U.S. patent application number 11/851908 was filed with the patent office on 2008-09-25 for method of reducing amount of peroxides, reducing fuel sediment and enhancing fuel system elastomer durability, fuel stability and fuel color durability.
Invention is credited to Joshua J. Bennett, Scott D. Schwab.
Application Number | 20080229656 11/851908 |
Document ID | / |
Family ID | 34194770 |
Filed Date | 2008-09-25 |
United States Patent
Application |
20080229656 |
Kind Code |
A1 |
Bennett; Joshua J. ; et
al. |
September 25, 2008 |
METHOD OF REDUCING AMOUNT OF PEROXIDES, REDUCING FUEL SEDIMENT AND
ENHANCING FUEL SYSTEM ELASTOMER DURABILITY, FUEL STABILITY AND FUEL
COLOR DURABILITY
Abstract
A reduction in the formation and presence of peroxides in low
sulfur diesel fuels is obtained through the combination of those
fuels with an organic nitrate combustion improver. The reduction in
the amount of peroxides means that the fuel system elastomers will
be more durable, as they are not being corroded by as much peroxide
formed in the fuel, fuel color durability is improved, fuel
stability is enhanced, and fuel sediments are reduced.
Inventors: |
Bennett; Joshua J.;
(Richmond, VA) ; Schwab; Scott D.; (Richmond,
VA) |
Correspondence
Address: |
Thomas & Raring, P.C;NewMarket Services Corporation
536 Granite Avenue
Richmond
VA
23226
US
|
Family ID: |
34194770 |
Appl. No.: |
11/851908 |
Filed: |
September 7, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10665907 |
Sep 18, 2003 |
7396450 |
|
|
11851908 |
|
|
|
|
Current U.S.
Class: |
44/603 |
Current CPC
Class: |
C10L 1/231 20130101;
C10L 10/04 20130101 |
Class at
Publication: |
44/603 |
International
Class: |
C10L 10/00 20060101
C10L010/00 |
Claims
1. (canceled)
2. (canceled)
3. (canceled)
4. (canceled)
5. (canceled)
6. (canceled)
7. (canceled)
8. (canceled)
9. A method of enhancing the durability of middle distillate fuel
system elastomers comprising the steps of: providing a middle
distillate fuel having a sulfur content of about 50 ppm or less;
combining the fuel with an organic nitrate combustion improver;
wherein the amount of organic nitrate combustion improver combined
with the fuel enhances the durability of middle distillate fuel
system elastomers as compared with the durability of elastomers in
a middle distillate fuel system combusting a middle distillate fuel
without the organic nitrate combustion improver.
10. A method as described in claim 9, wherein the organic nitrate
combustion improver comprises 2-ethylhexyl nitrate.
11. A method as described in claim 10, wherein the 2-ethylhexyl
nitrate is combined in an amount of from about 100 to 5000 ppm wt
of the fuel.
12. (canceled)
13. (canceled)
14. A method as described in claim 9, wherein the fuel has a sulfur
content of about 20 ppm or less.
15. (canceled)
16. (canceled)
17. (canceled)
18. A method as described in claim 9, wherein the amount of
peroxides in the fuel is less than about 8 ppm.
19. A method as described in claim 9, wherein the durability of the
elastomers is enhanced by up to 25% as measured by miles driven,
gallons of fuel combusted or days/years of service, relative to the
durability of elastomers in a middle distillate fuel system
combusting fuel without an organic nitrate combustion improver.
20. (canceled)
21. A method of enhancing the color durability of a middle
distillate fuel comprising the steps of: providing a middle
distillate fuel having a sulfur content of about 50 ppm or less;
combining the fuel with an organic nitrate combustion improver;
wherein the amount of organic nitrate combustion improver combined
with the fuel enhances the color durability of said middle
distillate fuel compared with the color durability of a middle
distillate fuel without the organic nitrate combustion
improver.
22. A method as described in claim 21, wherein the organic nitrate
combustion improver comprises 2-ethylhexyl nitrate.
23. A method as described in claim 22, wherein the 2-ethylhexyl
nitrate is combined in an amount of from about 100 to 5000 ppm wt.
of the fuel.
24. (canceled)
25. (canceled)
26. A method as described in claim 21, wherein the fuel has a
sulfur content of about 20 ppm or less.
27. (canceled)
28. (canceled)
29. A method as described in claim 21, wherein the amount of
peroxides in the fuel is less than about 8 ppm.
30. A method as described in claim 21, wherein the fuel color
durability is enhanced by up to 25% as measured by miles driven,
gallons of fuel combusted or days/years of service, relative to the
color durability of fuels without an organic nitrate combustion
improver.
31. (canceled)
32. A method of enhancing the fuel stability of a middle distillate
fuel comprising the steps of: providing a middle distillate fuel
having a sulfur content of about 50 ppm or less; combining the fuel
with an organic nitrate combustion improver; wherein the amount of
organic nitrate combustion improver combined with the fuel enhances
the fuel stability of said middle distillate fuel as compared with
the fuel stability of a middle distillate fuel without the organic
nitrate combustion improver.
33. A method as described in claim 32, wherein the organic nitrate
combustion improver comprises 2-ethylhexyl nitrate.
34. A method as described in claim 33, wherein the 2-ethylhexyl
nitrate is combined in an amount of from about 100 to 5000 ppm wt.
of the fuel.
35. (canceled)
36. (canceled)
37. A method as described in claim 32, wherein the fuel has a
sulfur content of about 20 ppm or less.
38. (canceled)
39. (canceled)
40. A method as described in claim 32, wherein the amount of
peroxides in the fuel is less than about 8 ppm.
41. A method as described in claim 32, wherein the fuel stability
enhanced by up to 25% as measured by miles driven, gallons of fuel
combusted or days/years of service, relative to the fuel stability
of fuels without an organic nitrate combustion improver.
42. (canceled)
43. A method of reducing fuel sediment in a middle distillate fuel
comprising the steps of: providing a middle distillate fuel having
a sulfur content of about 50 ppm or less; combining the fuel with
an organic nitrate combustion improver; wherein the amount of
organic nitrate combustion improver combined with the fuel reduces
fuel sediments in the middle distillate fuel as compared with the
fuel sediments in a middle distillate fuel without the organic
nitrate combustion improver.
44. A method as described in claim 43, wherein the organic nitrate
combustion improver comprises 2-ethylhexyl nitrate.
45. A method as described in claim 44, wherein the 2-ethylhexyl
nitrate is combined in an amount of from about 100 to 5000 ppm wt.
of the fuel.
46. (canceled)
47. (canceled)
48. A method as described in claim 43, wherein the fuel has a
sulfur content of about 20 ppm or less.
49. (canceled)
50. (canceled)
51. A method as described in claim 43, wherein the amount of
peroxides in the fuel is less than about 8 ppm.
52. A method as described in claim 43, wherein the fuel sediment is
reduced by up to 25% as measured by miles driven, gallons of fuel
combusted or days/years of service, relative to the fuel sediment
in a fuel without an organic nitrate combustion improver.
53. (canceled)
Description
[0001] This application is a divisional application of U.S.
application Ser. No. 10/665,907, filed Sep. 18, 2003.
[0002] This present invention relates to a method including the
addition of an organic nitrate combustion improver to a middle
distillate fuel to reduce formation or presence in the fuel of
peroxides. Especially in low or ultra-low sulfur fuels, the
addition of an organic nitrate combustion improver, for instance
2-ethylhexyl nitrate, retards the formation and/or reduces the
presence of peroxides, and prolongs the life of gaskets, hoses,
seals and other elastomeric parts exposed to the peroxides. Other
benefits include a reduction in fuel sediments, and enhanced fuel
stability and color durability.
BACKGROUND
[0003] There is a current trend towards the use of ultra low sulfur
diesel fuels, commonly referred to as fuels having 50 ppm sulfur or
less ("ULSD fuels"). This trend toward the use of ULSD fuels has
caused substantial combustion system changes and equally
significant changes in fuel specifications. Many industrialized
nations are reducing and/or have already reduced their mandatory
maximum specifications for sulfur content. As a result, there are
new concerns with respect to the performance and handling of the
fuels formulated to meet the new specifications.
[0004] One concern with ULSD fuels is that the removal of sulfur
compounds, some of which are effective peroxide scavengers and/or
decomposers, may allow peroxides to build up in these fuels. The
potential increase in peroxides is detrimental to fuel systems,
because peroxides are know to degrade fuel system elastomers. The
increase in peroxides, therefore, could cause the possible failure
of seals, gaskets and hoses in a fuel system that uses ULSD fuels.
See, for instance, Owen and Coley, Automotive Fuels Reference Book,
Second Edition, 1995, pp. 520-523. The potential seriousness of
this problem is also well documented in the problems with jet fuels
in the 1960's and 1970's where high peroxide content in those fuels
was associated with a high failure rate for fuel hoses, gaskets and
seals in those systems, E.g., Fodor, et al., "Peroxide Formation in
Jet Fuels," Energy and Fuels, 1988, pp. 729-34.
[0005] Other concerns that arise when peroxide levels increase
include fuel stability, color durability, and fuel sediments. These
concerns are discussed generally in Bacha and Lesnini, "Diesel Fuel
Thermal Stability at 300.degree. F.," Sixth International
Conference on Stability and Handling of Liquid Fuels, Vancouver,
Canada, Oct. 13-17, 1997; Vardi and Kraus, "Peroxide Formation in
Low Sulfur Automotive Diesel Fuels," SAE Paper No. 920826.
[0006] It is conventional wisdom that combustion improvers like
organic nitrate combustion improvers may affect peroxide formation.
It has been observed that combustion improvers may in fact promote
the formation of peroxides at relatively higher temperatures. This
observation is assumed true for all temperatures. Accordingly,
there is a possible concern that ULSD fuels, and particularly those
containing combustion improvers, may have a propensity to form
detrimental levels of peroxides and hydroperoxides during
storage.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a chart characterizing the fuels that were tested
as described herein.
[0008] FIG. 2 is a graph demonstrating hydroperoxide kinetics of
the fuels tested as described herein.
DETAILED DESCRIPTION
[0009] A reduction in the formation or presence of peroxides and
hydroperoxides in ultra low sulfur diesel fuels is obtained through
the combination of an organic nitrate combustion improver with the
fuel. By reducing the amount and/or formation of peroxides and
hydroperoxides, it is possible to enhance the durability of middle
distillate fuel system elastomers, enhance fuel stability, enhance
color durability and reduce formation of fuel sediments.
[0010] It is believed that the interaction between organic nitrate
combustion improvers and peroxides/hydroperoxides includes a
mechanism that is dependant on temperature "Peroxides" is meant
herein to include peroxides, hydroperoxides, mixtures thereof and
precursors thereof. As demonstrated in testing discussed herein,
fuels containing organic nitrate combustion improvers actually have
increased peroxide levels over time as compared to fuels without
any organic nitrate combustion improver, but only at high
temperatures (temperatures greater than about 70.degree. C.). This
finding generally of a higher amount of peroxides resulting from
the use of organic nitrate combustion improvers is consistent with
conventional wisdom. However, it has been discovered that at
temperatures below about 70.degree. C., there is actually an
unexpected reduction in the amount or the formation of peroxides
when an organic nitrate combustion improver is combined with an
ULSD fuel.
[0011] A method of reducing the amount of peroxides in low sulfur,
middle distillate fuels comprises the steps of: providing a middle
distillate fuel having a sulfur content of about 50 ppm or less;
combining the fuel with an organic nitrate combustion improver;
wherein the amount of organic nitrate combustion improver combined
with the fuel reduces the amount of peroxides in the fuel as
compared with a middle distillate fuel without the organic nitrate
combustion improver.
[0012] Fuels are rarely stored at temperatures of about 70.degree.
C. or higher. If a fuel ever reaches that temperature in the
operation of a combustion system, then the fuel would only remain
at that temperature for a very short time before combustion. As a
result, a relatively insignificant increase in peroxide presence
and/or formation would result, if at all, from the use of an
organic nitrate combustion improver. More importantly, middle
distillate fuel may often be stored for days/weeks/months before
use. Typical storage temperatures would be well below 70.degree. C.
Realistically, therefore, it is significant that an organic nitrate
combustion improver is discovered to retard the formation of or
reduce the amount of peroxides in ULSD fuels.
[0013] A presentation entitled "Hydroperoxide Formation in
Ultra-Low Sulfur Diesel Fuels" by Joshua J. Bennett and Scott D.
Schwab was prepared for the International Conference on Stability
and Handling of Liquid Fuels, Steamboat Springs, Colorado on Sep.
19, 2003. That presentation and the materials presented are
incorporated herein by reference as if set forth in their
entirety.
[0014] The hydrocarbonaceous fuels utilized herein are comprised in
general of mixtures of hydrocarbons which fall within the
distillation range of about 160 to about 370.degree. C. Such fuels
are frequently referred to as "middle distillate fuels" since they
comprise the fractions which distill after gasoline. Such fuels
include diesel fuels, biodiesel and biodiesel-derived fuels, burner
fuel, kerosenes, gas oils, jet fuels, and gas turbine engine
fuels.
[0015] In an embodiment, applicable middle distillate fuels are
those characterized by having the following distillation
profile:
TABLE-US-00001 .degree. F. .degree. C. IBP 250-500 121-260 10%
310-550 154-288 50% 350-600 177-316 90% 400-700 204-371 EP 450-750
232-399
[0016] Diesel fuels having a clear cetane number (i.e., a cetane
number when devoid of any cetane improver such as an organic
nitrate) in the range of 30 to 60 may also be used. In another
example are those in which the clear cetane number is in the range
of 40 to 50.
[0017] The organic nitrate combustion improvers (also frequently
known as ignition improvers) comprise nitrate esters of substituted
or unsubstituted aliphatic or cycloaliphatic alcohols which may be
monohydric or polyhydric. The organic nitrates may be substituted
or unsubstituted alkyl or cycloalkyl nitrates having up to about 10
carbon atoms, for example from 2 to 10 carbon atoms. The alkyl
group may be either linear or branched (or a mixture of linear and
branched alkyl groups). Specific examples of nitrate compounds
suitable for use as nitrate combustion improvers include, but are
not limited to the following: methyl nitrate, ethyl nitrate,
n-propyl nitrate, isopropyl nitrate, allyl nitrate, n-butyl
nitrate, isobutyl nitrate, sec-butyl nitrate, tert-butyl nitrate,
n-amyl nitrate, isoamyl nitrate, 2-amyl nitrate, 3-amyl nitrate,
tert-amyl nitrate, n-hexyl nitrate, n-heptyl nitrate, sec-heptyl
nitrate, n-octyl nitrate, 2-ethylhexyl nitrate, sec-octyl nitrate,
n-nonyl nitrate, n-decyl nitrate, cyclopentylnitrate, cyclohexyl
nitrate, methylcyclohexyl nitrate, isopropylcyclohexyl nitrate, and
the like. Also suitable are the nitrate esters of alkoxy
substituted aliphatic alcohols such as 2-ethoxyethyl nitrate,
2-(2-ethoxyethoxy) ethyl nitrate, 1-methoxypropyl-2-nitrate, and
4-ethoxybutyl nitrate, as well as diol nitrates such as
1,6-hexamethylene dinitrate and the like. For example the alkyl
nitrates and dinitrates having from 5 to 10 carbon atoms, and most
especially mixtures of primary amyl nitrates, mixtures of primary
hexyl nitrates, and octyl nitrates such as 2-ethylhexyl nitrate are
also included.
[0018] As is well known, nitrate esters are usually prepared by the
mixed acid nitration of the appropriate alcohol or diol. Mixtures
of nitric and sulfuric acids are generally used for this purpose.
Another way to making nitrate esters involves reacting an alkyl or
cycloalkyl halide with silver nitrate.
[0019] The concentration of nitrate ester or other organic nitrate
combustion improver in the middle distillate fuel can be varied
within relatively wide limits such that the amount employed is at
least sufficient to cause a reduction in the presence and/or
formation of peroxides. This amount may fall within the range of
100 to 5,000 parts by weight per million parts of fuel.
[0020] Other additives may be included within the fuel compositions
described herein provided they do not adversely affect the amount
or formation of peroxides otherwise obtained herein. Thus, use may
be made of one or more of such components as corrosion inhibitors,
antioxidants, anti-rust agents, detergents and dispersants, fuel
lubricity additives, demulsifiers, dyes, inert diluents, cold flow
improvers, conductivity agents, metal deactivators, stabilizers,
antifoam additives, de-icers, biocides, odorants, drag reducers,
combustion improvers, e.g., including MMT, oxygenates and like
materials. These additives may also be used in combinations as
additive packages.
[0021] Sulfur compounds themselves may reduce the amount of
peroxide in a fuel, so the present analysis is directed to low
sulfur fuels. For example, ultra-low sulfur fuels containing the
organic nitrate combustion improver may have less than about 100
ppm sulfur, or alternatively, less than about 50 ppm sulfur. Still
further alternatives includes a fuels having less than about 20 ppm
or less than about 10 ppm of sulfur.
[0022] The advantages achievable from the addition of an organic
nitrate combustion improver to a low sulfur fuel are demonstrated
in the following tests. For purposes of these tests, it is deemed
detrimental to have a concentration of peroxides greater than about
8 ppm. Accordingly, measurements made herein were with respect to
time/temperature conditions of specific fuels which result in a
concentration of a peroxide greater than about 8 ppm. First, two
different fuels were tested. These fuels were identified as Fuel A
and Fuel B. Fuels having significantly different properties were
identified in order to best evaluate how different fuels may have
different results FIG. 1 defines the two Fuels A and B that were
used in the testing.
[0023] Fuels A and B were each tested with and without the addition
of 2500 ppm 2-ethylhexyl nitrate combustion improver. As a result
of engine testing, it was determined the precise fuel conditions
(temperature and residence time) which generate detrimental
concentrations (greater than 8 ppm) of peroxides. Given the known
points on the graph, lines were calculated to represent the
peroxide formation kinetics. The specific peroxide kinetics that
were indicated are shown in FIG. 2.
[0024] As is evident from the kinetics demonstrated in FIG. 2, the
fuels containing the organic nitrate combustion improver (2-EHN)
each demonstrate a longer time to reach a detrimental level of
peroxides when fuel temperatures are below approximately 70.degree.
C. The specific temperature at which such detrimental levels of
peroxides would arise would be the intersection of the demonstrated
linear kinetics for the fuels with and without the organic nitrate
combustion improver.
[0025] The organic nitrate combustion improver with a middle
distillate fuel enables each of the (1) elastomer durability
benefit, (2) enhanced fuel stability, (3) fuel sediment reduction,
and (4) enhanced color durability obtained by keeping the amount of
peroxides in ULSD fuels less than about 8 ppm.
[0026] Based on the foregoing tests and calculation, it is seen
that peroxide formation and/or presence (i.e., the amount of
peroxide) is reduced in middle distillate fuels containing an
organic nitrate combustion improver. This may be a significant
benefit in prolonging the life of elastomeric materials contacting
the fuels when the fuels are stored for long periods of time. Other
benefits include enhanced fuel stability, color durability, and a
reduction in fuel sediments.
[0027] It is expected that the durability of elastomers susceptible
to degradation by exposure to peroxides in a fuel system might thus
be extended or enhanced by at least 25% in terms of miles driven,
gallons of fuel combusted or days/years of service as compared to
the durability of elastomers in a fuel system not containing an
organic nitrate combustion improver. In another embodiment, the
elastomer durability is extended or enhanced by at least 10% as
compared to the durability of elastomers exposed to fuels not
containing an organic nitrate combustion improver.
[0028] It is expected that the fuel stability of a middle
distillate fuel might thus be extended or enhanced by at least 25%
in terms of miles driven, gallons of fuel combusted or days/years
of service as compared to the fuel stability of a fuel not
containing an organic nitrate combustion improver. In another
embodiment, the fuel stability is extended or enhanced by at least
10% as compared to the stability of fuels not containing an organic
nitrate combustion improver.
[0029] It is expected that the durability of fuel color might thus
be extended or enhanced by at least 25% in terms of miles driven,
gallons of fuel combusted or days/years of service as compared to
the durability of fuel color in a fuel not containing an organic
nitrate combustion improver. In another embodiment, the fuel color
durability is expected to be extended or enhanced by at least 10%
as compared to the durability of fuels not containing an organic
nitrate combustion improver.
[0030] It is expected that the formation or presence of fuel
sediments is reduced by at least 25% in terms of miles driven,
gallons of fuel combusted or days/years of service as compared to
the amount of fuel sediments in a fuel not containing an organic
nitrate combustion improver. In another embodiment, the amount of
fuel sediments is reduced or enhanced by 10% as compared to the
amount of fuel sediments in fuels not containing an organic nitrate
combustion improver.
[0031] It is to be understood that the reactants and components
referred to by chemical name anywhere in the specification or
claims hereof, whether referred to in the singular or plural, are
identified as they exist prior to coming into contact with another
substance referred to by chemical name or chemical type (e.g., base
fuel, solvent, etc.). It matters not what chemical changes,
transformations and/or reactions, if any, take place in the
resulting mixture or solution or reaction medium as such changes,
transformations and/or reactions are the natural result of bringing
the specified reactants and/or components together under the
conditions called for pursuant to this disclosure. Thus the
reactants and components are identified as ingredients to be
brought together either in performing a desired chemical reaction
or in forming a desired composition (such as an additive
concentrate or additized fuel blend). It will also be recognized
that the additive components can be added or blended into or with
the base fuels individually per se and/or as components used in
forming preformed additive combinations and/or sub-combinations.
Accordingly, even though the claims hereinafter may refer to
substances, components and/or ingredients in the present tense
("comprises", "is", etc.), the reference is to the substance,
components or ingredient as it existed at the time just before it
was first blended or mixed with one or more other substances,
components and/or ingredients in accordance with the present
disclosure. The fact that the substance, components or ingredient
may have lost its original identity through a chemical reaction or
transformation during the course of such blending or mixing
operations or immediately thereafter is thus wholly immaterial for
an accurate understanding and appreciation of this disclosure and
the claims thereof.
[0032] At numerous places throughout this specification, reference
has been made to a number technical papers. All such cited
documents are expressly incorporated in full into this disclosure
as if fully set forth herein.
[0033] This invention is susceptible to considerable variation in
its practice. Therefore the foregoing description is not intended
to limit, and should not be construed as limiting, the invention to
the particular exemplifications presented hereinabove. Rather, what
is intended to be covered is as set forth in the ensuing claims and
the equivalents thereof permitted as a matter of law.
[0034] Patentee does not intend to dedicate any disclosed
embodiments to the public, and to the extent any disclosed
modifications or alterations may not literally fall within the
scope of the claims, they are considered to be part of the
invention under the doctrine of equivalents.
* * * * *