Note: Descriptions are shown in the official language in which they were submitted.
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FUEL COMPOSITIONS
The present invention relates to the use of certain
types of additive in fuel compositions containing
distillate fuels, for new purposes.
It is known to include cold flow additives in fuel
compositions containing distillate fuels, in particular
middle distillate fuels such as diesel fuel compositions,
so as to improve their performance at low temperatures.
This is done in particular for "winter" fuel compositions
which are intended for use in colder climates and/or at
colder times of the year. Known cold flow additives
include middle distillate flow improvers and wax
anti-settling agents.
It is also common to include detergent additives in
such fuel compositions, for the purpose of reducing,
removing or slowing the build-up of engine deposits.
It has been found, however, that the effects of cold
flow additives can be detrimentally affected by the
inclusion of detergent additives in a fuel composition
containing a distillate fuel. A detergent additive can in
cases deactivate (at least partially) a cold flow additive,
the combination of the two causing impaired cold flow
performance compared to that of the fuel composition
without the detergent additive.
It is an aim of the present invention to provide fuel
compositions containing distillate fuels, and/or additives
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for use in such compositions, which can overcome or at least
mitigate the above described problems.
According to a first aspect of the present invention
there is provided the use, in a fuel composition containing
a distillate fuel, a detergent additive and a cold flow
additive, of a further additive selected from:
(a) acids, in particular acids selected from carboxylic
acids or sulphonic acids, and especially carboxylic acids,
and mixtures thereof ; and
(b) lubricity enhancing additives, in particular
selected from carboxylic acids or carboxylic acid
derivatives for the purpose of reducing the effect of the
detergent additive on the cold flow performance of the
composition.
A second aspect of the present invention provides the
use, in a fuel composition containing a distillate fuel, a
detergent additive and a cold flow additive, of a further
additive as defined above, for the purpose of improving the
cold flow performance of the composition.
A third aspect of the present invention provides the
use, in a fuel composition containing a distillate fuel, a
detergent additive and a cold flow additive, of a further
additive as defined above, for the purpose of increasing the
concentration of detergent additive in the composition
either without impairing the cold flow performance of the
composition or with reduced impairment of the cold flow
performance compared to that which would otherwise be caused
by the increase in detergent additive concentration.
In the context of this third aspect of the present
invention, the term "increasing" embraces any degree of
increase, for instance 1 =6 or more of the original detergent
additive concentration, preferably 2 or 5 or 10 or 20 96 or
more. The increase may be as compared to the
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concentration of detergent additive which would otherwise
have been incorporated into the fuel composition in order
to achieve the properties and performance required and/or
desired of it in the context of its intended use. This may
for instance be the concentration of detergent additive
which was present in the fuel composition prior to the
realisation that a further additive could be used in the
way provided by the present invention, and/or which was
present in an otherwise analogous fuel composition intended
(e.g. marketed) for use in an analogous context, prior to
adding a further additive to it.
According to a fourth aspect of the present invention,
there is provided a method for formulating a fuel
composition, the method comprising (i) blending together a
distillate base fuel, a detergent additive and a cold flow
additive, optionally with other fuel components, (ii)
measuring the cold flow performance of the resultant blend
and (iii) incorporating a further additive as defined
above, in an amount sufficient to improve the cold flow
performance of the blend. This method may also involve
measuring the cold flow performance of the base fuel and
the cold flow additive, measuring the change in cold flow
performance as a result of incorporating the detergent
additive, and incorporating the further additive in an
amount sufficient to counter, at least partly and
preferably completely, any detrimental effect of the
detergent additive on the cold flow performance of the base
fuel/cold flow additive blend.
A fifth aspect of the present invention provides the
use of a further additive as defined above, in a fuel
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c ompositi on containing a distillate fuel, a detergent
additive and a cold flow additive, for the purpose of
reducing the amount of cold flow additive in the
composition. Since the further additive may be used to
counter, at least partly, any detrimental effect of the
detergent additive on cold flow performance, it potentially
enables lower levels of cold flow additive to be used in
order to achieve a desired target level of cold flow
performance in the overall composition.
In the context of this fifth aspect of the present
invention, the term "reducing" embraces any degree of
reduction - for instance 1% or more of the original cold
flow additive concentration, preferably 2 or 5 or 10 or 20%
or more - although suitably not reduction to zero. The
reduction may be as compared to the concentration of cold
flow additive which would otherwise have been incorporated
into the fuel composition in order to achieve the
properties and performance required and/or desired of it in
the context of its intended use. This may for instance be
the concentration of cold flow additive which was present
in the fuel composition prior to the realisation that a
further additive could be used in the way provided by the
present invention, and/or which was present in an otherwise
analogous fuel composition intended (e.g. marketed) for use
in an analogous context, prior to adding a further additive
to it.
In the case for example of a diesel fuel composition
intended for use in an automotive engine, a certain level
of cold flow performance may be desirable in order for the
composition to meet current fuel specifications, and/or to
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s a f eguard engine performance, and/or to satisfy consumer
demand, in particular in cold climates or seasons.
According to the present invention, such standards may
still be achievable even with reduced levels of cold flow
additives, due to the further additive reducing the
negative impact of any detergent additives present.
In the following description, the term "distillate
fuel composition" is used to mean a fuel composition
containing a distillate fuel, typically a middle distillate
fuel. Such a composition may contain 0.1 %v/v or more of a
distillate fuel, suitably 1 or 2 or 5 %v/v or more,
preferably 5 or 10 or 25 or 50 %v/v or more, typically 75
or 80 or 90 or 95 %v/v or more, in each case the distillate
fuel preferably being a middle distillate fuel. The
distillate fuel may itself comprise two or more fuel
components. Most preferably, a fuel composition prepared
according to the present invention is, overall, a middle
distillate fuel.
Middle distillate fuel compositions for which the
present invention is used may include for example heating
oils, industrial gas oils, automotive diesel fuels,
distillate marine fuels or kerosene fuels such as aviation
fuels or heating kerosene. Typically the composition will
be either an automotive diesel fuel or a heating oil.
Preferably, the fuel composition to which the present
invention is applied is for use in an internal combustion
engine; more preferably, it is an automotive fuel
composition, yet more preferably a diesel fuel composition
which is suitable for use in an automotive diesel
(compression ignition) engine.
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The fuel composition may in particular be adapted for,
and/or intended for, use in colder climates and/or during
colder seasons (for example, it may be a so-called "winter
fuel").
In the context of the present invention, a distillate
fuel composition will typically contain a major proportion
of, or consist essentially or entirely of, a distillate
hydrocarbon base fuel. A "major proportion" means
typically 80 96v/v or greater, more suitably 90 or 95 %-v/v
or greater, most preferably 98 or 99 or 99.596 v/v or
greater.
Such a base fuel may in particular be a middle
distillate base fuel, in particular a diesel base fuel, and
in this case it may itself comprise a mixture of middle
distillate fuel components (components typically produced
by distillation or vacuum distillation of crude oil), or of
fuel components which together form a middle distillate
blend. Middle distillate fuel components or blends will
typically have boiling points within the usual middle
distillate range of 125 to 550 C or 150 to 400 C.
A diesel base fuel may be an automotive gas oil (AGO).
A diesel base fuel used in the present invention will
preferably have a sulphur content of at most 2000 ppmw
(parts per million by weight). More preferably, it will
have a low or ultra low sulphur content, for instance at
most 500 ppmw, preferably no more than 350 ppmw, most
preferably no more than 100 or 50 or 10 ppmw, of sulphur.
Typical diesel fuel components comprise liquid
hydrocarbon middle distillate fuel oils, for instance
petroleum derived gas oils. Such base fuel components may
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be organically or synthetically derived. They will
typically have boiling points within the usual diesel range
of 125 or 150 to 400 or 550 C, depending on grade and use.
They will typically have densities from 0.75 to 1.0 g/cm3,
preferably from 0.8 to 0.86 g/cm3, at 15 C (IP 365) and
measured cetane numbers (ASTM D613) of from 35 to 80, more
preferably from 40 to 75 or 70. Their initial boiling
points will suitably be in the range 150 to 230 C and their
final boiling points in the range 290 to 400 C. Their
kinematic viscosity at 40 C (ASTM D445) might suitably be
from 1.5 to 4.5 mm2/s (centistokes). However, a fuel
composition for use according to the present invention may
contain fuel components outside of these ranges, since the
properties of an overall blend may differ, often
significantly, from those of its individual constituents.
Such fuels are generally suitable for use in a
compression ignition (diesel) internal combustion engine,
of either the indirect or direct injection type.
A diesel fuel composition which results from carrying
out the present invention will also preferably fall within
these general specifications. Suitably it will comply with
applicable current standard specification(s), such as for
example EN 590:99 (for Europe) or ASTM D-975-05 (for the
USA). By way of example, the fuel composition may have a
density from 0.82 to 0.845 g/cm3 at 15 C; a final boiling
point (ASTM D86) of 360 C or less; a cetane number (ASTM
D613) of 51 or greater; a kinematic viscosity (ASTM D445)
from 2 to 4.5 mm2/s (centistokes) at 40 C; a sulphur
content (ASTM D2622) of 350 ppmw or less; and/or a total
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aromatics content (IP 391(mod)) of less than 11 %m.
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.
A petroleum derived gas oil may be obtained from
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.
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.
In the methods of the present invention, a base fuel
may be or contain a so-called "biodiesel" fuel component,
such as a 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.
A base fuel may be or contain a Fischer-Tropsch
derived fuel component, in particular a Fischer-Tropsch
derived gas oil. Such fuels are known and in use in diesel
fuel compositions. They are, or are prepared from, the
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synthesis products of a Fischer-Tropsch condensation
reaction, as for example the commercially used gas oil
obtained from the Shell Middle Distillate Synthesis (Gas-
To-Liquid) process operating in Bintulu, Malaysia.
In general, other products of gas-to-liquid processes
may be suitable for inclusion in a fuel composition
prepared according to the present invention. The gases
which are converted into liquid fuel components using such
processes can include natural gas (methane), LPG (e.g.
propane or butane), "condensates" such as ethane, synthesis
gas (CO/hydrogen) and gaseous products derived from coal,
biomass and other hydrocarbons.
The detergent additive in the fuel composition may be
any additive containing a detergent. Many such additives
are known and commercially available; they are typically
added to automotive fuel compositions at levels intended to
reduce, remove, or slow the build up of engine deposits.
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.
The detergent additive may be present in the
composition at an active matter concentration of from 50 to
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1000 ppmw, suitably from 100 to 500 or from 100 to 300
ppmw.
The cold flow additive in the fuel composition may be
defined as any material capable of improving the cold flow
performance of the composition, as described below. The
cold flow additive may for example be a middle distillate
flow improver (MDFI) or a wax anti-settling agent (WASA) or
more typically a mixture thereof. In the context of the
present invention, the cold flow additive may in particular
be or at least include a wax anti-settling agent.
MDFIs may for example comprise vinyl ester-containing
compounds such as vinyl acetate-containing compounds, in
particular polymers. Copolymers of alkenes (for instance
ethylene, propylene or styrene, more typically ethylene)
and unsaturated esters (for instance vinyl carboxylates,
typically vinyl acetate) are for instance known for use as
MDFIs.
Other known cold flow additives (also referred to as
cold flow improvers) include comb polymers (polymers having
a plurality of hydrocarbyl group-containing branches
pendant from a polymer backbone), polar nitrogen compounds
including amides, amines and amine salts, hydrocarbon
polymers and linear polyoxyalkylenes. Examples of such
compounds are given in WO-A-95/33805, at pages 3 to 16 and
in the examples.
Yet further examples of compounds useable as cold flow
additives include those described in WO-A-95/23200. These
include the comb polymers defined at pages 4 to 7, in
particular those consisting of copolymers of vinyl acetate
and alkyl-fumarate esters; and the additional low
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temperature flow improvers described at pages 8 to 19, such
as linear oxygen-containing compounds, including alcohol
alkoxylates (e.g. ethoxylates, propoxylates or butoxylates)
and other esters and ethers; ethylene copolymers of
unsaturated esters such as vinyl acetate or vinyl
hexanoate; polar nitrogen containing materials such as
phthalic acid amide or hydrogenated amines (in particular
hydrogenated fatty acid amines); hydrocarbon polymers (in
particular ethylene copolymers with other alpha-olefins
such as propylene or styrene); sulphur carboxy compounds
such as sulphonate salts of long chain amines, amine
sulphones or amine carboxamides; and hydrocarbylated
aromatics.
Ideally compounds used as cold flow additives will
have or be associated with available protons.
Particularly preferred cold flow additives for use in
the present invention are those containing nitrogen atoms,
preferably in association with protons. Suitable compounds
are amines, amine salts and amides, in particular amines
and their salts, most particularly protonated amines.
Suitably at least one such compound is present in a fuel
composition prepared according to the present invention.
Cold flow additives are conventionally included in
middle distillate fuel compositions, such as diesel fuel
compositions, so as to improve their performance at lower
temperatures, and thus to improve the low temperature
operability of systems (typically vehicles) running on the
compositions.
The (active matter) concentration of the cold flow
additive in a fuel composition prepared according to the
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present invention may be up to 1000 ppmw, preferably up to
500 ppmw, more preferably up to 400 or 300 ppmw. Its
(active matter) concentration will suitably be at least 20
ppmw, preferably at least 30 or 50 ppmw, more preferably at
least 100 ppmw.
When practising the present invention, the cold flow
additive and the detergent additive are typically such that
the cold flow performance of the composition is worse when
both additives are present than it would be if only the
cold flow additive were present (at the same
concentration). In such cases the present invention can
provide a beneficial effect in countering the detrimental
interaction between the cold flow and detergent additives.
The cold flow performance of a fuel composition can
suitably be assessed by measuring its cold filter plugging
point (CFPP), preferably using the standard test method IP
309 or an analogous technique. The CFPP of a fuel
indicates the temperature at and below which wax in the
fuel will cause severe restrictions to flow through a
filter screen, and can correlate with vehicle operability
at lower temperatures. A reduction in CFPP will correspond
to an improvement in cold flow performance, other things
being equal. Improved cold flow properties increase the
range of climatic conditions or seasons in which a fuel can
efficiently be used.
Cold flow performance may be assessed in any other
suitable manner, for example using the Aral short sediment
test (EN 23015), and/or by assessing the low temperature
performance of a diesel engine, vehicle or other system
running on the fuel composition. The temperature at which
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such performance is measured may depend on the climate in
which the fuel composition is intended to be used - in
Greece, for example, "low temperature performance" may be
assessed at -5 C, whereas in Finland low temperature
performance may be required at -30 C; in hotter countries
where fuels are generally used at higher ambient
temperatures, "low temperature" performance may need to be
assessed at only 5 to 10 degrees below the ideal ambient
temperature. In general, an improvement in cold flow
performance may be manifested by a reduction in the minimum
temperature at which a system running on the fuel
composition can perform to a given standard.
An improvement in cold flow performance may be
manifested by a reduction in, ideally suppression of, so-
"hesitation" effects which can occur in a CFPP test
at temperatures higher than the CFPP value of a fuel.
"Hesitation" may be understood as an at least partial
obstruction of the CFPP test filter occurring at a
temperature higher than the CFPP. Such an obstruction will
be manifested - in a CFPP machine modified to allow such
measurements - by an increased filtration time, albeit at a
level below 60 seconds. If severe enough, hesitation
causes the test to terminate early and the CFPP value to be
recorded as the higher temperature - thus when hesitation
occurs to a great enough extent, it is not recognised as
hesitation but simply as a higher CFPP. References in this
specification to CFPP values may generally be taken to
include values which take account of - i.e. are raised as a
result of - such hesitation effects.
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A reduction in hesitation effects may be manifested by
complete elimination of a hesitation effect which would be
observed when measuring the CFPP of the fuel composition
without the further additive present; and/or by a reduction
in severity of such a hesitation effect (e.g. severe
hesitation becomes only mild hesitation); and/or by a
lowering of the temperature at which such a hesitation
effect occurs. Since hesitation effects can cause
variability in the measured CFPP of a fuel composition, in
severe test machines triggering an increase in the recorded
value, such a reduction may be beneficial because it can
allow the CFPP of the composition to be more reliably and
accurately measured, in turn allowing the composition to be
more readily tailored to meet, and proven to meet,
specifications such as industry or regulatory standards.
References to a "detrimental effect" on cold flow
performance may be construed in accordance with the above.
Such an effect will typically correspond to an increase in
the CFPP of the fuel composition, and/or an increase in
hesitation effects when measuring the CFPP of the
composition, and/or poorer performance of an engine or
vehicle or other system running on the composition,
particularly at low temperatures as described above.
In the context of the first aspect of the present
invention, "reducing" the effect of the detergent additive
on cold flow performance embraces any degree of reduction
in the effect (typically a detrimental effect, for instance
as manifested by an increased CFPP) of the detergent
additive on the cold flow performance of the fuel
composition. This can be assessed by measuring the cold
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flow performance of the composition (including the cold
flow additive) both before and after incorporation of the
detergent additive. Thus, the further additive may be
added for the purpose of reducing deactivation of the cold
flow additive by the detergent additive and/or by any other
moiety present in the fuel composition. Ideally, the
effect of the detergent additive on cold flow performance
will be entirely negated by the further additive; in other
words, the cold flow performance of the final composition
will be no worse than - and in some cases may be better
than - that of the composition with the cold flow additive
but without the detergent additive.
In the context of the second and fourth aspects of the
present invention, "improving" the cold flow performance of
the fuel composition embraces any degree of improvement
compared to the performance of the composition before the
further additive is incorporated. This may for example
involve adjusting the cold flow performance of the
composition, by means of the further additive, in order to
meet a desired target, for instance a desired target CFPP
value.
By using the present invention, the CFPP of the
composition may be reduced by at least 1 C compared to its
value prior to addition of the further additive, preferably
by at least 2 C, more preferably by at least 3 C and most
preferably by at least 4 or 5 or in cases 6 or 7 or 8 C.
By using the present invention, the CFPP of the
composition may be reduced by at least 0.3% of its value
(expressed in degrees Kelvin) prior to addition of the
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further additive, more preferably by at least 0.5% and most
preferably by at least 1 or 1.5 or 2 or even 3 or 4%.
A fuel composition prepared according to the present
invention may have a CFPP of -5 C or lower, preferably -10
or -15 C or lower. In a preferred embodiment, it may have
a CFPP of -20 C or lower, preferably -25 or -28 or -30 C or
lower.
In accordance with the present invention, the "further
additive" used in the distillate fuel composition is
selected from (a) acids and mixtures thereof and (b)
lubricity enhancing additives. A lubricity enhancing
additive (b) may itself contain one or more acids; thus a
further additive which is an acid (in particular a
carboxylic acid, and most particularly a fatty acid) may be
used as a constituent of another fuel additive such as a
lubricity enhancing additive.
An acid (a) may be an inorganic (nitric for example)
or organic acid, preferably the latter. In general terms
it may be defined as any material capable of supplying
protons. It may be a mono-, di-, tri- or poly acid,
preferably (especially if organic) a mono-acid. It may be
an oligomer or polymer functionalised with one or more acid
groups, for example an acid-functionalised olefin oligomer.
It may be present as an acid salt (for example a
carboxylate of a protonated amine), although suitably it
will possess or at least be associated with available
protons. In some cases compounds incorporating phenol,
ester, amide or protonated amine groups may be sufficiently
acidic, in the context of their ability to donate protons,
to be useable as a further additive (a) in the present
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invention - examples of such compounds include those having
electron withdrawing groups in proximity to a potentially
available hydrogen atom, for example compounds of the
formulae CH2(CO2R)2 or CH3COCH2002R, where R is a
hydrocarbyl, typically alkyl, group. In particular, fully
or partially hydrolysed carboxylate esters may be useable
as proton donors in this context.
Where the acid (a) is an organic acid, it may for
example be selected from carboxylic acids and sulphonic
acids (in particular benzene sulphonic acids, optionally
substituted for instance with alkyl or hydroxyl groups).
It is preferably a carboxylic acid, and may thus be any
organic acid containing a -CO2H or -0O2-14+ group. It may be
aliphatic (whether saturated or at least partially
unsaturated, and optionally including cyclic moieties) or
aromatic, straight or branched chain. It may for instance
contain from 1 to 30, preferably from 1 to 20, carbon
atoms. It may be substituted with other groups as well as
the acid group; for example it may be a hydroxyacid such as
lactic or glycolic acid, or a carbonyl substituted acid
such as levulinic acid. It may be an unsaturated acid such
as acrylic or methacrylic acid, or a derivative thereof in
particular an oligomer or polymer.
Particularly preferred carboxylic acids for use in the
present invention are fatty acids and mixtures thereof.
Such fatty acids may be saturated or unsaturated (which
includes polyunsaturated). They may for example contain
from 1 or 2 to 30 carbon atoms, suitably from 10 to 22
carbon atoms, preferably from 12 to 22 or from 14 to 20
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carbon atoms, more preferably from 16 to 18 carbon atoms
and most preferably 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 preferred, more
preferably oleic and linoleic acids.
Dimers or oligomers of fatty acids may also be useable
as further additives (a).
In one embodiment of the present invention, the
further additive (a) is tall oil fatty acid, which is
derived from tall oil and contains mostly fatty acids (such
as oleic and linoleic) with a small proportion of rosin
acids. Tall oil fatty acid is already in use as a
lubricity enhancing additive.
In another embodiment of the present invention, the
further additive (a) is acetic acid. Other C1 to 010 or C1
to 08 or C1 to C6 or C1 to C4 carboxylic acids may also be
of use as the further additive.
A mixture, for example containing two or more,
preferably three or more, suitably four or more, carboxylic
acids (ideally fatty acids) may be preferred for use in the
present invention. Such acids may for example be selected
from oleic, linoleic, linolenic, stearic and palmitic
acids.
An especially preferred mixture may contain from 25 to
85 %w/w (suitably from 35 to 75 or from 40 to 70 or from 50
to 60 %w/w) of oleic acid, and/or from 5 to 50 %w/w
(suitably from 10 to 40 or from 10 to 30 or from 15 to 25
%w/w) of linoleic acid, and/or from 1 to 30 %w/w (suitably
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from 2 to 20 or from 5 to 15 %w/w) of linolenic acid,
and/or from 1 to 30 %w/w (suitably from 2 to 20 or from 5
to 15 or from 5 to 10 %w/w) of stearic acid, and/or from 1
to 30 %w/w (suitably from 2 to 20 or from 5 to 15 or from 5
to 10 %w/w) of palmitic acid. Such a mixture preferably
contains at least oleic and linoleic acid, more preferably
at least oleic, linoleic and linolenic acids, and most
preferably oleic, linoleic, linolenic, stearic and palmitic
acids.
Another preferred carboxylic acid for use in the
present invention is an aromatic compound having at least
one carboxyl group attached to the aromatic nucleus, as
disclosed in WO-A-98/01516, in particular at page 2, lines
28 to 35, at page 4, line 3 to page 5, line 11 and at page
8, lines 4 to 18. Such aromatic acids can include
naphthalene and other diaromatic or polyaromatic acids, as
well as benzoic acids. They are preferably substituted
with one or more alkyl and/or alkoxy groups. Suitably the
acid is an alkyl-substituted salicylic acid having the
formula (R)n-C6H(4_n)(OH)CO2H, where each R is independently
selected from straight and branched chain, optionally
substituted (though preferably unsubstituted) alkyl groups
having from 6 to 30, preferably from 8 to 22, more
preferably from 8 to 18 carbon atoms, and n is an integer
from 1 to 4, preferably 1. The further additive (a) may of
course be a mixture of two or more such alkyl-substituted
aromatic acids.
A lubricity enhancing additive (b) is any additive
capable of improving the lubricity of a distillate fuel
composition and/or of imparting anti-wear effects when the
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composition is in use in an engine or other fuel-consuming
system. Although it is known to include such additives in
distillate fuel compositions, such as diesel fuels, it has
not previously been recognised that they could affect cold
flow performance, in particular in the presence of a
detergent additive which itself impairs the cold flow
performance.
The lubricity enhancing additive may contain,
typically as active constituent(s), one or more carboxylic
acids such as those defined above, in particular fatty
acids and/or alkylsalicylic acids. It may alternatively be
based on non-acid actives such as esters or amides.
Suitable esters for use in such additives are
carboxylic acid esters, in particular those derived from
fatty acids such as are described above. Ester-
functionalised oligomers or polymers (e.g. olefin
oligomers) may also be of use. Such esters may be mono-
alcohol esters such as methyl esters, or more suitably may
be polyol esters such as glycerol esters. Most preferred
is a mono-, di- or tri-glyceride of a fatty acid, or
conveniently a mixture of two or more such species.
Suitable amides for use in such additives are fatty
acid amides, wherein preferred fatty acids may be as
described above, for example fatty acid amides of mono- or
in particular di-alkanolamines such as diethanolamine.
Suitable commercially available lubricity enhancing
additives include the fatty acid-based R650 (ex. Infineum),
the fatty acid ester-based R655 (ex. Infineum) and the
amide-based HitecTM 4848A (ex. Afton).
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Other suitable lubricity enhancers are described for
example in:
- the paper by Danping Wei and H.A. Spikes, "The Lubricity
of Diesel Fuels", Wear, III (1986) 217-235;
- WO-A-95/33805 (see above) - cold flow improvers to
enhance lubricity of low sulphur fuels;
- 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; and
- US-A-5490864 - certain dithiophosphoric diester-
dialcohols as anti-wear lubricity additives for low sulphur
diesel fuels.
Preferably, a lubricity enhancing additive (b)
contains one or more fatty acids or fatty acid derivatives
(in particular esters and/or amides), for instance as
defined above. More preferably, it contains one or more
fatty acids. Commercially available examples of such
additives include Infineum's R650 and Lubrizol's Lz 539
series of products.
A lubricity enhancing additive (b) may contain other
ingredients in addition to the key lubricity enhancing
active(s), for example a dehazer and/or an anti-rust agent,
as well as conventional solvent(s) and/or excipient(s).
Alternatively, the further additive (b) may consist
essentially or even entirely of a lubricity enhancing
active, or mixture thereof, of the type described above.
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In accordance with the present invention, more than
one further additive may be used in the fuel composition.
In cases it may be appropriate for a lubricity
enhancing additive (b), used as a further additive in the
present invention, not to be a compound of the type
disclosed as a cold flow improver in WO-A-95/33805 at pages
3 to 16 and/or in the examples.
It may be appropriate for a lubricity enhancing
additive (b), used as a further additive in the present
invention, not to be a polymer and/or not to be an amine
salt, and/or in certain cases not to be an amide.
According to the present invention, the further
additive may be used in the distillate fuel composition at
any suitable concentration, for instance up to 3000 ppmw,
in cases up to 2000 or 1000 ppmw, preferably up to 700
ppmw, more preferably up to 500 ppmw, or up to 400 or 300
or in cases 200 ppmw. Its concentration may be at least 1
ppmw, preferably at least 5 or 10 ppmw, preferably at least
50 or 100 ppmw. The concentration used may depend on the
concentrations of the detergent and cold flow additives
present in the composition, and on the cold flow
performance desired of it. In certain cases it may be
appropriate for the concentration of the further additive
to be such as to yield an acidity equivalent to using oleic
acid at a concentration within the above defined ranges.
A further additive which is a lubricity enhancing
additive may be used in the fuel composition, in accordance
with the present invention, at a concentration which is
different to (for example higher than) its standard treat
rate. Thus, use of a lubricity enhancing additive in
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accordance with the present invention may involve
incorporating it at a concentration other than that which
would have been necessary or desirable or usual if it had
been incorporated into the composition purely for its
lubricity enhancing properties. The use may involve
incorporating the additive at a concentration higher than
that which would be necessary or desirable or usual in
order to impart adequate lubricity properties to the
overall fuel composition (e.g. taking account of any other
additives present in the composition).
In particular, use of a lubricity enhancing additive
in accordance with the present invention may involve
incorporating it into a fuel composition which already has
(typically because one or more lubricity enhancing
additives are already present) adequate lubricity.
In the context of the present invention, "use" of an
additive in a fuel composition means incorporating the
additive into the composition, typically as a blend (i.e. a
physical mixture) with one or more other fuel components.
An additive will conveniently be incorporated before the
composition is introduced into an internal combustion
engine or other system which is to be run on the
composition. Instead or in addition the use of an additive
may involve running a fuel-consuming system, typically a
diesel engine, on a fuel composition containing the
additive, typically by introducing the composition into a
combustion chamber of an engine.
"Use" of a further additive in the ways described
above may also embrace supplying such a further additive
together with instructions for its use in a distillate fuel
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composition to achieve the purpose(s) of any of the first
to the fifth aspects of the present invention, for instance
to achieve a desired target level of cold flow performance
(e.g. a desired target CFPP value) and/or to reduce the
concentration of cold flow additive in the composition.
The further additive may itself be supplied as a component
of a formulation suitable for and/or intended for use as a
fuel additive, in which case the further additive may be
included in such a formulation for the purpose of
influencing its effects on the cold flow performance of a
distillate fuel composition.
Thus, the further additive may be incorporated into an
additive formulation or package along with one or more
other fuel additives, for example the detergent additive
itself.
According to the present invention, the distillate
fuel composition - in particular when it is a diesel fuel
composition - may contain other components in addition to
the detergent and cold flow additives and the further
additive. Such components will typically be present in
fuel additives. 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 US-A-4208190 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
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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; anti-oxidants
(e.g. phenolics such as 2,6-di-tert-butylphenol, or
phenylenediamines such as N,N1-di-sec-butyl-p-
phenylenediamine); metal deactivators; static dissipator
additives; and combustion improvers. Such components may
be incorporated with other additives, for example in a
detergent additive.
A distillate fuel composition may for example include
a lubricity enhancer, in particular when the fuel
composition has a low (e.g. 500 ppmw or less) sulphur
content. A lubricity enhancer is conveniently used at a
concentration of less than 1000 ppmw, preferably from 50 to
1000 or from 100 to 1000 ppmw, more preferably from 50 to
500 ppmw. Suitable examples of lubricity enhancers include
those described above in connection with the further
additive (b).
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.
Unless otherwise stated, the concentration of each
such additional component in the fuel composition is
preferably up to 10000 ppmw, more preferably in the range
from 0.1 to 1000 ppmw, advantageously from 0.1 to 300 ppmw,
such as from 0.1 to 150 ppmw. (All additive concentrations
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quoted in this specification refer, unless otherwise
stated, to active matter concentrations by mass.)
The 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 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.
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 the
fuel composition in a suitable quantity.
A distillate fuel additive may for example contain a
detergent, optionally together with other components as
described above, and a distillate fuel-compatible diluent,
which in the case of a diesel fuel may be a non-polar
hydrocarbon solvent such as toluene, xylene, white spirits
and those sold by Shell companies under the trade mark
"SHELLSOL", and/or a polar solvent such as an ester or in
particular an alcohol, e.g. hexanol, 2-ethylhexanol,
decanol, isotridecanol and alcohol mixtures, most
preferably 2-ethylhexanol. The further additive may, in
accordance with the present invention, be incorporated into
such an additive formulation.
The total additive content in the fuel composition may
suitably be from 50 to 10000 ppmw, preferably below 5000
ppmw.
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Additives may be added at various stages during the
production of a fuel composition; those added at the
refinery for example might be selected from anti-static
agents, pipeline drag reducers, flow improvers, lubricity
enhancers, anti-oxidants and wax anti-settling agents.
When carrying out the present invention, a base fuel may
already contain such refinery additives. Other additives
may be added downstream of the refinery.
According to a sixth aspect of the present invention,
there is provided a fuel composition containing a
distillate base fuel, a detergent additive, a cold flow
additive and a further additive selected from:
(a) acids, in particular carboxylic acids, and mixtures
thereof; and
(b) lubricity enhancing additives.
The further additive may be as defined above in
connection with the first to the fifth aspects of the
present invention. In particular, it may be a carboxylic
acid, for example a C1 to C10 carboxylic acid such as
acetic acid. Again, the distillate base fuel is preferably
a middle distillate base fuel.
According to a seventh aspect of the present
invention, there is provided a process for the preparation
of a fuel composition, such as a composition according to
the sixth aspect, which process involves blending a
distillate (typically middle distillate) base fuel with a
detergent additive, a cold flow additive and a further
additive as defined above. The blending is ideally carried
out for one or more of the purposes described in connection
with the first to the fifth aspects of the present
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invention, in particular with respect to the cold flow
properties of the resultant fuel composition.
The process of the seventh aspect of the present
invention may form part of a process for, or be implemented
using a system for, controlling the blending of a fuel
composition, for example in a refinery. Such a system will
typically include means for introducing each of the
relevant additives and a distillate base fuel into a
blending chamber, flow control means for independently
controlling the volumetric flow rates of the additives and
the base fuel into the chamber, means for calculating the
proportions of each of the additives needed to achieve a
desired target cold flow property (e.g. a desired target
CFPP) input by a user into the system, and means for
directing the result of that calculation to the flow
control means which is then operable to achieve the desired
proportions of additives in the product composition by
altering the flow rates of its constituents into the
blending chamber.
In order to calculate the required proportions, a
process or system of this type will suitably make use of
known cold flow properties for the base fuel concerned, and
conveniently also a model predicting, and/or data
describing, the cold flow properties of fuel compositions
containing varying proportions of the relevant additives.
The process or system may then for example, according to
the present invention, select and produce a cold flow
additive concentration lower than that predicted to be
necessary if only the cold flow additive and the detergent
additive were present.
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The present invention may thus conveniently be used to
automate, at least partially, the formulation of a
distillate fuel composition, preferably providing real-time
control over the relative proportions of the additives and
base fuel incorporated into the composition, for instance
by controlling the relative flow rates or flow durations
for the constituents.
An eighth aspect of the present invention provides a
method of operating a fuel consuming system, which method
involves introducing into the system a fuel composition
according to the sixth aspect of the present invention,
and/or a fuel composition prepared in accordance with any
one of the first to the fifth or seventh aspects. Again
the fuel composition is preferably introduced for one or
more of the purposes described above in connection with the
first to the fifth aspects of the present invention. Thus,
the system is preferably operated with the fuel composition
of the present invention for the purpose of improving the
low temperature performance of the system.
The system may in particular be an internal combustion
engine, and/or a vehicle which is driven by an internal
combustion engine, in which case the method involves
introducing the relevant fuel composition into a combustion
chamber of the engine. The engine is preferably a
compression ignition (diesel) engine. Such a 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.
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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 are
not intended to (and do not) exclude other moieties,
additives, components, integers or steps.
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.
Preferred features of the second and subsequent
aspects of the present invention may be as described in
connection with any of the other aspects.
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.
Moreover, unless stated otherwise, any feature
disclosed herein may be replaced by an alternative feature
serving the same or a similar purpose.
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The following examples illustrate the properties and
performance of fuel compositions prepared in accordance
with the present invention, and assess the effects of
various additives on the cold flow performance of diesel
fuel compositions.
A number of commercially available diesel fuels were
sampled, some of which already contained cold flow
additives. For others, cold flow additives were blended
into the fuels in accordance with the additive supplier's
instructions (typically at 45 to 65 C, followed by cooling
to an ambient temperature of approximately 20 C) - in these
cases the cold flow additives included both a MDFI and a
WASA, each typically at a concentration of from 150 to 200
ppmw.
Other additives were blended into the fuels either
whilst still warm or at ambient temperature, as convenient.
Cold flow performance was assessed by measuring cold
filter plugging points (CFPPs) for the fuel/additive
blends, using a 5GS CFPP test machine (ex. ISL) and a
method analogous in key respects to the standard test
method IP 309.
The following lubricity enhancing additives were used:
Additive A a commercially available additive containing
a mixture of tall oil fatty acids;
Additive B a commercially available additive containing
a mixture of primarily C16 to C22 (primarily
C16 to C18) fatty acids;
Additive C a commercially available ester-based additive
containing a mixture of glycerol esters of
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linoleic acid, primarily glycerol
mono(linoleate), glycerol di(linoleate) and
glycerol tri(linoleate) in an approximate
ratio of 4:4:1;
Additive D a commercially available additive containing
a mixture of tall oil fatty acids;
Additive E a commercially available additive containing
a mixture of tall oil fatty acids;
Additive F an additive containing an alkylsalicylic acid
of the type described in WO-A-98/01516 at
page 8, lines 4 to 18; and
Additive G a commercially available amide-based additive
containing tall oil fatty acid amides of
diethanolamine, of the general formula
R-C(0)-N(CH2CH2OH)2.
Example 1
A commercially available diesel fuel composition,
obtained from Germany, was mixed with standard cold flow
additives (150 ppmw of a MDFI and 150 ppmw of a WASA) to
obtain a fuel composition falling within the EN 590:99
winter diesel specification for Germany. This composition
(fuel Fl) was then blended with a detergent additive and
with further additives in accordance with the present
invention. The cold filter plugging point (CFPP) of each
blend was measured as described above. Some measurements
were conducted in duplicate or in triplicate, using
different test kits, the CFPP measurements for each blend
being referred to as #1, #2 and #3.
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The fuel composition (prior to addition of the cold
flow additives) had the specification shown in Table 1
below.
Table 1
Fuel property Test method
Density @ 15 C (g/cm3) IP 365 0.8352
Cloud point ( C) IP 219 -8
CFPP ( C) IP 309 -11 (no
hesitation)
Kinematic viscosity @ IP 71 3.284
40 C
(mm2/s)(centistokes)
Cetane number by IQT IP 498 53.5
Distillation ( C) : IP 123
IBP 165.8
10% recovered 224.7
50% recovered 281.7
80% recovered 321.9
90% recovered 342.2
95% recovered 358.6
FBP 365.4
Aromatics (%m) IP 391
Mono 20.3
Di 3.4
Tri 0.4
Total 24.1
Total sulphur (mg/kg) ASTM D2622 < 5
The detergent additive used in the experiments was
OCTIMISETm D3016 (ex. Octel), containing a polyisobutene
succinimide of a polyamine (as a detergent active) and
minor amounts of other fuel additives including a silicone
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antifoam agent and a dehazer. Its nominal treat rate was
1000 ppmw.
The further additives used, in accordance with the
present invention, were the commercially available
lubricity enhancing additives A, B and C as described
above.
The results are shown in Table 2 below. For the
compositions containing neither detergent additive nor
further additive, the results quoted are a mean of several
replicate readings, with the range of the readings shown in
brackets. Table 2 also details hesitation effects where
observed; these can aid in the interpretation of the CFPP
readings.
Table 2
Detergent Further CFPP #1 CFPP #2 CFPP #3
additive additive ( C) ( C) ( C)
(PPmw) (PPmw)
0 0 -26 -25
(-24 to - (-24 to -
28) 25)
1000 0 -25 -19 -19
Severe
hesitation
at -15/-21
1000 Additive -26 -24
A (500)
1000 Additive -24 Severe -21 -26 Mild
A (300) hesitation hesitation
at -21 at -21
1000 Additive -26 -26
B (500)
1000 Additive -26 Mild -20 -27 Mild
C (500) hesitation hesitation
at -21 at -21
1000 Additive -26 -26
B (150)
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Table 2 shows that the CFPP of fuel composition Fl
(with the cold flow additives) is around -25 to -26 C.
Incorporation of the detergent additive results in a
significant rise in CFPP, demonstrating the detrimental
interaction between the cold flow additives and the
subsequently added detergent.
Addition of the lubricity enhancing additives,
however, in accordance with the present invention, results
in a surprising decrease in CFPP, thus countering the
negative effects of the detergent additive. The severe
hesitation observed in the CFPP #1 reading for detergent
alone is also reduced, and in most cases eliminated,
following addition of the further additive.
Two of the additives are shown to be effective at
different treat rates (Additive A at both 500 and 300 ppmw,
and Additive B at both 500 and 150 ppmw).
Example 2
A second commercially available diesel fuel
composition F2 (ex. Shell) was obtained from Germany. This
contained standard cold flow additives (80 to 120 ppmw of
the MDFI R252 and 150 ppmw of the WASA R474 (both ex.
Infineum)). F2 was blended with a detergent additive
(OCTIMISE'm D3016) and with further additives in accordance
with the present invention. For each blend, the CFPP was
measured as in Example 1.
The fuel composition F2 (already containing cold flow
additives) had the specification shown in Table 3 below.
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Table 3
Fuel property Test method
Density @ 15 C (g/cm3) IP 365 0.8448
Cloud point ( C) IP 219 -11
Kinematic viscosity @ IP 71 2.999
40 C
(mm2/s)(centistokes)
Cetane number by IQT IP 498 55.1
Distillation ( C) : IP 123
IBP 167.6
10% recovered 227.9
50% recovered 275.4
80% recovered 309.4
90% recovered 328.9
95% recovered 348.5
FBP 356.7
Aromatics (%m) IP 391
Mono 25.5
Di 5.6
Tri 0.5
Total 31.6
Total sulphur (mg/kg) ASTM D2622 11
The further additives used were (a) acetic acid, (b)
the lubricity enhancing additives A, B, D and E as
described above and (c) a mixture of fatty acids containing
oleic acid (55 %w/w), linoleic acid (19 %w/w), linolenic
acid (9 %w/w), stearic acid (8.5 %w/w) and palmitic acid
(8.5 %w/w).
The CFPP results are shown in Table 4 below. For the
compositions containing neither detergent additive nor
further additive, the results quoted are a mean of several
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replicate readings, with the range of the readings shown in
brackets.
Table 4
Detergent Further CFPP #1 CFPP #2 CFPP #3
additive additive ( C) ( C) ( C)
(PPmw) (PPmw) _
0 0 -30 -31 -29
(-29 to (-30 to (-28 to
-31) -31) -30)
1000 0 -20 -19
1000 Additive A -29 -30
(500)
1000 Acetic acid -25 -21 -30
(110)
1000 Additive A -29 -29
(300) _
1000 Additive B -27 -28
(500)
1000 Additive B -30 -30
(150)
1000 Additive D -28 -28 -29
(500)
1000 Additive E -30 -31 -32
(290)
1000 Mixed acids -30 -27 -30
(500) _
Table 4 shows that the CFPP of fuel composition F2 is
around -30 C. Incorporation of the detergent additive
results in a significant rise in CFPP to -20 C,
demonstrating the detrimental interaction between the cold
flow additives present in F2 and the subsequently added
detergent.
Incorporation of further additives in accordance with
the present invention, however, results in decreases in
CFPP, thus countering at least partially the negative
effects of the detergent additive. In some cases the
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effect of the detergent on cold flow performance appears to
be entirely negated by the further additive.
Particularly effective further additives include the
fatty acid mixture, and the fatty acid-based lubricity
enhancing additives such as Additives A, B and E.
Two of the additives are shown to be effective at
different treat rates (Additive A at both 500 and 300 ppmw,
and Additive B at both 500 and 150 ppmw).
Example 3
Example 1 was repeated but using as the detergent
additive a formulation containing a polyisobutylene
succinimide (based on polyisobutylene with a number-average
molecular weight of about 1000) of tetraethylenepentamine.
The standard treat rate for this additive is 636 ppmw.
The further additives used, in accordance with the present
invention, were (a) acetic and linolenic acids and (b) the
lubricity enhancing additives F, C, G and A.
The results are shown in Table 5 below. For the
compositions containing neither detergent additive nor
further additive, the results quoted are a mean of several
replicate readings, with the range of the readings shown in
brackets. Table 5 also details hesitation effects where
observed.
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Table 5
Detergent Further CFPP #1 CFPP #2 CFPP #3
additive additive ("C) ( C) ( C)
(PPmw) (Plomw)
0 0 -26 -25
(-24 to (-24 to
-28) -25)
636 0 -19 -19 -17
Severe
hesitation
at -17
636 Additive -20 -30 Severe -30 Mild
F (225) hesitation hesitation
at -21 at -20
636 Additive -26 -24
F (450)
636 Acetic -27 -24 -25
acid
(110)
636 Additive -25 -24
C (500)
636 Additive -24 -24
G (500)
'
636 Additive -27 -24 -26
A (500)
636 Additive -28 -28
C (1000)
636 Additive -25 -27 -25
G (1000)
636 Linolenic -26 -20 -26
acid
(500)
These data again show that using a further additive in
accordance with the present invention, the cold flow
performance of a diesel fuel containing both a cold flow
additive and a detergent additive can be improved,
countering the apparently detrimental effect of the
detergent.
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Example 4
Example 2 was repeated but using the same detergent
additive as in Example 3. The further additives used, in
accordance with the present invention, were (a) acetic acid
and (b) the lubricity enhancing additives F and A as
described above.
The results are shown in Table 6 below. For the
compositions containing neither detergent additive nor
further additive, the results quoted are a mean of several
replicate readings, with the range of the readings shown in
brackets.
Table 6
Detergent Further CFPP #1 CFPP #2 CFPP #3
additive additive ( C) ( C) ( C)
(PPmw) (PPmw)
0 0 -30 -31 -29
(-29 to (-30 to (-28 to
-31) -31) -30)
600 0 -18 -19
636 Additive F -31 -31 -20
(225)
636 Additive F -29 -30
(450)
636 Acetic acid -32 -31 -29
(110)
636 Additive A -31 -28 -30
(500)
Example 5
Further commercially available diesel fuels F3 to F5,
obtained during the winter, were tested in similar manner
to Examples 1 to 4 above. All either contained cold flow
additives or were blended with cold flow additives prior to
addition of any detergent or further additives.
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Fuel composition F3 was based on the same commercially
available German diesel fuel as used in Example 1, but
mixed with 200 ppmw of a MDFI additive and 150 ppmw of a
WASA additive. Its cloud point prior to incorporation of
the cold flow additives was -8 C.
Fuel composition F4 was a Dutch fuel containing 150
ppmw of a MDFI additive and 150 ppmw of a WASA additive.
Its cloud point prior to incorporation of the cold flow
additives was -10 C.
Fuel composition F5 was a German fuel containing
standard cold flow additives (including a MDFI and at least
150 ppmw of a WASA). Its cloud point prior to
incorporation of cold flow additives was -9 C.
The same detergent additive was used as in Example 1,
at its standard treat rate (1000 ppmw). Blends were
prepared with various further additives in accordance with
the present invention.
The CFPP results are shown in Table 7 below. For the
F3 compositions containing neither detergent additive nor
further additive, the results quoted are a mean of several
replicate readings, with the range of the readings shown in
brackets.
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Table 7
Fuel Detergent Further CFPP #1 CFPP #2 CFPP #3
(101=w) additive ( C) ( C) ( C)
(IpPmw)
F3 0 0 -31 -31
(-30 to (-)
-31)
F3 1000 0 -25 -24
F3 1000 Additive -27 -28
A (500)
F3 1000 Additive -28 -28
B (500)
F4 0 0 -21 -27 -20
F4 1000 0 _-15 ,-17 -15
F4 1000 Additive -20 -20
B (150)
F5 0 0 -28 -30
F5 1000 0 -20 -27 -21
F5 1000 Additive -30 -28
B (150)
Again the inclusion of a lubricity enhancing additive
is seen to counter the detrimental effect of the detergent
additive on cold flow performance.
Example 6
The diesel fuel used as the starting material in
Example 1 was blended with various additives selected from
(i) the detergent additive used in Example 1, (ii) two cold
flow additives (a MDFI and a WASA) and (iii) the lubricity
enhancing additive A. For each blend, the CFPP was
measured as in Example 1.
The CFPP results are shown in Table 8.
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Table 8
MDFI WASA Detergent Additive CFPP CFPP
CFPP '
additive additive additive A (ppmw) #1 #2 #3
(PPmw) (PPmw) (PPmw) ( C) ( C) ( C)
_ _
150 150 0 0 -27 -25
0 0 0 0 -11 -11
0 0 0 500 -9 -10
_ _
0 0 1000 500 -9 -10
_
150 150 0 500 -28 -28 _
The first line of Table 8 shows that the inclusion of
standard cold flow additives in the fuel composition
results in a CFPP of around -27 C. Without these additives
(second line of Table 8), the CFPP of the composition
increases to -11 C. Incorporation of a lubricity enhancer
alone or a lubricity enhancer together with a detergent
does not appear to affect the CFPP a great deal.
Nor does inclusion of the lubricity enhancer with the
cold flow additives appear to affect the CFPP
significantly, as compared to that for the fuel with cold
flow additives alone. This suggests that in order to
achieve the beneficial effects of the present invention (as
seen in Example 1 to 5, for instance), it is necessary to
include cold flow and detergent additives as well as the
further additive of the present invention. In other words,
an unexpected synergy appears to take place between the
three additives together, reducing the otherwise
detrimental interaction between the cold flow and detergent
additives alone.
Example 7
This example illustrates that a further additive may
be incorporated into a fuel composition, in accordance with
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the present invention, in order to reduce undesirable
hesitation effects when detergent and cold flow additives
are combined.
Fuel compositions Fl and F4, both containing standard
cold flow additives (in each case a combination of MDFI and
WASA), were blended with detergent additives and further
additives and subjected to CFPP tests as in the previous
examples.
Table 9 below shows the results for fuel Fl combined
with the OCTIMISE'm D3016 detergent additive used in Example
1. The further additives used, in accordance with the
present invention, were (a) stearic acid and (b) the
lubricity enhancing Additives B and C. Where hesitation
was observed, this is shown with the CFPP figures; all
values are quoted in C.
Table 9
Detergent Further CFPP #1 CFPP #2 ( C) CFPP #3
additive additive ( C) ( C)
(Plomw) (PPmw)
O 0 -25 -25
1000 0 -25 -19 -19
Severe
hesitation
at
-15/-21
1000 Additive -26 -26
B (150)
1000 Stearic -21 -20
acid
(500)
1000 Additive -26 Mild -20 -27 Mild
C (500) hesitation hesitation
at -21 at -21
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It can be seen that incorporation of the detergent
additive causes a marked increase in CFPP, and severe
hesitation effects in one of the test kits used. In the
presence of Additive C, only mild hesitation is observed,
and at -21 C rather than at both -15 and -21 C. The
hesitation at -15 C is also eliminated in the presence of
stearic acid. Inclusion of Additive B results in complete
elimination of hesitation effects. Thus, the further
additive of the present invention can reduce hesitation
effects, leading to a fuel which is likely to be less
problematic on CFPP testing.
Table 10 below shows the results for fuel F4 combined
with OCTIMISE'm D3016. The further additive used, in
accordance with the present invention, was the fatty acid-
lubricity enhancing Additive B. Where hesitation was
observed, this is shown with the CFPP figures; all values
are quoted in C.
Table 10
Detergent Further CFPP #1 CFPP #2 ( C) CFPP #3
additive additive ( C) ( C)
(PPmw) (PPmw)
0 0 -21 Mild -27 Mild -20
downphase downphase
hesitation hesitation
at -19 at -21
1000 0 -15 Severe -17 Mild -15 Mild
hesitation hesitation hesitation
at at -13 at -13
-13
1000 Additive -20 -20
B (150)
Here, incorporation of the detergent additive leads to
severe hesitation effects in one of the test kits used and
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mild hesitation in the other two test kits. Even without
the detergent additive, the fuel still appears to suffer
from mild hesitation. Incorporation of Additive B removes
the hesitation effects completely.
