Note: Descriptions are shown in the official language in which they were submitted.
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Aqueous Fuel Mixture
Internal combustion engines powered by combustible hydrocarbons
cause system-related emissions in the form of nitrogen oxides, carbon
monoxide and dioxide and particulates. Accordingly, the requirements
which the emission levels of internal combustion engines are expected to
satisfy have continuously increased in stringency in recent years. This
applies not only to engines for motor vehicles of all kinds, but also to
stationary units, for example the diesel engines used as generators or
block power stations. In the Federal Republic of Germany, emission levels
are regulated by the "Technische Annleitung Luft (TA Luft)" which
stipulates NOX limits of at most 2,000 mglm3 and limits for particulates of at
most 130 mg/m3 for stationary diesel units. These limits are to be lowered
even further in the future, NOX limits of 1,000 mg/m3 and limits for
particulates of 50 mg/m3 being planned.
Accordingly, there is a considerable demand for emission-reducing
measures in the affected industry. It has been known for some time that
the addition of water to the fuel during its combustion considerably reduces
NOX, particulates and CO levels. However, water dissolves only sparingly
in hydrocarbons. For example, only about 5% by weight of water dissolves
in diesel oil, phase separation occurring with larger amounts. Accordingly,
if relatively high percentages of water are to be formulated with
hydrocarbons, suitable emulsifier systems have to be used. DE-A 28 54
540 describes water-containing fuels comprising an emulsifier combination
of alcohols and addition of products of ethylene oxide or propylene oxide
onto C9_2~ carboxylic acid amides. The emulsifiers are present in quantities
of 0.5 to 26% by weight. C~_8 alcohols are disclosed as the alcohols. DE
37 09 195 A1 describes storable water-containing fuel compositions which,
besides hydrocarbons, contain a combination of 1.0 to 3.5% by weight of
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an emuslifier and 0.5 to 10% by weight of C~_$ alcohols. WO 85!04183
proposes water-based fuels containing 0.5 to 3.0% by weight of
ethyoxylated C~2_~a fatty alcohols as emulsifiers, the document in question
failing to disclose the exact degree of ethoxylation.
However, the proposed water-containing fuels on the one hand are
unable to satisfy the increased requirements the emission levels are
expected to meet; on the other hand, the presence of emulsifiers can lead
to engine problems, for example to the formation of deposits in and around
the injectors or valves.
Accordingly, the problem addressed by the invention was to provide
water-containing fuel systems that would not have any of the
disadvantages mentioned above. It has been found that this problem can
be solved by the choice of certain emulsifier systems.
In a first embodiment, the present invention relates to a fuel mixture
for internal combustion engines containing fuels, water and emulsifiers and
optionally other additives, the emulsifier being a mixture of (A) branched
chain, saturated or unsaturated C~2_za fatty alcohols and (B) ethoxylated
Cg-24 fatty alcohols containing 1 to 10 mol ethylene oxide per mol fatty
alcohol. It has surprisingly been found that this combination of emulsifiers
enables fuels and water to be emulsified effectively and very quickly. The
quantities of emulsifier used can be well below the known quantities. The
fuel mixtures according to the invention preferably contain 60 to 95% by
weight of the fuel, 5 to 35% by weight of water, 0.01 to 5% by weight of
emulsifiers (A) and (B) and 0 to 2.5% by weight of other additives.
Particularly preferred fuel mixtures contain 65 to 90% by weight of a fuel,
25 to 35% by weight of water, 0.01 to 0.5% by weight of emulsifiers (A) and
(B) and 0.01 to 0.5% by weight of other additives.
Fuels in the context of the present invention are understood to be
any energy-providing fuels of which the free combustion energy is
converted into mechanical work. These include all kinds of motor and
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aircraft fuels which are liquid at room temperature and normal pressure.
Motor fuels, for example for automobile or truck engines, generally contain
hydrocarbons, for example gasoline or higher-boiling petroleum fractions.
Diesel fuels are obtained from gas oil by cracking or from tars obtained in
the low-temperature carbonization of lignitic or hard coal. Typical products
have a density of 0.83 to 0.88 g/cm3, a boiling point of 170 to 360°C
and
flash points of 70 to 100°C. In the context of the teaching of the
present
invention, diesel and heating oils are preferred fuels. In the water-fuel
mixtures according to the invention, the water content - based on the
mixture - is at least 5% by weight and at most 35% by weight. Aqueous
mixtures containing about 70% by weight fuel and about 30% by weight
water are particularly preferred. The emulsifier system described below is
then added to these mixtures in the quantities indicated.
Emulsifier components (A) and (B) are known classes of
compounds. Fatty alcohols of component (A) are understood to be fatty
alcohols corresponding to formula (I):
R'OH (I)
in which R' is a branched hydrocarbon radical containing 12 to 24 carbon
atoms and 0 andlor 1, 2 or 3 double bonds. Typical examples are
isotridecyl, isohexadecyl, isostearyl or 2-hexyl-1-decane alcohol and 2-octyl
decanol and technical mixtures thereof. Branched fatty alcohols of the type
under discussion here may be obtained, for example, by standard methods,
for example by oxo or Guerbet synthesis. The products of the Guerbet
syntheses, which lead to alcohols all branched in the a-position, are
preferred alcohols for the purposes of the present invention. Particularly
preferred fuels contain branched, saturated C,a-24 fatty alcohols as
component (A).
The compounds of component (B) are also known compounds
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obtained by reaction of C~2_18 fatty alcohols with ethylene oxide under
pressure in the presence of acidic or alkaline catalysts. Particulars of the
process can be found in "Surfactants in Consumer Products", Editor J.
Falbe, Springer-Verlag, 1987, pages 87 to 93 and the literature cited
therein. Suitable fatty alcohol ethoxylates contain 1 to 10 mol ethylene
oxide units per mol fatty alcohol. C~2_~a fatty alcohols containing 1 to 4 mol
ethylene oxide per mol fatty alcohol are preferably used as starting
products for the ethoxylation. Examples of suitable fatty alcohols are lauryl,
myristyl, palmityl or stearyl alcohol. Suitable unsaturated fatty alcohols
are,
for example, oleyl alcohol and 10-undecen-1-ol. The fatty alcohol
ethoxylates may also be present in the fuels according to the invention as
mixtures of the various ethoxylates.
In another preferred embodiment, component (A) and component
(B) are used in quantity ratios of 1:1 to 1:4. The total quantity of
emulsifier
components (A) and (B) used is preferably from 0.01 to 5% by weight,
more preferably between 0.01 and 2% by weight and most preferably
between 0.01 and 1 % by weight, based on the quantity of fuel and water.
Besides the above-described emulsifiers (A) and (B), other nonionic
emulsifiers known to the expert may be used in small quantities (i.e. about
5 to 10% by weight, based on the quantity of (A) and (B)). In general,
however, there is no need for additional emulsifiers, i.e. fuels containing
emulsifiers (A) and (B) only will be used.
Besides the emulsifiers (A) and (B), the fuels may contain other
additives, preferably corrosion inhibitors, for example quaternized
ammonium compounds or carboxylic acid amides and derivatives thereof.
Particularly preferred corrosion inhibitors are ethoxylated carboxylic acid
amides. Such amides correspond to general formula (II):
R2-CO-NX R3 ( I I )
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in which R2 is a saturated or unsaturated, linear or branched, optionally
cyclic alkyl group containing 1 to 24 carbon atoms, X is a hydrogen atom or
a methyl group or a group -(C2H2-O)"-H and R3 is a group -(C2H2-O)~-H or
a group N-Y-(C2H2-O)m-H, where Y is a difunctional alkylene group
5 containing 1 to 4 carbon atoms and n and m independently of one another
have a value of 1 to 10. The compounds of formula (I) may be obtained by
amidation of fatty acids or fatty acid mixtures and subsequent ethoxylation.
Suitable fatty acids are octanoic, decanoic, lauric, myristic, palmitic,
stearic,
behenic, arachic, oleic, erucic, ricinoleic acid or mixtures thereof as found,
for example, in coconut oil, palm oil, sunflower oil, safflower oil, soybean
oil, castor oil, whale oil, fish oil or tallow. Preferred amides contain 12 to
24
carbon atoms and have been reacted with 0.5 to 5 mol ethylene oxide and
preferably with 1 to 3 mol ethylene oxide per mol carboxylic acid amide. It
is particularly preferred to use a tall oil fatty acid monoethanolamide
containing 1.5 mol ethylene oxide per mol amide. In the production of
these compounds, secondary products are formed in addition to the
desired reaction products or educts, more particularly ethanolamine,
triethanolamine or tall oil fatty acid, remain in the product. Technical
mixtures such as these are also part of the disclosure of the present
invention.
The emulsifier system according to the invention is added to the
fuels in quantities of 0.01 to at most 5% by weight. A water-free additive
concentrate containing components (A) and (B) and optionally other
additives may advantageously be used for this purpose. Accordingly, the
present invention also relates to water-free additive concentrates for water-
containing fuels for internal combustion engines containing branched-
chain, saturated or unsaturated 02_24 fatty alcohols, ethoxylated C$_24 fatty
alcohols containing 1 to 10 mol ethylene oxide per mol fatty alcohol and
ethoxylated carboxylic acid amides. The concentrates according to the
invention contain emulsifier component (A) in quanities of 10 to 30% by
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weight, emulsifier component (B) in quantities of 30 to 60% by weight and
the ethoxylated carboxylic acid amides in quantities of 15 to 30% by weight.
The present invention also relates to a process for the production of
water-containing fuels in which an additive concentrate as described above
is added to the water-containing fuel, i.e. to the waterlfuel mixture, in
quantities of 0.01 to 5% by weight, preferably in quantities of 0.01 to 2% by
weight and more particularly in quantities of 0.01 to 1 % by weight.
Examples
An additive concentrate containing 20% by weight of 2-hexyl-1-
decanol, 54% by weight of oleyl/cetyl alcohol x 2 EO and 26% by weight of
tall oil fatty acid monoethanolamide x 1.5 EO was prepared and was then
added to a mixture of 70% by weight diesel oil and 30% by weight water.
The additive concentrate was used in a quantity of 0.1 % by weight, based
on the quantity of water and diesel oil. After brief stirring, a stable
emulsion
was formed and could be burned without difficulty in a diesel unit.
The fuel/water mixtures according to the invention are suitable as
fuels for combustion engines of all kinds, but preferably for diesel engines,
more particularly stationary diesel engines as used for block power
startions. By using the fuels according to the invention, it is possible to
reduce the emission of particulates and NOX to below the present and
future limits stipulated in "TA Luft" without any adverse effect on the
combustion process or the engine. In addition, the fuel mixtures according
to the invention are stable in storage, particularly at low temperatures, and
may be obtained simply by mechanical mixing of the emulsifier system with
the aqueous fuel.
