U.S. patent application number 11/630497 was filed with the patent office on 2009-06-25 for process to prepare a lubricating base oil and its use.
Invention is credited to Etienne Duhoux, Gilbert Robert Bernard Germaine, Yunus Sajad Hussein, Janet Marian Smithers, Wiecher Derk Evert Steenge, David John Wedlock.
Application Number | 20090159492 11/630497 |
Document ID | / |
Family ID | 38100242 |
Filed Date | 2009-06-25 |
United States Patent
Application |
20090159492 |
Kind Code |
A1 |
Duhoux; Etienne ; et
al. |
June 25, 2009 |
Process to prepare a lubricating base oil and its use
Abstract
Lube base stocks and lube stock compositions, as well as a
process for preparing lube base stocks and lube stock compositions,
are disclosed. The lube oils preferably have a viscosity index
above about 115. The process involves obtaining feed-stocks that
have a 95% point below 1150.degree. F. and feedstocks that have 95%
point above 1150.degree. F. The feedstocks that have a 95% point
below 1150% are catalytically dewaxed, and the feedstocks that have
95% point above 1150% are solvent dewaxed. The resulting products
can optionally be blended, and the base stocks can be combined with
various additives to form lube oil compositions. Hydrotreatment can
optionally be performed on the lube base stocks to remove olefins,
oxygenates and other impurities. In one embodiment, one or more of
the fractions are obtained from Fisher-Tropsch synthesis. One or
more of the fractions can also be obtained from other sources, for
example, via distillation of crude oil, provided that the fractions
do not include appreciable amounts (i.e., amounts which would
adversely affect the catalyst used for catalytic isodewaxing) of
thiols or amines. The individual fractions can also includes
combinations of feedstocks, from Fisher-Tropsch and other
sources.
Inventors: |
Duhoux; Etienne; (Petit
Couronne, FR) ; Germaine; Gilbert Robert Bernard;
(Petit Couronne, FR) ; Sajad Hussein; Yunus;
(Amsterdam, NL) ; Smithers; Janet Marian;
(Cheshire, GB) ; Steenge; Wiecher Derk Evert;
(Amsterdam, NL) ; Wedlock; David John; (Cheshire,
GB) |
Correspondence
Address: |
SHELL OIL COMPANY
P O BOX 2463
HOUSTON
TX
772522463
US
|
Family ID: |
38100242 |
Appl. No.: |
11/630497 |
Filed: |
June 23, 2005 |
PCT Filed: |
June 23, 2005 |
PCT NO: |
PCT/EP05/52955 |
371 Date: |
December 21, 2006 |
Current U.S.
Class: |
208/46 |
Current CPC
Class: |
C10G 65/12 20130101;
C10G 2400/10 20130101; C10G 65/00 20130101; C10G 45/58
20130101 |
Class at
Publication: |
208/46 |
International
Class: |
C10G 65/02 20060101
C10G065/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 24, 2004 |
EP |
04258134.8 |
Claims
1. A process for preparing lube base stocks, the process
comprising: a) obtaining a first fraction with a 95% point above
1150.degree. F. as measured by ASTM D2887 and a second fraction
with a 95% point below 1150.degree. F. as measured by ASTM D2887;
b) subjecting the first fraction to Solvent Dewaxing conditions to
obtain a lube base stock with a VI of greater than or equal to 115;
and c) subjecting the second fraction to Catalytic Dewaxing
conditions to obtain a lube base stocks having a viscosity less
than the viscosity of the lube base stock of step b).
2. The process of claim 1 further comprising hydrotreating and
dewaxing at least one of the factions selected from the group
consisting of: hydrotreating followed by dewaxing, dewaxing
followed by hydrotreating, and combinations thereof.
3. The process of claim 1 further comprising Catalytic Dewaxing and
Solvent Dewaxing the first fraction selected from the group
consisting of: Solvent Dewaxing followed by Catalytic Dewaxing, and
Catalytic Dewaxing followed by Solvent Dewaxing.
4. The process of claim 3, wherein the Catalytic Dewaxing process
is a Hydroisomerization Dewaxing process.
5. The process of claim 4, wherein the Hydroisomerization Dewaxing
process is a Complete Hydroisomerization Dewaxing process.
6. The process of claim 1, wherein the Catalytic Dewaxing process
is a Hydroisomerization Dewaxing process.
7. The process of claim 6, wherein the Hydroisomerization dewaxing
process is a complete Hydroisomerization Dewaxing process.
8. The process of claim 1, wherein at least a portion of one of the
first and second fractions is derived the group consisting of
Fischer-Tropsch synthesis products, slack wax from conventional
petroleum lube production, distillates from crude oil, deasphalted
residual stocks from crude oil, and combinations thereof.
9. The process of claim 8, wherein at least a portion of one of the
first and second fractions is derived from a Fischer-Tropsch
synthesis products.
10. The process of claim 1, wherein at least one the lube base
stocks have a pour point/cloud point spread of less than 30.degree.
C.
11. The process of claim 1, wherein the lube base stocks have a
pour point/cloud point spread of less than 10.degree. C.
12. The process of claim 1, wherein the pour point of at least one
of the lube base stocks is less than -10.degree. C.
13. The lube base stocks produced from the process according to
claim 1 having a pour point between -15 and -40.degree. C., a VI
above 115, a cloud point of less than -10.degree. C., and a sulfur
content of less than 300 ppm.
14. The product according to claim 13, wherein at leas one of the
lube base stocks are combined with one or more lube oil additives
selected from the group consisting of lubricity improvers,
emulsifiers, wetting agents, densifiers, fluid-loss additives,
viscosity modifiers, corrosion inhibitors, oxidation inhibitors,
friction modifiers, demulsifiers, anti-wear agents, dispersants,
anti-foaming agents, pour point depressants, detergents, and rust
inhibitors.
15. The process of claim 1, wherein at least one of lube base
stocks are combined with one or more lube oil additives selected
from the group consisting of lubricity improvers, emulsifiers,
wetting agents, densifiers, fluid-loss additives, viscosity
modifiers, corrosion inhibitors, oxidation inhibitors, friction
modifiers, demulsifiers, anti-wear agents, dispersants,
anti-foaming agents, pour point depressants, detergents, and rust
inhibitors.
16. A lube base stock composition prepared by: a) obtaining a first
fraction with a 95% point above 1150.degree. F. and a second
fraction with a 95% point below 1150.degree. F., b) subjecting the
first fraction to Solvent Dewaxing conditions, and c) subjecting
the second fraction to Catalytic Dewaxing conditions, whereby the
compositions of step b) and c) have a pour point between -15 and
-40.degree. C., a VI above 115, a cloud point of less than
-10.degree. C., and a sulfur content of less than 300 ppm.
17. The compositions of claim 16, further comprising one or more
lube oil additives selected from the group consisting of lubricity
improvers, emulsifiers, wetting agents, densifiers, fluid-loss
additives, viscosity modifiers, corrosion inhibitors, oxidation
inhibitors, friction modifiers, demulsifiers, anti-wear agents,
dispersants, anti-foaming agents, pour point depressants,
detergents, and rust inhibitors.
18. A lube base stock composition comprising a blend of a first
fraction comprising a hydrocarbon stream prepared by Solvent
Dewaxing a hydrocarbon fraction with a 95% point above 1150.degree.
F. and a second fraction comprising a hydrocarbon stream prepared
by Catalytic Dewaxing a hydrocarbon fraction with a 95% point below
1150.degree. F.
19. The lube base stock composition of claim 23, further comprising
one or more lube oil additives selected from the group consisting
of lubricity improvers, emulsifiers, wetting agents, densifiers,
fluid-loss additives, viscosity modifiers, corrosion inhibitors,
oxidation inhibitors, friction modifiers, demulsifiers, anti-wear
agents, dispersants, anti-foaming agents, pour point depressants,
detergents, and rust inhibitors.
20. A process for preparing lube base stocks, having pour cloud
spreads less than 30.degree. C., the process comprising: a)
fractionating a lube base stock feedstock into at least a heavier
and a lighter fraction; b) catalytically dewaxing the fractions
using a Hydroisomerization Dewaxing Catalyst; c) measuring the
pour-cloud spread on the dewaxed lube base stocks from the
fractions; and d) modifying the process to achieve lube base stocks
having pour cloud spreads of less than 30.degree. C. from the
process steps selected from the group consisting of adjusting the
fractionation cut point, adjusting the fractionation efficiency, an
additional process step of Solvent Dewaxing the lube base stocks,
an additional process step of adsorbent treating the lube base
stocks and combinations thereof, whereby the lube base stocks have
a pour point between -15 and -40.degree. C., a VI above 115, a
cloud point of less than -10.degree. C., and a sulfur content of
less than 300 ppm.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a process for preparing lube base
stocks.
BACKGROUND OF THE INVENTION
[0002] Lubricants used in automobiles, diesel engines and other
equipment are composed of base stocks and/or base oils and
additives. Base stocks and base oils are typically hydrocarbons and
are divided into five groups according to their sulfur content,
saturates content, and viscosity index, according to the API
Interchange Guidelines (API Publication 1509).
TABLE-US-00001 Group Sulfur, ppm Saturates, % V.I. I >300 And/or
<90 80-120 II .ltoreq.300 And .gtoreq.90 80-120 III .ltoreq.300
And .gtoreq.90 >120 IV All Polyalphaolefins (PAOs) V All Stocks
Not Included in Groups I-IV
[0003] Plants that make Group I base stocks from crude oil-derived
lube base stock feedstocks typically solely use solvents such as
phenol or furfural to extract the lower VI components and increase
the VI of the fractions to the desired specifications. Solvent
extraction typically gives a product with less than 90% saturates
and more than 300 ppm sulfur. The majority of the lube production
is in the Group I category.
[0004] Plants that make Group II base stocks from crude oil
fractions in a "pre-lube base stock range" typically use
hydroprocessing (hydrocracking or severe hydrotreating) to increase
the VI of the fractions to the specification value. Hydroprocessing
typically increases the saturate content above 90 and reduces the
sulfur below 300 ppm. Combinations of solvent processing with
hydroprocessing are also used to make Group II base stocks.
Approximately 10% of the world lube base stock production, and
about 30% of U.S. production, is in the Group II category.
[0005] Plants that make Group III base stocks typically use
Hydroisomerization Dewaxing to make very high VI products. The
starting feed is typically a waxy vacuum gas oil (VGO) or wax which
contains essentially saturates and little sulfur. The Group III
products have saturate contents above 90 and sulfur contents below
300 ppm. Fischer Tropsch wax is an ideal feed for
Hydroisomerization Dewaxing to make Group III lubes. However, only
a small fraction of the world's lube supply is in the Group III
category. Group IV and V plants are specialty plants, and make up
even less of the world's lube supply.
[0006] In addition to specifications on saturates, viscosity index
and sulfur, lube base stocks are typically produced in a series of
viscosity grades. The lowest viscosity is almost always greater
than 3 cSt when measured at 40.degree. C., and more typically
greater than 4 cSt. The highest viscosity grade is almost always
less than 50 cSt when measured at 100.degree. C. The finished lube
oil formulator takes various viscosity grade products and blends
them with additives to make a finished lubricant that has a desired
viscosity. The proportions of the individual base stocks and/or
base oils are adjusted to achieve the desired viscosity of the
finished lubricant. Since a lube base oil plant must provide base
oils for a variety of customers, it is important that all viscosity
grades have other properties that are approximately constant, such
as viscosity index, pour point, cloud point, etc. The viscosity of
the lube base stock depends on the average molecular weight of the
base stock and this, in turn, depends on the boiling range.
[0007] Lube base stocks must have acceptable pour points and cloud
points in addition to an acceptable viscosity index. These
properties can be important for functional considerations (they
impact the actual performance of the final lubricant) and can be
important for general customer acceptance. Pour point is typically
measured using the ASTM 97 procedure, which measures the
temperature at which an oil no longer will flow when it is cooled.
Cloud point is typically measured using the ASTM D 2500 procedure,
which measures the temperature at which a cloud appears in the lube
base stock as it is cooled.
[0008] Pour point is of obvious functional significance as the
final lubricant must not become solid during storage or use.
Typical lube base stocks (Groups I-III) will have pour points below
+10.degree. F. (-12.degree. C.). These specifications are
satisfactory for the majority of lube base stocks used in engine
lubrication. Chemical pour point depressants can be added to lube
base stocks to further reduce their pour point, but these chemical
additives are expensive. For a few small volume applications
intended for cold climates, lower pour points may be needed.
[0009] Cloud point is also of functional significance where an oil
filter is used to remove solids from the lubricant. Lube base
stocks with high cloud points may plug the oil filter. Typical lube
Group I-III base stocks will have cloud points below +14.degree. F.
(-10.degree. C.). While chemical pour point depressants are known,
analogous cloud point depressants are not known. As with the pour
point, these cloud point specifications are satisfactory for the
majority of lube base stocks used in engine lubrication. For a few
small volume applications intended for cold climates, lower cloud
points may be needed.
[0010] Wax is commonly removed from lube base stocks by Solvent
Dewaxing. Solvent Dewaxing to make Lube Base stocks has been used
for over 70. An advantage of using Solvent Dewaxing is that the
product pour and cloud points are reduced to approximately the same
value. Limitations of Solvent Dewaxing include the high operating
costs, use of volatile and flammable solvents, environmental
problems due to solvent emissions in the air and groundwater, and
production of a slack wax for which there is a limited market.
[0011] The traditional method of Solvent Dewaxing is being
supplanted by Catalytic Dewaxing. The trend began with Conventional
Hydrodewaxing and has continued recently with Hydroisomerization
Dewaxing (for example, Chevron's Isodewaxing.TM. process). One
disadvantage of Catalytic Dewaxing is the tendency for the process
to generate oils that have cloud points higher than their pour
points.
[0012] It would be advantageous to have processes for preparing
lube base stock and lube stock compositions that minimize the
limitations associated with Solvent Dewaxing, and that also provide
lube base stocks with cloud points relatively close (i.e., within
about 30.degree. C., preferably with about 20.degree. C., most
preferably within about 10.degree. C.) to their pour points. The
smallest pour-cloud spread is preferred because this requires less
dewaxing and thus permits pertaining higher lube yields which
improves economics. The present invention provides such
processes.
SUMMARY OF THE INVENTION
[0013] In its broadest aspect, the present invention is directed to
an integrated process for producing more than one viscosity grade
of lube base stock and lube stock compositions. Hydrocarbons in the
lube base stock range are prepared by catalytically dewaxing
feedstocks that have a 95% point below 1150.degree. F. and solvent
dewaxing feedstocks that have a 95% point above 1150.degree. F.
Optionally, the solvent dewaxed fraction can additionally be
subjected to Hydroisomerization Dewaxing, preferably Complete
Hydroisomerization Dewaxing, before or after Solvent Dewaxing.
Hydrotreatment can optionally be performed on the lube base stock
to remove olefins, oxygenates and other impurities. By use of
different dewaxing processes depending on the 95% point, more than
one viscosity grade of lube base stock can be generated while
maintaining relatively consistent pour and cloud points.
[0014] In one embodiment, the process involves performing
Fischer-Tropsch synthesis on syngas to provide a range of products,
and isolating various fractions (i.e., fractions that have a 95%
point below 1150.degree. F. and fractions that have a 95% point
above 1150.degree. F.), typically via fractional distillation. The
fractions can also be obtained from other sources, for example via
distillation of crude oil, provided that the fractions do not
include appreciable amounts (i.e., amounts which would adversely
affect the Dewaxing Catalyst) of thiols or amines. The individual
fractions can also include combinations of feedstocks, from
Fischer-Tropsch and other sources. The resulting dewaxed
hydrocarbon products can optionally be combined with an additive
package to provide a lube oil composition.
[0015] Products with desired properties can be tailor made by
performing the appropriate Solvent Dewaxing or Catalytic Dewaxing
steps on representative samples of each fraction, blending the
resulting products, and assaying them for desired properties. Once
a product with optimized properties is obtained, the conditions can
be scaled up to provide a desired product stream.
DETAILED DESCRIPTION OF THE INVENTION
[0016] In its broadest aspect, the present invention is directed to
an integrated process for producing lube base stocks and lube oils.
As used herein, lube base stocks and/or base oils are generally
combined with an additive package to provide finished lube oils.
Hydrocarbons in the lube base stock range are prepared by
catalytically dewaxing feedstocks that have a 95% point below
1150.degree. F. and solvent dewaxing feedstocks that have 95% point
above 1150.degree. F. The 95% points can be measured by use of ASTM
D2887.
[0017] The process described herein is an integrated process. As
used herein the term "integrated process" refers to a process which
involves a sequence of steps, some of which may be parallel to
other steps in the process, but which are interrelated or somehow
dependent upon either earlier or later steps in the total
process.
[0018] As used herein, "pour point" is the temperature at which an
oil no longer will flow when it is cooled, "cloud point" is the
temperature at which a cloud appears in the lube base stock as it
is cooled, and the "95% point" is the temperature at which 95% of
the product distills.
[0019] An advantage of the present process is the effectiveness
with which the present process may be used to prepare high quality
base stocks useful for manufacturing lubricating oils, particularly
while minimizing the product loss associated with Solvent Dewaxing
and/or Catalytic Dewaxing of the entire feedstock, as well as
minimizing the spread between the pour and cloud points. The pour
point/cloud point spread, or pour-cloud spread, is defined as the
cloud point minus the pour point, as measured in .degree. C.
[0020] While not wishing to be bound to a particular theory, as
shown below in Example 1, Applicants have determined that fractions
with 95% points below about 1150.degree. F. have a pour point/cloud
point spread that is approximately constant, at about 7.degree. C.,
with little tendency for the spread to increase with an increase in
product VI. Accordingly, Catalytic Dewaxing can be performed with
minimal loss in product yield. However, fractions with 95% points
above about 1150.degree. F. have a relatively large pour
point/cloud point spread (for example, above 30.degree. C.) and
Catalytic Dewaxing may result in an unacceptable loss in product
yield. The process herein, by subjecting these two fractions to
different dewaxing conditions, maximizes product yield while
maintaining an acceptable pour point.
[0021] As used herein, "hydrocarbons in the lube base stock range"
are hydrocarbons having a boiling point in the lube oil range
(i.e., between 650 and 1200.degree. F.).
[0022] Feedstocks for the Solvent Dewaxing and Catalytic
Isodewaxing Steps
[0023] Any hydrocarbon feedstock including primarily paraffins and
isoparaffins and with a 95% point below 1150.degree. F. can be used
for Catalytic Dewaxing. Any hydrocarbon feedstock including
primarily paraffins and isoparaffins and with a 95% point above
1150.degree. F. can be used for Solvent Dewaxing. In one
embodiment, one or both fractions (1150.degree. F.+ and
1150.degree. F.- fractions) are derived at least in part from
Fischer-Tropsch synthesis. The fractions can also be obtained from
other sources, for example, via distillation of crude oil, provided
that the fractions do not include appreciable amounts (i.e.,
amounts which would adversely affect the Dewaxing Catalyst) of
thiols or amines. The individual fractions can also include
combinations of feedstocks, i.e., from Fischer-Tropsch and other
sources.
[0024] Examples of feedstocks that can be used in the processes
described herein include oils that generally have relatively high
pour points which it is desired to reduce to relatively low pour
points. Numerous petroleum feedstocks, for example, those derived
from crude oil, are suitable for use. Examples include petroleum
distillates having a normal boiling point above about 212.degree.
F., gas oils and vacuum gas oils, residuum fractions from an
atmospheric pressure distillation process, solvent-deasphalted
petroleum residues, shale oils, cycle oils, petroleum and slack
wax, waxy petroleum feedstocks, NAO wax, and waxes produced in
chemical plant processes. Straight chain n-paraffins either alone
or with only slightly branched chain paraffins having 16 or more
carbon atoms can be considered to be waxes.
[0025] Suitable feedstocks also include those heavy distillates
normally defined as heavy straight-run gas. The feedstock may have
been subjected to a hydrotreating and/or hydrocracking process
before being supplied to the present process. Alternatively, or in
addition, the feedstock may be treated in a solvent extraction
process to remove aromatics and sulfur- and nitrogen-containing
molecules before being dewaxed.
[0026] Additional examples of suitable feeds include waxy
distillate stocks such as gas oils, lubricating oil stocks,
synthetic oils and waxes such as those produced by Fischer-Tropsch
synthesis, high pour point polyalphaolefins, foots oils, synthetic
waxes such as normal alpha-olefin waxes, deoiled waxes and
microcrystalline waxes. Foots oil is prepared by separating oil
from the wax, where the isolated oil is referred to as foots
oil.
[0027] As used herein, the term "waxy petroleum feedstocks"
includes petroleum waxes. The feedstock employed in the process of
the invention can be a waxy feed which contains greater than about
50% wax, and in some embodiments, even greater than about 90% wax.
Wax content can be determined by use laboratory solvent dewaxing
methods. A 300-g portion of sample is dissolved in 1200 ml of 1:1
toluene-MEK solvent. Heating may be necessary to achieve complete
dissolution. The solution is then cooled overnight at -15 to -20
degrees F. to crystallize the wax. The wax crystals formed are
filtered and recovered. The filtrate is vacuum distilled to
separate the toluene-MEK solvent from the dewaxed oil. Occluded
solvent in the wax is removed by heating the wax on a hot plate
with nitrogen blowing on the surface. The weights of the recovered
oil and wax are divided by the original sample weight to obtain the
percent oil and wax.
[0028] Highly paraffinic feeds having high pour points, generally
above about 0.degree. C., more usually above about 10.degree. C.
are also suitable for use in the process of the invention. Such
feeds can contain greater than about 70% paraffinic carbon, and in
some embodiments, even greater than about 90% paraffinic carbon.
The content of paraffinic carbon can be determined by NMR
techniques.
[0029] The feedstocks should not include appreciable amounts of
olefins, heteroatoms, aromatics or other cyclic compounds.
Preferred feedstocks are products from Fischer-Tropsch synthesis or
waxes from petroleum products. If any heteroatoms, olefins or
cyclic compounds are present in the feedstock, they can be removed,
for example, by hydrotreating.
[0030] In one embodiment, one or more of the fractions (i.e., the
fraction boiling below 1150.degree. F. and the fraction boiling
above 1150.degree. F. the relatively low molecular weight fraction
are obtained via Fischer-Tropsch synthesis.
[0031] The Fischer-Tropsch synthesis may be effected in a fixed
bed, in a slurry bed, or in a fluidized bed reactor. The
Fischer-Tropsch reaction conditions may include using a reaction
temperature of between 190.degree. C. and 340.degree. C., with the
actual reaction temperature being largely determined by the reactor
configuration. Thus, when a fluidized bed reactor is used, the
reaction temperature is preferably between 300.degree. C. and
340.degree. C.; when a fixed bed reactor is used, the reaction
temperature is preferably between 200.degree. C. and 250.degree.
C.; and when a slurry bed reactor is used, the reaction temperature
is preferably between 190.degree. C. and 270.degree. C.
[0032] An inlet synthesis gas pressure to the Fischer-Tropsch
reactor of between 1 and 50 bar, preferably between 15 and 50 bar,
may be used. The synthesis gas may have a H.sub.2:CO molar ratio,
in the fresh feed, of 1.5:1 to 2.5:1, preferably 1.8:1 to 2.2:1.
The synthesis gas typically includes 0.1 wppm of sulfur or less. A
gas recycle may optionally be employed to the reaction stage, and
the ratio of the gas recycle rate to the fresh synthesis gas feed
rate, on a molar basis, may then be between 1:1 and 3:1, preferably
between 1.5:1 and 2.5:1. A space velocity, in m.sup.3 (kg
catalyst).sup.-1 hour.sup.-1, of from 1 to 20, preferably from 8 to
12, may be used in the reaction stage.
[0033] In principle, an iron-based, a cobalt-based or an
iron/cobalt-based Fischer-Tropsch catalyst can be used in the
Fischer-Tropsch reaction stage. The iron-based Fischer-Tropsch
catalyst may include iron and/or iron oxides which have been
precipitated or fused. However, iron and/or iron oxides which have
been sintered, cemented, or impregnated onto a suitable support can
also be used. The iron should be reduced to metallic Fe before the
Fischer-Tropsch synthesis. The iron-based catalyst may contain
various levels of promoters, the role of which may be to alter one
or more of the activity, the stability, and the selectivity of the
final catalyst.
[0034] Preferably, the catalysts are operated with high chain
growth probabilities (i.e., alpha values of 0.8 or greater,
preferably 0.9 or greater, most preferably 0.925 or greater).
Preferred promoters are those influencing the surface area of the
reduced iron (structural promoters), and these include oxides or
metals of Mn, Ti, Mg, Cr, Ca, Si, Al, or Cu or combinations
thereof.
[0035] The products from a slurry bed Fischer-Tropsch synthesis
generally include a gaseous reaction product and a liquid reaction
product. The gaseous reaction product includes hydrocarbons boiling
below about 650.degree. F. (e.g., tail gases through middle
distillates). The liquid reaction product includes hydrocarbons
boiling above about 650.degree. F. (e.g., vacuum gas oil through
heavy paraffins).
[0036] The minus 650.degree. F. product can be separated into a
tail gas fraction and a condensate fraction, i.e., equivalent to
about C.sub.5 to C.sub.20 normal paraffins and higher boiling
hydrocarbons, using, for example, a high pressure and/or lower
temperature vapor-liquid separator or low pressure separators or a
combination of separators. Advantageously, the C.sub.20+
Fischer-Tropsch products are used in the Catalytic Dewaxing
process, and C.sub.5 to C.sub.20 normal paraffins are used for
other purposes, for example, to prepare distillate fuel
compositions.
[0037] The fraction boiling above about 650.degree. F. primarily
contains C.sub.20 to C.sub.50 linear paraffins with relatively
small amounts of higher boiling branched paraffins.
[0038] The overall process generally involves obtaining a fraction
with a 95% point below 1150.degree. F. and a fraction with a 95%
point above 1150.degree. F. The fraction with a 95% point below
1150.degree. F. is subjected to Catalytic Dewaxing and the fraction
with a 95% point above 1150.degree. F. is subjected to Solvent
Dewaxing conditions. Optionally, the feedstock to the Solvent Dewax
process is additionally be subjected to Hydroisomerization
Dewaxing. Hydrotreatment can optionally be performed on the lube
base stock to remove olefins, oxygenates and other impurities.
[0039] Conditions for Solvent Dewaxing, Catalytic Dewaxing, and
hydrotreatment are described in more detail below.
[0040] The higher boiling fractions, e.g., the 1150.degree. F.+
fractions, are dewaxed in a conventional Solvent Dewaxing step to
remove high molecular weight n-paraffins. The recovered dewaxed
product, or dewaxed oil, can be fractionated under vacuum to
produce paraffinic lubricating oil fractions of different viscosity
grades, or blended directly with the catalytically dewaxed
fractions. High wax content 1150.degree. F.+feedstocks (those
containing greater than 50% wax such as from a Fischer Tropsch
process) are preferably first processed through Hydroisomerization
Dewaxing.
[0041] Solvent Dewaxing to make Lube Base stocks has been, used for
over 70 years and is described, for example, in Chemical Technology
of Petroleum 3rd Edition, William Gruse and Donald Stevens,
McGraw-Hill Book Company, Inc., New York, 1960, pages 566 to 570.
The basic process involves [0042] mixing a waxy hydrocarbon stream
with a solvent, typically comprising a ketone (such as methyl ethyl
ketone or methyl iso-butyl ketone) and an aromatic (such as
toluene), [0043] chilling the mixture to cause wax crystals to
precipitate, [0044] separating the wax by filtration, typically
using rotary drum filters, [0045] recovering the solvent from the
wax and the dewaxed oil filtrate.
[0046] There have been refinements in Solvent Dewaxing since its
inception. For example, Exxon's DILCHILL.RTM. dewaxing process
involves cooling a waxy hydrocarbon oil stock in an elongated
stirred vessel, preferably a vertical tower, with a pre-chilled
solvent that will solubilize at least a portion of the oil stock
while promoting the precipitation of the wax. Waxy oil is
introduced into the elongated staged cooling zone or tower at a
temperature above its cloud point. Cold dewaxing solvent is
incrementally introduced into the cooling zone along a plurality of
points or stages while maintaining a high degree of agitation
therein to effect substantially instantaneous mixing of the solvent
and wax/oil mixture as they progress through the cooling zone,
thereby precipitating at least a portion of the wax in the oil.
DILCHILL.RTM. dewaxing is discussed in greater detail in the U.S.
Pat. Nos. 4,477,333, 3,773,650 and 3,775,288. Texaco also has
developed refinements in the process. For example, U.S. Pat. No.
4,898,674 discloses how it is important to control the ratio of
methyl ethylketone (MEK) to toluene and to be able to adjust this
ratio, since it allows use of optimum concentrations for processing
various base stocks. Commonly, a ratio of 0.7:1 to 1:1 may be used
when processing bright stocks; and a ratio of 1.2:1 to about 2:1
may be used when processing light stocks.
[0047] Solvent dewaxing tends to reduce the product pour and cloud
points to approximately the same value. The solvent dewaxed
fraction can optionally be subjected to Catalytic Dewaxing, as
described in more detail below.
[0048] The lower boiling fractions, e.g., the 1150.degree. F.-
fractions, are dewaxed in a Catalytic Dewaxing step to remove high
molecular weight n-paraffins.
[0049] Catalytic Dewaxing consists to two main classes
(Conventional Hydrodewaxing and Hydroisomerization Dewaxing), and
Hydroisomerization Dewaxing can be further subdivided into Partial
and Complete Hydroisomerization Dewaxing. All classes involve
passing a mixture of a waxy hydrocarbon stream and hydrogen over a
catalyst that contains an acidic component to convert the normal
and slightly branched iso-paraffins in the feed to other non-waxy
species and thereby generate a lube base stock product with an
acceptable pour point. Typical conditions for all classes involve
temperatures from about 400 to 800.degree. F., pressures from about
200 to 3000 psig, and space velocities from about 0.2 to 5 hr-1.
The method selected for dewaxing a feed typically depends on the
product quality, and the wax content of the feed, with Conventional
Hydrodewaxing generally preferred for low wax content feeds. The
method for dewaxing can be effected by the choice of the catalyst.
The general subject is reviewed by Avilino Sequeira, in Lubricant
Base Stock and Wax Processing, Marcel Dekker, Inc pages 194-223.
The determination of the class of Dewaxing Catalyst among
Conventional Hydrodewaxing, Partial Hydroisomerization Dewaxing and
Complete Hydroisomerization dewaxing can be made by using the
n-hexadecane isomerization test as describe by Santilli et al. in
U.S. Pat. No. 5,282,958. When measured at 96% n-hexadecane
conversion under conditions described by Santilli et al,
Conventional Hydrodewaxing Catalysts will exhibit a selectivity to
isomerized hexadecanes of less than 10%, Hydroisomerization
Dewaxing Catalysts will exhibit a selectivity to isomerized
hexadecanes of greater than or equal to 10%, Partial
Hydroisomerization Dewaxing Catalysts will exhibit a selectivity to
isomerized hexadecanes of greater than 10% to less than 40%, and
Complete Hydroisomerization Dewaxing Catalysts will exhibit a
selectivity to isomerized hexadecanes of greater than or equal to
40%, preferably greater than 60%, and most preferably greater than
80%.
[0050] Conventional Hydrodewaxing is defined for purposes of this
document as a Catalytic Dewaxing process that uses a Conventional
Hydrodewaxing Catalyst. In Conventional Hydrodewaxing, the pour
point is lowered by selectively cracking the wax molecules, mostly
to smaller paraffins boiling between propane and about octane.
Since this technique converts the wax to less valuable by-products,
it is useful primarily for dewaxing oils that do not contain a
large amount of wax. Waxy oils of this type are frequently found in
petroleum distillate from moderately waxy crudes (Arabian, North
Slope, etc). Catalysts that are usefull for Conventional
Hydrodewaxing are typically 12-ring zeolites and 10-ring zeolites.
Zeolites of this class include ZSM-5, ZSM-11, ZSM-22, ZSM-23,
ZSM-35, and Mordenite. Conventional Hydrodewaxing catalysts favor
cracking in comparison to other method of conversion of paraffins.
This is demonstrated by use of the n-hexadecane isomerization test
by Santilli et al, in which Conventional Hydrodewaxing catalysts
exhibit a selectivity to isomerized hexadecane products of less
than 10%. In addition to the zeolites, metals may be added to the
catalyst, primarily to reduce fouling. Representative process
conditions, yields, and product properties for Conventional
Hydrodewaxing are described, for example, U.S. Pat. Nos. 4,176,050
to Chen et al., 4,181,598 to Gillespie et al., 4,222,855 to Pelrine
et al., 4,229,282 to Peters et al., 4,211,635 to Chen, by Sequeira
in the section titled "The Mobil Lube Dewaxing Process", pages
198-204 and references therein, J. D. Hargrove, G. J. Elkes, and A.
H. Richardson, Oil and Gas J., p. 103, Jan. 15, 1979; the contents
of each of which is incorporated herein by reference in their
entirety.
[0051] Hydroisomerization Dewaxing is defined for purposes of this
document as a Catalytic Dewaxing process that uses a
Hydroisomerization Dewaxing Catalyst. Hydroisomerization Dewaxing
converts at least a portion of the wax to non-waxy iso-paraffns by
isomerization, while at the same time minimizing the conversion by
cracking. When Conventional Hydrodewaxing and Hydroisomerization
Dewaxing are compared on the same feed, the conversion of wax to
non-waxy iso-paraffins during Hydroisomerization Dewaxing gives
benefits of reducing the yield of less valuable by-products,
increasing the yield of lube oil, and generating an oil with higher
VI and greater oxidation and thermal stability. Hydroisomerization
Dewaxing uses a dual-functional catalyst consisting of an acidic
component and a metal component. Both components are required to
conduct the isomerization reaction. Typical metal components are
platinum or palladium, with platinum most commonly used. The choice
and the amount of metal in the catalyst is sufficient to achieve
greater than 10% isomerized hexadecane products in the test
described by Santilli et al. When the selectivity for hexadecane
isomers following Santilli's test exceed 40%, the catalyst is a
Complete Hydroisomerization Dewaxing Catalyst. Since
Hydroisomerization Dewaxing converts wax to iso-paraffins which
boil in the lube base stock range, it is useful for dewaxing oils
that contain a large amount of wax. Waxy oils of this type are
obtained from slack waxes from solvent dewaxing processes, and
distillates from highly waxy crudes (Minas, Altamont, etc.) and
products from the Fischer Tropsch Process.
[0052] Partial Hydroisomerization Dewaxing is defined for purposes
of this document as a Catalytic Dewaxing process that uses a
Partial Hydroisomerization Dewaxing Catalyst. In Partial
Hydroisomerization Dewaxing a portion of the wax is isomerized to
iso-paraffins using catalysts that can isomerize paraffins
selectively, but only if the conversion of wax is kept to
relatively low values (typically below 50%). At higher conversions,
wax conversion by cracking becomes significant, and yield losses of
lube base stock becomes uneconomical. The acidic catalyst
components useful for Partial Hydroisomerization Dewaxing include
amorphous silica aluminas, fluorided alumina, and 12-ring zeolites
(such as Beta, Y zeolite, L zeolite). Because the wax conversion is
incomplete, Partial Hydroisomerization Dewaxing must be
supplemented with an additional dewaxing technique, typically
Solvent Dewaxing, Complete Hydroisomerization Dewaxing, or
Conventional Hydrodewaxing in order to produce a lube base stock
with an acceptable pour point (below about +10.degree. C. or
-12.degree. C.). The wax recovered from a solvent dewaxing
operation following a Partial Hydroisomerization Dewaxing can be
recycled to the Partial Hydroisomerization Dewaxing step.
Representative process conditions, yields, and product properties
for Partial Hydroisomerization Dewaxing are described, for example,
U.S. Pat. Nos. 5,049,536 to Belussi et al.; 4,943,672 to Hamner et
al., and EP 0 582 347 to Perego et al., EP 0 668 342 to Eilers et
al, PCT WO 96/26993 by Apelian et al.; PCT WO 96/13563 by Apelian
et al; the contents of each of which is incorporated herein by
reference in their entirety.
[0053] Complete Hydroisomerization Dewaxing is defined for purposes
of this document as a Catalytic Dewaxing process that uses a
Complete Hydroisomerization Dewaxing Catalyst. In Complete
Hydroisomerization Dewaxing, Complete Hydroisomerization Dewaxing
Catalysts are used which can achieve high conversion levels of wax
while maintaining acceptable selectivities to isomerization. Since
wax conversion can be complete, or at least very high, this process
typically does not need to be combined with additional dewaxing
processes to produce a lube base stock with an acceptable pour
point. Representative process conditions, yields, and product
properties for Complete Hydroisomerization Dewaxing are described,
for example, in U.S. Pat. Nos. 5,135,638 to Miller, 5,246,566 to
Miller; 5,282,958 to Santilli et al.; 5,082,986 to Miller;
5,723,716 to Brandes et al; the contents of each of which is
incorporated herein by reference in their entirety.
[0054] Fischer Tropsch stocks that have 95% points in excess of
about 1150.degree. F. (and most preferably those with VI values in
excess of 115) should preferably be processed by a combination of
operations which first involve isomerization of the paraffins
(Hydroisomerization Dewaxing) followed by Solvent Dewaxing.
Preferably the Hydroisomerization Dewaxing is a Complete
Hydroisomerization Dewaxing process. Fischer Tropsch stocks that
have 95% points below about 1150.degree. F. can be processed by
Catalytic Dewaxing alone, preferably using Hydroisomerization
Dewaxing (most preferably Complete Hydroisomerization Dewaxing) to
effect the Catalytic Dewaxing.
[0055] Solvent dewaxing and Catalytic Dewaxing can still leave
behind trace waxes. The presence of undesired wax can be detected
by visual inspection, or using analytical techniques, for example
light-scattering turbidity measurement as described in U.S. Pat.
No. 4,627,901.
[0056] Various methods have been developed for removing these trace
contaminants. For example, U.S. Pat. No. 4,950,382 discloses using
adsorbents to remove wax. U.S. Pat. Nos. 4,702,817 and 4,820,400
disclose performing electrophoresis on the hydrocarbons during
Solvent Dewaxing.
[0057] The contents of each of these patents is hereby incorporated
herein by reference in their entirety.
[0058] One or more of the fractions obtained by Solvent Dewaxing
and/or Catalytic Dewaxing (or feedstocks for these processes) may
include heteroatoms such as sulfur, oxygen or nitrogen; or olefins
that may adversely affect the resulting lube base stock and lube
stock compositions; or catalysts or solvents used in dewaxing. If
sulfur impurities are present, they can be removed using means well
known to those of skill in the art, for example, extractive Merox,
hydrotreating, adsorption, etc. Nitrogen-containing impurities can
also be removed using means well known to those of skill in the
art. Hydrotreating and hydrocracking are preferred means for
removing these and other impurities.
[0059] Accordingly, the fractions used in the process described
herein may be hydrotreated to remove the heteroatoms. As used
herein, the term "hydrotreating" are given their conventional
meaning and describe processes that are well known to those skilled
in the art. Hydrotreating refers to a catalytic process, usually
carried out in the presence of free hydrogen, in which the primary
purpose is the desulfuization and/or denitrification of the feed
stock. Generally, in hydrotreating operations cracking of the
hydrocarbon molecules, i.e., breaking the larger hydrocarbon
molecules into smaller hydrocarbon molecules, is minimized and the
unsaturated hydrocarbons are either fully or partially
hydrogenated.
[0060] Hydrocracking refers to a catalytic process, usually carried
out in the presence of free hydrogen, in which the cracking of the
larger hydrocarbon molecules is a primary purpose of the operation.
Desulfurization and/or denitrification of the feed stock usually
will also occur.
[0061] Catalysts used in carrying out hydrotreating and
hydrocracking operations are well known in the art. See for example
U.S. Pat. Nos. 4,347,121 and 4,810,357, the contents of which are
hereby incorporated by reference in their entirety, for general
descriptions of hydrotreating, hydrocracking, and typical catalysts
used in each process.
[0062] 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 unsulfided Group VIIIA 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. Other suitable catalysts are described, for
example, in U.S. Pat. No. 4,157,294, and U.S. Pat. No. 3,904,513.
The non-noble metal (such as nickel-molybdenum) hydrogenation metal
are usually present in the final catalyst composition as oxides, or
more preferably or possibly, as sulfides when such compounds are
readily formed from the particular metal involved. Preferred
non-noble metal catalyst compositions contain in excess of about 5
weight percent, preferably about 5 to about 40 weight percent
molybdenum and/or tungsten, and at least about 0.5, and generally
about 1 to about 15 weight percent of nickel and/or cobalt
determined as the corresponding oxides. The noble metal (such as
platinum) catalyst contain in excess of 0.01 percent metal,
preferably between 0.1 and 1.0 percent metal. Combinations of noble
metals may also be used, such as mixtures of platinum and
palladium.
[0063] The hydrogenation components can be incorporated into the
overall catalyst composition by any one of numerous procedures. The
hydrogenation components can be added to matrix component by
co-mulling, impregnation, or ion exchange and the Group VI
components, i.e.; molybdenum and tungsten can be combined with the
refractory oxide by impregnation, co-mulling or co-precipitation.
Although these components can be combined with the catalyst matrix
as the sulfides, that is generally not preferred, as the sulfur
compounds can interfere with the molecular averaging or
Fischer-Tropsch catalysts.
[0064] The matrix component can be of many types including some
that have acidic catalytic activity. Ones that have activity
include amorphous silica-alumina or may be a zeolitic or
non-zeolitic crystalline molecular sieve. Examples of suitable
matrix molecular sieves include zeolite Y, zeolite X and the so
called ultra stable zeolite Y and high structural silica:alumina
ratio zeolite Y such as that described in U.S. Pat. Nos. 4,401,556,
4,820,402 and 5,059,567. Small crystal size zeolite Y, such as that
described in U.S. Pat. No. 5,073,530, can also be used.
Non-zeolitic molecular sieves which can be used include, for
example, silicoaluminophosphates (SAPO), ferroaluminophosphate,
titanium aluminophosphate and the various ELAPO molecular sieves
described in U.S. Pat. No. 4,913,799 and the references cited
therein. Details regarding the preparation of various non-zeolite
molecular sieves can be found in U.S. Pat. Nos. 5,114,563 (SAPO);
4,913,799 and the various references cited in U.S. Pat. No.
4,913,799. Mesoporous molecular sieves can also be used, for
example the M41S family of materials (J. Am. Chem. Soc.,
114:10834-10843 (1992)), MCM-41 (U.S. Pat. Nos. 5,246,689;
5,198,203; 5,334,368), and MCM-48 (Kresge et al., Nature 359:710
(1992)).
[0065] Suitable matrix materials may also include synthetic or
natural substances as well as inorganic materials such as clay,
silica and/or metal oxides such as silica-alumina, silica-magnesia,
silica-zirconia, silica-thoria, silica-berylia, silica-titania as
well as ternary compositions, such as silica-alumina-thoria,
silica-alumina-zirconia, silica-alumina-magnesia, and
silica-magnesia zirconia. The latter may be either naturally
occurring or in the form of gelatinous-precipitates or gels
including mixtures of silica and metal oxides. Naturally occurring
clays which can be composited with the catalyst include those of
the montmorillonite and kaolin families. These clays can be used in
the raw state as originally mined or initially subjected to
calumniation, acid treatment or chemical modification.
[0066] Furthermore, more than one catalyst type may be used in the
reactor. The different catalyst types can be separated into layers
or mixed. Typical hydrotreating conditions vary over a wide range.
In general, the overall LHSV is about 0.25 to 2.0, preferably about
0.5 to 1.0. The hydrogen partial pressure is greater than 200 psia,
preferably ranging from about 500 psia to about 2000 psia. Hydrogen
recirculation rates are typically greater than 50 SCF/Bbl, and are
preferably between 1000 and 5000 SCF/Bbl. Temperatures range from
about 300.degree. F. to about 750.degree. F., preferably ranging
from 450.degree. F. to 600.degree. F.
[0067] Hydrotreating may also be used as a final step in the lube
base stock manufacturing process. This final step, commonly called
hydrofinishing, removes traces of aromatics, olefins, color bodies,
and solvents. Clay treating to remove these impurities is an
alternative final process step.
[0068] The contents of each of the patents and publications
referred to above is hereby incorporated by reference in its
entirety.
[0069] There are several optional upstream processes, each of which
have the opportunity to adjust either or both of the 95% and VI
values of the lube base stock and lube oils prepared from the base
stocks. The feedstocks can be subjected to fractional distillation,
and properties maximized by altering the temperatures, draw rates
and/or packing materials in the distillation columns, and/or by
changing the design of the internals of the columns. These changes
will adjust the 95% point but will likely have little effect on the
VI.
[0070] The feedstocks can be subjected to hydrocracking and/or
severe hydrotreating conditions. This will have effects on both the
95% point and the VI. Conversion can be increased by increasing the
temperature, thereby increasing the amount of hydrocracking and
decreasing the 95% point. The contact time of the product with the
hydrocracking catalysts can be increased (for example, by
decreasing the WHSV) which will also decrease the 95% point. These
changes will likely result in an increased product VI. More
effective hydrocracking catalysts will also decrease the 95% point
(and may decrease the VI).
[0071] In those embodiments in which one or more of the 1150+
and/or 1150.degree. F.- fractions are obtained via Fischer-Tropsch
synthesis, the chain length of the hydrocarbon products can be
altered by altering the syngas hydrogen/carbon monoxide ratio, the
reaction temperature and/or changing the catalyst.
[0072] The lube base stock properties can also be adjusted by
blending (before or after the process is performed). For example,
by blending a lube base stock prepared according to the process
described herein with a lube base stock with a higher 95% point,
for example, a 95% point above 1150.degree. F., one can increase
the 95% point. Analogously, adding a lube base stock with a VI
value higher or lower than the VI of the product stream will raise
or lower the VI of the resulting blend. This approach can be used
to upgrade otherwise unacceptable product streams to produce
salable products.
[0073] The lube base stock prepared according to the process
described herein can have virtually any desired average molecular
weight, depending on the desired physical and chemical properties
of the lube stock composition, for example, pour point, viscosity,
viscosity index and the like. The average molecular weight can be
controlled by adjusting the boiling range or carbon number range
and proportions of the Solvent Dewaxed and catalytically dewaxed
fractions. The preferred lube base stock composition can generally
be described as including hydrocarbons in the C.sub.20-500 range
that include branching typical of that observed in compositions
subjected to Catalytic Dewaxing preferably Hydroisomerization
Dewaxing processes.
[0074] Preferably, the lube base stock is obtained, at least in
part, via Solvent Dewaxing and Catalytic Dewaxing of fractions
derived from Fischer-Tropsch synthesis, and therefore, contains a
minimum of heteroaroms and aromatics and other cyclic compounds.
Most preferably the Catalytic Dewaxing process uses a
Hydroisomerization Dewaxing Catalyst, and most preferably a
Complete Hydroisomerization Dewaxing Catalyst.
[0075] Lube stock compositions with boiling points in the range of
between about 650 and 1400.degree. F. are preferred, with boiling
points in the range of between about 700 and 1200.degree. F. being
more preferred. However, the process is adaptable to generate
higher or lower boiling lube oils.
[0076] In a preferred embodiment, the lube base stock composition
includes branched hydrocarbons. Preferred Catalytic Dewaxing
catalyst and conditions tend to form isoparaffins. Solvent Dewaxing
does not form isoparaffins, but rather, removes waxy paraffins from
a product. Thus for waxy feedstocks, the feedstock to the Solvent
Dewaxing process is first subjected to Hydroisomerization Dewaxing
(preferably Complete Hydroisomerization Dewaxing). The solvent
dewaxed fraction can optionally be subjected to hydroisomerization
conditions to provide additional branching.
[0077] The lube base stock and/or lube stock compositions
preferably have pour points in the range of 10.degree. C. or lower,
more preferably 0.degree. C. or lower, still more preferably,
-15.degree. C. or lower, and most preferably, between -15 and
-40.degree. C. The degree of branching in the compositions is
preferably kept to the minimum amount needed to arrive at the
desired pour point or cloud point. Pour point depressants can be
added to adjust the pour point to a desired value.
[0078] The lube base stock and/or lube stock compositions
preferably have a viscosity index (a measure of the resistance of
viscosity change to changes in temperature) of at least 100, more
preferably at least 115, most preferably 140 or more. Further, the
compositions preferably have a pour point (as measured, for
example, by ASTM 97, which measures the temperature at which an oil
no longer will flow when it is cooled) of less than 10.degree. F.
The compositions preferably have a cloud point (as measured, for
example, by ASTM D 2500, which measures the temperature at which a
cloud appears in the lube base stock as it is cooled) of less than
about 14.degree. F. The ASTM 97 and D 2500 procedures are well
known to those of skill in the art.
[0079] Further definitions of lube base oil and lube base stock are
in API Publication 1509.
[0080] The lube base oil and/or lube base stock compositions can be
blended with suitable additives to form the lube oil composition
(also commonly known as a finished lube oil or simply lube oil or
lubricant). The lube oil composition includes various additives,
such as lubricity improvers, emulsifiers, wetting agents,
densifiers, fluid-loss additives, viscosity modifiers, corrosion
inhibitors, oxidation inhibitors, friction modifiers, demulsifiers,
anti-wear agents, dispersants, anti-foaming agents, pour point
depressants, detergents, rust inhibitors and the like. Other
hydrocarbons, such as those described in U.S. Pat. No. 5,096,883
and/or U.S. Pat. No. 5,189,012, may be blended with the lube oil
provided that the final blend has the necessary pour point,
kinematic viscosity, flash point, and toxicity properties. The
total amount of additives is preferably between 1-30 percent. All
percentages listed herein are weight percentages unless otherwise
stated. (Additives are commonly provided as a mixture with a
diluent oil prior to blending with the lube base stock and or base
oil.)
[0081] Examples of suitable lubricity improvers (also known as
friction modifiers) include polyol esters of C.sub.12-28 acids.
[0082] Examples of viscosity modifying agents include polymers such
as ethylene alpha-olefin copolymers which generally have weight
average-molecular weights of from about 10,000 to 1,000,000 as
determined by gel permeation chromatography.
[0083] Examples of suitable corrosion inhibitors include
phosphosulfurized hydrocarbons and the products obtained by
reacting a phosphosulfurized hydrocarbon with an alkaline earth
metal oxide or hydroxide.
[0084] Examples of oxidation inhibitors include antioxidants such
as alkaline earth metal salts of alkylphenol thioesters having
preferably C5-C12 alkyl side chain such as calcium nonylphenol
sulfide, barium t-octylphenol sulfide, dioctylphenylamine as well
as sulfurized or phosphosulfurized hydrocarbons. Additional
examples include oil soluble antioxidant copper compounds such as
copper salts of C10 to C18 oil soluble fatty acids.
[0085] Examples of friction modifiers include fatty acid esters and
amides, glycerol esters of dimerized fatty acids and succinate
esters or metal salts thereof.
[0086] Dispersants are well known in the lubricating oil field and
include high molecular weight alkyl succinimides being the reaction
products of oil soluble polyisobutylene succinic anhydride with
ethylene amines such as tetraethylene pentamine and borated salts
thereof.
[0087] Pour point depressants such as C8-C18 dialkyl fumarate vinyl
acetate copolymers, polymethacrylates and wax naphthalene are well
known to those of skill in the art.
[0088] Examples of anti-foaming agents include polysiloxanes such
as silicone oil and polydimethyl siloxane; acrylate polymers are
also suitable.
[0089] Examples of anti-wear agents include zinc
dialkyldithiophosphate, zinc diaryl diphosphate, and sulfurized
isobutylene.
[0090] Examples of detergents and metal rust inhibitors include the
metal salts of sulfonic acids, alkylphenols, sulfurized
alkylphenols, alkyl salicylates, naphthenates and other oil soluble
mono and dicarboxylic acids such as tetrapropyl succinic anhydride.
Neutral or highly basic metal salts such as highly basic alkaline
earth metal sulfonates (especially calcium and magnesium salts) are
frequently used as such detergents. Also useful is nonylphenol
sulfide. Similar materials made by reacting an alkylphenol with
commercial sulfur dichlorides. Suitable alkylphenol sulfides can
also be prepared by reacting alkylphenols with elemental sulfur.
Also suitable as detergents are neutral and basic salts of phenols,
generally known as phenates, wherein the phenol is generally an
alkyl substituted phenolic group, where the substituent is an
aliphatic hydrocarbon group having about 4 to 400 carbon atoms.
[0091] Antioxidants can be added to the lube oil to neutralize or
minimize oil degradation chemistry. Examples of antioxidants
include those described in U.S. Pat. No. 5,200,101, which discloses
certain amine/hindered phenol, acid anhydride and thiol
ester-derived products.
[0092] Additional lube oils additives are described in U.S. Pat.
No. 5,898,023 to Francisco, et al., the contents of which are
hereby incorporated by reference.
[0093] The resulting lube oil compositions can be used, for
example, in automobiles. When derived in whole in large part from
Fischer-Tropsch wax, the high paraffinic nature of the lube oil
gives it high oxidation and thermal stability, and the lube oil has
a high boiling range for its viscosity, i.e., volatility is low,
resulting in low evaporative losses.
[0094] The lube oil compositions can also be used as a blending
component with other oils. For example, the lube oil can be used as
a blending component with polyalpha-olefins, or with mineral oils
to improve the viscosity and viscosity index properties of those
oils, or can be combined with isomerized petroleum wax. The lube
oils can also be used as workover fluids, packer fluids, coring
fluids, completion fluids, and in other oil field and
well-servicing applications. For example, they can be used as
spotting fluids to unstick a drill pipe that has become stuck, or
they can be used to replace part or all of the expensive
polyalphaolefin lubricating additives in downhole applications.
Additionally, they can also be used in drilling fluid formulations
where shale-swelling inhibition is important, such as those
described in U.S. Pat. No. 4,941,981 to Perricone et al.
[0095] The present invention will be better understood with
reference to the following non-limiting examples.
Example 1
Formation of Lube Base Stock Compositions
[0096] A series of Hydroisomerization Dewaxing catalysts were
prepared and tested. The object was to find methods where the
pour-cloud spread was minimized. Between 0.25 and 10 grams of
catalyst were loaded in tubular reactors, reduced with hydrogen,
and evaluated with various waxy lubricant oils. From this study
results that generate lube base stocks with pour points between -25
and 0.degree. C. were selected. All catalysts contained zeolites
and molecular sieves known to be usefull for Hydroisomerization
Dewaxing either Complete or Partial. Catalysts tested include the
samples of the following structures either in pure phase or in
combination: SSZ-20, -25, -28, -31, -32, -41, -43, and -54;
SAPO-11, -31, and -41; ZSM-5, 11, 12, -23, and -48; Mordenite,
Ferrerite, Beta, SUZ-4 and EU-1.
[0097] The ranges of feedstocks and process conditions are shown
below.
TABLE-US-00002 Maximum Minimum Variable Value Value Average Feed
Paraffinic Carbon, ndM 99.4 51.2 72.4 Feed Saturates by HPLC 96.0
51.0 86.1 Feed Wax, Wt % 83.2 7.9 25.5 Feed 50% point by D2887,
.degree. F. 1198 633 887 Feed 95% point by D2887, .degree. F. 1360
696 1001 Feed 99% point by D2887, .degree. F. 1400 707 1048 Feed
Sulfur, ppm 1500 1.96 35.5 Feed Nitrogen, ppm. 120.96 0.05 2.01
Feed Oxygen, ppm 2480 9.0 367 Feed VI 197 76 118 Catalyst
Temperature, .degree. F. 790 451 652 Pressure, psig 2450 200 2082
WHSV, h-1 18.54 0.24 1.81 Conversion, Wt % 96.4 0.24 18.42 H2 Rate,
SCFB 24,714 1367 3910
[0098] The factors that were found to have a significant impact on
the pour-cloud spread were a surprising combination of both
feedstock boiling range (as measured by the heaviest fractions) and
the viscosity index of the product. The trends showed that the
pour-cloud spread depends primarily on the product 95% point, and
also on the product VI. Even selective Complete Hydroisomerization
Dewaxing catalysts were not able to achieve products with low
pour-cloud spread from feedstocks that had both 95% points in
excess of 1150.degree. F. and VI values in excess of 115.
[0099] Based on the data obtained, the following factors are not
believed to be significantly responsible for the pour-cloud
spread:
[0100] Structure of the zeolite or molecular sieve in the
catalyst.
[0101] Feed sulfur content
[0102] Feed nitrogen content
[0103] Feed oxygen content
[0104] Catalyst temperature
[0105] Pressure of operation
[0106] WHSV
[0107] Conversion
[0108] Gas Rate
[0109] As the product's VI increases, and as the product's 95%
point increases, the spread in pour-cloud can increase. For lube
base stocks with 95% points below 1150.degree. F., there is very
little trend for the pour-cloud spread to increase with increase in
product VI. It is approximately constant at 7.degree. C. However,
when stocks with 95% points in excess of 1150.degree. F. are
examined, pour cloud spread is much higher, and the product VI
plays a much stronger role. Products from feedstocks with 95%
points below 1150.degree. F. are in general, less viscous than
products from feedstocks with 95% points above 1150.degree. F.
TABLE-US-00003 95% Pt Range .ltoreq.1150 .ltoreq.1150 >1150
>1150 VI Range .ltoreq.115 >115 .ltoreq.115 >115 No. Data
Points 2744 869 95 134 95% Point Data, .degree. F. 95% Minimum 800
696 1160 1151 95% Maximum 1035 1125 1290 1360 95% Average 992 952
1280 1277 VI Data VI Minimum 60.9 115.1 97 115 VI Maximum 115 172
114.9 170 VI Average 101.4 130.9 108 129.6 Pour-Cloud Spread Data,
.degree. C. P-C Minimum -15 -3 3 12 P-C Maximum 69 56 46 67 P-C
Average 6.7 8.5 22.8 33.3
[0110] The change in the pour-cloud spread with product VI for
stocks with 95% points in excess of 1150.degree. F. is much larger
than for stocks with 95% points below 11150.degree. F. For stocks
with 95% points in excess of 1150.degree. F. and with conventional
VI values (i.e., less than about 115) the expected pour-cloud
spread will be approximately 30.degree. C., which is acceptable.
However, for stocks with a combination of 95% points in excess of
1150.degree. F. and with VI values in excess of 115, the pour-cloud
spread can be much larger, about 33.degree. C. and in some cases
approaching 60.degree. C.
[0111] Pour-cloud spreads above about 30.degree. C. are undesirable
because they require the process to dewax the base stock to very
low pour points in order to meet the cloud point specification.
This in turn results in unacceptable yield losses. The process
described herein avoids these yield losses by Solvent Dewaxing
stocks that have a combination of 95% points in excess of
1150.degree. F., preferably but not necessarily with VI values
above 115, and catalytically dewaxing stocks with 95% points less
than 1150.degree. F.
[0112] Fischer Tropsch stocks that have wax contents in excess of
50%, and that have 95% points in excess of about 1150.degree. F.
(and most preferably those which generate base stocks with VI
values in excess of 115) should preferably be processed by a
combination of operations which first involve isomerization of the
paraffins (Hydroisomerization Dewaxing) followed by Solvent
Dewaxing. Preferably the Hydroisomerization Dewaxing is a Complete
Hydroisomerization Dewaxing process. Fischer Tropsch stocks that
have 95% points below about 1150.degree. F. can be processed by
Catalytic Dewaxing alone, preferably using Hydroisomerization
Dewaxing (most preferably Complete Hydroisomerization Dewaxing) to
effect the Catalytic Dewaxing.
[0113] While the above data are presented in terms of the product
properties, there are also good correlations with the waxy
feedstock. For the 95% points, the product and feed values are
essentially equivalent. The waxy feed VI tends to be higher than
the product VI. For example, a product VI of 115 is roughly
equivalent to a waxy feedstock VI of 128 for an average feedstock
as evaluated in Example 1. The VI of a waxy feedstock can be
determined by measuring the viscosity at two temperatures where it
is fluid, say 70.degree. C. and 100 C, and then by extrapolation of
a value at 40.degree. C., which is used in the VI calculation.
[0114] While the present invention has been described with
reference to specific embodiments, this application is intended to
cover those various changes and substitutions that may be made by
those skilled in the art without departing from the spirit and
scope of the appended claims.
* * * * *