U.S. patent application number 10/747152 was filed with the patent office on 2005-06-30 for hydroisomerization processes using pre-sulfided catalysts.
This patent application is currently assigned to Chevron U.S.A. Inc.. Invention is credited to Miller, Stephen J..
Application Number | 20050139513 10/747152 |
Document ID | / |
Family ID | 34700701 |
Filed Date | 2005-06-30 |
United States Patent
Application |
20050139513 |
Kind Code |
A1 |
Miller, Stephen J. |
June 30, 2005 |
Hydroisomerization processes using pre-sulfided catalysts
Abstract
The present application relates to methods for producing a
lubricant base oil from a waxy hydrocarbon feed using a
pre-sulfided shape selective, intermediate pore size, noble
metal-containing molecular sieve catalyst. According to the present
invention, a shape selective, intermediate pore size, noble
metal-containing molecular sieve catalyst is pre-sulfided to
provide a sulfided catalyst, wherein the molar ratio of sulfur to
noble metal in the sulfided catalyst is greater than one, and a
waxy hydrocarbon feed is hydroisomerized by contacting the waxy
hydrocarbon feed with the sulfided catalyst at hydroisomerization
conditions, to produce a lubricant base oil.
Inventors: |
Miller, Stephen J.; (San
Francisco, CA) |
Correspondence
Address: |
BURNS DOANE SWECKER & MATHIS L L P
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
Chevron U.S.A. Inc.
|
Family ID: |
34700701 |
Appl. No.: |
10/747152 |
Filed: |
December 30, 2003 |
Current U.S.
Class: |
208/27 ;
208/950 |
Current CPC
Class: |
C10G 2400/10 20130101;
C10G 45/64 20130101 |
Class at
Publication: |
208/027 ;
208/950 |
International
Class: |
C10G 073/38 |
Claims
What is claimed is:
1. A method for producing a lubricant base oil from a waxy
hydrocarbon feed, the method comprising: a) pre-sulfiding a shape
selective, intermediate pore size, noble metal-containing molecular
sieve catalyst to provide a sulfided catalyst, wherein the molar
ratio of sulfur to noble metal in the sulfided catalyst is greater
than one; and b) hydroisomerizing the waxy hydrocarbon feed by
contacting the waxy hydrocarbon feed with the sulfided catalyst at
hydroisomerization conditions, to produce a lubricant base oil.
2. The method of claim 1, wherein the molar ratio of sulfur to
noble metal in the sulfided catalyst prior to the step of
hydroisomerizing is at least 2:1, and wherein the molar ratio of
sulfur to noble metal in the sulfided catalyst during the step of
hydroisomerizing is at least 3:1.
3. The method of claim 1, wherein the molar ratio of sulfur to
noble metal in the sulfided catalyst is at least 3:1.
4. The method of claim 1, wherein the molar ratio of sulfur to
noble metal in the sulfided catalyst is at least 5:1.
5. The method of claim 1, wherein the waxy hydrocarbon feed is
selected from the group consisting of gas oil, lubricating oil
stock, synthetic oil, Fischer-Tropsch derived wax, oligomerized
Fischer-Tropsch derived olefins, foots oil, slack wax, de-oiled
wax, normal alpha olefin wax, microcrystalline wax, and mixtures
thereof.
6. The method of claim 5, wherein the waxy hydrocarbon feed is a
Fischer-Tropsch derived wax.
7. The method of claim 1, wherein the molecular sieve has channel
diameters in the range of from about 4.0 to 7.1 .ANG..
8. The method of claim 1, wherein the molecular sieve is
non-zeolitic.
9. The method of claim 8, wherein the catalyst is a SAPO
catalyst.
10. The method of claim 9, wherein the SAPO catalyst is selected
from the group consisting of SAPO-11, SAPO-31, and SAPO-41.
11. The method of claim 1, wherein the noble metal is selected from
the group consisting of platinum, palladium, and mixtures
thereof.
12. The method of claim 1, wherein the pre-sulfiding step comprises
contacting the catalyst with a sulfur-containing species in the
presence of hydrogen, the sulfur-containing species being selected
from the group consisting of hydrogen sulfide, carbon disulfide,
and a mercaptan.
13. The method of claim 12, wherein the waxy hydrocarbon feed
contains less than about 10 ppm sulfur.
14. The method of claim 1, wherein the waxy hydrocarbon feed is a
sulfur spiked feedstock.
15. The method of claim 1, wherein the hydroisomerization
conditions include a total pressure of between about 150 and 1,000
psig.
16. The method of claim 15, wherein the hydroisomerization
conditions include a total pressure of between about 150 and 500
psig.
17. The method of claim 16, wherein the hydroisomerization
conditions include a total pressure of between about 150 and 300
psig.
18. The method of claim 15, wherein the hydroisomerization
conditions include a total pressure of between about 500 and 1,000
psig.
19. The method of claim 1, wherein between about 40 and 95 weight
percent of the lubricant base oil has a boiling point of between
about 650 and 1400.degree. F.
20. The method of claim 1, wherein the lubricant base oil has a
viscosity index between about 140 and 190.
21. The method of claim 1, wherein the lubricant base oil has a
pour point between about -5 and -60.degree. C.
22. The method of claim 1, wherein the lubricant base oil has a
viscosity at 100.degree. C. of greater than 3 cSt.
23. The method of claim 1, further comprising solvent dewaxing at
least a portion of the lubricant base oil, thereby removing a slack
wax.
24. The method of claim 23, further comprising hydroisomerizing the
slack wax with the waxy hydrocarbon feed.
25. A process for producing a lubricant base oil comprising: a)
contacting a shape selective, intermediate pore size, noble-metal
containing molecular sieve with a sulfur-containing species to
provide a pre-sulfided catalyst, wherein the molar ratio of sulfur
to noble metal in the pre-sulfided catalyst is greater than one; b)
providing a Fischer-Tropsch waxy hydrocarbon feed; c) contacting
the Fischer-Tropsch waxy hydrocarbon feed with the pre-sulfided
catalyst to hydroisomerize the feed; and d) isolating a lubricant
base oil.
26. The process of claim 25, wherein the lubricant base oil has a
pour point between about -5 and -60.degree. C. and a viscosity
index at 100.degree. C. of greater than 3 cSt.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] The present application is related to and hereby
incorporates by reference in its entirety U.S. patent application
Ser. No. ______ (Docket No. 005950-827), entitled
"Hydroisomerization Processes Using Re-Sulfided Catalysts," which
is filed herewith.
FIELD OF THE INVENTION
[0002] The present invention relates in general to the production
of Fischer-Tropsch derived lubricant base oils. More specifically,
the present invention is directed toward using pre-sulfided, shape
selective, intermediate pore size, noble metal-containing molecular
sieve catalysts to produce lubricant base oils, having high
viscosity indexes and low pour points, in high yield.
BACKGROUND OF THE INVENTION
[0003] Refining operations that produce large quantities of
high-quality lubricant base oils are desirable. The demand placed
on refineries for producing the high-quality lubricant base oils in
the operation of modern machinery and automobiles is increasing.
Many refining processes tend to produce large quantities of lighter
grade products at the expense of producing lubricant base oil
products.
[0004] It is well known in the art to produce lubricant base oils
using hydroisomerization processes. For example, U.S. Pat. Nos.
5,135,638 and 5,082,986 disclose highly shape selective catalysts
for hydroisomerizing waxy feeds. U.S. Pat. No. 5,135,638 discloses
that low pressure hydroisomerization dewaxing and low liquid hourly
space velocity provide enhanced isomerization selectivity, which
results in more isomerization and less cracking of the feed, thus
producing an increased yield. Accordingly, U.S. Pat. No. 5,135,638
discloses that the yield of lubricant base oil products obtained
may be enhanced by lowering the pressure at which a
hydroisomerization process is carried out.
[0005] It is also well known in the art to use base metal catalysts
and noble metal catalysts in hydroisomerization processes. These
catalysts may be used on molecular sieve supports. By way of
example, U.S. Pat. No. 5,885,438 discloses a process for producing
a high viscosity index lubricant from a waxy hydrocarbon feed
comprising catalytically dewaxing waxy paraffins present in the
feed by isomerization in the presence of hydrogen and in the
presence of a low acidity large pore zeolite isomerization
catalyst. The catalysts of U.S. Pat. No. 5,885,438 comprise a noble
metal hydroisomerization catalyst, such as Pt. U.S. Pat. No.
5,885,438 further discloses that platinum or palladium catalysts
have good hydrogenation activity, but only in the absence of
sulfur.
[0006] There remains a need for effective and efficient methods for
producing high yields of high quality lubricant base oil from a
waxy hydrocarbon feed.
SUMMARY OF THE INVENTION
[0007] Embodiments of the present invention are directed toward
methods for producing high yields of lubricant base oil from a waxy
hydrocarbon feed. In one embodiment, the method comprises
pre-sulfiding a shape selective, intermediate pore size, noble
metal-containing molecular sieve catalyst to provide a sulfided
catalyst. The molar ratio of sulfur to noble metal in the sulfided
catalyst is greater than one. The waxy hydrocarbon feed is
hydroisomerized by contacting the waxy hydrocarbon feed with the
sulfided catalyst at hydroisomerization conditions, to produce a
lubricant base oil.
[0008] In another embodiment, a process for producing a lubricant
base oil comprises contacting a shape selective, intermediate pore
size, noble-metal containing molecular sieve catalyst with a
sulfur-containing species to provide a pre-sulfided catalyst. The
molar ratio of sulfur to noble metal in the pre-sulfided catalyst
is greater than one. A Fischer-Tropsch waxy hydrocarbon feed is
provided. The Fischer-Tropsch waxy hydrocarbon feed is contacted
with the pre-sulfided catalyst to hydroisomerize the feed, and a
lubricant base oil is isolated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIGS. 1-2 illustrate the effect on yield and viscosity index
of using a sulfided SAPO-11 catalyst to hydroisomerize a
Fischer-Tropsch waxy feed at 1,000 psig.
[0010] FIGS. 3-4 illustrate the effect on yield and viscosity index
of using a sulfided SAPO-11 catalyst to hydroisomerize a
Fischer-Tropsch waxy feed at different pressures.
[0011] FIGS. 5-6 illustrate the effect on yield and viscosity index
of using a sulfided zeolite catalyst to hydroisomerize a
Fischer-Tropsch waxy feed at 1,000 psig.
[0012] FIG. 7 illustrates the effect on the iso-to-normal C.sub.4
ratio of using an on-stream sulfided SAPO catalyst.
[0013] FIG. 8 illustrates the effect on the amounts of light
hydrocarbons produced using a pre-sulfided SAPO catalyst.
[0014] FIGS. 9A-C illustrate the effect on yield, viscosity index,
and temperature of using a pre-sulfided SAPO catalyst to
hydroisomerize a Fischer-Tropsch waxy feed at different
pressures.
DETAILED DESCRIPTION OF THE INVENTION
[0015] According to the method of the present invention, it has
been surprising discovered that pre-sulfiding a shape selective,
intermediate pore size, noble metal-containing molecular sieve
catalyst improves selectivity of hydroisomerization over
hydrocracking, thus increasing the yield of a lubricant base oil
produced. Accordingly, contacting a waxy hydrocarbon feed with a
pre-sulfided shape selective, intermediate pore size, noble
metal-containing molecular sieve catalyst produces a high yield of
a high quality lubricant base oil.
[0016] Catalyst Sulfiding
[0017] It has been discovered that hydroisomerization selectivity
(the preference for isomerization reactions over cracking
reactions) for shape selective, intermediate pore size, noble
metal-containing molecular sieve catalysts is improved when the
catalyst is sulfided. According to the present invention,
preferably the catalyst is sulfided prior to conducting the
hydroisomerization reaction. A noble metal is any metal that is
resistant to corrosion or oxidation. A noble-metal containing
catalyst is any catalyst containing a noble metal. Noble metals
catalysts include platinum, palladium and mixtures thereof.
[0018] According to the present invention, the shape selective,
intermediate pore size, noble metal-containing molecular sieve
catalyst for conducting the hydroisomerization process is sulfided.
The catalyst may be sulfided at various stages in the
hydroisomerization process. The catalyst may be sulfided prior to
conducting the hydroisomerization reaction. According to the
present invention, the process for sulfiding is termed catalyst
"pre-sulfiding" if performed prior to introducing the waxy feed
into the reactor for conducting the hydroisomerization process. The
process for sulfiding is termed "on-stream sulfiding" if performed
after the hydroisomerization reaction has been initiated. The
on-stream sulfiding process may be conducted concurrently with the
hydroisomerization process by using a feed for the
hydroisomerization process that comprises the required sulfur for
sulfiding. In the alternative, the on-stream sulfiding process may
be conducted by pausing the hydroisomerization reaction process,
sulfiding the catalyst, and then resuming the hydroisomerization
reaction process. If the hydroisomerization process is paused, the
sulfiding of the catalyst may be conducted by the same techniques
employed for pre-sulfiding of the catalyst. The process for
sulfiding is termed "re-sulfiding" if the catalyst that was
initially pre-sulfided or sulfided in a previous on-stream
sulfiding step is then again subjected to a sulfiding process. The
re-sulfiding may be conducted concurrently with the
hydroisomerization process or by pausing the hydroisomerization
process, as described above for on-stream sulfiding. According to
the present invention, preferably the catalyst is pre-sulfided.
[0019] According to the present invention, the sulfiding of the
shape selective, intermediate pore size, noble metal-containing
molecular sieve catalyst may be carried out by techniques known to
those of skill in the art for sulfiding catalysts. By way of
example, the catalyst may be sulfided by contacting the catalyst
with a sulfur-containing species, usually in the presence of
hydrogen. Mixtures of hydrogen and hydrogen sulfide, carbon
disulfide or a mercaptan such as butyl mercaptan are conventionally
used for sulfiding. Sulfiding may be carried out by contacting the
catalyst with hydrogen and a sulfur-containing hydrocarbon oil
(called a non-spiked feedstock) such as a sour kerosene or gas oil,
or it may be accomplished by adding active sulfur to the waxy
hydrocarbon feed (referred to as a sulfur spiked feedstock).
[0020] In particular, pre-sulfiding may be accomplished by
techniques well-known to those of skill in the art. Procedures have
been developed by those skilled in the art to pre-sulfide fresh
catalyst charges for fixed bed reactor systems in-situ at the start
of each run. These procedures normally involve a gas heat up step
and catalyst drying step in the reactor vessel, followed by
catalyst wetting/soaking with startup oil, and then subsequently
sulfiding in a step that employs either non-spiked feedstock (a
feedstock containing naturally occurring sulfur compounds) or a
sulfur spiked feedstock (a feedstock to which active sulfur
compounds are added). Alternatively, the sulfiding step may employ
H.sub.2/H.sub.2S to sulfide the catalyst in the vapor phase.
Exemplary sulfiding techniques known in the art have been discussed
by Harman Hallie at a catalyst symposium in Amsterdam, May 1982,
and published in the Dec. 20, 1982, issue of Oil and Gas Journal.
Another description appears in a paper entitled "Properties and
Application of Commercial Presulfiding Agents," by William J.
Tuzynski, presented at the 1989 NPRA Meeting.
[0021] According to embodiments of the present invention, sulfiding
the catalyst comprises the addition of at least one mole of sulfur
per mole of noble metal contained in the catalyst, preferably,
platinum and/or palladium. The noble metal is dispersed within the
shape selective, intermediate pore size, noble metal-containing
molecular sieve catalyst. It is to be understood by those skilled
in the art that the number of moles of metal in the catalyst is
calculated by computing the grams of catalyst times the weight
percent of the metal, divided by the molecular weight of the metal.
In a preferred embodiment, the molar ratio of sulfur to noble metal
is at least 3:1. In an example of this embodiment, sufficient
sulfur is added in a pre-sulfiding treatment step to result in a
molar ratio of sulfur to noble metal of at least 2:1. During the
course of the hydroisomerization process, additional sulfur is
added to the catalyst to result in a molar ratio of sulfur to noble
metal of at least 3:1. In another embodiment, the ratio is 5:1.
[0022] Generally, pre-sulfiding techniques that make use of
non-spiked feedstocks involve decomposition of sulfur compounds
into H.sub.2S, where the sulfur compounds are naturally present in
a selected startup hydrocarbon feed. The reactor temperatures in
these techniques generally range from about 300 to 350.degree. C.
(572 to 662.degree. F.). In contrast, pre-sulfiding techniques that
make use of spiked feedstocks can be carried out by injecting
active, sulfur-containing organic compounds into a selected startup
hydrocarbon feed such that the injected compounds decompose into
H.sub.2S at temperatures lower than those that would be required to
decompose naturally occurring sulfur compounds (if present).
Preferred spiking agents are dimethylsulfide and dimethyldisulfide
as these compounds allow sulfiding procedures to be accomplished at
temperatures ranging from about 250 to 275.degree. C.
[0023] Pre-sulfiding and startup procedures are tailored to
maintain the quality of the initial waxy hydrocarbon feed and
reactor temperature conditions such that the sulfiding and
hydrogenation reactions do not create deleterious temperature
conditions in the interior of catalyst pellets. Such deleterious
temperature conditions may result in carbon deposition or metal
sintering, both of which reduce catalyst activity and thus are
undesirable. The severity of the hydrogenation reactions that occur
during the initial catalyst conditioning and sulfiding period is
limited by the quality of the initial waxy hydrocarbon feed (e.g.,
the sulfur content) and reactor temperatures, which persist until
the sulfiding reactions diminish or essentially stop. Present day
state of the art techniques allow in-situ presulfiding to be
initiated at temperatures below about 200.degree. C. (392.degree.
F.) and are completed before temperatures are elevated above about
300.degree. C. (572.degree. F.).
[0024] Techniques are known for pretreating catalysts by
impregnation with a sulfur compound (e.g., a polysulfide, as
described in U.S. Pat. No. 5,786,293) before the catalysts are
charged to the reactor. This is termed ex-situ presulfiding. When
using ex-situ presulfiding, the catalyst may still need to undergo
drying, wetting, and conversion to a metal sulfide state in-situ
within the reactor during startup procedures. An economical method
for ex-situ presulfiding of fresh batches of catalyst, which are to
be added to an on-stream reactor operating at elevated temperatures
and hydrogen pressures, is disclosed in U.S. Patent Application
2002/0043483, the contents of which is hereby incorporated by
reference in its entirety.
[0025] Waxy Hydrocarbon Feeds
[0026] Feeds useful in the hydroisomerization processes according
to the present invention are waxy hydrocarbons including gas oil,
lubricating oil stock, synthetic oil, Fischer-Tropsch derived wax,
oligomerized Fischer-Tropsch derived olefins, foots oil, slack wax,
de-oiled wax, normal alpha olefin wax, microcrystalline wax, and
mixtures thereof. The preferred feeds are Fischer-Tropsch derived
wax, slack wax, de-oiled wax, normal alpha olefin wax, and
oligomerized Fischer-Tropsch derived olefins. Fischer-Tropsch
derived waxes are especially preferred feedstocks.
[0027] In some embodiments of the present invention it is desirable
to use waxy hydrocarbon feeds containing less than 10 ppm sulfur.
Accordingly, waxy hydrocarbon feeds that contain high levels of
sulfur (greater than 10 ppm) are preferably hydrotreated prior to
the hydroisomerization reaction to remove sulfur. Therefore, waxy
hydrocarbon feeds having low amounts of sulfur, preferably less
than 10 ppm sulfur, are preferred. These low sulfur feeds include
Fischer-Tropsch derived wax, oligomerized Fischer-Tropsch derived
olefins, normal alpha olefin wax, and slack wax derived from
hydroprocessed feeds.
[0028] The waxy hydrocarbon feed contains at least 10 wt % wax, and
often contains greater than 50 wt % wax, and often greater than 80
wt % wax.
[0029] Fischer-Tropsch Synthesis
[0030] Preferably, the waxy hydrocarbon feed of the present
invention is derived from a Fischer-Tropsch waxy feed.
[0031] In Fischer-Tropsch chemistry, syngas is converted to liquid
hydrocarbons by contact with a Fischer-Tropsch catalyst under
reactive conditions. Typically, methane and optionally heavier
hydrocarbons (ethane and heavier) can be sent through a
conventional syngas generator to provide synthesis gas. Generally,
synthesis gas contains hydrogen and carbon monoxide, and may
include minor amounts of carbon dioxide and/or water. The presence
of sulfur, nitrogen, halogen, selenium, phosphorus and arsenic
contaminants in the syngas is undesirable. For this reason and
depending on the quality of the syngas, it is preferred to remove
sulfur and other contaminants from the feed before performing the
Fischer-Tropsch chemistry. Means for removing these contaminants
are well known to those of skill in the art. For example, ZnO
guardbeds are preferred for removing sulfur impurities. Means for
removing other contaminants are well known to those of skill in the
art. It also may be desirable to purify the syngas prior to the
Fischer-Tropsch reactor to remove carbon dioxide produced during
the syngas reaction and any additional sulfur compounds not already
removed. This can be accomplished, for example, by contacting the
syngas with a mildly alkaline solution (e.g., aqueous potassium
carbonate) in a packed column.
[0032] In the Fischer-Tropsch process, contacting a synthesis gas
comprising a mixture of H.sub.2 and CO with a Fischer-Tropsch
catalyst under suitable temperature and pressure reactive
conditions forms liquid and gaseous hydrocarbons. The
Fischer-Tropsch reaction is typically conducted at temperatures of
about 300-700.degree. F. (149-371.degree. C.), preferably about
400-550.degree. F. (204-228.degree. C.); pressures of about 10-600
psia, (0.7-41 bars), preferably about 30-300 psia, (2-21 bars); and
catalyst space velocities of about 100-10,000 cc/g/hr, preferably
about 300-3,000 cc/g/hr. Examples of conditions for performing
Fischer-Tropsch type reactions are well known to those of skill in
the art.
[0033] The products of the Fischer-Tropsch synthesis process may
range from C.sub.1 to C.sub.200+ with a majority in the C.sub.5 to
C.sub.100+ range. The reaction can be conducted in a variety of
reactor types, such as fixed bed reactors containing one or more
catalyst beds, slurry reactors, fluidized bed reactors, or a
combination of different type reactors. Such reaction processes and
reactors are well known and documented in the literature.
[0034] The slurry Fischer-Tropsch process, which is preferred in
the practice of the invention, utilizes superior heat (and mass)
transfer characteristics for the strongly exothermic synthesis
reaction and is able to produce relatively high molecular weight,
paraffinic hydrocarbons when using a cobalt catalyst. In the slurry
process, a syngas comprising a mixture of hydrogen and carbon
monoxide is bubbled up as a third phase through a slurry which
comprises a particulate Fischer-Tropsch type hydrocarbon synthesis
catalyst dispersed and suspended in a slurry liquid comprising
hydrocarbon products of the synthesis reaction which are liquid
under the reaction conditions. The mole ratio of the hydrogen to
the carbon monoxide may broadly range from about 0.5 to about 4,
but is more typically within the range of from about 0.7 to about
2.75 and preferably from about 0.7 to about 2.5. A particularly
preferred Fischer-Tropsch process is taught in EP0609079, also
completely incorporated herein by reference for all purposes.
[0035] In general, Fischer-Tropsch catalysts contain a Group VIII
transition metal on a metal oxide support. The catalysts may also
contain a noble metal promoter(s) and/or crystalline molecular
sieves. Suitable Fischer-Tropsch catalysts comprise one or more of
Fe, Ni, Co, Ru and Re, with cobalt being preferred. A preferred
Fischer-Tropsch catalyst comprises effective amounts of cobalt and
one or more of Re, Ru, Pt, Fe, Ni, Th, Zr, Hf, U, Mg and La on a
suitable inorganic support material, preferably one which comprises
one or more refractory metal oxides. In general, the amount of
cobalt present in the catalyst is between about 1 and about 50
weight percent of the total catalyst composition. The catalysts can
also contain basic oxide promoters such as ThO.sub.2,
La.sub.2O.sub.3, MgO, and TiO.sub.2, promoters such as ZrO.sub.2,
noble metals (Pt, Pd, Ru, Rh, Os, Ir), coinage metals (Cu, Ag, Au),
and other transition metals such as Fe, Mn, Ni, and Re. Suitable
support materials include alumina, silica, magnesia and titania or
mixtures thereof. Preferred supports for cobalt containing
catalysts comprise titania. Useful catalysts and their preparation
are known and illustrated in U.S. Pat. No. 4,568,663, which is
intended to be illustrative but non-limiting relative to catalyst
selection.
[0036] Certain catalysts are known to provide chain growth
probabilities that are relatively low to moderate, and the reaction
products include a relatively high proportion of low molecular
(C.sub.2-8) weight olefins and a relatively low proportion of high
molecular weight (C.sub.30+) waxes. Certain other catalysts are
known to provide relatively high chain growth probabilities, and
the reaction products include a relatively low proportion of low
molecular (C.sub.2-8) weight olefins and a relatively high
proportion of high molecular weight (C.sub.30+) waxes. Such
catalysts are well known to those of skill in the art and can be
readily obtained and/or prepared.
[0037] The product from a Fischer-Tropsch process contains
predominantly paraffins. The products from Fischer-Tropsch
reactions generally include a light reaction product and a waxy
reaction product. The light reaction product (i.e., the condensate
fraction) includes hydrocarbons boiling below about 700.degree. F.
(e.g., tail gases through middle distillate fuels), largely in the
C.sub.5-C.sub.20 range, with decreasing amounts up to about
C.sub.30. The waxy reaction product includes hydrocarbons boiling
above about 600.degree. F. (e.g., vacuum gas oil through heavy
paraffins), largely in the C.sub.20+ range, with decreasing amounts
down to C.sub.10.
[0038] Both the light reaction product and the waxy product are
substantially paraffinic. The waxy product generally comprises
greater than 70 weight percent normal paraffins, and often greater
than 80 weight percent normal paraffins. The light reaction product
comprises paraffinic products with a significant proportion of
alcohols and olefins. In some cases, the light reaction product may
comprise as much as 50 weight percent, and even higher, alcohols
and olefins. It is the waxy reaction product (i.e., the wax
fraction) that may be used as a feedstock for the processes of the
present invention.
[0039] According to the present invention, lubricant base oils may
be prepared by hydroisomerizing waxy Fischer-Tropsch reaction
products. Other processes that may be used in preparing lubricant
base oils from waxy Fischer-Tropsch reaction products include
hydrotreating, oligomerization, solvent dewaxing, atmospheric and
vacuum distillation, hydrocracking, hydrofinishing, and other forms
of hydroprocessing.
[0040] Hydroisomerization
[0041] According to the present invention, the waxy hydrocarbon
feeds are subjected to a hydroisomerization process using sulfided
shape selective, intermediate pore size, noble metal-containing
molecular sieve catalysts. Hydroisomerization is intended to
improve the cold flow properties of a lubricant base oil by
selective addition of branching into the molecular structure.
Hydroisomerization ideally will achieve high conversion of a waxy
hydrocarbon feed to non-waxy iso-paraffins while minimizing
conversion by cracking.
[0042] According to the present invention, hydroisomerization is
conducted using a shape selective, intermediate pore size, noble
metal-containing molecular sieve catalyst. The phrase "intermediate
pore size," as used herein means an effective pore aperture in the
range of from about 4.0 to 7.1 .ANG. when the porous inorganic
oxide is in the calcined form. The shape selective intermediate
pore size molecular sieves used in the practice of the present
invention are generally 1-D 10-, 11- or 12-ring molecular sieves.
The preferred molecular sieves of the invention are of the 1-D
10-ring variety, where 10-(or 11-or 12-) ring molecular sieves have
10 (or 11 or 12) tetrahedrally-coordinated atoms (T-atoms) joined
by oxygens. In the 1-D molecular sieve, the 10-ring (or larger)
pores are parallel with each other, and do not interconnect. The
classification of intrazeolite channels as 1-D, 2-D and 3-D is set
forth by R. M. Barrer in Zeolites, Science and Technology, edited
by F. R. Rodrigues, L. D. Rollman and C. Naccache, NATO ASI Series,
1984 which classification is incorporated in its entirety by
reference (see particularly page 75).
[0043] The shape selective, intermediate pore size, noble
metal-containing molecular sieve catalysts according to the present
invention may be zeolitic molecular sieves, non-zeolitic molecular
sieves, or mixtures thereof. Preferably, shape selective,
intermediate pore size, noble metal-containing molecular sieve
catalysts are non-zeolitic.
[0044] As used herein, non-zeolitic molecular sieve refers to a
molecular sieve comprising a crystalline, three-dimensional
microporous framework structure of tetrahedrally-bound AlO.sub.2
and PO.sub.2 oxide units, and optionally one or more metals in
tetrahedral coordination with oxygen atoms. Preferably non-zeolitic
molecular sieves are characterized by a three-dimensional
microporous framework structure of AlO.sub.2, and PO.sub.2
tetrahedral oxide units with a unit empirical formula on an
anhydrous basis of:
(M.sub.xA.sub.yP.sub.z)O.sub.2
[0045] wherein:
[0046] "M" represents at least one element, other than aluminum and
phosphorous, which is capable of forming an oxide in tetrahedral
coordination with AlO.sub.2 and PO.sub.2 oxide structural units in
the crystalline molecular sieve; and
[0047] "x", "y", and "z" represent the mole fractions,
respectively, of element "M", aluminum, and phosphorus, wherein "x"
has a value equal to or greater than zero (0), and "y" and "z" each
have a value of at least 0.01.
[0048] In a preferred embodiment, metallic element "M" is selected
from the group consisting of arsenic, beryllium, boron, chromium,
cobalt, gallium, germanium, iron, lithium, magnesium, manganese,
silicon, titanium, vanadium, nickel, and zinc, more preferably
selected from the group consisting of silicon, magnesium,
manganese, zinc, and cobalt; and still more preferably silicon. As
used herein, element "M" is considered to be a component of the
non-zeolitic molecular sieve.
[0049] According to the present invention, preferred shape
selective intermediate pore size molecular sieves used for
hydroisomerization are non-zeolitic molecular sieves. Preferred
shape selective intermediate pore size non-zeolitic molecular
sieves are based upon aluminum phosphates (i.e., SAPO catalysts),
such as SAPO-11, SAPO-31, and SAPO-41. SAPO-11 and SAPO-31 are more
preferred, with SAPO-11 being even more preferred. SM-3 is a
preferred shape selective intermediate pore size SAPO, which has a
crystalline structure falling within that of the SAPO-11 molecular
sieves. The preparation of SM-3 and its unique characteristics are
described in U.S. Pat. Nos. 4,943,424 and 5,158,665.
[0050] In another embodiment of the present invention, zeolitic
molecular sieve may be used. These include ZSM-22, ZSM-23, ZSM-35,
ZSM-48, ZSM-57, SSZ-32, offretite, and ferrierite, with SSZ-32 and
ZSM-23 being preferred.
[0051] A preferred intermediate pore size molecular sieve is
characterized by selected crystallographic free diameters of the
channels, selected crystallite size (corresponding to selected
channel length), and selected acidity. Desirable crystallographic
free diameters of the channels of the molecular sieves are in the
range of from about 4.0 to 7.1 .ANG., having a maximum
crystallographic free diameter of not more than 7.1 and a minimum
crystallographic free diameter of not less than 3.9 .ANG..
Preferably the maximum crystallographic free diameter is not more
than 7.1 and the minimum crystallographic free diameter is not less
than 4.0 .ANG.. Most preferably the maximum crystallographic free
diameter is not more than 6.5 and the minimum crystallographic free
diameter is not less than 4.0 .ANG.. 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.
[0052] A particularly preferred intermediate pore size molecular
sieve, which is useful in the present process is described, for
example, in U.S. Pat. Nos. 5,135,638 and 5,282,958, the contents of
which are hereby incorporated by reference in their entirety. In
U.S. Pat. No. 5,282,958, such an intermediate pore size molecular
sieve has a crystallite size of no more than about 0.5 microns and
pores with a minimum diameter of at least about 4.8 .ANG. and with
a maximum diameter of about 7.1 .ANG.. The catalyst has sufficient
acidity so that 0.5 grams thereof when positioned in a tube reactor
converts at least 50% of hexadecane at 370.degree. C., a pressure
of 1200 psig, a hydrogen flow of 160 ml/min, and a feed rate of 1
ml/hr. The catalyst also exhibits isomerization selectivity of 40
percent or greater (isomerization selectivity is determined as
follows: 100.times.(weight percent branched C.sub.16 in
product)/(weight percent branched C.sub.16 in product+weight
percent C.sub.13- in product) when used under conditions leading to
96% conversion of normal hexadecane (n-C.sub.16) to other
species.
[0053] Such a particularly preferred molecular sieve may further be
characterized by pores or channels having a crystallographic free
diameter in the range of from about 4.0 to 7.1 .ANG., and
preferably in the range of 4.0 to 6.5 .ANG.. 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.
[0054] If the crystallographic free diameters of the channels of a
molecular sieve are unknown, the effective pore size of the
molecular sieve can be measured using standard adsorption
techniques and hydrocarbonaceous compounds of known minimum kinetic
diameters. See Breck, Zeolite Molecular Sieves, 1974 (especially
Chapter 8); Anderson et al., J. Catalysis 58, 114 (1979); and U.S.
Pat. No. 4,440,871, the pertinent portions of which are
incorporated herein by reference. In performing adsorption
measurements to determine pore size, standard techniques are used.
It is convenient to consider a particular molecule as excluded if
does not reach at least 95% of its equilibrium adsorption value on
the molecular sieve in less than about 10 minutes
(p/po=0.5;25.degree. C). Intermediate pore size molecular sieves
will typically admit molecules having kinetic diameters of 5.3 to
6.5 .ANG. with little hindrance.
[0055] Hydroisomerization catalysts useful in the present invention
comprise a catalytically active noble metal. The presence of a
catalytically active noble metal leads to product improvement,
especially viscosity index and stability. Typical catalytically
active noble metals include platinum and palladium and mixtures
thereof, with platinum preferred. If platinum and/or palladium is
used, the total amount of active noble metal is typically in the
range of 0.1 to 5 weight percent of the total catalyst, usually
from 0.1 to 2 weight percent, and not to exceed 10 weight
percent.
[0056] The refractory oxide support may be selected from those
oxide supports, which are conventionally used for catalysts,
including silica, alumina, silica-alumina, magnesia, titania and
combinations thereof.
[0057] The conditions for hydroisomerization will be tailored to
achieve a lubricant base oil with specific branching properties, as
described above, and thus will depend on the characteristics of
feed used. In general, conditions for hydroisomerization in the
present invention are mild, such that the conversion of wax to
materials boiling between about 650 and 1400.degree. F. is
maintained between 40 and 95 weight percent in producing the
lubricant base oil.
[0058] Mild hydroisomerization conditions are achieved through
operating at a lower temperature, generally between about 390 and
650.degree. F. and a liquid hourly space velocity (LHSV) generally
between about 0.5 and 20 hr.sup.-1. The pressure is typically from
about 15 to 2,500 psig, preferably from about 50 psig to 2,000
psig, more preferably from about 100 to 1,500 psig, even more
preferably about 150 psig to 1,000 psig, and even more preferably
about 250 to 600 psig. Using the sulfided, shape selective,
intermediate pore size, noble metal containing molecular sieve
catalysts, low pressure may provide enhanced isomerization
selectivity, which results in more isomerization and less cracking
of the feed, thus producing an increased yield. Exemplary processes
are described in U.S. Pat. Nos. 5,135,638, 5,246,566, and
6,337,010, the contents of which are hereby incorporated by
reference in their entirety.
[0059] In addition, using the sulfided, shape selective,
intermediate pore size, noble metal containing molecular sieve
catalysts according to the present invention, the
hydroisomerization process may be conducted at higher pressures
while maintaining acceptable yield and quality of the lubricant
base oil product. In fact, the present invention provides a
hydroisomerization process which may be conducted at relatively
higher pressures and achieve an acceptable yield of a high quality
lubricant base oil product. Conducting a hydroisomerization process
using a sulfided, shape selective, intermediate pore size, noble
metal containing molecular sieve catalyst provides an acceptable
yield of a high quality lubricant base oil even at relatively high
pressures. Although sulfiding the catalyst improves the yield of
lubricant base oil produced when conducting the hydroisomerization
reaction at both relatively high and relatively low pressures, the
effect on yield of lubricant base oil product produced may be more
pronounced when conducting the hydroisomerization at high pressure.
Since there may be difficulties in operating the hydroisomerization
process at relatively lower pressures, using the sulfided catalysts
according to the present invention surprisingly provides a process
by which the hydroisomerization may be operated at a relatively
higher pressure while achieving acceptable yield of a high quality
lubricant base oil. Accordingly, in one embodiment it is preferable
to conduct the hydroisomerization at relatively higher pressure
(i.e., between about 500 and 1,000 psig).
[0060] Hydrogen is present in the reaction zone during the
hydroisomerization process, typically in a hydrogen to feed ratio
from about 0.5 to 30 MSCF/bbl (thousand standard cubic feet per
barrel), preferably from about 1 to 10 MSCF/bbl. Hydrogen may be
separated from the product and recycled to the reaction zone.
[0061] Solvent Dewaxing
[0062] According to the present invention, at least a portion of
the lubricant base oil produced by the hydroisomerization process
may be solvent dewaxed. Solvent dewaxing techniques are known in
the art. Solvent dewaxing may be used to remove any residual waxy
molecules by dissolving the waxy components into a solvent such as
methyl ethyl ketone, methyl iso-butyl ketone, or toluene;
precipitating the waxy components; and then removing the waxy
components by filtration. Solvent dewaxing has been discussed in
"Chemical Technology of Petroleum," 3rd Edition, by William Gruse
and Donald Stevens (McGraw Hill, New York, 1960) pages 566-570. See
also U.S. Pat. Nos. 4,477,333, 3,773,650, and 3,775,288.
[0063] According to the present invention, solvent dewaxing may be
advantageously used to dewax at least a portion of the product from
the hydroisomerization process to remove any residual unconverted
waxy components following the isomerization step(s). The wax
extracted from a solvent dewaxing process (referred to as "slack
wax"), may be recycled to the hydroisomerization process of the
present invention to obtain even higher lubricant base oil
yields.
[0064] Hydrotreating and Hydrofinishing
[0065] Hydrotreating and hydrofinishing are optional processing
steps that may also be included in the processes of the present
invention. Hydrotreating may be conducted on the waxy hydrocarbon
feed prior to the hydroisomerization process. Hydrotreating refers
to a catalytic process, usually carried out in the presence of free
hydrogen, the primary purpose of which is to remove various metal
contaminants such as arsenic; heteroatoms such as sulfur and
nitrogen, and aromatic compounds from the feedstock. Generally, it
is desirable during a hydrotreating step to minimize the amount of
cracking of hydrocarbon molecules (i.e., the breaking of larger
molecules into smaller ones). During hydrotreating, unsaturated
hydrocarbons are either fully or partially hydrogenated. The waxy
hydrocarbon feed to the present process may by hydrotreated prior
to hydroisomerization.
[0066] Catalysts used in carrying out hydrotreating operations are
well known in the art. See, for example, U.S. Pat. No. 4,347,121
and 4,810,357, the contents of which are hereby incorporated by
reference in their entirety, for general descriptions of
hydrotreating and of typical catalysts used in this process.
Suitable catalysts include noble metals from Group VIIIA (according
to the 1975 rules of the International Union of Pure and Applied
Chemistry), such as platinum or palladium on an alumina or
siliceous matrix, and Group VIII and Group VIB, such as
nickel-molybdenum or nickel-tin on an alumina or siliceous matrix.
U.S. Pat. No. 3,852,207 describes a suitable noble metal catalyst
and mild conditions for carrying out the reaction. Other suitable
catalysts are described, for example, in U.S. Pat. Nos. 4,157,294
and 3,904,513. The non-noble hydrogenation metals, such as
nickel-molybdenum, are usually present in the final catalyst
composition as oxides, but may be employed in their reduced or
sulfided forms.
[0067] Preferred non-noble metal catalyst compositions contain in
excess of about 5 weight percent, preferably about 5 to 40 weight
percent, molybdenum and/or tungsten, and at least about 0.5 weight
percent, and generally about 1 to 15 weight percent, of nickel
and/or cobalt determined as the corresponding oxides. Catalysts
containing noble metals, such as platinum, contain in excess of
0.01 percent metal; in some embodiments, between about 0.1 and 1.0
weight percent metal. Combinations of noble metals may also be
used, such as mixtures of platinum and palladium.
[0068] Typical hydrotreating conditions vary over a wide range. In
general, the overall LHSV is about 0.25 to 2.0 hr.sub.-1,
preferably about 0.5 to 1.0 hr.sub.-1. Hydrogen partial pressure in
hydrotreating may be greater than about 200 psia, preferably
ranging from about 500 to 2,000 psia. Hydrogen recirculation rates
are typically greater than about 50 SCF/Bbl, and are preferably
between 1,000 and 5,000 SCF/Bbl. Temperatures in a hydrotreating
reactor may range from about 300 to 750.degree. F. (150 to
400.degree. C.), preferably ranging from about 450 to 600.degree.
F. (230 to 315.degree. C.).
[0069] Hydrofinishing is a hydrotreating process that may be
conducted as a final step on the lubricant base oil product in the
lubricant base oil manufacturing process. This final step is
intended to improve the UV stability and appearance of the product
by removing trace amounts of aromatics, olefins, color bodies, and
solvents. As used in this disclosure, the term UV stability refers
to the stability of the lubricant base oil or the finished
lubricant when exposed to UV light and oxygen. Instability is
indicated when a visible precipitate forms, usually seen as floc or
cloudiness, or a darker color developing upon exposure to
ultraviolet light and air. A general description of hydrofinishing
may be found in U.S. Pat. Nos. 3,852,207 and 4,673,487. Clay
treating to remove these impurities is an alternative final process
step.
[0070] Oligomerization
[0071] The waxy hydrocarbon feed used in the processes of the
present invention may include oligomerized Fischer-Tropsch derived
olefins. Depending on the conditions under which the
Fischer-Tropsch synthesis is carried out, the Fischer-Tropsch
condensate will contain varying amounts of olefins. Additionally,
most Fischer-Tropsch condensates will contain some alcohols, which
may be readily converted into olefins by dehydration. As already
noted, the condensate may also be olefin enriched through a
cracking operation, preferably by thermal cracking. In one
embodiment of the present invention these olefins may be
oligomerized to produce Fischer-Tropsch derived olefins. During
oligomerization the lighter olefins are not only converted into
heavier molecules, but the carbon backbone of the oligomers will
display branching at the points of molecular addition. Due to the
introduction of branching into the molecule, the pour point of the
products is reduced.
[0072] Oligomerization of olefins has been reported in the
literature, and a variety of commercial processes are available.
See, for example, U.S. Pat. Nos. 4,417,088, 4,434,308, 4,827,064,
4,827,073, and 4,990,709. Although various types of reactor
configurations may be employed, the fixed catalyst bed reactor is
commercially in use. More recently, a method of performing the
oligomerization in an ionic liquid media has been proposed. Since
oligomerization catalysts are very active and the contact between
the catalyst and the reactants is efficient, the separation of the
catalyst from the oligomerization products is facilitated.
[0073] Oligomerization reactions proceed over a wide range of
conditions. Typical temperatures for carrying out the reaction
range from about 32 to 800.degree. F. (0 to 425.degree. C.). Other
conditions include a space velocity from 0.1 to 3 hr.sup.-1 and a
pressure ranging from about 0 to 2,000 psig. Catalysts for the
oligomerization reaction may comprise virtually any acidic
material, such as for example zeolites, clays, resins, BF.sub.3
complexes, HF, H.sub.2SO.sub.4, AlCl.sub.3, ionic liquids
(preferably ionic liquids containing a Bronsted or Lewis acidic
component or a combination of Bronsted and Lewis acid components),
transition metal-based catalysts (such as Cr/SiO.sub.2),
superacids, and the like. In addition, non-acidic oligomerization
catalysts including certain organometallic or transition metal
oligomerization catalysts may be used, such as, for example,
zirconocenes.
[0074] Lubricant Base Oil Products and Properties
[0075] Lubricant base oils made by the processes of the present
invention are of high quality, as characterized by viscosity index
and pour point of the lubricant base oil. Accordingly, the
lubricant base oils have high viscosities, low pour points, and
exceptionally high VI's.
[0076] Lubricant base oils having high viscosity indexes are
desirable. Viscosity Index (VI) is an empirical, unitless number
indicating the effect of temperature change on the kinematic
viscosity of the oil. Liquids change viscosity with temperature,
becoming less viscous when heated; the higher the VI of an oil, the
lower its tendency to change viscosity with temperature. High VI
lubricants are needed wherever relatively constant viscosity is
required at widely varying temperatures. For example, in an
automobile, engine oil must flow freely enough to permit cold
starting, but must be viscous enough after warm-up to provide full
lubrication. VI may be determined as described in ASTM D 2270-93.
The lubricant base oils of the present invention have a high
viscosity index ranging from about 140 to 190.
[0077] Pour point is the temperature at which a sample of the
lubricant base oil will begin to flow under carefully controlled
conditions. Where pour point is given herein, unless stated
otherwise, it has been determined by standard analytical method
ASTM D 5950-02. The lubricant base oils according to the present
invention have excellent pour points. The pour points of the
lubricant base oils are between about -5 and -60.degree. C.
Preferably, the pour points of the lubricant base oils are less
than -9 .degree. C., more preferably .ltoreq.-15.degree. C., and
even more preferably less than -15.degree. C.
[0078] Cloud point is a measurement complementary to the pour
point, and is expressed as a temperature at which a sample of the
lubricant base oil begins to develop a haze under carefully
specified conditions. Cloud point may be determined by, for
example, ASTM D 5773-95. The lubricant base oils with optimized
branching according to the present invention have cloud points of
less than 0.degree. C.
[0079] In addition, the lubricant base oils of the present
invention typically have high oxidation stability, high UV
stability, low volatility and excellent low temperature properties.
The lubricant base oils of the present invention have a kinematic
viscosity between about 2 and 40 cSt at 100.degree. C. Preferably
the lubricant base oils of the present invention have a kinematic
viscosity greater than 2.6 cSt at 100.degree. C., more preferably
greater than 3 cSt at 100.degree. C.
[0080] The American Petroleum Institute (API) has classified base
oils according to their chemical composition. As defined by the
API, Group III oils are very high viscosity index oils (>120)
having a total sulfur content less than 300 ppm and a saturates
content of greater than or equal to 90%. API Group III oils also
are traditionally manufactured by severe hydrocracking and or wax
isomerization. Lubricant base oils of the present invention are
generally classified as API Group III base oils. When they are made
from waxy feeds with a low total sulfur content, such as a
Fischer-Tropsch feeds, the lubricant base oils will also have a
total sulfur content less than 300 ppm.
[0081] Lubricant base oils according to the present invention made
from Fischer-Tropsch waxy feeds generally have total sulfur
contents of less than about 5 ppm. Total sulfur is determined using
ultraviolet fluorescence by ASTM D 5453-00.
[0082] Blends
[0083] The lubricant base oils of the present invention may be used
alone or may be blended with additional base oils selected from the
group consisting of conventional Group I base oils, conventional
Group II base oils, conventional Group III base oils, isomerized
petroleum wax, polyalphaolefins (PAO), poly internal olefins (PIO),
diesters, polyol esters, phosphate esters, alkylated aromatics, and
mixtures thereof.
[0084] Since the lubricant base oils of the present invention have
excellent cold flow properties, high VI's, and high oxidation
stability, they are ideal blending stocks for upgrading
conventional lubricant base oils.
[0085] It is preferred that when the lubricant base oils of the
present invention are blended with one or more additional lubricant
base oils, the additional base oils be present in an amount of less
than 95 wt % of the total resultant base oil composition.
[0086] Finished Lubricants
[0087] Lubricant base oils are the most important component of
finished lubricants, generally comprising greater than 70% of the
finished lubricants. Finished lubricants comprise a lubricant base
oil and at least one additive. Finished lubricants may be used in
automobiles, diesel engines, axles, transmissions, and industrial
applications. Finished lubricants must meet the specifications for
their intended application as defined by the concerned governing
organization.
[0088] The lubricant base oils of the present invention are useful
in commercial finished lubricants. As a result of their excellent
VI's and low temperature properties, the lubricant base oils of the
present invention are suitable for formulating finished lubricants
intended for many of these applications. In addition, the excellent
oxidation stability of the lubricant base oils of the present
invention makes them useful in finished lubricants for many high
temperature applications.
[0089] The lubricant base oils of the present invention are
suitable for blending into a wide variety of finished lubricants,
including but not limited to automotive engine oils, natural gas
engine oils, automatic transmission fluid, industrial gear oils,
turbine oils, textile oils, heat transfer oils, hydraulic oils,
paper machine oils, spindle oils, rock drill oils, pump oils,
compressor oils, way oils, and metalworking fluids. The lubricant
base oils of the present invention may also be used as workover
fluids, packer fluids, coring fluids, completion fluids, and in
other oil field and well-servicing applications.
[0090] Additives, which may be blended with the lubricant base oil
of the present invention, to provide a finished lubricant
composition include those which are intended to improve select
properties of the finished lubricant. Typical additives include,
for example, anti-wear additives, EP agents, detergents,
dispersants, antioxidants, pour point depressants, VI improvers,
viscosity modifiers, friction modifiers, demulsifiers, antifoaming
agents, corrosion inhibitors, rust inhibitors, seal swell agents,
emulsifiers, wetting agents, lubricity improvers, metal
deactivators, gelling agents, tackiness agents, bactericides,
fluid-loss additives, colorants, and the like.
[0091] Other hydrocarbons, such as those described in U.S. Pat.
Nos. 5,096,883 and 5,189,012, may be blended with the lubricant
base oil provided that the finished lubricant has the necessary
pour point, kinematic viscosity, flash point, and toxicity
properties. These other hydrocarbons include base oils particularly
useful in drilling fluids. By way of example, U.S. Pat. No.
5,096,883 relates to a substantially non-toxic base oil that
consists essentially of branched-chain paraffins or branched-chain
paraffins substituted with an ester functionality, or mixtures
thereof, the base-oil preferably having between about 18 and about
40 carbon atoms per molecule and, more preferably, between about 18
and about 32 carbon atoms per molecule. U.S. Pat. No. 5,189,012
relates to synthetic hydrocarbons selected from the group
consisting of branched chain oligomers synthesized from one or more
olefins containing a C.sub.2 to C.sub.14 chain length and wherein
the oligomers have an average molecular weight of from 120 to
1000.
[0092] Typically, the total amount of additives in the finished
lubricant will be approximately 1 to about 30 weight percent of the
finished lubricant. However, since the lubricant base oils of the
present invention have excellent properties including low pour
point, high VI's, and excellent oxidative stability, a lower amount
of additives may be required to meet the specifications for the
finished lubricant than is typically required with base oils made
by other processes. The use of additives in formulating finished
lubricants is well documented in the literature and well known to
those of skill in the art.
EXAMPLES
[0093] The invention will be further explained by the following
illustrative examples that are intended to be non-limiting.
[0094] Each of these examples were carried out in a
continuous-flow, high-pressure pilot plant designed to hydroprocess
waxy hydrocarbon feeds. The isomerization catalyst was laboratory
prepared platinum on SAPO-11 and contained 15 weight percent
Catapal alumina binder. The catalyst was crushed to 24-42 mesh
prior to being loaded into the reactor. Process conditions included
an LHSV of 1.0 hr.sup.-1 over the isomerization catalyst, and a
once-through H.sub.2 rate of 5300 SCF/bbl. The entire effluent from
the isomerization reactor was passed directly to a second reactor
containing crushed Pt--Pd/SiO.sub.2--Al.sub.2O.sub.3 hydrofinishing
catalyst, run at 450.degree. F. and LHSV of 2 hr.sup.-1. The feed
used for these examples was a hydrotreated, Fischer-Tropsch derived
wax, and the properties of the feed (the hydrotreated
Fischer-Tropsch wax) are as follows:
1 Gravity, API 40.3 Nitrogen, ppm 1.6 Sulfur, ppm 2 Sim. Dist., Wt
% Temperature (.degree. F.) St/5 512/591 10/30 637/708 50 764 70/90
827/911 95/EP 941/1047
[0095] In the following examples, the effectiveness of sulfiding
the hydroisomerization catalyst was evaluated by measuring the
650.degree. F.+yield (weight percent) and the viscosity index of
the isomerized Fischer-Tropsch wax. It is known in the art that
650.degree. F.+yield (weight percent) is the weight percent of the
total product boiling above 650.degree. F., and is defined or
calculated at a particular pour point.
Example 1
Hydroisomerization Using a Sulfided SAPO Catalyst at 1,000 psig
[0096] This example illustrates the effect of sulfiding a SAPO-11
catalyst. In FIG. 1, the 650.degree. F.+yield (weight percent)
obtained when a Fischer-Tropsch derived wax was hydroisomerized is
plotted as a function of pour point (.degree. C.) for three
situations: 1) when the SAPO 11 catalyst is not sulfided prior to
the hydroisomerization reaction, 2) when the catalyst was
pre-sulfided, and 3) when the catalyst was re-sulfided after being
on-stream for 2040 hours. Each of the three experiments was
conducted at a hydrogen partial pressure of 1,000 psig.
[0097] For comparative purposes, data points at a pour point of
about -15.degree. C. may be considered. The 650.degree. F.+yield
for the un-sulfided catalyst was about 32 weight percent, which
increased to a yield of about 50 weight percent when the catalyst
was pre-sulfided, representing an increase of about 18 weight
percent. After re-sulfiding the catalyst, the yield increased an
additional 15 weight percent, to about 65 weight percent.
[0098] The viscosity index was similarly enhanced with sulfiding,
as shown in FIG. 2. At a pour point of -15.degree. C., the
viscosity index of the hydroisomerized wax increased from about 155
to 162 by pre-sulfiding the catalyst, and with re-sulfiding after
2,040 hours on-stream, the viscosity index increased even further
to about 172. This represents an absolute increase of about 7 by
pre-sulfiding, and about 10 with re-sulfiding.
Example 2
Hydroisomerization Using a Sulfided SAPO Catalyst at Varying
Pressures
[0099] The effects of sulfiding at two different pressures (and the
effects of pressure without sulfiding), are shown in FIGS. 3 and 4.
The 1,000 psig curves in FIGS. 3 and 4 are the same as those in
FIGS. 1 and 2; in other words, the 1,000 psig data has simply been
re-plotted. Decreasing the hydrogen partial pressure from 1,000 to
300 psig during hydroisomerization results in a 650.degree.
F.+yield increase from about 35 to 68 weight percent, and an
increase in viscosity index of about 155 to 168. Thus, this example
shows that hydroisomerization yield and viscosity index are both
enhanced as the hydroisomerization pressure is decreased.
[0100] Additionally, comparing FIGS. 1 and 2 with FIGS. 3 and 4
illustrate that sulfiding a SAPO-11 had a larger beneficial effect
at higher pressures (e.g., 1,000 psig) than at lower pressures
(e.g., 300 psig). Sulfiding the SAPO-11 catalyst had a modest
effect on 650.degree. F.+yield at 300 psig, and a modest effect on
viscosity index (an increase of about 5), within the range of pour
points plotted. Again, the pressures in this context refer to the
hydrogen partial pressure within the hydroisomerization reactor,
although the hydrogen partial pressure is substantially the same
(or nearly the same) as the total pressure.
Example 3
Hydroisomerization Using a Sulfided Zeolite Catalyst
[0101] This example was conducted as described for Example 1, but
using SSZ-32 as the catalyst. FIG. 5 shows that the 650.degree.
F.+yield (weight percent) from Fischer-Tropsch wax hydroisomerized
at 1,000 psig for both sulfided and un-sulfided SSZ-32 catalysts.
The yield was about 55 (at a pour point of -15.degree. C.).
Likewise, the viscosity index was about 175.
Example 4
Hydroisomerization Using an On-Stream Sulfided SAPO Catalyst
[0102] The effect of on-stream sulfiding on the iso-to-normal
C.sub.4 ratio is shown in FIG. 7. In this example, a SAPO-11
catalyst was on-stream sulfided after 150 hours of a
hydroisomerization process, and the iso-to-normal C.sub.4 ratio
plotted as a function of time. FIG. 7 illustrates that on-stream
sulfiding the catalyst resulted in the iso-to-normal C.sub.4 ratio
increasing from about 0.2 to over 0.8, representing a more than
4-fold increase. A higher iso-to-normal C.sub.4 ratio indicates
improved selectivity to isomerization, over cracking, reactions by
the catalyst.
Example 5
Hydroisomerization Using a Pre-Sulfided SAPO Catalyst
[0103] The effect of pre-sulfiding a SAPO-11 catalyst on the
amounts of light hydrocarbons produced by hydroisomerization is
shown in FIG. 8. The total pressure in the reactor was 1,000 psig,
and the temperature was 650.degree. F. There is a substantial
reduction in the amounts of normal-C.sub.4 and normal-C.sub.5, and
much less of a decrease in the amounts of iso-C.sub.4 and
iso-C.sub.5.
Example 6
Hydroisomerization Using a Pre-Sulfided SAPO Catalyst at Varying
Temperature
[0104] FIGS. 9A-C illustrate some observed relationships between
hydroisomerization temperatures and pressures. The graph in FIG. 9C
is a plot of hydroisomerization temperature as a function of pour
point for each of the four runs (at total pressures of 150, 300,
500, and 1,000 psig) shown in FIGS. 9A and 9B, the former figure
reporting 650.degree. F.+yield (weight percent) results, and the
latter figure reporting viscosity index results. An advantage to
producing lubricant base oils at low pressure, in addition to
enhanced production yields and viscosity indexes with a sulfided
SAPO catalyst according to the present embodiments, is that the
hydroisomerization process may be accomplished at significantly
lower operating temperatures than otherwise would have been the
case.
[0105] Lowering the hydroisomerization reaction temperature
provides a greater temperature range for the reaction to operate.
Referring to FIG. 9C, for example, at a pour point of -15.degree.
C., the temperature required by the catalyst to properly
hydroisomerize decreases by about 22.degree. C. when the operating
pressure is reduced from 1,000 to 500 psig. Under analogous
conditions, the required temperature is decreased by about
37.degree. C. when the operating pressure is reduced from 1,000 to
300 psig. Finally, the required temperature is decreased by about
47.degree. C. when the operating pressure is reduced from 1,000 to
150 psig.
[0106] All of the publications, patents and patent applications
cited in this application are herein incorporated by reference in
their entirety to the same extent as if the disclosure of each
individual publication, patent application or patent was
specifically and individually indicated to be incorporated by
reference in its entirety.
[0107] Various modifications and alterations of this invention will
become apparent to those skilled in the art without departing from
the scope and spirit of this invention. Other objects and
advantages will become apparent to those skilled in the art from a
review of the preceding description. Accordingly, the invention is
to be construed as including all structure and methods that fall
within the scope of the appended claims.
* * * * *