FIELD OF THE INVENTION

The present invention relates to the field of the emulsifiers, in particular to an emulsifying mixture and its use as an additive for fuel/water emulsified mixtures.

STATE OF THE ART

In the last years the scientific and technological research has studied the possibility of obtaining, within internal combustion engines, more efficient combustion processes. This necessity arises from the need to reduce the amount of fuel used and, in parallel, to break down the load of pollutants emitted from such devices.

One of the most promising option is the use of emulsified fuel/water mixtures.

Indeed, water promotes the process of fuel particles dispersion during the combustion phase. In this way, besides the use of less fossil fuel, the engine is more efficient and disperses a lower amount of particulate and of partial oxidation products (carbon black, carbon monoxide, etc.).

However, due to the hydrophobic nature of the most commonly used fuels, these are not miscible with water. For this reason, it is necessary to use compounds, called surfactants, which promote the formation of stable emulsions of hydrophilic and hydrophobic compounds.

This technology is widely investigated since years and literature, both academic and patent, lists numerous examples of mixtures that can be used as surfactants for obtaining diesel/water emulsions.

For example in the patent CN10291 1749, Zhang uses a complex mixture of sorbitan mono-oleate, polyoxyethylene alkylphenol, sodium alkylbenzene sulfonate and sodium carboxymethylcellulose, obtaining a maximum amount of emulsified water equal to 14 wt%, relative to the overall fuel.

Also the patent EP0812615 by Ishida G. et al. describes the production of a water/diesel emulsion, containing as stabilizers derivatives of sorbitan oleate and eventually ethylene glycol or polyethylene glycol. However Rivolta et al. reports, in patent EP1721956, that standard surfactants based on sorbitan oleates produces carbon black and unburned particulate, offering as an alternative the use of surfactants obtained from the reaction between the polyolefin oligomer functionalized with dicarboxylic acids and polyoxyalkylenes. Fumagalli has recently filed the patent application WO2013/098630, which describes, as a solution to the problems associated to the emulsifying of water and diesel fuel, the use of a multi-component mixture consisting of a mixture of five compounds, including 1 . Esters of unsaturated fats, 2. the condensation products between an unsaturated fatty acid and an alkanolamine, 3. the condensation product between an unsaturated fatty acid and an ethylene oxide, 4. esters of sorbitanalkoxylate, 5. an alcohol ethoxylate. However, since in that patent derivatives of sorbitan are used, they cannot be guaranteed the inhibitory action against carbon black and particulate formation. In addition, there are no information on the performance of engines that use this fuel. Actually, one of the main problems associated with the use of emulsified fuels are the corrosion phenomena of mechanical components, due to the contact between said components and the aqueous phase of the emulsion.

An alternative to the use of emulsifying products is the use of micronizers and microemulsifier, capable of producing fuel particles of micrometric dimensions that, without adding further components, emulsify "spontaneously". However, no details are available regarding the stability of such compound, neither during the storage period neither during the use. In fact, a partial separation of the emulsion during the pumping could lead the water in contact with gears and pipes, causing problems of different nature. On one hand, the combustion would be less effective, invalidating the effects of the emulsification process. On the other hand, the presence of "free" water would lead to damages of the engine components (injectors, piping, sensors, etc.). Furthermore, the realization of microemulsions using mechanical equipment requires specially designed (vaporizers, pumps, condensers, etc.), not allowing an immediate use by the end user, since the latter must first of the required instrumentation. Among the proposed solutions, one consists in the addition of anti-corrosion components, as in Patent WO99/63026. In this case, in addition to the emulsifying agents, the final mixture contains also lubricants, anticorrosion products and antifreeze products. However, in addition to the high complexity of the system, the amount of pollutant emissions is only partially reduced, not reaching, however, the values obtained with other types of emulsions.

In the patent US2003/0196430 emissions are similar to those of the patent described above (approximately 50% compared to a non-emulsified fuel). To obtain consisting particulate reduction, an additional filter is necessary, which reduces of 80% the load, compared to the emission of "unfiltered" exhaust. However, this reduction is the same also in the case of pure diesel, not highlighting, from that point of view, a particular benefit derived from the use of an emulsified fuel.

The State of the Art proposes numerous and heterogeneous solutions to such problems. However no solutions, with an easy and inexpensive manufacturing, still emerge, in order to allow the simultaneously solution to the problems listed above. The aim of the present invention is to provide an additive (composed of one or more chemical compounds) capable of emulsifying mixtures consisting of water and hydrophobic substances (fuels), in order to obtain fuels to be used in internal combustion engines, for the production of mechanical, electrical or thermal energy. The aim of the present invention is also:

- Provide fuel emulsions (i.e. water/fuel emulsions) that can be used in internal combustion devices, without substantial changes to the mechanical system.

- Get output powers from the engine, powered by these emulsions, comparable with those obtained in the case of supply exclusively with non-emulsified fuel. - Achieve significant reductions of particulate loading and greenhouse gases emitted by the exhaust.

SUMMARY OF THE INVENTION

Surprisingly, the Applicant has developed, through a simple procedure, a two- component emulsifier mixture, obtainable from renewable raw materials. The present invention solves the above-described problems using an emulsifying mixture consisting of the following two components:

(A) mono- or diglycerides of long chain fatty acids in mixture with glycolester or glycerides of long chain fatty acids; and

(B) a salt of a long chain fatty acid with an amine compound;

in which the weight ratio A:B ranges from 65:35 to 80:20.

The above emulsifier mixture is particularly useful to form water/fuel emulsions. Subject of the present invention is therefore also a fuel emulsion, wherein the amount of emulsified water can also reach up to 35 wt%, said emulsion comprising the emulsifying mixture according to the invention. These emulsions have proved to be stable for at least 3 months and have shown that they can be used in internal combustion devices, without substantial changes to the mechanical system; to obtain output powers from the engine, fuelled by these emulsions, comparable with those provided in using exclusively non-emulsified fuel and to achieve significant reductions of particulate amount and greenhouse gases emitted by the exhausts.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention long-chain fatty acid means a carboxylic acid with aliphatic chain composed of a number of carbon atoms comprised between 14 and 20; said aliphatic chain may be saturated, polyunsaturated or monounsaturated. This definition includes palmitic acid, margaric acid, stearic acid, arachidic acid, palmitoleic acid, oleic acid, elaidic acid, vaccenic acid, gadoleic acid, linoleic, linolenic acid, stearidonic acid, arachidonic acid, timnodonic acid.

Preferably (and advantageously), the component (A) is the mixture obtained at the end of a partial transesterification reaction of a vegetable oil with glycol or glycerine. Said vegetable oil is preferably selected from the group consisting of sunflower oil, rapeseed oil, mixed seeds oil, corn oil.

Said glycol is preferably selected from the group consisting of diethylene glycol, triethylene glycol, tetraethylene glycol. As alternative to the glycol, it is possible to use glycerine. Said transesterification may be performed in presence of a molar ratio of vegetable oil/glycol ranging from 1 :1 to 1 :2.5.

Said transesterification is preferably carried out using the vegetable oil itself as solvent and heating the mixture oil/glycol at 100-200 °C (preferably 120-170 °C) in the presence of an alkaline catalyst (such as K2CO3) .The mixture is heated under stirring until disappearance of the turbidity.

As particularly preferred method, component A is constituted by the mixture of transesterification reaction between corn oil and glycerol in the molar ratio 1 :2 (in order to obtain as the main product monoglycerides of the fatty acids contained in theseed oil).

Preferably (and advantageously), the component (B) is the mixture obtained of a salification reaction of a long chain fatty acid with an amine compound (i.e., ammonia or an amine).

Preferably, said salified long chain fatty acid is selected from the group consisting of oleic, linoleic, stearic, palmitic, linolenic.

Said ammonia is preferably (and advantageously) in the formulation of an aqueous solution, commonly available as 30 wt%. Said amine may be primary, secondary or tertiary; preferably, said amine is selected from the group consisting of ethanolamine, diethanolamine, triethanolamine, ethylenediamine, tetraetilendiamine, diazobicyclooctane and methylamine.

In a particularly preferred method component (B) is the ammonium salt of oleic acid. Preferably, the components (A) and (B) are mixed in weight ratios comprised between 65:35 and 75:25; more preferably 70:30.

From one point of view, the present invention relates to a process for prepraring the emulsifying mixture as above described, said process comprising:

- preparing component (A) by way of a partial transterification of a vegetable oil with a glycol or glycerine;

- preparing component (B) by means of the salification reaction of a long chain fatty acid with an amine compound.

- mixing of component (A) with component (B). In preparing component (B), it is possible to dilute with a small amount of an aqueous solvent, or alcohol or mixtures thereof, if necessary to make the mixture stirrable. If 30% aqueous ammonia is used, further dilutions are not necessary. In some cases, it is possible to prepare component (B) directly in a mixture containing the component (A).

The invention concerns also the use of said emulsifying mixture as an emulsifying additive, in particular to create emulsions fuel/water, in which the fuel may be a biofuel, a vegetable oil, a diesel fuel or gasoline.

Then, a further subject-matter of the invention is also a fuel/water emulsion comprising an emulsifier mixture according to the invention; preferably comprising an amount of emulsifier mixture equal to 0.1 -3.0 wt%, referred to the total emulsion weight.

Preferably, the fuel is selected from the group consisting of a vegetable oil (e.g. rapeseed oil), a diesel and a gasoline. If the fuel is a vegetable oil, the emulsion contains preferably an amount of emulsifying mixture equal to 0.1 -0.3 wt% referred to the total emulsion weight. If the fuel is a diesel, the emulsion contains preferably an amount of emulsifying mixture equal to 0.8-1 .2 wt%, referred to the total emulsion weight.

Preferably, the emulsion according to the invention is made by:

67-99.9 wt% of a fuel selected from the group consisting of a biofuel, a vegetable oil, a diesel fuel or gasoline;

1 -35 wt% water of hardness between 0 and 150 °F; and

0.1 -3.0 wt% of emulsifying mixture;

where the % given are % by weight referred to the total weight of the emulsion. Preferably, in the emulsions according to the invention the amount of water is comprised between 10 and 25 wt%.

The emulsion process is carried out by way of fast stirring (rpm ranging between 2000 and 6000) within a vessel where all the components of the emulsion (oil, water and emulsifier) are placed.

In order to obtain an emulsion that provides mechanical performances comparable to those of the pure fuel and does not cause damage to the engine, the water used must have a hardness comprised between 0 and 150 ° F. The amount of water emulsifiable ranges from 1 to 35 wt% relative to the total weight; preferably from 5 to 30 wt%; still more preferably from 10 to 25 wt%. The present invention will be better understood in the light of the following embodiments.

EXPERIMENTAL PART

Example 1 - Preparation of the emulsifier

Component (A)

840 g of sunflower oil were mixed with 300 g of triethylene glycol and 0.2 g of potassium carbonate. The mixture was heated under stirring at 140 °C until disappearance of the turbidity.

Component (B)

282 g of oleic acid, 149 g of triethanolamine and 100 g of ethyl alcohol were mixed at room temperature.

Emulsifier

The component A is mixed with component B in a ratio of 70:30 wt%

Example 2 - Prepration of the emulsifier

Component (A)

840 g of corn oil were mixed with 184 g of glycerine and 1 .0 g of potassium carbonate. The mixture was heated under stirring at 170 °C until disappearance of the turbidity.

Component (B)

282 g of oleic acid, 56 g of ammonia in aqueous solution at 30 wt% and 200 ml of ethyl alcohol were mixed at room temperature for 20 min.

Emulsifier

The component A is mixed with component B in a ratio of 70:30 wt% Example 3 - Prepration of the emulsifier

Component (A)

840 g of sunflower oil were mixed with 124 g of ethylene glycol and 2.0 g of potassium carbonate. The mixture was heated under stirring at 120 °C until disappearance of the turbidity.

Component (B)

282 g of oleic acid, 149 g of triethanolamine and 100 g of ethyl alcohol were mixed at room temperature.

Emulsifier

The component A is mixed with component B in a ratio of 70:30 wt% Example 4 - Prepraration of an emulsified fuel

170 g of emulsifier obtained according to the description in Example 1 are added to 8 L of diesel fuel with a low sulfur content (> 10 ppm) and 2 L of demineralized water. The mixture is stirred vigorously at 3000 rpm for 10 minutes. At the end of this process, it is observed the formation of a white emulsion, to be used within internal combustion engines fuelled by diesel fuel. Example 5-Comparative test regarding the consumption of electrical motor generators

In order to evaluate the performances related to the power output and the consumed fuel, two motor generators were used, fuelled alternately with pure diesel and with diesel/water emulsion (80/20 v/v).

Diesel motor generator mod. LE201 543 kW

Fuel: diesel

Electrical load supplied: 300 kW

Fuel consumption: 125 L/h

Fuel: emulsion (75.5 wt% diesel, 22.5 wt% water, 2 wt% emulsifier) Electrical load supplied: 300 kW

Fuel consumption: 1 15 L / h (of which 92 L/h are diesel)

Diesel motor generator IVECO CURSOR mod. 87TE1 D common rail 200 kW Fuel: diesel

Electrical load supplied: 150 kW

Fuel consumption: 60 L/h

Fuel: emulsion (75.5 wt% diesel, 22.5 wt% water, 2 wt% emulsifier)

Electrical load supplied: 150 kW

Fuel consumption: 45 L/h (of which 36 L/h are diesel)

Example 6-Comparative test concerning the gaseous emissions of an electrical motor generator

In order to evaluate the reduction of the pollutant load resulting from the use of emulsified fuels, the exhaust composition of a motor generator fuelled alternately with pure diesel and with the emulsion of diesel/water (80/20 v/v) was measured.

Diesel motor generator IVECO CURSOR mod. 87TE1 D common rail 200 kW

Fuel: diesel

Carbon dioxide (%) 6.3

Carbon Monoxide (mg/Nimc) 585

Nitrogen oxides (mg/Nimc) 2994

Fuel: emulsion (75,5 wt% diesel 22,5 wt% water, 2 wt% emulsifier)

Carbon dioxide (%) 6.4

Carbon Monoxide (mg/Nimc) 493

Nitrogen oxides (mg/Nimc) 2097 Example 7-Comparative test concerning particulate emissions of an electrical motor generator

In order to evaluate the reduction of the pollutant load resulting from the use of emulsified fuels, the amount of particulate of a motor generator fuelled alternately with pure diesel and with the emulsion of diesel/water (80/20 v/v) was measured.

Diesel motor generator mod. LE201 543 kW

Fuel: diesel

Opacity: 0.16 (1 /m)

3,2%

Fuel: emulsion (75,5 wt% diesel, 22,5 wt% water, 2 wt% emulsifier)

Opacity: 0.03 (1 /m)

0,6%