U.S. patent application number 16/128615 was filed with the patent office on 2020-03-12 for fuel high temperature antioxidant additive.
The applicant listed for this patent is ExxonMobil Research and Engineering Company. Invention is credited to David J. Abdallah, Zsolt Lengyel, Mike T. Noorman.
Application Number | 20200080015 16/128615 |
Document ID | / |
Family ID | 67777474 |
Filed Date | 2020-03-12 |
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United States Patent
Application |
20200080015 |
Kind Code |
A1 |
Abdallah; David J. ; et
al. |
March 12, 2020 |
Fuel High Temperature Antioxidant Additive
Abstract
High temperature antioxidant additives and methods that improve
a liquid fuel composition's thermal oxidative stability are
disclosed. A liquid fuel composition may comprise a liquid fuel;
and a high temperature antioxidant additive comprising a nitroxide
radical having a formula: ##STR00001## wherein R.sub.1, R.sub.2,
R.sub.3, and R.sub.4 are individually selected from an alkyl group
or a hetero atom substituted alkyl group, and wherein R.sub.5 and
R.sub.6 are any atom or group except hydrogen which can bond
covalently to carbon.
Inventors: |
Abdallah; David J.;
(Moorestown, NJ) ; Lengyel; Zsolt; (Newtown,
PA) ; Noorman; Mike T.; (Doylestown, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ExxonMobil Research and Engineering Company |
Annandale |
NJ |
US |
|
|
Family ID: |
67777474 |
Appl. No.: |
16/128615 |
Filed: |
September 12, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10L 2270/023 20130101;
C10L 2200/0423 20130101; C10L 1/222 20130101; C10L 2230/081
20130101; C10L 2200/0469 20130101; C10L 2200/043 20130101; C10L
10/00 20130101; C10L 2200/0446 20130101; C10L 2270/04 20130101;
C10L 1/232 20130101; C10L 2200/0476 20130101; C10L 2270/026
20130101 |
International
Class: |
C10L 1/232 20060101
C10L001/232; C10L 10/00 20060101 C10L010/00 |
Claims
1. A liquid fuel composition comprising: a mixture of a motor
gasoline and ethanol; and a high temperature antioxidant additive
comprising a nitroxide radical having a formula: ##STR00008##
wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are individually
selected from an alkyl group or a hetero atom substituted alkyl
group, and wherein R.sub.5 and R.sub.6 are any atom or group except
hydrogen which can bond covalently to carbon.
2. The liquid fuel composition of claim 1, wherein the gasoline
comprises at least one hydrocarbon fuel selected from the group
consisting of a motor gasoline, an aviation gasoline, and
combinations thereof.
3. (canceled)
4. The liquid fuel composition of claim 1, wherein the gasoline is
present in an amount of about 98 vol. % or greater.
5. The liquid fuel composition of claim 1, wherein R.sub.1,
R.sub.2, R.sub.3, and R.sub.4 are individually selected from a
methyl group, an ethyl group, or a propyl group, and wherein
R.sub.5 and R.sub.6 form part of a ring of 4 carbon atoms or 5
carbon atoms.
6. The liquid fuel composition of claim 1, wherein R.sub.5 and
R.sub.6 are individually selected from halogen, cyano, --COOR
wherein R is alkyl or aryl, --CONH.sub.2, --S--C.sub.6H.sub.5,
--S--COCH.sub.3, --OCOC.sub.2H.sub.5, carbonyl, alkenyl where the
double bond is not conjugated with the nitroxide moiety, or an
alkyl of 1 to 15 carbon atoms.
7. The liquid fuel composition of claim 1, wherein the nitroxide
radical has a formula: ##STR00009## wherein R.sub.5, R.sub.6, and
R.sub.7 are individually selected from --CR'R'--, wherein each R'
is individually selected from hydrogen, a hydroxide group, an alkyl
group, or an alkoxy group.
8. The liquid fuel composition of claim 7, wherein R.sub.1,
R.sub.2, R.sub.3, and R.sub.4 are individually selected from a
methyl group, an ethyl group, or a propyl group.
9. The liquid fuel composition of claim 1, wherein the nitroxide
radical comprises 2,2,6,6-tetramethyl-1-piperidinyloxy free
radical.
10. The liquid fuel composition of claim 1, wherein the high
temperature antioxidant additive is present in an amount ranging
from about 0.1 ppm to about 500 ppm.
11. The liquid fuel composition of claim 1, wherein the liquid fuel
is present in an amount of about 99 vol. % or greater, and wherein
the high temperature antioxidant additive is present in an amount
ranging from about 1 ppm to about 100 ppm.
12. The liquid fuel composition of claim 1, further comprising at
least one additional additive selected from the group consisting of
a detergent, a rust inhibitor, a corrosion inhibitor, a lubricant,
an antifoaming agent, a demulsifier, a conductivity improver, a
metal deactivator, a cold-flow improver, a cetane improvers,
fluidizer, and combinations thereof.
13. A liquid fuel composition comprising: a gasoline in an amount
of about 98 vol. % or greater, wherein the gasoline comprises a
motor gasoline and ethanol; and a nitroxide radical in an amount
ranging from about 1 ppm to about 100 ppm and having a formula:
##STR00010## wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are
each a methyl group, and wherein R.sub.5 and R.sub.6 are
individually selected from --CR'R'--, wherein each R' is
hydrogen.
14. (canceled)
15. (canceled)
16. A method for improving thermal oxidative stability of a liquid
fuel, comprising: including an antioxidant additive comprising
nitroxide radical in the liquid fuel, wherein the nitroxide radical
has a formula: ##STR00011## wherein R.sub.1, R.sub.2, R.sub.3, and
R.sub.4 are individually selected from an alkyl group or a hetero
atom substituted alkyl, and wherein R.sub.5 and R.sub.6 are any
atom or group except hydrogen which can bond covalently to carbon,
wherein the liquid fuel comprises a mixture of a motor gasoline and
ethanol.
17. (canceled)
18. The method of claim 16, wherein R.sub.1, R.sub.2, R.sub.3, and
R.sub.4 are individually selected from a methyl group, an ethyl
group, or a propyl group, and wherein R.sub.5 and R.sub.6 form part
of a ring of 4 carbon atoms or 5 carbon atoms.
19. The method of claim 16, wherein the nitroxide radical has a
formula: ##STR00012## wherein R.sub.5 and R.sub.6 are individually
selected from --CR'R'--, and wherein each R' is individually
selected from hydrogen, a hydroxide group, an alkyl group, or an
alkoxy group.
20. The method of claim 16, wherein the nitroxide radical comprises
2,2,6,6-tetramethyl-1-piperidinyloxy free radical.
Description
FIELD
[0001] This application relates to high temperature antioxidant
additives for liquid fuels, and, more particularly, embodiments
relate to high temperature antioxidant additives and methods that
improve a liquid fuel's thermal oxidative stability.
BACKGROUND
[0002] Operation of an internal combustion engine can lead to
deposits in the fuel system. The deposits can adversely impact
engine performance, potentially resulting in fuel system component
malfunction or failure. For instance, the deposits can restrict the
flow of air and fuel entering the combustion chamber, which can
cause stalling and hesitation. One contributor to fuel system
deposits is fuel oxidation, caused by reactions between molecular
oxygen and the fuel. This process is accelerated with higher
temperatures. To achieve better combustion and reduced emissions,
modern engine designs have trended toward higher fuel system
operating temperatures and pressures, thus subjecting fuels to
higher thermal loads than has been typical in the past. However,
the increased thermal loads can lead to increased fuel oxidation
and, thus, increased deposits.
[0003] One technique that has been used for fuel-system deposit
control has been to use detergents. However, detergents typically
do not work across the entire fuel system and may be designed to
target specific components within the fuel system, e.g., carburetor
detergents, intake valve detergents, valve stem deposit fluidizers,
and direct injector detergents, among others. In some instances, a
detergent targeting a specific component can cause deposits in
other components of the fuel system. For instance, high levels of
carburetor detergents can increase piston ring belt deposits and
intake valve deposits, while intake valve detergents that can clean
the tops of valve tulips can create sticky valve stem deposits.
Additionally, these detergents and the fluidizers that often
accompany them are typically not conducive to combusting and tend
to contribute to combustion chamber deposits, which are known to
lead to octane rating increase, combustion chamber deposit
interference, disturbance of the air-fuel mixture formation, and/or
increased regulated emissions. In addition, while detergents are
designed to address the deposits that can result from oxidation,
they are not designed to stop oxidation from occurring. While
antioxidant additives have been included in fuels, they are
designed to combat oxidation and preserve fuel stability at ambient
storage conditions rather than engine operating temperatures. At
increased temperatures, these antioxidants can degrade and lead to
fuel system deposits.
SUMMARY
[0004] Disclosed herein is an example liquid fuel composition. The
example liquid fuel composition may comprise a liquid fuel; and a
high temperature antioxidant additive comprising a nitroxide
radical of the following Formula (1):
##STR00002##
wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are individually
selected from an alkyl group or a hetero atom substituted alkyl
group, and wherein R.sub.5 and R.sub.6 are any atom or group except
hydrogen which can bond covalently to carbon.
[0005] Further disclosed herein is another example liquid fuel
composition. The example liquid fuel composition may comprise a
liquid fuel in an amount of about 98 vol. % or greater; and a
nitroxide radical in an amount ranging from about 1 ppm to about
100 ppm and having the following Formula (2):
##STR00003##
[0006] Further disclosed herein is a method for improving thermal
oxidative stability of a liquid fuel. An example method may
comprise including an antioxidant additive comprising nitroxide
radical in the liquid fuel, wherein the nitroxide radical is of
Formula (1).
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] These drawings illustrate certain aspects of the present
invention and should not be used to limit or define the
invention.
[0008] FIG. 1 illustrates an autoxidative free radical chain
reaction process for a fuel oxidative degradation.
[0009] FIG. 2 is a chart showing the oxidation induction period for
a premium motor gasoline blendstock with 10 ppm of a nitroxide
radical and the oxidation induction period for comparative samples
without the nitroxide radical and with an alternative additive.
[0010] FIG. 3 is a chart showing the oxidation induction period for
a premium motor gasoline blendstock with 10 vol. % ethanol and 10
ppm of a nitroxide radical and the oxidation induction period for
comparative samples without the nitroxide radical and with an
alternative additive.
[0011] FIG. 4 is a chart showing the oxidation induction period for
a premium motor gasoline blendstock with 10 ppm of a nitroxide
radical and detergents and the oxidation induction period for
comparative samples without the nitroxide radical and without
detergent.
[0012] FIG. 5 is a chart showing the oxidation induction period for
a regular motor gasoline blendstock with 10 ppm of a nitroxide
radical and the oxidation induction period for comparative samples
without the nitroxide radical.
[0013] FIG. 6 is a chart showing the oxidation induction period for
a regular motor gasoline blendstock with varying concentrations a
nitroxide radical and the oxidation induction period for
comparative samples without the nitroxide radical.
[0014] FIG. 7 is a chart showing the oxidation induction period for
a diesel fuel with 10 ppm of a nitroxide radical and the oxidation
induction period for comparative samples without the nitroxide
radical and with an alternative additive.
[0015] FIG. 8 is a chart showing the oxidation induction period for
a B2 diesel fuel with 10 ppm of a nitroxide radical and the
oxidation induction period for comparative samples without the
nitroxide radical.
[0016] FIG. 9 is a charting showing average difference in injector
flow rate for various gasoline fuel injectors tested with 10 ppm of
nitroxide radical and a comparative sample without the nitroxide
radical.
DETAILED DESCRIPTION
[0017] This application relates to high temperature antioxidant
additives for liquid fuels, and, more particularly, embodiments
relate to high temperature antioxidant additives and methods that
improve a liquid fuel composition's thermal oxidative stability. As
used herein, the antioxidant additives are referred to as "high
temperature" antioxidant additives because the antioxidant
additives improve a liquid fuel composition's thermal oxidative
stability. Embodiments disclose an antioxidant additive that
includes a nitroxide radical to improve the thermal oxidative
stability of a liquid fuel composition. Thermal oxidative stability
is measured in terms of the liquid fuel composition's tendency to
form deposits in the fuel system, including fuel lines, heat
exchangers and nozzles of jet engines as well as on the intake
valves, ports, fuel injectors, and combustion chamber surfaces of
gasoline and diesel engines. By operation improvement of the
thermal oxidative stability, the antioxidant additives may not only
help with fuel storage stability but also provide benefits to the
liquid fuel composition at engine operating temperatures.
[0018] During heating of liquid fuel composition, for example, in
operation of an engine, fuel oxidative degradation proceeds through
an autoxidative free radical chain reaction process. An example
reaction scheme 100 for fuel oxidative degradation is provided in
FIG. 1. The fuel molecules (shown as FM) present in the liquid fuel
composition break down into free radicals (shown as FM.).
Propagation reactions may then occur in which the free radicals
combine with oxygen to form peroxide radicals (shown as FMOO.)
which abstract hydrogen from another fuel molecule, or within the
same fuel molecule, to form a new FM. and a hydroperoxide.
Termination reactions may then occur in which the peroxide radicals
are eliminated. The termination reactions include reaction of the
peroxide radicals with additional fuel molecule radicals to form
peroxides. Hydroperoxides formed from the chain reaction are
inherently unstable to heat and can readily decompose to yield
additional free radicals (e.g., FM. and OH.), which continue to
initiate additional chain reactions and additional hydroperoxides
(shown as FMOOH). Hydroperoxides are a primary product of
autoxidation and therefore may be considered the main initiators in
thermal oxidation. Hydroperoxides, and their decomposition products
are ultimately responsible for the changes in molecular structure
and fuel system deposits. Conventional antioxidants produce
hydroperoxides that stop the chain reaction at storage temperatures
but can decompose to produce free radicals when heated. However,
the high temperature antioxidant additive disclosed herein
comprising the nitroxide radical should delay the oxidation
induction period of the liquid fuel composition. As the oxidation
induction period is delayed less peroxide radicals are generated,
leading to less hydroperoxides and ultimately less deposits. In
other words, the antioxidant additive may be considered to block
fuel degradation pathways at high temperatures.
[0019] There may be several potential advantages to the
compositions and methods disclosed herein, only some of which may
be alluded to in the present disclosure. One of the many potential
advantages of the compositions and methods is that the nitroxide
radical should extend the oxidation induction period of the liquid
fuel composition. The oxidation induction period is an initial slow
stage of fuel oxidation after which the oxidation reaction
accelerates. By extending the oxidation induction period, fuel
oxidation in the fuel system that leads to deposits may be reduced
or potentially avoided. In some embodiments, the oxidation
induction period may be extended to a timeframe that is longer than
the liquid fuel composition will spend at elevated temperatures in
the fuel system components.
[0020] As used herein, the term "nitroxide radical" refers to
stable nitroxide free radicals. Nitroxide radicals may have either
a heterocyclic or linear structure. Suitable nitroxide radicals may
include, but are not limited to, a nitroxide radical of Formula (1)
as follows:
##STR00004##
wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are individually
selected from alkyl groups or hetero atom substituted alkyl. The
alkyl (or heteroatom substituted) groups R.sub.1, R.sub.2, R.sub.3,
and R.sub.4 may be the same or different and, in some embodiments,
include 1 carbon atom to 15 carbon atoms. In some embodiments,
R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are individually selected
from methyl, ethyl, or propyl groups.
[0021] The remaining valences (R.sub.5 and R.sub.6) in the formula
above may be satisfied by any atom or group except hydrogen which
can bond covalently to carbon, although some groups may reduce the
stabilizing power of the nitroxide structure and are undesirable.
In some embodiments, R.sub.5 and R.sub.6 are individually selected
from halogen, cyano, --COOR wherein R is alkyl or aryl,
--CONH.sub.2, --S--C.sub.6H.sub.5, --S--COCH.sub.3,
--OCOC.sub.2H.sub.5, carbonyl, alkenyl where the double bond is not
conjugated with the nitroxide moiety or alkyl of 1 to 15 carbon
atoms. R.sub.5 and R.sub.6 may also form a ring of 4 carbon atoms
or 5 carbon atoms and up to two heteroatoms, such as O, N or S by
R.sub.5 and R.sub.6 together. Examples of suitable compounds having
the structure above and in which R.sub.5 and R.sub.6 form part of
the ring are pyrrolidin-1-oxys, piperidinyl-1-oxys, the morpholines
and pierazines. Particular examples wherein the R.sub.5 and R.sub.6
above form part of a ring are
4-hydroxy-2,2,6,6-tetramethyl-piperindino-1-oxy,
2,2,6,6-tetramethyl-piperidino-1-oxy,
4-oxo-2,2,6,6-tetramethyl-piperidino-1-oxy and pyrrolin-1-oxyl. In
some embodiments, suitable R.sub.5 and R.sub.6 groups are
individually selected from methyl, ethyl, and propyl groups.
[0022] Another example of a suitable nitroxide radical may include,
but is not limited to, a nitroxide radical having the structure of
a six-member ring of Formula (2) as follows:
##STR00005##
wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are individually
selected from alkyl groups or hetero atom substituted alkyl, and
wherein R.sub.5 and R.sub.6 are individually selected from
--CR'R'--, wherein each R' is individually selected from hydrogen,
a hydroxide group, an alkyl group, or an alkoxy group. The alkyl
(or heteroatom substituted) groups R.sub.1, R.sub.2, R.sub.3, and
R.sub.4 may be the same or different and, in some embodiments,
include 1 carbon atom to 15 carbon atoms. In some embodiments,
R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are individually selected
from methyl, ethyl, or propyl groups. In some embodiments, each R'
may be the same or different and, in some embodiments, include 1
carbon atom to 15 carbon atoms. In some embodiments, each R' is
individually selected from methyl, ethyl, or propyl groups.
[0023] An example of a suitable hydroxide of Formula (2) includes
2,2,6,6-tetramethyl-1-piperidinyloxy free radical, commonly
referred to as TEMPO, which may also be referred to as
2,2,6,6-tetramethyl-piperidino-1-oxy, 2,2,6,6-tetramethylpiperidine
1-oxyl or 2,2,6,6-tetramethylpiperidinyloxy, of Formula (3) as
follows:
##STR00006##
[0024] Another example of a suitable nitroxide radical may include,
but is not limited to, a nitroxide radical having the structure of
a six-member ring of Formula (4) as follows:
##STR00007##
wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are individually
selected from alkyl groups or hetero atom substituted alkyl, and
wherein R.sub.5, R.sub.6, R.sub.7 are individually selected from
--CR'R'--, wherein each R' is individually selected from hydrogen,
a hydroxide group, an alkyl group, or an alkoxy group. The alkyl
(or heteroatom substituted) groups R.sub.1, R.sub.2, R.sub.3, and
R.sub.4 may be the same or different and, in some embodiments,
include 1 carbon atom to 15 carbon atoms. In some embodiments,
R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are individually selected
from methyl, ethyl, or propyl groups. In some embodiments, each R'
may be the same or different and, in some embodiments, include 1
carbon atom to 15 carbon atoms. In some embodiments, each R' is
individually selected from methyl, ethyl, or propyl groups.
[0025] As previously described, the high temperature antioxidant
additive comprising the nitroxide radical can be used to improve a
liquid fuel composition's thermal oxidative stability. The high
temperature antioxidant additive may be included in the liquid fuel
composition in any suitable amount as desired for improving thermal
oxidative stability. In some embodiments, the high temperature
antioxidant composition can be present in the liquid fuel
composition in an amount ranging from about 0.1 parts per million
("ppm") to about 500 ppm and, more particularly, ranging from about
1 ppm to about 100 ppm. In some embodiments, the high temperature
antioxidant additive may be present in the liquid fuel composition
in an amount of about 0.1 ppm, about 0.5 ppm, about 1 ppm, about 5
ppm, about 10 ppm, about 25 ppm, about 50 ppm, about 100 ppm, about
200 ppm, about 300 ppm, about 400 ppm, or about 500 ppm. One of
ordinary skill in the art with the benefit of this disclosure
should be able to select an appropriate amount of the high
temperature antioxidant additive based on a number of factors,
including, but not limited to, fuel system operating conditions,
the particular nitroxide radical used, and the liquid fuel's
hydrocarbon components, among others.
[0026] In some embodiments, the high temperature antioxidant
additive comprising the nitroxide radical may be included in a
liquid fuel composition to extend an oxidation induction period of
the liquid fuel composition, which should result in improved
thermal stability. The oxidation induction period may be extended
as compared to the liquid fuel composition without the high
temperature antioxidant additive, for example, from about 10% to
100%, or longer than the fuel without the additive. In some
embodiments, the oxidation induction period may be extended as
compared to the liquid fuel composition without the high
temperature antioxidant additive for period of about 200 seconds,
about 500 seconds, about 1,000 seconds, about 2,000 seconds, about
5,000 seconds, about 10,000 seconds, or even longer. The oxidation
induction period is an initial slow stage of fuel oxidation after
which the oxidation reaction accelerates. As used herein, the
oxidation induction period is determined using the PetroOXY
automatic oxidation stability tester using a test method developed
based on ASTM D 7245. In the test method, a 5 mL sample of the
liquid fuel composition is combined with starting oxygen at a
pressure of 500 kPa for motor gasoline or 700 kPa for diesel in a
small, hermetically seal test chamber and heated to a test
temperature. Pressure increases as the temperature of the vessel is
increased from the volatilization of the light components of the
fuel. Pressure is monitored over time. End of test is where a 10%
drop in pressure from the maximum vessel pressure is measured.
Tests temperatures are chosen that reflect relevant fuel end use
temperatures in fuel systems. It has been determined that the time
needed to achieve a pressure drop is directly related to induction
period of the fuel composition and, thus, the thermal oxidation
stability of the fuel composition. The test temperature for diesel
fuel is 200.degree. C. corresponding to a severe condition a fuel
would experience in a diesel fuel injector tip. The test
temperature for motor gasoline is 155.degree. C. corresponding to a
severe condition a fuel would experience in a gasoline fuel
injector tip. Lower temperatures were used when the fuel
composition was not able to obtain the severe conditions such as in
for biodiesel testing.
[0027] In some embodiments, the high temperature antioxidant
additive may be introduced into a fuel system of an internal
combustion engine. In some embodiments, the high temperature
antioxidant combination may be combined with the liquid fuel
composition in the internal combustion engine. In some embodiments,
the high temperature antioxidant composition may be introduced into
the internal combustion engine as a component of the liquid fuel
composition. In a combustion chamber of the internal combustion
engine, the liquid fuel composition may be burned. Suitable
internal combustion engines may include, but are not limited to,
rotary, turbine, spark ignition, compression ignition, 2-stroke, or
4-stroke engines. In some embodiments, the internal combustion
engines include marine diesel engines, aviation piston and turbine
engines, aviation supersonic turbine engines, low-load diesel
engines, and automobile and truck engines.
[0028] In addition to the high temperature antioxidant additive,
the liquid fuel composition may further include a liquid fuel. The
liquid fuel may include, but are not limited to, motor gasoline,
aviation gasoline, marine fuel, and diesel fuel. Combinations of
different liquid fuels may also be used. Motor gasoline includes a
complex mixture of relatively volatile hydrocarbons blended to form
a fuel suitable for use in spark-ignition engines. Motor gasoline,
as defined in ASTM Specification D4814, is characterized as having
a boiling range of 50.degree. C. to 70.degree. C. at the 10-percent
recovery point to 185.degree. C. to 190.degree. C. at the
90-percent recovery point. The diesel fuel can be a petroleum
distillate as defined by ASTM specification D975. The aviation
turbine fuels can be a petroleum distillate as defined by ASTM
specification D1655. The supersonic fuel can be a compound mixture
composed primarily of hydrocarbons; including alkanes,
cycloalkanes, alkylbenzenes, indanes/tetralins, and naphthalenes.
Additional examples of suitable liquid fuels may include, but are
not limited to, an alcohol, an ether, a nitroalkane, an ester of a
vegetable oil, or combinations thereof. In some embodiments, the
nonhydrocarbon fuels may include, but are not limited to, methanol,
ethanol, diethyl ether, methyl t-butyl ether, nitromethane, and
methyl esters of vegetable oils such as the methyl ester of
rapeseed oil. In some embodiments, the liquid fuel may include a
mixture of a motor gasoline and ethanol or a mixture of a diesel
fuel and a biodiesel fuel, such as an ester of a vegetable oil.
Without being limited by theory, it is believed that the
effectiveness of the high temperature antioxidant additive
comprising the nitroxide radical may be substantially reduced in
certain biodiesels. For example, the high temperature antioxidant
additive has shown little to no improvement in certain B100
biodiesels.
[0029] The liquid fuel may be present in the liquid fuel
composition with the high temperature antioxidant additive in any
suitable amount. As previously described, the liquid fuel may
include any suitable liquid fuel, including a combination of two or
more different fuels. In some embodiments, the liquid fuel may be
present in the liquid fuel composition in an amount ranging from
98% to 99.99999% by weight of the liquid fuel composition, from 98%
to 99.99999% by weight of the liquid fuel composition, or from 99%
to 99.999999% by weight of the liquid fuel composition. One of
ordinary skill in the art, with the benefit of this disclosure,
should be able to select an appropriate liquid fuel and amount
thereof to include in the liquid fuel composition for a particular
application.
[0030] In some embodiments, additional additives can be included in
the liquid fuel composition as desired by one of ordinary skill in
the art for a particular application. Examples of these additional
additives include, but are not limited to, detergents, rust
inhibitors, corrosion inhibitors, lubricants, antifoaming agents,
demulsifiers, conductivity improvers, metal deactivators, cold-flow
improvers, cetane improvers and fluidizers, among others. One of
ordinary skill in the art, with the benefit of this disclosure,
should be able to select additional additives and amounts thereof
as needed for a particular application.
EXAMPLES
[0031] To facilitate a better understanding of the present
invention, the following examples of certain aspects of some
embodiments are given. In no way should the following examples be
read to limit, or define, the entire scope of the invention.
Example 1
[0032] TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy free radical)
was added to a motor gasoline in an amount of 10 ppm. The oxidation
induction period was then measured for this sample liquid fuel
composition using the PetroOXY automatic oxidation stability tester
as described above. For comparative purposes, the oxidation
induction period for the same motor gasoline was also tested
without the addition of the TEMPO and with a comparative additive.
The comparative additive was 2,2,6,6-tetramethylpiperidine
(commonly referred to as "HALS"). The test temperature was
155.degree. C. The motor gasoline used for this test was a premium
gasoline blendstock for oxygenate blending ("PBOB"). The PBOB was
free of ethanol.
[0033] FIG. 2 is a chart showing the oxidation induction period for
these tests. As illustrated, the addition of 10 ppm TEMPO extended
the oxidation induction period for the PBOB by more than 2,000
seconds. Indeed, the addition of TEMPO extended the oxidation
induction period by approximately 130%. While the comparative
2,2,6,6-tetramethylpiperidine extended the oxidation induction
period for the premium motor gasoline, the improvement was
approximately 13% as compared to the approximately 130% improvement
for TEMPO. The point where there is a precipitous drop in the trace
highlights the end of tests and the time where the pressure
drop=10% from its maximum value. Extending this point to zero
pressure in the trace helps delineate the end point in the data
where the no further data was collected and the heating to the
sample was discontinued.
Example 2
[0034] Additional testing was performed to further evaluate TEMPO's
impact on a different liquid fuel's thermal stability in comparison
to other additives. In these additional tests, 10 ppm TEMPO was
added to a premium motor gasoline with 10 vol % ethanol. The
oxidation induction period was then measured for this sample liquid
fuel composition using the PetroOXY automatic oxidation stability
tester as described above. For comparative purposes, the oxidation
induction period for the same liquid fuel was also tested without
the addition of the TEMPO and with the addition of a comparative
antioxidant additive. The comparative antioxidant additive was N,
N'-Disec-butyl-p-phenylenediamine. The test temperature was
155.degree. C. The premium motor gasoline (commonly referred to as
"E10") contained 10 vol. % ethanol and had an octane rating of
92.
[0035] FIG. 3 is a chart showing the oxidation induction period for
these tests. As illustrated, the addition of 10 ppm TEMPO extended
the oxidation induction period for the premium motor gasoline with
ethanol. Indeed, the oxidation induction period for the sample
liquid composition with 10 ppm TEMPO was about 10 times greater
(approximately 980% improvement) than the comparative testes
without TEMPO or the comparative antioxidant. While the comparative
N, N'-Disec-butyl-p-phenylenediamine antioxidant additive extended
the oxidation induction period for the premium motor gasoline, the
improvement was approximately 80% as compared to the approximately
980% improvement for TEMPO.
Example 3
[0036] Additional testing was performed to further evaluate TEMPO's
effectiveness in combination with conventional detergents. In these
additional tests, 13.6 ppm TEMPO was added to a premium motor
gasoline that included 259 ppm of various detergent packages. The
oxidation induction period was then measured for these sample
liquid fuel compositions using the PetroOXY automatic oxidation
stability tester as described above. For comparative purposes, the
oxidation induction period for the same liquid fuel was also tested
without the addition of the TEMPO and with addition the 300 ppm of
the same detergent packages. The test temperature was 155.degree.
C.
[0037] FIG. 4 is a chart showing the oxidation induction period for
these tests. As illustrated, the addition of TEMPO extended the
oxidation induction period for the premium motor gasoline, even in
combination with the detergent packages. Indeed, the oxidation
induction period for the sample liquid compositions with TEMPO was
more than double the oxidation induction period for the comparative
tests, thus showing that TEMPO functioned independent of the
detergent packages, which is similar to the response when the
detergents were absent indicating that the two types of additives
are compatible.
Example 4
[0038] To further evaluate TEMPO's impact on a liquid fuel's
thermal stability, additional testing was performed by adding TEMPO
to another motor gasoline in the amount of 10 ppm. The oxidation
induction period was then measured for this sample liquid fuel
composition using the PetroOXY automatic oxidation stability tester
as described above. For comparative purposes, the oxidation
induction period for the same motor gasoline was also tested
without the addition of the TEMPO. The test temperature was
155.degree. C. The motor gasoline used for this test was a
reformulated gasoline blendstock for oxygenate blending ("RBOB").
The RBOB was free of ethanol.
[0039] FIG. 5 is a chart showing the oxidation induction period for
these tests. As illustrated, the addition of 10 ppm TEMPO extended
the oxidation induction period for the RBOB as compared to the RBOB
without TEMPO. Indeed, the oxidation induction period for the
sample liquid compositions with 10 ppm TEMPO was more than 4 times
(approximately 460% improvement) the oxidation induction period for
the comparative test.
Example 5
[0040] To evaluate concentration dependence of TEMPO on a liquid
fuel's thermal stability, additional testing was performed by
adding TEMPO to a motor gasoline in varying concentrations. The
oxidation induction period was then measured for this sample liquid
fuel composition using the PetroOXY automatic oxidation stability
tester as described above. For comparative purposes, the oxidation
induction period for the same motor gasoline was also tested
without the addition of the TEMPO. The test temperature was
155.degree. C. The motor gasoline used for this test was a
reformulated gasoline blendstock for oxygenate blending ("RBOB").
The RBOB was free of ethanol. The concentrations of TEMPO tested
were 10 ppm and 100 ppm of the liquid fuel.
[0041] FIG. 6 is a chart showing the oxidation induction period for
these tests. As illustrated, the addition of TEMPO extended the
oxidation induction period for the RBOB as compared to the RBOB
without TEMPO. In addition, the tests indicate that increasing
concentrations of TEMPO provide improved performance with 100 ppm
of TEMPO providing an oxidation induction period that was more than
4 times the oxidation induction period for 10 ppm of TEMPO.
Example 6
[0042] Additional testing was performed to further evaluate TEMPO's
impact on a different liquid fuel's thermal stability in comparison
to other additives. In these additional tests, TEMPO was added to a
diesel fuel in amount of 10 ppm. The oxidation induction period was
then measured for this sample liquid fuel composition using the
PetroOXY automatic oxidation stability tester as described above.
For comparative purposes, the oxidation induction period for the
same diesel fuel also tested without the addition of the TEMPO and
with addition of 10 ppm of a comparative antioxidant additive. The
comparative antioxidant additive was a phenylene diamine
antioxidant, available from Innospec, Inc. as AO-22 fuel
antioxidant. The test temperature was 200.degree. C. The diesel
fuel was a conventional diesel fuel without any biodiesel, commonly
referred to as BO diesel fuel.
[0043] FIG. 7 is a chart showing the oxidation induction for the
tests. As illustrated, the addition of 10 ppm TEMPO extended the
oxidation induction period for the diesel fuel. Indeed, the
oxidation induction period for the sample liquid compositions with
10 ppm TEMPO provided improved thermal oxidative stability as
compared to the comparative phenylene diamine antioxidant.
Example 7
[0044] Additional testing was performed to further evaluate TEMPO's
impact on different liquid fuels' thermal stability. In these
additional tests, TEMPO was added to a diesel fuel in an amount of
10 ppm. The oxidation induction period was then measured for this
sample liquid fuel composition using the PetroOXY automatic
oxidation stability tester as described above. For comparative
purposes, the oxidation induction period for the same diesel fuel
was also tested without the addition of the TEMPO. The diesel fuel
was a blend of conventional diesel fuel with up to 2% biodiesel,
commonly referred to as B2 diesel fuel. The test temperature was
170.degree. C. It should be noted that the test temperature was
170.degree. C. instead of the 200.degree. C. for conventional
diesel fuel since the fuel contained up to 2% biodiesel.
[0045] FIG. 8 is a chart showing the oxidation induction period for
the tests with the B2 diesel fuel. As illustrated, the addition of
10 ppm TEMPO extended the oxidation induction period for the B2
diesel fuel. Indeed, the oxidation induction period for the sample
liquid compositions with 10 ppm TEMPO was more than double
(approximately 120% improvement) the oxidation induction period for
the comparative test.
Example 8
[0046] Additional testing was performed to evaluate TEMPO in modern
gasoline engine direct injectors. The testing used a custom
benchtop heating assembly that included an aluminum heating block
with multiple gasoline direct injectors mounted inside as set forth
in the table below:
TABLE-US-00001 TABLE 1 Position Injector Type 1 Engine OEM A-
Injector Manufacturer A 2 Engine OEM B- Injector Manufacturer A 3
Engine OEM A- Injector Manufacturer B 4 Engine OEM C- Injector
Manufacturer C 5 Engine OEM D- Injector Manufacturer C 6 Engine OEM
B- Injector Manufacturer D 7 Engine OEM A- Injector Manufacturer
A
[0047] The injectors were flow tested before and after a thermal
stressing cycle. During heat ageing for 30 hours, the aluminum
heating block was maintained at a set temperature (170.degree. C.
at 100 bar) while the injectors alternated between a brief
discharge (15 seconds) and long heat soak periods (30 minutes). The
sample fuel composition used in the testing comprised 10 ppm TEMPO
in a motor gasoline. For comparative purposes, the same motor
gasoline was also tested without the addition of TEMPO.
[0048] FIG. 9 is a chart showing the results of the testing. As
illustrated, the inclusion of the TEMPO improved fuel flow at
estimated operating temperatures for all seven gasoline direct
injectors. It should be noted that the injector at position #6
regularly gives varied results, presumably due to its longer length
which leads to interference of the fuel release at the nozzle tip.
However, the results for the injector at position #6 in this test
are similar to the results for the other injectors.
Example 9
[0049] Additional testing was performed to further evaluate TEMPO's
impact on a liquid fuel's thermal stability. In these tests, thin
film oxidation was assessed using intake valve component testing.
Thin film oxidation describes a more rapid reaction than the
preceding tests in which a small amount of fuel in a thin film is
exposed to elevated temperatures and oxygen. Under these
conditions, hydrocarbons decompose much more quickly and the
oxidation products formed at the fuel-metal interface can rapidly
build up on the metal surface, leading to the formation of varnish
or deposits. The intake valve component testing was performed in
accordance with a test described in SAE Paper 972838 entitled "A
laboratory-scale tests to predict IVD," dated Oct. 13-16, 1997.
These tests were performed using TEMPO in an amount of either 10
ppm or 20 ppm in a PBOB. The PBOB was free of ethanol. Comparative
testing was also performed using the PBOB without the addition of
TEMPO. The tests were performed at specimen/chamber temperatures of
240.degree. C. and 265.degree. C. The results of the tests are
provided in the table below.
TABLE-US-00002 TABLE 2 Specimen/Chamber Temperature (.degree. C.)
240 265 Comparative Premium Deposit Weight (mg) blendstock 16.1
16.9 +10 ppm TEMPO 11.2 14.3 +20 ppm TEMPO 8.6 --
[0050] As illustrated, the addition of TEMPO reduced the amount of
deposits on the valves as compared to the same fuel without the
addition of TEMPO. This result was improved with an increase in the
concentration of the TEMPO.
[0051] While the invention has been described with respect to a
number of embodiments and examples, those skilled in the art,
having benefit of this disclosure, will appreciate that other
embodiments can be devised which do not depart from the scope and
spirit of the invention as disclosed herein. Although individual
embodiments are discussed, the invention covers all combinations of
all those embodiments.
[0052] While compositions, methods, and processes are described
herein in terms of "comprising," "containing," "having," or
"including" various components or steps, the compositions and
methods can also "consist essentially of" or "consist of" the
various components and steps. The phrases, unless otherwise
specified, "consists essentially of" and "consisting essentially
of" do not exclude the presence of other steps, elements, or
materials, whether or not, specifically mentioned in this
specification, so long as such steps, elements, or materials, do
not affect the basic and novel characteristics of the invention,
additionally, they do not exclude impurities and variances normally
associated with the elements and materials used.
[0053] For the sake of brevity, only certain ranges are explicitly
disclosed herein. However, ranges from any lower limit may be
combined with any upper limit to recite a range not explicitly
recited, as well as, ranges from any lower limit may be combined
with any other lower limit to recite a range not explicitly
recited, in the same way, ranges from any upper limit may be
combined with any other upper limit to recite a range not
explicitly recited.
* * * * *