U.S. patent application number 11/460307 was filed with the patent office on 2008-01-31 for hydrocracking process.
Invention is credited to Peter Kokayeff, Laura E. Leonard.
Application Number | 20080023372 11/460307 |
Document ID | / |
Family ID | 38982215 |
Filed Date | 2008-01-31 |
United States Patent
Application |
20080023372 |
Kind Code |
A1 |
Leonard; Laura E. ; et
al. |
January 31, 2008 |
Hydrocracking Process
Abstract
A catalytic hydrocracking process wherein a liquid phase stream
comprising a hydrocarbonaceous feedstock, a liquid phase effluent
from a hydrocracking zone, and a sufficiently low hydrogen
concentration to maintain a liquid phase continuous system is fed
into a hydrotreating zone to produce a first hydrocarbonaceous
stream comprising hydrocarbons having a reduced level of sulfur and
nitrogen. The resulting hydrocarbons having a reduced level of
sulfur and nitrogen are introduced into a hydrocracking zone with a
sufficiently low hydrogen concentration to maintain a liquid phase
continuous system to produce a hydrocracking zone effluent which
provides lower boiling range hydrocarbons.
Inventors: |
Leonard; Laura E.; (Oak
Park, IL) ; Kokayeff; Peter; (Naperville,
IL) |
Correspondence
Address: |
HONEYWELL INTELLECTUAL PROPERTY INC;PATENT SERVICES
101 COLUMBIA DRIVE, P O BOX 2245 MAIL STOP AB/2B
MORRISTOWN
NJ
07962
US
|
Family ID: |
38982215 |
Appl. No.: |
11/460307 |
Filed: |
July 27, 2006 |
Current U.S.
Class: |
208/113 |
Current CPC
Class: |
C10G 2300/1077 20130101;
C10G 2300/207 20130101; Y02P 30/20 20151101; C10G 2300/4081
20130101; C10G 2300/1011 20130101; C10G 65/12 20130101; C10G
2300/4006 20130101; C10G 2300/202 20130101; C10G 2300/301 20130101;
C10G 2300/107 20130101; C10G 2300/4012 20130101 |
Class at
Publication: |
208/113 |
International
Class: |
C10G 11/00 20060101
C10G011/00 |
Claims
1. A process for hydrocracking a hydrocarbonaceous feedstock which
comprises: (a) introducing a liquid phase stream comprising a
hydrocarbonaceous feedstock, at least a portion of a liquid phase
effluent from a hydrocracking zone and a sufficiently low hydrogen
concentration to maintain a liquid phase continuous system into a
hydrotreating zone to produce hydrogen sulfide and ammonia, and
provide a first hydrocarbonaceous stream comprising hydrocarbons
having a reduced level of sulfur and nitrogen; (b) introducing at
least a portion of the first hydrocarbonaceous stream comprising
hydrocarbons having a reduced level of sulfur and nitrogen into the
hydrocracking zone with a sufficiently low hydrogen concentration
to maintain a liquid phase continuous system; (c) separating a
second hydrocarbonaceous stream selected from the group consisting
of the first hydrocarbonaceous stream comprising hydrocarbons
having a reduced level of sulfur and nitrogen, and an effluent from
the hydrocracking zone in a separation zone to provide hydrocracked
hydrocarbons boiling in a temperature range lower than the
hydrocarbonaceous feedstock; (d) recovering the hydrocracked
hydrocarbons boiling in a temperature range lower than the
hydrocarbonaceous feedstock; and (e) recycling at least a portion
of the effluent from the hydrocracking zone to step (a).
2. The process of claim 1 wherein the hydrocarbonaceous feedstock
boils in the range from about 315.degree. C. (600.degree. F.) to
about 565.degree. C. (1050.degree. F.).
3. The process of claim 1 wherein the hydrotreating zone is
operated at conditions including a temperature from about
204.degree. C. (400.degree. F.) to about 482.degree. C.
(900.degree. F.) and a pressure from about 3.5 MPa (500 psig) to
about 17.3 MPa (2500 psig).
4. The process of claim 1 wherein the recovery of the unconverted
hydrocarbons boiling in the range of the hydrocarbonaceous
feedstock is conducted in a high pressure product stripper.
5. The process of claim 1 wherein the ratio of the unconverted
hydrocarbons boiling in the range of the hydrocarbonaceous
feedstock to the hydrocarbonaceous feedstock is from about 1:5 to
about 3:5.
6. The process of claim 1 wherein the recovery of the unconverted
hydrocarbons boiling in the range of the hydrocarbonaceous
feedstock is conducted in a fractionation zone.
7. The process of claim 1 wherein the hydrocracking zone is
operated at conditions including a temperature from about
232.degree. C. (450.degree. F.) to about 468.degree. C.
(875.degree. F.) and a pressure from about 3.5 MPa (500 psig) to
about 17.3 MPa (2500 psig).
8. A process for hydrocracking a hydrocarbonaceous feedstock which
comprises: (a) introducing a liquid phase stream comprising a
hydrocarbonaceous feedstock, a liquid phase effluent from a
hydrocracking zone, and a sufficiently low hydrogen concentration
to maintain a liquid phase continuous system into a hydrotreating
zone to produce hydrogen sulfide and ammonia and provide a
hydrocarbonaceous stream comprising hydrocarbons having a reduced
level of sulfur and nitrogen; (b) recovering unconverted
hydrocarbons boiling in the range of the hydrocarbonaceous
feedstock, hydrogen sulfide and ammonia from the hydrocarbonaceous
stream; (c) introducing the unconverted hydrocarbons boiling in the
range of the hydrocarbonaceous feedstock recovered in step (b) into
the hydrocracking zone with a sufficiently low hydrogen
concentration to maintain a liquid phase continuous system and; (d)
introducing the hydrocracking zone effluent from step (c) into the
hydrotreating zone in step (a), and; (e) recovering hydrocracked
hydrocarbons boiling in a temperature range lower than the
hydrocarbonaceous feedstock.
9. The process of claim 8 wherein the hydrocarbonaceous feedstock
boils in the range from about 315.degree. C. (600.degree. F.) to
about 565.degree. C. (1050.degree. F.).
10. The process of claim 8 wherein the hydrotreating zone is
operated at conditions including a temperature from about
204.degree. C. (400.degree. F.) to about 482.degree. C.
(900.degree. F.) and a pressure from about 3.5 MPa (500 psig) to
about 17.3 MPa (2500 psig).
11. The process of claim 8 wherein the recovery of the unconverted
hydrocarbons boiling in the range of the hydrocarbonaceous
feedstock is conducted in a high pressure product stripper.
12. The process of claim 8 wherein the ratio of the unconverted
hydrocarbons boiling in the range of the hydrocarbonaceous
feedstock recovered in step (b) to the hydrocarbonaceous feedstock
is from about 1:5 to about 3:5.
13. The process of claim 8 wherein the recovery of the unconverted
hydrocarbons boiling in the range of the hydrocarbonaceous
feedstock is conducted in a fractionation zone.
14. The process of claim 8 wherein the hydrocracking zone is
operated at conditions including a temperature from about
232.degree. C. (450.degree. F.) to about 468.degree. C.
(875.degree. F.) and a pressure from about 3.5 MPa (500 psig) to
about 17.3 MPa (2500 psig).
15. A process for hydrocracking a hydrocarbonaceous feedstock which
comprises: (a) introducing a liquid phase stream comprising a
hydrocarbonaceous feed stock, a liquid phase effluent from a
hydrocracking zone, and a sufficiently low hydrogen concentration
to maintain a liquid phase continuous system into a hydrotreating
zone to produce hydrogen sulfide and ammonia, and provide a first
hydrocarbonaceous stream comprising hydrocarbons having a reduced
level of sulfur and nitrogen; (b) introducing the first
hydrocarbonaceous stream comprising hydrocarbons having a reduced
level of sulfur and nitrogen into a hydrocracking zone with a
sufficiently low hydrogen concentration to maintain a liquid phase
continuous system to produce a hydrocracking zone effluent; (c)
introducing the hydrocracking zone effluent into a separation zone
to produce a second hydrocarbonaceous stream containing lower
boiling hydrocarbons and a liquid phase hydrocarbonaceous stream
comprising unconverted hydrocarbons; (d) introducing the liquid
phase hydrocarbonaceous stream comprising unconverted hydrocarbons
recovered in step (c) into step (a), and; (e) recovering
hydrocracked hydrocarbons boiling at a temperature range lower than
the hydrocarbonaceous feedstock.
16. The process of claim 15 wherein the hydrocarbonaceous feedstock
boils in the range from about 315.degree. C. (600.degree. F.) to
about 565.degree. C. (1050.degree. F.).
17. The process of claim 15 wherein the hydrotreating zone is
operated at conditions including a temperature from about
204.degree. C. (400.degree. F.) to about 482.degree. C.
(900.degree. F.) and a pressure from about 3.5 MPa (500 psig) to
about 17.3 MPa (2500 psig).
18. The process of claim 15 wherein the separation zone is a high
pressure product stripper.
19. The process of claim 15 wherein the ratio of the unconverted
hydrocarbons boiling in the range of the hydrocarbonaceous
feedstock recovered in step (c) to the hydrocarbonaceous feedstock
is from about 1:5 to about 3:5.
20. The process of claim 15 wherein the hydrocracking zone is
operated at conditions including a temperature from about
232.degree. C. (450.degree. F.) to about 468.degree. C.
(875.degree. F.) and a pressure from about 3.5 MPa (500 psig) to
about 17.3 MPa (2500 psig).
Description
FIELD OF THE INVENTION
[0001] The field of art to which this invention pertains is the
catalytic conversion of hydrocarbons to useful hydrocarbon
products. More particularly, the invention relates to catalytic
hydrocracking.
BACKGROUND OF THE INVENTION
[0002] The present invention pertains to the hydrocracking of a
hydro-carbonaceous feedstock. Petroleum refiners often produce
desirable products such as turbine fuel, diesel fuel and other
products known as middle distillates as well as lower boiling
hydrocarbonaceous liquids such as naphtha and gasoline by
hydrocracking a hydrocarbon feedstock derived from crude oil or
heavy fractions thereof. Feedstocks most often subjected to
hydrocracking are gas oils and heavy gas oils recovered from crude
oil by distillation. A typical heavy gas oil comprises a
substantial portion of hydrocarbon components boiling above about
371.degree. C. (700.degree. F.), usually at least about 50 percent
by weight boiling above 371.degree. C. (700.degree. F.). A typical
vacuum gas oil normally has a boiling point range between about
315.degree. C. (600.degree. F.) and about 565.degree. C.
(1050.degree. F.).
[0003] Hydrocracking is generally accomplished by contacting in a
hydro-cracking reaction vessel or zone the gas oil or other
feedstock to be treated with a suitable hydrocracking catalyst
under conditions of elevated temperature and pressure in the
presence of hydrogen as a separate phase in a two-phase reaction
zone so as to yield a product containing a distribution of
hydrocarbon products desired by the refiner. The operating
conditions and the hydrocracking catalysts within a hydrocracking
reactor influence the yield of the hydrocracked products.
[0004] Traditionally, the fresh feedstock for a hydrocracking
process is first introduced into a denitrification and
desulfurization zone having hydrogen in a gaseous phase and
particularly suited for the removal of sulfur and nitrogen
contaminants and subsequently introduced into a hydrocracking zone
containing hydrocracking catalyst and having hydrogen in a gaseous
phase. Another method of hydrocracking a fresh feedstock is to
introduce the fresh feedstock and the effluent from the
hydrocracking zone into the denitrification and desulfurization
zone. The resulting effluent from the hydrocracking zone is
separated to produce desired hydrocracked products and unconverted
feedstock which is then introduced into the hydrocracking zone.
Previously, at least a major portion of the hydrogen present in
reaction zones was present in a gaseous phase. This method or
technique is commonly referred to as "trickle bed" wherein the
continuous phase is gaseous and not liquid.
[0005] Although a wide variety of process flow schemes, operating
conditions and catalysts have been used in commercial activities,
there is always a demand for new hydrocracking methods which
provide lower costs, ease of construction, higher liquid product
yields and higher quality products.
INFORMATION DISCLOSURE
[0006] U.S. Pat. No. 5,720,872 B1 (Gupta) discloses a process for
hydroprocessing liquid feedstocks in two or more hydroprocessing
stages which are in separate reaction vessels and wherein each
reaction stage contains a bed of hydroprocessing catalyst. The
liquid product from the first reaction stage is sent to a low
pressure stripping stage and stripped of hydrogen sulfide, ammonia
and other dissolved gases. The stripped product stream is then sent
to the next downstream reaction stage, the product from which is
also stripped of dissolved gases and sent to the next downstream
reaction stage until the last reaction stage, the liquid product of
which is stripped of dissolved gases and collected or passed on for
further processing. The flow of treat gas is in a direction
opposite the direction in which the reaction stages are staged for
the flow of liquid. Each stripping stage is a separate stage, but
all stages are contained in the same stripper vessel.
[0007] U.S. Pat. No. 3,328,290 B1 (Hengstebeck) discloses a
two-stage process for the hydrocracking of hydrocarbons in which
the feed is pretreated in the first stage.
[0008] U.S. Pat. No. 5,403,469 B1 (Vauk et al) discloses a parallel
hydrotreating and hydrocracking process. Effluent from the two
processes are combined in the same separation vessel and separated
into a vapor comprising hydrogen and a hydrocarbon-containing
liquid. The hydrogen is shown to be supplied as part of the feed
streams to both the hydrocracking and the hydrotreater.
[0009] U.S. Pat. No. 5,980,729 (Kalnes et al) discloses a
hydrocracking process wherein a hydrocarbonaceous feedstock and a
hot hydrocracking zone effluent containing hydrogen is passed to a
denitrification and desulfurization reaction zone to produce
hydrogen sulfide and ammonia to thereby clean up the fresh
feedstock. The resulting hot, uncooled effluent from the
denitrification and desulfurization zone is hydrogen stripped in a
stripping zone maintained at essentially the same pressure as the
preceding reaction zone with a hydrogen-rich gaseous stream to
produce a vapor stream comprising hydrogen, hydrocarbonaceous
compounds boiling at a temperature below the boiling range of the
fresh feedstock, hydrogen sulfide and ammonia, and a liquid
hydro-carbonaceous stream containing unconverted feedstock. This
liquid hydrocarbonaceous stream is introduced into a hydrocracking
zone to produce a hydrocracking zone effluent which then joins the
fresh feedstock as described hereinabove and is subsequently
introduced into the denitrification and desulfurization zone.
[0010] U.S. Pat. No. 6,106,694 (Kalnes et al) discloses a
hydrocracking process wherein a hydrocarbonaceous feedstock and a
hot hydrocracking zone effluent is passed to a denitrification and
desulfurization reaction zone to produce hydrogen sulfide and
ammonia to thereby clean up the fresh feedstock. The resulting hot,
uncooled effluent from the denitrification and desulfurization zone
is hydrogen stripped in a stripping zone maintained at essentially
the same pressure as the preceding reaction zone with a
hydrogen-rich gaseous stream to produce a vapor stream comprising
hydrogen, hydrocarbonaceous compounds boiling at a temperature
below the boiling range of the fresh feedstock, hydrogen sulfide
and ammonia, and a liquid hydrocarbonaceous stream containing
unconverted feedstock. This liquid hydrocarbonaceous stream is
subsequently introduced into the hydrocracking zone to produce an
effluent which is subsequently introduced into the denitrification
and desulfurization reaction zone as described hereinabove.
[0011] U.S. Pat. No. 6,123,835 (Ackerson et al.) and U.S. Pat. No.
6,428,686 B1 (Ackerson et al.) disclose a hydro process where the
need to circulate hydrogen through the catalyst is eliminated by
mixing the hydrogen and the oil feedstock in the presence of a
diluent in which the hydrogen solubility is high relative to the
feedstock. The oil/diluent/hydrogen solution can then be fed to a
plug flow reactor containing catalyst.
BRIEF SUMMARY OF THE INVENTION
[0012] The present invention is a catalytic hydrocracking process,
in one embodiment, wherein a liquid phase stream comprising a
hydrocarbonaceous feedstock, a liquid phase effluent from a
hydrocracking zone, and a sufficiently low hydrogen concentration
to maintain a liquid phase continuous system is fed into a
hydrotreating zone to produce hydrogen sulfide and ammonia and
provide a first hydrocarbonaceous stream comprising hydrocarbons
having a reduced level of sulfur and nitrogen. The hydrocarbons
having a reduced level of sulfur and nitrogen are introduced into a
hydrocracking zone with a sufficiently low hydrogen concentration
to maintain a liquid phase continuous system to produce a
hydrocracking zone effluent which provides lower boiling range
hydrocarbons. In preferred embodiments, the first hydrocarbonaceous
stream comprising hydrocarbons having a reduced level of sulfur and
nitrogen is separated in a high pressure product stripper or by
conventional distillation to provide the hydrocarbons having a
reduced level of sulfur and nitrogen which are subsequently
introduced into the hydrocracking zone.
[0013] In a second embodiment, the present invention is a catalytic
hydrocracking process wherein a liquid phase stream comprising a
hydrocarbonaceous feedstock, a liquid phase effluent from a
hydrocracking zone, and a sufficiently low hydrogen concentration
to maintain a liquid phase continuous system is fed into a
hydrotreating zone to produce hydrogen sulfide and ammonia, and
provide a first hydrocarbonaceous stream comprising hydrocarbons
having a reduced level of sulfur and nitrogen. The first
hydrocarbonaceous stream comprising hydrocarbons having a reduced
level of sulfur and nitrogen is introduced into a hydrocracking
zone with a sufficiently low hydrogen concentration to maintain a
liquid phase continuous system to produce a hydrocracking zone
effluent. The hydrocracking zone effluent is introduced into a
separation zone which in one embodiment is preferably a high
pressure product stripper to produce a second hydrocarbonaceous
stream containing lower boiling hydrocarbons and a liquid phase
hydrocarbonaceous stream comprising unconverted hydrocarbons which
is introduced into the hydrotreating zone as hereinabove described.
Hydrocracked hydrocarbons boiling at a temperature range lower than
the hydrocarbonaceous feedstock are recovered.
[0014] Conventional hydroprocessing operations utilize trickle bed
technology. This technology necessitates the use of large amounts
of hydrogen relative to the hydrocarbon feedstock, sometimes
exceeding 1685 nm.sup.3/m.sup.3 (10,000 SCF/B), and requires the
use of costly recycle gas compression. The large amounts of
hydrogen relative to the hydrocarbon feedstock in conventional
hydroprocessing operations renders this type of operation a gas
phase continuous system. It has been discovered that it is neither
economical nor necessary to have this large excess of hydrogen to
effect the desired conversion. The desired conversion can be
effected with much less hydrogen, and can be economically and
efficiently performed with only sufficient hydrogen to ensure a
liquid phase continuous system. A liquid phase continuous system
would exist at one extreme with only sufficient hydrogen to fully
saturate the hydrocarbon feedstock and at the other extreme where
sufficient hydrogen is added to transition to a gas phase
continuous system. The amount of hydrogen that is added between
these two extremes is dictated by economic considerations.
Operation with a liquid phase continuous system avoids the high
costs associated with a recycle gas compressor.
[0015] Other embodiments of the present invention encompass further
details such as types and descriptions of feedstocks, hydrocracking
catalysts, hydrotreating catalysts, and preferred operating
conditions including temperatures and pressures, all of which are
hereinafter disclosed in the following discussion of each of these
facets of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The drawings are simplified process flow diagrams of
preferred embodiments of the present invention. The drawings are
intended to be schematically illustrative of the present invention
and not be a limitation thereof. While the drawings depict the
process as operating in a downflow mode it is presented for
illustrative purposes and is not intended to exclude an upflow mode
of operation.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The process of the present invention is particularly useful
for hydrocracking a hydrocarbon oil containing hydrocarbons and/or
other organic materials to produce a product containing
hydrocarbons and/or other organic materials of lower average
boiling point and lower average molecular weight. The hydrocarbon
feedstocks that may be subjected to hydrocracking by the method of
the invention include all mineral oils and synthetic oils (e.g.,
shale oil, tar sand products, etc.) and fractions thereof.
Illustrative hydrocarbon feedstocks include those containing
components boiling above 288.degree. C. (550.degree. F.), such as
atmospheric gas oils, vacuum gas oils, deasphalted, vacuum, and
atmospheric residua, hydrotreated or mildly hydrocracked residual
oils, coker distillates, straight run distillates,
solvent-deasphalted oils, pyrolysis-derived oils, high boiling
synthetic oils, cycle oils and cat cracker distillates. A preferred
hydrocracking feedstock is a gas oil or other hydrocarbon fraction
having at least 50% by weight, and most usually at least 75% by
weight, of its components boiling at a temperature above about
371.degree. C. (700.degree. F.). One of the most preferred gas oil
feedstocks will contain hydrocarbon components which boil above
288.degree. C. (550.degree. F.) with best results being achieved
with feeds containing at least 25 percent by volume of the
components boiling between 315.degree. C. (600.degree. F.) and
565.degree. C. (1050.degree. F.).
[0018] The selected hydrocarbonaceous feedstock and hydrogen are
introduced into a hydrotreating reaction zone at hydrotreating
reaction conditions. In addition, the resulting effluent from a
hereinafter described hydrocracking reaction zone is also
introduced into the hydrotreating reaction zone. Preferred
hydrotreating reaction conditions include a temperature from about
204.degree. C. (400.degree. F.) to about 482.degree. C.
(900.degree. F.), a pressure from about 3.5 MPa (500 psig) to about
17.3 MPa (2500 psig), a liquid hourly space velocity of the fresh
hydrocarbonaceous feedstock from about 0.1 hr.sup.-1 to about 10
hr.sup.-1 with a hydrotreating catalyst or a combination of
hydrotreating catalysts. Only enough hydrogen is introduced into
the hydrotreating reaction zone to maintain a liquid phase
continuous system. This means that in contrast to conventional
hydroprocessing processes which operate in trickle bed mode in
which it is the gas phase that is continuous, the present invention
operates in a liquid phase continuous system.
[0019] The term "hydrotreating" as used herein refers to a process
wherein a hydrogen-containing treat gas absorbed in the liquid
hydrocarbon is used in the presence of suitable catalysts which are
primarily active for the removal of heteroatoms, such as sulfur and
nitrogen from the hydrocarbon feedstock. Suitable hydrotreating
catalysts for use in the present invention are any known
conventional hydrotreating catalysts and include those which are
comprised of at least one Group VIII metal, preferably iron, cobalt
and nickel, more preferably cobalt and/or nickel and at least one
Group VI metal, preferably molybdenum and tungsten, on a high
surface area support material, preferably alumina. Other suitable
hydrotreating catalysts include zeolitic catalysts, as well as
noble metal catalysts where the noble metal is selected from
palladium and platinum. It is within the scope of the present
invention that more than one type of hydrotreating catalyst be used
in the same reaction vessel. The Group VIII metal is typically
present in an amount ranging from about 2 to about 20 weight
percent, preferably from about 4 to about 12 weight percent. The
Group VI metal will typically be present in an amount ranging from
about 1 to about 25 weight percent, preferably from about 2 to
about 25 weight percent.
[0020] In one embodiment of the present invention, the resulting
effluent from the hydrotreating reaction zone is directly
introduced into a hydrocracking reaction zone to provide lower
boiling hydrocarbons. In another embodiment of the present
invention, the resulting effluent is introduced into a separation
zone which is preferably a high pressure product stripper or a
conventional fractionation zone to recover lower boiling
hydrocarbons and to provide a hydrocarbonaceous stream containing
hydrocarbons boiling in the range of the fresh feedstock which is
subsequently introduced into a hydrocracking zone. The high
pressure product stripper is preferably operated at a temperature
from about 204.degree. C. (400.degree. F.) to about 482.degree. C.
(900.degree. F.) and a pressure from about 3.5 MPa (500 psig) to
about 17.3 MPa (2500 psig).
[0021] In a preferred embodiment where the hydrotreating zone
effluent is directly introduced into the hydrocracking zone, the
effluent from the hydrocracking reaction zone is preferably
introduced into a high pressure stripper preferably operated at a
temperature from about 204.degree. C. (400.degree. F.) to about
482.degree. C. (900.degree. F.) and a pressure from about 3.5 MPa
(500 psig) to about 17.3 MPa (2500 psig) to produce a vaporous
hydrocarbonaceous stream and a liquid hydrocarbonaceous stream
containing hydrocarbons boiling in the range of the fresh feedstock
which is introduced into the hydrotreating zone. In a preferred
embodiment where the hydrotreating zone effluent is separated
between the hydrotreating zone and the hydrocracking zone, the
effluent from the hydrocracking zone is directly introduced into
the hydrotreating zone.
[0022] In any event, the feed is introduced into the hydrocracking
zone along with the added hydrogen in an amount sufficiently low to
maintain a liquid phase continuous system. The hydrocracking zone
may contain one or more beds of the same or different catalyst. In
one embodiment, when the preferred products are middle distillates,
the preferred hydrocracking catalysts utilize amorphous bases or
low-level zeolite bases combined with one or more Group VIII or
Group VIB metal hydrogenating components. In another embodiment,
when the preferred products are in the gasoline boiling range, the
hydrocracking zone contains a catalyst which comprises, in general,
any crystalline zeolite cracking base upon which is deposited a
minor proportion of a Group VIII metal hydrogenating component.
Additional hydrogenating components may be selected from Group VIB
for incorporation with the zeolite base. The zeolite cracking bases
are sometimes referred to in the art as molecular sieves and are
usually composed of silica, alumina and one or more exchangeable
cations such as sodium, magnesium, calcium, rare earth metals, etc.
They are further characterized by crystal pores of relatively
uniform diameter between about 4 and 14 Angstroms (10.sup.-10
meters). It is preferred to employ zeolites having a relatively
high silica/alumina mole ratio between about 3 and 12. Suitable
zeolites found in nature include, for example, mordenite, stilbite,
heulandite, ferrierite, dachiardite, chabazite, erionite and
faujasite. Suitable synthetic zeolites include, for example, the B,
X, Y and L crystal types, e.g., synthetic faujasite and mordenite.
The preferred zeolites are those having crystal pore diameters
between about 8-12 Angstroms (10.sup.-10 meters), wherein the
silica/alumina mole ratio is about 4 to 6. A prime example of a
zeolite falling in the preferred group is synthetic Y molecular
sieve.
[0023] The natural occurring zeolites are normally found in a
sodium form, an alkaline earth metal form, or mixed forms. The
synthetic zeolites are nearly always prepared first in the sodium
form. In any case, for use as a cracking base it is preferred that
most or all of the original zeolitic monovalent metals be
ion-exchanged with a polyvalent metal and/or with an ammonium salt
followed by heating to decompose the ammonium ions associated with
the zeolite, leaving in their place hydrogen ions and/or exchange
sites which have actually been decationized by further removal of
water. Hydrogen or "decationized" Y zeolites of this nature are
more particularly described in U.S. Pat. No. 3,130,006 B1.
[0024] Mixed polyvalent metal-hydrogen zeolites may be prepared by
ion-exchanging first with an ammonium salt, then partially back
exchanging with a polyvalent metal salt and then calcining. In some
cases, as in the case of synthetic mordenite, the hydrogen forms
can be prepared by direct acid treatment of the alkali metal
zeolites. The preferred cracking bases are those which are at least
about 10 percent, and preferably at least 20 percent,
metal-cation-deficient, based on the initial ion-exchange capacity.
A specifically desirable and stable class of zeolites are those
wherein at least about 20 percent of the ion exchange capacity is
satisfied by hydrogen ions.
[0025] The active metals employed in the preferred hydrocracking
catalysts of the present invention as hydrogenation components are
those of Group VIII, i.e., iron, cobalt, nickel, ruthenium,
rhodium, palladium, osmium, iridium and platinum. In addition to
these metals, other promoters may also be employed in conjunction
therewith, including the metals of Group VIB, e.g., molybdenum and
tungsten. The amount of hydrogenating metal in the catalyst can
vary within wide ranges. Broadly speaking, any amount between about
0.05 percent and 30 percent by weight may be used. In the case of
the noble metals, it is normally preferred to use about 0.05 to
about 2 weight percent. The preferred method for incorporating the
hydrogenating metal is to contact the zeolite base material with an
aqueous solution of a suitable compound of the desired metal
wherein the metal is present in a cationic form. Following addition
of the selected hydrogenating metal or metals, the resulting
catalyst powder is then filtered, dried, pelleted with added
lubricants, binders or the like if desired, and calcined in air at
temperatures of, e.g., 371.degree.-648.degree. C.
(700.degree.-1200.degree. F.) in order to activate the catalyst and
decompose ammonium ions. Alternatively, the zeolite component may
first be pelleted, followed by the addition of the hydrogenating
component and activation by calcining. The foregoing catalysts may
be employed in undiluted form, or the powdered zeolite catalyst may
be mixed and copelleted with other relatively less active
catalysts, diluents or binders such as alumina, silica gel,
silica-alumina cogels, activated clays and the like in proportions
ranging between 5 and 90 weight percent. These diluents may be
employed as such or they may contain a minor proportion of an added
hydrogenating metal such as a Group VIB and/or Group VIII
metal.
[0026] Additional metal promoted hydrocracking catalysts may also
be utilized in the process of the present invention which
comprises, for example, aluminophosphate molecular sieves,
crystalline chromosilicates and other crystalline silicates.
Crystalline chromosilicates are more fully described in U.S. Pat.
No. 4,363,718 B1 (Klotz).
[0027] The hydrocracking of the hydrocarbonaceous feedstock in
contact with a hydrocracking catalyst is conducted in the presence
of sufficiently low concentrations of hydrogen to maintain a liquid
phase continuous system and preferably at hydrocracking reactor
conditions which include a temperature from about 232.degree. C.
(450.degree. F.) to about 468.degree. C. (875.degree. F.), a
pressure from about 3.5 MPa (500 psig) to about 17.3 MPa (2500
psig) and a liquid hourly space velocity (LHSV) from about 0.1 to
about 30 hr.sup.-1. In accordance with the present invention, the
term "substantial conversion to lower boiling products" is meant to
connote the conversion of at least 5 volume percent of the fresh
feedstock to products having a lower boiling point than the
hydrocarbonaceous feedstock. In a preferred embodiment, the per
pass conversion in the hydrocracking zone is in the range from
about 15% to about 75%. More preferably the per pass conversion is
in the range from about 20% to about 60%. Then the ratio of
unconverted hydrocarbons boiling in the range of the
hydrocarbonaceous feedstock to the hydrocarbonaceous feedstock is
from about 1:5 to about 3:5. The present invention is suitable for
the production of naphtha, diesel or any other desired lower
boiling hydrocarbons.
[0028] During the conversions or reactions occurring in the
hydrotreating and hydrocracking reaction zones, hydrogen is
necessarily consumed and must be replaced by one or more hydrogen
inlet points located in the reaction zones. The amount of hydrogen
added at these locations is controlled to ensure that the system
operates as a liquid phase continuous system. The limiting amount
of hydrogen that is added is that amount which causes a transition
from a liquid phase continuous system to a vapor phase continuous
system.
[0029] The relative amount of hydrogen required to maintain a
liquid phase continuous system in both the hydrotreating and the
hydrocracking zones is dependent upon the specific composition of
the hydrocarbonaceous feedstock, the level or amount of conversion
to lower boiling hydrocarbon compounds, the composition and
quantity of the lower boiling hydrocarbons and the reaction zone
temperature and pressure. Artisans skilled in the conversion and
hydrocracking of hydrocarbons will readily be able to determine the
appropriate amount of hydrogen to provide a liquid phase continuous
system once all of the above-mentioned variables have been
selected.
DETAILED DESCRIPTION OF THE DRAWINGS
[0030] With reference now to the FIG. 1, a feedstream comprising
vacuum gas oil is introduced into the process via line 1 and
admixed with a hereinafter described hydrocracking zone effluent
transported via line 16. A hydrogen-rich gaseous stream is
introduced via line 2 and also joins the feedstream and the
resulting admixture is transported via line 3 and introduced into
hydrotreating zone 4. Additional hydrogen-rich gas is introduced
via lines 5 and 6 into hydrotreating zone 4 in order to supplement
the required hydrogen which is consumed in hydrotreating zone 4.
The amount of hydrogen present in hydrotreating zone 4 is
sufficiently low to maintain a liquid phase continuous system. The
resulting effluent from hydrotreating zone 4 is carried via line 7
and introduced into high pressure product stripper 8. A
hydrocarbonaceous vaporous stream comprising hydrogen sulfide,
ammonia and hydrocarbons boiling in the range lower than the
feedstock is removed from high pressure product stripper 8 via line
9 and recovered. A liquid hydrocarbonaceous stream containing
hydrocarbon compounds boiling in the range of the feedstock is
removed from high pressure product stripper 8 via line 10 and is
joined with a hydrogen-rich stream provided via line 11 and the
resulting admixture is transported via line 12 and introduced into
hydrocracking zone 13. Additional hydrogen is provided via lines 14
and 15 to hydrocracking zone 13. The hydrogen provided to
hydrocracking zone 13 is in an amount sufficiently low to maintain
a liquid phase continuous system therein. A resulting hydrocracking
zone effluent is removed from hydrocracking zone 13 via line 16 and
joins the fresh feedstock provided via line 1 as hereinabove
described.
[0031] With reference now to FIG. 2, a feedstream comprising vacuum
gas oil is introduced into the process via line 1 and admixed with
a hereinafter described hydrocracking zone effluent transported via
line 16. A hydrogen-rich gaseous stream is provided via line 2 and
also joins the feedstream and the resulting admixture is
transported via line 3 and introduced into hydrotreating zone 4.
Additional hydrogen is introduced into hydrotreating zone 4 via
lines 5 and 6. The total supply of hydrogen to hydrotreating zone 4
is sufficiently low to maintain a liquid phase continuous system. A
resulting effluent stream is removed from hydrotreating zone 4 via
line 7 and is joined with a hydrogen-rich gaseous stream provided
via line 8 in an amount sufficiently low to maintain a liquid phase
continuous system and the resulting admixture is transported via
line 9 and introduced into hydrocracking zone 10. Additional
hydrogen is provided to hydrocracking zone 10 via lines 11 and 12
in an amount sufficiently low to maintain a liquid phase continuous
system therein. A resulting effluent stream is removed from
hydrocracking zone 10 via line 11 and is joined with a
hydrogen-rich gaseous stream provided via line 12 and the resulting
admixture is transported via line 13 and introduced into high
pressure product stripper 14. A hydrocarbonaceous vaporous stream
containing hydrocarbons boiling in a range below the feed is
removed from high pressure product stripper 14 via line 15 and
recovered. A liquid stream containing unconverted hydrocarbons is
removed from high pressure product stripper via line 16 and joins
the feedstream provided via line 1 as hereinabove described.
[0032] The foregoing description and drawings clearly illustrate
the advantages encompassed by the process of the present invention
and the benefits to be afforded with the use thereof.
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