cycle oil (HCO) 
product charged with or without the crude oil middle distillate fraction 
to the hydrocracking operation. This arrangement is particularly useful 
when effecting the FCC operation with an ultrastable catalytic cracking 
catalyst identified with the operation of copending application RI 815 
above incorporated herein by reference. The combined feed materials 
collected in drum 52 as specifically shown in the figure and comprising 
partially desulfurized and denitrogenated light and heavy cycle oil 
products of the fluid catalytic cracking operation as herein defined with 
or without middle distillate are passed by conduit 54 to heat exchanger 
56. In heat exchanger 56, the thus formed hydrocracker-desulfurizer 
demetallized feed is preheated to a temperature of about 600.degree. F. by 
heat exchange with a hot product effluent of hydrocracking obtained as 
discussed below. The preheated feed at a temperature of about 600.degree. 
F. may be further heated in furnace equipment not shown to raise the 
temperature thereof to within the range of about 600.degree. F. to 
800.degree. F. and suitable for effecting a temperature and pressure 
controlled desulfurization and denitrogenation of the feed above 
identified. Hydrogen obtained from catalytic reforming and other suitable 
process sources may be added by conduit 60 to the desulfurizer feed in 
conduit 58. The hydrogen addition may be before or after suitable 
preheating of the feed to be desulfurized and hydrocracked as herein 
provided. It is preferred that the oil feed and hydrogen be pressured to a 
pressure suitable for cascade through the operation before heating thereof 
by means not shown and that heating of the feed be accomplished in the 
presence of hydrogen. 
In addition to the above it is contemplated raising the pressure of the oil 
feed in admixture with a substantial portion of the hydrogen used in the 
process separately in equipment not shown prior to admixture with one 
another for processing as herein defined at a temperature up to 
800.degree. F. and a pressure up to about 3000 psig. Thus sufficiently 
high pressure hydrogen is charged to the desulfurizing step upstream of 
the hydrocracking operation to permit cascade of products thereof to the 
hydrocracking operation in the absence of intermittent processing or 
pressurization. On the other hand high pressure hydrogen recovered from 
the product of hydrocracking in a high pressure separator may be cooled 
and compressed for recycle to one or both of the desulfurizing and 
hydrocracking steps. Sufficiently cooled hydrogen is recycled to 
hydrocracking to adjust product temperature conditions between catalyst 
beds therein as practiced in the prior art to control the temperature rise 
in the separate catalyst beds of the operations. Thus all of the hydrogen 
charged to the desulfurizing and hydrocracking operation is a distributed 
arrangement to maintain temperatures and pressures thereof within a 
pre-selected range in cooperation with providing the hydrogen consumption 
requirements of the process for effecting desulfurization, 
denitrogenation, hydrogenation of multicyclic ring compounds and lower 
orders of cyclic compounds including mono and dicyclic ring compounds 
recovered as a product of the fluid catalyst cracking and hydrocracking 
operations in separation equipment 20 and 38. 
The recovered FCC cycle oil with or without middle distillate feed material 
to be hydrocracked and boiling above about 400.degree. F. is further 
heated in equipment not shown following a passage through exchanger 56 to 
a temperature of about 650.degree. F. to 750.degree. F. for charge to a 
desulfurizing and denitrogenation reactor zone 62. Desulfurizing zone 62 
is provided with one and preferably at least two sequentially arranged 
catalysts beds comprising for example a nickel-molybdenum or other 
suitable desulfurizing and denitrogenation catalyst composition also known 
in the prior art. Conduit means 64 is provided for adding cool hydrogen 
containing gas between the catalyst beds for exothermic temperature 
control so that the temperature of the desulfurization operation may be 
restricted to within the range of about 650.degree. to 825.degree. F. A 
desulfurized product comprising no more than about 10 ppm nitrogen is 
recovered from the hydrotreating zone 62 by conduit 66 for separation as 
desired or cascade passage to a hydrocracking zone 68 at a pressure below 
3000 psig but above 1500 psig. In the processing arrangement of this 
invention, the total product effluent of the desulfurizing-denitrogenation 
operation is shown passed directly to the hydrocracking operation without 
intermittent product separation, compression operations. 
Hydrocracking zone 68 comprises a plurality of sequentially arranged 
separate beds of hydrocracking catalyst which permits cooling of product 
between beds with injected cool hydrogen gas to maintain the exothermic 
hydrocracking temperatures within an acceptable range as herein provided. 
The catalyst beds may be of the same depth or of increasing depth in the 
direction of sequential hydrocarbon flow there through. Manifold conduit 
means 70 is provided for adding the cool hydrogen rich gas between 
catalyst beds for exothermic temperature control as above mentioned and 
taught in the prior art. Generally the hydrocracking operation is 
controlled within the temperature range of about 650.degree. F. up to 
about 800.degree. F., it being preferred to restrict the temperature below 
about 750.degree. F. The pressure particularly preferred may be in the 
range of 1500 to 2500 psig. In the combination of hydrotreating and 
hydrocracking described, the relatively high boiling components of the 
feed and comprising an incremental variety of multicyclic ring compounds 
in the range of 2 to 5 rings are subjected to hydrogenation and cracking 
of particularly exterior rings which contribute to the ultimate production 
of mono and dicyclic compounds. Unconverted high boiling hydrogenated ring 
compounds are also converted to lower forms thereof in the FCC unit under 
hydrogen transfer conditions as herein discussed. Thus the hydrocracking 
operation provides in substantial measure a product slate comprising 
relatively high octane gasoline and hydrogenated fuel oil materials 
boiling below about 400.degree. F. or 600.degree. F. according to choice 
in combination with the recovery of higher boiling materials for use as 
No. 2 fuel oils or to effect catalytic conversion thereof as herein 
provided. 
In the specific arrangements of the drawing, a high temperature effluent 
product of hydrocracking is recovered by conduit 72 for passage through 
heat exchanger 56 wherein the high temperature effluent exchanges heat 
with the feed charged thereto by conduit 54. In heat exchanger 56 the 
product is cooled to about 400.degree. F. before passage by conduit 74 to 
heat exchanger 76 wherein a further cooling of the product of 
hydrocracking is accomplished to about 250.degree. F. The cooled product 
is passed by conduit 78 to a high pressure separator 80 wherein high 
pressure hydrogen rich gas is recovered by conduit 82 from liquid product. 
The temperature of high pressure separator 80 is about 120.degree. F. and 
a pressure of about 25 to 100 pounds below reactor pressure. A liquid 
product is recovered by conduit 84 and passed to a low pressure zone 86 at 
a pressure of about 200 to 300 psig. A C.sub.2 minus product stream is 
separated in separator 86 and recovered by conduit 88. A liquid product of 
this separation step 86 is removed by conduit 90, passed through heat 
exchanger 76 wherein its temperature is raised to about 340.degree. F. The 
product of hydrocracking thus separated and heated is recovered by conduit 
92 and charged to a separation zone referred to as a splitter 94 
maintained at a pressure of about 20-50 psig wherein a separation is made 
to recover a product fraction with an end boiling point in the range of 
400.degree. to 600.degree. F. recovered therefrom by conduit 96 thereafter 
charged to prefactionator or flash zone 14 for separation as discussed 
above. The higher boiling product fraction separated in splitter 94 is 
recovered by conduit 98 for use as No. 2 fuel oil, a portion or all 
thereof may be recycled by conduit 100 to hydrocracking zone 68 or all or 
a portion thereof is passed by conduit 28 to hot drum 30 and then to fluid 
cracking with crude atmospheric tower bottoms as discussed above, thus 
completing the synergistic cyclic operation of the selective combination 
process particularly comprising fluid catalytic cracking and subsequent 
hydrocracking of 400.degree. F. plus hydrogenated product materials as 
above discussed. 
The unique and novel combination of cracking processing steps of this 
invention may be used to take advantage of one or more specific or select 
residual oil cracking processes designed to produce gasoline boiling range 
components varying in quality and yield in preference to the higher 
boiling cycle oils such as heavy cycle oil of reduced metals, sulfur and 
nitrogen content and suitable for subsequent hydrocracking upgrading to 
produce gasoline boiling products and hydrogenation of higher boiling 
material providing labile hydrogen available upon recycle to the FCC 
operation and contributing to improving the product selectivity obtained 
from the unique combination cracking operations of the present invention. 
The combination operation above discussed is more fully and particularly 
integrated with respect to hydrogen utilization by the inclusion of 
catalytic reforming, alkylation, a saturated gas recovery plant and a 
cryogenic gas plant to also further contribute to product selectivity and 
yield as well as hydrogen production and recovery for utilization as 
herein provided. 
Thus it is contemplated upgrading prticularly straight run gasoline boiling 
range material such as that boiling below about 400.degree. F. with or 
without a product of hydrocracking and recovered from the fractionation 
zones 20 and 38 by conduits 22 and 42 respectively in a catalytic 
reforming operation not shown. The reforming operation may be a single 
large unit normally encompassing three sequentially arranged reaction or 
reforming zones or two separate smaller and parallel multi reactor 
reforming operations may be employed which process feeds comprising 
C.sub.6 naphthenes in one reforming operation and feeds comprising C.sub.7 
plus naphthenes in the other reforming operation and high boiling gasoline 
product of hydrocracking. The combination process above discussed is 
product yield selectivity improved by incorporation of a suitable 
alkylation unit also not shown in the drawing of the processing 
combination to particularly form high octane gasoline product by the 
reaction of olefins recovered in the process with isobutane. The 
alkylation feed of C.sub.3 and C.sub.4 olefins are recovered primarily as 
a product of the fluid catalytic cracking operation and with or without a 
cryogenic gas plant operation discussed below. The isobutane feed is 
recovered from a provided saturate gas recovery plant not shown charged 
with materials from the hydrocracking operation, from the crude 
atmospheric distillation operation and from the reforming operations above 
discussed and from any available extraneous source. The alkylation 
operation may be one of sulfuric acid alkylation but more preferably is 
one of HF alkylation and known in the industry. High octane product of the 
alkylation operation is recovered for admixture with the gasoline product 
of fluid catalytic cracking and reforming of relatively high octane. In 
the combination operation of this invention the gasoline boiling range 
materials of the hydrocracking operation may be separately recovered or 
recovered with straight run material from the crude atmospheric 
distillation tower for reforming thereof as discussed above. 
To further implement the integrated combination process of this invention, 
a cryogenic gas plant may be provided for upgrading a hydrogen product 
stream of the refining operation obtained from fluid catalytic cracking, 
hydrocracking and reforming and from available off gas streams such as 
might be obtained from adjacent petrochemical operations. Thus the feed 
charged to the cryogenic operation may be substantially any dry gas feed 
material comprising hydrogen, nitrogen, CO, paraffins and olefins that are 
soluble in relatively light condensed hydrocarbons at low temperature and 
a pressure in the range of 300 to 650 psig. The cryogenic separation 
operation provided, thus is relied upon to provide a high purity hydrogen 
stream, a methane rich stream for use as refinery fuel, an ethane/ethylene 
stream separated from higher boiling olefins for petrochemical upgrading, 
an olefin rich stream comprising C.sub.3 and C.sub.4 olefins suitable as 
charge material to the alkylation operation of the combination process. 
Hydrogen recovered from the combination operation is thus available to 
form a pool thereof for use in the reforming and/or hydrocracking steps of 
the combination operation. 
It will be recognized by those skilled in the art that the above discussed 
operations of reforming, alkylation, saturate and cyrogenic gas plant 
separation facilities all contribute measurable to the integrated 
combination operation for the reasons herein discussed and particularly 
associated with upgrading C.sub.4 minus products to gasoline boiling range 
components and the recovery of hydrogen rich gas from product gas sources 
for distributed use within the combination operation where appropriately 
needed. In addition to the above, hydrogen accumulation and distribution 
operations each of the reforming, and hydrocracking steps comprise built 
in recycle operations with respect to separated hydrogen rich gas streams 
and unreacted feed materials for redistribution in the particularly 
integrated catalytic reforming and cracking operation of this invention 
and particularly directed to upgrading crude oils, selected portions of 
crude oils, combinations of crude oils including reduced crudes, residual 
or reduced portions thereof. 
It will be particularly recognized by those skilled in the art that the 
novel processing distribution of hydrocarbon fractions and utilization of 
hydrogen available in the crude oil feed considerably improves product 
selectivity and yield of quality product is enhanced. Thus the efficiency 
and economics of the gasoline producing combination of this invention is 
substantially improved over that of any known prior art combination of 
processing steps comprising FCC, hydrocracking, reforming, alkylation, gas 
plant separation operations and related product separation and recovery 
facilities. 
Having thus generally discussed the improved combination process of this 
invention and described specific embodiments in support thereof, it is to 
be understood that no undue restrictions are to be imposed by reasons 
thereof except as defined by the following claims.