EP0261002A1 - Use of composition with rare earth metals to stabilize diesel engine fuel - Google Patents

Abstract

Composition enabling the stability of diesel motor fuels to be improved by addition of certain rare-earth organic compounds to the diesel motor fuels. The invention also relates to the process for implementing it. The stabilisation of the diesel fuels is effected with the aid of an additive consisting of a rare-earth organometallic compound corresponding to the following formula: <IMAGE> in which M denotes one or more rare-earth elements and R a hydrocarbon group containing from 3 to 25 carbon atoms.

Description

The present invention relates to a composition allowing. improve the stability of fuels for diesel engines by adding certain rare earth organic compounds to fuels for diesel engines. The invention also relates to its method of implementation.

Fuels for diesel engines have a reputation for being very unstable. The term "diesel fuel" used in the description and the claims designates the fraction of hydrocarbons resulting from the distillation of kerosene. Generally, diesel fuel is a mixture of hydrocarbons with a melting point between about 177 ° C and about 371 ° C. The approximate ranges given below correspond to the specifications required for diesel fuels defined in "Federal Specification VV-F-800" of 1967. We distinguish diesel fuels DF-A (arctic), DF-1 (winter), DF- 2 (normal) and DF-4 (heavy). The "arctic" quality is used in high-speed automotive-type diesel engines and burner burner heaters used in environments where the ambient temperature is below -30 ° C. Winter quality is used in high-speed cars at temperatures down to - 30 ° C. "Normal" diesel fuel is used in high speed automobile engines and in medium speed stationary engines, when the average temperature is above + 5 ° C. "Heavy" diesel fuels are used in low and medium speed engines.

• - point d'éclair entre 38°C (arctique) et 54°C (lourd)
• - point de trouble : - 45°C
• - point d'écoulement : - 57°C
• - viscosité cinématique (à 38°C) : entre un minimum allant de 1,4 à 5,8 centistokes (1,4.10^-6 à 5,8.10^-6 m²/s) et un maximum allant de 4,0 à 20,6 centistokes (4,0.10^-6 à 2,06.10^-5 m²/s)
• -- teneur-limite en eau et sédiments (% en volume): entre 0,03 et 0,50 %
• - teneur en soufre : de 0,25 à 1,5 %
• - résidu de carbone (résidu à 10 %) : de 0,12 à 0,5 % maximum
• - teneur en cendres : de 0,01 à 0,10 % maximum
• - corrosion (mesurée sur une lamelle de cuivre pendant 3 h à 5C°C, n^OASTM, maxi) : 2-3
• - qualité de l'allumage (indice de cétane, minimum) : de 35 à 40

The properties of said fuels are as follows:

• - flash point between 38 ° C (arctic) and 54 ° C (heavy)
• - cloud point: - 45 ° C
• - pour point: - 57 ° C
• - kinematic viscosity (at 38 ° C): between a minimum ranging from 1.4 to 5.8 centistokes (1.4.10 ^-6 to 5.8.10 ^-6 m ² / s) and a maximum ranging from 4.0 to 20 , 6 centistokes (4.0.10 ^-6 to 2.06.10 ^-5 m ² / s)
• - limit water and sediment content (% by volume): between 0.03 and 0.50%
• - sulfur content: from 0.25 to 1.5%
• - carbon residue (10% residue): from 0.12 to 0.5% maximum
• - ash content: from 0.01 to 0.10% maximum
• - corrosion (measured on a copper strip for 3 h at 5C ° C, n ^O ASTM, max): 2-3
• - quality of ignition (cetane number, minimum): 35 to 40

Additional information relating to diesel fuels can be found in Bland et al, "Petroleum Processing Handbook" (Mc Graw - Hill Book Co., 1967), pages 11-35 et seq., Which are also an integral part of this application.

Diesel fuels have a large number of components. In addition to the petroleum fractions used as fuel, they contain many chemical compounds used for several purposes. These chemical additives are used for example to prevent oxidation and prevent the formation of sludge, prevent corrosion, produce a detergent and dispersing action, emulsify, deactivate metals, obtain an antistatic effect and as biocides.

The formulation of diesel fuels poses a significant problem. Indeed, certain components such as, for example, unsaturated hydrocarbons tend to react and precipitate during storage, causing various inconveniences including fouling of tanks and engines. In addition, some of these additives selectively combine with the precipitate, are therefore no longer present in the composition of the fuel and no longer play the role which was assigned to them.

Antioxidants are one of the most important classes among diesel fuel additives. Since diesel fuel is a mixture of hydrocarbons, it is very prone to radical oxidation and the formation of acids, ketones, aldehydes and esters. Oxidation forms gums which pass into the colloidal state, agglomerate and precipitate in the form of mud. Mud can clog the burner lines, filters and nozzles.

Many oxidation inhibitors work by eliminating peroxy radicals present in the reaction chain, thus stopping the reaction. This is how the oxidation inhibitors of phenolic type such as dimethyl-2,4-tert-butyl-6-phenol and di-tert-butyl-2,6-methyl-4-phenol. Among the other oxidation inhibitors, there are amines such as N, N'-di _- sec-butyl p-phenylene diamine and phosphorus and sulfur compounds such as. Dithiophosphoric acid esters, barium salts and zinc of said acids.

Another important class of additives in diesel fuel is metal deactivators. Generally, these compounds act by chelating the metals found in diesel fuels, the metals being surrounded and isolated in complexes which, instead of precipitating, remain soluble in the fuel.

It has been suggested that various other additives be used in diesel fuels to reduce particulate emissions. In particular, US patents 2,962,454, 3,410,670, 3,413,102, 3,539,312 and 3,499,742 which describe agents suppressing the fumes likely to be used in diesel fuels. US Pat. No. 4,207,078 describes a process for the reduction of smoke black and visible particles in the exhaust gases of diesel engines. This process consists in introducing into the diesel fuel an additive consisting of a mixture of an oxygenated compound and a tricarbonylalkylcyclopentadienylmanganese.

US Patent 4,222,746 describes another group of compounds for reducing the black smoke and visible particles contained in the exhaust gases of diesel internal combustion engines. According to this patent, it is possible to reduce the emissions of smoke black and visible particles by adding wax to the diesel fuel which oxidizes at the same time as an organometallic compound, soluble in the fuel, such as tricarbonylalkylcyclopentadienylmanganese.

Under the pressure of economic, regulatory and ecological problems, combustion promoters have been developed to improve the combustion efficiency of the hydrocarbons contained in diesel fuel. Combustion promoters promote the combustion of hydrocarbons during the operation of the diesel engine.

According to US Pat. No. 4,522,631, soluble promoters of rare earth octoate of formula:

Cerium octoates tend, however, to contribute to the formation of precipitate and mud in fuels.

One of the objectives of the present invention is to provide compounds which stabilize the diesel fuel and effectively prevent fouling of the diesel engine by reducing the accumulation of mud in the diesel fuel.

Another object of the present invention is to provide a method for reducing the precipitation of particles in diesel fuel during storage for a relatively long period of time.

The present invention also aims to provide a method for maintaining various additives of the diesel fuel in solution during storage so that they fulfill their function during storage and combustion.

Another object of the present invention is to provide a method making it possible to significantly reduce the precipitation in diesel fuels using certain rare earth compounds.

dans laquelle M représente un ou plusieurs éléments de terres rares choisis dans le groupe comprenant l'yttrium, le lanthane, le praséodyme,le néodyme, le samarium, l'europium, le gadolinium, le terbium, le dysprosium, l'hoîmium, l'erbium, le prométhium le thulium, l'ytterbium et le lutétium et R un groupe hydrocarbdné ayant de 3 à 25 atomes de carbone.The present invention relates to a diesel fuel stabilization additive making it possible to significantly reduce precipitation and the formation of mud during storage and transport, characterized in that it consists of an organometallic compound of rare earth corresponding to the following formula ':

in which M represents one or more rare earth elements chosen from the group comprising yttrium, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, hemium, erbium, promethium thulium, ytterbium and lutetium and R a hydrocarbdenum group having 3 to 25 carbon atoms.

As indicated in formula (I), said compounds contain. carboxyl groups linked to the rare earth element by an oxygen atom.

The most abundant lanthanide, cerium, is not in this group. Indeed, it is remarkable and surprising to note that the cerium compounds do not work in the context of the process according to the present invention. It is likely that the cerium compounds behave differently due to the ease with which the cerium enters the tetravalent state which seems responsible for its reactivity towards certain fuel components.

The preferred compounds of the present invention correspond to formula (I) in which M represents yttrium, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium or their mixtures, which may contain traces of the traces other trivalent lanthanides such as terbium, dysprosium, holmium, erbium, promethium, thulium, ytterbium and lutetium.

As regards the radical R of formula (I), R is a hydrocarbon group containing approximately from 3 to 25 carbon atoms.

R can represent a linear or branched, cycloaliphatic, saturated or unsaturated aliphatic hydrocarbon radical; a monocyclic or polycyclic aromatic radical, these radicals being able to form between them orthocondensed or ortho and pericondensed systems; a heterocyclic, saturated, unsaturated or aromatic, monocyclic or polycyclic radical comprising at least one of the heteroatoms 0, N and S.

The radical R more specifically represents a linear or branched alkyl radical having from 3 to 25 carbon atoms, an alicyclic radical having from 5 to 8 carbon atoms in the ring, an aryl radical such as phenyl, an alkylaryl radical comprising from 1 to 4 carbon atoms in the substituent such as tolyles, xylyles, a polycyclic aromatic radical having from 10 to 14 carbon atoms, such as the naphthyl radical, a heterocyclic radical comprising as long as at least one of the heteroatoms 0, N and S and containing from 5 to 10 atoms in the ring such as, for example, a furanyl, furomethyl, pyridyl, picolyl, indolinyl, etc. radical.

The radical R can carry substituent groups such as, for example, hydroxyl groups, alkyloxy radicals preferably having from 1 to 3 carbon atoms or halogen atoms, in particular chlorine.

Typical carboxylic groups which make the rare earth element soluble in diesel fuel are, for example, 2-ethyl hexoate (called octoate), naphthenate, neodecanoate, butyrate, hydroxystearate and the like.

One embodiment of the additive of the invention consists in adding it to diesel fuels, preferably in the form of a concentrate soluble in said diesel fuel. However, it can be added according to any method known to those skilled in the art.

Additives based on rare earths, intended for diesel fuels, must be soluble in diesel fuel within the limits of the desired concentration. The amount of rare earth element contained in diesel fuel can vary between about 5 and about 500 ppm. The amount of rare earth element is preferably between about 5 and 150 ppm.

The following examples illustrate the additives according to the present invention. It goes without saying that they serve not to limit, but simply to illustrate the scope of the present invention. The accelerated stability test that has been adopted is one of several ways to demonstrate the effect of rare earth additives on the stability of diesel fuel.

Examples 1 - 12

All the examples were carried out under strictly identical conditions. Each example represents a group of tests performed on the same day.

350 cm3 of diesel fuel are filtered and put in a 1 1 pyrex bottle made for this purpose. We introduce a quantity of additive corresponding to what is indicated in Table (I), column entitled "Concentration of the additive". This concentration is expressed by weight of rare earth element. The specific additives used in each of the tests are indicated in Table (I), column entitled "Additive". The bottle is purged with oxygen, capped and heated for 16 hours at 100 ° C in the absence of light.

After cooling, each sample is filtered on a Millipore filter, the bottle is washed four times with hexane and the filtrate is dried. The weight of the dried precipitate is noted. Then, the bottle is washed three times with a "mixture of three solvents" (toluene, methanol and acetone) to dissolve the gums and the washing liquids are evaporated. Separately, the weight of the gums retained by the mixture of three solvents is noted. The figure which appears in Table (I) under the heading "mg of sediment / 100 cm 3 of fuel" represents the total weight of precipitate and gums per 100 cm ³ of diesel fuel.

In Examples 9-12, commercial stabilizers are compared with the rare earth stabilizers used. according to the method of the present invention.

The tests were carried out with diesel fuel samples from four different sources. Three of these samples were specially selected for their low storage stability, due to their compositions which tend to precipitate during storage. The fourth sample is a commercial diesel fuel.

From one test to another, carried out on a given day, the fuel sample tends to change over time since a deposit is formed in the container. This is the reason why the fuel sample becomes more and more clean and forms less and less deposit on each test date. We can therefore only compare the values corresponding to a given example.

The samples are designated by the abbreviated name of the element, with the exception of samples marked "TR" which represents a mixture of rare earth elements, cerium, praseodymium and neodymium.

All the cerium derivatives have a high reactivity and form deposits which are clearly superior to those of the control test. It is surprising to note that the use of lanthanum, praseodymium, neodymium and other organometallic complexes of the aforementioned rare earths reduces the deposit and apparently changes the nature of the deposit as shown by the color of the deposit.

Claims (12)

1. Diesel fuel stabilization additive characterized by the fact that it consists of an organometallic compound of rare earth corresponding to the following formula:

in which M represents one or more rare earth elements chosen from the group comprising yttrium, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, l erbium, promethium, thulium, ytterbium and lutetium and R a hydrocarbon group having from 3 to 25 carbon atoms. 2. Additive according to claim 1 characterized in that M represents one or more rare earth elements chosen from the group comprising yttrium, lanthanum, praseodymium, neodymium, samarium, europium and gadolinium. 3. Additive according to one of claims 1 and 2 characterized in that R represents a linear or branched, cycloaliphatic, saturated or unsaturated aliphatic hydrocarbon radical; a monocyclic or polycyclic aromatic radical, these radicals being able to form between them orthocondensed or ortho and pericondensed systems; a heterocyclic, saturated, unsaturated or aromatic, monocyclic or polycyclic radical comprising at least one of the heteroatoms 0, N and S. 4. Additive according to one of claims 1 to 3 characterized in that R represents a linear or branched alkyl radical having from 3 to 25 carbon atoms, an alicyclic radical having from 5 to 8 carbon atoms in the ring, a aryl radical, an alkyl-aryl radical containing from 1 to 4 carbon atoms in the substituent, a polycyclic aromatic radical having from 10 to 14 carbon atoms, a heterocyclic radical comprising at least one of the heteroatoms O, N and S and containing 5 to 10 atoms in the ring. 5. Additive according to one of claims 1 to 4 characterized in that R is substituted by a hydroxyl group, an alkyloxy radical having from 1 to 3 carbon atoms, a halogen atom. 6. Additive according to one of claims 1 to 5 characterized in that the organometallic compound of rare earth corresponding to formula (I) is an octoate, a naphthenate, a neodecanoate, a butyrate, a hydroxystearate. 7. Additive according to one of claims 1 to 6 characterized in that the compound of formula (I) is a compound of formula:

8. A method for stabilizing diesel fuels, characterized in that it consists in adding, to the diesel fuel, an organometallic compound of rare earth described in one of claims 1 to 7. 9. The method of claim 8 characterized in that adding to the diesel fuel, said organometallic compound of rare earth in an amount such that the concentration of the rare earth element in said diesel fuel is between about 5 and about 500 ppm. 10. The method of claim 9 characterized in that said concentration is between about 5 and about 150 ppm. 11. Method according to one of claims 8 to 10 characterized in that one adds to the diesel fuel, said organometallic compound of rare earth in the form of concentrate soluble in said diesel fuel. 12. Method according to one of claims 8 to 11 characterized in that it consists in significantly reducing the precipitation in said diesel fuel maintained under storage conditions equivalent to maintaining said fuel at a temperature of 100 ° C , in the presence of oxygen, for at least 16 hours.