U.S. patent application number 17/282316 was filed with the patent office on 2021-12-09 for fuel compositions.
The applicant listed for this patent is SHELL OIL COMPANY. Invention is credited to Tushar BERA, Claire GRIFFITHS, Alastair Graham SMITH, Mark Clift SOUTHBY.
Application Number | 20210380894 17/282316 |
Document ID | / |
Family ID | 1000005835293 |
Filed Date | 2021-12-09 |
United States Patent
Application |
20210380894 |
Kind Code |
A1 |
SMITH; Alastair Graham ; et
al. |
December 9, 2021 |
FUEL COMPOSITIONS
Abstract
A fuel composition comprising a base fuel and at least one
viscosity index (VI) improving additive, wherein the viscosity
index (VI) improving additive is a star-shaped polyisoprene-based
polymer. The viscosity index improving additive can be used in a
fuel composition to provide improved lubricity as well as providing
improved power output and/or acceleration characteristics.
Inventors: |
SMITH; Alastair Graham;
(London, GB) ; GRIFFITHS; Claire; (London, GB)
; SOUTHBY; Mark Clift; (London, GB) ; BERA;
Tushar; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHELL OIL COMPANY |
HOUSTON |
TX |
US |
|
|
Family ID: |
1000005835293 |
Appl. No.: |
17/282316 |
Filed: |
October 3, 2019 |
PCT Filed: |
October 3, 2019 |
PCT NO: |
PCT/EP2019/076818 |
371 Date: |
April 1, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62741585 |
Oct 5, 2018 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10L 2200/0446 20130101;
C10L 2270/026 20130101; C10L 10/08 20130101; C10L 1/1658 20130101;
C10L 2250/04 20130101 |
International
Class: |
C10L 1/16 20060101
C10L001/16; C10L 10/08 20060101 C10L010/08 |
Claims
1. A fuel composition comprising a base fuel and at least one
viscosity index (VI) improving additive, wherein the viscosity
index (VI) improving additive is a star-shaped polyisoprene-based
polymer.
2. The fuel composition according to claim 1 wherein the
star-shaped polyisoprene-based polymer is characterized by the
formula: (D'-PA-D'')n-X; wherein D' represents a block derived from
at least one diene; PA represents a block derived from monoalkenyl
arene; D'' represents a block derived from diene; n represents the
average number of arms per star polymer formed by the reaction of 2
or more moles of a polyalkenyl coupling agent per mole of arms; and
X represents a nucleus of a polyalkenyl coupling agent; wherein at
least one of diene blocks D' and D'' is a copolymer block derived
from mixed diene monomer, in which from about 65 wt % to about 95
wt % of the incorporated monomer units are from isoprene and from
about 5 wt % up to about 35 wt % of the incorporated monomer units
are from butadiene, and wherein at least about 80 wt % of the
butadiene is incorporated in a 1,4-configuration; and wherein D'
has a number average molecular weight of from about 10,000 to about
120,000 daltons; PA has a number average molecular weight of from
about 10,000 to about 50,000 daltons; and D'' has a number average
molecular weight of from about 5,000 to about 60,000 daltons.
3. The fuel composition according to claim 1 wherein the
star-shaped polyisoprene-based polymer comprises a crosslinked
polystyrene core with arms of hydrogenated polyisoprene or
poly(alternated ethylene-propylene).
4. The fuel composition according to claim 1 wherein the fuel
composition is a diesel fuel composition.
5. The fuel composition according to claim 1 wherein the
concentration of the VI improving additive in the fuel composition
is from 0.001 to 0.5% w/w, preferably from 0.05 to 0.25% w/w.
6. A use of a viscosity index (VI) improving additive in an
automotive fuel composition, for the purpose of improving the
lubricity of the fuel composition, wherein the viscosity index (VI)
improving additive is a star-shaped polyisoprene-based polymer.
7. A use of a viscosity index (VI) improving additive in an
automotive fuel composition, for the purpose of improving the power
output of an internal combustion engine into which the viscosity
index (VI) improving additive, or an automotive fuel composition
containing the viscosity index (VI) improving additive, is or is
intended to be introduced or of a vehicle powered by such an
engine, wherein the viscosity index (VI) improving additive is a
star-shaped polyisoprene-based polymer.
8. A use of a viscosity index (VI) improving additive in an
automotive fuel composition, for the purpose of improving the
lubricity of the fuel composition at the same time as improving the
power output of an internal combustion engine into which the
viscosity index (VI) improving additive, or an automotive fuel
composition containing the viscosity index (VI) improving additive,
is or is intended to be introduced or of a vehicle powered by such
an engine, wherein the viscosity index (VI) improving additive is a
star-shaped polyisoprene-based polymer.
9. The use according to claim 7, wherein the VI improving additive
is pre-dissolved in a solvent or fuel component.
10. (canceled)
11. The use according to claim 8, wherein the VI improving additive
is pre-dissolved in a solvent or fuel component.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to automotive fuel
compositions, and in particular to automotive fuel compositions
comprising viscosity index improver (VII) components.
BACKGROUND OF THE INVENTION
[0002] Viscosity index (VI) is a commonly used method of measuring
a fluid's change of viscosity in relation to temperature. The
higher the VI, the smaller the relative change in viscosity with
temperature. VI improvers (also known as viscosity modifiers) are
additives that increase the viscosity of the fluid throughout its
useful temperature range.
[0003] It is known to use a viscosity increasing component in a
fuel composition in order to improve acceleration performance.
WO2009/118302 describes the use of a viscosity index (VI) improving
additive, in an automotive fuel composition, for the purpose of
improving the acceleration performance of an internal combustion
engine into which the fuel composition is or is intended to be
introduced or of a vehicle powered by such an engine.
[0004] It would be desirable to be able to further improve the
performance of a vehicle engine, by altering the composition and/or
properties of the fuel introduced into it, as this can be expected
to provide a more simple, flexible and cost effective route to
performance optimisation than by making structural or operational
changes to the engine itself.
[0005] In particular, as well as identifying new viscosity index
(VI) improving additives which provide improvements in power and/or
acceleration properties, it would be desirable to improve one or
more other aspects of the fuel composition such as, for example,
friction modification properties, lubricity, engine cleanliness,
cold temperature performance and pumpability.
[0006] US2013/0165362 discloses certain linear and star polymers
suitable for use as a viscosity index improver for lubricating oil
compositions. However there is no disclosure in US2013/0165362 of
the use of such polymers in a fuel composition.
SUMMARY OF THE INVENTION
[0007] According to the present invention there is provided a fuel
composition comprising a base fuel and a viscosity index improver,
wherein the viscosity index improver comprises a star-shaped
polyisoprene-based polymer.
[0008] According to a second aspect of the present invention there
is provided the use of a viscosity index improver in a fuel
composition for providing improved lubricity, wherein the viscosity
index improver comprises a star-shaped polyisoprene-based
polymer.
[0009] According to a further aspect of the present invention there
is provided the use of a viscosity index improver in a fuel
composition for providing improved power output and/or acceleration
characteristics, wherein the viscosity index improver is a
star-shaped polyisoprene-based polymer.
[0010] It has surprisingly been found that the viscosity index
improvers described herein can be used in a fuel composition to
provide improved lubricity as well as providing improved power
output and/or acceleration characteristics.
[0011] Hence, according to yet a further aspect of the present
invention there is provided the use of a viscosity index (VI)
improving additive in a fuel composition for the purpose of
improving the lubricity of the fuel composition at the same time as
improving the power output and/or acceleration performance of an
internal combustion engine into which the viscosity index (VI)
improving additive, or the fuel composition containing the
viscosity index (VI) improving additive, is or is intended to be
introduced or of a vehicle powered by such an engine, wherein the
viscosity index (VI) improving additive is a polyisoprene-based
star polymer.
[0012] It has also been found that the viscosity index improvers
used in the fuel compositions herein can provide one or more of
improved friction modification properties, improved filterability
properties, improved viscosity properties, improved low temperature
performance, improved pumpability especially at low temperatures
and no increase in engine fouling.
DETAILED DESCRIPTION OF THE INVENTION
[0013] As used herein the term `viscosity index (VI) improver`
means an additive that increases the viscosity of the fuel
throughout its useful temperature range. Viscosity index improvers
are also known as viscosity modifiers.
[0014] The fuel composition described herein is preferably a diesel
fuel composition and the internal combustion engine described
herein is preferably a diesel engine.
[0015] By "diesel engine" is meant a compression ignition internal
combustion engine, which is adapted to run on a diesel fuel.
[0016] In addition to using the present invention for improving the
power output and/or acceleration characteristics of the engine, the
present invention can be of use in improving the lubricity of a
fuel composition. As used herein, the term "lubricity" in relation
to a fuel means the capacity of the fuel for reducing friction
and/or wear in an internal combustion engine.
[0017] Lubricity performance may be assessed by measuring the
engine wear. Engine wear may be measured by any suitable method. A
suitable method for measuring the engine wear is the HFRR
(High-Friction Reciprocating Rig) test ISO 12156. In the context of
the present invention, an "improvement" in lubricity performance
embraces any degree of improvement. Similarly a reduction or
increase in a measured parameter--for example the reduction in
engine wear provided by a fuel composition--embraces any degree of
reduction or increase, as the case may be. The improvement,
reduction or increase--as the case may be--may be as compared to
the relevant parameter when using the fuel composition prior to
incorporation of the viscosity index (VI) improving additive. It
may be as compared to the relevant parameter measured when the same
engine is run on an otherwise analogous fuel composition which is
intended (e.g. marketed) for use in an internal combustion
(typically diesel) engine, prior to adding a viscosity index (VI)
improving additive to it.
[0018] The present invention may, for example, involve adjusting
the properties and/or performance and/or effects of the fuel
composition, in particular its effect on the lubricity performance
of a fuel composition, by means of the viscosity index (VI)
improving additive, in order to meet a desired target.
[0019] An improvement in lubricity performance may also embrace
mitigation, to at least a degree, of a decrease in lubricity
performance due to another cause, in particular due to another fuel
component or additive included in the fuel composition.
[0020] An improvement in lubricity performance may also embrace
restoration, at least partially, of lubricity performance which has
been reduced for another reason such as desulphurisation,
hydrotreatment or hydrocracking of diesel and diesel
components.
[0021] "Acceleration performance" includes generally the
responsiveness of the engine to increased throttle, for example the
rate at which it accelerates from any given engine speed. It
includes the level of power and/or torque and/or vehicle tractive
effort (VTE) generated by the engine at any given speed. Thus an
improvement in acceleration performance may be manifested by an
increase in engine power and/or torque and/or VTE at any given
speed.
[0022] Engine torque may be derived from the force exerted on a
dynamometer by the wheel(s) of a vehicle which is powered by the
engine under test. It may, using suitably specialised equipment
(for example the Kistler.TM. RoaDyn.TM.), be measured directly from
the wheels of such a vehicle. Engine power may suitably be derived
from measured engine torque and engine speed values, as is known in
the art. VTE may be measured by measuring the force exerted, for
example on the roller of a chassis dynamometer, by the wheels of a
vehicle driven by the engine.
[0023] The present invention can be of use in improving the
acceleration performance of an internal combustion engine or of a
vehicle powered by such an engine. Acceleration performance may be
assessed by accelerating the engine and monitoring changes in
engine speed, power, torque and/or VTE, air charge pressure and/or
turbo charger speed with time. This assessment may suitably be
carried out over a range of engine speeds.
[0024] Acceleration performance may also be assessed by a suitably
experienced driver accelerating a vehicle which is powered by the
engine under test, for instance from 0 to 100 km/hour, on a road.
The vehicle should be equipped with appropriate instrumentation
such as an engine speedometer, to enable changes in acceleration
performance to be related to engine speed.
[0025] In general, an improvement in acceleration performance may
be manifested by reduced acceleration times, and/or by any one or
more of the effects described above, for example a faster increase
in turbo charger speed, or an increase in engine torque or power or
VTE at any given speed.
[0026] In the context of the present invention, an "improvement" in
acceleration performance embraces any degree of improvement.
Similarly a reduction or increase in a measured parameter--for
example the time taken for the turbo charger to reach its maximum
speed--embraces any degree of reduction or increase, as the case
may be. The improvement, reduction or increase--as the case may
be--may be as compared to the relevant parameter when using the
fuel composition prior to incorporation of the viscosity index (VI)
improving additive. It may be as compared to the relevant parameter
measured when the same engine is run on an otherwise analogous fuel
composition which is intended (e.g. marketed) for use in an
internal combustion (typically diesel) engine, prior to adding a
viscosity index (VI) improving additive to it.
[0027] The present invention may, for example, involve adjusting
the properties and/or performance and/or effects of the fuel
composition, in particular its effect on the acceleration and/or
power output performance of an internal combustion engine, by means
of the viscosity index (VI) improver, in order to meet a desired
target.
[0028] An improvement in acceleration performance may also embrace
mitigation, to at least a degree, of a decrease in acceleration
performance due to another cause, in particular due to another fuel
component or additive included in the fuel composition. By way of
example, a fuel composition may contain one or more components
intended to reduce its overall density so as to reduce the level of
emissions which it generates on combustion; a reduction in density
can result in loss of engine power, but this effect may be overcome
or at least mitigated by the use of a viscosity index (VI) improver
in accordance with the present invention.
[0029] An improvement in acceleration performance may also embrace
restoration, at least partially, of acceleration performance which
has been reduced for another reason such as the use of a fuel
containing an oxygenated component (e.g. a so-called "biofuel"), or
the build-up of combustion related deposits in the engine
(typically in the fuel injectors).
[0030] Where the present invention is used to increase the engine
torque, typically during a period of acceleration, at a given
engine speed, the increase may be of at least 0.1%, preferably of
at least 0.2 or 0.3 or 0.4 or 0.5%, in cases of at least 0.6 or
0.7%, compared to that obtained when running the engine on the fuel
composition prior to incorporation of the viscosity index (VI)
improver. The increase may be as compared to the engine torque
obtained at the relevant speed when the same engine is run on an
otherwise analogous fuel composition which is intended (e.g.
marketed) for use in an internal combustion (typically diesel)
engine prior to adding a viscosity index (VI) improver to it.
[0031] Where the present invention is used to increase the engine
power, typically during a period of acceleration, at a given engine
speed, the increase may again be of at least 0.1%, preferably of at
least 0.2 or 0.3 or 0.4 or 0.5%, in cases of at least 0.6 or 0.7%,
compared to that obtained when running the engine on the fuel
composition prior to incorporation of the viscosity index improver.
The increase may be as compared to the engine power obtained at the
relevant speed when the same engine is run on an otherwise
analogous fuel composition which is intended (e.g. marketed) for
use in an internal combustion (typically diesel) engine prior to
adding a viscosity index improver to it.
[0032] Where the present invention is used to increase the engine
VTE, typically during a period of acceleration, at a given engine
speed, the increase may again be of at least 0.1%, preferably of at
least 0.2 or 0.3 or 0.4 or 0.5%, in cases of at least 0.6 or 0.7%,
compared to that obtained when running the engine on the fuel
composition prior to incorporation of the viscosity index (VI)
improver. The increase may be as compared to the VTE obtained at
the relevant speed when the same engine is run on an otherwise
analogous fuel composition which is intended (e.g. marketed) for
use in an internal combustion (typically diesel) engine prior to
adding a viscosity index (VI) improver to it.
[0033] Where the present invention is used to reduce the time taken
for the engine to accelerate between two given engine speeds, the
reduction may be of at least 0.1%, preferably of at least 0.2 or
0.3 or 0.4 or 0.5%, in cases of at least 0.6 or 0.7 or 0.8 or 0.9%,
compared to that taken when running the engine on the fuel
composition prior to incorporation of the viscosity index (VI)
improver. The reduction may be as compared to the acceleration time
between the relevant speeds when the same engine is run on an
otherwise analogous fuel composition which is intended (e.g.
marketed) for use in an internal combustion (typically diesel)
engine prior to adding a viscosity index (VI) improver to it. Such
acceleration times may for instance be measured over an engine
speed increase of 300 rpm or more, or of 400 or 500 or 600 or 700
or 800 or 900 or 1000 rpm or more, for example from 1300 to 1600
rpm, or from 1600 to 2200 rpm, or from 2200 to 3000 rpm, or from
3000 to 4000 rpm.
[0034] The automotive fuel composition in which the VI improving
additive is used, in accordance with the present invention, may in
particular be a diesel fuel composition suitable for use in a
diesel engine. It may be used in, and/or may be suitable and/or
adapted and/or intended for use in, any type of compression
ignition engine, for instance those described below.
[0035] Viscosity index improving additives (also referred to as VI
improvers) are already well known for use in lubricant
formulations, where they are used to maintain viscosity as constant
as possible over a desired temperature range by increasing
viscosity at higher temperatures. They are typically based on
relatively high molecular weight, long chain polymeric molecules
that can form conglomerates and/or micelles. These molecular
systems expand at higher temperatures, thus further restricting
their movement relative to one another and in turn increasing the
viscosity of the system.
[0036] The VI improving additives used in a fuel composition in
accordance with the present invention comprise polyisoprene-based
star polymers, especially styrene-isoprene star polymers.
[0037] Examples of suitable styrene-isoprene star polymers include
those disclosed in US2013/0165362, incorporated herein by reference
in its entirety. The star polymers disclosed in US2013/0165362 have
multiple triblock arms coupled to a central core, such as a
divinylbenzene (DVB) core, wherein the triblock arms contain a
block derived from monoalkenyl arene monomer positioned between two
partially or fully hydrogenated blocks derived from diene, wherein
at least one of the diene blocks is a copolymer derived from mixed
diene monomer, in which from about 65 wt % to about 95 wt % of the
incorporated monomer units are from isoprene and from about 5 wt %
up to about 35 wt % of the incorporated monomer units are from
butadiene, and wherein at least about 80 wt %, preferably at least
about 90 wt % butadiene is incorporated into the random copolymer
block in a 1,4-configuration.
[0038] Preferred viscosity index (VI) improver additives for use in
the fuel compositions are the star-shaped isoprene polymers
described in US2013/0165362 which can be characterized by the
formula:
(D'-PA-D'')n-X;
wherein D' represents an "outer" block derived from diene; PA
represents a block derived from monoalkenyl arene; D'' represents
an inner random derived from diene; n represents the average number
of arms per star polymer formed by the reaction of 2 or more moles
of a polyalkenyl coupling agent per mole of arms and X represents a
nucleus of a polyalkenyl coupling agent.
[0039] At least one of diene blocks D' and D'', preferably each of
diene blocks D' and D'', are copolymer blocks derived from mixed
diene monomer, in which from about 65 wt % to about 95 wt % of the
incorporated monomer units are from isoprene and from about 5 wt %
up to about 35 wt % of the incorporated monomer units are from
butadiene, and wherein at least about 80 wt % of butadiene,
preferably at least 90 wt % of the butadiene is incorporated in a
1,4-configuration. Preferably, at least about 15 wt % of the
incorporated monomer units are butadiene monomer units. Preferably,
no greater than about 28 wt % of the incorporated monomer units are
butadiene monomer units. Preferably, at least one of diene blocks
D' and D'', more preferably each of diene blocks D' and D'', are
random copolymer blocks. Blocks D' and D'' are preferably
hydrogenated to remove at least about 80% or 90% or 95% of
unsaturations, and more preferably, are fully hydrogenated.
[0040] Outer block D' has a number average molecular weight of from
about 10,000 to about 120,000 daltons, more preferably from about
20,000 to about 60,000 daltons, before hydrogenation. Block PA has
a number average molecular weight of from about 10,000 to about
50,000 daltons. Increasing the size of block PA can adversely
affect the thickening efficiency of the star polymer. Therefore,
the number average molecular weight of block PA is preferably from
about 12,000 to about 35,000 daltons. Inner block D'' has a number
average molecular weight of from about 5,000 to about 60,000
daltons, more preferably from about 10,000 to about 30,000 daltons,
before hydrogenation. The term "number average molecular weight",
as used herein, refers to the number average molecular weight as
measured by Gel Permeation Chromatography ("GPC") with a
polystyrene standard.
[0041] In the star polymers used herein, the ratio of the number
average molecular weight of outer block D' to the number average
molecular weight of inner block D'' is preferably at least about
1.4:1, such as at least about 1.9:1, more preferably at least about
2.0:1, and the ratio of the number average molecular weight of
block PA to the number average molecular weight of inner block D''
is preferably at least about 0.75:1, such as at least about 0.9:1,
more preferably at least about 1.0:1.
[0042] Preferably, no greater than 30 wt %, more preferably no
greater than 25 wt %, of the total amount of polydiene in the star
polymers is derived from butadiene. Preferably, at least about 80
wt %, more preferably at least about 90 wt %, of the total amount
of butadiene, which can be incorporated in the polymer as 1,2- or
1,4-configuration units, is incorporated into the star polymer is
incorporated in a 1,4-configuration. Increasing the percentage of
butadiene incorporated into the polymer as 1,4-units can increase
the thickening efficiency properties of the star polymer. An
excessive amount of polybutadiene, particularly polybutadiene
having a 1,2-configuration, can have an adverse effect on low
temperature pumpability properties.
[0043] Isoprene monomers used as the precursors of the copolymers
herein can be incorporated into the polymer in either a 1,4- or a
3,4-configuration, or a mixture thereof. Preferably, the majority
of the isoprene is incorporated into the polymer as 1,4-units, such
as greater than about 60 wt %, more preferably greater than about
80 wt %, such as about 80 wt % to 100 wt %, more preferably greater
than about 90 wt %, such as about 93 wt % to 100 wt %.
[0044] Suitable monoalkenyl arene monomers include monovinyl
aromatic compounds, such as styrene, monovinylnaphthalene, as well
as the alkylated derivatives thereof, such as o-, m- and
p-methylstyrene, alpha-methyl styrene and tertiary butyl styrene.
The preferred monoalkenyl arene is styrene.
[0045] Star polymers used herein can have from 4 to about 25 arms
(n=about 4 to about 25), preferably from about 10 to about 20 arms.
Star polymers used herein may have a total number average molecular
weight of about 100,000 to about 1,000,000 daltons, preferably from
about 400,000 to about 800,000 daltons, more preferably from about
500,000 to about 700,000 daltons.
[0046] Further details of the structure, properties and methods of
making these preferred star polymers, including various
polymerization preparation methods are disclosed in US2013/0165362,
incorporated herein by reference in its entirety.
[0047] Another suitable type of viscosity index (VI) improving
additive for use herein is a star-shaped polyisoprene polymer
comprising a crosslinked polystyrene core with arms of hydrogenated
polyisoprene or poly(alternated ethylene-propylene). An example of
such a polymer is SV300, commercially available from Infineum. As
disclosed in US2017/025370, SV300 contains 6% by weight of
crosslinked polystyrene star core with 30 arms of hydrogenated
polyisoprene, or poly(alternated ethylene-propylene), with overall
molecular weight of 875,000 and a hydrodynamic radius in PA04 (a
polyalphaolefin having a viscosity at 100.degree. C. of
approximately 4 mm.sup.2/s commercially available from Exxon Mobil)
of 25 nm.
[0048] The density of the viscosity index (VI) improving additive
for use herein at 15.6.degree. C. (ASTM D-4052) is 0.70 g/cm.sup.3
or greater, preferably 0.75 g/cm.sup.3 or greater.
[0049] Examples of commercially available viscosity index (VI)
improving additives suitable for use herein include those
commercially available from Infineum under the trade designations
SV300, SV600, SV260 and the like.
[0050] An especially preferred viscosity index (VI) improving
additive from the viewpoint of improving lubricity characteristics
of the fuel composition as well as providing improved power output
characteristics is SV600, commercially available from Infineum.
[0051] The VI improving additive may be pre-dissolved in a suitable
solvent, for example an oil such as a mineral oil or
Fischer-Tropsch derived hydrocarbon mixture; a fuel component
(which again may be either mineral or Fischer-Tropsch derived)
compatible with the fuel composition in which the additive is to be
used (for example a middle distillate fuel component such as a gas
oil or kerosene, when intended for use in a diesel fuel
composition); a poly alpha olefin; a so-called biofuel such as a
fatty acid alkyl ester (FAAE), a Fischer-Tropsch derived
biomass-to-liquid synthesis product, a hydrogenated vegetable oil,
a waste or algae oil or an alcohol such as ethanol; an aromatic
solvent; any other hydrocarbon or organic solvent; or a mixture
thereof. Preferred solvents for use in this context are mineral oil
based diesel fuel components and solvents, and Fischer-Tropsch
derived components such as the "XtL" components referred to below.
Biofuel solvents may also be preferred in certain cases.
[0052] The concentration of the VI improving additive in the fuel
composition may be up to 1% w/w (10,000 ppm), suitably up to 0.5%
w/w, in cases up to 0.4 or 0.3 or 0.25% w/w. It may be 0.001% w/w
or greater, preferably 0.01% w/w or greater, suitably 0.02 or 0.03
or 0.04 or 0.05% w/w or greater, in cases 0.1 or 0.2% w/w or
greater. Suitable concentrations may for instance be from 0.001 to
1% w/w, or from 0.001 to 0.5% w/w, or from 0.05 to 0.5% w/w, or
from 0.05 to 0.25% w/w, for example from 0.05 to 0.25% w/w or from
0.1 to 0.2% w/w.
[0053] The remainder of the composition will typically consist of
one or more automotive base fuels, for instance as described in
more detail below, optionally together with one or more fuel
additives.
[0054] The above concentrations are for the VI improving additive
itself, and do not take account of any solvent(s) with which its
active ingredient is pre-diluted. They are based on the mass of the
overall fuel composition. Two or more VI improving additives can be
used in the fuel composition herein. Where a combination of two or
more VI improving additives is used in the composition, the same
concentration ranges may apply to the overall combination, again
minus any pre-solvent(s) present.
[0055] The concentration of the VI improving additive will depend
on the desired viscosity of the overall fuel composition, the
viscosity of the composition prior to incorporation of the
additive, the viscosity of the additive itself and the viscosity of
any solvent in which the additive is used. The relative proportions
of the VI improving additive, fuel component(s) and any other
components or additives present, in an automotive fuel composition
prepared according to the present invention, may also depend on
other desired properties such as density, emissions performance and
cetane number, in particular density.
[0056] It has surprisingly been found that the VI improving
additive described herein can increase the lubricity of the fuel
composition, as well as increasing the power output and/or
acceleration characteristics.
[0057] Due to the inclusion of the VI improving additive, a fuel
composition prepared according to the present invention (in
particular a diesel fuel composition) will suitably have a VK 40 of
2.7 or 2.8 mm.sup.2/s or greater, preferably 2.9 or 3.0 or 3.1 or
3.2 or 3.3 or 3.4 mm.sup.2/s or greater, in cases 3.5 or 3.6 or 3.7
or 3.8 or 3.9 or even 4 mm.sup.2/s or greater. Its VK 40 may be up
to 4.5 or 4.4 or 4.3 mm.sup.2/s. In certain cases, for example
arctic diesel fuels, the VK 40 of the composition may be as low as
1.5 mm.sup.2/s, although it is preferably 1.7 or 2.0 mm.sup.2/s or
greater. References in this specification to viscosity are, unless
otherwise specified, intended to mean kinematic viscosity.
[0058] The composition preferably has a relatively high density,
for example for a diesel fuel composition 830 kg/m.sup.3 or greater
at 15.degree. C. (ASTM D-4052 or EN ISO 3675), preferably 832
kg/m.sup.3 or greater, such as from 832 to 860 kg/m.sup.3. Suitably
its density will be no higher than 845 kg/m.sup.3 at 15.degree. C.,
which is the upper limit of the current EN 590 diesel fuel
specification.
[0059] A fuel composition prepared according to the present
invention may be for example an automotive gasoline or diesel fuel
composition, in particular the latter.
[0060] A gasoline fuel composition prepared according to the
present invention may in general be any type of gasoline fuel
composition suitable for use in a spark ignition (petrol) engine.
It may contain, in addition to the VI improving additive, other
standard gasoline fuel components. It may, for example, include a
major proportion of a gasoline base fuel, which will typically have
a boiling range (ASTM D-86 or EN ISO 3405) of from 20 to
210.degree. C. A "major proportion" in this context means typically
85% w/w or greater based on the overall fuel composition, more
suitably 90 or 95% w/w or greater, most preferably 98 or 99 or
99.5% w/w or greater.
[0061] A diesel fuel composition prepared according to the present
invention may in general be any type of diesel fuel composition
suitable for use in a compression ignition (diesel) engine. It may
contain, in addition to the VI improving additive, other standard
diesel fuel components. It may, for example, include a major
proportion of a diesel base fuel, for instance of the type
described below. Again a "major proportion" means typically 85% w/w
or greater based on the overall composition, more suitably 90 or
95% w/w or greater, most preferably 98 or 99 or 99.5% w/w or
greater.
[0062] Thus, in addition to the VI improving additive, a diesel
fuel composition prepared according to the present invention may
comprise one or more diesel fuel components of conventional type.
Such components will typically comprise liquid hydrocarbon middle
distillate fuel oil(s), for instance petroleum derived gas oils. In
general such fuel components may be organically or synthetically
derived, and are suitably obtained by distillation of a desired
range of fractions from a crude oil. They will typically have
boiling points within the usual diesel range of 150 to 410.degree.
C. or 170 to 370.degree. C., depending on grade and use. Typically
the fuel composition will include one or more cracked products,
obtained by splitting heavy hydrocarbons.
[0063] A petroleum derived gas oil may for instance be obtained by
refining and optionally (hydro)processing a crude petroleum source.
It may be a single gas oil stream obtained from such a refinery
process or a blend of several gas oil fractions obtained in the
refinery process via different processing routes. Examples of such
gas oil fractions are straight run gas oil, vacuum gas oil, gas oil
as obtained in a thermal cracking process, light and heavy cycle
oils as obtained in a fluid catalytic cracking unit and gas oil as
obtained from a hydrocracker unit. Optionally a petroleum derived
gas oil may comprise some petroleum derived kerosene fraction.
[0064] Such gas oils may be processed in a hydrodesulphurisation
(HDS) unit so as to reduce their sulphur content to a level
suitable for inclusion in a diesel fuel composition.
[0065] A diesel base fuel may be or comprise a Fischer-Tropsch
derived diesel fuel component, typically a Fischer-Tropsch derived
gas oil. In the context of the present invention, the term
"Fischer-Tropsch derived" means that a material is, or derives
from, a synthesis product of a Fischer-Tropsch condensation
process. The term "non-Fischer-Tropsch derived" may be interpreted
accordingly. A Fischer-Tropsch derived fuel or fuel component will
therefore be a hydrocarbon stream in which a substantial portion,
except for added hydrogen, is derived directly or indirectly from a
Fischer-Tropsch condensation process.
[0066] 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. 0.5 to 10 MPa, preferably
1.2 to 5 MPa). Hydrogen:carbon monoxide ratios other than 2:1 may
be employed if desired.
[0067] The carbon monoxide and hydrogen may themselves be derived
from organic, inorganic, natural or synthetic sources, typically
either from natural gas or from organically derived methane.
[0068] A Fischer-Tropsch derived diesel fuel component of use in
the present invention may be obtained directly from the refining or
the Fischer-Tropsch reaction, or indirectly for instance by
fractionation or hydrotreating of the refining or synthesis product
to give a fractionated or hydrotreated product. Hydrotreatment can
involve hydrocracking to adjust the boiling range (see e.g.
GB-B-2077289 and EP-A-0147873) and/or hydroisomerisation which can
improve cold flow properties by increasing the proportion of
branched paraffins. EP-A-0583836 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
fraction(s), typically gas oil fraction(s), may subsequently be
isolated for instance by distillation.
[0069] Other post-synthesis treatments, such as polymerisation,
alkylation, distillation, cracking-decarboxylation, isomerisation
and hydroreforming, may be employed to modify the properties of
Fischer-Tropsch condensation products, as described for instance in
U.S. Pat. Nos. 4,125,566 and 4,478,955.
[0070] Typical catalysts for the Fischer-Tropsch synthesis of
paraffinic hydrocarbons comprise, as the catalytically active
component, a metal from Group VIII of the periodic table of the
elements, in particular ruthenium, iron, cobalt or nickel. Suitable
such catalysts are described for instance in EP-A-0583836.
[0071] An example of a Fischer-Tropsch based process is the
Shell.TM. "Gas-to-liquids" or "GtL" technology (formerly known as
the SMDS (Shell Middle Distillate Synthesis) and described in "The
Shell Middle Distillate Synthesis Process", van der Burgt et al,
paper delivered at the 5th Synfuels Worldwide Symposium, Washington
D.C., November 1985, and in the November 1989 publication of the
same title from Shell International Petroleum Company Ltd, London,
UK). In the latter case, preferred features of the hydroconversion
process may be as disclosed therein. This process produces middle
distillate range products by conversion of a natural gas into a
heavy long chain hydrocarbon (paraffin) wax which can then be
hydroconverted and fractionated.
[0072] For use in the present invention, a Fischer-Tropsch derived
fuel component is preferably any suitable component derived from a
gas to liquid synthesis (hereinafter a GtL component), or a
component derived from an analogous Fischer-Tropsch synthesis, for
instance converting gas, biomass or coal to liquid (hereinafter an
XtL component). A Fischer-Tropsch derived component is preferably a
GtL component. It may be a BtL (biomass to liquid) component. In
general a suitable XtL component may be a middle distillate fuel
component, for instance selected from kerosene, diesel and gas oil
fractions as known in the art; such components may be generically
classed as synthetic process fuels or synthetic process oils.
Preferably an XtL component for use as a diesel fuel component is a
gas oil.
[0073] Diesel fuel components contained in a composition prepared
according to the present invention will typically have a density of
from 750 to 900 kg/m.sup.3, preferably from 800 to 860 kg/m.sup.3,
at 15.degree. C. (ASTM D-4052 or EN ISO 3675) and/or a VK 40 of
from 1.5 to 6.0 mm.sup.2/s (ASTM D-445 or EN ISO 3104).
[0074] In a diesel fuel composition prepared according to the
present invention, the base fuel may itself comprise a mixture of
two or more diesel fuel components of the types described above. It
may be or contain a so-called "biodiesel" fuel component such as a
vegetable oil, hydrogenated vegetable oil or vegetable oil
derivative (e.g. a fatty acid ester, in particular a fatty acid
methyl ester) or another oxygenate such as an acid, ketone or
ester. Such components need not necessarily be bio-derived.
[0075] An automotive diesel fuel composition prepared according to
the present invention will suitably comply with applicable current
standard specification(s) such as for example EN 590 (for Europe)
or ASTM D-975 (for the USA). By way of example, the overall fuel
composition may have a density from 820 to 845 kg/m.sup.3 at
15.degree. C. (ASTM D-4052 or EN ISO 3675); a T95 boiling point
(ASTM D-86 or EN ISO 3405) of 360.degree. C. or less; a measured
cetane number (ASTM D-613) of 51 or greater; a VK 40 (ASTM D-445 or
EN ISO 3104) from 2 to 4.5 mm.sup.2/s; a sulphur content (ASTM
D-2622 or EN ISO 20846) of 50 mg/kg or less; and/or a polycyclic
aromatic hydrocarbons (PAH) content (IP 391(mod)) of less than 11%
w/w. Relevant specifications may, however, differ from country to
country and from year to year, and may depend on the intended use
of the fuel composition.
[0076] A diesel fuel composition prepared according to the present
invention suitably contains no more than 5000 ppmw (parts per
million by weight) of sulphur, typically from 2000 to 5000 ppmw, or
from 1000 to 2000 ppmw, or alternatively up to 1000 ppmw. The
composition may, for example, be a low or ultra low sulphur fuel,
or a sulphur free fuel, for instance containing at most 500 ppmw,
preferably no more than 350 ppmw, most preferably no more than 100
or 50 or even 10 ppmw, of sulphur.
[0077] An automotive fuel composition prepared according to the
present invention, or a base fuel used in such a composition, may
be additivated (additive-containing) or unadditivated
(additive-free). If additivated, e.g. at the refinery, it will
contain minor amounts of one or more additives selected for example
from anti-static agents, pipeline drag reducers, flow improvers
(e.g. ethylene/vinyl acetate copolymers or acrylate/maleic
anhydride copolymers), lubricity additives (other than the VI
improving additive described hereinabove), antioxidants and wax
anti-settling agents. Thus, the composition may contain a minor
proportion (preferably 1% w/w or less, more preferably 0.5% w/w
(5000 ppmw) or less and most preferably 0.2% w/w (2000 ppmw) or
less), of one or more fuel additives, in addition to the VI
improving additive.
[0078] The composition may for example contain a detergent.
Detergent-containing diesel fuel additives are known and
commercially available. Such additives may be added to diesel fuels
at levels intended to reduce, remove or slow the build up of engine
deposits.
[0079] Examples of detergents suitable for use in fuel additives
for the present purpose include polyolefin substituted succinimides
or succinamides of polyamines, for instance polyisobutylene
succinimides or polyisobutylene amine succinamides, aliphatic
amines, Mannich bases or amines and polyolefin (e.g.
polyisobutylene) maleic anhydrides. Succinimide dispersant
additives are described for example in GB-A-960493, EP-A-0147240,
EP-A-0482253, EP-A-0613938, EP-A-0557516 and WO-A-98/42808.
Particularly preferred are polyolefin substituted succinimides such
as polyisobutylene succinimides.
[0080] A fuel additive mixture useable in a fuel composition
prepared according to the present invention may contain other
components in addition to the detergent. Examples are lubricity
enhancers; dehazers, e.g. alkoxylated phenol formaldehyde polymers;
anti-foaming agents (e.g. polyether-modified polysiloxanes);
ignition improvers (cetane improvers) (e.g. 2-ethylhexyl nitrate
(EHN), cyclohexyl nitrate, di-tert-butyl peroxide and those
disclosed in U.S. Pat. No. 4,208,190 at column 2, line 27 to column
3, line 21); anti-rust agents (e.g. a propane-1,2-diol semi-ester
of tetrapropenyl succinic acid, or polyhydric alcohol esters of a
succinic acid derivative, the succinic acid derivative having on at
least one of its alpha-carbon atoms an unsubstituted or substituted
aliphatic hydrocarbon group containing from 20 to 500 carbon atoms,
e.g. the pentaerythritol diester of polyisobutylene-substituted
succinic acid); corrosion inhibitors; reodorants; anti-wear
additives; antioxidants (e.g. phenolics such as
2,6-di-tert-butylphenol, or phenylenediamines such as
N,N'-di-sec-butyl-p-phenylenediamine); metal deactivators;
combustion improvers; static dissipator additives; cold flow
improvers; and wax anti-settling agents.
[0081] Such a fuel additive mixture may contain a lubricity
enhancer (in addition to the viscosity improving (VI) additive
described hereinabove), especially when the fuel composition has a
low (e.g. 500 ppmw or less) sulphur content. In the additivated
fuel composition, the lubricity enhancer is conveniently present at
a concentration of less than 1000 ppmw, preferably between 50 and
1000 ppmw, more preferably between 70 and 1000 ppmw. Suitable
commercially available lubricity enhancers include ester- and
acid-based additives. Other lubricity enhancers are described in
the patent literature, in particular in connection with their use
in low sulphur content diesel fuels, for example in: [0082] the
paper by Danping Wei and H. A. Spikes, "The Lubricity of Diesel
Fuels", Wear, III (1986) 217-235; [0083] WO-A-95/33805--cold flow
improvers to enhance lubricity of low sulphur fuels; [0084]
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; [0085] U.S. Pat. No.
5,490,864--certain dithiophosphoric diester-dialcohols as anti-wear
lubricity additives for low sulphur diesel fuels; and [0086]
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.
[0087] Since inclusion of the viscosity improving (VI) additives
disclosed hereinabove can improve the lubricity of the fuel
composition, an advantage of the present invention is that the
amount of other lubricity additives can be reduced or even
eliminated.
[0088] It may also be preferred for the fuel composition to contain
an anti-foaming agent, more preferably in combination with an
anti-rust agent and/or a corrosion inhibitor and/or a lubricity
enhancing additive.
[0089] Unless otherwise stated, the (active matter) concentration
of each such additive component in the additivated fuel composition
is preferably up to 10000 ppmw, more preferably in the range of 0.1
to 1000 ppmw, advantageously from 0.1 to 300 ppmw, such as from 0.1
to 150 ppmw.
[0090] The (active matter) concentration of any dehazer in the fuel
composition will preferably be in the range from 0.1 to 20 ppmw,
more preferably from 1 to 15 ppmw, still more preferably from 1 to
10 ppmw, advantageously from 1 to 5 ppmw. The (active matter)
concentration of any ignition improver present will preferably be
2600 ppmw or less, more preferably 2000 ppmw or less, conveniently
from 300 to 1500 ppmw. The (active matter) concentration of any
detergent in the fuel composition will preferably be in the range
from 5 to 1500 ppmw, more preferably from 10 to 750 ppmw, most
preferably from 20 to 500 ppmw.
[0091] If desired, one or more additive components, such as those
listed above, may be co-mixed--preferably together with suitable
diluent(s)--in an additive concentrate, and the additive
concentrate may then be dispersed into a base fuel or fuel
composition. The VI improving additive may, in accordance with the
present invention, be incorporated into such an additive
formulation.
[0092] In the case of a diesel fuel composition, for example, the
fuel additive mixture will typically contain a detergent,
optionally together with other components as described above, and a
diesel fuel-compatible diluent, which may be a mineral oil, a
solvent such as those sold by Shell companies under the trade mark
"SHELLSOL", a polar solvent such as an ester and, in particular, an
alcohol, e.g. hexanol, 2-ethylhexanol, decanol, isotridecanol and
alcohol mixtures such as those sold by Shell companies under the
trade mark "LINEVOL", especially LINEVOL 79 alcohol which is a
mixture of C.sub.7-9 primary alcohols, or a C.sub.12-14 alcohol
mixture which is commercially available.
[0093] The total content of the additives in the fuel composition
may be suitably between 0 and 10000 ppmw and preferably below 5000
ppmw.
[0094] In this specification, amounts (concentrations, % v/v, ppmw,
% w/w) of components are of active matter, i.e. exclusive of
volatile solvents/diluent materials.
[0095] Different types and/or concentrations of additives may be
appropriate for use in gasoline fuel compositions, which for
example may contain polyisobutylene/amine and/or
polyisobutylene/amide copolymers as detergent additives.
[0096] Suitably, the VI improving additive, and the concentration
at which it is used in the fuel composition, will be such as to
cause an increase in the cold filter plugging point (CFPP) of the
composition of 10.degree. C. or less, preferably 5 or 2 or
1.degree. C. or less. Preferably it will be such as to cause no
increase in CFPP. In cases it may be such as to cause a decrease in
CFPP. Increases in CFPP may be as compared to the CFPP of the fuel
composition prior to incorporation of the VI improving additive.
They may be as compared to the CFPP of an otherwise analogous fuel
composition which is intended (e.g. marketed) for use in an
internal combustion (in particular diesel) engine, prior to adding
a VI improving additive to it. CFPPs may be measured using the
standard test method EN 116.
[0097] Suitably, the VI improving additive, and the concentration
at which it is used in the fuel composition, will be such as to
cause an increase in the cloud point of the composition of
10.degree. C. or less, preferably 5 or 2 or 1.degree. C. or less.
Preferably it will be such as to cause no increase in cloud point.
In cases it may be such as to cause a decrease in cloud point.
Increases in cloud point may be as compared to that of the fuel
composition prior to incorporation of the VI improving additive.
They may be as compared to the cloud point of an otherwise
analogous fuel composition which is intended (e.g. marketed) for
use in an internal combustion (in particular diesel) engine, prior
to adding a VI improving additive to it. Cloud points may be
measured using the standard test method EN 23015.
[0098] In the context of the present invention, "use" of a VI
improving additive in a fuel composition means incorporating the VI
improving additive into the composition, typically as a blend (i.e.
a physical mixture) with one or more fuel components (typically
diesel base fuels) and optionally with one or more fuel additives.
The VI improving additive is conveniently incorporated before the
composition is introduced into an engine which is to be run on the
composition. Instead or in addition the use may involve running an
engine on the fuel composition containing the VI improving
additive, typically by introducing the composition into a
combustion chamber of the engine.
[0099] "Use" of a VI improving additive, in accordance with the
present invention, may also embrace supplying such an additive
together with instructions for its use in an automotive fuel
composition to achieve one or more of the purpose(s) described
above, in particular to improve the acceleration performance of an
internal combustion (typically diesel) engine into which the
composition is, or is intended to be, introduced.
[0100] The VI improving additive may itself be supplied as a
component of a formulation which is suitable for and/or intended
for use as a fuel additive, in particular a diesel fuel additive,
in which case the VI improving additive may be included in such a
formulation for the purpose of influencing its effects on the
lubricity of an automotive fuel composition, and/or its effects on
the acceleration performance and/or power output of an engine into
which a fuel composition is, or is intended to be, introduced.
[0101] Thus, the VI improving additive may be incorporated into an
additive formulation or package along with one or more other fuel
additives. It may, for instance, be combined, in an additive
formulation, with one or more fuel additives selected from
detergents, anti-corrosion additives, esters, poly alpha olefins,
long chain organic acids, components containing amine or amide
active centres, and mixtures thereof. In particular, it may be
combined with one or more so-called performance additives, which
will typically include at least a detergent.
[0102] The VI improving additive may be dosed directly into a fuel
component or composition, for example at the refinery. It may be
pre-diluted in a suitable fuel component which subsequently forms
part of the overall automotive fuel composition.
[0103] In accordance with the present invention, two or more VI
improving additives may be used in an automotive fuel composition
for the purpose(s) described above.
[0104] According to a further aspect of the present invention,
there is provided a process for the preparation of an automotive
fuel composition, which process involves blending an automotive
base fuel with a VI improving additive, wherein the VI improving
additive is a star-shaped isoprene polymer. The blending may be
carried out for one or more of the purposes described above, in
particular with respect to the lubricity of the resultant fuel
composition and/or its effect on the acceleration performance
and/or power output of an internal combustion engine into which it
is, or is intended to be, introduced. The composition may in
particular be a diesel fuel composition.
[0105] The VI improving additive may, for example, be blended with
other components of the composition, in particular the base fuel,
at the refinery. Alternatively, it may be added to an automotive
fuel composition downstream of the refinery. It may be added as
part of an additive package which contains one or more other fuel
additives.
[0106] A further aspect of the present invention provides a method
of operating an internal combustion engine, and/or a vehicle which
is powered by such an engine, which method involves introducing
into a combustion chamber of the engine a fuel composition
described hereinabove. Again the fuel composition is preferably
introduced for one or more of the purposes described in connection
with the present invention. Thus, the engine is preferably operated
with the fuel composition for the purpose of improving its
lubricity and/or acceleration performance and/or power output.
[0107] Again the engine may in particular be a diesel engine. It
may be a turbo charged engine, in particular a turbo charged diesel
engine. The diesel engine may be of the direct injection type, for
example of the rotary pump, in-line pump, unit pump, electronic
unit injector or common rail type, or of the indirect injection
type. It may be a heavy or a light duty diesel engine. It may in
particular be an electronic unit direct injection (EUDI)
engine.
[0108] Throughout the description and claims of this specification,
the words "comprise" and "contain" and variations of the words, for
example "comprising" and "comprises", mean "including but not
limited to", and do not exclude other moieties, additives,
components, integers or steps.
[0109] Throughout the description and claims of this specification,
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.
[0110] Preferred features of each aspect of the present invention
may be as described in connection with any of the other
aspects.
[0111] Other features of the present invention will become apparent
from the following examples. Generally speaking, the present
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 present invention are to be understood to be applicable to any
other aspect, embodiment or example described herein unless
incompatible therewith.
[0112] Moreover, unless stated otherwise, any feature disclosed
herein may be replaced by an alternative feature serving the same
or a similar purpose.
[0113] The following examples illustrate the properties of
automotive fuel compositions prepared according to the present
invention, and assess the effects of such compositions on the
performance of a diesel engine.
EXAMPLES
[0114] Fuel blends were prepared by combining a diesel base fuel
(meeting the European diesel fuel specification EN590) with a
viscosity index (VI) improving additive. The viscosity index (VI)
additives used in the present experiments were SV150, SV260, SV300
and SV600, at a treat rate of either 500 mg/kg or 1000 mg/kg.
[0115] SV150 is a linear, di-block polymer commercially available
from Infineum and is used in the present examples as a
comparison.
[0116] SV260 is a star-shaped styrene-polyisoprene polymer
commercially available from Infineum.
[0117] SV300 is a star-shaped styrene-polyisoprene polymer
commercially available from Infineum.
[0118] SV600 is a star-shaped styrene-polyisoprene polymer
commercially available from Infineum.
[0119] Before being added to the diesel base fuel, the VI improving
additives were pre-blended with Shellsol A150 solvent (commercially
available from Shell). The weight ratio of VI improving additive to
Shellsol A150 was 1:8.
[0120] The fuel specification of the diesel base fuel used in the
present examples is shown in Table 1 below.
TABLE-US-00001 TABLE 1 Specification of Diesel Base Fuel (CEC
RF-79-07) Limits Property Units Min. Max. Cetane Number -- 52.0
54.0 Density at 15.degree. C. kg/m.sup.3 833.0 837.0 Distillation
IBP .degree. C. -- -- Distillation 10% v/v .degree. C. -- --
Distillation 50% v/v .degree. C. 245.0 -- Distillation 90% v/v
.degree. C. -- -- Distillation 95% v/v .degree. C. 345.0 350.0
Distillation FBP .degree. C. -- 370.0 Flash Point .degree. C. 62 --
CFPP .degree. C. -- -5 Viscosity at 40.degree. C. mm.sup.2/ s 2300
3300 Aromatics, Total % wt -- -- Aromatics, Mono % wt -- --
Aromatics, Di Wt % -- -- Aromatics, Tri+ Wt % -- -- Aromatics, Poly
% wt 3.0 6.0 (2 + 3) Sulfur mg/kg -- 10 Corrosion - Copper -- Max 1
Carbon Residue on % wt 0.2 10% Distillation Residue Ash Content %
wt -- 0.010 Water % wt -- 0.0200 Strong Acid Number mg/KOH/g --
0.02 Oxidation Stability mg/mL -- 0.025 Carbon % wt -- -- Hydrogen
% wt -- -- C:H Ratio (H = 1) -- -- H:C Ratio (C = 1) -- -- Net
Heating Value MJ/kg -- -- Net Heating Value Btu/lb -- -- HFRR (wsd
1, 4) .mu.m -- 400 Element Analysis -- Al mg/kg -- 0.1 Ag mg/kg --
0.1 B mg/kg -- 0.1 Ba mg/kg -- 0.1 Ca mg/kg -- 0.1 Cd mg/kg -- 0.1
Ce mg/kg -- 0.1 Cr mg/kg -- 0.1 Cu mg/kg -- 0.1 Fe mg/kg -- 0.1 K
mg/kg -- 0.1 Mg mg/kg -- 0.1 Sn mg/kg -- 0.1 Mn mg/kg -- 0.1 Mo
mg/kg -- 0.1 Na mg/kg -- 0.1 Ni mg/kg -- 0.1 P mg/kg -- 0.1 Pb
mg/kg -- 0.1 Si mg/kg -- 0.1 Sn mg/kg -- 0.1 Ti mg/kg -- 0.1 V
mg/kg -- 0.1 Ni mg/kg -- 0.1 Zn mg/kg -- 0.1
Demonstration of Power Benefit
[0121] The fuel blends described above, containing a VI additive
pre-blended in Shellsol A150, were used in a bench test engine in
order to assess the effects of the VI improving additive on the
power performance of an engine. The bench test engine chosen for
this study was a PSA DW10B. This engine is specified in CEC
F-98-09, the industry standard test for injector nozzle fouling in
modern DI car engines, and as such there is a vast amount of
historical test data available supporting the performance and
characteristics of the engine. DW10B test details are listed in
Table 2 below:
TABLE-US-00002 TABLE 2 Manufacturer Peugeot Engine Code DW10XE
Displacement (ltr)/layout 2.0/In line 4 Max Power (kW) @ (rpm) 100
kW@4000 r/min Max Torque (Nm) (rpm) 320 Nm@2000 r/min Injection
Type/Manufacturer Common Rail (CR)/Continental, 1600 bar EMS
Manufacturer Continental Emissions Class Euro 4 Lubricant Shell
Helix Ultra
[0122] A constant test speed of 4000 r/min was used and maximum
accelerator pedal position (100% APP) was applied using DW10B CEC
specification nozzles. The engine was run in cycles of 24 minutes
per fuel, alternating between base fuel without additive and
candidate fuel, and the power output was measured. The results of
the power testing are set out in Table 3 below. The power benefit
(%) is compared to the unadditised base fuel (containing Shellsol
A150) (designated as Example 1 in Table 3).
Demonstration of Lubricity
[0123] The fuel blends were also subjected to an HFRR test
(according to ISO 12156) in order to measure their lubricity. The
HFRR (High Friction Reciprocating Rig) is a controlled
reciprocating friction and wear testing device employed to assess
the lubricity performance of fuels and lubricants. The test uses a
6 mm diameter steel ball loaded and reciprocated against the flat
surface of a stationary steel disc immersed in fuel. At the end of
each test, the ball and disc are removed from the test rig, rinsed
with toluene and iso-propanol, and then treated with a 0.05 wt %
solution of ethylenediaminetetraacetic acid (EDTA) for 60 s.
Topography images were then obtained and analysed to determine wear
volumes of the wear scars on the ball and the disc using the SWLI
Veeco Wyko model NT9100. The instrument was set in Vertical
Scanning Interferometry (VSI) mode, calibrated to measure rough
surfaces with a nanometer detection range. The results of the HFRR
tests are set out in Table 4 below. The % change in wear scar
diameter is compared to the unadditised base fuel (containing
Shellsol A150) (designated in Table 4 as Example 8). A negative
result in % change denotes a benefit.
TABLE-US-00003 TABLE 3 ppm of Shellsol Dose of VII Power Benefit
E.g. A150 VII (mg/kg) (%) 1* 8000 -- -- -- 2 8000 SV150 1000 0.46 3
4000 SV150 500 0.20 4 8000 SV300 1000 0.67 5 4000 SV300 500 0.35 6
8000 SV600 1000 0.36 7 4000 SV600 500 0.09 ppm of Wear scar Delta
wear scar Lubricity Shellsol Dose of VII diameter diameter (%
change in wear E.g. A150 VII (mg/kg) (.mu.m) (.mu.m) scar diameter)
8* 8000 -- -- 359 -- -- 9 8000 SV150 1000 339 -20 -5.6 10 4000
SV150 500 346 -13 -3.6 11 8000 SV300 1000 349 -10 -2.8 12 4000
SV300 500 320 -39 -10.9 13 8000 SV600 1000 192 -167 -46.5 14 4000
SV600 500 331 -28 -7.8 15 8000 SV260 1000 298 -61 -17.0 *Not
according to the present invention
DISCUSSION
[0124] The fuel blend which contained the star-shaped
styrene-polyisoprene polymer SV300 showed a significant increase in
power benefit (both at 1000 mg/kg and 500 mg/kg) (see Examples 4
and 5) compared with the fuel blends which contained the linear,
di-block polymer SV150 (see Examples 2 and 3).
[0125] The fuel blend which contained the star-shaped
styrene-polyisoprene polymer SV600 at 1000 mg/kg showed an increase
in power benefit compared to the base fuel (see Examples 6 and 7).
Although the fuel blend containing the star-shaped
styrene-polyisoprene polymer SV600 at 1000 mg/kg did not show as
large a power benefit as the fuel blend containing the linear,
di-block polymer SV150, it exhibited significantly better lubricity
performance (see Examples 6 and 13).
[0126] The fuel blend which contained 1000 mg/kg of the star-shaped
styrene-polyisoprene polymer SV260 (Example 15) showed improved
lubricity performance compared to the fuel blend containing 1000
mg/kg of SV150 (Example 9).
* * * * *