EP0058605B1 - Microemulsion of water in a liquid combustible - Google Patents

Description

The present invention relates to microemulsions of water in liquid fuels, in particular hydrocarbons or mixtures of hydrocarbons with oxygenated organic compounds. It also includes the process for their preparation as well as the application of such microemulsions as fuels which can be used in particular in engines or burners.

Microemulsions, consisting of hydrocarbons with a lower proportion of water and possibly alcohols, are well known at the present time: many works have been devoted to the preparation of this type of systems, whose industrial interest is undeniable. . It is known, in fact, that a fuel containing water and alcohol, in the form of microemulsion, brings marked advantages over the fuel alone; used in an engine, it can in fact give rise to a much reduced formation of carbon monoxide, nitrogen oxides and hydrocarbons in the gases formed. It can also improve the anti-detonating properties. Thus, the incorporation of water, and preferably also alcohol, into a liquid fuel, makes it possible to increase the rate of combustion and to attenuate the effects of pollution. On the other hand, the addition of an alcohol, and more particularly of methanol, fuel itself, results in a saving of hydrocarbons. It may be noted, in this connection, that already fifty years ago, attempts were made with a view to the use of a "national fuel" constituted by a mixture of hydrocarbon petrol and methanol. However, the advantages of incorporating water or water with an alcohol into a fuel have only been realized in recent years, thanks to surfactants which make it possible to create a stable emulsion that is to say a microemulsion, avoiding the separation of water during storage. Also, the paramount factor, in the preparation of the half-, sememulsions in question, is the appropriate choice of the surfactant (s) with a view to obtaining a microemulsion of desired stability. The numerous works of our time relate precisely to this factor. Thus, for example, in US Pat. No. 3,876,391, the use of surface-active agents consisting of an aliphatic ester of diethylene glycol, polyoxyalkylated aliphatic esters or derivatives of polyalkanolamines is proposed. US patent 4002435 recommends the use of polyoxyethylated alkyl phenols and seems to relate only to ordinary emulsions. US Pat. No. 4,046,519 uses surfactants whose hydrophilic-lipophilic balance (HLB) is from 3 to 4.5, this agent being a combination of mono and diglycerides of oleic acid with oxide of bis- (hydroxy-2-ethyl) stearylamine. In the publication of European patent 12 345, polyethoxylated amides, that is to say non-ionic agents, are proposed.

However, despite all the efforts made, according to the prior art, in the search for a suitable agent, which would make it possible to obtain a perfectly stable microemulsion of water in a fuel, such an emulsion is not not yet developed and often gives rise to storage separations, possibly at low temperature; some even lead to corrosion effects due to the nature or the amount of surfactants added. The examples of microemulsions for fuels described in the literature show that the proportion of surfactant to be used is high relative to the water contained in the system.

The present invention brings, in this way, an important improvement by the choice of an unforeseen surfactant compound, very different from all those found in the prior art, and which has the advantage of providing emulsions perfectly homogeneous, clear, isotropic, Newtonian and stable. In addition, the microemulsions according to the invention have the property of being independent of the order in which their constituents are introduced.

dans laquelle au moins un des radicaux R¹ et R² désigne un alkyle, linéaire ou ramifié, pouvant comporter 1 à 24 de préférence 6 à 18 atomes de carbones; le deuxième radical est de l'hydrogène lorsqu'un seul radical est un alkyle; n est généralement un nombre entier de 1 à 6 et, le plus souvent, 1 ou 2. Le cation M est de préférence monovalent, en particulier Na, K, Li, NH₄ ou RNH₃ où R est un groupe hydrocarboné, pouvant porter des substituants, notamment des hydroxyles.The process according to the invention for the preparation of a microemulsion of water, optionally accompanied by another adjuvant, in particular alcohol, in a liquid fuel, in the presence of a surfactant, is characterized in that that the surfactant is an alkylphenoxyalkanoate of a metal, of ammonium or of organic base of formula:

in which at least one of the radicals R ¹ and R ² denotes an alkyl, linear or branched, which can contain 1 to 24 preferably 6 to 18 carbon atoms; the second radical is hydrogen when a single radical is an alkyl; n is generally an integer from 1 to 6 and, most often, 1 or 2. The cation M is preferably monovalent, in particular Na, K, Li, NH ₄ or RNH ₃ where R is a hydrocarbon group, which can carry substituents, in particular hydroxyls.

Typical surfactants, which are very suitable for carrying out the invention, are alkylphenoxyacetates, the phenyl nucleus of which carries a relatively long alkyl, in particular in C ₁₈ -C _18. These are, by way of nonlimiting examples : sodium p-octyl-phenoxyacetate, potassium p-decyl-phenoxyacetate, ammonium m-nonylphenoxyacetate, sodium dioctyl-3,5-phenoxyacetate, ammonium p-laurylphenoxyacetate, p-nonylphenoxyacetate of hexylamine, m- diethanolamine stearyl phenoxyacetate, etc. However, other corresponding alkanoates, for example alkyl phenoxy propionates or alkyl phenoxy butyrates, are also suitable.

Given the lack of interest that the compounds indicated in the second paragraph of the description have aroused so far, probably because of their relatively low efficacy in comparison with the various surfactants Active ingredients commonly used in industry, it is entirely surprising that, in the particular case of the emulsion of water and / or alcohols in liquid fuels, these agents give remarkable results. It is an unforeseen fact that the (-CH ₂ ) _n COOM group brings, in the application of the invention, excellent results, while it is known in the art that, in order to have powerful emulsifiers with starting from alkyl phenols, a more or less long chain of polyoxyethylene should be grafted onto the phenol function, as moreover indicated in US Pat. No. 4,002,435 cited above.

The surfactants according to the invention can be used alone or in admixture with other surfactants whose activity they enhance.

The numerous conventional adjuvants of microemulsions, which are generally designated by the term co-surfactants, in particular such as alcohols and amines, are very compatible with the alkylphenoxyalkanoates used according to the invention. In particular, the excellent stability of microemulsions obtained, with alcohols as co-surfactants, makes it possible, according to the invention, to have very stable fuels, containing water and alcohols, in a wide range of concentration. The use of alcohols as co-surfactants constitutes a preferred form of the invention: in fact it has a double advantage; first of all alcohol being a fuel in itself, the co-surfactant is part of the combustible mixture; moreover, since the fuel is a microemulsion of water in a hydrocarbon, it is possible to use alcohols which are not completely dehydrated, which constitutes an advantage from an economic point of view, especially when it is known that in the case of Ethanol-water mixture in particular, there is an azeotrope which makes it difficult and expensive to extract the alcohol in its pure state.

With the adjuvants according to the invention, it is possible to adapt the composition of the microemulsion to the temperature range, where the microemulsion must remain stable (between - 20 ° and 100 ° C and particularly between -10 ° and + 20 ° C ), by adjusting the proportion and / or the nature of the phenoxyalkanoate.

It should be noted that, unlike most surfactants of the prior art, used for the formation of microemulsions of liquid fuels, those of the invention do not contain sulfur or phosphorus, which avoids any emission of products toxic during combustion. The amount of nitrogen contained in the microemulsion, when the co-surfactant is an amine, is extremely small.

The process for the preparation of microemulsions, according to the invention, characterized in that the surfactant is an alkylphenoxyalkanoate, can be carried out in the manner known per se, that is to say by mixing adjuvants affected with liquid fuel. A slight agitation is enough to obtain a stable microemulsion. An advantage of this process is that the adjuvants can be mixed with the fuel in any order: thus one can first dissolve the surfactant in water, in the co-surfactant, or in a mixture of the two, and introduce the solution or dispersion obtained in the liquid fuel, with gentle and brief agitation. However, it is also possible to put these various additives directly into the fuel and to stir them just for the time necessary for homogenization.

By way of nonlimiting example, the stirring of the medium can be carried out by means of a paddle stirrer, rotating at about 20 to 100 rpm (peripheral speed of the order of 0.5 to 5 m / s ), for 1 to 10 minutes.

The following examples are non-limiting illustrations of the invention.

Examples 1 to 9

On voit qu'il est possible de faire varier les proportions d'eau et de co-tensioactifs dans des limites assez larges, intéressantes pour la pratique. Toutes les microémulsions 1 à 10 sont homogènes, limpides, isotropes, newtoniennes et stables à la température ambiante. Leurs viscosités sont voisines de celles de l'essence utilisée. Les microémulsions de l'eau ou de l'eau et d'un adjuvant (alcool ou amine) peuvent contenir de 1 à 10% d'eau, 1 à 27% d'un alcool ou d'une amine, 1 à 10% de tensio-actif, et de préférence 1 à 6%, microémulsionnés dans un combustible liquide.Microemulsions of water with different co-surfactants were prepared by the above-mentioned method, in which water, previously mixed with the co-surfactant and the surfactant, according to the invention, was added to ordinary auto gasoline (fraction of oil boiling between 20 ° and 200 ° C). The operations related to 1 liter of gasoline which was agitated for 3 minutes, after the addition of the adjuvants. The table below indicates the proportions of the components in% of the total weight of microemulsion, the surfactant being sodium p-lauryl-phenoxyacetate.

It can be seen that it is possible to vary the proportions of water and of co-surfactants within fairly wide limits, which are advantageous for practice. All microemulsions 1 to 10 are homogeneous, clear, isotropic, Newtonian and stable at room temperature. Their viscosities are close to those of the gasoline used. Microemulsions of water or water and an adjuvant (alcohol or amine) can contain from 1 to 10% of water, 1 to 27% of an alcohol or an amine, 1 to 10% of surfactant, and preferably 1 to 6%, microemulsified in a liquid fuel.

Examples 11 and 12

Comme les précédentes, les émulsions de ces exemples sont bien stables et ne laissent que des proportions très réduites d'oxyde de carbone à la combustion.The procedure being the same as in the previous examples the surfactant used was monoethanolamine p-lauryl-phenoxyacetate, that is to say that its cation was [NH ₃ CH ₂ CH ₂ OH] ⁺ .

Like the previous ones, the emulsions of these examples are very stable and leave only very small proportions of carbon monoxide on combustion.

Example 13

In a preparation similar to that of the previous examples, sodium p-nonyl-phenoxyacetate was used as surfactant in an amount of 3.5% of the total. With 1.3% isobutanol and 9.5% water, a perfectly stable emulsion was obtained, containing 85.7% gasoline.

Example 14

In Example 1, we replace ordinary auto gasoline with light fuel oil, known under the name of “domestic fuel oil”. The stable microemulsion obtained is used in a central heating boiler burner. There is a CO content of approximately 80 ppm in the fumes, while the combustion of household fuel alone, in the same burner, at the same speed, leads to the presence of 400 ppm in the fumes.

Example 15

The microemulsion of Example 6 is used to power an automobile engine with a capacity of 1,200 ml, at an average speed of 3,500 rpm. The fuel consumption is then 9.25 per 100 km (which corresponds to a consumption of 7.9 1 of petrol), the CO release being 6 g / km and that of NO, 0.4 g / km, while - under the same operating conditions - petrol alone leads to a consumption of 9.6 liters per 100 km, with a CO emission of 26 g / km and NO _x of 1.6 g / km .

We see that the emulsion of water and ethanol in gasoline provides very marked advantages over gasoline as such.

Although the above examples are not limiting, and the invention can be applied to the preparation of microemulsions with concentrations of constituents different from those of these examples, a very practical type of microemulsified fuel comprises by weight 1 to 10% water, 1 to 27% alcohol and 1 to 6% surfactant, the rest being liquid fuel.

dans laquelle R¹, R², n, M ont des significations données au cours de la description.The invention also comprises, as new surfactants, the alkyl-phenoxy-alkanoates of a metal, of ammonium or of organic base of general formula

in which R ¹ , R ² , n, M have meanings given during the description.

Claims (11)

1. Method of preparing a microemulsion of water or of water and another additive, more particularly alcohol or amine, in a liquid fuel in the presence of a surface active agent, characterised in that the said agent is an alkylphenoxyalkanoate of a metal, of ammonium or has an organic base.

2. Method according to claim 1, characterised in that the surface active agent has the formula

wherein at least one of the radicals R¹ and R designates a linear or branched C₁ to C₂₄ alkyl, the second radical being hydrogen when only one radical is an alkyl; n being a number between 1 and 6 and usually 1 or 2, and M is a cation, preferably monovalent.

3. Method according to claim 2, characterised in that at least one of the symbols R¹ and R designates a C₆ to C₁₈ alkyl.

4. Method according to claim 1 or 3, characterised in that the cation is Na, K, Li, NH₄ or RNH₃, R being a hydrocarbon group, which may carry substituents, in particular hydroxyls.

5. Method according to any one of the preceding claims, characterised in that the surface acting agent is an alkylphenoxyacetate of Na, K, Li, NH₄, or of an amine, the alkyl being a C₆ to C₁₈ alkyl.

6. Method according to any one of the preceding claims, characterised in that the additive to the co-surfactant is an alcohol, more particularly a C₁ to C₈ alcohol.

7. Method according to any one of claims 1 to 5, characterised in that the additive to the co-surfactant is an amine, more particularly benzylamine.

8. A microemulsion of water or of water and an additive, more particularly alcohol or amine, in a liquid fuel, containing a suitable surfactant, characterised in that the latter is an alkylphenoxyalkanoate of a metal or an amine.

9. A microemulsion according to claim 8, characterised in that it contains, by weight, 1 to 10% water, 1 to 27% of an alcohol or an amine and 1 to 10%, and preferably 1 to 6%, surfactant.

10. Use of a microemulsion of water or a water accompanied by an alcohol or an amine, in a liquid fuel, for combustion in a motor or in a burner, characterised in that the microemulsion contains a surface acting agent, comprising an alkylphenoxyalkanoate of a metal or of an organic base, more particularly an alkali metal, an ammonia or an aliphatic amine.

11. A surface acting agent comprising an alkylaryl group, characterised in that it is formed by a phenoxyalkanoate of a metal, of ammonia or an organic base having the formula

wherein at least one of the radicals R¹ and R designates a linear or branched C₁ to C₂₄ alkyl, the second radical being hydrogen when only one radical is an alkyl; n being a number between 1 and 6 and usually 1 or 2, and M is a cation, preferably monovalent.