U.S. patent application number 14/018766 was filed with the patent office on 2014-03-06 for fuel composition.
This patent application is currently assigned to SHELL OIL COMPANY. The applicant listed for this patent is SHELL OIL COMPANY. Invention is credited to Aldo CAIAZZO, Lionel CLARKE, Tor Kit GOH, George Robert LEE, David Alexander PARKER, Richard John PRICE.
Application Number | 20140059923 14/018766 |
Document ID | / |
Family ID | 46799135 |
Filed Date | 2014-03-06 |
United States Patent
Application |
20140059923 |
Kind Code |
A1 |
CAIAZZO; Aldo ; et
al. |
March 6, 2014 |
FUEL COMPOSITION
Abstract
A fuel composition comprising: a diesel base fuel; from 1 to 10%
v/v of a fatty acid alkyl ester; and more than 10% v/v of an ether
component, the ether component comprising one or more ether
compounds having in the range of from 8 to 12 carbon atoms and
selected from compounds of formula I R.sub.1--O--R.sub.2 (I)
wherein R.sub.1 and R.sub.2 are independently primary or secondary
alkyl.
Inventors: |
CAIAZZO; Aldo; (Amsterdam,
NL) ; CLARKE; Lionel; (Chester, GB) ; GOH; Tor
Kit; (Kuala Lumpur, MY) ; LEE; George Robert;
(Chester, GB) ; PARKER; David Alexander; (Chester,
GB) ; PRICE; Richard John; (Chester, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHELL OIL COMPANY |
Houston |
TX |
US |
|
|
Assignee: |
SHELL OIL COMPANY
Houston
TX
|
Family ID: |
46799135 |
Appl. No.: |
14/018766 |
Filed: |
September 5, 2013 |
Current U.S.
Class: |
44/388 ;
44/447 |
Current CPC
Class: |
Y02E 50/13 20130101;
C10L 2200/0476 20130101; C10L 10/12 20130101; C10L 2200/04
20130101; C10L 1/02 20130101; C10L 1/1852 20130101; C10L 2200/0446
20130101; C10L 1/026 20130101; Y02E 50/10 20130101 |
Class at
Publication: |
44/388 ;
44/447 |
International
Class: |
C10L 1/185 20060101
C10L001/185 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 5, 2012 |
EP |
12183067.3 |
Claims
1. A fuel composition comprising: a diesel base fuel; from 1 to 10%
v/v of a fatty acid alkyl ester; and more than 10% v/v of an ether
component, said ether component comprising one or more ether
compounds having in the range of from 8 to 12 carbon atoms and
selected from compounds of formula I R.sub.1--O--R.sub.2 (I)
wherein R.sub.1 and R.sub.2 are independently primary or secondary
alkyl.
2. The fuel composition of claim 1 wherein the ether component
comprises symmetrical ether compounds.
3. The fuel composition of claim 1 wherein the ether component
comprises dipentyl ether.
4. The fuel composition of claim 1 wherein the ether component has
a density of at least 0.770 g/cm.sup.3.
5. The fuel composition of claim 1 wherein the ether component has
a flash point of at least 50.degree. C.
6. The fuel composition of claim 1 wherein the ether component has
a vapour pressure at 25.degree. C. of at most 5 Torr.
7. The fuel composition of claim 1 wherein the ether component has
a boiling point of at least 100.degree. C.
8. The fuel composition of claim 1 wherein the ether component is a
biofuel component.
9. The fuel composition of claim 1 wherein the ether component is
present in an amount of from 15% to 90% v/v.
10. The fuel composition of claim 9 wherein the ether component is
present in an amount of from 15% to 50% v/v.
11. The fuel composition of claim 1 wherein the ether component
consists of one or more ether compounds having in the range of from
8 to 12 carbon atoms and selected from compounds of formula I
R.sub.1--O--R.sub.2 (I) wherein R.sub.1 and R.sub.2 are
independently primary or secondary alkyl.
12. The fuel composition of claim 1 wherein the ether component has
a density of at least 0.770 g/cm.sup.3, a flash point of at least
50.degree. C., a vapour pressure at 25.degree. C. of at most 5
Torr, and a boiling point of at least 100.degree. C.
13. The fuel composition of claim 1 wherein the fuel composition
has a measured cetane number of 40 or greater.
14. A method of increasing the concentration of a biofuel component
in a diesel fuel composition comprising blending more than 10% v/v
of an ether compounds having in the range of from 8 to 12 carbon
atoms and selected from compounds of formula I R.sub.1--O--R.sub.2
(I) wherein R.sub.1 and R.sub.2 are independently primary or
secondary alkyl.
15. The method of claim 14 wherein the diesel fuel composition
contains a fatty acid ester or a fatty alcohol ester.
Description
[0001] This present application claims the benefit of European
Application No. 12183067.3, filed Sep. 5, 2012.
FIELD OF THE INVENTION
[0002] This invention relates to diesel fuel compositions
comprising certain ethers, their preparation and their use, as well
as to the use of certain ethers in fuel compositions for new
purposes.
BACKGROUND TO THE INVENTION
[0003] Many diesel fuel compositions contain cetane boost
components, also known as ignition improvers. The cetane number of
a fuel or fuel composition/formulation is a measure of its ease of
ignition. With a lower cetane number fuel a compression ignition
(diesel) engine tends to be more difficult to start and may run
more noisily when cold. There is a general preference therefore for
a diesel fuel composition to have a high cetane number, and as such
automotive diesel specifications generally stipulate a minimum
cetane number.
[0004] It is also desirable, in the interest of the environment, to
increase the amount of biofuels or biocomponents used in automotive
diesel fuels. Biofuels are combustible fuels, derived from
biological sources, which result in a reduction in "well-to-wheels"
(ie from source to combustion) greenhouse gas emissions. For use in
diesel engines, fatty acid alkyl esters (FAMEs), in particular
fatty acid methyl esters (FAMEs) such as rapeseed methyl ester,
soybean methyl ester and palm oil methyl ester, are the biofuels
most commonly blended with conventional diesel fuel components.
[0005] It is known in the art that certain (FAAEs), in particular
FAMEs, can be used in low concentrations as cetane boost components
in diesel fuels.
[0006] Currently FAMEs concentrations in light duty automotive
diesel are limited to a maximum of 7% v/v, primarily because of
transfer of the ester into the vehicle's sump, where its
accumulation causes a dilution of, and property changes in, the
lubricating oil. This is a consequence of both the high boiling
points of FAMEs (typically of the order of 340.degree. C.) and
possibly also their polarity. Moreover, due to the incomplete
esterification of oils (triglycerides) during their manufacture,
FAMEs can contain trace amounts of glycerides which on cooling can
crystallise out before the FAMEs themselves, causing fuel filter
blockages and compromising the cold weather operability of fuel
compositions containing them.
[0007] In any event, from the perspective of improving cetane
number, it is known that the cetane boosting effect of FAMEs
diminishes as the blend ratio of FAME to base fuel is increased.
The potential of FAMEs as cetane boost components is thus limited
for more than one reason, necessitating additional cetane boost
additives, at least in some applications.
[0008] It would therefore be desirable to identify alternative
cetane boost components for use in diesel fuel compositions, which
suffer from fewer of the drawbacks and limitations associated with
FAAEs.
[0009] It is an object of the invention to address one or more of
the limitations associated with prior art cetane boost
components.
SUMMARY OF THE INVENTION
[0010] It has now been found that certain types of ethers can be
particularly advantageous for use in diesel fuel compositions,
particularly at high concentrations, due to their effects on cetane
numbers in fuel blends.
[0011] According in one embodiment of the invention, a fuel
composition is provided comprising: a diesel base fuel; from 1 to
10% v/v of a fatty acid alkyl ester; and more than 10% v/v of an
ether component, said ether component comprising one or more ether
compounds having in the range of from 8 to 12 carbon atoms and
selected from compounds of formula I
R.sub.1--O--R.sub.2 (I)
wherein R.sub.1 and R.sub.2 are independently primary or secondary
alkyl.
[0012] In another embodiment is provided, a method of increasing
the concentration of a biofuel component in a diesel fuel
composition comprising blending more than 10% v/v of an ether
compounds having in the range of from 8 to 12 carbon atoms and
selected from compounds of formula I
R.sub.1--O--R.sub.2 (I)
wherein R.sub.1 and R.sub.2 are independently primary or secondary
alkyl.
DETAILED DESCRIPTION OF THE INVENTION
[0013] Ideally such components should be biologically derivable, ie
biofuels, and also have minimal transfer into the engine sump and
cause minimal dilution of lubricant as a result.
[0014] Cetane boost components need to offer a good property fit
with fossil-derived diesel fuels, not only in terms of their cetane
number but also in terms of volatility, flash point, melting and
boiling points and cold flow properties. Flash point in particular
can be a handling issue for diesel fuels, and in an overall fuel
composition must be above a specified limit to ensure that
flammable mixtures of fuel and air do not form within the fuel
supply and distribution system. The melting point of a molecule,
meanwhile, will directly affect the cloud point and cold filter
plugging point of a fuel composition into which it is blended, and
these properties must also be controlled in order to allow
satisfactory vehicle operability during winter months.
[0015] Ideally, an alternative cetane boost component, particularly
if it is a biofuel oxygenate component, will have properties--in
particular a flash point and melting point--which allow it to be
blended into diesel fuel compositions at concentrations above the
current 7% v/v limit for FAMEs.
[0016] U.S. Pat. No. 5,520,710 in the name of Olah suggests
symmetrical or unsymmetrical ethers comprising 2 to 24 carbon atoms
as cetane enhancing supplements. The ether supplements are added in
an amount of 0.5-10 v/v %, preferably 1-5% v/v. Data provided in
U.S. Pat. No. 5,520,710 in relation to dihexyl ether and dioctyl
ether suggests that the effectiveness of ethers as cetane boost
additives reduces considerably with increasing concentration, e.g.
at a concentration of 5% v/v compared to at a concentration of 2%
v/v. This work contrasts with that of U.S. Pat. No. 2,221,839 which
considers the use of straight-chain aliphatic ethers as fuels or as
ignition accelerators for compression ignition engine fuels. One
example documents the ignition acceleration activity resulting from
incorporating one of 10% v/v n-butyl ether, 25% v/v n-amyl ether,
and 25% v/v mono-butyl ether of diethylene glycol. Increase in
cetane number is used as an indicator for usefulness as an ignition
accelerator.
[0017] In US 2002/0134008, it is proposed to provide a diesel fuel
formulations of a pre-determined flash point and cetane number
increase by including two oxygenate compounds, a first oxygenate of
lower flash point than the diesel base fuel and of equal to or
higher cetane number, and a second oxygenate having a higher than
or equal flash point to that of the diesel base fuel and a higher
cetane number. The first oxygenates proposed are selected from
monoglyme, diethylether and diisopropylether and are utilised in
bulk quantities; the second oxygenate proposed is selected from
diglyme, triglyme and dipentylether and is proposed for use in
quantities of 10% v/v or less.
[0018] Anastopoulos et al in Fuel 81 (2002) 1017-1024 `The
tribiological behaviour of alkyl ethers and alcohols in low sulphur
automotive diesel` reviews the behaviours of seven alkyl ethers and
five alcohols on the lubricity of automotive diesel. Their results
led them to the conclusion that alcohols offer the best lubricant
potential, as only six of the seven ethers tested provided a
benefit and then at concentrations of the order of 750 to 1500
ppm.
[0019] According in one embodiment of the present invention there
is provided a fuel composition comprising: a diesel base fuel; from
1 to 10% v/v of a fatty acid alkyl ester; and more than 10% v/v of
an ether component, the ether component comprising or consisting of
one or more ether compounds having in the range of from 8 to 12
carbon atoms and selected from compounds of formula I
R.sub.1--O--R.sub.2 (I)
wherein R.sub.1 and R.sub.2 are independently C.sub.2 to C.sub.10
primary or secondary alkyl. By ether compounds are meant compounds
that contain only one ether group. The term "consisting" wherever
used herein also embraces "consisting substantially", but may
optionally be limited to its strict meaning of "consisting
entirely".
[0020] Contrary to the trend visible in U.S. Pat. No. 5,520,710, it
has been found that C8+ ethers can function highly effectively as
cetane boost additives in diesel fuel at high concentrations in
excess of 10% v/v e.g. up to 50% v/v. The ether component may be a
biofuel and generally does not suffer from the drawbacks associated
with FAAEs in the context of lubricant dilution. For example, the
ether component is less prone to accumulation in vehicle sumps. The
ether component can thus be incorporated into diesel fuel
compositions at concentrations significantly higher than the
current 7% v/v FAME limit, without build-up of biofuel components
in engine oil and whilst maintaining a positive effect on cetane
numbers of the overall compositions.
[0021] The ether component is to be understood herein as an added
component. Preferably, the ether component may be, or be taken to
be, the sole source of the ether compound(s) that it consists of in
the composition, but this is not essential.
[0022] The ether component is defined herein as comprising or
consisting of one or more ether compounds having at least 8 carbon
atoms (C8+ ether), or at least 9 carbon atoms (C9+ ether), or most
preferably at least 10 carbon atoms (C10+ ether). Thus, in
preferred embodiments of the invention, the ether component may
comprise, or be, C8+ ether, C9+ ether, or C10+ ether. Higher
molecular weight ethers tend to have particularly advantageous
volatility and cetane properties.
[0023] In some embodiments of the invention, the ether compounds of
the ether component may comprise at most 12 carbon atoms, or most
preferably at most 10 carbon atoms. Ether compounds with a
relatively low number of carbon atoms may be preferred for their
ease of biological synthesis. C10 ethers, are particularly
preferred.
[0024] The ether compound(s) of the ether component may be
symmetrical or asymmetrical; dialkyl, dicycloalkyl, or
alkylcycloalkyl. Symmetrical compounds are preferred. A
particularly preferred ether is dipentyl ether (DPE).
[0025] Suitably, the ether compound(s) may be selected from
compounds of formula I
R.sub.1--O--R.sub.2 (I)
wherein R.sub.1 and R.sub.2 are independently C.sub.2 to C.sub.24
primary or secondary alkyl, provided that the total number of
carbon atoms in formula (I) is as required, e.g. at least 8, 9 or
10, or as defined anywhere hereinabove.
[0026] Preferably, R.sub.1 and/or R.sub.2 may be C.sub.3 to
C.sub.15 alkyl, more preferably C.sub.4 to C.sub.7. In a
particularly preferred embodiment, R.sub.1 and/or R.sub.2 may be
C.sub.5 alkyl.
[0027] Since the ether component may preferably comprise or consist
of symmetrical compounds, R.sub.1 and R.sub.2 may preferably be the
same.
[0028] The ether component may comprise or consist of one or more
of the ether compounds or ether compound mixtures described
hereinabove. Most preferably, the ether component may comprise or
consist of dipentyl ether.
[0029] The ether component may comprise a mixture of two or more
ether compounds as defined hereinabove. For predictability of
properties, in some embodiments of the invention, the ether
component may comprise at least 50% v/v, or 70% v/v or 90% v/v, or
even 95% v/v of any one of the ether compounds or ether compound
mixtures described hereinabove.
[0030] In some embodiments of the invention, the ether component
may be accompanied by a small amount of impurities, for example
by-products of ether synthesis that have no substantive effect on
the overall properties of the ether component. Such impurities may,
for example, be present in an amount of at most about 3%, e.g. as
measured by gas chromatography (GC) commonly employed by suppliers
such as Sigma Aldrich. In embodiments of the invention, such
impurities up to 3% as measured by GC may be considered part of the
ether component, in which case the component consists substantially
of the ether compounds.
[0031] The cetane number of the ether component will typically be
higher than the cetane number of the diesel base fuel. Suitably,
the cetane number of the ether component may be at least 90,
preferably at least 100, or at least 102, most preferably at least
104.
[0032] Suitably, the ether component may offer a good property fit
with the diesel base fuel, particularly with a view to the
composition meeting EN590 or another specification.
[0033] The ether component may preferably have a density, measured
according to ASTM D 4052, of at least 0.750 g/cm.sup.3, more
preferably at least 0.770 g/cm.sup.3. The density of the ether
component may, for example, be at most 0.830 g/cm.sup.3.
[0034] The ether component may preferably have a flash point,
measured according to ASTM D 93, of at least 20.degree. C., more
preferably at least 50.degree. C.
[0035] The ether component may preferably have a vapour pressure,
measured at 25.degree. C., of at most 500 Torr (66661.2 Pa),
preferably at most 50 Torr (6666.1 Pa), or even at most 5 Torr
(666.6 Pa). The vapour pressure of the ether component may, for
example, be at least 0.5 Torr (66.6 Pa).
[0036] The ether component may preferably have a boiling point,
measured according to ASTM D 86, of at least 40.degree. C., more
preferably at least 100.degree. C. The boiling point of the ether
component may, for example, be at most 480.degree. C.
[0037] The ether component may be prepared by any suitable process
known in the art. One well known synthesis is the Williamson ether
synthesis, which involves treatment of a parent alcohol with a
strong base to form an alkoxide, followed by addition of an
appropriate aliphatic compound bearing a leaving group such as
halide or sulfonate. This synthesis works particularly well for
acyclic, unencumbered open chain primary aliphatic compounds. The
Ullmann ether synthesis, which is also well known and based on a
similar mechanism, albeit generally in the presence of a catalyst,
is particularly suitable for the formation of aryl ethers. Other
methods of forming ethers include the electrophilic addition of
alcohols to alkenes, e.g. alkoxymercuration of alkenes using
mercury trifluoroacetate as catalyst and hydroboration of alkenes
followed by oxidation. Further methods of synthesizing ethers,
including cyclic and polycyclic systems are described, for example,
in U.S. Pat. No. 5,520,710.
[0038] On an industrial scale, symmetrical ethers are typically
prepared by the dehydration of a parent alcohol. Dipentyl ether,
for example, may be prepared by dehydrating 1-pentanol in the
presence of sulphuric acid.
[0039] The alcohols or other starting materials for the synthesis
of ethers may be obtained from any available source. For example
parent alcohols, such as amyl alcohol, may be obtained by the
hydroformylation of olefins, which may in turn be petroleum derived
(see e.g. K Weissermel and H-J Arpe, Industrial Organic Chemistry,
Wiley-Vch, p 205). Further alternatives may be i) Markovnikov
hydration of olefins in the presence of acids and/or metal
catalysts; ii) Anti-Markovnikov addition via the sequence
hydroboration/oxidation of alkenes (see e.g. M. G. Loudon, (2002).
"Addition Reactions of Alkenes". Organic Chemistry (Fourth Edition
ed.) Oxford University Press pp. 168); iii) the reduction of
organic acids (such as but not limited to acids obtained via
fermentation), via intermediates aldehydes (see e.g. Y. Li, et al.
Huaxue Tongbao (2002), 65(7), 452-457); and iv) deep hydrogenation
of furfural through intermediates such as methylfuran and methyl
tetrahydrofuran (see e.g. H.-Y. Zheng, et al, Journal of Molecular
Catalysis A: Chemical, 246(1-2), 18-23; 2006).
[0040] In a preferred embodiment of the invention, the ether
component may be a biofuel component, ie derived from a biological
source. In such embodiments, the ether component may comprise or
consist of ether compounds derived from parent molecules, e.g.
alcohols, which are in turn obtained from a renewable carbonaceous
feedstock. For example, it is known to obtain alcohols by
fermentation, e.g. by distillation of fusel oil. Other biological
routes to alcohols, such as pentanol, via fermentation of renewable
feedstocks (organic carbon sources) using microorganisms, fungi
(such as members of the genus Saccharomyces), protists, algae,
bacteria (including cyanobacteria) and archaea are increasingly
being proposed. Alternatively, alcohols can be biologically derived
via gasification/pyrolysis from renewable carbonaceous feedstock,
followed by Fischer-Tropsch synthesis.
[0041] In some embodiments of the invention, the ether component
may comprise at least about 0.1 dpm/gC of carbon-14. It is known in
the art that carbon-14, which has a half-life of about 5700 years,
is found in biologically derived materials but not in fossil fuels.
Carbon-14 levels can be determined by measuring its decay process
(disintegrations per minute per gram carbon or dpm/gC) through
liquid scintillation counting.
[0042] The concentration of the ether component in the overall fuel
composition (or at least in the base fuel/ether component mixture)
is preferably 90% v/v or less, more preferably 80% v/v or less, yet
more preferably 70 or 60 or 50% v/v or less, based on the total
composition/mixture. As a minimum it is more than 10% v/v, or 12%
v/v or greater, such as 15% or 25% v/v or greater, or even 30 or
40% v/v or greater, based on the total composition/mixture. The
amount of the ether component may represent a balance of the fuel
composition: after inclusion of the base fuel component, and any
further (optional) components and additives, the ether component
may therefore be present in an amount to represent the balance to
100% v/v in the composition.
[0043] The diesel base fuel may be any fuel component, or mixture
thereof, which is suitable and/or adapted for use in a diesel fuel
composition 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 or
contain a kerosene fuel component.
[0044] It may be petroleum derived. 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.
[0045] A diesel base fuel will typically boil in the range from 150
or 180 to 370.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 to 70.
[0046] However, because the ether component has a positive effect
on cetane number, a fuel composition according to the invention may
include (or may include a greater proportion of) a base fuel which
has a relatively low cetane number. This can increase the options
available to the fuel formulator. The ether component may therefore
be used for the purpose of allowing the inclusion, in a diesel fuel
composition, of one or more lower cetane number fuel components
(for example diesel base fuels), or of a higher concentration of
one or more such fuel components, without, or without undue,
detriment to the cetane number of the overall composition. In this
context a "lower cetane number" fuel component may for example have
a measured cetane number of less than 50, or of less than 45 or 40
or in cases of less than 35. "Without undue detriment to the cetane
number" may for example mean without reducing the cetane number by
more than 30%, or in cases by more than 20 or 10 or 5 or 1%, of its
value if a higher cetane number fuel component (for example, with a
measured cetane number of 40 or greater, or of 45 or 50 or greater)
were to be used in the fuel composition, at the same concentration,
in place of the lower cetane number fuel component. It may entail
the overall fuel composition meeting a desired target
specification, for example the European diesel fuel specification
EN 590.
[0047] The diesel base fuel may suitably be present in the
composition in an amount of 10% v/v or greater, or 20 or 30 or 40%
or 50% v/v or greater, based on the total composition. It may be
present in an amount of less than 90% v/v, or up to 85 or up to 80
or 75% v/v, or up to 70 or 65 or 60% v/v, based on the total
composition. The amount of the base fuel may represent a balance of
the fuel composition: after inclusion of the ether component, the
fatty acid alkyl ester, and any further (optional) components and
additives, the diesel base fuel may therefore represent the balance
to 100% v/v in the composition.
[0048] The fuel composition may be prepared by simple blending of
its components in any suitable order, and such methods of blending
any of the fuel compositions herein are embraced by the
invention.
[0049] The fuel composition may comprise, in addition to the diesel
base fuel, the fatty acid alkyl ester, and the ether component, one
or more fuel or refinery additives, in particular additives which
are suitable for use in automotive diesel fuels. Many such
additives are known and commercially available. The composition may
for example comprise one or more additives selected from cetane
boost additives, antistatic additives, lubricity additives, cold
flow additives, and combinations thereof. Such additives may be
included at a concentration of up to 300 ppmw (parts per million by
weight), for example of from 50 to 300 ppmw. Due to the inclusion
of the ether component, however, it may, as described below, be
possible for the composition to contain lower levels of cetane
boost additive, or in cases for the composition not to contain such
type of additive.
[0050] The fuel composition should be suitable and/or adapted for
use in a compression ignition (diesel) internal combustion engine.
It may in particular be an automotive fuel composition. In further
embodiments it may be suitable and/or adapted for use as an
industrial gas oil, or as a domestic heating oil.
[0051] The fuel composition may 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 composition 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 40 or greater, ideally of
51 or greater; a kinematic viscosity at 40.degree. C. (VK40) (ASTM
D445 or EN ISO 3104) from 2 to 4.5 centistokes (mm.sup.2/s); a
flash point (ASTM D93 or EN ISO 2719) of 55.degree. C. or greater;
a sulphur content (ASTM D2622 or EN ISO 20846) of 50 mg/kg or less;
a cloud point (ASTM D2500/IP 219/ISO 3015) of less than -10.degree.
C.; and/or a polycyclic aromatic hydrocarbons (PAH) content (EN
12916) of less than 11% w/w. It may have a lubricity, measured
using a high frequency reciprocating rig for example according to
ISO 12156 and expressed as a "HFRR wear scar", of 460 .mu.m or
less.
[0052] Relevant specifications may however differ from country to
country and from year to year, and may depend on the intended use
of the composition. Moreover the composition may contain individual
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.
[0053] The fuel composition comprises, in addition to the diesel
base fuel and the ether component, a fatty acid alkyl ester, in
particular a fatty acid methyl ester (FAME) such as rapeseed methyl
ester or palm oil methyl ester. It is further possible for one or
more further biofuel components, particularly other than ether or
FAME, to be present. The biofuel component may suitably comprise an
alcohol, for example ethanol, and/or a fatty alcohol ester, and/or
a hydrogenated vegetable oil. The fatty acid alkyl ester may be
present in an amount of at least 1% v/v, or 2 or 3 or 4 or 5% v/v,
and up to 10 or 7 or 5% v/v, based on the total composition.
Typically, the amount of further biofuel component may be at least
1% v/v, or 2 or 3 or 4 or 5% v/v, and up to 30% v/v, or up to 20 or
10 or 7 or 5% v/v, based on the total composition. Due to the
inclusion of the ether component, it may, as described below, be
possible for the composition to contain lower levels of biofuel
components, or in cases for the composition not to contain
additional biofuel components.
[0054] It has been found that the ether component can significantly
boost cetane number when the fuel composition also comprises a a
fatty acid alkyl ester.
[0055] According to a further aspect of the invention, there is
provided the use of an ether component as defined above, in a
diesel fuel composition containing a fatty acid alkyl ester, for
the purpose of increasing the cetane number of the composition.
[0056] If it is desired to include a fatty acid ester or a fatty
alcohol ester in a diesel fuel composition, for example in order to
increase the biofuel content of the composition, and/or for the
lubricity benefits described in US-A-2011/0154728, the present
invention can provide for a further cetane boost. In accordance
with the invention, the ether component may be used to replace all
or part of a fatty acid ester or fatty alcohol ester which was
previously, or was intended to be, or would otherwise have been,
included in the diesel fuel composition.
[0057] The ether component may be used to achieve any degree of
increase in the cetane number of the diesel fuel composition,
and/or for the purpose of achieving a desired target cetane number,
for example a target set by an applicable regulatory standard such
as EN 590, or a target set by a user (which includes a handler,
keeper or distributor) or potential user of the composition. It may
be used to achieve a cetane number increase which is greater than
that which would be possible using the same concentration of
another biofuel component, in particular of a fatty alcohol ester
such as an alkyl acetate, or of a fatty acid alkyl ester such as a
FAME. The increase in cetane number will typically be as compared
to the cetane number of the composition prior to adding ether
component to it.
[0058] In the present context, "achieving" a desired target
property also embraces--and in an embodiment involves--improving on
the relevant target. Thus, for example, the ether component may be
used to produce a diesel fuel composition which has a cetane number
higher than a desired target standard.
[0059] The cetane number of a fuel composition may be determined
using any suitable method, for instance using the standard test
procedure ASTM D613 (ISO 5165, IP 41) which provides a so-called
"measured" cetane number obtained under engine running conditions.
Alternatively the cetane number may be determined using the more
recent "ignition quality test" (IQT) (ASTM D6890, IP 498), which
provides a "derived" cetane number based on the time delay between
injection and combustion of a fuel sample introduced into a
constant volume combustion chamber. This relatively rapid technique
can be used on laboratory scale (ca 100 ml) samples of a range of
different fuels.
[0060] Alternatively, cetane number may be measured by near
infrared spectroscopy (NIR), as for example described in U.S. Pat.
No. 5,349,188. This method may be preferred in a refinery
environment as it can be less cumbersome than for instance ASTM
D613. NIR measurements make use of a correlation between the
measured spectrum and the actual cetane number of a sample. An
underlying model is prepared by correlating the known cetane
numbers of a variety of fuel samples with their near infrared
spectral data.
[0061] The present invention preferably results in a diesel fuel
composition which has a measured cetane number (ASTM D613) of 40 or
greater, or of 45 or 50 or 51 or greater, for example of 55 or 60
or 65 or greater, in cases of 70 or 75 or greater.
[0062] The invention may additionally or alternatively be used to
adjust any property of the diesel fuel composition which is
equivalent to or associated with cetane number, for example to
improve the combustion performance of the composition (eg to
shorten ignition delays, to facilitate cold starting and/or to
reduce incomplete combustion and/or associated emissions in a
fuel-consuming system running on the fuel composition) and/or to
improve fuel economy.
[0063] By using the present invention, it can be possible to
include in a diesel fuel composition a higher concentration of a
biofuel component than would have been predicted to be
possible--whilst still achieving a desired target cetane
number--based on the properties of the fatty acid/alcohol esters.
It can be desirable to increase biofuel concentrations for a number
of reasons, for instance to meet regulatory requirements or
consumer expectations or more generally to reduce the
"well-to-wheels" carbon dioxide emissions associated with the
production and use of the fuel. It can also be desirable to
increase the concentration of fatty alcohol esters, not only as
biofuel components but also, for example, in order to improve the
lubricity of a fuel composition containing an acid-based lubricity
additive, as described in US-A-2011/0154728. However it would have
been thought necessary, in the past, to balance such benefits
against the potential reduction in cetane number which would be
expected to result from increasing the concentration of a fatty
alcohol ester, particularly for those esters having shorter (for
example C10 or less) carbon chains. According to the present
invention, such benefits can now be achieved with the added option
of a cetane number increase and without leading to excessive
lubricant dilution.
[0064] Thus according to an additional aspect, the invention
provides the use of an ether component as defined above, in a
diesel fuel composition, for the purpose of increasing the
concentration of a biofuel component in the composition, without
undue detriment to: the cetane number of the composition; and/or
lubricant dilution under engine operating conditions. The biofuel
component may, for example, comprise a fatty alcohol ester: the
ether component may therefore be used to increase the concentration
of fatty alcohol esters in the diesel fuel composition, without or
without undue detriment to its cetane number and/or lubricant
dilution properties under engine operating conditions.
Alternatively, the biofuel component may be taken as including all
biologically derived fuel components in the composition. In this
way the invention may be used to increase the options available, to
the fuel formulator, for increasing the biofuel content of a diesel
fuel composition whilst still meeting relevant fuel
specifications.
[0065] In the present context, "without undue detriment to the
cetane number" may for example mean without reducing the cetane
number by more than 30%, or in cases by more than 20 or 10 or 5 or
1%, of its original value.
[0066] In the present context, "without undue detriment to
lubricant dilution under engine operating conditions" may for
example mean without increasing at all the lubricant dilution
compared to a comparable or identical fuel composition without the
ether component. Lubricant dilution may be measured in any suitable
manner, e.g. based on gas chromatography (GC) analysis of lubricant
sump samples. Expressed in another way, the ether component may be
used to enhance or maintain lubricant lifetime during use of the
composition, or to maintain or increase the oil drain interval.
[0067] In accordance with this embodiment of the invention, the
ether component may be used to achieve any degree of increase in
the concentration of the relevant biofuel component. In an
embodiment, the ether component is used to increase the
concentration of the biofuel component whilst at the same time
increasing (which again embraces any degree of increase) the cetane
number of the diesel fuel composition.
[0068] Because the ether component can increase the cetane number
of a diesel fuel composition in which it is used, the composition
may as a consequence require a lower level of cetane boost
additives than might otherwise have been needed in order to achieve
a desired target cetane number. This can in turn reduce the cost
and complexity of preparing the composition, and/or can provide
greater versatility in fuel formulation practices. Thus, a further
aspect of the invention provides the use of an ether component as
defined above in a diesel fuel composition, for the purpose of
reducing the concentration of a cetane boost additive in the
composition.
[0069] In the context of this embodiment 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
concentration of the cetane boost additive, or 25 or 50 or 75 or
90% or more. The reduction may be as compared to the concentration
of the cetane boost 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 the additive which was present in the composition
prior to the realisation that the ether component could be used in
the way provided by the present invention, and/or which was present
in an otherwise analogous fuel composition intended (eg marketed)
for use in an analogous context, prior to adding the ether
component to it in accordance with the invention.
[0070] The reduction in concentration of the cetane boost additive
may be as compared to the concentration of the additive which would
be predicted to be necessary to achieve a desired cetane number for
the composition in the absence of the ether component.
[0071] A cetane boost additive may be any additive which is capable
of increasing, or intended to increase, the cetane number of a
diesel fuel composition to which it is added, and/or to improve the
ignition properties of such a composition when it is used in an
engine or other fuel-consuming system. A cetane boost additive may
also be known as a cetane improver, a cetane number improver or an
ignition improver. Many such additives are known and commercially
available; they typically function by increasing the concentration
of free radicals when a fuel begins to react in a combustion
chamber of a fuel-consuming system. Examples include organic
nitrates and nitrites, in particular (cyclo)alkyl nitrates such as
isopropyl nitrate, 2-ethylhexyl nitrate (2-EHN) and cyclohexyl
nitrate, and ethyl nitrates such as methoxyethyl nitrate; and
organic (hydro)peroxides such as di-tert-butyl peroxide. Cetane
boosting diesel fuel additives are commercially available for
instance as HITEC.TM. 4103 (ex Afton Chemical) and as CI-0801 and
CI-0806 (ex Innospec Inc).
[0072] In the context of the present invention, "use" of the ether
component in a diesel fuel composition means incorporating the
ether component into the composition, typically as a blend (ie a
physical mixture) with one or more other diesel fuel components,
for example a diesel base fuel and optionally one or more diesel
fuel additives. The ether component will conveniently be
incorporated before the composition is introduced into an engine or
other system which is to be run on the composition. Instead or in
addition, the use of the ether component may involve running a
fuel-consuming system, typically an internal combustion engine, on
a diesel fuel composition containing the ether component, typically
by introducing the composition into a combustion chamber of an
engine. It may involve running a vehicle which is driven by a
fuel-consuming system, on a diesel fuel composition containing the
ether component. In such cases the engine is suitably a compression
ignition (diesel) engine.
[0073] "Use" of the ether component in the ways described above may
also embrace supplying the ether component together with
instructions for its use in a diesel fuel composition in order to
increase the cetane number of the composition. The ether component
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
ether component may be included in such a composition for the
purpose of influencing its effects on the cetane number of a diesel
fuel composition.
[0074] In general, references to "adding" a component to, or
"incorporating" a component in, a fuel composition may be taken to
embrace addition or incorporation at any point during the
production of the composition or at any time prior to its use.
[0075] In embodiments, the present invention may be used to produce
at least 1,000 litres of the ether component-containing fuel
composition, or at least 5,000 or 10,000 or 20,000 or 50,000
litres.
[0076] A fuel composition prepared or used according to the
invention may be marketed with an indication that it benefits from
an improvement due to the inclusion of the ether component, in
particular a higher cetane number. The marketing of such a
composition may comprise an activity selected from (a) providing
the composition in a container that comprises the relevant
indication; (b) supplying the composition with product literature
that comprises the indication; (c) providing the indication in a
publication or sign (for example at the point of sale) that
describes the composition; and (d) providing the indication in a
commercial which is aired for instance on the radio, television or
internet. The improvement may be attributed, in such an indication,
at least partly to the presence of the ether component. The
invention may involve assessing the relevant property (in
particular the cetane number) of the composition during or after
its preparation. It may involve assessing the relevant property
both before and after incorporation of the ether component, for
example so as to confirm that the ether component contributes to
the relevant improvement in the composition.
[0077] 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.
[0078] 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. For example, for
the avoidance of doubt, the optional and preferred features of the
fuel composition, the diesel base fuel, the ether component or the
biofuel component apply to all aspects of the invention in which
the fuel composition, the diesel base fuel, the ether component or
the biofuel component are mentioned.
[0079] Moreover unless stated otherwise, any feature disclosed
herein may be replaced by an alternative feature serving the same
or a similar purpose.
[0080] Where upper and lower limits are quoted for a property, for
example for the concentration of a fuel component, then a range of
values defined by a combination of any of the upper limits with any
of the lower limits may also be implied.
[0081] In this specification, references to fuel and fuel component
properties are--unless stated otherwise--to properties measured
under ambient conditions, ie at atmospheric pressure and at a
temperature from 16 to 22 or 25.degree. C., or from 18 to 22 or
25.degree. C., for example about 20.degree. C.
[0082] The present invention will now be further described with
reference to the following non-limiting examples.
Example 1 (Comparative)
[0083] Diesel fuel compositions were prepared by blending a diesel
base fuel with an ether component consisting of dipentyl ether
(DPE).
[0084] The base fuel was a zero sulphur diesel fuel (ex Shell),
which conformed to the European diesel fuel specification EN 590.
It did not contain any detergent or lubricity additives, or any
oxygenates such as FAMEs. Its properties are summarised in Table 1
below.
TABLE-US-00001 TABLE 1 Property Units Test method Base fuel Density
@ 15.degree. C. kg/m.sup.3 ASTM D 4052 825 VK40 mm.sup.2/s IP 71
2.08 Distillation ASTM D 86 0% .degree. C. 172.0 10% 195.6 20%
205.3 30% 215.0 40% 226.7 50% 239.9 60% 254.4 70% 269.6 80% 288.2
90% 311.2 95% 328.6 100% 342 Rec at 250.degree. C. % v/v 57.5 Rec
at 370.degree. C. % v/v 97.7 Cetane (CRF engine) ASTM 613 53.8
Derived cetane (IQT) IP 498 54.1 HFRR (averaged) .mu.m ISO 12156
272
[0085] The ether component tested consisted of 97% pure (measured
by GC) dipentyl ether sourced from Sigma Aldrich. Relevant
properties (literature values) for the ether component are as
follows: boiling point=188.degree. C.; flash point=57.degree. C.;
vapour pressure at 25.degree. C.=1.0 Torr; density=0.791
g/cm.sup.3.
[0086] The ether component was blended with the base fuel at 2, 5,
10, 15, 30 and 50% v/v. The resultant blends were tested for cetane
number using the IQT method specified in Table 1. The results are
shown in Table 2.
[0087] From the measured cetane numbers of the blends and the
diesel base fuel, blending cetane number values were calculated for
the ether component as follows.
blending CN.sub.DPE=(CN.sub.comp-(1-x)*CN.sub.diesel)/x
where: [0088] blending CN.sub.DPE is the blending cetane number of
the ether component when used at volume fraction x; [0089]
CN.sub.comp is the measured cetane number of the base fuel/ether
component blend; and [0090] CN.sub.diesel is the measured cetane
number of the diesel base fuel.
[0091] The resultant blend values are also shown in Table 2.
TABLE-US-00002 TABLE 2 Diesel DPE CN.sub.comp Blending Comp (% v/v)
(% v/v) (IQT) CN.sub.DPE 1 98 2 55.3 99.4 2 95 5 56.6 98.4 3 90 10
58.1 91.4 4 85 15 60.4 94.4 5 70 30 66.6 95.1 6 50 50 76.7 99.0
[0092] The blending cetane number of the ether component is a
measure of the contribution of the ether component to the measured
cetane number of the fuel composition. It can be seen that the
blending cetane number of the ether component increases from 91.4
at 10% v/v to 99 at 50% v/v. The effectiveness of the ether
component in boosting cetane is thus increased at higher
concentrations.
Example 2 (Comparative)
[0093] Diesel fuel compositions were prepared, for comparison with
those of Example 1, by blending a diesel base fuel with a fatty
acid methyl ester (FAME) component.
[0094] The diesel base fuel was as in Example 1.
[0095] The FAME component consisted of 100% refinery grade palm oil
methyl esters (POME).
[0096] Relevant properties for the FAME component are as follows:
flash point=156.degree. C. (IP 34); viscosity at 40.degree. C.=4.45
mm.sup.2/s (IP 71); density=0.877 g/cm.sup.3 (IP 365).
[0097] The FAME component was blended with the base fuel at 2, 5,
10, 15, 30 and 50% v/v. The resultant blends were tested for cetane
number using the IQT method specified in Table 1. The results are
shown in Table 3.
[0098] From the measured cetane numbers of the blends and the
diesel base fuel, blending cetane number values were calculated for
the FAME component as follows.
blending CN.sub.FAME=(CN.sub.comp-(1-x)*CN.sub.diesel)/x
where: [0099] blending CN.sub.FAME is the blending cetane number of
the FAME component when used at volume fraction x; [0100]
CN.sub.comp is the measured cetane number of the base fuel/ether
component blend; and [0101] CN.sub.diesel is the measured cetane
number of the diesel base fuel.
[0102] The resultant blend values are also shown in Table 3.
TABLE-US-00003 TABLE 3 Diesel FAME CN.sub.comp Blending Comp (%
v/v) (% v/v) (IQT) CN.sub.FAME 7 98 2 54.7 69.4 8 95 5 56 86.4 9 90
10 56.5 75.4 10 85 15 57.2 73.1 11 70 30 59.1 70.1 12 50 50 62.4
70.4
[0103] The blending cetane number of the FAME component is a
measure of the contribution of the FAME component to the measured
cetane number of the fuel composition. It can be seen that the
blending cetane number of the FAME component decreases from 75.4 at
10% v/v to 70.4 at 50% v/v. The effectiveness of the FAME component
in boosting cetane is thus decreased at higher concentrations.
Example 3
[0104] Diesel fuel compositions were prepared, according to the
invention, by blending a diesel base fuel with an ether component
consisting of dipentyl ether and a fatty acid methyl ester (FAME)
component.
[0105] The diesel base fuel and the dipentyl ether components were
as in Example 1. The FAME component was as in Example 2.
[0106] The ether and FAME components were blended with the base
fuel in the amounts shown in Table 4. The resultant blends were
tested for cetane number using the IQT method specified in Table 1.
The results are shown in Table 4.
[0107] From the measured cetane numbers of the blends and the
diesel base fuel, blending cetane number values were calculated for
the combined ether and FAME components as follows.
blending CN.sub.DPE+FAME=(CN.sub.comp-(1-x)*CN.sub.diesel)/x
where: [0108] blending CN.sub.DPE+FAME is the blending cetane
number of the combined ether and FAME components when used at a
total volume fraction x; [0109] CN.sub.comp is the measured cetane
number of the base fuel/ether component blend; and [0110]
CN.sub.diesel is the measured cetane number of the diesel base
fuel.
[0111] The resultant blend values are also shown in Table 4.
TABLE-US-00004 TABLE 4 Diesel FAME DPE CN.sub.comp Blending Comp (%
v/v) (% v/v) (% v/v) (IQT) CN.sub.DPE+FAME 13 90 5 5 56 70.4 14 85
5 10 58.7 83.1 15 70 5 25 64 86.4 16 50 5 45 74.5 94.6 17 85 7.5
7.5 58.6 82.4 18 70 15 15 62.9 82.7 19 50 25 25 68.4 82.4
[0112] The blending cetane number of the combined ether and FAME
components is a measure of the contribution of these components to
the measured cetane number of the fuel composition. It can be seen
that, at a consistent concentration of the FAME component, the
blending cetane number of the combined components increases from
70.4 at 5% v/v ether component to 94.6 at 45% v/v ether component.
At equivalent concentrations of ether and FAME components, the
blending cetane number of the combined components stays relatively
constant, irrespective of concentration.
Example 4
[0113] The properties of a diesel fuel composition from Example 1
were examined to determine their compliance with fuel
specifications. Table 5 shows the properties of composition 3 from
Example 1.
TABLE-US-00005 TABLE 5 Property Units Test method Comp 3 Density @
15.degree. C. kg/m.sup.3 ASTM D 4052 822 VK40 mm.sup.2/s IP 71 1.92
Distillation ASTM D 86 0% .degree. C. 174.3 10% 191.6 20% 198.8 30%
207.6 40% 218.1 50% 230.4 60% 246.7 70% 264.7 80% 284.8 90% 309.3
95% 328.3 100% 340.3 Rec at 250.degree. C. % v/v 61.9 Rec at
370.degree. C. % v/v 97 Flash point .degree. C. ASTM D 93 65 Cetane
(CRF engine) ASTM D 613 56.8 Derived cetane (IQT) IP 498 58.4 HFRR
(averaged) .mu.m ISO 12156 445 Cloud point .degree. C. IP 219 -14
CFPP (pot A) IP 309 -35 CFPP (pot B) IP 309 -35
Example 5
[0114] The dilution of diesel engine lubricant with ether component
and other biofuel components was examined.
[0115] The standardised experimental procedure was as follows:
[0116] A diesel engine was flushed with new lubricant and operated
for 16 hours under steady-state conditions. The engine speed and
load was then increased to a higher speed/load point at the start
of test, after which the lubricant sump temperature reached
120.degree. C. [0117] The diesel fuel used to run the engine did
not contain any biofuels (ie. free of FAME and ether). [0118] To
simulate accumulation of a bio-component transferred from a diesel
fuel, known volumes of the ether component and/or FAME component
(as in the Examples above) were dosed in separate runs directly
into the lubricant sump. [0119] Samples at the start, end and
intermediate time points were collected and analysed.
[0120] The components tested were Ether component only, FAME
component only, and an equivolume Ether-FAME component mixture. The
loss of bio-component (measured as percentage remaining in the
lubricant; % remaining) was determined from GC analysis of
lubricant sump samples.
[0121] The results are shown in Table 6.
TABLE-US-00006 TABLE 6 Ether-FAME component Ether FAME (1:1 v/v)
Time component component FAME % Ether % (min) % remaining %
remaining remaining remaining 0 100 100 100 100 60 34.4 -- -- --
120 15.4 -- -- -- 180 2.7 -- -- -- 240 2 -- -- -- 300 0.1 -- -- --
360 0 -- -- -- 420 0 94.3 95.5 0
[0122] It is observed that the ether component is volatilized from
the lubricant in less than 7 hours, whereas the FAME component is
persistent. When an ether-FAME mixture is added, the ether
component is volatilized in the same manner as when it was present
as a single component.
Discussion of Examples
[0123] The effectiveness of the ether component in boosting cetane
has been found to increase at higher concentrations. This is
unexpected, both in view of the behaviour of other cetane boost
components such as FAME and in view of the behaviour of the ether
component at concentrations below 10% v/v. The ether component has
been found to boost cetane effectively in diesel fuel compositions
both with and without a FAME component, but provided a significant
boost when both components were present.
[0124] Furthermore, it was found that any dilution of lubricant by
the ether component was rapidly reversible by volatilization under
engine operating conditions. Therefore, lubricant performance
properties such as protection and durability are not affected. This
behaviour of the ether component contrasts with that of FAMEs,
which accumulate in the lubricant.
* * * * *