Molecular sieve abstract
A catalyst composition containing a medium pore molecular sieve
having deposited thereon an active metal oxide and at least one
hydrogenation metal selected from the Group VIII and Group VIB metals
for use in hydrodewaxing lube oil boiling range feedstreams.
Molecular sieve claims
1. A catalyst suitable for upgrading lube oil boiling range feedstreams,
wherein said catalyst comprises: a) at least one medium pore molecular
sieve; b) at least one active metal oxide selected from the rare
earth metal oxides; and c) at least one hydrogenation metal selected
from the Group VIII and Group VIB metals.
2. The catalyst according to claim 1 wherein said medium pore molecular
sieve is selected from acidic metallosilicates and zeolites.
3. The catalyst according to claim 2 wherein said acidic metallosilicates
is a silicoaluminophosphates (SAPOs).
4. The catalyst according to claim 3 wherein said SAPO is selected
from SAPO-11 SAPO-34 and SAPO-41.
5. The catalyst according to claim 1 wherein said medium pore molecular
sieve is a zeolite.
6. The catalyst according to claim 5 wherein said zeolite is selected
from ZSM-22 ZSM-23 ZSM-35 ZSM-57 ZSM-48 and ferrierite.
7. The catalyst according to claim 6 wherein said zeolite is ZSM-48.
8. The catalyst according to claim 1 wherein said medium pore molecular
sieve is composited with a suitable porous binder or matrix material
selected from alumina, silica, titania, calcium oxide, strontium
oxide, barium oxide, carbons, zirconia, diatomaceous earth, lanthanide
oxides including cerium oxide, lanthanum oxide, neodymium oxide,
yttrium oxide, and praseodymium oxide; chromia, thorium oxide, urania,
niobia, tantala, tin oxide, zinc oxide, and aluminum phosphate in
an amount of less than about 15 parts zeolite to one part binder.
9. The catalyst according to claim 8 wherein said suitable porous
binder or matrix material is alumina.
10. The catalyst according to claim 1 wherein said active metal
oxide is selected from the rare earth metal oxides of Group IIIB
of the periodic table including yttria.
11. The catalyst according to claim 10 wherein said rare earth
metal oxide is yttria.
12. The catalyst according to claim 1 wherein said at least one
active metal oxide and said at least one hydrogenation metal are
deposited onto the medium pore molecular sieve by a method selected
from incipient wetness, ion exchange, mechanical mixing of metal
oxide precursor(s) with the medium pore molecular sieve and binder,
and any combination thereof.
13. The catalyst according to claim 12 wherein said at least one
active metal oxide is deposited onto the medium pore molecular sieve
in an amount greater than 0.1 wt. %, based on the catalyst.
14. The catalyst according to claim 13 wherein said at least one
active metal oxide is deposited onto the medium pore molecular sieve
in an amount ranging from about 0.1 to about 10 wt. %.
15. The catalyst according to claim 1 wherein said at least one
hydrogenation metal is selected from the Group VIII metals.
16. The catalyst according to claim 18 wherein said at least one
hydrogenation metal is selected from the Group VIII noble metals.
17. The catalyst according to claim 15 wherein said at least one
hydrogenation metal is selected from Pt, Pd and mixtures thereof.
18. The catalyst according to claim 17 wherein said at least one
hydrogenation metal is Pt.
19. The catalyst according to claim 1 wherein said at least one
hydrogenation metal is deposited onto the medium pore molecular
sieve in and amount ranging from between about 0.1 to about 30 wt.
%, based on catalyst.
20. The catalyst according to claim 1 wherein said at least one
hydrogenation metal is deposited onto said medium pore molecular
sieve after said at least one active metal oxide is deposited thereon.
Molecular sieve description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims benefit of U.S. Provisional Patent
Application Ser. No. 60/607808 filed Sep. 8 2004.
FIELD OF THE INVENTION
[0002] The present invention relates to a catalyst suitable for
use in dewaxing lube oil boiling range feedstreams. More particularly,
the present invention is directed at a catalyst composition containing
a medium pore molecular sieve having deposited thereon an active
metal oxide and at least one hydrogenation metal selected from the
Group VIII and Group VIB metals.
BACKGROUND OF THE INVENTION
[0003] Further, most lubricating oil feedstocks must be dewaxed
in order to produce lubricating oils which will remain fluid down
to the lowest temperature of use. Dewaxing is the process of separating
or converting hydrocarbons which solidify readily (i.e., waxes)
in petroleum fractions. The hydrodewaxing of wax and waxy feeds
boiling in the lubricating oil range and catalysts useful in such
processes is well known in the art. Generally these processes utilize
catalysts comprising a molecular sieve component and a component
selected from the Group VIII and/or Group VIB metals.
[0004] As finished oil performance requirements increase so does
the requirement for improved lube oil basestocks properties. To
address this need the search for new and different processes, catalysts
and catalyst systems that exhibit improved activity, selectivity
and/or longevity is an ongoing exercise. Thus, there currently is
a need in the art for an improved dewaxing catalyst and method of
making the dewaxing catalyst.
BRIEF DESCRIPTION OF THE FIGURES
[0005] FIG. 1 is a graph relating pour point to yield of lube oil
basestocks obtained by hydrodewaxing a 150N slack wax with a ZSM-48
catalyst according to the present invention compared a conventional
ZSM-48 based hydrodewaxing catalyst.
[0006] FIG. 2 is a graph comparing the pour point to viscosity
index of lube oil products obtained by hydrodewaxing a 150N slack
wax with a ZSM-48 catalyst according to the present invention compared
to a conventional ZSM-48 based hydrodewaxing catalyst.
[0007] FIG. 3 is a graph relating yield to time on stream at constant
pour point of for a catalyst according to the present invention.
[0008] FIG. 4 is a graph relating yield to time on stream at constant
pour point fir a conventional ZSM-48 hydrodewaxing catalyst.
SUMMARY OF THE INVENTION
[0009] The present invention is directed at a catalyst suitable
for use in upgrading feedstreams boiling in the lube oil range.
The catalyst comprises:
[0010] a) at least one medium pore molecular sieve;
[0011] b) at least one active metal oxide selected from the rare
earth metal oxides; and
[0012] c) at least one hydrogenation metal selected from the Group
VIII and Group VIB metals.
[0013] In one embodiment of the instant invention, the at least
one active metal oxide of the hydrodewaxing catalyst is selected
from the Group IIIB rare earth metal oxides.
[0014] In yet another embodiment, the rare earth metal oxide is
yttria.
[0015] In still another embodiment, the at least one hydrogenation
metal selected from the Group VIII and Group VIB metals of the hydrodewaxing
catalyst is selected from the Group VIII noble metals.
[0016] In still another embodiment, the at least one hydrogenation
metal selected from the Group VIII and Group VIB metals of the hydrodewaxing
catalyst is selected from Pt, Pd, and mixtures thereof.
[0017] In still another embodiment, the at least one Group VIII
metal is selected from Pt, Pd, and mixtures thereof.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The present invention is a catalyst suitable for use in
the upgrading of hydrocarbon feedstreams boiling in the lubricating
oil range. The hydrodewaxing catalyst comprises at least one medium
pore molecular sieve, at least one active metal oxide selected from
the rare earth metal oxides, and at least one Group VIII metal.
[0019] As stated above, the catalysts according to the present
invention comprise at least one medium pore molecular sieve. Medium
pore molecular sieves suitable for use in the present invention
can be selected from acidic metallosilicates, such as silicoaluminophophates
(SAPOs), and unidimensional 10 ring zeolites, i.e. medium pore zeolites
having unidimensional channels comprising 10 member rings. It is
preferred that the molecular sieve be a zeolite.
[0020] The silicoaluminophophates (SAPOs) useful as the at least
one molecular sieve can be any of the SAPOs known. Preferred SAPOs
include SAPO-11 SAPO-34 and SAPO-41.
[0021] The medium pore zeolites, sometimes referred to as unidimensional
10 ring zeolites, suitable for use in the dewaxing catalyst employed
herein can be any of those known. Medium pore zeolites as used herein
can be any zeolite described as a medium pore zeolite in Atlas of
Zeolite Structure Types, W. M. Maier and D. H. Olson, Butterworths.
Zeolites are porous crystalline materials and medium pore zeolites
are generally defined as those having a pore size of about 5 to
about 7 Angstroms, such that the zeolite freely sorbs molecules
such as n-hexane, 3-methylpentane, benzene and p-xylene. Another
common classification used for medium pore zeolites involves the
Constraint Index test which is described in U.S. Pat. No. 4016218
which is hereby incorporated by reference. Medium pore zeolites
typically have a Constraint Index of about 1 to about 12 based
on the zeolite alone without modifiers and prior to treatment to
adjust the diffusivity of the catalyst. Preferred unidimensional
10-ring zeolites are ZSM-22 ZSM-23 ZSM-35 ZSM-57 ZSM-48 and
ferrierite. More preferred are ZSM-22 ZSM-23 ZSM-35 ZSM-48 and
ZSM-57. The most preferred is ZSM-48. The most preferred synthesis
route to ZSM-48 is that described in U.S. Pat. No. 5075269.
[0022] The medium pore molecular sieves used in the present invention
are preferably combined with a suitable porous binder or matrix
material. Non-limiting examples of such materials include active
and inactive materials such as clays, silica, and/or metal oxides
such as alumina. Non-limiting examples of naturally occurring clays
that can be composited include clays from the montmorillonite and
kaolin families including the subbentonites, and the kaolins commonly
known as Dixie, McNamee, Georgia, and Florida clays. Others in which
the main mineral constituent is halloysite, kaolinite, dickite,
nacrite, or anauxite may also be used. The clays can be used in
the raw state as originally mixed or subjected to calcination, acid
treatment, or chemical modification prior to being combined with
the at least one molecular sieve. It is preferred that the porous
matrix or binder material comprises at least one of silica, alumina,
or a kaolin clay. It is more preferred that the binder material
comprise alumina. The amount of molecular sieve in the at least
one molecular sieve is from 10 to 100 wt. %, preferably 35 to 100
wt. %, based on the composited molecular sieve. Such molecular sieves
can be formed by methods such spray drying, extrusion and the like.
Catalysts according to the present invention may be used in the
sulfided or unsulfided form, and is preferably in the sulfided form.
[0023] Hydrodewaxing catalysts according to the present invention
also comprise at least one active metal oxide selected from the
rare earth metal oxides. As used herein, "rare earth metal
oxides" is meant to refer to those metal oxides comprising
those elements of the periodic table having atomic numbers between
57 and 71 and yttrium, which has an atomic number of 39 but behaves
similar to the rare earth metals in many applications. It is preferred
that the at least one active metal oxide be selected from those
rare earth metal oxides of Group IIIB of the periodic table including
yttrium, more preferably the at least one active metal oxide is
yttria.
[0024] The at least one active metal oxide can be incorporated
onto the above-described medium pore molecular sieve by any means
known to be effective at doing so. Non-limiting examples of suitable
incorporation means include incipient wetness, ion exchange, mechanical
mixing of metal oxide precursor(s) with molecular sieve and binder,
or a combination thereof, with the incipient wetness technique being
the preferred method.
[0025] The amount of active metal oxide incorporated, i.e. deposited,
onto the medium pore molecular sieve is greater than 0.1 wt. %,
based on the catalyst. Preferably the amount of mixed metal oxide
ranges from about 0.1 wt. % to about 10 wt. %, more preferably from
about 0.5 .wt. % to about 8 .wt. %, most preferably from about 1
wt. % to about 4 wt. %.
[0026] Hydrodewaxing catalysts according to the present invention
also include at least one hydrogenation metal selected from the
Group VIII and Group VIB metals. Thus, hydrodewaxing catalysts suitable
for use in the present invention are bifunctional. The at least
one hydrogenation metal selected from the Group VIII and Group VIB
metals functions as a metal hydrogenation component. Preferred Group
VIII metals are those selected from the Group VIII noble metals,
more preferably selected from Pt, Pd and mixtures thereof with Pt
representing the most preferred Group VIII metal. Preferred Group
VIB metals include Molybdenum and Tungsten. In a particularly preferred
embodiment, the at least one hydrogenation metal is selected from
the Group VIII metals with preferred, etc. Group VIII metals being
those described above.
[0027] The at least one hydrogenation metal can be incorporated,
i.e. deposited, onto the medium pore molecular sieve before or after,
preferably after, the at least one active metal oxide has been deposited
thereon. The at least one hydrogenation metal can also be incorporated
onto the above-described active metal oxide-containing medium pore
molecular sieve by any means known to be effective at doing so.
Non-limiting examples of suitable incorporation means include incipient
wetness, ion exchange, mechanical mixing of metal oxide precursor(s)
with molecular sieve and binder, or a combination thereof, with
the incipient wetness technique being the preferred method.
[0028] The amount of the at least one hydrogenation metal incorporated,
i.e. deposited, onto the metal oxide-containing medium pore molecular
sieve is between about 0.1 to about 30 wt. %, based on catalyst.
Preferably the amount of the at least one hydrogenation metal ranges
from about 0.2 wt. % to about 25 wt. %, more preferably from about
0.5 wt. % to about 20 wt. %, most preferably from about 0.6 to about
20 wt. %.
[0029] The catalysts of the present invention are suited for use
in upgrading hydrocarbon feedstreams boiling in the lube oil range.
They are especially suited for use in catalytically hydrodewaxing
lube oil boiling range feedstreams. The inventors hereof have found
that catalytic hydrodewaxing processes employing the present invention
provide the processes with improved yields and lube oil boiling
range products having better viscosity indexes ("VI")
when compared to processes utilizing currently available commercial
hydrodewaxing catalysts. The increase in yields, sometimes referred
to as yield credits, are on the order of 10%, based on the feed,
and the VI increase, sometimes referred to as VI credits, are on
the order of about 1-5 VI points.
[0030] When used in lubricating oil-upgrading processes, the instant
invention can be used to upgrade a variety of lube oil boiling range
feedstreams. These feedstreams are typically wax-containing feeds
that boil in the lubricating oil range, typically having a 10% distillation
point greater than 650.degree. F. (343.degree. C.), measured by
ASTM D 86 or ASTM 2887 and are derived from mineral sources, synthetic
sources, or a mixture of the two. Non-limiting examples of suitable
lubricating oil feedstreams include those derived from sources such
as oils derived from solvent refining processes such as raffinates,
partially solvent dewaxed oils, deasphalted oils, distillates, vacuum
gas oils, coker gas oils, slack waxes, foots oils and the like,
dewaxed oils, automatic transmission fluid feedstocks, and Fischer-Tropsch
waxes. Preferred lubricating oil feedstreams are those selected
from raffinates and dewaxed oils.
[0031] These feedstreams may also have high contents of nitrogen-
and sulfur-contaminants. Feeds containing up to 0.2 wt. % of nitrogen,
based on feed and up to 3.0 wt. % of sulfur can be processed utilizing
the present invention. Feeds having a high wax content typically
have high viscosity indexes of up to 200 or more. Sulfur and nitrogen
contents may be measured by standard ASTM methods D5453 and D4629
respectively.
[0032] The conditions employed by the lube oil boiling range upgrading
processes utilizing the instant invention can be any conditions
suitable for use in that process. For example, if the present invention
was utilized in a catalytic hydrodewaxing process effective catalytic
hydrodewaxing conditions as generally include temperatures of from
250.degree. C. to 400.degree. C., preferably 275.degree. C. to 350.degree.
C., pressures of from 791 to 20786 kPa (100 to 3000 psig), preferably
1480 to 17339 kPa (200 to 2500 psig), liquid hourly space velocities
of from 0.1 to 10 hr.sup.-1 preferably 0.1 to 5 hr.sup.-1 and hydrogen
treat gas rates from 45 to 1780 m.sup.3/m.sup.3 (250 to 10000 scf/B),
preferably 89 to 890 m.sup.3/m.sup.3 (500 to 5000 scf/B).
[0033] The above description is directed to preferred embodiments
of the present invention. Those skilled in the art will recognize
that other embodiments that are equally effective could be devised
for carrying out the spirit of this invention.
[0034] The following examples will illustrate the improved effectiveness
of the present invention, but is not meant to limit the present
invention in any fashion.
EXAMPLES
Example 1
Catalyst Preparation
Comparative Catalyst--Catalyst A
[0035] A base case catalyst for comparison was prepared by extruding
65 parts of ZSM-48 crystal (Si/Al2.about.200/1) with 35 parts of
pseudoboehmite alumina. After extrusion, the extrudate was dried
at 121.degree. C. in air, followed by calcination in nitrogen at
538.degree. C. to decompose the organic template in the zeolite.
After decomposition, the extrudate was exchanged with 1 N NH4NO3
nitrate to remove sodium, followed by an additional drying step
at 121.degree. C. After the second drying step, the catalyst was
calcined in air at 538.degree. C. to convert the NH4-form of the
ZSM-48 to the H-form and to remove any residual carbon remaining
on the catalyst after nitrogen decomposition. The H-form of the
extrudate was then impregnated with 0.6 wt. % Pt by incipient wetness
impregnation using platinum tetraammine nitrate and water. After
impregnation, the catalyst is dried again at 121.degree. C. to remove
excess water, followed by a mild air calcination at 360.degree.
C. to decompose the metal salt to platinum oxide.
A Catalyst According to the Present Invention--Catalyst B
[0036] A 1 wt. % yttrium containing ZSM-48 catalyst was prepared
in similar fashion to the base case catalyst described above, but
prior to the platinum tetraammine nitrate impregnation, the H-form
of the extrudate was impregnated with yttrium nitrate (1 wt. % yttrium)
using the incipient wetness technique. The yttrium containing catalyst
was then calcined in flowing air at 538.degree. C. to decompose
the yttrium nitrate to yttrium oxide. After calcination, the yttrium
containing ZSM-48 extrudate was impregnated with 0.6 wt. % Pt by
incipient wetness impregnation using platinum tetraammine nitrate
and water. After Pt impregnation, the resulting catalyst was dried
again at 121.degree. C. to remove excess water, followed by mild
air calcination at 360.degree. C. to decompose the metal salt to
platinum oxide.
Example 2
Catalyst Use
[0037] Catalyst A and B, described in Example 1 above, were separately
used to dewax a previously hydrotreated 150N slack wax having about
5 wppm sulfur, about 4 wppm nitrogen, and having a mean average
boiling point of 420.degree. C., as determined by gas chromatography.
Both Catalyst A and Catalyst B were used under identical process
conditions described below.
[0038] Catalyst A and B were used in two separate experiments each
employing the same dewaxing conditions including temperatures of
about 325.degree. C., pressures of 1000 psig (6996 kPa), liquid
hourly space velocities of 1 hr.sup.-1 and hydrogen treat gas rates
of 2500 scf/bbl (445 m.sup.3/m.sup.3). The dewaxing of the 150N
slack wax feed was carried out in a simple vertical tubular reactor,
which allowed co-feeding of the hydrocarbon feeds and hydrogen.
The results of these experiments are illustrated in FIGS. 1 2
3 and 4.
[0039] FIG. 1 illustrates that a catalyst according to the present
invention, Catalyst B, shows an unexpected improvement over a conventional
hydrodewaxing catalyst, Catalyst A. As illustrated in FIG. 1 one
of the unexpected improvements of the present invention is that,
at constant pour point of -20.degree. C., under identical hydrodewaxing
conditions, a hydrodewaxing process employing Catalyst A produces
a 49 wt. % yield, based on the feed, while a hydrodewaxing process
utilizing Catalyst B, a catalyst according to the present invention,
produces a yield of 59 wt. %, based on the feed.
[0040] FIG. 2 illustrates a further unexpected improvement of the
current invention. FIG. 2 illustrates that a hydrodewaxing process
employing the present invention produced a product having a Viscosity
Index ("VI") 2 to 5 VI points higher than the product
produced by a hydrodewaxing process utilizing Catalyst A.
[0041] FIGS. 3 and 4 when compared, illustrate another unexpected
improvement of the present invention. FIG. 3 illustrates that a
process utilizing a catalyst according to the present invention,
a catalyst such as Catalyst B, lines out after less than 5 days,
and exhibits yields (as defined as 370.degree. C.+Hi-Vac yields)
of 82% over a period from 5 to 23 days on oil at constant pour point.
FIG. 4 however, illustrates that a hydrodewaxing process using
the same hydrodewaxing conditions but utilizing Catalyst A, takes
much longer to line out. As illustrated in FIG. 4 the hydrodewaxing
process employing Catalyst A, even after 75+ days on oil has not
reached a steady state. Further this process has not attained the
high 370.degree. C.+ Hi-Vac yields of the hydrodewaxing process
employing Catalyst B. Thus, FIGS. 1 2 3 and 4 illustrate that
the present invention provides a lube oil upgrading catalyst having
an unexpectedly rapid line out time, and higher yields of a product
having a better VI than a process employing a conventional ZSM-48
based hydrodewaxing catalyst. |