U.S. patent application number 12/425124 was filed with the patent office on 2010-10-21 for method for removing impurities from hydrocarbon oils.
This patent application is currently assigned to General Electric Company. Invention is credited to John Matthew Bablin, Thomas Joseph Fyvie, Paul Burchell Glaser, Gregory Allen O'Neil, John Aibangbee Osaheni, Alison Liana Palmatier, Grigorii Lev Soloveichik.
Application Number | 20100264067 12/425124 |
Document ID | / |
Family ID | 42562858 |
Filed Date | 2010-10-21 |
United States Patent
Application |
20100264067 |
Kind Code |
A1 |
Osaheni; John Aibangbee ; et
al. |
October 21, 2010 |
METHOD FOR REMOVING IMPURITIES FROM HYDROCARBON OILS
Abstract
A method for removing impurities from a feedstock comprising a
hydrocarbon oil is provided. The method comprises contacting the
feedstock with an oxygen-containing gas under conditions effective
to oxidize at least a portion of the impurities, as well as
contacting the feedstock with a Lewis acid under conditions
effective so that any Lewis base impurity(ies) in the feedstock can
react with the Lewis acid. Any impurities so oxidized and/or
reacted are then removed.
Inventors: |
Osaheni; John Aibangbee;
(Clifton Park, NY) ; Palmatier; Alison Liana;
(Corinth, NY) ; Soloveichik; Grigorii Lev;
(Latham, NY) ; Bablin; John Matthew; (Malta,
NY) ; Glaser; Paul Burchell; (Albany, NY) ;
Fyvie; Thomas Joseph; (Schenectady, NY) ; O'Neil;
Gregory Allen; (Clifton Park, NY) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY;GLOBAL RESEARCH
ONE RESEARCH CIRCLE, BLDG. K1-3A59
NISKAYUNA
NY
12309
US
|
Assignee: |
General Electric Company
Schenectady
NY
|
Family ID: |
42562858 |
Appl. No.: |
12/425124 |
Filed: |
April 16, 2009 |
Current U.S.
Class: |
208/221 |
Current CPC
Class: |
C10G 53/14 20130101;
C10G 27/04 20130101; C10G 17/09 20130101 |
Class at
Publication: |
208/221 |
International
Class: |
C10G 17/02 20060101
C10G017/02 |
Claims
1. A method for removing impurities from a hydrocarbon oil
comprising: (a) contacting the hydrocarbon oil with an
oxygen-containing gas under conditions effective to oxidize at
least a portion of the impurities; (b) contacting the hydrocarbon
oil with a Lewis acid under conditions effective so that any Lewis
base impurity(ies) in the feedstock can react with the Lewis acid;
and (c) removing any impurities so oxidized and/or reacted from the
hydrocarbon oil.
2. The method of claim 1, wherein the oxygen-containing gas
comprises air, ozone enriched air or a combination of these.
3. The method of claim 1, wherein the oxygen-containing gas
comprises mixture of nitric oxide and air, nitrogen dioxide or a
combination of these.
4. The method of claim 2, wherein the oxygen-containing gas
comprises air, and the conditions effective to oxidize include the
use of a catalyst.
5. The method of claim 4, wherein the catalyst comprises
molybdenum, copper, manganese, cobalt, tungsten, iron or
combinations of these.
6. The method of claim 1, wherein the impurities comprise sulfur,
vanadium, nickel, or combinations of these.
7. The method of claim 6, wherein the impurities comprise
sulfur.
8. The method of claim 7, wherein the impurities comprise
substituted and unsubstituted benzothiophenes, dibenzothiophenes,
phenanthiophenes, benzonathiophenes, alkyl sulfides, aryl sulfides
or derivatives thereof.
9. The method of claim 8, wherein at least a portion of the sulfur
impurities are oxidized to form sulfoxides and sulfones.
10. The method of claim 1, wherein the Lewis acid comprises
AlCl.sub.3, GaCl.sub.3, FeCl.sub.3, or combinations of these.
11. The method of claim 10, wherein the Lewis acid is used as a
solution in an aprotic solvent.
12. The method of claim 11, wherein the aprotic solvent is
nitromethane.
13. The method of claim 11, wherein the oxidized or reacted
impurities are removed by centrifugation and/or decantation.
14. The method of claim 1, wherein contact with the
oxygen-containing gas and contact with the Lewis acid are caused to
occur relatively simultaneously.
15. The method of claim 1, wherein at least one step is repeated at
least once.
16. The method of claim 1, further comprising the pretreatment of
the fuel oil.
17. The method of claim 16, wherein the pretreatment comprises
addition of a fuel solvent, removal of insoluble particulates, or
both of these.
18. The method of claim 17, wherein the fuel solvent comprises
petroleum ether, hexanes, pentane, cyclohexane, heptane, propane,
butane, or combinations of these.
19. The method of claim 17, further comprising recovering and
recycling the fuel solvent.
20. A method for removing sulfur impurities from a hydrocarbon oil,
the method comprising: (a) contacting the hydrocarbon oil with a
gas comprising nitric oxide and oxygen, nitrogen dioxide or
mixtures thereof under conditions effective to oxidize at least a
portion of the sulfur impurities; (b) contacting the oxidized
feedstock with a Lewis acid under conditions effective so that
Lewis base sulfur impurity(ies) in the feedstock can react with the
Lewis acid; and (c) removing any impurities so oxidized and/or
reacted from the hydrocarbon oil.
21. The method of claim 21 further comprising the step of
regeneration of the Lewis acid.
Description
BACKGROUND
[0001] Petroleum is the world's main source of hydrocarbons used as
fuel and petrochemical feedstock. Because of the presence of
impurities, crude oil is seldom used in the form produced at the
well, but rather, is typically converted in oil refineries into the
wide range of fuels and petrochemical feedstocks appropriate for
their intended end-use applications. While compositions of natural
petroleum or crude oils vary significantly, all crudes contain
sulfur compounds. Generally, sulfur concentrations in crude oils
range from about 0.5 to about 1.5 percent, but may deviate upwardly
to up to about 8 percent. When combusted, sulfur containing
compounds are converted to sulfur oxides (SOx), considered to be an
environmental pollutant. Catalytic oxidation of sulfur and the
subsequent reaction thereof with water can result in the formation
of sulfuric acid mist, thereby also contributing to particulate
emissions. And so, such crudes typically must be desulfurized to
yield products, which meet performance specifications and/or
environmental standards.
[0002] In fact, it is likely that sulfur removal from petroleum
feedstocks and products will become increasingly important in years
to come. While legislation on sulfur in diesel fuel, for example,
in Europe, Japan and the US has recently lowered the specification
for on-road vehicles from 0.05 to 0.001 (EU) or 0.0015 (US) percent
by weight, indications are that future specifications may go below
this level and include off-road vehicles.
[0003] Hydrodesulfurization (HDS) has been used to remove
impurities from hydrocarbon oils, and can remove a major portion of
sulfur. However, conventional hydrodesulfurization processes do not
effectively remove aromatic sulfur compounds, such as
benzothiophene and dibenzothiophene. Intensifying certain
hydrodesulfurization processing conditions, e.g., reaction
temperature, hourly space velocity, etc., may result in improved
removal of these more recalcitrant contaminants, however,
intensification of processing conditions may add costs to an
already capital intensive process. Further, using conventional
hydrodesulfurization catalysts at high temperatures can result in
yield loss, faster catalyst coking and product quality
deterioration.
[0004] Efficient, more cost effective, methods for removal of
sulfur compounds from crude oils are thus needed. Desirably, such
methods would be capable of removing aromatic sulfur compounds to
the very low levels required in many applications.
BRIEF DESCRIPTION
[0005] Provided herein are methods for removing sulfur impurities
from a hydrocarbon oil. The method comprises contacting the
hydrocarbon oil with an oxygen-containing gas under conditions
effective to oxidize at least a portion of the impurities. The
method further comprises contacting the hydrocarbon oil with a
Lewis acid under conditions effective so that any Lewis base
impurity(ies) in the hydrocarbon oil can react with the Lewis acid.
Any impurities so oxidized and/or reacted are removed from the
hydrocarbon oil.
[0006] Also provided are methods for removing sulfur impurities
from a hydrocarbon oil. The method comprises contacting the
hydrocarbon oil with a gas comprising nitrogen dioxide, or nitric
oxide and oxygen, under conditions effective to oxidize at least a
portion of the sulfur impurities. The hydrocarbon oil comprising
oxidized sulfur impurities is then contacted with a Lewis acid
under conditions effective so that any Lewis base sulfur
impurity(ies) in the hydrocarbon oil can react with the Lewis acid.
Any impurities so oxidized and/or reacted are then removed from the
hydrocarbon oil.
DRAWINGS
[0007] These and other features, aspects, and advantages of the
present invention will become better understood when the following
detailed description is read with reference to the accompanying
drawings in which like characters represent like parts throughout
the drawings, wherein:
[0008] FIG. 1 is a flow chart schematically illustrating one
embodiment of the present method;
[0009] FIG. 2 is a flow chart schematically illustrating another
embodiment of the present method;
[0010] FIG. 3 is a flow chart schematically illustrating another
embodiment of the present method;
[0011] FIG. 4 is a flow chart schematically illustrating another
embodiment of the present method;
[0012] FIG. 5 is a flow chart schematically illustrating another
embodiment of the present method; and
[0013] FIG. 6 is a flow chart schematically illustrating an
additional embodiment of the present method.
DETAILED DESCRIPTION
[0014] Unless defined otherwise, technical and scientific terms
used herein have the same meaning as is commonly understood by one
of skill in the art to which this invention belongs. The terms
"first", "second", and the like, as used herein do not denote any
order, quantity, or importance, but rather are used to distinguish
one element from another. Also, the terms "a" and "an" do not
denote a limitation of quantity, but rather denote the presence of
at least one of the referenced item, and the terms "front", "back",
"bottom", and/or "top", unless otherwise noted, are merely used for
convenience of description, and are not limited to any one position
or spatial orientation. If ranges are disclosed, the endpoints of
all ranges directed to the same component or property are inclusive
and independently combinable (e.g., ranges of "up to about 25 wt.
%, or, more specifically, about 5 wt. % to about 20 wt. %," is
inclusive of the endpoints and all intermediate values of the
ranges of "about 5 wt. % to about 25 wt. %," etc.). The modifier
"about" used in connection with a quantity is inclusive of the
stated value and has the meaning dictated by the context (e.g.,
includes the degree of error associated with measurement of the
particular quantity).
[0015] Provided herein are methods for removing impurities from a
hydrocarbon oil. The methods comprise contacting the hydrocarbon
oil with an oxygen containing gas under conditions effective to
oxidize at least a portion of the impurities. The hydrocarbon oil
is also contacted with a Lewis acid so that any impurities capable
of acting as a Lewis base can react with the Lewis acid. Any
impurities so oxidized and/or reacted are then removed from the
hydrocarbon oil.
[0016] The methods disclosed herein may advantageously be applied
to any hydrocarbon oil, or mixture of one or more hydrocarbon oils,
comprising impurities. Exemplary hydrocarbon oils suitable for the
present invention include, but are not limited to, liquid oils
obtained from bitumen (often called tar sands or oil sands),
petroleum, oil shale, coal, as well as synthetic crude oils
produced by the liquefaction of coal, heavy crude oils, oil
distillates, and petroleum refinery residual oil fractions, such as
bottoms or fractions produced by atmospheric and vacuum
distillation of crude oil.
[0017] The hydrocarbon fuel oil may be subjected to the present
method "as is", without pretreatment, or addition of solvents.
However, in some embodiments, the addition of a fuel solvent may be
desired to facilitate processing. In such embodiments, the
hydrocarbon oil may optionally be provided in combination with a
fuel solvent or a mixture of solvents to further liquefy, or form a
slurry with, the hydrocarbon oil, and thus potentially facilitating
processing. Exemplary suitable non-polar fuel solvents include, but
are not limited to, petroleum ether, hexanes, pentane, cyclohexane,
heptane, propane, butane, mixtures of these, and the like.
[0018] In embodiments wherein the same is desired, the ratio of the
fuel solvent to the hydrocarbon oil will desirably be sufficient so
that the hydrocarbon oil-fuel solvent mixture is provided with a
viscosity of up to about 32.60 API gravity crude oil (from about
0.342 cSt at 17.8.degree. C. to about 23.2 cSt at 15.6.degree. C.).
Ratios of fuel solvent to the hydrocarbon oil expected to be
capable of providing the desired viscosity range from about 0.5:1
to about 10:1, or from about 1:1 to about 2:1. Optionally, any fuel
solvent utilized may be recovered, in whole or in part, and
recycled for this, or other, uses.
[0019] The hydrocarbon oil may also optionally be pretreated, e.g.,
to remove high molecular weight and/or particulate impurities,
prior to being subjected to the present method. For example, the
hydrocarbon oil may be subjected to centrifugation, or other
suitable separation techniques, to remove such particulate
residues. Alternatively, any particulate residues may be removed
from the hydrocarbon oil (or vice versa) by filtration,
decantation, and the like. If desired, an amount of fuel solvent
can be utilized to enhance the processability of the hydrocarbon
oil in any desired pretreatment step.
[0020] Such pretreatment may result in the removal of at least a
portion of any precipitates present in the hydrocarbon oil, and as
such, may reduce the interference of the same in the oxidation and
Lewis acid complexation steps. For example, hydrocarbon oils may
typically contain amounts of asphaltenes, which contain heteroatoms
that may interfere with the removal of the impurities by competing
for the oxygen-containing gas/Lewis acid. By removal of at least
part of the asphaltenes prior to oxidation or the addition of the
Lewis acid to the hydrocarbon oil, the efficiency of the oxidation
and/or Lewis acid complexation may be improved.
[0021] The impurities desirably removed from the hydrocarbon oil by
the disclosed method may include any species capable of being
oxidized and/or forming a complex with a Lewis acid (referred to
herein as "Lewis acid-base complexes"), either as oxidized or
unoxidized. In one embodiment of the present invention, the
impurities may comprise one or more of sulfur, nickel, or vanadium,
i.e., the impurities may comprise any ions, salts, complexes,
and/or compounds including nickel, vanadium, and sulfur. Examples
of impurities comprising vanadium that may be removed by the
present method include, but are not limited to vanadium porphyrins
and oxides, such as for example, vanadium pentoxide. Examples of
impurities comprising nickel include nickel porphyrins, salts
etc.
[0022] In one embodiment, the impurities comprise organic
sulfur-containing compounds, such as alkyl sulfides or aromatic
sulfur containing compounds. Examples of organic sulfur-containing
compounds that may typically contaminate hydrocarbon oils include
thiophene and its derivatives. Exemplary derivatives of thiophene
include various substituted benzothiophenes, dibenzothiophenes,
phenanthrothiophenes, benzonapthothiophenes, thiophene sulfides,
and the like. The particular impurities and concentration(s)
thereof, in the hydrocarbon oil may be dependent on the
geographical source of the hydrocarbon oil, as well as the form and
prior processing (if any) of the hydrocarbon oil.
[0023] The present method involves contacting the hydrocarbon oil
comprising impurities with an oxygen-containing gas. Any
oxygen-containing gas can be used, so long as the oxidation ability
and concentration of oxygen-containing species, including molecular
oxygen (O.sub.2), in the gas is sufficient so that oxidation of at
least a portion of the impurities in the hydrocarbon oil can be
achieved. As those of ordinary skill in the art recognize, the
concentration of oxygen utilized should be chosen to avoid
explosive compositions. Effective concentrations within these
parameters can be between about 0.01 volume % (vol. %) and about 21
vol. %, or between about 0.5 vol. % to about 10 vol. %.
[0024] For example, air, or oxygen depleted air, ozone, nitrogen
dioxide or combinations of these may be utilized as the oxygen
containing gas. Advantageously, it has now been discovered that
oxidation of certain impurities in hydrocarbon oils may be readily
and easily oxidized by a combination of nitric oxide/air without
the use of catalysts. Nonetheless, in certain embodiments air, or
oxygen depleted air may be utilized, and in these embodiments,
oxidation of at least a portion of the impurities in the
hydrocarbon oil can be facilitated by the use of a catalyst, such
as any of those comprising molybdenum, copper, manganese, cobalt,
tungsten, iron, and the like.
[0025] In those embodiments wherein the oxygen-containing gas
comprises nitrogen dioxide, or combinations of nitric oxide with
e.g., air, catalysts are not required, and efficiencies are
provided. In such embodiments, concentrations of from 1 vol. % to
20 vol. %, or from about 4 vol. % to about 10 vol. % nitric oxide
in air, or nitrogen dioxide in any gas, may be utilized. The
oxygen-containing gas will further desirably be provided with a
pressure of at least about 1 bar, or from about 1 bar to about 200
bar, or even from about 10 bar to about 30 bar. The oxidation of at
least a portion of the impurities in the hydrocarbon oil may be
further facilitated by providing the hydrocarbon oil with a
temperature of at least about 20.degree. C., or from about
20.degree. C. to about 150.degree. C., or even from about
80.degree. C. to about 120.degree. C.
[0026] In some embodiments, the insoluble oxidation products formed
via contact with the oxygen containing gas may desirably be
removed, e.g., prior to contacting the hydrocarbon oil with the
Lewis acid/Lewis acid solution, which may increase the efficiency
with which the Lewis acid-base complexes are formed. Any method
suitable to remove the oxidation products can be utilized, and
exemplary methods for doing so, include for example, filtration,
decantation, centrifugation, etc.
[0027] The hydrocarbon oil is also contacted with a Lewis acid. The
Lewis acid may be any ion or chemical compound that can accept a
pair of electrons from a corresponding Lewis base (e.g., an
oxidized or unoxidized impurity). It is believed that many of the
impurities typically found in hydrocarbon oils, and in particular
impurities comprising sulfur, nickel, and vanadium can act as Lewis
bases that, in turn, are capable of forming stable complexes with
Lewis acids. Lewis acid-base complexes have low to no solubility in
the hydrocarbon oil, and thus may be removed from the hydrocarbon
oil.
[0028] Examples of Lewis acids suitable for use in the methods
disclosed herein include one or more cations of H.sup.+, Li.sup.+,
Na.sup.+, Au.sup.+,Be.sup.2+, Mg.sup.2+, Ca.sup.2+, Sn.sup.2+,
Sn.sup.4+, Al.sup.3+, Ga.sup.3+, In.sup.3+, La.sup.3+, Ce.sup.3+,
Cr.sup.3+, Co.sup.3+, Fe3+, As.sup.3+, Ir.sup.3+, Si.sup.4+,
Ti.sup.4+, Zr.sup.4+, Th.sup.4+, U.sup.4+, Pu.sup.4-, VO.sup.2+,
UO.sub.2.sup.2+, (CH.sub.3).sub.2Sn.sup.2+, and metal halogenides,
alkyls, hydrides, alkoxides, for example, BeMe.sub.2, AlCl.sub.3,
GaCl.sub.3, FeCl.sub.3, AlH.sub.3, BF.sub.3, BCl.sub.3,
B(OR).sub.3, Al(CH.sub.3).sub.3, Ga(CH.sub.3).sub.3,
In(CH.sub.3).sub.3. Cationic Lewis acids may typically be provided
in combination with a counterion, and any suitable counterion may
be utilized in forming a metal salt with the Lewis acid.
[0029] Many of the exemplary Lewis acids listed above may also be
classified as Pearson Lewis acids, and these may be particularly
suitable for forming complexes with the sulfur, vanadium, and
nickel impurities sometimes found in hydrocarbon oils. Accordingly,
in one embodiment, the Lewis acid may comprise a hard Pearson Lewis
acid. Hard Pearson Lewis acids are generally characterized by the
fact they have atomic centers of a small ionic radius; have a
relatively high positive charge; do not contain electron pairs in
their valence shells; have a low electron affinity; are likely to
be strongly solvated; and have high energy low unoccupied molecular
orbitals (LUMOs). Examples of hard Pearson Lewis acids are
identified in R. G. Pearson. J. Am. Chem. Soc. 1963, 85:3533-3543;
R. G. Pearson, Science, 1966, 151:172-177; R. G. Pearson, Chem.
Br., 1967, 3:103-107; and R. G. Pearson, J. Chem. Ed., 1968,
45:581-587; all of which are hereby incorporated by reference
herein for any and all purposes.
[0030] In one embodiment, the Lewis acid may comprise one or more
of AlCl.sub.3, GaCl.sub.3, FeCl.sub.3, which can be particularly
effective at forming complexes with thiophene compounds and their
derivatives, e.g., according to the following reaction scheme:
##STR00001##
Where MX.sub.n=AlCl.sub.3, GaCl.sub.3, FeCl.sub.3. 235961-1
[0031] The Lewis acid may desirably be provided as a solution,
i.e., the Lewis acid may be provided in combination with an
appropriate solvent. The solvent may desirably be an aprotic
solvent, i.e., one that does not exchange protons with a substance
dissolved in it. Desirably, the aprotic solvent will be one capable
of easily forming two phases when mixed with the hydrocarbon oil.
To facilitate separation, the aprotic solvent may be selected to
solvate the positively charged species of the Lewis acid. For
example, in certain embodiments, the aprotic solvent may be
acetonitrile, nitromethane, 1,2-dichloroethane, or combinations
thereof.
[0032] The Lewis acid may form complexes with any impurities
capable of acting as Lewis bases when provided in a stoichiometric
amount relative thereto. However, due to the likely presence of
competing components in the hydrocarbon oil, in one embodiment, a
stoichiometric excess of the Lewis acid may advantageously be
provided to increase the likelihood of complexation of
substantially all of the impurities in the hydrocarbon oil with the
Lewis acid. For example, the Lewis acid may be provided in a
slight, e.g., a 1%, stoichiometric excess relative to the
impurities in the hydrocarbon oil, or, the Lewis acid may be
provided in about a 300% (3 times) stoichiometric excess relative
to the impurities.
[0033] Advantageously, added heat and pressure are not necessary
for carrying out the Lewis acid complexation. Optionally then, the
complexing of at least a portion of impurities in the hydrocarbon
oil capable of acting as Lewis bases may be further facilitated by
providing the hydrocarbon oil with a temperature of at least about
15.degree. C., or from about 20.degree. C. to about 50.degree. C.,
or even from about 20.degree. C. to about 35.degree. C. The
hydrocarbon oil will further desirably be provided with a pressure
of at least about 1 atmosphere, or from about 1 atmosphere to about
5 atmospheres, or even from about 1 atmosphere to about 2
atmospheres, while being contacted with the Lewis acid.
[0034] The impurities so oxidized and/or reacted may then be
removed from the hydrocarbon oil. More particularly, the oxidized
and/or reacted impurities will move to or begin to form a separate
and distinct phase from the hydrocarbon oil, and optional fuel
solvent, so that a first layer comprising the hydrocarbon oil and
optional fuel solvent and a second layer comprising the Lewis
acid-base complexes, and optional aprotic solvent, are formed.
Although the mixture is expected to be capable of separating on its
own, the separation of the mixture into the first and second layers
may be promoted by centrifugation, or any other suitable
method.
[0035] After separation, the layers may be separated by any
suitable extraction method or apparatus known in the art, such as
by decantation or via a separatory funnel. Thereafter, the
hydrocarbon oil treated by the disclosed method may be delivered to
a point-of-use, or, may be subjected to further processing, e.g.,
to remove any fuel solvent originally added to the hydrocarbon oil,
or to be re-treated via one or more steps of the disclosed method.
If, for example, fuel solvent has been employed and is desirably
removed post-processing, it may be removed by any suitable method,
such as by evaporation.
[0036] The contacting steps may be performed in any order, or
relatively simultaneously, but advantageously may be carried out in
sequence, with the oxidation step occurring first. In these
embodiments of the invention, the step of contacting the
hydrocarbon oil with the Lewis acid may remove any oxidized
impurities capable of acting at Lewis bases, as well as any
impurities resistant to oxidation. In such embodiments, the
contacting steps may act synergistically, i.e., to result in the
ability to remove more impurities than may be removed via either
step alone.
[0037] Either or both of the contacting steps may also be repeated
in parallel or sequence to further purify the hydrocarbon oil. For
example, the separated layer comprising the hydrocarbon oil may be
contacted with another amount of the Lewis acid, or Lewis acid
solution, and/or may be contacted with the same, or a different
oxygen-containing gas any number of times. As would be appreciated
by one skilled in the art, the number of times the process is
performed can be dependent on the desired purity of the final
hydrocarbon product, and one or more of the contacting steps can be
repeated until the desired purity has been substantially
achieved.
[0038] The separated layer comprising the Lewis acid may be further
processed to recover the Lewis acid so that it may be reused,
whether in the disclosed method or otherwise. If recovery and
recycling of the Lewis acid is desired, the layer containing the
Lewis acid may be contacted with an acid capable of competing with
the Lewis acid complexed with the impurities. One example of an
acid capable of competing with the Lewis acid is hydrochloric acid,
in concentrations ranging from about 0.001M to about 3.5 M. The
acid will be preferably substituted for the Lewis acid in the Lewis
acid-base complexes, so that the Lewis acid will be freed. Once
freed, the Lewis acid may be recovered by any suitable method,
e.g., crystallization, distillation, etc. for reuse in this, or
another process, or stored until such reuse is desired.
[0039] The present invention is effective to remove a substantially
higher number of impurities than other known techniques, such as
HDS and solvent extraction, or either oxidation or Lewis acid
complexation separately. For example, the disclosed method is
capable of removing substantially all of the sulfur impurities from
a hydrocarbon oil having greater than about 0.5% by weight sulfur
with an effective amount of Lewis acid. In another aspect of the
present invention, the processes and systems described herein are
capable of removing substantially all of the sulfur impurities
(e.g. to a level of less than about 1% by weight) from a
hydrocarbon oil material having greater than 3% sulfur content.
Aspects of the present invention are particularly useful for gas
turbine applications where it is often desirable to lower the
sulfur impurity content from 4% by weight sulfur (or greater) to
less than about 1% by weight sulfur. Accordingly, in one aspect,
the present invention provides an efficient, low-cost process for
the removal of sulfur impurities, e.g. thiophenes and their
derivatives, from high sulfur-content fuels.
[0040] Referring now to FIG. 1, one embodiment of the disclosed
method for removing impurities from a hydrocarbon oil is shown in
flow chart form. More specifically, FIG. 1 shows method 100,
wherein a hydrocarbon oil comprising impurities is provided at 101.
The impurities capable of being removed by method 100 include any
species capable of being oxidized and/or forming a complex with a
Lewis acid, and in some embodiments, may include one or more of a
sulfur, nickel, or vanadium impurity. In one particular embodiment,
the impurities comprise organic sulfur-containing compounds, such
as thiophene and its derivatives, including various
benzothiophenes, dibenzothiophenes, phenanthrothiophenes,
benzonapthothiophenes, sulfides, such as aromatic and non-aromatic
alkyl sulfides, and the like.
[0041] Optionally, the hydrocarbon oil may be combined with a fuel
solvent to enhance the processability thereof, as shown as step
102. The optional fuel solvent may comprise any appropriate
non-polar solvent such as, for example, petroleum ether, hexanes,
pentane, cyclohexane, heptane, propane, butane, any other non-polar
hydrocarbon solvent with a relatively low boiling point, or
combinations of these. In such embodiments, The ratio of the fuel
solvent to the hydrocarbon oil may be from about 0.5:1 to about
10:1, or from about 1:1 to about 2:1.
[0042] The hydrocarbon oil, or hydrocarbon oil/fuel solvent mixture
is contacted with an oxygen-containing gas at step 103. The
oxygen-containing gas may be any capable of oxidizing at least a
portion of the impurities desirably removed from the hydrocarbon
oil, e.g., air, oxygen depleted air, ozone enriched air, nitrogen
dioxide, nitric oxide in air, or mixtures of these. Although
catalysts comprising molybdenum, copper, manganese, cobalt,
tungsten, iron, or combinations of these may advantageously be
employed in those embodiments wherein the oxygen containing gas
comprises air, or oxygen depeleted air, advantageously, catalysts
are not required in those embodiments wherein the oxygen-containing
gas comprises nitric oxide or nitrogen dioxide.
[0043] As shown at step 104, the hydrocarbon oil is also contacted
with a Lewis acid, either provided neat, or in combination with a
solvent to provide a Lewis acid solution. Desirably, if the use of
a solvent is desired or required, an aprotic solvent may be used,
e.g., acetonitrile, nitromethane, 1,2-dichloroethane, or
combinations thereof. The Lewis acid may be any ion or compound
that can accept a pair of electrons from a corresponding Lewis
base, in this case, oxidized and/or unoxidized impurities capable
of acting as Lewis bases. The resulting Lewis acid-base complexes
are readily separated from the hydrocarbon oil, in particular, in
those embodiments wherein an aprotic solvent is utilized to provide
the Lewis acid as a Lewis acid solution. The Lewis acid may
desirably comprise a Pearson Hard Lewis acid, and in some
embodiments, comprises AlCl.sub.3, GaCl.sub.3, FeCl.sub.3, or
combinations of these. Any of steps 101-104 may be optionally
heated or pressurized, but advantageously, the disclosed methods do
not require added heat and pressure to carry out the oxidation or
Lewis acid complexation.
[0044] Once the hydrocarbon oil and Lewis acid solution are
combined, Lewis acid-base complexes will begin to form between the
Lewis acid and any impurities of the hydrocarbon oil capable of
acting as Lewis bases, and the combined solution will begin to
fractionate, i.e., to form two distinct phases. One phase will
comprise hydrocarbon oil (and any added fuel solvent, if present)
while another phase will comprise the Lewis acid-base complexes and
the aprotic solvent, if used. If desired or required,
centrifugation may be utilized to facilitate the fractionation. As
shown at step 105, the phases may then be separated, such as by
decantation or filtration or, if the aprotic solvent used via a
liquid-liquid extractor or a separatory funnel, and the purified
hydrocarbon oil stored or further processed. If any fuel solvent
was added to facilitate processing of the hydrocarbon oil, it may
be removed from the purified hydrocarbon oil, e.g., by
evaporation.
[0045] In some embodiments, it may be desirable to repeat either or
both of the oxidation and/or Lewis acid complexation steps.
Repetition of one or both of the oxidation and/or Lewis acid
complexation steps can further reduce the amount of impurities in
the hydrocarbon oil, so that more pure fractions may be obtained,
or cruder grades may be started with. One such embodiment is shown
in FIG. 2, in which, at step 206, the mixture is subjected to both
an additional oxidation and Lewis acid complexation step. FIG. 3
shows an additional such embodiment, wherein only the Lewis acid
complexation step is repeated at step 306.
[0046] Another embodiment is illustrated in FIG. 4, which shows
method 400 further comprising pre-processing purification step 407
in which particulates, or other high molecular weight impurities
may be removed from the hydrocarbon oil. Hydrocarbon oils may
typically contain amounts of asphaltenes, or other particulates,
that may interfere with the removal of the sulfur containing
impurities from the hydrocarbon oil. By removal of at least some of
the asphaltenes prior to oxidation and/or the addition of the Lewis
acid to the hydrocarbon oil, the efficiency of the oxidation and/or
Lewis acid complexation may be enhanced.
[0047] More particularly, pre-processing purification step 407 may
comprise the addition of a solvent to improve the processability of
the hydrocarbon oil, and then the centrifugation of this mixture to
provide the precipitation of at least a portion of any particulates
or impurities having a higher molecular weight or density than the
hydrocarbon oil. Pre-processing purification step may also comprise
filtration, decantation, or combinations of these. The pre-treated
hydrocarbon oil may then be separated from the precipitates and
further processed according to the method disclosed herein.
[0048] Yet another embodiment is shown in FIG. 5, wherein method
500 further comprises separation of fractionated mixture into a
purified hydrocarbon oil fraction and a fraction comprising the
Lewis acid complexes, and at step 508, recovery of the Lewis acid.
More particularly, step 508 may involve the addition of an acid to
the Lewis acid fraction, which is expected to regenerate the Lewis
acid that may then recovered via any suitable method, e.g.,
crystallization or distillation. The Lewis acid may then be stored
for future use, or as shown at step 509, recycled and reused in
method 500 at step 504. Any acid capable of regenerating the Lewis
acid may be used at step 508, and one example of a suitable acid is
hydrochloric acid having a concentration in the range of from about
0.001 M to about 3.5 M.
[0049] In some embodiments, the oxidation products formed via
contact with the oxygen containing gas may be removed prior to
contacting the hydrocarbon oil with the Lewis acid/Lewis acid
solution, which may increase the efficiency with which the Lewis
acid-base complexes are formed. Such an embodiment is shown in FIG.
6, wherein method 600 comprises removal of formed oxidation
products at step 610. Any method suitable to remove the oxidation
products can be utilized at step 610, and suitable methods for
doing so, include for example, filtration, centrifugation,
decantation, and the like. FIG. 6 also illustrates that embodiment
of the invention wherein the hydrocarbon oil is not combined with a
fuel solvent prior to contacting the hydrocarbon oil with the
oxygen containing gas and/or the Lewis acid.
EXAMPLE 1
[0050] 4.02 grams of a 1% solution of benzothiophene (BZT) in
decalin (a model hydrocarbon oil) was weighed into a 15 ml
centrifuge tube. 5.04 grams of nitromethane was added to extract
the benzothiophene. The tube was shaken vigorously for about 2
minutes and then centrifuged at 2100 rpm for 10 minutes. The top
phase (supernatant) was pipetted off and the sulfur content
measured by XRF. Approximately 50% of the sulfur in the decalin was
extracted by 5.04 g of nitromethane.
EXAMPLE 2
[0051] 4.00 grams of a 1% solution of benzothiophene in decalin,
which was previously treated with NO.sub.2 by bubbling of 3%
NO.sub.2 in air at 75.degree. C. during 2 hours at the rate 150
sccm in a flask equipped with a water cooled condenser, was weighed
into a 15 ml centrifuge tube. 5.04 grams of nitromethane was added
to extract the benzothiophene/NO.sub.2 oxidation products. The tube
was shaken vigorously for about 2 minutes and then centrifuged at
2100 rpm for about 10 minutes. The top phase (supernatant) was
pipetted off and the sulfur content therein measured by XRF.
Approximately 52% of the sulfur in the decalin was extracted to
nitromethane.
EXAMPLE 3
[0052] 4.01 grams of a 1% solution of benzothiophene in decalin,
which was previously treated with NO.sub.2 as described in Example
2, was weighed into a 15 ml centrifuge tube. 5.01 grams of a 0.56M
Lewis acid solution of iron (III) chloride in nitromethane was
added. The tube was shaken vigorously for about 2 minutes and then
centrifuged at 2100 rpm for 10 minutes. The top phase was pipetted
off and the sulfur content measured by XRF. Approximately 88% of
the original sulfur in the decalin was extracted using oxidation
followed by treatment with Lewis acid.
EXAMPLE 4
[0053] 4.02 grams of a 1% solution of benzothiophene in decalin,
which was previously treated with NO.sub.2 as described in Example
2, was weighed into a 15 ml centrifuge tube. 2.50 grams of a 0.56M
Lewis acid solution of iron (III) chloride in nitromethane was
added. The tube was shaken vigorously for about 2 minutes and then
centrifuged at 2100 rpm for 10 minutes. The top phase (supernatant)
was pipetted off and the sulfur content measured by XRF.
Approximately 82% of the original sulfur in the decalin was
extracted. Thus, with only half of the Lewis acid used, most of the
benzothiophene was removed from the decalin phase after the
NO.sub.2/Lewis acid treatment.
EXAMPLE 5
[0054] 4.03 grams of a 1% solution of octyl sulfide (OS) in
decalin, which was previously treated with NO.sub.2 as described in
Example 2, was weighed into a 15 ml centrifuge tube. 4.0 grams of
nitromethane was added to extract the octyl sulfide oxidation
products. The tube was shaken vigorously for about 2 minutes and
then centrifuged at 2100 rpm for about 10 minutes. The top phase
was pipetted off and the sulfur content measured by XRF.
Approximately 31% of the sulfur in the decalin was extracted to
nitromethane.
EXAMPLE 6
[0055] 4.01 grams of a 1% solution of octyl sulfide in decalin,
which was previously treated with NO.sub.2 as described in Example
2, was weighed into a 15 ml centrifuge tube. 4.01 grams of a 0.56M
Lewis acid solution of iron (III) chloride in nitromethane was
added. The tube was shaken vigorously for about 2 minutes and then
centrifuged at 2100 rpm for about 10 minutes. The top phase was
pipetted off and the sulfur content measured by XRF. Approximately
82% of the sulfur in the decalin was removed.
EXAMPLE 7
[0056] 4.0 grams of a 1% solution of octyl sulfide in petroleum
ether was weighed into a 15 ml centrifuge tube. 4.01 grams of a
0.56M Lewis acid solution of iron (III) chloride in nitromethane
was added. The tube was shaken vigorously for about 2 minutes and
then centrifuged at 2100 rpm for 10 minute. The top phase was
pipetted off and the sulfur content measured by XRF. Approximately
44% of the sulfur in the petroleum ether was removed.
[0057] The results of Examples 1-7 are summarized in Table 1,
below. Briefly, Example 3 shows that the combination of oxidation
with Lewis acid treatment removes significantly more aromatic
sulfur (BZT) than pure solvent extraction (Example 1) and oxidation
alone (Example 2). Example 4 shows that this is true at even 1/2
the Lewis acid concentration, i.e., a similar sulfur removal
percent was seen in Example 4 as compared to Example 3, while using
Lewis acid at half the concentration of that used in Example 3.
And, Example 6 shows the synergistic effect of using oxidation and
Lewis acid extraction to remove aliphatic sulfur, i.e., the
combination of oxidation with Lewis acid extraction removed more
aliphatic sulfur than either oxidation (Example 5) or Lewis acid
extraction (Example 7) alone.
TABLE-US-00001 Sulfur Initial Final .DELTA. (% S Example source % S
% S removed) Comments 1 BZT 0.254 0.127 50% Extraction only
(neither oxidation nor Lewis acid treatment) 2 BZT 0.256 0.123 52%
Oxidation + extraction 3 BZT 0.256 0.031 88% Oxidation + Lewis acid
treatment 4 BZT 0.256 0.046 82% Oxidation + Lewis acid treatment at
1/2 concentration of Example 3 5 OS 0.139 0.096 31% Oxidation +
extraction 6 OS 0.139 0.025 82% Oxidation + Lewis acid treatment 7
OS 0.426 0.239 44% Lewis acid treatment only (no oxidation)
[0058] While various embodiments of the present invention have been
shown and described herein, it will be understood that such
embodiments are provided by way of example only and not of
limitation. Numerous variations, changes and substitutions will
occur to those skilled in the art without departing from the
teaching of the present invention. Accordingly, it is intended that
the invention be interpreted within the full spirit and scope of
the appended claims.
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