U.S. patent application number 11/736790 was filed with the patent office on 2007-10-18 for formulating fuel compositions.
Invention is credited to Christopher William CLAYTON, Douglas Miller.
Application Number | 20070240361 11/736790 |
Document ID | / |
Family ID | 36951580 |
Filed Date | 2007-10-18 |
United States Patent
Application |
20070240361 |
Kind Code |
A1 |
CLAYTON; Christopher William ;
et al. |
October 18, 2007 |
FORMULATING FUEL COMPOSITIONS
Abstract
A method of preparing a fuel composition containing a distillate
fuel, a detergent additive and a cold flow additive, of a further
additive selected from (a) acids and mixtures thereof; and (b)
lubricity enhancing additives are provided, for the purpose of
reducing the effect of the detergent additive on the cold flow
performance of the composition, and/or improving the cold flow
performance of the composition, and/or reducing the amount of cold
flow additive in the composition, and/or increasing the
concentration of detergent additive in the composition without
undue impairment of the cold flow performance. The further additive
is preferably selected from carboxylic acids, more preferably fatty
acids, and mixtures thereof. The distillate fuel is preferably a
middle distillate fuel. The overall fuel composition is preferably
an automotive fuel composition, more preferably a diesel fuel
composition.
Inventors: |
CLAYTON; Christopher William;
(Cheshire, GB) ; Miller; Douglas; (Cheshire,
GB) |
Correspondence
Address: |
SHELL OIL COMPANY
P O BOX 2463
HOUSTON
TX
772522463
US
|
Family ID: |
36951580 |
Appl. No.: |
11/736790 |
Filed: |
April 18, 2007 |
Current U.S.
Class: |
44/385 |
Current CPC
Class: |
C10L 1/143 20130101;
C10L 1/19 20130101; C10L 1/224 20130101; C10L 1/1881 20130101; C10L
10/08 20130101; C10L 1/14 20130101; C10L 1/2383 20130101; C10L
1/191 20130101; C10L 1/189 20130101 |
Class at
Publication: |
44/385 |
International
Class: |
C10L 1/18 20060101
C10L001/18 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 18, 2006 |
EP |
06252092.9 |
Claims
1. 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, (ii) measuring the
cold flow performance of the resultant blend and (iii)
incorporating a further additive selected from: (a) acids and
mixtures thereof; and (b) lubricity enhancing additives, in an
amount effective to improve the cold flow performance of the
blend.
2. The method of claim 1 wherein the distillate fuel is a middle
distillate fuel.
3. The method of claim 1 wherein the fuel composition is a diesel
fuel composition.
4. The method of claim 1 wherein the further additive is a
carboxylic acid or mixture thereof.
5. The method of claim 2 wherein the further additive is a
carboxylic acid or mixture thereof.
6. The method of claim 1 wherein the further additive is a fatty
acid or mixture thereof.
7. The method of claim 2 wherein the further additive is a fatty
acid or mixture thereof.
8. A fuel composition made by the method of claim 1.
9. A method of operating a fuel consuming system, which method
involves introducing into the system a fuel composition of claim 8.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a certain method of
formulating fuel compositions containing distillate fuels.
BACKGROUND OF THE INVENTION
[0002] Cold flow additives are included 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. Cold flow additives
include middle distillate flow improvers and wax anti-settling
agents.
[0003] It is common to include detergent additives in such fuel
compositions, for the purpose of reducing, removing or slowing the
build-up of engine deposits.
SUMMARY OF THE INVENTION
[0004] A method for formulating a fuel composition is provided, the
method comprising (i) blending together a distillate base fuel, a
detergent additive and a cold flow additive, (ii) measuring the
cold flow performance of the resultant blend and (iii)
incorporating a further additive selected from:
[0005] (a) acids and mixtures thereof; and
[0006] (b) lubricity enhancing additives,
in an amount effective to improve the cold flow performance of the
blend.
DETAILED DESCRIPTION OF THE INVENTION
[0007] It has been found 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.
[0008] It is desirable to provide fuel compositions containing
distillate fuels, and/or additives for use in such compositions,
which can overcome or at least mitigate the above described
problems.
[0009] One of the aspects of the present invention provides a
method of 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.
[0010] In the context of this aspect of the present invention, the
term "increasing" embraces any degree of increase, for instance 1%
or more of the original detergent additive concentration,
preferably 2 or 5 or 10 or 20% or more. The increase may be as
compared to the 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.
[0011] According to another 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.
[0012] A further aspect of the present invention provides the use
of a further additive as defined above, in a fuel composition
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.
[0013] In the context of this 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.
[0014] 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 safeguard 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.
[0015] 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.
[0016] 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.
[0017] 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").
[0018] 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% v/v or greater, more
suitably 90 or 95% v/v or greater, most preferably 98 or 99 or
99.5% v/v or greater.
[0019] 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.degree. C. or 150 to
400.degree. C.
[0020] 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.
[0021] Typical diesel fuel components comprise liquid hydrocarbon
middle distillate fuel oils, for instance petroleum derived gas
oils. Such base fuel components may be organically or synthetically
derived. They will typically have boiling points within the usual
diesel range of 125 or 150 to 400 or 550.degree. C., depending on
grade and use. They will typically have densities from 0.75 to 1.0
g/cm.sup.3, preferably from 0.8 to 0.86 g/cm.sup.3, at 15.degree.
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.degree. C. and
their final boiling points in the range 290 to 400.degree. C. Their
kinematic viscosity at 40.degree. C. (ASTM D445) might suitably be
from 1.5 to 4.5 mm.sup.2/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.
[0022] Such fuels are generally suitable for use in a compression
ignition (diesel) internal combustion engine, of either the
indirect or direct injection type.
[0023] 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/cm.sup.3
at 15.degree. C.; a final boiling point (ASTM D86) of 360.degree.
C. or less; a cetane number (ASTM D613) of 51 or greater; a
kinematic viscosity (ASTM D445) from 2 to 4.5 mm.sup.2/s
(centistokes) at 40.degree. C.; a sulphur content (ASTM D2622) of
350 ppmw or less; and/or a total 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.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] 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 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] The detergent additive may be present in the composition at
an active matter concentration of from 50 to 1000 ppmw, suitably
from 100 to 500 or from 100 to 300 ppmw.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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 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.
[0036] Ideally compounds used as cold flow additives will have or
be associated with available protons.
[0037] 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.
[0038] 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.
[0039] The (active matter) concentration of the cold flow additive
in a fuel composition prepared according to the 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.
[0040] 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.
[0041] 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.
[0042] 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 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.degree. C., whereas in Finland low temperature
performance may be required at -30.degree. 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.
[0043] An improvement in cold flow performance may be manifested by
a reduction in, ideally suppression of, so-called "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.
[0044] 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.
[0045] 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.
[0046] 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 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.
[0047] In the context of the above 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.
[0048] By using the present invention, the CFPP of the composition
may be reduced by at least 1.degree. C. compared to its value prior
to addition of the further additive, preferably by at least
2.degree. C., more preferably by at least 3.degree. C. and most
preferably by at least 4 or 5 or in cases 6 or 7 or 8.degree.
C.
[0049] 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 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%.
[0050] A fuel composition prepared according to the present
invention may have a CFPP of -5.degree. C. or lower, preferably -10
or -15.degree. C. or lower. In a preferred embodiment, it may have
a CFPP of -20.degree. C. or lower, preferably -25 or -28 or
-30.degree. C. or lower.
[0051] 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.
[0052] 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 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
CH.sub.2(CO.sub.2R).sub.2 or CH.sub.3COCH.sub.2CO.sub.2R, 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.
[0053] 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 --CO.sub.2H or
--CO.sub.2.sup.-H.sup.+ 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.
[0054] 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 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.
[0055] Dimers or oligomers of fatty acids may also be useable as
further additives (a).
[0056] 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.
[0057] In another embodiment of the present invention, the further
additive (a) is acetic acid. Other C.sub.1 to C.sub.10 or C.sub.1
to C.sub.8 or C.sub.1 to C.sub.6 or C.sub.1 to C.sub.4 carboxylic
acids may also be of use as the further additive.
[0058] 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.
[0059] 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 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.
[0060] 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).sub.n--C.sub.6H.sub.(4-n)(OH)CO.sub.2H, 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.
[0061] 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 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.
[0062] 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.
[0063] 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.
[0064] 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.
[0065] 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
Hitec.TM. 4848A (ex. Afton).
[0066] Other suitable lubricity enhancers are described for example
in: [0067] the paper by Danping Wei and H. A. Spikes, "The
Lubricity of Diesel Fuels", Wear, III (1986) 217-235; [0068]
WO-A-95/33805 (see above)--cold flow improvers to enhance lubricity
of low sulphur fuels; [0069] 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 [0070] U.S. Pat. No. 5,490,864--certain dithiophosphoric
diester-dialcohols as anti-wear lubricity additives for low sulphur
diesel fuels.
[0071] 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.
[0072] 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.
[0073] In accordance with the present invention, more than one
further additive may be used in the fuel composition.
[0074] 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.
[0075] 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.
[0076] 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.
[0077] 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 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).
[0078] 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.
[0079] 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.
[0080] 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.
[0081] 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.
[0082] 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 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; anti-oxidants (e.g.
phenolics such as 2,6-di-tert-butylphenol, or phenylenediamines
such as N,N'-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.
[0083] 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).
[0084] 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.
[0085] 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 quoted in this specification refer,
unless otherwise stated, to active matter concentrations by
mass.)
[0086] 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.
[0087] 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.
[0088] 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.
[0089] The total additive content in the fuel composition may
suitably be from 50 to 10000 ppmw, preferably below 5000 ppmw.
[0090] 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.
[0091] According to another 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: [0092] (a) acids, in particular carboxylic acids,
and mixtures thereof; and [0093] (b) lubricity enhancing
additives.
[0094] The further additive may be as defined above in connection
with the above-mentioned aspects of the present invention. In
particular, it may be a carboxylic acid, for example a C.sub.1 to
C.sub.10 carboxylic acid such as acetic acid. Again, the distillate
base fuel is preferably a middle distillate base fuel.
[0095] According to yet another aspect of the present invention,
there is provided a process for the preparation of a fuel
composition, such as a composition according to the above-mentioned
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
above, in particular with respect to the cold flow properties of
the resultant fuel composition.
[0096] The process of the 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.
[0097] 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.
[0098] 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.
[0099] Another 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
above aspects of the present invention, and/or a fuel composition
prepared in accordance with any one of the above aspects. Again the
fuel composition is preferably introduced for one or more of the
purposes described above in connection with the above 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.
[0100] 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.
[0101] 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.
[0102] 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.
[0103] 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.
[0104] Moreover, unless stated otherwise, any feature disclosed
herein may be replaced by an alternative feature serving the same
or a similar purpose.
[0105] 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. These
examples are not intended to limit the scope of the invention.
[0106] 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.degree. C., followed by cooling to an ambient temperature
of approximately 20.degree. 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.
[0107] Other additives were blended into the fuels either whilst
still warm or at ambient temperature, as convenient.
[0108] 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.
[0109] The following lubricity enhancing additives were used:
[0110] Additive A a commercially available additive containing a
mixture of tall oil fatty acids; [0111] Additive B a commercially
available additive containing a mixture of primarily C.sub.16 to
C.sub.22 (primarily C.sub.16 to C.sub.18) fatty acids; [0112]
Additive C a commercially available ester-based additive containing
a mixture of glycerol esters of linoleic acid, primarily glycerol
mono(linoleate), glycerol di(linoleate) and glycerol tri(linoleate)
in an approximate ratio of 4:4:1; [0113] Additive D a commercially
available additive containing a mixture of tall oil fatty acids;
[0114] Additive E a commercially available additive containing a
mixture of tall oil fatty acids; [0115] 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 [0116] Additive G a
commercially available amide-based additive containing tall oil
fatty acid amides of diethanolamine, of the general formula
R--C(O)--N(CH.sub.2CH.sub.2OH).sub.2.
EXAMPLE 1
[0117] 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 F1) 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.
[0118] The fuel composition (prior to addition of the cold flow
additives) had the specification shown in Table 1 below.
TABLE-US-00001 TABLE 1 Fuel property Test method Density @
15.degree. C. (g/cm.sup.3) IP 365 0.8352 Cloud point (.degree. C.)
IP 219 -8 CFPP (.degree. C.) IP 309 -11 (no hesitation) Kinematic
viscosity @ IP 71 3.284 40.degree. C. (mm.sup.2/s)(centistokes)
Cetane number by IQT IP 498 53.5 Distillation (.degree. 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
[0119] The detergent additive used in the experiments was
OCTIMISE.TM. D3016 (ex. Octel), containing a polyisobutene
succinimide of a polyamine (as a detergent active) and minor
amounts of other fuel additives including a silicone antifoam agent
and a dehazer. Its nominal treat rate was 1000 ppmw.
[0120] The further additives used, in accordance with the present
invention, were the commercially available lubricity enhancing
additives A, B and C as described above.
[0121] 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-US-00002 TABLE 2 Detergent Further additive additive CFPP #1
CFPP #2 CFPP #3 (ppmw) (ppmw) (.degree. C.) (.degree. C.) (.degree.
C.) 0 0 -26 -25 (-24 to -28) (-24 to -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)
[0122] Table 2 shows that the CFPP of fuel composition F1 (with the
cold flow additives) is around -25 to -26.degree. 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.
[0123] 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.
[0124] 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
[0125] 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.TM. D3016) and with further additives in
accordance with the present invention. For each blend, the CFPP was
measured as in Example 1.
[0126] The fuel composition F2 (already containing cold flow
additives) had the specification shown in Table 3 below.
TABLE-US-00003 TABLE 3 Fuel property Test method Density @
15.degree. C. (g/cm.sup.3) IP 365 0.8448 Cloud point (.degree. C.)
IP 219 -11 Kinematic viscosity @ IP 71 2.999 40.degree. C.
(mm.sup.2/s)(centistokes) Cetane number by IQT IP 498 55.1
Distillation (.degree. 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
[0127] 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).
[0128] 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 replicate
readings, with the range of the readings shown in brackets.
TABLE-US-00004 TABLE 4 Detergent Further additive additive CFPP #1
CFPP #2 CFPP #3 (ppmw) (ppmw) (.degree. C.) (.degree. C.) (.degree.
C.) 0 0 -30 -31 -29 (-29 to -31) (-30 to -31) (-28 to -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)
[0129] Table 4 shows that the CFPP of fuel composition F2 is around
-30.degree. C. Incorporation of the detergent additive results in a
significant rise in CFPP to -20.degree. C., demonstrating the
detrimental interaction between the cold flow additives present in
F2 and the subsequently added detergent.
[0130] 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 effect of the detergent on cold flow
performance appears to be entirely negated by the further
additive.
[0131] Particularly effective further additives include the fatty
acid mixture, and the fatty acid-based lubricity enhancing
additives such as Additives A, B and E.
[0132] 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
[0133] 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.
[0134] 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.
TABLE-US-00005 TABLE 5 Detergent Further additive additive CFPP #1
CFPP #2 CFPP #3 (ppmw) (ppmw) (.degree. C.) (.degree. C.) (.degree.
C.) 0 0 -26 -25 (-24 to -28) (-24 to -25) 636 0 -19 -19 -17 Severe
hesitation at -17 636 Additive F -20 -30 Severe -30 Mild (225)
hesitation hesitation at -21 at -20 636 Additive F -26 -24 (450)
636 Acetic -27 -24 -25 acid (110) 636 Additive C -25 -24 (500) 636
Additive G -24 -24 (500) 636 Additive A -27 -24 -26 (500) 636
Additive C -28 -28 (1000) 636 Additive G -25 -27 -25 (1000) 636
Linolenic -26 -20 -26 acid (500)
[0135] 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.
EXAMPLE 4
[0136] 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.
[0137] 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-US-00006 TABLE 6 Detergent Further additive additive CFPP #1
CFPP #2 CFPP #3 (ppmw) (ppmw) (.degree. C.) (.degree. C.) (.degree.
C.) 0 0 -30 -31 -29 (-29 to -31) (-30 to -31) (-28 to -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
[0138] 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.
[0139] 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.degree. C.
[0140] 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.degree.
C.
[0141] 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.degree. C.
[0142] 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.
[0143] 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.
TABLE-US-00007 TABLE 7 Further Detergent additive CFPP #1 CFPP #2
CFPP #3 Fuel (ppmw) (ppmw) (.degree. C.) (.degree. C.) (.degree.
C.) 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)
[0144] 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
[0145] 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.
[0146] The CFPP results are shown in Table 8.
TABLE-US-00008 TABLE 8 MDFI WASA Detergent CFPP CFPP CFPP additive
additive additive Additive #1 #2 #3 (ppmw) (ppmw) (ppmw) A (ppmw)
(.degree. C.) (.degree. C.) (.degree. 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
[0147] 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.degree. C. Without these additives (second line
of Table 8), the CFPP of the composition increases to -11.degree.
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.
[0148] 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
[0149] This example illustrates that a further additive may be
incorporated into a fuel composition, in accordance with the
present invention, in order to reduce undesirable hesitation
effects when detergent and cold flow additives are combined.
[0150] Fuel compositions F1 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.
[0151] Table 9 below shows the results for fuel F1 combined with
the OCTIMISE.TM. 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 .degree. C.
TABLE-US-00009 TABLE 9 Detergent Further additive additive (ppmw)
(ppmw) CFPP #1 (.degree. C.) CFPP #2 (.degree. C.) CFPP #3
(.degree. C.) 0 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
[0152] 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.degree. C. rather than at both
-15 and -21.degree. C. The hesitation at -15.degree. 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.
[0153] Table 10 below shows the results for fuel F4 combined with
OCTIMISE.TM. D3016. The further additive used, in accordance with
the present invention, was the fatty acid-based lubricity enhancing
Additive B. Where hesitation was observed, this is shown with the
CFPP figures; all values are quoted in .degree. C.
TABLE-US-00010 TABLE 10 Detergent Further additive additive (ppmw)
(ppmw) CFPP #1 (.degree. C.) CFPP #2 (.degree. C.) CFPP #3
(.degree. C.) 0 0 -21 Mild -27 Mild -20 downphase downphase
hesitation hesitation at at -19 -21 1000 0 -15 Severe -17 Mild -15
Mild hesitation hesitation at hesitation at -13 at -13 -13 1000
Additive -20 -20 B (150)
[0154] Here, incorporation of the detergent additive leads to
severe hesitation effects in one of the test kits used and 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.
* * * * *