U.S. patent application number 14/742200 was filed with the patent office on 2015-12-24 for fischer tropsch derived diesel fuel formulation.
The applicant listed for this patent is SHELL OIL COMPANY. Invention is credited to Ratchatapong BOONWATSAKUL, Richard Hugh CLARK, Paul Anthony STEVENSON.
Application Number | 20150368576 14/742200 |
Document ID | / |
Family ID | 50982867 |
Filed Date | 2015-12-24 |
United States Patent
Application |
20150368576 |
Kind Code |
A1 |
BOONWATSAKUL; Ratchatapong ;
et al. |
December 24, 2015 |
FISCHER TROPSCH DERIVED DIESEL FUEL FORMULATION
Abstract
A method of operating a diesel fuel-consuming system, and/or
apparatus which is driven by such a system, the method comprising
introducing into the system a diesel fuel formulation containing
10% v/v or more of paraffinic hydrocarbons and an antioxidant and a
species selected from: (iii) detergents; (iv) mixtures containing
both a lubricity improver and a conductivity improver; and (v)
combinations of (i) and (ii). The methods results in an increase in
the oxidative stability of the formulation and/or in a reduction of
the concentration of an antioxidant which is present in the
formulation. The formulation may comprise a Fischer-Tropsch derived
diesel fuel component or mixture thereof.
Inventors: |
BOONWATSAKUL; Ratchatapong;
(Kuala Lumpur, MY) ; CLARK; Richard Hugh;
(Manchester, GB) ; STEVENSON; Paul Anthony;
(Chester, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHELL OIL COMPANY |
Houston |
TX |
US |
|
|
Family ID: |
50982867 |
Appl. No.: |
14/742200 |
Filed: |
June 17, 2015 |
Current U.S.
Class: |
123/1A ; 44/320;
44/385; 44/411 |
Current CPC
Class: |
C10L 1/12 20130101; C10L
2230/14 20130101; C10L 2250/04 20130101; C10L 2270/026 20130101;
C10L 2230/20 20130101; C10L 1/1817 20130101; C10L 1/224 20130101;
C10L 2200/0272 20130101; C10L 2300/30 20130101; C10L 10/08
20130101; C10L 2200/0259 20130101; C10L 1/1616 20130101; C10L
2290/42 20130101; C10L 1/22 20130101; C10L 1/223 20130101; C10L
1/18 20130101; C10L 1/14 20130101; C10L 2230/081 20130101; C10L
1/1832 20130101; C10L 1/19 20130101; C10L 1/2222 20130101; C10L
1/1291 20130101; C10L 1/1824 20130101; C10L 1/236 20130101; C10L
1/2437 20130101; C10L 2200/0446 20130101 |
International
Class: |
C10L 1/22 20060101
C10L001/22; C10L 1/18 20060101 C10L001/18; C10L 10/08 20060101
C10L010/08; C10L 1/12 20060101 C10L001/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 18, 2014 |
EP |
14250082.6 |
Claims
1. A method of operating a diesel fuel-consuming system, and/or
apparatus which is driven by such a system, the method comprising
introducing into the system a diesel fuel formulation containing
10% v/v or more of paraffinic hydrocarbons and an antioxidant and a
species selected from: (i) detergents; (ii) mixtures containing
both a lubricity improver and a conductivity improver; and (iii)
combinations of (i) and (ii).
2. The method of claim 1, wherein the antioxidant is selected from
phenolic antioxidants, in particular hindered phenols; amines, in
particular aromatic amines; and mixtures thereof.
2. The method of claim 1, wherein the antioxidant is selected from
amines, in particular aromatic amines, and mixtures thereof.
3. The method of claim 1, wherein the diesel fuel formulation
contains 25% v/v or greater of a Fischer-Tropsch derived diesel
fuel component.
4. The method of claim 2, wherein the diesel fuel formulation
contains 25% v/v or greater of a Fischer-Tropsch derived diesel
fuel component.
5. The method of claim 3, wherein the diesel fuel formulation
contains 25% v/v or greater of a Fischer-Tropsch derived diesel
fuel component.
6. The method of claim 1, wherein the diesel fuel formulation
contains 60% v/v or more of paraffinic hydrocarbons.
7. The method of claim 2, wherein the diesel fuel formulation
contains 60% v/v or more of paraffinic hydrocarbons.
8. The method of claim 3, wherein the diesel fuel formulation
contains 60% v/v or more of paraffinic hydrocarbons.
9. The method of claim 1, wherein species (i) or (iii) comprises a
nitrogen-containing detergent, in particular an amine- or
polyamine-containing detergent, for example a polyisobutenyl (PIB)
succinimide.
10. The method of claim 2, wherein species (i) or (iii) comprises a
nitrogen-containing detergent, in particular an amine- or
polyamine-containing detergent, for example a polyisobutenyl (PIB)
succinimide.
11. The method of claim 3, wherein species (i) or (iii) comprises a
nitrogen-containing detergent, in particular an amine- or
polyamine-containing detergent, for example a polyisobutenyl (PIB)
succinimide.
12. The method of claim 1, wherein species (ii) or (iii) comprises
an ester-based lubricity improver, in particular a fatty acid
ester.
13. The method of claim 2, wherein species (ii) or (iii) comprises
an ester-based lubricity improver, in particular a fatty acid
ester.
14. The method of claim 3, wherein species (ii) or (iii) comprises
an ester-based lubricity improver, in particular a fatty acid
ester.
15. The method of claim 1, wherein species (ii) or (iii) comprises
a sulphonic acid conductivity improver, in particular a naphthyl
sulphonic acid conductivity improver.
16. The method of claim 2, wherein species (ii) or (iii) comprises
a sulphonic acid conductivity improver, in particular a naphthyl
sulphonic acid conductivity improver.
17. The method of claim 3, wherein species (ii) or (iii) comprises
a sulphonic acid conductivity improver, in particular a naphthyl
sulphonic acid conductivity improver.
18. A method of operating a diesel fuel-consuming system and/or
apparatus which is driven by such a system, the method comprising
introducing into the system a diesel fuel additive composition
containing an antioxidant and a species selected from: (i)
detergents; (ii) mixtures containing both a lubricity improver and
a conductivity improver; and (iii) combinations of (i) and
(ii).
19. A method for preparing a diesel fuel formulation, the method
comprising the steps of: (a) providing a diesel fuel component or
mixture thereof, which contains 10% v/v or greater of paraffinic
hydrocarbons and also an antioxidant; (b) optionally assessing the
oxidative stability of the component or mixture; (c) adding to the
component or mixture a species selected from: (i) detergents; (ii)
mixtures containing both a lubricity improver and a conductivity
improver; and (iii) combinations of (i) and (ii), and (d) assessing
the oxidative stability of the resultant formulation.
Description
[0001] This non-provisional application claims the benefit of
European Application No. 14250082.6 filed Jun. 18, 2014, which is
hereby incorporated by reference in its entirety.
FIELD OF THE INVENTION
[0002] This invention relates to the use of certain compounds in
diesel fuel formulations, and in diesel fuel additive compositions,
for new purposes.
BACKGROUND TO THE INVENTION
[0003] Hydrocarbon fuels are prone to degradation through
oxidation, especially at high temperatures. This degradation
manifests itself as changes in the colour and acidity of the fuel,
and in extreme cases in the formation of deposits, such as gums and
particulates, which can cause operational problems in fuel storage
and distribution systems and in engines and other systems in which
the fuel is used. Stability of hydrocarbon fuels is a balance
between the natural propensity of the hydrocarbon to oxidize versus
the level of natural antioxidancy present. In the case of synthetic
paraffinic fuels, paraffin molecules are inherently highly stable
towards oxidation, but there is a low level of natural antioxidant.
Provided there are no factors to promote oxidation, such fuels have
excellent stability.
[0004] Operating conditions in internal combustion engines and
other fuel-consuming systems are becoming increasingly severe, in
particular the operating temperatures and pressures to which the
fuel is exposed. This means that oxidative stability will be more
of an issue for fuel formulators in the future.
[0005] It is known to include antioxidant additives in fuel
formulations to mitigate the above described problems. Many such
additives are known and commercially available; examples include
hindered phenols and aromatic amines.
[0006] It can be desirable to improve the performance of such
antioxidant additives, and/or to provide alternative antioxidant
additives with comparable or ideally superior performance, so as in
turn to improve the oxidative stability of vulnerable fuel
formulations.
[0007] It may also be desirable to reduce the concentrations of
antioxidant additives in fuel formulations. This may be driven by
consumer preferences and/or by technical or economic
considerations. Reductions in additive concentrations can be
achieved through improvements in additive performance, and/or
through the provision of better-performing alternatives.
SUMMARY OF THE INVENTION
[0008] According to a first aspect of the present invention there
is provided the method of operating a diesel fuel-consuming system,
and/or apparatus which is driven by such a system, the method
comprising introducing into the system a diesel fuel formulation
containing 10% v/v or more of paraffinic hydrocarbons and an
antioxidant and a species selected from: [0009] (i) detergents;
[0010] (ii) mixtures containing both a lubricity improver and a
conductivity improver; and [0011] (iii) combinations of (i) and
(ii).
[0012] Said apparatus can be, for example, a vehicle, or a heating
appliance.
[0013] The method of the present invention may comprise introducing
the formulation into a combustion chamber of a fuel-consuming
system. The system may for example be an internal combustion
engine.
[0014] A method according to the first aspect of the present
invention may be carried out with the intention of increasing the
oxidative stability of the diesel fuel formulation following its
introduction into the diesel fuel-consuming system.
[0015] The increase in stability may be measured relative to that
achieved using the antioxidant alone (ie in the absence of species
(i), (ii) or (iii)), at the same concentration.
[0016] It has surprisingly been found that when species (i), (ii)
or (iii) is combined with an antioxidant, in a relatively high
paraffin content diesel fuel formulation, the oxidative stability
of the formulation is increased compared to that achieved using the
antioxidant alone. This synergy appears possible even where the
species (i), (ii) or (iii) is not itself active as an antioxidant.
Indeed, species (i), (ii) and (iii) would not be expected to
contribute significant antioxidant activity to a fuel
formulation.
[0017] The combination of species (i), (ii) or (iii) with an
antioxidant, in a relatively high paraffin content diesel fuel
formulation, also appears to lead to an overall antioxidant effect
which is greater than might be predicted from the sums of the
antioxidant effects of the relevant individual additive components.
Thus, in accordance with the invention, species (i), (ii) or (iii)
may be used in the diesel fuel formulation for the purpose of
increasing the oxidative stability of the formulation by an amount
which is greater than the sum of the increases in oxidative
stability caused by species (i), (ii) or (iii) and the antioxidant
individually.
[0018] In effect, therefore, species (i), (ii) or (iii) may be used
to increase the effectiveness of the antioxidant, and its presence
may allow the use of a lower concentration of the antioxidant than
would otherwise have been necessary or desirable. Instead or in
addition, its presence may allow the use of an alternative
antioxidant, for example one which gives a smaller antioxidant
effect than would otherwise have been necessary or desirable.
[0019] These effects can offer greater flexibility for the fuel
formulator, in terms of types and concentrations of additives which
can be used to achieve a desired level of oxidative stability in a
diesel fuel formulation.
[0020] In the present context, an antioxidant is a substance which
is capable of reducing the rate of oxidation of a fuel formulation
to which it is added, or of a component of such a formulation. It
is therefore capable of increasing the oxidative stability of such
a fuel formulation or component. Typically, antioxidants inhibit
the oxidation of other molecules by removing free radical
intermediates, a process which involves their own oxidation: they
are therefore usually reducing agents.
[0021] According to the invention, an exemplary antioxidant may be
selected from phenolic antioxidants, in particular hindered phenols
such as butylated hydroxytoluene; quinones; hydroquinones; amines,
in particular aromatic amines; and mixtures thereof. It may be
selected from phenolic antioxidants, in particular hindered
phenols; amines, in particular aromatic amines; and mixtures
thereof.
[0022] In an embodiment, the antioxidant is a phenolic antioxidant,
in particular a hindered phenol. It may for example be selected
from 2,6-di-t-butyl-4-methylphenol (also known as
2,6-di-t-butyl-p-cresol, 3,5-di-t-butyl-4-hydroxytoluene or
butylated hydroxytoluene (BHT)); 2,4-dimethyl-6-t-butylphenol;
2,6-di-t-butylphenol; and mixtures of t-butylphenols. The
antioxidant may in particular be BHT.
[0023] Such phenolic antioxidants may in particular be used (a)
when the diesel fuel formulation comprises a Fischer-Tropsch
derived diesel fuel component (as described below), a hydrogenated
vegetable oil (HVO), or a mixture thereof, and a detergent (i) is
used to increase the oxidative stability of the formulation; (b)
when the diesel fuel formulation comprises a Fischer-Tropsch
derived diesel fuel component, or a combination of a HVO and a
Fischer-Tropsch derived diesel fuel component, and a mixture (ii)
is used to increase oxidative stability; or (c) when the diesel
fuel formulation comprises a Fischer-Tropsch derived diesel fuel
component, or a combination of a HVO and a Fischer-Tropsch derived
diesel fuel component, and a combination (iii) is used to increase
oxidative stability.
[0024] In an embodiment, the antioxidant is an amine. It may be an
aromatic amine, in particular a phenylene diamine containing one or
more alkyl and/or aryl groups. It may for example be selected from
N,N'-di-2-butyl-1,4-phenylenediamine;
N-isopropyl-N'-phenyl-p-phenylene diamine; N-(1,3-dimethyl
butyl)-N'-phenyl-p-phenylene diamine;
N-(1-methylheptyl)-N'-phenyl-p-phenylene diamine;
N-cyclohexyl-N'-phenyl-p-phenylene diamine;
N,N'-di-sec-butyl-p-phenylene diamine; N,N'-diisopropyl-p-phenylene
diamine; N,N'-diphenyl-p-phenylene diamine;
N,N'-ditolyl-p-phenylene diamine; N-tolyl-N'-xylenyl-p-phenylene
diamine; and mixtures thereof. In an embodiment, it is
N,N'-di-t-butyl-1,4-phenylenediamine.
[0025] Such amine antioxidants may be used when a mixture (ii) or a
combination (iii), more particularly a mixture (ii), is used to
increase the oxidative stability of the fuel formulation. They may
in particular be used when the fuel formulation comprises a
Fischer-Tropsch derived diesel fuel component and/or a HVO, more
particularly a Fischer-Tropsch derived diesel fuel component.
[0026] Such amine antioxidants may be used (a) when the diesel fuel
formulation comprises a Fischer-Tropsch derived diesel fuel
component or a combination of a Fischer-Tropsch derived diesel fuel
component and a HVO, and a detergent (i) is used to increase the
oxidative stability of the formulation; (b) when the diesel fuel
formulation comprises a Fischer-Tropsch derived diesel fuel
component and/or a HVO and a mixture (ii) is used to increase
oxidative stability; or (c) when the diesel fuel formulation
comprises a HVO, or a combination of a HVO and a Fischer-Tropsch
derived diesel fuel component, and a combination (iii) is used to
increase oxidative stability.
[0027] In an embodiment, the antioxidant is selected from BHT;
N,N'-di-t-butyl-1,4-phenylenediamine; and mixtures thereof.
[0028] Alternatively, the diesel fuel formulation may contain a
mixture of two or more antioxidants.
[0029] The antioxidant may for example be used in the diesel fuel
formulation at an (active matter) concentration of up to 1000 ppmw
or up to 750 or 500 ppmw. It may for example be used at a
concentration of 10 ppmw or greater, or 50 or 100 or 200 or 250
ppmw or greater, for example from 10 to 1000 ppmw or from 50 to 500
ppmw. It may be used at a concentration below its normal treat
rate, due to the additional stabilising effect of the species (i),
(ii) or (iii).
[0030] The diesel fuel formulation in which species (i), (ii) or
(iii) is used contains an antioxidant and also 10% v/v or more of
paraffinic hydrocarbons. In other respects it may be any type of
diesel fuel formulation, typically in liquid form, suitable and/or
adapted for use as a combustible fuel in a compression ignition
fuel-consuming system. It may be hydrocarbon-based, ie comprising a
major proportion (for example 80% v/v or more, or 85 or 90 or 95%
v/v or more) of hydrocarbon fuel components such as alkanes,
cycloalkanes, alkenes and aromatic hydrocarbons. The hydrocarbon
fuel components may be mineral-derived, or derived from a
biological source, or synthetic. Such a formulation may contain one
or more fuel components in addition to its hydrocarbon fuel
components, for example selected from oxygenates and fuel
additives.
[0031] A diesel fuel formulation may be suitable and/or adapted for
use in a diesel fuel-consuming system such as an engine (in
particular an internal combustion engine) or a heating appliance.
It may be selected from automotive diesel fuel formulations, marine
diesel fuel formulations, industrial gas oil formulations, and
heating oil formulations. In an embodiment, it is an automotive
diesel fuel formulation.
[0032] The diesel fuel formulation suitably comprises a diesel base
fuel. A diesel base fuel may be any fuel component, or mixture
thereof, which is suitable and/or adapted for combustion within a
compression ignition fuel-consuming system. It may be a liquid
hydrocarbon middle distillate fuel, for example, a gas oil. It may
be petroleum-derived (ie mineral). It may be or contain a kerosene
fuel component. It may be or contain a synthetic fuel component,
for instance a product of a Fischer-Tropsch condensation process as
described below. It may be or contain a fuel component derived from
a biological source. It may be or contain an oxygenate such as a
fatty acid alkyl ester, in particular a fatty acid methyl ester
(FAME) such as rapeseed methyl ester (RME) or palm oil methyl ester
(POME).
[0033] A diesel base fuel will typically boil in the range from 150
or 180 to 370.degree. C. (ASTM D86 or EN ISO 3405). It will
suitably have a measured cetane number (ASTM D613) of from 40 to 70
or from 40 to 65 or from 51 to 65 or 70.
[0034] A diesel fuel formulation prepared or used according to the
invention may comprise a diesel base fuel at a concentration of 50%
v/v or greater, or 60 or 70 or 80% v/v or greater, or 85 or 90 or
95 or 98% v/v or greater. The base fuel concentration may be up to
99.99% v/v, or up to 99.95% v/v, or up to 99.9 or 99.8 or 99.5%
v/v. It may be up to 99% v/v, for example up to 98 or 95 or 90%
v/v, or in cases up to 85 or 80% v/v.
[0035] Where the diesel fuel formulation comprises an oxygenate
and/or a biologically derived component such as a FAME, its
concentration may be 1% v/v or greater, or 2 or 5% v/v or greater,
based on the overall formulation, or in cases 7 or 10% v/v or
greater. The FAME concentration may be up to 30% v/v, or up to 25
or 20% v/v. Oxidative stability can be more of an issue in fuel
formulations containing oxygenates, and the present invention may
therefore be of particular use in such cases. The FAME
concentration may be between 1 and 5% v/v, or between 5 and 10%
v/v, or between 10 and 20% v/v.
[0036] A diesel fuel formulation prepared or used according to the
invention will suitably comply with applicable current standard
diesel fuel specification(s) such as for example EN 590 (for
Europe) or ASTM D975 (for the USA). By way of example, the overall
formulation may have a density from 820 to 845 kg/m.sup.3 at
15.degree. C. (ASTM D4052 or EN ISO 3675); a T95 boiling point
(ASTM D86 or EN ISO 3405) of 360.degree. C. or less; a measured
cetane number (ASTM D613) of 40 or greater, ideally of 51 or
greater; a kinematic viscosity at 40.degree. C. (VK40) (ASTM D445
or EN ISO 3104) from 2 to 4.5 centistokes (mm.sup.2/s); a flash
point (ASTM D93 or EN ISO 2719) of 55.degree. C. or greater; a
sulphur content (ASTM D2622 or EN ISO 20846) of 50 mg/kg or less,
preferably 10 mg/kg or less; a cloud point (IP 219) of less than
-10.degree. C.; and/or a polycyclic aromatic hydrocarbons (PAH)
content (EN 12916) of less than 8% w/w. Relevant specifications may
however differ from country to country, from season to season and
from year to year, and may depend on the intended use of the
formulation. Moreover a formulation prepared or used according to
the invention may contain individual fuel components with
properties outside of these ranges.
[0037] A diesel fuel formulation prepared or used according to the
invention may comprise, in addition to the antioxidant and species
(i), (ii) or (iii), one or more fuel or refinery additives. Many
such additives are known and commercially available and may be
present in a base fuel, or may be added to the formulation at any
point during its preparation. Non-limiting examples of additives
which can be included in a diesel base fuel or diesel fuel
formulation include cetane improvers, antistatic additives,
lubricity additives, cold flow additives, detergents, and
combinations thereof, as well as solvents, diluents and carriers
therefor. Such additives may be included in the fuel formulation at
a concentration of up to 4,000 ppmw (parts per million by weight),
or up to 3,000 or 2,000 or 1,000 or 500 or 300 ppmw, for example
from 50 to 4,000 ppmw or from 50 to 1,500 ppmw or from 50 to 1,000
ppmw or from 50 to 500 ppmw or from 50 to 300 ppmw.
[0038] In an embodiment of the invention, the diesel fuel
formulation contains a Fischer-Tropsch derived diesel fuel
component or mixture thereof. It may for instance contain 15% v/v
or greater, or 25% v/v or greater, or 50% v/v or greater of a
Fischer-Tropsch derived diesel fuel component or mixture thereof.
It may contain up to 50% v/v of such a component or mixture, or up
to 75% v/v, or up to 100% v/v. It may contain, for example, from 15
to 25% v/v, or from 25% to 50% v/v, or from 40 to 60% v/v, or from
50% to 75% v/v, or from 75% to 100% v/v of a Fischer-Tropsch
derived diesel fuel component or mixture thereof. In an embodiment,
the diesel fuel formulation consists essentially of one or more
Fischer-Tropsch derived diesel fuel components, ie in addition to
the antioxidant, the species (i), (ii) or (iii) and any optional
diesel fuel additives, it contains only Fischer-Tropsch derived
diesel fuel components.
[0039] By "Fischer-Tropsch derived diesel fuel component" is meant
a hydrocarbon mixture that is, or derives from, a synthesis product
of a Fischer-Tropsch condensation process. The Fischer-Tropsch
reaction converts carbon monoxide and hydrogen into longer chain,
usually paraffinic, hydrocarbons:
n(CO+2H.sub.2).dbd.(--CH.sub.2--).sub.n+nH.sub.2O+heat,
in the presence of an appropriate catalyst and typically at
elevated temperatures (e.g., 125 to 300.degree. C., preferably 175
to 250.degree. C.) and/or pressures (e.g., 5 to 100 bar, preferably
12 to 50 bar). Ratios of hydrogen to carbon monoxide other than 2:1
may be employed if desired.
[0040] The carbon monoxide and hydrogen may themselves be derived
from organic or inorganic, natural or synthetic sources, typically
either from natural gas or from organically derived methane.
[0041] A middle distillate fuel product may be obtained directly
from the Fischer-Tropsch reaction, or indirectly for instance by
fractionation of a Fischer-Tropsch synthesis product or from a
hydrotreated Fischer-Tropsch synthesis product. Hydrotreatment can
involve hydrocracking to adjust the boiling range of the product
(see, e. g. GB2077289 and EP0147873) and/or hydroisomerisation
which can improve cold flow properties by increasing the proportion
of branched paraffins. EP0583836 describes a two-step
hydrotreatment process in which a Fischer-Tropsch synthesis product
is firstly subjected to hydroconversion under conditions such that
it undergoes substantially no isomerisation or hydrocracking (this
hydrogenates the olefinic and oxygen-containing components), and
then at least part of the resultant product is hydroconverted under
conditions such that hydrocracking and isomerisation occur to yield
a substantially paraffinic hydrocarbon fuel. The desired middle
distillate fuel fraction(s) may subsequently be isolated for
instance by distillation.
[0042] Typical catalysts for the Fischer-Tropsch synthesis of
paraffinic hydrocarbons comprise, as the catalytically active
component, a Group VIII metal, in particular ruthenium, iron,
cobalt or nickel. Suitable catalysts are described for instance in
EP0583836.
[0043] An example of a Fischer-Tropsch based process is the SMDS
(Shell Middle Distillate Synthesis) described in "The Shell Middle
Distillate Synthesis Process", van der Burgt et al (vide supra).
This process produces middle distillate range products by
conversion of a natural gas (primarily methane) derived synthesis
gas into a heavy long-chain hydrocarbon (paraffin) wax which can
then be hydroconverted and fractionated to produce liquid transport
fuels such as the gas oils useable in diesel fuel compositions.
Versions of the SMDS process, utilising fixed-bed reactors for the
catalytic conversion step, are currently in use in Bintulu,
Malaysia, and in Pearl GTL, Ras Laffan, Qatar. Middle distillate
fuels prepared by the SMDS process are commercially available for
instance from the Royal Dutch/Shell Group of Companies. Such
Fischer-Tropsch middle distillate fuels are described in Technical
Specification CEN TS 15940.
[0044] A Fischer-Tropsch derived diesel fuel component may suitably
have a cetane number (ISO 5165) of 70 or greater; a density at
15.degree. C. (ISO 3675) of from 770 to 800 kg/m.sup.3; a sulphur
content (ISO 14596) of 3.0 mg/kg or less; a total aromatics content
(EN 12916) of 0.5% w/w or less; a polycyclic aromatics content (EN
12916) of 0.1% w/w or less; a total olefin content (ASTM D1159) of
0.1% w/w or less; a paraffin content of 97% w/w or more; a
kinematic viscosity at 40.degree. C. (ISO 3104) of from 2.0 to 4.5
mm.sup.2/s; a flash point (EN 2719) of 68.degree. C. or greater;
and/or a cold filter plugging point (EN 116) of -9.degree. C. or
lower or (in particular for use in or as a winter grade fuel) of
-20.degree. C. or lower. Such a component may have a distillation
curve (ISO 3405) such that the recovery at 250.degree. C. is 65%
v/v or less; the recovery at 350.degree. C. is 85% v/v or greater;
and/or 95% v/v recovery is achieved at 360.degree. C. or less.
[0045] A diesel fuel formulation prepared or used according to the
invention may comprise a mixture of (a) one or more Fischer-Tropsch
derived diesel fuel components and (b) one or more other diesel
fuel components, for example petroleum-derived, optionally with one
or more diesel fuel additives. In such a mixture, the volume ratio
of the Fischer-Tropsch derived diesel fuel component(s) to the
other diesel fuel component(s) may for example be from 1:10 to
10:1; or from 1:5 to 5:1; or from 1:4 to 4:1; or from 1:3 to 3:1;
or from 1:2 or 2:1. In an embodiment, the diesel fuel formulation
comprises a 1:1 v/v mixture of (a) one or more Fischer-Tropsch
derived diesel fuel components and (b) one or more other diesel
fuel components, for example petroleum-derived diesel fuel
components.
[0046] In an embodiment, the diesel fuel formulation contains 0.5%
v/v or greater, or 1 or 5% v/v or greater, of non-Fischer-Tropsch
paraffinic diesel components such as hydrotreated vegetable oils or
fats or a mixture thereof (hereafter referred to as HVO). HVO is
also known as "Hydrogenation-Derived Renewable Diesel" (HDRD) and,
in the context of the U.S. Renewable Fuel Standard, as "Non-ester
renewable diesel" (ref. 40CFR Part 80: Subpart M in the Code of
Federal Regulations). It may contain up to 75% v/v of such a
component or mixture, or up to 50% v/v, for example from 0.5 to 75%
v/v or from 5 to 75% v/v or from 5 to 50% v/v. In an embodiment,
the diesel fuel formulation consists essentially of one or more
hydrogenated vegetable oils, ie in addition to the antioxidant, the
species (i), (ii) or (iii) and any optional diesel fuel additives,
it contains only HVO diesel fuel components.
[0047] In this context, the HVO component or mixture should be
suitable and/or adapted for use as a diesel fuel component. Such
products are commercially available, for example the NExBTL
renewable diesel products ex Neste Oil. They may be used in the
form of a blend containing two or more HVOs selected for example
from soybean, palm, canola and rapeseed oils; animal tallow;
vegetable oil waste and brown trap grease; and mixtures
thereof.
[0048] The HVO component or mixture will, in certain embodiments,
have a paraffin content of at least 97% by weight, a cetane number
of at least 70, a density at 15.degree. C. of between 770 and 790
kg/m3, an aromatics content of not greater than 1% by weight, a
polyaromatics content of not greater than 0.1% by weight, a sulfur
content of not greater than 5 ppm, and a flash point of at least
59.degree. C.
[0049] The diesel fuel formulation may comprise a mixture of (a)
one or more HVO diesel fuel components and (b) one or more other
diesel fuel components, for example petroleum-derived, optionally
with one or more diesel fuel additives. In such a mixture, the
volume ratio of the HVO diesel fuel component(s) to the other
diesel fuel component(s) may for example be from 1:200 to 3:1, or
from 1:20 to 2:1, or from 1:20 to 1:1, such as about 1:1. In an
embodiment, the diesel fuel formulation comprises a 1:1 v/v mixture
of (a) one or more HVO diesel fuel components and (b) one or more
other diesel fuel components, for example petroleum-derived diesel
fuel components.
[0050] In an embodiment, the diesel fuel formulation comprises a
mixture of (a) one or more Fischer-Tropsch derived diesel fuel
components and (b) one or more HVO diesel fuel components,
optionally with one or more diesel fuel additives. In such a
mixture, the volume ratio of the Fischer-Tropsch derived diesel
fuel component(s) to the HVO diesel fuel component(s) may for
example be from 1:10,000 to 10,000:1, or from 1:990 to 990:1, or
from 1:99 to 99:1, or from 1:9 to 9:1, or from 1:5 to 5:1, or from
1:3 to 3:1, or from 1:2 to 2:1, such as about 1:1. In an
embodiment, the diesel fuel formulation comprises a 1:1 v/v mixture
of (a) one or more Fischer-Tropsch derived diesel fuel components
and (b) one or more HVO diesel fuel components.
[0051] Thus in an embodiment of the invention, the diesel fuel
formulation is selected from (1) a formulation consisting
essentially of one or more Fischer-Tropsch derived diesel fuel
components; (2) a formulation consisting essentially of one or more
HVO diesel fuel components; (3) a mixture of one or more
Fischer-Tropsch derived diesel fuel components and one or more HVO
diesel fuel components; and (4) a mixture of one or more
Fischer-Tropsch derived diesel fuel components and one or more
petroleum-derived diesel fuel components. It may be selected from
(1) a formulation consisting essentially of one or more
Fischer-Tropsch derived diesel fuel components; (2) a formulation
consisting essentially of one or more HVO diesel fuel components;
and (3) a mixture of one or more Fischer-Tropsch derived diesel
fuel components and one or more HVO diesel fuel components.
[0052] Even in embodiments where the diesel fuel formulation
includes a mixture of two or more diesel fuel components, the
overall formulation shall contain 10% v/v or more of paraffinic
hydrocarbons. A paraffinic hydrocarbon is a saturated hydrocarbon
(alkane); it may be a straight chain (normal) paraffin or a
branched chain (iso) paraffin. The diesel fuel formulation suitably
comprises a mixture of normal and isoparaffins, since such mixtures
can provide a suitable balance between low freezing point
(isoparaffins) and good ignition quality (normal paraffins).
Typically the weight ratio of isoparaffins to normal paraffins in a
paraffinic hydrocarbon mixture employed in a diesel fuel
formulation will be from 0.5 to 10, preferably from 1 to 9. A
paraffinic hydrocarbon will typically contain from 5 to 40 carbon
atoms, for example from 9 to 30 carbon atoms.
[0053] In an embodiment of the invention, the diesel fuel
formulation contains 20% v/v or more of paraffinic hydrocarbons. It
may contain 30 or 40 or 50 or 60% v/v or more of paraffinic
hydrocarbons. It may for example contain up to 99% v/v of
paraffinic hydrocarbons, or up to 90 or 80 or 75% v/v, such as from
20 to 99% v/v or from 30 or 50 or 60 to 99% v/v. In an embodiment,
it consists essentially of paraffinic hydrocarbons, ie it contains
at least 99% v/v, or at least 99.5 or 99.8 or 99.9 or 99.95% v/v,
of paraffinic hydrocarbons, together with relatively small
concentrations of the antioxidant and other optional diesel fuel
additives.
[0054] In certain cases, it may be preferred for the diesel fuel
formulations that include the species (i), (ii) or (iii) that such
formulations do not to contain a petroleum-derived fuel components,
or to contain less than 50% v/v of such components, or less than 40
or 30 or 20% v/v, or that such formulations contain between 10 and
20% v/v, or between 20 and 30% v/v.
[0055] According to the invention, a species (i), (ii) or (iii) may
be used in the diesel fuel formulation to enhance its oxidative
stability beyond what is achieved by the already-present
antioxidant. Each of species (i), (ii) and (iii) should be suitable
and/or adapted for use as an additive in a diesel fuel formulation,
in particular an automotive diesel fuel formulation.
[0056] The species (i) is a detergent, by which is meant an agent
(suitably a surfactant) which, when added to a fuel formulation,
can act to remove, and/or to prevent the accumulation of, deposits
such as combustion-related deposits within a fuel-consuming system
in which the formulation is used, in particular within a fuel
injection system such as in or on the fuel injector nozzles. Many
such materials are known and commercially available for use as
diesel fuel additives.
[0057] Detergents suitable for use in fuel formulations include
those disclosed in WO-A-2009/50287, which is incorporated herein by
reference.
[0058] Suitable detergents typically have at least one hydrophobic
hydrocarbon radical having a number average molecular weight (Mn)
of from 85 to 20,000 and at least one polar moiety selected
from:
(1) mono- or polyamino groups having up to 6 nitrogen atoms, of
which at least one nitrogen atom has basic properties; (2)
polyoxy-C2- to -C4-alkylene groups which are terminated by hydroxyl
groups, mono- or polyamino groups, in which at least one nitrogen
atom has basic properties, or by carbamate groups; (3) moieties
derived from succinic anhydride and having hydroxyl and/or amino
and/or amido and/or imido groups; and/or; (4) moieties obtained by
Mannich reaction of substituted phenols with aldehydes and mono- or
polyamines.
[0059] The hydrophobic hydrocarbon radical in the above detergents,
which ensures adequate solubility in the base fluid, has a number
average molecular weight (Mn) of from 85 to 20,000, especially from
113 to 10,000, in particular from 300 to 5000. Typical hydrophobic
hydrocarbon radicals, especially in conjunction with the polar
moieties (1), (3) and (4), include polyalkenes (polyolefins), such
as polypropenyl, polybutenyl or polyisobutenyl radicals each having
Mn of from 300 to 5000, or from 500 to 2500, or from 700 to 2300,
such as from 700 to 1000.
[0060] Detergents comprising mono- or polyamino groups (1) may be
polyalkenemono- or polyalkenepolyamines based on polypropene or
conventional (ie having predominantly internal double bonds)
polybutene or polyisobutene having Mn of from 300 to 5000.
[0061] Other suitable detergents comprising monoamino groups (1)
are the hydrogenation products of the reaction products of
polyisobutenes having an average degree of polymerisation of from 5
to 100, with nitrogen oxides or mixtures of nitrogen oxides and
oxygen, as described in particular in WO-A-97/03946.
[0062] Additional suitable detergents comprising monoamino groups
(1) are the compounds obtainable from polyisobutene epoxides by
reaction with amines and subsequent dehydration and reduction of
the amino alcohols, as described in particular in DE-A-196 20
262.
[0063] Detergents comprising polyoxy-C2-to-C4-alkylene moieties (2)
may be polyethers or polyetheramines which are obtainable by
reaction of C2- to C60-alkanols, C6- to C30-alkanediols, mono- or
di-C2-to-C30-alkylamines, C1-to-C30-alkylcyclohexanols or
C1-C30-alkylphenols with from 1 to 30 mol of ethylene oxide and/or
propylene oxide and/or butylene oxide per hydroxyl group or amino
group and, in the case of the polyether-amines, by subsequent
reductive amination with ammonia, monoamines or polyamines. Such
products are described in particular in EP-A-310 875, EP-A-356 725,
EP-A-700 985 and U.S. Pat. No. 4,877,416. In the case of
polyethers, such products also have carrier oil properties. Typical
examples of these are tridecanol butoxylates, isotridecanol
butoxylates, isononylphenol butoxylates and polyisobutenol
butoxylates and propoxylates and also the corresponding reaction
products with ammonia.
[0064] Detergents comprising moieties (3) derived from succinic
anhydride and having hydroxyl and/or amino and/or amido and/or
imido groups may be corresponding derivatives of
polyisobutenylsuccinic anhydride which are obtainable by reacting
conventional or highly reactive polyisobutene having Mn of from 300
to 5000 with maleic anhydride by a thermal route or via the
chlorinated polyisobutene. Of particular interest are derivatives
with aliphatic polyamines such as ethylenediamine,
diethylenetriamine, triethylenetetramine or tetraethylenepentamine.
Such additives are described in particular in U.S. Pat. No.
4,849,572.
[0065] Detergents comprising moieties (4) obtained by Mannich
reaction of substituted phenols with aldehydes and mono- or
polyamines may be reaction products of polyisobutene-substituted
phenols with formaldehyde and mono- or polyamines such as
ethylenediamine, diethylenetriamine, triethylenetetramine,
tetraethylenepentamine or dimethylaminopropylamine. The
polyisobutenyl-substituted phenols may stem from conventional or
highly reactive polyisobutene having Mn of from 300 to 5000. Such
"polyisobutene-Mannich bases" are described in particular in
EP-A-831 141.
[0066] In an embodiment of the invention, a detergent (i) used in
the diesel fuel formulation is a nitrogen-containing detergent, in
particular an amine- or polyamine-containing detergent. In an
embodiment, such a detergent contains a hydrophobic hydrocarbon
radical having a number average molecular weight in the range from
300 to 5000. The nitrogen-containing detergent may be selected from
the group comprising polyalkene monoamines, polyetheramines,
polyalkene Mannich amines, polyalkene succinimides, and mixtures
thereof. Conveniently, the nitrogen-containing detergent may be a
polyalkene monoamine. It may be a succinimide, in particular a
polyalkene succinimide.
[0067] In an embodiment of the invention, the detergent (i) is a
detergent of the type referred to as (1) above, for example a
polyisobutenyl (PIB) succinimide.
[0068] According to the invention, a mixture of two or more
detergents (i), for example of the types defined above, may be used
in the diesel fuel formulation.
[0069] The detergent (i) may for example be used in the diesel fuel
formulation at an (active matter) concentration of up to 1,500 ppmw
or up to 1,000 or 500 ppmw. It may for example be used at a
concentration of 250 ppmw or greater, or 500 or 1,000 ppmw or
greater, for example from 250 to 1,500 ppmw or from 250 to 1,000
ppmw.
[0070] According to the invention, a mixture (ii) of a lubricity
improver and a conductivity improver may be used in the diesel fuel
formulation to enhance its oxidative stability. By "lubricity
improver" is meant an agent which is capable of improving the
lubricity of a diesel fuel formulation to which it is added, and/or
imparting anti-wear effects when such a formulation is used in an
engine or other fuel-consuming system. Many such compounds are
known and commercially available for use as diesel fuel additives,
for example the "R" series of additives ex Infineum (trade mark) or
the Hitec (trade mark) additives ex Afton.
[0071] Known lubricity improvers include acid-based, ester-based
and amide-based agents. They can be available in the form of
lubricity additives, which may contain one or more additional
active ingredients as well as the lubricity improver, for example
dehazers, anti-rust agents, conductivity improvers, and
combinations thereof.
[0072] An acid-based lubricity improver comprises an acid,
typically a mono-acid, more typically an organic acid, as a
lubricity-enhancing active ingredient. The acid may for example be
a carboxylic acid, such as a fatty acid or aromatic acid, in
particular the former. Such fatty acids may be saturated or
unsaturated (which includes polyunsaturated). They may contain from
1 or 2 to 30 carbon atoms, or from 10 to 22 carbon atoms, or from
12 to 22 or from 14 to 20 carbon atoms, or from 16 to 20 or 16 to
18 carbon atoms, such as 18 carbon atoms. Examples include oleic
acid, linoleic acid, linolenic acid, linolic acid, stearic acid,
palmitic acid and myristic acid. Of these, oleic, linoleic and
linolenic acids may be used, in particular oleic and linoleic
acids.
[0073] Examples of acid-based lubricity additives are known and
commercially available, for example as R650 (trade mark), ex
Infineum; products in the Lz 539 (trade mark) series, ex Lubrizol;
and ADX4101B.TM. (ex Adibis).
[0074] An ester-based lubricity improver comprises, as a
lubricity-enhancing active ingredient, an ester such as a
carboxylic acid ester, in particular an ester of a fatty acid. Such
fatty acids may be as described above in connection with acid-based
lubricity improvers. Ester-based lubricity improvers may
alternatively be based on ester-functionalised oligomers or
polymers (eg olefin oligomers). Such esters may be mono-alcohol
esters such as methyl esters, or more suitably may be polyol esters
such as glycerol esters. In an embodiment of the invention, an
ester-based lubricity improver contains a mono-, di- or
tri-glyceride of a fatty acid, or a mixture of two or more such
species.
[0075] An amide-based lubricity improver may for example comprise,
as a lubricity-enhancing active ingredient, a fatty acid amide. The
fatty acid element of such an ingredient may be as described above
in connection with acid-based lubricity improvers. The ingredient
may for example be a fatty acid amide of a mono- or in particular
di-alkanolamine such as diethanolamine.
[0076] Other suitable lubricity improvers are described for example
in: [0077] the paper by Danping Wei and HA Spikes, "The Lubricity
of Diesel Fuels", Wear, III (1986) 217-235; [0078]
WO-A-95/33805--cold flow improvers to enhance lubricity of low
sulphur fuels; [0079] WO-A-94/17160--certain esters of a carboxylic
acid and an alcohol wherein the acid has from 2 to 50 carbon atoms
and the alcohol has 1 or more carbon atoms, particularly glycerol
monooleate and di-isodecyl adipate, as fuel additives for wear
reduction in a diesel engine injection system; [0080] U.S. Pat. No.
5,490,864--certain dithiophosphoric diester-dialcohols as anti-wear
lubricity additives for low sulphur diesel fuels; and [0081]
WO-A-98/01516--certain alkyl aromatic compounds having at least one
carboxyl group attached to their aromatic nuclei, to confer
anti-wear lubricity effects particularly in low sulphur diesel
fuels.
[0082] In an embodiment of the invention, the lubricity improver
used in the mixture (ii) is an ester-based lubricity improver. In
an embodiment, it is used in the form of the lubricity-enhancing
additive R662 (trade mark), ex Infineum, which is described by the
supplier as a combination of ester chemistry lubricity improver and
conductivity additives.
[0083] According to the invention, a mixture of two or more
lubricity improvers, for example of the types defined above, may be
used in the diesel fuel formulation.
[0084] The lubricity improver may for example be used in the diesel
fuel formulation at a concentration of up to 1,000 ppmw or up to
750 or 500 ppmw. It may for example be used at a concentration of
50 ppmw or greater, or 100 or 150 or 250 ppmw or greater, for
example from 50 to 1,000 ppmw or from 50 to 500 ppmw.
[0085] By "conductivity improver" is meant an agent which is
capable of increasing the electrical conductivity of a diesel fuel
formulation to which it is added. Also referred to as "static
dissipaters" or "antistatic additives", they reduce the risk of
electrostatic charge accumulation, which can occur for example
during pumping of a fuel and can increase fire and explosion
hazards during subsequent fuel handling.
[0086] Fuels with an inherently lower conductivity generally
require higher levels of conductivity improvers. Low conductivity
fuels include in particular those which are low in polar fuel
components such as aromatics and sulphur- or nitrogen-containing
compounds: Fischer-Tropsch derived fuels can fall into this
category. As pressure to reduce sulphur levels in fuels, in
particular automotive fuels, increases, this in turn increases the
need for conductivity improvers.
[0087] A conductivity improver may for example comprise an active
ingredient selected from organic acids, in particular
(benzene)sulphonic acids; amines, in particular polyamines;
sulphones, in particular polysulphones; and other
hydrocarbon-soluble (co)polymers such as vinyl (co)polymers, in
particular those containing cationic monomer units.
[0088] Examples of conductivity improvers include those having
components selected from aliphatic amines-fluorinated polyolefins
(U.S. Pat. No. 3,652,238); chromium salts and amine phosphates
(U.S. Pat. No. 3,758,283); alpha-olefin-sulphone copolymer
class-polysulphone and quaternary ammonium salt (U.S. Pat. No.
3,811,848); polysulphone and quaternary ammonium salt
amine/epichlorhydrin adducts; dinonylnaphthylsulphonic acid (U.S.
Pat. No. 3,917,466); copolymers of alkyl vinyl monomers and
cationic vinyl monomers (U.S. Pat. No. 5,672,183);
alpha-olefin-maleic anhydride copolymer class (U.S. Pat. No.
3,677,725 and U.S. Pat. No. 4,416,668); methyl vinyl ether-maleic
anhydride copolymers and amines (U.S. Pat. No. 3,578,421);
alpha-olefin-acrylonitriles (U.S. Pat. No. 4,333,741 and U.S. Pat.
No. 4,388,452); alpha-olefin-acrylonitrile copolymers and polymeric
polyamines (U.S. Pat. No. 4,259,087); copolymers of an alkylvinyl
monomer, a cationic vinyl monomer and a polysulphone (U.S. Pat. No.
6,391,070); ethoxylated quaternary ammonium compounds (U.S. Pat.
No. 5,863,466); hydrocarbyl monoamines or hydrocarbyl-substituted
poly(alkyleneamine (U.S. Pat. No. 6,793,695); acrylic-type
ester-acrylonitrile copolymers and polymeric polyamines (U.S. Pat.
No. 4,537,601 and U.S. Pat. No. 4,491,651); and diamine
succinamides reacted with adducts of a ketone and SO.sub.2
(.beta.-sutlone chemistry) (U.S. Pat. No. 4,252,542).
[0089] Commercially available static dissipaters, for use as fuel
additives, include Stadis (trade mark) 450 and Stadis 425 (both ex
Innospec), Tolad (trade mark) 3514 (ex Baker-Petrolite) and HiTEC
(trade mark) 4545 (ex Afton Chemical). Stadis 450 for example
contains dinonylnaphthyl sulphonic acid as an active ingredient; it
is typically used in distillate fuels, solvents, commercial jet
fuels and certain military fuels. Stadis 425 contains similar
active(s) to Stadis 450 and is typically used in distillate fuels
and solvents. Tolad 3514 contains a hydrocarbon-soluble copolymer
of an alkylvinyl monomer and a cationic vinyl monomer.
[0090] A conductivity improver may be included in a diesel fuel
additive package in combination with one or more additional active
ingredients, such as a lubricity improver.
[0091] In an embodiment of the invention, the conductivity improver
used in the mixture (ii) is a sulphonic acid, in particular a
naphthyl sulphonic acid, more particularly an alkylnaphthyl
sulphonic acid such as dinonylnaphthyl sulphonic acid. In an
embodiment, it is used in the form of the combined
lubricity-enhancing and conductivity-improving additive R662 (trade
mark), ex Infineum.
[0092] According to the invention, a mixture of two or more
conductivity improvers, for example of the types defined above, may
be used in the diesel fuel formulation.
[0093] The conductivity improver may for example be used in the
diesel fuel formulation at a concentration of up to 10 ppmw or up
to 5 or 3 or 2 or 1 ppmw. It may for example be used at a
concentration of 0.1 ppmw or greater, or 0.5 ppmw or greater, for
example from 0.1 to 5 ppmw or from 0.1 to 3 ppmw.
[0094] Where a mixture (ii) of a lubricity improver and a
conductivity improver is used in the present invention, the two
components may be added to the diesel fuel formulation together
(for example as part of a multi-functional additive package) or
separately. In an embodiment, they are added together. They may be
added in the form of an additive composition which contains one or
more other fuel additives in addition to the lubricity improver and
the conductivity improver.
[0095] In an embodiment, the mixture (ii) is a mixture of an
ester-based lubricity improver and a sulphonic acid (in particular
a naphthyl sulphonic acid) conductivity improver. In particular, it
may be the commercially available combined lubricity-enhancing and
conductivity-improving additive R662.
[0096] Other products which contain mixtures of lubricity improvers
and conductivity improvers, and which can therefore be used as the
component (ii) in accordance with the present invention, include
the PC 32xx (trade mark) range available from Total Group; the
OLI-9101.x (trade mark) range from Innospec; and HiTec 4898AS
(trade mark) from Afton Chemical.
[0097] In the mixture (ii), the weight ratio of the lubricity
improver to the conductivity improver may for example be up to
2,500, or up to 1,000, or up to 500 or 250. The ratio may for
example be 20 or greater, or 50 or 75 or 100 or greater, such as
from 100 to 250. In accordance with the invention, a combination
(iii) of a detergent (i) and a lubricity improver/conductivity
improver mixture (ii) may be used to enhance the oxidative
stability of the diesel fuel formulation. In the combination (iii),
the natures of the species (i) and (ii) may be as described above.
Moreover, the species (i) and (ii) may be used in the diesel fuel
formulation at concentrations as described above. However, due to
their combined effect on antioxidant activity, it may be possible
to use a lower concentration of either or both of the individual
species (i) and (ii).
[0098] Where species (iii) is used in the present invention, the
two component species (i) and (ii) may be added to the diesel fuel
formulation together (such as part of a multi-functional additive
package) or separately. In an embodiment, they are added
together.
[0099] In a combination (iii), the weight ratio of the detergent
(i) to the mixture (ii) may for example be from 0.5:1 to 10:1, or
from 0.5:1 to 2:1, or from 2:1 to 4:1, or from 4:1 to 6:1, or from
6:1 to 8:1, or from 8:1 to 10:1. The ratio may for example be 0.5:1
or greater, or 1:1 or greater, or 2:1 or greater. The ratio may for
example be 10:1 or less, 5:1 or less, 2:1 or less.
[0100] In an embodiment of the invention, a detergent (i) is used
to increase the oxidative stability of the diesel fuel formulation.
In an embodiment, a mixture (ii) of a lubricity improver and a
conductivity improver is used to increase the oxidative stability
of the diesel fuel formulation. In an embodiment, a combination
(iii) of a detergent (i) and a mixture (ii) of a lubricity improver
and a conductivity improver is used to increase the oxidative
stability of the diesel fuel formulation. In embodiments of the
invention, the weight ratio, in the diesel fuel formulation, of the
antioxidant to the species (i), (ii) or (iii) may for example be up
to 0.02, or up to 0.1, or up to 0.4, or up to 0.6, or up to 0.8 or
up to 1. The ratio may for example be less than 1, or less than
0.8, or less than 0.6, or less than 0.4, or less than 0.2, or less
than 0.1, or less than 0.05. In certain embodiments, the ratio may
be between 0.02 and 1, alternatively between 0.02 and 0.1, or
between 0.1 and 0.2, or between 0.2 and 0.4, or between 0.4 and
0.6, or between 0.6 and 0.8, or between 0.8 and 1.
[0101] According to the present invention, the species (i), (ii) or
(iii) may be used to achieve any degree of improvement in the
oxidative stability of the diesel fuel formulation, and/or to
achieve or exceed a desired target level of oxidative
stability.
[0102] Oxidative stability may be determined using any suitable
method, for instance ASTM D7545-09 "Standard test method for
oxidation stability of middle distillate fuels: Rapid small-scale
oxidation test (RSSOT)", as in the examples below. Another suitable
test method is EN 16091:2011 "Liquid petroleum products--Middle
distillates and fatty acid methyl ester (FAME) fuels and
blends--Determination of oxidation stability by rapid small scale
oxidation method", available from the European Committee for
Standardisation (CEN), which involves subjecting a test fuel to
accelerated oxidation conditions, and measuring the induction
period to breakpoint in a pressure bomb apparatus, to provide a
measure of the oxidation stability of the fuel. As for ASTM
D7545-09, a longer measured induction period indicates that a more
oxidation resistant test fuel. Another potentially suitable test
method is the standard test method ASTM D2274-03, which measures
residues of oxidation products generated in a test fuel under
specified conditions, a lower residue indicating a higher oxidative
stability. D2274-03 is equivalent to IP 388 (Energy Institute,
London) and EN ISO 12205:1996 (CEN).
[0103] In general terms, the oxidative stability of a fuel
formulation may be assessed with reference to the generation of an
oxidation product, such as a carboxylic acid or peroxide, in the
formulation. For a fuel formulation containing a biodiesel
component such as a FAME, for example, CEN Test Method EN
15751:2009 "Fatty acid methyl ester (FAME) fuel and blends with
diesel fuel--Determination of oxidation stability by accelerated
oxidation method" (also known as a "Modified Rancimat" test method)
may be used to assess oxidative stability.
[0104] The invention may additionally or alternatively be used to
adjust any property of the diesel fuel formulation which is
equivalent to or associated with oxidative stability. For example,
improved oxidative stability may be associated with reduced deposit
formation, with improved combustion and energy efficiency for a
system running on the fuel formulation, with improved storage
stability and/or with overall better retention of fuel
properties.
[0105] In accordance with the invention, species (i), (ii) or (iii)
may be added to the diesel fuel formulation at any suitable time
and location. It may be premixed with the antioxidant and the
resultant premix then added to the fuel formulation, or
alternatively species (i), (ii) or (iii) may be added separately,
to a diesel fuel formulation which already contains, and/or is
subsequently to be mixed with, an antioxidant. A premixed additive
composition comprising species (i), (ii) or (iii) and an
antioxidant may constitute an essential element for the carrying
out of the present invention. Such an additive composition may
comprise one or more appropriate solvents or carriers, as described
below in connection with the second aspect of the invention. It may
contain one or more additional diesel fuel additives.
[0106] According to a second aspect, the present invention provides
the method of operating a diesel fuel-consuming system, and/or
apparatus which is driven by such a system, the method comprising
introducing into the system a diesel fuel additive composition
containing an antioxidant and a species selected from: [0107] (iv)
detergents; [0108] (v) mixtures containing both a lubricity
improver and a conductivity improver; and [0109] (vi) combinations
of (i) and (ii).
[0110] The method of the present invention may comprise introducing
the diesel fuel additive composition into a combustion chamber of a
fuel-consuming system. The system may for example be an internal
combustion engine.
[0111] A method according to the second aspect of the present
invention may be carried out with the intention of increasing the
oxidative stability of the diesel fuel additive composition
following its introduction into the diesel fuel-consuming
system.
[0112] A diesel fuel additive composition is a composition which
contains a diesel fuel additive and which is suitable and/or
adapted and/or intended, in particular suitable and/or adapted, for
use in a diesel fuel formulation, for instance a diesel fuel
formulation of the type described above in connection with the
first aspect of the invention. In particular, a diesel fuel
additive composition prepared or used according to the second
aspect of the invention may be suitable and/or adapted and/or
intended, in particular suitable and/or adapted, for use in a
diesel fuel formulation containing 10% v/v or more of paraffinic
hydrocarbons.
[0113] An increase in the antioxidant activity of the additive
composition means that the composition causes a greater increase in
the oxidative stability of a diesel fuel formulation to which it is
added. The increase may be measured relative to that achieved using
the antioxidant alone (ie in the absence of species (i), (ii) or
(iii)), at the same concentration.
[0114] An additive composition prepared or used according to the
second aspect of the invention may comprise a solvent or other
carrier, or mixture thereof, for the additives present in it.
Suitable such solvents are well known and commercially available.
They may in particular be liquid carriers. They may conveniently be
of low polarity, and/or hydrophobic, and/or non-aqueous, to render
them suitable for use in diesel fuel formulations.
[0115] Commonly used additive solvents include hydrocarbon solvents
such as alkanes, alkenes and aromatic hydrocarbons; mixtures of
hydrocarbons such as in distillate fractions; and more polar
solvents such as alcohols and ethers. The nature of the carrier or
carrier mixture used in the additive composition (in particular its
polarity) may be chosen to suit the natures and polarities of the
additives present, as well as of a diesel fuel formulation in which
the additive composition is to be used, so as to optimise the
stability and efficacy of the composition during use.
[0116] A detergent (i) may be used in the additive composition at a
concentration sufficient to provide a level of detergent in the
finished fuel of 100 ppmw or greater, or 250 ppmw or greater, or
500 ppmw or greater, or 1000 ppmw or greater. It may be used at a
concentration of up to 250 ppmw, or up to 500 ppmw, or up to 1000
ppmw, or up to 2000 ppmw, for example from 100 to 2000 ppmw, or
between 100 and 250 ppmw, or between 250 and 500 ppmw, or between
500 and 1000 ppmw, or between 1000 and 2000 ppmw.
[0117] A mixture (ii) of a lubricity improver and a conductivity
improver may be used in the additive composition at a concentration
sufficient to provide a level of (ii) in the finished fuel of 25
ppmw or greater, or of 50 ppmw or greater, or 100 ppmw or greater,
or 200 ppmw or greater, or 300 ppmw or greater. It may be used at a
concentration of up to 50 ppmw, or up to 100 ppmw, or up to 200
ppmw, or up to 300 ppmw, or up to 500 ppmw, for example from 25 to
500 ppmw, or from 25-100 ppmw, or from 100 to 200 ppmw, or from 200
to 300 ppmw, or from 300 to 500 ppmw.
[0118] Where a combination (iii) is used in the additive
composition, the concentrations of its component species (i) and
(ii) may be as just described. However, due to their combined
effect on antioxidant activity, it may be possible to use a lower
concentration of either or both of the individual species (i) and
(ii).
[0119] The antioxidant may be used in the additive composition at a
concentration sufficient to provide a level in the finished fuel of
20 ppmw or greater, or 50 ppmw or greater, or 100 ppmw or greater,
or 250 ppmw or greater. It may be used at a concentration of up to
50 ppmw, or up to 100 ppmw, or up to 250 ppmw, or up to 500 ppmw,
for example from 10 to 500 ppmw, or from 20 to 250 ppmw, or from 20
to 100 ppmw.
[0120] An additive composition prepared or used according to the
second aspect of the invention may for example be included in a
diesel fuel formulation at a concentration of 100 ppmw or greater,
or 250 ppmw or greater, or 500 ppmw or greater, or 750 ppmw or
greater, or 1000 ppmw or greater. Its concentration may for example
be up to 250 ppmw, or up to 500 ppmw, or up to 750 ppmw, or up to
1000 ppmw, or up to 2000 ppmw, such as from 100 to 2000 ppmw, or
from 500 to 1000 ppmw, or from 750 to 1250 ppmw, or from 1000 to
2000 ppmw.
[0121] Other preferred features of the second aspect of the
invention, for example the natures of the species (i), (ii) and
(iii) and the antioxidant; the purpose(s) for which, and the
concentrations at which, these additives are used; and the nature
of the diesel fuel formulation in which they are suitable to be
used, may be as described above in connection with the first aspect
of the invention.
[0122] According to a third aspect, the invention provides a method
for preparing a diesel fuel formulation, the method comprising (a)
providing a diesel fuel component (for example a diesel base fuel)
or mixture thereof, which contains 10% v/v or greater of paraffinic
hydrocarbons and also an antioxidant; (b) optionally assessing the
oxidative stability of the component or mixture; (c) adding to the
component or mixture species (i), (ii) or (iii) as defined above,
and (d) assessing the oxidative stability of the resultant
formulation. Step (d) may be carried out in order to assess the
effect of species (i), (ii) or (iii) on the oxidative stability of
the diesel fuel formulation and/or on the activity of the
antioxidant.
[0123] In an embodiment of the third aspect of the invention,
species (i), (ii) or (iii) is added to the diesel fuel component,
or mixture thereof, in the form of an additive composition prepared
according to the second aspect. One or more additional diesel fuel
additives may also be added to the fuel component or mixture,
either with or separately to species (i), (ii) or (iii). Preferred
features of the antioxidant, of species (i), (ii) or (iii) and of
the diesel fuel component(s) and additive(s) with which they are
mixed, may be as described above in connection with the first and
second aspects of the invention, as may the ways in which oxidative
stability is assessed.
[0124] Because species (i), (ii) or (iii) can act to improve the
activity of an antioxidant present in a diesel fuel formulation
containing 10% v/v or greater of paraffinic hydrocarbons, it can
make possible the use of lower concentrations of the, or other,
antioxidant additives in the formulation or in an additive
composition for use in the formulation, without or without undue
reduction in the oxidative stability of the formulation. This can
in turn reduce the cost and complexity of preparing the formulation
or composition, and/or can provide greater versatility in diesel
fuel or additive formulation practices.
[0125] Thus, according to a fourth aspect, the invention provides a
method for reducing the concentration of the or an antioxidant
present in a diesel fuel formulation or an a diesel fuel additive
composition wherein the method comprises introducing a species (i),
(ii) or (iii) as defined above, into a diesel fuel additive
composition or in a diesel fuel formulation containing 10% v/v of
paraffinic hydrocarbons, in combination with an antioxidant.
[0126] In the context of the fourth aspect of the invention, the
term "reducing" embraces any degree of reduction, including
reduction to zero. The reduction may for instance be 10% or more of
the original concentration of the antioxidant, or 25 or 50 or 75 or
90% or more. The reduction may for instance be 2 ppmw or more, or 5
or 10 ppmw or more, or in cases 25 or 50 or 75 ppmw or more. The
reduction may be as compared to the concentration of the
antioxidant which would otherwise have been incorporated into the
composition or formulation in order to achieve the properties and
performance required and/or desired of it in the context of its
intended use. This may be the concentration of the antioxidant
which was present in the composition or formulation prior to the
realisation that species (i), (ii) or (iii) could be used in the
way provided by the present invention, and/or which was present in
an otherwise analogous additive composition or diesel fuel
formulation which was intended (eg marketed) for use in an
analogous context, prior to adding species (i), (ii) or (iii) to it
in accordance with the invention.
[0127] The reduction in concentration of the antioxidant may be as
compared to the concentration of the antioxidant which would be
predicted to be necessary to achieve a desired property or
performance (for instance a desired level of oxidative stability)
for the composition or formulation in the absence of species (i),
(ii) or (iii). It may be as compared to the "standard treat rate"
of the antioxidant in the relevant type of diesel fuel
formulation.
[0128] In accordance with a fifth aspect of the invention, there is
provided a method of operating a diesel fuel-consuming system,
and/or apparatus (for example a vehicle, or a heating appliance)
which is driven by such a system, the method comprising introducing
into the system a diesel fuel formulation prepared according to the
third aspect of the invention. This method may comprise introducing
the formulation or the additive composition into a combustion
chamber of a fuel-consuming system. The system may for example be
an internal combustion engine.
[0129] In the context of the present invention, "use" of species
(i), (ii) or (iii) as defined above in a diesel fuel formulation
means incorporating the relevant species into the formulation,
typically as a blend (ie a physical mixture) with one or more
diesel fuel components, for example diesel base fuels, and
optionally in combination with one or more additional diesel fuel
additives.
[0130] Species (i), (ii) or (iii) will conveniently, although not
necessarily, be incorporated before the formulation is introduced
into a fuel-consuming system. Instead or in addition, the use of
species (i), (ii) or (iii) may involve running a diesel
fuel-consuming system on a diesel fuel formulation containing the
relevant species, typically by introducing the formulation into a
combustion region of the system. It may involve running a vehicle
or other apparatus which is driven by a diesel fuel-consuming
system, on a diesel fuel formulation containing the relevant
species.
[0131] "Use" of species (i), (ii) or (iii) in the ways described
above may also embrace supplying the relevant species together with
instructions for its use in a diesel fuel formulation for one or
more of the purposes described above in connection with the first
to the fifth aspects of the invention. The species (i), (ii) or
(iii) may itself be supplied as part of a composition which is
suitable and/or adapted for use as a diesel fuel additive, in
particular an additive composition prepared according to the second
aspect of the invention. In this case, species (i), (ii) or (iii)
may be included in such a composition for any one or more of the
purposes described above in connection with the first to the fifth
aspects of the invention.
[0132] Thus species (i), (ii) or (iii) may be used, in a diesel
fuel formulation, in the form of an additive composition which has
been prepared according to the second aspect of the invention, ie
in which species (i), (ii) or (iii) is used to enhance the activity
of an antioxidant additive. "Use" of species (i), (ii) or (iii) may
therefore comprise use of such an additive composition.
[0133] "Use" of species (i), (ii) or (iii) in an additive
composition means incorporating the relevant species into the
composition, typically as a blend (ie a physical mixture) with one
or more solvent carriers and optionally in combination with one or
more additional diesel fuel additives. Species (i), (ii) or (iii)
will conveniently, although not necessarily, be incorporated before
the composition is introduced into a diesel fuel formulation or
into a diesel fuel-consuming system. Instead or in addition, the
use of species (i), (ii) or (iii) may involve running a diesel
fuel-consuming system on a diesel fuel formulation containing the
relevant species in the additive composition, typically by
introducing the formulation into a combustion region of the system.
It may involve running a vehicle or other apparatus which is driven
by a diesel fuel-consuming system, on a diesel fuel formulation
containing species (i), (ii) or (iii) in the additive
composition.
[0134] "Use" of species (i), (ii) or (iii) in the ways described
above may also embrace supplying the relevant species together with
instructions for its use in an additive composition for one or more
of the purposes described above in connection with the first to the
fifth aspects of the invention.
[0135] In general, references to "adding" a component to, or
"incorporating" a component in, an additive composition or a diesel
fuel formulation may be taken to embrace addition or incorporation
at any point during the production of the composition or
formulation or at any time prior to its use.
[0136] In certain embodiments, the present invention may be used to
produce at least 1000 litres of an additive composition or diesel
fuel formulation containing a species (i), (ii) or (iii), or at
least 5,000 or 10,000 or 20,000 or 50,000 litres.
[0137] A diesel fuel formulation which is prepared or used
according to the invention may be marketed with an indication that
it benefits from an improvement due to the inclusion of species
(i), (ii) or (iii), for example increased oxidative stability
and/or a lower concentration of an antioxidant in the formulation.
The marketing of such a formulation may comprise an activity
selected from: (a) providing the formulation in a container that
comprises the relevant indication; (b) supplying the formulation
with product literature that comprises the indication; (c)
providing the indication in a publication or sign (for example at
the point of sale) that describes the formulation; and (d)
providing the indication in a commercial which is aired for
instance on the radio, television or internet. The improvement may
be attributed, in such an indication, at least partly to the
presence of species (i), (ii) or (iii). The invention may involve
assessing the relevant property of the formulation during or after
its preparation. It may involve assessing the relevant property
both before and after incorporation of species (i), (ii) or (iii),
for example so as to confirm that the species contributes to the
relevant improvement in the formulation.
[0138] A diesel fuel additive composition prepared or used
according to the invention may be marketed with an indication that
it benefits from an improvement due to the inclusion of species
(i), (ii) or (iii), for example increased oxidative stability in a
diesel fuel formulation in which the composition is used, and/or a
lower concentration of an antioxidant in the composition. The
marketing of such a composition may comprise an activity selected
from: (a) providing the composition in a container that comprises
the relevant indication; (b) supplying the composition with product
literature that comprises the indication; (c) providing the
indication in a publication or sign (for example at the point of
sale) that describes the composition; and (d) providing the
indication in a commercial which is aired for instance on the
radio, television or internet. The improvement may be attributed,
in such an indication, at least partly to the presence of species
(i), (ii) or (iii). The invention may involve assessing the
relevant property of the composition during or after its
preparation. It may involve assessing the relevant property both
before and after incorporation of the species (i), (ii) or (iii),
for example so as to confirm that the species contributes to the
relevant improvement in the composition.
[0139] In certain cases the invention can have use in diesel fuel
formulations having paraffinic hydrocarbon contents of less than
10% v/v.
[0140] Throughout the description and claims of this specification,
the words "comprise", "include" and "contain" and variations of
these words, for example "comprising" and "comprises", mean
"including but not limited to", and do not exclude other moieties,
additives, components, integers or steps. Moreover the singular
encompasses the plural unless the context otherwise requires: in
particular, where the indefinite article is used, the specification
is to be understood as contemplating plurality as well as
singularity, unless the context requires otherwise.
[0141] Preferred features of each aspect of the invention may be as
described in connection with any of the other aspects. Other
features of the invention will become apparent from the following
examples. Generally, the invention extends to any novel one, or any
novel combination, of the features disclosed in this specification
(including any accompanying claims and drawings). Thus features,
integers, characteristics, compounds, chemical moieties or groups
described in conjunction with a particular aspect, embodiment or
example of the invention are to be understood to be applicable to
any other aspect, embodiment or example described herein unless
incompatible therewith. For example, for the avoidance of doubt,
optional and preferred features (including concentrations) of the
antioxidant, the species (i) to (iii), any additional additive(s)
and the diesel fuel formulation can apply to all aspects of the
invention in which the antioxidant, the species (i), (ii) or (iii),
the additional additive(s) or the fuel formulation are
mentioned.
[0142] Unless stated otherwise, any feature disclosed herein may be
replaced by an alternative feature serving the same or a similar
purpose.
[0143] Where upper and lower limits are quoted for a property, for
example, concentration of an additive or fuel component, then a
range of values defined by a combination of any of the upper limits
with any of the lower limits may also be implied.
[0144] In this specification, references to physical properties
such as antioxidant, detergent, lubricity improver, conductivity
improver, additive, fuel and fuel component properties are, unless
stated otherwise, to properties measured under ambient conditions,
ie at atmospheric pressure and at a temperature from 16 to 22 or
25.degree. C., or from 18 to 22 or 25.degree. C., for example about
20.degree. C.
[0145] The present invention will now be further described with
reference to the following non-limiting examples.
General
[0146] Fuel formulations were prepared, in accordance with the
invention, by incorporating antioxidants into diesel base fuels,
together with (i) a detergent, (ii) a mixture of a lubricity
improver and a conductivity improver, and (iii) a combination of
(i) and (ii). For comparison purposes, further formulations were
prepared by incorporating antioxidants into the base fuels in the
absence of the components (i) to (iii).
[0147] The oxidative stability of each fuel formulation was
assessed using the standard test method ASTM D7545-09 and a
Petrospec (trade mark) "PetroOxy" test apparatus. A 5 ml sample of
the test formulation was introduced into a pressure chamber which
was then charged with oxygen at 700 kPa and ambient temperature.
The test was initiated by switching on a heater and heating the
chamber to 140.degree. C. The pressure inside the chamber was
recorded continuously until a breakpoint was reached, this being
the point at which the pressure had fallen by 10% from the maximum
pressure attained in the chamber. The "induction period" was
defined as the time between the start of the test and the
breakpoint. This provided an indication of the resistance of the
test formulation to oxidation.
[0148] In the event that no breakpoint was reached within a
specified time period T, the result was recorded as "greater than
T".
[0149] Induction periods recorded in these examples are averages of
two measurements.
[0150] Two antioxidants were used in the tests, designated AO1 and
AO2. AO1 was butylated hydroxytoluene (BHT), obtained as Baynox
(trade mark), a 20 g/l solution in biodiesel, ex Lanxess. BHT is
employed in fuel formulations to reduce autoxidation rates by
reacting with peroxy radicals, converting them to more stable
hydroperoxides and non-radical products, thereby terminating the
chain reactions that might otherwise occur. It is typically used in
distillate fuels at treat rates from 10 to 200 ppmw; in these tests
it was included at a concentration of 100 ppmw.
[0151] AO2 was N,N'-di-2-butyl-1,4-phenylenediamine, available from
Octel Starreon (trade mark) as AO-22. It was included in the
formulations at a concentration of 20 ppmw.
[0152] Other additives used in the tests were as follows. Neither
was expected to cause a large, if any, increase in oxidative
stability of a fuel to which it was added.
[0153] D1--a multi-functional diesel performance additive package
suitable for use in automotive diesel fuels, ex Innospec (trade
mark). This contained as its main (detergent) active ingredient a
polyisobutenyl (PIB) succinimide of a polyamine. It also contained
minor amounts of other fuel additives, including a silicone
antifoaming agent and a dehazer. It was used in the test
formulations at a treat rate of 500 ppmw.
[0154] LC1--a commercially available performance additive package
suitable for use in automotive distillate fuels, ex Infineum (trade
mark). This contained both a fatty ester-based lubricity improver
and a conductivity improver. It was used at a treat rate of 250
ppmw.
EXAMPLE 1
Base Fuel 1
[0155] This example used a Fischer-Tropsch derived diesel base fuel
BF1. This was a paraffinic gas oil made from natural gas via a
Fischer-Tropsch synthesis, sourced from Qatar Shell GTL. It was
free of additives, such as detergents, lubricity improvers and
conductivity improvers. Its properties are summarised in Table 1
below.
TABLE-US-00001 TABLE 1 Property Units Test method BF1 Density at
15.degree. C. kg/m.sup.3 ASTM 778.9 D4052 Kinematic viscosity
mm.sup.2/s EN ISO 3104 2.334 at 40.degree. C. Distillation: ASTM
D86 Initial boiling point .degree. C. 174.1 50% 255.6 90% 320.1 95%
333.9 Final boiling point 343.9 Cetane number ASTM D613 >75
Paraffin content % w/w Two- >99 dimensional gas
chromatography
[0156] The results of the oxidative stability tests for BF1 and for
test formulations containing BF1 blended with one or more of the
additives AO1, AO2, D1 and LC1 are shown in Table 2 below. The
third column shows the increase in induction period relative to
that of BF1 alone.
[0157] For formulations containing two or more different additives,
the fourth column shows the predicted increase in induction period
relative to that of BF1 alone. These predictions assumed that the
effects of a combination of additives on oxidative stability would
be additive, eg that a combination of additives A and B would give
an overall increase in stability equal to the sum of the increases
which the two additives caused when used alone at the same
concentrations. Thus, numerically, the predicted induction period
(IP.sub.mixture) for a fuel formulation containing a mixture of
additives A, B and C is defined by the formula:
Predicted IP.sub.mixture=IP.sub.none*[1+(% increase due to A+%
increase due to B+% increase due to C)]
[0158] where IP.sub.none is the induction period for the same
formulation but without any of the three additives.
[0159] The fifth column in Table 2 shows the percentage benefit
provided by the invention, ie the difference between the measured
increase in induction period and the predicted increase, as a
percentage of the predicted increase for the formulations
containing two or more additives. A deficit (when the measured
increase was smaller than predicted) is shown as a negative number.
Synergistic combinations (positive benefit compared to predicted
results) are indicated by positive numbers.
TABLE-US-00002 TABLE 2 Measured Induction induction period
Predicted % Test period increase increase benefit/ formulation
(hours) (hours) (hours) deficit BF1 1.419 0.00 BF1 + D1 1.933 0.51
BF1 + AO1 2.224 0.80 BF1 + AO2 3.908 2.49 BF1 + LC1 1.468 0.05 BF1
+ D1 + 2.976 1.56 1.319 18 AO1 BF1 + D1 + 4.847 3.43 3.002 14 AO2
BF1 + D1 + 1.858 0.44 0.563 -22 LC1 BF1 + AO1 + 2.434 1.01 0.853 19
LC1 BF1 + AO2 + 4.774 3.35 2.537 32 LC1 BF1 + D1 + 2.909 1.49 1.367
9 AO1 + LC1 BF1 + D1 + 3.974 2.55 3.051 -16 AO2 + LC1
[0160] It can be seen from Table 2 that antioxidants AO1 and AO2
both increased the oxidative stability (and hence the induction
period) of the Fischer-Tropsch derived base fuel alone, as did the
detergent D1 to a much smaller extent. The lubricity
improver/conductivity improver mixture LC1 did not cause any
significant increase in oxidative stability, and the combination of
D1 and LC1 caused a significant reduction in stability.
[0161] Surprisingly, when detergent D1 was used together with the
antioxidants, the combined effect on oxidative stability was
greater than would have been predicted from their individual
effects, indicating some form of synergistic interaction between
them. The detergent appeared to enhance the activity of the
antioxidants. Similar synergies were observed when LC1 was used
with the antioxidants. The combination of D1 and LC1 also appeared
to enhance the antioxidant activity of the phenolic antioxidant
AO1.
[0162] In the case of this Fischer-Tropsch derived base fuel,
unexpectedly good results were observed for binary additive
combinations containing an antioxidant with either a detergent or a
lubricity improver/conductivity improver mixture, especially the
combination of the amine antioxidant AO2 and the lubricity
improver/conductivity improver mixture.
EXAMPLE 2
Base Fuel 2
[0163] Example 1 was repeated using a hydrogenated vegetable oil
(HVO) blend BF2 as a base fuel. BF2, ex Neste Oil, was a biodiesel
fuel produced by hydrotreating vegetable oils and other
biologically derived lipids. Its chemical composition was similar
to that of Fischer-Tropsch derived base fuels, being paraffinic
with essentially no aromatic components or sulphur, although with a
relatively narrow carbon chain length distribution. Its properties
are summarised in Table 3 below.
TABLE-US-00003 TABLE 3 Property Units Test method BF2 Density at
15.degree. C. kg/m.sup.3 ASTM 776.2 D4052 Kinematic viscosity
mm.sup.2/s EN ISO 3104 2.57 at 40.degree. C. Distillation: ASTM D86
Initial boiling point .degree. C. 161.7 50% 273.9 90% 287.7 95%
291.4 Final boiling point 298.2 Cetane number (CID) ASTM D7668 79.4
Paraffin content % w/w Two-dimensional 99.5 gas chromatography
[0164] As indicated in Table 3, analysis revealed that BF2
comprised 99.5% w/w paraffins. More than 90% of the paraffins
content of BF2 was represented by carbon chain lengths of C12 to
C18. The results of the oxidative stability tests are shown in
Table 4 below, for BF2 and for test formulations containing BF2
blended with one or more of the additives AO1, AO2, D1 and LC1. The
third, fourth and fifth columns correspond to those in Table 2.
TABLE-US-00004 TABLE 4 Measured Induction induction period
Predicted % Test period increase increase benefit/ formulation
(hours) (hours) (hours) deficit BF2 1.284 0.00 BF2 + D1 1.737 0.45
BF2 + AO1 3.022 1.74 BF2 + AO2 4.097 2.81 BF2 + LC1 1.316 0.03 BF2
+ D1 + 3.642 2.36 2.191 8 AO1 BF2 + D1 + 4.209 2.93 3.266 -10 AO2
BF2 + D1 + 1.686 0.40 0.485 -17 LC1 BF2 + AO1 + 2.367 1.08 1.771
-39 LC1 BF2 + AO2 + 5.174 3.89 2.845 37 LC1 BF2 + D1 + 3.395 2.11
2.223 -5 AO1 + LC1 BF2 + D1 + 5.057 3.77 3.298 14 AO2 + LC1
[0165] Table 4 shows that both antioxidants increased the oxidative
stability of the HVO base fuel alone, as did detergent D1 to a much
smaller extent. The lubricity improver/conductivity improver
mixture LC1 did not cause any significant increase in oxidative
stability, and the combination of D1 and LC1 caused a significant
reduction.
[0166] Surprisingly, when detergent D1 was used with the phenolic
antioxidant AO1, the combined effect on oxidative stability was
unexpectedly greater than would have been predicted from their
individual effects, indicating some form of synergistic interaction
as the detergent appeared to enhance the activity of the
antioxidant. An even more marked synergy was observed when LC1 was
used with the amine antioxidant AO2, and when a combination of D1
and LC1 was used in combination with the amine antioxidant.
[0167] In the case of this HVO base fuel, particularly good results
were thus seen for the formulations containing an amine antioxidant
and a lubricity improver/conductivity improver mixture, both with
and without the detergent additive D1.
COMPARATIVE EXAMPLE 3
Base Fuel 3
[0168] Example 1 was repeated using a petroleum-derived diesel base
fuel BF3. This was a commercially available, EN 590-compliant ultra
low sulphur diesel base fuel, ex Shell, formulated without fatty
acid methyl esters (FAMES). Its properties are summarised in Table
5 below.
TABLE-US-00005 TABLE 5 Property Units Test method BF3 Density at
15.degree. C. kg/m.sup.3 ASTM 832.8 D4052 Kinematic viscosity at
mm.sup.2/s EN ISO 3104 2.839 40.degree. C. Distillation: ASTM D86
Initial boiling point .degree. C. 172.9 50% 269.5 90% 337.0 95%
351.6 Final boiling point 363.4 Cetane number ASTM D613 54.8
Aromatics content % w/w EN 12916 22.5 (HPLC)
[0169] The results of the oxidative stability tests for
BF3-containing formulations are shown in Table 6 below. The third,
fourth and fifth columns correspond to those in Table 2.
TABLE-US-00006 TABLE 6 Measured Induction induction period
Predicted % Test period increase increase benefit/ formulation
(hours) (hours) (hours) deficit BF3 0.733 0.00 BF3 + D1 1.540 0.81
BF3 + AO1 1.365 0.63 BF3 + AO2 3.096 2.36 BF3 + LC1 0.940 0.21 BF3
+ D1 + 1.842 1.11 1.440 -23 AO1 BF3 + D1 + 4.377 3.64 3.171 15 AO2
BF3 + D1 + 1.495 0.76 1.016 -25 LC1 BF3 + AO1 + 1.440 0.71 0.840
-16 LC1 BF3 + AO2 + 1.935 1.20 2.571 -53 LC1 BF3 + D1 + 1.930 1.20
1.648 -27 AO1 + LC1 BF3 + D1 + 4.248 3.52 3.378 4 AO2 + LC1
[0170] Table 6 shows that the surprising effects of the present
invention were not generally observed in the case of the
petroleum-derived base fuel BF3, which had a relatively low
paraffin content. Although antioxidants AO1 and AO2 increased the
oxidative stability of the base fuel, the detergent additive D1
only enhanced that stability for the amine antioxidant AO2. The
lubricity improver/conductivity improver combination LC1 was
detrimental to the antioxidant activities of AO1 and AO2, and when
combined with D1 reduced the antioxidant activity of the phenolic
antioxidant AO1.
[0171] Thus, with petroleum-derived diesel base fuels, improvements
in oxidative stability were achieved only with the amine
antioxidant AO2, and only in the presence of the detergent
additive.
EXAMPLE 4
Base Fuel 4
[0172] Example 1 was repeated using a base fuel BF4, which was a
1:1 v/v blend of BF1 and BF2 having an overall paraffinic
hydrocarbon content of greater than 99% v/v.
[0173] The results of the oxidative stability tests are shown in
Table 7 below. The third, fourth and fifth columns correspond to
those in Table 2.
TABLE-US-00007 TABLE 7 Measured Induction induction period
Predicted % Test period increase increase benefit/ formulation
(hours) (hours) (hours) deficit BF4 1.359 0.00 BF4 + D1 1.711 0.35
BF4 + AO1 2.418 1.06 BF4 + AO2 4.210 2.85 BF4 + LC1 1.361 0.00 BF4
+ D1 + 2.899 1.54 1.411 9 AO1 BF4 + D1 + 4.848 3.49 3.203 9 AO2 BF4
+ D1 + 1.647 0.29 0.354 -19 LC1 BF4 + AO1 + 2.493 1.13 1.061 7 LC1
BF4 + AO2 + 4.670 3.31 2.853 16 LC1 BF4 + D1 + 2.821 1.46 1.413 3
AO1 + LC1 BF4 + D1 + 5.534 4.18 3.205 30 AO2 + LC1
[0174] Table 7 shows antioxidants AO1 and AO2 greatly increased
oxidative stability of the Fischer-Tropsch fuel/HVO blend BF4.
Detergent D1 did so to a smaller extent. The lubricity
improver/conductivity improver mixture LC1 did not cause any
significant increase in oxidative stability, and the combination of
D1 and LC1 caused a significant reduction in stability.
[0175] Surprisingly, when the detergent D1 was used with the
antioxidants, the combined effect on oxidative stability was
greater than would have been predicted from their individual
effects, indicating a synergistic interaction between them. Similar
synergies were observed when LC1 was used with antioxidants, and
also when D1 and LC1 were used to enhance antioxidant activity
(despite the fact that a D1/LC1 mixture on its own caused a large
reduction in the oxidative stability of BF4).
[0176] In this case, the Fischer-Tropsch derived and HVO base fuels
blend provided particularly good results for formulations
containing both the amine antioxidant AO2 and the lubricity
improver/conductivity improver mixture LC1.
EXAMPLE 5
Base Fuel 5
[0177] Example 1 was repeated using a base fuel BF5, which was a
1:1 v/v blend of BF1 and BF3, having a synthetic paraffinic
hydrocarbon content of 50% v/v.
[0178] The results of the oxidative stability tests are shown in
Table 8 below. The third, fourth and fifth columns correspond to
those in Table 2.
TABLE-US-00008 TABLE 8 Measured Induction induction period
Predicted % Test period increase increase benefit/ formulation
(hours) (hours) (hours) deficit BF5 1.444 0.00 BF5 + D1 1.800 0.36
BF5 + AO1 1.928 0.48 BF5 + AO2 2.858 1.41 BF5 + LC1 1.551 0.11 BF5
+ D1 + 1.932 0.49 0.840 -42 AO1 BF5 + D1 + 4.990 3.55 1.770 100 AO2
BF5 + D1 + 1.779 0.34 0.463 -28 LC1 BF5 + AO1 + 1.755 0.31 0.591
-47 LC1 BF5 + AO2 + 2.962 1.52 1.521 0 LC1 BF5 + D1 + 2.293 0.85
0.947 -10 AO1 + LC1 BF5 + D1 + 5.565 4.12 1.877 120 AO2 + LC1
[0179] Table 8 shows that antioxidants AO1 and AO2 increased the
oxidative stability of the Fischer-Tropsch fuel/mineral fuel blend,
as did detergent D1. The lubricity improver/conductivity improver
mixture LC1 did not cause any sizeable increase in oxidative
stability, and the combination of D1 and LC1 caused a significant
reduction.
Surprisingly, when detergent D1 was used together with amine
antioxidant AO2, the combined effect on oxidative stability was far
greater than would have been predicted from their individual
effects, indicating a synergistic interaction between them. A
similarly high level of synergy was observed when a combination of
D1 and LC1 was used with the amine antioxidant.
[0180] In the case of this blend of Fischer-Tropsch derived and
mineral base fuels, particularly good results were achieved using
an amine antioxidant and a detergent. This pattern reflected that
observed for the mineral base fuel alone (BF3), although the
addition of Fischer-Tropsch derived fuel components and the
resultant increase in paraffin content appeared to enhance the
synergistic interaction between the antioxidant and the
detergent.
[0181] It can be seen from the above examples that species (i),
(ii) or (iii), as defined above, can be used to enhance the
antioxidant activity in a relatively high paraffin content diesel
fuel formulation. It can be used to improve the oxidative stability
of such formulations, which are likely to be more prone to
oxidation because of the paraffinic hydrocarbons they contain. A
species (i), (ii) or (iii) can similarly be used to reduce the
concentration of an antioxidant which is needed in such a diesel
fuel formulation, without or without undue detriment to the
oxidative stability of the formulation. The present invention thus
provides more options for the diesel fuel formulator.
[0182] Moreover, these results can be achieved through the use of
conventional diesel fuel additives (detergents, lubricity improvers
and conductivity improvers) which can be of value in a diesel fuel
formulation for other purposes as well as their effects on
oxidative stability. Species (i) to (iii) are able to interact
synergistically with antioxidants in higher paraffin content diesel
fuel formulations. This unexpected effect can allow new uses for
fuel additives which are not normally regarded as antioxidants.
[0183] Thus, in recognising that the species (i) to (iii) may be
used for such novel purposes, the invention allows the formulator
to achieve more than one aim through the use of a particular
additive. This can allow a reduction in overall additive
concentrations, with its associated processing benefits, yet
without undue loss of fuel stability.
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