U.S. patent application number 14/540689 was filed with the patent office on 2016-05-19 for synthesis of base oils and fuels from fatty acids.
This patent application is currently assigned to Chevron U.S.A. Inc.. The applicant listed for this patent is Ann Jia-Bao Liang, Stephen Joseph Miller. Invention is credited to Ann Jia-Bao Liang, Stephen Joseph Miller.
Application Number | 20160137944 14/540689 |
Document ID | / |
Family ID | 55961140 |
Filed Date | 2016-05-19 |
United States Patent
Application |
20160137944 |
Kind Code |
A1 |
Liang; Ann Jia-Bao ; et
al. |
May 19, 2016 |
SYNTHESIS OF BASE OILS AND FUELS FROM FATTY ACIDS
Abstract
Processes and systems for producing base oils and fuels from
fatty acids comprising, in an embodiment, oligomerizing at least
one unsaturated fatty acid to provide a mixture of fatty acid
oligomers, wherein the mixture of fatty acid oligomers comprises
fatty acid trimers and heavier molecules; and hydrotreating the
mixture of fatty acid oligomers to provide a product comprising
hydrotreated fatty acid oligomers including hydrotreated trimers
and heavier molecules, wherein the product has a pour point and
other characteristics suitable for use as a base oil, and wherein
such processes for base oil production do not require an
isomerization step.
Inventors: |
Liang; Ann Jia-Bao; (Walnut
Creek, CA) ; Miller; Stephen Joseph; (San Francisco,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Liang; Ann Jia-Bao
Miller; Stephen Joseph |
Walnut Creek
San Francisco |
CA
CA |
US
US |
|
|
Assignee: |
Chevron U.S.A. Inc.
San Ramon
CA
|
Family ID: |
55961140 |
Appl. No.: |
14/540689 |
Filed: |
November 13, 2014 |
Current U.S.
Class: |
585/315 ;
585/310 |
Current CPC
Class: |
C10M 105/24 20130101;
C10N 2020/04 20130101; C10M 109/02 20130101; C10M 2203/1025
20130101; C10M 107/02 20130101; C10N 2020/02 20130101 |
International
Class: |
C10M 105/24 20060101
C10M105/24 |
Claims
1. A process for base oil production, comprising: a) oligomerizing
at least one unsaturated fatty acid to provide an oligomerization
product comprising a mixture of fatty acid oligomers; and b)
hydrotreating at least a portion of the oligomerization product to
provide a base oil product having a pour point less than
-12.degree. C., wherein the process does not include a step for
isomerizing the oligomerization product.
2. The process according to claim 1, wherein the base oil product
has a pour point less than -18.degree. C.
3. The process according to claim 1, wherein the base oil product
comprises at least 10 wt % hydrotreated fatty acid trimers and
heavier molecules.
4. The process according to claim 1, wherein: step a) comprises
contacting the at least one unsaturated fatty acid with an
oligomerization catalyst in the presence of water in an
oligomerization zone under oligomerization conditions to provide
the mixture of fatty acid oligomers; and step b) comprises
contacting the mixture of fatty acid oligomers with a hydrotreating
catalyst in the presence of hydrogen gas in a hydrotreating zone
under hydrotreating conditions to provide the base oil product.
5. The process according to claim 4, wherein: the oligomerization
conditions comprise a temperature in the range from 400 to
500.degree. F., a pressure in the range from 0 to 500 psig, and a
LHSV in the range from 0.05 to 1.0 hr.sup.-1, and the
oligomerization catalyst comprises an acidic clay catalyst.
6. The process according to claim 4, wherein: the oligomerization
zone is separate from the hydrotreating zone, and step a) is
performed in the absence of hydrogen pressure.
7. The process according to claim 1, wherein the oligomerization
product further comprises unconverted fatty acids monomers, and the
process further comprises: c) separating the unconverted fatty
acids from the mixture of fatty acid oligomers, and wherein step b)
comprises hydrotreating the mixture of fatty acid oligomers after
step c).
8. The process according to claim 1, wherein the base oil product
has a kinematic viscosity at 100.degree. C. in the range from 4 to
10 cSt.
9. The process according to claim 1, wherein the base oil product
constituents have an average molecular weight in the range from 400
to 800.
10. The process according to claim 1, wherein the base oil product
has a Viscosity Index in the range from 120 to 150.
11. The process according to claim 1, wherein the base oil product
has an NMR branching index in the range from 10 to 30.
12. The process according to claim 1, wherein the base oil product
has an average degree of molecular branching in the range from 2 to
4 alkyl branches per 100 carbon atoms.
13. A process for base oil production, comprising: a) contacting a
fatty acid feed comprising at least one unsaturated fatty acid with
an oligomerization catalyst in an oligomerization zone under
oligomerization conditions to provide a mixture of fatty acid
oligomers; and b) contacting the mixture of fatty acid oligomers
with a hydrotreating catalyst in a hydrotreating zone under
hydrotreating conditions to provide a base oil product having a
pour point less than -12.degree. C., wherein the process is
performed in the absence of an isomerization step.
14. The process according to claim 13, wherein: the oligomerization
conditions comprise a temperature in the range from 400 to
500.degree. F., a pressure in the range from 0 to 500 psig, and a
LHSV in the range from 0.05 to 1.0 hr.sup.-1, step a) is performed
in the absence of hydrogen pressure, and the fatty acid feed
comprises from 0.5 to 3.0 wt % water.
15. The process according to claim 13, wherein the base oil product
has a kinematic viscosity at 100.degree. C. in the range from 4 to
10 cSt, a Viscosity Index in the range from 120 to 150, an NMR
branching index in the range from 10 to 30, and an average degree
of molecular branching in the range from 2 to 4 alkyl branches per
100 carbon atoms.
16. The process according to claim 13, wherein: the fatty acid feed
comprises at least 90 wt % C.sub.16-C.sub.20 free fatty acids, and
at least 20 wt % of the base oil product boils at a temperature
above 900.degree. F.
17. A process for base oil production, comprising: a) oligomerizing
at least one unsaturated free fatty acid to provide an
oligomerization product comprising a mixture of fatty acid
oligomers, wherein the mixture of fatty acid oligomers comprises
fatty acid trimers and heavier molecules; and b) hydrotreating the
mixture of fatty acid oligomers to provide a base oil product,
wherein: the base oil product comprises hydrotreated fatty acid
trimers and heavier molecules, the hydrotreated fatty acid trimers
and heavier molecules jointly represent from 15 to 20 wt % of the
base oil product, and the base oil product has a pour point less
than -12.degree. C.
18. The process according to claim 17, wherein the base oil product
is obtained in the absence of an isomerization step.
19. The process according to claim 17, wherein: the at least one
unsaturated free fatty acid is selected from a C.sub.12 to C.sub.22
fatty acid, step a) comprises contacting the at least one
unsaturated free fatty acid with an oligomerization catalyst in an
oligomerization zone under oligomerization conditions in the
absence of hydrogen pressure to provide the mixture of fatty acid
oligomers, the oligomerization catalyst comprises an acidic clay
catalyst, the oligomerization conditions comprise an
oligomerization temperature in the range from 400 to 500.degree.
F., and the base oil product constituents have an average molecular
weight in the range from 400 to 800.
20. The process according to claim 19, wherein the base oil
product, as provided by step b) and in the absence of an
isomerization step, has a kinematic viscosity at 100.degree. C. in
the range from 4 to 10 cSt, a Viscosity Index in the range from 120
to 150, and a pour point less than -18.degree. C.
Description
TECHNICAL FIELD
[0001] This disclosure relates to processes and systems for
synthesizing base oils and fuels from fatty acids.
BACKGROUND
[0002] Previous attempts to use dimeric fatty acids prepared from
vegetable oils or other fatty biomass as base oils and fuels have
failed. For example, vegetable oils have been reacted at relatively
low conversion to produce fatty acid dimers in a product that is
typically waxy and requires dewaxing, e.g., in an additional,
separate isomerization step.
[0003] There is a need for processes and systems for efficiently
producing a base oil product from fatty acid feedstocks.
SUMMARY
[0004] In an embodiment there is provided a process comprising
oligomerizing at least one unsaturated fatty acid to provide an
oligomerization product comprising a mixture of fatty acid
oligomers; and hydrotreating at least a portion of the
oligomerization product to provide a base oil product having a pour
point less than -12.degree. C. (10.4.degree. F.), wherein the
process does not include a step for isomerizing the oligomerization
product.
[0005] In another embodiment there is provided a process comprising
contacting a fatty acid feed comprising at least one unsaturated
fatty acid with an oligomerization catalyst in an oligomerization
zone under oligomerization conditions to provide a mixture of fatty
acid oligomers; and contacting the mixture of fatty acid oligomers
with a hydrotreating catalyst in a hydrotreating zone under
hydrotreating conditions to provide a base oil product having a
pour point less than -12.degree. C., wherein the process is
performed in the absence of an isomerization step.
[0006] In a further embodiment there is provided a process
comprising oligomerizing at least one unsaturated free fatty acid
to provide an oligomerization product comprising a mixture of fatty
acid oligomers, wherein the mixture of fatty acid oligomers
comprises fatty acid trimers and heavier molecules; and
hydrotreating the mixture of fatty acid oligomers to provide a base
oil product, wherein the base oil product comprises hydrotreated
fatty acid trimers and heavier molecules, the hydrotreated fatty
acid trimers and heavier molecules jointly represent from 10 to 20
wt % of the base oil product, and the base oil product has a pour
point less than -12.degree. C.
BRIEF DESCRIPTION OF THE DRAWING
[0007] FIG. 1 schematically represents a process and system for the
production of base oil from fatty acids without an isomerization
step or an isomerization zone, according to an embodiment of the
present invention.
DETAILED DESCRIPTION
[0008] Applicant has discovered a new route to make a base oil
product by hydrotreating an oligomerization product obtained by
catalytic oligomerization of a feedstock comprising at least one
unsaturated fatty acid. The base oil product, which comprises
hydrotreated fatty acid oligomers larger than dimers, has an
unexpectedly low pour point and other characteristics which make it
suitable for use as a base oil without isomerization dewaxing. Due
to the presence of oligomers larger than dimers, e.g., trimers and
heavier molecules (in addition to dimers), the oligomerization
product has a sufficiently high average molecular weight with
sufficient branching in the oligomer molecules to provide a product
with a pour point suitable for use as a base oil without the need
for further processing beyond hydrotreating, i.e., the base oil
product may be obtained, in the absence of an isomerization
step.
[0009] In processes as disclosed herein, branches may be introduced
into the fatty acid oligomers as a result of the oligomerization
reaction, instead of by a separate isomerization step as taught by
the prior art. In an embodiment, the oligomerization step does not
take place under hydrogen pressure, since hydrogen pressure could
lead to the saturation of the olefinic bond in the fatty acid
feedstock, thereby preventing oligomerization from occurring. In an
embodiment, the oligomerization step and the hydrotreating step may
be conveniently and advantageously performed in separate vessels
(separate reactors). The use of separate reactors for the
oligomerization and hydrotreating steps allows much more control
over the oligomerization reaction, thereby enabling the production
of an oligomeric mixture comprising a suitable amount of trimers
and heavier molecules, such that hydrotreatment of the oligomeric
mixture provides a low pour point base oil product without the need
for an isomerization step. Similarly, the use of separate reactors
for oligomerization and hydrotreating allows the hydrotreatment
temperature to be carefully controlled so as to be high enough to
remove all of the oxygen from the oligomeric mixture, and at the
same time low enough to prevent excessive cracking
[0010] "Oligomerization," as defined herein, refers to an additive
reaction of like or similar molecules (e.g., unsaturated fatty
acids) to form larger, oligomeric molecules. For example,
unsaturated fatty acids of the present invention can react or
combine via the double bonds in their structures. When two or more
such fatty acid species combine to form a larger molecule, the
larger molecule may be referred to herein as a fatty acid
"oligomer."
[0011] A fatty acid oligomer or mixture of fatty acid oligomers
that has undergone hydrotreating may be referred to herein as
"hydrotreated fatty acid oligomer." Hydrotreated fatty acid
oligomers may comprise saturated and deoxygenated derivatives of
fatty acid oligomers. It is to be understood that the number of
carbon atoms in the hydrotreated fatty acid oligomers may not be an
exact multiple of the number of carbon atoms in the fatty acid
monomeric unit(s); for example, a hydrotreated fatty acid oligomer
may have lost a carbon atom as CO.sub.2 or CO during
hydrotreating.
[0012] The term "fatty acid oligomer" may include fatty acid dimers
formed from two fatty acid molecules, as well as larger fatty acid
oligomers. In an embodiment, processes for base oil production as
disclosed herein may be particularly concerned with hydrotreated
mixtures of fatty acid oligomers comprising fatty acid trimers and
larger fatty acid oligomers.
[0013] Base Oil Production by Fatty Acid Oligomerization and
Hydrotreating
[0014] In an embodiment, a process for base oil production may
comprise oligomerizing at least one unsaturated fatty acid to
provide an oligomerization product comprising a mixture of fatty
acid oligomers, and hydrotreating at least a portion of the
oligomerization product to provide a base oil product. In an
embodiment, the oligomerizing may be performed in a first reactor
or vessel and the hydrotreating may be performed in a second
reactor or vessel. In an embodiment, the first and second vessels
may be separate from each other such that the oligomerizing may be
performed in the absence of hydrogen pressure while the
hydrotreating may be performed under hydrogen pressure, e.g., in
the range from 400 to 2000 psig hydrogen pressure. In an embodiment
the base oil product, which may be obtained in the absence of an
isomerization step, may have a pour point less than -12.degree. C.
(10.4.degree. F.), or less than -18.degree. C. (-0.4.degree. F.),
or -23.degree. C. (-9.4.degree. F.) or less. In a sub-embodiment,
the base oil product may have a pour point in the range from
-12.degree. C. to -50.degree. C. (10.4 to -58.degree. F.).
[0015] In an embodiment, the base oil product may comprise at least
10 wt % of hydrotreated fatty acid trimers and heavier molecules.
The expression "fatty acid trimers and heavier molecules" may be
used herein to refer to fatty acid oligomers that are at least as
large as trimers of fatty acid molecules. Or, stated differently,
the expression "fatty acid trimers and heavier molecules" may be
used to refer to a mixture comprising: i) fatty acid trimers and
ii) fatty acid oligomers larger than trimers. In a sub-embodiment,
the base oil product may comprise from 10 to 20 wt % of
hydrotreated fatty acid trimers and heavier molecules, and often
the base oil product may comprise from 15 to 20 wt % of
hydrotreated fatty acid trimers and heavier molecules.
[0016] In an embodiment, the base oil product prepared as disclosed
herein may have a kinematic viscosity at 100.degree. C. in the
range from 4 to 10 cSt, or from 4 to 8 cSt. In an embodiment, the
base oil product constituents may have an average molecular weight
in the range from 400 to 800, or from 500 to 800. In an embodiment,
the base oil product may have a Viscosity Index in the range from
120 to 150, or from 120 to 140.
[0017] In an embodiment, the base oil product may have an NMR
branching index in the range from 10 to 30, or from 10 to 30. In an
embodiment, the base oil product may have an average degree of
molecular branching in the range from 2 to 4 alkyl branches per 100
carbon atoms. The extent of branching and branching position can be
determined by NMR branching analysis (see, for example, Example 5,
infra). The NMR Branching Index may be calculated from .sup.1H NMR
analysis as the ratio in percent of non-benzylic methyl hydrogen in
the range of 0.5 to 1.0 ppm chemical shift, to the total
non-benzylic aliphatic hydrogen in the range of 0.5 to 2.1 ppm
chemical shift.
[0018] In an embodiment, the oligomerizing step may comprise
contacting the at least one unsaturated fatty acid with an
oligomerization catalyst in an oligomerization zone under
oligomerization conditions to provide the mixture of fatty acid
oligomers. In an embodiment, the at least one unsaturated fatty
acid may be contacted with the oligomerization catalyst in the
presence of a defined amount of water during the oligomerization
step, e.g., water may be present in an amount in the range from 0.5
to 3.0 wt % of the fatty acid feed to the oligomerization zone, or
from 1.0 to 2.5 wt %.
[0019] In an embodiment, the oligomerization conditions may
comprise a temperature in the range from 350 to 525.degree. F.
(177-274.degree. C.), or from 400 to 500.degree. F.
(204-260.degree. C.), or from 400 to 475.degree. F.
(204-246.degree. C.). In an embodiment, the oligomerization
conditions may further comprise a pressure in the range from 0 to
500 psig, and a LHSV in the range from 0.05 to 1.0 hr.sup.-1. In an
embodiment, a suitable oligomerization catalyst may comprise an
acidic clay catalyst, e.g., as described hereinbelow. In an
embodiment, the oligomerization conditions will not include
hydrogen pressure, since hydrogen pressure could prevent fatty acid
oligomerization by saturating olefinic bonds in the unsaturated
fatty acid feedstock.
[0020] In an embodiment, the hydrotreating step may comprise
contacting the mixture of fatty acid oligomers with a hydrotreating
catalyst in a hydrotreating zone under hydrotreating conditions to
provide the base oil product. In an embodiment, the hydrotreating
catalyst may comprise a metal and a support material, wherein the
metal may be selected from Ni, Mo, Co, W, and combinations thereof,
and the support may comprise a refractory oxide, such as
alumina.
[0021] During the hydrotreating step oxygen is removed from the
fatty acid oligomers. In addition, during the hydrotreating step
olefins and aromatics may be converted to saturated compounds
(e.g., isoalkanes and cycloalkanes). However, any isomerization of
the fatty acid oligomers during hydrotreating is expected to be
minimal and insufficient to significantly affect pour point, since
the hydrotreatment catalyst will typically lack substantial
isomerization activity for the fatty acid oligomers under the
hydrotreating conditions. Instead, sufficient branches are
introduced into the fatty acid oligomers as a result of the earlier
oligomerization reaction such that subsequent isomerization of the
fatty acid oligomers is unnecessary. Accordingly, processes for
base oil production as disclosed herein may be performed in the
absence of a step for isomerizing the oligomerization product or
the mixture of fatty acid oligomers, either before or after
hydrotreating.
[0022] Exemplary hydrotreating conditions for producing base oil
from oligomerized fatty acids may comprise a temperature in the
range from 550 to 800.degree. F. (288 to 427.degree. C.), a
pressure generally in the range from 400 to 2000 lbin.sup.-2 gauge
(psig), a LHSV in the range from 0.25 to 5 hr.sup.-1, and a
hydrogen flow rate typically in the range from 300 to 6000 SCF/bbl,
or from 500 to 5000 SCF/bbl.
[0023] It is to be understood that the oligomerization conditions
for producing base oil from oligomerized fatty acids according to
the instant disclosure may be distinct from, and may be controlled
independently of, the hydrotreating conditions, or vice versa. As a
non-limiting example, the oligomerization step is typically
performed in the absence of hydrogen pressure. Exposure to hydrogen
pressure during the oligomerization step may cause saturation of
the olefinic bond in unsaturated fatty acid components of the
feedstock, thereby preventing fatty acid oligomerization from
occurring.
[0024] In an embodiment, the whole liquid (initial) product from
the oligomerization step may comprise various amounts of
unconverted fatty acid monomers in addition to fatty acid
oligomers. Processes for base oil production may further comprise
separating the unconverted monomeric fatty acids from the mixture
of fatty acid oligomers, and recycling at least a portion of the
unconverted fatty acids to the oligomerization zone (see, for
example, FIG. 1).
[0025] In an embodiment, the step of hydrotreating the mixture of
fatty acid oligomers may be performed after separation (removal) of
the unconverted fatty acids monomers. Alternatively, the
oligomerization product comprising unconverted fatty acid monomers
as well as fatty acid oligomers may be hydrotreated en masse, and
the hydrotreated product may subsequently undergo separation to
remove one or more lighter fractions including monomeric fatty acid
materials. Such separation of unconverted monomeric fatty acids may
involve various types of distillation including vacuum
distillation.
[0026] In an embodiment, the hydrotreated material comprising
hydrotreated fatty acid oligomers may be further processed to
remove water, either before or after the separation of unconverted
monomeric material, to provide a dried hydrocarbon fraction
comprising hydrotreated fatty acid oligomers. As noted previously
herein, such hydrotreated fatty acid oligomers typically include at
least 10 wt % of hydrotreated fatty acid trimers and heavier
molecules.
[0027] In an embodiment, the fatty acid feed to the oligomerization
zone may comprise at least one unsaturated free fatty acid. In an
embodiment, the fatty acid to be oligomerized may be combined with
from 0.5 to 3.0 wt % water, and in a sub-embodiment the fatty acid
to be oligomerized may be combined with from 1.0 to 2.5 wt % water.
In an embodiment, a fatty acid feed to the oligomerization zone may
comprise at least one unsaturated free fatty acid selected from a
C.sub.12 to C.sub.22 fatty acid. In an embodiment, the fatty acid
feed to the oligomerization zone may comprise at least 50 wt %
C.sub.16-C.sub.20 free fatty acids, or at least 75 wt %
C.sub.16-C.sub.20 free fatty acids, or at least 90 wt %
C.sub.16-C.sub.20 free fatty acids. In an embodiment, at least 20
wt % of a base oil product produced from a feed comprising
C.sub.16-C.sub.20 free fatty acids according to processes disclosed
herein will boil at a temperature above 900.degree. F.
[0028] It is to be understood that processes as disclosed herein
are not limited to any particular fatty acid(s), but rather that
base oil products may be prepared using a range of different fatty
acid containing feedstocks. Furthermore, boiling point data for the
various base oil products may vary depending on the nature (e.g.,
carbon chain length) of the starting materials (e.g., fatty acid
feed) used in particular embodiments of such processes.
[0029] In contrast to prior art processes, the base oil product,
having a suitable pour point and other characteristics as disclosed
herein, may be prepared by fatty acid oligomerization to provide an
oligomerization product and hydrotreating at least a portion of the
oligomerization product to provide the base oil product in the
absence of an isomerization step, e.g., without isomerizing either
the initial (non-hydrotreated) oligomerization product or the
hydrotreated oligomerization product.
[0030] Catalysts for Oligomerization
[0031] Catalysts for oligomerization can be almost any acidic
material including zeolites, clays, resins, and acidic ionic
liquids. In an embodiment, the oligomerization catalyst may
comprise montmorillonite clay. The oligomerization catalyst may be
disposed within an oligomerization zone. The oligomerization
catalyst and the oligomerization zone will typically be separate
from the hydrotreating catalyst and the hydrotreating zone. The
oligomerization zone may also be referred to herein as an
oligomerization reactor. The oligomerization zone is not limited to
any particular reactor type. For example, the oligomerization zone
may comprise a fixed-, fluidized-, or moving bed reactor. The
oligomerization stage or step may be performed in batch or
continuous mode, with recycling of unconsumed starting materials if
required.
[0032] Catalysts for Hydrotreating
[0033] In an embodiment, the hydrotreating catalyst may comprise a
metal and a support material, wherein the metal may be selected
from Ni, Mo, Co, W, and combinations thereof, and the support may
comprise a refractory oxide, such as alumina. The hydrotreating
catalyst may be disposed within a hydrotreating zone. The
hydrotreating zone may also be referred to herein as a
hydrotreating reactor.
[0034] The hydrotreating zone is not limited to any particular
reactor type. For example, the hydrotreating zone may comprise a
fixed-, fluidized-, or moving bed reactor. The hydrotreating stage
or step may be performed in batch or continuous mode. The
hydrotreating catalyst and the hydrotreating zone will typically be
separate from the oligomerization catalyst and the oligomerization
zone. For example, the hydrotreating zone will typically be housed
in a vessel that is separate from that housing the oligomerization
zone (see, for example, FIG. 1).
[0035] Feedstocks for Base Oil Production
[0036] In an embodiment, feedstocks for oligomerization may
comprise at least one fatty acid reactant or a mixture of fatty
acid reactants. In an embodiment, the at least one fatty acid
reactant for oligomerization may comprise a mixture of at least two
(2) fatty acids. In an embodiment, reactants for oligomerization
may comprise C.sub.12-C.sub.22 unsaturated fatty acids. In an
embodiment, feedstocks for oligomerization as disclosed herein may
be derived from a triglyceride-containing biomass source such as
oils or fats from plants, animals, and/or other biological
organisms or biological systems. In an embodiment, a fatty acid
feed may comprise at least 90 wt % free fatty acids, or at least 95
wt % free fatty acids, or at least 97 wt % free fatty acids. In an
embodiment, the fatty acid feed to the oligomerization zone may
comprise at least 90 wt % C.sub.16-C.sub.20 free fatty acids.
[0037] In an embodiment, fatty acid-containing feedstocks for
oligomerization may be derived from one or more
triglyceride-containing materials including, but not limited to,
canola oil, soy oil, rapeseed oil, palm oil, peanut oil, jatropha
oil, and the like, and their respective fatty acid constituents,
and combinations thereof. Additional or alternative sources of
triglycerides, which can be hydrolyzed to yield fatty acids,
include, but are not limited to, algae, animal tallow, and
zooplankton, or the like. Some non-limiting examples of unsaturated
fatty acids include, without limitation, palmitoleic acid, oleic
acid, and linoleic acid.
[0038] In an embodiment, in situations where a fatty acid feedstock
may contain a mixture of saturated fatty acids, mono-unsaturated
fatty acids, and polyunsaturated fatty acids, one or more
techniques may be employed to isolate, concentrate, or otherwise
separate one or more types of fatty acids from one or more other
types of fatty acids in the mixture (see, e.g., U.S. Pat. No.
8,097,740 to Miller).
[0039] Systems for Base Oil Production by Fatty Acid
Oligomerization and Hydrotreating
[0040] Systems and processes for base oil production will now be
described with reference to the drawing. FIG. 1 schematically
represents a process and system, according to the instant
disclosure, for the production of base oil from fatty acids without
an isomerization step or an isomerization zone. In system 110, a
fatty acid feedstock 12 (e.g., as described hereinabove) may be fed
to an oligomerization reactor 120. Oligomerization reactor 120 may
also be referred to herein as an oligomerization zone. Feedstock 12
may be contacted with an oligomerization catalyst (e.g., as
described hereinabove) under oligomerization conditions within
oligomerization reactor 120 to provide an oligomerization product
122. Suitable oligomerization conditions are described hereinabove.
In an embodiment, oligomerization reactor 120 is not under hydrogen
pressure, since hydrogen pressure in the oligomerization zone may
saturate the olefinic bond, thereby preventing fatty acid
oligomerization.
[0041] The oligomerization product 122 (e.g., effluent from
oligomerization reactor 120) may be fed to a fractionation unit 130
for the separation of oligomerization product 122. For example, a
lighter fraction comprising unconverted fatty acid monomers 12' may
be separated from a heavier fraction comprising a mixture of fatty
acid oligomers 132 via fractionation unit 130. The unconverted
fatty acid monomers 12' may be recycled to oligomerization reactor
120. As a non-limiting example, fractionation unit 130 may comprise
one or more distillation columns.
[0042] The heavier portion of the oligomerization product may be
fed from fractionation unit 130 to a hydrotreating unit 140 for
hydrotreating the mixture of fatty acid oligomers 132, i.e., for
the removal of oxygen, using a suitable hydrotreating catalyst
(e.g., as described hereinabove) to provide a base oil product 142
having the characteristics as described herein, without the need
for isomerization or other dewaxing step(s). In an alternative
configuration for base oil production, the oligomerization product
may be hydrotreated prior to separating the lighter fraction from
the heavier base oil containing fraction.
[0043] Suitable hydrotreating conditions are described hereinabove.
In addition to the removal of oxygen, the hydrotreating catalyst in
hydrotreating reactor 140 may also saturate olefins or other
unsaturated constituents of the oligomerization product to
saturated hydrocarbons under the hydrotreating conditions disclosed
herein. However, the hydrotreating catalyst in hydrotreating
reactor 140 will typically lack any substantial isomerization
activity for the oligomerization product under the hydrotreating
conditions disclosed herein.
[0044] The use of separate reactors for oligomerization and
hydrotreating, as shown in FIG. 1, allows much more control over
the oligomerization reaction so as to obtain a mixture of
oligomeric fatty acids containing a suitable amount of trimers and
heavier molecules and having a suitable degree of branching in the
trimers and heavier molecules as a result of the oligomerization
reactions per se. In this manner, a low pour point base oil product
can be conveniently prepared solely by hydrotreating the oligomeric
fatty acid mixture and in the absence of an isomerization step.
Obtaining such a mixture of oligomeric fatty acids using a single
reactor to house both the oligomerization and hydrotreating
catalysts would be difficult or impossible, since hydrogen pressure
used for hydrotreating may eliminate olefins from the feedstock and
so prevent oligomerization, and furthermore since during
hydrotreating the temperature needs to be carefully controlled so
as to be high enough to remove all of the oxygen but low enough to
prevent excessive cracking.
[0045] Thus, according to systems and processes as disclosed
herein, the efficient production of base oil product 142 from fatty
acid containing feedstock 12 may be achieved in the absence of an
isomerization step, i.e., without a step for isomerizing either the
oligomerization product or its constituents either before or after
the hydrotreating step. In an embodiment, base oil product 142 may
be blended with other base oils and/or combined with various
additives to provide finished lubricants.
EXAMPLES
Example 1
Oligomerization of Oleic Acid Using a Batch Reactor
[0046] In this Example 1, 90% technical grade oleic acid was used
(Alfa Aesar.RTM., Ward Hill, Mass.). The composition and properties
of this material were as follows:
TABLE-US-00001 Fatty Acid, total % 100.0 Fatty acid composition:
Linoleic acid, % 5 Oleic acid, % 93 Other fatty acid, % 2 Acid
number, mg KOH/g 188 Bromine number 54
[0047] One hundred grams (100 g) of the technical grade oleic acid
was mixed with 8 wt % Montmorillonite K-10 powder (Sigma-Aldrich
Corp., St Louis, Mo.) and 2 wt % water. The mixture was introduced
into a 300 ml autoclave and heated to 400.degree. F. in 60 minutes.
After 4 hours at 400.degree. F. the reactor was cooled to room
temperature. The Montmorillonite K-10 powder was then filtered out
to provide liquid products only.
[0048] The conversion of the technical grade oleic acid was 55.9%
and the oligomer yield was 50.9%, expressed as conversion of the
technical grade oleic acid to fatty acid oligomers. Simulated
distillation (SimDist) analysis (ASTM D-2887) of the whole liquid
product of Example 1 is presented in Table 1.
TABLE-US-00002 TABLE 1 Simulated distillation analysis of the whole
liquid product of Example 1 SimDist (D2887) (vol %, .degree. F.)
0.5/5 546/644 10/30 665/681 50 709 70/90 960/988 95/99.5
1043/1123
Example 2
Oligomerization of Oleic Acid Using a Continuous Stirred
Reactor
[0049] The 90% technical grade oleic acid (as described in Example
1) was mixed with 4 wt % Montmorillonite K-10 powder and 2 wt %
water, and the mixture was stirred continuously to prevent
settling. The stirred mixture was introduced into a 300 ml
autoclave at a feed rate of 5 cc/hr. The autoclave was equipped for
continuous stirring and with a dip tube for products to flow out of
the reactor. The equilibrium liquid level inside the reactor was 60
cc. The autoclave was blanketed with nitrogen at a flow rate of 15
cc/min to maintain the unit pressure at 500 psig. Once the
autoclave was filled with the fatty acid mixture, the autoclave was
heated to 400.degree. F. in 60 minutes and held at 400.degree. F.
throughout the run. Products were collected once the unit was line
out. The Montmorillonite K-10 powder was then filtered out to
obtain liquid products only. The properties of the whole liquid
product of Example 2 are presented in Table 2.
TABLE-US-00003 TABLE 2 Properties of the whole liquid product of
Example 2 Oligomer Yield, wt % 35.0 API 23.4 C, wt % 77.3 H, wt %
12.2 O, wt % 10.5 Acid number, mg KOH/g 169 Bromine number,
g-Br/100 g 35 SimDist (D2887) (vol %, .degree. F.) 0.5/5 485/641
10/30 659/683 50 692 70/90 795/964 95/99.5 998/1143
[0050] It was observed that the oleic acid conversion and oligomer
yield was much higher in Example 1 than in Example 2. However,
based on SimDist analysis the amount of fatty acid trimers produced
in Example 2 was higher than in Example 1. While not being bound by
theory, the increased production of fatty acid trimers observed in
Example 2 as compared with Example 1 may be due to the longer
residence time in the CSTR as compared with the batch reactor
(Example 1).
Example 3
Hydrotreating of Whole Liquid Product from Example 2
[0051] In this Example 3, the whole liquid products collected in
Example 2 were used as feed for hydrotreating. A conventional Ni/Mo
hydrotreating catalyst was loaded into a down-flow fixed bed
reactor. The catalyst was presulfided prior to introducing the feed
into the hydrotreating reactor. The run conditions were as follows:
a pressure of 1000 psig, a temperature of 575.degree. F., a LHSV of
1.0 h.sup.-1, and an inlet H.sub.2 flow rate of 5000 scf/bbl. The
properties of the effluent from the hydrotreating reactor
(hydrotreated mixture) are presented in Table 3.
TABLE-US-00004 TABLE 3 Properties of hydrotreated mixture from
Example 3 CO, wt % 0.05 CO.sub.2, wt % 0.74 H.sub.2O 8.41 C4-, wt %
0.1 C5-180.degree. F., wt % 0.2 180-700.degree. F., wt % 60.4 700+
.degree. F., wt % 30.1 C5+, wt % 90.71 SimDist (D2887) (vol %,
.degree. F.) 0.5/5 512/565 10/30 576/593 50 606 70/90 660/890
95/99.5 915/1044
Example 4
Separation of Fatty Acid Oligomers from Hydrotreated Mixture
[0052] The effluent from the hydrotreating reactor (Example 3) was
subjected to gas-liquid separation at a pressure of about 1000 psig
to provide a liquid fraction comprising a hydrotreated mixture of
fatty acid oligomers and unconverted fatty acid monomers. After the
removal of water, the hydrotreated mixture was distilled under
vacuum at 285.degree. F. to separate unconverted monomers from the
fatty acid oligomers. Properties of the hydrotreated fatty acid
oligomer fraction from the vacuum distillation are presented in
Table 4. The combined yield of hydrotreated fatty acid trimers and
higher oligomers was determined to be about 16.55 wt % of the total
yield of hydrotreated fatty acid oligomers based on SimDist
analysis.
TABLE-US-00005 TABLE 4 Properties of hydrotreated fatty acid
oligomers (700+ .degree. F.) VI 130 Vis @40.degree. C., cSt 42.96
Vis @100.degree. C., cSt 7.208 Cloud, .degree. C. 18 Pour, .degree.
C. -23 SimDist (D2887) (vol %, .degree. F.) 0.5/5 658/771 10/30
828/867 50 881 70/90 904/1054 95/99.5 1129/1284
Example 5
NMR Analysis of Hydrotreated Fatty Acid Oligomers
[0053] .sup.1H NMR analysis of the hydrotreated fatty acid
oligomers (base oil product) from Example 4 was performed using a
Bruker Avance 500 MHz spectrometer operating at 500.11 MHz and
using 50% solutions in CDCl.sub.3. All spectra were obtained under
quantitative conditions using 30.degree. pulse (9.0 .mu.s), recycle
delay of 2 second and 128 scans to ensure good signal-to-noise
ratios. TMS was used as an internal reference. The results of the
NMR analysis are presented in Table 5.
[0054] In Table 5, the Branching Index (BI) is the percent methyl
hydrogens among the total aliphatic hydrogens, the Branching
Proximity (BP) is the percent epsilon-CH.sub.2 carbons among the
total carbons, the Free Carbon Index (FCI) is the total number of
epsilon-CH.sub.2 carbons, and the term "epsilon-CH.sub.2" carbons
is defined as recurring CH.sub.2 carbon located five or more (5+)
CH.sub.2 carbon atoms away from a branched carbon along the
hydrocarbon chain.
TABLE-US-00006 TABLE 5 .sup.1H NMR analysis of hydrotreated fatty
acid oligomers (base oil product) NMR Analysis: 2-methyl 0.25
3-methyl 0.06 4-methyl 0.11 5+ methyl 0.30 Internal ethyl 0.13
Adjacent methyl 0.00 Internal propyl 0.07 Sum 0.92 Branching Index
(BI) 20.19 Branching Proximity (BP) 18.61 Alkyl branches per
molecule 0.92 Methyl branches per molecule 0.71 BI - 0.5BP 29.50 BI
+ 0.85BP 36.01 Free Carbon Index (FCI) 5.62 FCI/END methyl ratio
1.75 Alkyl branches per 100 carbons 3.05 Methyl branches per 100
carbons 2.36 % Branches at 2 position 27.11 % Branches at 3
position 6.06 % Branches at 2 + 3 positions 33.17 % Branches at 4
position 12.19 % Branches at 5+ positions 32.20 % Olefins 0.99
[0055] The data presented in Table 5 indicate that the hydrotreated
fatty acid oligomeric mixture comprises mostly singly branched
molecules with various branching positions, which is consistent
with the observed low pour point of the base oil product. The small
amount (0.99%) of olefinic materials in the sample may also
contribute to the low pour point of the base oil sample from
Example 4.
[0056] For the purposes of this specification and appended claims,
unless otherwise indicated, all numbers expressing quantities,
percentages or proportions, and other numerical values used in the
specification and claims, are to be understood as being modified in
all instances by the term "about." Furthermore, all ranges
disclosed herein are inclusive of the endpoints and are
independently combinable. Whenever a numerical range with a lower
limit and an upper limit are disclosed, any number falling within
the range is also specifically disclosed. Additionally, chemical
species including reactants and products designated by a numerical
range of carbon atoms include any one or more of, or any
combination of, or all of the chemical species within that
range.
[0057] Any term, abbreviation or shorthand not defined is
understood to have the ordinary meaning used by a person skilled in
the art at the time the application is filed. The singular forms
"a," "an," and "the," include plural references unless expressly
and unequivocally limited to one instance. All publications,
patents, and patent applications cited in this application are
incorporated by reference herein in their entirety to the extent
not inconsistent herewith.
[0058] Modifications of the exemplary embodiments disclosed above
may be apparent to those skilled in the art in light of this
disclosure. Accordingly, the invention is to be construed as
including all structure and methods that fall within the scope of
the appended claims. Unless otherwise specified, the recitation of
a genus of elements, materials or other components, from which an
individual component or mixture of components can be selected, is
intended to include all possible sub-generic combinations of the
listed components and mixtures thereof.
* * * * *