WO2013098630A1

WO2013098630A1 - Emulsion of diesel oil and water

Info

Publication number: WO2013098630A1
Application number: PCT/IB2012/002778
Authority: WO
Inventors: Enrico Carlo FUMAGALLI
Original assignee: E.Fuel S.A.
Priority date: 2011-12-29
Filing date: 2012-12-21
Publication date: 2013-07-04
Also published as: EP2798049A1; AR089530A1; ITRM20110694A1

Abstract

Emulsion of water in diesel oil which is stable and uniform over an indefinite time period, comprising a mixture of surfactant substances constituted of fatty acids and alkyl polyglycol ethers.

Description

EMULSION OF DIESEL OIL AND WATER

OBJECT OF THE INVENTION

Object of the present invention, is to obtain emulsions stabilized with additives, of diesel oil and water, in order to reduce costs, emissions and consumptions of any internal-combustion engine that normally uses, as fuel, diesel oil or a derivative thereof. In addition, the present patent Application proposes the object of significantly reducing the emission of pollutant agents based on nitrogenous components, normally designated NOx, which are produced as a consequence of the high temperatures reached in the combustion chamber during the so called combustion peaks.

The attainment of the results that will be minutely described in the following, occurs thanks to the combustion of an innovative stable emulsion, provided with a continuous or dispersant phase constituted of diesel oil, and with a dispersed phase constituted of water. Said emulsion has specific concentrations of its components that allow the stabilization of the emulsion itself thanks to the presence of a plurality of surfactants added in advance to the dispersant phase, i.e., to the diesel oil itself. Said surfactants, thanks to their amphiphilic properties, when are present at specific concentrations, can aggregate resulting in the formation of chemically stable micelles.

Once the emulsion has been created, said micelles being dispersed in the continuous or dispersant phase constituted of diesel oil, enclose in their inside the water representing the dispersed phase, leading to the afore said chemically stable emulsion.

State of the Art

Diesel oil is a derivative of oil and is chemically constituted of a mixture of hydrocarbons like paraffins, aliphatic hydrocarbons and cyclic hydrocarbons and has a boiling temperature in the range from 453K to 633K (from 180°C to 360°C). The use of diesel oil as fuel for internal-combustion engines is known since many years.

The basic function principle of an engine using diesel oil as fuel, consists in the fact that when a gas is compressed, its temperature increases. Such a property is used in internal-combustion engines, by compressing the atmospheric air within the cylinder up to the achievement of high values, i.e., up to the achievement of the temperature at which the diesel oil, injected in the proximity of the top dead center, spontaneously ignites sparking the detonation of the air- fuel mixture. Such type of internal combustion engines, is therefore defined as compression- ignition engine, in contrast with the spark-ignition engine, as the gasoline engines, where the ignition is sparked by an electric discharge sparked by the plug.

In a traditional internal-combustion engine making use of diesel oil as fuel, the gaseous combustive agent that is compressed, up to the achievement of temperatures within 700 °C to 900°C, is the atmospheric air.

In this kind of diesel oil engines the refueling system is of fundamental importance and in particular the fuel pump which adjusts the amount of fuel introduced in each cylinder.

On the basis of the fuel amount introduced at any rotation speed, the engine provides higher or lower power because its air intake is a constant value, i.e., the produced power is not directly bind to the amount of air-fuel mixture introduced into the cylinder, but only to the quantity of injected fuel. For such a reason, over the years, different kinds of diesel oil engines have been developed in order to introduce an increase of the power of the engine itself and the consequent enhancement of its performance. In the internal- combustion engines of next generation, the fuel intake is regulated by making use of devices that allow to calibrate the stoichiometric quantity of fuel to be injected and especially the time frame for doing that, intended as the exact intake time. Thanks to this technique, the engine efficiency is maximized and the noxious emissions are reduced. However, the injection timing takes on a critical aspect. Either a delay or an advance of the fuel injection with respect to the optimal timing, can involve combustion problems. An advance of the injection time can determine the increase, in exhaust gases, of the worried nitrogen oxides (NOX), whereas a delay causes the production of particulate excess in the form of particulate matter emissions. All this worsening the overall efficiency of the engine and incrementing consumptions. It is therefore clear that there is the need of avoiding the occurrence of ecological problems, due to the emission of poison gas in the atmosphere and, at the same time, of enhancing engine performance relative to consumptions, performance and time durability. For this purpose one of the recently used tricks consists of the simple addition of water into the diesel oil itself. The final aim is to obtain diesel oil emulsified with water which is commercially known as "white diesel oil" for its peculiar color. Said emulsion is mainly used in the field of public transport. Technically it is an emulsion of water in diesel oil, i.e., an emulsion in which water, in the form of small particles or droplets, is uniformly distributed within the diesel oil itself to which imparts the peculiar milky color (white). The system stabilization is obtained by mechanical stirrers or else, with the use of specific surfactant substances, which allow the emulsion to stay homogeneous over a period of time sufficiently long to be used without the separation occurrence between the two immiscible phases.

The interest recently expressed on emulsion use as a possible fuel alternative to only diesel oil in some user fields, comes from the water capacity, once added to the combustion chamber, of reducing some poison emissions such as nitrogen oxides and particulate matter. Moreover, the water addition allows the reduction of the combustion thermal peaks, thus significantly reducing, if not avoiding, the creation of combustion unwanted by-products as the worried nitrogen oxides ΝΟχ.

It has been mentioned that the expedient providing the water dispersion in diesel oil, using common surfactant agents, with the aim of reducing poison emissions and enhancing engine performance, it is already known from time. However, first methodologies used to introduce water in the diesel oil provides for the need of making some modifications to the combustion apparatus and, in addition, they did not guarantee an optimal dispersion of water in diesel oil, which is a fundamental requirement in order to obtain a significant reduction of the emitted pollutants, without compromising the calorific yield of the combustion process.

For such a reason, over years several researches focused on the definition of emulsion formulations, of liquid hydrocarbons and water, by using surfactant agents with the intent of obtaining a uniform dispersion of water in the diesel oil, thanks to the formation of micellar structures.

For example, Patent EP-A-475 620 describes microemulsions, of a Diesel fuel oil with water, which contain a cetane and an emulsifying system comprising a hydrophilic surfactant and a lipophilic surfactant. These surfactants are selected from Ci₂-Cis ethoxylated alkylammonium salts and from Cg-C₂₄ carboxylic or sulfonic acids salts: the hydrophilic surfactant contains at least six ethylene oxide units whereas the lipophilic one contains less than six ethylene oxide units. Patent EP-A-630 398 describes instead a diesel oil in the form of an emulsion made of hydrocarbon diesel oil, from 3 to 35 wt% of water and of at least 0.1 wt% of an emulsifying system comprising a sorbitan oleate, a polyalkylene glycol and an ethoxylated alkylphenol. Patent Application WO 97/34969 describes an emulsion between water and a group of hydrocarbons, for example a Diesel fuel oil. This emulsion is stabilized by the addition of a peculiar emulsifier made essentially of sorbitan sesquioleate, polyethylene glycol monooleate and an ethoxylated nonylphenol. This emulsifier has an overall HLB value (hydrophilic-lipophilic balance) between 6 and 8.

Patent EP-A-812 615 describes a process for the production of a stabilized emulsion of diesel oil and water. This process provides the preparation of a first emulsion obtained by mixing diesel oil, water and the surfactant, and then the mixing of the so obtained emulsion with more water to produce the final emulsion. The emulsion is stabilized using a hydrophilic or lipophilic surfactant or a mixture thereof. Lipophilic surfactants that can be used are esters of sorbitol fatty acids, e.g. sorbitan monooleate, whereas the hydrophilic surfactants which are suitable for the purpose are esters of fatty acids of sorbitol containing a polyoxyalkylene chain, e.g., a sorbitan trioleate polyoxyethylene. In addition, the stabilization can be obtained by adding ethylene glycol or polyethylene glycol. Patent Application WO 92/19701 discloses a process for the reduction of NOx from gas turbines, by using a Diesel fuel oil and water emulsion. The emulsion is stabilized by adding an emulsifier selected from: alkanolamides obtained by condensing an alkylamine or a hydroxy-alkylamine with a fatty acid; and from ethoxylated alkylphenols. The emulsifier has preferably a HLB value lower or equal to 8. Physical stabilizers like waxes, by-products of cellulose or resins, can be added to improve the stability. As described in the Patent Application WO 93/07238, the above mentioned emulsion can be further stabilized by adding a bi-functional block polymer with a primary hydroxyl end-group, particularly a co-polymer containing propylene oxide/ ethylene oxide blocks.

For all the diesel oil and water emulsions, a high stability of the emulsified diesel oil, over time and in a wide temperature range (e.g., at least three months under normal storage conditions and between -20°C and +50°C) is required, in order to avoid, during the residence of the emulsion in the tank, the formation of a substantial aqueous phase tending to deposit at the bottom of the tank. The separation of the two immiscible phases, diesel oil and water, is in fact a problem present in several of the above mentioned emulsions.

The bulky presence of the said aqueous phase in the combustion chamber, could involve a considerable worsening of the performance level of the engine and even its permanent damage.

Moreover, it has been recently discovered that the addition of emulsifiers to improve the emulsion stability can involve, during the combustion, the formation of carbonaceous deposits adhering to the inner surface of the combustion chamber and of the injection apparatus. This phenomenon can negatively affect the engine operation and involves a necessary and continuous maintenance to remove these unwanted carbonaceous deposits. Next generation emulsions of diesel oil and water have been recently formulated using a surfactant polymer as emulsifying agent, as disclosed in the Patent Application EP 1 721 956 A2. The obtained emulsified diesel oil has a high stability over time and in a wide range of temperatures without the formation of carbonaceous deposits adhering to metallic surfaces. The used emulsifier is a polymeric surfactant that can be obtained by reacting an oligomer of a functionalized olefin with at least a group deriving from a di-carboxylic acid or a by-product thereof and a polyoxyalkylene comprising oxyalkylene linear units, the polyoxyalkylene units being bonded to a long chain alkyl group containing, optionally, one or more ethylene unsaturations. The oligomer of said polyolefin has a molecular weight varying from 300 to 10000 and preferably from 500 to 5000. Despite the several advantages offered by these last formulations of emulsified diesel oil, their limit is due to water amount, in terms of weight percentage that can be included inside the diesel oil, and especially to the chemico-physical stability of the emulsion over time, which is usually of medium-short time.

Emulsions described in the present invention differ from those formulated until now for their peculiar dispersion uniformity of the phases, which is stable over an indefinite time period and therefore they do not need any stirring.

DESCRIPTION OF THE INVENTION

The present invention refers to an innovative emulsion of diesel oil and water, which is made chemically stable thanks to the addition of a mixture of surfactants of different nature. Said surfactants are combined in such percentages to form a mixture of surfactants whose fundamental action is to indefinitely stabilize said emulsion of diesel oil and water. The diesel oil represents the dispersant or continuous phase, while water represents the dispersed phase. Said emulsion stabilized by surfactants can be used, independently from when it is implemented, as fuel alternative to diesel oil in any internal-combustion engine, offering advantages in terms of performances, consumptions and also on a level of poison emissions reduction.

The present invention refers to a surfactants mixture made of fatty acids and alkyl polyglycol ethers, and in particular:

1 ) from 10 wt% to 80 wt% of an ester, produced by Fisher reaction, i.e., following an acetylation reaction of an alcohol or a phenol with a carboxylic acid or a derivative thereof. And having the general formula of the type:

R C=0

0-R₂

wherein Ri is a radical of an unsaturated fatty acid (linoleic acid, oleic acid, tall oil, olive fatty acids);

R₂ is a polyalcohol (ethylene glycol at 7%, diethylene glycol, propylene glycol, trimethylol propane, glycerin) which serves as anti-freeze.

2) From 10 to 80 wt.% of a condensation product between an unsaturated fatty acid and an alkanolamine of general formula:

R C=0 R C=0

I I

0-R₃ NH-R₃

where Ri is a radical of an unsaturated fatty acid (linoleic acid, oleic acid, tall oil, olive fatty acids);

R₃ is an alkanolamine (monoethanolamine, diethanolamine, triethanolamine, aminoethylethanolamine).

3) From 10 wt% to 80 wt% of a condensation product between an unsaturated fatty acid and ethylene oxide, of formula:

R C=0 O + CH2-CH2-O + nCH₂-CH₂-OH

Where Ri is a radical of an unsaturated fatty acid (linoleic acid, oleic acid, tall oil, olive fatty acids) and n is an integral number from 3 to 20. 4) From 10 wt% to 80 wt% of alkoxylated sorbitan esters (Sorbitan Monooleate, SMO).

5) From 10 wt.% to 80 wt.% of an ethoxylated alcohol with a C12-C14 chain. In the following some of the chemico-physical properties of the afore said mixture of surfactants according to the present invention are listed:

- Appearance : yellowish/ amber-colored liquid

- Odor : soft peculiar

- pH sol 5% : 5-6.5

- Boiling point : > 100 °C

- Flash point : < 125 °C

The properties of the present mixture of surfactants and surfactants generally called surfactants, is mainly the reduction of the surface tension of the liquid they are in contact with, facilitating the surfaces wettability and the miscibility of different liquids that are normally not miscible between each other. Generally, the surfactants are substances constituted of a polar group or moiety and of a non-polar group or moiety, i.e., they are substances chemically defined as amphiphilic.

Usually a surfactant molecule is provided with a polar hydrophilic "head", to which a non-polar hydrophobic "tails" is bonded.

Surfactants, based on their nature, are divided in several classes.

1) anionic surfactants, such as salts constituted by long chains of carbon atoms ending with a carboxylate or sulfonate group, e.g., sodium lauryl sulphate (SLS) and lauryl ethoxy sulphate (LES) and several alkyl-benzene-sulfonic acids (ABS),

2) cationic surfactants, such as salts constituted by long chains of carbon atoms ending with a cationic group such as quaternary ammonium, e.g., the benzalkonium chloride (BAC),

3) non-ionic surfactants, such as long chains alcohols as the polyoxyethilene derivative of fatty acids or the alkyl-polyglucosides (APG),

4) amphoteric surfactants which are zwitterions and behave, depending on the solution acidity or basicity, as acids or bases.

Several surfactants, above a certain concentration value known as the critical micelle concentration (CMC), organizes themselves in supramolecular aggregates named micelles.

According to one of the most used models to describe the structures of the micelles and their sizes, i.e., the Hartley's model, the micellar aggregates have variable sizes, and in particular, in case of spherical micelles, the micelle radius corresponds about to the length of the extended hydrocarburic chain of the surfactant. The head groups and the associated counter-ions (e.g. in case of ionic micelles) form the so called Stern layer. The counter-ions which are in this layer, sufficient to neutralize even more of the 50% of the surface charge, are strongly bonded and can take part to the micellar kinetic. An increase of the concentration and hydrophobicity of the counter-ion leads to an increase of the charge fraction which, at the micellar surface, is neutralized by the inclusion of the counter-ions in the Stern layer. The remaining counter-ions are localized beyond the Stern layer and form another electrical layer known as the Gouy- Chapmann, and are free from the micelle and able to be exchanged with other ions present in the solution. Usually these dispersed colloidal systems of supramolecular aggregates have sizes varying from 1 nm to 0.5 pm.

Micelles are aggregates of molecules in colloidal phase having, being formed by surfactants, amphiphilic properties, i.e., they contain both hydrophobic and hydrophilic functional groups. The micellar aggregates form when, at temperature conditions equal or above the Krafft temperature (the temperature above which the surfactant solubility clearly increases), the surfactant concentration reaches a certain critical level named critical micelle concentration (CMC). Micelle structures can have different forms: spherical, cylindrical, lamellar and discoidal. In polar solvents, generally, the hydrophobic and lipophilic part is oriented inwards the sphere, while the hydrophilic part is oriented outwards. In non-polar solvents, the orientation is opposite and it is defined as inverse micelle. The inverse micelle is an extremely useful aggregate to allow chemical reactions in unconventional media to occur because, in place of the hydrophobic micellar core, in this way a micro droplet of water is present, having variable sizes, and confined within the inverse micelle itself.

When a surfactant is added in a medium, e.g. of aqueous type, the micelles do not form immediately, provided that it is not present in such a quantity to exceed the critical micelle concentration (CMC). Before the system reaches the CMC, the surfactant arranges at the water-air interface with the hydrophobic chains towards the air and the polar heads towards the phase they have more affinity therewith, i.e., the aqueous phase. When the surfactant concentration exceeds the CMC, the emulsifying effect takes place.

The mixture with surfactant properties described in the present invention gives rise, when it reaches the critical micelle concentration, to the classic inverse micelle made of non-polar and lipophilic phase oriented outwards, i.e., towards the non-polar continuous phase made of diesei oil and the polar phase oriented inwards the micelle containing the water which represents the dispersed polar phase.

In the preferred embodiment of the invention, the above said mixture is stoichiometrically made of:

1 ) 20 wt% of an ester produced by Fisher reaction, i.e., following an acetylation reaction of an alcohol or a phenol with a carboxylic acid or a derivative thereof. And having the general formula of the type:

R C=0

I

0-R₂

wherein Ri is a radical of an unsaturated fatty acid (linoleic acid, oleic acid, tall oil, olive fatty acids).

2) 18 wt.% of a condensation product between an unsaturated fatty acid and an alkanolamine of general formula:

Ri-C=O R_!-C=0

I I

0-R₃ NH-R₃

where ^ is a radical of an unsaturated fatty acid (linoleic acid, oleic acid, tall oil, olive fatty acids);

R₃ is an alkanolamine (monoethanolamine, diethanolamine, triethanolamine, aminoethylethanolamine);

3) 15 wt.% of a condensation product between an unsaturated fatty acid and an ethylene oxide of formula:

R C=O O + CH2-CH2-O + nCH₂-CH₂-OH

where Ri is a radical of an unsaturated fatty acid (linoleic acid, oleic acid, tall oil, olive fatty acids) and n is an integral number from 3 to 20.

4) 29 wt% of alkoxylated sorbitan esters (Sorbitan Monooleate, SMO).

5) 1 1 wt.% of an ethoxylated alcohol with a C12-C14 chain.

Water addition to the simple diesel oil is an expedient already known from time and offers several advantages among which the reduction of fuel consumptions. The stability of the emulsions that are obtained by adding water to diesel oil, is guaranteed by the presence of additives that "hook" the small water droplets and maintain them uniformly dispersed in the fuel.

However, the commercially known emulsions of diesel oil and water and nowadays available on the market, are characterized by containing water in a quantity usually not higher than 10%.

The water quantity within the diesel oil is a very important factor, because water improves the fuel miscibility with air such that the combustion results to be more complete and homogeneous thus reducing the particulate and NOx formation at the same time. As a matter of fact, water addition in diesel oil allows to reduce the peak temperature reached in the combustion chamber, drastically reducing the production and then the emission of NOx in exhaust gases.

The innovative aspect of the present invention is relative to the fact that emulsions of diesel oil and water, that are obtained through the addition of the mixture of surfactants the invention refers to, can include a higher water quantity while staying stable over time. The included water percentages vary in the following ranges:

from 8% to 15% for automotive

from 12% to 20% for heating in general up to 40% for ship refueling.

Moreover, the surfactant addition aids the combustion of the two phases. An additional advantage offered by the present invention is represented by the fact that the combustion of the diesel oil added with water is a dry combustion, i.e., within the combustion chamber there is not the presence of oils due to lubricant use, because the used surfactant acts as lubricant itself. The emulsion of diesel oil and water obtained by adding the above mentioned surfactants to diesel oil, moreover proved to be very stable over time. With emulsion stables over time, it is intended that the water colloidal particles present in the diesel oil, are and remain uniformly dispersed in the dispersant, for a period of time substantially longer with respect to the already known emulsions, even without any stirring.

Thanks to this characteristic, the emulsions described in the present invention avoid even the serious phenomenon of water condense formation in the tank and offer advantages in term of particulate reduction, absence of additional nitrogen-based compounds and absence of toxic by-products.

A very important factor affecting the dispersion uniformity of phases and general stability of the emulsion described in the present invention, is the electrical charge resulting on the surface of the dispersed droplets within the continuous phase. The charge present on the colloid surface, i.e., at the interface between the two immiscible compounds, actually avoids coalescence phenomena between the colloidal microparticles that, precisely due to the electrical charge repulsion, do not coalesce and remain uniformly dispersed within the continuous phase. In the preparation of any emulsion, the energy necessary to reach the emulsified state, is considerable and is higher when the surface tension of the two phases results to be very high. This determines an accumulation of internal energy of the system such to cause the thermodynamic instability of the resulting emulsion. For such a reason, in order to reduce the energy content of the water in diesel oil emulsions, it is important not only to add surfactant substances having the purpose of inducing a surface tension reduction, but to ensure the formation of the highest possible number of colloidal particles, thus, in this way, contributing to the increase of the system entropy and the resulting internal energy reduction. These are factors deducible from the known Gibbs' equation, relative to the standard free energy connected to any system: AG = ΔΗ - TAS. The presence of an electrical charge on the colloids surface avoids the particles coalescence thanks to the presence of Coulombian repulsions and ensures the latter will remain uniformly dispersed in the continuous phase.

Here in the following a table reporting some of the most relevant characteristics of a typical emulsion of diesel oil and water is shown, obtained by adding the mixture of surfactants described in the present invention.

Property Unit Result Test method

Density at 15°C Kg/m³ 859.2 EN ISO 12185

Flash Point (Grabner) °C 78 Grabner2

Pour point °C -33 ISO 3016

Water (KF) % m/m 14.1 DIN 51777/1

Copper corrosion (50°C) 0 ASTM D 130 mod

Ash mg/kg 6 ISO 6245

Sulphur mg/kg 8.5 EN ISO 20846

Nitrogen mg/kg 32 ASTM D 4629

Polyaromatic % (m/m) 1 .9 EN 12916

Polychlorinated Biphenyl (PCB) mg/kg < 1 DIN 51527-1 1

Trace elements SOP 6132

Ag Silver mg/kg <0,1

Al Aluminum mg/kg 0.1

B Boron mg/kg 0.1

Ba Barium mg/kg <0,1

Ca Calcium mg/kg 0.2

Cd Cadmium mg/kg <0,1

Cr Chromium mg/kg <0,1

Cu Copper mg/kg <0,1

Fe Iron mg/kg 0.6

Mg Magnesium mg/kg <0,1

Mn Manganese mg/kg <0,1

Mo Molybdenum mg/kg <0,1

Ni Nichel mg/kg <0,1

P Phosphorus mg/kg <0,5

Pb Lead mg/kg <0,5

Si Silicon mg/kg 0.2

Sn Tin mg/kg <0,5 Ti Titanium mg/kg <0,1

V Vanadium mg/kg <0,1

Zn Zinc mg/kg 0.1

Na Sodium mg/kg 1.3 ICP-OES

K Potassium mg/kg <1 ICP-OES

CI Chlorine mg/kg <5 Chlorine

At the outlet of the admitting injector, when particles of emulsified fuel, as described in the present invention, are introduced into the combustion chamber, the water droplets present within said fuel particles progressively expand until causing, by means of a series of explosions, a further subdivision of the emulsified fuel particle. This process causes the formation of particles with very fine sizes. This aspect represents a considerable advantage because it is precisely the fine subdivision that facilitates the combustion reaction and the air mixing with the combustive agent. As a matter of fact, it is the fine subdivision of the fuel that significantly increases the surface contact between the finely subdivided fuel and the air intake to the motor. As a consequence, the air excess required to aid the combustion is reduced, and it is moreover more probable that the combustion reaction goes to completeness thus avoiding the formation of unburned fuel residues which then lead to a series of unwanted byproducts as the particulate. This innovative aspect of the present invention, ensures that times and spaces required for the combustion are reduced, and in particular, that the combustion time of the emulsion is reduced with respect to the untouched oil which results to be reduced of about 50% whereas powder emissions are cut down even to more than 90%.

Hereinafter combustion stoichiometric reactions are reported involving the main elements constituting the fuel and the energies developed under the form of heat which are expressed in Kj/Kg.

1 ) C + O₂ = CO₂ + 33910 Kj/Kg 2) 2H₂ + O₂ = 2H₂O + 143000 Kj/Kg

3) S + O₂ = SO₂ + 8800 Kj/kg

The atomic weights of the elements are: C = 12

0 = 1 6

S = 32

H = 1 .

Therefore in reaction 1 ) the amount of oxygen required to burn 1 Kg of carbon h is 32/12 Kg, whereas the amount of CO₂ produced by the combustion of 1 Kg of carbon h is 44/12 Kg. Being the weight ratio between air and oxygen contained therein equal to 4.31 , the air amount necessary to bum 1 Kg of carbon is equal to 4.31 ^*32/12 = 11 .493 Kg.

In an analogous way from reaction 2) it follows that the oxygen amount required to burn 1 Kg of hydrogen h is 32/4 Kg, whereas the amount of H2O produced from the combustion of 1 Kg of hydrogen h is 36/4 Kg. Therefore the amount of air required to burn 1 Kg of hydrogen is 4.31 *32/4 = 34.48 Kg.

In an analogous way from reaction 3) can be deduced that the amount of oxygen required to burn 1 Kg of sulfur h is 32/32 Kg, whereas the amount of SO2 produced from the combustion of 1 Kg of sulfur h is 64/32 Kg. The amount of air required to burn 1 Kg of sulfur is therefore 4.31 ^*32/32 = 4.31 Kg.

The theoretical oxygen will be therefore given by the sum: O theoretical = 2.67^*%C + 8^*H% + S% -Ocomb.

And the theoretical air will be: Air_{t eo} = 4,31 ^*O_theo-

On the contrary, the weight of the theoretical fumes, defined as PFT, is given by the relation: PFT = Theoretical air +1 - ashes, where the ashes represent the mineral substances remaining in the combustion chamber. Moreover, being:

V = M^*R^* T/P:

where R = gas constant (J/KgK)

M = mass in Kg

P = absolute pressure of the fuel

T = absolute temperature (K)

It will follow that the higher the efficiency of the combustion will be, the smaller the temperature of the fumes will be and the smaller the air excess will be, such conditions are easily obtainable by using the emulsions described in the present invention.

Claims

1 . Emulsion of diesel oil and water which is stable and uniform over an indefinite time period, comprising a mixture of surfactant substances constituted of fatty acids and alkyl polyglycol ethers, characterized in that said mixture includes: from 10 wt.% to 80 wt.% of an ester produced by Fisher reaction of general formula:

R.- 0

i

0-R₂

wherein Ri is a radical of an unsaturated fatty acid such as linoleic acid, oleic acid, tall oil and the fatty acids of olive oil;

R₂ is a polyalcohol;

from 10 wt.% to 80 wt.% of a condensation product between an unsaturated fatty acid and an alkanolamine of general formula:

R C = O R_rC = O

I I

wherein Ri is a radical of an unsaturated fatty acid;

R₃ is an alkanolamine such as monoethanolamine, diethanolamine, triethanolamine or an aminoethylethanolamine;

from 10 wt.% to 80 wt.% of a condensation product between an unsaturated fatty acid and an ethylene oxide of general formula:

R C = O

I

O + CH_rCH_rO + nCH_rCH_rOH

wherein Ri is a radical of an unsaturated fatty acid and n is an integer from 3 to 20; from 10 wt.% to 80 wt.% of alkoxylated sorbitan esters;

from 0 wt.% to 80 wt.% of an ethoxylated alcohol with a C₁₂-C14 chain.

2. Stabilized emulsion according to Claim 1 , characterized in that said emulsion includes:

20 wt.% of an ester produced by Fisher reaction of general formula:

R_rC=0

I

0-R₂

wherein Ri is a radical of an unsaturated fatty acid;

R₂ is a polyalcohol;

18 wt.% of a condensation product between an unsaturated fatty acid and an alkanolamine of general formula:

R,-C = O R,-C = 0

0-R₃ NH-R₃ wherein Ri is a radical of an unsaturated fatty acid;

R₃ is an alkanolamine;

15 wt.%) of a condensation product between an unsaturated fatty acid and an ethylene oxide of formula:

R,-C = O

I

O + CHrCHrO + nCH₇-CH_rOH

wherein Ri is a radical of an unsaturated fatty acid and n is an integer from 3 to 20

29 wt.%) of alkoxylated sorbitan esters

1 wt.% of an ethoxylated alcohol with a Ci₂-Ci₄ chain.

3. Emulsion according to any one of Claims 1 to 2, characterized in that said emulsion includes:

an ester produced by Fisher reaction of general formula:

I

0-R2

wherein Ri is a radical of an unsaturated fatty acid and particularly

Iinoleic acid, oleic acid, tall oil, olive fatty acids;

R₂ is a polyalcohol such as ethylene glycol, diethylene glycol, propylene glycol, trimethylolpropane, glycerine;

a condensation product between an unsaturated fatty acid and an alkanolamine of formula:

RrC = 0 R_rC = 0

I I

0-R3 NH-R3 wherein is a radical of an unsaturated fatty acid and particularly Iinoleic acid, oleic acid, tall oil, olive fatty acids;

R₃ is an alkanolamine and particularly monoethanolamine, diethanolamine, triethanolamine, aminoethylethanolamine;

a condensation product between an unsaturated fatty acid and an ethylene oxide of formula:

R_rC=0 i

O + CH₂-CH_rO + nCH_rCH_rOH wherein Ri is a radical of an unsaturated fatty acid and particularly Iinoleic acid, oleic acid, tall oil, olive fatty acids, and n is an integral number from 3 to 20;

an alkoxylated sorbitan ester and particularly sorbitan monooleate, SMO.

4. Stabilized emulsion according to any one of Claims 1 to 3, characterized in that said emulsion includes a product produced by Fisher reaction and having general formula:

R_rOO

!

0-R₂ wherein Ri is a radical of an unsaturated fatty acid such as linoleic acid, oleic acid, tall oil, olive fatty acids, and R₂ is ethylene glycol at 7 wt.%.

5. Stabilized emulsion according to Claim 4, characterized in that the ethylene glycol at 7 wt.% is the anti-freeze agent of said emulsion.

6. Stabilized emulsion according to any one of Claims 1 to 5, characterized in that it includes from 8 wt.% to 15 wt.% of water.

7. Stabilized emulsion according to any one of Claims 1 to 5, characterized in that it includes from 12 wt.% to 20 wt.% of water.

8. Stabilized emulsion according to any one of Claims 1 to 5, characterized in that it includes up to 40 wt.% of water.

9. Use of a stabilized emulsion of diesel oil and water according to any one of Claims 1 to 5 for automotive applications, preferably when said emulsion includes from 8 wt.% to 15 wt.% of water.

10. Use of a stabilized emulsion of diesel oil and water according to any one of Claims 1 to 5 for heating applications, and preferably when said emulsion includes from 12 wt.% to 20 wt.% of water.

11. Use of a stabilized emulsion of diesei oil and water according to any one of Claims 1 to 5 for ship refueling, preferably when said emulsion includes up to 40 wt.% of water.

12. Emulsion according to any one of Claims 1 to 11 , characterized in that said emulsion is stable and uniform over an indefinite time period even without stirring.