FR2894977A1 - Component improving cetane in diesel fuels and useful to prepare diesel fuels, comprises a stearic acid ester comprised e.g. in (a pure state added with a mixture of) vegetable or animal oil esters in crude or partially hydrogenated form - Google Patents

Abstract

Component improving cetane in diesel fuels, comprises a stearic acid ester: comprised in a vegetable/animal oil ester in crude/partially hydrogenated form; in a pure state added with a mixture of vegetable/animal oil ester in crude/partially hydrogenated form; or in a mixture of esters of vegetable and/or animal oil in crude or partially hydrogenated form, where the mixtures of saturated and unsaturated esters being such as the mass ratio of the stearic ester content over the total sum of the unsaturated ester contents present in vegetable or animal oil esters is 1-12%. An independent claim is included for a diesel fuel comprising a hydrocarbon resulting from distillates of 180-350[deg]C boiling point and the component comprising at least a saturated ester of more than than 16 carbon atoms, preferably the stearic ester (>=0.5 wt.%).

Description

COMPONENT ENHANCING CETANE FOR DIESEL AND FUEL FUELS

  FIELD OF THE INVENTION The present invention relates to a cetane improving component without degradation of the cold resistance and without degradation of the oxidation stability of diesel fuels, as well as diesel fuels comprising this component. Elie more particularly relates to the incorporation of components deriving from products of vegetable or animal origin in diesel fuels. BACKGROUND OF THE INVENTION Fuels containing vegetable oil derivatives have a reduced emission rate and increased biodegradability, but they usually exhibit a very high sensitivity to oxidation and show very poor cold properties. Despite these drawbacks, the sale of fuels comprising these derivatives has increased significantly in recent years as the derivation of these derivatives becomes more competitive with traditional petroleum fuels. Above all, the production of such fuels makes it possible to envisage the future in a more favorable way while the oil stocks decrease. However, the poor cold properties of these components and their high sensitivity to oxidation have for a long time been limiting factors for their use at high concentrations in diesel fuels their physicochemical characteristics likely to compromise the proper functioning of the engines of the market. Currently, it is difficult given these engines, to use these derivatives at levels greater than 5% in diesel fuels and to obtain optimum performance.

  These vegetable oil derivatives are often products of the transesterification of triglycerides of vegetable or animal oils. They present a high cetane index corresponding to a good behavior of burning fuel. For these derivatives, a cetane number of at least 47 is required according to United States standards (ASTM D 6751) and an index of 51 in some European countries (eg Germany). Since cetane numbers are correlated with low nitrogen oxide emissions, the addition of these products may be of great importance for the production of diesel fuels supplemented with products derived from vegetable and animal oils. G. Knothe et al., Fuel 82, 971975 (2003) describes the cetane numbers of many fatty acid esters such as palmitic acid, stearic acid, oleic or linoleic acid, and especially the favorable effect of The increase in the length and the saturated nature of the chain on the cetane index, as is the case for the esters of palmitic acid and stearic acid. It is further noted that the right or ramifying character of fester has no influence. In the European application EP 1484385 has been described a biofuel containing 100% by weight of a mixture of palm oil esters, this mixture having a low pour point, particularly suitable for cold countries without adding additives . This biofuel is produced by esterification of a mixture of fatty acids C18 (stearic), C18: 1 (oleic) and C18: 2 (linoleic) with methanol or ethanol, followed by the fractional distillation of the methyl and ethyl esters, finally crystallization. The biofuel is prepared by mixing these fractions from the distillation of palm oil. It is used as fuel, in an environmental concept, as a substitute for diesel fuels, obtained from palm oil and conventional mixtures of palm oil esters. The olefinic fatty acid esters comprising more than 16 carbon atoms and especially the methyl esters are known for their good cold properties but also for their high sensitivity to oxidation. In addition, although having the advantage of high cetane numbers, saturated fatty acid esters of up to 18 carbon atoms are known to have a tendency to degrade the flow properties of biodiesels. SUMMARY OF THE INVENTION It has now been found that among these saturated fatty acid esters the addition of at least one carbon-chain saturated acid ester of at least 16 carbon atoms, particularly from At least one ester of stearic acid, hereinafter referred to as stearic ester, at a particular concentration in a diesel fuel, could not only improve the cetane index of this fuel but could stabilize its resistance to oxidation, without seriously deteriorating. his outfit was cold.

  The present invention relates to a cetane improving component and oxidation stabilizer for diesel fuels, comprising at least one stearic ester a) included in at least one ester of a crude or partially hydrogenated vegetable or animal oil, b) in the pure state added to a mixture of at least one crude or partially hydrogenated vegetable or animal oil ester c) or included in a mixture of esters of one or more vegetable and / or animal oils under raw or partially hydrogenated form, the saturated and unsaturated ester mixtures being such as the mass ratio of the ester (s) content (s) to the sum total of unsaturated esters present in the vegetable oil esters or animal ranges from 1 to 12% by weight.

  DETAILED DESCRIPTION OF EMBODIMENTS In the remainder of the present description, the reference to vegetable or animal oil stearate esters will cover esters resulting from the esterification of vegetable and animal oils, whether they are totally or partially hydrogenated, whether they are be extracted or not. It would not be departing from the scope of the present invention if stearic acid diacid was used in the pure state, optionally in admixture with at least one unsaturated linear acid ester of more than 16 carbon atoms. The component is used in a concentration such that the stearic esters contribute to improving the cetane number without deteriorating the cold behavior of the fuel and improving the oxidation stability of the hydrocarbons. The ratio by weight of esters (ester (s) stearic / ester (s) unsaturated fatty acids of 18 carbon atoms and more] generally ranging from 1 to 12%, and preferably between 5 and 9.6 % and more preferably between 7 and 9.0%. The stearic ester may be advantageously chosen from esters of linear or branched monohydric alcohols containing 1 to 6 carbon atoms. In particular, methyl or ethyl esters, or even the n-propanol, isopropanol, n-butanol or tert-butanol esters, and more particularly the methyl or ethyl esters of stearic acid are preferred. The stearic ester may be of natural or synthetic origin. The stearic esters are present in all esters of vegetable or animal oils. Particularly, it may be derived from the partial or total hydrogenation of esters of vegetable or animal oils with a high content of unsaturated, linear C18 fatty acid esters. preferably, esters of oleic, linoleic and linolenic acids. The stearic ester may be introduced into a fuel as part of an ester of a vegetable or animal oil or as part of the mixture of several esters of vegetable oils and / or animates. It would not be departing from the scope of the invention, if instead of using the products resulting from the crude esterification, each ester contained by type of esterifying acid was refined and / or separated and if these esters were mixed of acids in the proportions required for carrying out the invention in the fuel. Among the other esters present in the mixtures, unsaturated esters of acids containing 18 or more carbon atoms are preferred in mixture with the stearic esters, because of their good influence on the cold properties of diesel fuels: they are effective for temper the negative effect of stearic esters on these properties. Preferred unsaturated esters are esters of oleic, linoleic or linolenic acids. These unsaturated fatty acid esters may be of natural or synthetic origin. They are present in esters of vegetable or animal oils at varying concentrations depending on the variety of the esterified oil.

  The stearic acid present in these mixtures makes it possible to limit the well-known oxidation of these unsaturated esters and to stabilize this effect. The increase in cetane and the improvement of the cold operability of the fuels are optimal when there is an appropriate combination of stearic ester with unsaturated acid esters containing at least 18 carbon atoms, preferably linear ones. It is well known that vegetable or animal oils include triglycerides of monocarboxylic fatty acids. The number and nature of acid residues in the composition of glycerides define the variety of each of these oils. The mixtures of esters may possibly come from a mixture of esters of vegetable or animal oils such as, in particular, rapeseed oil esters (methyl or ethyl ester of rapeseed, for example), esters of palm oil (ester for example, methyl or ethyl palm oil), esters of pine oil (methyl or ethyl ester of pine for example), esters of soybean oil (methyl or ethyl ester of soy for example), oil esters sunflower (methyl ester and or ethyl sunflower for example), the esters of mg oil (methyl or ethyl ester of maize for example), safflower oil esters (methyl or ethyl ester of safflower, for example), esters of cottonseed oil (methyl and ethyl esters of cotton, for example), esters of coriander oil (methyl and ethyl esters of coriander, for example), esters of mustard oil (methyl and ethyl ester of mustard) for example), the esters of tallow oil (ester m ethylic and ethyl tallow for example) and all other esters containing stearic esters and / or acid esters containing at least 18 unsaturated carbon atoms. The esterification of fatty acid triglycerides present in these oils can be carried out according to the known methods. In particular, it can be carried out by alcoholysis, using the alcohols mentioned above as described by J.-C. Guibet et al., Fuels and Engines, Ed. Technip Paris or according to the European patent application EP 860,494. In the context of the present invention, it is possible to use, in a mixture, several esters of vegetable and / or animal oils to introduce the necessary quantities of stearic esters and unsaturated fatty acid esters of at least 18 carbon atoms. The mixture may advantageously comprise 2, 3 or more esters of different oils. It is understood that the suitable mixtures are limited to those which make it possible to reach a value of the mass ratio [ester (s) stearique / sum of unsaturated esters of C18 and more] between 1 and 12%, preferably from 5 to 9.6% and still more favorably from 7 to 9%. The present invention also relates to the use of a cetane improving and oxidation stabilizing component for diesel fuels, as previously defined, for the preparation of an improved diesel fuel with no deterioration of the cold properties and the stability to the oxidation of said fuel, from a mixture of esters of vegetable oils and / or animal. Another object of the present invention also relates to a diesel fuel comprising: at least one hydrocarbon derived from distillate boiling temperature ranging from 180 to 350 C, at least one component comprising at least one ester saturates more than 16 atoms carbon, preferably at least one stearic ester: • a) included in at least one ester of a vegetable or animal oil in raw or partially hydrogenated form, • b) pure state added to a mixture with d at least one vegetable or animal oil ester in crude or partially hydrogenated form, or c) or included in a mixture of esters of one or more vegetable and / or animal oils in raw or partially hydrogenated form, the mixtures saturated and unsaturated esters such that the mass ratio of the ester (s) content (s) to the total sum of the unsaturated esters present in the esters of vegetable or animal oils ranges from 1 to 12% , the ester content of the acid stearique in the said fuel being at least 0.5% by mass. The hydrocarbons are derived from speech distillation cups, but also from biomass, essentially paraffinic hydrocarbon mixtures resulting from the conversion of the gas into hydrocarbons or any other process making it possible to obtain all or part of such mixtures or a mixture. of these various sources of hydrocarbons. The saturated or unsaturated fatty acid esters required for carrying out the invention have been defined above in the present description. If the stearic ester is introduced in pure form or in any other form into the fuel, its concentration shall be maintained at less than or equal to 2.4% by mass. When stearic fester is introduced into the fuel, in mixture with other compounds such as esters of vegetable or animal oils, the ester mixtures of one or more vegetable and / or animal oils, the stearate content in the The fuel content may vary between 0.5 and 2.4%, preferably between 0.5 and 1.2%, and the ratio by weight of the ester / stearic ester of the unsaturated esters present in the fuel may vary between and 12%, preferably between 5 and 9.6% by weight and more particularly between 7 and 9% by weight.

  Mixtures of esters of several vegetable and / or animal oils are advantageously used to achieve the optimum composition of stearic esters / unsaturated esters comprising at least 18 carbon atoms. It is understood that the optimal mixtures are limited to those which make it possible, depending on the amount of stearic ester present, to have a final stearic ester content always less than or equal to 2.4% by weight, to a value of the ratio in mass [sodium ester / sum of the ester (s) of unsaturated acids] of between 1 and 12% and preferably between 5 and 9.6% and more particularly between 7 and 9%. Preferably, irrespective of the composition of the component, preferably, the stearic ester content will be between 0.5 and 1.2% by weight in the fuel and the mass ratio [stearic ester / sum of the ester (s) of the unsaturated acids] will be between 7 and 9%. When the stearic esters are in the presence of high concentrations of at least one second C16 saturated acid ester, the palmitic ester should be taken into account. Indeed, the effects of these esters are similar to those of the stearic esters, in particular on the cold behavior of the fuel. The Applicant has thus found that the sum of the stearic esters and palmitic esters, that is to say the sum of the C16 and Cl8 saturated acid esters, was a limiting factor for vegetable oil ester mixtures in the diesel fuels. Thus, the amount of C16 and C18 saturated esters can not exceed 10% by weight of the fuel. By playing on the combination of vegetable and / or animal oil esters while respecting the conditions mentioned above, the amount of vegetable oil esters contained in the fuels can be very greatly increased up to 10 % by weight without being limited to only rapeseed oil esters. Thus, it is possible in a preferred manner to introduce palm oil, soybean and sunflower esters at higher concentrations in the fuels. In particular, the concentration of the combination in the fuel, may be set beyond 10% and even 20%, to increase the cetane while maintaining the stability of the fuels with the oxidation with good properties of flow and cold filterability. Elie allows in particular that the filterability additives, especially the EVA (polyethylenevinylacetates) have a good efficiency on the resulting fuel filterability temperature. Of course, in order to give the fuel all the properties which are necessary for the proper functioning of the vehicle engines, the said fuel may also comprise other additives intended to improve the cold properties, the flow or the filterability, as well as anti-foam additives, lubricity, conductivity, anticorrosion, detergency and demulsification that any professional would not forget to introduce, as well as bactericides.

  The fuel may be low in sulfur, preferably less than 500 ppm sulfur, preferably less than 100 ppm. The following examples are given by way of illustration of the present invention but do not constitute a limitation thereof.

  EXAMPLES Example 1 The present example aims to demonstrate the feasibility of introducing mixtures of two vegetable oil esters of different types chosen from the methyl esters of rapeseed (EMC), soya (EMS) and palm (EMP) and The influence of these mixtures introduced at different concentrations in a diesel type EN590 (GO I) and a heating oil (FOD1) whose characteristics are given in Table I below.

  TABLE I GO FOD PTE (C) -12 -18 PT (C) -4 -6 IP 387 1.01 MV15 0.8327 0.8388 Sulfur content ppm 39.8 1740 Viscosity at 40 C mm / s 2.725 2.451 Cetane calculates 50.1 48.5 Mono Aromatic% 22.7 21.2 Di Aromatic% 6.2 6.9 Poly Aromatic% 0.6 0.6 stilling D86 Starting point 167.6 168 5% 190.1 188, 5 10% 203 196.3 20% 224.7 210.8 30% 244.9 227 40% 260.7 242.3 50% 274.5 258.9 60% 288.1 274.3 70% 301.7 290.7 80% 317.1 310.1 90% 337.4 333.7 End point 356 356.315 Table II gathers the respective amounts of C16 and C18 saturated acid esters and unsaturated fatty acids of minus 18 carbon atoms in the different esters envisaged.

  TABLE II C16 C18: 1 C18: 2 C18: 3 C20 C20: 1 C22 Sat EMP 44 `x • 38 10 0.5 0.5 0 0 51.5 EMC 5 59 21 9 0.4 1 0.5 7, 9 EMT 6 19 68 0.5 0.5 0 0.5 12 EMSoja 10 '= Hy 23 53 8 0.5 0.5 0.5 15 Insat Sat / Insat 48.5 91 88 84.5 Mixtures according to the invention were carried out by varying the respective concentrations of methyl ester rapeseed and palm methyl ester and varying the concentration of the mixture in each of the two hydrocarbons. Each test will be referenced by X; for GO and Y, for FOD as described in Table III below.

  TABLE III Hydrocarbon EMP EMC C18 sat C16 + 18 sat C18sat / C18 insensor Additive TLFI% wt% wt% wt Without 200 ppm 00 ppm Gasol 100 0 0 0 0 0 -4 -14 90 0 10 0.2 0.79 2, 25 -4 -13 90 10 0 0.6 5.15 12.37 -2 -10 90 3 7 0.3 2.1 5.28 -4 -14 90 7 3 0.5 3.84 9.33 - 3 -14 80 0 20 0.4 1.58 2.25 -3 -13 80 10 10 0.8 5.94 7.31 -3 -11 80 16 4 0.989 8.56 10.4 -2 -9 80 20 0 1,2 10,3 12,37 -3 -8 70 0 30 0.6 2,37 2,25 -3 -13 70 21 9 1,4 11,5 9,33 -2 -7 -8 70 24 6 1.6 12.8 10.35 -3 -7 -3 70 30 0 _ 1.8 _ 15.5 12.37 -3 -5 -2 FOD 100 0 0 0 0 0 -5 -16 90 0 0.2 0, 79 2.25 -5 -16 90 10 0 0.6 5,15 12.37 -4 -15 90 3 7 0.3 2.1 5.28 -6 -17 90 7 30 , 3.84, 9.33 -5 -16 80 0 20 0.4 1.58 2.25 -4 -17 80 10 10 0.8 5.94 7, 31 -5 -15 80 16 4 0.989 8, 56 10.4 -5 -13 80 20 0 1.2 10.3 12.37 -5 -11 70 0 30 0.6 2,37 2,25 -4 -16 70 21 9 1,4 11,5 9 , 33 -5 -10 -9 70 24 6 1,6 12,8 10,35 -5 -11 -9 70 30 0 1,8 15,5 12,37 -6 -8 _ -8 In this table the contents in saturated C18 and in saturated C 16 + C 18 are given in the mel angel Middle distillate methyl ester of fatty acid. The ratio C18 saturates ICI 8 unsaturated with the ratio of these esters in the mixture of methyl esters of fatty acid. Table III shows that it is possible to introduce more than 20% of a mixture of vegetable oil esters into hydrocarbons such as gas oil and heating oil, insofar as the concentration of stearic ester (C18 sat) is always less than 1.2% by weight for a minimum deterioration of the limit temperature of filterability (TLF) measured by application of the standard EN 116 by increasing the temperature of 6 C. The reactivity TLF is not degraded and the gain remains at a level above 6 C compared to the non-additive mixture. Depending on the case, it is possible to correct this deterioration by the addition of an EVA-based TLF additive (polyethylenevinylacetate). However, the addition of EVA only has an effect when the mass ratio of [C 18 saturations / sum of C18 unsaturated] is kept below or equal to 9% by mass, and especially a content of (C16 + C18 sat) corresponding to the sum of the stearic and palmitic esters, always less than 10% by weight in said fuel. EXAMPLE 2 In this example, in addition to the characteristics of cetane and filterability of the mixtures in a diesel type EN590, the characteristics of the stability of the oxidation of the mixtures are measured by the iodine number (IN) determined by the standard EN 14214. The description of these compositions is the following (% by mass): A = 5ES + 95EMC B = 40EMC + 60EMP C = 30EMC + 70EMP D = 70EMC + 30EMP E = 8ES + 92 (EMC + EMS + EMP) F = 100EMC These components A, B, C, D, E and F were added to the gas oil in a proportion of 20% component to 80% by weight of gas oil. The physico-chemical characteristics of these compositions are summarized in Table IV below.

  TABLE IV Composition IN # TLF C ~ tane ES / GO ES / EAG (% wt.) (% Wt.) + EVA Gasoil -16 -21 51 - - A 110 -13 -19b 52 1.34 7.6 B 82 -9 -13a 54.5 1.16 7.95 C 76 -9 -13b 55 1, 33 9.34 _ D 99 -9 -19a 53 0.76 4.6 E 107 0 -2b 53.8 9.7 1.94 F 116 -13 -20a 51.6 0.36 1.94 *) Diesel iodine index comprising esters a) addition of 100ppm of EVA b) addition of 400ppm of EVA

  Examples A to D according to the invention correspond to the criteria of the ratio of steric ester / unsaturated esters and of stability to oxidation, while also leading to compositions having good cold properties and an iodine number of less than 110.

Claims (17)

  A cetane improving component for diesel fuels characterized in that it comprises at least one ester of stearic acid: a) included in at least one ester of a vegetable or animal oil in raw or partially hydrogenated form, b ) in the pure state added to a mixture of at least one crude or partially hydrogenated vegetable or animal oil ester c) or included in a mixture of esters of one or more vegetable and / or animal oils in crude or partially hydrogenated form, the mixtures of saturated and unsaturated esters being such as the mass ratio of the ester (s) content (s) to the sum total of the unsaturated esters present in the esters of oils vegetable or animal varieties range from 1 to 12%.   2. Component according to claim 1, characterized in that the ester of stearic acid is chosen from esters of linear or branched monoalcohols containing 1 to 6 carbon atoms.   3. Component according to Claim 2, characterized in that the ester of stearic acid is chosen from methyl or ethyl esters, or by n-propanol, isopropanol, n-butanol or tert-butanol esters.   4. Component according to rune of claims 1 to 3, characterized in that in the component containing unsaturated fatty acid esters, the ratio by mass [stearic ester content / sum of unsaturated fatty acid ester (s) content (s)] is 5 to 9.6% and preferably 7 to 9.0%.   5. Component according to one of claims 1 to 4, characterized in that the unsaturated fatty acid esters present in the composition are mono or poly unsaturated acid esters containing 18, 20 or 22 carbon atoms.   6. Component according to claim 5, characterized in that the unsaturated fatty acid esters are part of the group consisting of esters of oleic, linoleic or linolenic acids.   7. Component according to one of claims 1 to 6, characterized in that fester stearic acid or unsaturated fatty acid esters are of natural or synthetic origin.   8. Component according to one of claims 1 to 7, characterized in that fester stearic acid or unsaturated fatty acid esters are derived from the transesterification of triglycerides contained in vegetable oils and / or animal.   9. Component according to rune of claims 1 to 8, characterized in that it consists of a mixture of esters of vegetable oils selected from the methyl or ethyl esters of rapeseed, palm, pine, soybean, sunflower, tallow, maize, safflower, cotton, coriander, mustard and all other esters containing stearic esters and / or esters of at least 18 unsaturated carbon atoms.   10. Diesel fuel characterized in that it comprises: at least one hydrocarbon derived from distillates with a boiling temperature ranging from 180 to 350 ° C, at least one component comprising at least one ester saturates with more than 16 carbon atoms, preferably at least one stearic ester: • a) included in at least one ester of a vegetable or animal oil in crude or partially hydrogenated form, • b) in the pure state added to a mixture of at least a crude or partially hydrogenated vegetable or animal oil ester (c) or included in a mixture of esters of one or more vegetable oils and / or animal oils in crude or partially hydrogenated form, the ester mixtures saturates and unsaturates being such that the mass ratio of the ester (s) content (s) to the total sum of unsaturated esters present in esters of vegetable or animal oils varies from 1 to 12%, the content as an ester of stearic acid in said fuel being at least 0.5% by weight. 20   11. Fuel according to claim 10, characterized in that the content of stearic ester is between 0.5 and 2.4%, and the ratio by weight of stearic ester / sum of unsaturated acid esters present ranges from 5 to 9.6%. by weight and preferably from 7 to 9% by weight.   12. Fuel according to one of claims 10 and 11, characterized in that the stearic ester content varies from 0.5 to 1.2%.   13. Fuel according to any of claims 10 to 12 characterized in that it comprises at most 10% by weight of the sum of the saturated esters of C6 and C18.   14. Fuel according to one of Claims 10 to 13, characterized in that it contains more than 10% by weight of a mixture of esters of vegetable and animal oils taken in combination, preferably more than 20% by weight. of such a mixture.   15. Fuel according to any one of claims 10 to 14 characterized in that the fuel contains at least one cold filterability additive. 35   16. Fuel according to any one of claims 10 to 15, which is low in sulfur, preferably less than 500 ppm sulfur, preferably less than 100 ppm.   17. Use of a component according to any one of claims 1 to 9, for the preparation of an improved cetane diesel fuel without deterioration of cold properties and stability to oxidation of said fuel, from a mixture esters of vegetable and / or animal oils.