U.S. patent application number 10/722241 was filed with the patent office on 2004-09-02 for co-extraction of a hydrocarbon material and extract obtained by solvent extraction of a second hydrotreated material.
This patent application is currently assigned to ExxonMobil Research and Engineering Company. Invention is credited to Boucher Ashe, Heather A., Taylor, Ronald J..
Application Number | 20040168955 10/722241 |
Document ID | / |
Family ID | 32913037 |
Filed Date | 2004-09-02 |
United States Patent
Application |
20040168955 |
Kind Code |
A1 |
Boucher Ashe, Heather A. ;
et al. |
September 2, 2004 |
Co-extraction of a hydrocarbon material and extract obtained by
solvent extraction of a second hydrotreated material
Abstract
The present invention relates to a process to increase
extraction yields and improve dewaxing performance of a lube
boiling range stream. More particularly, the present invention is a
process to produce at least one base oil by contacting a light lube
stream with a polar solvent in a solvent extraction zone, then
mixing the resulting extract with a second, heavier lube stream,
extracting the mixture with a polar solvent, and dewaxing the
resultant raffinate.
Inventors: |
Boucher Ashe, Heather A.;
(Point Edward, CA) ; Taylor, Ronald J.; (Samla,
CA) |
Correspondence
Address: |
EXXONMOBIL RESEARCH AND ENGINEERING COMPANY
P.O. BOX 900
1545 ROUTE 22 EAST
ANNANDALE
NJ
08801-0900
US
|
Assignee: |
ExxonMobil Research and Engineering
Company
Annandale
NJ
08801-0900
|
Family ID: |
32913037 |
Appl. No.: |
10/722241 |
Filed: |
November 25, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60450968 |
Feb 28, 2003 |
|
|
|
60464709 |
Apr 23, 2003 |
|
|
|
Current U.S.
Class: |
208/87 ;
208/18 |
Current CPC
Class: |
C10G 2400/10 20130101;
C10G 21/00 20130101 |
Class at
Publication: |
208/087 ;
208/018 |
International
Class: |
C10G 021/00; C10G
067/04 |
Claims
1. A process to improve dewaxing performance and extraction yields
of a lube boiling range stream comprising: a) contacting a light
lube stream in a first solvent extraction zone with a first
extraction solvent to produce at least a first aromatics-rich
extract solution and a first aromatics-lean raffinate solution; b)
removing at least a portion of said first extraction solvent from
said first aromatics-rich extract solution to produce at least a
first aromatics-rich extract; c) mixing at least a portion of said
first aromatics-rich extract with a heavier lube stream to produce
a mixed lube stream; d) contacting said mixed lube stream in a
second solvent-extraction zone with a second extraction solvent to
produce at least a second aromatics-rich extract solution and a
second aromatics-lean raffinate solution; e) removing at least a
portion of said second extraction solvent from said second
aromatics-lean raffinate solution to produce at least a second
aromatics-lean raffinate; and f) dewaxing said second
aromatics-lean raffinate to produce at least one base oil.
2. The process of claim 1 wherein said light lube stream is
characterized as having a mid boiling point range of about
350.degree. C. to about 450.degree. C.
3. The process according to claim 2 wherein said heavier lube
stream has a mid boiling point range greater than 450.degree.
C.
4. The process of claim 3 wherein said light lube stream is a
hydrocracked light lube stream.
5. The process of claim 4 wherein said first extraction solvent and
said second extraction solvent are selected from the group
consisting of sulfolane, furfural, phenol, and N-methyl pyrrolidone
(NMP).
6. The process of claim 5 wherein at least about 5 volume percent
of said first aromatics-rich extract is conducted to said mixing
zone.
7. The process of claim 6 wherein at least about 25 volume percent
of said first aromatics-rich extract is conducted to said mixing
zone.
8. The process of claim 7 wherein at least about 35 volume percent
of said first aromatics-rich extract is conducted to said mixing
zone.
9. The process according to claim 8 wherein the mixed lube stream
comprises less than about 70 volume percent, based on the mixed
lube stream, of the first aromatics-rich extract.
10. The process according to claim 9 wherein the mixed lube stream
comprises less than about 30 volume percent, based on the mixed
lube stream, of the first aromatics-rich extract.
11. The process according to claim 10 wherein the mixed lube stream
comprises about 15 volume percent, based on the mixed lube stream,
of the first aromatics-rich extract.
12. The process of claim 5 wherein said second aromatics-lean
raffinate is dewaxed in a catalytic dewaxing zone.
13. The process according to claim 5 wherein said second
aromatic-lean raffinate is dewaxed in a solvent dewaxing zone.
14. The process of claim 13 wherein said at least one base oil is
characterized as having a mid-boiling point range (50% LV), as
determined by ASTM D6417, of about 400 to about 490.degree. C., and
a Viscosity Index of about 80-120.
15. The base oil of claim 14.
16. The process of claim 13 wherein said heavier lube stream is a
hydrocracked heavier lube stream.
17. A process to improve dewaxing performance and extraction yields
of a lube boiling range stream comprising: a) contacting at least
one light lube stream in a first solvent extraction zone with a
first extraction solvent to produce at least a first aromatics-rich
extract solution and a first aromatics-lean raffinate solution; b)
removing at least a portion of said first extraction solvent from
said first aromatics-rich extract solution to produce at least a
first aromatics-rich extract; c) contacting at least one other
light lube stream in a second solvent extraction zone with a second
extraction solvent to produce at least a second aromatics-rich
extract solution and at least a second aromatics-lean raffinate
solution; d) removing at least a portion of said second extraction
solvent from said second aromatics-rich extract solution to produce
at least a second aromatics-rich extract; e) mixing at least a
portion of said first aromatics-rich extract and at least a portion
of said second aromatics-rich extract with a heavier lube stream to
produce a mixed lube stream; f) contacting said mixed lube stream
in a solvent-extraction zone with a third extraction solvent to
produce at least a third aromatics-rich extract solution and at
least a third aromatics-lean raffinate solution; g) removing at
least a portion of said third extraction solvent from said third
aromatics-lean raffinate solution to produce at least a first
aromatics-lean raffinate; h) dewaxing said third aromatics-lean
raffinate to produce at least one base oil.
18. The process according to claim 17 wherein said at least one
light lube stream is a hydrocracked light lube stream and said at
least one other light lube stream is a hydrocracked light lube
stream.
19. The process according to claim 18 wherein said third
aromatics-lean raffinate is dewaxed in said dewaxing zone by the
use of solvent dewaxing methods or processes.
20. The process according to claim 19 wherein there exists more
than two light lube streams that are hydrocracked light lube
streams, hydrotreated light lube streams, or any combination
thereof.
21. The process according to claim 20 wherein said heavier lube
stream is a heavier hydrocracked lube stream.
22. The process according to claim 20 wherein said first
aromatics-lean extract and said second aromatics-lean extract are
mixed prior to being mixed in the mixing zone with the heavier lube
stream.
23. The product according to claim 18.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. Provisional Patent
Applications Ser. Nos. 60/450,968 filed Feb. 28, 2003 and
60/464,709 filed Apr. 23, 2003.
FIELD OF THE INVENTION
[0002] The present invention relates to a process to increase
extraction yields and improve dewaxing performance of a lube
boiling range stream. More particularly, the present invention is a
process to produce at least one base oil by contacting a light lube
stream with a polar solvent in a solvent extraction zone, then
mixing the resulting extract with a second, heavier lube stream,
extracting the mixture with a polar solvent, and dewaxing the
resultant raffinate.
BACKGROUND OF THE INVENTION
[0003] The separation of aromatics from hydrocarbon streams by
solvent extraction has long been practiced in the refining
industry, particularly in the production of lubricating oil. This
process involves the use of solvents, such as for example, phenol
or N-methyl pyrrolidone ("NMP"), that are selective for extracting
aromatic hydrocarbons present in the hydrocarbon streams. During
the extraction process, a hydrocarbon stream and solvent are
intimately contacted resulting in the formation of a
solvent/aromatics-rich phase commonly called the extract solution
and a solvent/aromatics-lean phase commonly called the raffinate
solution. Typically, the extract solution and the raffinate
solution are separately processed, i.e. stripped, in distillation
units to recover the solvent contained in each stream. The stripped
hydrocarbon streams are called the extract (aromatics-rich) and the
raffinate (aromatics-lean).
[0004] However, because no solvent extraction process can be one
hundred percent selective, the aromatics-rich phase typically
contains minor, but economically significant, quantities of
non-aromatic hydrocarbons that are valuable lube oil molecules.
Thus, many processes have been proposed to recover these valuable
lube oil molecules. For example, U.S. Pat. No. 4,311,583, teaches
that the primary extract solution produced from a solvent
extraction process can be further separated by cooling or by the
addition of water or a wet solvent. The separation produces a
secondary extract solution and a secondary raffinate solution. At
least a portion of the secondary raffinate solution is combined
with the primary raffinate solution to obtain an increased yield of
desired lube oil product. In addition, at least a portion of the
secondary raffinate solution may be mixed with fresh feed entering
the extraction zone.
[0005] Likewise, U.S. Pat. No. 5,616,238, teaches that the extract
solution produced from a solvent extraction zone can be separated
into a pseudo-raffinate solution phase by subjecting the extract
solution to water injection in the absence of cooling. The
pseudo-raffinate solution is then combined with the feed to the
extraction zone without manipulating the flow rate of the solvent
so that increased yields of improved products are produced.
[0006] U.S. Pat. No. 5,242,579, also teaches a similar process,
although this patent is directed to a method of controlling the
solvent extraction process. In this patent, it is taught to solvent
extract a feedstock to produce a primary raffinate solution and a
primary extract solution phase. The primary extract solution phase
is then forced to separate into two phases in a separation zone by
lowering its temperature. The separation zone thus produces a
secondary extract and a secondary raffinate stream. This secondary
raffinate solution stream is passed to the extraction zone to
produce an improved yield of primary raffinate having a specified
polynuclear aromatic content.
[0007] A process similar to that of U.S. Pat. No. 5,242,579 is
taught in U.S. Pat. No. 2,299,426. In this patent, the extract
solution produced during the extraction stage is divided and at
least a portion is recycled to the lower part of the extraction
tower in order to maintain a constant hydraulic loading of the feed
distributors.
[0008] However, there still exists a need in the art whereby one
can effectively produce a quality base oil through increasing the
dewaxing performance and extraction yields of a lube stream.
SUMMARY OF THE INVENTION
[0009] The present invention is a process to improve dewaxing
performance and extraction yields from lube oil streams
comprising:
[0010] a) contacting a light lube stream in a first solvent
extraction zone with a first extraction solvent to produce at least
a first aromatics-rich extract solution and a first aromatics-lean
raffinate solution;
[0011] b) removing at least a portion of said first extraction
solvent from said first aromatics-rich extract solution to produce
at least a first aromatics-rich extract;
[0012] c) mixing at least a portion of said first aromatics-rich
extract with a heavier lube stream to produce a mixed lube
stream;
[0013] d) contacting said mixed lube stream in a second
solvent-extraction zone with a second extraction solvent to produce
at least a second aromatics-rich extract solution and a second
aromatics-lean raffinate solution;
[0014] e) removing at least a portion of said second extraction
solvent from said second aromatics-lean raffinate solution to
produce at least a second aromatics-lean raffinate; and
[0015] f) dewaxing said second aromatics-lean raffinate to produce
at least one base oil.
[0016] In one embodiment, the light lube stream is contacted with a
hydrocracking catalyst under hydrocracking conditions before said
light lube stream is contacted with said first extraction solvent
in said first extraction zone.
[0017] In another embodiment, the second, heavier lube stream is
also contacted with a hydrocracking catalyst under hydrocracking
conditions before said heavier lube stream is mixed with said first
aromatics rich extract.
[0018] In still another embodiment, the first aromatics-rich
extract that is mixed with the heavier lube stream is a mixture of
extracts resulting from the separate solvent extraction of at least
two different light lube streams.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The present invention provides a process that involves
mixing the aromatics-rich extract produced by the solvent
extraction of a light lube stream with a heavier lube stream. The
mixture of the aromatics-rich extract and the heavier lube stream
is referred to herein as a mixed lube stream. The mixed lube stream
is contacted with a second extraction solvent in a solvent
extraction zone to produce at least a second aromatics-lean
raffinate. At least a portion of the second aromatics-lean
raffinate is conducted to a dewaxing zone wherein at least one base
oil is produced. Through the use if the instant invention,
extraction yields are improved because there are good lube-range
molecules present in the first aromatics-rich extract. By combining
the first aromatics-rich extract with the heavier lube stream and
co-extracting them, at least a portion of the good lube-range
molecules present in the first aromatics-rich extract can be
recovered.
[0020] It should be noted that the phrases "aromatics-lean
raffinate solution" and "aromatics-rich extract solution" are not
synonymous with the phrases "aromatics-lean raffinate" and
"aromatics-rich extract". The phrases "aromatics-lean raffinate
solution" and "aromatics-rich extract solution" are meant to refer
to the products of solvent extraction before the solvent has been
removed, i.e. distilled or stripped, from the respective phases.
Thus, the phrases "aromatics-lean raffinate" and "aromatics-rich
extract" refer to the respective products after at least a portion
of the solvent contained in the "aromatics-lean raffinate solution"
and "aromatics-rich extract solution" has been removed.
[0021] As used herein, aromatics-rich is meant to refer to the
concentration of aromatics present in the extract phase produced by
solvent extraction in relation to the concentration of aromatics
present in the raffinate phase produced by solvent extraction.
Also, the use of the word "heavier" in conjunction with "lube
stream" is meant to refer to the fact that this lube stream has a
higher boiling point in relation to the light lube stream.
Likewise, the use of the word light to refer to a lube stream is
meant to refer to the fact that this lube stream has a lower
boiling point with respect to the heavier lube stream.
[0022] In the practice of the present invention, the light lube
stream typically has a mid-boiling point range (50% LV), as
determined by ASTM D6417, of about 350.degree. C. to about
450.degree. C., preferably from about 375.degree. C. to 430.degree.
C. In a most preferred embodiment, the light lube stream used in
the practice of the present invention has a mid-boiling point in
the range of about 400.degree. C. to about 425.degree. C.
[0023] The heavier lube stream referred to herein is distinct from
the light lube stream and has a mid-boiling point range greater
than 450.degree. C., preferably from 450.degree. C. to about
550.degree. C., more preferably from about 460.degree. C. to about
525.degree. C., and most preferably from about 465.degree. C. to
about 490.degree. C. By distinct, it is meant that the heavier lube
stream is not generated by "splitting", either mechanically or by
temperature separation, the light lube stream into more than one
stream. The heavier lube stream is also not a recycle or other
stream generated by the processing of the light lube stream.
[0024] It is also preferred that the light lube stream be a
hydrocracked light lube stream. Thus, it is preferred to produce
the light lube stream by contacting a hydrocarbonaceous feedstream
with a hydrocracking catalyst under hydrocracking conditions. The
hydrocracking of the hydrocarbonaceous feedstream produces a
hydrocracked stream that is subjected to fractionation in the
fractionation tower associated with the hydrocracking unit
utilized. The fractionation of this hydrocracked stream preferably
produces at least two fractions, one of which is a higher-boiling
bottoms fraction and one of which is a lower-boiling lighter
fraction. The hydrocracked light lube stream is preferably the
lighter fraction.
[0025] It should also be noted that any conventional hydrocracking
catalyst can be used in the hydrocracking of the hydrocarbonaceous
feedstream. Typical catalysts contain a hydrogenation component and
a cracking component. It is preferred that the hydrogenation
component is supported on a refractory cracking base. Typical
cracking bases include two or more refractory oxides, and typical
hydrogenation components are chosen from Group VIB metals, Group
VIII metals, their oxides, or mixtures thereof. The conditions
under which the hydrocracking is conducted are also conventional.
These conditions include reaction temperatures in the range of
about 400.degree. F.(204.degree. C.) to about 800.degree.
F.(427.degree. C.). Total pressures typically range from about 100
to about 1000 psig with hydrogen partial pressures ranging from
about 50 to about 450 psig. Typical gas hourly space velocities are
between about 200 to about 2000 v/v/hr. Thus, the practitioner of
the present invention may utilize any known hydrocracking catalyst
known under any known hydrocracking conditions to produce a
hydrocracked light lube stream having the above-defined boiling
point parameters.
[0026] In the practice of the present invention, the heavier lube
stream is typically a non-hydrocracked, i.e. conventional, heavier
lube stream. However, it is within the scope of the present
invention, and preferred, that the heavier lube stream be a
hydrocracked heavier lube stream. Thus, the heavier lube stream can
be produced by contacting a hydrocarbonaceous feedstream with any
known hydrocracking under any known hydrocracking conditions. The
hydrocracking of this lube stream also produces a hydrocracked
stream that is subjected to fractionation in the fractionation
tower associated with the hydrocracking unit utilized. The
fractionation of this hydrocracked stream preferably produces at
least two fractions, one of which is a bottoms fraction. By bottoms
fraction it is meant that fraction having the higher boiling point
from the fractionation tower. The heavier lube stream is preferably
the bottoms fraction and has the above-defined boiling parameters
discussed in relation to the heavier lube stream.
[0027] As previously stated, in the practice of the present
invention, the above-defined light lube stream is subjected to
solvent extraction in a first solvent extraction zone. In the first
solvent extraction zone, the light lube stream is contacted with a
first extraction solvent. The first extraction solvent can be any
solvent known that has an affinity for aromatic hydrocarbons in
preference to non-aromatic hydrocarbons. Non-limiting examples of
such solvents include sulfolane, furfural, phenol, and N-methyl
pyrrolidone ("NMP"). Furfural, phenol, and NMP are preferred.
[0028] The light lube stream can be contacted with the first
extraction solvent by any suitable solvent extraction method.
Non-limiting examples of such include batch, semi-batch, or
continuous. It is preferred that the extraction process be a
continuous process, and it is more preferred that the continuous
process be operated in a counter-current fashion. In a
counter-current configuration, it is preferred that the light lube
stream be introduced into the bottom of an elongated contacting
zone or tower and caused to flow in an upward direction while the
first extraction solvent is introduced at the top of the tower and
allowed to flow in a downward direction, counter-current to the
upflowing light lube stream. In this configuration, the light lube
stream is forced to pass counter-currently to the first extraction
solvent resulting in the intimate contact between the first
extraction solvent and the light lube stream. The extraction
solvent and the light lube stream migrate to opposite ends of the
contacting zone.
[0029] The conditions under which the first extraction solvent is
contacted with the light lube stream include tower top temperatures
from about 180.degree. F.(82.degree. C.) to about 225.degree.
F.(107.degree. C.), preferably from about 160.degree. F.(71.degree.
C.) to about 205.degree. F.(96.degree. C.). Tower bottom
temperatures are typically about 40.degree. F., preferably
30.degree. F., lower than the tower top temperatures. Pressures
typically range from 0 about psi(0kPa) to about 20 psi(138kPa),
preferably from about 5 psi(34 kPa) to about 15 psi(103 kPa). In a
most preferred embodiment, the temperature and pressure are
selected to prevent complete miscibility of the light lube stream
in the first extraction solvent.
[0030] The contacting of the light lube stream with the first
extraction solvent produces at least a first aromatics-rich extract
solution and a first aromatics-lean raffinate solution. The first
aromatics-rich extract solution is then treated to remove at least
a portion of the first extraction solvent contained therein, thus
producing the first aromatics rich extract. The removal of at least
a portion of the first extraction solvent can be done by any means
known in the art effective at separating at least a portion of an
extraction solvent from an aromatics rich extract solution.
Preferably the first aromatics rich extract is produced by
separating at least a portion of the first extraction solvent from
the first aromatics-rich extract solution in a stripping or
distillation tower. By at least a portion, it is meant that at
least about 80 vol. %, preferably about 90 vol. %, more preferably
95 vol. %, based on the first aromatics-rich extract solution, of
the first extraction solvent is removed from the first
aromatics-rich extract solution. Most preferably substantially all
of the first extraction solvent is removed from the first
aromatics-rich extract solution.
[0031] However, the removal of at least a portion of the first
extraction solvent from the first extract solution is best
accomplished by use of vacuum distillation tower that continuously
and preferentially separates at least a portion of the first
extraction solvent from the hydrocarbon fraction present in the
first extract solution. The temperatures at the bottom and top of
the vacuum distillation tower can be any temperatures that allow
the vacuum distillation to effectively separate at least a portion
of the first extraction solvent from the hydrocarbon fraction
present in the first extract solution. Preferably, the temperatures
at the bottom and top of the distillation tower are about
585.degree. F. and 485.degree. F. respectively, more preferably
about 575.degree. F. and 475.degree. F., respectively. Vacuum
pressures suitable for use herein can be any pressures that when
used allow the vacuum distillation tower to effectively separate at
least a portion of the first extraction solvent from the
hydrocarbon fraction present in the first extract solution.
Preferably, the vacuum distillation tower pressure is 45-60 psig
(vacuum), most preferably 50-55 psig (vacuum). It is preferred to
recycle the recovered solvent to the start of the extraction
process.
[0032] The first aromatics-lean raffinate solution can be passed to
further processing. However, it is preferred that the first
aromatics-lean raffinate solution be treated in the same manner as
the first aromatics-rich extract solution, i.e. be treated to
remove at least a portion of the first extraction solvent, to
produce at least an aromatics-lean raffinate.
[0033] At least a portion of the first aromatics-rich extract is
then mixed with a heavier lube stream. The amount of the first
aromatics-rich extract mixed with the heavier lube stream is based
on the relative amounts of the first aromatics-rich extract and
heavier lube stream available, their physical characteristics, and
the degree of improvement desired. Typically, at least a portion is
about 5 vol.% preferably about 25 vol.%, more preferably about 35
vol.%, and most preferably about 50 vol.%, based on the aromatics
rich extract, of the aromatics-rich extract is mixed with the
heavier lube stream. The amount of the first aromatics-rich extract
not mixed with the heavier lube stream can be passed to further
processing such as, for example, solvent recovery processes or
catalytic cracking operations. The amount of first aromatics-rich
extract solution or aromatics-rich extract not mixed with the
heavier lube stream can also be used to benefit the first solvent
extraction zone in any manner. Some beneficial processes are
described in the art, such as, for example, those processes
described in U.S. Pat. No. 4,311,583, U.S. Pat. No. 5,616,238, U.S.
Pat. No. 5,242,579, and U.S. Pat. No. 2,299,426, all of which have
been previously mentioned and all of which are herein incorporated
by reference.
[0034] As previously stated, after the first extraction zone, at
least a portion of the first aromatics-rich extract is mixed with a
heavier lube stream to form a mixed lube stream. Mixing can be
accomplished by any suitable technique as long as adequate mixing
is achieved. Non-limiting examples of suitable mixing techniques
include the use of a storage vessel, an agitated storage vessel, a
simple "t-valve", any valve suitable for introducing one stream
into another stream, or any other mixing apparatus known in the art
that will provide a substantially homogenous mixed lube stream made
up of at least a portion of the first aromatics-rich extract and
the heavier lube stream. Preferably, they are mixed in a storage
vessel.
[0035] The mixed lube stream typically comprises less than about 70
vol.%, based on the total volume of the mixed lube stream, of the
first aromatics-rich extract, preferably less than about 50 vol.%,
and more preferably less than about 30 vol.%. In a most preferred
embodiment, the mixed lube stream comprises about 15 vol.% of the
first aromatics-rich extract.
[0036] After mixing, the mixed lube stream is conducted to a second
solvent extraction zone that is operated in a manner such that the
mixed lube stream is intimately contacted with a second extraction
solvent. The second extraction solvent can be selected from those
solvents suitable for use in the first extraction zone.
[0037] In the second extraction zone, the mixed lube stream can be
contacted with the second extraction solvent by any suitable
solvent extraction method or process. Non-limiting examples of such
methods or processes include batch, semi-batch, or continuous. It
is preferred that the process is a continuous process, and that the
continuous process be operated in a counter-current fashion, as
previously described.
[0038] The conditions under which the second extraction solvent is
contacted with the mixed lube stream include tower top temperatures
from about 180.degree. F.(82.degree. C.) to about 225.degree.
F.(107.degree. C.), preferably from about 160.degree. F.(71.degree.
C.) to about 205.degree. F.(96.degree. C.). Tower bottom
temperatures are typically about 40.degree. F., preferably
30.degree. F., lower than the tower top temperatures. Pressures
typically range from about 0 psi(0 kPa) to about 20 psi(138 kPa),
preferably from about 5 psi(34 kPa) to about 15 psi(103 kPa). In a
most preferred embodiment, the temperature and pressure are
selected to prevent complete miscibility of the mixed lube stream
in the second extraction solvent.
[0039] The contacting of the mixed lube stream with the second
extraction solvent also produces at least an aromatics-rich extract
solution phase and at least an aromatics-lean raffinate solution
phase, referred to herein as the second aromatics-rich extract
solution and the second aromatics-lean raffinate solution. The
second aromatics-lean raffinate solution is treated, as described
above in reference to the first aromatics-rich extract solution, to
remove at least a portion of the second extraction solution
contained therein, thus producing a second aromatics-lean
raffinate. By at least a portion, it is meant that at least about
50 vol. %, preferably about 80 vol. %, more preferably about 95
vol. %, based on the first aromatics-lean raffinate solution, of
the second extraction solvent is removed from the second
aromatics-lean raffinate solution. Most preferably substantially
all of the second extraction solvent is removed from the second
aromatics-lean raffinate solution. The second aromatics-rich
extract solution can be treated in any manner described above in
relation to the first aromatics-rich extract solution. The second
aromatics-rich extract solution or the aromatics-rich extract can
also be used to benefit the second solvent extraction zone in any
manner described in relation to the first solvent extraction zone.
The second aromatics-rich extract can also be sent to solvent
recovery processes or catalytic cracking processes.
[0040] After contacting the mixed lube stream with the second
extraction solvent, the second aromatics-lean raffinate thus
produced is dewaxed in a dewaxing zone wherein at least one base
oil is produced. The manner in which the second aromatics-lean
raffinate is dewaxed can be any suitable dewaxing method or
process. Non-limiting examples of suitable dewaxing methods include
catalytic and solvent dewaxing. Preferred is solvent dewaxing. In
solvent dewaxing the second aromatics-lean raffinate, it is
critical that the second aromatics-lean raffinate and the dewaxing
solvent remain as a single phase at the dewaxing temperature. It is
especially important that the hydrocarbon molecules and the
dewaxing solvent remain as a single phase at the filtration
temperature. In other words, the hydrocarbons contained in the
aromatics-lean raffinate and the dewaxing solvent must be miscible
at the filter temperature because it is extremely difficult to
filter a stream that has separated into two phases. Therefore, the
miscibility temperature of the hydrocarbons contained in the
aromatics-lean raffinate in the dewaxing solvent limits the
conditions under which the dewaxing can effectively operate. Lower
miscibility temperatures are desirable because this increases the
operating flexibility of the solvent dewaxing process. Thus, any
way of lowering the miscibility temperature, i.e. the minimum
temperature at which the hydrocarbon and dewaxing solvent are
miscible, is very advantageous. The addition of the first
aromatics-rich extract to the heavier lube stream lowers the
miscibility temperature of the second aromatics-lean raffinate,
thus making it easier to dewax.
[0041] In the solvent-dewaxing of the second raffinate phase, an
effective amount of any suitable dewaxing solvent may be used, for
example, between about 50 and about 700 vol. % solvent to oil
ratio, most preferably between about 100 and 500 vol. % solvent to
oil ratio may be used. Non-limiting examples of suitable dewaxing
solvents include methyl ethyl ketone ("MEK") and methyl isobutyl
ketone ("MIBK"). Preferred dewaxing solvents include a mixture of
MEK and MIBK, preferred are those mixtures containing about 30 vol.
% MEK, based on the total volume of the solvent.
[0042] The base oil produced in the dewaxing stage will typically
have a mid-boiling point range (50% LV), as determined by ASTM
D6417, of about 400 to about 490.degree. C., preferably about 420
to about 470.degree. C., and will have a Viscosity Index of about
80-120.
[0043] In another embodiment of the present invention, there exists
at least two hydrocracked light lube streams that are subjected to
solvent extraction to produce at least two aromatics-rich extract
phases. These at least two hydrocracked light lube streams are
produced in the same manner described above in relation to the
light hydrocracked lube stream. Suitable hydrocracking conditions
and catalysts are those described above. In this embodiment, the at
least two hydrocracked light lube streams are conducted to
respective solvent extraction zones wherein the solvent extraction
of each hydrocracked light lube stream produces at least one
aromatics-rich extract. The solvent extraction processes, solvents,
and conditions used in this embodiment are those that are described
above. After solvent extraction, at least a portion of the
respective aromatics-rich extracts are mixed with a heavier lube
stream. Suitable mixing means are those described above. In this
embodiment, it is contemplated that the respective portions of the
aromatics-rich extracts be mixed prior to being mixed with the
heavier lube stream. Suitable mixing means for mixing the
respective portions of the aromatics-rich extracts are also those
described above in relation to the mixing zone.
[0044] In yet another embodiment of the present invention, the
aromatics rich extract phase that is mixed with the heavier lube
stream comprises at least a portion of each of the aromatics-rich
extracts produced from the solvent extraction of at least two light
lube streams. One of the light lube streams can be a hydrocracked
light lube stream, and the other can be a hydrotreated light lube
stream, both streams having boiling range characteristics described
above in relation to the light lube stream. The hydrocracked light
lube stream can be produced by the same hydrocracking process
described above. The hydrotreated light lube stream can be produced
by contacting a light lube feedstream with a suitable hydrotreating
catalyst under hydrotreating conditions. Suitable hydrotreating
catalysts include those containing at least one Group VIII metal,
such as Ni or Co, and at least one Group VI metal such as Mo or W.
Non-limiting examples of preferred hydrotreating catalysts include
Ni/Mo on alumina, Ni/W on alumina, Co/Mo on alumina, etc.
Conditions under which the hydrotreating is performed include
temperatures from about 280.degree. C. to about 400.degree. C. with
hydrogen treat gas rates in the range of about 500 to about 5000
SCF/bbl and liquid hourly space velocities ranging from about 0.1
to 5 v/v/hr (volume of feed/volume of catalyst/per hour).
Preferably the hydrotreating is conducted under conditions
including temperatures in the range of about 340.degree. C. to
about 425.degree. C., more preferably 370.degree. C. to about
400.degree. C., with hydrogen partial pressures ranging from about
500 to about 2500 psig, more preferably about 1000 to about 1500
psig. It is also preferred to use hydrogen treat gas rates of 1000
to about 2000 SCF/bbl with liquid hourly space velocities ranging
from about 0.1 to about 2.0 v/v/hr, more preferably 0.2 to about
0.5 v/v/hr. After the light lube feedstreams have been subjected to
hydrotreating and hydrocracking, the hydrocracked light lube stream
and the hydrotreated light lube stream are solvent extracted in
respective solvent extraction zones. The solvent extraction is
conducted under the same conditions described above with a suitable
solvent such as the solvents described above, and the solvent
extraction of each stream produces at least one aromatics-rich
extract through the process described above, i.e. distillation or
fractionation of the aromatics-rich extract solution. At least a
portion of each of the aromatics-rich extracts produced through the
respective solvent extractions is mixed with a heavier lube stream
as described above. Suitable mixing techniques are described above.
In this embodiment, it is contemplated that the portions of the
respective aromatics-rich extract phases be mixed prior to being
mixed with the heavier lube stream. Suitable mixing techniques for
mixing the portions of the respective aromatics-rich extracts are
also those that are described above in relation to the mixing zone.
In this embodiment, it is also contemplated that the at least two
light lube streams be hydrotreated light lube streams.
[0045] It should be noted that the inventors herein contemplate
that the aromatics-rich extract mixed with the heavier lube stream
comprise portions of the aromatics-rich extracts produced through
solvent extraction of more than two light lube streams. The more
than two light lube streams are preferably hydrocracked light lube
streams, hydrotreated light lube streams, or any combination
thereof.
[0046] Thus, through the practice of the presently claimed
invention a less desirable lube feedstream, the second, heavier
lube stream described above, with a variable Viscosity and
Viscosity Index, is used to produce a suitable base oil. Extraction
yields and dewaxing performance of the second, heavier lube stream
are also improved.
[0047] The above description is directed at preferred embodiments
of the present invention and it is not intended to limit the
invention thereto. One having ordinary skill in the art will
recognize that there are modifications and variations that are
still within the spirit and scope of the present invention. The
inventors herein contemplate any such variations and modifications
and contemplate to cover such variations and modifications within
the true spirit and scope of the present invention with the
attached claims.
[0048] The following examples will be useful in better illustrating
the practice of the present invention.
EXAMPLES
[0049] In the following examples, a low viscosity aromatics-rich
extract was added at various ratios to a high viscosity
hydrocracked lube stream and the mixture was solvent extracted
using phenol. The raffinates resulting from the solvent extraction
of the mixed lube stream were solvent dewaxed under the same
conditions to produce dewaxed base oils.
[0050] The following procedure was used to determine the
miscibility temperature in all of the Examples below. A 5 ml sample
of the dewaxed oil (base oil) and 15 ml of ketone or a mixture
containing ketone was mixed in a test tube containing a mixer and a
thermometer. The mixture was slowly cooled in a bath maintained at
-32.degree. C. while under constant stirring until the mixture
became cloudy, then it was removed from the bath. The temperature
at which the liquid became clear was noted to the nearest
0.5.degree. C. The test was repeated at least two more times and
the results were averaged to give the miscibility temperature. The
miscibility temperature was determined for three different ketone
mixtures, 100%MEK, 80%MEK/20%MIBK, and 60%MEK/40%MIBK. If desired,
the miscibility temperature can be plotted against the solvent
composition and a line drawn between the points. Above this
"miscibility line" the oil/solvent mixture is miscible, and below
the line the oil/solvent mixture is immiscible. It should be
apparent that lower miscibility temperatures are very desirable
because they allow single-phase dewaxing to be carried out at lower
temperatures.
Example 1
[0051] A hydrocracked light lube stream having a boiling point
range of about 340.degree. C. to about 520.degree. C.) was solvent
extracted using phenol containing 0 to 0.5% water, using a tower
top temperature of about 70.degree. C. and a bottom tower
temperature of about 55.degree. C., (nominally a 15.degree. C.
tower temperature gradient). The viscosity of the aromatics-rich
extract resulting from the solvent extraction was measured
according to ASTM D445, and the viscosity was calculated to be
4.861 cSt at 100.degree. C. The aromatics-rich extract was added in
0%, 7.5% and 10% amounts to a heavy hydrocracked lube stream
boiling between about 400.degree. C. and 620.degree. C. and having
a viscosity of 7.716 cSt at 100.degree. C., according to ASTM D445,
to form mixed lube streams. Each mixed lube stream was phenol
extracted under conditions including 1.5% water in the phenol
solvent, 1 to 2 v/v solvent/oil, 90.degree. C. tower top
temperature/75.degree. C. tower bottom temperature to produce
second aromatics-rich raffinate solutions. The phenol was removed
from the raffinate solutions using vacuum distillation to produce
aromatics-rich extracts for each of the respective mixed lube
streams.
[0052] The aromatics-rich raffinates were each solvent dewaxed
using dry 30% MEK/ 70% MIBK, 3:1 v/v solvent/oil at -18.degree. C.
filter temperature and the solvent was removed using vacuum
distillation. The miscibility temperatures of each of the dewaxed
oils in dry MEK/MIBK mixtures were measured by the method outlined
above. The pour point of the base oils recovered after dewaxing was
measured according to ASTM D5949. Also, the raffinate yield on
total feed was calculated by averaging the Refractive Index (RI)
yield and the Density yield, defined by the following formulae:
RI Yield=(Extract RI at 75.degree. C.-Feed RI at 75.degree.
C.)*100/(Extract RI at 75.degree. C.-Raffinate RI at 75.degree.
C.)
Density Yield=(Extract Density at 75.degree. C.-Feed Density at
75.degree. C.)*100/(Extract Density at 75.degree. C.-Raffinate
Density at 75.degree. C.)
[0053] The results are reported in Table 1 below.
1TABLE 1 Raffinate Raffinate yield on yield on Dewaxed Miscibility
temperature, .degree. C. % extract total fresh oil pour In 100% In
80% In 60% In 40% added feed, % feed, % point, .degree. C. MEK MEK
MEK MEK 0 96.2 96.2 -13 22.0 12.5 3.0 -9.5 7.5 94.8 102.5 -12 21.5
11.5 2.0 -10.5 10.0 94.3 104.8 -12 21.0 11.0 1.0 -11.0
[0054] As can be seen from the results contained in Table 1, the
raffinate yield based on the heavy hydrocracked lube stream
increased as the amount of aromatics-rich extract added was
increased. Thus, valuable lube molecules were recovered from the
aromatics-rich extract. For oils dewaxed at -18.degree. C. filter
temperature, miscibility temperatures became progressively lower as
the percentage of extract added to the heavy hydrocracked lube
stream was increased. The decrease in miscibility temperatures
indicates that these base oils would be easier to dewax.
Example 2
[0055] The raffinates produced in Example 1 were dewaxed at
-12.degree. C. filter temperature using dry 30% MEK/70% MIBK under
conditions including 3:1 v/v solvent/oil at -18.degree. C. filter
temperature and the solvent was removed using vacuum distillation.
Miscibility temperatures were measured according to the same
procedure outlined in Example 1 above. The pour point of the base
oils recovered after dewaxing was measured according to ASTM D5949.
Also, the raffinate yield was calculated using the formulae defined
in Example 1. The results are reported in Table 2 below.
2 TABLE 2 Miscibility temperature, .degree. C. % extract Dewaxed
oil In 100% In 80% In 60% In 40% added Raffinate yield, % pour
point, .degree. C. MEK MEK MEK MEK 0 96.2 -10 18.4 8.6 -0.4 -10.8
7.5 94.8 -10 -17.4 8.1 -1.8 -11.6 10.0 94.3 -9 17.1 7.5 -1.9
-11.8
[0056] It is seen that for oils dewaxed at -12.degree. C. filter
temperature, miscibility temperatures became progressively lower as
the percentage of extract added was increased. This indicates that
these raffinates would be easier to dewax.
* * * * *