EP0915944B1 - Use of an additive for the improvement of lubricating properties of a fuel with low sulphur content for diesel engines - Google Patents

Abstract

The invention concerns a fuel for diesel engines, with a sulphur content of less than 500 ppm containing in a major proportion at least one average distillate from a straight-run distilling cup of crude oil, with temperature ranges between 150 and 400 °C and in a minor proportion a lubricating additive containing monocarboxylic and polycyclic acids. The said fuel is characterised in that it contains at least 20 ppm of the additive consisting of at least one monocarboxylic aliphatic hydrocarbon, saturated or unsaturate, of linear chain between 12 and 14 carbon atoms, and at least one polcyclic hydrocarbon compound, containing at least two cycles each formed of 5 to 6 atoms one of which at most is optionally a heteroatom such as nitrogen or oxygen and the other atoms are carbon atoms, these two cycles having further two carbon atoms in common, preferably vicinal, these said cycles being saturated or unsaturate, substituted or non-substituted by at least one single grouping selected among the carboxylic, amine carboxyl, ester and nitrile groupings, the fuel containing more than 60ppm of additive when the said combination is tall oil.

Description

The present invention relates to a fuel containing a creaminess additive to improve lubricating properties of fuels, whether diesel or aviation fuel (jet fuel), and more particularly of low-content diesel fuels in sulfur.

It is well known that diesel fuels and aviation fuels must have skills in lubrication for the protection of pumps, systems injection and all moving parts with which these products come into contact with in a internal combustion. With the desire to use products increasingly pure and non-polluting, especially devoid of sulfur, the refining industry was brought to improving their treatment processes more and more removal of sulfur compounds. However we observed that by losing the sulfur compounds we also lost the aromatic and polar compounds often associated, which caused a loss of the lubricating power of these fuels. Thus, below certain levels, the removal of sulfur compounds in the composition of these products very significantly promotes wear phenomena and rupture of moving parts at the pumps and injection systems. As the regulation of many countries imposed to limit the upper content acceptable as sulfur compounds in fuels at 0.05% by weight to reduce emissions from cars, trucks or buses with polluting combustion gases, particularly in urban agglomerations, it is necessary to replace these lubricating compounds by other non-polluting compounds with regard to the environment but presenting a power sufficient lubricant to avoid the risk of wear.

To solve this problem, several types additives have already been proposed. So we added to diesel fuel additives anti-wear, known for some in the field of lubricants, of the fatty acid ester type and unsaturated dimer fatty acids, amines aliphatics, esters of fatty acids and diethanolamine and long chain aliphatic monocarboxylic acids as described in US Patents 2,252,889, US 4,185,594, US 4,204,481, US 4,208,190, US 4,428,182. The most of these additives have a lubricating power sufficient but at concentrations too high which is very economically unfavorable to purchase. In addition, additives containing dimer acids, such as those containing trimer acids, cannot be used in fuels for vehicles in which the fuel may come into contact with lubrication because these acids form by chemical reaction deposits that are sometimes insoluble in oil, but above all incompatible with commonly used detergents.

US Patent 4,609,376 recommends the use anti-wear additives obtained from acid esters mono- and poly-carboxylic and polyhydric alcohols in fuels containing alcohols in their composition.

US Patent 2,686,713 recommends the introduction of tall oil up to 60 ppm in diesel fuels to prevent rust from forming on surfaces metal in contact with these fuels.

Another chosen route is to introduce esters vegetable oils or the vegetable oils themselves in these fuels to improve their lubricity or their smoothness. Among these are derivative esters rapeseed, linseed, soybean, sunflower or oils themselves (see patents EP 635,558 and EP 605,857). One of the major drawbacks of these esters is their low lubricity at a concentration of less than 0.5% by weight in fuels.

To improve the lubricating power of gas oils, patent application WO 95/33805 recommends the introduction of a cold-keeping additive consisting of nitrogenous additives comprising one or more NR ¹³ groups in which R ¹³ comprises from 12 to 24 atoms carbon, is linear, slightly branched or alicyclic and aromatic, the nitrogen group which can be linked by CO or CO ₂ and form amine carboxylates or amides.

FR-A-1388295 describes a process for incorporating solids in a liquid as well as liquids as well obtained. The carrier organic liquid can be diesel but this liquid is never used alone. Such a liquid is not suitable as "diesel engine fuel"; he there is no mention of diesel oil lubrication.

The patent US2658823 describes the use of a salt of tall oil as an anti-sedimentation additive in fuels. There is no mention of the sulfur content diesel oil or the lubricating effect of tall oil.

Patent US2907646 describes the use of tall oil in combination with an imidazoline as an anti-rust additive in fuels. There is no mention of the content of diesel fuel sulfur if not enough to be likely to react), or the lubricating effect of tall oil.

US Pat. No. 2,686,713 describes the use of tall oil as an anti-rust additive in fuels. There is no mention of the sulfur content of diesel or the lubricating effect of tall oil. Tall oil content in the case of a diesel fuel is necessarily at most 60ppm.

The patent US3667152 (corresponding to DE2022585) describes the use of tall oil fatty acid as an anti-wear additive, water separation and stability thermal. However, this document indicates that tall oil in as long as it is not appropriate.

The present invention aims to solve the problems encountered with the additives proposed by the prior art, that is to say to improve the lubricating power of desulfurized and flavored fuels, while remaining compatible with other additives, especially detergents, and lubricating oils, especially forming no deposits and reducing the cost, in particular by a lower additive content, well below 0.5%.

The invention therefore provides a use, for improve the lubricating properties of diesel fuels low sulfur, oiliness additive consisting of a combination of at least one hydrocarbon aliphatic monocarboxylic, saturated or unsaturated, of chain linear between 12 and 24 carbon atoms, and at minus one polycyclic hydrocarbon compound selected from the group consisting of the natural resin acids obtained from the distillation residues of natural oils extracted from coniferous trees, especially conifers resinous, and derivatives amine carboxylates, esters and nitriles of these acids.

Particular embodiments are the subject of claims 2 to 11.

We realized that the lubricating power provided by the oiliness additive containing such a combination is much higher than foreseeable by adding powers lubricants of each of its components taken separately. This unpredictable result reflects the synergistic effect of different components of the said combination with regard to the lubrication.

In a first mode of realization, the polycyclic hydrocarbon compound is chosen from the group consisting of the natural resin acids obtained from the distillation residues of natural oils extracted from coniferous trees, especially conifers resinous, as well as amine carboxylates, esters and the nitriles of these acids.

Among the resin acids, the acid is preferred. abietic, dihydroabietic acid, acid tetrahydroabietic, dehydroabietic acid, acid neoabietic, pimaric acid, levopimaric acid and parastrinic acid and their derivatives.

According to the invention, the aliphatic hydrocarbon monocarboxylic is in the form of acid, carboxylate amines and esters.

In a more advanced mode of the invention, the combination comprises from 1 to 50% by weight of at least one polycyclic hydrocarbon compound, and from 50 to 99% by weight of at least one acid linear monocarboxylic, saturated or unsaturated, comprising 12 to 24 carbon atoms, these products being present under form of acid, carboxylate of amines or esters.

By amine carboxylates is meant the compounds resulting from the reaction of these acids with amines or primary, secondary and tertiary polyamines including from 1 to 8 carbon atoms per chain and the alkylene amines and primary, secondary or tertiary alkylene polyamines comprising from 2 to 8 carbon atoms. In a preferred mode of the invention, these amine salts are derived from selected amines in the group consisting of ethyl-2-hexylamine, N, N-dibutylamine, ethylenediamine, diethylenetriamine and tetraethylenepentamine.

Among the esters, alkanol esters are preferred primary with 1 to 8 carbon atoms or polyalcohols from the group consisting of ethylene glycol, propylene glycol, glycerol, trimethylolpropane, pentaerythritol, diethanolamine, triethanolamine and their derivatives.

In a preferred embodiment of the invention, the fuel contains 50 to 1000 ppm of the oiliness additive.

According to the present invention, one can add to the said fuel at least one additive from the group of additives usually added in such fuels such as detergent additives, additives improving the index of cetane, demulsifying additives, anti-corrosion additives, additives improving cold resistance, and odor modifying additives.

To explain the advantages of this invention with regard to the prior art, examples are given below by way of illustration but not limiting of the scope of the claimed invention.

EXAMPLE I

This example describes the choice of additives in function of their solubility in a weak diesel sulfur.

Each additive in test is diluted to 5% by weight in a diesel (GO) at 500 ppm sulfur, at room temperature.

The additives according to the invention are designated by Y and by C the comparative examples in Table I below. Additives Y consist, on the one hand, of a mixture of a combination of fatty acids containing by weight 50 to 55% oleic acid, 30 to 40% linoleic acid, 3 to 5% palmitic acid and 1 with 2% linolenic acid, and for another part in resin acids obtained by distillation of tall oil, by-product of the manufacture of wood pulp by the sulphate process. For the comparative examples, C ₁ corresponds to pure oleic acid, C ₂ to rosin which is a mixture of resin acids corresponding to the distillation residue of pine gems and C ₃ is a mixture of dimer acids obtained by thermal dimerization and / or catalytic of unsaturated fatty acids. Additive % Fatty acids % resin acids solubility in GO Y ₁ 70 30 soluble Y ₂ 85 15 soluble Y ₃ 98 2 soluble C ₁ 100 0 soluble C ₂ 0 100 very cloudy K ₃ 0 0 soluble

It can be seen from this table that, with the exception of resin acids (C ₂ ), all of these compounds are very soluble in diesel.

EXAMPLE II

This example studies the lubricating power of additives described in Example I.

The lubricity of these additives has been measured under the conditions of the HFRR test (High Frequency Reciprocating Rig) as described in article SAE 932692 by J.W. HADLEY of the University of Liverpool.

The test consists in imposing jointly with a ball of steel in contact with a stationary metal plate, a pressure corresponding to a weight of 200 g and a displacement alternating 1 mm at a frequency of 50 Hz. The ball in movement is lubricated by the composition to be tested. The temperature is maintained at 60 ° C for the duration of the test, i.e. 75 min. The lubricity is expressed as the average value of the footprint diameters wear of the ball on the plate. A small diameter wear (generally less than 400µm) indicates good lubricity; conversely, a wear diameter important (greater than 400µm) translates a power of as much more insufficient than the value of the wear diameter is high.

The lubricating power of the additives was measured on a gas oil identical to that of Example I, each tested sample containing only 100 ppm of additive. The results are given in Table II below. Sample Wear diameter (µm) Diesel only (GO) 510 GO + Y ₁ 350 GO + Y ₂ 385 GO + Y ₃ 410 GO + C ₁ 440 GO + C ₂ 470 GO + C ₃ 380

This table shows that the additives (Y ₁ and Y ₂ ) according to the invention have an identical effect if not better than the dimer acids (C ₃ ). In addition, it is found that the mixture of fatty acids with resin acids has a much better lubricating power than those obtained with these same compounds taken separately, translating a synergy of these components between them.

EXAMPLE III

This example studies the compatibility of additives described in Example I with lubricants usually used in diesel engines according to the protocol described below.

70 ml of engine oil with total basicity equal to 15 mg of KOH per gram are mixed with 700 ml of diesel at 500 ppm of sulfur identical to that of Example I, in which is added 35 g of additive. Each mixture as well constituted is placed in an oven at 50 ° C, then evaluated visually the presence or absence of deposits, a precipitate or disorder resulting from incompatibility between so-called "oiliness" additives sufficient lubricant, with an engine lubricant called KM2 + marketed by the company of Huiles Renault Diesel.

The compatibility results are collated in Table III below. Additive Compatibility with lubricant Y ₁ No deposit - clear solution Y ₂ No deposit - clear solution Y ₃ No deposit - very light veil C ₁ Very slight cloudiness after 48 hours C ₂ Presence of some insolubles K ₃ Formation of a disorder upon addition of additive GO

The additives of the invention, Y ₁ and Y ₂ give no deposit or cloudiness when the diesel fuel with 100 ppm additive is added to the oil.

EXAMPLE IV

The purpose of this example is to describe additives oiliness adapted to be introduced into fuels according to the invention.

These are, on the one hand, esters obtained by reacting alcohols with the additive Y ₁ of Example I in an equimolar mixture, in maintaining this mixture at reflux between 130 and 150 ° C. under atmospheric pressure, then in distilling l water / toluene azeotrope.

On the other hand, they are amine carboxylates obtained by simple mixing at room temperature and at atmospheric pressure of Y ₁ with an amine or polyamine according to the invention, thus allowing the neutralization of the carboxylic sites.

These additives are introduced into a diesel such as described in Example II at a concentration of 100 ppm.

Table IV collates below the results of the wear test described in Example II obtained with the diesel fuel thus doped to characterize their lubricating power. Nature of the additive (Y1 + ..) Wear diameter (µm) triethanolamine 365 N, N dimethylethanolamine 375 ethylene glycol 385 glycerol 360 propylene glycol 380 ethyl-2-hexanol 385 N, N-dimethyl-1,3-propanediamine 360 ethyl-2-hexylamine 370 N, N-dibutylamine 375 ethylenediamine 355

From these results, it is confirmed that the fuels doped with such additives according to the invention have good lubricity.

Claims (11)

1. The use, for improving the lubricating properties of low-sulphur content diesel fuels, of a lubricity additive constituted by a combination of at least one saturated or unsaturated, linear monocarboxylic aliphatic hydrocarbon containing from 12 to 24 carbon atoms, and at least one polycyclic hydrocarbon compound chosen from the group consisting of the natural rosin acids obtained from residues of distillation of natural oils extracted from resinous trees, especially resinous coniferous trees, and the derivatives: amine carboxylates, esters and nitriles of these acids.
2. Use according to claim 1, wherein the diesel engine fuel has a sulphur content lower than 500 ppm, and corresponds to at least one middle distillate originating from a direct distillation cut of crude oil, at temperatures of between 150 and 400°C.
3. Use according to claim 1 or 2, wherein the additive is used in an amount of at least 20 ppm and more than 60 ppm of additive when the said additive is tall oil.
4. Use according to claim 3, wherein the additive is used in an amount of from 50 to 1000 ppm.
5. Use according to one of claims 1 to 4, wherein the rosin acids are chosen from the group consisting of abietic acid, dihydroabietic acid, tetrahydroabietic acid, dehydroabietic acid, neoabietic acid, pimaric acid, levopimaric acid, parastrinic acid and their derivatives.
6. Use according to one of claims 1 to 5, wherein the monocarboxylic aliphatic hydrocarbon is in the form of acid, of amine carboxylate and/or of esters.
7. Use according to one of claims 1 to 6, wherein the additive comprises from 1 to 50 % by weight of at least one polycyclic hydrocarbon compound, and from 50 to 99 % by weight of at least one saturated or unsaturated, linear monocarboxylic aliphatic hydrocarbon containing from 12 to 24 carbon atoms.
8. Use according to one of claims 1 to 7, wherein the amine carboxylates result from the reaction of these acids with primary, secondary and tertiary amines or polyamines containing from 1 to 8 carbon atoms per chain and primary, secondary or tertiary alkyleneamines and alkylenepolyamines containing from 2 to 8 carbon atoms.
9. Use according to claim 8, wherein the amines from which the amine carboxylates are derived are chosen from the group consisting of 2-ethylhexylamine, N,N-dibutylamine, ethylenediamine, diethylene triamine and tetraethylenepentamine.
10. Use according to one of claims 1 to 7, wherein the esters result from the reaction of these acids with alcohols of the group consisting of the primary alcohols containing from 1 to 8 carbon atoms and polyalcohols of the ethylene glycol, propylene glycol, glycerol, trimethylolpropane, pentaerythritol, diethanolamine and triethanolamine type.
11. Use according to one of claims 1 to 10, wherein at least one additive from the group of the additives usually added to such fuels is added to the said fuel, such as detergent additives, cetane-improving additives, deemulsifying additives, anticorrosion additives, cold-flow additives and odour-modifying additives.