U.S. patent application number 12/845605 was filed with the patent office on 2012-02-02 for multi-stage hydroprocessing for the production of high octane naphtha.
This patent application is currently assigned to Chevron U.S.A. Inc.. Invention is credited to Cong-Yan Chen, Ann J. Liang, Stephen J. Miller, James N. Ziemer.
Application Number | 20120024752 12/845605 |
Document ID | / |
Family ID | 45525620 |
Filed Date | 2012-02-02 |
United States Patent
Application |
20120024752 |
Kind Code |
A1 |
Chen; Cong-Yan ; et
al. |
February 2, 2012 |
Multi-Stage Hydroprocessing for the Production of High Octane
Naphtha
Abstract
An integrated process is provided for producing high octane
naphtha. Hydrocracked naphtha from a hydrocracking reaction zone is
contacted with a reforming catalyst that includes a silicate having
a silica to alumina molar ratio of at least 200, and a crystallite
size of less than 10 microns. Products from the reforming include a
reformed naphtha and a hydrogen-rich stream, which is passed to the
hydrocracking reaction zone.
Inventors: |
Chen; Cong-Yan; (Alameda,
CA) ; Miller; Stephen J.; (San Francisco, CA)
; Ziemer; James N.; (Martinez, CA) ; Liang; Ann
J.; (Walnut Creek, CA) |
Assignee: |
Chevron U.S.A. Inc.
|
Family ID: |
45525620 |
Appl. No.: |
12/845605 |
Filed: |
July 28, 2010 |
Current U.S.
Class: |
208/60 ;
422/620 |
Current CPC
Class: |
C10G 2300/305 20130101;
C10G 2400/02 20130101; C10G 2300/301 20130101; C10G 69/10 20130101;
C10G 35/085 20130101; C10G 2300/4081 20130101; C10G 2300/1044
20130101; C10G 2300/4018 20130101 |
Class at
Publication: |
208/60 ;
422/620 |
International
Class: |
C10G 69/10 20060101
C10G069/10; C10G 47/02 20060101 C10G047/02 |
Claims
1. An integrated process for producing high octane naphtha,
comprising a. isolating a hydrocracked naphtha from a hydrocracking
reaction zone effluent; b. providing at least a portion of the
hydrocracked naphtha to a reforming reaction zone containing a
reforming catalyst that comprises a silicate having a silica to
alumina molar ratio of at least 200, and a crystallite size of less
than 10 microns; c. contacting the at least a portion of the
hydrocracked naphtha with the reforming catalyst at reforming
reaction conditions and producing a hydrogen-rich stream and a
reformed naphtha; and d. passing the hydrogen-rich stream to the
hydrocracking reaction zone.
2. The process of claim 1, wherein step (a) comprises contacting a
hydrocarbonaceous feedstock that boils in the range of from
550.degree. F. to 1100.degree. F. (288-593.degree. C.) in a
hydrocracking reaction zone to form the effluent.
3. The process of claim 1, wherein step (a) comprises isolating the
hydrocracked naphtha that comprises at least 70 wt % C.sub.4 to
C.sub.10 hydrocarbons.
4. The process of claim 1, wherein step (a) comprises isolating the
hydrocracked naphtha having an octane of less than 90.
5. The process of claim 2, wherein step (a) comprises fractionating
the hydrocracking reaction zone effluent and isolating at least the
hydrocracked naphtha and a bottoms stream.
6. The process of claim 5, further comprising recycling at least a
portion of the bottoms stream to the hydrocracking reaction
zone.
7. The process of claim 1, wherein step (b) comprises providing at
least a portion of the hydrocracked naphtha to a reforming reaction
zone containing a reforming catalyst that comprises a silicate
having a silica to alumina molar ratio of at least 500 and a
crystallite size of less than 10 microns;
8. The process of claim 1, wherein step (b) comprises providing at
least a portion of the hydrocracked naphtha to a reforming reaction
zone containing a reforming catalyst that comprises a silicate
having a silica to alumina molar ratio of at least 200, a
crystallite size of less than 10 microns, and an alkali content of
less than 5000 ppm.
9. The process of claim 1, wherein step (b) comprises providing at
least a portion of the hydrocracked naphtha to a reforming reaction
zone containing a reforming catalyst that comprises a silicate
having a silica to alumina molar ratio of at least 200 and a
crystallite size of less than 10 microns, the catalyst further
comprising one or more of iridium, palladium, platinum or a
combination thereof.
10. The process of claim 1, wherein step (c) comprises contacting
the at least a portion of the hydrocracked naphtha with the
reforming catalyst at reforming conditions, including a pressure in
the range of between 0 psig and 250 psig, a temperature in the
range of between 600.degree. and 1100.degree. F. and a liquid feed
rate in the range of between 0.1 and 20 hr.sup.-1.
11. The process of claim 1, wherein step (c) comprises producing
the reformed naphtha that comprises at least 70 wt % C.sub.5 to
C.sub.9 hydrocarbons.
12. The process of claim 4, wherein step (c) comprises producing
the reformed naphtha having an octane that is greater than the
octane of the hydrocracked naphtha.
13. The process of claim 4, wherein step (c) comprises producing
the reformed naphtha having an octane of greater than 90.
14. The process of claim 1, further comprising combining at least a
portion of the hydrocracked naphtha with at least a portion of the
reformed naphtha.
15. An integrated process for producing high octane naphtha,
comprising a. isolating a hydrocracked naphtha from a hydrocracking
reaction zone effluent; b. providing a first portion of the
hydrocracked naphtha to a reforming reaction zone containing a
reforming catalyst that comprises a silicate having a silica to
alumina molar ratio of at least 200, and a crystallite size of less
than 10 microns; c. contacting the first portion of the
hydrocracked naphtha with the reforming catalyst at reforming
reaction conditions and producing a hydrogen-rich stream and a
reformed naphtha; d. passing the hydrogen-rich stream to the
hydrocracking reaction zone; and e. combining the reformed naphtha
with a second portion of the hydrocracked naphtha to form a
combined naphtha having an octane of greater than 90.
16. A system for producing high octane naphtha, comprising: a. a
hydrocracking reaction zone for producing a hydrocracked naphtha
from a hydrocarbonaceous feedstock; b. a reforming reaction zone
for reforming the hydrocracked naphtha and for producing a reformed
naphtha and a reformer hydrogen; and c. a means for supplying the
reformer hydrogen to the hydrocracking reaction zone.
17. The system of claim 16, further comprising forming a combined
naphtha by blending at least a portion of the hydrocracked naphtha
with at least a portion of the reformed naphtha.
18. The system of claim 16, wherein the reformer reaction zone
contains a reforming catalyst that comprises a silicate having a
silica to alumina molar ratio of at least 200, and a crystallite
size of less than 10 microns.
19. The system of claim 16, wherein the hydrocracked naphtha
comprises at least 70 wt % C.sub.4 to C.sub.10 hydrocarbons and the
reformed naphtha comprises at least 70 wt % C.sub.5 to C.sub.9
hydrocarbons.
20. The system of claim 16, wherein the hydrocracked naphtha has an
octane of less than 90 and the reformed naphtha has an octane of
greater than 90.
21. The system of claim 16, wherein the combined naphtha has an
octane of greater than 90.
Description
FIELD OF THE INVENTION
[0001] The present invention provides a multi-stage integrated
process for the production of high octane naphtha from a
hydrocarbonaceous feedstock.
BACKGROUND
[0002] Different processes exist for upgrading hydrocarbonaceous
feedstocks. As the demand for transportation fuels such as
gasoline, diesel, and jet fuel grows, processes for upgrading low
grade distillates and residuum are becoming increasingly important.
Hydroprocessing reactions such as hydrotreating, hydrocracking, and
reforming use catalysts to upgrade various feedstocks. Because
heteroatoms can damage hydrocracking and/or reforming catalysts
they are generally removed prior to hydrocracking and/or reforming
by hydrotreating. Hydrotreating removes nitrogen, sulfur, and other
impurities in hydrocarbon feedstocks. Subsequently, these
feedstocks can be used in other refinery processes such as
hydrocracking and reforming. In hydrocracking, heavy feedstocks
including low grade distillates and gas oils with high molecular
weights are converted to lower molecular weight effluents such as
naphthas. Large amounts of hydrogen are consumed in typical
hydrocracking processes. Reforming is used for upgrading light
hydrocarbon feedstocks such as naphthas. Products from catalytic
reforming can include high octane gasoline useful as automobile
fuel, aromatics (for example benzene, toluene, xylenes and
ethylbenzene), and/or hydrogen. Reactions typically involved in
catalytic reforming include dehydrocyclization, isomerization and
dehydrogenation of naphtha range hydrocarbons, with
dehydrocyclization and dehydrogenation of linear and slightly
branched alkanes and dehydrogenation of cycloparaffins leading to
the production of aromatics.
[0003] Many refinery processes use a combination of hydroprocessing
reactions to upgrade heavy feedstocks. For example, in an initial
stage, the feedstock can be hydrotreated to reduce the amount of
heteroatoms which can have a deleterious effect on downstream
hydrocracking and/or reforming catalysts. The multistage process
can use a common hydrogen supply system as disclosed in, for
example, U.S. Pat. No. 5,009,768. Other U.S. patents which are
directed to multistage hydroprocessing within a single high
pressure hydrogen loop include, for example, U.S. Pat. No.
6,797,154. In this patent high conversion of heavy gas oils and the
production of high quality middle distillate products are possible
in a single high-pressure loop with reaction stages operating at
different pressure and conversion levels. The flexibility offered
is great and allows the refiner to avoid decreases in product
quality while at the same time minimizing capital cost. Feeds with
varying boiling ranges are introduced at different sections of the
process, thereby minimizing the consumption of hydrogen and
reducing capital investment.
[0004] U.S. Pat. No. 6,787,025 also discloses multi-stage
hydroprocessing for the production of middle distillates. A major
benefit of this invention is the potential for simultaneously
upgrading difficult cracked stocks such as Light Cycle Oil, Light
Coker Gas Oil, Visbroken Gas Oil, and/or Straight-Run Atmospheric
Gas Oils utilizing the high-pressure environment required for mild
hydrocracking.
[0005] U.S. Pat. No. 7,238,277 provides very high to total
conversion of heavy oils to products in a single high-pressure
loop, using multiple reaction stages. The second stage or
subsequent stages may be a combination of co-current and
counter-current operation. The benefits of this invention include
conversion of feed to useful products at reduced operating
pressures using lower catalyst volumes. Lower hydrogen consumption
also results.
[0006] U.S. Publication 20050103682 relates to a multi-stage
process for hydroprocessing gas oils. Preferably, each stage
possesses at least one hydrocracking zone. The second stage and any
subsequent stages possess an environment having a low heteroatom
content. Light products, such as naphtha, kerosene and diesel, may
be recycled from fractionation (along with light products from
other sources) to the second stage (or a subsequent stage) in order
to produce a larger yield of lighter products, such as gas and
naphtha. Pressure in the zone or zones subsequent to the initial
zone is from 500 to 1000 psig lower than the pressure in the
initial zone, in order to provide cost savings and minimize
overcracking.
[0007] Catalytic reforming is a well-known refinery process for
upgrading light hydrocarbon feedstocks, frequently referred to as
naphtha feedstocks. Products from catalytic reforming can include
high octane gasoline, useful as automobile fuel, and/or aromatics,
such as benzene and toluene, useful as chemicals. Reactions
typically involved in catalytic reforming include
dehydrocyclization, isomerization and dehydrogenation.
Dehydrocyclization is a well known reaction wherein alkanes are
converted to aromatics. For example, hexane may be dehydrocyclized
to benzene. Thus, reforming typically includes dehydrocyclization.
However, dehydrocyclization or aromatization of alkanes can be
directed more narrowly than reforming.
[0008] Even with the advances in hydroprocessing catalysts and
processes, a need still exists to develop new and improved methods
to provide high liquid yield of valuable gasoline, diesel, and jet
fuel products, improve hydrogen production, and minimize the
formation of less valuable low molecule weight (C.sub.1-C.sub.4)
products. Thus, further improvements for reducing refinery
operating costs by maximizing the production of valuable high
octane products from low grade feedstocks and minimizing the amount
of hydrogen needed during the hydroprocessing reactions are
desirable.
SUMMARY OF THE INVENTION
[0009] Accordingly, a process is provided for producing high octane
naphtha, including (a) isolating a hydrocracked naphtha from a
hydrocracking reaction zone effluent; (b) providing at least a
portion of the hydrocracked naphtha to a reforming reaction zone
containing a reforming catalyst containing a silicate having a
silica to alumina molar ratio of at least 200, and a crystallite
size of less than 10 microns; (c) contacting the at least a portion
of the hydrocracked naphtha with the reforming catalyst at
reforming reaction conditions and producing a hydrogen-rich stream
and a reformed naphtha; and (d) passing the hydrogen-rich stream to
the hydrocracking reaction zone.
[0010] In embodiments, the hydrocracked naphtha contains at least
70 wt % C.sub.4 to C.sub.10 hydrocarbons, and has an octane of less
than 90. In embodiments, the reformed naphtha includes at least 70
wt % C.sub.5 to C.sub.9 hydrocarbons, and has an octane of greater
than 95.
[0011] In embodiments, at least a portion of the hydrocracked
naphtha and at least a portion of the reformed naphtha are blended
as a combined naphtha, to be used as a fuel or fuel blendstock.
[0012] In embodiments, reformer reaction conditions include a
pressure in the range of between 0 psig and 250 psig, a temperature
in the range of between 600.degree. and 1100.degree. F. and a
liquid feed rate in the range of between 0.1 and 20 hr.sup.-1.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic diagram of one embodiment of the
invention.
[0014] FIG. 2 is a schematic diagram of a second embodiment of the
invention.
DETAILED DESCRIPTION
[0015] While the invention is susceptible to various modifications
and alternative forms, specific embodiments thereof are herein
described in detail. It should be understood, however, that the
description herein of specific embodiments is not intended to limit
the invention to the particular forms disclosed, but on the
contrary, the intention is to cover all modifications, equivalents,
and alternatives falling within the spirit and scope of the
invention as defined by the appended claims.
[0016] The upgrading process integrates two upgrading zones. A
first upgrading zone produces a hydrocracked naphtha which is
upgraded in a second zone. The second upgrading zone in turn
produces a hydrogen-rich stream that is used in the first upgrading
zone. The first upgrading zone reduces the molecular weight of a
hydrocarbonaceous feed. A fuel intermediate isolated from the
effluent from the first upgrading zone is reformed in the second
zone to produce a fuel or fuel-blending component. In embodiments,
the catalyst employed in the reforming zone is an intermediate pore
size crystalline molecular sieve having a crystalline framework
characterized by a range of silica to alumina ratios. In
embodiments the intermediate pore size molecular sieve is further
characterized by a X-ray diffraction pattern. In embodiment, the
intermediate pore size molecular sieve is further characterized by
an alkali content. In embodiments, the intermediate pore size
molecular sieve is further characterized by a crystallite size
range.
[0017] The process involves using an integrated petroleum upgrading
system for producing a high octane naphtha blend component. The
system involves a hydrocracking reaction zone for producing a
naphtha product and a reforming zone for upgrading the naphtha
product and for producing a hydrogen-rich stream for use in the
hydrocracking reaction zone. In hydrocracking reactions the
molecular weight of the feedstock is greater than the molecular
weight of the effluent produced due to bond cleavage reactions
which occur during hydrocracking Hydrogen is a necessary component
of hydrocracking reactions, both to protect the hydrocracking
catalysts from premature fouling and to provide the hydrogen needed
for the cracked, hydrogenated and/or heteroatom reduced reaction
products.
DEFINITIONS
[0018] The following terms will be used throughout the
specification and will have the following meanings unless otherwise
indicated.
[0019] As used herein, the terms "hydrocarbon" or
"hydrocarbonaceous" or "petroleum" are used interchangeably to
refer to carbonaceous material originating from crude oil, natural
gas or biological processes.
[0020] As used herein "Group VIB" or "Group VIB metal" refers to
one or more metals, or compounds thereof, selected from Group VIB
of the Chemical Abstract Services Periodic Table. The Chemical
Abstract Services Periodic Table may be found, for example, behind
the front cover of CRC Handbook of Chemistry and Physics, 81.sup.st
Edition, 2000-2001.
[0021] As used herein "Group VIII" or "Group VIII metal" refers to
one or more metals, or compounds thereof, selected from Group VIII
of the Chemical Abstract Services Periodic Table.
[0022] Hydrocracking is a chemical reaction of liquid feed
materials, including hydrocarbons, petroleum and other biologically
derived material, in the presence of hydrogen and one or more
catalysts, resulting in product molecules having reduced molecular
weight relative to that of the liquid feed materials. Additional
reactions, including olefin and aromatic saturation and heteroatom
(including oxygen, nitrogen, sulfur and halogen) removal may also
occur during hydrocracking.
[0023] Reforming is a chemical reaction of liquid feed materials,
including hydrocarbons, petroleum and other biological derived
material, in the presence of one or more catalysts, resulting in
product molecules such as automobile fuel, aromatics (for example
benzene, toluene, xylenes and ethylbenzene), and/or hydrogen.
Reactions typically involved in catalytic reforming include
dehydrocylization, isomerization and dehydrogenation of naphtha
range hydrocarbons, with dehydrocyclization and dehydrogenation of
linear and slightly branched alkanes and dehydrogenation of
cycloparaffins leading to the production of aromatics.
[0024] As used herein, a paraffin refers to a non-cyclic, linear or
branched saturated hydrocarbon. For example, a C.sub.8 paraffin is
a non-cyclic, linear or branched hydrocarbon having 8 carbon atoms
per molecule. Normal octane, methylheptanes, dimethylhexanes,
trimethylpentanes are examples of C.sub.8 paraffins. A
paraffin-containing feed comprises non-cyclic saturated
hydrocarbons, such as normal paraffins, isoparaffins, and mixtures
thereof.
[0025] As used herein, a naphthene is a type of alkane having one
or more rings of carbon atoms in its chemical structure. In
embodiments, the naphthene is a cyclic, non-aromatic hydrocarbon.
In some such embodiments, the naphthene is saturated. In some such
embodiments, the naphthene is a cyclic, non-aromatic, saturated
hydrocarbon having in the range of 5 to 8 carbon atoms in the cycle
structure.
[0026] As used herein, naphtha is a distillate hydrocarbonaceous
fraction boiling within the range of from 50.degree. to 550.degree.
F. In some embodiments, naphtha boils within the range of
70.degree. to 450.degree. F., and more typically within the range
of 80.degree. to 400.degree. F., and often within the range of
90.degree. to 360.degree. F. In some embodiments, at least 85 vol.
% of naphtha boils within the range of from 50.degree. to
550.degree. F., and more typically within the range of from
70.degree. to 450.degree. F. In embodiments, at least 85 vol. % of
naphtha is in the C.sub.4-C.sub.12 range, and more typically in the
C.sub.5-C.sub.11 range, and often in the C.sub.6-C.sub.10 range.
Naphtha can include, for example, straight run naphthas, paraffinic
raffinates from aromatic extraction or adsorption, C.sub.6-C.sub.10
paraffin containing feeds, bioderived naphtha, naphtha from
hydrocarbon synthesis processes, including Fischer Tropsch and
methanol synthesis processes, as well as naphtha from other
refinery processes, such as hydrocracking or conventional
reforming.
[0027] As disclosed herein, boiling point temperatures are based on
the ASTM D-2887 standard test method for boiling range distribution
of petroleum fractions by gas chromatography, unless otherwise
indicated. The mid-boiling point is defined as the 50% by volume
boiling temperature, based on an ASTM D-2887 simulated
distillation.
[0028] As disclosed herein, carbon number values (i.e. C.sub.5,
C.sub.6, C.sub.8, C.sub.9 and the like) of hydrocarbons may be
determined by standard gas chromatography methods.
[0029] Unless otherwise specified, liquid feed rate to a catalytic
reaction zone is reported as the volume of feed per hour per volume
of catalyst. In effect, the feed rate as disclosed herein, referred
to as liquid hourly space velocity (LHSV), is reported in
reciprocal hours (i.e. hr.sup.-1).
[0030] The term "silica to alumina ratio" refers to the molar ratio
of silicon oxide (SiO.sub.2) to aluminum oxide (Al.sub.2O.sub.3).
ICP analysis may be used to determine silica to alumina ratio.
[0031] As used herein, the value for octane refers to the research
octane number (RON), as determined by ASTM D2699.
[0032] As used herein, the quantity of pressure in units of psig
(pounds per square inch gauge) is reported as "gauge" pressure,
i.e. the absolute pressure minus the ambient pressure, unless
otherwise indicated. The quantity of pressure in units of either
psi (pounds per square inch) or kPa (kilopascals) is reported as
absolute pressure, unless otherwise indicated.
[0033] As used herein "penultimate stage" does not refer
necessarily to the second to last stage in a multistage reforming
process but rather refers to a stage preceding at least one
additional stage. As used herein "final stage" does not refer
necessarily to the last stage of a multi stage reforming process
but rather refers to the stage after a penultimate stage.
[0034] The equilibrium reaction for the conversion of toluene to
xylene and benzene products normally yields about 24 wt. %
para-xylene (PX), about 54 wt. % meta-xylene (MX), and about 22 wt.
% ortho-xylene (OX) among xylenes. For a more complete description
of equilibrium product distributions for xylene isomerization see
R. D. Chirico and W. V. Steele, "Thermodynamic Equilibria in xylene
isomerization. 5. Xylene isomerization equilibria from
thermodynamic studies and reconciliation of calculated and
experimental product distributions", Journal of Chemical
Engineering Data, 1997, 42 (4), 784-790, herein incorporated by
reference in its entirety.
[0035] The catalysts employed in the process of the invention may
be employed in the form of pills, pellets, granules, cylinders,
extrudates, broken fragments, or various special shapes, disposed
as a fixed bed within a reaction zone, and the charging stock may
be passed there through in the liquid, vapor, or mixed phase, and
in either upward, downward or radial flow. Alternatively, they can
be used in moving beds or in fluidized-solid processes, in which
the charging stock is passed upward through a turbulent bed of
finely divided catalyst. However, a fixed bed system or a
dense-phase moving bed system often result in lower catalyst
attrition losses and other operational advantages. In a fixed bed
system, the feed can be preheated (by any suitable heating means)
to the desired reaction temperature and then passed into a reaction
zone containing a fixed bed of the catalyst. This reaction zone may
be one or more separate reactors.
Hydrocracking
[0036] The hydrocracking reaction zone is maintained at conditions
sufficient to effect a boiling range conversion of the
hydrocarbonaceous feed to the hydrocracking reaction zone, so that
the liquid hydrocrackate recovered from the hydrocracking reaction
zone has a normal boiling point range below the boiling point range
of the feed. The hydrocracking step reduces the size of the
hydrocarbon molecules, hydrogenates olefin bonds, hydrogenates
aromatics, and removes traces of heteroatoms resulting in an
improvement in fuel or base oil product quality.
[0037] The hydrocracking catalyst generally comprises a cracking
component, a hydrogenation component and a binder. Such catalysts
are well known in the art. The cracking component may include an
amorphous silica/alumina phase and/or a zeolite, such as a Y-type
or USY zeolite. If present, the zeolite is at least about 1 percent
by weight based on the total weight of the catalyst. A zeolite
containing hydrocracking catalyst generally contains in the range
of from 1 wt. % to 99 wt. % zeolite, and more typically in the
range of 2 wt. % to 70 wt. % zeolite. Actual zeolite amounts will,
of course be adjusted to meet catalytic performance requirements.
The binder is generally silica or alumina. The hydrogenation
component will be a Group VI, Group VII, or Group VIII metal or
oxides or sulfides thereof, preferably one or more of molybdenum,
tungsten, cobalt, or nickel, or the sulfides or oxides thereof. If
present in the catalyst, these hydrogenation components generally
make up from about 5% to about 40% by weight of the catalyst.
Alternatively, platinum group metals, especially platinum and/or
palladium, may be present as the hydrogenation component, either
alone or in combination with the base metal hydrogenation
components molybdenum, tungsten, cobalt, or nickel. If present, the
platinum group metals will generally make up from about 0.1% to
about 2% by weight of the catalyst.
[0038] The process of the invention can employ a wide variety of
hydrocarbonaceous feedstocks from many different sources, such as
crude oil, virgin petroleum fractions, recycle petroleum fractions,
shale oil, liquefied coal, tar sand oil, synthetic paraffins from
normal alphaolefin, recycled plastic feedstocks, petroleum
distillates, solvent-deasphalted petroleum residua, shale oils,
coal tar distillates, hydrocarbon feedstocks derived from plant,
animal, and/or algal sources, and combinations thereof. Other
feedstocks that can be used in the process of the invention include
synthetic feeds, such as those derived from a Fischer Tropsch
processes. Other suitable feedstocks include those heavy
distillates normally defined as heavy straight-run gas oils and
heavy cracked cycle oils, as well as conventional fluid catalytic
cracking feed and portions thereof. In general, the feed can be any
carbon containing feedstock susceptible to hydroprocessing
catalytic reactions, particularly hydrocracking and/or reforming
reactions. A suitable liquid hydrocracker feedstock is a vacuum gas
oil boiling in a temperature range above about 450.degree. F.
(232.degree. C.) and more typically within the temperature range of
550.degree.-1100.degree. F. (288-593.degree. C.). In embodiments,
at least 50 wt. % of the hydrocarbonaceous feedstock boils above
550.degree. F. (288.degree. C.). The term liquid refers to
hydrocarbons, which are liquid at ambient conditions.
[0039] The liquid hydrocracker feedstock, which may be used in the
instant invention, contains impurities such as nitrogen and sulfur,
at least some of which are removed from the hydrocarbonaceous
feedstock in the hydrocracking zone. Nitrogen impurities present in
the hydrocarbonaceous feedstock may be present as organonitrogen
compounds, in amounts greater than 1 ppm. Sulfur impurities may
also be present. Feeds with high levels of nitrogen and sulfur,
including those containing up to 0.5 wt % (and higher) nitrogen and
up to 2 wt % and higher sulfur may be treated in the present
process. However, feedstocks which are high in asphaltenes and
metals will usually require some kind of prior treatment, such as
in a hydrotreating operation, before they are suitable for use as a
feedstock for the hydrocracking process step. A suitable liquid
hydrocarbon feedstock generally contains less than about 500 ppm
asphaltenes, more typically less than about 200 ppm asphaltenes,
and often less than about 100 ppm asphaltenes.
[0040] According to one embodiment, the hydrocarbonaceous feedstock
is placed in contact with the hydrocracking catalyst in the
presence of hydrogen, usually in a fixed bed reactor in the
hydrocracking reaction zone. The conditions of the hydrocracking
reaction zone may vary according to the nature of the feed, the
intended quality of the products, and the particular facilities of
each refinery. Hydrocracking reaction conditions include, for
example, a reaction temperature within the range of 450.degree. F.
to 900.degree. F. (232.degree. C.-482.degree. C.), and typically a
reaction temperature in the range of 650.degree. F. to 850.degree.
F. (343.degree. C.-454.degree. C.); a reaction pressure within the
range of 500 to 5000 psig (3.5-34.5 MPa), and typically a reaction
pressure in the range of 1500-3500 psig (10.4-24.2 MPa); a liquid
reactant feed rate, in terms of liquid hourly space velocity (LHSV)
within the range of 0.1 to 15 hr.sup.-1 (v/v), typically in the
range of 0.25 to 2.5 hr.sup.-1; and hydrogen feed rate, in terms of
H.sub.2/hydrocarbon ratio, is within the range of 500 to 5000
standard cubic feet per barrel of liquid hydrocarbon feed (89.1-445
m.sup.3 H.sub.2/m.sup.3 feed). The hydrocrackate is then separated
into various boiling range fractions. The separation is typically
conducted by fractional distillation preceded by one or more
vapor-liquid separators to remove hydrogen and/or other tail
gases.
[0041] In some situations, the hydrocracking reaction conditions
are established to achieve a target conversion of the
hydrocarbonaceous feedstock within the hydrocracking reaction zone.
For example, the hydrocracking reaction conditions may be set to
achieve a conversion of greater than 30%. As an example, the target
conversion may be greater than 40% or 50% or even 60%. As used
herein, conversion is based on a reference temperature, such as,
for example, the minimum boiling point temperature of the
hydrocracker feedstock. The extent of conversion relates to the
percentage of feed boiling above the reference temperature which is
converted to products boiling below the reference temperature.
[0042] The hydrocracking reaction zone that contains the
hydrocracking catalyst may be contained within a single reactor
vessel, or it may be contained in two or more reactor vessels,
connected together in fluid communication in a serial arrangement.
In embodiments, hydrogen and the hydrocarbonaceous feed are
provided to the hydrocracking reaction zone in combination.
Additional hydrogen may be provided at various locations along the
length of the reaction zone to maintain an adequate hydrogen supply
to the zone. Furthermore, relatively cool hydrogen added along the
length of the reactor may serve to absorb some of the heat energy
within the zone, and help to maintain a relatively constant
temperature profile during the exothermic reactions occurring in
the reaction zone.
[0043] Catalysts within the hydrocracking reaction zone may be of a
single type. In embodiments, multiple catalyst types may be blended
in the reaction zone, or they may be layered in separate catalyst
layers to provide a specific catalytic function that provides
improved operation or improved product properties. The catalyst may
be present in the reaction zone in a fixed bed configuration, with
the hydrocarbonaceous feed passing either upward or downward
through the zone. In embodiments, the hydrocarbonaceous feed passes
co-currently with the hydrogen feed within the zone. In other
embodiments, the hydrocarbonaceous feed passes countercurrent to
the hydrogen feed within the zone.
[0044] The effluent from the hydrocracking reaction zone is the
total of materials passing from the hydrocracking reaction zone,
and generally includes normally liquid hydrocarbonaceous materials,
normally gas phase hydrocarbonaceous reaction products, one or more
of H.sub.2S, NH.sub.3 and H.sub.2O from reaction of heteroatoms
with hydrogen in the reaction zone and unreacted hydrogen.
[0045] In general, the hydrocracking reaction zone effluent is
first processed to recover at least a portion of the unreacted
hydrogen in one or more initial separation steps, using flash
separation or fractional distillation processes. These initial
separation steps are well known, and their design and operation are
dictated by the specific process requirements. The flash separation
steps are usually operated at a pressure within the range of from
ambient pressure up to the pressure of the hydrocracking reaction
zone, and at a temperature within the range of 100.degree. F. up to
the hydrocracking reaction zone temperature.
[0046] At least a portion of the effluent from the hydrocracking
reaction zone is separated by means of fractional distillation into
various fractions based on the initial and final boiling points of
the components. In embodiments, the separation is conducted in an
atmospheric distillation column, operated at a pressure of roughly
equal to or slightly above ambient pressures, including a pressure
from 0 psig to 100 psig. Distillate fractions from an atmospheric
column may include one or more of C.sub.4- fractions,
C.sub.5-C.sub.8 fraction, and one or more C.sub.9+ fractions, with
each fraction being distinguished by a unique boiling point range.
Such atmospheric distillation processes are well known. In
embodiments, the bottoms fraction from the atmospheric distillation
is further separated in a vacuum distillation column, operated at
subatmospheric pressure. Distillate fractions from vacuum
distillation include one or more vacuum gas oil fractions, boiling
within a range of from approximately 500.degree.-1100.degree. F. In
general, a distillate fraction recovered from the distillation is
in the vapor phase at the conditions of the distillation but in the
liquid phase at ambient conditions; a gaseous overhead fraction
recovered from the distillation is in the vapor phase at the
conditions of the distillation and also in the vapor phase at
ambient conditions; and a bottoms fraction recovered from the
distillation remains in the liquid phase at the conditions of the
distillation.
[0047] In embodiments, the C.sub.8 containing paraffin feedstock is
a hydrocracked naphtha. An exemplary hydrocracked naphtha that is
useful in the process is recovered from the atmospheric
distillation of at least a portion of the effluent from the
hydrocracking reaction zone. Exemplary hydrocracked naphthas that
are recovered from atmospheric distillation generally have a normal
boiling point range within the range of from 50.degree. to
550.degree. F. and more typically within the range of from
70.degree. to 450.degree. F. The distillation may be generally
operated to produce a naphtha stream comprising at least 60 wt. %
C.sub.4 to C.sub.10 hydrocarbons, more typically at least 70 wt. %
C.sub.4 to C.sub.10 hydrocarbons, and often at least 80 wt. %
C.sub.4 to C.sub.10 hydrocarbons. In embodiments, the distillation
may be generally operated to produce a naphtha stream comprising at
least 60 wt. % C.sub.5 to C.sub.9 hydrocarbons, more typically at
least 70 wt. % C.sub.5 to C.sub.9 hydrocarbons and often at least
80 wt. % C.sub.5 to C.sub.9 hydrocarbons. In embodiments, the
distillation may be generally operated to produce a naphtha stream
comprising at least 60 wt. % C.sub.6 to C.sub.8 hydrocarbons, more
typically at least 70 wt. % C.sub.6 to C.sub.8 hydrocarbons, and
often at least 80 wt. % wt. % C.sub.6 to C.sub.8 hydrocarbons.
[0048] In an embodiment, the hydrocracked naphtha generally
contains at least about 5 wt. % paraffinic C.sub.8 hydrocarbons,
more typically at least about 10 wt. % paraffinic C.sub.8
hydrocarbons, and often at least about 12 wt. % paraffinic C.sub.8
hydrocarbons, or at least about 15 wt. % paraffinic C.sub.8
hydrocarbons. In a separate embodiment, the hydrocracked naphtha
generally contains at least about 40 wt. % paraffinic C.sub.8
hydrocarbons, more typically at least about 50 wt. % paraffinic
C.sub.8 hydrocarbons and often at least about 60 wt. % paraffinic
C.sub.8 hydrocarbons. Tailoring the hydrocracked naphtha to yield a
desired paraffinic C.sub.8 hydrocarbon content is achieved, at
least in part, by selection of the distillation design and
operating parameters.
[0049] In embodiments, the hydrocracked naphtha contains less than
10 wt. % aromatics, more typically less than 5 wt. % aromatics, and
often less than 2 wt. % aromatics. In embodiments, the hydrocracked
naphtha contains less than 1000 ppm sulfur, more typically less
than 100 ppm sulfur, and often less than 10 ppm sulfur and even
less than 1 ppm sulfur. In embodiments, the hydrocracked naphtha
contains less than 1000 ppm nitrogen, more typically less than 100
ppm nitrogen, and often less than 10 ppm nitrogen and even less
than 1 ppm nitrogen. In embodiments, the hydrocracked naphtha has
an octane number of less than 90, more typically less than 85,
often less than 80, and even less than 75.
Reforming
[0050] At least a portion of the hydrocracked naphtha is upgraded
in a reforming reaction zone to a reformed naphtha. In embodiments,
the entire hydrocracked naphtha is upgraded in this way. In the
process, at least a portion of the hydrocracked naphtha is
contacted in a reforming reaction zone with a reforming catalyst
comprising a silicate having a silica to alumina ratio of at least
200, a crystallite size of less than 10 microns and an alkali
content of less than 5000 ppm at reforming conditions to produce a
hydrogen-rich stream and a reformed naphtha.
[0051] The reforming catalyst is selected to provide a high
selectivity for the production of aromatic compounds at a reduced
pressure, which increases the selectivity of C.sub.6 to C.sub.8
paraffin dehydrocyclization while maintaining low catalyst fouling
rates. In embodiments, the reforming catalyst comprises at least
one medium pore zeolite. The molecular sieve is a porous inorganic
oxide characterized by a crystalline structure which provides pores
of a specified geometry, depending on the particular structure of
each molecular sieve. The phrase "medium pore" as used herein means
having a crystallographic free diameter in the range of from about
3.9 to about 7.1 Angstrom when the porous inorganic oxide is in the
calcined form. The crystallographic free diameters of the channels
of molecular sieves are published in the "Atlas of Zeolite
Framework Types", Fifth Revised Edition, 2001, by Ch. Baerlocher,
W. M. Meier, and D. H. Olson, Elsevier, pp 10-15, which is
incorporated herein by reference. Non-limiting examples of medium
pore zeolites include ZSM-5, ZSM-11, ZSM-22, ZSM-23, ZSM-35,
ZSM-38, ZSM-48 MCM-22, SSZ-20, SSZ-25, SSZ-32, SSZ-35, SSZ-37,
SSZ-44, SSZ-45, SSZ-47, SSZ-58, SSZ-74, SUZ-4, EU-1, NU-85, NU-87,
NU-88, IM-5, TNU-9, ESR-10, TNU-10 and combinations thereof. In
embodiments, the medium pore zeolite is a zeolite, which is a
crystalline material that possess three-dimensional frameworks
composed of tetrahedral units (TO.sub.4/2, T=Si, Al, or other
tetrahedrally coordinated atom) linked through oxygen atoms. An
medium pore zeolite that is useful in the present process includes
ZSM-5. Various references disclosing ZSM-5 are provided in U.S.
Pat. No. 4,401,555 to Miller. Additional disclosure on the
preparation and properties of high silica ZSM-5 may be found, for
example, in U.S. Pat. No. 5,407,558 and U.S. Pat. No.
5,376,259.
[0052] In embodiments, the reforming catalyst includes a silicate
having a form of ZSM-5 with a molar ratio of
SiO.sub.2/M.sub.2O.sub.3 of at least 40:1, or at least 200:1 or at
least 500:1, or even at least 1000:1, where M is selected from Al,
B, or Ga. In embodiments, the ZSM-5 has a silica to alumina molar
ratio of at least 40:1, or at least 200:1, or at least 500:1, or
even at least 1000:1. The silicate that is useful further is
characterized as having a crystallite size of less than 10 .mu.m,
or less than 5 .mu.m or even less than 1 .mu.m. Methods for
determining crystallite size, using, for example Scanning Electron
Microscopy, are well known. The silicate that is useful is further
characterized as having at least 80% crystallinity, or at least 90%
crystallinity, or at least 95% crystallinity. Methods for
determining crystallinity, using, for example, X-ray Diffraction,
are well known.
[0053] Strong acidity is undesirable in the catalyst because it
promotes cracking, resulting in lower selectivity to C.sub.5+
liquid product. To reduce acidity, a silicate that contains alkali
metal and/or alkaline earth metal cations is useful for reforming
the naphtha. The alkali or alkaline earth cations may be
incorporated into the catalyst during or after synthesis of the
molecular sieve. Suitable molecular sieves are characterized by
having at least 90% of the acid sites, or at least 95% of the acid
sites, or at least 99% of the acid sites being neutralized by
introduction of the alkali or alkaline earth cations. In one
embodiment, the medium pore zeolite contains less than 5000 ppm
alkali. Such molecular sieves are disclosed, for example, in U.S.
Pat. No. 4,061,724, in U.S. Pat. No. 5,182,012 and in U.S. Pat. No.
5,169,813. These patents are incorporated herein by reference,
particularly with respect to the description, preparation and
analysis of molecular sieves having the specified molar silica to
alumina molar ratios, having a specified crystallite size, having a
specified crystallinity and having a specified alkali and/or
alkaline earth content.
[0054] In embodiments, the silicate is a ZSM-5 type medium pore
zeolite. In some such embodiments, the silicate is silicalite, a
very high ratio silica to alumina form of ZSM-5. In embodiments,
the silicalite has a silica to alumina molar ratio of at least
40:1, or at least 200:1, or at least 500:1, or even at least
1000:1. Various references disclosing silicalite and ZSM-5 are
provided in U.S. Pat. No. 4,401,555 to Miller and U.S. Pat. No.
6,063,723 to Miller. These references include the aforesaid U.S.
Pat. No. 4,061,724 to Grose et al.; U.S. Pat. Reissue No. 29,948 to
Dwyer et al.; Flanigen et al., Nature, 271, 512-516 (Feb. 9, 1978)
which discusses the physical and adsorption characteristics of
silicalite; and Anderson et al., J. Catalysis 58, 114-130 (1979)
which discloses catalytic reactions and sorption measurements
carried out on ZSM-5 and silicalite. The disclosures of these
publications are incorporated herein by reference.
[0055] Other zeolites which can be used in the process of the
present invention include those as listed in U.S. Pat. No.
4,835,336; namely: ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, ZSM-38,
ZSM-48, and other similar materials.
[0056] ZSM-5 is more particularly described in U.S. Pat. No.
3,702,886 and U.S. Pat. Re. 29,948, the entire contents of which
are incorporated herein by reference.
[0057] ZSM-11 is more particularly described in U.S. Pat. No.
3,709,979 the entire contents of which are incorporated herein by
reference.
[0058] ZSM-12 is more particularly described in U.S. Pat. No.
3,832,449, the entire contents of which are incorporated herein by
reference.
[0059] ZSM-22 is more particularly described in U.S. Pat. Nos.
4,481,177, 4,556,477 and European Patent No. 102,716, the entire
contents of each being expressly incorporated herein by
reference.
[0060] ZSM-23 is more particularly described in U.S. Pat. No.
4,076,842, the entire contents of which are incorporated herein by
reference.
[0061] ZSM-35 is more particularly described in U.S. Pat. No.
4,016,245, the entire contents of which are incorporated herein by
reference.
[0062] ZSM-38 is more particularly described in U.S. Pat. No.
4,046,859, the entire contents of which are incorporated herein by
reference.
[0063] ZSM-48 is more particularly described in U.S. Pat. No.
4,397,827 the entire contents of which are incorporated herein by
reference.
[0064] In embodiments, the crystalline silicate may be in the form
of a borosilicate, where boron replaces at least a portion of the
aluminum of the more typical aluminosilicate form of the silicate.
Borosilicates are described in U.S. Pat. Nos. 4,268,420; 4,269,813;
and 4,327,236 to Klotz, the disclosures of which patents are
incorporated herein, particularly that disclosure related to
borosilicate preparation. In a suitable borosilicate, the
crystalline structure is that of ZSM-5, in terms of X-ray
diffraction pattern. Boron in the ZSM-5 type borosilicates takes
the place of aluminum that is present in the more typical ZSM-5
crystalline aluminosilicate structures. Borosilicates contain boron
in place of aluminum, but generally there is some trace amounts of
aluminum present in crystalline borosilicates.
[0065] Still further crystalline silicates which can be used in the
present invention are ferrosilicates, as disclosed for example in
U.S. Pat. No. 4,238,318, gallosilicates, as disclosed for example
in U.S. Pat. No. 4,636,483, and chromosilicates, as disclosed for
example in U.S. Pat. No. 4,299,808.
[0066] The reforming catalyst further contains one or more Group
VIII metals, e.g., nickel, ruthenium, rhodium, palladium, iridium
or platinum. In embodiments, the Group VIII metals include iridium,
palladium, platinum or a combination thereof. These metals are more
selective with regard to dehydrocyclization and are also more
stable under the dehydrocyclization reaction conditions than other
Group VIII metals. When employed in the reforming catalyst, these
metals are generally present in the range of between 0.1 wt. % and
5 wt. % or between 0.3 wt. % to 2.5 wt. %. The catalyst may further
comprise a promoter, such as rhenium, tin, germanium, cobalt,
nickel, iridium, tungsten, rhodium, ruthenium, or combinations
thereof. In an illustrative embodiment, the catalyst comprises in
the range of 0.1 wt. % to 1 wt. % platinum and in the range of 0.1
wt. % to 1 wt. % rhenium.
[0067] In forming the reforming catalyst, the crystalline molecular
sieve is preferably bound with a matrix. Satisfactory matrices
include inorganic oxides, including alumina, silica, naturally
occurring and conventionally processed clays, such as bentonite,
kaolin, sepiolite, attapulgite and halloysite.
[0068] Reforming reaction conditions employed in the reforming
reaction zone will depend, at least in part, on the characteristics
of the naphtha feed, whether highly aromatic, paraffinic or
naphthenic. Reaction conditions of temperature, pressure,
hydrocarbon to hydrogen ratio, and LHSV can be tuned in order to
maximize production of reformate products of a desired octane,
depending at least in part on the particular performance advantages
of the reforming catalyst. In the process, the hydrocracked naphtha
fraction is contacted with reforming catalyst in the reforming
reaction zone at reforming reaction conditions. In embodiments,
reforming reaction conditions include a pressure in the range of
between 0 psig (0 kPa) and 250 psig (1720 kPa). In some cases
pressure range is between 0 psig (0 kPa) and 100 psig (689 kPa),
and in some cases is between 25 psig (172 kPa) and 75 psig (517
kPa). In embodiments, reforming reaction conditions include a
liquid hourly space velocity (LHSV) in the range of between 0.1 and
20 hr.sup.-1, and in some cases in the range of between 0.3 and 5
hr.sup.-1. In embodiments, reforming conditions include a
temperature in the range of between 600.degree. F. (316.degree. C.)
and 1100.degree. F. (593.degree. C.), and in some cases in the
range of between 640.degree. F. (338.degree. C.) and 1050.degree.
F. (566.degree. C.). Hydrogen may be added as an additional feed to
the final reforming zone, but it is not required. In embodiments,
reforming reaction conditions include conditions to maintain a
molar H.sub.2/hydrocarbon ratio in the range of 1:1 to 10:1. A
molar H.sub.2/hydrocarbon ratio in the range of 1:1 to 4:1 is
exemplary.
[0069] The naphtha stream is contacted in a reforming reaction zone
with a reforming catalyst to produce a hydrogen-rich stream and
reformed naphtha. Additional C.sub.5- liquids and gases, including
additional C.sub.4- liquids and gases, may also be produced. In
embodiments, these lighter reaction products are separated from the
reformed naphtha in a fractionation unit, using, for example a
flash separation zone or a multi-stage distillation unit. The
reformed naphtha has an increased octane relative to that of the
hydrocracked naphtha, such as, for example, an octane of at least
90, or at least 95, or at least 98. The reformed naphtha further
boils in the gasoline range, such as, for example, having a normal
boiling point range within the range of from 70.degree. F.
(21.degree. C.) to 280.degree. F. (138.degree. C.), or in the range
of from 100.degree. F. (38.degree. C.) to 260.degree. F.
(127.degree. C.), or in the range of 100.degree. F. (38.degree. C.)
to 230.degree. F. (110.degree. C.).
[0070] In some aspects, the reformed naphtha comprises at least 60
wt % or at least 70 wt % or at least 80 wt % C.sub.4 to C.sub.10
hydrocarbons. In some of these situations, the reformed naphtha
comprises at least 60 wt % or at least 70 wt % or at least 80 wt %
wt % C.sub.5 to C.sub.9 hydrocarbons. In some of these situations,
the reformed naphtha comprises at least 60 wt % or at least 70 wt %
or at least 80 wt % wt % C.sub.6 to C.sub.8 hydrocarbons. In
embodiments, the reformed hydrocracked naphtha contains in the
range of 1% to 40% aromatics, or in the range of 5% to 30%
aromatics. In embodiments, the reformed naphtha contains less than
1000 ppm sulfur, or less than 100 ppm sulfur or less than 10 ppm
sulfur or even less than 1 ppm sulfur. In embodiments, the reformed
naphtha contains less than 1000 ppm nitrogen, or less than 100 ppm
nitrogen or less than 10 ppm nitrogen or even less than 1 ppm
nitrogen.
[0071] The reformed naphtha is useful as a fuel or as a blend stock
for a fuel. In some embodiments, at least a portion of the final
reformate from the final reforming zone is blended with at least a
portion of the heavy stream, which is recovered from the
penultimate zone; the blend may be used as a fuel or as a blend
stock for a fuel. In embodiments, a portion of the hydrocracked
naphtha is caused to bypass the reformer reaction zone, and is
combined with at least a portion of the reformed naphtha.
[0072] A combined naphtha is prepared by combining a portion of the
hydrcarcked naphtha with a portion of the reformed naphtha. For
example, the combined naphtha is suitable for use as a fuel or fuel
blendstock, such as gasoline or a gasoline blend stock. In
embodiments, the combined naphtha has an octane of greater than 90.
Exemplary combined naphthas have an octane of greater than 91, or
greater than 92, or greater than 93, or greater than 94, or even
greater than 95.
[0073] In embodiments, the integrated process for producing high
octane naphtha comprises: (a) isolating a hydrocracked naphtha from
a hydrocracking reaction zone effluent; (b) providing a first
portion of the hydrocracked naphtha to a reforming reaction zone
containing a reforming catalyst that comprises a silicate having a
silica to alumina molar ratio of at least 200, and a crystallite
size of less than 10 microns; (c) contacting the first portion of
the hydrocracked naphtha with the reforming catalyst at reforming
reaction conditions and producing a hydrogen-rich stream and a
reformed naphtha; (d) passing the hydrogen-rich stream to the
hydrocracking reaction zone; and (e) combining the reformed naphtha
with a second portion of the hydrocracked naphtha to form a
combined naphtha having an octane of greater than 90. In some such
embodiments, a portion of the hydrocracked naphtha is provided to
the reforming reaction zone; the remainder of the hydrocracked
naphtha is combined with the reformed naphtha to form the combined
naphtha.
[0074] At least a portion of the hydrogen that is isolated from the
reforming reaction zone is passed as at least a portion of the
hydrogen feed to the hydrocracking reaction zone. The hydrogen-rich
stream may be isolated from the liquid products recovered from the
reforming reaction zone in a high pressure separator or other flash
zone. Any C.sub.4-- hydrocarbons in the effluent from the reforming
reaction zone may also be isolated in a flash zone, either along
with the hydrogen or in a subsequent flash zone. Depending on the
type of feed to the reforming reaction zone, a stream having a
boiling point that is relatively higher than that of the final
reformate may further be isolated from the reforming reaction zone
effluent.
[0075] Reference is now made to embodiments of the invention
illustrated in FIG. 1. The integrated process includes a
hydrocracking reaction zone and a reforming reaction zone,
operating in combination to improve operational efficiency and
product quality. In the integrated process, a hydrocarbonaceous
feedstock 12 is supplied to a first hydrocracking reaction zone 10.
Separating at least a portion of the hydrocracking reaction zone
effluent 16 yields at least recycle hydrogen 22 and naphtha 26. The
naphtha is passed to reforming reaction zone 40 for increasing the
octane of the naphtha and for producing reformer hydrogen 42, which
is used as one of the sources of hydrogen feed to the hydrocracking
reaction zone. Reformed naphtha 44 having increased octane is
available, for example, as a fuel or fuel blendstock, a
petrochemical feedstock or a refinery feedstock.
[0076] A detailed description of the present invention is made with
reference to specific embodiments thereof as illustrated in the
appended drawings. The drawings depict only typical embodiments of
the invention and therefore are not to be considered to be limiting
of its scope.
[0077] In the embodiment illustrated in FIG. 1, a hydrocarbonaceous
feedstock 112 boiling in a temperature range of above about
450.degree. F. (232.degree. C.) is passed to a hydrocracking
reaction zone 110 and is contacted with a hydrocracking catalyst in
the presence of hydrogen. The reaction zone 110 may contain one or
more beds of the same or different catalyst. Process conditions in
the hydrocracking reaction zone include a temperature from about
450.degree. F. to about 900.degree. F., a pressure from about 500
psig to about 5000 psig, a liquid feed rate of from about 0.1 to
about 15 hr.sup.-1, and a hydrogen circulation rate from about 500
to about 5,000 standard cubic feet per barrel. Hydrogen passed to
the hydrocracking reaction zone 110 is a combination of fresh
hydrogen feed 114, recycle hydrogen 121 and reformer hydrogen
142.
[0078] Hydrocracking reaction zone effluent 116 is passed to
separation zone 120 for isolation of hydrocracked naphtha 123. In
embodiments, additional streams may be produced during the
separation process, including recycle hydrogen 122, one or more
light distillates 123, one or more heavy distillates 126 and a
bottoms stream 127. In embodiments, the one or more light
distillates include C.sub.4- hydrocarbons. In embodiments, the one
or more heavy distillates include C.sub.9+ hydrocarbons. Exemplary
heavy distillates include C.sub.10+ hydrocarbons or C.sub.11+
hydrocarbons, or C.sub.12+ hydrocarbons.
[0079] Isolation of the various fractions from the hydrocracking
reaction zone effluent generally takes place in one or more single
and/or multiple stage fractional distillation units. In
embodiments, isolation of the hydrocracked naphtha and production
of the additional streams occur in a single separation zone using a
fractionator, such as a multiple stage distillation column. In
other embodiments, this separation is done in sequential zones,
with the hydrogen, and optionally one or more light distillates
being separated in one or more preliminary separation zones, for
example in single stage flash separation zones, prior to the
isolation of the hydrocracked naphtha 123, the one or more heavy
distillates 126 and the bottoms stream 127.
[0080] In some situations, at least a portion of the bottoms stream
127 is recovered as heavy product 128. In embodiments, at least 10
wt. % of the bottoms stream is recovered as heavy product 128. In
an exemplary process, at least 50 wt. % of the bottoms stream is
recovered as heavy product 128. In an exemplary process, 100 wt. %
of the bottoms stream is recovered as heavy product 128. Depending
on the type of hydrocarbonaceous feedstock and the hydrocracking
reaction conditions in a particular application, bottoms stream 127
is suitable as a lubricant base stock or a similar product or as a
feedstock for additional processing, using, for example one or more
of hydroisomerization and hydrotreating and hydrofinishing to
prepare the lubricant oil base stock.
[0081] In some situations, at least a portion of the bottoms stream
127 is passed as recycle 129 to hydrocracking reaction zone 110. In
embodiments, at least 10 wt. % of the bottoms stream 127 is passed
as recycle 129 to the hydrocracking reaction zone. In an exemplary
process, at least 50 wt. % of the bottoms stream 127 is passed as
recycle 129 to the hydrocracking reaction zone. In an exemplary
process, 100 wt. % of the bottoms stream 127 is passed as recycle
129 to the hydrocracking reaction zone.
[0082] In the process, hydrocracked naphtha 123 is provided, with
additional heating as needed to raise the temperature to reforming
temperature, to reforming reaction zone 140 for contacting at
reforming reaction conditions over a catalyst that includes a
silicate having a silica to alumina molar ratio of at least 200 and
a crystallite size of less than 10 microns. In embodiments, the
silicate further has an alkali content of less than 5000 ppm. In
general, reformer hydrogen 142, C.sub.4- hydrocarbons 146 and
reformed naphtha 144 are recovered during reforming of the
hydrocracked naphtha 123 and any subsequent fractional separation
process. In embodiments, reformed naphtha 144 has an octane (RON)
of greater than 90. An exemplary reformed naphtha has an octane of
greater than 92 or greater than 95 or even greater than 98. The
reformed naphtha can be used as a fuel such as gasoline, diesel, or
jet fuel depending on the desired application. The reformed naphtha
can also, or in the alternative, be a component in a blended fuel
stock.
[0083] In embodiments, at least a portion of hydrocracked naphtha
123 is combined with at least a portion of reformed naphtha 144 to
form combined naphtha 146. The fraction of hydrocracked naphtha 123
that bypasses reforming reaction zone 140 can cover a wide range,
from as low as 0 wt. % to as high as 95 wt. % of the hydrocracked
naphtha 123.
[0084] In addition, reformer hydrogen 142, a hydrogen-rich stream
containing greater than 95 vol. %, that is produced during the
reforming reaction is recycled to the hydrocracking reaction zone
110. The generation of hydrogen by the process of the invention
provides an economic benefit by minimizing the additional hydrogen
needed for the hydrocracking reaction zone.
[0085] In the embodiment illustrated in FIG. 2, a hydrocarbonaceous
feedstock 212 boiling in a temperature range of above about
450.degree. F. (232.degree. C.) is passed to a first hydrocracking
reaction zone 210 and is contacted with a hydrocracking catalyst in
the presence of hydrogen. The reaction zone 210 may contain one or
more beds of the same or different catalyst. Process conditions in
the first hydrocracking reaction zone include a temperature from
about 450.degree. F. to about 900.degree. F., a pressure from about
500 psig to about 5000 psig, a liquid feed rate from about 0.1 to
about 15 hr.sup.-1, and a hydrogen circulation rate from about 500
to about 5,000 standard cubic feet per barrel. Hydrogen passed to
the hydrocracking reaction zone 210 is a combination of fresh
hydrogen feed 214, recycle hydrogen 222 and reformer hydrogen
242.
[0086] First zone effluent 216 is passed to separation zone 220 for
isolation of hydrocracked naphtha 225. In embodiments, additional
streams may be produced during the separation process, including
recycle hydrogen 222, one or more light distillates 224, one or
more heavy distillates 228 and a bottoms stream 229. In
embodiments, the one or more light distillates include C.sub.4-
hydrocarbons. In embodiments, the one or more heavy distillates
include C.sub.9+ hydrocarbons. Exemplary heavy distillates include
C.sub.10+ hydrocarbons or C.sub.11+ hydrocarbons, or C.sub.12+
hydrocarbons.
[0087] Isolation of the various fractions from the hydrocracking
reaction zone effluent generally takes place in one or more single
and/or multiple stage fractional distillation units. In
embodiments, isolation of the hydrocracked naphtha and production
of the additional streams occur in a single separation zone using a
fractionator, such as a multiple stage distillation column. In
other embodiments, this separation is done in sequential zones,
with the hydrogen, and optionally one or more light distillates
being separated in one or more preliminary separation zones, for
example in single stage flash separation zones, prior to the
isolation of the hydrocracked naphtha 225, the one or more heavy
distillates 228 and the bottoms stream 229.
[0088] At least a portion of the bottoms stream 229 is passed to a
second hydrocracking reaction zone 230 for additional hydrocracking
The second reaction zone 230 may contain one or more beds of the
same or different catalyst. Furthermore, the catalyst(s) in the
second reaction zone 230 may be the same as or different from the
catalyst(s) in the first reaction zone 210. In embodiments, at
least a portion of second zone effluent 232 is returned as
hydrocracked recycle 234 to separation zone 220. Depending on the
particular application, from as little as 0 wt. % to as much as 100
wt. % of second zone effluent 232 is recycled; the remaining
bottoms product 236 is recovered for use elsewhere.
[0089] In the process, hydrocracked naphtha 225 is passed, with
additional heating as needed to raise the temperature to reforming
temperature, to reforming reaction zone 240 for contacting at
reforming reaction conditions over a catalyst comprising a silicate
having a silica to alumina ratio of at least about 40:1. Reformed
naphtha 244 that is produced by the reforming reactions in zone 240
has an octane (RON) of greater than 90. An exemplary reformed
naphtha has an octane of greater than 92 or greater than 95 or even
greater than 98. The reformed naphtha can be used as a fuel such as
gasoline, diesel, or jet fuel depending on the desired application.
The reformed naphtha can be a component in a blended fuel
stock.
[0090] Notwithstanding that the present invention has been
described above in terms of alternative embodiments, it is
anticipated that still other alterations, modifications and
applications will become apparent to those skilled in the art after
having read this disclosure. It is therefore intended that such
disclosure be considered illustrative and not limiting, and that
the appended claims be interpreted to include all such
applications, alterations, modifications and embodiments as fall
within the true spirit and scope of the invention.
* * * * *