Note: Descriptions are shown in the official language in which they were submitted.
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EMULSIFIED WATER/HYDROCARBON FUEL, PREPARATION
AND USES THEREOF
The present invention relates to a fuel composed of
an emulsion of water and of liquid hydrocarbons which is
intended to be used in heat engines and thermal machines.
More specifically, the present invention relates to an
emulsified water/hydrocarbon fuel, the content of certain
paraffins in the hydrocarbon phase of which makes it
possible to reduce emissions during combustion.
For several years, the majority of oi.l companies have
been working on the development of fuels (and in
particular of engine fuels) comprising substitution
products for hydrocarbons of petroleum origin, with a
view both to economizing on hydrocarbons and to limiting
pollution. Thus, water very quickly appeared as a
particularly advantageous partial substi.tutent, provided
that it is maintained in a stable emulsion with the
hydrocarbons.
Thus, patent applications WO 93/18:117, WO 97/34969
and WO 01/48123 disclose fuels composed of a mixture
generally comprising at least 5s by weight of water and
hydrocarbons, maintained in emulsion by virtue of the use
of specific compositions comprising surfactant additives.
In comparison with a conventional engine fuel composed
solely of hydrocarbons, these fuels make it possible,
during combustion in a diesel engine, to reduce the
emissions of polluting compounds, such a.s, in particular,
nitrogen oxides, carbon monoxide, solid particles and
nonincinerated hydrocarbons.
Patent application DE 3023372 discloses an engine
fuel for diesel engines composed of an emulsion
comprising at least 80% by volume of hydrocarbons and
from 12 to 20% by volume of water, as well as from 0.5 to
1.5% by volume of an emulsifying agent which is an ether
of alkylphenol and of polyglycol. The hydrocarbons are a
mixture of at least 10% by volume of a "middle oil" (of
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the conventional diesel fuel type) and of at most 90% by
volume of a "heavy oil" which can be composed in
particular, in all or part, of vegetable oil. The main
advantage of this engine fuel is that it makes it
possible to achieve a substantial saving with regard to
the hydrocarbon fractions on which conventional diesel
fuels are based by partially substituting them by two
other constituents (water and vegetable oils).
The purpose of the present invention is to provide an
l0 emulsified fuel based on hydrocarbons and on water which
makes it possible to further reduce polluting emissions
in comparison with the emulsified engine fuels known in
the prior art.
This is because the applicant company has discovered
IS that, surprisingly, these emissions could be
substantially reduced provided that the hydrocarbons
participating in the composition of the emulsion comprise
a substantial amount of a specific family of paraffins,
namely C8 to C22 normal paraffins (linear paraffins)
20 (that is to say, the backbone of which is composed of 8
to 22 carbon atoms). Mixtures of such normal paraffins
are envisaged.
To this end, the present invention provides an
emulsified fuel comprising a hydrocarbon liquid phase, an
25 aqueous phase and at least one emulsifying additive and
exhibiting a water/hydrocarbons ratio by weight ranging
from 5/95 to 35/65. This fuel is characterized in that
the hydrocarbon phase comprises from 5 to 35% by weight
of Ca to C22 normal paraf f ins .
30 In comparison with the known emulsified fuels, the
fuel according to the present invention makes it possible
to significantly reduce emissions during combustion in a
heat engine or a boiler, in particular emissions of
nitrogen oxides and of solid particles. This effect
35 becomes greater when said normal paraffins are C13 to C19
normal paraffins. Thus, according to a preferred
embodiment, the hydrocarbon phase comprises from 5 to 35%
by weight of C13 to C19 normal paraffins.
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Furthermore, the presence in the hydrocarbon phase of
the above normal paraffins proved to have a particularly
beneficial effect on the autoignition delay time and the
cetane number of the fuel. This advantage is particularly
noticeable when said fuel is an engine fuel for diesel
vehicles, since these parameters represent the quality of
the combustion of the engine fuel in a standard diesel
engine. The implementation of the invention makes it
possible, in comparison with an otherwise identical
l0 conventional water/hydrocarbon emulsion, to gain up to 10
cetane number points.
This effect is all the more advantageous as the
normal paraffins under consideration in the invention
have proved to have, with regard to the increase in the
cetane number, a synergistic effect with the additives
conventionally employed to increase the cetane number of
diesel engine fuels, or "cetane number improvers"
(generally alkyl nitrates or organic peroxides). The
invention thus makes it possible, at an equal content of
cetane number improver, to obtain more efficient engine
fuels. The invention also makes it possible to reduce the
content of cetane number improver in the engine fuel. In
other words, the invention makes it possible to obtain
fuels exhibiting an excellent combustion quality without
using higher contents of cetane number improvers capable
of negatively interacting with the other additives or
having undesirable side effects when they are used at
high doses.
Finally, the present invention has proved to have a
beneficial effect on the stability of the emulsion as
measured by centrifuging according to the standard NF M07
101. In particular, the stability on storage, both at
ambient temperature and under hot conditions (75°C), is
substantially improved.
The emulsified fuel according to the invention
comprises a hydrocarbon liquid phase and an aqueous
phase. Preferably, the water/hydrocarbons ratio by weight
is between 8/92 and 20/80.
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According to the invention, the hydrocarbon phase
comprises from 5 to 35% by weight of C8 to C22 normal
paraffins. Advantageously, said hydrocarbon phase
comprises from 8 to 20% by weight and preferably from 10
to 20 % by weight of said C8 to C22, preferably C13 to C19,
normal paraffins.
The hydrocarbon phase can be composed of any mixture
of hydrocarbons, provided that it comprises the required
normal paraffins in an appropriate amount.
to According to a first embodiment of the invention, the
hydrocarbon phase comprises at least one petroleum
fraction of gasoline, diesel fuel or kerosene type
selected so that it comprises from 5 to 35% by weight,
preferably from 8 to 20% by weight, more preferably still
from 10 to 20% by weight of Ca to C22, preferably C13 to
C19, normal paraf f ins .
According to a second embodiment, which is the
preferred embodiment, the hydrocarbon phase is composed
of a conventional hydrocarbon engine fuel to which at
least one fraction rich in normal paraffins has been
added. The hydrocarbon phase then comprises a mixture
composed of one or more hydrocarbon fractions and of at
least one fraction rich in Ce to C2z, preferably C13 to
Clg, normal paraffins. The term "rich" is understood to
mean that said fraction comprises at least 50% by weight
of said normal paraffins, preferably at least 80% by
weight, more preferably still at least 90% by weight.
The said fraction rich in normal paraffins is then
mixed with the hydrocarbon fractions) according to their
respective contents of normal paraffins, in proportions
such that the resulting hydrocarbon phase comprises from
5 to 35% by weight, preferably from 8 to 20% by weight,
more preferably still from 10 to 20% by weight of Ce to
C22, preferably C13 to C19, normal paraffins.
Said fraction rich in normal paraffins can have
various origins.
It can be, according to a first alternative form, a
fraction of petroleum origin obtained during oil refining
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operations. Some fractions, such as gasolines, kerosenes,
indeed even light diesel fuels, can, in a way known per
se, include large amounts of normal paraffins. Mention
may be made, as nonlimiting examples, of straight-run
5 gasolines, kerosenes and distillates (resulting directly
from the distillation of crude oil), or those resulting
from catalytic cracking, hydrocracking or hydrotreating
processes. It is then possible to fractionate such
fractions by distillation, so as to isolate a fraction
including a substantial amount of the normal paraffins
required in the present invention. It is possible in
particular, starting from such fractions, to isolate the
normal paraffins using appropriate molecular sieves,
which make it possible to separate the normal paraffins
IS from the other hydrocarbons (in particular isoparaffins),
and to thus prepare fractions of petroleum origin
comprising at least 80% by weight of the required normal
paraffins.
According to a second alternative form, said fraction
rich in normal paraffins comprises synthetic paraffins
obtained by oligomerization of olefins comprising from 2
to 5 carbon atoms or by the Fischer-Tropsch synthesis
starting from light hydrocarbons, such as methane or
natural gas.
According to a third particularly advantageous
alternative form, said fraction rich in normal paraffins
comprises at least one hydrotreated animal or vegetable
oil and/or fat. This is because, in a way known per se,
complete hydrotreating of the fatty acid triglycerides
present in animal or vegetable fatty substances makes it
possible, by hydrocracking of the triglyceride structure
and complete hydrogenation of the fatty acids, to obtain
normal paraffin fractions in a particularly pure form,
that is to say virtually devoid of other hydrocarbons. By
appropriately choosing the starting oils or fats, in
particular according to the length and the structure of
the fatty acids, and by applying a treatment comprising a
hydrotreating under appropriate conditions, followed by
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fractionation (generally by distillation) of the
effluents, it is possible to obtain fractions very rich
in Ce to C22 normal paraf f ins .
The starting oil or fat can advantageously be chosen
f rom
vegetable oils, such as, for example, rapeseed oil,
soybean oil, sunflower oil, palm oil, canola oil or oils
extracted from resinous trees (in particular resinous
conifers);
animal fats, such as, for example, purified fats
(yellow grease), tallow or poultry fats;
waste food oils or fats, such as those recovered
from the catering industry, which generally comprise a
mixture of animal fats and vegetable oils;
and the mixtures of the above products.
The operating conditions under which these oils or
fats are converted to paraffins comprise a key stage of
hydrotreating in the presence of a catalyst based on
transition metals, at a temperature preferably of between
350 and 450°C and a hydrogen pressure ranging from 4 MPa
to 15 MPa. The effluents are then recovered and
fractionated, so as to obtain the desired normal
paraffins. Use may be made, for example, of the processes
as disclosed in patents US 4 992 605 and US 5 705 722.
It is, of course, possible to combine the three
alternative forms described above and to simultaneously
incorporate, in the hydrocarbon phase, a fraction rich in
normal paraffins of petroleum origin and/or a fraction
rich in normal paraffins comprising synthetic paraffins
and/or a fraction rich in normal paraffins based on
hydrotreated animal or vegetable oil or fat.
It is possible to employ, as hydrocarbon fraction
with which the fraction rich in normal paraffins is mixed
in order to obtain the hydrocarbon phase according to the
invention, fractions and mixtures of fractions of very
diverse origins and natures. This choice is essentially
dictated by the use for which the fuel is intended, by
the availability of the various hydrocarbon fractions and
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by economic considerations (cost of the fuel).
When the fuel is intended for use as engine fuel for
heat engines, the hydrocarbon fraction, with which the
fraction rich in normal paraffins is mixed in order to
obtain the hydrocarbon phase according to the invention,
is advantageously chosen from the bases which are
constituents of the composition of conventional engine
fuels and which comprise in particular gasoline fractions
(distillation range generally within the span 25 to
200°C), middle distillates, such as, for example,
kerosene fractions (distillation range generally within
the span 160 to 240°C) and diesel fuel fractions
(distillation range generally within the span 160 to
400°C), biofuels, and the mixtures of such fractions.
These fractions can result from oil refining or from
agriculture (case of biofuels) or can be synthetic
hydrocarbons.
The term "biofuel" denotes light alcohols, such as
ethanol, oils of vegetable or animal origin, and the
esters of such oils. The hydrocarbon phase of the fuel
according to the invention can thus advantageously
comprise from 0.1 to 60% by weight and preferably from
0 . 5 to 50 o by weight of biofuel . The preferred biofuels
are the esters of alcohols comprising from 1 to 4 carbon
atoms and of fatty acids or of mixtures of fatty acids
comprising from 16 to 22 carbon atoms. The particularly
preferred biofuels are the methyl esters of vegetable
oils, such as, for example, but not limitingly, soybean
oil, rapeseed oil, sunflower oil, olive oil or palm oil.
When the fuel is intended for other uses, the
hydrocarbon fraction, with which the fraction rich in
normal paraffins is mixed in order to obtain the
hydrocarbon phase according to the invention, can be
chosen from the fractions mentioned above for the engine
fuels but also from intermediate vacuum distillates
(distillation range generally within the span 350 to
450°C), heavy vacuum distillates (distillation range
generally within the span 400 to 550°C), indeed even
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bottom cuts, and generally from all the fractions
conventionally employed in fuels, such as, for example,
FFOs (Furnace Fuel Oils), fuel oils, heating oils, heat
oils, and the mixtures of such fractions.
The engine fuel according to the invention exists in
the form of an emulsion of fine droplets of aqueous phase
evenly dispersed in the hydrocarbon phase.
Advantageously, the mean diameter of the droplets of
aqueous phase evenly dispersed in the hydrocarbon phase
is less than or equal to 5 ~Cm, preferably less than or
equal to 3 ~.m, more preferably still less than or equal
to 1 Vim. Preferably, the particle size profile of the
drop sizes is of the type monodispersed around a value of
approximately 0.5 Vim. The above values for mean size of
the droplets correspond to measurements carried out by
the laser particle sizing technique.
In order for the emulsion to be stable over time
(that is to say, in order for the water droplets to
remain homogeneously dispersed in the hydrocarbon phase
and to prevent their coalescence, eventually resulting in
the separation of the aqueous phase and the organic
phase), it comprises at least one emulsifying agent. The
term "emulsifying agent" denotes any additive or mixture
of additives having surfactant properties capable of
guaranteeing the stability of the fine droplets of
aqueous phase in the organic phase. Numerous additives
can be employed for this purpose, in particular ionic or
nonionic emulsifiers of synthetic or natural origin, such
as, for example, but not limitingly, compounds chosen
from fatty acids, fatty acid derivatives, fatty alcohols,
ethoxylated fatty amines, polyol esters, functionalized
polymers, and their mixtures.
Advantageously, the emulsifying agent comprises at
least one nonionic organic emulsifying additive
preferably of natural origin. Mention may be made, as
examples, of fatty acids and their derivatives, polyol
esters or functionalized polymers.
In a particularly advantageous way, the emulsifying
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agent is composed of a mixture of at least two
emulsifying additives. Examples of such emulsifying
agents are disclosed in patent applications WO 97/34969
and WO 01/48123.
The content of emulsifying agent in the fuel depends,
in a way known per se, on the nature and on the
effectiveness of this agent. Generally, the additives
used as emulsifying agents are generally incorporated in
the emulsions at contents which can range from 0.5 to 5%
by weight. Preferably, the fuel according to the
invention exhibits a content of emulsifying agent of
between 1 and 3% by weight.
The emulsified fuel according to the present
invention can advantageously comprise one or more
biocidal agents, preferably in its aqueous phase. This
biocidal agent is preferably a bactericide and/or a
fungicide. Mention may be made, as nonlimiting examples
of biocidal agents, of isothiazolones and their
chlorinated derivates, benzalkonium chlorides, organic
peroxides or isothiocyanates.
The emulsified fuel can also comprise at least one
antifreeze. Use may be made, as antifreezes, for example,
of alcohols, glycols, derivatives of glycols or of
alcohols, or saline solutions.
It can also comprise at least one soot remover.
Mention may be made, as examples of such removers, of the
additives composed of one or more metal or alkaline earth
metal catalysts capable of promoting soot postcombustion
reactions. The preferred catalysts are based on
magnesium, calcium, barium, cerium, copper, iron or their
mixtures. These catalytic promoters of the destruction of
soot are also easy to introduce as they are generally
compounds whose salts are soluble in water and thus in
the aqueous phase of the emulsions according to the
invention.
When the fuel is intended for use as engine fuel for
heat engines, its sulfur content, determined according to
the standard NF M 07-100, is preferably less than or
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equal to 350 ppm, preferably less than or equal to 50 ppm
and more preferably still less than or equal to 10 ppm.
When the fuel is intended for use as fuel for thermal
machines, its sulfur content, determined according to the
5 standard NF M 07-100, is preferably less than or equal to
1% by weight, preferably less than or equal to 2% by
weight and more preferably still less than or equal to
0.1% by weight.
Whatever its use, the content of polycyclic aromatic
10 hydrocarbons in the fuel according to the invention,
determined according to the standard IP 391, is
preferably less than or equal to 11% by weight, more
preferably less than or equal to 6% by weight.
Furthermore, for use as engine fuel, the emulsified
fuel according to the invention preferably comprises one
or more other additives which can be any additive
conventionally employed in engine fuels, including, for
example, but not limitingly:
- one or more cetane number improvers, such as, for
example, alkyl nitrates, in which the saturated or
unsaturated and linear or branched (preferably saturated
and branched) alkyl radical comprises from 3 to 20 and
preferably from 5 to 15 carbon atoms (in particular
2-ethylhexyl nitrate), or organic peroxides and in
particular aryl peroxides, in which the aryl group is a
benzyl group or a substituted benzyl group (for example
benzoyl peroxide), or alkyl peroxides, in which the
saturated or unsaturated and linear or branched
(preferably saturated and branched) alkyl radical
comprises from 2 to 20 and preferably from 2 to 15 carbon
atoms (for example tert-butyl peroxide);
- one or more flow improvers, such as, for example,
ethylene/vinyl acetate (EVA), ethylene/vinyl propionate
(EVP), ethylene/vinyl ethanoate (EVE), ethylene/methyl
methacrylate (EMMA) or ethylene/alkyl fumarate
copolymers;
- one or more antifoaming agents, such as, for
example, polysiloxanes, oxyalkylated polysiloxanes, or
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fatty acid amides;
- one or more detergent additives and/or corrosion
inhibitors, such as, for example, amines, succinimides,
alkenylsuccinimides, polyalkylamines, polyalkylpolyamines
and polyetheramines;
- one or more slip additives or antiwear additives,
such as, for example, fatty acids and their ester or
amide derivatives or mono- and polycyclic carboxylic
acids and their ester or amide derivatives;
- one or more cloud point additives, such as, for
example, olefin comprising a long chain/(meth)acrylic
ester/maleimide terpolymers or fumaric or malefic acid
ester derivatives;
- one or more additives for combating
sedimentation, such as, for example, (meth)acrylic
acid/alkyl (meth)acrylate copolymers where the alkyl
group is amidated by a polyamine, polyamine
alkenylsuccinimides, or derivatives of phthalamic acid
and of fatty amine comprising a double chain;
- one or more polyfunctional additives for
operability under cold conditions, such as, for example,
polymers based on olefin and on alkenyl nitrate.
In particular, as was set out above, due to the
synergistic effect observed between the Ce to C22 normal
paraffins and the cetane number improvers, the emulsified
fuel according to the invention makes it possible to
reduce the levels of incorporation of such improvers or,
at the same level of cetane number improver, to obtain
more efficient engine fuels. This synergistic effect is
particularly effective when the ratio of the content by
weight of C8 to C22 (preferably C13 to C19) normal
paraffins in the hydrocarbon phase to the content by
weight of cetane number improvers in the engine fuel is
between 5/0.5 and 15/0.5, preferably between 5/0.3 and
15/0.1.
The fuel according to the invention can be prepared
in various ways and in particular by any conventional way
for preparing emulsions.
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Advantageously, the hydrocarbon phase is prepared
beforehand, before emulsifying the latter with the
aqueous phase.
The invention thus also relates to a process for the
preparation of an emulsified fuel comprising at least the
following stages:
(a) selecting at least one petroleum fraction of
gasoline, diesel fuel or kerosene type comprising from 5
to 35% by weight, preferably from 8 to 20% by weight,
more preferably still from 10 to 20 % by weight of Ce to
Czz, preferably C13 to C19, normal paraffins; or
(a') mixing one or more hydrocarbon fractions and at
least one fraction comprising at least 50% by weight of
Ca to Czz, preferably C13 to C19, normal paraffins, so as to
obtain a hydrocarbon phase comprising from 5 to 35% by
weight, preferably from 8 to 20% by weight, more
preferably still from 10 to 20% by weight of C8 to Czz,
preferably C13 to C19, normal paraffins; then
(b) emulsifying, in the presence of at least one
emulsifying agent, the hydrocarbon phase obtained in (a)
or (a') with an aqueous phase according to a
water/hydrocarbons ratio by weight ranging from 5/95 to
35/65.
The emulsification proper, and the incorporation of
the various additives (including the emulsifying agent),
can be carried out in various ways.
It is advantageous to mix all or a portion of the
additives with one and/or other of the phases, prior to
the emulsification. For example, stage (b) can be carried
out in the way disclosed in patent application
WO 00/34419 by mixing the emulsifying agent with the
hydrocarbon phase and then passing the resulting mixture
one or more times into an emulsifier system fed with the
water necessary for the formation of the emulsion.
It is also advantageous to carry out stage (b) in the
way disclosed in patent application WO 01/36569, by:
(bl) premixing the water and the emulsifying
agent, followed by dispersion in the hydrocarbon phase,
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or simultaneous mixing of the hydrocarbon phase with the
water and the emulsifying agent, then
(b2) emulsifying proper using an appropriate
device, for example chosen from rotor-stators, emulsifier
apparatuses, static mixers or in-line turbine systems.
The emulsified fuel according to the present
invention can be employed in various applications. It can
be employed in particular as engine fuel for heat engines
or as fuel for fuel cells. Its use as engine fuel for
diesel engines is particularly advantageous.
The fuel according to the invention can also be used
as fuel for thermal machines, such as, for example,
industrial or domestic boilers, furnaces, turbines or
generators. A particularly advantageous use is that as
FFOs (or Furnace Fuel Oils) , that is to say as fuel for
domestic boilers.
Finally, the invention relates to a method for
reducing the emissions from heat engines or thermal
machines, comprising the use of an emulsified fuel as
described above.
The examples below are targeted at illustrating the
invention, without limiting the scope thereof.
Example 1:
Use is made, as reference hydrocarbon liquid phase
P1, of a conventional diesel fuel fraction which has the
following properties:
Content of C13 to C19 normal paraf f ins : 4 % by weight
Distillation range (standard ASTM D86)
initial point: 179°C
10 vol % point: 201°C
50 vol % point: 254°C
90 vol o point: 331°C
final point: 360°C
Sulfur content (standard ASTM D5453): 218 ppm
Nitrogen content (standard ASTM D4629): 189 ppm
Content of aromatic compounds (standard ASTM D5186):
10.5 vol
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Viscosity at 40°C (standard ASTM D445): 2.59 cSt
A second hydrocarbon phase P2 is prepared from P1 by
mixing 74.1 parts by weight of P1 with 6 parts by weight
of a fraction rich in normal paraffins of petroleum
origin composed to more than 99% by weight of C14 normal
paraffin. The content of C13 to C19 normal paraffins in
the hydrocarbon phase P2 thus obtained is 11.2% by weight.
The respective emulsified fuels A1 and A2 are
prepared from P1 and P2 by emulsifying 80.1% by weight of
l0 the respective hydrocarbon phases P1 and P2 with 17.4% by
weight of water in the presence of 2.5% by weight of
emulsifying agent. The emulsifying agent employed for
this purpose is composed of a mixture of three surfactant
additives, namely an ester of fatty acid and sorbitan, an
ethoxylated fatty acid and an ethoxylated fatty alcohol.
The emulsions A1 and A2 are tested as engine fuel on
a "Detroit Diesel Corporation Series 60" diesel engine
according to the test and emission measurement procedures
described in the "California Exhaust Emission Standards
and Test Procedures for 1985 and Subsequent Model Heavy-
Duty Diesel Powered Engines and Vehicles", as
incorporated by reference in the California Code of
Regulations, Title 13, Section 1956.8(b).
During these tests, it is found that, in comparison
with the reference emulsified engine fuel A1, the
emulsified engine fuel A2 according to the invention
makes it possible to reduce emissions of nitrogen oxides
by 3%.
Example 2:
This example illustrates the synergistic effect which
is exerted over the increase in the cetane number of the
water/hydrocarbon emulsions when the emulsion comprises
both the Ca to CZZ normal paraffins considered in the
invention and a (or several) cetane number improver.
Four emulsified water/hydrocarbons engine fuels (A3
to A7) are prepared from the same reference diesel fuel
G. All these emulsions exhibit a water/hydrocarbons ratio
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by weight of 10/90 and comprise 2% by weight of an
emulsifying agent composed of a mixture of three
surfactant additives, namely an ester of fatty acid and
of sorbitan, an ethoxylated fatty acid and an ethoxylated
5 fatty alcohol.
In the emulsions A3 and A4, the hydrocarbon phase is
composed to 100% of the diesel fuel G. In the emulsions
A5 and A6, the hydrocarbon phase is composed of a mixture
of 90% by weight of diesel fuel G and of 10% by weight of
10 a fraction C rich in normal paraffins. The fraction C is
composed of hydrotreated animal fats and comprises more
than 95% by weight of Ce to C22 normal paraffins with a
predominance of C15 to C18 (inclusive) normal paraffins.
0.2% by weight (with respect to the total weight of
15 the emulsion) of a conventional cetane number improver,
composed of 2-ethylhexyl nitrate, is added to the
emulsions A4 and A6.
The cetane number of each of the emulsified engine
fuels A3 to A6 was measured in accordance with the method
described in the standard ASTM D613. The compositions of
the emulsified engine fuels are summarized in table I
below, which also gives the cetane numbers obtained for
each.
Table I
Content of Cetane
Hydrocarbon
cetane number number Cetane
phase
Emulsion improver in measured increase/
composition
the emulsion (standard A3
(% by weight)
(% by weight) ASTM D613)
A3 100% G 0% 43.2 -
A4 100% G 0.2% 48.7 5.5
A5 90% G + 10% 0% 46.4 3.2
C
A6 90% G + 10% 0.2% 53 9.8
C
The above results show that, while the incorporation
in the emulsified engine fuel of a cetane number improver
or of a fraction C rich in C8 to C22 normal paraffins
makes it possible to increase the cetane number of the
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engine fuel (cf. the emulsions A4 and A5, which
respectively comprise the cetane number improver and the
fraction C and which have cetane numbers greater by 5.5
and 3.2 points respectively with respect to the emulsion
A3 which comprises neither one nor the other), the joint
incorporation of these two components in the emulsified
engine fuel makes it possible to obtain a cetane number
increase which is greater than the sum of the individual
increases (cf. the emulsion A6, which comprises both the
cetane number improver and the fraction C and for which
the cetane number increase is 9.8, i.e. 1.1 points more
than the sum of the increases obtained for A4 and A5,
i.e. 8.7) .
In other words, the presence in the hydrocarbon phase
of a high content of C8 to Cz2 normal paraffins makes it
possible to significantly increase the effect of the
cetane number improver. Specifically, in the conventional
emulsion A3, the addition of 0.2% by weight of cetane
number improver makes it possible to increase the cetane
number by 5.5 points, whereas, in the emulsion A5
according to the invention, the addition of 0.2o by
weight of cetane number improver makes it possible to
increase the cetane number by 6.6 points. The invention
thus makes it possible, at a constant content of cetane
number improver, to enhance the performance of the
emulsified engine fuel or, at a constant performance, to
reduce the contents of cetane number improver.
Thus, the presence in the emulsions according to the
invention of high contents of C8 to C22 normal paraffins
in conjunction with the use of a conventional cetane
number improver provides a true synergistic effect with
regard to the cetane number of the emulsified engine fuel.
Example 3:
This example illustrates the improvement in the
stability of the emulsified fuels according to the
invention.
The stability of the emulsified engine fuels A3 and
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A5 of example 2 was determined at ambient temperature in
accordance with the centrifuging stability test described
in the standard NF M07 101. The graph presented in figure
1 below illustrates the results obtained in terms of
sedimentation of the engine fuel (i.e. phase separation
of the emulsion) during the centrifuging time. The
greater the degree of sedimentation, the more unstable
the emulsion.
The results presented in figure 1 clearly illustrate
the beneficial effect, in terms of stability of the
emulsion, of the presence in the hydrocarbon phase of a
significant content of C8 to Cz2 normal paraffins: the
emulsion A5, in the hydrocarbon phase of which a fraction
C rich in C$ to C2z normal paraffins has been incorporated
in accordance with the invention, exhibits a markedly
better stability than that of the emulsion A3, the
hydrocarbon phase of which is composed solely of a
conventional diesel fuel.
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