GB2106135A - Improved fuel based on gas oil, containing water and an alcohol - Google Patents

Abstract

The gas oil fuel contains 0.1-0.5% of water and 0.001-0.5% alcohol in the form of a micellar clear limpid solution, stabilised by the addition of one or more surfactants associated with one or more co-surfactants, the surfactant being a salt of an N-acyl-???-amino acid.

Description

SPECIFICATION Improved fuel based on gas oil, containing water and an alcohol The invention relates to a process of improvement of the properties of combustion of gas oils, by the addition to the gas oil of suitable quantities of water and of one or more surface-active agents, associated if required with one or more co-surface active agents, the latter being compounds capable of forming hydrogen bonds with the water. The gas oil treated according to the invention has a completely clear and limpid appearance, the water being completely solubilised and not separating out.

It is known to utilise organometallic salts of Ca++, Ba++, Mn++, Fe+++ and others to improve the combustion of gas oil. Such additives, incorporated in gas oils in amounts of the order of 10 to 1000 ppm, allow reduction of the emission of carbon, non-combusted solids, CO and non-combusted hydrocarbons, by initiating the formation of free radicals. However, these additives have a certain number of disadvantages, in particular toxic emissions in the exhaust, particularly in the case of salts of Ba++ and, in a general manner, formation in the combustion chambers of metallic oxides which can exert an abrasive action.

The beneficial effect of water on the combustion of hydrocarbons is known. Thus it was proposed in 1954 according to French Patent Number 1,100,551 to incorporate in liquid fuels small quantities of water in the presence of emulsifying agents, for example the products of condensation of fatty alcohols, phenols or fatty acids with ethyl oxide. However, in practice stable emulsions were not obtained and the water incorporated separated in time, leading to disadvantages in storage reservoirs including corrosion and bacterial growth. Moreover, the water droplets, entrained into filters, caused swelling and distortion, leading to unexpected interruption in the supply from the reservoir, clogging of pumps etc.

The presence of drops of water causes the formation of ice crystals in cold weather, causing frosting up and blockage of filters in the feed circuit to the engine.

More recently, attempts have been made to remedy the disadvantages of the prior art by the utilisation of special mixtures of surfactant compounds, giving stable emulsions containing water in the form of very fine particles dispersed in the hydrocarbon. Thus, US Patent 3,876,391 describes the incorporation of 6% to 16% of water in motor fuel in the presence of 3% to 8% of a fatty acid ester, polyoxyethylated if required, and also a surfactant based on an amine, a polyoxyethylated alkyl-phenol, a polyoxyethylated amide of a fatty acid or a polyoxyethylated fatty ester or sorbitol. However, it is necessary to add 0.5% to 10% of a water-soluble amide or amine, such as, for example, acetamide, formamide, monoethanolamine, ethylenediamine, etc. The solution proposed is thus highly complicated.

The question has remained complex during recent years, as can be seen from US Patent 4,083,698 which still recommends mixtures of salts of fatty acids with polyethoxylated non-ionic surfactants, to obtain very fine stable emulsions containing 0.1% to 10% of water and 1% to 10% of a lower alcohol in a fuel. When the latter is relatively heavy, in particular a diesel fuel, that is to say a gas oil, the combustion proposed is not generally sufficient and the patent explains (columns 24 and 25) that it is necessary to add up to about 1 5% of cyclohexanol and/or cyclohexanone.

The present invention provides a marked improvement in this technique in that it permits a considerable improvement in the combustion of fuels of the gas oil type, that is to say hydrocarbons boiling between about 200 and 4250C, in a manner which is simpler, more economical and easier to carry out than the known art.

This invention results from two unexpected discoveries: 1; the desired improvement of a gas oil can be obtained by the incorporation of small proportions of water, namely from 0.01% to 0.5%, in contrast to the several percent utilised in the prior art; 2; the water is capable of being put into a completely clear and very stable emulsion by means of certain specific surface-active compounds, which have never been employed for this purpose previously.

The new process according to the invention, which consists in emulsifying 100 to 5000 parts per million of water in a gas oil in the presence of a surface-active agent, is characterised in that the surface-active agent is constituted by one or more compounds of the formula:

where each of the radicals R and R' is an aliphatic group, particularly alkyl or alkenyl, R being from C2 to C28 and R' from C1 to C1O- The radical R is preferably a relatively heavy alkyl radical, that is one containing at least 6 carbon atoms and particularly from C8 to C24. The acyl group can be lower, such as acetyl, propionyl, butyryl etc., but it can also be derived from a fatty acid, R' being C6 or higher, although it is preferably C1 to C4.

While the radicals R and R' most frequently are alkyls, they can nevertheless also be constituted by unsaturated hydrocarbon radicals, particularly alkenyl radicals.

By way of non-limitative example, some of the salts according to the invention, which are particularly suitable both as emulsifiers and micro-emulsifiers, are as follows: potassium N-acetyl-(z-amino-caprylate sodium N-butyryl-a-amino-decanoate diethylamine N-propionyl-a-a mino-dodecanoate sodium N-acetyl-cz-amino-dodecanoate ammonium N-octanoyl-a-amino-dodecanoate potassium-N-acetyl-a-amino-tetradecanoate pyridinium N-caproyl-a-amino-tetradecanoate ethylene-diamine di-(N-propionyl-a-amino-hexadecanoate) sodium N-acetyl-a-amino-oleate sodium N-acetyl-a-amino-octadecanoate isobutylamine N-acetyi-a-amino-linoleate sodium N-acetyl-a-amino-tetradecanoate sodium N-oleyl--amino-octadecanoate potassium N-linoleyl-o-amino-hexanoate, etc.

The salts of the acids according to formula (1) utilisable according to the invention are derived from any mineral or organic base, provided they are at least slightly soluble in water, in the hydrocarbon selected or in both. In practice, the alkali metal salts, particularly those of potassium and sodium, and possibly also the alkaline earth metal salts, are most suitable. Ammonium salts can also be suitable, such as those of primary, secondary or tertiary amines, particularly methyl, ethyl, propyl, butyl, hexyl etc., amines, ethylene-diamine, diethylene-triamine, propylene-diamine, hexamethylene-diamine, mono- di- or triethanolamine, pyridine, piperidine, piperazine etc.

The co-surface-active agent, solvent and/or stabiliser for the salt according to the invention can be selected from those known in the prior art, particularly from various alcohols. There is thus a vast choice in the general class of alcohols, such as isopropyl, butyl, isobutyl, amyl, isoamyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, the mono-butyl ether of ethylene-glycol, the dibutyl ether of ethylene-glycol, various ethoxylated alcohols, cyclohexanol, methylcyclohexanol, benzyl alcohol and others; this list is given merely by way of illustration without having any limitative character.

The invention is carried out with the conjoint use of one of these co-surfactants of the known types utilised in general for such emulsions; lower alcohols, such as methanol, ethanol, propanol, isopropanol and butanols are particularly suitable.

The proportion of the co-surfactant, like the surfactant itself, is of the order of 10 to 5000 ppm and particularly from 25 to 2000 ppm or 0.0025% to 0.2% of the gas oil. Depending on the case, the weight of the co-surfactant is in general from 0.1 to 1 part and often 0.5 to 1 part per 1 part by weight of the surfactant.

The quantity of the surfactant to be utilised is proportional to the quantity of water to be solubilised. In a general manner, aromatic gas oils having an aromatics content higher than 25% require lesser quantities of the surfactant than paraffinic gas oils, where the aromatics content is of the order of 10% to 15%.

Addition of the surfactant, if required in association with the co-surfactant, allows very considerable diminution of the water/gas oil interfacial tension to a value of the order of 30 to 40 dynes cm-'. The system obtained has the form of a liquid dispersion, the continuous external phase of which is the gas oil, while the disperse phase is constituted by the water in droplets or micelles having a size less than 0.4 micron. The entire dispersion has an appearance which is transparent to light. The system formed is thermodynamically stable and, in contrast to known emulsions, the water does not separate out even after a very long time of the order of several months.

In a general manner, the process of the invention is carried out by the addition of the gas oil of 100 to 5000 ppm of water, 10 to 5000 ppm of the surface active agent and 10 to 5000 ppm of the cosurfactant compound, the weight ratio of the latter to the agent being from 0.1 to 1. However, very good results can be obtained with 100 to 1000 ppm of water and 25 to 2000 ppm of the surfactant compound, accompanied by 0.5 to 1 part of its weight of the co-surfactant compound.

The non-limitative examples which follow illustrate the invention in several of its aspects, with specific surfactants.

In these examples, a diesel engine was operated with the gas oil containing no additive and - on the other hand - with the gas oils treated according to the invention.

A gas oil was used having the following characteristics: relative density at 1 50C with respect 0.831 to water at 40C 50% distillation point 2550C 90% distillation point 3630C final distillation point 3400C viscosity at 200C 4.1 cst initial water content 75 ppm The water utilised was de-mineralised.

The vehicle utilised for the tests was placed upon a dynamometric chassis. The area in which the tests were carried out was climatised so that it was possible to place it under completely known and reproducible conditions (200 C). In a first stage, a test period of 45 minutes was followed at a stable speed, the engine operating substantially at two-thirds of its nominal power. The tank of the vehicle contained the gas oil intended for the tests. The tests were carried out when good thermal equilibrium of the engine had been established.

An operative mode which was entirely similar has also been carried out with an engine on a test bench.

The tests were conducted in accordance with the standards of the Journal Officiel de la République Française for recognition of vehicles by the EEC, namely: tests at stabilised speed: the engine is operated normally, measurements are effected in a uniform manner divided between the regime corresponding to maximum power of the engine and the greater of the following regimes: (1) 45% of operation at rotation corresponding to maximum power and (2)1000 revs per min.

free acceleration tests: the gearbox of the vehicle is put into neutral and the engine is accelerated; with the engine idling, the accelerator is operated rapidly but carefully, so as to obtain the maximum output from the injection pump; this position is maintained until the throttle operates; as soon as this speed is obtained, the accelerator is relaxed until the engine returns to its idling speed.

The operation is repeated at least six times to clear the exhaust system and to effect any required adjustment of the apparatus.

The measurements consist in determining the opacity of the fumes recovered from the vehicle exhaust. The apparatus utilised is an opacimeter of the type and mode of operation according to the description published in the Journal Officiel de la République Franchise of 21st March 1974, annexes 7 and 8.

The test vehicle is provided with a 3.3 litre capacity engine, developing an output of 56 Kw at 3200 revs. per min.

EXAMPLES 1 to 4 Tests were carried out on the engine at 1500, 2000, 2500 and 3200 revs per min, on the one hand with the gas oil without additives and on the other with the various additives indicated in the results Table The latter are expressed as coefficients of absorption in m-' found for the exhaust gases following the opacity measurements mentioned above.

Each result is the average of four determinations showing deviations which do not exceed 5%.

By way of comparison, tests were also effected with, as additives, Ba alklyl-benzene-sulphonate, designated "SB", and a known surfactant based on polyoxyethylated alcohols (UKANYL 36 of Société Péchiney-Ugine-Kuhimann), designated "UK".

Microemulsions of water and 3-methyl-butanol-1 in the gas oil were prepared by means of sodium 1 -docosyl- 1 -acetamido-acetate

as the surfactant.

The gas oil utilised has a distillation point of 2550C at 50%, 3630C at 90% and a final point of 34O0C; its initial water content was 75 ppm.

The microemulsions formed with this fuel were tested in a 3.3 litre diesel engine having an output of 56 Kw at 3200 revs per min, the tests being effected at four different levels, running from 1 500 to 3200 revs per min.

During these tests, the opacity of the exhaust gases sof the engine was measured by the French regulatory method (Journal Officiel de la République Franchise, 21st March 1974, annexes 7 and 8).

The coefficients of absorption of light, thus determined in m-', are indicated below for the treated gas oil, as well as for the same gas oil without additives tested by way of comparison.

Example Example "UK" "SB" Control 1 2 3 4 Water content added % 0 0.1 0.5 0.1 0.1 Me-butanol content % 0 0.05 0.2 0.06 0.1 Surfactant content 0 0.05 0.2 0.06 0.01 Rate: Revs/min Coefficients of absorption, m-': 1 500 1.94 1.45 1.25 1.70 1.40 2000 1.47 1.00 0.90 1.35 0.95 2500 2.61 1.60 1.20 2.20 1.50 3200 4.45 3.10 3.10 3.70 3.50 It can be seen that improvements, that is reductions in opacity of the exhaust gases, from about 30% to more than 50% are obtained using the microemulsions according to the invention. Thus, at 2500 revs per min and 0.5% of water, with respect to the control, there is an improvement of (2.61-1.20):1.2O= 54%.

On the other hand, the results of Examples 1 and 2 according to the invention are better than those of the standard polyethoxylated surfactant ("UK" -- Example 3). They are virtually the same as those given with Ba alkyl-benzene-sulphonate (Example 4).

EXAMPLE 5 The operations of Example 2 are repeated with 0.2% Na N-acetyl--amino-oleate as the surfactant. The results are equivalent to those of Example 2.

EXAMPLE 6 0.3% of water was microemulsified with 0.1% of isopropanol and 0.1% of diethylamine N-butyryl a-amino-dodecanoate in the same gas oil as in the preceding Examples. The coefficient of absorption of the exhaust gas was reduced by 40% with respect to the control at 2500 revs per min.

EXAMPLES 7 and 8 Gas oils containing water according to Examples 1 and 2 respectively were tested under free acceleration in comparison with the untreated gas oil. The following results were obtained: Examples: 7 8 Control % water in the microemulsion 0.1 0.45 0 % n-butanol 0.07 0.25 0 % Na N-propionyl-a-amino-stearate 0.06 0.20 0 Coefficient of absorption m-' 0.91 0.85 1.20

Claims (7)

1. A fuel comprising a microemulsion containing, by weight,98.5% to 99.98% of gas oil, 0.1% to 0.5% of water,0.001 to 0.5% of an alcohol and, as a surface-active agent,0.001 to 0.5% of a salt of an N-acyl-a-amino-acid of 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 or alkaline earth metal, ammonium or amine cation.

2. A fuel according to claim 1, in which R is a C5 to C24 alkyl or alkenyl group and R' is a C1 to C6 alkyl group.

3. A fuel according to claim 1 or 2, in which one or both of R and R' are groups containing one or more aromatic rings.

4. A fuel according to any preceding claim, which contains, by weight, 0.1% to 0.5% of the surface-active agent, 0.1% to 0.5% of water and 0.1% to 0.5% of alcohol.

5. A fuel according to any preceding claim, in which 0.5 to 1 part by weight of surfactant is present per 1 part of water.

6. A fuel according to any preceding claim, in which 0.5 to 1 part by weight of alcohol is present per 1 part of surfactant.

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