Note: Descriptions are shown in the official language in which they were submitted.
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FUEL FORMULATIONS
Field of the Invention
This invention relates to fuel formulations, their
preparation and their use, and to the use of certain
materials in fuel formulations for new purposes.
Background to the Invention
In the interests of the environment, and to comply
with increasingly stringent regulatory demands, it is
necessary to increase the amount of biofuels used in
automotive fuels.
Biofuels are combustible fuels, typically derived
from biological sources, which result in a reduction in
"well-to-wheels" (i.e. from source to combustion)
greenhouse gas emissions. In gasoline fuels for use in
spark ignition engines, the most common biofuels are
alcohols, in particular ethanol. These are typically
blended with more traditional gasoline fuel components.
For use in diesel engines, fatty acid methyl esters
(FAMEs) such as rapeseed methyl ester and palm oil methyl
ester are the biofuels most commonly blended with
conventional diesel fuel components.
Dialkyl carbonates, in particular the lower dialkyl
carbonates dimethyl carbonate (DMC) and diethyl carbonate
(DEC) are also biofuels which have in the past been added
to both gasoline and diesel fuels. DMC and DEC have been
used for instance as oxygenates, as combustion improvers
and to reduce pollution levels. However, there are a
number of practical constraints on the concentrations at
which DMC and DEC can be included in automotive fuels. In
particular, they appear to cause undesirable swelling of
elastomeric engine components such as fuel pump seals, an
effect which can reach unacceptable levels at as low as
CA 02722462 2010-11-24
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5% v/v for DEC. In gasoline formulations, oxygen content
specifications limit DMC and DEC concentrations to around
5% v/v. In diesel fuels, at least for use in the European
Union, flash point and density specifications tend to
limit DMC concentrations to less than 2% v/v and DEC
concentrations to around 3% v/v. As a result, dialkyl
carbonates have received little attention as fuel
components other than at relatively low levels.
It would be desirable to provide new
biofuel-containing fuel formulations which could overcome
or at least mitigate the above problems.
Statements of the Invention
According to a first aspect of the present invention
there is provided a fuel formulation containing a dialkyl
carbonate (DAC) having 6 or more carbon atoms.
It has surprisingly been found that higher molecular
weight DACs can cause less elastomer damage than DMC and
DEC in blends with both gasoline and diesel fuels. It has
also surprisingly been found that these DACs can improve
the lubricity of gasoline and diesel fuels. The use of a
higher molecular weight DAC as a replacement for either
DMC or DEC can therefore provide fuel benefits. Their
reduced elastomer damaging effects can also allow the
higher molecular weight DACs to be included in fuels at
higher concentrations, thus providing increased bioenergy
contents.
There can be a number of advantages to the use of
DACs in fuel formulations, which advantages can be
increased if the DACs can be included at higher
concentrations. DACs for instance have low toxicity and
are biodegradable. They have good octane blending
properties, making them suitable for use in gasoline
fuels. Unlike ethanol, which at blend ratios less than
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7o v/v typically requires base fuel modification to
compensate for undesirable RVP (Reid vapour pressure)
boost, DACs do not significantly impact on the RVP of the
base fuel blend at any blend ratios, making it easier to
control evaporative emissions when they are used as
components of gasoline formulations.
The use of DACs in diesel fuels can cause less
environmental impact than the more traditional use of
FAME biofuel components. DACs also show resistance to
phase separation in hydrocarbon-water mixtures, which
makes them less likely to migrate into water which may be
present in wet storage tanks; they can also therefore
help to stabilise ethanol-containing fuels.
DACs can be produced from renewable ingredients
(carbon dioxide and bio-alcohols). DEC in particular can
be produced from azeotropic ethanol, thus avoiding the
energy penalty associated with breaking the azeotropic
ethanol/water mix to produce anhydrous ethanol. DACs can
thus provide a route to including an alcohol-based (in
particular ethanol-based) oxygenate in a fuel, but with
less carbon consumption.
A fuel formulation according to the invention may be
suitable for use in an internal combustion engine. It may
in particular be an automotive fuel formulation. In an
embodiment, it is a gasoline fuel formulation which is
suitable and/or adapted for use in a spark ignition
(petrol) engine. In an alternative embodiment it is a
diesel fuel formulation which is suitable and/or adapted
for use in a compression ignition (diesel) engine. In
further embodiments it may be suitable and/or adapted for
use as an industrial gas oil, or as a domestic heating
oil.
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The DAC used in a fuel formulation according to the
invention has 6 or more carbon atoms, including the
carbonate ( -C(O)O- ) carbon. It is referred to herein as
a "?C6 DAC". It may contain 7 or 8 or more carbon atoms.
It may contain up to 15 carbon atoms, or up to 14 or 13
or 12 or 11 or 10 or 9 carbon atoms. It may be a
symmetric or an asymmetric DAC. In an embodiment, it is a
symmetric DAC. Each of its two alkyl groups may
independently be either straight chain (n-) or branched
(as in for example an isopropyl or tert-butyl group). In
an embodiment, at least one of the alkyl groups is a
straight chain alkyl group. In an embodiment, both of the
alkyl groups are straight chain alkyl groups.
Suitable symmetric ?C6 DACs for use in the
formulation of the invention include di-n-propyl
carbonate (DPrC), di-isopropyl carbonate (DiPrC),
di-n-butyl carbonate (DBC), and mixtures thereof. Other
suitable symmetric 2!C6 DACs include dipentyl carbonate
(DPeC), dihexyl carbonate (DHexC), diheptyl carbonate
(DHeptC) and mixtures thereof; in each case the two alkyl
groups may independently be either straight chain or
branched.
Suitable asymmetric >C6 DACs include propyl ethyl
carbonate (PrEC), butyl ethyl carbonate (BEC), pentyl
ethyl carbonate (PeEC), hexyl ethyl carbonate (HexEC),
heptyl ethyl carbonate (HeptEC), and mixtures thereof; in
each case the alkyl group having three or more carbon
atoms may be either straight chain or branched, suitably
the former.
A fuel formulation according to the invention may
contain a mixture of two or more ?C6 DACs. The mixture
may have been produced from a mixture of two or more
alcohols: for example, ethanol and butanol together may
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be used to prepare a mixture of DEC and DBC, or of DEC,
BEC and DBC.
In an embodiment of the invention, the DAC is
selected from DBC, BEC and mixtures thereof. In an
embodiment, the DAC is DBC, in particular when the fuel
formulation is a diesel fuel formulation.
In particular where the formulation is a gasoline
fuel formulation, it may be preferred for the >C6 DAC to
contain fewer than 9 carbon atoms, or fewer than 8 carbon
atoms. In general, lower molecular weight DACs are likely
to have boiling points within the normal gasoline range.
In particular where the formulation is a gasoline
fuel formulation, the ?C6 DAC may be selected from PrEC,
BEC, DPrC, DiPrC and mixtures thereof. It may be selected
from PrEC, BEC, DPrC and mixtures thereof.
In particular although not necessarily when the
formulation is a gasoline fuel formulation, it may be
preferred for the >C6 DAC not to be PrEC, or for the PrEC
to be included at a concentration of less than 10% v/v or
of 9 or 8 or 7 or 6% v/v or less.
In particular where the formulation is a diesel fuel
formulation, it may be preferred for the ?C6 DAC to
contain at least 7 carbon atoms, or at least 8 carbon
atoms. In general, higher molecular weight DACs are
likely to have higher viscosities and higher flash
points, thus making them more suitable for use as diesel
fuel components; they are also more likely to have
boiling points within the normal diesel range.
In particular where the formulation is a diesel fuel
formulation, the >C6 DAC may be selected from BEC, DPrC,
DiPrC, DBC and mixtures thereof. It may be selected from
BEC, DPrC, DBC and mixtures thereof, or (in particular
where the DAC concentration is 8 or 9 or loo v/v or
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greater) from DPrC, DBC and mixtures thereof. It may be
selected from di(n-alkyl) carbonates having 7 or more
carbon atoms, and mixtures thereof. It may be selected
from BEC, DBC and mixtures thereof. In an embodiment, it
is DBC.
In an embodiment, in particular where the
formulation is a diesel fuel formulation, it may be
preferred for the ?C6 DAC to be selected from PrEC, DiPrC
and mixtures thereof, or for the >C6 DAC to be PrEC, or
for the ZC6 DAC to be an asymmetric DAC.
Where the formulation is a gasoline fuel
formulation, the ?C6 DAC suitably has a boiling point
(ASTM D86) of from 0 to 250 C. Where the formulation is a
diesel fuel formulation, the ?C6 DAC suitably has a
boiling point (ASTM D86) of from 150 or 180 to 360 C.
The ?C6 DAC may be included in the fuel formulation
at a concentration of 0.56 v/v or greater, or of at least
1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or loo v/v. Its
concentration may in some embodiments be 25 or 50 or
75% v/v or greater. It may be included at a concentration
of up to 100% v/v, or of up to 99 or 98% v/v; in other
words, the ?C6 DAC may itself be used as a fuel, or may
represent the major proportion of a fuel formulation
which may optionally contain minor amounts of fuel
additives and/or additional fuel components.
The ~C6 DAC may be included in the fuel formulation
of the invention at a concentration of up to 95 or 90 or
80 or 70 or 60% v/v. In embodiments, it may be included
at a concentration of up to 50% v/v, or of up to 40 or
30% v/v, or of up to 25 or 20 or 18 or 15 or 12 or
10% v/v. Its concentration may for instance be from 5 to
20% v/v or from 5 to 10% v/v. In particular where the DAC
is DBC and the formulation is a diesel fuel formulation,
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the DAC may be included at a concentration of up to 15 or
18 or 20% v/v or in cases of up to 30 or 40 or 50% v/v,
or of up to 60 or 70 or 80 or 90 or 100% v/v.
The ?C6 DAC may be obtained from any suitable
source, of which many are available. It can for example
be prepared by oxidative carbonylation of alcohols, or by
transesterification of dimethyl carbonate with alcohols,
or it may be generated as a co-product in the synthesis
of monoethylene glycol from ethylene oxide and carbon
dioxide via ethylene carbonate. The alcohols used in such
processes may themselves be derived from biological
sources.
In an embodiment, it may be preferred for the >C6
DAC not to have been synthesised using phosgene (COC12),
as this may introduce undesirable impurities such as
chlorides or carbonochloridic acid derivatives. Such
impurities may contribute to deposit, stability and
corrosion problems in a fuel formulation.
A fuel formulation according to the invention may
contain other fuel components, as desired. Where it is a
gasoline fuel formulation, for example, it may contain
one or more gasoline fuel components, which are typically
liquid hydrocarbon distillate fuel components containing
hydrocarbons which boil in the range from 0 to 250 C
(ASTM D86 or EN ISO 3405). A gasoline fuel component
suitably has a research octane number (RON) (ASTM D2699)
of from 85 to 115 or from 95 to 115 and/or a motor octane
number (MON) (ASTM D2700) of from 75 to 95 or from 85 to
95.
Where the formulation is a diesel fuel formulation,
it may contain one or more diesel fuel components, which
are typically liquid hydrocarbon middle distillate fuel
components (for example gas oils) containing hydrocarbons
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which boil in the range from 150 or 180 to 360 C (ASTM
D86 or EN ISO 3405). A diesel fuel component suitably has
a measured cetane number (ASTM D613) of from 40 to 70 or
from 40 to 65 or from 51 to 65 or 70.
Such additional fuel components may be derived from
any suitable source. They may for example be petroleum
derived. Alternatively they may be synthetic products
such as from a Fischer-Tropsch synthesis. Additional fuel
components may also be derived from biological sources.
They may be or include oxygenates such as alcohols (in
particular Cl to C3 aliphatic alcohols, more particularly
ethanol) or fatty acid methyl esters (FAMEs) such as
rapeseed methyl ester or palm oil methyl ester.
The formulation of the invention may contain one or
more lower molecular weight DACs, for example selected
from DMC, DEC and mixtures thereof, in addition to the
>C6 DAC.
Where the formulation is a gasoline fuel
formulation, it will suitably comply with applicable
current standard gasoline fuel specification(s) such as
for example EN 228 in the European Union. By way of
example, the overall formulation may have a density from
0.720 to 0.775 kg/m3 at 15 C (ASTM D4052 or EN ISO 3675);
a final boiling point (ASTM D86 or EN ISO 3405) of 210 C
or less; a RON (ASTM D2699) of 95.0 or greater; and/or a
MON (ASTM D2700) of 85.0 or greater. Relevant
specifications may however differ from country to country
and from year to year, and may depend on the intended use
of the formulation. Moreover a formulation according to
the invention may contain fuel components with properties
outside of these ranges, since the properties of an
overall blend may differ, often significantly, from those
of its individual constituents.
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Where the formulation is a diesel fuel formulation,
it will suitably comply with applicable current standard
diesel fuel specification(s) such as for example EN 590
(for Europe) or ASTM D975 (for the USA). By way of
example, the overall formulation may have a density from
820 to 845 kg/m3 at 15 C (ASTM D4052 or EN ISO 3675); a
T95 boiling point (ASTM D86 or EN ISO 3405) of 360 C or
less; a measured cetane number (ASTM D613) of 51 or
greater; a kinematic viscosity at 40 C (ASTM D445 or
EN ISO 3104) from 2 to 4.5 centistokes; a sulphur content
(ASTM D2622 or EN ISO 20846) of 50 mg/kg or less; and/or
a polycyclic aromatic hydrocarbons (PAH) content
(IP 391(mod)) of less than l1o w/w. Relevant
specifications may however differ from country to country
and from year to year, and may depend on the intended use
of the formulation. Moreover a formulation according to
the invention may contain individual fuel components with
properties outside of these ranges.
A fuel formulation according to the invention may
contain standard fuel or refinery additives, in
particular additives which are suitable for use in
automotive gasoline or diesel fuels. Many such additives
are known and commercially available. The formulation may
for example contain a corrosion inhibitor, since DACs -
in common with many other oxygenates - are known to be
slightly corrosive and may reduce the performance of
standard anti-corrosion additives. Suitable corrosion
inhibitors include alkyl phosphates, esters, amine salts
of alkenyl succinic acids, alkyl phosphoric acids and
aryl suiphonic acids: commercially available examples
include the products DCITM 4a and 6a (ex. Innospec),
HitecTM 580 (ex. Afton), NalcoTM 5403 and 5405 (ex. Nalco),
Spec-AidTM 8Q22 (ex. GE Betz), and ToladTM 351 and 4410
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(ex. Baker Petrolite). They may be included at a
concentration of up to 25 ppmw (parts per million by
weight): slightly higher than usual treat rates may be
required due to the presence of the DAC.
In an embodiment, the formulation contains a
lubricity enhancing additive, although as discussed below
the lubricity-enhancing properties of the >!C6 DAC may
make this unnecessary, or may make possible the use of
lower levels of such additives.
According to a second aspect of the present
invention, there is provided a process for the
preparation of a fuel formulation, which process involves
blending together a DAC having 6 or more carbon atoms and
one or more additional fuel components such as those
described above. The additional fuel component(s) may for
example be gasoline or diesel base fuels. The >C6 DAC and
the additional fuel component(s) may also be mixed with
one or more fuel additives. The process may be used to
produce at least 1,000 litres of the fuel formulation, or
at least 5,000 or 10,000 or 25,000 litres, or at least
50,000 or 75,000 or 100,000 litres.
A third aspect of the invention provides a method of
operating an internal combustion engine, and/or a vehicle
which is driven by an internal combustion engine, which
method involves introducing into a combustion chamber of
the engine a fuel formulation according to the first
aspect of the invention. The engine may be a spark
ignition (petrol) engine. It may be a compression
ignition (diesel) engine.
According to a fourth aspect of the invention there
is provided the use of a DAC having 6 or more carbon
atoms, in a fuel formulation, for the purpose of
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improving the lubricity of the formulation. The
formulation is suitably a diesel fuel formulation.
In the context of the fourth aspect of the
invention, it may be preferred for the DAC to be an
asymmetric DAC. In an embodiment, it may be selected from
PrEC, BEC and mixtures thereof.
The lubricity of a fuel formulation can be assessed
by any suitable method. One such method involves
measuring the wear scar produced on an oscillating ball
from contact with a stationary plate whilst immersed in
the formulation. This "wear scar" may be measured for
example using the test described in Example 3 below.
An "improvement" in the lubricity of a formulation
may be manifested for example by a lower degree of wear
scar, or of other friction-induced damage, in two
relatively-moving components which are exposed to the
formulation. The invention may be used to achieve any
degree of improvement in the lubricity of the fuel
formulation, and/or for the purpose of achieving a
desired target lubricity.
A fifth aspect of the invention provides the use of
a DAC having 6 or more carbon atoms, in a fuel
formulation, for the purpose of reducing the
concentration of a lubricity-enhancing additive in the
formulation. Again the formulation is suitably a diesel
fuel formulation.
In the context of this fifth aspect of the
invention, the term "reducing" embraces any degree of
reduction, including reduction to zero. The reduction may
for instance be 10% or more of the original
lubricity-enhancing additive concentration, or 25 or 50
or 75 or 90% or more. The reduction may be as compared to
the concentration of lubricity-enhancing additive which
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would otherwise have been incorporated into the fuel
formulation 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 lubricity-enhancing additive which was
present in the formulation prior to the realisation that
a >C6 DAC could be used in the way provided by the
present invention, and/or which was present in an
otherwise analogous fuel formulation intended (e.g.
marketed) for use in an analogous context, prior to
adding a >C6 DAC to it in accordance with the invention.
The reduction in lubricity-enhancing additive
concentration may be as compared to the concentration of
lubricity-enhancing additive which would be predicted to
be necessary to achieve a desired target lubricity for
the formulation in the absence of the 2!C6 DAC.
The lubricity-enhancing additive may be any additive
which is capable of, or intended to, improve the
lubricity of the formulation. Many such additives are
known; they include for example R655TM (an ester-based
additive ex. Infineum) and LZ 539CTM (an acid-based
additive ex. Lubrizol).
A sixth aspect of the invention provides the use of
a first DAC having 6 or more carbon atoms, in a fuel
formulation, for the purpose of replacing all or part of
a second DAC having fewer carbon atoms than the first DAC
which is, or would otherwise have been, included in the
formulation, whilst at the same time reducing the
elastomer damaging effects (in particular the elastomer
swelling effects) of the formulation due to the presence
of the DAC(s).
The second DAC may be a DAC having 5 or fewer carbon
atoms. It will typically be selected from dimethyl
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carbonate (DMC), diethyl carbonate (DEC) and mixtures
thereof. It may have been included, or intended to be
included, in the formulation for any purpose, for example
as an oxygenate, to increase the bioenergy content of the
fuel, or as a combustion improver, or to reduce pollution
levels caused by combustion of the fuel.
The first DAC may have 7 or more carbon atoms, or 8
or 9 or more carbon atoms.
The sixth aspect of the invention allows a higher
molecular weight DAC to be used in place of a lower
molecular weight DAC such as DMC or DEC, in order to
reduce the elastomer damaging effects which can be caused
by the use of DMC and DEC in fuel formulations. This
mitigation of elastomer damaging - in particular
elastomer swelling - effects can allow higher
concentrations of DAC to be included in a formulation. It
therefore allows a fuel to benefit from the advantages of
including a DAC, but with less of an increase in the
elastomer damaging effects of the overall formulation
than would be caused by including the same concentration
of DMC or DEC alone.
The first DAC (which has 6 or more carbon atoms) may
therefore be used, in a DAC-containing fuel formulation,
for the purpose of increasing the overall DAC
concentration whilst maintaining the elastomer damaging
effects of the formulation within a desired
specification, and/or for the purpose of reducing the
elastomer damaging effects of the formulation relative to
those that would be caused by the inclusion of the same
amount of a second DAC which typically has 5 or fewer
carbon atoms.
Thus the present invention is able to provide more
optimised methods for formulating biofuel-containing fuel
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formulations, in particular to achieve target levels of
elastomer damage and/or lubricity.
In the context of the sixth aspect of the invention,
an elastomer damaging effect may be any effect which
reduces the ability of an elastomeric material to
function correctly in a fuel-consuming system and/or in
the presence of a fuel formulation. It may comprise
swelling of the elastomer when in contact with the fuel
formulation. It may comprise a change (typically a
reduction) in the hardness and/or flexibility of the
elastomer when in contact with the fuel formulation.
Elastomer swell measurements in particular provide a
measure of the compatibility of elastomeric materials,
such as are used in fuel pump seals and other engine
components, with a fuel component or formulation or
additive. Generally this compatibility is evaluated by
assessing changes in the properties of an elastomer due
to its immersion in a test fluid. The elastomer swelling
effects of a fuel formulation may for instance be
assessed by measuring the increase or percentage increase
in volume of an elastomeric material on immersion in the
formulation for a predetermined period of time. A smaller
volume increase indicates a reduction in elastomer
swelling effects. This assessment may for example be
carried out for nitrile and/or fluorocarbon elastomers,
suitably both. A suitable assessment method is described
in Example 1 below. Alternatively a standard test method
such as ISO 1817:1998 may be used to measure elastomer
swell effects.
Changes in the hardness and/or flexibility of an
elastomeric material may be assessed using standard test
methods such as the Shore hardness test or TMS 556.
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In the context of the present invention, "use" of a
DAC in a fuel formulation means incorporating the DAC
into the formulation, typically as a blend (i.e. a
physical mixture) with one or more other fuel components.
The DAC will conveniently be incorporated before the
formulation is introduced into an engine or other system
which is to be run on the formulation. Instead or in
addition the use of a DAC may involve running a
fuel-consuming system, typically an internal combustion
engine, on a fuel formulation containing the DAC,
typically by introducing the formulation into a
combustion chamber of an engine.
"Use" of a DAC in the ways described above may also
embrace supplying the DAC together with instructions for
its use in a fuel formulation to achieve the purpose(s)
of any of the fourth to the sixth aspects of the
invention, for instance to improve the lubricity of the
formulation. The DAC may itself be supplied as part of a
composition which is suitable for and/or intended for use
as a fuel additive, in which case the DAC may be included
in such a composition for the purpose of influencing its
effects on the lubricity and/or elastomer damaging
effects of a fuel formulation.
Use of a DAC in a fuel formulation for a particular
purpose may also embrace using the DAC itself as a fuel
for the relevant purpose, optionally together with minor
amounts of one or more fuel additives.
Throughout the description and claims of this
specification, the words "comprise" and "contain" and
variations of the words, for example "comprising" and
"comprises", mean "including but not limited to", and do
not exclude other moieties, additives, components,
integers or steps. Moreover the singular encompasses the
CA 02722462 2010-11-24
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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 each aspect of the invention
may be as described in connection with any of the other
aspects. Other features of the invention will become
apparent from the following examples. Generally speaking
the invention extends to any novel one, or any novel
combination, of the features disclosed in this
specification (including any accompanying claims and
drawings). Thus features, integers, characteristics,
compounds, chemical moieties or groups described in
conjunction with a particular aspect, embodiment or
example of the invention are to be understood to be
applicable to any other aspect, embodiment or example
described herein unless incompatible therewith. Moreover
unless stated otherwise, any feature disclosed herein may
be replaced by an alternative feature serving the same or
a similar purpose.
The present invention will now be further described
with reference to the following non-limiting examples.
Example 1
Gasoline fuel formulations were prepared by blending
a number of DACs, each at both 5% v/v and 10% v/v, with a
gasoline base fuel GBF. The base fuel was a commercially
available EN 228-compliant unleaded gasoline with 95 RON
(ex. Shell).
The DACs tested were dimethyl carbonate (DMC),
diethyl carbonate (DEC), n-propyl ethyl carbonate (PrEC),
n-butyl ethyl carbonate (BEC), di-n-propyl carbonate
(DPrC) and di-isopropyl carbonate (DiPrC). Their
CA 02722462 2010-11-24
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properties are summarised in Table 1 below. Table 1 also
shows the properties of di-n-butyl carbonate (DBC), which
was used in Examples 2 to 5.
Table 1
Property DMC DEC PrEC BEC DPrC DiPrC DBC
Molecular 90 118 132 146 146 146 174
weight
Symmetric S S A A S S S
(S) or
asymmetric
(A)
Research >120 >120 n.d. n.d. n.d. n.d. n.d.
octane no.
(RON)
Motor >118 105.7 n.d. n.d. n.d. n.d. n.d.
octane no.
(MON)
Cetane no. <20 <20 n.d. n.d. n.d. n.d. n.d.
(CN)
Flash 16.5 34.5 29 53 59 45.5 89
point ( C)
Boiling 90 126 175 174 175 150 215
point ( C)
Density @ 1.076 0.981 0.966 0.945 0.949 0.927 0.929
15 C
(g/cm3)
Water 151 29 19 9 5 14 5
solubility
(g/L)
Kinematic 0.48 0.66 0.849 0.976 1.097 0.967 1.462
viscosity
@ 40 C
(cSt)
Lower 14.5 21.6 22.9 25.0 25.1 25.4 28.2
heating
value
(LHV)
(MJ/kg)
n.d. = not determined
Properties were measured using the test methods
indicated in Table 2 below.
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Table 2
Property Test method
RON ASTM D2699
MON ASTM D2700
CN ASTM D613
Flash point IP 34
Boiling point (& IP 123
other distillation
properties)
Density @ 15 C IP 365
Water solubility Internal
method (see
Example 4)
Kinematic viscosity IP 71
Q 40 C
LHV IP 12
Table 3 summarises some of the physicochemical
properties of the gasoline base fuel GBF and of blends of
the base fuel with DMC and DEC at both 5 and 10% v/v.
Table 3 also shows, where applicable, the values required
by the European gasoline specification EN 228.
CA 02722462 2010-11-24
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M 01 O O rHi N M to
a)
r-i Ln
00 x N O 00 r--I
F' N( I I N N
O
S'. O O
00 0 l0
W N rl N [fl
al 00
O
Oc)OOOOO rX4 r
:v -i Ln O H 01 l0 O dl co
01 l0 Lfl L- O w H O N 01 00
01 00 O W O
0 M Tv H H N N d~
S4 U O
~ U ri U U U
H H o\o \o o\o rsa W
-r1 0 0 0
A o N H LO 01
W
-ri
H Q
CA 02722462 2010-11-24
- 20 -
Table 4 summarises some of the physicochemical
properties of blends of GBF with the higher molecular
weight dialkyl carbonates PrEC, BEC, DPrC and DiPrC,
again at both 5 and 10% v/v.
CA 02722462 2010-11-24
L N Lfl 01 O
+ H H 00 N
o\o Ln 00 tl7 M N
N
o N c1' H H H
Ln
+ U N M M O N
\ Ln
00 H H N
[~ L oD a+ W O p Ul O N d~
O M H H
m 00 N
N M 01 O Ill
CQ H Q a~ 0c) 0 M d' H H H .1
N N H N co co + U Ol
W o\o 4 H r- U) O l0 wO 00 dl d'
O M d~ H H N N d'
0) CC)
M l0 01 00 H O
+
r, o W
Ill l0 H M O l0 01 N dl
r~I C~7 r PU 00 0 M d~ H H H
Lfl M N
M H M 00
E I o\o U Lo M O Ill
[ra W ul O ~0 O N di
fUA mn 01 a0 p N ::v H H N
M O r Ln M O M
o\o W C O O N
O w Ln Ln O N d'
H 04 M 00 p H N
M
+ 00 01 H O t` dl O
Ln to N
o\o W ~` O t11 u1
0 ~ 0 N
a 01 O Q M d~ rI r-I d'
r1 ~"
N U N N 4) O
v zz4-1 -(d a4 M~
00 -ci H H o\0 0\0 o\o (3+ W [z1
}l ~" U H ul 0)
w L H
H 0
CA 02722462 2010-11-24
- 22 -
It can be seen from Table 4 that all of the blends
containing ?C6 DACs were compliant with the EN 228
gasoline specification in terms of their octane numbers
and densities. Indeed, the DACs increased the octane
numbers of the base fuel, the >-C6 DACs performing
generally better in this respect than DMC and DEC and
also in many cases reducing the fuel sensitivity (RON -
MON) better than DMC and DEC. Although the blends
containing ?C6 DACs had E100 values below the EN 228
minimum, it is expected that such issues could be
resolved fairly readily by minor adjustments to base fuel
specifications prior to the addition of a zC6 DAC.
The elastomer damaging effects caused by each of the
GBF/DAC blends, and by the base fuel itself and the neat
DACs, were then assessed using the following test method,
which is a modified version of the standard test method
ISO 1817:1998. Two elastomeric materials were tested: a
hydrogenated nitrile elastomer ("Elast-o-LionTM" 280) and
a fluorocarbon tetrapolymer elastomer ("VitonTM" LR 6316),
both ex. James Walker & Co Ltd, UK. The volumes of
elastomer samples of initial dimensions 50 mm x 25 mm x
3 mm were measured after immersion in 100 ml of the
relevant test fluid at ambient temperature and pressure
for 24 hours. After immersion, the samples were quickly
dried, and weighed in air and in water (within 8 hours of
removal from the test fluid). Percentage changes in
volume were then calculated.
Shore hardness values were also measured for the
elastomer samples both before and after immersion in the
test fluids; hardness was measured at ambient temperature
using a Type A Shore DurometerTM (ex. Shore Instruments,
Instron Corp, USA).
CA 02722462 2010-11-24
- 23 -
The results are shown in Tables 5a (DMC and DEC) and
5b (other DACs) below. FC refers to tests on the
fluorocarbon elastomer, Ni to tests on the nitrile
elastomer. In each cell of the table, the first figure is
the percentage change in elastomer volume, and the second
the percentage change in elastomer hardness. DMC and DEC
were also tested at 20 v/v in the base fuel.
CA 02722462 2010-11-24
\ N \ N \ M \
H
H N = M = d1 Ol
N rl N M 00 z 0a , O = rn , C'
rl U \ \ N N N Q N to r-i ~O r-1 d~
'T W N ri \ \ N N (N H
Q ~ dl l0
l~ 0l
N N m M d
M U I i i \
N4 r- n W
04 o = N = L~ 00
Pr4
=rl ri M M
N M d~ O
M H
N M
%lo
H
M
U t N H fit i L
U W i\ I U\ N \ M \ l0
W \ U) \ \ =rl ~-I N dl = M
Q N O N Z 0+ = O N = o = Ln
N H Q N N
N C N H N
N l0 N N
H H
U
04 U U ~\t`tn n N o
44 04 (N . N = g
dl N Q N N d~ N N
ri CO
ri M N co
U
W i 1 N 'Cl
z A 0 M\ Q I
N M \ N \ N \ lO \ l0
l~ r I O r1 U N = d' = lO
~U N M d~ d' CO Z = O = O = M = O
Q M Ln W L N( N O H O M
N N M to
In U
W i
rl Oa U \ [~ \ r~ \ Ol
\
U (D
W 0 M N '
M L` N N N N
CC)
Ln in
= =d~ O dl M
rT4
Q ~. <`= \ ' N ~, rl W N N H Ol H
LO N
00 N N M N Z H O N = O = 0l
T-i
04 N N Ol H N M N
N m Ln
u 0) co
u W o N
G4 4 = H ' N ' M do N
04 (N M L9 CO
U
O o
O yoNLn~o~o U^
\ O~ 0 0
p U 5 o Ln 0 o
r-I
Q v
CA 02722462 2010-11-24
- 25 -
The data in Tables 5a and 5b show that at any given
concentration, the >C6 DACs (PrEC, BEC, DPrC and DiPrC)
cause less elastomer damage (swelling and reductions in
hardness) than the lower molecular weight DACs, DMC and
DEC. For the >C6 DACs, nitrile elastomer swell levels
were well within the "normal" range (a 20-306 volume
change) recorded for a selection of available gasoline
base fuels, at both 5 and 10% v/v. In contrast, DMC at
10% v/v caused a nitrile elastomer swell which was well
above the normal base fuel range. In the fluorocarbon
elastomer tests, the ?C6 DACs performed mostly in line
with the normal base fuel range (a 1-4% volume change),
whilst DMC and DEC caused significantly higher swell at
both 5 and 10% v/v.
Thus, DMC and DEC can cause elastomer damage
problems when blended in gasoline fuels, even at 5% v/v.
However, >C6 DACs may be used in gasoline fuel
formulations in place of either DMC or DEC, in order to
reduce such problems. They may be incorporated at
concentrations of at least 10% v/v without undue concerns
over elastomer damage issues.
Example 2
Diesel fuel formulations were prepared by splash-
blending a number of DACs, each at both 5% v/v and
10% v/v, with a diesel base fuel DBF. The base fuel was a
commercially available, EN 590-compliant zero sulphur
diesel (ex. Shell).
The DACs tested were those used in Example 1, and in
addition di-n-butyl carbonate (DBC). Their properties are
summarised in Table 1 above.
Table 6 summarises some of the physicochemical
properties of the diesel base fuel DBF and of blends of
the base fuel with DMC and DEC at both 5 and 10% v/v.
CA 02722462 2010-11-24
- 26 -
Table 6 also shows, where applicable, the values required
by the European diesel specification EN 590.
CA 02722462 2010-11-24
+ Ln to ri r- Ln dt
o\o U N H O =
G4 O ~n N M N m M N
H N 00 N Ln N N Vt Ln
Ln o H H M M M
+ U N Ln H Ln 0 N 00 r- m C'
(L4 o\o .' M zi OD 0 M Lf
(~ Q Ln 00 LO
Ln n H 00 N M dt Ln
0 ri N M M M
+ m Lr) LI) L-
oo U 01 O Ln 00 tD
G4 O Ln dt * co r- O Ili L-
H Ul 00 V N co rl N M dt Ln
0 rI M M M
+ aD L0o M O
U N 00 O Lr) . .
0\0 - dt . d00 O t Lfl ~Il (J4 pq Ln LLn n co V N 00 H
9) 01 L- M III Lr)
0 rl N M LYl m
H
Ln
l z 01 (ti i 0O0 i 1 I L tD 0
I
Ln E m
0
Z 0 O O 0
rn 00 to L L L L i L
'n Ln o Ln
0) Ln /D N
W H 00 Ln M .
00
In 00 Ln ri H H M L-
N Ln to H N co m m I:r Ln
rI N M M M
0
0
H U U U
4-) 04 ~ H ~~
U) .~: - H H o\o o\o o\o o\o W
U ~ HLLnnrnrn
a Q ul w rA
ri A
CA 02722462 2010-11-24
- 28 -
Table 7 summarises some of the physicochemical
properties of blends of DBF with the higher molecular
weight dialkyl carbonates PrEC, BEC, DPrC, DiPrC and DBC,
again at both 5 and 10% v/v.
CA 02722462 2010-11-24
+ M o M l0 d+ N l0
o\o U
G4 O M rl r- 01 r M 0 H
ri OD 1- O I'D M di ~o
0 r-I N N M M M
+ V' 00 Ol N M
U
W o\o M O 0) H Ln H N
Q Ln Q O l0 00 O "zv M Ln l0
O H N N M M M
+ 00 w ri rn c
o\o ~4 w N = IN = 0
G4 O a ' M rl N O l0 M Ln H
H Lrfl OD U) ;I' 1 M M l0
0 r-I H M M
+ U d' co rn t` Ol 00 ri
X14 Ln !1, rn 00 co 0l O Lfl N H
(Ya ri If) Ln I:v O r- M Ln w
Q Q 0 ri ri N M M M
ri 01 d~ d~ M
+ o U O U)
w O
4 M
H04 Lf 00 61 d' C` M O N
Lfl W 00 l0 M Lfl '.o
0 H H N M M
+ U l0 In Ln w Ln 00 N H dT 44 (Y)
Lfl N N aD H \0 rl W N M
H pq Q w w O N M Ln \o Lf)
O r-I ri N M M M
H
+ N In M 00 N
o\o U N O O . O
fsa O W N a:V LO o Ln W .1' 00 M Lfl N
(Q rl Ln r 1 co l0 M M l0
Q 0 rl N M M
+ ul :v Ln In Ln 01 ri
o U M M
rZ4 U') Lfl l0 r{ Lfl O N
w O Ln
l0 01 N M L11 \o
1 Q O H H N M M M
al
N + U d~ 00 Ln O1 , c4 N 01
o\
(T4 O co 00 [r M 00 d' 01 ri I-T (~ r I a Lfl d~ r- w m dl W
H H N M M M
+ U Lfl l0 00 l0 l0 M <v
o\ W M -14 M N ri Ln ri N
rX4 Lfl ~-I M co Ln Ln O't N M Ln w
a In rl rl N M M M
}=1 U Li O
Q) U ., rl U U U U
~~j U ~' v U2 v ri H (D 0 0 1n
0 rd H Ln m 0)
Q U
L4 111 r-) W
rl Q
CA 02722462 2010-11-24
- 30 -
Table 7 shows that all of the blends containing ?C6
DACs were compliant with the EN 590 diesel fuel
specification in terms of their distillation curves,
cetane numbers and densities. At 5% v/v DAC, all but one
of the ?C6 DAC blends (that containing PrEC) were
compliant with the EN 590 flash point specification. The
BEC-, DPrC- and DBC-containing blends were also EN 590
compliant (in terms of their flash points) at loo v/v.
Base fuels having higher initial flash points could be
used in order to ensure EN 590 compliance with all of the
tested ?C6 DACs. All the blends were also found to be
EN 590-compliant in terms of their viscosities
(individual data not shown).
The elastomer damaging effects of each of the
DBF/DAC blends, and of the base fuel itself and the neat
DACs, was then assessed using the Example 1 test method,
but immersing the elastomer samples in the test fluids
for 7 days at 70 C. Shore hardness values were measured
at 70 C.
The results are shown in Tables 8a (DMC and DEC) and
8b (other DACs) below. FC refers to tests on the
fluorocarbon elastomer, Ni to tests on the nitrile
elastomer. In each cell of the table, the first figure is
the percentage change in elastomer volume, and the second
the percentage change in elastomer hardness. Again, DMC
and DEC were also tested in 2%- v/v blends.
CA 02722462 2010-11-24
- 31 -
Table 8a (DMC & DEC)
DAC cons' FC Ni FC Ni
(o v/v) DMC DMC DEC DEC
0 0.0/-0.6 1.7/-1.6 0.0/-0.6 1.7/-1.6
2 2.5/-4 5.3/-6 0.6/0 3.0/-3.0
9.0/-11.0 12.4/-12.3 2.4/-7.2 4.8/-4.8
21.7/-19.0 27.3/-21 6.8/-3 9.1/-8.3
100 82.9/-35 58.3/-28.7 111.2/- 54.6/-28.5
36.3
CA 02722462 2010-11-24
i I
00 00
P4 In = O
Z Q N = 11, 00 H
H N N H
1 I
U \ "0 In m 01
N = M = Ln = (lq
F14
= N = M O M
rI
0 0
U I I 1
a In = H QD 0-) .
Z -H = N = N = r-I M
H N N
U ~-I \ l0 \ N \ 0 110 00
W N 01 = 01 H
-H = N N M a'
O 0 H 0
r-H
U
(-14 I I I
-ri u 00 \ d' \ r-I \ l0
z 4 Ln = Ln . ri In
= N = N cl,
H N
H N M d,
U
a
U I 1 I O
U N l0 N N N
W a = N= N N OD
W Q 0 0
ri
fY1
U I I
14 U 00 00 O \ 1
a Z in = r i = co . O
= N O
rI M d' Ln
co 1 1 \ M
N U \~0\OLn O
rT4 W r- = CO M
U
W = N = M M N N
O O H
E- co
1 I I
W 00 N N N
z ~-I Ln = N = w = 01
N = In
04 H M l0 rl N
l
I I I
U l0 l0 \ rI \ co
u ~I N M N M
= N = N
a 0 H M W 00 N
>
U U \ O
r. o In O
0 H H
U o\0
CA 02722462 2010-11-24
- 33 -
The data in Tables 8a and 8b show that at any given
blend ratio, the ?C6 DACs cause less elastomer damage
(both swelling and reductions in hardness) than the lower
molecular weight DACs, DMC and DEC. For the >C6 DACs,
both nitrile and fluorocarbon elastomer swell levels were
well within the "normal" ranges (2-12% volume change for
the nitrile elastomer; 0-4% volume change for the
fluorocarbon) recorded for a selection of available
diesel base fuels, at both 5 and 106 v/v. In contrast,
DMC at 10% v/v caused a nitrile elastomer swell which was
well above the normal base fuel range, and even at 5% v/v
caused a higher than average elastomer swell. In the
fluorocarbon elastomer tests, both DMC and DEC gave rise
to elastomer swell levels well above the normal base fuel
range at 10% v/v, as did DMC at 5% v/v.
Thus, DMC and DEC can cause elastomer damage
problems when blended in diesel fuels. However, ?C6 DACs
may be used in diesel fuel formulations in place of
either DMC or DEC, in order to reduce such problems. For
this purpose they can be incorporated at concentrations
of at least 10% v/v.
Example 3
Diesel fuel formulations were prepared by blending
together a second diesel base fuel DBF2 and the DACs
which were tested in Example 2. All blends contained
10% v/v of the relevant DAC.
DBF2 was a commercially available Swedish Class I
diesel fuel. It had a density at 15 C (ASTM D4052) of
813.7 kg/m3, an initial boiling point (ASTM D86) of
181 C, a T95 boiling point (ASTM D86) of 286 C, a final
boiling point (ASTM D86) of 294 C, a measured cetane
number (ASTM D613) of 56.3 and a kinematic viscosity at
C (ASTM D445) of 1.96 mm2/s.
CA 02722462 2010-11-24
- 34 -
The lubricity of each DBF2/DAC blend, and of the
base fuel itself, was then assessed using the following
test method, which is a HFRR (high friction reciprocating
rig) wear scar test based on EN ISO 12156-1. A sample of
the fuel or blend under test was placed in a test
reservoir which was maintained at a specified test
temperature. A fixed steel ball was held in a vertically
mounted chuck and forced against a horizontally mounted
stationary steel plate with an applied load. The test
ball was oscillated at a fixed frequency and stroke
length while the interface with the plate was fully
immersed in the fluid reservoir. The metallurgies of the
ball and plate, and the temperature, load, frequency, and
stroke length were as specified in EN ISO 12156-1. The
ambient conditions during the test were then used to
correct the size of the wear scar generated on the test
ball to a standard set of ambient conditions, again as
per EN ISO 12156-1. The corrected wear scar diameter
provides a measure of the test fluid lubricity.
The lubricity results are shown in Table 9 below.
Table 9
Fuel/blend Wear
scar
(Jim)
DBF2 670.5
+ 10% DMC 613
+ 10% DEC 496
+ 10% PrEC 403.5
+ 10% BEC 414.5
+ 10% DPrC 477.5
+ 10% DiPrC 466.5
+ 10% DBC 492
MAX 460 urn 460
It can be seen that the addition of 10% v/v of a >-C6
DAC significantly improves the lubricity of the base
fuel, bringing the wear scar close to or even below the
CA 02722462 2010-11-24
- 35 -
EN 590 maximum specification of 460 ppm. It is expected
that the addition of suitable lubricity additives, at
standard or indeed below standard treat rates, will bring
the lubricity of all the DBF2/?C6 DAC blends above
specification (ie the wear scar will be below the
maximum).
Of note is the fact that the lubricity enhancing
effects of the DACs do not vary linearly with molecular
weight. Although all of the >C6 DACs outperform both DMC
and DEC, in this respect PrEC seems to increase lubricity
the best of all the ?C6 DACs tested, whilst DiPrC
performs slightly better than, and BEC much better than,
the same molecular weight DPrC.
Thus, ~C6 DACs may be used to improve the lubricity
of a diesel base fuel or fuel formulation, either with or
without lubricity additives. Instead or in addition they
may be used to reduce the concentration of
lubricity-enhancing additives necessary in a diesel fuel
formulation, without or without undue reduction in
overall lubricity. Improvements in lubricity may also be
accompanied by improvements in fuel economy when a
fuel-consuming system is run on a fuel formulation
according to the invention.
Example 4
The water tolerance of the DAC/base fuel blends
prepared in Examples 1 and 2 was assessed using the
following method.
Distilled water was added to a sample of the
relevant blend, in incremental amounts, and the sample
agitated by hand until a slight haze persisted. The
volume of added water at this point was converted to a
mass M (in grams) using an appropriate density. The water
tolerance W = M/400 (g/mL). Water was added to further
CA 02722462 2010-11-24
- 36 -
samples of the blend in amounts sufficient to give water
contents of 0.25W, 0.5W, W, 2W and 4W g/mL. The moisture
content of the organic phase in each of these samples was
tested using the standard test method IP 386, and its
phase transition temperature was measured according to
ASTM D2386.
All the gasoline blends were found to have good
water tolerance. On addition of further water, the water
content of the organic fuel phase was generally
maintained (indicating effective phase separation of the
added water), as was the DAC content in the organic phase
(indicating that the DAC had not migrated into the added
water). Thus, in this respect the DACs behave better than
ethanol which does separate into water phases when
present. This water-rejecting effect also highlights the
potential for DACs, in particular >C6 DACs, to be
incorporated into gasoline/alcohol fuel blends in order
to stabilise the alcohol in the organic phase. They may
also be used to allow the incorporation of hydrous
alcohols into gasoline fuels, the hydrous alcohols
requiring less energy to produce than their anhydrous
counterparts.
There were no water tolerance issues with any of the
diesel fuel blends.
Example 5
The effects of neat DACs on both nitrile and
fluorocarbon elastomers were assessed using the same
method as in Examples 1 and 2. The results are shown in
Table 10; the figures are percentages increases in
volume/changes in hardness.
CA 02722462 2010-11-24
- 37 -
Table 10
DAC Nitrile Fluorocarbon
DMC 58.3/-28.7 82.9/-35
DEC 54.6/-28.5 111.2/-36.3
PrEC 53.2/-29.1 88.2/-23.8
BEC 50.6/-30.3 82.0/-23.3
DPrC 41.3/-25.3 78.2/-25.6
DiPrC 14.9/-9.4 104.6/-18.0
DBC 18.6/-15.4 24.2/-14.9
These results confirm those found for the
DAC-containing fuel blends. The ?C6 DACs in general show
a reduced tendency to cause elastomer damage. This means
that the ?C6 DACs are likely to be easier to store and
transport, as well as causing fewer problems when used in
automotive fuel formulations.
However, these data, together with those from
Examples 1 and 2, also show that elastomer damaging
effects do not vary linearly with DAC molecular weight.
Although the >C6 DACs all outperform DMC and DEC, it is
of note that in the neat DACs, for example, fluorocarbon
elastomer swell is markedly greater in DiPrC than in
DPrC. Thus, performance in fuel formulations cannot
necessarily be predicted from the elastomer damaging
properties of the neat DACs, or solely from the DAC
molecular weight, although it has now been found that
using DACs of 6 or more carbon atoms can yield consistent
advantages over the more conventionally used DMC and DEC.
