U.S. patent application number 13/905230 was filed with the patent office on 2013-10-03 for catalytic processes and systems for base oil production from heavy feedstock.
This patent application is currently assigned to Chevron U.S.A. Inc.. The applicant listed for this patent is Kamala Raghunathan Krishna, Guan-Dao Lei. Invention is credited to Kamala Raghunathan Krishna, Guan-Dao Lei.
Application Number | 20130260985 13/905230 |
Document ID | / |
Family ID | 45351522 |
Filed Date | 2013-10-03 |
United States Patent
Application |
20130260985 |
Kind Code |
A1 |
Krishna; Kamala Raghunathan ;
et al. |
October 3, 2013 |
CATALYTIC PROCESSES AND SYSTEMS FOR BASE OIL PRODUCTION FROM HEAVY
FEEDSTOCK
Abstract
A catalyst system is provided for dewaxing a heavy hydrocarbon
feedstock to form a lubricant base oil. A layered catalyst system
of the present invention may comprise a first hydroisomerization
dewaxing catalyst disposed upstream from a second
hydroisomerization dewaxing catalyst. Each of the first and second
hydroisomerization dewaxing catalysts may be selective for the
isomerization of n-paraffins. The first hydroisomerization catalyst
has a first level of selectivity for the isomerization of
n-paraffins, the second hydroisomerization dewaxing catalyst has a
second level of selectivity for the isomerization of n-paraffins,
and a layered catalyst system comprising the first and second
hydroisomerization dewaxing catalysts has a third level of
selectivity for the isomerization of n-paraffins. The third level
of selectivity may be higher than each of the first level of
selectivity and the second level of selectivity.
Inventors: |
Krishna; Kamala Raghunathan;
(Danville, CA) ; Lei; Guan-Dao; (Walnut Creek,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Krishna; Kamala Raghunathan
Lei; Guan-Dao |
Danville
Walnut Creek |
CA
CA |
US
US |
|
|
Assignee: |
Chevron U.S.A. Inc.
San Ramon
CA
|
Family ID: |
45351522 |
Appl. No.: |
13/905230 |
Filed: |
May 30, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13159665 |
Jun 14, 2011 |
8475648 |
|
|
13905230 |
|
|
|
|
Current U.S.
Class: |
502/74 |
Current CPC
Class: |
B01J 37/0201 20130101;
C10G 45/64 20130101; C10G 65/043 20130101; C10G 2300/1022 20130101;
B01J 29/74 20130101; C10G 2300/4025 20130101; B01J 2229/42
20130101; C10G 2300/304 20130101; B01J 23/58 20130101; B01J 29/70
20130101; C10G 2300/301 20130101; B01J 37/0244 20130101; C10G
2400/10 20130101 |
Class at
Publication: |
502/74 |
International
Class: |
B01J 29/74 20060101
B01J029/74 |
Claims
1. A layered catalyst, comprising: a first layer comprising a first
hydroisomerization catalyst; and a second layer comprising a second
hydroisomerization catalyst, wherein each of the first
hydroisomerization catalyst and the second hydroisomerization
catalyst comprises a 1-D, 10-ring molecular sieve and a Group VIII
metal, wherein: the first hydroisomerization catalyst is disposed
upstream from the second hydroisomerization catalyst, the first
hydroisomerization catalyst has a first level of selectivity for
the isomerization of n-paraffins, the second hydroisomerization
catalyst has a second level of selectivity for the isomerization of
n-paraffins, the layered catalyst has a third level of selectivity
for the isomerization of n-paraffins, and wherein the third level
of selectivity is higher than each of the first level of
selectivity and the second level of selectivity, and the first
level of selectivity is at least substantially the same as the
second level of selectivity.
2. The layered catalyst according to claim 1, wherein: the first
hydroisomerization catalyst has a higher concentration of the
molecular sieve than the second hydroisomerization catalyst, the
first hydroisomerization catalyst has a higher concentration of the
Group VIII metal than the second hydroisomerization catalyst, each
of the first hydroisomerization catalyst and the second
hydroisomerization catalyst further comprises a metal modifier
selected from the group consisting of Mg, Ca, Sr, Ba, K, La, Pr,
Nd, Cr, and combinations thereof, and wherein the first
hydroisomerization catalyst and the second hydroisomerization
catalyst are disposed within a single reactor.
3. The layered catalyst according to claim 1, wherein: the
molecular sieve of each of the first hydroisomerization catalyst
and the second hydroisomerization catalyst comprises zeolite
SSZ-32, the Group VIII metal of each of the first
hydroisomerization catalyst and the second hydroisomerization
catalyst comprises Pt, and wherein the ratio of the volume of the
first hydroisomerization catalyst to the volume of the second
hydroisomerization catalyst is in the range from about 3:2 to about
2:3.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of co-pending
application Ser. No. 13/159,665, filed on Jun. 14, 2011 and claims
priority therefrom.
FIELD OF THE INVENTION
[0002] This invention relates to catalyst systems for dewaxing
hydrocarbon feedstocks.
BACKGROUND OF THE INVENTION
[0003] High quality lubricating oils are critical for the operation
of modern machinery and motor vehicles. However, current crude oil
supplies are inadequate to meet present demands for such
lubricants. Therefore, it is necessary to upgrade crude oil
fractions otherwise unsuitable for lubricant manufacture. As an
example, high-quality lubricating oils must often be produced from
waxy feeds. Numerous processes have been proposed for producing
lubricating base oils by upgrading ordinary and low quality
feedstocks.
[0004] Hydrocarbon feedstocks may be catalytically dewaxed by
hydrocracking or hydroisomerization. Hydrocracking generally leads
to a loss in yield due to the production of lower molecular weight
hydrocarbons, such as middle distillates and even lighter
C.sub.4-products, whereas hydroisomerization generally provides
higher yields by minimizing cracking.
[0005] U.S. Pat. No. 7,384,538 discloses hydroisomerization of waxy
feed for base oil production in an isomerization zone comprising a
catalyst bed having at least two isomerization catalysts, wherein a
first catalyst has a channel diameter of at least 6.2 .ANG., and a
second catalyst has a channel diameter not more than 5.8 .ANG..
U.S. Patent Application Publication No. 2008/0083657 discloses
dewaxing a hydrocarbon feed with a metal-modified small crystallite
MTT framework molecular sieve. U.S. Patent Application Publication
No. 2009/0166252 discloses lube basestock production using two
isomerization catalysts, wherein a first catalyst has a Constraint
Index (CI) of not more than 2, and a second catalyst has a CI
greater than 2.
[0006] Apart from product yield, another important factor in the
catalytic production of base oil is the minimization of catalyst
aging. In this regard, U.S. Pat. No. 5,951,848 discloses the use of
a two catalyst system comprising a hydrotreating catalyst and a
dewaxing catalyst. The aging of the dewaxing catalyst may be slowed
by the presence of the hydrotreating catalyst layer.
[0007] U.S. Pat. Nos. 6,468,417 and 6,468,418 disclose the
production of lube oil having a reduced tendency to form a haze by
a process including contacting a dewaxed lube stock or base oil
feed with a solid sorbent to produce a dehazed base oil having a
reduced cloud point relative to that of the dewaxed lube stock or
base oil feed.
[0008] There is a continuing need for improved dewaxing processes
and catalyst systems showing increased isomerization selectivity
and conversion of waxy hydrocarbon feedstocks for the production of
valuable Group II and Group III base oils.
SUMMARY OF THE INVENTION
[0009] This invention relates to processes for efficiently
converting wax-containing hydrocarbon feedstocks into high-grade
products, including lubricant base oils having a low pour point, a
low cloud point, a low pour-cloud spread, and a high viscosity
index (VI). Such processes employ a layered catalyst system
comprising a plurality of hydroisomerization dewaxing catalysts.
Hydroisomerization converts aliphatic, unbranched paraffinic
hydrocarbons (n-paraffins) to isoparaffins and cyclic species,
thereby decreasing the pour point and cloud point of the base oil
product as compared with the feedstock. In an embodiment, a layered
catalyst system of the present invention may further comprise a
hydrotreating catalyst as a guard layer, whereby "aging" of the
hydroisomerization catalysts is decelerated, and base oil product
yield can be maintained for longer periods of time, as compared
with conventional processes, at a temperature in the range from
about 450.degree. F. to about 725.degree. F. (232.degree. C. to
385.degree. C.).
[0010] According to one aspect of the present invention there is
provided a process for catalytically dewaxing a waxy hydrocarbon
feedstock comprising contacting the hydrocarbon feedstock in a
first hydroisomerization zone under first hydroisomerization
dewaxing conditions with a first hydroisomerization catalyst to
provide a first isomerization stream, and contacting at least a
portion of the first isomerization stream in a second
hydroisomerization zone under second hydroisomerization dewaxing
conditions with a second hydroisomerization catalyst to provide a
second isomerization stream. Each of the first hydroisomerization
catalyst and the second hydroisomerization catalyst may comprise a
molecular sieve and a Group VIII metal. Each of the first
hydroisomerization catalyst and the second hydroisomerization
catalyst may be selective for isomerization of n-paraffins in the
feedstock. The first hydroisomerization zone and the second
hydroisomerization zone may be disposed within the same reactor.
Each of the first hydroisomerization catalyst and the second
hydroisomerization catalyst may be doped with a metal modifier
selected from the group consisting of Mg, Ca, Sr, Ba, K, La, Pr,
Nd, Cr, and combinations thereof.
[0011] In an embodiment the present invention provides a process
for catalytically dewaxing a heavy hydrocarbon feedstock comprising
contacting the hydrocarbon feedstock in a first hydroisomerization
zone under first hydroisomerization dewaxing conditions with a
first hydroisomerization catalyst to provide a first isomerization
stream, contacting at least a portion of the first isomerization
stream in a second hydroisomerization zone under second
hydroisomerization dewaxing conditions with a second
hydroisomerization catalyst to provide a second isomerization
stream, and contacting the second isomerization stream with a
hydrofinishing catalyst to provide a base oil product having a pour
point of not more than about -12.degree. C. and a pour-cloud spread
of not more than about 5.degree. C. Each of the first
hydroisomerization catalyst and the second hydroisomerization
catalyst may comprise a 1-D, 10-ring molecular sieve and a Group
VIII metal. Each of the first hydroisomerization catalyst and the
second hydroisomerization catalyst may be doped with a metal
modifier selected from the group consisting of Mg, Ca, Sr, Ba, K,
La, Pr, Nd, Cr, and combinations thereof. The first and second
hydroisomerization catalysts may be disposed in the same
reactor.
[0012] In another embodiment, the present invention provides a
layered catalyst system comprising a first hydroisomerization zone
comprising a first hydroisomerization catalyst, and a second
hydroisomerization zone comprising a second hydroisomerization
catalyst. Each of the first hydroisomerization catalyst and the
second hydroisomerization catalyst may comprise a 1-D, 10-ring
molecular sieve and a Group VIII metal. The first
hydroisomerization catalyst has a first level of selectivity for
the isomerization of n-paraffins, the second hydroisomerization
catalyst has a second level of selectivity for the isomerization of
n-paraffins, the layered catalyst system has a third level of
selectivity for the isomerization of n-paraffins. The third level
of selectivity may be higher than each of the first level of
selectivity and the second level of selectivity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 schematically represents a system for hydrocarbon
dewaxing processes, according to an embodiment of the present
invention;
[0014] FIG. 2A-B each schematically represents a catalytic dewaxing
system having a single dewaxing catalyst;
[0015] FIG. 2C schematically represents a layered catalytic
dewaxing system, according to an embodiment of the present
invention; and
[0016] FIG. 3 shows the yield of 800.degree. F.+ lube oil versus
cloud point for individual dewaxing catalysts and a layered
dewaxing catalyst system, according to an embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The present invention provides a hydrocarbon dewaxing
process which involves contacting a hydrocarbon feedstock with a
layered catalyst system comprising a first hydroisomerization
catalyst and a second hydroisomerization catalyst. In an
embodiment, the present invention also provides a catalyst system
for dewaxing a hydrocarbon feedstock, wherein the first
hydroisomerization catalyst may be upstream from the second
hydroisomerization catalyst.
[0018] In an embodiment, the first hydroisomerization catalyst may
be in a first hydroisomerization layer or zone of the catalyst
system, and the second hydroisomerization catalyst may be in a
second hydroisomerization layer or zone of the catalyst system. The
first hydroisomerization catalyst and the second hydroisomerization
catalyst may be in the same reactor. The first hydroisomerization
catalyst and the second hydroisomerization catalyst may be disposed
in separate beds in the same reactor. Alternatively, at least a
portion of the first hydroisomerization catalyst may be in the same
bed as at least a portion of the second hydroisomerization
catalyst, and/or at least a portion of the second
hydroisomerization catalyst may be in the same bed as at least a
portion of the first hydroisomerization catalyst.
[0019] Applicants have now demonstrated that layered catalyst
systems of the present invention comprising first and second
hydroisomerization catalysts with a combined volume, V, can provide
superior results, e.g., overall greater isomerization selectivity
as determined by increased yield and/or higher viscosity index (VI)
of the base oil product, as compared with the same volume (V) of
either the first hydroisomerization catalyst alone or the second
hydroisomerization catalyst alone.
[0020] In an embodiment, catalyst systems of the present invention
may further comprise a hydrotreating catalyst. The hydrotreating
catalyst may comprise, and may function as, a guard layer or guard
bed. The hydrotreating catalyst of the guard layer may be disposed
upstream from the first hydroisomerization catalyst. The
hydrotreating catalyst of the guard layer may serve to protect the
first and second hydroisomerization catalysts from contaminants in
the feedstock that could deactivate the hydroisomerization
catalysts. Thus, the presence of the guard layer can substantially
increase the longevity of the first and second hydroisomerization
catalysts. In an embodiment, the guard layer may be disposed in the
same reactor as the first and second hydroisomerization catalysts.
Accordingly, processes of the present invention may be practiced in
a single reactor.
[0021] In an embodiment, the reaction conditions for processes of
the present invention may be determined, inter alia, by the
temperature required for the first and second hydroisomerization
catalysts to achieve a target pour point of a desired base oil
product of the invention. Typically, the hydroisomerization
catalysts may have an operating temperature in the range from about
390.degree. F. to about 800.degree. F. (199.degree. C. to
427.degree. C.), and usually from about 550.degree. F. to about
750.degree. F. (288.degree. C. to 399.degree. C.). In practice, the
process temperature may depend on various other process parameters,
such as the feed composition, the feed rate, the operating
pressure, the formulation of the catalyst system, and the "age" of
the hydroisomerization catalysts.
Definitions
[0022] The following terms used herein have the meanings as defined
herein below, unless otherwise indicated.
[0023] The term "hydrotreating" refers to processes or steps
performed in the presence of hydrogen for the hydrodesulfurization,
hydrodenitrogenation, hydrodemetallation, and/or
hydrodearomatization of components (e.g., impurities) of a
hydrocarbon feedstock, and/or for the hydrogenation of unsaturated
compounds in the feedstock. Depending on the type of hydrotreating
and the reaction conditions, products of hydrotreating processes
may have improved viscosities, viscosity indices, saturates
content, low temperature properties, volatilities and
depolarization, for example.
[0024] The terms "guard layer" and "guard bed" may be used herein
synonymously and interchangeably to refer to a hydrotreating
catalyst or hydrotreating catalyst layer. The guard layer may be a
component of a catalyst system for hydrocarbon dewaxing, and may be
disposed upstream from at least one hydroisomerization
catalyst.
[0025] As used herein the term "molecular sieve" refers to a
crystalline material containing pores, cavities, or interstitial
spaces of a uniform size in which molecules small enough to pass
through the pores, cavities, or interstitial spaces are adsorbed
while larger molecules are not. Examples of molecular sieves
include zeolites and non-zeolite molecular sieves such as zeolite
analogs including, but not limited to, SAPOs
(silicoaluminophosphates), MeAPOs (metalloaluminophosphates),
AlPO.sub.4, and ELAPOs (nonmetal substituted aluminophosphate
families).
[0026] As used herein, the term "pour point" refers to the
temperature at which an oil will begin to flow under controlled
conditions. The pour point may be determined by, for example, ASTM
D5950.
[0027] "Target pour point" means the desired or required pour point
of a lubricant base oil product. The target pour point is generally
less than about -10.degree. C., and typically in the range from
about -10.degree. C. to -50.degree. C.
[0028] As used herein, "cloud point" refers to the temperature at
which a lube oil sample begins to develop a haze as the oil is
cooled under specified conditions. The cloud point of a lube base
oil is complementary to its pour point. Cloud point may be
determined by, for example, ASTM D5773.
[0029] The "pour point/cloud point spread," or "pour-cloud spread"
of a base oil, refers to the spread or difference between the cloud
point and the pour point, and is defined as the cloud point minus
the pour point, as measured in .degree. C. Generally, it is
desirable to minimize the spread between the pour and cloud
points.
[0030] The Periodic Table of the Elements referred to in this
disclosure is the CAS version published by the Chemical Abstract
Service in the Handbook of Chemistry and Physics, 72.sup.nd edition
(1991-1992).
[0031] "Group VIII metal" refers to elemental metal(s) selected
from Group VIII of the Periodic Table of the Elements and/or to
metal compounds comprising such metal(s).
[0032] Unless otherwise specified, the "feed rate" of a hydrocarbon
feedstock being fed to a catalytic reaction zone is expressed
herein as the volume of feed per volume of catalyst per hour, which
may be referred to as liquid hourly space velocity (LHSV) with
units of reciprocal hours (h.sup.-1).
[0033] The term "hydroisomerization" refers to a process in which
n-paraffins (n-alkanes) are isomerized to their more branched
counterparts in the presence of hydrogen over a hydroisomerization
(dewaxing) catalyst.
[0034] Unless otherwise specified, the recitation of a genus of
elements, materials, or other components from which an individual
component or mixture of components can be selected is intended to
include all possible sub-generic combinations of the listed
components and mixtures thereof. Also, "include" and its variants
are intended to be non-limiting, such that recitation of items in a
list is not to the exclusion of other like items that may also be
useful in the materials, compositions, and methods of this
invention.
[0035] Properties for the materials described herein may be
determined as follows: [0036] (a) SiO.sub.2/Al.sub.2O.sub.3 Ratio
(SAR): determined by ICP elemental analysis. A SAR of infinity
(.infin.) represents the case where there is no aluminum in the
zeolite, i.e., the mole ratio of silica to alumina is infinity. In
that case, the molecular sieve is comprised essentially of all
silica. [0037] (b) Surface area: determined by N.sub.2 adsorption
at its boiling temperature. BET surface area is calculated by the
5-point method at P/P.sub.0=0.050, 0.088, 0.125, 0.163, and 0.200.
Samples are first pre-treated at 400.degree. C. for 6 hours in the
presence of flowing, dry N.sub.2 so as to eliminate any adsorbed
volatiles like water or organics. [0038] (c) Micropore volume:
determined by N.sub.2 adsorption at its boiling temperature.
Micropore volume is calculated by the t-plot method at
P/P.sub.0=0.050, 0.088, 0.125, 0.163, and 0.200. Samples are first
pre-treated at 400.degree. C. for 6 hours in the presence of
flowing, dry N.sub.2 so as to eliminate any adsorbed volatiles like
water or organics. [0039] (d) Mesopore pore diameter: determined by
N.sub.2 adsorption at its boiling temperature. Mesopore pore
diameter is calculated from N.sub.2 isotherms by the BJH method
described in E. P. Barrett, L. G. Joyner and P. P. Halenda, "The
determination of pore volume and area distributions in porous
substances. I. Computations from nitrogen isotherms" J. Am. Chem.
Soc. 1951 73, 373-380. Samples are first pre-treated at 400.degree.
C. for 6 hours in the presence of flowing, dry N.sub.2 so as to
eliminate any adsorbed volatiles like water or organics. [0040] (e)
Total pore volume: determined by N.sub.2 adsorption at its boiling
temperature at P/P.sub.0=0.990. Samples are first pre-treated at
400.degree. C. for 6 hours in the presence of flowing, dry N.sub.2
so as to eliminate any adsorbed volatiles like water or
organics.
[0041] Where permitted, all publications, patents and patent
applications cited in this application are incorporated by
reference herein in their entirety, to the extent such disclosure
is not inconsistent with the present invention.
Hydrotreating Catalysts
[0042] In an embodiment, catalyst systems of the present invention
may include a hydrotreating catalyst, e.g., in the form of a guard
layer. Hydrotreating catalysts of the present invention may
comprise a refractory inorganic oxide support and a Group VIII
metal. The oxide support may also be referred to herein as a
binder. The support of the hydrotreating catalyst may be prepared
from or comprise alumina, silica, silica/alumina, titania,
magnesia, zirconia, and the like, or combinations thereof. The
catalyst support may comprise amorphous materials, crystalline
materials, or combinations thereof. Examples of amorphous materials
include, but are not limited to, amorphous alumina, amorphous
silica, amorphous silica-alumina, and the like.
[0043] In an embodiment, the support may comprise amorphous
alumina. When using a combination of silica and alumina, the
distribution of silica and alumina in the support may be either
homogeneous or heterogeneous. In some embodiments, the support may
consist of an alumina gel in which is dispersed the silica,
silica/alumina, or alumina base material. The support may also
contain refractory materials other than alumina or silica, such as
for example other inorganic oxides or clay particles, provided that
such materials do not adversely affect the hydrogenation activity
of the final catalyst or lead to deleterious cracking of the
feedstock.
[0044] In a sub-embodiment, silica and/or alumina will generally
comprise at least about 90 wt. % of the support of the
hydrotreating catalyst, and in some embodiments the support may be
at least substantially all silica or all alumina. Regardless of the
type of support material in the hydrotreating catalyst, the
hydrotreating catalyst used in processes and catalyst systems of
the present invention will typically have low acidity. Where
appropriate, the acidity of the support can be decreased by
treatment with alkali and/or alkaline earth metal cations.
[0045] Various crystalline and non-crystalline catalyst support
materials that may be used in practicing the present invention, as
well as the quantification of their acidity levels and methods for
neutralizing acid sites in the catalyst support, are described in
co-pending, commonly assigned U.S. Patent Application Publication
No. 2011/0079540, the disclosure of which is incorporated by
reference herein in its entirety.
[0046] The Group VIII metal component(s) of the hydrotreating
catalyst may comprise platinum, palladium, or combinations thereof.
In an embodiment, the hydrotreating catalyst comprises platinum and
palladium with a Pt:Pd ratio in the range from about 5:1 to about
1:5, typically from about 3:1 to about 1:3, and often from about
1:1 to about 1:2. The Group VIII metal content of the hydrotreating
catalyst may generally be in the range from about 0.01 wt. % to
about 5 wt. %, typically from about 0.2 wt. % to about 2 wt. %. In
an embodiment, the hydrotreating catalyst may comprise platinum at
a concentration in the range from about 0.1 to about 1.0 wt. %, and
palladium at a concentration in the range from about 0.2 to about
1.5 wt. %. In a sub-embodiment, the hydrotreating catalyst may
comprise about 0.3 wt. % platinum and about 0.6 wt. % palladium.
Hydrotreating catalysts of the present invention generally exhibit
sulfur tolerance as well as high catalytic activity.
[0047] In an embodiment, the Group VIII metal of the hydrotreating
catalyst may be dispersed on the inorganic oxide support. A number
of methods are known in the art to deposit platinum and/or
palladium metal, or compounds comprising platinum and/or palladium,
onto the support; such methods include ion exchange, impregnation,
and co-precipitation. In an embodiment, the impregnation of the
support with platinum and/or palladium metal may be performed at a
controlled pH value. The platinum and/or palladium is typically
added to the impregnating solution as a metal salt, such as a
halide salt, and/or an amine complex, and/or a salt of a mineral
acid. Ammonium salts have been found to be particularly useful in
preparing solutions for Group VIII metal impregnation. Other
examples of metal salts that may be used include nitrates,
carbonates, and bicarbonates, as well as carboxylic acid salts such
as acetates, citrates, and formates.
[0048] Optionally, the impregnated support may be allowed to stand
with the impregnating solution, e.g., for a period in the range
from about 2 to about 24 hours. Following impregnation of the oxide
support with the Group VIII metal, the impregnated support can be
dried and/or calcined. After the hydrotreating catalyst has been
dried and calcined, the prepared catalyst may be reduced with
hydrogen, as is conventional in the art, and placed into
service.
Hydroisomerization Catalysts
[0049] In an embodiment, processes of the present invention use a
layered catalyst system comprising a first hydroisomerization
catalyst and a second hydroisomerization catalyst, wherein the
first hydroisomerization catalyst may be disposed upstream from the
second hydroisomerization catalyst. In an embodiment, both of the
first and second hydroisomerization catalysts may be selective for
the isomerization of n-paraffins in the hydrocarbon feed. In an
embodiment, the first and second hydroisomerization catalysts have
different formulations. According to various embodiments of the
present invention, the first and second hydroisomerization
catalysts may have different levels of selectivity for the
isomerization of n-paraffins in the hydrocarbon feed, or the first
and second hydroisomerization catalysts may have at least
substantially the same level of selectivity for the isomerization
of n-paraffins.
[0050] Each of the first and second hydroisomerization catalysts
may comprise a molecular sieve and a Group VIII metal. In an
embodiment, the molecular sieve of each of the first
hydroisomerization catalyst and the second hydroisomerization
catalyst may comprise a 1-D, 10-ring molecular sieve. The Group
VIII metal of the first and second hydroisomerization catalysts may
comprise platinum, palladium, or a combination thereof. In an
embodiment, each of the first and second hydroisomerization
catalysts may comprise from about 0.1 to about 1.5 wt. % of the
Group VIII metal, typically from about 0.2 to about 1.0 wt. %, and
usually from about 0.325 to about 1.0 wt. % of the Group VIII
metal. In an embodiment, at least one of the first
hydroisomerization catalyst and the second hydroisomerization
catalyst may further comprise a metal modifier selected from the
group consisting of Mg, Ca, Sr, Ba, K, La, Pr, Nd, Cr, and
combinations thereof, substantially as described herein below.
[0051] Typically, each of the first and second hydroisomerization
catalysts will still further comprise a support or binder. The
support may comprise a refractory inorganic oxide.
[0052] Suitable inorganic oxide supports for the hydroisomerization
catalysts include silica, alumina, titania, magnesia, zirconia,
silica-alumina, silica-magnesia, silica-titania, and the like, and
combinations thereof. Each of the first hydroisomerization catalyst
and the second hydroisomerization catalyst may comprise from about
5 to about 95 wt. % or more of the molecular sieve component,
typically from about 15 to about 85 wt. % of the molecular sieve,
and usually from about 25 to about 75 wt. % of the molecular sieve.
Generally, it is advantageous to minimize the molecular sieve
component for economic reasons, provided that the catalyst retains
the required activity and selectivity levels. Each of the first
hydroisomerization catalyst and the second hydroisomerization
catalyst may comprise from about 0 to about 95 wt. % of the support
material, and more typically from about 5 to about 90 wt. %.
[0053] In an exemplary catalyst system for dewaxing hydrocarbon
feedstocks according to processes of the present invention, each of
the first hydroisomerization catalyst and the second
hydroisomerization catalyst may comprise a 1-D, 10-ring molecular
sieve and a Group VIII metal. The molecular sieve of at least one
of the first hydroisomerization catalyst and the second
hydroisomerization catalyst may comprise a medium pore zeolite,
e.g., a zeolite having a pore aperture in the range from about 0.39
nm to about 0.7 nm. In an embodiment, each of the first
hydroisomerization catalyst and the second hydroisomerization
catalyst may further comprise from about 0.325 wt. % to about 1 wt.
% platinum. Examples of molecular sieves that may be useful in
formulating at least one of the first and second hydroisomerization
catalysts include molecular sieves of the AEL framework type code,
such as SAPO-11, SAPO-31, SM-3, SM-6; as well as zeolite type
materials of the MTT or TON codes. Molecular sieves of the MTT code
include ZSM-23, SSZ-32, EU-13, ISI-4, and KZ-1. Molecular sieves of
the TON code that may be useful in practicing the present invention
include Theta-1, ISI-1, KZ-2, NU-10, and ZSM-22. The parameters of
MTT and TON type molecular sieves are further described in the
Atlas of Zeolite Framework Types which is published by the
International Zeolite Association (IZA). In an embodiment, at least
one of the first hydroisomerization catalyst and the second
hydroisomerization catalyst contain zeolite SSZ-32. In a
sub-embodiment, each of the first hydroisomerization catalyst and
the second hydroisomerization catalyst contain SSZ-32. Processes of
the present invention are not limited to any particular
hydroisomerization catalyst formulations.
Metal Loading of Catalysts
[0054] In an embodiment, at least one of the first
hydroisomerization catalyst and the second hydroisomerization
catalyst may further comprise one or more metal modifier(s). In a
sub-embodiment, both the first hydroisomerization catalyst and the
second hydroisomerization catalyst may each comprise a metal
modifier. Typically, the metal modifier(s) may be selected from the
group consisting of Mg, Ca, Sr, Ba, K, La, Pr, Nd, Cr, and
combinations thereof. In a sub-embodiment, the metal modifier may
comprise Mg. As a non-limiting example, the first and second
hydroisomerization catalysts may comprise a 1-D, 10-ring molecular
sieve, such as SSZ-32; a Group VIII noble metal, such as platinum;
and in some embodiments a metal modifier such as magnesium. In an
embodiment, a metal-modified catalyst of the present invention may
comprise from about 0.5 to about 3.5 wt. % of Mg or other metal
modifier(s), typically from about 0.5 to about 2.5 wt. %, and
usually from about 0.9 to about 2.5 wt. % of Mg or other metal
modifier(s).
[0055] In formulating a catalyst or catalyst system for dewaxing
processes of the present invention, a mixture of a molecular sieve
and an oxide binder may be formed into a particle or extrudate
having a wide range of physical shapes and dimensions. In an
embodiment, the extrudate or particle may be dried and calcined
prior to metal loading. Calcination may be performed at
temperatures typically in the range from about 390.degree. F. to
about 1100.degree. F. (199.degree. C. to 593.degree. C.) for
periods of time ranging from about 0.5 to about 5 hours, or more.
The calcined extrudate or formed particle may then be loaded with
at least one metal modifier selected from the group consisting of
Ca, Cr, Mg, La, Na, Pr, Sr, K, Nd, and combinations thereof. While
not being bound by theory, such metals may effectively reduce the
number of acid sites on the molecular sieve of the metal-modified
hydroisomerization catalyst, thereby increasing the catalyst's
selectivity for isomerization (versus cracking) of n-paraffins in
the feed.
[0056] The loading of modifying metal(s) on the catalyst(s) may be
accomplished by techniques known in the art, such as by
impregnation or ion exchange. Ion exchange techniques typically
involve contacting the extrudate or particle with a solution
containing a salt of the desired metal cation(s). A variety of
metal salts, such as halides, nitrates, and sulfates, may be used
in this regard. Following contact with a salt solution of the
desired metal cation(s), the extrudate or particle may be dried,
e.g., at temperatures in the range from about 150.degree. F. to
about 800.degree. F. (66.degree. C. to 427.degree. C.). The
extrudate or particle may thereafter be further loaded with a Group
VIII metal component of the catalyst.
[0057] In an embodiment, a molecular sieve or catalyst of the
invention may be co-impregnated with a modifying metal and a Group
VIII metal. After loading the Group VIII and modifying metals, the
catalyst may be calcined in air or inert gas at temperatures in the
range from about 500.degree. F. to about 900.degree. F.
(260.degree. C. to 482.degree. C.). The preparation of molecular
sieve catalysts comprising a metal modifier is disclosed in
commonly assigned U.S. Pat. No. 7,141,529 and in U.S. Patent
Application Publication No. 2008/0083657, the disclosure of each of
which is incorporated by reference herein in its entirety.
Dewaxing Catalyst Systems
[0058] According to an embodiment of the present invention, a
dewaxing catalyst system 10 for the production of base oils from a
hydrocarbon feedstock may be described with reference to FIG. 1, as
follows. Catalyst system 10 may be a layered system comprising a
plurality of hydroisomerization catalyst layers. In an embodiment,
each of the layers of hydroisomerization catalyst may have a
different formulation, activity, and/or n-paraffin isomerization
selectivity. By "n-paraffin isomerization selectivity" is meant the
propensity of a given catalyst to isomerize, as opposed to crack,
n-paraffins in the feedstock.
[0059] Catalyst system 10 may include a hydrotreating zone or guard
layer 12, a first hydroisomerization zone 14, and a second
hydroisomerization zone 16. Guard layer 12, first
hydroisomerization zone 14, and second hydroisomerization zone 16
may contain, respectively, a hydrotreating catalyst 18, a first
hydroisomerization catalyst 20, and a second hydroisomerization
catalyst 22. Guard layer 12 may be disposed upstream from first
hydroisomerization catalyst 20, and first hydroisomerization
catalyst 20 may be disposed upstream from second hydroisomerization
catalyst 22. In an embodiment as shown in FIG. 1, guard layer 12,
first hydroisomerization zone 14, and second hydroisomerization
zone 16 may be housed within a single reactor 24. Although the
invention has been described with reference to FIG. 1 as comprising
two hydroisomerization zones and a guard layer, other numbers of
zones and layers are also possible under the present invention.
[0060] A hydrocarbon feed 26 may be introduced into reactor 24 via
a first conduit 28a, while hydrogen gas may be introduced into
reactor 24 via a second conduit 28b. Within reactor 24, feed 26 may
be contacted with hydrotreating catalyst 18 in the presence of
hydrogen to provide a hydrotreated feedstock 30. Hydrotreated
feedstock 30 may be contacted with first hydroisomerization
catalyst 20 under first hydroisomerization conditions in first
hydroisomerization zone 14 to provide a first isomerization stream
32. First isomerization stream 32 may be contacted with second
hydroisomerization catalyst 22 under second hydroisomerization
conditions in second hydroisomerization zone 16 to provide a second
isomerization stream 34. Second isomerization stream 34 may be fed
to a hydrofinishing unit (not shown) to provide a suitable quality
and yield of the desired base oil product. The base oil product may
have a pour point not higher than about -9.degree. C., typically
not higher than about -12.degree. C., and usually not higher than
about -14.degree. C. The base oil product may have a cloud point
not higher than about -5.degree. C., typically not higher than
about -7.degree. C., and usually not higher than about -12.degree.
C. The base oil product may have a pour-cloud spread of not more
than about 7.degree. C., typically not more than about 5.degree.
C., and usually not more than about 3.degree. C. In an embodiment,
the base oil product having the above properties may be obtained at
a yield of at least about 89%.
[0061] In general, dewaxing catalysts having higher isomerization
selectivity are favored for lube oil production, since catalysts
with higher selectivity tend to provide higher base oil yields.
However, a longstanding but heretofore unresolved problem in the
art is the correlation between catalyst selectivity and cloud point
of the oil product, namely a higher cloud point of products
obtained using catalysts of increased selectivity. This correlation
between catalyst selectivity and cloud point is particularly
pronounced for heavy feeds. The correlation between catalyst
selectivity and cloud point can be seen, for example, in FIG. 3,
which plots cloud point versus yield for i) a first dewaxing
catalyst (A), ii) a second dewaxing catalyst (B), and iii) a
layered catalyst system (A/B) comprising the first catalyst
upstream from the second catalyst. It can be seen from FIG. 3 that
the first and second dewaxing catalysts gave similar yields at a
given cloud point, indicating similar or substantially the same
levels of isomerization selectivity for the first and second
dewaxing catalysts. Therefore, it was unexpected that the layered
catalyst system comprising a combination of the first and second
dewaxing catalysts showed substantially higher selectivity and
about a 3% increase in yield at a given cloud point, as compared
with either the first or second dewaxing catalyst alone.
[0062] In an embodiment, hydrotreating catalyst 18 may be a high
activity catalyst capable of operating effectively at a relatively
high hourly liquid space velocity (e.g., LHSV>1 h.sup.-1) and at
a temperature in the range from about 550.degree. F. to about
750.degree. F. (288.degree. C. to 399.degree. C.). The
hydrotreating catalyst (guard layer) may occupy from about 3% to
about 30% by volume of the total catalyst volume, i.e., the
hydrotreating catalyst may comprise from about 3% to about 30% of
the sum of the volume of the hydrotreating catalyst plus the volume
of the first hydroisomerization catalyst plus the volume of the
second hydroisomerization catalyst. Typically, the hydrotreating
catalyst may comprise from about 5% to about 20% of the total
catalyst volume, and usually from about 5% to about 15% of the
total catalyst volume.
[0063] In an embodiment, the ratio of the volume of the first
hydroisomerization catalyst to the volume of the second
hydroisomerization catalyst may be in the range from about 7:3 to
about 3:7, typically from about 3:2 to about 2:3, and usually from
about 5:4 to about 4:5. In a sub-embodiment, the ratio of the
volume of the first hydroisomerization catalyst to the volume of
the second hydroisomerization catalyst may be about 1:1.
Feed for Base Oil Production
[0064] The instant invention may be used to dewax a wide variety of
hydrocarbon feedstocks, including whole crude petroleum, reduced
crudes, vacuum tower residua, cycle oils, synthetic crudes, gas
oils, vacuum gas oils, foots oils, Fischer-Tropsch derived waxes,
and the like. In an embodiment, the hydrocarbon feedstocks can be
described as waxy feeds having pour points generally above about
0.degree. C., and having a tendency to solidify, precipitate, or
otherwise form solid particulates upon cooling to about 0.degree.
C. Straight chain n-paraffins, either alone or with only slightly
branched chain paraffins, having 16 or more carbon atoms may be
referred to herein as waxes. The feedstock will usually be a
C.sub.10+ feedstock generally boiling above about 350.degree. F.
(177.degree. C.).
[0065] The present invention may also be suitable for processing
waxy distillate stocks such as middle distillate stocks including
gas oils, kerosenes, and jet fuels, lubricating oil stocks, heating
oils, and other distillate fractions whose pour point and viscosity
need to be maintained within certain specification limits.
[0066] Feedstocks for processes of the present invention may
typically include olefin and naphthene components, as well as
aromatic and heterocyclic compounds, in addition to higher
molecular weight n-paraffins and slightly branched paraffins.
During processes of the present invention, the degree of cracking
of n-paraffins and slightly branched paraffins in the feed is
strictly limited so that the product yield loss is minimized,
thereby preserving the economic value of the feedstock.
[0067] Typical feedstocks include hydrotreated or hydrocracked gas
oils, hydrotreated lube oil raffinates, brightstocks, lubricating
oil stocks, synthetic oils, foots oils, Fischer-Tropsch synthesis
oils, high pour point polyolefins, normal alphaolefin waxes, slack
waxes, deoiled waxes and microcrystalline waxes. Other hydrocarbon
feedstocks suitable for use in processes of the present invention
may be selected, for example, from gas oils and vacuum gas oils;
residuum fractions from an atmospheric pressure distillation
process; solvent-deasphalted petroleum residua; shale oils, cycle
oils; animal and vegetable derived fats, oils and waxes; petroleum
and slack wax; and waxes produced in chemical plant processes.
[0068] In an embodiment, the feedstock may comprise a heavy feed.
Herein, the term "heavy feed" may be used to refer to a hydrocarbon
feedstock wherein at least about 80% of the components have a
boiling point above about 900.degree. F. (482.degree. C.). Examples
of heavy feeds suitable for practicing the present invention
include heavy neutral (600 N) and bright stock.
[0069] In an embodiment, the hydrocarbon feedstocks of the present
invention may generally have a pour point above 0.degree. C., and
in some embodiments above about 20.degree. C. In contrast, the base
oil products of processes of the present invention, resulting from
hydroisomerization dewaxing of the feedstock, generally have pour
points below 0.degree. C., typically below about -12.degree. C.,
and often below about -14.degree. C.
[0070] In an embodiment, the feedstock employed in processes of the
present invention can be a waxy feed which contains more than about
20% wax, more than about 50% wax, or even greater than about 70%
wax. More typically, the feed will contain from about 5% to about
30% wax. As used herein, the term "waxy hydrocarbon feedstocks" may
include plant waxes and animal derived waxes in addition to
petroleum derived waxes.
[0071] According to one aspect of the present invention, a wide
range of feeds may be used to produce lubricant base oils in high
yield with good performance characteristics, including low pour
point, low cloud point, low pour-cloud spread, and high viscosity
index. The quality and yield of the lube base oil product of the
instant invention may depend on a number of factors, including the
formulation of the hydroisomerization catalysts comprising the
layered catalyst systems and the configuration of the catalyst
layers of the catalyst systems.
[0072] In an embodiment, the present invention may provide base oil
production, e.g., from a heavy feed, using a layered catalyst
system. The layered catalyst system may comprise first and second
hydroisomerization catalysts, wherein the first hydroisomerization
is disposed upstream from the second hydroisomerization catalyst.
The first hydroisomerization catalyst may have a first level of
selectivity for the isomerization of n-paraffins, the second
hydroisomerization catalyst may have a second level of selectivity
for the isomerization of n-paraffins. In an embodiment, the first
and second levels of selectivity may be the same or at least
substantially the same. Applicants have now discovered that the
layered catalyst system may have a third level of selectivity for
the isomerization of n-paraffins, wherein the third level of
selectivity is higher than each of the first level of selectivity
and the second level of selectivity. Therefore, a layered catalyst
system according to the present invention may provide superior
results as compared with conventional dewaxing processes and
catalysts. As an example, FIG. 3 shows that the first and second
dewaxing catalysts alone gave similar yields at a given cloud
point, indicating similar or substantially the same levels of
isomerization selectivity for the first and second dewaxing
catalysts. Therefore, it was unexpected that the layered catalyst
system comprising a combination of the first and second dewaxing
catalysts showed substantially higher selectivity and about a 3%
increase in yield at a given pour point, as compared with either
the first or second dewaxing catalysts alone.
Dewaxing Processes
[0073] According to one embodiment of the present invention a
catalytic dewaxing process for the production of base oils from a
heavy hydrocarbon feedstock may involve introducing the feed into a
reactor containing a dewaxing catalyst system. Hydrogen gas may
also be introduced into the reactor so that the process may be
performed in the presence of hydrogen, e.g., as described herein
below with reference to the process conditions.
[0074] Within the reactor, the feed may be contacted with a
hydrotreating catalyst under hydrotreating conditions in a
hydrotreating zone or guard layer to provide a hydrotreated
feedstock. Contacting the feedstock with the hydrotreating catalyst
in the guard layer may serve to effectively hydrogenate aromatics
in the feedstock, and to remove N- and S-containing compounds from
the feed, thereby protecting the first and second
hydroisomerization catalysts of the catalyst system. By
"effectively hydrogenate aromatics" is meant that the hydrotreating
catalyst is able to decrease the aromatic content of the feedstock
by at least about 20%. The hydrotreated feedstock may generally
comprise C.sub.10+ n-paraffins and slightly branched isoparaffins,
with a wax content of typically at least about 20%.
[0075] The hydrotreated feedstock may be contacted with the first
hydroisomerization catalyst under first hydroisomerization dewaxing
conditions in a first hydroisomerization zone to provide a first
isomerization stream. Thereafter, the first isomerization stream
may be contacted with the second hydroisomerization catalyst under
second hydroisomerization dewaxing conditions in a second
hydroisomerization zone to provide a second isomerization stream.
The guard layer, the first hydroisomerization catalyst, and the
second hydroisomerization catalyst may all be disposed within a
single reactor. The hydrotreating and hydroisomerization conditions
that may be used for catalytic dewaxing processes of the present
invention are described herein below.
[0076] The second isomerization stream may be fed to a
hydrofinishing unit to provide a suitable quality and yield of the
desired base oil product. Such a hydrofinishing step, may remove
traces of any aromatics, olefins, color bodies, and the like from
the base oil product. The hydrofinishing unit may include a
hydrofinishing catalyst comprising an alumina support and a noble
metal, typically palladium, or platinum in combination with
palladium. In an embodiment, the noble metal content of the
hydrofinishing catalyst may typically be in the range from about
0.1 to about 1.0 wt. %, usually from about 0.1 to about 0.6 wt. %,
and often from about 0.2 to about 0.5 wt. %.
[0077] Each of the first hydroisomerization catalyst and the second
hydroisomerization catalyst may comprise a 1-D, 10-ring molecular
sieve and a Group VIII metal, e.g., substantially as described
herein above under "Hydroisomerization Catalysts." Each of the
first hydroisomerization catalyst and the second hydroisomerization
catalyst may be selective for the isomerization of n-paraffins in
the feedstock, such that feedstock components are preferentially
isomerized rather than cracked.
[0078] FIG. 2A schematically represents a first catalytic dewaxing
system 10A disposed in a reactor 24, wherein dewaxing system 10A
may consist essentially of a first hydroisomerization catalyst 120.
FIG. 2B schematically represents a second catalytic dewaxing system
10B disposed in a reactor 24, wherein dewaxing system 10B may
consist essentially of a second hydroisomerization catalyst 122.
First hydroisomerization catalyst 120 and second hydroisomerization
catalyst 122 may have, respectively, first and second levels of
selectivity for the isomerization of n-paraffins. In an embodiment,
the first and second levels of selectivity may be similar or at
least substantially the same. Systems 10A and 10B may provide a
dewaxed product A and a dewaxed product B, respectively, by
dewaxing a hydrocarbon feed in the presence of hydrogen, wherein
the yield of products A and B may be at least substantially the
same. The hydrocarbon feed may be a heavy feed. Optionally, systems
10A and 10B may include a guard layer.
[0079] FIG. 2C schematically represents a layered dewaxing catalyst
system 10C, according to an embodiment of the present invention.
Catalyst system 10C may comprise first hydroisomerization catalyst
120 disposed upstream from second hydroisomerization catalyst 122.
In an embodiment, catalyst system 10C has a third level of
selectivity for the isomerization of n-paraffins, wherein the third
level of selectivity is higher than each of the first level of
selectivity of catalyst 120 and the second level of selectivity of
catalyst 122. As a result, system 10C may provide a dewaxed product
C at a significantly higher yield, for a given cloud point, as
compared with the yield of either product A or product B. In an
embodiment, layered dewaxing system 10C may include a guard layer
disposed upstream from first hydroisomerization catalyst 120 (see,
for example, FIG. 1).
[0080] Thus, according to an embodiment of the present invention,
applicants have found that the combination of first and second
hydroisomerization catalysts 120 and 122 (see, e.g., FIG. 2C) can
provide superior results, as compared with the same volume of
either first hydroisomerization catalyst 120 alone or second
hydroisomerization catalyst 122 alone. Such superior results may be
manifest not only as increased product yield but also improved
product qualities.
Reaction Conditions
[0081] The conditions under which processes of the present
invention are carried out will generally include a temperature
within a range from about 390.degree. F. to about 800.degree. F.
(199.degree. C. to 427.degree. C.). In an embodiment, each of the
first and second hydroisomerization dewaxing conditions includes a
temperature in the range from about 550.degree. F. to about
700.degree. F. (288.degree. C. to 371.degree. C.). In a further
embodiment, the temperature may be in the range from about
590.degree. F. to about 675.degree. F. (310.degree. C. to
357.degree. C.). The pressure may be in the range from about 15 to
about 3000 psig (0.10 to 20.68 MPa), and typically in the range
from about 100 to about 2500 psig (0.69 to 17.24 MPa).
[0082] Typically, the feed rate to the catalyst system/reactor
during dewaxing processes of the present invention may be in the
range from about 0.1 to about 20 h.sup.-1 LHSV, and usually from
about 0.1 to about 5 h.sup.-1 LHSV. Generally, dewaxing processes
of the present invention are performed in the presence of hydrogen.
Typically, the hydrogen to hydrocarbon ratio may be in a range from
about 2000 to about 10,000 standard cubic feet H.sub.2 per barrel
hydrocarbon, and usually from about 2500 to about 5000 standard
cubic feet H.sub.2 per barrel hydrocarbon.
[0083] The above conditions may apply to the hydrotreating
conditions of the hydrotreating zone as well as to the
hydroisomerization conditions of the first and second
hydroisomerization zones (see, for example, FIG. 1). The reactor
temperature and other process parameters may vary according to
factors such as the nature of the hydrocarbon feedstock used and
the desired characteristics (e.g., pour point, cloud point, VI) and
yield of the base oil product.
[0084] The hydrotreating catalyst may be disposed upstream from the
hydroisomerization catalysts and in the same reactor as the
hydroisomerization catalysts. In an embodiment, a temperature
difference may exist between the first and second
hydroisomerization zones. For example, the first hydroisomerization
zone may be at a first temperature and the second
hydroisomerization zone may be at a second temperature, wherein the
second temperature may be from about 20.degree. F. to about
60.degree. F. higher than the first temperature, more typically
from about 30.degree. F. to about 50.degree. F. higher, and usually
from about 35.degree. F. to about 45.degree. F. higher than the
first temperature.
[0085] The effluent or stream from a catalyst system of the present
invention, e.g., the second hydroisomerization stream from the
second hydroisomerization zone, may be further treated by
hydrofinishing. Such hydrofinishing may be performed in the
presence of a hydrogenation catalyst, as is known in the art. The
hydrogenation catalyst used for hydrofinishing may comprise, for
example, platinum, palladium, or a combination thereof on an
alumina support. The hydrofinishing may be performed at a
temperature in the range from about 400.degree. F. to about
650.degree. F. (204.degree. C. to 343.degree. C.), and a pressure
in the range from about 400 psig to about 4000 psig (2.76 to 27.58
MPa). Hydrofinishing for the production of lubricating oils is
described, for example, in U.S. Pat. No. 3,852,207, the disclosure
of which is incorporated by reference herein.
Base Oil Product
[0086] In an embodiment, processes of the invention provide a high
value, high quality lubricant oil in good yield from a low value
waxy hydrocarbon feedstock. The lubricant oils of the present
invention will typically have a pour point less than about
-9.degree. C., usually less than about -12.degree. C., and often
less than about -14.degree. C., e.g., as measured by ASTM D97. In
an embodiment, the lubricant oil product may have a pour point in
the range from about -10.degree. C. to about -30.degree. C. The
products of the present invention will generally have viscosities
in the range of 3 to 30 cSt at 100.degree. C., and a VI in the
range from about 95 to about 170 as measured by ASTM D445.
[0087] As noted herein above, the dewaxed second hydroisomerization
stream (FIG. 1) may be further hydrotreated, for example, over one
or more hydrofinishing catalysts to obtain a final lubricant oil
product having the desired characteristics. As an example, at least
a portion of the second hydroisomerization stream may be
hydrofinished to remove any colored materials and/or to hydrogenate
any aromatic species in order to meet the desired lubricant oil
specifications and/or to improve the stability of the base oil
product.
[0088] The following Examples illustrate but do not limit the
present invention.
EXAMPLES
Example 1
Preparation of Dewaxing Catalysts
[0089] Hydroisomerization catalyst A was prepared as follows.
Zeolite SSZ-32 was composited with alumina to provide a mixture
containing 75 wt. % zeolite, and the mixture was extruded, dried,
and calcined. The dried and calcined extrudate was impregnated with
a solution containing both platinum and magnesium, and the
co-impregnated catalyst was then dried and calcined. The overall
platinum loading was 1 wt. %, and the magnesium loading was 0.9 wt.
%.
[0090] Hydroisomerization catalyst B was prepared generally as
described for catalyst A, except the mixture contained 65 wt. %
zeolite. The dried and calcined extrudate was co-impregnated with
platinum and magnesium to give a platinum loading of 0.325 wt. %
and a magnesium loading of 0.9 wt. %.
[0091] A layered hydroisomerization dewaxing catalyst system A/B
was prepared by combining a layer of catalyst A with an equal
volume of a layer of catalyst B, such that catalyst A was the upper
layer, i.e., catalyst A was disposed upstream from catalyst B.
Catalysts A alone, catalyst B alone, as well as catalyst system A/B
were each used for dewaxing a heavy hydrocarbon feed, as described
in Example 2.
Example 2
Comparative Catalytic Dewaxing of Heavy Feed
[0092] The layered catalyst system A/B was compared with an equal
volume of catalyst
[0093] A alone and catalyst B alone in dewaxing a waxy heavy
hydrocrackate (600 N) feed using a down-flow reactor under
isothermal conditions. A previous generation dewaxing catalyst C
(SSZ-32 loaded with 0.325 wt. % Pt and prepared without a modifier
metal, e.g., Mg) was also tested (as base case) using the same feed
and process conditions. The reactors for catalysts A and C
contained 100% catalyst A and 100% catalyst C, respectively; the
reactor for catalyst B contained 91 vol. % of catalyst B downstream
from 9 vol. % guard layer; and the reactor for catalyst system A/B
contained 45 vol. % of catalyst B downstream from 46 vol. % of
catalyst A and 9 vol. % guard layer. The guard layer in each case
comprised alumina loaded with 0.3 wt. % Pt and 0.6 wt. % Pd.
[0094] FIG. 3 shows the yield of 800.degree. F.+ lube oil versus
the cloud point obtained using the layered catalyst system A/B
(catalyst A+catalyst B) and catalysts A, B, and C alone. The
yield/cloud point data was generated by changing the operating
temperature of the dewaxing catalyst; for example, a lower cloud
point is generally achieved by increasing the catalyst temperature.
It can be seen from FIG. 3 that the layered catalyst system A/B,
unexpectedly gave an approximately 3% increase in yield as compared
with the same volume of either catalyst A alone or catalyst B
alone. This result was particularly unexpected in light of the
substantially similar selectivities shown by catalysts A and B
alone (see, e.g., FIG. 3).
[0095] Thus, according to one aspect of the present invention, a
less expensive catalyst (e.g., having a lower concentration of
molecular sieve and/or a lower concentration of Group VIII noble
metal) may be combined with a more expensive catalyst to form a
catalyst system that provides better performance at a lower cost,
as compared with the same amount of the more expensive catalyst
alone.
[0096] Numerous variations of the present invention may be possible
in light of the teachings and examples herein. It is therefore
understood that within the scope of the following claims, the
invention may be practiced otherwise than as specifically described
or exemplified herein.
* * * * *