U.S. patent application number 12/953214 was filed with the patent office on 2011-07-07 for fuel formulations.
Invention is credited to Caroline Nicola Orlebar, Richard John Price, Garo Garbis Vaporciyan.
Application Number | 20110162262 12/953214 |
Document ID | / |
Family ID | 42076610 |
Filed Date | 2011-07-07 |
United States Patent
Application |
20110162262 |
Kind Code |
A1 |
Orlebar; Caroline Nicola ;
et al. |
July 7, 2011 |
FUEL FORMULATIONS
Abstract
A diesel fuel formulation containing (i) a lower molecular
weight dialkyl carbonate (DAC) selected from dimethyl carbonate
(DMC), diethyl carbonate (DEC) and mixtures thereof; (ii)
di-n-butyl carbonate (DBC); and optionally (iii) an additional
diesel fuel component is provided.
Inventors: |
Orlebar; Caroline Nicola;
(Cheshire, GB) ; Price; Richard John; (Cheshire,
GB) ; Vaporciyan; Garo Garbis; (Houston, TX) |
Family ID: |
42076610 |
Appl. No.: |
12/953214 |
Filed: |
November 23, 2010 |
Current U.S.
Class: |
44/387 |
Current CPC
Class: |
C10L 10/00 20130101;
C10L 1/19 20130101 |
Class at
Publication: |
44/387 |
International
Class: |
C10L 1/19 20060101
C10L001/19 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 24, 2009 |
EP |
09176885.3 |
Claims
1. A diesel fuel formulation comprising (i) a lower molecular
weight dialkyl carbonate (DAC) selected from dimethyl carbonate
(DMC), diethyl carbonate (DEC) and mixtures thereof; and (ii)
di-n-butyl carbonate (DBC).
2. The fuel formulation of claim 1 further comprising (iii) an
additional diesel fuel component.
3. The fuel formulation of claim 1 wherein the lower molecular
weight DAC is DEC.
4. The fuel formulation of claim 2 wherein the lower molecular
weight DAC is DEC.
5. The fuel formulation of claim 1 wherein the concentration of the
lower molecular weight DAC is from 0.5 to 20% v/v.
6. The fuel formulation of claim 2 wherein the concentration of the
lower molecular weight DAC is from 0.5 to 20% v/v.
7. The fuel formulation of claim 1 wherein the concentration of the
DBC is from 0.5 to 99.5% v/v.
8. The fuel formulation of claim 1 wherein the volume ratio of the
lower molecular weight DAC to the DBC is approximately 1:1.
9. The fuel formulation claim 1 wherein the flash point of the
formulation (ASTM D92 or D93) is 50.degree. C. or higher.
10. The fuel formulation claim 2 wherein the flash point of the
formulation (ASTM D92 or D93) is 50.degree. C. or higher.
11. A process for the preparation of a diesel fuel formulation
comprising blending together (i) a lower molecular weight DAC
selected from DMC, DEC and mixtures thereof; and (ii) DBC.
12. The process of claim 11 wherein at least one additional diesel
fuel component is blended.
13. A method of operating an internal combustion engine, and/or a
vehicle which is driven by an internal combustion engine comprising
introducing into a combustion chamber of the engine a diesel fuel
formulation of claim 1.
14. A method of operating an internal combustion engine, and/or a
vehicle which is driven by an internal combustion engine comprising
introducing into a combustion chamber of the engine a diesel fuel
formulation of claim 2.
15. A method of operating an internal combustion engine, and/or a
vehicle which is driven by an internal combustion engine comprising
introducing into a combustion chamber of the engine a diesel fuel
formulation of claim 5.
16. A method of operating an internal combustion engine, and/or a
vehicle which is driven by an internal combustion engine comprising
introducing into a combustion chamber of the engine a diesel fuel
formulation of claim 7.
17. A method of operating an internal combustion engine, and/or a
vehicle which is driven by an internal combustion engine comprising
introducing into a combustion chamber of the engine a diesel fuel
formulation of claim 8.
18. A method for increasing the flash point of a diesel fuel
formulation which contains a lower molecular weight DAC selected
from DMC, DEC and mixtures thereof, comprising adding to the
formulation a concentration c of DBC, wherein c is lower than the
minimum concentration c' of DBC which theory would predict needed
to be added to the formulation in order to achieve flash point X.
Description
[0001] This application claims the benefit of European Application
No. 09176885.3 filed Nov. 24, 2009 which is incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] This invention relates to diesel fuel formulations, their
preparation and their use.
BACKGROUND TO THE INVENTION
[0003] 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.
[0004] Biofuels are combustible fuels, typically derived from
biological sources, which result in a reduction in "well-to-wheels"
(ie from source to combustion) greenhouse gas emissions. In diesel
fuels for use in compression ignition engines, the most common
biofuels are fatty acid alkyl esters (FAAEs), in particular fatty
acid methyl esters (FAMEs) such as rapeseed methyl ester and palm
oil methyl ester; these are used in blends with conventional diesel
fuel components.
[0005] Lower dialkyl carbonates, in particular dimethyl carbonate
(DMC) and diethyl carbonate (DEC), are also biofuels which have in
the past been added to both gasoline and diesel fuels. They 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 diesel fuels. In particular, their
low flash points--and the consequently reduced flash points of
blends containing them--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.
[0006] FAMEs have much higher flash points than both DMC and DEC,
and as a result could potentially be blended with the dialkyl
carbonates in order to increase their suitability for use as diesel
fuel components. However, there can be a number of drawbacks
associated with the use of FAMEs in diesel fuels, in particular at
higher concentrations. The addition of a FAME to a diesel fuel
formulation raises its cloud point, to an extent dependent on the
FAME concentration. It also raises the cold filter plugging point
(CFPP) of the formulation. Moreover, due to the incomplete
esterification of oils (triglycerides) during their manufacture,
FAMEs can contain trace amounts of glycerides, in particular
monoglycerides. These glycerides tend, on cooling, to crystallise
out before the FAMEs themselves, and can cause fuel filter
blockages. These three effects can compromise the cold weather
performance of a FAME-containing diesel fuel. It can therefore be
difficult to formulate diesel fuel/FAME blends within the relevant
regulatory specifications, particularly in colder climates.
[0007] FAMEs and their oxidation products also tend to accumulate
in engine oil; this too has limited their use in modern FAME/diesel
blends. At higher concentrations they can also cause fouling of
fuel injectors. FAMEs are also more expensive to produce than
ethanol (the biofuel most commonly included in gasoline
formulations), and their world production levels much lower.
[0008] It would be desirable to provide new biofuel-containing
diesel fuel formulations which could overcome or at least mitigate
the above problems.
SUMMARY OF THE INVENTION
[0009] According to one embodiment of the present invention there
is provided a diesel fuel formulation containing (i) a lower
molecular weight dialkyl carbonate (DAC) selected from dimethyl
carbonate (DMC), diethyl carbonate (DEC) and mixtures thereof; and
(ii) di-n-butyl carbonate (DBC).
[0010] The formulation may also contain (iii) an additional diesel
fuel component.
[0011] In another embodiment, a process is provided for the
preparation of a diesel fuel formulation comprising blending
together (i) a lower molecular weight DAC selected from DMC, DEC
and mixtures thereof; and (ii) DBC.
DETAILED DESCRIPTION OF THE INVENTION
[0012] It has been found that DBC can raise the flash points of
diesel fuel formulations containing DMC or DEC, to a greater extent
than might have been predicted based on its own flash point of
89.degree. C. In particular, its flash point raising effect appears
to be significantly greater, at any given concentration, than that
of the same concentration of the common biodiesel component
rapeseed methyl ester (RME), despite the fact that the flash point
of neat RME (170.degree. C.) is far higher than that of DBC.
[0013] This discovery allows DBC to be used as a component of DMC-
or DEC-containing diesel fuel formulations, for the purpose of
raising their flash points, but without the drawbacks potentially
associated with the inclusion of a FAME for the same purpose. In
turn, diesel fuels can be formulated with higher concentrations of
DMC and DEC, without or without undue impact on their overall flash
points. The inclusion of the DBC can help to bring a DMC- or
DEC-containing diesel fuel within a desired flash point
specification; this can be of particular value where the fuel is
for use in a warmer climate. Thus the present invention is able to
provide more optimised methods for formulating biofuel-containing
diesel fuel formulations, in particular summer grade diesel fuels,
more particularly to achieve target flash points.
[0014] There can be a number of advantages to increasing the
concentration of DACs in a diesel fuel formulation. Not only does
DBC have a lower cloud point (-60.degree. C.) and CFPP (-36.degree.
C.) than FAMEs, and thus the ability to lower the cloud point and
CFPP of a fuel formulation to which it is added; it also has low
toxicity and is biodegradable. Its inclusion in a diesel fuel
formulation can increase the total bioenergy content of the
formulation, so long as the DBC is derived from a biological
source, and in turn reduce the greenhouse gas emissions associated
with the production and use of the fuel, yet with fewer of the
drawbacks associated with higher FAME concentrations. DBC can also
be produced from renewable ingredients (carbon dioxide and
bio-butanol). When used in diesel fuels, it can be a cheaper
alternative to the more traditionally used FAME biofuel components
such as RME.
[0015] In an embodiment of the invention, the lower molecular
weight DAC used in the formulation is DMC. In an embodiment, it is
DEC.
[0016] The dialkyl carbonates used in a fuel formulation according
to the invention (DMC and/or DEC, and DBC) may be obtained from any
known source, of which many are available. They can for example be
synthesised from the corresponding alcohol(s): methanol may be used
as a starting material for the production of DMC, ethanol for the
production of DEC, and butanol for the production of DBC. Such
alcohols may themselves be derived from biological sources.
[0017] DACs can also be prepared by oxidative carbonylation of
alcohols, or by transesterification of dimethyl carbonate with
alcohols, or they may be generated as co-products in the synthesis
of monoethylene glycol from ethylene oxide and carbon dioxide via
ethylene carbonate.
[0018] In an embodiment, it may be preferred for the DACs not to
have been synthesised using phosgene (COCl.sub.2), 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.
[0019] The concentration of the DMC, DEC or mixture thereof, in a
diesel fuel formulation according to the invention, may be 0.5% v/v
or greater, or 1 or 2 or 3% v/v or greater, or in cases 3.5 or 4 or
4.5 or 5% v/v or greater. Its concentration may be up to 20% v/v,
or up to 15 or 12 or 10% v/v.
[0020] The concentration of the DBC in the formulation may be 0.5%
v/v or greater, or 1 or 2 or 3% v/v or greater, or in cases 3.5 or
4 or 4.5 or 5% v/v or greater. Its concentration may be up to 99.5
or 99 or 98% v/v, or up to 95 or 90% v/v, or up to 80 or 70 or 60
or 50 or 30 or 25 or 20% v/v, or up to 15 or 12 or 10% v/v.
[0021] The volume ratio of the lower molecular weight DAC (i) to
the DBC (ii) in the formulation may for instance be up to 25:1, or
up to 10:1 or 5:1 or 2:1. The ratio may be 1:199 or greater, or
1:99 or greater, or 1:90 or greater, or 1:75 or greater, or 1:50 or
greater. It may be 1:25 or greater, or 1:10 or 1:5 or 1:2 or
greater. It may be 1:1 or approximately 1:1.
[0022] The additional diesel fuel component (iii), if present, may
be any fuel component suitable for use in a diesel fuel formulation
and therefore for combustion within a compression ignition (diesel)
engine. It will typically be a liquid hydrocarbon middle distillate
fuel, more typically a gas oil. It may be petroleum derived. It may
be or contain a kerosene fuel component.
Alternatively it may be synthetic: for instance it may be the
product of a Fischer-Tropsch condensation. It may be derived from a
biological source. It may be or include an oxygenate such as an
alcohol (in particular a C1 to C4 or C1 to C3 aliphatic alcohol,
more particularly ethanol).
[0023] An additional fuel component (iii) will typically boil in
the range from 150 or 180 to 360.degree. C. (ASTM D86 or EN ISO
3405). It will suitably have a measured cetane number (ASTM D613)
of from 40 to 70 or from 40 to 65 or from 51 to 65 or 70.
[0024] In one embodiment, a formulation according to the invention
may contain a mixture of two or more additional diesel fuel
components (iii).
[0025] The concentration of the component(s) (iii) in the
formulation, if present, may be 2 or 5 or 10% v/v or greater, or 20
or 30 or 40% v/v or greater. In embodiments of the invention, it
may be 50 or 60 or 70% v/v or greater, or 75 or 80 or 85% v/v or
greater, or 90 or 92 or 95% v/v or greater. It may be up to 98%
v/v, or up to 95 or 92 or 90 or 85 or 80% v/v. In cases it may be
up to 70 or 60 or 50% v/v. The component(s) (iii) may represent the
major part of the fuel formulation: after inclusion of the lower
molecular weight DAC (i), the DBC (ii) and any optional fuel
additives, the component(s) (iii) may therefore represent the
balance to 100%. Alternatively, the fuel formulation may comprise
the lower molecular weight DAC and the DBC, optionally with one or
more diesel fuel additives, but without any additional diesel fuel
components.
[0026] A fuel formulation according to the invention suitably has a
flash point (ASTM D92 or D93, or IP 34) of 38.degree. C. or higher,
or of 40 or 45.degree. C. or higher, or of 50 or 55 or in cases 60
or 65 or 70 or 75.degree. C. or higher.
[0027] The formulation of the invention should be suitable for use
in a compression ignition (diesel) internal combustion engine. Such
an engine may be either heavy or light duty. The formulation may in
particular be suitable for use as an automotive diesel fuel.
[0028] In an embodiment, the formulation is suitable and/or adapted
for use as a "summer grade" automotive diesel fuel, for use in
warmer climates such as Australasia and/or in warmer seasons. In an
embodiment, it is suitable and/or adapted for high temperature use
such as at 30.degree. C. or higher.
[0029] In further embodiments, the formulation may be suitable
and/or adapted for use as an industrial gas oil, or as a domestic
heating oil.
[0030] The formulation will suitably comply with applicable current
standard diesel fuel specification(s) such as for example EN 590
(for Europe) or ASTM D975 (for the USA). By way of example, the
overall formulation may have a density from 820 to 845 kg/m.sup.3
at 15.degree. C. (ASTM D4052 or EN ISO 3675); a T95 boiling point
(ASTM D86 or EN ISO 3405) of 360.degree. C. or less; a measured
cetane number (ASTM D613) of 51 or greater; a kinematic viscosity
at 40.degree. 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 11% w/w. Relevant specifications
may however differ from country to country and from year to year,
and may depend on the intended use of the 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.
[0031] The relative concentrations of the components (i) to (iii)
may be chosen to achieve desired properties for the formulation as
a whole, for example a minimum desired flash point. Thus the
relative concentrations will also depend on the physicochemical
properties of the individual components. Suitable concentrations
may be calculated by applying appropriate blending rules to the
properties (in particular the flash points, but also potentially
other properties such as cloud points and/or cetane numbers) of the
individual components, and may be visualised using a two- or
three-way composition plot.
[0032] A fuel formulation according to the invention may contain
standard fuel or refinery additives which are suitable for use in
diesel fuels. Many such additives are known and commercially
available.
[0033] According to another embodiment of the present invention,
there is provided a process for the preparation of a diesel fuel
formulation, which process involves blending together (i) a lower
molecular weight DAC selected from DMC, DEC and mixtures thereof
and (ii) DBC, optionally with (iii) one or more additional diesel
fuel components, and optionally 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.
[0034] In an embodiment, the lower molecular weight DAC (i) and the
DBC are premixed in an appropriate volume ratio, and if necessary
the mixture then blended with one or more additional fuel
components (iii). The DAC mixture may for instance be blended with
the component(s) (iii) at a concentration of up to 30% v/v based on
the product fuel formulation, or at a concentration of up to 25 or
20% v/v, or up to 15 or 10% v/v. It may be blended at a
concentration of 1% v/v or greater based on the product
formulation, or of 2 or 3 or 4 or 5% v/v or greater, or in cases of
6 or 7 or 8 or 9 or 10% v/v or greater. Mixing the DBC with the
lower molecular weight DAC can, by raising its flash point, help to
improve its handling and storage properties.
[0035] In another embodiment 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 diesel fuel
formulation according to the first aspect of the invention. The
engine is suitably 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.
[0036] In another embodiment also embraces introducing DBC into a
reservoir which contains a DMC- and/or DEC-containing diesel fuel
formulation, prior to introduction of the resultant mixture into a
combustion chamber of the engine. In other words, the diesel fuel
formulation of the invention may be prepared in situ in a reservoir
from which fuel is fed into an internal combustion engine.
[0037] According to another embodiment of the invention there is
provided the use of DBC, in a diesel fuel formulation containing a
lower molecular weight DAC selected from DMC, DEC and mixtures
thereof, for the purpose of increasing the flash point of the
formulation.
[0038] The flash point of a fuel formulation is the lowest
temperature at which, under a predetermined set of test conditions,
the application of an ignition source causes the vapour above a
sample of the formulation to ignite and the flame to propagate
across the surface of the liquid. It can be measured using a
standard test method such as ASTM D92 or D93, IP 34, or an
analogous method: a suitable procedure is described in Example 1
below.
[0039] The invention may be used to achieve any degree of increase
in the flash point of the formulation. It may be used for the
purpose of achieving a flash point at or above a desired target
value.
[0040] By way of example, the invention may be used to increase the
flash point of the formulation by at least 0.2% of its value
(expressed in Kelvin) prior to addition of the DBC, or by at least
0.5 or 0.6%, or by at least 0.8 or 1% or in cases even by 2 or 5 or
8 or 10% or more.
[0041] The diesel fuel formulation may contain one or more
additional diesel fuel components (iii) in addition to the lower
molecular weight DAC. It may in particular be a summer grade diesel
fuel formulation. It will typically have a flash point, prior to
addition of the DBC, which is lower than that of the DBC alone
(i.e. which is lower than 89.degree. C.)
[0042] It has been found that DBC can "boost" the flash point of a
diesel fuel formulation containing DMC and/or DEC, above the level
that would be expected if conventional blending rules applied. This
phenomenon has a number of potential uses. Firstly, it can allow
the achievement of a higher flash point than was previously thought
possible, for any given concentration of DBC, in a DMC- and/or
DEC-containing diesel fuel formulation. Secondly, it can allow the
achievement of a target flash point using a lower than predicted
concentration of DBC. This in turn can reduce the costs which might
be associated with the addition of DBC to the formulation. Thirdly,
it can allow the use of a higher DMC and/or DEC concentration than
would have been predicted to be feasible, whilst still maintaining
the flash point of the overall formulation at or above a desired
target value; this in turn can boost the bioenergy content of the
formulation, as well as increasing the advantages associated with
the DMC and/or DEC, for example reductions in cloud point and CFPP.
Fourthly, the DBC may be used to replace, at least partially, a
FAAE which would otherwise have been included in the formulation in
order to increase its flash point.
[0043] There is provided a method for increasing the flash point of
a diesel fuel formulation which contains a lower molecular weight
DAC selected from DMC, DEC and mixtures thereof, in order to
achieve a target minimum flash point X, which method comprises
adding to the formulation a concentration c of DBC, wherein c is
lower than the minimum concentration c' of DBC which theory would
predict needed to be added to the formulation in order to achieve
flash point X.
[0044] The theoretical DBC concentration, c', may be calculated
using any suitable flash point blending rule. It may for instance
be calculated as follows, making use of the Wickey-Chittenden flash
point model.
[0045] The flash point index of a blend of fuel components (in this
case of the lower molecular weight DAC, the DBC and any additional
diesel fuel components present) is calculated by combining the
flash point indices of the blend components as a function of their
volume fractions in the blend:
Index blend = i V i Index i ##EQU00001##
where V.sub.i is the volume fraction of component i and Index.sub.i
is the flash point index for component i.
[0046] The flash point index for each component can be calculated
using the Wickey-Chittenden model (Wickey R. O. and Chittenden D.
H., Hydrocarbon Processing, 42(6), 1963: 157-158):
Log 10 ( Index i ) = - 6.1188 + 2414 FP + 230.5556 ( equation 1 )
##EQU00002##
where FP is the flash point of the component.
[0047] When using equation (1), the blending flash point of DMC may
be taken to be 0.degree. C., and that of DEC 17.7.degree. C. These
figures take account of potential mismatches in Hansen solubility
parameters between the DAC and any hydrocarbon fuel components
present.
[0048] Having calculated the flash point index for the overall
blend, the Wickey-Chittenden equation (1) may be used to calculate
back the flash point for the blend. By inserting suitable values
into these equations, it is possible to work back from a target
flash point X to determine the volume fraction or concentration c'
(of DBC) which would be required to achieve X.
[0049] In an embodiment, the actual DBC concentration c may be at
least 0.5% v/v lower than the predicted concentration c', or at
least 1 or 2 or 5% v/v lower, or in cases at least 10 or 25 or 50
or 75% v/v lower.
[0050] In another embodiment, DBC is used at a concentration c, in
a diesel fuel formulation which contains a lower molecular weight
DAC selected from DMC, DEC and mixtures thereof, for the purpose of
increasing the flash point of the formulation by an amount x,
wherein x is greater than the flash point increase x' which theory
would predict would result from adding DBC to the formulation at
concentration c.
[0051] The theoretical (predicted) flash point increase x' may be
calculated using the equations above. The actual flash point
increase x may for instance be at least 0.5.degree. C. higher than
the predicted increase x', or at least 1 or 1.5 or 2.degree. C.
higher, or in cases at least 5 or 8 or 10.degree. C. higher.
[0052] There is provided the use of DBC, at a concentration c, in a
diesel fuel formulation which contains a lower molecular weight DAC
selected from DMC, DEC and mixtures thereof, for the dual purposes
of: [0053] a) achieving a target minimum flash point X for the
formulation; and [0054] b) allowing an increase in the
concentration of the lower molecular weight DAC to a level above
the maximum concentration d' which theory would predict could be
included in the formulation, after addition of the DBC at
concentration c, without reducing the flash point of the
formulation below the target minimum X.
[0055] Again, the theoretical maximum concentration d', for the
lower molecular weight DAC, may be calculated using the above
rules.
[0056] It may be desirable to include DMC and/or DEC in a diesel
fuel formulation for a number of reasons, for example to improve
the cold flow properties of the formulation (in particular to
reduce its cloud point and/or CFPP), and/or to reduce emissions
from a fuel-consuming system (typically an engine) running on the
formulation, and/or to reduce greenhouse gas emissions associated
with the production and use of the formulation, and/or to increase
the bioenergy content of the formulation, and/or as a combustion
improver. However it has been necessary, in the past, to balance
such benefits against the generally undesirable reduction in flash
point which results from increasing the concentration of the DMC
and/or DEC. The ability to increase their concentration without
undue detriment to the flash point of the formulation can therefore
provide significant advantages. Generally speaking the present
invention can provide greater flexibility in fuel formulation,
allowing a target flash point to be achieved more readily by
altering the concentration of the added DBC.
[0057] DBC may be used in a diesel fuel formulation containing a
lower molecular weight DAC selected from DMC, DEC and mixtures
thereof, for the purpose of replacing, at least partially, a fatty
acid alkyl ester (FAAE) which is or would otherwise have been
included in the formulation.
[0058] The FAAE may in particular be a fatty acid methyl ester
(FAME). It may for instance be RME. It may have been included, or
intended to be included, at least partly for the purpose of
increasing the flash point of the DMC- and/or DEC-containing
formulation. According to the eighth aspect of the invention, the
DBC may again be used at a lower concentration than theory would
predict to be necessary in order to achieve a target flash point
after reduction of the amount of the FAAE in the formulation. Thus,
the DBC may be used to achieve a greater reduction in the FAAE
concentration (including in cases reduction to zero) than theory
would predict to be possible whilst still achieving the target
flash point.
[0059] In the context of the present invention, "use" of DBC in a
diesel fuel formulation means incorporating the DBC into the
formulation, typically as a blend (ie a physical mixture) with one
or more other diesel fuel components. The DBC 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 DBC may involve running a fuel-consuming
system, typically an internal combustion engine, on a diesel fuel
formulation containing the DBC, typically by introducing the
formulation into a combustion chamber of an engine.
[0060] In the context of the invention, "achieving" a desired
target property also embraces--and in an embodiment
involves--improving on the relevant target. Thus for instance the
DBC may be used to produce a fuel formulation which has a flash
point above a desired target value.
[0061] 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 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.
[0062] 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.
[0063] The present invention will now be further described with
reference to the following non-limiting examples.
Example 1
[0064] Diesel fuel formulations were prepared by blending one or
more of diethyl carbonate (DEC), di-n-butyl carbonate (DBC) and
rapeseed methyl ester (RME) with a diesel base fuel DBF1. The DEC,
DBC and RME were each added to the formulations at a concentration
of 5% v/v.
[0065] The base fuel was a commercially available zero sulphur
automotive diesel base fuel, ex. Shell. It had a flash point (IP
34) of 72.5.degree. C. It had a density at 15.degree. C. (ASTM
D4052) of 840.9 kg/m.sup.3, an initial boiling point (ASTM D86) of
177.5.degree. C., a T95 boiling point (ASTM D86) of 357.degree. C.,
a final boiling point (ASTM D86) of 363.degree. C., a measured
cetane number (ASTM D613) of 55.4, an E250 (IP 123) of 22.4.degree.
C. and an E350 (IP 123) of 89.7.degree. C.
[0066] The DEC and DBC were sourced from Sigma Aldrich, UK and the
RME from ADM.
[0067] The flash points of the prepared formulations were measured
by the Pensky-Martens Closed Cup method (IP 34), as follows. A
sample of the formulation under test was placed in the test cup of
a Pensky-Martens apparatus and heated to give a constant rate of
temperature increase with continuous stirring. An ignition source
was directed through an opening in the test cup lid at regular
temperature intervals, with simultaneous interruption of stirring.
The lowest temperature at which the application of the ignition
source caused the vapour of the sample to ignite and the flame to
propagate over the surface of the liquid was recorded as the flash
point at the ambient barometric pressure. This value was corrected
to standard atmospheric pressure as per IP 34.
[0068] Three readings were taken for each formulation, in order to
calculate an average (mean) flash point. The results are shown in
Table 1 below, together with the flash points for the neat DEC, DBC
and RME, which were obtained using the standard test method IP
34.
[0069] Table 1 also shows theoretical flash points for the
formulations, calculated using the Wickey-Chittenden equation above
using a blending flash point of 17.7.degree. C. for the DEC.
TABLE-US-00001 TABLE 1 Predicted Measured Measured Average flash
improvement improvement flash point by relative to relative to %
v/v % v/v % v/v point W-C 5% v/v DEC that predicted DEC RME DBC
(.degree. C.) (.degree. C.) (.degree. C.) by W-C (.degree. C.) 0 0
0 72.5 -- -- -- 5 0 0 51 51.9 -- 0.9 5 5 0 53 52.0 +2 +1.0 5 0 5
54.5 52.0 +3.5 +2.5 100 0 0 25 -- -- -- 0 100 0 170 -- -- -- 0 0
100 89 -- -- --
[0070] It can be seen from Table 1 that the base fuel alone, with
no dialkyl carbonate or FAME present, has an average flash point of
72.5.degree. C. The addition of 5% v/v DEC (neat flash point only
25.degree. C.) reduces this considerably, to 51.degree. C.
[0071] RME has a neat flash point of 170.degree. C., far higher
than that of the base fuel. Yet the addition of 5% v/v RME to the
base fuel/DEC blend raises its flash point by only 2.degree. C. In
contrast, the addition of 5% v/v DBC to the base fuel/DEC blend, in
accordance with the invention, raises the average flash point by
3.5.degree. C., to 54.5.degree. C. This increase is particularly
surprising since the flash point for neat DBC is 89.degree. C.,
much lower than that of neat RME. It would therefore have been
expected that RME would have a greater effect on the flash point of
a DEC/base fuel blend than would the same volume of DBC. As can be
seen from the fifth column of Table 1, the increase in flash point
caused by the addition of 5% v/v DBC to the DEC/base fuel blend is
in fact greater than the Wickey-Chittenden model would have
predicted.
[0072] These results suggest that there is a synergistic
interaction between the DEC and the DBC, which is not present
between DEC and RME.
Example 2
[0073] Example 1 was repeated, but adding the DEC, DBC and RME to a
second diesel base fuel, DBF2, at 10% v/v. DBF2 was a commercially
available zero sulphur automotive diesel base fuel, ex. Shell. It
had a flash point (IP 34) of 65.degree. C. It had a density at
15.degree. C. (ASTM D4052) of 833 kg/m.sup.3, an initial boiling
point (ASTM D86) of 165.degree. C., a T95 boiling point (ASTM D86)
of 340.degree. C., a final boiling point (ASTM D86) of 352.degree.
C., a measured cetane number (ASTM D613) of 54.1, an E250 (IP 123)
of 28.2.degree. C. and an E350 (IP 123) of 96.8.degree. C.
[0074] The flash point results are shown in Table 2 below. Again,
the table shows predicted flash points as calculated using the
Wickey-Chittenden equation, using a DEC blending flash point of
17.7.degree. C.
TABLE-US-00002 TABLE 2 Predicted Measured Measured Average flash
improvement improvement flash point by relative to relative to %
v/v % v/v % v/v point W-C 10% v/v that predicted DEC RME DBC
(.degree. C.) (.degree. C.) DEC (.degree. C.) by W-C (.degree. C.)
0 0 0 65 -- -- 10 0 0 44 44.2 -- 0.2 10 10 0 45 44.4 +1 0.6 10 0 10
46 44.3 +2 +1.7
[0075] Here the addition of 10% v/v DEC reduces the flash point of
the base fuel from 65 to 44.degree. C. Adding 10% v/v RME to the
DEC/base fuel blend increases its flash point by only 1.degree. C.,
whereas adding 10% v/v DBC to the blend increases the flash point
by 2.degree. C. Again, the DBC unexpectedly has a greater impact on
the blend flash point than does the RME, despite the fact that neat
DBC has a much lower flash point than neat RME. The DBC also
increases the blend flash point by more than would have been
predicted using the Wickey-Chittenden model.
Example 3
[0076] Example 1 was repeated, but using dimethyl carbonate (DMC)
instead of DEC, and the base fuel DBF2 as in Example 2. The DMC was
sourced from Sigma Aldrich, UK.
[0077] The flash point results are shown in Table 3 below. The
fifth column shows predicted flash points as calculated using the
Wickey-Chittenden equation, using a blending flash point of
0.degree. C. for the DMC.
TABLE-US-00003 TABLE 3 Predicted Measured Measured Average flash
improvement improvement flash point by relative to relative to %
v/v % v/v % v/v point W-C 5% v/v that predicted DEC RME DBC
(.degree. C.) (.degree. C.) DMC (.degree. C.) by W-C (.degree. C.)
0 0 0 65 -- -- -- 5 0 0 30 31.5 -- 1.5 5 5 0 31 31.6 +1 0.6 5 0 5
66 31.6 +36 +34.4 10 0 0 16.5 -- -- --
[0078] DBC can be seen to have an even greater effect on the flash
point of a DMC/base fuel blend than on a DEC/base fuel blend.
Again, the addition of 5% v/v of DBC to a blend of 5% v/v DMC in
the diesel base fuel causes a far greater increase in the blend
flash point than does the addition of 5% v/v RME, despite the
higher flash point of neat RME. This increase is also significantly
greater than the Wickey-Chittenden model would have predicted.
Again there appears to be a synergistic interaction between the DMC
and the DBC as regards their combined flash points.
Example 4
[0079] Example 1 was repeated, but using dimethyl carbonate (DMC)
instead of DEC, and the base fuel DBF3. DBF3 was a commercially
available zero sulphur automotive diesel base fuel, ex. Shell. It
had a flash point (IP 34) of 65.degree. C. It had a density at
15.degree. C. (ASTM D4052) of 825 kg/m.sup.3, an initial boiling
point (ASTM D86) of 172.degree. C., a T95 boiling point (ASTM D86)
of 329.degree. C., a final boiling point (ASTM D86) of 342.degree.
C., a measured cetane number (ASTM D613) of 53.8, an E250 (IP 123)
of 57.5.degree. C. and no E350 (IP 123). The DMC was sourced from
Sigma Aldrich, UK.
[0080] The flash point results are shown in Table 4 below. The
fifth column shows predicted flash points as calculated using the
Wickey-Chittenden equation, using a blending flash point of
0.degree. C. for the DMC and 89.degree. C. for the DBC.
TABLE-US-00004 TABLE 4 Measured Predicted improvement flash point
relative to % v/v % v/v Average flash by W-C that predicted DMC DBC
point (.degree. C.) (.degree. C.) by W-C (.degree. C.) 0 0 65 10 0
19 23.8 -4.8 10 10 26 23.8 2.2 15 0 17.5 19.4 -1.9 15 10 25.5 19.4
6.1 20 0 18.5 16.3 2.2 20 10 23.5 16.3 7.2 20 20 25.5 16.3 9.2
[0081] DBC can be seen to have an even greater effect on the flash
point of a DMC/base fuel blend than on a DEC/base fuel blend. This
increase is also significantly greater than the Wickey-Chittenden
model would have predicted. Again there appears to be a synergistic
interaction between the DMC and the DBC as regards their combined
flash points.
Example 5
[0082] Example 1 was repeated, but using diethyl carbonate (DEC)
instead of DMC, and the base fuel DBF3 from Example 4. The DMC was
sourced from Sigma Aldrich, UK.
[0083] The flash point results are shown in Table 5 below. The
fifth column shows predicted flash points as calculated using the
Wickey-Chittenden equation, using a blending flash point of
17.7.degree. C. for the DEC and 89.degree. C. for the DBC.
TABLE-US-00005 TABLE 5 Measured Predicted improvement flash point
relative to % v/v % v/v Average flash by W-C that predicted DEC DBC
point (.degree. C.) (.degree. C.) by W-C(.degree. C.) 0 0 65 10 0
42 43.1 -1.1 10 10 49.5 43.4 6.1 15 0 38.5 38.8 -0.3 15 10 45.5
39.0 6.5 20 0 36 35.6 0.4 20 10 43.5 35.7 7.8 20 20 45.5 35.9
9.6
[0084] This increase is also significantly greater than the
Wickey-Chittenden model would have predicted. Again there appears
to be a synergistic interaction between the DEC and the DBC as
regards their combined flash points.
* * * * *