GB2101628A - Improved fuel comprising hydrocarbons containing alcohol - Google Patents

Abstract

Improved fuel, constituted by a microemulsion of water and an alcohol or an amine in a combustible hydrocarbon liquid, containing a surfactant, characterised in that this agent is a salt of an N-acyl- alpha -amino acid.

Description

SPECIFICATION Improved fuel comprising hydrocarbons containing alcohol The present invention relates to improved fuels and more particularly to those having their properties improved by the addition of water and, if required, another combustible additive.

In view of the importance of fuels and combustible liquids at the present time, various studies have been carried out in order to improve the hydrocarbon mixtures currently employed, that is to say petrols, gas oils and fuels, particularly those derived from the distillation of petroleum. The aim of the workers is two-fold: to improve combustion, in particular to increase the output of engines utilising the given fuel, and, on the other hand, to reduce pollution caused by the fumes resulting from utilisation of these fuels.

Attempts have also been made to substitute other combustible liquids at least partially, particularly alcohols, for hydrocarbons, as their cost increases more and more.

The earliest studies along this line, about fifty years ago, were based on the addition of alcohol, principally methanol, to motor-car fuel; not only did this solution cause complications in the operation of combustion engines, but also it produced unstable mixtures which altered with time, because the stability to changes of temperature of the mixtures left much to be desired, particularly when the mixtures contained water. However, small proportions of water in hydrocarbons are in fact very favourable to the behaviour of the fuel on combustion. Attempts were thus made to emulsify water and other additives, but known emulsions have not given sufficient stability. Considerable progress was made in this technique by the creation of microemulsions which certain surface-active agents allowed to be produced.Thus, during the last decade, various studies have led workers to the production of microemulsions of liquid hydrocarbon fuels, containing water and other additives, particularly alcohols.

In this manner, it is possible to increase the rate of combustion and to reduce the effects of pollution.

When alcohols, which are themselves combustible, are incorporated, a corresponding fraction of the hydrocarbon is saved. Examples of such results are described in several patents, e.g. US-PS 3,876,391, which proposes the use of surface-active agents constituted by an aliphatic ester of diethylene glycol, polyoxyalkylated aliphatic esters or derivatives of polyalkanolamines. US-P S 4,002,435 recommends the use of polyoxyethylated alkyl-phenol, whilst US-P S 4,046,519 utilises a combination of mono and diglycerides of oleic acid with the oxide of bis(2-hydroxy-ethyl)stearylamine, this mixture being produced in proportions such that the hydrophylic-lipophilic balance (HLB) is from 3 to 4.5.Despite the progress made by the utilisation of microemulsions, fuels containing water, alcohol and other additives do not have all the desired properties, in particular as regards their thermodynamic and chemical stability. Separation during storage, particularly at low temperature, is always to be expected and, in certain cases, the additives produce a corrosive effect in engines and boilers where the hydrocarbon is employed.

According to a current concept in this technique, the surface-active agent employed for the formation of the microemulsion should be non-ionic, this condition being particularly important for avoiding corrosion in engines. This is explained, particularly, in European Patent 1 2345 at the foot of page 6 and is described implicitly in the publication of German Patent Number 2,633,462 which utilises non-ionic emulsions, namely ethoxylated fatty materials, for the preparation of stable systems of liquid hydrocarbons with water and lower alcohols. Examples of microemulsions for fuels, described in the literature, show that the proportion of the surface-active agent to be utilised is large in relation to the water contained in the system.

Contrary to these concepts taken from the prior art, the present invention is based upon the unexpected discovery that certain surface-active substances, particularly anionic, give better results and lead to very stable, non-polluting and non-corrosive microemulsified fuels.

The new fuel according to the invention, constituted by a microemulsion of water and another additive and containing a surface-active agent, is characterised in that the anionic surface-active agent is a salt of a mineral or organic cation of an N-acyl-a-amino acid.

The surface-active agents suitable for carrying out the invention can be represented by the formula:

in which R and R' are aliphatic hydrocarbon radicals, while M designates a metallic cation, preferably an alkali metal, or an ammonium or amine cation.

Preferably, R is a straight or branched alkyl or alkenyl group containing 2 to 28 carbon atoms, while R', likewise a straight or branched alkyl or alkenyl group, is C, to C20. Each of the radicals R and R' can comprise one or more aromatic rings.

Both for reasons of facility of preparation and also for their efficacy, the surface-active agents particularly recommendable for carrying out the invention can be selected from those where the group R is a C8 to C24 alkyl or alkenyl group, R' being C1 to C6. For the same reason, it is particularly practicai to utilise sodium salts.

The names of the surface-active agents utilised according to the invention can be derived from amino-acids and the corresponding acyl derivatives or also from acids and amides formed on the amino group. They are, in effect salts of N-acyl-a-amino acids, that is, 1 -alkyl-1-alkanamido-acetic acids.

By way of non-limitative example, the following are some of the salts which are suitable for preparation of the improved fuel according to the invention, in the form of a clear, isotropic, newtonian and highly-stable microemulsions.

Potassium N-acetyl-a-amino-caprylate, sodium N-butyryl--decanoate, diethylamine N-propionyl-a-amino dodecanoate, sodium N-acetyl--a mino-dodecanoate, ammonium N-octanoyl-a-amino-dodecanoate, potassium N-a cetyl-cr-a mi no-tetradeca noate, pyridinium N-caprnyl-a-a mino-tetradeca noate, ethylene-diamine di-(N-propionyl-a-amino-hexadecanoate), sodium N-acetyl-a-amino-oleate, sodium N-acetyl--amino-octadecanoate, isobutylamine N-acetyl-a-amino-linoleate, sodium N-acetyl--amino-tetradecanoate, sodium N-oleyl-a-amino-octadecanoate potassium N-linoleyl-a-amino-hexanoate, etc.

Utilisation of this class of surface-active agents, described in French Patent Number 78,32005, also gives the advantage of operating over an enormous range of hydrophylic-lipophilic balance (HLB) values, in particular HLB's of 3 to 1 5, in contrast to most agents utilised previously, which only give stable microemulsions with very narrow limits of HLB.

Like most known fuels based on microemulsions, those according to the invention contain water in a range of 0.1% to 25% of the total, the proportions most frequently used being from 1% to 10%.

The additive necessary for the formation of a microemulsion, generally called a "co-surfactant", can be selected from various additives known in this technique. However, C, to C8 alcohols are of particular interest, as well as certain liquid amines. Also, the most suitable forms of the novel fuel contain methanol, ethanol, propanol and/or octanol etc., in a proportion of 0.1% to 40% by weight of the total and most frequently 2% to 10%. The same applies to amines which can replace or accompany the alcohols.

As regards the concentration of surfactant necessary, it is generally quite low, of the order of 0.1% to 10%, preferably 1.5% to 3.5%, by weight of the total microemulsion.

The invention is illustrated non-limitatively by the examples which follow.

EXAMPLE 1 The surface-active agent employed is sodium N-butytyl-a-amino-stearate:

which can also be named sodium 1-stearyl-1-butyramido-acetate.

1.7 parts by weight of this compound are mixed with 8.8 parts of absolute ethanol and 1 part of water. This mixture is added to 88.5 parts of ordinary motor fuel (petroleum fraction boiling between 200 and 2000 C); the whole is agitated for 3 minutes. The formation of a homogeneous, clear, isotropic liquid is given. The fuel so obtained remains stable for several months, both at 0 and 400 C.

EXAMPLES 2 TO 7 A mixture of two salts of N-acyl-a-amino acids is employed as the surface-active agent. The first is the sodium N-buWryl-a-aminostearnte (called C18 below) of Example 1. The second is sodium 1docosyl-1 -butyramido-acetate.

or sodium N-butyryl-cr-amino docosanoate; the latter is designated below by C22.

Using the operative mode of Example 1, a series of microemulsified fuels is prepared, by varying the proportions of the two surfactants C,8 and C22, as well as the nature and proportions of the alcohol.

The percentage by weight of the constituents of the stable microemulsion obtained are given in the following table.

TABLE 1

Ex. C1a(C22 %ofsur- No ratio factant Alcohol % Water Petrol 2 10/90 2.7 2-Ethyl-hexanol 1.8 9 81.5 + Methanol 5.0 3 20/80 2.25 2-Ethyl-hexanol 2.25 9 81.5 + Methanol 5.0 4 20/80 2.74 2-Ethyl-hexanol 1.82 9.24 83.2 + Methanol 3 5 20/80 2.74 2-Ethyl-hexanol 1.82 9.24 83.2 + Ethanol 3 6 20/80 3.20 Isobutanol 4.6 9.2 83 7 20/80 3.20 Isobutanol 4.1 9.2 83 + Ethanol 0.5 The fuels obtained, all containing about 9% of water, have excellent stability between 100 and 40C.

EXAMPLE 8 A mixture is used, comprising sodium N-butyryl--amino-docosanoate with sodium N-butyryl-ce- amino-hexacosanoate;

called C26 below.

By the technique of the foregoing Examples, an emulsion was prepared composed of: C22 surfactant 1.6bE by weight C28 surfactant 1.6% by weight Benzylamine 4.6% by weight Water 9.2% by weight Petroleum 83.0% by weight The fuel so obtained, which contains benzylamine in place of alcohol, contains, as can be seen, more than 9% of water. It is stable and gives good results in engines.

EXAMPLE 9 Identical emulsions to those of Example 8 are obtained with a C2C28surfactant ratio =30/70.

EXAMPLE 10 The fuel containing water and alcohols according to Example 3 is utilised to drive a 1200 cc capacity engine operating at an average rate of 3500 revs per min. Comparative tests are effected with the fuel alone, without water or alcohol.

The fuel of Example 3 gives a consumption of 8 litres per 100 km, as against 9.3 litres for the petroleum alone.

The CO content of the exhaust gases is 0.3%, instead of 1.2% in the case of the petroleum alone.

Claims (9)

1. A fuel comprising a microemulsion of water and an alcohol or an amine in a combustible hydrocarbon liquid in an amount of 80% to 90% by weight of the microemulsion, in which the microemulsion also contains as a surface-active agent, a salt of an N-acyl--amino acid in an amount of not more than 3.5% by weight.

2. A fuel according to claim 1, in which the surface-active agent has the formula:

wherein R is a straight or branched alkyl or alkenyl group containing 2 to 28 carbon atoms, R' is a straight or branched alkyl or alkenyl group containing 1 to 20 carbon atoms and M is an alkali metal, ammonium or amine cation.

3. A fuel according to claim 2, in which one or both of R and R' are groups containing one or more aromatic rings.

4. A fuel according to claim 2 or 3, in which R is a C8 to C24 alkyl or alkenyl group and R' is a C1 to C6 alkyl group.

5. A fuel according to any preceding claim, in which two mono-alcohols, one containing 1 or 2 carbon atoms and the other 4 to 8 carbon atoms, are present.

6. A fuel according to any of claims 1 to 4, in which benzylamine is present.

7. A fuel according to any preceding claim, which contains by weight 1% to 10% of water, 2% to 10% of alcohol or amine and 1.5% to 3.5% of surface-active agent.

8. A fuel according to any of claims 1 to 6, which contains by weight 9% of water and 1.5% to 3.5% of surface-active agent.

9. A fuel according to claim 1, substantially as described with reference to the foregoing Examples.